Samie Safar DS FRCP(Ed) FRCS(Eng, Ed, Glas) FACS

• Consultant general surgeon, Newham
• University Hospital, London, UK
• Formerly Professor of surgery, University of
• Baghdad, Baghdad, Iraq

Dietary fibre by increasing bulk and needing more chewing may reduce the food intake infection staph purchase ciprofloxacin 500mg without prescription. The carbohydrate absorption is slowed antibiotic resistance concentration order 750mg ciprofloxacin amex, which helps to regulate blood sugar and lowers insulin need of diabetics antibiotic bladder infection cheap ciprofloxacin. Rapid transit of stools may reduce content of carcinogens in colon mucosa and thus reduce risk of colon cancer infection in bone discount ciprofloxacin 250mg on-line. Some problems due to high fibre diets: Dietary fibre is best taken from natural foods and not as fibre supplements bacterial 16s rrna universal primers purchase ciprofloxacin us. Food sources provide a variety of fibres antimicrobial needleless connectors cheap ciprofloxacin 250mg with visa, vitamins and minerals in combination antimicrobial cleaning products buy 1000 mg ciprofloxacin, whereas fibre supplements do not supply any nutrients antibiotic eye drops for stye buy cheap ciprofloxacin 1000 mg. An excessive intake of fibre may result in intestinal obstruction, if it is not accompanied by a liberal intake of water. If fibre intake is increased suddenly, complaints such as cramping, diarrhoea and excessive intestinal gas are common. To minimise these effects, the fibre content of the diet should be gradually increased over a period of several weeks. Sugar Substitutes Commercial sugar substitutes or artificial sweeteners are used by people, who wish to reduce their calorie intake. As the dipeptides are unstable to heat, this sweetener cannot be used in cooked or baked foods. It has been used as a sugar substitute for about hundred years without any adverse effects. The vital organs (brain, heart, liver) are protected by a Fats and Other Lipids 4747474747 sheath of fat and water, which holds them in place and prevents injury. The fat around the joints acts as a lubricant and allows us to move these smoothly. They constitute an important part of our Indian dietary and supply 10–30 per cent of the total energy needs. Food fats include solid fats, liquid oils and related compounds such as fat-soluble vitamins and cholesterol. In the middle of last century, fats were expensive and a meal containing large amounts of fat was called a ‘rich meal’. But with the improvement in the methods of production and their availability, there has been an indiscriminate increase in fat intake in some sections of society leading to overweight and obesity. The weight increase discourages movement, increases pressure on the circulation, respiration and skeletal frame. In this chapter, let us consider fats not only as essential body component, nutrient and compact storage fuel, but also as a health hazard. We need to achieve a realistic balance between meeting our needs and avoid health problems due to excessive intake. Composition Lipids is an overall group, which includes all fats and related compounds. Like carbohydrates, lipids contain the elements carbon, hydrogen and oxygen, and some contain phosphorus and nitrogen. Body fat accounts for 15 to 20 per cent of body weight in healthy non-obese men and 18 to 25 per cent in healthy non-obese women. The fat content of body increases in sedentary individuals and senior citizens if they do not have active leisure time activities. They are soluble in organic solvents, namely, ether, chloroform, benzene and other fat solvents. Fatty acids, fats and oils, phospholipids, sterols and lipoproteins are some of the groups of lipid compounds, which are important in the study of nutrition. Sources Vegetable oils, used in food preparation, are extracts of oilseeds and nuts. Vanaspati is usually fortified with vitamin A and D, as it is used in place of ghee. Oils, butter, ghee and vanaspati contribute the visible fats in the Indian dietary. As these are expensive foods, the amount and kind used in the dietary, varies with the socio-economic status of the family. The animal foods, milk, egg, meat and liver, which contain fat, are sources of hidden fat in the diet. Nuts, oilseeds, milk, eggs and meat supply not only fat but also protein, minerals and vitamins of the B-complex group. Some refined oils and 4848484848 Fundamentals of Foods, Nutrition and Diet Therapy vanaspati are fortified with vitamin A. Use of ghee, butter, fortified refined oil or vanaspati helps to meet a part of the day’s need for vitamin A. Fats and Other Lipids 4949494949 Vegetable oils contain poly-unsaturated fatty acids such as linoleic, linolenic and arachidonic acid. Linoleic and arachidonic acid are required for growth and maintenance of integrity of the skin. It may be noted that vegetable oils are a fairly good source of essential fatty acids. Invisible fats include the cream in the milk and dahi, nuts used in preparation and as such, egg yolk, oil used in seasoning vegetables, dal and salads. Classification Lipids are classified into three groups on the basis of their chemical structure: 1. The term is applied to foods which are fatty, immiscible in water and greasy in texture. The nature of the fat or the oil depends on the kind of fatty acids linked to the glycerol. The hardness, melting-point and the flavour of the fat is related to the length of the carbon chain and the level of the saturation of the fatty acid. If the substance is a liquid at 20°C it is called an oil, if solid at that temperature, it is known as fat. Saturated fatty acids are found in solid fats whereas most of the oils contain unsaturated fatty acids. In the commercial process, hydrogen is added to some (not all) of the double bonds of the unsaturated fatty acids to increase the firmness and the melting point of the product. However, this processing also changes the isomers (shape, configuration) of some of the remaining unsaturated fatty acids. Most unsaturated bonds in nature are in a ‘cis’ form (folded pattern), but after hydrogenation, many double bonds are in a linear pattern, a ‘trans’ form. Thus although they are still unsaturated, these ‘trans’ fatty acids behave like saturated fatty acids. The fatty acids have three important aspects, chain length, saturation and essential fatty acids. Thus short chain fatty acids contain 4 to 6 carbon atoms, medium chain 8 to 12 carbon atoms, long chain fatty acids have 14–18 carbon atoms and extra-long-chain fatty acids have more than 20 carbon atoms in the molecule. Milk, fat, vinegar and coconut contain short chain fatty acids, long chain fatty acids are found in most vegetable oils and animal fats. Fats and Other Lipids 5151515151 Saturated fatty acid has a single bond between its carbon atoms, thus the molecule is saturated with hydrogen. Unsaturated fatty acids have one or more double bonds in their molecule and are thus not saturated with hydrogen. If the first double bond in the fatty acid is in the third carbon atom from the methyl end, it is called omega-3 fatty acid; if it is in the sixth carbon from the methyl end, it is called omega-6 fatty acid and when it is in the ninth carbon, it is called omega-9 fatty acid. Palmitic (16 carbons), stearic (18 C), oleic (18 C) and linoleic (18 C) are some of the common fatty acids. A small part of free fatty acids are bound to the protein albumin of the blood and are transferred from the adipose cells to the liver, muscles and other sites. Diglycerides have two fatty acids and triglycerides three fatty 5252525252 Fundamentals of Foods, Nutrition and Diet Therapy acids attached to glycerol. Most of the fatty acids in the body as also in foods occur in the form of triglycerides. The fatty acids which combine with glycerol may vary in the length of the chain (–R) and vary in degrees and type of saturation. Every time a triglyceride crosses a cell membrane, it must be broken or deesterified and after it enters the cell it is reesterified. In digestion, most triglycerides are hydrolysed to form free fatty acids, monoglycerides and glycerol, which are absorbed into the intestinal cells and the majority of these are rebuilt into triglycerides. Phospholipids, which are present in every cell, are formed mainly in the liver from fatty acids, glycerol, phosphoric acid and a nitrogenous base. Phospholipids look like triglycerides, but contain a phosphate attached to glycerol in place of one fatty acid. For example, lecithin, a phospholipid contains choline-phosphate attached to one hydroxyl of the glycerol molecule (formula at the end of the chapter). Two other phospholipids – sphingomyelins and cerebrosides – are found in the brain. It is not necessary to provide phospholipids in the diet, as our body makes these when and where it needs. Phospholipids are important as components of active tissues (brain, nervous tissue and liver). They are powerful emulsifying agents and are essential for the digestion and absorption of fats. Phospholipids help to carry lipid particles across the cell membrane in the blood stream. Three sterols with functions associated with nutrition are: Ergosterol a plant sterol 7-dehydrocholesterol an animal sterol and cholesterol an animal sterol Ergosterol and 7-dehydrocholesterol are two precursors of vitamin D. It is the best known of the sterols and has attracted attention because of the association of elevated blood cholesterol levels with heart ailments. Triglycerides, phospholipids and sterols share a common background — most parts of these molecules are synthesised from a derivative of acetic acid, which is the smallest fatty acid. Cholesterol is an essential part of each cell and every type of human cell makes cholesterol. Each day our liver makes about 800 mg of cholesterol, which circulates through the blood stream and is used wherever it is needed. The hormones made from cholesterol include corticosteroids, estrogens, testosterone and calcitriol (the active vit. The cholesterol content of heart, liver, kidney and egg (embryonic stage of life) is quite high. In infancy and toddlers stage, new tissues are formed, especially brain which need cholesterol. Hence fat should not be restricted in the diet of children up to five years of age. The blood is mainly water and fat needs a water soluble cover of protein to permit it to be carried by blood. The lipoproteins contain triglycerides, cholesterol and other substances such as fat soluble vitamins. Like cholesterol, there is much interest now in these lipoproteins because their concentration in the blood plasma needs to be maintained within certain limits for good health. Their levels in blood plasma are routinely tested to detect lipid disorders, which are related