Order Of Inhibitory Effect Research Articles

Thermal reactions of aromatic hydrocarbons in the pyrolysis of ethane and propane

The influence of aromatics on the pyrolysis of ethane and propane was studied using benzene, toluene, α-methylnaphthalene and anthracene as model compounds. The experiments were performed in a tubular flow reactor at ordinary pressure, temperatures of 700-850°C, residence times between 0.1-1s and low concentration of aromatics (1-6%mole). Aromatic hydrocarbons inhibited the pyrolysis rate of ethane and propane and the following order of inhibitory effect - which decreases with the increase of temperature - was found: toluene > α-methylnaphthalene > benzene > anthracene. The C1-C4 composition of the effluent was only slightly influenced by the presence of aromatics, which were found to suffer an appreciable transformation to alkylated derivatives, depending on their structure and despite their thermal stability when highly diluted with N2 at the same temperatures. The transformation of the aromatic hydrocarbons was explained by the interference of the main chain propagators (·H, ·CH3, ·C2H3, ·C2H5) with the aromatic and benzyl type radicals. Benzene has only a small contribution to soot formation, a phenomenon which however was found to increase when alkylaromatic and polycyclic hydrocarbons are present in the feed.

Inhibitory effects of echinoisoflavanone and sophoraisoflavanone D in Sophora chrysophylla SEEM on lipid peroxidation of mice brain homogenate by interaction of ferrous ion and hydrogen peroxide, in vitro.

We present the results of an in vitro investigation of the inhibitory effects of echinoisoflavanone and sophoraisoflavanone D isolated from Sophora chrysophylla SEEM on lipid peroxidation of mice brain homogenate by interaction of ferrous ion and hydrogen peroxide, in vitro. They inhibited lipid peroxidation. The order of inhibitory effects of these isoflavanones and mannitol as a hydroxy radical scavenger was echinoisoflavanone > mannitol > sophoraisoflavanone D. The results suggest that some isoflavanones may be of use in cases where oxidative stress is present.

Influence of Organic Phosphonates on Hydroxyapatite Crystal Growth Kinetics

Phosphonate additives have important applications both in biomineralization processes and in industrial mineral scale formation. The kinetics of crystal growth of hydroxyapatite (HAP) has been investigated in the presence of seven phosphonate additives: HEDP (hydroxyethylenediphosphonic acid), DETPMP (diethylenetriaminepenta(methylenephosphonic acid)), DHTPMP (dihexyltriaminepenta (methylenephosphonic acid)), AMP (aminotris(methylenephosphonic acid)), HDTMP (hexyldiaminetetra(methylenephosphonic acid)), EDTMP (ethylenediaminetetra(methylenephosphonic acid)), and DETMP (diaminoethoxytetra(methylenephosphonic acid)). The constant composition (CC) method, used in this study, enabled reliable crystal growth rate data to be obtained even when the reactions were appreciably inhibited. The experiments were performed at pH 7.40, ionic strength 0.15 mol L-1 (maintained with NaCl), and an HAP relative supersaturation, σ, of 5.5. The results indicate that traces of some phosphonates (≤10-6 mol L-1) are extremely effective in inhibiting crystal growth. Assuming that the adsorbed additives block discrete growth sites on the crystal surfaces, the kinetic results may be interpreted in terms of a Langmuir adsorption model yielding kinetic affinity constants. The order of inhibitory effectiveness, DETMP > EDTMP > DETPMP > HEDP ≥ DHTPMP > HDTMP ≥ AMP, reflects the ability of the phosphonates to bind to the apatite surfaces. ζ potential measurments of HAP surfaces in the presence of additives provide important corroboratory data for the interpretation of the crystal growth results.

Role of calcium in biphasic germination of Bacillus cereus T spores sensitized to lysozyme.

Biphasic germination induced by inosine in the presence of Ca2+ was examined using Bacillus cereus T spores treated with sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) at pH 10. The first phase of the germination was stimulated by Ca2+ in the concentration-dependent manner, showing the optimal concentration at 0.5-1.0 mM. The second phase appeared to be insensitive to the cation. The optimal temperatures for the first and the second phase were 25 C and 40 C, respectively; the optimal pHs for the two phases were 7-9 and around 7.5, respectively. Heat resistance and dipicolinic acid of the SDS-DTT-treated spores were lost mostly during the first phase. A Ca(2+)-specific chelator, glycoletherdiamine-N,N,N',N'-tetraacetic acid (GEDTA), inhibited the first phase evoked by Ca2+, while it had no inhibitory effect on the second phase. In contrast, the divalent cations examined, except Mg2+ and Sr2+, affected not only the first phase but also the second phase. The order of inhibitory effect on the first phase was Hg2+ > Zn2+ > Ba2+, Co2+, Cu2+ > Mn2+; on the second phase, it was Hg2+ > Cu2+ > Zn2+ > Co2+ > Mn2+ > Ba2+.

