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Biomedical subjects

E L McGown

Publications and source records attributed to E L McGown.

At least 19 recordsLinked to original sources
PubMed1992

Regeneration of functional hemoglobin from iron(III) hemoglobin by reduction with hydrogen and a heterogeneous catalyst.

Functional hemoglobin was regenerated from partially autoxidized hemoglobin by reduction with molecular hydrogen in the presence of a heterogeneous catalyst consisting of elemental platinum embedded in an electroactive polymer. The visible spectrum of the regenerated hemoglobin was identical to that of native iron(II) hemoglobin. The regenerated hemoglobin displayed highly cooperative oxygen-binding characteristics. P50 values for oxidized-regenerated hemoglobin samples were not different from native hemoglobin. The Hill coefficients for regenerated hemoglobin were slightly lower than the controls, possibly because of small amounts of irreversibly oxidized hemoglobin arising during the initial autoxidation. The advantages of the reduction system include: (1) the heterogeneous catalyst avoids the problem of protein adsorption onto bare platinum, (2) catalyst and reducing agent are easily removed from the protein, and (3) the by-product H+ is buffered easily.

Buffers↗
PubMed1991

Substituent effects on the binding constants of arsenical-dithiol adducts.

Proton nuclear magnetic resonance spectroscopy (1H NMR) was used to determine the relative binding constants for several arsenical-dithiol adducts. The compounds investigated were 2,3-dimercaptopropanol (British anti-lewisite; BAL), 1,2-ethane dithiol (ET), and 1,2-propane dithiol (PDT). It was found that PDT has a significantly higher affinity than ET or BAL for phenyldichloroarsine (PDA) in methanol.

Arsenicals↗
PubMed1990

Reduction of extracellular methemoglobin by erythrocytes.

Erythrocytes, suspended in a glucose-containing buffer, catalyzed the partial reduction of extracellular methemoglobin. Physiological concentrations of ascorbic acid or dehydroascorbic acid greatly enhanced the rate of reaction and the ultimate extent of reduction. The relationship between erythrocyte concentration and initial reaction rate was nonlinear, which suggested that the rate limiting factor was not an erythrocyte membrane enzyme. Also, significant dehydroascorbate-stimulated reduction occurred even when the erythrocytes and methemoglobin were separated by a dialysis membrane. The above observations indicate that the transfer of reducing equivalents across the erythrocyte membrane and reduction of extracellular methemoglobin can be accomplished by release and recycling of ascorbic acid.

Ascorbic Acid↗
PubMed1988

Gas chromatographic analysis of urinary dimercaptosuccinic acid.

The therapeutic use of disulfhydryl compounds such as 2,3-dimercaptosuccinic acid (DMSA) for the treatment of heavy metal poisoning has generated a requirement for specific and sensitive methods to determine those compounds in biological media. We have developed a gas chromatographic assay for DMSA in urine. The use of capillary column technology eliminates the requirement for a preliminary clean-up step. Samples are first reduced electrochemically to liberate DMSA present as disulfides. The reduced product is then extracted into ethyl acetate and the organic phase removed by evaporation. The residue is derivatized with N,O-bis (trimethylsilyl) acetamide for gas chromatography. The silylated DMSA derivative is then detected with a flame ionization detector. The detection limit for DMSA is 1.9 nmol per 1-microliter aliquot of derivatized extract injected on column (detector sensitivity at 1.10(-11) A/mV). The utility of the method was demonstrated by analyzing the urine of rats orally dosed with DMSA.

Administration, Oral↗
PubMed1987

One-dimensional and two-dimensional nuclear magnetic resonance studies of the reaction of phenyldichloroarsine with glutathione.

14C-labeled phenyldichloroarsine (PDA) enters the red blood cell and forms a 1:2 adduct with intracellular glutathione. Upon gel filtration of the hemolysate, [14C]PDA was recovered with the glutathione-containing fractions. One-dimensional and two-dimensional nuclear magnetic resonance spectroscopy were used to confirm the structure of the adduct and elucidate its stereochemistry, stability, and reactivity.

Arsenicals↗
PubMed1987

Histologic changes in nude mouse skin and human skin xenografts following exposure to sulfhydryl reagents: arsenicals.

This report documents the histological changes in nude mouse skin and in human skin xenografts on nude mice following exposure to phenyldichloroarsine (PDA), a vesicant arsenical. Under light microscopy, we observed in PDA-treated human skin grafts: 1) degeneration of epidermal cell nuclei (apparent by 2 hr after exposure with increasing severity through 48 hr); 2) loss of epidermal cytoplasmic basophilia (apparent by 4 hr, maximal within 12 hr); 3) epidermal cytoplasmic vacuolization (vacuoles appeared within 4 hr and increased in size through 24 hr); 4) cleft formation within the basement membrane zone (apparent by 12 hr, increasing in severity through 24 hr); 5) inflammation evidenced by polymorphonuclear leukocyte (PMN) infiltration (apparent by 4 hr and increasing through 48 hr). The PMNs frequently formed a wall around the lesion, but did not infiltrate the treated area. Nude mouse skin reacted faster to PDA than did the grafts, but the histological changes were similar. Nude mouse hair follicles and sebaceous glands showed similar cellular changes at approximately the same time as did epidermal cells. Transmission electron microscopy of mouse skin exposed to PDA revealed a widening of intercellular spaces with attenuation of desmosomes. The subepidermal clefts resulted from separation within the lamina lucida with the lamina densa forming the base of the cleft. Diphenylchloroarsine caused lesions histologically indistinguishable from those of PDA. Lesions resulting from exposure to other sulfhydryl-binding compounds were very different from arsenical lesions. The arsenical-sensitive cellular constituents were not identified.

