Comparative biochemistry and physiology. C: Comparative pharmacology最新文献

1. The major ionmotive ATPase, in animal cells, is the Na⁺, K⁺-ATPase or sodium pump.

2. This membrane bound enzyme is responsible for the translocation of Na⁺ ions and K⁺ ions across the plasma membrane, an active transport mechanism that requires the expenditure of the metabolic energy stored within the ATP molecule.

3. This ubiquitous enzyme controls directly or indirectly many essential cellular functions, such as, cell volume, free calcium concentration and membrane potential.

4. It is, therefore, apparent that alterations in its regulation may play key roles in pathological processes.

1. The survival and metabolic adjustments of the blood clam S. inaequivalvis have been determined at environmental anoxia and tissue anoxia induced by sulfide and cyanide.

2. Times to 50% mortality were established in clams placed in oxygenated seawater with and without dissolved sulfide or free cyanide or deoxygenated seawater with and without dissolved sulfide.

3. Anaerobic metabolism was studied in live animals and in red blood cells incubated in vitro. Tissue anoxia due to sulfide and cyanide caused greater changes in the levels of aspartate and the pyruvate derivatives, compared to environmental anoxia.

1. A globulin fraction prepared from the meal of Callosobruchus maculatus-resistant cowpea (Vigna wiguiculata) seeds was shown to be detrimental to this bruchid when incorporated in artificial seeds.

2. The performance of C. maculatus was also shown to be strongly hindered by vicilins from resistant seeds when these storage proteins were incorporated in artificial seeds at the level of 2%.

3. The purified vicilins from seeds of both resistant and susceptible cowpea varieties were shown to have the same SDS-PAGE pattern but different mobilities in non-denaturing polyacrylamide gel electrophoresis.

4. These results and previous ones obtained by us (Silva and Xavier-Filho, 1991; Sales et al., 1992) strongly suggest that the resistance of cowpea seeds from the cultivar TVu 2027 and from others bred from it is associated with the presence of vicilin molecules which are refractory to digestion by bruchid midgut proteinases.

1. The metabolism of 2-, 3-, 4-bromo-, 2-, 4-chloro-, and 2-fluorobiphenyl by hepatic microsomes isolated from control and Aroclor 1254-treated rats and pigeons was studied.

2. Meta and para as well as dihydroxylated metabolites were detected, but para hydroxylation was the preferred route of metabolism with all of the substrates used.

3. The overall rates of hydroxylation were greater with hepatic microsomes from rats than from pigeons.

4. Treatment with Aroclor 1254, a potent inducer of hepatic monooygenases, resulted in increased rates of metabolism and in the enhanced formation of diol metabolites. Metabolism of halobiphenyls by induced P450 isoenzymes altered the regioselective hydroxylation pathways.

5. Ortho- and meta halosubstituted biphenyls were less rapidly metabolised when compared with paru substituted isomers.

1. This paper describes the effects of several cholinergic agonists and antagonists, and of β-phenylethylamine (PEA) and some of its derivatives, on the articular capsule, or ligament, of the primary spines of Eucidaris tribuloides.

2. Carbamylcholine (CCh), methacholine (MeACh), nicotine, and muscarine exert a stiffening effect similar to that of acetylcholine (ACh), although the time course of their actions varies widely.

3. Atropine induced stiffening and blocked and responses to muscarine and MeACh. The responses to MeACh were blocked also by 4-diphenylacetoxy-N-methylpiperidine, suggesting the presence in the ligament of type M₃ muscarinic receptors, in addition to nicotinic ones. d-Tubocurarine induced stiffness of the ligament and failed to block the responses to ACh and nicotine.

4. While ACh induced only a slight desensitization, CCh caused a long-lasting blockade of the stiffening effects of the cholinergic agonists. This shows that the receptors for ACh have a site or sites that recognize the ester moieties of these molecules.

5. Eserine and neostigmine potentiate the responses to acetylcholine, indicating the presence of aeetyl-cholinesterase in the ligament.

6. β-Phenylethy lamine, epinephrine, norepinephrine, and dopamine induce diphasic responses; usually a brief softening followed by a slow and irreversible stiffening of the ligament.

