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Biomedical subjects

A A Galoian

Publications and source records attributed to A A Galoian.

At least 19 recordsLinked to original sources
PubMed1993

[The effects of a cardioactive hypothalamic neurohormone on the isolated rat heart].

On the isolated perfused by Langendorf at heart the cardioactive hypothalamic neurohormone NG3a (2 x 10(-5) g/ml) significantly decreased the coronary flow rate; the effect persisted during 5-10 min, after that the second phase appeared which was expressed by the increase of coronary flow rate. The maximum effect was 122% compared with control. The second phase appeared in 30-45 min after infusion of NG3a. NG3a did not influence the heart rate, but sometimes (7.3% cases) during the maximum increase of coronary flow the bradyarrhythmia was registered. It has been concluded that NG3a influences directly the coronary vessels.

Animals↗
PubMed1992

[The neuroendocrine heart and the hypothalamus--hormones of the integration and regulation of coronary vascular tonus].

Neurosecretory hormone formation by atrial ganglionic cells plays a major role in self-regulation of the heart and its coronary circulation, as well as in integration of the atrium with endocrinal hypothalamus. New data on polypeptide hormones and their precursors is presented. Some atrial glycopeptides play the role of the liberins of hypothalamic cardio-active neurohormones thus carrying out the function of integration of endocrinal hypothalamus with the neuroendocrine heart. The problem of neural and humoral ways of the integration are discussed.

Animals↗
PubMed1990

[Distribution of neurospecific cardioactive protein-hormone complex in the rat body during experimental myocardial ischemia].

For more than 25 years the chemistry and the function of the protein-hormonal complexes (produced by magnocellular nuclei of human and same animals) have been studied. The methods of radioimmunological analyses (RIA) for the detection of new neuropecific cardioactive protein-hormone "K" (RHK) in rat organism with myocardial ischemia has been developed. Concentration of PHK in various regions of the brain by RIA a four days after the occlusion of the carotid artery has a sharp decrease. Particularly concentration of PHK decreases 100-fold in the cerebral cortex. At the same time the level of PHK content in the blood increased from 13 +/- 0.85 to 630 +/- 3.9 ng/ml. The maximum concentration of PHK shows a sharp rise in the spleen 200-fold of their original level. This distribution pattern implies that PHK may be of importance for peripheral tissues and to the scarring in heart neurosis zone.

Animals↗
PubMed1987

[p-Nitroanilides of amino acids and peptides and fluorescence peptide with inner fluorescence quenching as substrates for cathepsins H, B, D and high molecular weight aspartic peptidase in the brain].

p-Nitroanilides of amino acids and peptides were used to study the specificity of cathepsins H and B from human and bovine brain, respectively. The specific activity of cathepsin H decreased in the following order: Arg-pNa greater than or equal to Leu-pNa greater than Ala-pNa greater than or equal to Phe-pNa greater than Pro-pNa greater than Glu-pNa; Arg-pNa was split by the enzyme 12 times as fast as Bz-Arg-pNa. Among other oligopeptide p-nitroanilides tested (Ala-Ala, Ala-Leu, Ala-Ala-Ala, Ala-Ala-Leu, Gly-Gly-Leu, Gly-Gly-Phe, Gly-Leu-Phe, pGlu-Phe-Leu, pGlu-Phe-Ala, pGlu-Phe), PGlu-Phe-Leu and pGlu-Phe-Ala appeared to be the best substrates for cathepsin B; Km for hydrolysis were 0.1 mM and 0.165 mM, respectively, kcat were 5.1 and 8.3 s-1, respectively. A comparative study of substrate specificity of cathepsin D and high molecular weight aspartic peptidase with the use of fluorescent substrate with inner fluorescence quenching, Abz-Ala-Ala-Phe-Phe-pNa, revealed that both peptidases hydrolyzed the single bond between two phenylalanine residues, resulting in the increase of fluorescence (4.5-5-fold) of anthraniloyl tripeptide. The Km values for the substrate hydrolysis by cathepsin D and high molecular weight aspartic peptidase were 6.2 microM and 11.2 microM; kcat were 7.2 s-1 and 1.3 s-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1980

[Isoenzyme composition of cathepsin D from bovine hypothalamus].

The isoenzyme composition of cathepsin D from bovine hypothalamus was studied by isoelectric focusing. It was found that the soluble fraction of hypothalamic proteins contains five peaks of endopeptidase activity at pH 3.2. The properties studied allowed to identify these peaks of endopeptidase activity as isoenzyme forms of cathepsin D.

Animals↗
PubMed1978

[Chemistry and biology of hypothalamic cardioactive proteins and peptides].

The data presented concern the chemistry and biology of cardiotrop peptides and proteins isolated by us from the hypothalamus. The molecular mechanisms of the effect of neurohormone "C" (NC) as well as of a new cardiotrop hexapeptide from cattle hypothalamus are discussed. In in vitro studies on homogenates NC has been found to inhibit greatly not only 3'--5'-cyclo-AMP phosphodiesterase activity of brain and heart but also 3'--5'-cyclo-GMP phosphodiesterase activity. NC has been shown to be bound to specific proteins and to the regulatory unit of cyclo-AMP-dependent histone kinase of brain. It seems to compete with cyclo-AMP for the same proteins and is considered to be a regulator of intracellular cyclic nucleotides. NC has been shown to be combined to specific proteins in brain with non covalent bonds. A new cardiotrop hexapeptide has been shown to be present in bovine hypothalamus and its chemical structure has been found to be Tyr-Leu-Gly-Arg-Pro-Gly-amide. The acetylated form of this hexapeptide, which may be also present in brain, is much more active. The radioimmunochemical experiments carried out with antiserum 744 (from prof. Schally) by us have confirmed the existence of this hexapeptide and other fragments of LH-RH in the bovine hypothalamus. The effect of this hexapeptide on cardiac function and metabolism has been compared with a number of polypeptides (luliberin fragments). The hexapeptide has been shown to have not only cardiotropic but also a hypoglycaemic effect. It enhances the secretion of insulin and counteracts the inhibitory action of somatostatin on the insular apparatus. The hexapeptide produces significant changes in the activities of phosphorylase a and b as well as in that of phosphoprotein phosphatases. It reduces the amount of kinines in blood. Certain fractions of substance P, have been shown to have cardiotrop actitivty--they increase the rate of blood leaving the heart. The organotrop effects of a number of peptide neurohormones are discussed in connection with the hexapeptide. The results obtained have shown that the mechanisms underlying the effects of the cardioactive substances found by us are quite different. The data presented show that in brain a number of chemical factors (mainly peptides) are formed, which are involved in the regulation of heart function.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

[Breakdown of luliberin, somatostatin and substance P as an effect of hypothalamic endopeptidases].

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.

Animals↗
PubMed1978

[Specific hypothalamic proteins].

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.

Amino Acids↗
PubMed1977

[Inhibition of rat heart and brain cyclic adenosine-3',5'-monophosphate phosphodiesterase in vitro under the influence of neurohormone C].

The work was devoted to one of the new neurohormones (neurohormone "C") obtained from the bovine hypothalamus which produced a pronounced relaxation of the coronary vessels. A study of the effect of "C" on cyclic 3',5'-adenosine monophosphate (cAMP) phosphodiesterase (PDE) showed "C" to be a potent inhibitor of PDE in the crude PDE-preparations of the rat heart and brain. Experiments were carried out on the 2000 g supernatant obtained from the homogenized tissues. It is supposed that the relaxant effect of "C" on the coronary vessels is due to its inhibitory action on PDE mediated by the accumulated cAMP.

3',5'-Cyclic-AMP Phosphodiesterases↗