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Biomedical subjects

K Boer

Publications and source records attributed to K Boer.

At least 55 records · Page 3Linked to original sources
PubMed1999

Intracellular and extracellular, ionized and total magnesium in pre-eclampsia and uncomplicated pregnancy.

Magnesium (Mg) and calcium (CA) concentrations in women with pre-eclampsia, women with an uncomplicated pregnancy and non-pregnant women were compared. Ionized serum magnesium and calcium concentrations and intracellular magnesium concentrations were measured in 15 pregnant women with severe pre-eclampsia, 34 uncomplicated pregnant women early, at midterm and preterm in their pregnancy and 24 non-pregnant women. The ionized calcium concentration did not chance during normal pregnancy or during pre-eclampsia relative to non-pregnant women. In contrast, elevated total and ionized magnesium serum concentrations were found in women with severe pre-eclampsia (total Mg = 0.85+/-0.11 mM, ionized Mg = 0.61+/-0.06 mM) relative to uncomplicated pregnant women (total Mg = 0.72+/-0.06 mM, ionized Mg = 0.53+/-0.03 mM). Total magnesium in pre-eclamptic women were similar to non-pregnant women. Intracellular ionized and total magnesium concentrations in mononuclear blood cells and erythrocytes were similar in pre-eclamptic women and women with uncomplicated pregnancy. Serum magnesium concentrations are elevated in severe pre-eclamptic women relative to women with uncomplicated pregnancy and are related to birth weight and gestational age at delivery. There may be a causal relationship since magnesium is involved in blood pressure regulation through an intracellular inhibition of NO synthase in endothelial cells.

Calcium↗
PubMed1998

[Vertical HIV-I-transmission. I. Risk and prevention in pregnancy].

Without anti-HIV treatment, mother to child HIV-I transmission occurs in 15-30% of HIV positive pregnancies. Transmission occurs mostly in the last trimester or at birth. The maternal virus load in the last trimester and around birth is strongly related to the risk of HIV transmission to the child. This risk can be reduced during pregnancy by anti-HIV treatment and in certain cases by performing a caesarean section. It is recommended to determine the plasma virus load several times during pregnancy. If the virus load is found to be high, measurement of plasma anti-HIV drug concentrations and anti-HIV drug resistance may prompt modification of the anti-HIV drug regimen with the objective of achieving maximal suppression of virus replication in the last trimester.

Adolescent↗
PubMed1998

Safety evaluation of nonoxynol-9 gel in women at low risk of HIV infection.

OBJECTIVE: To determine the safety of a vaginal microbicide, COL-1492, containing 52.5 mg nonoxynol-9, applied once daily for 14 days among healthy volunteers. METHODS: A randomized, double-blind controlled trial with three arms, COL-1492 gel versus placebo gel versus no-treatment controls, was conducted. Outcomes of interest were reported genital symptoms, incidence of gynaecological signs, and incidence of genital lesions revealed by colposcopy. Participants were enrolled in four centres (Belgium, The Netherlands, and two in Thailand). RESULTS: A total of 534 women participated in the study: 179 used COL-1492, 178 used placebo, and 177 were no-treatment controls. Study visits were scheduled 1 week prior to enrollment (day -7), day 0 (enrollment), day 8 and day 14. The most frequently reported genital symptom was vaginal discharge in both the COL-1492 and placebo groups. This appeared to be related to leakage of the product out of the vagina. The incidence of lesions associated with epithelial disruption (ulcers and abrasions) was very low (< 2%) and there was no statistically significant difference between the three groups. Of the lesions observed by colposcopy that did not involve epithelial disruption, petechial haemorrhage was the most frequently detected, with an incidence of 20.1, 9.0 and 7.3% in the COL-1492, placebo and control groups, respectively. COL-1492 users had a higher incidence of erythema (8.4 versus 2% in the other groups). CONCLUSION: COL-1492 showed minimal toxicity when applied once daily. A Phase III trial to assess the product's effectiveness in HIV prevention is currently ongoing.

Adult↗
PubMed1998

Fetal and maternal diurnal rhythms during the third trimester of normal pregnancy: outcomes of computerized analysis of continuous twenty-four-hour fetal heart rate recordings.

