Biomedical subjects

T Stijnen

Publications and source records attributed to T Stijnen.

At least 127 records · Page 7Linked to original sources

PubMed1993

Flow velocity waveforms in the ductus venosus, umbilical vein and inferior vena cava in normal human fetuses at 12-15 weeks of gestation.

The objective was to determine the normal Doppler flow velocity waveform patterns in the human fetal ductus venosus, inferior vena cava and umbilical vein correlated with fetal heart rate, and to examine their reproducibility and their inter-relationship at 12 to 15 weeks of gestation. Cross-sectional recordings of 45 normal pregnant women were collected for a data reference range transvaginally and transabdominally depending on fetal size and position. Maximum flow velocity waveforms were obtained from the ductus venosus, the intra-abdominal part of the umbilical vein and inferior vena cava. Time-averaged velocities were calculated in all three vessels together with peak systolic, peak diastolic and time-averaged velocities in the ductus venosus and inferior vena cava. Doppler recordings in 21 other patients displayed good reproducibility. Continuous forward flow in the umbilical vein was associated with pulsatile systolic and diastolic forward flow in the ductus venosus. Retrograde flow was present only in the inferior vena cava. Mean time-averaged velocity (SD) in the ductus venosus was 28.8 (6.1) cm/s, in the umbilical vein 9.7 (2.9) cm/s and in the inferior vena cava 10.9 (2.5) cm/s. No correlation could be established between waveform parameters and fetal heart rate. Combined transvaginal and transabdominal Doppler ultrasound allows reproducible blood flow velocity recordings at venous level in early pregnancy. Relatively high velocities were observed in the ductus venosus compared with the umbilical vein and inferior vena cava. Differences in flow velocities in the ductus venosus and inferior vena cava suggest that little or no mixing of blood occurs, a situation well described in sheep.

Adult↗

PubMed1993

Effect of growth hormone administration frequency on 24-hour growth hormone profiles and levels of other growth related parameters in girls with Turner's syndrome. Dutch Working Group on Growth Hormone.

OBJECTIVE: The optimal dose and frequency of GH administration in Turner's syndrome is unknown. There is some evidence that a schedule which mimics normal pulsatile GH secretion may be more effective than a single daily dose. We therefore wished to study the influence of the frequency of GH administration on 24-hour GH profiles and levels of other growth-related factors in Turner's syndrome. DESIGN: Four weeks after initiation of 0.05 microgram/kg/day ethinyl oestradiol, we compared twice daily (b.i.d.-fractionated dose) with once daily (o.d.) s.c. injections of 6 IU GH/m2/day in a 2-week cross-over design with a 2-week washout interval. Each treatment period was concluded with 24-hour GH profile tests. Pretreatment plasma/serum levels of GH, IGF-I, binding proteins for GH (GHBP) and IGF-I (IGFBP-3) were used as a basis for comparison of the levels found after each regimen. A one-compartment open model was used for estimation of pharmacokinetic parameters. SUBJECTS: Ten previously untreated girls with Turner's syndrome aged > or = 11 years. MEASUREMENTS: Plasma levels of GHBP by standardized binding assay; GH, IGF-I, and IGFBP-3 serum/plasma levels by radioimmunoassay. RESULTS: There were significantly higher maximum GH levels and a greater area under the curve with o.d. than with b.i.d. GH, while GH clearance was greater with b.i.d. The pharmacokinetic values with o.d. injections were in conformity with values for healthy and GH-deficient children. Pretreatment GHBP levels tended to be high compared with values in healthy prepubertal children. These levels decreased with GH therapy, significantly so with b.i.d. GH only. There was a significant increase in levels of IGF-I and IGFBP-3, irrespective of regimen. The IGF-I to IGFBP-3 ratio, a possible indicator of the growth response, rose significantly and comparably with both regimens. There was no consistent diurnal variation with either regimen in GHBP, IGF-I or IGFBP-3 levels. Four-hourly levels of GH, GHBP, IGF-I and IGFBP-3 were not correlated. CONCLUSIONS: Although the 24-hour profiles differed during once or twice daily administration of the same total growth hormone dose, the diurnal pattern and mean levels of factors involved in the biological effects of GH are comparable for both regimens.

