PubMed Health⌕ Search

Biomedical subjects

F Beckers

Publications and source records attributed to F Beckers.

At least 19 recordsLinked to original sources
PubMed2005

Influence of supplemental magnesium, tryptophan, vitamin C, and vitamin E on stress responses of pigs to vibration.

Our objectives were to investigate and compare the effects of supplemental Mg, Trp, vitamin E (vit E), and vitamin C (vit C) on stress responses of pigs undergoing transport simulation. In this study, 126 pigs (25.1 +/- 4.4 kg BW) were allocated to one of the six following treatments: 1) negative control (no supplementation); 2) positive control (i.m. injection with 0.5 mg of carazolol/20 kg BW 12 h before vibration, beta-blocker); 3) Trp (additional amount of 6 g/kg of feed for 5 d, as-fed basis); 4) Mg (3 g/L drinking water for 2 d); 5) vit E (additional amount of 150 mg/kg of feed for 21 d, as-fed basis); 6) or vit C (additional amount of 300 mg/kg of feed for 21 d, as-fed basis). Pigs were treated in groups of three, and each treatment was replicated seven times. Feed and water intake were not different among treatments. Heart rate variables (mean, peak, and minimum heart rate, ventricular ectopic beats, and ST elevation of Channels A and B) and heart rate variability were registered from the night before vibration. Pigs were subjected to vibration in a transport simulator (8 Hz, 3 m/s) for 2 h and allowed to recover for 2 h. Generally, the positive control pigs had the lowest heart rate values (mean, peak, minimum heart rate, ST elevation of Channel A; P < 0.05), whereas Mg and Trp decreased ventricular ectopic beats and ST elevation of Channel B, respectively. The effect of vit C and E as vagal stimulators was clearly visible, whereas carazolol and Mg clearly blocked the sympathetic pathways of the autonomic nervous system. During vibration, the negative control pigs lay the least, and Mg pigs the most (P < 0.05). Salivary cortisol concentrations (taken before and after vibration and after recovery) showed that vit E pigs produced the least cortisol during stress periods. Intermediary metabolites (glucose, lactate, creatine kinase, and NEFA) were analyzed in plasma from blood taken before and after vibration. At the two sampling points, the vit E and Mg pigs had the lowest NEFA concentrations (P < 0.05), and the vit E pigs also had the lowest lactate concentrations before vibration. Urine samples were collected before and after vibration to determine catecholamine concentrations; only negative control pigs had an increase (P = 0.04) in epinephrine concentration, despite large individual variation. In general, these results indicate that the supplementation of Trp, Mg, vit E, or vit C improved coping ability of pigs during vibration comparison with the negative control treatment. A muscular injection of carazolol influenced only the heart rate variables.

Adaptation, Psychological↗
PubMed2004

Feasibility of a quality assurance programme of bedside blood glucose testing in a hospital setting: 7 years' experience.

AIMS: Description of the long-term use of a quality assurance (QA) programme for bedside capillary blood glucose (CBG) testing in a general hospital. METHODS: The main points of the programme were selection of instrumentation using a standardized testing procedure, design and implementation of a quality control (QC) procedure, and training and motivation of nurses. The QC procedures consisted of a daily aqueous control and a weekly split-sample control (a measurement on a capillary blood sample using the glucose meter and on a simultaneously drawn venous sample with the laboratory analyser). When the result was out of range, a laboratory technician visited the ward to investigate the problem. All wards received a weekly report. RESULTS: The programme was introduced in 1995 and followed up through 2002. The split-sample control was more efficient in detecting clinically relevant errors than the aqueous control. Most errors (91-97%) were operator-related rather than instrument-related. The compliance with the split-sample controls remained high, with 84-91% of weekly controls performed over 7 years. Respectively 91, 95 and 96% of the measurements remained within the range of +/- 20% of the laboratory value in the years 2000, 2001 and 2002. CONCLUSION: A QA programme of bedside CBG testing can successfully be implemented. It is feasible to obtain a satisfying level of measurement accuracy and to maintain a high level of compliance with the programme over several years. Split-sample controls are an essential part of the control procedure.

Blood Glucose↗
PubMed2003

Parasympathetic heart rate modulation during parabolic flights.