OBJECTIVE: We quantified the presence of diurnal rhythms in various computerized fetal heart rate parameters in normal pregnancies to assess their clinical relevance. STUDY DESIGN: Modified cosine analysis was applied to the outcomes of computerized analysis of continuous 24-hour fetal heart rate recordings in 26 normal pregnancies. Diurnal rhythms in maternal heart rate and plasma hormones were assessed in 15 and 17 pregnancies, respectively. Correlations between maternal and fetal rhythms were calculated. RESULTS: A significant diurnal rhythm in basal heart rate was present in 73% of the fetuses and was closely related to the maternal heart rate rhythm. Diurnal rhythms in heart rate variability, accelerations, and activity were present in only 30% to 50% of the fetuses. CONCLUSIONS: The mother entrains fetal diurnal rhythms. The normal variability in neural development may account for the absence of diurnal rhythms in some fetuses.

Circadian Rhythm↗
PubMed1998

Prenatal exposure to anticonvulsant drugs and spatial ability in adulthood.

By disturbing steroid hormone balances in the fetus, the anticonvulsant drugs phenobarbital and phenytoin may affect certain aspects of cognitive functioning. In order to test this hypothesis, we studied hormone related cognitive functioning in 72 men and 75 women who had been prenatally exposed to these drugs and equal numbers of matched control subjects. The groups did not differ on word fluency, dichotic listening and a Water Level Test. On Card Rotations, however, anticonvulsant-exposed males and females obtained significantly lower scores than control subjects. These results suggest that in both males and females prenatal exposure to phenobarbital and phenytoin may affect holistic spatial processing.

Adult↗
PubMed1997

The diurnal rhythm in fetal heart rate in a twin pregnancy with discordant anencephaly: comparison with three normal twin pregnancies.

In a discordant anencephalic twin the hypothesis was tested that the fetal brain is necessary for the expression of a diurnal rhythm in fetal heart rate. Fetal heart rate recordings were made over a 24 h period in a discordant anencephalic twin pregnancy and in three normal twin pregnancies. Cosinor analysis was used to assess rhythmicity in fetal heart rate and maternal heart rate or activity. Correlations between maternal and fetal rhythms were calculated. A significant diurnal rhythm was found for the fetuses of the control twins, but in neither of the fetuses of the discordant anencephalic twin pregnancy. The maternal rhythm was 1-2 h in advance of the heart rate rhythms in all fetuses except the anencephalic one, whose heart rate did not show any correlation with the maternal diurnal rhythm. We conclude that the fetal brain contributes to the generation of the diurnal rhythm in fetal heart rate and synchronization of maternal-fetal rhythms.

Adult↗
PubMed1997

Can flow cytometric detection of platelet activation early in pregnancy predict the occurrence of preeclampsia? A prospective study.

OBJECTIVES: An increased platelet activation status is present in patients with preeclampsia. Our purpose was (1) to establish by means of flow cytometry whether platelets circulate in an activated state during the first and second trimesters of pregnancy and (2) to establish whether early platelet activation predicts the onset of preeclampsia. STUDY DESIGN: Consecutively, 244 pregnant women were included in a prospective study design. Platelets in whole blood samples from the pregnant women in the first trimester, the second trimester, and after delivery were labeled with the following antibodies associated with platelet activation: anti-CD62P (P-selectin, alpha-granule secretion), anti-CD63 (GP53, lysosomal secretion), anti-CD31 (GPIIa', platelet endothelial cell adhesion molecule-1). The surface antigen exposure was determined by double-label flow cytometry with anti-CD42b (GPIb, a platelet-specific monoclonal glycoprotein) to select platelets and platelet-derived materials. Preeclampsia was defined as a diastolic blood pressure > or = 90 mm Hg and proteinuria > or = 0.3 gm in a 24-hour urine sample (International Society for Study of Hypertension in Pregnancy criteria). RESULTS: Seventeen of 244 patients had preeclampsia (6.9%). Only first-trimester CD63 expression had an area under the curve > 0.5 by receiver-operator characteristic curve analysis and was selected as a possible predictor of preeclampsia. We found a sensitivity of 47% and a specificity of 76% with use of a percentage of activated platelets above 2% as a positive test. Likelihood ratios were 1.94 for positive likelihood and 0.69 for negative likelihood. Univariate logistic regression analysis results were odds ratio 2.8 (95% confidence interval 1.0 to 7.6). Multivariate logistic regression analysis results were odds ratio 2.9 (95% confidence interval 0.92 to 8.9). However, the odds ratio of first antenatal diastolic blood pressure was two to four times higher than the odds ratio of first-trimester CD63 expression. The combination of first-trimester CD63 and first antenatal diastolic blood pressure increases the positive likelihood ratio from 1.94 to 9.4, with a sensitivity of 41%, a specificity of 96%, and a negative likelihood ratio of 0.62. CONCLUSIONS: Increased first-trimester CD63 expression is an independent risk factor for development of preeclampsia. CD63 expression might be useful to identify a subgroup of patients with a high risk for development of preeclampsia, especially in combination with first-trimester antenatal diastolic blood pressure. This method of patient selection may enable more efficient intervention studies in patients at risk than do the selection methods used so far.

