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Biomedical subjects

A A Jansen

Publications and source records attributed to A A Jansen.

At least 37 records · Page 2Linked to original sources
PubMed1985

Alcohol effects on signal detection performance.

The acute effects of alcohol (0.7 g/kg) on visual signal detection performance and critical flicker fusion frequency (CFF) of normal volunteers were investigated using a signal detection theory analysis. When signal probability was low, alcohol affected the stimulus sensitivity and the reaction times of hits. Under a high signal probability these indices were not affected, whereas the response bias did not change after the administration of alcohol under both signal probabilities. CFF values were not altered by alcohol. A correlation was found between the magnitude of the alcohol effect and the performance level under placebo. Changing the signal probability caused significant differences between the sensitivity measures, the response bias measures and the reaction times of hits. It is concluded that alcohol affects signal detection performance under conditions of low signal probability. Individuals with a relatively low performance level are more susceptible to the effects of alcohol.

Adult↗
PubMed1984

On the variation of toxic effects over species, its cause, and analysis by "structure-selectivity relations".

The intractable problems of how to select and to develop a toxicant against a particular target species while leaving most other species unaffected are analyzed. It is proposed to study the mean and variation over species in general, as tolerance is concerned, as a function of the structure in much the same way that tolerances of target species are analyzed by quantitative structure-activity relations (QSAR). This approach enables the dissection of the complex problem into three parts, which together provide rational information on how it may be solved or at least on how decisions should be made. It is argued that variation in tolerance over species, in general, must be due to variation in binding energy over macromolecular binding sites in general. The latter variation likely depends on the surface area or, better, on the "complexity" of the toxicant. It is however, not clear as to how to express complexity in an appropriate way. To illustrate the approach, it was applied to a limited series of toxicity data for seven species, from five taxonomic classes, to seven organophosphorus insecticides. A quantitative measure of the degree of variation over species correlates significantly with the connectivity index, as developed by Randić (1975, J. Amer. Chem. Soc. 97, 6609-6615), a known correlate of the surface area of the molecule. Due to several limitations, this finding mainly serves to stimulate further work on more extended data series.

Animals↗
PubMed1984

Machakos project studies No. XXIV. Anthropometric changes during pregnancy in rural African women.

Anthropometric data of 1739 pregnant women followed in the period 1 May 1978 - 31 December 1980 are presented. Mean height was 157.1 +/- 5.5 cm. Weight gain between 3 months and term was 5.8 kg. Significant changes in the course of pregnancy were observed in upper arm circumference, triceps and subscapular skinfolds. Women started pregnancy with a higher mean weight-for-height ratio than the reference; in the course of pregnancy the ratio decreased from 107.0% to 95.7%.

Adult↗
PubMed1983

Lactation performance of mothers with contrasting nutritional status in rural Kenya.

Breastmilk yields and its composition during the first 6 months of lactation were measured in 46 women with low weight-for-height during the third trimester of pregnancy (WH minus group) and in 52 mothers with good weight-for-height in the same period (WH plus group). On average WH minus mothers produced 695 g per 24 hours and WH plus mothers 790 g. In the WH minus group yield was affected by feeding frequency, season, mother's energy intake during lactation and infant's weight-for-age. In the WH plus group feeding frequence, parity and sex were the affecting variables (male infants consumed more milk). The difference in yield between WH minus and WH plus mothers corrected for feeding frequency, sex and season was significant but was only 80 g per 24 hours. Protein and lactose concentrations in milk were in both groups comparable with that of British mothers, fat concentrations were lower.

Birth Weight↗