Near visual acuity of dental hygienists with and without magnification.

OBJECTIVES: The aim of this study was (i) to evaluate the visual performance of dental hygienists in their clinical environment and (ii) to analyse the relationship between self-assessed and objectively measured visual acuity. METHODS: The near visual acuity of 191 dental hygienists and dental hygiene students was self-assessed with a visual analogue scale and objectively measured with miniaturized visual tests in a simulated clinical setting. The visual acuity was also measured with magnification aids if they were part of the individual clinical equipment. The influence of age and magnification on the near visual acuity was analysed. RESULTS: The visual performance with respect to dental working distance showed a variability of 300% in the dimension of the smallest recognized structure. A weak positive correlation between the self-assessed and objectively measured visual performance (Spearman's rank correlation = 0.27) and a highly significant impact of the test person's age and the use of loupes (both P < .0001) were found. Test subjects ≥40 years exhibited a similar visual acuity when using loupes compared to the visual acuity of test subjects <40 years without loupes. CONCLUSIONS: The visual performance with respect to dental working distance cannot be self-assessed and varies individually. Dental hygienists and students of dental hygiene with a weak near visual acuity were not aware of their deficiencies. Optical aids should be used to compensate for individual visual deficiencies and are mandatory above an age of 40 years due to the effects of presbyopia.

Exposure to environmental tobacco smoke and risk factors for heart disease among never smokers in the Third National Health and Nutrition Examination Survey.

The relative risk of coronary artery disease among never smokers exposed to environmental tobacco smoke (ETS) versus never smokers not exposed to ETS is approximately 1.2 based on more than a dozen epidemiologic studies. Most of these studies have controlled for the major heart disease risk factors, but residual or uncontrolled confounding remains a possible explanation for the epidemiologic findings. The authors studied 3,338 never-smoking adults aged 17 years or older, who are representative of all US never smokers, in the 1988-1991 Third National Health and Nutrition Examination Survey (NHANES III) to determine whether selected risk factors for heart disease differ between ETS-exposed and -nonexposed persons. Both self-reported ETS exposure (at home and at work) and serum cotinine levels were available, the latter reflecting recent ETS exposure. After adjustments were made for age, sex, race, and education among adults aged 17 years or older, no significant differences were found between the ETS exposed and the nonexposed for any of 13 cardiovascular risk factors with the exception of dietary carotene, which was lower among the exposed. On the other hand, significant positive linear trends were found between serum cotinine and two risk factors (body mass index and alcohol consumption), and significant inverse trends were found with dietary carotene. There were also few differences between exposed and nonexposed never smokers among adults aged 40 years or older, who are most at risk of heart disease. In this group, however, there was an inverse linear trend between serum cotinine and high density lipoprotein cholesterol (p < 0.001). This finding could result from ETS exposure rather than be an indication of confounding; a similar inverse trend was found for children, confirming other results in the literature. Overall, these data suggest little potential for confounding by the heart disease risk factors studied here when ETS exposure is determined by self-report.

Incidence of tuberculosis infection among New York State prison employees.

OBJECTIVES: This study examined tuberculosis skin test conversions among 24,487 New York State prison employees in 1992. METHODS: Conversions were analyzed by prison and by job category. RESULTS: The conversion rate was 1.9%. Employees in prisons with low and high numbers of prisoner cases had odds ratios for conversion of 1.67 (95% confidence interval [CI] = 1.27, 2.19) and 2.20 (95% CI = 1.69, 2.87), respectively, relative to employees in prisons with no prisoner cases. In prisons with cases, guards and medical personnel had odds ratios of 1.64 (95% CI = 1.11, 2.43) and 2.39 (95% CI = 1.40, 4.08), respectively, relative to employees with little prisoner contact. CONCLUSIONS: In 1992, approximately one third of new infections among New York State prison employees were due to occupational exposure.

Age-cohort differences in treating symptoms of mental illness: a process approach.

This study examines age-cohort differences in conceptually organizing, observing, and responding to unclustered symptoms of mental illness. Older (M = 70.8) and younger (M = 19.9) adults sorted symptoms of depression, schizophrenia, and age-associated changes into similarity groupings. Hierarchical cluster analysis showed that both older and younger adults sorted the statements similarly, although labels given for depressive symptoms differed across groups. Participants then reported which symptoms they had observed within their families and listed what actions were taken. Age groups showed significant differences in symptom reporting, with older individuals observing depressive symptoms less frequently. There were small differences in the kinds of actions reported. These results suggest that differences in help-seeking behavior for mental illness may be explained by differences in the way symptoms are observed by younger and older cohorts.