to heart ailments. Fat forms the fatty centre of cell walls, helping to carry nutrient materials across cell membranes. The vital organs in the body are supported and protected by a web-like padding of this tissue. Nerve fibres are protected by the fat covering and it aids relay of nerve impulses. Since fat is a poor conductor of heat, a layer of fat beneath the skin helps to conserve body heat and regulate body temperature. The slower rate of digestion of fat as compared to carbohydrates results in a feeling of satisfaction. They are essential for growth in the young and maintenance of normal healthy skin. Their other functions are as components of membranes to ensure their permeability to water and other small molecules. They are precursors of eicosanoids, a group of important metabolites which regulate vascular function, one of these are prostaglandins. These acids also protect against rheumatoid arthritis and cardiovascular diseases. Common plant oils with the exception of coconut are good sources of linoleic acid. Green leafy vegetables, cabbage and lettuce are good sources of omega-3-fatty acids. Fatty fish, such as tuna, sardines and salmon are good sources of omega-3-fatty acids and a weekly consumption of any of these fish can help to meet the need. Prostaglandins also reduce inflammation and thus reduce pain in certain ailments. These symptoms of deficiency appear in low-birth weight infants fed fat-free formulas and in adults fed for long periods on intravenous solutions, which contain no lipid. Digestion and Absorption the digestion of fats starts in the stomach, where a coarse emulsion forms due to churning action. The entry of fat in the duodenum, the first part of the small intestine stimulates secretion of the bile from the gall bladder. The fat is broken into small particles, thus increasing the surface area and the surface tension is lowered improving the enzyme action and penetration. Thus one fatty acid plus a diglyceride, then another fatty acid plus a monoglyceride and glycerol are produced. The cholesterol esterase from pancreatic juice acts on the free cholesterol to form a combination of cholesterol and fatty acids for absorption first into the lymph vessels and finally into the blood stream. Lecithinase, secreted by the small intestine, acts on lecithin to break into its components for absorption. The products of digestion are absorbed through the walls of the small intestine and circulated through the lymph. Some of these are used to synthesise important lipid compounds needed for body function. In addition invisible fat intake may vary from 16 to 30 g and in some population groups 50g/day. The nature of edible oil used in the diet varies from one part of the country to another; it is groundnut oil in west and south India, coconut oil in Kerala, rape/mustard oil from punjab to West Bengal along the Gangetic plain and safflower in north Karnataka and parts of southern Maharashtra. Hence the minimum level and the safe upper limit of fat intake have to be considered. Recommended Dietary Allowances the fat requirement is based on two factors, namely to meet energy and the essential fatty acids needs. A minimum of 5 per cent of total energy needs to be provided as visible fat in the diet. A higher, level of intake of 20 g/day is desirable to provide energy density and palatability for normal adults. It is desirable that an upper limit of 20 g/day of fat intake for adults and 25 g/day for young children be followed, in view of the possible complications resulting from excessive intake of fat. However, in order to meet the essential fatty acid needs, the diet should contain at least 10 g of vegetable oil, which is a good source of linoleic acid. Diet and Heart Ailments Fat is essential for our health, but too much of it can lead to ill health. A section of Indians have a high intake of fat, a large part of it is saturated fats (milk sweets, eggs and other flesh foods), and a very sedentary lifestyle. Their energy intake in excess of needs leads to obesity and an unacceptable blood lipid profile. If unchecked, there is deposition of fatty material with formation of plaques in the arteries, which disturbs the movement of oxygen and nutrients. It leads to a variety of heart ailments, such as atherosclerosis, high blood pressure and others. There are a number of factors associated with susceptibility to heart ailments that can be controlled to a great extent. These include elevation of plasma lipid levels, obesity, physical inactivity and heavy smoking. For instance, it moves it to your liver when it needs it, to your muscles when you are exercising or to your waistline when you are not. In one study, healthy, normal weight volunteers were placed on either an ultralean 10 per cent fat diet or a rich 40 per cent fat diet. Each volunteer ate the number of calories required to maintain his/her body weight. They found that the volunteers on high-fat diet were manufacturing little or no fat. Sensing that a fat famine was under way, their bodies had cranked up the machinery that converts carbohydrates into fat, one of the built-in mechanisms that permits humans to survive in lean times. Research findings suggest that meal patterns may influence the blood lipid levels. Thus it is possible for us to prevent disabling heart disease and ensure the health of our heart. It accounts for about a sixth of the live body weight and a third of it is found in the muscles, a fifth in the bones and cartilage, a tenth in the skin and the remainder in other tissues and body fluids. There are thousands of different specific proteins in the body, each having a unique structure and function. For this reason, the word protein implies not one but a large group of complex compounds. They are essential to life because vital parts of the nucleus and protoplasts of every cell are proteins.

Exposure to methyl mercury from birth to adulthood opportunities antibiotic 932264 order ciprofloxacin 500mg free shipping, limits and regulatory status antibiotic alternatives trusted ciprofloxacin 1000 mg. Methylation pharma havioral function with computerized tests in a population of Hispanic cogenetics: catechol O-methyltransferase antibiotics with penicillin purchase ciprofloxacin with a visa, thiopurine methyltransfer adolescents working in agriculture antibiotics how long buy 750mg ciprofloxacin otc. Mechanisms of Toxicity chapter Zoltán Gregus 3 Step 1—Delivery: From the Site Covalent Binding Step 4—Inappropriate Repair of Exposure to the Target Hydrogen Abstraction and Adaptation Electron Transfer Absorption versus Presystemic Mechanisms of Repair Enzymatic Reactions Elimination Molecular Repair Effects of Toxicants on Cellular Repair Absorption Presystemic Elimination Target Molecules Tissue Repair Dysfunction of Target Molecules Distribution To and Away Mechanisms of Adaptation Destruction of Target Molecules from the Target Adaptation by Decreasing Delivery Neoantigen Formation Mechanisms Facilitating Distribution to the Target Toxicity Not Initiated by Reaction Adaptation by Decreasing the Target to a Target Mechanisms Opposing Distribution with Target Molecules Density or Responsiveness to a Target Adaptation by Increasing Repair Step 3—Cellular Dysfunction Adaptation by Compensating Excretion versus Reabsorption and Resultant Toxicities Dysfunction Excretion Toxicant-Induced Cellular When Repair and Adaptation Fail Reabsorption Dysregulation When Repair Fails Toxication versus Detoxication Dysregulation of Gene Expression When Adaptation Fails Toxication Dysregulation of Ongoing Toxicity Resulting from Detoxication Cellular Activity Inappropriate Repair and Step 2—Reaction of the Toxic Alteration of Cellular Adaptation Ultimate Toxicant with Maintenance Tissue Necrosis the Target Molecule Impairment of Internal Cellular Fibrosis Maintenance: Mechanisms of Carcinogenesis Attributes of Target Molecules Toxic Cell Death Types of Reactions Impairment of External Cellular Conclusions Noncovalent Binding Maintenance Depending primarily on the degree and route of exposure virus checker cost of ciprofloxacin, chemi repair (eg - virus doctor sa600cb order ciprofloxacin no prescription, alkylating agents) to transcription antimicrobial non stick pads buy on line ciprofloxacin, translation antimicrobial uv light order 750mg ciprofloxacin with visa, and sig cals may adversely affect the function and/or structure of living nal transduction pathways (eg, chemicals acting through transcrip organisms. Continued research on target molecules, and how the organism deals with the insult. Such information provides this chapter reviews the cellular mechanisms that contribute to a rational basis for interpreting descriptive toxicity data, estimat the manifestation of toxicities. Although such mechanisms are also ing the probability that a chemical will cause harmful effects, dealt with elsewhere in this volume, they are discussed in detail in establishing procedures to prevent or antagonize the toxic effects, this chapter in an integrated and comprehensive manner. We provide designing drugs and industrial chemicals that are less hazardous, an overview of the mechanisms of chemical toxicity by relating a and developing pesticides that are more selectively toxic for their series of events that begins with exposure, involves a multitude of target organisms. Elucidation of the mechanisms of chemical tox interactions between the invading toxicant and the organism, and icity has led to a better understanding of fundamental physiologic culminates in a toxic effect. Chemicals that precipi Toxicant tate in renal tubules and block urine formation represent another example for such a course (step 2b). First, the toxicant is delivered to its target or targets (step 1), after which the ultimate toxicant interacts with endog enous target molecules (step 2a), triggering perturbations in cell Delivery function and/or structure (step 3), which initiate repair mecha nisms at the molecular, cellular, and/or tissue levels as well as adaptive mechanisms to diminish delivery, boost repair capac ity, and/or compensate for dysfunction (step 4). When the per turbations induced by the toxicant exceed repair and adaptive capacity or when repair and adaptation becomes malfunctional, toxicity occurs. Tissue necrosis, cancer, and fibrosis are examples 2a 2b of chemically induced toxicities whose development follow this 4-step course. Often the ultimate toxicant is the X original chemical to which the organism is exposed (parent com pound). Inappropriate T the concentration of the ultimate toxicant at the target mol repair and adaptation ecule depends on the relative effectiveness of the processes that Y increase or decrease its concentration at the target site (Fig. The accumulation