Biomedical subjects
Publications and source records attributed to T H Tan.
Peripheral lymphography was carried out in 17 patients with elephantiasis and microfilaremia (Brugia malayi) and the findings compared to ten patients with "idiopathic tropical eosinophilia." There were extensive changes in peripheral lymphatic and regional nodal architecture in each group suggesting that "occult filariasis" is the cause of idiopathic tropical eosinophilia.
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We studied 16 adults with chronic bronchial asthma by measuring the plasma theophylline concentrations and evaluating clinically the control of asthma following oral administration of choline theophyllinate (CT) and a sustained-release theophylline preparation (SRT). All 16 patients were studied in 3 one-weekly phases. These patients received CT 200 mg t.i.d. during the 1st week, no theophylline during the 2nd week and SRT 250 mg 12-hourly during the 3rd week. All other anti-asthmatic medications were maintained during the study. After the night dose of a theophylline preparation, the mean plasma trough concentration the next morning was significantly higher for SRT (9.4 mcg/ml +/- SEM 1.0) than for CT (3.6 mcg/ml +/- SEM 0.6). The mean plasma peak concentration after the morning dose was also significantly higher for SRT (11.5 mcg/ml +/- SEM 1.0) than for CT (7.4 mcg/ml +/- SEM 1.0), The mean forced expiratory volume in one second (FEV1) obtained during SRT treatment was significantly higher than during CT treatment. There was no significant difference between FEV1 measured at trough concentrations during CT treatment and during the period without theophylline. The patients had fewer symptoms of asthma and fewer side-effects from theophylline during the week they received SRT compared with the week they received CT. In this study, using the conventional dosage schedule as practised in Singapore, SRT has distinct advantages over CT in the treatment of chronic asthma.
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Tuberculosis associated with systemic lupus erythematosus (SLE) was studied in a cohort of 311 patients seen between 1963 to 1979. There were 16 such patients, giving rise to a prevalence rate of 5%. The characteristics of SLE-associated tuberculosis include a high incidence of miliary and far-advanced pulmonary disease, delay in establishing diagnosis, especially the extrapulmonary form, and tendency to attribute symptoms like fever, malaise, and weight loss to the lupus process. Treatment was successful in 9 patients. Of the 7 death 5 were attributed directly to the mycobacterial infection and 2 to complications of SLE.
The biologic effects of a series of sugar-substituted analogs of tubercidin were evaluated and compared with the effects of the homologous series of adenosine analogs in combination with 2'-deoxycoformycin. The greatest cytotoxicity against cultured mouse L1210 leukemia cells was exhibited by tubercidin and by 3'-deoxyadenosine or xylosyladenine in combination with 2'-deoxycoformycin. Somewhat less active were xylotubercidin and the combination of arabinosyladenine (araA) plus 2'-deoxycoformycin. The arabinosyl and 2'- and 3'-deoxyribosyl derivatives of tubercidin were relatively ineffective in their ability to inhibit proliferation of L1210 cells. The major biochemical effects of the most active agents were inhibition of RNA synthesis (3'-deoxyadenosine and xylosyladenine) and depletion of cellular ATP plus general inhibition of macromolecular synthesis (tubercidin). The in vitro activities of xylosyladenine and 3'-deoxyadenosine (in combination with 2'-deoxycoformycin) and xylotubercidin (as a single agent) were greater than or equivalent to that of araA (in combination with 2'-deoxycoformycin).
Serum concentrations of lithium after i.p. administration to normal mice declined with biphasic kinetics. Treatment of mice bearing ascitic L1210 leukemia with lithium resulted in a modest protection against the myelosuppressive effects of vinblastine. Lithium as a single agent was without effect on the survival times of mice bearing either the L1210 or P388 leukemia. Similarly, there was no evidence of significant antiproliferative or cytotoxic activity when cultured L1210 leukemia and murine neuroblastoma cells were exposed to lithium at levels comparable to those observed in the serum of lithium-treated mice. The therapeutic activity of vinblastine against the L1210 and P388 leukemias was not significantly altered by either simultaneous or subsequent administration of lithium. Lithium did not antagonize the antiproliferative or cytotoxic action of vinblastine against L1210 leukemia or murine neuroblastoma cells and was without effect in experiments with neuroblastoma cells that assessed vinblastine inhibition of a biological function dependent on formation of cytoplasmic microtubules (neurite formation induced by serum deprivation). The results obtained suggest that administration of lithium to reduce myelosuppression is not likely to counteract the tumoricidal activity of vinblastine.
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The antiproliferative activity of 9-beta-D-arabinofuranosyladenine 5'-monophosphate against a cultured line of mouse leukemia cells (L1210/C2) was enhanced by addition of either 2'-deoxycoformycin or erythro-9-(2-hydroxy-3-nonyl)adenine. The activity of 9-beta-D-arabinofuranosyladenine 5'-monophosphate, alone or in combination with either of the two inhibitors of adenosine deaminase, was comparable to that of 9-beta-D-arabinofuranosyladenine (ara-A), apparently reflecting the rapid conversion of 9-beta-D-arabinofuranosyladenine 5'-monophosphate to ara-A by L1210/C2 cells. Several ara-A analogs were assayed for antiproliferative activity against L1210/C2 cells; of these, only 9-beta-D-arabinofuranosyladenine 5'-O-methylphosphate and 2'-deoxy-2'-amino-9-beta-D-arabinofuraosyladenine were active. Addition of 2'-deoxycoformycin to cell culture fluids enhanced the activity of 9-beta-D-arabinofuranosyladenine 5'-O-methylphosphate suggesting conversion to an adenosine deaminase-sensitive intermediate, presumably ara-A.
More than 600 cases of ovarian tumors were analyzed for histological type, age of patient, bilateral occurrence, mobility and malignant degeneration in restant ovaries. Tumors of germinal epithelial origin show the highest incidence (24%) of malignant degeneration, tumors of germ cells the lowest (3,5%). Incidence of malignant degeneration increases in relation to the age of the patient from 2% (and under 30 years) to 36,5% (60-70 years). Each form of tumor has its typical age peak, which is about 20 years higher for carcinomas than for their benign counterpart. Bilateral ovarian tumors are malignant in 29%, one-sided only in 13%. Among freely movable ovarian tumors, only 6% enclose a malignant tumor, among adhaerent ones 34%. The examination of the prognosis of granulosacell-tumors, dysgerminomas and teratoblastomas is based on a larger material.
The effect of posture on maternal capillary blood Po(2) and Pco(2) was studied in pregnant and non-pregnant women. There was a significant decrease of Po(2) (mean 13.0 mm. Hg) and significant decrease of Pco(2) (mean 2.4 mm. Hg) when pregnant women sat up, but these changes did not occur in the non-pregnant. These findings may be relevant to debate on the optimum posture for labour.
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