Penetration of the mosquito (Aedes aegypti) midgut wall by the ookinetes of Plasmodium gallinaceum.

We observed Plasmodium gallinaceum ookinetes in both intracellular and intercellular positions in the midgut epithelium of the mosquito Aedes aegypti. After epithelial cell invasion intracellular ookinetes lacked a parasitophorous vacuolar membrane and were surrounded solely by their own pellicle. Thus, the ookinete in the midgut epithelium of the mosquito differs from erythrocytic and hepatic stages in that the parasite in the vertebrate host is surrounded by a vacuole. The midgut epithelial cytoplasm around the apical end of invading ookinetes was replaced by fine granular material deprived of normal organelles. Membranous structure was observed within the fine granular area. Most ookinetes were seen intracellularly on the luminal side and intercellularly on the haemocoel side of the midgut epithelial cells. These observations suggest that the ookinete first enters into the midgut epithelial cell, then exists to the space between the epithelial cells and moves to the basal lamina where the ookinete develops to the oocyst.

Rapid isolation of a neurohormone from mosquito heads by high-performance liquid chromatography.

Methods were developed for the isolation of the egg development neurosecretory hormone, EDNH, from heads of the mosquito Aedes aegypti. This hormone stimulates ecdysone production by ovaries. Methods used for the successful isolation of insulin-like peptides from vertebrate tissues were modified to develop a four-step procedure involving extraction in acidified ethanol, precipitation by neutralization, followed by sequential separation on size-exclusion, ion-exchange and reversed-phase high-performance liquid chromatography columns.

The peritrophic membrane as a barrier: its penetration by Plasmodium gallinaceum and the effect of a monoclonal antibody to ookinetes.

We studied the point at which a monoclonal antibody (mAb C5) to a surface protein (Pgs25) on Plasmodium gallinaceum ookinetes blocked the infection of Aedes aegypti mosquitoes. The antibody did not block the development of zygotes to ookinetes in vitro. Development of ookinetes to oocysts in the mosquito was blocked to the same extent whether zygotes grew to ookinetes in the presence of mAb C5 or the antibody was added after the ookinetes had reached full development. When ookinetes developed in vitro in the presence of mAb C5, antibody remained on the surface of the parasite for the next 50 hr and did not block attachment to the peritrophic membrane. When ookinetes were fed to mosquitoes, two subpopulations of mosquitoes were observed (high numbers of oocysts per midgut and low numbers of oocysts per midgut). mAb C5 reduced the number of oocysts per midgut in the subpopulation that had low numbers of oocysts. The subpopulation that had high numbers of oocysts was unaffected by antibody, indicating that the antibody did not block invasion of the midgut epithelium. When mAb C5 was fed with gametocytes, the parasites invaded the epithelium at the same time (between 30 and 35 hr after the blood meal) as in controls, although at a markedly reduced rate. The ultrastructural observations were consistent with a block of parasites within the peritrophic membrane and not with a block at the epithelium, as parasites were not seen to accumulate within the space between the peritrophic membrane and the epithelium. The mechanism by which mAb C5 to Pgs25 of P. gallinaceum blocks the penetration of the peritrophic membrane remains undefined. We present evidence that the parasite modifies the peritrophic membrane during penetration, an observation first made for Babesia microti during penetration of the peritrophic membrane in Ixodes ticks. Ookinetes in the absence of antibodies appeared to disrupt the layers of the peritrophic membrane, suggesting an enzymatic mechanism for penetration.

Matrix-isolation of H-induced free radicals from purines in acidic glasses.

H.(D.)-atoms produced by photo-oxidation (lambda = 254 nm) of Fe2+ in acidic glasses (6 mol dm-3 H2SO4/H2O or D2SO4/D2O) at 77K were allowed to react with the purine bases adenine, guanine, hypoxanthine and xanthine as well as with ribo- and deoxyribosides (-tides) of adenine and guanine by annealing to 110-130 K. The ensuing free radicals were studied by electron spin resonance (ESR) spectroscopy at 77 K. Individual radical species were assigned by simulation of patterns isolated from thermal annealing studies up to 180 K. It is shown that H.-atom reaction with the bases produces C2- and C8-addition radicals for adenine and C8-addition species for guanine. Guanine is also photo-oxidized directly in the glass, producing a cation or its deprotonated successor species. In the nucleosides (-tides) of both bases, H. atoms were found to abstract hydrogen from carbon sites C1', C2' or C3', and C5' for ribosides and C1', C2', and C5' for deoxyribosides (-tides), respectively.