of the ultimate toxicant at its target is facilitated by its absorption, distribution to the site of action, reabsorption, and Figure 3-1. Potential stages in the development of toxicity after chemical toxication (metabolic activation). A common course is when a toxicant Absorption Absorption is the transfer of a chemical from the site delivered to its target reacts with it, and the resultant cellular of exposure, usually an external or internal body surface (eg, skin, dysfunction manifests itself in toxicity. An example of this route mucosa of the alimentary and respiratory tracts), into the systemic to toxicity is that taken by the puffer fish poison, tetrodotoxin. No repair mechanisms can prevent the onset transporter, and arsenate by phosphate transporters), the vast major of such toxicity. The rate of absorption is related get molecule but rather adversely influences the biological to the concentration of the chemical at the absorbing surface, which (micro) environment, causing molecular, organellar, cellular, or depends on the rate of exposure and the dissolution of the chemical. For example, It is also related to the area of the exposed site, the characteristics 2,4-dinitrophenol, after entering the mitochondrial matrix space of the epithelial layer through which absorption takes place (eg, (step 1), collapses the outwardly directed proton gradient across the thickness of the stratum corneum in the skin), the intensity of the inner membrane by its mere presence there (step 2b), caus the subepithelial microcirculation, and the physicochemical prop ing mitochondrial dysfunction (step 3), which is manifest in toxic erties of the toxicant. In general, lipid-soluble chemicals Distribution To and Away from the Target are absorbed more readily than are water-soluble substances. Toxicants exit the blood during the distribution phase, enter the Presystemic Elimination During transfer from the site of expo extracellular space, and may penetrate into cells. Lipid-soluble being distributed to the rest of the body by the systemic circulation. For example, ethanol is oxidized by alcohol unless specialized membrane carrier systems are available to dehydrogenase in the gastric mucosa (Lim et al. Some mechanisms facilitate, whereas nese is taken up from the portal blood into liver and excreted into others delay, the distribution of toxicants to their targets. Such processes may prevent a considerable quantity of chemi Mechanisms Facilitating Distribution to a Target Dis cals from reaching the systemic blood. Thus, presystemic or first tribution of toxicants to specific target sites may be enhanced by pass elimination reduces the toxic effects of chemicals that reach (1) the porosity of the capillary endothelium, (2) specialized mem their target sites by way of the systemic circulation. In contrast, brane transport, (3) accumulation in cell organelles, and (4) revers the processes involved in presystemic elimination may contribute ible intracellular binding. Particles, such as asbestos and manufactured nanomaterial, elimination D may also enter cells by endocytosis, depending on their size and Distribution e Distribution shape. Lipoprotein receptor–mediated endocytosis contributes to toward target l away from target entry of lipoprotein-bound toxicants into cells equipped with such i transporters. Membrane recycling can internalize cationic amino Reabsorption v Excretion glycosides associated with anionic phospholipids in the brush bor e der membrane of renal tubular cells (Laurent et al. Toxication Detoxication Such uptake mechanisms facilitate the entry of toxicants into spe y cific cells, rendering those cells targets. Thus, carrier-mediated uptake of paraquat by pneumocytes and internalization of amino glycosides by renal proximal tubular cells expose those cells to toxic concentrations of those chemicals. Accumulation in Cell Organelles Amphipathic xenobiotics with Ultimate toxicant a protonable amine group and lipophilic character accumulate in lysosomes as well as mitochondria and cause adverse effects there. Lysosomal accumulation occurs by pH trapping, that is, diffusion Target molecule (Protein, lipid, nucleic acid of the amine (eg, amiodarone, amitriptyline, fluoxetine) in unpro macromolecular complex) tonated form into the acidic interior of the organelle, where the amine is protonated, preventing its efflux. The entrapped amine Target site inhibits lysosomal phospholipases, impairing degradation of lyso somal phospholipids and causing phospholipidosis. The process of toxicant delivery is the first step in the develop tonated in the intermembrane space (to where the mitochondria ment of toxicity. The cation thus formed will then be sucked into the matrix space by the strong negative potential there (−220 mV), fenestrae (50–150 nm in diameter) that permit passage of even pro where it may impair β-oxidation and oxidative phosphorylation. This favors the accumulation of chemicals By such mechanisms, the valued antiarrhytmic drug amiodarone in the liver and kidneys. By mimicking Na, Li may enter + chondrial energy production and causing cardiac failure. The release of melanin-bound toxicants is thought to con tant to microcystin-induced liver injury (Lu et al. As keratins are abundant in extrudes chemicals and contributes to the blood–brain barrier cysteine residues, they can sequester thiol-reactive metal ions and (Schinkel, 1999). Compared with normal mice, mice with disrupted metalloid compounds, whose nail and hair contents are indicative mdr1a gene exhibit 100-fold higher brain levels of and sensitivity of exposure. Release of keratin-bound arsenic in keratinocytes may to ivermectin, a neurotoxic pesticide and human antihelmintic drug adversely affect these cells, leading to dermal lesions common in that is one of many P-glycoprotein substrates (Schinkel, 1999). The ooctye is also equipped with P-glycoprotein that provides pro tection against chemicals that are substrates for this efflux pump Mechanisms Opposing Distribution to a Target Distribution (Elbling et al. Hematopoietic stem cells (and perhaps other of toxicants to specific sites may be hindered by several processes. Even Excretion Excretion is the removal of xenobiotics from the blood if they exit the bloodstream through fenestrae, they have difficulty and their return to the external environment. Dissociation from proteins is required nism, whereas biotransformation is a chemical mechanism for for most xenobiotics to leave the blood and enter cells. This blood–brain barrier prevents the blood into the renal tubules and bile canaliculi, respectively. Renal transport the oocyte in the ovary is surrounded by multiple layers of gran ers have a preferential affinity for smaller (<300 Da), and hepatic ulosa cells, and the spermatogenic cells are supported by Sertoli transporters for larger (>400 Da) amphiphilic molecules. A less cells that are tightly joined in the seminiferous tubules to form the common “excretory” mechanism consists of diffusion and partition blood–testis barrier (see Chap. Transfer of hydrophilic toxi into the excreta on the basis of their lipid content (see below) or cants across the placenta is also restricted. For example, morphine is transferred into milk and amphet barriers are effective against lipophilic substances. This is facilitated by pH trapping of those organic bases in those fluids, Distribution to Storage Sites Some chemicals accumulate in which are acidic relative to plasma (see Chap. The route and speed of excretion depend largely on the For example, highly lipophilic substances such as chlorinated physicochemical properties of the toxicant. The major excretory hydrocarbon insecticides concentrate in adipocytes, whereas lead is organs—kidney and liver—can efficiently remove only highly deposited in bone by substituting for Ca2+ in hydroxyapatite. Such hydrophilic, usually ionized chemicals such as organic acids and storage decreases the availability of these toxicants for their tar bases. The reasons for this are as follows: (1) in the renal glomeruli, get sites and acts as a temporary protective mechanism. However, only compounds dissolved in plasma water can be filtered; (2) trans insecticides may return to the circulation and be distributed to their porters in hepatocytes and renal proximal tubular cells are special target site, the nervous tissue, when there is a rapid lipid loss as ized for secretion of highly hydrophilic organic acids and bases; (3) a result of fasting. This contributes to the lethality of pesticide only hydrophilic chemicals are freely soluble in the aqueous urine exposed birds during migration or during the winter months, when and bile; and (4) lipid-soluble compounds are readily reabsorbed by food is restricted. There are no efficient elimination mechanisms for nonvola tile, highly lipophilic chemicals such as polyhalogenated biphe Association with Intracellular Binding Proteins Binding to nyls and chlorinated hydrocarbon insecticides. If they are resistant nontarget intracellular sites also reduces the concentration of tox to biotransformation, such chemicals are eliminated very slowly icants at the target site, at least temporarily. Three cytoplasmic protein, serves such a function in acute cadmium rather inefficient processes are available for the elimination of such intoxication (Klaassen et al. This occurs in brain capillary with biliary micelles and/or phospholipid vesicles; and (3) intestinal endothelial cells. In their luminal membrane, these cells contain excretion, an incompletely understood transport from blood into the 54 intestinal lumen. Volatile, nonreactive toxicants such as gases and contributes to renal injury after prolonged anesthesia; some cepha volatile liquids diffuse from pulmonary capillaries into the alveoli losporin antibiotics (eg, cephoperazone) may cause hemorrhage and are exhaled. The ionization of weak organic acids, such as salicylic acid with susceptible functional groups. This increased reactivity may and phenobarbital, and bases, such as amphetamine, procainamide, be due to conversion into (1) electrophiles, (2) free radicals, (3) and quinidine, is strongly pH-dependent in the physiologic range. Therefore, their reabsorption is influenced significantly by the pH of the tubular fluid. Acidification of urine favors the excretion of Formation of Electrophiles Electrophiles are molecules contain weak organic bases, whereas alkalinization favors the elimination ing an electron-deficient atom with a partial or full positive charge of weak organic acids. Some organic compounds may be reab that allows it to react by sharing electron pairs with electron-rich sorbed from the renal tubules by transporters. The formation of electrophiles is involved can move peptidomimetic