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Biomedical subjects

T Stijnen

Publications and source records attributed to T Stijnen.

At least 91 records · Page 5Linked to original sources
PubMed1995

Comparison of intravascular ultrasonic findings after coronary balloon angioplasty evaluated in vitro with histology.

This study investigated whether vascular damage and quantitative changes observed with intravascular ultrasound at the most stenotic site are representative of the ultimate outcome after coronary balloon angioplasty. Atherosclerotic coronary arteries (n = 40) were studied in vitro with intravascular ultrasound. From each vascular specimen, 10 corresponding intravascular ultrasound cross sections obtained before and after balloon angioplasty were selected for comparison with their histologic counterpart. Morphologic and quantitative data obtained from all cross sections were compared with data derived from the most stenotic site. The incidence of vascular damage (i.e., dissection, plaque rupture, and media rupture) at the most stenotic site was lower than that seen for each vascular specimen. The sensitivity of intravascular ultrasound in detecting these morphologic features for each vascular specimen was high for dissection and media rupture (79% and 76%, respectively), and low for plaque rupture (37%). After balloon angioplasty, quantitative changes seen at the most stenotic site were greater than those in all cross sections: free lumen area +58% versus +29%, media-bound area +17% versus +12%, and plaque area reduction -9% versus -6%, respectively. The increase in free lumen area was caused predominantly by media-bound area increase (81%) and to a lesser extent by plaque area decrease (19%). This study revealed that a higher incidence of vascular damage is found when the whole segment is analyzed rather than 1 single cross section at the most stenotic site. Quantitative effects of coronary balloon angioplasty seen with intravascular ultrasound were greater at the most stenotic site than at all cross sections.

Adult↗
PubMed1995

Late lumen loss after coronary angioplasty is associated with the activation status of circulating phagocytes before treatment.

BACKGROUND: The purpose of this pilot study was to identify biological risk factors for restenosis after percutaneous transluminal coronary angioplasty (PTCA) to predict the long-term outcome of PTCA before treatment. METHODS AND RESULTS: To investigate whether blood granulocytes and monocytes could determine luminal renarrowing after PTCA, several characteristics of these phagocytes were assessed before angioplasty in 32 patients who underwent PTCA of one coronary artery and who had repeat angiograms at 6-month follow-up. The plasma levels of interleukin (IL)-1 beta, tumor necrosis factor-alpha, IL-6, fibrinogen, C-reactive protein, and lipoprotein(a) before angioplasty were assessed as well. We found that the expression of the membrane antigens CD64, CD66, and CD67 by granulocytes was inversely associated with the luminal renarrowing normalized for vessel size (relative loss) at 6 months after PTCA, while the production of IL-1 beta by stimulated monocytes was positively associated with the relative loss. Next, these univariate predictors were corrected for the established clinical risk factors of dilation of the left anterior descending coronary artery and current smoking, which were statistically significant classic predictors in our patient group. Only the expression of CD67 did not predict late lumen loss independent of these established clinical risk factors. Multiple linear regression analysis showed that luminal renarrowing could be predicted reliably (R2 = .65; P < .0001) in this patient group on the basis of the vessel dilated and only two biological risk factors that reflect the activation status of blood phagocytes, ie, the expression of CD66 by granulocytes and the production of IL-1 beta by stimulated monocytes. CONCLUSIONS: The results of the present study indicate that activated blood granulocytes prevent luminal renarrowing after PTCA, while activated blood monocytes promote late lumen loss. To validate this new finding, further study in an independent patient group is required.

Angina Pectoris↗
PubMed1995

Glucose intolerance, hyperinsulinaemia and cognitive function in a general population of elderly men.

