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Biomedical subjects

J Knops

Publications and source records attributed to J Knops.

32 records · Page 2Linked to original sources
PubMed1985

Ventilatory anaerobic threshold in healthy children. Age and sex differences.

The ventilatory anaerobic threshold (VAT) during graded exercise was defined as the oxygen uptake (VO2) immediately below the exercise intensity at which pulmonary ventilation increased disproportionally relative to VO2. Since VAT is considered to be a sensitive and noninvasive measure for evaluating cardiorespiratory endurance performance, the purpose of the present study was to determine normal values in children. We examined 257 healthy children (140 boys and 117 girls) varying in age from 5.7 to 18.5 years, during treadmill exercise. The data were analyzed in relation to sex and age. In boys the lowest VO2max (ml X min-1 X kg-1) was found in the youngest age group (5-6 year). In girls, on the other hand, no significant increase occurred with age. For VAT, expressed as ml O2 X min-1 X kg-1 or as a percent of VO2max, a significant decrease was found in boys and girls with age. This suggests an increase in lactacid anaerobic capacity during growth. In contrast to observations in adults, only low correlations were found between VO2max and VAT (r = 0.28 in boys and r = 0.52 in girls), which suggests that the development of the underlying physiological mechanism does not occur at the same rate in growing children. These data provide normal values for VAT that can be used for clinical exercise testing in the pediatric age group.

Adolescent↗
PubMed1985

Increased frequency of lymphocytic mitotic non-disjunction in recurrent spontaneous aborters.

Hypermodal chromosomal spreads occurred significantly more frequently in lymphocytes from couples with recurrent spontaneous abortion than from comparison populations. Previously, we reported a similarly increased frequency in couples with aneuploid offspring. Considering the frequency of aneuploidy among first trimester spontaneous abortions, we suggest that there may be a sub-population of persons predisposed to non-disjunction among couples with reproductive wastage.

Abortion, Habitual↗
PubMed1982

Effects of flecainide on contractile force and electrophysiological parameters in cardiac muscle.

The action of N-(2-piperidylmethyl)-2,5-bis-(2,2, 2-trifluoroethoxy)-benzamide acetate (flecainide, Tambocor) on contractile force and electrophysiological parameters was studied in isolated calf ventricular fibres. Increasing flecainide concentrations (2-10 mg/l) induced a progressive decrease of force of contraction. At the highest concentration the peak of contraction was reduced by 50-40% of the control value, accompanied by a similar fall of the maximal rate of the rise of contraction (dP/dtmax). The negative inotropic effect was not significantly different at driving frequencies of 0.2 and 1 Hz. 5 mg/l flecainide reduced the tonic as well as the phasic components in high potassium contractures and induced a reduction of the action potential maximal upstroke velocity (Vmax). The suppression of Vmax was augmented by increasing the stimulation frequency from 0.2 to 1 Hz. This frequency dependence could partially be explained by a flecainide induced delay of Vmax recovery from inactivation. Plateau height and duration of the action potential were not significantly effected. The height and duration of slow potentials in 22 mmol/l K+-Tyrode solution were reduced under 5 mg/l flecainide. This effect was frequency independent, since the recovery of the slow potentials from inactivation was not delayed by flecainide. The results indicate that the new antiarrhythmic drug flecainide possesses two different sites of action, indicated by the different frequency dependence on Vmax and slow potential system under flecainide. The observed negative inotropic effect seems to be induced by the depressing effect of flecainide on the slow potential system.

Action Potentials↗
PubMedDate not supplied

Safety and immunogenicity of an Haemophilus influenzae type b-tetanus toxoid conjugate (PRP-T) and diphtheria-tetanus-pertussis (DTP) combination vaccine administered in a dual-chamber syringe to infants in Belgium and Chile.

To document any unexpected differences in the immune response between study populations and to evaluate immunogenicity and safety of a simplified presentation (dual-chamber syringe) of an Haemophilus influenzae type b-tetanus toxoid conjugate (PRP-T) and diphtheria-tetanus-pertussis (DTP) combination vaccine, a multicentre, randomized, comparative study was conducted in Belgium and Chile. A total of 537 healthy infants, 270 in Chile and 267 in Belgium, received PRP-T and DTP vaccines combined in a dual-chamber syringe (D-Ch group, DTP/PRP-T, reconstituted by pressing the plunger of the syringe immediately before injection, n = 239) or combined in a single-chamber syringe (C-In group, DTP@PRP-T, reconstituted immediately before injection, n = 61) or in separate injections (S-In group, DTP + PRP-T, simultaneously injected at separate sites, n = 237) at 3, 4, and 5 months of age. Serum samples were collected before vaccination and at 6 months of age. In the D-Ch group, the incidence of adverse events was comparable to administration of DTP vaccine alone. Higher rates of local and systemic reactions were observed in the Chilean population, possibly due to differences in surveillance practice. The immune response to each vaccine component compared well to that of the separate administration of PRP-T and DTP vaccines, except for higher post-immunization anti-PRP geometric mean titre (GMT) values after separate injections (25.6 micrograms mL-1) than after combined injection with the dual-chamber syringe (17.6 micrograms mL-1) (p = 0.001). An unexpected 'syringe' effect was seen: a greater post-immunization anti-PRP GMT was observed in the D-Ch group (17.6 micrograms mL-1) than in the C-In group (7.7 micrograms mL-1) (p = 0.0001). Whereas pre-immunization GMTs of some antibodies were significantly lower in Chilean than in Belgian infants, the post-immunization GMTs of Chilean infants were two to three times greater for all of the antibodies studied (p < 0.005). Differences in reactogenicity and in the immune response between the study populations or the different vaccine presentations were striking, but are probably of no clinical relevance. The convenient dual-chamber syringe presentation of DTP and PRP-T vaccines is safe and highly immunogenic.

Antibodies, Bacterial↗
PubMedDate not supplied

The increase in number of orchidopexies: rather cause than prevention of male infertility.

Because of the present tendency to operate early on undescended testes, the indication for orchidopexy amounts to six-to-seven times the justified number in the Netherlands and two-to-three times in Flanders! The tendency to operate early has surely caused more fertility damage than prevented it. This critical statement asks for consideration and urges everybody concerned to a more accurate and repeated physical examination of the genital region and to a conservative attitude regarding treatment.

Adolescent↗