drugs, such as some β-lactam antibiot in the toxication of numerous chemicals (Table 3-2) (see Chap. Carriers for the physiologic oxyanions mediate which withdraws electrons from the atom it is attached to , mak the reabsorption of some toxic metal oxyanions in the kidney. This is the case when aldehydes, ketones, chromate and molybdate are reabsorbed by the sulfate transporter, epoxides, arene oxides, sulfoxides, nitroso compounds, phospho whereas arsenate is reabsorbed by the phosphate transporter. Because compounds secreted into bile are usually organic this occurs when α,β-unsaturated aldehydes and ketones as well acids, their reabsorption is possible only if they are sufficiently lipo as quinones, quinoneimines, and quinone methides are produced philic or are converted to more lipid-soluble forms in the intestinal (Table 3-2). For example, glucuronides of toxicants such as diethylstil is catalyzed by cytochrome P450s (Leung et al. For example, methyl-substituted aromat nated biphenyls are hydrolyzed by the β-glucuronidase of intes ics, such as 7,12-dimethylbenzanthracene, and aromatic amines tinal microorganisms, and the released aglycones are reabsorbed (amides), such as 2-acetylaminofluorene, are hydroxylated to form (Gregus and Klaassen, 1986). Glutathione conjugates of hexachlo benzylic alcohols and N-hydroxy arylamines (amides), respectively robutadiene and trichloroethylene are hydrolyzed by intestinal and (Miller and Surh, 1994). These metabolites are then esterified, typi pancreatic peptidases, yielding the cysteine conjugates, which are cally by sulfotransferases. Heterolytic cleavage of the C–O or N–O reabsorbed and serve as precursors of some nephrotoxic metabolites bonds of these esters results in a hydrosulfate anion and the concom (Anders, 2004). The antiestrogen tamoxifen undergoes Toxication versus Detoxication similar activation by hydroxylation and sulfation to form a carbo Toxication A number of xenobiotics (eg, strong acids and bases, cationic metabolite (Kim et al. For example, oxalic acid formed from ethylene gly carbonium cation, depending on the site of C-hydroxylation that col may cause acidosis and hypocalcaemia as well as obstruction initiates its decomposition. Formally, spontaneous heterolytic of renal tubules by precipitation as calcium oxalate. Occasionally, cleavage of the C–Cl bond results in formation of reactive episulfo chemicals acquire structural features and reactivity by biotrans nium ion from the vesicant chemical warfare agent sulfur mustard formation that allows for a more efficient interaction with specific (2,2′ bis-chloroethylsulfide). For example, the organophosphate insec the ultimate toxicant produced from the fumigant 1,2-dibromoethane ticide parathion is biotransformed to paraoxon, an active cholin following its conjugation with glutathione to form S-(2-bromoethyl) estrase inhibitor; the rodenticide fluoroacetate is converted in the glutathione conjugate, a so-called half-sulfur mustard (Anders, citric acid cycle to fluorocitrate, a false substrate that inhibits acon 2004). Bone marrow and liver injury 4-Hydroxynon-2-enal Fatty acids Lipid peroxidation Cellular injury (? Growth factor receptor stimulation in these non phagocytotic cells is coupled to Nox activation. The significance of O2 stems to a large extent from the fact that O•¯ is a starting compound in two toxi 2 Figure 3-3. Quinones are reduction of arsenate into the more toxic thiol-reactive arsenite not only reactive electrophiles (Table 3-2) but also electron (Gregus et al. Polycyclic aromatic hydro molecular fragment that contains one or more unpaired electrons in carbons with sufficiently low ionization potential, such as its outer orbital. Radicals are formed by (1) accepting an electron, benzo[a]pyrene and 7,12-dimethylbenzanthracene, can be (2) losing an electron, or (3) homolytic fission of a covalent bond. Xenobiotics such as paraquat, doxorubicin, and nitrofurantoin toxicants for these carcinogens (Cavalieri and Rogan, 1992). These radicals typically transfer the extra electron the oxidation of aminophenols to semiquinone radicals and to molecular oxygen, forming a superoxide anion radical (O•¯) quinoneimines. Hydroxyl radical formation is the ultimate •¯ toxication for xenobiotics that form O2 (see Fig. Free radicals are also formed by homolytic bond fission, which reduction in the intestine or from esters of nitrous or nitric acids 57 can be induced by electron transfer to the molecule (reductive in reaction with glutathione. Reductants such as ascorbic acid and reductases such port chain (reductive dehalogenation) (Recknagel et al. This is catalyzed by transition metal ions, typically by conversion to electrophiles. Complexation with some endogenous cases, detoxication may compete with toxication for a chemical. Initially, a functional group is a direct or indirect by-product of several enzymatic reactions, such as hydroxyl or carboxyl is introduced into the molecule, most including monoamine oxidase, acyl-coenzyme A oxidase, xanthine often by cytochrome P450 enzymes. It is produced in large quantities by sponta is added to the functional group by a transferase. An alternative mechanism for the elimination of Formation of Nucleophiles the formation of nucleophiles thiols, amines, and hydrazines is oxidation by flavin-containing is a relatively uncommon mechanism for activating toxicants. Some alcohols, Examples include the formation of cyanide from amygdalin, which such as ethanol, are detoxicated by oxidation to carboxylic acids is catalyzed by bacterial β-glucosidase in the intestine; from acry by alcohol and aldehyde dehydrogenases. A specific detoxication lonitrile after epoxidation and subsequent glutathione conjugation; mechanism is the biotransformation of cyanide to thiocyanate by and from sodium nitroprusside by thiol-induced decomposition. Carbon monoxide is a toxic metabolite of dihalomethanes that Detoxication of Electrophiles A general mechanism for the undergo oxidative dehalogenation. Hydrogen selenide, a strong detoxication of electrophilic toxicants is conjugation with the thiol nucleophile and reductant, is formed from selenite by reaction with nucleophile glutathione (Ketterer, 1988). Whereas some relatively stable loss of the peroxidase function of Prx; however, in this form Prx functions as a molecular chaperone (see later). When Detoxication Fails Detoxication may be insufficient for 59 several reasons: Attributes of target: Reactivity 1. Toxicants may overwhelm detoxication processes, leading to . Accessibility saturation of the detoxication enzymes, consumption of the. Critical function cosubstrates, or depletion of cellular antioxidants such as glu tathione, ascorbic acid, and α-tocopherol. For example. Dysfunction 2-naphthylamine, a bladder carcinogen, is N-hydroxylated Ultimate Target 3. Destruction toxicant molecule. Neoantigen and glucuronidated in liver, with the glucuronide excreted into formation urine. While in the bladder, the glucuronide is hydrolyzed, and the released arylhydroxylamine is converted by protonation and dehydration to the reactive electrophilic arylnitrenium ion (Bock and Lilienblum, 1994). Isocyanates and isothiocyanates form labile glutathione conjugates from which they can be 2 released. Thus, methylisocyanate readily forms a glutathione conjugate in the lung after inhalation. From there, the conju Reaction types: gate is distributed to other tissues, where the reactive elec-. Noncovalent binding trophilic parent compound may be regenerated (Baillie and. Covalent binding Kassahun, 1994). Such conjugates are considered transport. Hydrogen abstraction forms of toxicants. Sometimes detoxication generates potentially harmful by products, such as the glutathione thiyl radical and glutathione Figure 3-7. Reaction of the ultimate toxicant with the target molecule: the disulfide, which are produced during the detoxication of free second step in the development of toxicity. Whereas glutathi frequently involved, whereas cofactors such as coenzyme A and one conjugation detoxifies this epoxide if it takes place at the pyridoxal rarely are involved. Technical advances in the field of proteonomics cant with a target molecule (step 2a in Fig. Subsequently, a make it increasingly possible to identify potential protein targets series of secondary biochemical events occur, leading to dysfunc of reactive chemicals as chemical–protein adducts. A compen tion or injury that is manifest at various levels of biological orga dium of proteins adducted by reactive toxicant metabolites has nization, such as at the target molecule itself, cell organelles, cells, been established at the University of Kansas tpdb. The first target for reactive metabolites tion of the ultimate toxicant with the target molecule triggers the is often the enzyme that catalyzes their production or the adja toxic effect, consideration is given to (1) the attributes of target cent intracellular structures. For example, thyroperoxidase, the molecules, (2) the types of reactions between ultimate toxicants enzyme involved in thyroid hormone synthesis, converts some and target molecules, and (3) the effects of toxicants on the target nucleophilic xenobiotics (such as methimazole, amitrole, and molecules (Fig. Finally, consideration is given to toxicities resorcinol) into reactive free radicals that inactivate thyroper that are initiated not by reaction of the ultimate toxicant with target oxidase (Engler et al. This is the basis for the antithyroid molecules, but rather by alteration of the biological (micro)envi as well as the thyroid tumor–inducing effect of these chemicals. Several mitochondrial enzymes Attributes of Target Molecules are convenient targets for nephrotoxic cysteine conjugates such as Practically all endogenous compounds are potential targets for tox dichlorovinyl cysteine, because these conjugates are converted to icants. The identification and characteristics of the target molecules electrophiles by mitochondrial enzymes with cysteine conjugate 60 β-lyase activity (eg, aspartate aminotransferase and branched Types of Reactions chain amino acid aminotransferase) that can readily channel their the ultimate toxicant may bind to the target molecules noncova reactive products to neighboring enzymes such as α-ketoglutarate lently or covalently and may alter it by hydrogen abstraction, elec dehydrogenase (Anders, 2004). Thus, while carbon monoxide causes toxicity by bind these chemicals are toxic because the steric arrangement of ing to ferrohemoglobin, it also associates with the iron in cyto their atoms allows them to combine with complementary sites on chrome P450 with little or no consequence. Covalent binding of the endogenous molecule more or less as a key fits into a lock.