Response properties of fibers in the hamster superior laryngeal nerve

The purpose of the present investigation was to record electrophysiological responses from single fibers in the hamster superior laryngeal nerve (SLN) that were responsive to chemical stimulation of the larynx. Twenty chemical solutions, commonly used in studies of mammalian gustatory physiology, were applied to taste buds on and around the epiglottis. These stimuli were dissolved in physiological saline. Responses were the number of impulses elicited over a 15-s period following stimulus onset, above or below the background activity elicited by a previous rinse with saline. Unlike fibers in the hamster chorda tympani or glossopharyngeal nerves, SLN units were not easily classifiable into response types. Excitatory stimuli were primarily acids and bitter-tasting stimuli, with the order of their effectiveness being urea ⪢ tartaric acid > HCl > KCl > citric acid > caffeine > quinine hydrochloride > acetic acid. The sweet-tasting stimuli and most salts other than KCl were primarily inhibitory, with the order of inhibitory effectiveness being CaCl 2 > sucrose > fructose > LiCl > NaNO 3 > Li 2SO 4 > NaCl. A hierarchical cluster analysis of fibers yielded no distinct clusters, yet differing sensitivities across the fibers were suggested. SLN fibers are highly responsive to sour and bitter stimuli, although they are not sensitive to fine differences in taste quality, as are fibers in other gustatory nerves.

Effect of class I antiarrhythmic agents on slow Ca2+ channels of myocardial cells.

The effects of several class I antiarrhythmic drugs (aprindine, cibenzoline, disopyramide, mexiletine, lidocaine, tocainide and 711389-S) were studied on slow Ca2+ channels of rabbit sinus node cells using a double microelectrode voltage clamp technique. All these drugs decreased the heart rate, the maximum rate of rise (Vmax), the action potential amplitude and the slope of the phase 4 depolarization in spontaneously beating sinus node preparations. The order of inhibitory potency on the heart rate was: aprindine greater than 711389-S greater than cibenzoline greater than or equal to disopyramide greater than mexiletine greater than or equal to lidocaine greater than tocainide. On the current systems, these drugs decreased the slow inward current (Isi) and the time-dependent potassium current (Ik). However, the major effect was a reduction of Isi. These agents also exerted a frequency-dependent block of Isi. Furthermore, comparing the effects of class I antiarrhythmic agents on slow Ca2+ channels, the order of inhibitory effect on Vmax of sinus node cells was: aprindine greater than 711389-S greater than cibenzoline greater than or equal to disopyramide greater than mexiletine greater than lidocaine greater than tocainide. These electrophysiological observations suggest that class I antiarrhythmic drugs have a depressant effect on slow Ca2+ channels as well as fast Na+ channels of myocardial cells, and that so-called "slow" kinetic drugs may depress slow Ca2+ channels more strongly than "fast" kinetic drugs.

Inhibition of adenosine 3',5'-cyclic monophosphate phosphodiesterase by lignan glucosides of Eucommia bark.

Studies were conducted on adenosine 3', 5'-cyclic monophosphate (cyclic AMP) phosphodiesterase inhibition by lignan glucosides from bark of Eucommia ulmoides OLIV. (Eucommiaceae). Various lignan diglucosides. (+)-syringaresinol di-O-β-D-glucopyranoside (1c), (+)-medioresinol di-O-β-D-glucopyranoside (2c), (+)-pinoresinol di-O-β-D-glucopyranoside (3c) and (+)-1-hydroxy-pinoresinol 4', 4-di-O-β-D-glucopyranoside (4d), showed strong inhibitory activity.The structure-inhibitory activity relationships of the aglycone and its glucosides are discussed. The order of inhibitory effect was diglucoside g aglycone > monoglucoside.

In vitro effects of butyltin compounds on glucose-6-phosphate dehydrogenase.

Butyltin compounds were found to inhibit the activity of purified yeast glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in an in vitro system. The order of inhibitory effect, after tetrabutyltin, was dibutyltin, tributyltin and monobutyltin. The concentration of tetrabutyltin giving 50% inhibition of the yeast enzyme was 4.3×10-6 M. On the other hand, the activity of the human erythrocyte enzyme was inhibited only by tributyltin, but not by monobutyltin, dibutyltin or tetrabutyltin. The inhibition of glucose-6-phosphate dehydrogenase of yeast by tributyltin and tetrabutyltin could be prevented by the addition of bovine serum albumin, whereas the inhibition of the activity of the erythrocyte enzyme by tributyltin was not affected by bovine serum albumin. However, the addition of albumin to the once-inactivated enzyme did not restore the enzyme activity. Cysteine slightly protected the yeast enzyme from the inhibition by dibutyltin but did not affect the inhibitions by tributyltin and tetrabutyltin.

Obstruction of estrogen-receptor complex formation. Further analysis of the nature and steroidal specificity of the effect.

