Inhibitory effects

In contrast to the situation in the absence of catalytically active Lewis acids, micelles of Cu(DS)2 induce rate enhancements up to a factor 1.8710 compared to the uncatalysed reaction in acetonitrile. These enzyme-like accelerations result from a very efficient complexation of the dienophile to the catalytically active copper ions, both species being concentrated at the micellar surface. Moreover, the higher affinity of 5.2 for Cu(DS)2 compared to SDS and CTAB (Psj = 96 versus 61 and 68, respectively) will diminish the inhibitory effect due to spatial separation of 5.1 and 5.2 as observed for SDS and CTAB. 

In contrast to SDS, CTAB and C12E7, CufDSjz micelles catalyse the Diels-Alder reaction between 1 and 2 with enzyme-like efficiency, leading to rate enhancements up to 1.8-10 compared to the reaction in acetonitrile. This results primarily from the essentially complete complexation off to the copper ions at the micellar surface. Comparison of the partition coefficients of 2 over the water phase and the micellar pseudophase, as derived from kinetic analysis using the pseudophase model, reveals a higher affinity of 2 for Cu(DS)2 than for SDS and CTAB. The inhibitory effect resulting from spatial separation of la-g and 2 is likely to be at least less pronoimced for Cu(DS)2 than for the other surfactants. 

Acrylate polymerizations are markedly inhibited by oxygen therefore, considerable care is taken to exclude air during the polymerization stages of manufacturing. This inhibitory effect has been shown to be caused by copolymerization of oxygen with monomer, forming an alternating copolymer (81,82). 

Benzoates. The sodium and potassium salts of ben2oic acid [65-85-0], C2H 02, ate most effective against yeast and mold. They ate used in beverages, fmit products, chemically leavened baked goods, and condiments. Owing to their inhibitory effect on yeast, they cannot be used in yeast-leavened products. Potassium ben2oate was developed for use in reduced-sodium products. Ben2oates ate permitted for use in foods up to a level of 0.1% (76). 

The mode of action has been a subject for research for a number of years. While it was originally thought that maleic hydrazide replaced uracil in the RNA sequence, it has been deterrnined that the molecule may be a pyrimidine or purine analogue and therefore base-pair formation is possible with uracil and thymine and there exists the probabiHty of base-pair formation with adenine however, if maleic hydrazide occurs in an in vivo system as the diketo species, then there remains the possibiHty of base-pairing with guanine (50). Whatever the mechanism, it is apparent that the inhibitory effects are the result of a shutdown of the de novo synthesis of protein. 

Prosta.te Ca.ncer, Estrogen has an inhibitory effect on the prostate in addition to its suppression of gonadotropin secretion by the pituitary. The three- and five-year survival rates in prostate cancer patients with metastatic disease improved when treated with DES (7) alone or along with castration. However, DES does not improve the survival rates in patients whose carcinoma is confined to the prostate. Small doses of DES (1 mg/d) appear to retard prostate cancer growth and could reduce the cardiovascular complications associated with larger doses (5 mg/d) (135) (see... 

AVP is excitatory in the ventral hippocampus, either directly or by potentiation of glutamatergic responses. An inhibitory effect has been observed in AVP may be involved in the formation of long-term potentiation and thus learning and memory. However, AVP is proconvulsive, may augment the formation of dmg tolerance and dependence, and affects cardiovascular regulatory processes. 

A common strategy for treating chronic opiate addiction iavolves the substitution of methadone which can either be provided as maintenance therapy or tapered until abstinence is achieved. Naltrexone and buprenorphine [52485-79-7] have also been used ia this manner. The a2 adrenergic agonist clonidine [4205-90-7] provides some rehef from the symptoms of opiate withdrawal, probably the result of its mimicking the inhibitory effect of opiates on the activity of locus coerukus neurons. 

Distilled spirits and the industry have always been subject to heavy taxation. Not only has it been an excellent source of revenue for many governments throughout the world, but high taxes can also be rationalized as having an inhibitory effect on consumption. 

In contrast to heparin, the coumarinic acid anticoagulants are inactive in vitw ]6k.e heparin they are active in vivo. The phenylindanedione-type compounds (7) (36) and warfarin (2) produce their in vivo inhibitory effect on the coagulation system by competitively antagonizing the normal activity of vitamin (8) (37—44). 

In view of the well-documented inhibition of dihydrofolate reductase by aminopterin (325), methotrexate (326) and related compounds it is generally accepted that this inhibitory effect constitutes the primary metabolic action of folate analogues and results in a block in the conversion of folate and dihydrofolate (DHF) to THF and its derivatives. As a consequence of this block, tissues become deficient in the THF derivatives, and this deficiency has many consequences similar to those resulting from nutritional folate deficiency. The crucial effect, however, is a depression of thymidylate synthesis with a consequent failure in DNA synthesis and arrest of cell division that has lethal results in rapidly proliferating tissues such as intestinal mucosa and bone marrow (B-69MI21604, B-69MI21605). 

Formation of an 11-methoxybenzyl ether occurs in satisfactory yield during the preparation of a 17,21 -benzylidene derivative [e.ff., (26)]. The usefulness of this ether and of related mixed acetals in removing the inhibitory effect of the 11 j5-hydroxyl group on the 20-ketone reduction has been reported. ... 

The results were simple and clear-cut Only the two terms ofa° and Emin were involved for the a-cyclodextrin systems, and the two terms of k and Emin, for (S-cyclodextrin systems. This means that the stabilities of the inclusion complexes are mainly governed by the electronic and steric interactions in a-cyclodextrin systems and by the hydro-phobic and steric interactions in (i-cyclodextrin systems, regardless of the position of the substituents in the phenols. These observations agree well with those by Harata23), who showed that there is no appreciable difference in thermodynamic parameters between cyclodextrin complexes of m- and p-di substituted benzenes and that the contribution of the enthalpy term to the complexation is more significant in a-cyclodextrin systems than in P-cyclodextrin systems, where the inhibitory effect... 

Table I. Inhibitory Effect of Kasugamycin on Growth of Piricularia oryzae at pH 5.0 and pH 7.0 in Rice Plant Juice Medium...

Achieving optimal concentrations is difficult because components in the medium and the biomass itself may neutralise the inhibitory effects of these reagents. This is especially true if complex, non-defined media, such as comsteep liquor, are used. 

High agitation and aeration cause major problems such as foaming, which may lead the fermentation vessel to unknown contamination. Antifoam cannot be always added for the reduction of foam it may have inhibitory effects on the growth of microorganisms, so the simplest devices have rakes mounted on the stirrer shaft and located on the surface of the fluid. 

Cucumber cotyledons were inoculated with purified tobacco mosaic virus (TMV) 20 to 24 hours before vacuum infiltration with different concentrations of crude water extracts of plant leaves (4). After 7 days, inoculated leaves were harvested and stored 24 hours in the dark in a moist chamber to remove excess starch. Starch lesions were counted after clearing with alcohol and staining with an iodine-potassium iodide-lactic acid mixture. The inhibitory effects of various extracts were demonstrated by comparing lesion counts of treated cotyledons to counts on control cotyledons. 

Volatile Inhibitors. Of the volatile components that influence plant growth and development, ethylene has received the most attention. Literature concerned with the variety of effects produced by ethylene, factors which influence its production, and the mechanisms through which responses are expressed has been reviewed by Evenari (57). Other gaseous excretions with inhibitory effects considered by Evenari include hydrogen cyanide, ammonia, essential oils, and mustard oils (probably allyl isothiocyanate and /3-phenethyI isothiocyanate). 

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