Inhibition of the synthesis

In general, penicillins exert thek biological effect, as do the other -lactams, by inhibiting the synthesis of essential structural components of the bacterial cell wall. These components are absent in mammalian cells so that inhibition of the synthesis of the bacterial cell wall stmcture occurs with Htde or no effect on mammalian cell metaboHsm. Additionally, penicillins tend to be kreversible inhibitors of bacterial cell-wall synthesis and are generally bactericidal at concentrations close to thek bacteriostatic levels. Consequently penicillins have become widely used for the treatment of bacterial infections and are regarded as one of the safest and most efficacious classes of antibiotics. 

Three hormones regulate turnover of calcium in the body (22). 1,25-Dihydroxycholecalciferol is a steroid derivative made by the combined action of the skin, Hver, and kidneys, or furnished by dietary factors with vitamin D activity. The apparent action of this compound is to promote the transcription of genes for proteins that faciUtate transport of calcium and phosphate ions through the plasma membrane. Parathormone (PTH) is a polypeptide hormone secreted by the parathyroid gland, in response to a fall in extracellular Ca(Il). It acts on bones and kidneys in concert with 1,25-dihydroxycholecalciferol to stimulate resorption of bone and reabsorption of calcium from the glomerular filtrate. Calcitonin, the third hormone, is a polypeptide secreted by the thyroid gland in response to a rise in blood Ca(Il) concentration. Its production leads to an increase in bone deposition, increased loss of calcium and phosphate in the urine, and inhibition of the synthesis of 1,25-dihydroxycholecalciferol. 

This is not discussed in detail since mechanisms of resistance have been carefully reviewed (Ghannoum and Rice 1999). It was pointed out that resistance has not been associated with modification of the structure. For the 1,2,4-triazoles that have been widely used, their effect is due to inhibition of the synthesis of ergosterol that is the dominant component of fungal cell membranes. Resistance is generally associated with modification of the target enzymes, for example, the epoxidation of squalene (Terbinafine) or 14a-demethylase (Fluconazole). Resistance of Candida albicans to the azole antifungal agent fluconazole demonstrated, however, the simultaneous occurrence of several types of mechanism for resistance (Perea et al. 2001) ... 

The answer is b. (Hardman, p 1061.) Sulfasalazine consists of sul-fapyridine with 5-aminosalicylic acid linked by an azo- bond. This bond is broken by bacteria that release the salicylic acid, which is believed to be the active agent. Sulfa drugs or salicylic acid used alone is not as effective. The mechanism of action is unknown, but it is believed to be protective action on the mucosa by inhibition of the synthesis of prostaglandins and leukotrienes. 

Toxi-ChromoPad (EBPI, Ontario, Canada) is a simple method for evaluation of the toxicity of solid particles [25,26,32,39]. The test is based on the inhibition of the synthesis of (3-galactosidase in E. coli after exposure to pollutants. The method has been used to measure acute toxicity of sediment and soil and other solid samples. The test bacterial suspension is mixed with homogenized samples and incubated for 2 hours. A drop of the test solution is pipetted onto a fiberglass filter containing an adsorbed substrate. A color reaction indicates the synthesis of enzyme, while a colorless reaction indicates toxicity. It has previously been shown... 

Isoniazid (INH) is a synthetic derivative of isonico-tinic acid. It has bactericidal activity against both intra- and extra-cellular mycobacteria. It also displays anti-bacterial activity in caseous lesions, but only in proliferating cells. Losing genes which code for catalase and peroxidase is the major mechanism through which resistance occurs. Single mutations can rapidly result in such resistance if isoniazid is used alone. Its mechanism of action is presumably based on inhibition of the synthesis of mycolic acids, unique and essential components of the mycobacterial cell wall. 

D) Inhibition of the synthesis of GTP, which is required for viral genomic replication and is a cofactor 4. for cellular enzymes required for viral replication... 