Antigens, CD↗
PubMed1997

Extensive platelet activation in preeclampsia compared with normal pregnancy: enhanced expression of cell adhesion molecules.

OBJECTIVES: Platelets play an important role in the pathophysiologic mechanisms of preeclampsia. Our purpose was to investigate by means of flow cytometry to what extent platelets circulate in an activated state during normal pregnancy and whether this activation is more extensive in preeclampsia. STUDY DESIGN: Platelets in whole blood from 10 preeclamptic third-trimester pregnant women (highest diastolic blood pressure range 100 to 130 mm Hg, proteinuria range 0.59 to 11.5 gm/24 hr) and from 10 normotensive third-trimester pregnant controls were analyzed with the following activation markers: anti-P-selectin (alpha-granule secretion), anti-CD63 (lysosomal secretion), PAC-1 (monoclonal antibody against fibrinogen receptor conformation of the glycoprotein IIb/IIIa complex), anti-platelet endothelial cell adhesion molecule-1, and annexin-V (a placental protein that binds to negatively charged phospholipids, present on the outside of the platelet plasma membrane after activation). The differences in surface antigen exposure between the two groups were determined by double-label flow cytometry. Flow cytometric data were analyzed in two ways: first, the percentages of activated platelets above a certain threshold compared with a nonpregnant control sample were determined, indicative for activation of a subpopulation of cells, and, second, the mean fluorescence intensities were determined, indicative of the mean surface antigen expression of the total platelet population. RESULTS: Analysis of the percentage of activated platelets proved most informative. With this analysis an enhanced platelet activation status was present in 4 of 10 normotensive patients and a more extensive platelet activation status in all 10 preeclamptic patients, as indicated by P-selectin (p = 0.008) and CD63 (p = 0.03) expression. Increased platelet endothelial cell adhesion molecule-1 (p = 0.005) expression was also observed in preeclampsia. CONCLUSIONS: Flow cytometric analysis clearly indicated that platelets circulate in a more extensively activated state during preeclampsia than during normal pregnancy. The increased platelet endothelial cell adhesion molecule-1 expression in preeclamptic patients demonstrates that, besides alpha-granular and lysosomal release, other hitherto unknown mechanisms are involved. Platelet endothelial cell adhesion molecule-1 appears to be the best marker to distinguish preeclamptic patients from normotensive pregnant women. Only a subpopulation of the platelets appears to be activated.

Adult↗
PubMed1997

Clearance of cervical human papillomavirus infection by treatment for cervical dysplasia.

OBJECTIVES: The aim of this study was to investigate the prevalence of human papillomavirus (HPV) after treatment for cervical dysplasia. STUDY DESIGN: The presence of HPV was investigated in cervical scrapes of 91 patients, before and after treatment, using consensus primers in the polymerase chain reaction. RESULTS: Before treatment for cervical dysplasia, 89 of 91 patients (98%) were HPV-positive compared with 28 of 91 patients (31%) after treatment. The HPV type present before treatment was found in the scrapes of only 9 of 89 patients (10%). Detection of HPV after treatment was associated with human immunodeficiency virus infection and incomplete conization. CONCLUSION: The HPV type present before treatment was frequently cleared by treatment for cervical dysplasia.

Adult↗
PubMed1997

Vasopressin and oxytocin levels during normal pregnancy: effects of chronic dietary sodium restriction.