7. In contrast to the above, tyramine and octopamine elicit a simple softening of ligaments which are stiff as a result of handling or by exposure to cholinergic agonists. However, tyramine and octopamine do not soften ligaments which become stiff as a result of exposure to adrenergic agonists.

1. Soluble butyrylcholinesterase (BuChE) was isolated from the visual ganglia of the squid Todarodes sagittatus L. Gel-chromatography on Sephadex G-200 columns resulted in its separation into three molecular forms.

2. The major component with a molecular mass of 180kDa was used for kinetic study.

3. The substrate analysis revealed squid enzyme to be BuChE of unusual type.

4. Unlike typical BuChE (EC 3.1.1.8), squid enzyme splits acetyl-β-methylcholine (AMCh) with a relatively high rate, alongside with common BuChE substrates—butyrylcholine (BCh), propionylcholine (PCh), acetylcholine (ACh), butyrylthiocholine (BTCh) and acetylthiocholine (ATCh), the enzymic hydrolysis being suppressed by excess of all these substrates.

5. Among them, the highest values of k_{cat and}k_cat/K_m were found for BCh and BTCh. Maximal activity of the enzyme was noticed at low BCh and BTCh concentrations (1–2 mM).

6. Tetraalkylammonium ions exhibit a mixed type of inhibition and suppress the substrate inhibition of squid BuChE.

7. Among organophosphorus inhibitors (OPI), the methylthiophosphonates are most potent for squid BuChE, and for some phosphates, selective OPI of typical BuChE, are potent as well.

8. By the pattern of selectivity to OPI, squid enzyme differs from both typical BuChE of horse serum and acetylcholinesterase (EC 3.1.1.7) from bovine erythrocytes.

9. Some details of the active center structure of squid BuChE compared to that of typical enzymes are discussed.

1. The study has been carried out on Wistar rats. The aim of the present study was to trace the effect of aluminum on enzyme activities and hematological parameters on erythrocytes.

2. Aluminum decreased activities of acetylcholinesterase, glutathione reductase, glucose-6-phosphate dehydrogenase, and lactate dehydrogenase in the erythrocytes of the animals tested.

3. In the peripheral blood, a significant decrease in the erythrocyte count, hemoglobin level and hematocrit index and increased percentage of reticulocytes and polychromatophilic erythrocytes were observed.

4. The increase in the neutrophilic granulocyte and lymphocyte count was significant.

5. An inhibitory effect of aluminum on the phagocytic activity of granulocytes was also observed.

1. The effects of diltiazem have been investigated in isolated rat heart mitochondria exposed to conditions possibly attained in ischemia-damaged cells.

2. The results obtained indicate that diltiazem, at the concentrations expected within cells following pharmacological treatment, does not significantly affect the mitochondrial calcium content.

3. Diltiazem did not appear to modify ATP synthesis, and hence the capacity of mitochondria to sustain the ATP-requiring processes needed for the recovery of cardiac cells.

1. The metabolism of a wide range of di-, tri-, tetra-, penta- and hexachlorobiphenyls by hepatic microsomes isolated from control animals and animals treated with Aroclor 1254 was studied.

2. Hepatic microsomes isolated from control rats expressed higher rates of oxidations than avians.

3. Treatment of rats and pigeons with Aroclor 1254 induced cytochrome P450 dependent mono-oxygenases leading to an increased regioselective metabolism of PCB isomer and congeneres.

4. There was an inverse relationship between the degree of halosubstitution and microsomal oxidation. Meta-para carbon atoms free of halosubstitution were the preferred side for oxidation.

5. A good correlation was found between the in vitro metabolism of PCBs and their relative abundance in tissue extracts, thus suggesting oxidative metabolism to be the major route of metabolic disposal.

1. Perifusion of dispersed pituitary cells and pituitary cell culture was used to investigate the effects of cholinergic drugs on the secretion of maturational gonadotropin (GtH₂) in carp.

2. Nicotine strongly, and in a dose dependent manner, stimulated GtH₂ release in male and in female carp (from 10⁻⁸M in the Perifusion and 10⁻¹⁰M in the cells cultures).

3. Nicotine is 10 times more active in females than in males.

4. The results suggest that in carp, nicotine stimulates GtH₂ release directly from the pituitary cells, indicating a possible involvement of a cholinergic system in the regulation of GtH₂ secretion in teleost fish.