Adolescent↗

PubMed1993

Effect of intravenous fluid administration on recovery after running a marathon.

After the Rotterdam Marathon on 21 April 1991 (ambient temperature 5.8 degrees C, relative humidity 74%, wind velocity 5 m s-1) data from 66 athletes were analysed for information concerning total recovery and recovery from pain, stiffness, loss of appetite, sleep disturbance and fatigue. The pulse rate, body weight and temperature were measured. The athletes were divided at random into two groups. Thirty-four athletes received an intravenous infusion of 2.5 l of a 2.5% glucose/0.45% NaCl solution. Thirty-two athletes received a placebo infusion of 100 ml 0.9% NaCl. Recovery took 9.2 days in the placebo group and 10.2 days in the infusion group. All athletes had pain and/or stiffness after the marathon. The immediate replacement of 2.5 l of fluid had no significant influence on the rate of total recovery, the number of days with pain or stiffness, the appetite, sleep or fatigue. On the first day after the marathon the pulse rate was increased. The rectal temperature was not affected. The athletes were also divided into fast and slow runners without regard to fluid replacement. Fast runners (those running the race in less than 2 h 55 min) needed more time to recover than slower runners and pain and/or stiffness lasted longer in the fast group. Athletes who equalled or improved their best previous results also needed more time to recover than athletes who did not, although there were no significant differences in pain and stiffness. Athletes did not benefit from immediate fluid replacement after running the 1991 Rotterdam Marathon.

Adult↗

PubMed1993

Cigarette smoking and the development and progression of aortic atherosclerosis. A 9-year population-based follow-up study in women.

BACKGROUND: Cigarette smoking has been recognized as an important risk factor for cardiovascular disease in men and women. Whether the increased risk results from an atherogenic effect of smoking is still debated. We examined the relation between cigarette smoking and atherosclerotic changes in the abdominal aorta. METHODS AND RESULTS: The association between cigarette smoking and atherosclerotic changes in the abdominal aorta was examined in a population-based cohort of 758 women, initially aged 45 to 64 years. All women were examined radiographically for calcified deposits in the abdominal aorta, which have been shown to represent intimal atherosclerosis. After 9 years of follow-up, atherosclerotic changes, indicating development or progression of plaques, could be demonstrated in 37% of women. A direct association was found between atherosclerotic change and number of cigarettes smoked per day. Compared with women who had never smoked, the relative risks of those who smoked 1 to 9, 10 to 19, and 20 or more cigarettes per day were 1.4 (95% confidence interval, 1.0 to 2.0), 2.0 (1.6 to 2.5), and 2.3 (1.8 to 3.0), respectively, after adjustment for age and other cardiovascular risk factors. Associations of atherosclerotic change with inhaling habit and duration of smoking were borderline significant after number of cigarettes smoked per day was taken into account. Among former smokers, the risk decreased with increasing duration of stopping but a significant excess risk was still observed after 5 to 10 years since quitting (relative risk, 1.6; 95% confidence interval, 1.1 to 2.2). CONCLUSIONS: These follow-up data support the evidence for an effect of cigarette smoking on atherosclerosis. The findings suggest that the rate of atherosclerotic change may be reduced by cessation of smoking, but a residual effect appears to be present for at least 10 years.

Aorta, Abdominal↗

PubMed1993

Epithelium removal and peptidase inhibition enhance relaxation of human airways to vasoactive intestinal peptide.

