Biomedical subjects
Publications and source records attributed to M Wilson.
A young Asian male was admitted to hospital suffering from severe lower limb and facial injuries. He was subsequently found to be a carrier of hepatitis B virus and HBeAg positive. The management of 38 health care workers with significant blood and body fluid exposure involving this patient is discussed.
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Suspensions of Streptococcus mutans, S. sobrinus, Lactobacillus casei and Actinomyces viscosus were exposed to light from a gallium aluminium arsenide laser in the presence of aluminium disulphonated phthalocyanine and the numbers of survivors determined. Exposure to the laser light in the absence of the dye, or the dye in the absence of the laser light, had no significant effect on the viability of the organisms. However, a light-dose-related decrease in the viable count of all four target organisms was found on exposure to the laser light in the presence of the dye. The kills attributable to lethal photosensitization amounted to approximately 10(6) CFU in the case of each organisms. As appreciable kills were achieved within clinically convenient exposure times (30-90 s), these results imply that lethal photosensitization may be a useful technique for eliminating bacteria from carious lesions prior to restoration.
Cultured retinal amacrine cells show quantal GABAergic synaptic transmission. Voltage clamping pre- and post-synaptic cells of an isolated pair has allowed us to examine the entry and removal of Ca2+ at synaptic terminals. Brief presynaptic Ca2+ currents elicit an initial postsynaptic current that probably reflects the roughly synchronous exocytosis of docked vesicles. Prolonged Ca2+ currents elicit an additional second phase of release whose time course can greatly exceed that of the presynaptic voltage step. The time course of this second phase reflects a sustained increase in cytosolic Ca2+ and is matched closely by the activity of the presynaptic Na-Ca exchanger, as revealed by an exchange current. Eliminating the activity of the exchanger by removal of external Na+ prolongs this second phase of transmission greatly. Because transmitter release at these synapses outlasts Ca+ channel opening, Na-Ca exchange plays a significant role in shaping transmission.
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Patients attending five Health Centres in areas of NW London with a high Asian population were asked to complete a questionnaire screening for non-psychotic psychiatric illness and to state why they had come to see their doctor. The GPs were also asked to rate the purpose of the consultation for those patients who scored above the cut-off point on the questionnaire. The screening questionnaire revealed equivalent rates of non-psychotic psychiatric morbidity in the White and Asian samples and no differences in the way their symptoms were presented. The differences that did emerge showed that Asian patients scoring above the cut-off for psychiatric caseness were more likely to state that they were consulting their GP about a physical problem and GPs were more likely to identify psychiatric morbidity in White than Asian patients who exceeded the cut-off threshold. The results suggest the possibility of an interaction between the ways in which patients experience and communicate psychological distress, their ethnic origin, and their GP's mode of responding.
We compared a plate enzyme-linked immunosorbent assay (ELISA) with an immunoblot--or enzyme-linked immunoelectrotransfer blot--assay (EITB) for the identification of cases of human neurocysticercosis due to Taenia solium and of risk factors for this disease in two Mexican villages. Findings related to age- and sex-specific seroprevalence, risk factors for transmission, and associated morbidity differed significantly according to the assay used. Rates of EITB positivity were significantly higher among persons with a history of convulsions than among those without such a history (29% vs 8%; P < .05); in contrast, ELISA results were negative for all persons with a history of convulsions. The association of seizures with neurocysticercosis in this population was strengthened by the higher rate of abnormal findings compatible with neurocysticercosis on computed tomography of the brain among individuals with a history of convulsions than among those without such a history (70% vs 14%; P < .001). In summary, EITB was more sensitive and specific than ELISA for epidemiological studies of neurocysticercosis.
To assess the possibility of standardization of a commonly used indirect immunofluorescent antibody (IFA) test for detection of Babesia microti antibody in human sera, the results from four reference laboratories were compared. Patients with babesiosis from southern New England (n = 25) and subjects with no history of babesiosis from southern New England (n = 55) and Iceland (n = 50) were enrolled in the study. Anti-Babesia antibody titers were determined in a blinded fashion by IFA test. The range of test results in the four laboratories was 88%-96% sensitivity, 90%-100% specificity, 69%-100% positive predictive value, and 96%-99% negative predictive value. Interlaboratory and intralaboratory concordance ranged from 84% to 85% and 94% to 100%, respectively. This B. microti IFA procedure is a sensitive, specific, and reproducible method for diagnosing babesiosis and is suitable for use as a standard in laboratories testing human sera for B. microti antibody.
