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Biomedical subjects

V V Adler

Publications and source records attributed to V V Adler.

At least 19 recordsLinked to original sources
PubMed1990

A novel sequence-specific DNA binding protein which interacts with three regularly spaced direct repeats of the CCCTC-motif in the 5'-flanking sequence of the chicken c-myc gene.

The chicken c-myc 5'-flanking sequence has previously been shown to bind multiple proteins present in undifferentiated and differentiated red blood cells. In this report the protein binding to one specific region within a hypersensitive site approximately 200 base pairs upstream of the start of transcription has been analysed in detail. Using a combination of a modified agarose gel retardation assay with O-phenanthroline-copper footprinting in situ, missing contact point and methylation interference techniques, two proteins were found to bind to overlapping sequences within 180-230 bp upstream of the start of transcription. One protein resembles the transcription factor Sp1, the other is a protein which binds to three regularly spaced repeats of the core sequence CCCTC. This CCCTC-binding factor was termed CTCF. It requires additional sequences outside the three recognition motifs for tight binding. CTCF was purified to near homogeneity by sequence-specific DNA chromatography. The approximate molecular weight of the CTCF was estimated to be 130,000. Removal of 110 bp sequence binding both CTCF and Sp1-like proteins leads to a 4 to 8-fold increase in transcription of stably transfected c-myc fusion constructs in chicken embryonic fibroblasts, suggesting that the CTCF is likely to be one of multiple nuclear factors involved in the transcriptional regulation of the chicken c-myc gene.

Animals↗
PubMed1990

[Regulation of proliferative and protein-synthesizing reactions in human peripheral blood lymphocytes by glucocorticoids].

Glucocorticoids control protein synthesis and [3H]thymidine incorporation into DNA in resting and mitogen-stimulated in vitro human peripheral blood lymphocytes. This effect depends on the dose and time of hormone addition to the culture medium. Using two-dimensional electrophoresis, it was demonstrated that the steroids can regulate the expression of various proteins in intact and mitogen-stimulated human peripheral blood lymphocytes. This is suggestive of a dynamic control by glucocorticoids of the synthesized protein transcription during the cell cycle of a given population. These results also indicate that such a dynamic control is not due to the fluctuations in the number of receptor macromolecules, the presence or absence of the acceptor site on the DNA but, rather, to the modulation of the biological activity of specific nuclear factors capable of regulating the transcription of definite genes.

Cells, Cultured↗
PubMed1989

A liver-specific nuclear protein that binds to the distal promoter element of the rat tyrosine aminotransferase gene.

Using a gel retardation assay and exonuclease III footprinting, we have analyzed sequence-specific DNA-binding nuclear factors which interact with the distal promoter element of the rat tyrosine aminotransferase gene. A factor called LspA1, binding to a sequence that resembles the consensus binding site for the transcription factor Ap-1, was shown to be present in adult rat-liver nuclear protein extracts but not in the extracts from embryonic liver or spleen nuclei.

Animals↗
PubMed1989

[Inhibition of proliferation of normal and neoplastic liver cells under conditions of prolonged hormonal stimulation].

Single injections of rats with hydrocortisone led to the inhibition of regenerating liver cell proliferation and protooncogene++ Ha-ras mRNA synthesis within 48 hours of hormonal induction. Administration of hydrocortisone to rats daily for 10 days resulted in a persistent decrease of the liver cell capacity to proliferate in response to partial hepatectomy. This inhibiting effect was observed for at least 7 days after cessation of hormonal stimulation; the level of Ha-ras mRNA was thereby decreased. A marked inhibition of ascite hepatoma cell growth was demonstrated after injections of those cells to mice induced with hydrocortisone for 10 days. Such a persistent effect of hydrocortisone is thought to be due to the depletion of the hormone-dependent hepatotrophic factors. The effect of the glucocorticoid hormone in vivo can be supposed to involve both the direct and indirect regulation of target cell proliferation. The latter is mediated via the changes in the activity of exogenous factors which control cell growth and proliferation.

Animals↗
PubMed1987

[Autogenic regulation of the sensitivity of liver cells to glucocorticoids during prolonged hormonal stimulation].

The mechanisms of reversible decrease of hormone-dependent induction of tyrosine aminotransferase (TAT) by rat liver cells after prolonged administration of the glucocorticoid was studied. It was shown that the main links of the glucocorticoid action mechanism (i.e., the formation of a cytoplasmic hormone-receptor complex and the hormone accumulation in the nuclei) do not change under these conditions. It was found also that one of the necessary prerequisites for the decrease of the hormone-dependent induction of TAT is the constant production by liver cells of large amounts of TAT irrespective of whether this process is induced by the glucocorticoid or by a non-hormonal inducer, e.g., tryptophan. Using the dot-hybridization technique, it was demonstrated that the inhibition of hormone-dependent induction of TAT is correlated with the reduction of mRNA TAT. It was supposed that the main links in the mechanism of inhibition of the hormone-dependent induction are the formation of a large excess of the inducible protein--TAT--in the cells as well as the accumulation of end products of the TAT-catalyzed transamination reaction which cause a feed-back repression of the de novo synthesis of TAT. Studies with cell cultures of Morris hepatoma which is known to be sensitive to glucocorticoids revealed the ability of glucose, the end product of gluconeogenesis reactions, to provide for selective inhibition of the hormone-induced accumulation of mRNA TAT in hepatoma cells.