There are several types of -class CAs i.e., a-CA I-VII, reported in the literature, out of which the human carbonic anhydrase II (HCA II), the most extensively studied carbonic anhydrase, has an exceptionally high CO2 hydration rate and a wide tissue distribution 107). The HCA II comprises a single polypeptide chain with a molecular mass of 29.3 kDa and contains one catalytic zinc ion, coordinated to three histidine residues, His 94, His 96, and His 119. A tetrahedral coordination geometry around the metal center is completed with a water molecule, which forms a hydroxide ion with a pK value of 7.0 108). Quigley and co-workers 109,110) reported that the inhibition of the synthesis of HCO3 from CO2 and OH- reduces aqueous humor formation and lowers intra-ocular pressure, which is a major risk factor for primary open-angle glaucoma. 

Carbon tetrachloride causes centrilobular liver necrosis and steatosis after acute exposure, and liver cirrhosis, liver tumors, and kidney damage after chronic administration. The mechanism underlying the acute toxicity to the liver involves metabolic activation by cytochrome P-450 to yield a free radical (trichloromethyl free radical). This reacts with unsaturated fatty acids in the membranes of organelles and leads to toxic products of lipid peroxidation including malondialdehyde and hydroxynonenal. This results in hepatocyte necrosis and inhibition of various metabolic processes including protein synthesis. The latter leads to steatosis as a result of inhibition of the synthesis of lipoproteins required for triglyceride export. 

The inhibition of the synthesis of auxin by D-galactose was also shown to be a contributory factor in the retardation of growth ofA vena coleoptiles.538-539 On the other hand, D-galactose-induced evolution of ethylene is known to retard the growth of mung-bean seedlings.540... 

One such function is inhibition of tyrosine hydroxylase (TH), independently of the inhibition of release. In analogy to release, it results in a feedback inhibition of the synthesis of dopamine (Table 2). Like the release-inhibiting autoreceptors, those inhibiting dopamine synthesis are D2-like and, where identified further, D2 or D3... 

When cucurbit cells are fed O-acetylserine or its metabolic precursors the rate of hydrogen sulfide emission in response to sulfate declines, and the incorporation of labeled sulfur from 35S-sulfate into cysteine increases (18). Inhibition of the synthesis of the O-acetylserine precursor acetyl coenzyme A by 3-fluoropyruvate (22) enhances hydrogen sulfide emission, but inhibits cysteine synthesis (1 ). These observations indicate that the availability of O-acetylserine is the rate limiting factor in cysteine synthesis. Hydrogen sulfide may be emitted to the extent the amount of sulfate reduced exceeds the synthesis of O-acetylserine. Therefore, direct release of sulfide from carrier-bound sulfide appears to be responsible for the emission of hydrogen sulfide in response to sulfate (Figure 1, pathway 1). 

Lead adversely affects a number of systems in the body. The inhibition of the synthesis of hemoglobin by lead has just been noted. This effect, plus a shortening of the life span of erythrocytes, results in anemia, a major manifestation of lead poisoning. 

Drugs with a narrow therapeutic index are candidates for therapeutic drug monitoring, as in the case of the anticoagulant warfarin. The adverse effect of warfarin, namely excessive anticoagulation that can result in fatal hemorrhaging, is an extension of its pharmacological effect (inhibition of the synthesis of... 

Phenol, hydroquinone, catechol, benzoquinone, and 1,2,4-trihydroxybenzene form adducts in bone marrow mitochondria, resulting in the inhibition of the synthesis of mitochondrial proteins that are necessary for mitochondrial function (Kalf et al. 1982). 

I. Inhibition of the Synthesis of Prostaglandins in Inflammatory Exudate and Mucus Membrane in Rats... 

The ability of aspirin to diminish inflammation is apparently due to its inhibition of the synthesis of prostaglandins, a group of C-20 molecules that enhance inflammation. Aspirin alters the oxygenase activity of prostaglandin synthetase by moving the acetyl group to a terminal amine group of the enzyme. 

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