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Biomedical subjects

D R Roberts

Publications and source records attributed to D R Roberts.

At least 91 records · Page 5Linked to original sources
PubMed1985

Multivariate analysis of glycosylated haemoglobin in insulin-treated diabetics.

Glycosylated haemoglobin (HbA1), as an assessment of overall control, was estimated in 858 insulin-treated diabetics attending for changeover to U100 insulin in North East Wales. Details of age, sex, duration of diabetes, insulin regimen and monitoring method were recorded. Multivariate analysis revealed lower HbA1 in patients receiving twice-daily (mean 11.01) as compared with once-daily insulin (11.42, P = 0.011), but no difference was found between urine and blood glucose testers when other variables were taken into consideration. HbA1 was lower in men (mean 10.94) compared with women (mean 11.39, P = 0.004) and there was a positive correlation of HbA1 in men with age (P = 0.046) and in women with duration of disease (P = 0.005).

Age Factors↗
PubMed1985

Identification of Plasmodium vivax sporozoites in mosquitoes using an enzyme-linked immunosorbent assay.

A sandwich enzyme-linked immunosorbent assay (ELISA) for identifying Plasmodium vivax sporozoites in mosquitoes is described. Monoclonal antibodies produced against Thailand P. vivax sporozoites were used in an ELISA to detect and identify homologous sporozoites of Southeast Asian, Mexican and North Korean origin in extracts of frozen or dried infected mosquitoes. The assay was sensitive enough to detect 1 infected mosquito in a pool of 20 insects or 125-250 sporozoites per 30 microliter of mosquito extract. The use of a nonionic detergent and a single freeze-thaw to disrupt the circumsporozoite antigen significantly increased the sensitivity of the method.

Animals↗
PubMed1985

Trypanosoma brucei rhodesiense: enhancement of infection rates in the tsetse fly, Glossina morsitans, by feeding artificial bloodmeal mixtures.

Low mature salivary gland (SG) infection rates (6%) in less than 24-hour-old flies fed on blood containing bloodform trypanosomes can be significantly enhanced by feeding flies an artificial mixture containing procyclic forms in a red cell: culture medium mixture (procyclic mixture, SG rate = 21.0%). However, enhancement is not solely a function of the use of procyclic forms since blood forms fed to flies in the same red cell: culture medium mixture produce SG rates (15.4%) intermediate to those of blood forms in blood and procyclic mixtures. Use of these artificial mixtures produces a similar result in 24- to 48-hour-old flies and also tends to equalize their infection rates with those found in less than 24-hour-old flies. The possible relationships between the different infection rates observed and digestive proteinases in the tsetse fly are discussed.

Animals↗
PubMed1984

Identification of malaria-infected mosquitoes by a two-site enzyme-linked immunosorbent assay.

A micro enzyme-linked immunosorbent assay (ELISA) for identifying malaria sporozoites in mosquitoes is described. Using an extract of dried infected mosquitoes as antigen, a two-site ELISA was sensitive enough to detect one infected mosquito in a pool of 20. The species specificity, sensitivity and ease of performance of this assay, as well as the stability of the reagent, should make it a useful epidemiological tool.

Animals↗
PubMed1983

Worker exposure to perchloroethylene in the commercial dry cleaning industry.

The National Institute for Occupational Safety and Health (NIOSH) conducted industrial hygiene surveys at 44 commercial dry cleaning facilities in five states as part of an industry wide study to assess the health effects of long-term, low-level exposure to perchloroethylene (PCE). Time-weighted average (TWA) and peak exposures to PCE were determined by collecting personal air samples using activated charcoal tubes and battery-operated pumps. TWA exposures of the machine operators ranged from 4.0 to 149.0 ppm PCE. The geometric mean PCE exposure of the machine operators (22 ppm) differed significantly from the mean exposures of the pressers (3.3 ppm), seamstresses (3.0 ppm), and the concentrations in the front counter areas of the facilities (3.1 ppm). Te geometric mean 5-minute peak PCE exposure during textile transfer was 44 ppm while the mean 15-minute exposure was 33 ppm. No significant differences were found between exposures when either the TWA or the peak data were grouped by geographic location (i.e., state), or by the type of processing equipment used (i.e., "Combination" units vs. separate washing and drying units). Recommendations for work practices, ventilation, maintenance, plant layout and personal protective equipment are presented to reduce PCE exposures to lowest achievable levels.