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Hsl symbol for a residue of the a-amino lactone L-homoserine lac Hudson’s convention a convention antibiotic resistance project discount ciprofloxacin 1000mg fast delivery, no longer used antibiotics meningitis buy ciprofloxacin on line, for designat tone ucarcide 42 antimicrobial order 250 mg ciprofloxacin fast delivery. Other family mem series antibiotic resistant klebsiella uti discount ciprofloxacin generic, the anomer with the lowest positive rotation (or the highest bers are Grp94/gp96 in the endoplasmic reticulum and HtpG in the negative rotation) being designated the a form antibiotics for sinus staph infection purchase ciprofloxacin 250 mg without a prescription. Unlike Hsp70 antibiotic resistance research grants buy ciprofloxacin australia, which promiscuously recog scriptors now refer to the absolute structural relationships antimicrobial agents 1 discount 1000 mg ciprofloxacin amex. See nizes a large number of proteins bacteria classification purchase generic ciprofloxacin, Hsp90 is characterized by the spe anomer, Haworth representation. It consists of a Hsp90 substrates (usually referred to as ‘client’ proteins) are in steel cylinder in which a paste of the microorganisms in question, volved in regulatory processes, the classical examples being sig mixed with abrasives, is subjected to sudden blows by a steel piston nalling kinases and steroid hormone receptors. Maintenance of the driven by a fly-press; the piston forces the crushed material out of biochemical activity of the clients is entirely dependent on con the cylinder into a reservoir. F (371 humanized antibody a modified antibody; since human mono 1 kDa) has the subunit composition: 3a,3b,c,d,e. The e and c sub clonal antibodies cannot be generated in the same way as in mice, units form a shaft inserted at one end into F0 and at the other into and the body reacts to a mouse antibody the 6 complementary de F1. The a and b (catalytic) subunits are arranged round it alter termining regions of a high affinity rodent monoclonal antibody nately; the three b subunits have different conformations during the are grafted on to a completely human IgG framework without loss synthesis cycle. There are several proteins in the F0 component, the main sub humectant 1 producing moisture. The C chain is the protein humic acid any of the mixture of complex macromolecules having that accumulates in ceroid lipofuscinosis (Batten’s disease). Two B subunits are anchored, with an A subunit, into the humidity is maintained at a constant, often high level. They have an important role in the formation of proteoglycan ag humoral immunity any specific immunity mediated by antibodies gregates. These en humus the dark-brown or black complex mixture of colloidal or zymes have in common the ability to depolymerize hyaluronidate ganic material that results from the decomposition of plant and an by cleavage of glycosidic bonds;. The gene, which encodes a 3145-residue product, solved in a scintillation cocktail for counting. It is also used as a huntingtin, of unknown function, contains a polymorphic trinu topical anti-infective agent. In no case has any individual with more than 41 repeats been found to be free of the disease. Hutchinson–Gilford syndrome a rare form of premature ageing hybrid 1 something derived from heterogeneous sources or com characteristic of children and associated with truncation of lamin A. It is considered that protein cule in which the combining sites are of different specificities. The method has been used to map Hxc symbol for the cyclohexyl group (alternative to cHx). Such hydrides are salt-like ionic specific immune potential of the normal parental cell. The term is compounds, are solids at ambient temperatures, and on fusion can derived from a contraction of ‘hybrid’ and ‘myeloma’. Si3H8; in myeloma cells, and lymphocytes that have not fused do not survive the latter type certain of the hydrogen atoms may be present as in culture. Such hybrid anion that may be considered as formed by coordination of a hy cells are both permanently adapted to growth in culture and capa dride ion to an uncharged hydride. A B LiAlH4; such compounds are widely used in organic chemistry as reducing agents or for introduction of tritium, 3H. See also hybrid-arrested transla without such an ion ever existing as a free entity. When an isocyanate reacts with the N-terminal amino conjunction with ninhydrin in the chromogenic determination or group of a peptide, the corresponding hydantoin is formed, with si visualization of amino or imino groups. It is available as a hydrate and as vari hydrodynamic shear the microscopic shear force caused by the ous salts. This acts to break any molecule sufficiently long to at 100°C with hydrazine in anhydrous conditions to form the corre bridge the layers. This reaction is useful in the determina hydrodynamic volume (of a molecule in solution) the sum of the tion of C-terminal amino-acid residues in peptides and proteins as time-average of the molecular volume and the volume of the sol all the other amino-acid residues will be converted to their hy vent molecules associated with it. The most useful catalyst is platinum hydrogen symbol: H; the lightest of the elements and the most abun black on a platinum substrate. It exists as an odourless, colourless, flammable equilibrium between dihydrogen molecules (or hydrogen atoms) diatomic gas, dihydrogen, H2, and forms compounds with most of and the hydrogen ions. If the partial pressure (in atm) of dihy There are two naturally occurring isotopes, hydrogen-1 (protium) drogen gas at the electrode is p, the half-cell potential, E, of re H2 H and hydrogen-2 (deuterium), and one artificial isotope, hydrogen-3 action (1) is given by: (tritium), which is radioactive. Hydrogen is produced by hydrogenases during where R is the gas constant, F the faraday constant, T the thermo the photosynthetic cleavage of water, and by fermentation dynamic temperature, and a + the hydrogen-ion activity. Hydrogen is also produced standard potential of the hydrogen electrode, is, by convention, by nitrogenase as a by-product of the nitrogen-reducing reaction, zero at all temperatures, hence at pH2 = 1, the usual standard state, but this enzyme not defined as a hydrogenase. In order to react with other ples of the same protein and for providing insight into the dynamics electron carriers the hydrogenases employ various cosubstrates. This enzyme is struc servation of the kinetics of the noncatalysed exchange of hydrogen turally related to mitochondrial Complex I. The defining characteristic is an active site hydrogen ion or (formerly) hydrion the cation, H+, derived from containing iron that has carbonyl and usually cyanide ligands. In aqueous solution it is mostly in the hydrated main nonhomologous classes are recognized: (1) hydrogenases con form, oxonium (H O+). In nonaqueous solution it is likely, by anal 3 taining an H cluster comprising a dimer of iron atoms linked to a ogy, that it is attached particularly to one solvent molecule. In addition there is a third type, containing iron and no hydrogen-ion concentration see pH. It pro bonding is due to interaction between dipoles, the force of attraction duces a continuous emission spectrum over the range 180–350 nm. The spatial relation of the donor and acceptor atoms is such that hydrogenosome an organelle with a double membrane occurring the hydrogen atom lies very close to the straight line between them. They are hydrogen carrier a name sometimes used for any electron carrier chromatic granules of high density containing enzymes, including that undergoes oxidation–reduction reactions by the loss or gain of hydrogenase, that catalyse the conversion of pyruvate to acetate, hydrogen atoms. These organelles may substitute for mitochondria hydrogen dehydrogenase the recommended name for the enzyme, (which are absent from such organisms). It may form part of a system involving hydroge eliminated by catalase, glutathione peroxidase, and thioredoxin nase(def. C–O, C–N, C–C, phosphoric anhydride bonds, drogen gas over a metal wire or a piece of foil whose surface is able etc. Often the name of a hydrolase is formed from the name of the to catalyse the reaction: substrate and the suffix ‘-ase’. It usually consists of a glass (or plastic) bulb, hydrophobic chromatography or hydrophobic affinity chro weighted at the bottom so that it floats upright, and fitted with a matography or hydrophobic interaction chromatography a technique stem carrying a scale. The point on the scale that is level with the for the separation and purification of proteins and other substances surface of the liquid indicates the (relative) density of the liquid. These hydrophobic centres on the gel interact also hydrogen ion, proton (defs 1, 2). For example, the are calculated in a sliding window and plotted for each residue in binding site for the aromatic side chains of the specific substrates in the sequence. Resulting graphs show characteristic peaks and chymotrypsin is a hydrophobic pocket, consisting of a groove in the troughs, corresponding to the most hydrophobic and hydrophilic enzyme, 100–120 nm deep, and 35–40 nm by 55–65 nm in cross sec regions of the sequence respectively. The most notable are 5(S) fungi that are involved in cell adhesion and morphogenesis. Their member of a class of aromatic p-diols derivable from p-quinones species distribution follows that of the lipoxygenases. It is used in orthopedic and dental prostheses and in the prevention of osteoporosis. It may be used to cleave specifically Asp-|-Gly bonds in pep characterized by hypoglycemia, metabolic acidosis, hyperammone tides. It is caused by inactivating hydroxylase the common name for many monooxygenase and a few mutations in the gene (at 1p35. See also hydroxymethylglutaryl-CoA reductase, hydroxymethyl hydroxylysine the trivial name for d-hydroxylysine; d-hydroxy-a, e glutaryl-CoA lyase. In collagen, 15–20% of the lysine residues are enzymically CoA and acetoacetate from (S)-3-hydroxy-3-methylglutaryl-CoA. In mammals it is a homo chains are still attached to ribosomes; some of the hydroxyl groups dimer (each subunit in humans contains 298 amino acids) mostly of of the hydroxylysine side chains are subsequently glycosylated. In mammals it is an integral membrane glycopro tein of endoplasmic reticulum and peroxisomes. It thereby activates the latter en boxylic acid, are noncoded amino acids found in peptide linkage in zyme. In collagen, nearly 50% of the proline residues are hydrox hydroxymethylglutaryl-CoA synthase abbr. In col patic enzyme that catalyses the reaction: lagen formation, enzymic hydroxylation of proline residues occurs acetoacetyl-CoA + acetyl-CoA + H O → hydroxymethylglutaryl while the growing peptide chains are still attached to ribosomes. Residues of both the cis-(2S,3R) and the trans-(2S,3S)-isomers of 3-hydroxy-L-proline, one of each per molecule, occur in the peptide 5-hydroxynorleucine an older name (no longer recommended) for antibiotic telomycin. One residue per molecule of cis-4-hydroxy-L 2-amino-5-hydroxyhexanoic acid; a non-protein (non-coded) proline, the (2S,4S)-isomer, occurs in every member of the amatoxin amino acid found in plants. It is of no clinical consequence and is hormones from cholesterol in the adrenal cortex. In humans, two genes at 1p13 result Hylys former symbol for a residue of (5-)hydroxy-L-lysine (5Hyl or in two isozymes: type 1 is expressed in nonsteroidogenic tissues. Mutations in the gene for nium (thorn apple) and related to atropine in its structure and ef the type 2 isozyme are a rare cause of a salt-losing congenital fects; it is a tertiary ammonium compound noted for its actions as a adrenal hyperplasia in which there is deficiency of aldosterone, cor muscarinic receptor antagonist. It has found use as a sedative and tisol, and adrenal androgens (the three final products of the above preanesthetic and for prevention of motion sickness. It differs from the 3b-hydroxysteroid dehydrogenase, for which the substrates are C21 and C19 steroids. A very rare deficiency produces hyoscyamine 3a-tropanyl S-(–)-tropate; an anticholinergic mater a syndrome of jaundice, hepatosplenomegaly, pale stools, and dark ial obtained from Atropa belladonna and other plants. If untreated the condi partial racemization on isolation; this process is completed by alkali tion progresses to hepatic cirrhosis. It kills bacterial, fungal, and higher eukaryotic cells by In primary aldosteronism, there is overproduction of aldosterone inhibiting protein synthesis. In secondary aldosteronism the overproduc allows selection of recombinants when these are plated out on tion is caused by excessive levels of stimulatory hormones, espe medium containing this antibiotic. See also ornithine–urea Hyl or (formerly) Hylys symbol for a residue of any of the hydroxy cycle. It occurs in used to assign particular nuclear resonances and to determine mol liver disease or biliary obstruction, and is characteristic of neonatal ecular conformations. Activity of the en plot obtained for enzymes exhibiting Michaelis–Menten kinetics. It may be due to X-linked and autosomal re higher than normal concentrations of calcium in the blood. It arises from a multiplicity concentrations of specific antibody are present in the serum, of causes including malignancy, primary hyperparathyroidism, hy brought about by hyperimmunization. It typically in hypercapnia or hypercarbia the presence of greater than normal volves the repeated administration of immunogen, often in amounts of carbon dioxide in a vertebrate or in its blood. If untreated it often leads to diabetes mellitus type hypercholesterolemia or (esp. Hyperlipidemias have been classified light, usually measured at 260 nm, shown by a solution of any nat into various types according to which lipoprotein class is found to ural or synthetic polynucleotide with a hydrogen-bonded structure be elevated in the blood. Hyper hyperchromism the increased absorption of electromagnetic radia lipidemia may be secondary to other conditions; several drugs cause tion exhibited by an ordered structure above that predicted on the or exacerbate hyperlipidemia, including thiazides, beta blockers basis of its constitution. Es hyperfine splitting the splitting of a spectral line into multiplets of trogens may lower hypercholesterolemia, but may cause or exacer closely spaced lines. In electron spin resonance spectra hyperfine bate hypertriglyceridemia; hypothyroidism is commonly associated splitting is due to the interaction of unpaired electrons with neigh with hypercholesterolemia; high alcohol intake causes hypertrigly bouring nuclei and can be used to determine the structure of a free ceridemia, but modest alcohol intake may have a beneficial effect radical or to identify the ligands of a paramagnetic ion and to mea on cholesterol status, as it tends to increase high-density lipoprotein sure the degree of covalent binding that exists between them. The associated nervousness, irritability, fatigue, heat intoler associated with conditions in which body water is depleted. It may be primary, as a result of a tumour of the parathyroid vated amounts of uric acid in the blood. This may be due to in gland, or secondary, as a result of a disturbance in calcium metabo creased purine synthesis arising from a metabolic disorder, inher lism. Hyper renal insufficiency, but may also accompany hypoparathyroidism, uricemia is associated with gout. The part thus af hypo+ or (before a vowel) hyp+ prefix denoting under, beneath, fected retains its normal form. Such responses may result from agents in generated by the enzyme myeloperoxidase in azurophilic granules of cluding pollen or drugs, or from genuine pathogens. Also of impor neutrophils and lysosomes of monocytes, in response to the entry of tance are the different kinds of tissue damage seen in autoimmune bacteria. In general terms the reactions may be classified into four hypocholesterolemia or (esp. In the latter it occurs also as the N hypotension the state or condition of having a lower than normal L-glutamyl derivative, hypoglycin B. It is degraded in animals to methylenecyclopropyl hypothalamic (regulatory) factor or hypothalamic hormone or acetate, either free or conjugated to glycine or coenzyme A. In hypoglycin poisoning butyrate and glu neural and/or chemical stimuli, and that regulates the secretion tarate accumulate in the blood and lead to metabolic acidosis and (and perhaps also the synthesis) of a specific polypeptide hormone excessive urinary excretion of these compounds. Sev hypothetical protein a translation product that cannot be related eral types of this condition are recognized. Abetalipoproteine that of some given solution, particularly the fluid in or surrounding mia is a rare autosomal recessive disorder. It may be due to hemorrhage or to redistribu present with hypobetalipoproteinemia. Hypoalphalipoproteinemia tion of fluid from the plasma to the extravascular tissues and is in some cases familial, and may result from defective apo A-I. Compare action between 5-phospho-a-D-ribose 1-diphosphate and either hy epiphase. Partial deficiency is associated with Lesch–Nyhan syn in vitamin D deficiency, primary hyperparathyroidism, incorrect par drome and gout. They are inducible in c or m may be added to indicate whether it is expressed based on 12–24 hours by cytokines such as gamma interferon, interleukin-1b, concentration or molality respectively. The I-bands of striated muscle con alous entropies of solution of noble gases and other nonpolar sub tain the thin filaments and correspond to the light bands. The name stances in water, suggesting that water tends to organize itself into derives from the fact that they are isotropic in polarized light. See quasi-solid supramolecular structures around the molecules of such also sarcomere. In the case of alkyl compounds, this tendency increases IjB kinase a heterotrimeric complex (≈700 kDa) that acts on IjB to markedly with the length of the alkyl chain. They inhibit named because their histological features are intermediate between the cyclooxygenase activity of prostaglandin-endoperoxide synthase, those of S cells and L cells. See also I-cell reversibly over short time intervals, followed by time-dependent disease. The racemic mixture is present in many mal recessive disease in which most of the lysosomes in the connec over-the-counter drugs, but the (S)-enantiomer is the active form. These enzymes, which are synthesized in the endoplas mic reticulum, are secreted into the extracellular medium rather H3C H than being directed to the lysosomes. The failure of the phosphorylation in the cis H3C Golgi network means that the enzymes are not segregated by the (S)-ibuprofen mannose 6-phosphate receptors into the appropriate transport vesicles in the trans Golgi network. The patients have an abnormally high level of lysosomal enzymes in their sera and body fluids. It is taken as the tem where li is the chemical potential of the ith component and xi is its perature (273. An autosomal recessive form is caused by deficiency of self-produced, arising within. If divided into more than four smaller triangles, idiopathic autonomic neuropathy a severe subacute disorder the original faces will not be flat, in which case the 12 pentameric caused by autoantibodies to ganglionic acetylcholine receptors. A regular idiotype 1 an antigenic specificity, particularly of antibodies di icosahedron has faces that are congruent plane equilateral trian gles; there is twofold rotational symmetry about an axis through rected against a single antigen. Ig-Hepta a rat glycoprotein (1389 amino acids) that is a G-protein coupled membrane receptor with a long N-terminal extracellular region containing two C2-type Ig-homology units. IdUrd symbol for 5-iodo-2′-deoxyuridine (see idoxuridine) (preferred ignose the name first proposed for ascorbic acid by A. Various interleukins are distinguished by suf hydroxyl group from iduronic acid or iduronate. Eukaryotic initia image analysis analysis of a digital image, characterizing its con tion factors are generally denoted by the prefix ‘e’. Suffixed Greek letters are added to differen magnetic resonance scanning, radionuclide scanning, or thermogra tiate the main classes. There is reduced hepatic clearance imidazole or (formerly) glyoxaline or iminazole 1,3-diazole; 1,3 of IgA, which deposits in the renal glomeruli. IgA protease; a secreted bacterial serine protease that catalyses the cleavage of immunoglobulin A molecules at certain Pro-|-Xaa N bonds in the hinge region. A signal peptide guides the enzyme pre cursor to the periplasmic space, and the C-terminal helper domain forms a pore in the outer membrane for exit of the protease do N main. In biochemistry, the term is commonly idazolines, imidazolidines, guanidines, and oxazolines, and having applied also to certain cyclic alkylamino (especially a-alkylamino) a putative endogenous ligand, agmatine. H3C S imidazolium 1 the cation formed by addition of a proton (hydron) N to a molecule of imidazole. It occurs within minutes of exposure to antigen and de different) are derived formally or actually from a diacid. An example is succinimide: immobilize or immobilise to render any agent, whether a micro or macrosolute, a particle, or an intact cell, nondispersible in an aque ous medium with retention of its specific ligating, antigenic, cat alytic, or other properties.