Cognitive impairment is highly prevalent among the elderly. Subjects with disturbed glucose metabolism may be at risk of impaired cognitive function, as these disturbances can influence cognition through atherosclerosis, thrombosis and hypertension. We therefore studied the cross-sectional association of cognitive function with hyperinsulinaemia, impaired glucose tolerance and diabetes mellitus in a population-based cohort of 462 men aged 69 to 89 years. Cognitive function was measured by the 30-point Mini-Mental State Examination. Results were expressed as the rate ratio (95% confidence interval) of the number of erroneous answers given on the Mini-Mental State Examination by the index compared to the reference group. Compared to subjects with normal glucose tolerance, known diabetic patients had a rate ratio of 1.23 (1.04-1.46), newly-diagnosed diabetic patients of 1.16 (0.91-1.48) and subjects with impaired glucose tolerance of 1.18 (0.98-1.41), after adjustment for confounding due to age, occupation and cigarette smoking (p-trend = 0.01). Non-diabetic subjects in the highest compared to the lowest quartile of the area under the insulin curve had a rate ratio of 1.24 (1.03-1.50), after adjustment for confounding (p-trend = 0.02). The results did not change appreciably when potentially mediating factors, including cardiovascular diseases and risk factors associated with the insulin resistance syndrome, were taken into account. These results suggest that diabetes, as well as impaired glucose tolerance and hyperinsulinaemia in non-diabetic subjects are associated with cognitive impairment.

Aged↗
PubMed1995

Astigmatism and visual recovery after phacoemulsification and conventional extracapsular cataract extraction.

In this study we wanted to investigate the post-operative astigmatism and visual acuity after phacoemulsification and conventional extracapsular cataract surgery. Patients operated between April and June 1993 (n = 150) were retrospectively analyzed. The patients were examined prior to surgery and at day 1, at day 10, and in week 6 post-operatively. The difference between the post-operative log mean visual acuity in the Phaco group and in the CECCE group was significant after 1 and 10 days, however it was not significant (p = 0.191) after 6 weeks. The mean astigmatism was significantly less in the Phaco group than in the CECCE group during the whole post-operative check-up period. This study suggests that Phaco results in a lower post-operative astigmatism and an earlier visual rehabilitation compared to the CECCE technique.

Astigmatism↗
PubMed1995

Does experience influence the forces exerted on maxillary incisors during laryngoscopy? A manikin study using the Macintosh laryngoscope.

The influence of the level of experience of the laryngoscopist on the duration of laryngoscopy, the forces exerted on the tongue and on the maxillary incisors during laryngoscopy, were investigated. Five groups (anaesthetists, residents in anaesthesia, nurse anaesthetists, surgeons and medical students), each consisting of 15 individuals, participated in the study. An intubation manikin was used with a laryngoscope modified so that the forces applied during laryngoscopy could be measured. The mean duration of laryngoscopy in these groups was 23.4 sec, 17.6 sec, 27.1 sec, 26.8 sec and 42.7 sec, respectively. The maximally applied forces on the tongue were 71.7 N, 60.5 N, 65.9 N, 74.2 N and 69.7 N, respectively. The maximally applied forces on the maxillary incisors were 49.9 N, 36.3 N, 41.1 N, 58.3 N and 53.9 N, respectively. These results indicate the level of experience has a significant influence on the duration of laryngoscopy but seems to have little influence on the forces applied to the tongue and the maxillary incisors.

Anesthesiology↗
PubMed1995

No demonstrated effect of pre-enucleation irradiation on survival of patients with uveal melanoma.

PURPOSE: To evaluate the hypothetical effect of pre-enucleation irradiation on survival of patients with uveal melanoma. METHODS: In a prospective study between 1978 and 1990, 145 patients with uveal melanoma were treated by irradiation in two fractions of 4 Gy before enucleation. A historical control group of 89 patients with uveal melanoma treated by enucleation alone was operated on between 1971 and 1990. Patients were followed up until December 1992 or until death. The mean follow-up period was 65 months in the irradiated group and 88 months in the control group. RESULTS: The preoperatively irradiated group of patients showed no significant improvement of the survival rate after 7 1/2 years (75.9%) compared with the control group (72.1%). Preoperative irradiation was not associated with survival (P = .93), as assessed by Cox proportional hazard analysis, adjusted for age, gender, tumor location, tumor size, cell type, and year of enucleation. Women in both the irradiated and control groups had a better prognosis than men (P = .002). CONCLUSION: Preoperative irradiation in this nonrandomized study had no effect on survival of patients with uveal melanoma.

Eye Enucleation↗
PubMed1995

Fetal pressure gradient estimations across the ductus venosus in early pregnancy using Doppler ultrasonography.