During parabolic flight short periods of microgravity and hypergravity are created. These changes influence cardiovascular function differently according to posture. During the 29th parabolic flight campaign of the European Space Agency (ESA), the electrocardiogram (ECG) was recorded continuously in seven healthy volunteers in two positions (standing and supine). Five different phases were differentiated: 1 g (1 g=9.81 m/s(2)) before and after each parabola, 1.8 g at the ascending leg of the parabola (hypergravity), 0 g at the apex, 1.6 g at the descending leg (hypergravity). We assessed heart rate variability (HRV) by indices of temporal analysis [mean RR interval (meanRR), the standard deviation of the intervals (SDRR), and the square root of the mean squared differences of successive intervals (rMSSD) and coefficient of variation (CV)]. In the supine position no significant differences were shown between different gravity phases for all HRV indices. In the standing position the 0 g phase showed a tendency towards higher values of meanRR compared to the control and to the other phases ( p=NS). SDRR, rMSSD and CV were significantly higher compared to control ( p<0.05). Significantly higher values for meanRR in the supine position at 1 g and hypergravity ( p<0.05) were found when compared to standing. SDRR was significantly higher at 0 g in the standing position compared to supine [95 (44) ms vs. 50 (15) ms; p<0.05] and lower in other phases. rMSSD and CV showed the same trend ( p=NS). We confirm that, during parabolic flights, position matters for cardiovascular measurements. Time domain indices of HRV during different gravity phases showed: (1) higher vagal modulation of the autonomic nervous system in microgravity, when compared with normo- or hypergravity in standing subjects; and (2) no differences in supine subjects between different g phases.

Adaptation, Physiological↗
PubMed2002

Effects of melanocortins on cardiovascular regulation in rats.

1. Of the melanocortin peptides, gamma(2)-melanocyte-stimulating hormone (MSH) has been attributed a cardiovascular effect, inducing an increase in blood pressure and heart rate. Although still controversial, this effect, based on pharmacological blockade experiments, is supposed to be mediated through sympathetic activation. 2. The aims of the present study were to identify the N-terminal pro-opiomelanocortin (N-POMC) fragments and melanocortins that influence blood pressure and heart rate and to investigate the real-time changes in baroreflex sensitivity and in sympathetic and vagal modulation underlying cardiovascular effects in conscious rats without the use of pharmacological blockade. 3. Intracerebroventricular administration of different melanocortins and N-POMC induced a long-lasting dose- dependent pressor response from 1 nmol onwards, with only a small initial bradycardic response with the highest dose. 4. Coinciding with this pressor response, an elicitation of the low-frequency (LF) component was observed in spectral analysis of both blood pressure variability (BPV) and heart rate variability (HRV), followed by the high-frequency (HF) component in at least BPV. Baroreflex sensitivity remained unchanged. 5. After intravenous administration, gamma(2)-MSH produced a short-lasting dose-dependent pressor and cardioaccelerator response with very rapid onset with concentrations from 1 nmol onwards. 6. Continuous infusion of gamma(2)-MSH depressed baroreflex sensitivity and simultaneously increased both components of BPV, with a radical reduction of the LF component and a preserved vagal HF component in HRV. 7. Of all the intravenously administered melanocortins, only gamma(2)-MSH was active. The central effect is likely to depend on an increase of (alpha-)sympathetic outflow. 8. For the peripheral effect, gamma(2)-MSH appeared to act as a baroreceptor reflex-blocking agent, being compatible with a role in the acute stress response.

Animals↗
PubMed2002

Heart rate variability during gravity transitions.

During parabolic flight short periods of microgravity and hypergravity are created. During standing position time domain analysis showed higher vagal modulation of the autonomic nervous system in microgravity compared to hypergravity. We hypothesised that this behaviour could better be unravelled by analysis of frequency domain heart rate variability (HRV) techniques. During parabolic flights a subject is exposed to 20-25 sec periods of microgravity (at the top of the parabola), preceded and followed by 20 sec duration episodes of hypergravity. No significant differences were found in the frequency parameters in supine position for each of the phases. In standing position higher values for Total Power, high frequency (HF), low frequency (LF), LF/HF and HF% in 0 g phase were found in comparison with the 3 other phases. LF% was significant lower in standing position at 0 g compared with 1.8 g. These results show that despite the time window limitations, frequency analysis is still possible on ultra short data segments.

Adult↗
PubMed2002

Head out of water immersion as simulation study: an heart rate variability study.

