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Biomedical subjects

R Tsang

Publications and source records attributed to R Tsang.

At least 55 records · Page 3Linked to original sources
PubMed1985

The role of calcium in eicosanoid production induced by ricinoleic acid or the calcium ionophore A23187.

Rat isolated intestine incubated in Krebs solution converted exogenous [14C]-arachidonic acid into products that chromatographed with prostaglandins, leukotriene B4 and 5-hydroxy-eicosatetraenoic acid. Accumulation of these products was increased by the laxative ricinoleic acid (0.34 mM) or the calcium ionophore A23187 (7.6 microM). In the presence of the calcium antagonists TMB-8 (0.43 microM) or verapamil (0.2 microM) the mean effects of ricinoleic acid or the calcium ionophore were smaller. Stimulation of arachidonic acid metabolism by ricinoleic acid therefore seems likely to involve a calcium-dependent mechanism.

Animals↗
PubMed1984

Bone mineralization in infants.

The major physiologic control of bone mineralization in infancy involves calcium and phosphorus. Ca and P metabolism in turn is affected by endogenous stores at birth and the ability to deliver and absorb exogenous sources of these minerals. Calciotropic hormones (parathyroid hormone, calcitonin and 1,25 dihydroxyvitamin D) modulate the response of major end organs - intestine, kidney and bone - to balance the need to maintain a relatively stable extracellular biochemical environment with the need for adequate mineralization of the bone. Many other factors such as glucocorticoids under pathological circumstances may disturb bone mineralization; however, the mechanisms by which they control bone mineralization in infancy under physiologic circumstances is ill understood. Clinical bone demineralization occurs primarily in infants born with extreme prematurity. In the presence of conventional vitamin D supplementation, deficiency of calcium and phosphorus appears to play a major role in its causation.

24,25-Dihydroxyvitamin D 3↗
PubMed1983

A double-blind, placebo-controlled study of sucrose polyester in hypercholesterolemic outpatients.

Sucrose polyester (SPE) was studied in a double-blind, placebo-controlled trial in 91 outpatients with primary hypercholesterolemia. All patients maintained an isocaloric diet with cholesterol intake of 400 mg/day and a polyunsaturated to saturated fat ratio of 0.8 to 1.2 for the duration of the study. The study sequence consisted of a diet lead-in period, a first 8-wk treatment period, a 4-wk washout period, and a second 8-wk treatment period. Subjects were randomly assigned to six groups that differed by SPE dose (8, 16, and 32 g/day) and by the treatment period in which either SPE or an olive oil placebo was given in a bread spread formulation. Compared to placebo, the 8, 16, and 32 g/day doses of SPE decreased low-density lipoprotein cholesterol by 2%, 4% (p less than 0.05), and 5% (p less than 0.05) respectively, without changing high-density lipoprotein cholesterol. On SPE, 14/91 (15%) of the subjects experienced a decrease in low-density lipoprotein cholesterol greater than or equal to 10%, while only 2/91 (2%) showed this decrease with placebo.

Adult↗
PubMed1982

Power and heat measurement by direct calorimetry of individual insect response to allelo- and toxic compounds.

A microcalorimeter was constructed for the individual insect in order to measure the insect's power output as a function of time (the thermogram). The instrument has a figure of merit of 7 microW/microV. It includes a Peltier pumped thermoelectric control loop which protects from intruding ambient thermals, and holds baseline drift to less than 2 microV/day. the design is a conventional twin, or differential heat conduction calorimeter, with two insect-holding vessels of glass. The vessels are connected by a stopcock, to give the insect the option of crawling from the sample chamber to the reference chamber. Continuous, metered air flow is provided. A small pulse of compound may be born in, as vapor with the air flow, for the study of attractants, toxic compounds, anesthetics and allelochemicals. The insect's reaction to such compounds, appears in the thermogram. Cabbage looper larvae were examined in their irritative exothermic reaction to microgram amounts of benzene, and in their neutral behavior toward similar amounts of aliphatic hydrocarbons delivered as a single pulse of vapor. The male northern corn rootworm was monitored in his attraction to female rootworm extract ("pheromone') and his tendency to move upwind, or up airflow, toward the pheromone. The instrument enables discrimination of the transient metabolism of muscle use, from that of the resting state power which is probably the true basal metabolic rate power.

Animals↗
PubMed1980

The occurrence of hyperaldosteronism in infants with congestive heart failure.

