Biochemistry and experimental biology最新文献

In order to determine the factors affecting the maturation of the functional hypothalamo-pituitary-thyroid axis, Ambystoma gracile (Baird) larvae of different ages and acclimated to different temperature regimes were exposed to a concentration of thyroxine (T4) which activates the pituitary-thyroid axis. A. gracile from a montane and low-altitude population were utilized. These studies, plus observations concerning spontaneous metamorphosis, indicated that populations of Ambystoma gracile are highly polymorphic as suggested by Sprules (1974 b). A. gracile populations consist of 'obligate transformers', 'obligate neotenes', and 'facultative transformers'--which will metamorphose depending on environmental conditions. The colder high-altitude conditions tend to select against facultative individuals, whereas the less certain low-altitude conditions permit a much higher proportion of animals that exhibit a facultative response with respect to metamorphosis. Interrelationships between environment and physiological parameters that determine morphology in salamanders are discussed with regard to these findings.

The effects of some drugs on the isolated intestine of the Giant African land snail (Archachatina marginata, Swainson) have been investigated. The isolated intestine of the snail contracted in response to chemical stimulation by some cholinergic and adrenergic drugs. Acetylcholine and its analogues; nicotine and dimethylphenylpiperazinium, contracted the tissue preparation in a dose-related manner. Some also contracted the tissue preparation. These results were taken to imply the presence of cholinergic and sympathetic innervations in the tissue. The receptors present in the muscle have been classified as: (1) "nicotinic" and "muscarinic" cholinoreceptors, and (2) "alpha"-adrenoceptors respectively.

The substrate concentration-velocity relationship as influenced by age of animal was determined. At all stages of growth of rat and mouse ethanolamine kinase activity responded with a hyperbolic pattern to substrate concentration. Choline kinase on the other hand, underwent "enzyme differentiation". In rat liver up to 4 days of age of animal, in mouse liver up to 7 days and in mouse kidney up to 15 days, choline kinase activity responded with a hyperbolic pattern; but from then onwards the response to substrate concentration was sigmoid. The results obtained pointed to the regulatory nature of choline kinase and a possible distinction between the proteins catalyzing the phosphorylation of the two bases.

The interaction of polyamines with enzymatically generated free radicals was investigated. The superoxide anion (O-2) was generated in vitro using the xanthine oxidase-hypoxanthine system. Our results show that spermidine or spermine at different concentrations (20-200 mM) inhibit the reduction of cytochrome c; the highest levels of inhibition were obtained adding 200 mM spermidine or spermine. Putrescine (200 mM) affected the reduction of cytochrome c very little.

Using hepatectomized rats it was shown that immediately after partial liver removal (PLR) the Kupffer macrophages were accumulated in liver remnant. At the maximal mitotic activity (36 hours following PLR) the relative amount of Kupffer cells keeps low, but 72 hours later turns out to be higher again. The periodic changes of the Kupffer cell amount in hepatectomized rats are accompanied by remarkable increase (1.5-3 fold) of free and total lysosomal enzyme activity (acid DNA-ase, acid RNA-ase, cathepsin D). The activation of the Kupffer macrophage lysosomes goes ahead of labilization of hepatocyte lysosomal membranes. The blockade of mononuclear phagocyte system by means of carbonate iron overloading in the early prereplicative period leads to an as long as 10-12 hours retardation of hepatocyte proliferation. The role of Kupffer macrophages in reparative liver regeneration is discussed.

In a continuation of studies on the metabolism of foreign compounds under the influence of diet or other factors in relation to neoplasia development, male and female weanling rats, in-bred Wistar-derived rats (50-60 g) free from disease or infection were obesified with N, N-bis (B-chloroethyl)-4, 4-bipiperidine (BPN) prior to determining the biliary excretion of tartrazine. Obese and normal animals excreted the dye unchanged and in sex-related proportions.

The present study was designed to examine the osmotic resistance of erythrocytes measured by a new method-Coil Planet Centrifuge under the glutaraldehyde incubation, and to determine free cholesterol and adenine nucleotide contents of glutaraldehyde-treated erythrocytes compared with that of control erythrocytes. Glutaraldehyde increased the osmotic resistance of erythrocytes. Hemolysis end point of glutaraldehyde-treated erythrocytes shifted to hypo-osmolar side after 2.5 h hours incubation (p less than 0.001). Free cholesterol content of erythrocytes was not changed by the addition of glutaraldehyde, however, ATP content significantly increased when compared with controls (p less than 0.001). Moreover, the osmotic resistance of erythrocytes in 55 patients with alcoholic liver injuries and the relation between the disease were examined by Coil Planet Centrifuge. Hemolysis end point shifted to hypo-osmolar side in the patients, and our results suggest that the increase in osmotic resistance is partly responsible for the increase in the rigidity of erythrocytes. This new method was also helpful in evaluation in the clinical course of alcoholic liver injuries.

CoQ10 is intrinsic to human tissues and is a vitamin, according to the basic science of nutrition. It is known that CoQ10, plays a role in the respiratory process, moreover it seems to be involved in the mechanism of blood coagulation. As a vitamin a deficiency of CoQ10 may be related to some disease, that is, first of all, a disease is bioenergetics. It has been demonstrated that during aging, other than a diminution of EFA (and an increase of palmitoleic and eicosatrienoic fatty acids), a decrease of about the 20-30% in the heart CoQ10 levels occurs in the rat. Perhaps these modifications may be intrinsic to the "biochemical" changes of aging.

Serum cholinesterase enzyme (E.C. 3.1.1.8) shows a considerable degree of genetically determined heterogeneity. In this communication we describe some kinetic properties of serum cholinesterase variants (Km and Vmax) from individuals predisposed to prolonged apneic periods after administration of the anesthetic, succinylcholine. Isoelectric focusing, in a narrow pH range (pH 4-6) of sera from normal and atypical phenotypes permitted the detection of differences in protein bands near the isoelectric pH of the enzyme.