Qualitative and quantitative aspects of inhibition of 17β-estradiol-receptor complex formation by a number of natural and synthetic hormonal agents have been investigated in rat anterior pituitary cytosol. The initial velocity of the interaction between 17β-estradiol and its receptors is impeded by preincubation with androgenic compounds in a dose-related manner, the order of inhibitory effectiveness being: 3β-androstanediol > 3α-androstanediol = 5α-dihydrotestosterone > testosterone. Equivalence of 3α-androstanediol and 5α-dihydrotestosterone effectiveness can be accounted for by high cytoplasmic activity of 3α-hydroxysteroid dehydrogenase. Both initial velocity and inhibitory response to a given level of androgen are lower in the male than in female cytosol; the variation appears to be the consequence of different endogenous androgen levels. Weak androgens (dehydroepiandrosterone and etiocholanolone) and anti-androgens (flutamide, cyproterone and Ro7-8117) are effective inhibitors, but the degree of inh...

Effects of clofibrate on mitochondrial function

The effects of ethyl and sodium clofibrate on mitochondrial function were studied. Both compounds exerted similar effects, the ethyl derivative being more potent. State 3 respiration was inhibited; the order of inhibitory effectiveness was NAD +-dependent substrates > succinate > ascorbate. State 4 NAD +-linked oxidation was not significantly affected, but state 4 oxidations of succinate and ascorbate were stimulated by ethyl clofibrate. Energy production was inhibited, as evidenced by the decrease in the respiratory control ratio, the P/O ratio and the ATP- 32P exchange reaction. Energy utilization, assessed by substrate or ATP-supported energy-linked Ca 2+ uptake, was also inhibited. By contrast, energy-independent Ca 2+ uptake was not affected. Clofibrate interfered with the integrity of the mitochondrial membranes, since it stimulated ATPase activity and increased the normally low permeability of intact mitochondria toward NADH. The transfer of reducing equivalents into the mitochondria, catalyzed by the α-glycerophosphate, fatty acid or malate-aspartate shuttles, was inhibited by sodium clofibrate. These results may explain our previous finding that the reconstituted a-glycerophosphate shuttle was not stimulated in rats fed clofibrate, despite an increase in the activity of mitochondrial α-glycerophosphate dehydrogenase.

Effects of Diphenylether Herbicides on Reactions of Mitochondria and Chloroplasts

Effects of three diphenylether herbicides [2,4-dichlorophenyl-p-nitrophenyl ether (nitrofen); 2,4,6-trichlorophenyl-4′-nitrophenyl ether (hereinafter referred to as MC-1478); and 2,4′-dinitro-4-trifluoromethyl-diphenylether (hereinafter referred to as C-6989)] were measured on phosphorylation and electron transport in spinach(Spinacia oleraceaL.) chloroplasts, and mung bean(Phaseolus aureusL., var. Jumbo) and white potato tuber(Solarium tuberosumL.) mitochondria. All of the diphenylethers acted primarily as inhibitors of chloroplast noncyclic electron transport, and the coupled photophosphorylation. The compounds ranked in the following decreasing order of inhibitory effectiveness: MC-1478 ≥ C-6989 >> nitrofen. A site of action close to light reaction II was suggested. At high molar concentrations, marginal interference with cyclic electron transport or phosphorylation was obtained. In mitochondria, MC-1478 and nitrofen acted primarily as electron transport inhibitors with malate, NADH, and succinate as substrates. MC-1478 was a slightly stronger inhibitor than nitrofen. Only slight stimulation of ADP-limited oxygen uptake was obtained during the oxidation of NADH and succinate; whereas, strong inhibition of oxygen uptake was obtained with malate. C-6989 also weakly stimulated ADP-limited oxygen uptake with NADH and succinate but differed from the two chlorinated diphenylethers in that electron transport was not inhibited when ADP was present in excess. Interference with ATP generation could be one of the mechanisms through which the phytotoxicity of diphenylether herbicides is expressed.

Effect of certain inorganic chemicals on growth and spore germination of Alternaria tenuis auct., the fungus causing core rot of mandarin oranges in India

Laboratory studies to determine the tolerance of an isolate ofAlternaria tenuis causing a black core rot of mandarin oranges (Citrus reticulata) have shown that presence of low amounts of manganese, zinc, iron, copper, boron, and molybdenum in a synthetic medium stimulated growth and sporulation of the fungus. Concentrations of 20 ppm or more of copper sulphate, boric acid, and ammonium molybdate, however, caused significant reduction of growth. Conidia of the fungus were very sensitive to even low amounts of copper, zinc, and iron. Copper sulphate was most toxic to spore germination followed, in order of inhibitory effect, by zinc sulphate, ferrous sulphate, and boric acid. Ammonium molybdate and manganese sulphate were stimulatory to spore germination at 5 ppm. There was a positive correlation between percentage of spore germination and average length of germ tubes in different concentrations of various chemicals. The possibility of using copper sulphate, zinc sulphate, and ferrous sulphate as spray materials for trees and as dip for ripe fruits to prevent black core rot are discussed.