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Biomedical subjects

M R Rao

Publications and source records attributed to M R Rao.

At least 145 records · Page 8Linked to original sources
PubMed1988

Interaction of rat testis protein, TP, with nucleosome core particle.

Circular dichroism studies have revealed that addition of testis specific protein, TP in vitro, to rat testes nucleosome core particle resulted in a decrease in the compaction of the core particle DNA. This was also corroborated by thermal denaturation analysis. Addition of TP to nucleosome core particle resulted in the conversion of a biphasic transition towards a single phase. However, at the same time there was a 20% reduction in the overall hyperchromicity of core particle DNA at core particle to TP molar ratios of 1:2 and 1:3. These observations along with our earlier report, showing the DNA melting properties of TP, suggest that TP may play an important role in the disassembly process of nucleosome core particle during spermiogenesis.

Animals↗
PubMed1987

Identification of a meiotic prophase-specific nuclear matrix protein in the rat.

We have identified a 110-kDa pI 5.6 phosphoprotein with DNA binding properties in the rat pachytene spermatocyte nuclear matrix. By immunoblotting and indirect immunofluorescence assays using polyclonal antibodies against the 110-kDa protein, we observed that it was germ cell nuclear matrix specific, more prominent in pachytene spermatocytes compared to premeiotic spermatogonia or postmeiotic round spermatids, and present in rat oocytes and in germ cells of mouse and monkey. We propose that this protein could play an important role in the meiotic process.

Animals↗
PubMed1987

DNase I site mapping and micrococcal nuclease digestion of pachytene chromatin reveal novel structural features.

A comparison of the DNase I digestion products of the 32P-5'-end-labeled pachytene nucleosome core particles (containing histones H2A, TH2A, X2, H2B, TH2B, H3, and H4) and liver nucleosome core particles (containing somatic histones H2A, H2B, H3, and H4) revealed that the cleavage sites that are 30, 40, and 110 nucleotides away from the 5'-end are significantly more accessible in the pachytene core particles than in the liver core particles. These cleavage sites correspond to the region wherein H2B interacts with the nucleosome core DNA. These results, therefore, suggest that the histone-DNA interaction at these sites in the pachytene core particles is weaker, possibly because of the presence of the histone variant TH2B interacting at similar topological positions in the nucleosome core as that of its somatic counterpart H2B. Such a loosened structure may also be maintained even in the native pachytene chromatin since micrococcal nuclease digestion of pachytene nuclei resulted in a higher ratio of subnucleosomes (SN4 + SN7) to mononucleosomes than that observed in liver chromatin.

Animals↗
PubMed1987

Interaction of rat testis protein, TP, with nucleic acids in vitro. Fluorescence quenching, UV absorption, and thermal denaturation studies.

The nucleic acid binding properties of the testis protein, TP, were studied with the help of physical techniques, namely, fluorescence quenching, UV difference absorption spectroscopy, and thermal melting. Results of quenching of tyrosine fluorescence of TP upon its binding to double-stranded and denatured rat liver nucleosome core DNA and poly(rA) suggest that the tyrosine residues of TP interact/intercalate with the bases of these nucleic acids. From the fluorescence quenching data, obtained at 50 mM NaCl concentration, the apparent association constants for binding of TP to native and denatured DNA and poly(rA) were calculated to be 4.4 X 10(3) M-1, 2.86 X 10(4) M-1, and 8.5 X 10(4) M-1, respectively. UV difference absorption spectra upon TP binding to poly(rA) and rat liver core DNA showed a TP-induced hyperchromicity at 260 nm which is suggestive of local melting of poly(rA) and DNA. The results from thermal melting studies of binding of TP to calf thymus DNA at 1 mM NaCl as well as 50 mM NaCl showed that although at 1 mM NaCl TP brings about a slight stabilization of the DNA against thermal melting, a destabilization of the DNA was observed at 50 mM NaCl. From these results it is concluded that TP, having a higher affinity for single-stranded nucleic acids, destabilizes double-stranded DNA, thus behaving like a DNA-melting protein.

Amino Acid Sequence↗
PubMed1986

Androgen binding protein levels and FSH binding to testicular membranes in vitamin A deficient rats and during subsequent replenishment with vitamin A.

ABP levels in the testes and epididymides of vitamin A deficient-retinoic acid maintained rats were only 20 and 6% respectively as compared with those in normal rats. The number of FSH receptors in the testes of vitamin A deficient rats, as measured by [125I]ovine FSH binding to isolated testicular membranes, was only 40% of that in the testes of normal rats. Supplementation of retinyl acetate to these vitamin A deficient rats for 16 days resulted in restoration of the number of FSH receptors to normal levels. On the other hand, ABP levels were restored to 32 and 34% only in the testes and epididymides respectively.

Androgen-Binding Protein↗
PubMed1986

Relaxin increases calcium efflux from rat myometrial cells in culture.

Relaxin and isoproterenol treatment rapidly increased 45Ca2+ efflux from mature rat myometrial cells in culture in a time- and concentration-dependent manner. This effect on Ca2+ efflux was specific for myometrial cells and was not observed in stromal cells isolated from the same uteri. This rapidly exchangeable Ca2+ may be mobilized from a loosely bound peripheral Ca2+ pool in myometrial cells. Relaxin may promote uterine relaxation in part by affecting Ca2+ dynamics in the myometrium.