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The results of this study demonstrate that saline extracted surface-associated material (SAM) of Actinobacillus actinomycetemcomitans and Eikenella corrodens stimulates bone resorption at picomolar concentrations. Various inhibitors of known osteolytic mediators--indomethacin, interleukin-1 receptor antagonist (IL-1ra) and a neutralising antibody to murine tumour necrosis factor (TNF) alpha--were tested to determine the mechanism of action of these SAMs. Bone resorption induced by SAM from E. corrodens was slightly inhibited by indomethacin and almost completely inhibited by blocking the action of TNF alpha; that from A. actinomycetemcomitans was not significantly affected by either of these inhibitors.
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A redox dye, methylene blue, was compared with subgingival root surface debridement and sterile water in the treatment of adult periodontitis. Plaque and gingival indices, bleeding on probing, and microbiological samples were obtained at baseline, and at 1, 4, 8 and 12 weeks following treatment. All subjects had matched pockets in each of the 4 quadrants, of 5 mm or more. One treatment consisted of 0.1% methylene blue gel irrigated professionally at 0, 1 and 4 weeks, and by subjects at days in between up to 4 weeks, at chosen sites within a randomly selected quadrant (split-mouth design). A 2nd treatment was sterile water irrigation as above. A 3rd quadrant received subgingival debridement, and sites in the 4th received methylene blue incorporated into a slow-release device of a biodegradable collagen alginate vicryl composite. All sites showed improvements in clinical and microbiological parameters. However, no statistically significant differences between treatment types were found for clinical measurements. Although plaque index tended to increase after week 1, gingival index was reduced, as was the papilla bleeding index. Probing depth reductions were approximately 1.2 mm for all treatments. Microbiological variables showed an increase in cocci and a decrease in motile organisms for all groups, the latter reaching statistical significance for subgingival debridement. The reductions in spirochaetes were significant for subgingival debridement and methylene blue by slow-release. Culture demonstrated an increase in the aerobe:anaerobe ratio for all groups, which was statistically significant initially (weeks 1 and 4) for subgingival debridement. Methylene blue was also effective statistically in improving this ratio, both by irrigation and slow-release (week 4). Methylene blue also significantly reduced the numbers of black-pigmented anaerobes during the trial period, both by irrigation and slow-release, which sterile water and subgingival debridement failed to do. No serious adverse experiences were seen, however, significantly greater morbidity was associated with subgingival debridement. These results clearly demonstrate that in altering the microflora to one that is more compatible with periodontal health, methylene blue treatment is comparable, or even better, than the currently standard treatment of subgingival debridement, and is better tolerated.
The levels of coexistence between Pseudomonas syringae and various nonpathogenic epiphytic species in the phyllosphere of beans (Phaseolus vulgaris) were assessed by using replacement series. The epiphytic species Pseudomonas fluorescens, Pantoea agglomerans, Stenotrophomonas maltophilia, and Methylobacterium organophilum were all capable of exhibiting higher levels of coexistence with P. syringae than was observed with a near-isogenic P. syringae strain pair. The ecological similarity of the epiphytes was estimated with niche overlap indices derived from in vitro carbon source utilization profiles. The level of coexistence of the epiphytes was inversely correlated with the ecological similarity of the strains. Hence, the level of coexistence between the epiphytes was proportional to the degree of niche differentiation, defined as the ability to utilize carbon sources not utilized by a competing strain. Comparisons of utilization profiles for groups of carbon sources (amino acids, organic acids, and carbohydrates) indicated the types of carbon sources for which the strains likely competed in the bean phyllosphere. P. fluorescens and P. syringae strains probably competed for most carbon sources. S. maltophilia and M. organophilum strains probably competed with P. syringae for most organic acids but few amino acids or carbohydrates. P. agglomerans strains probably competed with P. syringae for most amino acids and organic acids but few carbohydrates. A variable level of coexistence observed between P. agglomerans and P. syringae probably reflected the variability in abundance in the bean phyllosphere of the carbohydrates that P. agglomerans utilized exclusively.
