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Biomedical subjects

V S Shapot

Publications and source records attributed to V S Shapot.

At least 55 records · Page 3Linked to original sources
PubMed1983

[Tumor-induced hypoglycemia and bioelectric activity of the brain in cancer patients].

Changes in bioelectric activity of the brain were observed in 56 patients with disseminated breast cancer which pointed to the activation of the hypothalamus. Hyperglycemia, with blood-sugar levels being 4-6 times the basal normal one, was induced in 16 patients by a single injection of glucose. As a result, a 50-80% transient improvement in electroencephalographic indexes was obtained, hypothalamic excitation subsiding and optimal indexes matching peaks of hyperglycemia. It is concluded that the said changes in the bioelectric activity of the brain in cancer patients are largely of compensatory nature and should be regarded as a response to tumor-induced hypoglycemia.

Adult↗
PubMed1982

Rearrangements of DNA-protein interactions in animal cells coupled with cellular growth-quiescence transitions.

Overall DNA-protein interactions in animal cells undergo drastic changes coupled with cellular transitions from quiescence to growth and reversely as revealed by nucleoprotein-Celite chromatography. DNA of chromatin was found to exist in one of the two sharply distinct alternative forms, namely, either tightly or weakly bound to protein moiety. These forms are specific for cycling and quiescent cells, respectively. The tight DNA-protein interactions characterize all cycling cells independent of the cell cycle phase. Transition of DNA of cycling cells from one form to another was observed as a result of treatment of isolated nuclei with DNase I.

Animals↗
PubMed1982

Thiamine metabolism in the liver of mice with Ehrlich ascites carcinoma.

Thiamine pyrophosphate (TPP) content, activities of thiamine pyrophosphokinase (TPKase), thiamine pyrophosphatase, transketolase (TK), pyruvate (PDG) and oxoglutarate dehydrogenases (OGDG) were measured in the liver and cells of Ehrlich ascites carcinoma (EAC) on the 5th, 10th and 15th day after transplantation of the tumor to mice fed a thiamine-deficient diet. The TPP level gradually decreased in the liver of tumor-bearing mice but remained constant in tumor cells (1.06 +/- 0.02 microgram/g tissue). Deprivation of dietary thiamine lowered the liver TPP level even to a greater extent, and subsequent daily 10 micrograms thiamine/mouse injections did not restore it. The TPKase activity in the liver of mice with EAC decreased by 24% and in thiamine deficiency, by 44%. The liver PDG, OGDG and TK activities were reduced but slightly in mice with EAC, whereas thiamine deprivation resulted in a decrease of the enzyme activities: PDG by 60%, OGDG by 25% and TK by 45%. TK activity in tumor cells was 90 mumol S-7-P/g tissue/h, and the TPP effect amounted to 24%. Thiamine deprivation decreased the TK activity by 45% and raised the TPP effect up to 180%. Thiamine injections restored the TK activity in tumor cells and reduced the TPP effect.

Animals↗
PubMed1982

[Proteins and the functional properties of the chromatin fractions from the nuclei of the normal liver and of experimental hepatomas].

Chromatin fragments generated in normal liver and solid hepatoma nuclei due to the action of endogenous nucleases and in ascites hepatomas nuclei treated with micrococcal nuclease differ in the ability to be released from the nuclei into a medium of low ionic strength. It is suggested that such a fractionation is based on different solubility of DNP fragments attached to the nuclear skeleton and of those that are not bound with it. DNP fragments extracted in a low-salt buffer contain all five histones with a negligible admixture of nonhistone proteins having the protein/DNA ratio about 1.1. No endogenous RNA-polymerase activity could be detected in these DNP fragments. The bulk of the RNA-polymerase activity is found in the matrix-associated DNP fragments that appear to be enriched in nonhistone proteins (their protein/DNA ratio amounted to 2.5). The possibility that transcribable DNP fragments are associated with the matrix through low-salt-stable linkages like those in the DNA-(RNA-polymerase-RNA or RNP)-matrix seems to be confirmed by the data obtained.

Animals↗
PubMed1982

[Early changes in template DNA structure following glucocorticoid injection].

The structure of chromatin is changed at early stages of glucocorticoid hormone interaction with rat hepatocytes. These changes consist in: a) increase of actidine orange binding in rate liver nuclei after injection of the hormone; b) decrease of the number of sites in chromatin which are sensitive to nuclease S1; c) inhibition of the nuclei capacity for DNA synthesis in the presence of E. coli DNA polymerase and d) increase of molecular weight of DNA fragments. The data obtained suggest that at early stages of hormonal induction part of template DNA ruptures is reconstituted, which can result in an increase of DNA molecular weights and changes in chromatin superstructure and the template properties of the protein.

Animals↗
PubMed1982

[DNA-protein interactions in HeLa cells at different phases of the mitotic cycle and in the resting state].