Doppler ultrasonography was used to estimate the pressure gradient across the ductus venosus at 8-20 weeks of gestation. According to a cross-sectional study design, flow velocity waveform recordings were obtained from the umbilical vein and ductus venosus in 147 uncomplicated singleton pregnancies. Pressure gradients were calculated using the Bernoulli equation. The pressure gradient was estimated at 0.1-1.9 mmHg during ventricular systole and at 0-0.5 mmHg during atrial contraction. Time-averaged pressure gradients ranged between 0.1 and 1.3 mmHg. No statistically significant correlation could be established between the absence or presence of umbilical venous pulsations and estimated pressure gradient. Crude estimates of the pressure gradient across the ductus venosus can be established in the late first and early second trimester of pregnancy. The large scatter of data suggests limited accuracy of venous pressure gradient calculation in early gestation. However, it may also indicate that, in early gestation, venous hemodynamics function at very low pressures.

Adult↗
PubMed1995

Quantitative assessment of infant body fat by anthropometry and total-body electrical conductivity.

Measurement of total-body electrical conductivity (TOBEC) has emerged as a rapid, safe, and reproducible method for estimation of infant total body fat (TBF). Agreement of two anthropometric methods [by Dauncey et al (1977) and Weststrate et al (1989)] with TOBEC-TBF was assessed in 435 healthy infants aged 21-365 d. Dauncey-TBF correlated with TOBEC-TBF by r2 = 0.61 and exceeded TOBEC-TBF by 0.14 +/- 0.25 kg in infants < 4 mo of age. Thereafter, TOBEC-TBF exceeded Dauncey-TBF by 0.20 +/- 0.47 kg. We modified Dauncey's method, which significantly improved the correlation to r2 = 0.75. Weststrate-TBF correlated with TOBEC-TBF by r2 = 0.87, but exceeded TOBEC-TBF by 0.5 kg. Both methods showed poor agreement with TOBEC-TBF. We conclude that both methods, although suitable for comparison of TBF between groups, cannot be used to accurately assess TBF in an individual infant.

Adipose Tissue↗
PubMed1995

Body fat and fat-free mass in infants: new and classic anthropometric indexes and prediction equations compared with total-body electrical conductivity.

Anthropometry is frequently used for nutritional assessment. Little is known in infants about the validity of anthropometric measurements in relation to whole-body fat (TBF) and fat-free mass (FFM) composition. We compared TBF and FFM estimations by total-body electrical conductivity (TOBEC) with anthropometry in 435 healthy infants ages 21-365 d. TBF was best correlated with weight-for-length and calf circumference (r2 = 0.84, r2 = 0.83). FFM was best correlated with body weight (r2 = 0.93). Upper-arm anthropometry, skinfold thickness, and Quetelet's and Ponderal indexes were poorly correlated with TBF and FFM (r2 < 0.65). New anthropometry-based prediction equations were calculated (r2 = 0.90 for TBF and r2 = 0.95 for FFM). New simple indexes (analogous to Quetelet's index) were calculated for TBF (weight x calf circumference/length; r2 = 0.87) and for FFM (square root of weight x length; r2 = 0.95). Prediction equations and indexes were cross-validated in a second population by a second observer. Interobserver variation was largest for equations with skinfold thicknesses included. We conclude that anthropometry can be used for rough estimations of infant body composition, although indexes different than those used in children and adults are preferred.

Adipose Tissue↗
PubMed1995

DNA flow cytometry in uveal melanoma: the effect of pre-enucleation irradiation.

BACKGROUND: For uveal melanoma it has been demonstrated that aneuploidy correlates with worse clinical outcome. However, a striking variation in incidence of aneuploidy is reported for uveal melanomas. METHODS: Flow cytometry was used to study retrospectively DNA-ploidy of 132 uveal melanomas on paraffin embedded material. Thirty five patients received 2 x 4 Gy doses of irradiation 24 and 48 hours before enucleation. Correlation between DNA-ploidy and histopathological grading, largest tumour diameter, tumour height, tumour location, scleral invasion, and TNM classification was assessed. Survival analysis methods were used to investigate the predictive value of these variables on clinical outcome. RESULTS: Of the tumours 37% were aneuploid and 63% were diploid. Intratumour ploidy heterogeneity was minimal (92% concordance). A strong correlation (p = 0.009) was found between DNA-ploidy and cell type. No correlation was found between DNA-ploidy and other conventional prognostic variables. Irradiated melanomas were significantly more aneuploid than non-irradiated tumours (p < or = 0.01). CONCLUSION: In survival analysis DNA-ploidy and the largest tumour diameter were significant in predicting metastatic outcome (p < or = 0.03 and 0.01 respectively); histological cell type and tumour location were of borderline significance.

