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Biomedical subjects

G I Chipens

Publications and source records attributed to G I Chipens.

At least 73 records · Page 4Linked to original sources
PubMed1976

[Potentiation of in vitro lipolytic effect of ACTH by its fragment].

The influence of fragment ACTH 11-14 analogues with amino acid sequences H-Lys-Pro-Val-Gly-OH (fragment I) and H-Lys-Pro-Val-Gly-NH2 (fragment II), possessing structural elements, similar for certain groups of peptide hormones and kinins, on lipolytic effect of ACTH in adipose tissue and isolated epydidymal fat cells of rat, was studied. Both fragments have no effect on the lipolysis; they potentiate the ACTH-induced lipolysis 1,5--2,0 fold, but do not alter the maximal effect at concentrations 0,1--1,0 mkg/ml in tissue and fragment I--at concentrations from 0,01 to 0,1 mkg/ml in isolated fat cell system. The role of "common" fragments in hormone-receptor interactions as well as mechanism of their potentiating effect is discussed. It is assumed that the "common" fragment of ACTH--ACTH11-14--is a second, non-specific active site of hormone directly involved in secondary signal formation.

Adipose Tissue↗
PubMed1976

[Use of specific angiotensin inhibitors in the study of hormone-receptor interaction].

The specificity of receptors participating in the interaction with angiotensin II (AT 1--8) fragments, e. g. N-terminal tri-(AT 1--3), C-terminal penta-(AT 4--8), and middle tetrapeptide (at 3--6), was studied in experiments on rat ascending colon which were performed to investigate the influence of a specific angiotensin antagonist, /1-hydantoic acid, 5-valine, 8-alanine/-angiotensin (HAAT 1--8), on myotropic effects of these fragments as well as the influence of the fragments on the myotropic activity of the whole hormone molecule. Competitive antagonism was found between HAAT 1--8 and AT 4--8 and AT 3--6 and between these fragments and AT 1--8. No antagonisma was revealed between AT 1--3 and HAAT 1--8, and between AT 1--3 and AT 1--8. It is assumed that the fragments AT 4--8 and AT 3--6 interact at the level of angiotensin receptors, and that of AT 1--3 at the level of non-specific receptors. A new model for the structural and functional organization of angiotensin is proposed.

Angiotensin II↗
PubMedDate not supplied

[A model of intra- and intermolecular interactions of peptide chains].

Results of attempts to determine the code of interaction of amino acids in peptide chains proceeding from their coding nucleotide sequences have been summarized. According to the model suggested the G/C and A/U complementarity of codon roots determines the mutual binding of coded amino acid residues. Structures of analogs of the immunoactive peptide, a fragment of IgG1 (336-370) EPQVY have been constructed on the basis of the model.

Amino Acid Sequence↗
PubMedDate not supplied

[Changes in the complex conditioned reflex activity of rat pups under the influence of penta-peptide].

Influence of YFRKD, modified fragment of interferon-alpha, on the formation of two-links system of feed-procuring conditioned reflexes was studied in rats in ontogenesis. The experiments have shown that YFRKD impedes both current learning and use of previous experience. The process of synthesis of two reflexes in united complicated functional complex is disturbed.

Animals↗
PubMedDate not supplied

[The evolution of the structures of amino acid families].

Natural amino acids possessing common antiamino acids are divided into groups and families according to the genetic code algorithm a-n-n-a (amino acid-codon-anticodon-antiamino acid). In an attempt to study structural evolution of amino acid families, artificial genetic code models were constructed. It is suggested that after inclusion of asparaginase and glutamine into the coding system, one of the two natural amino acid families is split into two parts ("half-families").

Algorithms↗
PubMedDate not supplied

[Asymmetry in the symmetric structure of the genetic code].

The genetic code is characterized by hidden symmetry. Amino acids possessing common antiamino acids are located symmetrically in the graphic models of the code. There is only one exception--apolar amino acids V, M, I, L and F are asymmetrically arranged. Asymmetric disposition of these amino acids is apparently due to divergence in the course of structural evolution of amino acid families as a result of inclusion of new members into the coding system.

Algorithms↗
PubMedDate not supplied

[The slowing of the extinction of a conditioned reaction and the antiamnesic action of arginine vasopressin and des-glycine-(8-arginine) vasopressin].

In the experiments on mice there were analysed the effects of arginine-vasopressin (AVP) and its analogue des-glycine-arginine-vasopressin (DG-AVP) on the extinction of the conditioned reaction of passive avoidance and the reproduction of memory trace in amnesia caused by detaining the animal in the dangerous section of the unit after electrocutaneous stimulation. An increase of resistance of the conditioned reaction to a sharp extinction at systemic administration of AVP and DG-AVP was shown.

Amnesia↗
PubMedDate not supplied

[Regrouping of peptide chains in molecules and molecular complexes: recognition and spatial conjugation codes of amino acids].

