Biomedical subjects
Publications and source records attributed to K Singh.
Free access to contraception and effective legislation measures, have resulted in a decline in fertility in Singapore. A new population policy of 'three children or more if you can afford it' was therefore introduced in 1986. This paper discusses the new population policies and measures their effect on fertility in Singapore.
The pharmacokinetics and pharmacodynamics of biochemical effect of a selective thromboxane synthase inhibitor, CGS 12970, were studied in healthy male volunteers after a dosing scheme of either 200 mg once daily or 100 mg twice a day for 6 days. The peak plasma concentration appeared 1 to 2 hours after administration, followed by a biexponential decline with half life values of about 1 and 7 hours, respectively. The mean oral clearance was 16 L/hr. Biochemically, the capacity of the platelets to form thromboxane A2 ex vivo (serum) was inhibited greater than 90% at both doses. In contrast to the short plasma half-life, the suppression of ex vivo serum thromboxane production was maintained greater than 70% to 80% at 48 hours after dosing. Inhibition of the thromboxane production in vivo (urine) was also substantial, but incomplete at both doses (200 mg daily; thromboxane B2, 75%; 2,3-dinor-thromboxane B2, 83%; 11-dehydrothromboxane B2, 90%). The urinary excretion, however, returned to the predose level at the end of a 1-week follow-up period after the last dosing. In conclusion, CGS 12970 is an orally active, reversible inhibitor of thromboxane synthase with a prolonged duration of action in humans.
The purpose of this study was to compare the bioavailability of dl-alpha-tocopheryl acetate and d-alpha-tocopheryl succinate when administered to sheep in a single oral dose weekly. The sheep, five per treatment, were given a basal diet without vitamin E supplement (control) or basal diet with weekly administration of 2225 IU of dl-alpha-tocopheryl acetate, 2225 IU of d-alpha-tocopheryl succinate, or 6675 IU of d-alpha-tocopheryl succinate. Increases in plasma alpha-tocopherol concentration levels over the 3-wk period of study were determined and compared. The greater availability of dl-alpha-tocopheryl acetate was indicated by the significantly higher peak plasma alpha-tocopherol concentrations and the greater area under the curve produced by administration of the acetate than the succinate esters at the same dosage. Reported data on plasma alpha-tocopherol concentrations suggest that bioavailability in sheep of d-alpha-tocopheryl succinate versus dl-alpha-tocopheryl acetate is 3:1.
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Forty-two patients of typhoid perforation of the gut have been studied. All the patients were subjected to surgery after resuscitation. Simple closure (with or without serosal patch) and temporary ileostomy were the commonly performed surgical procedures. The overall mortality was 14.2%. Postoperative morbidity included wound dehiscence, fistula, encephalopathy, septicaemia, intra-abdominal abscesses and incisional hernia. Faecal fistula formed in 5 out of 42 cases. Ileostomy was found to be the best procedure with regard to morbidity and mortality.
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We report a case of Kaposi's sarcoma in a young woman who presented with unusual clinical and histologic features. The unusual clinical features were the absence of cutaneous lesions; the presence of a splenic mass; and extensive involvement of the peritoneum, resulting in massive ascites and intestinal and ureteral obstruction. We postulate that the spleen was the primary site of the tumor. The unusual histologic features were the presence of both sclerotic and cavernous hemangioma variants in the same tumor and extensive areas of calcium deposits in the tumor. Such atypical clinical and histologic features can pose diagnostic difficulties for both clinicians and pathologists.
Five cases of primary lymphoma of the brain are reported and the literature reviewed. The diverse clinical spectrum at presentation and variable response to therapy are few of its unique features. The literature is reviewed briefly and the importance of diagnosis at an early stage and prompt institution of therapy in form of radiation therapy and chemotherapy when indicated is stressed.
Primary melanoma of the meninges, a rare CNS tumor, is presented. Criteria for diagnosing a primary CNS melanoma are elucidated. Literature is reviewed in this context. The histogenesis of tumor, problem of occult primary melanoma and the role of CT scan and CSF cytology in early diagnosis have also been highlighted.
Pulmonary functions including transfer factor for CO and its components (TIco, Dm, Vc) were studied in 45 asymptomatic subjects (25 smokers, 20 non smokers) using single breath technique. Ventilatory functions of smokers were significantly reduced; these improved significantly after salbutamol inhalation but most still remained lower than in non smokers. VA and Dm were marginally higher while Vc was significantly reduced in smokers. Their TIco1(20) was influenced only insignificantly. However, after salbutamol, both Dm and Vc were significantly lowered, resulting in further reduction (p 0.01) of TIco120 in smokers. The effect of salbutamol in non smokers was insignificant.
