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Biomedical subjects

S H Goh

Publications and source records attributed to S H Goh.

51 records · Page 3Linked to original sources
PubMed1992

Cardiovascular responses in the normotensive rat produced by intravenous injection of gambirine isolated from Uncaria callophylla B1. ex Korth.

Among several alkaloids, including dimeric indoles, isolated from Uncaria callophylla, gambirine which is an alkaloid unique to this plant, has been found to be another hypotensive principle from the plant. Intravenous injections of gambirine in the dose range of 0.2 to 10.0 mg/kg caused a dose-related fall in both systolic and diastolic blood pressures as well as heart rate. At all doses gambirine showed a prompt onset of action and at the higher doses (5.0-10 mg/kg), marked persistence of hypotension accompanied by severe bradycardia were observed. In addition, higher doses of gambirine produced a more marked decrease in diastolic than systolic pressure while at lower doses both decreased equally. It is suggested that the hypotensive effect of gambirine may be peripheral in origin and is associated, at least in part, with a cardiac action.

Alkaloids↗
PubMed1992

Induction of tumor necrosis factor and interleukin-1 by purified staphylococcal toxic shock syndrome toxin 1 requires the presence of both monocytes and T lymphocytes.

Highly purified staphylococcal toxic shock syndrome toxin 1 (TSST-1) was tested for its ability to induce the cytokines tumor necrosis factor (TNF) and interleukin-1 (IL-1) from fractionated human peripheral blood mononuclear cells prepared from seven healthy donors. Highly purified monocytes alone or T lymphocytes alone did not produce TNF or IL-1 when incubated with TSST-1 at 37 degrees C for up to 72 h. However, the addition of 10 micrograms of TSST-1 per ml to a 1:1 mixture of monocytes and T cells resulted in significant TNF (predominantly TNF-alpha) and IL-1 beta production after 24 h at 37 degrees C. The nature of the monocyte/T-cell interaction did not appear to involve gamma interferon (IFN-gamma), since 10 micrograms of rabbit anti-IFN-gamma per ml did not neutralize TNF-alpha production after TSST-1 induction. Similarly, L243, a monoclonal antibody to HLA-DR which blocks TSST-1 binding to monocytes, did not inhibit TNF-alpha production following TSST-1 induction. However, direct contact between monocytes and T cells was required, since physical separation of cells in double-chamber culture wells abolished TNF-alpha secretion after TSST-1 stimulation. Furthermore, paraformaldehyde fixation of either monocytes or T cells prior to addition to viable T cells or monocytes, respectively, also abolished TNF-alpha secretion, suggesting that aside from cell contact, soluble factors were also involved. Our results suggest that cytokine production involves more than binding of TSST-1 to its receptor on monocytes alone and that cell contact with T cells and the release of a soluble factor(s) other than IFN-gamma may be essential for the induction of cytokines by this toxin.

Anti-Infective Agents, Local↗
PubMed1992

Molecular typing of Staphylococcus aureus on the basis of coagulase gene polymorphisms.

Staphylocoagulase, a major phenotypic determinant of Staphylococcus aureus, exists in multiple allelic forms, in part because of the existence of gene variants within the 3'-end coding region. This region contains a series of repeating 81-bp DNA sequences which differ both in the number of tandem repeats and the location of AluI restriction sites among different isolates. Utilizing this finding, we developed a novel typing method for S. aureus based on polymerase chain reaction amplification of the variable region of the coagulase gene followed by AluI restriction enzyme digestion and analysis of restriction fragment length polymorphism (RFLP). Among 30 S. aureus isolates studied initially, a total of 10 distinct RFLP patterns were observed. There was excellent correlation of the RFLP patterns with typing of these isolates by multilocus enzyme electrophoresis at 20 chromosomal loci. This coagulase RFLP method was used to analyze an additional 39 S. aureus isolates and successfully traced the source of an outbreak of methicillin-resistant S. aureus infections at a local hospital.

Bacterial Typing Techniques↗
PubMed1990

The treatment of visible signs of senescence: the Asian experience.