Adrenalectomy↗
PubMed1987

[Effect of glucocorticoid hormones on DNA synthesis and expression of ras proto-oncogenes in proliferating rat liver cells].

A single injection of partially hepatectomized rats with glucocorticoids results in the blocking of DNA synthesis as well as in the inhibition of the protooncogene Ha-ras-1 mRNA accumulation in proliferating rat liver cells. The kinetics of the both hormone-induced effects differ from those observed for tyrosine aminotransferase induction. The effect of glucocorticoids persists for at least 48 hours and does not depend on the time of the hormone injection.

Animals↗
PubMed1987

[Glucocorticoid-mediated degradation of DNA in thymocytes of rats with transplantable Zajdela ascites hepatoma].

Tumour growth was shown to be associated with DNA breakdown in thymocytes of rats bearing Zajdela ascites hepatomas. The tumour action on the thymus is mediated through adrenal glands since bilateral adrenalectomy completely prevents DNA breakdown in thymocytes. Using Southern hybridization of DNA genome with probes for histone, ribosomal and heat shock gene (hsp 70), it was shown that the degradation products of specific DNA sequences are as heterogenous as those of total DNA, although marked differences in appearance of nucleosomal ladder were seen. These data were interpreted to indicate different patterns of DNA breakdown in dying thymocytes. DNA breakdown in thymocytes in vivo and in isolated rat liver nuclei in vitro seems to proceed by similar mechanisms.

Animals↗
PubMed1985

[Hormonal induction of tyrosine aminotransferase and RNA synthesis in the cells of Morris hepatoma strain 7777].

The transfer of Morris hepatoma cells induced by the hormone within 10-60 min in to a hormone-free medium is associated with the augmentation of tyrosine aminotransferase synthesis. The kinetics of this process does not differ from that of the hormone-induced enzyme. The return of tyrosine aminotransferase synthesis to the basal level occurs 15-20 hours after the hormone withdrawal from the medium, although the concentration of the intranuclear hormone sharply decreases already after 3 hours. It was demonstrated that the presence in the hepatoma cell nuclei of 20-25% of the initially bound hormone for at least 20 hours after the cell transfer to the hormone-free medium is not sufficient for maintaining a high level of tyrosine aminotransferase gene expression. Using two-dimensional electrophoresis of 3H-labeled hepatoma cell proteins, it was demonstrated that the observed high activity of tyrosine aminotransferase is due to the de novo synthesis of enzyme molecules rather than to the existence of preformed long-living tyrosine aminotransferase molecules inside the cell. Study of [14C]uridine incorporation into non-ribosomal nuclear RNA of hepatoma cells showed a long-term presence of the label in the RNA throughout the chase experiment. It was assumed that the high activity of the enzyme for 10-15 hours after the hormone release from the hepatoma cell nuclei is due to the accumulation in the nuclei of long-living pre-mRNA molecules synthesized after the hormone addition to the cells and during the first hours after the cell transfer to the hormone-free medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Interaction of triamcinolone acetonide with Morris hepatoma cells in the presence antibiotics--inhibitors of RNA synthesis].

Some regularities of [3H]triamcinolone acetonide (TA)binding to glucocorticoid-sensitive Morris hepatoma cell nuclei were studied. It was shown that part of the hormone incorporated into the nuclei form highly stable complexes with nuclear structures that are not destroyed during nuclei lysis with 0.25% SDS. Such complex formation is not practically suppressed by a 500-fold excess of non-labeled TA. As the time of incubation of Morris hepatoma cells with the hormone rises from 10 min to 24 hours, the specific binding of TA to the nuclei decreases, while the specific radioactivity of the [3H]TA-nuclei complexes resistant to 0.25% SDS increases. The stable complexes are eluted from Sepharose 6B together with the bulk of the nuclear proteins and do not contain DNA. Actinomycin D extrudes, to some extent, the [3H]TA from the complexes having specific binding sites that are localized in the nuclei and induces the accumulation of the steroid in the firmly bound nuclear complexes resistant to 0.25% SDS. The ability to suppress hormonal induction of tyrosine aminotransferase was detected only in the antibiotics with a high affinity for the GC-pairs of DNA. i.e., actinomycin D and mitramycin. It was assumed that high concentrations of TA specifically bound to the nuclei are necessary only at initial steps of hormonal induction. At later stages, gradual dissociation of the complexes takes place and the hormone is accumulation within the composition of the SDS-resistant firmly bound complexes.

Animals↗
PubMed1983

[Stages of the interaction of steroid hormones with intranuclear acceptor sites of Morris hepatoma cells].