All γ-humulene synthase variants were designed based on the systematic remodeling and constructed by site-directed saturation mutagenesis and site-directed mutagenesis antimicrobial cleaner buy ciprofloxacin with a mastercard. The ability to make subtle changes in the expression of enzymes that catalyze the synthesis of desired molecules is important for balancing and optimizing metabolic pathways natural antibiotics for acne infection ciprofloxacin 750mg fast delivery. Although there are very good expression systems for high-level production of recombinant proteins antibiotics for sinus infection and ear infection generic ciprofloxacin 750mg on-line, simultaneous overexpression of several enzymes from strong promoters may not improve existing pathways but instead stress the organisms by increasing the metabolic burden [23 antibiotics used for sinus infections uk discount 750mg ciprofloxacin overnight delivery,38] homeopathic antibiotics for dogs discount 1000mg ciprofloxacin free shipping. In most cases virus game online discount ciprofloxacin 750 mg line, it is sufcient to express the genes encoding a metabolic pathway at relatively low levels antibiotic with food cheap ciprofloxacin online, such that only catalytic amounts of the enzymes in the pathway are pro duced bacteria unicellular purchase ciprofloxacin 1000mg with amex. The ability to fne-tune production of the desired enzymes allows one to balance the metabolic pathway and requires the use of inducible promoters [30,31]. Although regulatable promoters (propi onate-inducible [32], salicylate-inducible [71], and tetracycline-inducible [58] promoters) are available, most widely used, inducible promoters. Recently, several laboratories have created artifcial, constitutive promoters that cover a wide range of gene expression levels [2,22,39,60]. Tese promoters are of great value for steady-state expression of genes because they have a single expression level without the need for an inducer. On the other hand, the use of regulatable promoters may be better for tuning metabolic pathways and expressing toxic proteins that should be tightly repressed until a certain time point or density of the culture is reached. When tuning the expression of multiple genes encoding the enzymes of a metabolic pathway, it is ofen desirable to place the genes under the control of independent, inducible promoters. This allows one to alter the expression level of one or more genes independently of other genes in the same meta bolic pathway or in competing metabolic pathways [29]. However, some pairs of promoters sufer from cross-talk—an inducer of one promoter afects expression from another promoter—making it difcult to simultaneously and independently control the expression of multiple genes. Since the number of inducible promoters available is limited, it is necessary to place several genes under control of a single promoter (Figure 12. Alternatively, low-copy plasmids are excellent for expression of heterologous genes when extreme stability and low metabolic burden imposed on the cells are desired [23]. Due to the metabolic burden associated with high plasmid copy number, multi-copy plasmids may not be appropriate for some metabolic engineering applications, even when the objective is to increase the intracellular concentration of an enzyme in order to improve fux through an existing pathway. To maximize product titers/ yields, it is important to alleviate, to the extent possible, the negative impacts of the heterologous path way on the host. Because cellular metabolism is complex, it is ofen difcult to determine how a heter ologous pathway is deleterious to the host and then use directed pathway engineering to alleviate the negative interactions. In the past, such deleterious efects of the introduced or native, up-regulated path ways were alleviated by random mutagenesis of the host and selection for improved producers. However efective, little information about the reasons for the improvements are gleaned from such eforts and therefore little can be learned for future directed, pathway engineering projects. In pathway optimization, therefore, several of these diferent techniques should be used in parallel to obtain a global understanding of the host and the introduced pathway and to identify and engineer targets to improve production [7] (Figure 12. As a result, point mutations were identifed in fve genes, and introduction of three of these mutations into the wild-type strain increased L-lysine productivity two-fold. Because they compared only a limited fraction of the genome (only those genes directly responsible for production of L-lysine), it is likely that several mutations in other genes were present and contributed to the high product titers. Although it might have been too expensive or impractical at the time to sequence the entire genome to fnd all mutations, continued decreases in the cost and time to sequence whole genomes is making genome-wide sequence comparisons less costly and more routine, enabling one to determine all mutations in an evolved host. Unlike the genome, which is roughly fxed for a given cell, the transcriptome can vary dramatically with external environmental conditions. Tere are some examples of how this technique has been used in the feld of metabolic engineering. The transcript profle of the ethanol-tolerant strain indicated increased glycine metabolism, a loss of function of a regulatory pro tein, and increased metabolism of serine and pyruvate. Tus, it is neces sary to profle biomolecules that are more indicative of the physiology of the cell, namely the proteome, metabolome, and fuxome. Proteome analysis, the large-scale analysis of all, or most, proteins in an organism [46], potentially allows one to understand gene regulation better than transcriptome analysis, but it is one step away from the direct efects of genetic changes. The changes in the protein levels in diferent mutants or under diferent environmental conditions can be deter mined and used to identify target enzymes/proteins for further manipulation [20]. Most generally, the com plex protein mixture is separated using either two-dimensional gel electrophoresis or liquid chromatograph prior to identifcation and quantifcation of individual proteins using mass spectrometry [1,17,59]. Based on the information gleaned from the proteomics analysis, they coexpressed and cycK, encoding cysteine synthase, with the leptin gene and successfully enhanced leptin productivity two-fold and the host cell growth rate [19]. Metabolome analysis covers the quantifcation of intracellular and extracellular metabolite concentrations in the response of living systems to physiological stimuli or genetic modi fcation. Analysis of the metabolome might aid inverse metabolic engineering by giving insight into metabolic function of mutated genes by comparison with a reference strain. Since the metabolism of an organism directly impacts synthesis of macromolecules and thus the physiology of the cells, metabolo mics should yield a more complete picture of the impact of pathway engineering on the cell. Determination of as many fuxes as possible is the goal of fuxome analysis, and it is the result of this analysis that can potentially be the most insightful for improving metabolic pathways. By determining how the cell’s metabolic fuxes change in response to environmental or genetic perturba tion, one can begin to determine the fexibility of the network to genetic changes that might improve product titers [5,25]. Metabolic fux analysis can be performed in several ways: under determined, exactly determined, and over determined [63]. All methods rely on knowing the underlying metabolic network, which can be gotten more easily lately with the advances in genome sequencing and annotation. Under determined analysis of metabolic fuxes typically relies on measuring the inputs (substrate uptake rates) and out puts (biomass composition and growth rate, synthesis rates of extracellular products, etc. Exactly determined methods typically rely on the same types of information but require the determination of one or more fuxes or elimination of unknowns to make the system soluble. In addition to its other benefts, isotopomer analysis allows one to determine the error in specifc metabolic fuxes. The major challenge in fuxome analysis is that fux data rarely reveal a direct engineering target, primarily because fuxes are controlled at multiple levels. Tus, metabolic fux analysis is most ofen used to document changes in metabolic fuxes afer a particular genetic or environmental change has been efected. The challenge going forward will be to integrate the data from the various omics methods into a coherent representation of the cell to allow one to predict what genes should be changed to efect the desired impact on the productivity of the desired metabolite [57]. For cost savings and high production, it is important to improve the biological cell factories by manipulating enzymatic, transport and regulatory functions that are not directly related to the engineered metabolic pathways. Tese cell properties include exten sion of the substrate range, elimination of substrate and product toxicity, and improvement of global 12-10 Gene Expression Tools for Metabolic Pathway Engineering regulatory functions. Sugars (from sugarcane and sugar beets) and starches (from corn and root crops) have been used as a potential substrate for ethanol fermentation by microbial processes. Recently, attention shifed from starch to cellulose and hemicel lulose (from wood and plants), because it is the most abundant source of carbohydrates in biomass for the production of bioenergy and biomaterials [53]. The major fermentable sugars derived from cellulose and hemicellulose hydrolysis are glucose and xylose [75]. In another example, lactose is abundant in milk and a major constituent of whey, a by-product of cheese production. Some attempts to use whey as a substrate for biotech processes have been made by expressing either lactose lactose permease plus β-galactosidase from Klyveromyces [12] or a secreted β-galactosidase from Aspergillus [27] in order to convert lactose to fermentable sugars, galactose and glucose. The general solution for such inhibitory phenomena is to maintain the concentrations of the inhibitors as low as possible by altering and improving process conditions. The product concentration can be kept low inside the cell by trans porting the fnal products out of the cell (by overexpressing native or engineered transporters) or by extracting the product from the medium. In the case of toxic intermediates, balancing production and consumption of the intermediate without signifcantly slowing product formation is essential [49,50]. Using the typical, single-gene