In this study we evaluated the role of epithelial versus subepithelial peptidases in the responses of isolated peripheral and central human airways to VIP. Human airways were obtained at thoracotomies (n = 8) and studied in organ baths. Intact or epithelium-denuded strips of central and peripheral airways were incubated with or without a cocktail of peptidase inhibitors containing phosphoramidon (2.5 micrograms/ml), leupeptin, aprotinin, captopril, soybean trypsin inhibitor (all 20 micrograms/ml), and bestatin (2.8 micrograms/ml). After precontraction with histamine (5 x 10(-6) M), cumulative concentration-response curves to VIP (10(-10) to 10(-7) M) were obtained. Both intact central and peripheral airways showed only minor relaxations to VIP irrespective of the precontraction level. Removal of the epithelium and addition of peptidase inhibitors additively increased the sensitivity (> 20-fold) and maximal response to VIP in both central and peripheral airways. We conclude that (1) VIP relaxes both central and peripheral human airways but only in the absence of epithelium and/or the presence of peptidase inhibitors, and (2) both epithelial and subepithelial peptidases are important in the inactivation of VIP in human airways.

Adult↗

PubMed1993

Long-term effects of treatment for acute lymphoblastic leukemia with and without cranial irradiation on growth and puberty: a comparative study.

We investigated the comparative effect on long-term growth of CNS prophylactic treatment for acute lymphoblastic leukemia (ALL) with either 25-Gy cranial irradiation or moderate-dose i.v. methotrexate. In 80 children with complete continuous first remission, data on growth and pubertal development were investigated up to 11 y from ALL diagnosis. Forty patients had 25-Gy cranial irradiation, 16 of them with high-risk factors and 24 without. Another 40 non-high-risk ALL patients had moderate-dose methotrexate. Chemotherapy lasted 3 1/4 y for high-risk ALL patients and 2 1/4 y for those not at high risk. Pubertal development and final height were assessed separately for girls diagnosed before or after age 7 and for boys before or after age 9. All patients had a similar decline in height SD score during the first 6 mo of treatment, which persisted in irradiated children only. The nonirradiated group had no further decline. Catch-up growth only started when chemotherapy ended for irradiated and non-irradiated patients alike. Five y after cessation of treatment, changes in height SD score for nonirradiated children remained within the range for healthy children against a significant decline in height SD scores for irradiated children. Pubertal development in irradiated girls diagnosed before age 7 was within normal range, but their final height was disappointing due to a blunted growth spurt. In contrast, irradiated girls diagnosed later had a delayed onset of puberty but satisfactory final height. Comparable results were found in boys.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

Levels of growth hormone, insulin-like growth factor-I (IGF-I) and -II, IGF-binding protein-1 and -3, and cortisol in prednisone-treated children with growth retardation after renal transplantation.

Growth retardation after renal transplantation (RTx) is generally attributed to prednisone (PDN) administration, although the exact mechanism is poorly understood. In a group of 19 growth-retarded post-RTx children, we studied the effect of alternate day (AD; n = 12) and daily (D; n = 7) PDN therapy (0.10-0.25 mg/kg.day) on 24-h plasma GH and cortisol profiles, once in group D and twice on successive days in group AD. The maximal plasma GH response to arginine provocation (ATT) and plasma levels of insulin-like growth factor-I (IGF-I), IGF-II, and serum IGF-binding proteins (IGFBP) were also determined. The pulsatile character of the 24-h GH secretion was sustained in all patients. However, mean GH levels were significantly lower as compared with published data for healthy children, corrected for pubertal stage and sex. The highest mean GH levels were found in boys and girls in late puberty. Group AD had similar 24-h GH profiles whether on or off PDN treatment, which did not differ significantly from the GH profiles observed in group D. The maximal GH response during ATT was greater than 10 micrograms/L in 57% of the children. Group D had significantly lower mean and maximal cortisol levels than group AD, but all patients had a normal diurnal variation. Plasma immunoreactive IGF-I and IGF-II, and serum IGFBP-1 levels were normal, but serum levels of IGFBP-3 were increased. A significant negative correlation was found between the glomerular filtration rate and serum IGFBP-3 levels. In conclusion, our findings indicate that growth-retarded renal allograft patients, receiving either alternate day or daily PDN therapy, have decreased GH secretion, but a normal diurnal rhythm of GH and cortisol secretion as well as normal plasma IGF-I and -II levels. However, growth retardation after RTx may not solely be the result of decreased GH secretion. Renal graft impairment together with decreased IGF bioavailability may, in addition to the presumed direct effects of PDN on cartilage, contribute to the growth retardation after RTx.