Aneuploidy↗
PubMed1995

Does phase 2 of the expiratory PCO2 versus volume curve have diagnostic value in emphysema patients?

It has been postulated that serial inhomogeneity of ventilation in the peripheral airways in emphysema is represented by the shape of expiratory carbon dioxide tension versus volume curve. We examined the diagnostic value of this test in patients with various degrees of emphysema. The volumes between 25-50% (V25-50) and 25-75% (V25-75) of the expiratory carbon dioxide tension versus volume curve were determined in 29 emphysematous patients (20 severely obstructed and 9 moderately obstructed), 12 asthma patients in exacerbation of symptoms, and 28 healthy controls. Discriminant analysis was used to examine whether these diagnostic groups could be separated. With regard to phase 2 of the expiratory CO2 versus volume curve (mixture of anatomic deadspace and alveolar air), a plot of intercept versus slope of the relationships of (V25-50) and (V25-75) versus inspiratory volume (VI) from functional residual capacity (FRC), obtained during natural breathing frequency, proved to be most discriminating in the separation between healthy controls and severely obstructed emphysema patients. Separating healthy controls and severely obstructed emphysema patients on the basis of the discriminant line for V25-50, 9 of the 12 asthma patients in exacerbation were classified as normal, and only 5 of the 9 moderately obstructed emphysema patients as emphysematous. For V25-75 involvement of phase 3 of the curve (alveolar plateau) in asthma patients in exacerbation caused a marked overlap with the severely obstructed emphysema patients. In the healthy controls, a fixed breathing frequency of 20 breaths.min-1 led to an increase of both volumes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Conjugacy of eyelid movements in vertical eye saccades.

PURPOSE: To examine the conjugacy of lid saccades in normal subjects. METHODS: Saccades of both upper eyelids were recorded simultaneously by means of small, lightweight, magnetic search coils, fixed on each lid. Subjects then made vertical eye saccades between fixed targets. The associated eye saccades were recorded simultaneously by means of magnetic search coils. The authors further examined whether the position of the lid coils affected the recordings. RESULTS: Lid saccades were not as conjugate as their associated eye saccades. Nonconjugacy of lid saccades averaged approximately 8% of the target amplitude, irrespective of saccadic direction. By contrast, nonconjugacy of the associated eye saccades averaged approximately 1% of the target amplitude. Coil position significantly (P < 0.05) affected the recordings. CONCLUSIONS: Lid saccades are not as conjugate as their associated eye saccades. Coil position is critical for the recordings of lid saccades.

Adult↗
PubMed1995

Immunohistochemical and prognostic analysis of apoptosis and proliferation in uveal melanoma.

Neoplasia can be defined as deregulated tissue homeostasis caused by an imbalance between proliferation and apoptosis. Many genes are involved in the maintenance of tissue homeostasis, eg, the c-myc oncoprotein, which is an important regulator of cell proliferation and Bcl-2 protein, which is involved in the regulation of apoptosis. We studied retrospectively indices of proliferation, such as mitotic count and the Mib-1 index, on 51 uveal melanomas and compared their prognostic significance with established indicators of prognosis such as cell type and tumor size. Along the same line we investigated the expression of the regulating proteins c-myc and Bcl-2. Of all parameters tested, the largest tumor diameter and mitotic count were most strongly associated with tumor-related death (P < 0.001 and P = 0.005, respectively). In addition, cell type, the presence of epithelioid cells, the Mib-1 index, and the percentage of cytoplasmic c-myc-positive cells were significant predictive factors. Multivariate analysis showed that the Mib-1 index, largest tumor diameter, and the percentage of cytoplasmic c-myc-positive cells were independent prognostic parameters. Bcl-2 expression did not correlate with clinical outcome. The Mib-1 index correlated with the presence of epithelioid cells (P < 0.03) and the presence of apoptotic bodies (P < 0.001) and c-myc. A strong inverse relationship was found between (nuclear and cytoplasmic) c-myc and Bcl-2 (P < 0.00004 and P < 0.006, respectively), suggesting that Bcl-2 cooperates with c-myc to immortalize uveal melanoma cells.

Apoptosis↗
PubMed1994

Growth hormone treatment in growth-retarded adolescents after renal transplant.

