Voprosy biokhimii mozga最新文献

Three copper-containing proteins were obtained from bovine brain soluble fraction. Two of them were purified to electrophoretically homogenous states. Some physicochemical properties of these proteins were studied. From mitochondrial fraction of grey matter of bovine brain cytochrome oxidase was obtained, which was similar to that obtained from cardiac muscle.

The quantitative changes of histones and their fractions and of nonhistone proteins in nuclei of cerebral cells have been studied in normal animals and following removal of the right superior cervical ganglion. On the next day after sympathectomy the total amount of histones was shown to increase by 17% in nuclei of cells of the right hemisphere while in nuclei of cells of the left hemisphere an increase of 38% was observed 3 days after sympathectomy. Histone fractions rich in lysine were also found to increase. The amount of nonhistone proteins begins to decrease on the next day after sympathectomy and reaches 33% of control values by the third day.

The participation of glutamate and alanine in lipogenesis and gluconeogenesis of brain was investigated. 5(14)C glutamate was injected intracisternally in an amount of 5 mcCu/l g tissue and 3(14)C-alanine was injected subcutaneously 30 mcCu/100 g body weight. Labels from glutamate and alanine were recovered in different lipid franctions -- in phospholipids, glycerides, free fatty acids and cholesterol, as well as in glucose and glycogen. An intensive incorporation of label from 5(14)C glutamate into various amino acids--aspartic acid, glutamine, serine, glycine and alanine--was demonstrated. The data presented indicate the participation of amino acids in lipogenesis and gluconeogenesis of brain.

The spectre of active antigens in brain is studied. The presence of 3 protein and 3 glycoprotein brain specific antigens is demonstrated. The possible participation of brain specific antigens in increased antibody formation in schizophrenics, multiple sclerosis and lateral ammiotrophic sclerosis is studied. The data obtained indicate the role of brain specific antigens to autoimmunity in those patients. The possible participation of one of the specific antigens of the brain, sialoglycoprotein GP-350, in physiological processes connected with the mechanism of memory is also studied. In experiments of inbred trained rats an activation of the synthesis of GP-350 is observed.

We had previously shown the presence of four protein fractions in hypothalamus of cattle having a coronarodilatatory effect. In this study we have developed methods for the isolation of these proteins and have studied some of their physicochemical properties, amino acid composition, molecular weight, iso-electric point etc. The results obtained have shown that the methods used enable the isolation of quite pure coronaroactive proteins, the content of which in the hypothalamus is equal to 12 mg/kg of fresh tissue. A study of the amino acid composition of these proteins has shown that they are not of the same type. They also differ in molecular weight, in their electrophoretic properties on 7.5% polyacrylamide gel and their iso-electric points. The possibility of a dual function of these proteins as carriers and precursors of corresponding neurohormones is discussed.

When rats are put on a diet that is low in protein or contains no protein, decrease in brain weight can be observed. Changes in adults are minimal. In the young there is a 10--30% decrease in cell number and protein content; the cell size (protein per cell) does not change significantly. The change is greater, the earlier the diet is started and the more severe the protein dificiency is. The longer the malnutrition period lasts, the smaller is the recovery to normal values on subsequent control diets. Amino acid incorporation in the brain decreased 10--30% under these experimental conditions; it seems the decrease was to a great extent in the more slowly metabolized protein pool. Changes in other organs were greater; for example, in liver the decrease was up to 75% under similar conditions. The changes in the brain were heterogeneous; there were regional differences, and not all proteins were affected to the same degree; choline acetyltransferase was not affected. Cellular amino acid transport as studied with incubated slices of brain was not altered under these conditions.

Chronically alcoholized intoxication (1.5--2 months) induces adaptation of cerebral neurones to changing equilibrium states of biochemical processes by altering the activity of enzymes of GABA metabolism, reduction of alanine and aspartate transaminase activity and increase of LDH and succinate dehydrogenase activity. In the cerebellum and cerebral hemispheres during alcohol abstinacy the activity of GABA-T, succinate dehydrogenase and aspartate transaminase was reduced while that of LDH and alanine transaminase was increased. The administration of fusarinic acid (100 mg/kg i. p.) to control animals induced a sharp increase of GAD activity in both structures of the brain. The stimulatory effects of fusarinic acid were not observed when it was administered to animals receiving alcohol chronically. Motor activity or rats was markedly reduced during chronical alcoholism and the first days of alcohol abstinacy (24--48 h), as well as following injection fusarinic acid and homopantothenic acid. The increase of locomotion and the vertical component of motor activity was observed only following one week or one month after alcohol abstinacy.

Acid and neutral proteinases were isolated with the purpose of investigating their participation in the breakdown of hypothalamic peptides and proteins. The acid proteinase was purified about 1000-fold from hypothalamus by precipitation with acetone, chromatography on SP-Sephadex G-50, gel filtration through column of G-100 and chromatography on DEAE-Sephadex A-50. The molecular weight of the enzyme was approximately 50.000. Maximal activity against hemoglobin was obtained at pH 3,2--3,5: serum albumin was split much more slowly. Hypothalamus acid proteinase was partially inhibited by beta-phenyl pyruvate, benzothonium cloride, and was completely inhibited by low concentrations of pepstatin. This proteinase splits somatostatin, Substance P and some C-fragments of Substance P. The probable sites of enzyme action on these peptides were determined by the end group dansyl technique. Neutral proteinase was isolated from the supernatant fraction(100.000 g) of a 0,3 M sucrose homogenate of bovine hypothalamus by chromatography on DEAE Sephadex A-50, gel filtration through Sephadex G-100 and rechromatography on DEAE sephadex A-50 using luliberin as substrate. The rates of breakdown of luliberin and denaturated hemoglobin were measured by fluorometric estimation of acid-soluble peptides wieht o-phthaldialdehyde. The purifed enzyme preparations have a pH optimum of activity at 7--7,5. The enzymes molecular weight was approximatelyy 30--40.000. Enzyme activity was inhibited by L-1-tosylamide-2-phenylethylchloromethyl ketone, p-chloromercuribenzoate and divalent ions Co2+, Zn2+ and was significantly enhanced by dithiothreitol. The Km values for the reaction of hydrolysis of luliberin and hemoglobin were 1,33.10(-5) and 5,2.10(-5) M respectively. The neutral proteinase from the hypothalamus cleaves luliberin, somatostatin and Substance P. Sites of action of the enzyme upon those peptides were determined by means of the dansyl technique. The acid proteinase, most likely cathepsin D, and neutral proteinase from hypothalamus, may play an important role in the formation and breakdown of peptide hormones in the hypothalamus.