Pseudomonas syringae inocula containing cell concentrations ranging from 10 to 10 cells per ml were applied to the primary leaves of bean plants. The plants were incubated under conditions of high temperature and illumination and low relative humidity. Bacterial mortality rates and the proportional population decline of the inoculum were lowest at the highest inoculum concentrations. Addition of a high concentration of heat-killed cells to the inoculum containing a low concentration of viable cells significantly reduced both the mortality rate and the proportional population decline of the viable cells. The mechanisms underlying this density-dependent mortality may include cooperative protective effects of extracellular factors, such as bacterial extracellular polysaccharides, and physical protection by neighboring cells. Although epiphytic populations derived from inoculum concentrations of 10 or 10 cells per ml tended toward 10 CFU/g, the presumed carrying capacity of the leaf, populations derived from lower inoculum concentrations never achieved this carrying capacity. Assuming that epiphytic populations of P. syringae reside in discrete protected sites, our results suggest that at low inoculum concentrations, following a period of environmental stress, the number of viable cells may have dropped to zero in some sites; hence, the carrying capacity of the leaf could not be achieved.
De Wit replacement series were used to study competitive interactions between epiphytic IcePseudomonas syringae strains and the biological frost control agents IceP. syringae TLP2del1 and Pseudomonas fluorescens A506. Mixtures containing two strains in different proportions but at a constant total population size were inoculated onto potato leaves. The population sizes of each strain and the total population size were determined when the community had reached equilibrium. A near-isogenic P. syringae strain pair exhibited an interaction similar to that expected for strains competing equally for limiting environmental resources. Replacement series with nonisogenic Ice and IceP. syringae strain pairs suggested that these strains competed for limiting resources according to their relative competitive abilities. There was no evidence of any niche differentiation between the IceP. syringae strains and the IceP. syringae strain. The growth responses of epiphytes following addition of nutrients to the phyllosphere indicated that the epiphytic P. syringae populations were nutrient limited and that, under growth chamber conditions, the populations were more limited by the availability of carbon than by the availability of nitrogen. Determination of in vitro carbon source utilization profiles provided further evidence for the lack of niche differentiation between the Ice and the IceP. syringae strains. Niche overlap indices calculated for the IceP. syringae strains with respect to IceP. syringae TLP2del1 were uniformly high, indicating ecological similarity, and were consistent with the observed low level of coexistence. The biological frost control agent P. fluorescens A506 replaced P. syringae. This was correlated with a high degree of niche overlap between these species.
Two patients sustained the rare complication of skin infarction following administration of intravenous streptokinase for acute myocardial infarction. We report evidence that dissolution of thrombus from an unsuspected source and subsequent microembolization of the skin may be responsible for this complication. In patients known to have an aortic aneurysm or ventricular thrombus, careful consideration should be given to the use of intravenous streptokinase following myocardial infarction.
In this study, hepatic production of bile acid was considered together with intestinal cholesterol absorption as potential regulatory sites responsive to dietary cholesterol. Sequential liver biopsies were taken from 45 feral African green monkeys studied during three different diet periods. Low-fat Monkey Chow was fed during the baseline period, a cholesterol and fat-enriched diet was then fed for 12 wk during period 2, and finally, after a washout period of 10 wk, three subgroups were fed low-, moderate-, and high-cholesterol diets for 12 mo during period 3. The percentage of cholesterol absorbed in the intestine was significantly lower when higher levels of cholesterol were fed; however, this percentage was significantly and positively correlated to plasma cholesterol concentration at each dietary cholesterol level. Hepatic free and esterified cholesterol content were significantly elevated by dietary cholesterol challenge and remained elevated even after 20 wk of low-cholesterol diets. Hepatic mRNA abundance for cholesterol 7 alpha-hydroxylase (C7H) was significantly lower (approximately 60%) when the high-cholesterol diet was fed, with the decrease being greater than that seen for low density lipoprotein (LDL) receptor mRNA. At the same time, hepatic mRNA abundance for apolipoprotein B and hepatic lipase were not diet sensitive. C7H activity was decreased to a similar extent by diet as was C7H mRNA, although the correlation between enzyme activity and mRNA abundance was only r = 0.5, suggesting that dietary regulation includes factors in addition to transcriptional regulation. Activity and mRNA abundance of C7H remained decreased when liver esterified cholesterol content was reduced to only a two- to three-fold elevation over baseline, at a time when plasma cholesterol and hepatic LDL receptor mRNA abundance had returned to baseline levels. These data on liver C7H, obtained in one of the few primate species predisposed to cholesterol gallstone formation, support the hypothesis that the liver may attempt to downregulate intestinal cholesterol absorption by decreasing bile acid production when increased amounts of absorbed dietary cholesterol reach the liver. Presumably this represents attempted downregulation of intestinal cholesterol absorption by limiting bile acid availability as a means to maintain hepatic cholesterol balance.