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Biomedical subjects

S Oh

Publications and source records attributed to S Oh.

At least 127 records · Page 7Linked to original sources
PubMed1995

The iron component of sodium nitroprusside blocks NMDA-induced glutamate accumulation and intracellular Ca2+ elevation.

These studies were designed to compare the effects of nitric oxide (NO) generating compounds with those of several iron containing compounds which do not generate NO on glutamate receptor function. Stimulation of primary cultures of cerebellar granule cells with N-methyl-D-aspartate (NMDA) or kainate results in the elevation of intracellular calcium ([Ca2+]i) and cGMP and the release of glutamate. The iron containing compounds, sodium nitroprusside (SNP), potassium ferrocyanide (K4Fe(CN)6) and potassium ferricyanide (K3Fe(CN)6) decrease the NMDA-induced release of glutamate. SNP is the only compound of the above 3 agents which generates NO. A non-iron, NO generating compound, S-nitroso-N-acetylpenicillamin (SNAP), has no effect on the NMDA-induced glutamate release. Potassium ferrocyanide (Fe II), but not potassium ferricyanide (Fe III), blocks NMDA-induced cGMP elevations after 3 min exposure times. This contrasts with the NO generating compounds (both SNP and SNAP) which elevate cGMP levels. Furthermore, both potassium ferrocyanide (Fe II) and SNP (Fe II) suppress the elevation of [Ca2+]i induced by NMDA but neither potassium ferricyanide (Fe III) nor SNAP are effective in this regard. These effects are also independent of cyanide as another Fe II compound, ferrous sulfate (FeSO4) is also able to suppress NMDA-induced elevations of [Ca2+]i. SNP was unable to suppress kainate receptor functions. Collectively, these results indicate that Fe II, independently of NO, has effects on NMDA receptor function.

Animals↗
PubMed1995

Deposition of transforming growth factor-beta in the marrow in myelofibrosis, and the intracellular localization and secretion of TGF-beta by leukemic cells.

The marrows of 10 patients with hematologic malignancies were examined by immunohistochemistry using anti TGF-beta antibody, CC(1-30), which detects secreted TGF-beta, and compared with four normal marrows. TGF-beta was not demonstrated in marrows with a normal level of reticulin fibrosis; however, TGF-beta was observed within collagen in marrows having collagen fibrosis or increased reticulin fibrosis. The extent of TGF-beta deposition paralleled the severity of fibrosis (P < .0001), and occurred even with normal or reduced numbers of megakaryocytes. Using another TGF-beta antibody, LC(1-30), which detects intracellular TGF-beta, TGF-beta was detected by immunofluorescence in discrete sites in the cytoplasm of immature and mature myeloid and large granular lymphocytic leukemia cells. These sites colocalized with areas detected by an anti-granule antibody (D545) suggesting that TGF-beta was stored in granules. However, neither the TGF-beta mRNA content nor the degree of TGF-beta secretion by these leukemic cells correlated with the extent of TGF-beta deposition in the marrow. Thus, TGF-beta deposition in marrow may contribute to myelofibrosis, but the source of this cytokine in the absence of megakaryocytes requires further study.

Adult↗
PubMed1995

Optimizing conditions for the growth of Lactobacillus casei YIT 9018 in tryptone-yeast extract-glucose medium by using response surface methodology.

This study was undertaken to find optimum conditions of tryptone, yeast extract, glucose, Tween 80, and incubation temperature for the growth of Lactobacillus casei YIT 9018 and to assess the effects of these factors by use of response surface methodology. A central composite design was used as an experimental design for allocation of treatment combinations. A second-order polynomial regression model, which was used at first for analysis of the experiment, had a significant lack of fit. Therefore, cubic and quartic terms were incorporated into the regression model through variable selection procedures. Effects involving incubation temperature, yeast extract, glucose, and tryptone were significant, whereas the only significant effect involving Tween 80 was the interaction effect between temperature and Tween 80. It turned out that growth of L. casei YIT 9018 was most strongly affected by the incubation temperature. Estimated optimum conditions of the factors for growth of L. casei YIT 9018 are as follows: tryptone, 3.04%; yeast extract, 0.892%; glucose, 1.58%; Tween 80, 0%; incubation temperature, 35 degrees C.