During head out of water immersion (HOI), the hydrostatic pressure on the tissues of the lower limbs causes an increase in thoracic blood volume and a high vascular perfusion. This blood shift results in changes in autonomic balance. The aim of this study was to evaluate the activity of the autonomic nervous system, as obtained from the analysis of heart rate variability (HRV), during HOI at 2 different temperatures and compare these results with data obtained during parabolic flight. In HOI, two different positions (sitting and standing) were compared. Results showed a shift to vagal activity as well during HOI as in microgravity during parabolic flight.

Comparative Study↗
PubMed2001

Analysis of heart rate variability with correlation dimension method in a normal population and in heart transplant patients.

INTRODUCTION: The correlation dimension (CD) method is related to chaos theory and is used to quantify heart rate variability (HRV). The CD is a measure for the amount of correlations present in the signal. METHODS: The algorithm used to calculate the CD is based on the method of Grassberger and Proccacia. The method was first validated on signals with known CD and then applied to HRV-signals of heart transplants and an age-matched control group of healthy subjects. The CD of the corresponding surrogate time series was calculated to investigate non-linear correlations in the HRV-signal. Circadian variations of the CD were studied in 20 healthy subjects, including men and women. RESULTS: The value of the CD for healthy subjects ranged from 2.12 to 5.53 with a mean value of 4.32. For heart transplants, only a few time series showed a finite value of the CD that varied between 2.10 and 5.60. Also, a significant difference was found between the CD of the original and the surrogate time series in healthy subjects. The CD of women is higher than the CD of men, and this difference was more pronounced during the night than during the day. CONCLUSIONS: This limited study shows that the CD alone cannot be used to make a distinction between HRV-signals of healthy subjects and of heart transplants. However, there is evidence that there are non-linear correlations present in the HRV-signal and that there are significant gender and circadian differences in the CD.

Algorithms↗
PubMed2001

Wavelet decomposition analysis of heart rate variability in aerobic athletes.

Heart rate variability (HRV) can be quantified, among others, in the frequency domain using digital signal processing (DSP) techniques. The wavelet transform is an alternative tool for the analysis of non-stationary signals. The implementation of perfect reconstruction digital filter banks leads to multi resolution wavelet analysis. Software was developed in LabVIEW. In this study, the average power was compared at each decomposition level of a tachogram, containing the consecutive RR-intervals of two groups of subjects: aerobic athletes and a control group. Compared to the controls, the aerobic athletes showed an increased power in all frequency bands. These results are in accordance with values obtained by spectral analysis using the Fourier transform, suggesting that wavelet analysis could be an appropriate tool to evaluate oscillating components in HRV, but in addition to classic methods, it also gives a time resolution.

Adolescent↗
PubMed2001

Short-term heart rate variability in young athletes.

OBJECTIVES: The purpose of this study was to determine whether the type of training in a young population differentiates heart rate variability parameters between athlete groups and sedentary subjects. METHODS: The effect of different types of physical training on heart rate variability was evaluated in 10 aerobic trained athletes, in 7 anaerobic trained athletes, in 7 rugby players (mixed type training) and in 10 sedentary control subjects. All groups were age matched (18-34 years). Electrocardiogram tracings were recorded digitally in the supine position and standing position. Measures of heart rate variability were obtained, from both time- and frequency analysis of 10 min resting heart rate. After these tests, blood pressure was measured using an automatic inflation cuff. RESULTS: Resting heart rate was lower in aerobic and mixed type athletes compared to controls. Only aerobic athletes had evidence of increased vagal activity in the time domain compared with control subjects (increased SDNN supine, increased rMSSD supine and standing and pNN50 standing). In the frequency domain, aerobic athletes presented with both higher low-frequency and high-frequency power in the standing position and low-frequency power in the supine position compared to controls. CONCLUSIONS: It can be concluded that heart rate variability is affected by chronic exercise, especially in endurance trained athletes. This infers that especially aerobic exercising can have beneficial effects on the cardiovascular risk profile.

Adolescent↗
PubMed1999

The analysis of heart rate variability in unrestrained rats. Validation of method and results.