A two-step model for reactions between peptide and protein molecules in aqueous medium is considered. The first stage of the reaction involves specific recognition and primary complex formation. This process is governed by the amino acid interaction code a-a as a part of genetic code (algorithm a-n-n-a, amino acid-codon-anticodon-anti-amino acid). According to the a-a code, the primary complex formation is determined by amino acid pairs of opposite polarity. During the second stage of the reaction, when the contacting ligand and receptor surfaces undergo dehydration, the primary complex becomes rearranged. The new structure is mainly determined by pairwise contacts of amino acids having similar polarity and belonging to the same amino acid family.

Amino Acid Sequence↗
PubMedDate not supplied

[Polarity and hydropathic properties of natural amino acids].

A new classification of amino acids according to their polarity and symmetric location in the spatial structure of the genetic code is suggested. The polar amino acids are: R, S (codons AGC and AGU), K, N, Q, H, W, C, Y, G, E, D; apolar ones are: T, M, I, P, L, S (codons UCN). Polar and apolar amino acids are grouped into three families whose members possess complementarity with respect to the symmetric structure of the genetic code. Interaction of these complementary polar and apolar amino acids encodes formation of the space structures and ligand-receptor complexes of proteins. Correlation between the polar and hydropathic properties of amino acids is investigated. Normalization of 38 hydrophobicity scales of natural amino acids is carried out. A discrepancy between structures of polar/hydrophilic and apolar/hydrophobic groups of amino acids is demonstrated. According to the signature principle this discrepancy is due to different properties of amino acid side radicals which, in turn, depend on the second component of the reaction and on environmental conditions.

Amino Acids↗
PubMedDate not supplied

[The effect of modification of the carboxyl group in short D-arginine 2-containing enkephalin analogs on their affinity and selectivity for opiate receptors].

Radioreceptor binding assay using a membrane fraction from the rat brain was applied to study [D-Arg2, Leu5] enkephalin and two series of its analogues truncated at the C-terminus with a free or modified carboxyl group: tetra- and tripeptide amides and ethyl esters. The affinity to mu-specific opiate receptor subtype of the N-terminal [D-Arg2] tetrapeptide ethyl ester was 44 times as high as that of the tripeptide with a free carboxyl, and thus the ester retained up to 10% of leucine-enkephalin binding potency. However, a comparable esterification of the carboxyl group in the N-terminal [D-Arg2] tripeptide led to a 6-fold reduction in its affinity to mu-receptors. Consequently, identical modifications of the C-terminal carboxyl group in enkephalin analogues of various length can have completely different effects. Substitution of the natural glycine residue by D-arginine residue in position 2 of the enkephalin molecule truncated at the C-terminus increased the mu-receptor binding potency of the tetrapeptide, whereas its delta receptor binding potency declined by more than one order of magnitude. Simultaneous replacement of glycine2 by D-arginine2 and carboxyl amidation resulted in the short enkephalin analogue Tyr--D--Arg--Gly--Phe--NH2, whose affinity to mu receptors was four times as high as that of leucine--enkephalin, the tetrapeptide being 284 times more selective for the mu vs. delta opiate receptors.

Amino Acid Sequence↗
PubMedDate not supplied

[Non-classic effects of luliberin confirming the pleiotropy of neuropeptides].

The effects of synthetic neuropeptide LH-RH and its analogues were studied in experiments on 174 white male rats. The influence of the substances was shown on instrumental avoidance learning in Y-shaped maze. Convulsive and anticonvulsive effects of the preparations were studied on experimental model of corasol seizures. The analgetic effect of the substances was evaluated by behavioural pain reaction to electrical stimulation of the tail root. Analgetic, anticonvulsive, and psychostimulating LH-RH properties confirm polyfunctionality and "pleiotropy" of neuropeptides as a class of new endogenous informational compounds.

Analgesics↗
PubMedDate not supplied

[Origin and evolution of peptide-protein bioregulators].

Possible evolutionary pathways of cellular regulatory systems are discussed. Analysis of animal evolution suggests that peptide and protein bioregulators emerged at an early stage during formation of biochemical systems in prokaryotic cells involving protein synthesis on ribosomes, the processes of exo- and endocytosis and limited proteolysis reactions. Primary autocrine bioregulators are compared with growth factors. Models for cellular bioregulation are discussed in which both cell receptors and peptide/protein ligands, primarily immunoglobins, act as prehormones. Their internalization and limited proteolysis can lead to formation of low-molecular peptides (tetines) acting as autocrine or paracrine bioregulators. Basing on the concept of biochemical universality, it is suggested that the effects of many growth factors, hormones, immunoglobulins, mono- and lymphokins are mediated by identical or similar (carrying the same signatures) fragments which are produced in cells due to limited proteolysis reactions and which are directly involved in activation of biochemical systems in these cells.

Animals↗
PubMedDate not supplied

[Immunologically active peptides stimulating the T-cell system].

The known immunologically active peptides are compared from the standpoint of their chemical structure. Homologous potentially active fragments are determined. The revealed regularities in formation of peptides and active sites of proteins permit supposing that the process of peptide biogenesis from precursors involve the quasicyclization simultaneously with the limited proteolysis.

Adjuvants, Immunologic↗