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Biomedical subjects

A A Jansen

Publications and source records attributed to A A Jansen.

At least 19 recordsLinked to original sources
PubMed1994

The influence of reproductive status on rural Kenyan women's time use.

To determine the effects that pregnancy and infant care have on Embu women's commercial, agricultural and household activities, time use patterns were studied for women at different stages of pregnancy and lactation. Time allocation data were collected from 169 households, visited at random intervals over a year, by use of the spot observations technique. Detailed reproductive data were collected monthly, and household socioeconomic data quarterly. Analyses of Embu women's time use by reproductive status reveal that the demands of pregnancy and lactation require women to decrease the amount of time spent on subsistence agriculture, commercial activities, housework, and tending animals; and to devote more time to resting, breastfeeding, and child care. Agricultural and economic activities are curtailed especially in the 3rd trimester of pregnancy and the 1st period of lactation. This data provide insight into how pregnancy and lactation require women to adjust their time allocation between reproductive and farm labor activities. This decrease in time spent on subsistence agriculture, commercial activities, and household work increases the risk of household economic insecurity during the woman's reproductive years.

Activities of Daily Living↗
PubMed1993

Pharmacokinetics of the novel antipsychotic agent risperidone and the prolactin response in healthy subjects.

The pharmacokinetics of a novel antipsychotic agent, risperidone, and the prolactin response were studied in 12 dextromethorphan-phenotyped healthy men after administration of 1 mg risperidone intravenously, intramuscularly, and orally. The formation of the equipotent major metabolite, 9-hydroxyrisperidone, exhibited CYP2D6-related polymorphism. The plasma area under the concentration-time curve from time zero to infinity ratio of 9-hydroxyrisperidone to risperidone averaged 3 (intravenous and intramuscular) and 6 (oral administration) in the extensive metabolizers and 0.2 in the poor metabolizers. Risperidone half-life was about 3 hours in extensive metabolizers and 22 hours in poor metabolizers. Risperidone absolute oral bioavailability was 66%. The pharmacokinetics of the active moiety (risperidone plus 9-hydroxyrisperidone) varied little among subjects (mean terminal half-life, 20 +/- 2 1/2 hours; absolute oral and intramuscular bioavailability, 100%). The prolactin response correlated best with the plasma active moiety, which showed little hysteresis. It is concluded that risperidone metabolic polymorphism on increased plasma prolactin is minimal and that the active moiety is clinically relevant.

Adult↗
PubMed1993

Ritanserin, a selective 5-HT2/1C antagonist, and negative symptoms in schizophrenia. A placebo-controlled double-blind trial.

The effectiveness of ritanserin, a selective 5-HT2 and 5-HT1c antagonist, in reducing negative symptoms in schizophrenia was investigated in a double-blind, placebo-controlled trial. Trial treatment was added to a stable neuroleptic treatment in 33 schizophrenic patients with predominantly negative symptoms. Ritanserin reduced the negative symptoms, as measured with the SANS. The main reduction was for the items facial expression, global affective flattening, and relationships with friends and peers. Also a reduction in total BPRS score was found, which approached statistical significance. Significant reductions were observed for the BPRS items emotional withdrawal and depressive mood. Ritanserin or other drugs blocking 5-HT2 and/or 5-HT1c receptors could be important in reducing specific symptoms in schizophrenic patients.

Antipsychotic Agents↗
PubMed1992

Statistical model for assessing the quality and cost of inspection procedures in forensic and environmental analysis.

Legal regulations on the composition and safety of food products require inspection programmes to maintain the standards required or to obtain an insight in the real situation. Such programmes consist of a sampling procedure followed by analysis of the samples. When monitoring environmental contamination similar programmes are required. When large numbers of samples have to be analysed in order to monitor contaminants in either environmental or food-chain samples, and the majority fulfil the legal requirements, a two-stage control system is desirable. Firstly, samples are analysed by a simple 'screening method', to sift out the large number of samples that fulfil the requirements (negative results). The minority not fulfilling the requirements (positive results) are investigated further by a more sophisticated confirmatory method, specific for the analyte(s) of interest, for an ultimate judgement. For this type of inspection a simple model is used in this study, in order to calculate the fraction of false negative results in the final decision. It is assumed, that, when the quality criteria for the confirmatory method are appropriate, the fraction of false positive results is negligibly small. The quality of the inspection is expressed in terms of the fraction f of false negative results with respect to the real positive samples and is related to labour and costs. In an example given, the costs of analysing 40,000 samples with f = 6.6% are ecu 7,800,000. Improving f down to 3.2% creates additional costs of ecu 16,000,000. The proposed model might not be sufficiently realistic, but more realistic models can be implemented.(ABSTRACT TRUNCATED AT 250 WORDS)

