Hepatic and extra-hepatic glutathione-S-transferase activity in wild pigeons (Columba livia)

Glutathione-S-transferase (EC 2.5.1.18) activity was assayed in hepatic and extra-hepatic tissues of pigeons using l-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates. Gluthathione-S-transferase activity towards 1-chloro-2,4-dinitrobenzene in pigeon was in the order: kidney > liver > testes > brain > lung> heart. The enzyme activity with 1-chloro-2,4-dinitrobenzene as substrate was 40–44 times higher in pigeon liver and kidney than that observed with 1,2-dichloro-4-dinitrobenzene as substrate.K _m values of hepatic and renal glutathione transferase with l-chloro-2,4-dinitrobenzene as substrate were 2.5 and 3 mM respectively. Double reciprocal plots with varying reduced gluthathione concentrations resulted in biphasic curves with twoK _m values (liver 0.31 mM and 4mM; kidney 0.36 mM and 1.3 mM). The enzyme activity was inhibited by oxidized gluthathione in a dose-dependent pattern. 3-Methylcholanthrene elicited about 50% induction of hepatic glutathione transferase activity whereas phénobarbital was ineffective.     

A general multistate model for the analysis of hydrogen-exchange kinetics

In proton nmr, the chemical exchange rates of slowly exchanging labile hydrogens (with lifetimes in the range ～ 10 msec – ～ 1 sec) of peptides, proteins, and nucleic acids can be measured in H₂O by a combination of two separate experiments: (1) the transfer of solvent saturation and (2) saturation-recovery experiments. When these molecules exist in a dynamic equilibrium among different conformations, the experiments cannot be analyzed in a straightforward manner to derive the intrinsic exchange rates. In the present study we have derived analytical expressions for the above two experiments on a biomolecule under certain limiting conditions: (1) the extreme low-motility limit, where each of the conformational transitions is much slower than the corresponding hydrogen exchange rate with the solvent; (2) the high-motility limit (EX₂ mechanism), which is the opposite extreme of the previous limit; and (3) the low-motility limit (EX₁ mechanism), which is a mixture of limits (1) and (2), i.e., for some of the conformations, the exchange rate with the solvent is much faster than their conformational transition rates, while for the remaining conformations the reverse situation is realized. The results may be considered as a generalization to an arbitrary number of states of the two-state model treated by Hvidt. Equations have also been derived that are applicable to the iostope exchange method of measuring very slow exchange rates (with life-times of the order of minutes and longer) in biomolecules. The saturation recovery experiments performed in H₂O on the active pentapeptide fragment of thymopoietin serve to illustrate the high-motility limit. The theoretical formulation presented in this study can be easily adapted to other double-resonance techniques and also to situations where the kinetics of an arbitrary system existing in a multistate equilibrium are of interest.     

Fine structure of seminiferous tubules in antarctic seals

Summary The fine structure of seminiferous tubules from 5 crabeater, 2 leopard and 2 Ross seals showed that during the nonbreeding season the tubules were essentially similar in possessing spermatogenic and Sertoli cells. However, the tubules of leopard and Ross seals had more primary and secondary spermatocytes and spermatids than the crabeater seals. In general, the tubules were devoid of spermatozoa. The spermatids showed stages of maturation such as Golgi phase of acrosome formation, acrosomal cap formation and condensation of nuclei. Some spermatids degenerated in tubules. Both maturing and degenerating spermatids were closely associated with Sertoli cells. Junctional complexes with plaques of filaments were observed between Sertoli cells and the spermatogenic cells. Sertoli cells, irregular and polygonal, contained highly convoluted nuclei, strands of rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi complexes, small mitochondria, variable amounts of lipid droplets, lysosomes, lipofuscin granules and highly plicated plasma membranes. In brief, the spermatogenic activity had practically ceased in the testes and the animals probably secreted low levels of testosterone during the nonbreeding season.This research was supported in part by National Science Foundation Grants G.U. 30270 and G.U. 29829X from the Office of Polar Program and by NIH Grant 5 R01 AM11-376     

The amino acid sequence of ferredoxin from the alga Mastigocladuslaminosus

Ferredoxin was purified from the thermophilic blue-green alga, Mastigocladuslaminosus. The physicochemical properties of this ferredoxin are similar to those of other [2Fe-2S] plant ferredoxins except for its unusual thermal stability. The primary structure of the protein was determined and consists of 98 amino acid residues, 5 of which are cysteines. The positions of 4 cysteines which bind the iron atoms of the active centre are identical to those in other ferredoxins. The primary structure of the ferredoxin does not reveal any special features to account for its high thermal stability.     

