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Biomedical subjects

G I Chipens

Publications and source records attributed to G I Chipens.

At least 55 records · Page 3Linked to original sources
PubMed1984

[Conformational aspects of the molecular mechanism of action of bradykinin. II. Conformation and selectivity of action of bradykinin cycloanalogs].

Conformation energy calculations performed for cyclo[(epsilon-lysine1, glycine6)]bradykinin and cyclo-epsilon-kallidin indicate the absence of spatially equivalent low-energy structures for bradykinin and cyclobradykinin molecules, whereas cyclokallidin has conformations similar to the "biologically active" ones for bradykinin that are implicated in binding to both B1 and B2 type receptors.

Animals↗
PubMed1983

[High-performance liquid chromatography of peptide bioregulators, their fragments and derivatives. I. Chromatographic pattern of corticotropin fragments of Zorbax ODS sorbent].

The influence of acetonitrile concentration in the eluent and of the peptide hydrophobicity on the capacity factors has been studied. The equation is proposed that describes retention as a function of the eluent characteristics and the peptide composition. The hydrophobicity increments for -COOH, -NH2, and greater than CHCONH-fragments in the studied chromatographic system have been determined. The proposed model of peptide retention is useful for a prior evaluation of the eluent composition that is necessary to elute a compound at a given capacity factor. It can be also used for the qualitative interpretation of peptide chromatograms.

Acetonitriles↗
PubMed1983

Cyclokinins.

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Animals↗
PubMed1982

[Immunochemical properties of C-modified analogs of angiotensin].

The interaction of angiotensin analogs modified at position 8 with specific antibodies has been studied. Modification of phenylalanine in the angiotensin molecule results in a decrease or disappearance of activity of the compounds tested. This allowed to develop a selective approach for determination of angiotensin antagonists in the blood.

Angiotensins↗
PubMed1981

Rigin, another phagocytosis-stimulating tetrapeptide isolated from human IgG. Confirmations of a hypothesis.

Structure-function and conformational studies of the molecule of phagocytosis-stimulating tetrapeptide tuftsin permitted the conclusion that among products resulting from splitting of H-chain of IgG Human EU by trypsin, besides tuftsin (sequence 289-292), tuftsin-like tetrapeptide Gly-Gln-Pro-Arg may be also present; theoretical conformational analysis shows a considerable similarity of spatial arrangement of this tetrapeptide and tuftsin which testifies in favour of potential tuftsin-like activity of the tetrapeptide. Gly-Gln-Pro-Arg was synthesized and its phagocytosis stimulating activity was found equal to that of tuftsin.

Amino Acid Sequence↗
PubMed1981

Cyclic analogue of bradykinin possessing selective and prolonged biological activity.

Cyclo-[(N epsilon 1-Lys1, Gly6)-bradykinin] and its deprotected non-cyclic precursor, PheGlyProPheArg LysProProGly, were synthesized using the conventional methods of peptide chemistry. Similar to bradykinin, the cyclopeptide elicits a depressor reaction in rats, as revealed by the experiments in vivo. Its duration of action, however, is greater by several orders of magnitude. At the same time, it appears to exhibit no myotropic activity when applied in vitro to extravasal smooth muscle preparations (uterus and ileum of the rat). The non-cyclic precursor lacks the depressor activity, but produces a slight myotropic effect (alpha = 0.6 +/- 0.09; pD2 = 5.9 +/- 0.17).

Animals↗
PubMed1980

[Effect of peptide hormone fragments and thyroliberin on mouse blood glucose homeostasis].

The comparative effects of thyroliberin (TRH), pentagastrin, C-terminal tripeptides of gastrin (MNF), luliberin (RPG) and its analog (RPF), oxytocin (PLG) and N-terminal tripeptide of angiotensin (NRV) on the glucose concentration in mouse blood, as well as the interrelationship between the peptides under study and insulin and somatostatin, were studied. It was found that all the peptides (except PLG) at doses 5, 50 and 100 mg/kg (intraperitoneally) exert a hypoglycemic effect comparable to that of insulin at the dose of 0,15 MU/kg (subcutaneously). The dose-dependent effect is observed only in the case of TRH. Somatostatin reverses the hypoglycemic action of TRH, MNF and NRV. TRH and RPF decrease the glucose-induced rise in insulin concentration measured by RIA. The structure-activity relationship and possibility of the formation of endogenous peptide hormone fragments as products of hormone molecules enzymatic cleavage and their glucoregulatory role are discussed.

Angiotensins↗
PubMed1979

Theoretical conformational analysis of oxytocin molecule.

The total semi-empirical conformational analysis of the oxytocin molecule has been carried out. It has been revealed the two main types of stable structures of cyclic moiety backbone and the great lability of the tail. The optimal spacing of cyclic moiety side chains has been found for every backbone structure. The calculation results are in good agreement with the data of physico-chemical investigations. Among the set of stable molecule structures reported in the present study are structures with beta-turn conformation of the cyclic moiety backbone and without closer spacing of the cyclic moiety and the tail, as well as structures with closely spaced N- and C-terminal parts which, however, lack beta-turn in the cyclic moiety.