Humans↗
PubMed1981

Oropouche virus. III. Entomological observations from three epidemics in Pará, Brazil, 1975.

Urban epidemics of Oropouche (ORO) fever in three municipalities in Pará, Brazil were studied in 1975. Culicoides paraensis (Goeldi) were collected during each of the epidemics and there was a positive correlation, by study areas within the city of Santarém, between human seropositivity to ORO virus and population densities of C. paraensis and Culex quinquefasciatus Say. The best numerical correlation was with populations of C. paraensis. The relative absence of other species in the areas of high disease attack rates was further evidence C. paraensis were the probable vectors of ORO virus. These biting midges were found to bite readily inside of houses, with an indoor/outdoor ratio of 29%, and were most active around 1700-1800 hours. Other biological observations on C. paraensis are presented.

Animals↗
PubMed1981

Oropouche virus. IV. Laboratory transmission by Culicoides paraensis.

Biological transmission of Oropouche (ORO) virus by Culicoides paraensis (Goeldi) has been successfully demonstrated in the laboratory. Adult Culicoides, collected in an area where ORO virus was absent, were infected by feeding on viremic hamsters and then periodically exposed to susceptible hamsters at specific intervals post-infectious blood meal. These C. paraensis were capable of biological transmission of the virus 4-9 days post-feeding on viremic hamsters circulating 6.7-9.9 log10SMLD50/ml virus. Infection rates of 54% and 80% were found for C. paraensis assayed 7 days post-feeding. Virus transmission rates for these experiments were 83% and 25%, respectively. No evidence of mechanical transmission of ORO virus by C. paraensis was observed when interrupted feeding of Culicoides on viremic hamsters was followed by feeding on susceptible hamsters.

Animals↗
PubMed1978

Purification, characterization and inhibition of human skin collagenase.

1. The neutral collagenase released into the culture medium by explants of human skin tissue was purified by ultrafiltration and column chromatography. The final enzyme preparation had a specific activity against thermally reconstituted collagen fibrils of 32mug of collagen degraded/min per mg of enzyme protein, representing a 266-fold increase over that of the culture medium. Electrophoresis in polyacrylamide disc gels showed it to migrate as a single protein band from which enzyme activity could be eluted. Chromatographic and polyacrylamide-gel-elution experiments provided no evidence for the existence of more than one active collagenase. 2. The molecular weight of the enzyme estimated from gel filtration and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis was approx. 60000. The purified collagenase, having a pH optimum of 7.5-8.5, did not hydrolyse the synthetic collagen peptide 4-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-d-Arg-OH and had no non-specific proteinase activity when examined against non-collagenous proteins. 3. It attacked undenatured collagen in solution at 25 degrees C, producing the two characteristic products TC(A)((3/4)) and TC(B)((1/4)). Collagen types I, II and III were all cleaved in a similar manner by the enzyme at 25 degrees C, but under similar conditions basement-membrane collagen appeared not to be susceptible to collagenase attack. At 37 degrees C the enzyme attacked gelatin, producing initially three-quarter and one-quarter fragments of the alpha-chains, which were degraded further at a lower rate. As judged by the release of soluble hydroxyproline peptides and electron microscopy, the purified enzyme degraded insoluble collagen derived from human skin at 37 degrees C, but at a rate much lower than that for reconstituted collagen fibrils. 4. Inhibition of the skin collagenase was obtained with EDTA, 1,10-phenanthroline, cysteine, dithiothreitol and sodium aurothiomaleate. Cartilage proteoglycans did not inhibit the enzyme. The serum proteins alpha(2)-macroglobulin and beta(1)-anti-collagenase both inhibited the enzyme, but alpha(1)-anti-trypsin did not. 5. The physicochemical and enzymic properties of the skin enzyme are discussed in relation to those of other human collagenases.

Blood Proteins↗