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Biomedical subjects

D D Clarke

Publications and source records attributed to D D Clarke.

At least 37 records · Page 2Linked to original sources
PubMed1985

Gastric acid secretory function in preterm infants.

To establish normal values for gastric secretory function in preterm infants, we studied 34 healthy preterm infants once a week during hospitalization. Basal acid output, pentagastrin-stimulated acid output, fasting serum gastrin, and fasting serum pancreatic polypeptide were measured during each study. Basal acid output at 1 week of age was 12 mumol/kg/hr, increasing over the first 4 weeks to 30 mumol/kg/hr. Administration of pentagastrin 6 micrograms/kg subcutaneously increased acid output in all age groups. Pentagastrin-stimulated acid output at 1 week was 21 mumol/kg/hr, increasing over the first 4 weeks to 44 mumol/kg/hr. Acid secretion did not change significantly over the next 4 to 6 weeks. Fasting serum gastrin concentration was stable over the first 6 weeks of life, but doubled during the end of the second month. Pancreatic polypeptide was found at low levels throughout the study. These studies confirm that the majority of healthy preterm infants secrete acid in quantity sufficient to maintain the gastric pH less than or equal to 4, providing a barrier to bacteria and protein antigens.

Achlorhydria↗
PubMed1985

Effect of age on contrast sensitivity function: uniocular and binocular findings.

Monocular and binocular contrast sensitivity function for a range of spatial frequencies was measured in two groups of subjects with normal vision. Statistically significant differences in performance between the younger group (age 20-30 years) and the older group (age 50-87 years) were found at all spatial frequencies sampled between 0.40 and 19 X 25 cpd. In the age range 50-87 years there was a linear decline in contrast sensitivity with age for medium and high spatial frequencies, but sensitivity for low spatial frequencies was independent of age.

Adult↗
PubMed1984

Contrast sensitivity and visual disability in chronic simple glaucoma.

A battery of vision tests was used to quantify visual defect in a group of 50 patients with chronic simple glaucoma. The vision tests were near and distance visual acuity, visual fields, and contrast sensitivity to static and temporally modulated sinusoidal grating patterns. Of these, static contrast sensitivity function appears to be the most sensitive method of measuring visual defect in glaucoma patients. The visual disability experienced by the glaucoma patients was quantified by means of a questionnaire, and the relationship between perceived visual disability and visual defect was examined. It was found that results from a group of tests, near visual acuity, visual field, and contrast sensitivity measures, are the best predictors of the difficulty experienced by patients in performing visually dependent daily activities.

Activities of Daily Living↗
PubMed1983

Acetylation of synaptosomal protein: inhibition by veratridine.

Incubation of synaptosomes with [3H]acetate results in rapid labeling of protein. Labeling is decreased in the presence of veratridine, and the effect of veratridine is blocked by tetrodotoxin. Most of the radioactivity can be removed by base or acid hydrolysis, and is probably incorporated as acetate; it is this fraction that is affected by the veratridine. The data suggest that veratridine stimulates deacetylation is involved in membrane function.

Acetates↗
PubMed1983

Is acetylation of protein involved in membrane function?

[3H]-acetate is rapidly incorporated as the acetyl moiety into synaptosomal protein and the apparent rate appears to decrease after approximately 1-2 minutes. A second dose of labeled acetate given 6 minutes after the first shows the same time dependent process suggesting that the protein substrate is not depleted. The apparent fall-off in the rate may represent the approach to a steady state of the mixing of the added acetate with internal cold acetate. Veratridine or batrachotoxin appears to stimulate a deacetylation process and tetrodotoxin blocks the effect of veratridine. Several proteins are acetylated at least one of which appears to be a glycoprotein of relatively low molecular weight. The presence of cold pyruvate or glucose competes with the incorporation of labeled acetate; the implication is that glucose and pyruvate can serve as a source of acetyl CoA for protein acetylation. The studies suggest that acetylation-deacetylation processes may be involved in membrane function, possibly in ion and/or transmitter channels.

Acetates↗
PubMed1980

Oxidative metabolism of 4-aminobutyrate by rat brain mitochondria: inhibition by branched-chain fatty acid.

The oxidation of 4-aminobutyric acid (GABA) by nonsynaptosomal mitochondria isolated from rat forebrain and the inhibition of this metabolism by the branched-chain fatty acids 2-methyl-2-ethyl caproate (MEC) and 2.2-dimethyl valerate (DMV) were studied. The rate of GABA oxidation, as measured by O2 uptake, was determined in medium containing either 5 or 100 mM-[K+]. The apparent Km for GABA was 1.16 +/- 0.19 mM and the Vmax in state 3 was 23.8 +/- 5.5 ng-atoms O2 x min-1 x mg protein-1 in 5 m M-[K+]. In a medium with 100 mM-[K+] the apparent Km was 1.11 +/- 0.17 mM and Vmax was 47.4 +/- 5.7 ng-atoms O2 x min-1 x mg protein-1. The Ki for MEC was determined to be 0.58 +/- 0.24 or 0.32 +/- 0.08 mM, in 5 or 100 mM-[K+], respectively. For DMV, the Ki was 0.28 +/- 0.05 or 0.34 +/- 0.06 mM, in 5 or 100 mM-[K+] medium, respectively. The O2 uptake of the mitochondria in the presence of GABA was coupled to the formation of glutamate and aspartate; the ratio of oxygen uptake to the rate of amino acid formation was close to the theoretical value of 3. Neither the [K+] nor any of the above inhibitors had any effect on this ratio. The metabolism of exogenous succinic semialdehyde (SSA) by these same mitochondria was also examined. The Vmax for utilization of oxygen in the presence of SSA was much greater than that found with exogenously added GABA, indicating that the capacity for GABA oxidation by these mitochondria is not limited by SSA dehydrogenase. In addition, the branched-chain fatty acids did not inhibit the metabolism of exogenously added SSA. Thus, the inhibitors examined apparently act by competitively inhibiting the GABA transaminase system of the mitochondria.

Animals↗
PubMed1978

Amino acid analogs IV:4-fluoroisoleucine.

4-Fluoroisoleucine was produced by ammonolysis of 2-bromo-4-fluoro-3-methylpentanoic acid, which resulted from the bromofluorination of 4-methyl-2-pentenoic acid. It did not inhibit Plasmodium berghei in mice at 640 mg/kg and was not toxic to the animals. The fluoroamino acid inhibited Aspergillus niger, Trichoderma viride, Myrothecium verrucaria, Trichophyton mentagrophytes, and Mucor mucedo in Czapek solution agar at a concentration between 10(4) and 10(3) microgram/ml. Growth of Escherichia coli was inhibited 25% at 900 microgram/ml in a defined medium.

Animals↗
PubMed1978

The teaching of medical ethics: University College, Cork, Ireland.

Dolores Dooley Clarke describes how the course in medical ethics at University College, Cork is structured, how it has changed and how it is likely to change as time goes on. Originally, the students seemed to view it as an intrusion 'to be tolerated' in their programme of 'strictly medical' studies. However, having moved on from that and away from the lecturer always being a Roman Catholic priest as well as a member of the Philosophy Department, the students now appear to view it as producing a stimulus for a new interest in the area of ethics for physicians. This seems to have come about through the more extensive participation of students in researching and presenting issues of medical ethics.

Bioethical Issues↗