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Biomedical subjects

K Boer

Publications and source records attributed to K Boer.

At least 91 records · Page 5Linked to original sources
PubMed1992

Perinatal development of human circadian rhythms: role of the foetal biological clock.

The development of circadian rhythms and the neuronal mechanisms underlying their generation (particularly the suprachiasmatic nucleus of the hypothalamus) were reviewed. Based on perinatal animal studies and data from human foetuses and/or preterm infants it was concluded that human circadian rhythms are present as early as at 30 weeks of gestation. The significance of the mother and/or the environment regarding the entrainment of the "endogenous" foetal biological clock was emphasized.

Circadian Rhythm↗
PubMed1992

Jejunal atresia related to the use of methylene blue in genetic amniocentesis in twins.

OBJECTIVE: To calculate the incidence of jejunal atresia in newborns in The Netherlands. To study the relation between the occurrence of jejunal atresia and genetic amniocentesis to determine a possible iatrogenic cause for the unexpected high incidence of this anomaly in twins. DESIGN: Retrospective study. SUBJECTS: Eighty-nine consecutive twin pregnancies in which amniocentesis had been performed for prenatal diagnosis. In 86 methylene blue solution had been used to mark the amniotic cavity that was punctured first. MAIN OUTCOME MEASURE: The occurrence of jejunal atresia in one of the two twin infants. RESULTS: The incidence of jejunal atresia at birth in The Netherlands is estimated to be 1 in 14,000. This anomaly occurred in 17 out of 89 twin pregnancies (19%). In 15 of the 17 it was possible to determine which of the two children had been exposed to intra-amniotic methylene blue. In all 15 pregnancies, the infant exposed to the dye was suffering from jejunal atresia. CONCLUSION: A causal relation between the use of methylene blue in second trimester amniocentesis and the occurrence of jejunal atresia is strongly suggested. We recommend that no dyes should be injected into the amniotic sac.

Amniocentesis↗
PubMed1991

Umbilical vein administration of oxytocin for the management of retained placenta: is it effective?

In a multicenter randomized controlled trial involving 220 women with retained placenta no beneficial effects could be established of intraumbilical vein administration of 10 IU of oxytocin in 20 ml of saline solution. A reduction was not gained in the rate of manual removal of the placenta and there was no decrease in the amount of blood loss. Oxytocin only induced a minor shortening of the median time interval from administration to the spontaneous expulsion of the placenta as compared with a placebo injection. Maternal serum alpha-fetoprotein levels before and after intraumbilical vein injection did not show evidence of fetomaternal transfusion.

Adult↗
PubMed1990

[HIV prevalence in pregnant women in and around Amsterdam in 1989].

The HIV prevalence among pregnant women in 3 hospitals in Amsterdam was found to be 0.28% in 1988. As the population of these 3 hospitals is not representative of all pregnant women in Amsterdam, this study--which is done on a voluntary basis--in 1989 was slowly extended to all hospitals, clinics and practices of midwives. Of 5,176 pregnant women who were eligible in 1989, 4,812 (93.0%) participated in the study. Non-Dutch women were overrepresented among the refusers. Antibodies to HIV were found in 5/4, 812 women (0.10%, 95% confidence interval 0.01-0.19) and all 5 infected women reported an AIDS risk factor either for themselves or for their present or previous partner(s). Three of the infected women were only tested during the third trimester; the 2 others were tested in the first trimester of their pregnancy and underwent an abortion. The prevalence in 1989 was lower than that found in 1988 and this may have been influenced by an increased effort to counsel seropositive women--and especially intravenous drug users--on the risk of pregnancy.

Adult↗
PubMed1990

An evaluation of 75 terminations of pregnancy based on abnormal laboratory findings at first trimester CVS.

Seventy-five selective terminations, based on abnormal laboratory findings at first-trimester CVS, were performed in 1581 consecutive pregnancies. In all cases a (semi-) direct method of cytogenetic analysis was used. The 75 abortions were analysed in number of ways. Confirmatory studies showed that three cases had to be considered as false-positive findings, and in one other case the results were inconclusive. Based on literature data, it was estimated that 41 of the 75 pregnancies would have resulted in seriously handicapped children, surviving beyond the age of 1 year, if no termination of pregnancy had taken place. Negative side-effects of the procedure include: spontaneous abortion of chromosomally normal fetuses due to the CVS procedure itself and the need for a number of secondary amniocenteses (5.1%). The advantage of DNA diagnosis in X-linked diseases is illustrated by comparing the CVS results with a previously published amniocentesis study.

Abortion, Eugenic↗
PubMed1989

[The prevalence of HIV in pregnant women at 3 outpatient clinics in Amsterdam].

Pregnant women who were seen in 3 hospitals in Amsterdam were tested for antibodies to HIV, after informed consent. Out of 2,308 eligible pregnant women, 2,094 (90.7%) participated by name and 21 (0.9%) anonymously; 193 (8.4%) refused to participate. Among refusers there were significantly more women with a non-Dutch nationality or born in other countries. Of 2,115 pregnant women, 6 were found to be HIV-infected (0.28%, 95% confidence interval (0.05-0.51). Among women who at their first prenatal visit reported no AIDS-risk factor either for themselves or their partner(s), the HIV prevalence was 1/1,893 (0.05%) and among women with such risk factor the prevalence was 5/180 (2.78%). Three of the seropositive pregnant women knew before they were tested that they were HIV-infected. Of the 6 HIV-infected women one had a spontaneous abortion and the 4 women who were tested within the period when therapeutic abortion was still possible, decided to continue their pregnancy.