Ageing of the skin is of growing concern. People living in the Far East are exposed to bright sunlight all year round so photoageing of exposed skin is inevitable. Visible signs of photoageing include hyperpigmentation, which is an early and prominent feature. In contrast, wrinkling and coarseness are late and inconspicuous features. Tretinoin has been shown to be effective in the improvement of these visible signs. The adverse effects of tretinoin present in the early phase of treatment: with adequate counselling from the dermatologist, and patience and preseverence on the part of the patient, these effects are only temporary and disappear with prolonged treatment. It seems that the longer the treatment and the stronger the concentration of tretinoin, the better the result.

Administration, Topical↗
PubMed1989

Results of dacryocystorhinostomy in Singapore General Hospital.

A total of fifty dacryocystorhinostomies (DCRs) done between 1983 and 1988 were reviewed. A success rate of 86% was found in 47 patients who had obstruction of the lacrimal sac and/or duct. Our results, surgical technique and reasons for failure will be discussed.

Adolescent↗
PubMed1986

Structure of the gene encoding the exoglucanase of Cellulomonas fimi.

In Cellulomonas fimi the cex gene encodes an exoglucanase (Exg) involved in the degradation of cellulose. The gene now has been sequenced as part of a 2.58-kb fragment of C. fimi DNA. The cex coding region of 1452 bp (484 codons) was identified by comparison of the DNA sequence to the N-terminal amino acid (aa) sequence of the Exg purified from C. fimi. The Exg sequence is preceded by a putative signal peptide of 41 aa, a translational initiation codon, and a sequence resembling a ribosome-binding site five nucleotides (nt) before the initiation codon. The nt sequence immediately following the translational stop codon contains four inverted repeats, two of which overlap, and which can be arranged in stable secondary structures. The codon usage in C. fimi appears to be quite different from that of Escherichia coli. A dramatic (98.5%) bias occurs for G or C in the third position for the 35 codons utilized in the cex gene.

Amino Acid Sequence↗
PubMed1983

The promoter sequence of a yeast tRNAtyr gene.

Thirty-one base substitution mutations within the yeast SUP4 tRNAtyr gene were used to probe the effects of different intragenic sequences on promoter activity. The various mutant plasmids were tested quantitatively for their in vitro template activity and for their ability to block competitively the transcription of a reference gene. Five mutations within the coding sequence of SUP4 decreased template activity for pre-tRNAtyr synthesis. The competition assays revealed 11 mutant genes that behaved differently than SUP4-o. Six were weaker competitors and five were stronger. The 12 mutations affecting template activity or competition are clustered in three regions: those encoding the dihydrouracil (D) arm, the extra loop, and the T psi arm of the tRNA. All of the mutations that reduce competition involve base changes that decrease homology to a eucaryotic tRNA consensus sequence in the highly conserved D and T psi regions. Three of the five up mutations increased homology to the tRNA consensus sequence.

Base Sequence↗
PubMed1981

Regulation of protein synthesis: translational control by procollagen-derived fragments.

Previous studies have shown that a type I procollagen-derived peptide, called pN alpha 1(I)-Col 1, selectively inhibits collagen synthesis by fibroblasts in culture and the translation of procollagen mRNA in a rabbit reticulocyte lysate system. We prepared the 10,700-dalton peptide from dermatosparactic calf skin, which contained high levels of incompletely processed type I procollagen, by collagenase digestion. Time-course and dose-response studies showed that the peptide specifically inhibited the translation of procollagen mRNA in preparations of human fibroblast RNA while not affecting the translation of globin mRNA or of other messenger RNAs in fibroblast RNA. After reduction and alkylation, the peptide lost its specificity but became a nonspecific inhibitor of translation. Enzymatic cleavage enabled us to localize the nonspecific activity to a short sequence -Pro-Thr-Asp-Glu, an assignment confirmed by peptide synthesis. Using pactamycin, a specific inhibitor of translational initiation, we showed that the intact peptide acts on procollagen mRNA translation by inhibition of polypeptide chain elongation or termination, or both, whereas the nonspecific inhibitory activity of the unfolded peptide and its derivatives can be attributed to an inhibition of chain initiation. Although the native peptide may function in feedback regulation of collagen synthesis, the physiological role of the lower molecular weight fragments, if any, is uncertain.