An experimental setting and software were developed to evaluate cardiac autonomic function in unrestrained rats. Subcutaneously implanted ECG electrodes and an indwelling venous catheter were tunneled to a tail cuff in five rats. The ECG was A/D converted at 1000 Hz. After peak detection, a time series of RR intervals was obtained. Programs for the analysis of heart rate variability (HRV) were implemented in LabVIEW. Statistical properties were determined in the time domain. After cubic spline function curve fitting, resampling at 0.1 s and test for stationarity, power spectral analysis was performed on sampled records of 30 min duration after applying a sliding Hanning window (Welch method: 256 points (duration 25.6 s), 50% overlap and 0.039 Hz resolution). Algorithms were tested with simulated signals consisting of isolated frequency components, which were retrieved at their exact locations. Physiological validation of the system was performed by, beta-adrenergic and cholinergic blockade and by forced breathing at a fixed rate. Measurements were performed on five unrestrained rats under basal conditions. Mean RR was 174.2 +/- 3.6 ms; S.D., 13.3 +/- 4.6 ms; rMSSD, 5.2 + /- 1.2 ms; pNN10, 3.5 +/- 1.9% and pNN5, 18.7 +/- 6.4%. Low (0.19-0.74 Hz) and high frequency (0.78-2.5 Hz) power were determined (and also percent of low to total and high to total): 18.42 +/- 10.74 ms2 (22.9 +/- 6.5%) and 15.66 +/- 5.56 ms2 (19.9 +/- 2.7%), and the ratio low/high: 1.16 +/- 0.39. In conclusion, HRV analysis programs were developed and thoroughly tested through simulations and in vivo, under basal conditions and after pharmacological blockades. Using this software, HRV data from unrestrained rats were obtained.

Animals↗
PubMed1998

Estrogen modulates AT1 receptor gene expression in vitro and in vivo.

BACKGROUND: The AT1 receptor has been implicated in the pathogenesis of hypertension and atherosclerosis. Estrogen deficiency is also associated with cardiovascular diseases. Therefore, we examined the AT1 receptor gene expression in ovariectomized rats with and without estrogen replacement therapy and the influence of estrogen on AT1 receptor expression in cultured vascular smooth muscle cells. METHODS AND RESULTS: Rat aortic tissue was examined 5 weeks after ovariectomy. In one group, estrogen (1.7 mg estradiol) was administered during the 5-week period. Functional experiments assessed angiotensin II-induced contraction of aortic rings. AT1 receptor mRNA levels were measured by quantitative polymerase chain reaction and Northern blotting. AT1 receptor density was assessed by radioligand binding assays. These techniques were also applied in cultured vascular smooth muscle cells. The efficacy of angiotensin II on vasoconstriction was significantly increased in aortas from ovariectomized rats. As assessed by radioligand binding assays, AT1 receptor density was increased to 160% without changes in receptor affinity during estrogen deficiency. AT1 receptor mRNA levels were consistently increased to 187% in ovariectomized rats compared with sham-operated animals. Estrogen substitution therapy in ovariectomized rats reversed this AT1 receptor overexpression. To explore the underlying mechanisms, the direct influence of estradiol on AT1 receptor expression was investigated in VSMCs. Estradiol (1 micromol/L) led to a time-dependent downregulation of AT1 receptor mRNA, with a maximum of 33.3% at 12 hours. There was a correlative decrease in AT1 receptor density. CONCLUSIONS: This novel observation of estrogen-induced downregulation of AT1 receptor expression could explain the association of estrogen deficiency with hypertension and atherosclerosis, because activation of the AT1 receptor plays a key role in the regulation of blood pressure, fluid homeostasis, and vascular cell growth.

Angiotensin II↗
PubMed1998

Zinc regulation of insulin-like growth factor-I (IGF-I), growth hormone receptor (GHR) and binding protein (GHBP) gene expression in rat cultured hepatocytes.

Dietary zinc depletion in vivo attenuates growth, decreases circulating insulin-like growth factor-I (IGF-I) and liver growth hormone (GH) receptors (GHR). In order to investigate a direct role of zinc in the regulation of IGF-I, GHR and GH binding protein (GHBP) gene expression, we evaluated the response of their mRNAs to changes in zinc availability in primary culture of rat hepatocytes. Exposition of cells to the zinc chelator DTPA (diethylenetriaminepenta-acetic acid) did not decrease IGF-I and GHBP mRNAs while it strongly inhibited metallothionein (MT) gene expression. On the other hand, zinc excess (50 vs. 1.5 microM) decreased IGF-I, GHR and GHBP mRNAs while it stimulated MT mRNA. However, the response of IGF-I to GH was not affected by the exposure to DTPA nor zinc excess. Furthermore, zinc repletion of primary cultured hepatocytes isolated from zinc-deprived rats did not increase IGF-I nor GHR/GHBP mRNAs. Therefore, our results suggest that the IGF-I decline induced in vivo by zinc deficiency is not caused by reduced extracellular zinc availability at the hepatocyte level. Although IGF-I and MT gene expression is down-regulated by dietary zinc depletion, underlying mechanisms of regulation are different for both genes.