AIDS Serodiagnosis↗
PubMed1989

Cytogenetic findings in 1250 chorionic villus samples obtained in the first trimester with clinical follow-up of the first 1000 pregnancies.

First-trimester chorionic villus sampling (CVS) was performed in a series of 1250 pregnancies. The direct method of karyotyping was successful in 1205 (96.4%). Abnormal laboratory findings resulted in 60 terminations of pregnancy (4.8%). In addition, six unexpected balanced chromosome rearrangements were detected. False-positive cytogenetic findings occurred in 2.3%, comprising 22 with mosaicism confined to the trophoblast, and a further six non-mosaic false-positive discrepancies were detected, four after termination of pregnancy. The outcome of the first 1000 pregnancies is known in all but one. There were no false-negative findings. Of 947 pregnancies meant to be continued, 34 (3.6%) ended in pregnancy loss before 28 weeks gestation. However, obstetricians with an experience of over 150 procedures had a pregnancy loss of 1.3%.

Adult↗
PubMed1987

[AIDS and pregnancy].

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1981

Reproduction in Brattleboro rats with diabetes insipidus.

The Brattleboro diabetes insipidus mutant is incapable of synthesizing vasopressin, but is activated in its production and release of oxytocin. In the homozygous female mutant, there were abnormally short and long oestrous cycles and reduced conception rates after mating with mutant males, a shortened gestation length, and a shorter time-course of labour. A better conception rate when mutant females were mated with normal Brattleboro males indicates the involvement of a male factor in the subfertility. The reduced litter size in diabetes insipidus rats appeared neither dependent of the male's genotype, nor due to a decreased viability of diabetes insipidus fetuses.

Animals↗
PubMed1980

Effect of low-frequency stimulation of the pituitary stalk on neurohypophysial hormone release in vivo.

Because of the usually low spontaneous activity of oxytocin producing cells, the effect of low frequency (6 Hz) electrical stimulation of the pituitary stalk in vivo upon plasma oxytocin concentration, uterine contractions and intramammary pressure was studied. 30 min of stimulation increased plasma oxytocin concentration. The same type of stimulation elicited both uterine contractions in early post partum rats and milk ejection in the lactating rat, but the latter phenomenon was not considered to mimic physiological events as contrasted with the former. It was concluded that in contrast to previous data, below 10 Hz stimulation of the pituitary stalk in vivo is also effective in producing hormone release and, furthermore, that it may have physiological consequences.

Animals↗
PubMed1980

Pituitary content of oxytocin, vasopressin and alpha-melanocyte-stimulating hormone in the fetus of the rat during labour.

The pituitary contents of oxytocin, vasopressin and alpha-MSH were measured in fetal and newborn rats to assess possible changes in their release during the process of labour. In the 24 h period during which delivery is likely to occur in the Wistar rat, both the oxytocin and vasopressin content of the fetal pituitary gland increased, whereas alpha-MSH content remained the same. During and/or just before labour, the oxytocin content was found to decrease by 30%, indicating an enhanced fetal release of the hormone at this stage. It was concluded that the expulsion of each fetus did not provide an extra stimulus for release of oxytocin by the fetus. In addition, if the fetus remained in the uterus after decapitation of the mother, the oxytocin content of the fetal pituitary gland decreased a further 30%. Neither vasopressin nor alpha-MSH content was altered by the process of labour or by the fetus remaining in the uterus after decapitation of the mother. The levels of vasopressin and alpha-MSH were, however, 20 times higher than the oxytocin content in the fetus and the newborn, which might have obscured the demonstration of a relatively small change in levels of these two hormones.

Animals↗
PubMed1978

Hypothalamic paraventricular unit activity during labour in the rat.

The spike activity of 191 antidromically identified paraventricular units was recorded during labour and the oestrous cycle of rats under urethane anaesthesia. Accelerated bursts of neuronal activity, as reported to occur during suckling, were not observed and changes in firing rate were not correlated with individual uterine contractions. There was, however, an increase in the magnitude of the mean spontaneous firing rate of antidromically identified neurosecretory cells during labour, as compared with all stages of the oestrous cycle. This increase was mainly caused by (1) a marked reduction (greater than 25%) in the percentage of totally silent cells and (2) an increase in the magnitude of the mean firing rate of the phasically firing units (1.58-3.44 spikes/s). It was concluded from these increases in spike activity that the tonic release of neurohypophysial hormones is stimulated during labour, and that this may contribute to the induction and course of labour.

Action Potentials↗
PubMed1977

The influence of the fetal hypothalamus and pituitary on the onset and course of parturition.

The possibility that the fetal brain or pituitary either initiates parturition or influences the course of labour was studied in human and rat. The results when corticotropin or neurohypophysial hormones were injected directly into human anencephalic fetuses in utero, and data obtained from 147 clinical records of such fetuses, seemed to show that the fetal brain does not trigger the onset of parturition. On the other hand, the course of labour was seriously protracted in anencephalic fetuses. Gestation length of brain-aspirated rat fetuses was not significantly longer than in sham-operated controls. However, the course of labour was protracted in the brain-aspirated fetuses. A similarly protracted expulsion pattern was observed in Brattleboro rats homozygous for a hypothalamic form of diabetes insipidus. These data all pointed to the likelihood that fetal neurohypophysial hormones stimulate the course of labour. Neither oxytocin nor vasopressin could be demonstrated in the rat fetus on the last day of pregnancy, when specific immunofluorescence was used. However, a closely related compound was found that was identified as most probably being vasotocin. The hypothesis is put forward that this fetal hormone normally stimulates the course of labour.

Anencephaly↗