Adolescent↗

PubMed1993

Common arterial trunk, uncommon coronary arterial anatomy.

Macroscopic investigation was done in 44 postmortem specimens of hearts with common arterial trunk. In 38 hearts, the normal distribution in left and right coronary arteries was found. Of the coronary orifices, five were pinpoint and three showed a double orifice. The left coronary orifice was positioned in the posterior part of the truncus (p < 0.0001); the right coronary orifice was positioned in the right anterior and lateral part (p < 0.0001). In 19 hearts, coronary orifices were found above sinus level, left coronary orifices more often than right coronary orifices (p < 0.001). In seven hearts, type I truncus was found, in seven type II truncus was found, in 17 the truncus was intermediate between types I and II, in two type III truncus was found. In 11 hearts, the pulmonary artery distribution could no longer be identified. The truncal valve was bicuspid in 11 hearts, tricuspid in 25 hearts, and quadricuspid in eight hearts. The truncal valve showed overriding of 5% to 100%. Malformations of the coronary arteries were found in 28 hearts (64%). In 27 hearts (61%), the coronary arterial anatomy might have had clinical consequences. In nine hearts, coronary arterial orifices were at risk in excision of the pulmonary arteries from the common arterial trunk. The role of the neural crest as an etiologic factor of coronary arterial malformations in common arterial trunk should be taken into account.

Cadaver↗

PubMed1992

Normal Doppler flow velocity waveforms in the fetal ductus arteriosus in the first half of pregnancy.

Ductus arteriosus flow velocity patterns were studied in 298 women between 9 and 25 weeks of gestation using transvaginal or transabdominal Doppler ultrasound. Technically acceptable recordings were first obtained at 11 weeks resulting in 231 women for further analysis. Ductal waveforms show a significant change in shape from early pregnancy to mid-pregnancy, in that end-diastolic velocities are absent until 13 weeks, are present in 50% at 15 weeks and are present in all cases from 17 weeks. Regression analysis demonstrated a statistically significant linear increase with advancing gestational age for all flow velocity parameters except for the pulsatility index which remained stable during the entire study period.

Journal Article↗

PubMed1992

Effects of gonadotropin releasing hormone agonist addition to gonadotropin induction of ovulation in polycystic ovary syndrome patients.

Meta-analysis of all randomised trials published so far, was performed to compare the effect of additional gonadotropin releasing hormone (GnRH)-agonist treatment to exogenous gonadotropins for ovulation induction in clomiphene-resistant polycystic ovary syndrome (PCOS) patients. Five clinical studies were included, of which only one showed significant differences in pregnancy rate. In addition, pretreatment with GnRH-agonist was once reported to lead more often to cancellation of medication. Combining the results of all five trials, a significant difference in favour of additional GnRH-agonist administration could only be observed for pregnancy rate. No significant differences in ovulation rate could be found. Due to the relative small number of patients in each separate group, no conclusions could be drawn concerning the influence of GnRH-agonist treatment on gonadotropin doses necessary to induce ovulation, and the incidence of multiple pregnancy, abortion and ovarian hyperstimulation.

Female↗

PubMed1992

Fetal atrioventricular and outflow tract flow velocity waveforms during conducted and blocked supraventricular extrasystoles.

Maximum flow velocity waveforms at atrioventricular and outflow tract level were studied cross-sectionally in 19 human fetuses with conducted and/or blocked supraventricular extrasystoles ranging from 25 to 38 weeks of gestation. At outflow tract level, peak systolic velocity and acceleration time for extrasystolic and post-extrasystolic beats were compared with those for the immediately preceding normal beat. Regression lines were calculated for peak systolic velocities with filling time. At atrioventricular level, peak-E wave and peak-A wave velocities and E/A ratio for the extrasystolic and post-extrasystolic beats were compared with those for the normal beat. At all levels, time-averaged velocities were compared with reference charts standardized for gestational age.Peak systolic velocity and acceleration time during the post-extrasystolic beat were higher than during the normal beat; the Frank-Starling mechanism, post-extrasystolic potentiation as well as reduced ventricular afterload may all play a role in this. At all measuring levels, time-averaged velocity during the extrasystolic beat was strikingly lower than the reference velocities. It is postulated that the increased blood volume and contraction force during the post-extrasystolic beat cause the valve area to become larger, resulting in a relative decrease in velocities measured by Doppler ultrasound.