Growth failure is a psychosocial problem for many patients who have undergone renal transplantation. 18 adolescents (mean age 15.6, range 11.3-19.5) with severe growth retardation after renal transplantation were treated with biosynthetic growth hormone (GH) for 2 years. All received prednisone, administered daily or on alternate days, with azathioprine and/or cyclosporin A. 16 were blindly assigned to one of two GH doses (4 vs 8 IU per m2 per day). Growth, bone maturation, renal graft function, plasma insulin-like growth factors, serum binding proteins, and other biochemical parameters were checked regularly. Glomerular filtration rate and effective renal plasma flow were tested with 125I-Thalamate and 131I-Hippuran. Data on growth and glomerular filtration rate during GH treatment were also compared with those of matched non-GH-treated controls. Mean (standard deviation) increment in height after 2 years of GH was 15.7 (5.1) cm, significantly greater (p < 0.0001) than in matched controls, 5.8 (3.4) cm. Results were similar for the two GH dosage groups. Bone maturation was not accelerated. Glomerular filtration rate and effective renal plasma flow did not change significantly. The incidence of a > 25% reduction in glomerular filtration rate over 2 years was not significantly higher in GH-treated patients than in non-GH-treated controls (39% vs 32%, p = 0.97). Although a few patients had deterioration of graft function, we could not find a relation with GH treatment. Our results show that sustained improvement of height can be achieved with GH in severely growth-retarded adolescents after renal transplantation.

Adolescent↗
PubMed1994

Doppler flow velocity waveforms in the fetal ductus arteriosus during the first half of pregnancy: a reproducibility study.

Reproducibility of flow velocity waveform measurement in the fetal ductus arteriosus was studied in 52 normal pregnancies between 11 and 25 weeks of gestation. The flow velocity parameters studied were the peak systolic velocity, mean velocity, end-diastolic velocity, flow velocity integral and acceleration time. In each woman two consecutive measurements were performed with a time delay of 15 min. An acceptable reproducibility was achieved for all flow velocity parameters, except for the acceleration time and end-diastolic velocity.

Journal Article↗
PubMed1994

J-shaped relation between change in diastolic blood pressure and progression of aortic atherosclerosis.

The J-shaped relation between diastolic blood pressure and mortality from coronary heart disease continues to provoke controversy. We examined the association between diastolic blood pressure and progression of aortic atherosclerosis in a population-based cohort of 855 women, aged 45-64 years at baseline. The women were examined radiographically for calcified deposits in the abdominal aorta, which have been shown to reflect intimal atherosclerosis. After 9 years of follow-up, slight progression of atherosclerosis was noted in 19% of women and substantial progression in 16%. The age-adjusted relative risk of substantial atherosclerotic progression in women with a decrease in diastolic pressure of 10 mm Hg or more was 2.5 (95% CI 1.3-5.6), compared with the reference group of women who had a smaller decrease or no change. The excess risk in this group was confined to women whose increase in pulse pressure was above the median (3.9 [1.5-9.9] vs 1.1 [0.3-4.2] in women with an increase in pulse pressure below the median). The relative risks for women with rises in diastolic pressure of 1-9 mm Hg and 10 mm Hg or more were 2.2 (1.1-4.3) and 3.5 (1.6-8.0), respectively. These findings suggest that a decline in diastolic blood pressure indicates vessel wall stiffening associated with atherosclerotic progression. They support the hypothesis that in low-risk subjects progression of atherosclerosis may be accompanied by a decrease in diastolic blood pressure rather than the opposing idea that low diastolic blood pressure precipitates the occurrence of atherosclerotic events.

Age Factors↗
PubMed1994

Presence of pulsations and reproducibility of waveform recording in the umbilical and left portal vein in normal pregnancies.

Reproducibility and inter-observer variability of intra- and extra-abdominal umbilical venous flow velocity and left portal venous flow velocity as well as heart-synchronous waveform pulsations in these vessels were studied in 23 women at 34-38 weeks of normal pregnancy.Limited reproducibility, expressed by large intra-patient coefficients and limits of agreement between two observers, was established for all standardized recording sites. Pulsations, defined as negative venous deflections of at least 10% of the mean velocity, were demonstrated at all locations ranging from 19.6% of the measurements at the free-floating loop of the umbilical vein to 78.4% of the measurements at the left portal vein. The present study shows that the limited reproducibility of venous flow velocity waveforms should be taken into consideration, and that the presence of pulsations can be demonstrated in normal late pregnancy.

Journal Article↗