Amino Acid Sequence↗
PubMed1978

Glucose transport in Achlya: characterization and possible regulatory aspects.

The freshwater fungus Achlya transported D-(+)glucose (glucose) and 2-deoxy-D-glucose (deoxyglucose) by an energy-related system. Their transport4 was inhibited by uncouplers of metabolic energy such as 2,4-dinitrophenol, cyanide, azide, and carbonylcyanide-p-chlorophenylhydrazone. Besides inhibiting each other, glucose and deoxyglucose transport was inhibited by D-(+)galactose, D-(+)mannose, and D-(+)xylose. Many other sugars tested failed to inhibit glucose transport implying a certain degree of specificity. Glucose transport was pH (optimum at 6.5) and temperature (optimum at 30-40 degrees C) dependent. Glucose transport was also inhibited by citrate, N6-substituted adenines (cytokinins), and iodine. None of these agents penetrated the cell membrane within the brief (1-3-min) period in which glucose transport was measured. In every case, transport was inhibited within 10 s (the shortest time in which measurements could be made). When cells were osmotically shocked to release a cell-wall membrane phosphorylated proteoglycan (PPG), they became incapable of transporting glucose for several hours until new PPG material was reisolable from the membrane by osmotic-shock treatment. The osmotically shocked cells could not transport glucose or deoxyglucose. No glucose-binding protein was detected in the shock fluid. Practically all of the glucose transported within 1-2 min was recovered as glucose-6-phosphate. No other phosphorylated sugar was detected suggesting that glucose may be phosphorylated in transport. Related studies have shown that citrate removed calcium bound by PPG; N6-substituted adenines were bound by PPG while three polyphosphorylated dinucleosides, HS3, HS2, and HS1, were displaced from it. Iodine formed stable complexes with the HS compounds. All of these agents inhibited glucose transport without entering the cell. It is therefore possible that HS compounds, calcium and PPG may be involved in maintaining the cell membrane in proper form for glucose transport.

Biological Transport, Active↗
PubMed1977

Inhibition of mammalian ribonucleotide reductase by a dinucleotide produced in eucaryotic cells.

HS3, a highly phosphorylated dinucleoside originally purified from the fungus Achlya, has been isolated from Chinese hamster ovary cells undergoing glutamine starvation. The HS3 compounds obtained from the fungal and mammalian sources exhibited similar physical and chemical properties. This unusual dinucleotide may be an important regulator of eucaryotic ribonucleoside diphosphate reductase activity; for 50 micrometer HS3, isolated from either mammalian or fungal cells, significantly inhibited CDP reduction in Achlya or hamster cell preparations, but only marginally affected the activity of the enzyme from E. coli. Studies with HS3 isolated from Achlya and partially purified mammalian ribonucleotide reductase indicated that the compound noncompetitively inhibited the reduction of varying concentrations of the substrates CDP, ADP and GDP with Ki values of 23 micrometer, 14 micron and 16 micron respectively. These inhibitor concentrations are well below the estimated intracellular levels of HS3 in glutamine starved cells and suggest that HS3 inhibition of ribonucleotide reduction may be responsible for the rapid inhibition of DNA synthesis seen under these culture conditions.

Adenosine Diphosphate↗
PubMedDate not supplied

Emergency department organisation for disasters: a review of emergency department disaster plans in public hospitals of Singapore.

Disaster management plans of emergency departments (EDs) in four major public hospitals were reviewed. A comparison was made between these plans, and they were analyzed to gain an understanding of the differing objectives and doctrines behind the practices. These were summarized into five major management concepts, which are considered to be critical to the success of a disaster plan: 1) staff mobilization systems (cascading vs batch mobilization); 2) staff deployment systems; 3) team organization (surgeons vs residents); 4) area management (the role of the area manager); 5) casualty volume management (accommodation vs expansion vs extension concepts). The concepts derived should serve as a useful guide to the development of an ED disaster plan and potentially influence how new ED facilities could be planned.

Disaster Planning↗