Biomedical subjects

A Subramaniam

Publications and source records attributed to A Subramaniam.

23 records · Page 2Linked to original sources

PubMed1990

Role of cytosol in the stimulation of RNA transport in vitro during cardiac hypertrophy in rats.

The 100,000 g supernatant isolated from hypertrophic hearts on fractionation by (NH4)2SO4 and DEAE-cellulose chromatography showed an enhanced RNA-transport activity when incubated with isolated nuclei from sham-operated hearts in vitro. Proteins of Mr 73,000, 68,000, 43,000 and 32,000 are enriched in the DEAE-cellulose fractions exhibiting maximal transport activity, and they are phosphorylatable. Pretreatment of the cytosol with antibodies to the Mr-68,000 and -32,000 proteins decreases the transport activity of the cytosol from 14% to 4.25%. Proteins of Mr 73,000, 68,000, 43,000 and 32,000 are translocated from the cytosol to the nuclear envelope under conditions of RNA transport in vitro. Our results here suggest that at least two of these proteins, those of Mr 68,000 and 32,000, play an indispensible role in the nucleocytoplasmic RNA transport in vitro. By making use of a specific myosin heavy-chain B-gene probe and hybridization, we have also shown the effect of cytosol on the transport of myosin heavy-chain mRNA from nucleus to cytosol.

Ammonium Sulfate↗

PubMed1990

Incidence and avoidance of zona fracture in cryopreserved bovine ova and embryos.

Ova (n=62), which were collected from slaughterhouse bovine ovaries, and embryos (n=26), which were non-surgically recovered from 11 superovulated crossbred donor cows, were frozen. The frozen ova and embryos were then thawed using two conventional thawing protocols, i.e. at 37 degrees C for 30 seconds in a water bath and at 25 degrees C for 2 minutes in air. Some 64.5% of the ova and 53.8% of the embryos thawed in the water bath and 16.1% of the ova and 7.7% of the embryos thawed in ambient air exhibited fractured zonae pellucidae. The slow thawing protocol had a lower incidence of zona damage in cryopreserved oval and embryos than the fast thawing protocol. A low pregnancy rate (12.5%) was recorded for embryos transferred with zona fracture while embryos transferred with intact zonae had a rate of 35.3%) indicating that embryos with zona damage are less viable.

Journal Article↗

PubMed1989

A multipurpose vector for the study of transcriptional control.

To facilitate the insertion of transcriptional control regions next to a reporter gene, plasmid vectors containing multiple cloning sites next to the cat have been constructed. These vectors also contain features which make their use convenient for the construction of deletions in the inserted transcriptional control regions, as well as for the direct sequencing of the deletion series produced. The vectors have been constructed such that the control region cassette (and the deletions produced) may be easily removed with or without the reporter gene for placement into transgenic mice. The system's utility has been demonstrated by deletion analysis of a chicken myosin heavy chain-encoding gene promoter.

Animals↗

PubMed1989

Demonstration of a direct inhibitory effect of cyclosporine on normal human T-cells with two novel models of T-cell activation as probes.

Two novel models of activation of human peripheral blood quiescent T-cells (T-cells) were utilized herein as probes to analyze the mechanisms and to locate the site of action of cyclosporine (CsA) in the T-cell activation pathway. Highly purified T-cells were activated, independently of accessory cells, with either crosslinked anti-CD2 + anti-CD3 monoclonal antibodies (mAbs) or with sn-1,2-dioctanoylglycerol (DAG) and ionomycin. CsA inhibited the expression of 55-kDa interleukin-2 receptors (IL-2R) and T-cell proliferation in these accessory cell-independent models of T-cell activation. Recombinant IL-2, over a wide range of concentrations that included different binding affinities of cellular receptors for IL-2, did not completely reverse CsA-associated inhibition of IL-2R expression and/or proliferation. In additional experiments, designed to examine early activation related events, CsA did not interfere with the increase in intracellular free calcium concentration initiated with anti-CD2, anti-CD3, anti-CD2 + anti-CD3 mAbs or with ionomycin. DAG-induced and PKC-activation-dependent down-regulation of cell surface expression of CD3 antigens was similarly unaffected by CsA. Our findings unambiguously indicate that CsA has a direct inhibitory effect on T-cells. Moreover, CsA's cellular site of action is distal to calcium mobilization and PKC activation but proximal to IL-2R expression and IL-2-dependent DNA synthesis in normal human T-cells.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1988

Activation of human T cells with the physiological regulator of protein kinase C.

We investigated whether sn-1,2-dioctanoylglycerol (diC8) activates highly purified human T cells. diC8's signaling activity was also compared with that of 12-O-tetradecanoylphorbol-13-acetate (TPA). diC8 and ionomycin were synergistic in promoting T-cell proliferation. The proliferative response was dependent upon an operational interleukin-2 (IL-2) system and exhibited a high degree of specificity; sn-1,2-diC8 was twice as active as racemic-1,2-diC8, and diC8 and TPA were not synergistic. diC8's signaling activity differed from that of TPA. diC8, unlike TPA, failed to elicit IL-2 receptors or proliferation, independently of ionomycin. diC8 also failed to promote the proliferation of T cells signaled with anti-CD3 or -CD2 monoclonal antibodies. Two different inhibitors of PKC, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine or staurosporine, inhibited T-cell proliferation induced with diC8 and ionomycin, but not with TPA and ionomycin. These observations, in addition to demonstrating the differential activity of diC8 and TPA, document a signaling role for diacylglycerol in the activation of normal T cells.

Antigens, Differentiation, T-Lymphocyte↗