Transformation-associated protein (TAP) has been detected in MSV-M-transformed rat cell lines as glycosylated, weakly phosphorylated protein of molecular weight (Mr) 66,000 and 68,000. In the ts-MSV-M-transformed rat kidney cell line (6m2), the synthesis of TAP and the v-mos gene product is temperature-sensitive and accompanies the expression of transformation phenotypes. Therefore, TAP potentially plays a role in cellular transformation. On the other hand, SPP represents a family of glycosylated phosphoprotein with apparent Mr ranging from 42,000 to 69,000. SPP has been detected in osteoblasts and in avian and murine retrovirus-transformed rat and mouse epithelial cells. Therefore, the potential relatedness of TAP and SPP was studied. Using the 6m2 cells, we found that SPP was strongly phosphorylated and was synthesized at both the permissive (33 degrees C) and non-permissive (39 degrees C) temperatures. By contrast, TAP was weakly phosphorylated, and was synthesized, as we found previously, only at the permissive temperature of 33 degrees C. Furthermore, in 35S-methionine incorporation studies, TAP became heavily labelled whereas SPP was not (consistent with its amino acid composition having few methionine residues). Using 125I-TAP in both immunoprecipitation and radioimmunoassays, it was found that an antiserum raised against SPP did not cross-react with 125I-TAP. Additionally, SPP has now been found in many human and rodent cells, while TAP thus far has only been detected in MSV-transformed rat cells. These data suggest that structurally, TAP and SPP are not closely related phosphoproteins.
In a previous study we have shown that normal rat kidney (NRK) cells in vitro secrete a 69-kDa osteopontin in both phosphorylated (pp69) and nonphosphorylated (np69) forms. Only pp69 interacts with the cell surface and np69 forms a heat-dissociable complex with plasma fibronectin, suggesting functional modulation of osteopontin by phosphorylation. Using tunicamycin, an inhibitor of N-linked glycosylation, and peptide:N-glycosidase F, which removes N-linked oligosaccharide chains from glycoproteins, we show here that np69, but not pp69, contains N-linked carbohydrates. Our results also demonstrate that tunicamycin treatment does not inhibit the cell surface binding of pp69; however, np69 secreted by the treated cells fails to complex with plasma fibronectin, suggesting importantly, our data show that pp69 forms a heat-stable complex with cell surface fibronectin, suggesting that it is an integral component of the extracellular matrix of NRK cells. Finally, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of deglycosylated and in vitro translated osteopontin suggests that the acidic nature of osteopontin as well as its post-translational modifications play a role in the anomalous behavior of osteopontin in sodium dodecyl sulfate gels, observed in several laboratories. The data presented here provide evidence for possible functional roles of 69-kDa osteopontin and suggest that its physiological properties are regulated by post-translational modifications.
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The functional properties of the anaerobic responsive element (ARE) of the maize Adh1 gene have been analysed using a transient expression assay in electroporated maize protoplasts. The ARE functions in both orientations although inversion of the ARE sequence relative to the TATA box element produces slightly weaker promoter activity under anaerobic conditions and elevated expression under aerobic conditions. Promoter activity under anaerobic conditions is proportional to the number of complete ARE sequences in the Adh1 promoter. The ARE contains two sub-regions and dimers of sub-region II are as efficient as the wild-type sequence in activating gene expression under anaerobic conditions. However, sub-region I dimers do not appear capable of inducing gene expression in response to anaerobic stress. We conclude that sub-region II is essential for anaerobic induction of gene expression. Reporter gene expression remains constant when the spacing between sub-regions of the ARE is increased up to at least 64 bp, but increased spacing of 136 bp or greater abolishes expression in both aerobic and anaerobic conditions, indicating that a close association of the two sub-regions is required both for anaerobic responsiveness and for maximal levels of aerobic gene expression. When the ARE is placed upstream of position -90 of the CaMV 35S promoter, the ARE produces a high level of expression in both aerobic and anaerobic conditions. The general enhancement of gene expression driven by the hybrid ARE/35S promoter in aerobic conditions requires an intact sub-region II motif since mutation or deletion of sub-region II from the hybrid promoter reduces the level of expression to that observed for the truncated 35S promoter alone. In addition, mutation of the sub-region I sequences in the ARE/35S hybrid promoter does not significantly reduce expression in aerobic conditions, relative to pARE/delta 35S(-90), suggesting that sub-region I does not contribute to this general enhancer function.
A three-year clinical evaluation of Norplant-2 rods in Singapore shows that no pregnancy occurred during the three years of use. The continuation rate at the end of three years was 74%. Desire for planned pregnancy was the main reason for removal during the three years. The post-removal conception rate in women desiring planned pregnancy was 50.0% at the end of one year. This low rate could be attributed to the four women deciding against a pregnancy after removal. However, despite this apparent reason one needs to monitor the post-removal return of fertility closely in the years to come.
In this longitudinal study involving 100 Singaporean women, the effects of Norplant-2 rods on metabolic function were evaluated. With respect to liver function, the results indicate possible hepatocellular dysfunction as evidenced by a significant rise in serum bilirubin and a significant fall in total proteins and globulin during the three years of use. As regards lipid metabolism total triglycerides, cholesterol and LDL cholesterol were significantly decreased as compared to their preinsertion values at the end of three years. The HDL-cholesterol was also significantly decreased during the second and third year of use. Despite this, the HDL-cholesterol/total-cholesterol-HDL-cholesterol remained above 0.200. Thus, though speculative, it still appears to indicate that use of Norplant-2 rods is not directly contributory to cardiovascular risk. The use of Norplant-2 was not associated with any significant effect on carbohydrate metabolism after three years of use.