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Biomedical subjects

D Yeung

Publications and source records attributed to D Yeung.

At least 37 records · Page 2Linked to original sources
PubMed1984

Pathologic hip fractures secondary to amyloidoma. Case report and review of the literature.

Amyloidoma primarily involving bone and lymph node is described in a 60-year-old male patient. The patient had pathologic fractures of both hips through a deposit of amyloid in the neck of the femur. The prolonged insidious course of the disease was uncomplicated by hypercalcemia, hematologic abnormalities, or renal failure so characteristic of untreated myeloma. The bone marrow contained less than 10 percent plasma cells in different stages of maturity. Radionuclide bone scanning demonstrated other osseous amyloid lesions that were not detected by routine radiologic examination. This is the first reported case of pathologic fractures of both hips secondary to amyloidoma.

Amyloidosis↗
PubMed1983

Benzoyl peroxide: percutaneous penetration and metabolic disposition. II. Effect of concentration.

The effect of drug concentrations of 2.5%, 5%, and 10% upon the transepidermal penetration of 14C-benzoyl peroxide in a lotion vehicle was assessed in excised human skin and in vivo in the rhesus monkey. In vitro, penetration of benzoyl peroxide was concentration-dependent, both as to rate and to amount, as measured by the hourly recovery of the metabolite, benzoic acid, from the dermal side of the model. In vivo, the higher the concentration of benzoyl peroxide applied, the greater the amount absorbed, as indicated by the urinary excretion of 14C-benzoic acid. Metabolic disposition of benzoyl peroxide, in turn, was unaffected by drug concentration. In all instances, the benzoyl peroxide absorbed was excreted rapidly in urine as benzoic acid; no hippuric acid was detected at any time. We conclude that (1) use of the excised human skin model for this compound can provide useful data in studies of the effects of vehicle and concentration on topical drug delivery, (2) the transepidermal delivery of benzoyl peroxide, but not its metabolic disposition, is concentration-dependent, and (3) the renal clearance of the systemically absorbed drug is so rapid that it precludes passage through the liver--therefore, no systemic toxicity due to drug accumulation can be expected.

Administration, Topical↗
PubMed1983

Percutaneous absorption, blood levels, and urinary excretion of resorcinol applied topically in humans.

The absorption and metabolic disposition of 2% resorcinol applied topically in a hydroalcoholic vehicle was determined in three human subjects. The drug penetrated the skin at a rate of 0.37 micrograms/cm2/hour. After 2 weeks of bid application of 800 mg resorcinol to about 30% of body surface of each subject, an average of 1.64% of the dosage was being excreted in 24-hour urine specimens as the glucuronide or as the sulfate conjugate. There was no resorcinol in blood drawn at weeks 1, 2, 3, and 4, or nor were there any abnormalities in thyroid function or blood chemistries at weeks 2, 3, and 4. Resorcinol (2%) appears safe for topical use in humans.

Administration, Topical↗
PubMed1982

Influence of morphinization on the development of isoenzymes of pyruvate kinase in rat liver.

1. Acute administration or morphine to foetuses and neonates either directly or via the mother leads to a decrease in the total pyruvate kinase activity. 2. The L-type isoenzyme is selectively suppressed while the M-type isoenzyme is not altered to any significant extent with a consequent lowering of the L/M ratio. 3. The decrease in the total pyruvate kinase activity and the L/M ratio is more prominent when the route of administration of morphine is via the mother. 4. The possible explanation for this difference in the route of administration is that morphine can be converted into a more active metabolite with greater biological potency in adult animals.

Animals↗
PubMed1982

Pharmacokinetics of resorcinol in the rat.

Pharmacokinetic data on resorcinol were obtained from studies in the rat. The drug, administered subcutaneously in an aqueous solution, rapidly cleared plasma vir urine and did not accumulate in tissues. In the urine, the major metabolite of resorcinol was the glucuronide. Repeated dosing for 30 days with maximum tolerated daily doses of 100 mg/kg did not alter pharmacokinetic parameters, nor did it cause overt toxic signs or adverse reactions. The animals' body weight, blood values, levels of serum T3 and T4' and the gross and microscopic appearance of the thyroid gland and spinal cord remained within normal limits throughout the study.