The tight association between DNA and protein in chromatin is characteristic of HeLa cells in all stages of the cell cycle as revealed by nucleoprotein-celite-chromatography. The complex can be dissociated only by 4 M LiCl and 8 M urea at 90 degrees C (form II). The arrest in G1, S and mitosis did not induce any changes in DNA-protein interactions, chromatin remained in form II. Transition of the cells into quiescence induced by medium exhaustion or by serum deprivation was coupled with weakening of DNA-protein bonds. A significant part of DNA was released from the complex with protein by 1.5 M LiCl, 8 M urea at 2-4 degrees C (form I). Simultaneously with form I appearance the increase of DNA one-strand breaks was observed. The qualitative differences in the DNA-protein interactions of chromatin between cycling and quiescent cells evidence the existence of alternative to the cell cycle stage of cell quiescence--Go-phase.

Cell Division↗
PubMed1981

[Interaction of SV40 T-antigen with homologous and heterologous DNA].

Using the DNA filter binding assay, the effects of ionic strength and pH on SV40 T-antigen interaction with viral DNA were studied. The apparent association constants for T-antigen binding to SV40 DNA in Scatchard coordinates in the presence of 40 mM NaCl are equal to 0.67 . 10(6) M-1 (pH 6.0) and 0.86 x 10(7) M-1 (pH 7.4). These data indicate that the interaction between T-antigen and SV40 DNA is more specific at pH 7.4. The coincident values of association constants for T-antigen binding to viral and cellular DNAs (Ka = 0.9 x 10(7) M-1 for cellular DNA) at pH 7.4 and the absence of competition between the two DNA species upon binding with T-antigen suggest that viral and cellular DNAs possess similar sites for T-antigen binding. Denatured DNA competes with viral DNA only at pH 6.0, when the T-antigen--SV40 DNA interaction is less specific.

Antigen-Antibody Complex↗
PubMed1981

[Morphologic and biochemical changes in the lymphoid and hematopoietic tissues of rats with Zajdela hepatoma].

The growth of allogeneic ascites hepatoma is accompanied by involution of the thymus, leukemoid response and anemia. Tumor cells disseminate throughout the body appearing in many organs including the spleen, liver, bone marrow and lymph nodes. The activity of adenosine deaminase and the adenosine deaminase/purine nucleosidephosphorylase ratio decrease in the host thymus as well as in the cellular elements of the spleen. The above phenomena reflect the impairment of lymphocyte differentiation and presumably contribute to the decreased efficiency of the host immune response.

Adenosine Deaminase↗
PubMed1981

[Genetic aspects of neoplasia].

The aggregation of cancer in families, possible causes of tissue specificity of hereditary susceptibility to cancer, as well as various kinds of inherited enzyme disorders regarded as the basis of this susceptibility are discussed. Different aspects of the relationship between cell neoplastic transformation and differentiation are analysed. Special attention is given to the capacity of differentiation inducers to reverse in some instances the malignant phenotype of the tumor cell progeny. In addition, some data are cited that indicate instability of DNA molecule in neoplastic cell transformation, differentiation and hormone action.

Animals↗
PubMed1980

[Chromatin fractionation according to the strength of its matrix bond].

Extraction in low salt concentration followed by centrifugation allows rat liver nuclear chromatin to be divided into two fractions: the supernatant chromatin and matrix chromatin. The former fraction contains about 60-70% of initial DNA and about 15% of initial protein along with all five histones, and an insignificant amount of non-histone proteins. RNA synthesis in the matrix chromatin fraction is 2-3 times more intense than that in the original nuclei. The data on gradient centrifugation do not suggest the elongation of RNA molecules synthesized in the matrix fraction. The results obtained as compared with the literature data suggest that the matrix chromatin fraction is enriched with active genes.

Animals↗
PubMed1980

[Existence of a form of SV40 T antigen incapable of interacting with DNA].

The interaction of SV40 T-antigen and viral DNA was studied by using adsorption of DNA-protein complexes on nitrocellulose filters. The T-antigen purification procedure included ion-exchange chromatography on DEAE-cellulose, selective adsorption of cellular proteins on single-stranded DNA-cellulose, chromatography on heparin-Sepharose and removal of cell proteins by an immunosorbent. Only the latter step allowed to remove the contamination of cellular DNA-binding proteins, judging from the reaction of T-antigen neutralization by specific antibodies. It was shown that T-antigen and cellular DNA-binding proteins interact with SV40 DNA at different values of pH, namely ah 6,0-6,4 and 7,9, respectively. The T-antigen obtained was passed through a column with native DNA-cellulose at pH and ionic strength values optimal for interaction with DNA. The bulk of T-antigen (30-40%) did not bind to native thymus DNA and did not interact with SV40 DNA. It is assumed that this fraction is a form of T-antigen, which undergoes structural or functional changes during specific interaction with viral or cellular DNAs.

Animals↗