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Biomedical subjects

P Dunham

Publications and source records attributed to P Dunham.

33 records · Page 2Linked to original sources
PubMed1979

Health administration: devolution philosophy heads towards a better tomorrow.

Reorganisation preached it; the Royal Commission commended it, the new Government has welcomed it. But the 'greater degree of delegation of authority and responsibility' that is the devolutionist's dream has already come true for Claybury Mental Illness Hospital on London's periphery. What Claybyry does today others might wish to try tommorrow. Authors believe they have seen that tomorrow--and it works.

England↗
PubMed1979

Inhibitors of membrane transport reduce lysosomal enzyme secretion from dogfish phagocytes and their killing of sea urchin eggs.

Blood phagocytes of the dogfish Mustelus canis attack oocytes of the sea urchin Arbacia punctulata, first provoking a surrogate fertilization response and then killing the eggs. To test the hypothesis that secretion of lysosomal contents is critical in this model of phagocyte-mediated cell injury, we studied effects of agents that modify lysosomal enzyme secretion. Inhibitors of membrane transport (>0.1 mM) inhibited postphagocytic secretion of lysosomal beta-glucuronidase from dogfish phagocytes: phloretin > ethacrynate > furosemide > 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid >> pyridoxal phosphate > ouabain. The same order of activity was found for inhibition by these agents of killing of Arbacia eggs by phagocytes. Cell activation (fertilization response) and cytotoxicity were quantitated both morphologically and by measurements of enzyme (beta-glucuronidase, catalase) release. The agents neither inhibited fertilization responses of eggs to calcium ionophore A23187 nor impaired their viability. Vital staining demonstrated that ethacrynate prevented phagocytes from degranulating upon contact with zymosan particles. The data not only suggest that agents primarily known for their capacity to inhibit membrane transport systems can inhibit lysosomal enzyme secretion from phagocytes but also support the hypothesis that secretion of lysosomal contents mediates activation and killing of target cells in phagocyte-mediated tissue injury.

Animals↗
PubMed1978

Retention of bilateral performance as a function of practice order.

The purpose of this study was to investigate the effect of practice order and initial performance hand on the bilateral retention of a simple tracking skill for 44 undergraduate volunteers. The apparatus was a Lafayette Model 30014 photoelectric rotary pursuit. The circle template was employed with rotation speed set at 20 rpm. Subjects were given 20-sec. trials and required to reach a criterion of 70% time on target twice in succession with both hands. For original practice, subjects were randomly assigned to one of four practice groups: preferred serial, non-preferred serial, preferred sequence and non-preferred sequence. Subjects' performance was recorded as the number of trials required to achieve criterion for both hands. One month later subjects were retested and scored in the same manner. A 2 X 2 X 2 analysis of variance with repeated measures on the last factor was used to determine the effects of initial hand, order of practice, testing periods, and the appropriate interactions. The results indicated that subjects' performance for the two testing periods differed significantly; retest was superior. Order of practice was significant and the sequential order more efficient during both learning and retest.

Adolescent↗
PubMed1977

Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes.

Fusion between vesicles, cells, or organelles may be defined as confluence of two membrane-bound compartments without access of their solutes to external milieu. To study fusion by this criterion, we have trapped the metallochromic calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIII-Ca) in one population of liposomes (phoshatidylcholine 90:dicetylphosphate 10), and ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetate (EGTA) in a second. In such mixtures, interaction of EGTA with AIII-Ca was measured by a large color shift from blue leads to red (decreased absorbance at 660 nm). Fusion of liposomes (but also lysis and diffusion across the membranes) was proportional to these decrements. The exogenous "fusogens," lysolecithin and retinol, were added to liposomes for 5-24 hr at 37 degrees; after rechromatography, measurements were made of total dye, fraction of dye converted from AIII-Ca to AIII, and total lipid. After correction for lysis and diffusion, lysolecithin (200 microng/ml) induced 23% fusion (volume of AIII liposomes confluent with EGTA liposomes) and retinol (300 microng/ml) induced 15%. With one molar percent cortisol (a membrane stabilizer) in the liposome membranes, fusion induced by fusogens was reduced 2-fold. Neither multi-nor unilamellar liposomes fused with each other in the absence of exogenous fusogens, despite wide variations in molar lipid ratios. Results suggest that liposome-liposome fusion is a slow process requiring exogenous fusogens, which may depend upon contributions of other membrane constituents to mimic closely the fusion of natural membranes.

Arsenicals↗
PubMed1976

Membrane perturbation: studies employing a calcium-sensitive dye, arsenazo III, in liposomes.

A metallochromic dye, arsenazo III [2,7-bis-(2-arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid], has been incorporated into the aquenous interspaces of multilamellar liposomes. multilamellar liposomes. Addition of Ca produced no shift in the absorbance spectrum of dye captured by liposomes, whereas disruption of liposomes by Triton X-100, followed by Ca, produced the spectrum chracteristic of the dye-Ca complex: evidence of latency. Addition of excess ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) reversed the spectal shift. Differences between spectra obtained in this sequence yielded dye efflus. To measure Ca efflux, difference spectra (+/-EGTA) were obtained from cationic liposomes containing Ca after detergent lysis (sensitivity less than 10 mmol/ml). Since liposomes were impermeable either to dye or Ca until perturbed, it was possible to test a variety of membrane-active steroids (diethylstilbesterol, deoxycorticosterone, etiocholanolone) for their capacity to provoke dye efflux from liposomes; preincorporation of cortisol stablized liposomes against dye leak. Immunoglobulin-coated liposomes containing dye were taken up by phagocytes of Mustelus canis, and phagocytic vacuoles stained red-purple after ingestions. Liposomes containing the calcium-sensitive dye constitute a simple, accurate means for determining membrane perturbation and Ca fluxes; their uptake by cells or organelles remains to be exploited further.

Animals↗
PubMedDate not supplied

HK/LK polymorphism and its genetic determination in Speke's gazelle.

Concentrations of potassium (K) and sodium (Na) were determined in the erythrocytes of 28 members of an interbreeding herd of Speke's gazelle. The distribution of K concentrations and Na/K concentration ratios suggested the presence of the high-K/low-K (HK/LK) polymorphism known in erythrocytes of domestic bovids. The pedigree of the herd of gazelles is known completely, permitting examination of the inheritance of HK/LK polymorphism by overlaying the distribution of phenotypes on the pedigree. Statistical analyses clearly indicate a strong genetic component in the phenotypic variability that is entirely consistent with a single autosomal locus, two-allele mode of inheritance, with the LK allele being dominant. This is the first demonstration of HK/LK polymorphism in a wild bovid species. The evidence indicates that HK/LK polymorphism is of considerable evolutionary age, is of monophyletic origin, and is maintained by selection.

Alleles↗
PubMedDate not supplied

Co-operative learning opportunities.

Government initiatives which encourage joint ventures between the public and independent health-care sectors offer opportunities for the development of student and trained nurse educational curricula. Peter Dunham outlines the proposals initiated by East Surrey Health Authority and BUPA Gatwick Park Hospital to facilitate quality learning experiences for the nurses of both authorities. The measures, he believes, open the door to future developments.

Education, Nursing↗