Hydrogen Bonding↗
PubMed1978

[The antigen activity and structure of analogues and fragments of angiotensin, which contain enantiomeric forms of amino acids and aza-alpha'-homoamino acids].

The antigen activity of angiotensin, its fragments and analogues, which contain enantiomeric forms of amino acids and aza-alpha'-homoamino acids is studied by cross reactions with specific antibodies, obtained for angiotensin and its central tetrapeptide. It is found that the inclusion of additional NH-group between alpha carbon and carboxyl group of peptide chain, although in few cases radically changes spatial structure of compounds, does not deprivate their antigen activity. The replacement of NH-group to the C-end of the angiotensin molecule by affection the antigen determinant considerably decreases the antigen activity of the analogues. The important role in the determination of the antigen activity play the tyrosine residue and its specific orientation with respect to the antigen molecule. Low molecular weight fragments and analogues of the central part of angiotensin molecule, which have less "rigid" spatial structures, are capable to reorganize their spatial structure during interaction with antibodies.

Amino Acids↗
PubMed1977

[Structurally functional organization of corticotropin: lipolytic and steroidogenic activity of some of its fragments].

The influence of ACTH fragments, possessing structural elements, common for certain groups of peptide hormones and kinins--"common" fragments and cluster of basic amino-acids--(Lys 17,18-ACTH 11-18-NH2--I; ACTH 11-13-NH2--II; NH2CO-ACTH18-20-NH2--III) on lipolytic effect of ACTH in rat isolated fat cells and on the steroidogenic effect of ACTH in isolated rat adrenal cells was studied. Fragment I exerts a steroidogenic effect (alpha=0,84) at concentrations of 1--100 microng/ml. At low concentrations (10(-8)--10(-3) microng/ml) fragment I potentiates ACTH-induced steroidogenesis. Fragment I has no effect on the lipolysis;however, it potentiates ACTH-induced lipolysis at concentrations of 10--100 microng/ml. The results obtained support our previous supposition that "common" fragments are essential secondary non-specific active sites of hormones.

Adipose Tissue↗
PubMed1977

[Comparison of structural and functional organization of adrenocorticotropic hormone and wasp kinin].

A comparative study of structural and functional organization of the polypeptides -- ACTH and wasp kinin was made. The effects of fragments Lys 17, 18-ACTH11(-18)-NH2--(I) and WK4(-12)--(II), possessing "common" fragments and a cluster of basic amino-acids, on the lipolytic and steroidogenic effects of ACTH and myotropic effects of bradykinin were studied. Both fragments I and II potentiate ACTH-induced lipolysis and steroidogenesis in isolated rat fat and adrenal cells but suppress the myotropic effect of bradykinin on guinea pig ileum. The similarity of biological effects of ACTH and WK fragments support our supposition on the similarity in structurally functional organization of these peptides.

Adipose Tissue↗
PubMed1977

[Radioimmunoassay for the determination of angiotensin II and its fragments].

A radioimmunoassay procedure for the determination of angiotensin and its fragments: C-terminal hexapeptide and middle tetrapeptide has been developed. The sensitivity of the method reaches up to 5 ng/ml. The accuracy calculated from the standard deviation, for angiotensin and of its fragments presents the average +/- 1,5%; reproducibility (n = 10) is +/- 0,51% for angiotensin, +/- 2,12% for C-terminal hexapeptide and +/- 6,93% for the middle tetrapeptide. Using the Ouchterlony test with the cross-reactions showed that antibodies elicited to angiotensin interact with its fragments--middle tetrapeptide and C-terminal hexapeptide.

Angiotensin II↗
PubMed1977

[Antigenic activity of angiotensin II and its fragments].

The antigenic activity of angiotensin and its seven fragments has been studied in cross-reaction with specific antibodies, elicited to angiotensin and its fragments: C-terminal hexapeptide and middle tetrapeptide. It has been found that all the fragments studied possess certain affinity for antibodies elicited to angiotensin, C-terminal hexapeptide and middle tetrapeptide. The middle tetrapeptide was identified to be the immunologically active centre of the angiotensin molecule.

Angiotensin II↗
PubMed1976

[Potentiation of ACTH action by a fragment of it: a decrease in the rat adrenal ascorbic acid concentration in vivo].

The effect of tripeptide NH2CO-Arg-Pro-Val-NH2, the analogue of common fragments of some peptide hormones and kinins, on the content of ascorbic acid in rat adrenal glands in vivo is studied. It is shown that the peptide (5 divided by 3000 mkg/100 g body weight) produces no effect on the content of ascorbic acid in adrenal glands, but its injection half an hour before the administration of native ACTH canses a significant increase in the ACTH activity. The peptide possesses the myotropic activity; it exerts sinergism and potentiation of the ACTH action on rat ascending colon.

Adrenal Glands↗