The maximal amount of specifically bound triamsinolone acetonide (TA) penetrates into Morris hepatoma cells at initial steps of hormonal induction. This amount is gradually decreased during incubation of the cells with the hormone. As the incubation time rises, the inhibition of [3H]TA binding to the nuclear fraction induced by an excess of the non-labelled hormone is further decreased, which is paralleled with deceleration of the [3H]TA efflux from the nuclei to a hormone-free medium. After removal of the hormone the cells retain their ability to induce the synthesis of tyrosine aminotransferase for 10 hours, although after 3 hours the amount of the bound hormone falls down to 20-25% of the original level. The rate of further deinduction of tyrosine aminotransferase synthesis depends on the incubation time, i.e. in the cells preincubated with TA for 10 min the deinduction occurs at a slower rate than in the cells preincubated with the hormone for 48 hours. The increase in the amount of specifically bound TA 10 min after hormone addition leads to augmented synthesis of tyrosine aminotransferase which surpasses the synthesis providing for the maintenance of maximal induction. An addition of actinomycin D to a hormone-free medium containing the cells preincubated with TA for 48 hours prevents the deinduction. It is assumed that Morris hepatoma cells contain an actinomycin D-sensitive feed-back mechanism which controls the concentration and distribution of specifically bound intranuclear TA depending on hormonal response.

Animals↗
PubMed1983

[Biochemical criteria of mammalian cell sensitivity to glucocorticoids].

The resistance of Morris hepatoma cells strain 8994 to glucocorticoids which lack hormonal induction of tyrosine aminotransferase synthesis was studied. The cells of Morris hepatoma 7777 were used as a sensitive strain by a criterion of the enzyme synthesis. Using two-dimensional polyacrylamide gel electrophoresis, it was demonstrated that, i) in the cells of the "resistant" Morris hepatoma strain 8994 glucocorticoids change the rate of synthesis of at least five proteins, ii) two of these proteins are common for both cell strains, while the other ones are individual for each line, iii) in the cells of Morris hepatoma 8994 tyrosine aminotransferase is not controlled by glucocorticoids, iiii) glucocorticoids may not only control the activated genes but also the genes whose expression is suppressed. It was assumed that in the absence of disturbances in the receptor apparatus the resistance of any cell population to glucocorticoids can only be established by the use of a great variety of experimental approaches. The resistance of a cell population to the hormones cannot be judged upon by an analysis of the intensity of synthesis of one or even several proteins.

Animals↗
PubMed1983

[Aminomethylol compounds inhibit the initiation of RNA chain synthesis beginning with adenylic nucleotides].

It was found that the previously established inhibition of DNA transcription in vitro caused by aminomethylol compounds depends on the suppression of the RNA chains initiation beginning with adenylic but not with guanylic acid. The RNA polymerase binding to DNA is not impaired thereby; the enzyme affinity for the binding sites and RNA elongation also remain unaffected. A comparison of aminomethylol compounds with other alkylating agents demonstrated that the former are the only known alkylating compounds which specifically influence the initiation step. The nature of DNA structural changes (initiation inhibition) caused by aminomethylol compounds is discussed.

Adenine Nucleotides↗
PubMed1983

[Kinetics of the development of the glucocorticoid effect on the thymus in adrenalectomized rats].

It was shown that the kinetics of distribution of cortisol and the synthetic glucocorticoid triamcinolone acetonide in the subcellular fractions of rat thymus after a single injection of subphysiological doses of the hormones is identical. Extraction of the nuclear fraction by 0.4 and 2 M NaCl did not reveal any differences in the mode of the hormone interactions with the nuclear acceptor sites. A single injection of triamcinolone acetonide resulted in inhibition of the precursor incorporation into DNA after 8 hours. This effect was dependent on the type and concentration of the precursor as well as on the steroid dose. The inhibiting effect of glucocorticoids is a specific one; progesterone injected under identical conditions did not affect the precursor incorporation into DNA. The inhibition of thymidine incorporation into DNA was paralleled with a drop in the thymidine kinase activity in thymus cytosol. The inhibiting effect of triamcinolone acetonide on thymidine incorporation into thymus DNA is not due to the changes in the trapping and intracellular pool of thymidine phosphates.

Adrenalectomy↗
PubMed1983

[Possible reasons for decrease in the proliferating activity of the rat thymus after a single injection of glucocorticoids].

A single injection of triamcinolone-acetonide evoked multiple changes in adrenectomized rat thymuses, e.g. decrease of DNA polymerase and thymidine kinase activities, incorporation of [3H]thymidine into DNA and fragmentation of chromatin. The decrease of proliferating activity of thymus was preceded by inactivation of cytoplasmic DNA polymerase responsible for DNA replication. Fragmentation of DNA caused by double strand ruptures at the linkage sites affected primarily the non-proliferating thymocytes. Incubation of nuclei isolated from the thymuses of control and hormone-treated animals in Ca2+ and Mg2+-containing media increased the level of low molecular weight compounds in them. It was assumed that the inhibiting action of triamcinolone-acetonide on cytoplasmic DNA polymerase prevents the involvement of proliferating thymocyte subpopulation in a new generation cycle and provides for their terminal differentiation and decay, eventually resulting in fragmentation of DNA.

Adrenalectomy↗