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Biomedical subjects

R Clarke

Publications and source records attributed to R Clarke.

At least 253 records · Page 14Linked to original sources
PubMed1983

Reduction of the anti-metabolic and anti-proliferative effects of methotrexate by 17 beta-oestradiol in a human breast carcinoma cell line, MDA-MB-436.

We have investigated the modifying influence of 17 beta-oestradiol on the anti-metabolic and growth inhibitory actions of methotrexate (MTX) in a human breast cancer cell line, MDA-MB-436. This cell line contains detectable oestrogen receptors but is progesterone receptor-negative. Furthermore, 17 beta-oestradiol (10(-10) - 10(-6)M) failed to influence DNA synthetic rate as assessed by [3H]-TdR or [3H]-UdR incorporation and cell proliferative rate was similarly unaffected. Although by these criteria 17 beta-oestradiol failed to elicit a biological response in the MDA-MB-436 cell line, 10(-6)M 17 beta-oestradiol significantly reduced the anti-metabolic and anti-proliferative actions of MTX. In the presence of 17 beta-oestradiol approximately twice the concentration of MTX was required to inhibit cell proliferation to the same extent as was observed following exposure to MTX alone. This partial reversal of MTX effects was accompanied by a 20% reduction in the steady-state intracellular MTX concentration when cells were exposed to the drug in the presence of 10(-6)M 17 beta-oestradiol.

Breast Neoplasms↗
PubMed1981

Rapid oxidation in vitro of endogenous and exogenous glutathione in bile of rats.

Biliary excretion of glutathione has recently been described but poorly characterized. Controversy has existed concerning the relative contribution of oxidized and reduced glutathione to total glutathione efflux from the liver into bile. We found that bile, unlike liver cytosol or buffer, had the unique ability to oxidize GSH rapidly (t 1/2 = 5 min) to the disulfide form by a nonenzymatic, O2, and pH-dependent chemical reaction inhibited by only certain chelating agents. Significant oxidation of GSH occurred during the collection of bile samples resulting in significant time-dependent alterations in the ratio of biliary GSH to GSSG. Thus the preponderance of GSSG in bile in the normal state reported by others represents a postexcretory in vitro artifact. Inhibition of oxidation by acidification of bile during its collection established the true contribution of GSH and GSSG to total biliary efflux.

Animals↗
PubMed1981

Progressive hearing loss in children: hearing aids and other factors.

A sample of 20 children monitored for progressive hearing loss combined with 25 progressive loss cases were obtained. The effects of hearing aid use on progressive loss were examined in the context of etiology and other factors, particularly the time relations between hearing aid application and the period of progression. Results indicate a limited role played by hearing aids in progressive hearing loss. Hearing aid use was not implicate in 30 (69%) of the progressive loss subjects, questionably implicated in nine (20%), and probably implicated in five (11%). In the identification and monitoring of progressive hearing loss, it is unwise to conclude that hearing aid use is the cause of the deterioration without considering all other plausible factors.

Adolescent↗
PubMed1980

Correlation between soma size and dendritic morphology in cat retinal ganglion cells: evidence of further variation in the gamma-cell class.

The morphology of ganglion cells in the cat's retina has been examined in Golgi-impregnated whole mounts. The alpha-, beta-, and gamma-cell groups described by Boycott and Wässle ('74) were observed. Also observed were many cells with wide dentritic fields typical of gamma-cells, and medium-sized somas more usually associated with beta-cells. It is suggested that these cells belong to the gamma-cell group, adding to the variety already described by Boycott and Wässle among gamma-cells.

Animals↗
PubMed1980

Gradients between nasal and temporal areas of the cat retina in the properties of retinal ganglion cells.

Evidence is presented of gradients between nasal and temporal areas of the cat's retina in the properties of their ganglion cell populations. Mean ganglion cell size is greater in temporal retina than in nasal retina, partly because the alpha- and beta-cells of temporal retina are distinctly bigger than their counterparts in nasal retina, and partly because more medium-sized cells, and fewer small cells, are to be found in temporal retina. This high proportion of medium-sized ganglion cells may reflect a high proportion of beta-cells or of the medium sized gamma-cells described by Stone and Clarke ('80). Several of these differences can be related to prior morphological, electrophysiological, and behavioural observations in the cat, and similar differences have been reported in several other mammalian species. Evidence is presented that, in the cat, at least some of these differences are less marked near the vertical meridian of the retina than more temporally or nasally. The present results may therefore, be evidence of a nasal-temporal gradient in retinal structure and funtion common to many mammals, and distinct from previously recognised gradients in ganglion cell properties related to the area centralis and visual streak specialisations.

Animals↗
PubMed1978

Concentration of antibiotics in normal bone after intravenous injection.

The concentrations in serum, cancellous bone, and cortical bone of three antibiotics--nafcillin, cefazolin, and gentamicin--were measured in eleven normal dogs. All antibiotics rapidly penetrated into bone. The peak concentration in serum was reached within twenty minutes of intravenous injections, and the concentration in bone generally paralleled that in serum. Cancellous bone had higher concentrations than did cortical bone because of the admixture of blood.

Animals↗
PubMed1977

Biomedical survey in North Samar Province, Philippine Islands.

A biomedical survey was carried out in North Samar Province, Philipines to update information on the prevalence of parasitic and other infectious diseases. A total of 1,394 stool specimens, 1,859 blood smears and 1,274 sera were collected from persons living in 8 barrios. Stools were examined for intestinal parasites, bloods smears for malaria and filariasis and sera tested for antibodies to Schistosoma japonicum, Entamoeba histolytica, Toxoplasma gondii, influenza A and B, and Japanese encephalitis virus. The prevalence rates for intestinal parasites were: Trichuris trichiura 90%, Ascaris lumbricoides 78%, hookworm 65%, Schistosoma japonicum 15%, Strongyloides stercoralis 1%, Entamoeba coli 16%, Endolimax nana 6%, entamoeba histolytica 5%, Giardia lamblia 3%, Entaemoeba hartmanii 1%, Chilomastix mesnili 1%. No malaria was found but microfilariae of Wuchereria bancrofti were detected in 4% of the blood smears; the MfD50 was 12.9. The circumoval precipitin test (COPT) was used to detect antibodies to Schistosoma japonicum and 65% of 994 sera was considered positive. The indirect hemagglutination test (IHA) was used for detecting antibodies to Entamoeba histolytica and Toxoplasma gondii and 5% and 3% of 1,274 sera tested were positive at titers equal to or greater than 1:128 and 1:256, respectively. Hemagglutination inhibition tests (HI) were used to detect antibodies to Influenza A2HK68, Influenza A2HK68, Influenza B2T62 and Japanese encephalitis virus and 72%, 12% and 78%, respectively, of 1201 sera were considered positive at titers equal to or greater than 1:20.

Adolescent↗
PubMed1975

Cerebral hemispheric asymmetry in humans. Cortical speech zones in 100 adults and 100 infant brains.

Morphological asymmetry of the frontal operculum and temporal planum becomes measurable at the 29th week of gestation. There is evidence of subsequent differential development of the planum in favor of the left, with the left planum larger than the right. While both the frontal operculum and left planum were always present, the right planum ranged in size from absent (10%)to larger than the left (about 10%). Females predominated (P less than .05) in the latter group. The findings suggest that (1) a higher percentage of persons may have right-sided cerebral representation for speech than has been assumed previously; (2) a predetermined morphological asymmetry contributes to establishing the ultimate pattern of cerebral speech representation following an early insult to a predisposed hemisphere; and (3) it is necessary to scrutinize clinical material for the differential organization of hemispheric development between sexes.

Adolescent↗