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Biomedical subjects

L R White

Publications and source records attributed to L R White.

At least 109 records · Page 6Linked to original sources
PubMed1987

Effect of chromate ion on the membrane of established human cells as measured by uptake of a permeant lipophilic cation.

Cells from the established human cell line NHIK3025 concentrate the permeant lipophilic cation triphenylmethylphosphonium (TPMP+) against a concentration gradient, indicating the existence of an electrical potential across the cell membrane (interior negative). Cells exposed to potassium chromate or dichromate (7.7 mumol Cr/l) for 2 h subsequently showed reduced uptake of TPMP+, whereas similar exposure to a trivalent chromium salt (7.7 mumol/l chromic chloride) had similar uptake of TPMP+ as control cells. These preliminary results suggest that a primary effect of chromate on these cells is to reduce the electrical potential across the cell membrane.

Cell Line↗
PubMed1987

Pulmonary response following intratracheal instillation of potroom dust from an aluminum reduction plant into rat lung.

Rats were examined for lung changes 7 days and 22 weeks after a single intratracheal instillation of potroom dust from an aluminum reduction plant. In the acute study, 0.5 mg potroom dust induced changes at the pulmonary surface, and a 5.0-mg dose caused marked changes both at the pulmonary surface and in lung tissue. By contrast, 5.0 mg virginal alumina caused only a mild increase in the number of polymorphonuclear leukocytes in the lung. In the long-term study, potroom dust, virginal alumina, and DQ12 alpha-quartz were instilled at a dose of 5.0 mg. In the cases of potroom dust and virginal alumina, all parameters measured had returned to control levels after 22 weeks, whereas DQ12 induced a massive inflammation and an accumulation of pulmonary surfactant. It is concluded that this air sample of potroom dust causes marked acute irritation and inflammation in rat lung and that this type of dust may therefore be active in human lung and thus contribute to the acute respiratory symptoms experienced by some potroom workers. However, despite the marked acute toxicity of the comparatively high 5.0-mg dose, rat lung appears to return to normal within 22 weeks with no signs of chronic toxicity from this single instillation.

Aluminum↗
PubMed1987

Blood pressure and cognitive performance. The Framingham Study.

In 1976-1978, a battery of eight neuropsychologic tests were administered to 2,123 participants in the Framingham Study who were aged 55-89 years. Performance on each test was examined in relation to concurrently measured systolic and diastolic blood pressure while controlling for age, sex, education, antihypertensive medication, alcohol consumption, and smoking. Those with a diagnosis of stroke were excluded from the analysis. In the remaining sample of 2,032, neither blood pressure nor antihypertensive treatment was significantly associated with cognitive performance. Even after excluding persons on antihypertensive medication, blood pressure was still unrelated to cognitive performance. In contrast to other studies, the authors found no consistent relation between blood pressure and cognitive performance.

Aged↗
PubMed1986

Methodological issues in screening for dementia: the problem of education adjustment.

The methodological problems of developing efficient and unbiased screening methods for population-based studies of dementia have received scant attention. The potential advantages of education-adjusted screening methods are discussed. The implications for adjustment techniques of a negative correlation of educational attainment with age are emphasized. Two education adjustment methods, a stratified regression method and a nonparametric method, which take the age-education correlation into account are described, compared, and illustrated.

Age Factors↗
PubMed1985

Epidemiology of disability in the oldest old: methodologic issues and preliminary findings.

Little is known about the health problems of the fastest-growing segment of the population. Three major community-based studies present prevalence information on physical and mental disabilities among the oldest old. These data also illustrate the limitations of interpretations in cross-sectional studies, and emphasize the value of prospective investigations of populations aged 85 and older. Although more costly and time-consuming, such prospective longitudinal studies are indispensable to sound policy planning.

Aged↗
PubMed1984

Effects of fixing and staining on images of tropomyosin Mg-paracrystals.

Tropomyosin Mg-paracrystals have been studied by positive and negative staining with uranyl acetate and sodium phosphotungstate, either unfixed or fixed with glutaraldehyde. Fixation causes changes in some of the paracrystal bands. Some of the bands are more intense when a positively-charged staining ion is used than when a negatively-charged ion is used, in both negative and positive-staining techniques. This result rules out the suggestion that negative staining is not affected by the charge of the stain in tropomyosin, and agrees with findings in other specimens. Therefore it is unlikely that any simple parameter based on residue size can be used to predict the image intensity from the amino acid sequence for tropomyosin. These staining patterns cast doubt on the earlier interpretation of a prominent white band in the paracrystal as an overlap of alpha-helical molecular ends.

Animals↗
PubMed1984

Race and sex differences in hip fracture incidence.