Animals↗
PubMed1981

The composition of the skin surface lipids of the gerbil.

The skin surface lipids of the gerbil were found to consist sterol esters (10%), wax diesters (36.3%), triacylglycerol (26.1%), free fatty alcohols (8.8%), free fatty acids (5.4%), cholesterol (8.4%) and polar lipids (5%). The wax diesters, identified as Type II, were made up of saturated 1,2-diols with odd carbon number, esterified with two molecules of unsubstituted fatty acids with even carbon number. Both the triacylglycerols and the free fatty acid fractions had saturated and unsaturated components. The free and esterified sterols were all cholesterol. The sterol esters contained saturated monoenoic and dienoic fatty acids, with both straight- and branched-chain components. The fatty alcohols were all straight-chain in structure, mostly of even carbon number. Comparison of these results with those previously reported for other species, indicates that the gerbil skin surface lipids are unique in that they contain diacyl alkane diols and fatty alcohols, both of which consist exclusively of saturated components.

Animals↗
PubMed1981

Benzoyl peroxide: percutaneous penetration and metabolic disposition.

The transepidermal penetration and metabolic disposition of 14C-benzoyl peroxide were assessed in vitro (excised human skin) and in vivo (rhesus monkey). In vitro, the benzoyl peroxide penetrated into the skin, through the stratum corneum or the follicular openings, or both, and was recovered on the dermal side as benzoic acid. In vivo, benzoic acid was recovered from urine in amounts equivalent to 45% and 98% of the radiolabel following, respectively, topical and intramuscular administration of small amounts of 14C-benzoyl peroxide. We conclude that benzoyl peroxide penetrates as such into the skin layers and is converted therein to benzoic acid, which, in turn is absorbed into the systemic circulation. Renal clearance of the metabolite is sufficiently rapid as to preclude its hepatic conjugation with glycine, since following topical administration to rhesus monkeys, no hippuric acid was found in the urine, as could have been expected had a significant amount of benzoic acid passed through the liver.

Administration, Topical↗
PubMed1980

Comparative studies on threonine and serine dehydratases in rat liver.

1. Two isoenzymes of serine (threonine) dehydratase can be separated by DEAE cellulose chromatography. 2. Each of these isoenzymes possesses different S:T (serine dehydratase activity: threonine dehydratase activity) ratio and kinetic properties. 3. In early postnatal development, the S:T ratio shows marked variation. 4. The hepatic S:T ratio also changes with dietary manipulations. Furthermore L-alanine inhibits enzymic activities towards serine and threonine to different extent. 5. The results are consistent with the hypothesis postulating the presence of two distinct proteins each having a different activity ratio towards serine and threonine.

Alanine↗
PubMed1979

Apparent inhibition of pyruvate kinase by phosphocreatine and phosphoarginine.

1. Addition of a non-dialysable, heat-labile and acid-precipitable factor which was not absorbed on DEAE-cellulose column, could restore the sensitivity of the chromatographed muscle pyruvate kinase from Marphysa sanguinea towards phosphocreatine inhibition. 2. This factor, being non-specific as it acts on pyruvate kinase isozymes from different sources, demonstrated high creatine kinase activity. 3. High concentrations of ADP, creatine or replacement of ADP with IDP/UDP or high pH abolished the inhibition indicating that the inhibition was mediated through creatine kinase by depleting ADP. 4. Apparent inhibition of phosphocreatine was related to the relative activities of 3 intracellular enzymes--pyruvate kinase, creatine kinase and adenosine triphosphatase.

Animals↗
PubMed1978

Comparative studies of vertebrate and invertebrate pyruvate kinases.

1. Electrophoretic patterns showed that among the vertebrates studied, L isozyme was present in rat and frog liver and also in rat kidney. 2. M2 is a frequent component in vertebrate tissues, giving support to the proposal that M2 is the ancestral form differentiating to other isozymes. 3. The above trend cannot simply apply to invertebrates. 4. Muscle pyruvate kinases from various animals were inhibited by the particular phosphagen present in their muscle. 5. The inhibition may have an important role in the regulation of glycolysis in muscle.

Animals↗