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Biomedical subjects

V Ulrich

Publications and source records attributed to V Ulrich.

27 records · Page 2Linked to original sources
PubMed1983

Wheelchair batteries: driving cycles and testing.

The battery performance of electric wheelchairs was measured under indoor and outdoor conditions, and simulated driving cycles for these two environments were derived from these tests. Driving cycles were used to bench-test deep discharge wet cell and gel cell lead-acid batteries, nickel-cadmium batteries, and experimental nickel-zinc batteries. Results of this study support the conclusion that deep discharge wet cell lead-acid batteries satisfy wheelchair requirements and are the most economical choice. The effect of simulated wheelchair controller pulse width modulation on battery discharge compared to d.c. discharge was found to be negligible. A simple model analogous to Miner's Rule (3) plus results plotted on a Ragone chart of average power versus discharge time were found to correlate the effect of the highly variable actual power requirements of an electric wheelchair. Miner's Rule can predict battery performance for a given driving cycle.

Electric Power Supplies↗
PubMed1981

The mechanism of the reductive dehalogenation of polyhalogenated compounds by microsomal cytochrome P450.

Polyhalogenated ethanes are metabolized by reductive dehalogenation under anaerobic and also hypoxic conditions in vitro in the presence of NADPH and hepatic microsomal cytochrome P450. The cytochrome P450 dependence was shown by induction and inhibition experiments using microsomal fractions from livers of rats receiving various pretreatments. The main products of the in vitro metabolism of hexa- and pentachloroethane were tetra- and trichloroethene, respectively. Minor products were penta- (0.5%) and 1.1.2.2.-tetrachloroethane (4%). The stoichiometry of NADPH-oxidation and product formation was 1:1. From these results and earlier investigations on polyhalogenated methanes, a reaction scheme is proposed. The reductive dehalogenation probably proceeds by two sequential one electron reductions forming first a radical and then a carbanion. The carbanion may undergo protonation, alpha-, or beta-elimination forming a monodehalogenated haloalkane, an olefin or a carbene, respectively.

Anaerobiosis↗
PubMed1979

Electrophoretic comparisons of liver chromatin proteins isolated from heterotic rats during postweaning development.

Electrophoretic comparisons of histones and other acid-extractable chromatin proteins isolated from the livers of growing F344 inbred rats and a heterotic paternal hybrid derived by crossing F344 males with Holtzman females reveal significant heterogeneity among a class of nonhistone components soluble in acid. These variations appear to be age and line specific and show more variation in the inbred than the hybrid. Comparisons of the acid-insoluble nonhistone proteins by sodium dodecylsulfate gel electrophoresis reveal significant quantitative changes in a 28,600 dalton polypeptide present in large quantities at 30, 35, and 50 days of age in the hybrid and at 40 and 45 days only in the inbred. Other minor variations were noted in a class of proteins of 40,000--45,000 molecular weight and in those of very high molecular weight (100,000-200,000). Such variations could be a reflection of or prelude to changes in genetic activity and could ultimately be important in the control of growth patterns of developing heterotic animals.

Aging↗
PubMed1975

Weight gain and heterosis at different stages of development of the rat.

Diallel crosses among four highly inbred lines of rats were made in order to evaluate their combining ability at 10 day intervals during postnatal growth. Analyses were undertaken to consider the relative magnitudes of different components of variation, including a heterotic effect, over a long developmental period. A general analysis of variance for least square means of body weights indicated that postnatal growth was influenced greatly by the maternal lines and to a lesser extent by the paternal line. Heterosis was measured as a statistically significant difference in body weight gain at 10 day intervals between the hybrid and either the averaged mean of the parent lines or the mean of the largest parent line. Of the effects analyzed, heterosis accounted for a major part of body weight variability in both sexes between 30 and 100 days of age but reached much higher levels in male than in female progeny. The heterotic response was most pronounced during the rapid growth phase; that is, between the ages of 20 to 50 days. Although interesting specific exceptions were observed, heterotic responses generally became more pronounced with increasing age through 100 days. Evidence for differential heterosis associated with particular lines was present in male progeny at growth stages immediately preceding and following the phase of most rapid growth. Specific combining ability, however, was generally lacking. Analyses of specific matings indicated that heterosis, in the lines tested, is a variable phenomenon which may be dependent upon the degree of genetic divergence between inbred parent lines and the combining ability of the genotype involved.