Bacteriological Techniques↗
PubMed1995

The generation of nitric oxide and its roles in neurotransmission and neurotoxicity.

The N-methyl-D-aspartate (NMDA) receptor plays a key role in synaptic plasticity and is thought to underlie memory, learning and development of the nervous system. The NMDA receptor is a ligand-gated ion channel complex that contains distinct recognition sites for endogenous and exogenous ligands, including glutamate, glycine, Mg2+, Zn2+ and noncompetitive blockers such as MK-801. In the central nervous system, nitric oxide (NO) is produced in some neurons following activation of excitatory amino acids receptors, particularly those of the NMDA receptor. Nitric oxide is synthesized from a L-arginine by the cytoplasmic enzyme nitric oxide synthase (NOS) which is a calcium dependent enzyme, and this pathway is inhibited by the analogues of L-arginine such as NG-monomethyl-L-arginine (L-NMMA) and is augmented by NMDA receptor activation. Activation of the NMDA receptor results in the elevation of intracellular calcium ([Ca2+]i) which in turn activates NOS via the calcium-calmodulin complex. Nitric oxide is not a classical neurotransmitter in the central nervous system since it is not released by exocytosis and does not interact with a receptor protein but rather diffuses rapidly across the membrane and binds with the iron in heme-containing proteins. Nitric oxide can serve as both an oxidizing and reducing agent. It has strong affinity for heme proteins such as guanylyl cyclase, but there is evident that NO may have a regulatory role by oxidizing sulfhydryl groups of non-heme proteins such as those on the NMDA receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1994

Nahm et al. reply.

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Journal Article↗
PubMed1994

Basic fibroblast growth factor (bFGF) contributes to the enlargement of brown adipose tissue during cold acclimation.

The contribution of basic fibroblast growth factor to brown adipose tissue (BAT) enlargement during cold acclimation was investigated using rat brown adipocytes in primary culture. After cold exposure (at 5 degrees C) for 28 days, the level of bFGF messenger ribonucleic acid (mRNA) in BAT of cold-acclimated rats was markedly increased with the increase in the BAT weight. In addition, the blood plasma from cold-acclimated rats considerably enhanced the expression of basic fibroblast growth factor mRNA in rat brown adipocytes. Likewise, the blood plasma from cold-acclimated rats significantly stimulated the growth of rat brown adipocyte precursor cells compared with that from warm-acclimated rats, whereas there was no difference of effect between the two blood plasmas on the growth of bovine capillary endothelial cells. Basic fibroblast growth factor, but not platelet-derived growth factor stimulated the growth of brown adipocyte precursor cells. The conditioned medium from brown adipocyte primary culture markedly stimulated the growth of bovine capillary endothelial cells and the effect was inhibited considerably by antibasic fibroblast growth factor antibody. These results suggest that some factors concerned with the growth of brown adipocyte precursor cells are present in the blood plasma from cold-acclimated rats, and that basic fibroblast growth factor produced by brown adipocytes may significantly contribute to BAT enlargement by autocrine mechanisms during cold exposure.

Acclimatization↗
PubMed1994

Finite-element analysis of balloon angioplasty.

Finite-element modelling is used to simulate the response of atherosclerotic arteries to a balloon angioplasty procedure. Material properties for the normal wall are derived from experimental data, and the properties of the plaque are varied over a wide range. Comparison with experimental data shows that the normal arterial wall can be appropriately modelled using a hyperelastic material definition. Large strain, non-linear analysis was used to simulate the dilatation of three typical plaque configurations by an angioplasty balloon. Stress contour plots are presented for each configuration. Results show good agreement with previous histologic studies.

Angioplasty, Balloon, Coronary↗
PubMed1993

Human cDNA encoding DnaJ protein homologue.

We have cloned a cDNA encoding a DnaJ-like protein from the human fibrosarcoma HT-1080 cDNA library. This cDNA encodes a protein of 397 amino acid residues whose sequence shows 38.2% identity with the Escherichia coli DnaJ protein and 47.2% with the yeast DnaJ homologue along the entire length. Since the sequence contains the N-terminal domain region conserved in DnaJ family members and the four repeats of the Cys-X-X-Cys-X-Gly-X-Gly motif which are characteristic of DnaJ proteins, we conclude that this cDNA clone encodes the human homologue of DnaJ.

Amino Acid Sequence↗