Journal Article↗

PubMed1992

Reproductive behaviour and prenatal diagnosis following genetic termination of pregnancy in women of advanced maternal age.

One hundred and fifty-one women of advanced maternal age who underwent genetic termination of pregnancy (TOP) were studied for their reproductive behaviour and the type of procedure for prenatal diagnosis in a subsequent pregnancy. A total of 59 women (39 per cent) had a further pregnancy. In all continuing pregnancies prenatal diagnosis was performed, of which 75 per cent consisted of chorionic villus sampling (CVS). Reproductive behaviour following a genetic termination was negatively correlated with maternal age and parity. Both reproductive behaviour and the choice to undergo a diagnostic procedure in the next pregnancy were independent of the type of diagnostic procedure in the previous affected pregnancy.

Abortion, Therapeutic↗

PubMed1992

Intensification of GVHD prophylaxis interferes with the effects of pretransplant herpes virus serology on the occurrence of grades II-IV acute graft-versus-host disease.

The effects of pretransplant herpes virus serology on the occurrence of grades II-IV acute graft-versus-host disease (GVHD) were studied in 262 recipients and their HLA-identical family donors. In 131 recipients on standard GVHD prophylaxis (either methotrexate or cyclosporin A) significant effects were observed for donor HSV serology (seropositivity associated with increased risk for GVHD) and donor EBV serology (seronegativity associated with increased risk). However, these effects were nonsignificant in the other 131 recipients on intensified GVHD prophylaxis (i.e., methotrexate combined with cyclosporin A, in vivo anti-T-cell monoclonal antibodies, or various procedures to reduce the T-cell numbers in the transplants.

Acute Disease↗

PubMed1992

Normal fetal Doppler inferior vena cava, transtricuspid, and umbilical artery flow velocity waveforms between 11 and 16 weeks' gestation.

OBJECTIVES: Our objectives were to determine flow velocity waveform patterns in the fetal inferior vena cava and to relate these waveforms to transtricuspid and umbilical artery waveforms and fetal heart rate in early gestation. STUDY DESIGN: Doppler waveforms were recorded in 40 normal fetuses at 11 to 16 weeks of gestation. Only transvaginal scanning was carried out at 11 to 12 weeks and only transabdominal scanning was used at 15 to 16 weeks. RESULTS: The ratio of time velocity integrals of flow from the inferior vena cava during systole and early diastole, the percentage of reverse flow in this vessel, the pulsatility index from the umbilical artery, and the fetal heart rate were negatively correlated with gestational age. Peak E-wave and A-wave velocities and E/A ratios from the transtricuspid waveforms were positively correlated with gestational age. CONCLUSION: Early normal pregnancies are associated with remarkable changes in fetal flow velocity waveforms at both the cardiac and the extracardiac level.

Adult↗

PubMed1992

Conventional and controlled release valproate in children with epilepsy: a cross-over study comparing plasma levels and cognitive performances.

We studied plasma levels and behavioural effects of a newly developed controlled release formulation of valproate (VPA-CR) in children with epilepsy. Valproate plasma levels and performances in attention and vigilance tasks were monitored during a 12-h period (daytime), both during monotherapy of conventional valproate (VPA) and 4 weeks after switching to a similar dosage of VPA-CR taken once daily. There was no significant difference between the two formulations with respect to mean diurnal trough and peak valproate plasma levels, and to mean fluctuation. The significantly higher Cmax/Cmin ratio during VPA-CR seems mainly due to low valproate plasma levels early in the morning. Neuropsychological assessment showed no significant differences, either between patients and controls, or within patients and controls when comparing the results obtained on the VPA and VPA-CR day. During both VPA and VPA-CR treatment, no correlation was found between cognitive performance and valproate plasma levels. The advantage of VPA-CR is that the once daily regimen may increase compliance and is more convenient for schoolchildren.