Age Factors↗
PubMedDate not supplied

Health, health care, and the environment. Econometric evidence from German micro data.

The paper develops and applies a Grossman-style health production model set up in discrete time to explain the impact of environmental pollution on the demand for both health and health care. In order to introduce the environment, our analysis takes changes in environmental conditions to influence the rate at which an individual's stock of health depreciates. While the theoretical part of our paper also contains a discussion of the full model, we restrict our empirical analysis to a submodel which is known as the pure investment model. This is because the other submodel, the pure consumption model, implies a rather implausible case of satiation with respect to the individual's preferences. Our empirical findings are based on data taken from the German Socio-economic Panel. The stock of health capital and environmental pollution are treated as latent variables and estimated using a Linear Covariance Structures model. The quality of the environment turns out to be an important determinant of health capital. From the point of view of health economics, improvements in environmental conditions can be interpreted as preventive measures. In terms of prevention, public policies designed to protect the environment also yield significant health effects. As regards health care demand the influence is not clearcut, i.e., one cannot necessarily expect a reduction in resource use.

Data Interpretation, Statistical↗
PubMedDate not supplied

Screening for migraine in the general population: validation of a simple questionnaire.

We present validation of a simple questionnaire designed to screen the general population for migraine. It comprises four questions: (1) "Have you ever had migraine?" (2) "Have you ever had severe headache accompanied by nausea?" (3) "Have you ever had severe headache accompanied by hypersensitivity to sound and light?" (4) "Have you ever had visual disturbances lasting 5-60 min followed by headache?" A telephone interview carried out by a physician was used as an index of validity. The study population was 5,360 twins from the population-based Danish Twin Registry. All twin pairs where at least one twin had answered "yes" to at least one of our questions were eligible for the telephone interview (n=2,272 twins). The response rate to the questionnaire was 87%; the participation rate in the telephone interview was 90%. The questionnaire ascertained 85% of all migraineurs (sensitivity). A combination of two questions (questions 1 and 4) extracted 93% of the twins with migraine with aura and 74% of the twins with migraine without aura, yet only 26% of the sample needed to be interviewed. We conclude that in the Danish population two simple questions are sufficient to screen for migraine in selecting participants for a diagnostic clinical interview. Our questionnaire clearly merits further study to document its universal applicability.

Adult↗
PubMedDate not supplied

In vitro transcriptional probes of heterotic rat liver chromatin.

DNA-dependent RNA polymerase I from E. coli has been used as probe for determining the capacity of purified chromatin isolated from inbred and hybrid rats during the course of postweaning development to serve as template for RNA synthesis in vitro. An analysis of variance reveals both strain- and age-specific differences in the incorporation of [3H]UTP into RNA. The ability of inbred chromatin to support synthesis exceeds that of the hybrid at every age examined except 50 days, with values in the inbred line approaching those in the hybrid line with increasing age. These data suggest that template characteristics may vary substantially with regard to strain and age and may contribute to differences in heterotic development.

Animals↗
PubMedDate not supplied

Chromatographic comparisons of heterotic rat liver histones.

Chromatographic comparisons of histones isolated by acid extraction of liver chromatin preparations from F344 inbred rats and their paternal heterotic F344 X H hybrid progeny reveal the presence of a number of age-and line-specific nonhistones also extractable in acid. The patterns of the core histones (H2A, H2B, H3, and H4) remain relatively constant during development, while histone H1 shows unusual chromatographic properties in the 30- and 35-day hybrid preparations. In general, the complexity of the nonhistone fraction decreases as the animal ages. Such variations may be a reflection of a prelude to altered genetic activity in organisms undergoing growth and development at different rates, and may have significant implications for transcriptional processes.

Age Factors↗