Costs and Cost Analysis↗
PubMed1991

Trauma of the ureter.

Thirty-three ureteric injuries were treated over a 2-year period. The majority of patients presented late. The most common modes of repair were either ureteroneocystostomy or transuretero-ureterostomy. Complications were few and of little significance.

Adult↗
PubMed1989

Cognitive abilities of Kenyan children in relation to nutrition, family characteristics, and education.

The purpose of this study was to determine whether nutritional factors, family characteristics, and the duration of schooling were associated with cognitive and attentional capacities in children growing up in rural Kenya. Food intake was measured by direct observation and weighment twice monthly over the course of a year. Families were characterized in terms of socioeconomic status and the literacy of the parents. Children who were better nourished had higher composite scores on a test of verbal comprehension and the Raven's matrices. Better-nourished females were more attentive during classroom observations than malnourished female schoolchildren. Family characteristics and duration of school participation were associated with cognitive abilities for both boys and girls. For the children considered as a group, cognitive scores were best predicted by a combination of factors including duration of schooling, food intake, physical stature, and SES.

Aptitude↗
PubMed1988

Acute effects of bromazepam on signal detection performance, digit symbol substitution test and smooth pursuit eye movements.

Effects of 6 and 12 mg bromazepam on reaction time, stimulus sensitivity and response bias in a 1-hour visual attention task, on smooth pursuit eye movements, and on performance in the digit symbol substitution test (DSST) were investigated in 12 healthy male volunteers. It was a placebo-controlled, double-blind, crossover study that used repeated measures. Three saliva samples and a blood sample were taken for correlating drug concentration and performance. Bromazepam lowered stimulus sensitivity dose-dependently. Response times for hits and response bias were affected by the 12-mg dose only. DSST performance decreased dose-dependently. Smooth pursuit was equally impaired by 6 and 12 mg. Concentrations in serum correlated with concentrations in saliva, but serum and saliva concentrations did not correlate with task performance.

Adolescent↗
PubMed1986

Maternal nutrition and birthweight: selective review and some results of observations in Machakos, Kenya.

A selective review of maternal nutrition and birthweight is presented. Data from an observational, longitudinal study in Machakos, Kenya show that the habitual diet of pregnant women provided about 1600 kcal and 50 g of protein per day. Nevertheless the birthweight was acceptable, i.e., the mean value was 3058 g. This good reproductive performance was attributed to the fact that weight-for-height remained acceptable during pregnancy, in spite of low weight gain because of an acceptable pre-pregnant weight. However, the birthweight was found to be influenced by the mother's weight in the third month of pregnancy, her weight gain and her height.

Adult↗
PubMed1986

Diazepam-induced changes in signal detection performance. A comparison with the effects on the Critical Flicker-Fusion Frequency and the Digit Symbol Substitution Test.

The effects of 10 mg diazepam on signal detection theory measures (stimulus sensitivity, response bias) and reaction times were studied in a 1-hour visual signal detection task with high and low signal probability, and on performance in two short-duration tasks: Critical Flicker-Fusion Frequency (CFF) and the Digit Symbol Substitution Test (DSST). 12 healthy volunteers participated in this placebo-controlled, double-blind cross-over study. Diazepam affected the stimulus sensitivity and the reaction times of hits in the signal detection task. DSST performance was also impaired while CFF did not change after diazepam treatment. No relationship between serum diazepam concentration and change in task performance was found. It is concluded that diazepam affects signal detection performance, independent of signal probability. A short-duration task like the DSST is as sensitive to the effects of diazepam as the (long-duration) signal detection task.

Adolescent↗