modifcation methods such a task can be daunting, if not impossible. To enable multigene modifcations to a host cell, an alternative approach for reprogramming gene transcription by altering global transcriptional regulators was proposed by Stephanopoulos and coworkers [3]. Using this technique, Stephanopoulos and coworkers improved ethanol tolerance and production by S. It is now a rapidly growing area with great poten tial to impact industrial biocatalysis. In the future, it will be a powerful tool to synthesize structurally diverse and complex chemicals and useful compounds from abundant renewable biomass [53]. Tus, metabolic pathway engineering will have a signifcant impact on society in terms of the production of fuels, chemicals, materials and novel drugs. Proceedings of the National Academy of Sciences of the united States of America 102: 12678–12683. Engineering yeast tran scription machinery for improved ethanol tolerance and production. Amplifed expression of fructose 1,6-bisphosphatase in Corynebacterium glutamicum increases in vivo fux through the pentose phosphate pathway and lysine production on diferent carbon sources. Improvement of galactose uptake in Saccharomyces cerevisiae through overexpression of phosphoglucomutase: Example of tran script analysis as a tool in inverse metabolic engineering. Biochimica Et Biophysica Acta-Protein Structure and Molecular Enzymology 1543:434–455. Translational initiation on structured messengers—another role for the Shine-Dalgarno interaction. Evaluation oftwo-dimensional gel electrophoresis-based proteome analysis technology. Proceedings of the National Academy of Sciences of the united States of America 97:9390–9395. Engineering Escherichia coli for increased produc tivity of serine-rich proteins based on proteome profling. Stable isotope-mass spectrometric measurements of molecular fuxes in vivo: Emerging applications in drug development. Low-copy plasmids can perform as well as or better than high-copy plasmids for metabolic engineering of bacteria. Comparative metabolic fux analysis of lysine-producing Corynebacterium glutamicum cultured on glucose, or fructose. Saccharomyces cer evisiae cells secreting an Aspergillus niger beta-galactosidase grow on whey permeate. Proteome changes afer metabolic engineering to enhance aerobic mineralization of cis-1,2-dichlo roethylene. Directed evolution of AraC for improved compatibility of arabinose and lactos-inducible promoters. Biochimica Et Biophysica Acta-Protein Structure and Molecular Enzymology 1545:114–121. A novel methodology employing Corynebacterium glutamicum genome information to generate a new L-lysine-producing mutant. Biosynthesis of yersiniabactin, a complex polyketide-nonribosomal peptide, using Escherichia coli as a heterologous host. Balancing a heterologous mevalonate pathway for improved isoprenoid production in Escherichia coli. Stoichiometric model of Escherichia coli metabolism: Incorporation of growth-dependent biomass composition and mechanistic engergy requirements. Production of the antimalarial drug precursor artemisinic acid in engineered yeast. Microbial pathway engineering for industrial pro cesses: evolution, combinatorial biosynthesis and rational design. Use of the tetracycline promoter for the tightly regulated production of a murine antibody fragment in Escherichia coli. Optimization of the isotope coded afnity tag-labeling procedure for quantitative proteome analysis. Evolutionary engineering of Saccharomyces cerevisiae for anaer obic growth on xylose. Pathway con frmation and fux analysis of central metabolic pathways in Desulfovibrio vulgaris Hildenborough using gas chromatography-mass spectrometry and Fourier transform-ion cyclotron resonance mass spectrometry. Homofermentative lactate production cannot sustain anaerobic growth of engineered Saccharomyces cerevisiae: Possible consequence of energy-dependent lactate export. Stoichimetric interpretation of Escherichia coli glucose catabolism under various oxygenation rates. Proceedings of the National Academy of Sciences of the united States of America 98:3778–3783. Construction of cloning cartridges for development of expression vectors in Gram negative bacteria. Engineering cotton (+)-delta-cadinene synthase to an altered function: Germacrene D-4-ol synthase. Ethanol fermentation of acid-hydrolyzed cellulosic pyrolysate with Saccharomyces cerevisiae. Over the years, signifcant strides have been made in engineering micro organisms to produce fuels, bulk chemicals, and valuable drugs from inexpensive starting materials; to detect and degrade nerve agents as well as less toxic organic pollutants; and to accumulate metals and reduce radionuclides. Besides gene expression tools to control metabolism and mathematical models to assess metabolic fux, there is a general need for functional genomics tools to assess the impact of metabolic pathways on the host. Engineering metabolic chemistry generally begins with the introduction of one or more genes encod ing enzymes that transform readily available, intracellular intermediates into a desired chemical. Unlike production of pharmaceutical proteins in which the genes are highly expressed to maximize produc tion of the target protein, the genes encoding the transformational enzymes do not need to be highly expressed; rather the enzymes need to be produced in catalytic amounts only sufcient to adequately transform the metabolic intermediates into the desired products at a sufcient rate. In addition to decreasing fnal product titers, overexpression of the genes in a metabolic path way many elicit a number of stress responses in the host cell that will decrease cell growth and further decrease product titers. Furthermore, because intermediates of a foreign metabolic pathway can be toxic to a heterologous host [5], which can result in decreased production of the desired fnal compound, it is essential that the relative levels of the enzymes be coordinated in such a way that no intermediate in the pathway accumulates to toxic levels. The ability to assess the impact of metabolic pathways on cellular metabolism is essential to optimize cells for production of the desired product. In analogy to the creation of computer programs, the development of sofware has been made possible only through the development and use of debugging sofware to quickly identify and correct problems with code [2,8]. The development of similar tools for biological debugging would reduce development times for building and optimizing engineered cells. For the development of microbial chemical facto ries, functional genomics can serve in the role of debugging routines [1,9,10], because the introduction of a metabolic pathway ofen elicits the equivalent of a “bug” in the cell’s natural program, which will be indicated by various stress responses. Overexpression of a metabolic pathway might rob the cell of central metabolic intermediates resulting in decreased cell growth, a change in the profles of intracellular and extracellular metabolites, which would be refected in the metabolite profle, and a change in metabolic fuxes, which would be refected in the fux profle. Imbalances in a metabolic pathway will result in an accumulation of potentially toxic metabolites that inhibit growth [5]. Information from one or more of these techniques can be used to then modify expression of genes in the metabolic pathway or in the host to improve titers and/or productivity of the fnal product. Because of the complexity and amount of information that must be collected and correlated, computational bioinformatics methods to manage and analyze the data are essential. An example of the use of functional genomics to assess the toxicity associated with a heterologous metabolic pathway and correct the problems associated with the pathway was recently demonstrated by Kizer and coworkers [4]. They analyzed the toxicity associated with a heterologous mevalonate-based isopentenyl pyrophosphate biosynthetic pathway that had been engineered into Escherichia coli so that the strain would produce large quantities of isoprenoids. This work demonstrates the utility of using transcriptomic and metabolomic methods to optimize synthetic bio logical systems. We anticipate this type of work will become commonplace as the technologies become easier to use and more afordable. Monton and Soga describe the use of metabolomics to assess changes in cellular metabolism. And Alm and Arkin describe the use of bio informatics to compile and analyze the large datasets that arise from these techniques. The integration of these debugging technologies will certainly make metabolic engineering more predictable, easier, and faster. A comparative study of global stress gene regulation in response to overexpression of recombinant proteins in Escherichia coli. Functional genomics for pathway optimiza tion: application to isoprenoid production. Engineering the mevalonate pathway in Escherichia coli for production of terpenoids. Metabolic engineering of Escherichia coli for the production of L-valine based on transcriptome analysis and in silico gene knockout simulation. Global physi ological understanding and metabolic engineering of microorganisms based on omics studies. The organisms are a complex system and their genomes are immense, and thus powerful tech nologies are being developed to meet the demands in analysis of thousands of genes and their products and functions. Compared to traditional methodologies which were typically based on one target in one experiment, recently developed omics technologies, including transcriptomics, proteomics, metabo lomics, and physiomics are allowing us to generate large amounts of these data. Accessibility to these omics data is providing a foundation for in-depth understanding of living organisms. Genome-wide technologies were based on the two-dimensional experimental methods which were initially developed by O’Farrell et al. Tanks to these methodologies, experiments are no longer limited to one by one type, and can be performed for hundreds to tens of thousands of targets and conditions simultane ously. Proteome profling is conducted by two-dimensional gel electrophoresis and mass spectrometry. Phenotype microarrays is used for simultaneous testing of a large number of cellular phenotypes. Nowadays, these tech nologies have successfully been applied to biological research, and are providing new information on global cellular physiology and regulations of the cells (Figure 13. Together with computational analy ses, these high-throughput omics technologies gave birth of systems biology [5]. In recent years, systems biotechnology [6], which allows development of improved strains and bioprocesses by taking systems level analytical approaches, also appeared.