Incidence rates for hip fracture in the United States were estimated using non-federal hospital discharges from the National Hospital Discharge Survey for the years 1974-1979. Age-specific incidence curves for women and for men showed similar patterns of increase in risk with age, with risks approximately doubling every five years after age 50. Age-specific rates by five-year age groups were compared among the four race-sex groups. No significant differences were observed between Black females, Black males, and White males. In contrast, rates for White females were one and one-half to four times those for Black females after age 40 and were approximately double those for White males after age 50. Analysis based on an independent data source of non-federal hospital discharges in Washington, DC confirmed these relationships. In the Washington study, White women were at twice the risk for hip fracture (controlled for age) compared with Black women and at 2.7 times the risk for hip fracture (controlled for age) compared to White men. No significant differences were observed between Black women and Black men.

Adult↗
PubMed1984

Absence of menopausal effect on hip fracture occurrence in white females.

The rate of hip fracture among White females rises sharply between ages 40 and 44 and then continues at a constant rate of acceleration doubling every five to six years throughout life with no deviation during, or in the years immediately following, menopause. We suggest that the important role of sex hormones and other factors in osteoporosis commences prior to menopause. A premenopause prevention strategy which postpones the onset of the osteoporotic process by five or six years would be expected to reduce the risk of hip fracture by 50 per cent throughout the remainder of a woman's life.

Adult↗
PubMed1983

Biochemical and cytological studies of rat lung after inhalation of methanol vapour.

Rats were examined for changes at the lung surface and in lung tissue after inhalation of methanol vapour for up to 6 weeks at doses of up to 10 000 ppm. No significant changes were found in any of the parameters measured. Methanol vapour therefore does not appear to exert appreciable toxicity at these exposure levels towards rat lung.

Animals↗
PubMed1983

Response of bovine alveolar macrophages in vitro to welding fume particles.

Alveolar macrophages (AM) from bovine lungs were exposed in culture to manual metal are (MMA) welding fume particles, chromium (Cr), UICC chrysotile A or anatase for 17-20 hr. All the welding particle samples were more cytotoxic to AM than to anatase. Particles from the welding of mild steel with a rutile-coated electrode were less cytotoxic than those produced with a basic-coated electrode. Particles from the welding of stainless steel were slightly more cytotoxic, and much of this activity was probably due to CrVI. Selective release of N-acetyl-beta-glucosaminidase (beta-NAG) was only detected after exposure of AM to chrysotile. Supplementation of the incubation medium with 10% serum increased the viability of all exposed AM cultures, an effect not produced by serum albumin alone. Incubation of particle samples with dipalmitoyl phosphatidylcholine (DPPC) prior to addition to AM reduced the cytotoxicity of the "rutile" welding particles and of chrysotile.

Acetylglucosaminidase↗
PubMed1982

Effects of potassium dichromate on the cell cycle of an established human cell line (NHIK 3025).

The effect of K2Cr2O7 exposure on the cell cycle phases of the human cell line NHIK 3025 has been studied. Inhibition of cell proliferation was found to depend on the concentration and length of exposure. An effect on cell proliferation was observed 6-9 h after addition of K2Cr2O7, whereas cell death was not observed until 3-4 days later. The cells were most sensitive in G2 phase. After exposure to 8 mumol/l K2Cr2O7 the greatest prolongation of the cell cycle was in G2 + M phase, but an increase of S phase was also observed. No prolongation of G1 phase could be measured. Our results thus indicate that K2Cr2O7 delays progression through the cell cycle.

Cell Cycle↗
PubMed1982

Biochemical studies of rat lung following exposure to potassium dichromate or chromium-rich welding fume particles.

Rats were examined for biochemical changes at the lung surface and in lung tissue 1, 4, and 13 weeks after a single instillation of the soluble of insoluble fraction of stainless steel welding particles, or potassium dichromate containing concentrations of hexavalent chromium (CrVI) equivalent to those found in the welding particles. Most of the toxicity of the welding particles 1 week after instillation could be related to the content of soluble CrVI, though the insoluble particles also produced changes at the alveolar surface. The regression of inflammatory changes 4 and 13 weeks after instillation was probably due to the removal of soluble components such as CrVI from the lung.

Air Pollutants↗
PubMed1981

Response of a human tumour cell line to chronic potassium dichromate exposure.

Cultures of the human cell line NHIK 3025 were exposed over an 18-month period to 0.5 mumol/1 potassium dichromate (K2Cr2O7) containing 1 mumol/1 hexavalent chromium. The chronically exposed cells increased their tolerance to K2Cr2O7 in comparison to control populations. The doubling time of the chronically exposed cell populations increased even in the absence of K2Cr2O7, but they did not change their morphology (light level), nor contain as many giant cells as newly exposed control populations. Cells returned to control medium for 6 months after 12-months exposure to K2Cr2O7 showed a gradual but incomplete reversal of these effects. The results are compared with those obtained from cells of non-tumour origin.

Cell Line↗