Adolescent↗

PubMed1992

The perfused human bronchiolar tube characteristics of a new model.

Strips or rings of airway tissue are often used to study contractile responses of human airways in vitro. These preparations have the disadvantage that it is impossible to deliver stimuli selectively to the mucosal or serosal surface. Hence, they allow only for a limited evaluation of the modulatory role of the airway epithelium. We developed an in vitro model that allows independent stimulation from either the serosal or the mucosal side of human peripheral airways. Segments of human peripheral airways were perfused with a Krebs solution at a constant pressure, and responsiveness was measured as a change in flow rate. Pressure/flow relationships indicated laminar flow over a wide pressure range, and a working pressure of 6 cm H2O was chosen because this is a physiological transpulmonary pressure. When stepwise stretching the airway to 180% of its length, we noted an increase in baseline flow and a decrease in flow reduction after methacholine 10(-5) M. At 140% of the length, accurate and reproducible measurements of the sensitivity (EC50) to methacholine were obtained, and airway closure did not occur. A one-way analysis of variance (ANOVA) revealed that the between-patients differences accounted for 91% of the total variability for -log EC50. We conclude that this in vitro model offers interesting possibilities for evaluating the modulatory effects of the human airway epithelium. In addition, the model provides the opportunity to study human small-airway mechanical properties and secretory functions.

Adult↗

PubMed1992

Normal fetal cardiac flow velocity waveforms between 11 and 16 weeks of gestation.

OBJECTIVES: The purpose of our study was to determine the nature of fetal cardiac flow velocity waveforms in late-first- and early-second-trimester pregnancies. STUDY DESIGN: Eighty-eight normal pregnancies were studied according to a cross-sectional study design between 11 and 16 weeks of gestation. RESULTS: Fetal waveforms at the semilunar level showed a gestational age-related rise in peak systolic flow velocities, with significantly higher velocities in the ascending aorta. Similarly, a gestational age-related rise in peak-E wave (early diastolic filling) and peak-A wave (atrial contraction) velocity was observed at the atrioventricular level, with significantly higher velocities at the tricuspid valve level. CONCLUSIONS: Compared with late gestation, these data suggest a reduced ventricular compliance or ventricular relaxation rate and a raised cardiac afterload in the normally developing late-first- and early-second-trimester fetus.

Adult↗

PubMed1992

Cerebral blood flow pattern and autoregulation during open-heart surgery in infants and young children: a transcranial, Doppler ultrasound study.

OBJECTIVES: To elucidate the effect of cardiopulmonary bypass on cerebral perfusion and on the autoregulatory ability of the cerebral vascular bed of infants and young children. SETTING: Operating room. DESIGN: Prospective study. PATIENTS: Thirteen newborn infants and young children undergoing open-heart surgery. INTERVENTIONS: Cerebral blood flow velocity was monitored in the patients undergoing open-heart surgery from just before the induction of anesthesia until the discontinuation of anesthesia after completion of the surgery. MEASUREMENTS AND MAIN RESULTS: Cerebral blood flow velocity was assessed by semicontinuous measurement of temporal mean blood flow velocity in the middle cerebral artery using a range-gated, pulsed Doppler flowmeter with a transducer that was firmly attached to the left temporal region of the head. Mean arterial pressure (MAP) and nasopharyngeal temperature were continuously monitored. During hypothermic (18.4 degrees C to 31.9 degrees C) cardiopulmonary bypass, cerebral blood flow velocity decreased and showed a close relationship with nasopharyngeal temperature (p less than .0001). During steady-state cardiopulmonary bypass, cerebral blood flow velocity showed a correlation with MAP (p less than .01). The nasopharyngeal temperature influenced this relationship: at lower (absolute) nasopharyngeal temperatures, lack of cerebral autoregulation was more common. CONCLUSIONS: The finding suggests that cerebral blood flow decreases with decreasing nasopharyngeal temperature. During hypothermic cardiopulmonary bypass, cerebral autoregulation seems to be easily disturbed, especially at low nasopharyngeal temperatures.

Anesthesia↗