Animals↗
PubMed1985

Testis-specific histone H1t is antigenically distinct among H1 subtypes.

Histone H1t has been purified from rat testes and antibodies were elicited in rabbits. Immunoblotting studies with anti-histone H1t-IgG have shown that it reacted specifically with histone H1t but not with other histone H1 subtypes, namely H1a, -b, -c, -d, -e and H10. The anti-histone H1t-IgG also did not react with chicken erythrocyte histone H5. Immunoblotting studies have also revealed that the polyclonal anti-histone H1t-IgG reacted with (a) two polypeptide fragments, NBS-N and NBS-C, derived from N-bromosuccinimide cleavage of histone H1t, (b) two polypeptide fragments, CT-N and CT-C, derived from alpha-chymotrypsin cleavage of histone H1t, and (c) GH1t, globular domain of histone H1t obtained after trypsin cleavage. The indirect immunofluorescence studies on nuclei isolated from adult rat testes with anti-histone H1t-IgG showed that the fluorescence, particularly, of the pachytene nucleus was the brightest. On the other hand, anti-histone H1t-IgG did not stain nuclei from either liver or nuclei isolated from the testes of 10-day-old rats.

Animals↗
PubMed1984

Effect of vitamin A deprivation on the mitogenic factor activity in the rat testes.

The seminiferous tubules of rat testes contain a protease and heat sensitive factor capable of stimulating (3H)-thymidine incorporation into quiescent cultures of NIH 3T3 mouse fibroblast cells. This mitogenic factor activity was only 4% in the testes of vitamin A deficient-retinoic acid maintained rats as compared to that of normal rats. Supplementation of retinyl acetate to these vitamin A deficient rats for 4 days resulted in a 56% recovery in the mitogenic factor activity while by day 16, the recovery was 80 percent. Incorporation of (3H)-thymidine into DNA of the seminiferous tubules of vitamin A deficient rats was only 46% of that of normal rats which was restored to normal levels by retinyl acetate supplementation for 24 days.

Animals↗
PubMed1984

Purification and partial characterization of a 19kD/pI 4.5 nucleolar phosphoprotein.

Two-dimensional PAGE analysis of proteins associated with the slowly sedimenting "fibrillar" structures of HeLa nucleoli revealed a protein with a M of 19,000 and a pI of 4.5 which was highly labeled both with 32P-orthophosphate and 35S-methionine. The protein was isolated from Novikoff hepatoma nucleoli by extraction in 0.35 M NaCl and 5 mM DTT followed by chromatography in EDTA on DEAE-cellulose and Sephadex G-100. The protein was homogeneous with respect to two-dimensional PAGE, number of tryptic peptides and carboxyl terminal analysis. The protein contained an acidic/basic amino acid ratio of 2.1, 7 residues of methionine, 2 residues of cysteine, a blocked amino terminus and a carboxyl terminal lysylleucine.

Amino Acids↗
PubMed1984

Effect of treatment with different doses of bromocriptine on plasma profiles of prolactin, gonadotrophins and testosterone in mature male rats and mice.

The influence of different doses of bromocriptine (CB-154) on plasma levels of prolactin (Prl), FSH, LH and testosterone (T) in mature male rats and mice was studied. Daily subcutaneous administration of 360 micrograms of CB-154 in sesame oil was sufficient to induce maximal suppression of plasma Prl levels in mature male rats whilst subcutaneous implantation of two pellets of CB-154 and cholesterol, each containing approximately 6 mg CB-154, was effective in suppressing serum Prl levels in mature rats for at least four weeks. This was accompanied by a significant elevation of plasma levels of LH and FSH. A similar dose-response study in mature male mice suggested that relatively higher doses of CB-154 are required to suppress plasma levels of Prl in this species, although large doses of CB-154 can still increase plasma levels of gonadotrophins and T in male mice.

Animals↗
PubMed1983

Structural organization of the meiotic prophase chromatin in the rat testis.

Pachytene nuclei were isolated from rat testes by the unit gravity sedimentation technique and contained histone variants H1a, H1t, TH2A, TH2B, and X2 in addition to the somatic histones H1bde, H1c, H2A, H2B, H3, and H4. The basic organization of the pachytene chromatin namely the nucleosome repeat length and the accessibility to micrococcal nuclease, was similar to that of rat liver interphase chromatin. However, when digested by DNase I, the susceptibility of pachytene chromatin was 25% more than liver chromatin under identical conditions. Nucleosome core particles were isolated from both liver and pachytene nuclei and were characterized for their DNA length and integrity of the nucleoprotein on low ionic strength nucleoprotein gels. While liver core particles contained all the somatic histones H2A, H2B, H3, and H4, in the pachytene core particles, histone variants TH2A, X2, and TH2B had replaced nearly 60% of the respective somatic histones. A comparison of the circular dichroism spectra obtained for pachytene and liver core particles indicated that the pachytene core particles were less compact than the liver core particles. Studies on the thermal denaturation properties of the two types of core particles revealed that the fraction of the pachytene core DNA melting at the premelting temperature region of 55-60 degrees C was significantly higher than that of the liver core DNA.

Animals↗