Neurohypophysial hormones are thought to be involved in alterations in fluid balance during pregnancy and delivery. In the course of normal pregnancy intravascular volume is increased whereas sodium restriction is thought to reduce plasma volume and cardiac output. In the present study, we measured the effect of long-term severe sodium restriction on vasopressin (AVP) and oxytocin (OT) levels during normal pregnancy and after delivery. Fifty-nine healthy nulliparous women were randomized either for a low sodium diet (20 mmol sodium daily) or for a normal diet from week 12 of pregnancy onwards. Circulating plasma levels and urinary excretion of AVP and OT, their neurophysins (Np-AVP and Np-OT) and AVP bound to platelets were determined at regular intervals during pregnancy and after delivery. After completion of the study, women on a sodium-restricted diet were compared with control women on a normal diet using repeated measurement ANOVA with adjustment for potentially confounding variables. After randomization, a reduction in urinary sodium excretion of, on average, 40-82% was found. In general, no effect of sodium restriction could be demonstrated on the various parameters (0.53 < P < 0.98) with the exception of a significantly lower 24-h urinary AVP excretion by non-smokers with sodium restriction compared with non-smokers having a normal diet (P = 0.018). For all parameters, clear changes were found in the course of pregnancy and puerperium (P < 0.0001 to P < 0.005). Platelet-bound AVP decreased and Np-OT increased during pregnancy. After birth, free plasma AVP, platelet-bound AVP, OT, osmolality, sodium and potassium increased, while Np-AVP and Np-OT decreased. Although elevated Np-AVP and Np-OT levels during pregnancy seem to indicate increased release of neurohypophysial hormones, pregnancy up to 36 weeks of gestation is accompanied by low circulating AVP and OT levels. Long-term severe sodium restriction diminishes urinary AVP excretion in (non-smoking) pregnant women, without changing circulating levels of AVP and OT, despite the known reduction in circulating volume. The reduced circulating (platelet-bound) AVP levels during pregnancy, whether or not in combination with severe sodium restriction, support the absence of significant non-osmotic stimulation of AVP during pregnancy.

Adult↗
PubMed1996

[Results of screening for HIV antibodies in pregnant women in Amsterdam reference stations, 1988-1995].

In order to determine the prevalence of HIV in the general heterosexual population of Amsterdam, 16,709 pregnant women attending two hospitals and one maternity clinic in the period 1988-1995 were asked to undergo a HIV test, of whom 15,276 gave informed consent (91.4%). Pregnant women with a risk of HIV infection were possibly overrepresented in those who refused. The overall HIV prevalence in 1988-1995 was 0.28% and showed no significant differences over the years. In women with a known risk factor for infection the prevalence was 240:10,000, in those without 5:10,000. Whereas intravenous drug use was the most probable cause of infection before 1993, since then it was observed in only 2/20 of the HIV positive pregnant women. Heterosexual transmission appears to be increasing.

AIDS Serodiagnosis↗
PubMed1996

[Poor prognosis in children with ultrasonographically diagnosed abnormalities of the central nervous system].

OBJECTIVE: Long-term follow-up of children with a prenatally diagnosed malformation of the central nervous system. DESIGN: Descriptive study. SETTING: Department of prenatal diagnosis, Academic Medical Center, Amsterdam, the Netherlands. METHODS: Evaluation of all documented ultrasound examinations between 1985 and 1990 (6 years). These ultrasound examinations were performed in women with an increased risk for a foetal malformation, because of obstetrical complications or when a foetal malformation was suspected on ultrasound examination performed elsewhere. Paediatricians and general practitioners were asked to provide follow-up data on the children who were still alive. RESULTS: Seven out of 67 foetuses with a prenatally diagnosed malformation of the central nervous system lived longer than one month. Two out of these 7 children developed normally, one child died after several years and four children were severely retarded. The two children who developed normally both had mild hydrocephaly. CONCLUSION: Prognosis of children with a prenatally diagnosed malformation of the central nervous system is poor. Children with mild hydrocephaly may have a better prognosis.

Adult↗
PubMed1996

Type II and type III deiodinase activity in human placenta as a function of gestational age.

Thyroid hormones are essential for fetal development. T4 can be activated by type I (ID-I) and type II (ID-II) iodothyronine deiodinase or inactivated by type III deiodinase (ID-III). The influence of placental ID-II and ID-III on the regulation of fetal thyroid hormone levels was investigated. Using [125I]T4 and [125I]T3, respectively, ID-II and ID-III activities were measured in homogenates of normal human placentas from 6-43 weeks gestational age and in placentas from five term neonates with a total thyroid hormone synthesis defect. ID-II and ID-III activities related to protein or DNA concentration decreased and total placental ID-III activity increased significantly during pregnancy, whereas the increase in total placental ID-II activity was not significant. Absolute placental ID-II activity was approximately 200 times lower than ID-III activity at all gestational ages. Therefore, fluctuations in ID-II activity were not likely to have a significant influence on fetal thyroid hormone concentrations, but may play a role in the regulation of intraplacental T3 generation. The high ID-III activity most likely influences the thyroid hormone economy of the fetus. Severely hypothyroid newborns showed strongly decreased serum T4 levels, but serum T3 and placental ID-III activities were similar to those in euthyroid newborns. These results suggest that placental ID-III activity is regulated by serum T3, but not by serum T4.

Female↗