Hydroxylamine inhibition of the nitrate reductase complex from Amaranthus

Nitrate reductase from Amaranthus viridis is similar to nitrate reductase from other plant sources. NH₂OH inhibits nitrate reduction from NADH by the nitrate reductase complex, but it does not inhibit either the NADH-dehydrogenase activity or nitrate reduction from reduced flavin mononucleotides. The inhibition observed was non-competitive with nitrate when the enzyme was pre-incubated with NH₂OH and NADH, and competitive with nitrate without pre-incubation. The K_i values for NH₂OH were 5 μM and 30 μM with or without pre-incubation respectively.     

Ultraviolet induced mutations in Aspergillus wentii.

Aspergillus wentii (IMI 17295) and its three nutritional mutant strains were irradiated with UV rays. New mutants obtained differed from the parent strains in colour of the conidia, growth factor requirements and amylase activity. Arginine deficient strains showed greater amylase activity.     

NMR studies of the variant-3 neurotoxin from Centruroides sculpturatus Ewing

We report a preliminary high-resolution proton nuclear magnetic resonance characterization of the variant-3 toxin from the scorpion Centruroides sculpturatus Ewing (range Southwestern USA). This toxin assumes a well defined folded conformation in aqueous solutions at room temperature and undergoes reversible thermal denaturation. A number of amide hydrogens exhibit exchange life times varying from several minutes to several hours. A few tentative assignments of the low field aromatic CH resonances has been made on the basis of 2D-COSY and NOE experiments. The upfield shifts exhibited by Trp-47 suggest a unique microenvironment for this residue. The NMR data suggest that there is some degree of correlation between the solution structure of the variant-3 toxin and its crystallographic structure. Our studies provide a basis for a detailed elucidation of the structure-function relationships of these interesting scorpion toxins which bind to the sodium channels of excitable membranes and delay sodium current inactivation.     

Oxidative metabolism of hydralazine. Evidence for nitrogen centered radicals formation

The oxidative metabolism of hydralazine, a hydrazine-containing hypotensive drug, has been studied using a spin-trapping technique. In the presence of Cu²⁺, Fe²⁺ and Fe³⁺, hydralazine rapidly forms a nitrogen-centered-DMPO adduct with a^N = 15.0G, a_β^H = 16.7G and a_β^N = 2.55G. While catalase has a very small inhibitory effect, superoxide dismutase completely inhibits the formation of the DMPO adduct. Mass spectral analysis of the adduct indicates that the hydralazyl radical is trapped with DMPO. Human red blood cells also catalyze the formation of a nitrogen-centered-DMPO adduct, a^N = 15.9G, a_β^H = 19.4G and a_β^N = 1.7G, which is different than that obtained with metal ions. DMPO-H adduct is also formed in the red cells from hydralazine.     

Effect of propranolol on ECG of Myna, Acridotheres tristis, and Goh, Varanus bengalensis

Effect of propranolol (1 and 3 mg/kg body wt), a sympathetic blocking agent, on ECG patterns was studied in Varanus and Acridotheres. ECG was recorded before and after 5 min (immediate), 15 min and in some cases 25 min of drug infusion. All animals responded to propranolol with bradycardia. The effectiveness is dose dependent and it is also associated with the high heart rate both in Acridotheres and in Varanus. The P-R or P-S interval increased in all cases of Varanus after infusion. In Acridotheres height and duration of P-wave were increased slightly with the lower dose and decreased with the higher dose. The Q-S shortened with the lower dose and widened late with the higher dose in Varanus whereas in Acridotheres it is widened with lower and higher doses of propranolol. The Q-T interval has been increased in both groups of animals. An increased amplitude of T-wave height was observed in Varanus after 5 and 15 min of drug infusion. But it was noted with decrease in amplitude under high dose after 15 min of drug infusion. In Acridotheres it was on increase with lower dose and decrease with higher dose. The delta-wave disappeared after the administration of propranolol in Acridotheres.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gross structure and dimensions of the gills in a hill-stream sisorid catfish,Glyptothorax pectinopterus

Gross structure and dimensions of the gills have been examined in a hill-stream sisorid catfish,Glyptothorax pectinopterus, which remains adhered to rocks by means of an adhesive organ developed on the ventral side of the thorax. The fish shows a greater weight-specific gill area and greater length of the gill filaments by comparison with other hill-stream fishes. Adaptation for life in a hill-stream habitat is shown by the presence of additional filaments on the gills and patches of specialised cells on the filament epithelium.