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Biomedical subjects

D A Black

Publications and source records attributed to D A Black.

9 recordsLinked to original sources
PubMed1988

Oxypurine cycle in human erythrocytes regulated by pH, inorganic phosphate, and oxygen.

The effect of pH, PO2, and inorganic phosphate on the uptake and metabolism of hypoxanthine by erythrocytes has been studied. Uptake of hypoxanthine and accumulation of inosine 5'-monophosphate (IMP) were markedly increased at acid pH, high external phosphate concentrations, and low PO2. Release of accumulated IMP as hypoxanthine occurred at alkaline pH values and low external phosphate concentrations. Conditions favoring IMP accumulation gave rise, in the absence of hypoxanthine, to a corresponding increase in 5'-phosphoribosyl-1-pyrophosphate. Intracellular phosphate concentrations were markedly pH dependent and a model is presented whereby hypoxanthine uptake and release are controlled by intracellular concentrations of inorganic phosphate and 2,3-bisphosphoglycerate. These allosteric effectors influence, in opposing ways, two enzymes governing IMP accumulation, namely 5'-phosphoribosyl-1-pyrophosphate synthetase and 5'-nucleotidase. These metabolic properties suggest that the erythrocyte could play a role in the removal of hypoxanthine from anoxic tissue.

Adenosine Diphosphate↗
PubMed1978

A rapid technique for producing silver-stained nucleolus organizer regions and trypsin-giemsa bands on human chromosomes.

A simple and rapid technique is described whereby the nucleolus organizer regions (NORs) of human chromosomes can be differentially stained with silver. This staining is followed by trypsin-Giemsa banding on the same metaphase chromosomes. The metaphases simultaneously exhibit silver-stained NORs and G bands, allowing for the unequivocal identification of all chromosomes and greatly facilitating studies involving the NOR-bearing acrocentrics.

Azure Stains↗
PubMed1977

Syphla-Chek: a qualitative study.

A qualitative evaluation of the newly marketed Syphla-Chek Test (Hyland, Div. of Travenol Laboratories, Inc., Costa Mesa, Calif.), a macroscopically read, nontreponemal card test, was undertaken in order to further evaluate the validity of this procedure as an aid in the diagnosis of syphilis. A total of 1,074 randomly selected sera submitted to the Texas Department of Health Resources for routine analysis, for confirmational analysis, and as a result of problems in analysis, were examined using the Venereal Disease Research Laboratory (VDRL) slide test, the Rapid Plasma Reagin (circle) Card Test (RPRCT), Syphla-Chek Test, and the fluorescent treponemal antibody absorption (FTA-ABS) test. Comparison of the reagin testing procedures studied versus the FTA-ABS procedure led to the following order of agreement with FTA-ABS reactive results: Syphla-Chek, 88.8%; RPRCT, 87.1%; and VDRL, 83.2%. Agreement with FTA-ABS nonreactive results was in order: RPRCT, 86.7%; Syphla-Chek, 79.6%; and VDRL, 78.7%. The relatively few minor procedural problems encountered with the Syphla-Chek Test during this study are also discussed.

Antibodies↗
PubMed1976

Qualitative evaluation of the reagin screen test.

After a preliminary study of 557 sera used as a procedural training exercise, the Reagin screen test (RST) for the macroscopic detection of reagin (as an aid to detecting syphilis) was qualitatively compared to the rapid plasma Reagin (RPR) (circle) card test and Veneral Disease Research Laboratory (VDRL) slide test on 435 random portions of sera using fluorescent treponemal antibody adsorption (FTA-ABS) results as a comparative base. A comparison of total agreement (positive and negative) with the FTA-ABS results led to the following order. RPRCT (I5.5%), VDRL (79.8%), and RST (74.5%). Of the total samples shown to be reactive by the FTA-ABS procedure, the percentage of these interpreted as nonreactive (i.e., "false negative") by the procedures compared was considerably higher with the RST procedure (29.3%) than with either the RPRCT (10.9%) or the VDRL (7.1%) procedures. Minor problems encountered with procedural techniques are also mentioned.

Antibodies↗
PubMed1975

Sleep cycle control and cholinergic mechanisms: differential effects of carbachol injections at pontine brain stem sites.

Muscular atonia and cortical desynchronization, two signs of desynchronized sleep, can be enhanced or suppressed by direct injection of carbachol into the pontine brain stem of cats. The positive effects are graded, being maximal in the gigantocellular tegmental field and less marked in adjacent nuclei. These positive effects are dose-dependent. Suppressive effects of carbachol are maximal in the region of the locus coeruleus and are dose-dependent but do not exceed those of the vehicle alone. The results support the hypothesis that cholinergic mechanisms of the pontine tegmentum are involved in desynchronized sleep generation.

Acetylcholine↗
PubMed1975

Priorities in biomedical research. Indices of burden.

The relative burden of different diseases is a legitimate component in the consideration of priorities for biomedical research. Simple prevalence statistics do not directly reflect the different burdens on services imposed by diseases of comparable prevalence. This paper sets out for each 54 categories of disease five indices of the burden on services, based respectively on inpatient days, outpatient referrals, consultations in family practice, sickness benefit, and loss of expectation of life. There is considerable variation in the rank-order of categories of disease, in their contribution to the five burdens; but for each burden the number of categories accounting for 50% of the total burden is not large, ranging from 3 to 9 out of the possible 54.

England↗