Inhibitor, definition

On the other hand, ATP depletion caused by MPP+, potassium cyanide or antimycin A (the latter two substances are known as definite inhibitors of mitochondrial respiratory chain) could lead to decreased GSH concentrations independent of oxidative stress, because substrates for glycolytic production of ATP counteract the GSH depletion caused by mitochondrial respiratory chain inhibitors (Mithoferet al., 1992). 

Terminology The International Standards Organization has recently defined a corrosion inhibitor as a chemical substance which decreases the corrosion rate when present in the corrosion system at a suitable concentration, without significantly changing the concentration of any other corrosive agent. This last point is significant since it excludes chemicals employed for deaeration or pH control from the definition of a corrosion inhibitor. On the other hand, it should be noted that the inhibitor is .. . present in the corrosion system. . . , and thus arsenic when added to brasses to prevent dezin-cihcation may be classified as an inhibitor. 

The mechanisms of corrosion inhibition will be described separately for acid and neutral solutions, since there are considerable differences in mechanisms between these two media. Definitions and classifications of inhibitors are given in Section 17.2 and by Fischer. ... 

In addition to effects on biochemical reactions, the inhibitors may influence the permeability of the various cellular membranes and through physical and chemical effects may alter the structure of other subcellular structures such as proteins, nucleic acid, and spindle fibers. Unfortunately, few definite examples can be listed. The action of colchicine and podophyllin in interfering with cell division is well known. The effect of various lactones (coumarin, parasorbic acid, and protoanemonin) on mitotic activity was discussed above. Disturbances to cytoplasmic and vacuolar structure, and the morphology of mitochondria imposed by protoanemonin, were also mentioned. Interference with protein configuration and loss of biological activity was attributed to incorporation of azetidine-2-carboxylic acid into mung bean protein in place of proline. 

There are few definitive data to substantiate the efficacy of LTRA therapy in refractory asthma, except for patients with aspirin-sensitive asthma. This is a fairly uncommon form of asthma that occurs generally in adults who often have no prior (i.e., childhood) history of asthma or atopy, may have nasal polyposis, and who often are dependent upon oral corticosteroids for control of their asthma. This syndrome is not specific to aspirin but is provoked by any inhibitors of the cycloxygenase-1 (COX-1) pathway. These patients have been shown to have a genetic defect that causes... 

A fully automated instrumental procedure has been developed for analyzing residual corrosion inhibitors in production waters in the field. The method uses ultraviolet (UV) and fluorescence spectrophotometric techniques to characterize different types of corrosion inhibitors. Laboratory evaluations showed that fluorescence is more suitable for field application because errors from high salinity, contamination, and matrix effect are minimized in fluorescence analysis. Comparison of the automated fluorescence technique with the classic extraction-dye transfer technique showed definite advantages of the former with respect to ease, speed, accuracy, and precision [1658],... 

Oxime carbamates are generally applied either directly to the tilled soil or sprayed on crops. One of the advantages of oxime carbamates is their short persistence on plants. They are readily degraded into their metabolites shortly after application. However, some of these metabolites have insecticidal properties even more potent than those of the parent compound. For example, the oxidative product of aldicarb is aldicarb sulfoxide, which is observed to be 10-20 times more active as a cholinesterase inhibitor than aldicarb. Other oxime carbamates (e.g., methomyl) have degradates which show no insecticidal activity, have low to negligible ecotoxicity and mammalian toxicity relative to the parent, and are normally nondetectable in crops. Therefore, the residue definition may include the parent oxime carbamate (e.g., methomyl) or parent and metabolites (e.g., aldicarb and its sulfoxide and sulfone metabolites). The tolerance or maximum residue limit (MRL) of pesticides on any food commodity is based on the highest residue concentration detected on mature crops at harvest or the LOQ of the method submitted for enforcement purposes if no detectable residues are found. For example, the tolerances of methomyl in US food commodities range from 0.1 to 6 mg kg for food items and up to 40 mg kg for feed items. ... 

Stable in acidic, neutral and basic aqueous solutions Pale yellowish solid, faint characteristic odor Flash point 119°C (Pensky-Martens closed tester) Pyriproxyfen is an insect growth regulator which acts both as an ovacide and as an inhibitor of development (juvenile hormone mimic) against white flies, scale, and psylla. The specificity of pyriproxyfen, and its low mammalian toxicity, allow for some variation in application timing. For example, the lack of toxicity to bees allows pyriproxyfen to be applied during bloom on apple trees, and its low mammalian toxicity allows for a very short pre-harvest interval on citrus The residue definition is for pyriproxyfen alone... 

Pratt, R. F. On the definition of mechanism-based enzyme inhibitors. Bioorg. Med. Chem. Lett. 1992, 2, 1323-1326. 

More definitive diagnostic tests include endoscopy (via endoscope or Pillcam ESO capsule), 24-hour ambulatory pH monitoring, diagnostic proton pump inhibitor (PPI) administration, or esophageal manometry. 

ACE inhibitors and angiotensin-receptor blockers (ARB) have definite benefits in patients with nephropathy and are believed to have renoprotective effects in most patients. Due to their ability to cause an initial bump in serum creatinine, these agents should be used cautiously when employed in combination with the calcineurin inhibitors. The dihydropyridine calcium channel blockers have demonstrated an ability to reverse the nephrotoxicity associated with cyclosporine and tacrolimus (Table 52-8). In general, antihypertensive therapy should focus on agents with proven benefit in reducing the progression of cardiovascular disease and should be chosen on a patient-specific basis.55 See Chapter 2 for further recommendations for treating HTN. 

Despite the mechanistic differences in the definitions of kimcl and A) between quiescent affinity labels and mechanism-based inactivators, the dependence of kohs on [/] is the same for both mechanism. Hence we cannot determine whether or not a compound is acting as a mechanism-based inhibitor, based merely on this two-step kinetic behavior. However, there is a set of distinguishing features of mechanism-based inactivation that are experimentally testable. Compounds that display all of these features can be safely defined as mechanism-based inactivators. 

Motoyuki T, Kaoru K, Hironori N, Akira T, Hajime I, Hideto M. Definition of crucial structural factors of acetogenins, potent inhibitors of mitochondrial complex I. Biochim Biophys Acta 2000 1460 302-310. 

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