Serum aldosterone and plasma renin were measured in 20 normal infants and 15 infants with congestive cardiac failure. Serum aldosterone was significantly increased (151 +/- 38 ng/dl mean +/- standard error of the mean) in patients before treatment when compared with aldosterone in normal infants (29 +/- 7 ng/dl). Increasing serum aldosterone was related to increasing plasma renin. The response to furosemide appeared to be inversely related to serum aldosterone concentrations. In four infants, administration of an aldosterone antagonist (spironolactone) resulted in improved diuresis and decreased serum aldosterone. Hyperaldosteronism is an important factor contributing to fluid and sodium retention in infants with heart failure.

Aldosterone↗
PubMed1975

Study of the genetic transmission of hypercholesterolemia and hypertriglyceridemia in a 195 member kindred.

A pedigree of complex structure, comprising 195 individuals, is shown to be segregating for an autosomal dominant gene for hypercholesterolemia. The same pedigree shows two groups of individuals with respect to plasma triglyceride levels; the cause of this appears to be independent of the locus demonstrated, which accounts for over 50% of the variability in cholesterol levels in the kindred studied. The power of bivariate analyses of multigenerational data, as used in this study, is discussed. The lipid disorders in this family, however, differ from the usual familial hypercholesterolemia described by Harlan et al. (1966) in that there is a group of individuals who have elevated triglycerides, there is a substantial amount of premature cardiovascular disease, and not very many individuals have tendonous xanthomas. It is of course possible that in this family the genetic entity is a variant of the usual hypercholesterolemia mutant; or it may be the usual mutant, acting in concert with some other unknown factor. The cause of the two groups with respect to triglycerides is not clear; but, whether it is genetic or environmental, it is independent of the segregation for hypercholesterolemia.

Cholesterol↗
PubMed1975

Bivariate analyses of cholesterol and triglyceride levels in families in which probands have type IIb lipoprotein phenotype.

Univariate and bivariate analyses of cholesterol and triglycerides are performed after appropriate age adjustment on 247 individuals in 33 families where the probands have elevations of cholesterol, low density lipoprotein and triglycerides, and type IIb lipoprotein phenotype. Mixture of lognormal distributions are fitted by maximum likelihood to the data. Best fitting single and mixtures of lognormal distributions are compared with empirical cumulative plots, and the likelihood-ratio criterion is used to test for significance. A mixture of two lognormal distributions fits significantly better than one lognormal distribution for cholesterol but not for triglycerides. When a mixture of bivariate lognormals is fitted to the data, only one local maximum is found, suggesting action of a single genetic determinant in this sample. The best cutoff line is almost parallel to the triglyceride axis, indicating the relatively high involvement of cholesterol compared to triglycerides in separating the normal and abnormal groups. Using the best linear function, the difference in the two bivariate means is found to account for 61% of the total variation in log cholesterol and log triglycerides. To determine if the results are due to enrichment of the sample with familial hypercholesterolemia syndrome, seven families where the proband and/or any relative has tendon xanthomas are removed and the analyses repeated on the remaining 26 kindreds. The results of these analyses are virtually the same as those of the total sample. Also, a subsample of 21 families in which the proband and at least one additional kindred member are affected is analyzed in the same manner with similar results. For comparison, data from a study of families with combined hyperlipidemia [1] are analyzed in an analogous manner, bearing in mind that the populations sampled are probably different. Fitting a mixture of two bivariate distributions and finding the best cutoff to these data indicate that triglycerides are more involved in separating the two groups. Probably because of major differences in ascertainment, the distribution of lipid levels in oour patient group is practically indistinguishable from that of hypercholesterolemia, and the Seattle data [1] are more nearly similar to hypertriglyceridemia. It may be premature to consider familial combined hyperlipidemia as an entity distinct from both hypercholesterolemia and hypertriglyceridemia. We hope it will eventually be possible to analyze these data using a refined genetic model that includes both major gene and polygenic effects and to combine this form of analysis with quantitative tissue culture methods.

Adult↗
PubMed1973

The experimental production of hyaline membranes in premature rhesus monkeys.

When premature rhesus monkeys are ventilated with oxygen or air, hyaline membranes are formed within 5 minutes in alveolar ducts and respiratory bronchioles. Studies with fluorescein-labeled antiserum to porcine pepsinogen provide evidence that the monkey fetuses have aspirated gastric fluid. The findings suggest that some component of gastric fluid plays an important role in the formation of the hyaline membranes, either directly by causing necrosis of susceptible bronchiolar epithelium or secondarily by sensitizing the bronchiolar epithelium to another necrotizing agent such as oxygen.

Animals↗