Animals↗
PubMed1982

Erythrocyte filterability, fragility, and membrane proteins in folic acid deficient guinea pigs.

The purpose of this study was to determine if erythrocytes from folic acid-deficient guinea pigs could be used as a model for the study of defects which have been reported in megaloblastic anemic patients. Reported defects include decreased deformability and abnormal membrane proteins. Red cell filterability was studied with polycarbonate sieves and cellulose filters. Membrane proteins were analyzed by polyacrylamide gel electrophoresis in sodium in sodium dodecyl sulfate. Severe folate deficiency in guinea pigs caused no change in erythrocyte filterability or membrane proteins. Thus, the defects which have been reported in human folic acid or vitamin B-12 deficiency are not present in all animals with the same nutrient deficiency. Folate deficiency, however, did cause guinea pig erythrocytes to be markedly less susceptible to hypotonic lysis than cells from control animals, a feature which is not characteristic of human megaloblastic anemia.

Animals↗
PubMed1982

Interactions between folate and ascorbic acid in the guinea pig.

Possible interactions between folic acid (folate) and ascorbic acid (AA) have been suspected because megaloblastic anemia is occasionally observed in scorbutic patients, and it may or may not respond to folate treatment. Male weanling guinea pigs were fed diets containing high levels of folate and AA or diets deficient in one or both vitamins. A total of 36 animals, including 9 controls, were studied. When anorexia began to appear in the deficient groups, all animals were killed by exsanguination, and tissue samples (blood, liver, adrenal, kidney, spleen, and intestinal mucosa) were removed for AA and folate analyses. Folate and AA deficiency lowered tissue folate and AA levels, respectively. AA deficiency, either alone or in combination with folate restriction, did not affect tissue folate levels, nor did AA deficiency significantly exacerbate the anemia and leukopenia caused by folate deficiency. However, there was an unexpected decrease in AA levels in the liver and adrenal glands with folate deficiency. Although AA does not appear to be needed for normal folate metabolism, the lower AA levels associated with a folate deficiency are indicative of an interaction between the two vitamins.

Anemia, Megaloblastic↗
PubMed1982

A continuous-flow (AutoAnalyzer II) procedure for measuring erythrocyte transketolase activity.

In this semiautomated method, an AutoAnalyzer II is used to measure the enzymic production of glyceraldehyde 3-phosphate in hemolysates, to assay erythrocyte transketolase (EC 2.2.1.1) activity. Hemolysate and indicator reactions are separated by dialysis to eliminate hemoglobin interference and increase sensitivity. Internal standards of glyceraldehyde 3-phosphate in hemolysate carriers were quantitatively measured with good precision and accuracy in the presence or absence of the transketolase substrate, ribose 5-phosphate. Chart-recorder values for these standards were used to calibrate the AutoAnalyzer output in IUB units (U) of transketolase activity. Substrate-product relationships were examined to characterize reaction kinetics and optimize assay conditions. AutoAnalyzer transketolase results correlated well with those from two manual procedures.

Autoanalysis↗
PubMed1981

The relationship of the urinary ascorbate metabolites to specific levels of ascorbate supplementation in the monkey.

This study was designed to investigate urinary ascorbic acid (AA) and its metabolites derived from (1-14C) AA administered to trained monkeys fed different levels of ascorbate for extended periods of time. A chromatographic procedure was developed which rapidly separates the urinary compounds into four major fractions with minimal degradation. The distribution of 14C in the four peaks was dependent upon the ascorbate nutritional status of the monkey and remained constant for at least 30 days postlabel. The two major fractions were identified as oxalate and unmetabolized ascorbate. The ascorbate metabolites in the two minor fractions have not been identified. In monkeys maintained on low ascorbate intakes, unmetabolized ascorbate accounted for 10 to 20% and oxalate 25 to 48% of the urinary 14C. The average percentages of 14C in the urine of monkeys fed high levels of ascorbate were 75% for ascorbate and 7% for oxalate. The urine also contained an ascorbate metabolite which degraded during storage and/or chromatography, yielding 14CO2. Ascorbate sulfate was not detected as a urinary metabolite.

Animals↗
PubMed1980

Thiamin, riboflavin, and vitamin B6 contents of selected foods as served.

Information of thiamin, riboflavin, and vitamin B6 contents of eighty-one food items is presented. The data represent over two hundred samples collected from serving lines in dining halls of two military installations. Ninety per cent of the vitamin B6 values and 35 per cent of the thiamin and riboflavin diata are not available in the current literature. In contrast to most previously published data, the emphasis in this study was on the vitamin contents of prepared food items on an "as served" basis.

Cooking↗