Animals↗
PubMed1997

Continuous profiles and within-day variations of metabolites and hormones in cows fed diets varying in alimentary supplies before short-term feed deprivation.

We investigated continuous profiles and within-day variations of some metabolites and hormones in four nonpregnant, nonlactating cows fed hay-based diets in two equal meals. Diets supplied either too much or too little N (approximately 1.3 or .8 times the maintenance requirements) and NE1 (approximately 1.2 or .8 times). Continuous collection of ruminal liquor, blood, and urine samples was performed for 42 consecutive hours, the last 16 h covering a period without feed. For twice-daily feeding, nitrogenous and energetic underfeeding decreased average ruminal propionate and the insulin:growth hormone ratio. However, only the energetic underfeeding increased plasma 3-methylhistidine and urinary excretion of 3-methylhistidine, and decreased body weight and ruminal acetate, butyrate, and total VFA. Conversely, only the nitrogenous underfeeding decreased glycemia. Whatever the dietary level, the 42-h patterns of metabolites and hormones were mainly affected by the time from the last meal. An energy deficit progressively took place during feed deprivation and the nocturnal interprandial period but not during the diurnal interprandial period. During the feed deprivation and nocturnal periods, glycemia was maintained despite a shortage in ruminal propionate. We conclude that in twice-daily fed cattle 1) the dietary supply of energy is the main trigger for an energy deficit and the subsequent muscle protein mobilization; 2) the nocturnal interprandial period may be considered as short-term feed deprivation; 3) the diurnal patterns of metabolites and hormones are not affected by the nitrogenous and(or) energetic supplies of the diet.

Acetates↗
PubMed1996

Cardiovascular risk factors in children from the Belgian province of Luxembourg. The Belgian Luxembourg Child Study.

The Province of Luxembourg is an area in Belgium with a high prevalence of risk factors for cardiovascular disease and non-insulin-dependent diabetes mellitus among adults. In the present study, children in the age groups 6-8, 8-10, and 10-12 years were selected at random from school classes (n = 1,028), with a participation rate of 70.3%. Anthropometric factors, blood pressure, and fasting blood glucose, plasma cholesterol, triglyceride, and insulin levels were measured in 1992. All anthropometric and metabolic variables increased with age, except for waist: hip circumference ratio in boys and cholesterol in girls. In the oldest group, girls who had passed menarche were taller and heavier and had greater skinfold, body mass index, insulin, and systolic blood pressure values but lower total cholesterol levels and waist: hip ratios than girls who had not passed menarche. Boys had lower skinfolds and higher waist: hip ratios than girls in all age groups, and were significantly shorter and lighter in the oldest age group. There was no difference in body mass index between the two sexes. Girls had higher triglyceride and insulin levels in the 10- to 12-year age group, lower blood glucose values in the 8-10 and 10-12 age groups, and lower diastolic blood pressures in the 8-10 age group. Obesity, blood glucose, triglycerides, insulin, and blood pressure were highly interrelated. Cholesterol, triglycerides, insulin, and blood pressure values were all among the highest of values previously reported in other studies. The deciles of body mass index above 50 appeared to be particularly elevated, suggesting that obesity, when present, was pronounced in this population of children. These findings suggest an accumulation of genetic susceptibility to cardiovascular disease and non-insulin-dependent diabetes mellitus in this stable, ethnically homogeneous, and rather isolated part of continental Europe.

Anthropometry↗
PubMed1995

Realized heritability of longevity in Drosophila melanogaster.

From the data of an experiment of selection for increased longevity, a realized heritability of longevity was calculated. The low value of this heritability (3.4%) was very close to values observed in other experiments concerning Drosophila melanogaster wild strains. The error variance of the heritability estimator was calculated through the use of orthogonal contrasts. In this way, it was possible to calculate the confidence interval of the realized heritability. The amplitude of this interval was wide although the size of the sample was large. This shows the difficulty of estimating with precision the heritability of longevity from data obtained in selection experiments.

Animals↗
PubMed1995

Familial trends of obesity through three generations: the Belgian-Luxembourg child study.

Province de Luxembourg in Belgium is an area with clustering of obesity as well as other risk factors for cardiovascular diseases and non-insulin dependent diabetes mellitus. In this study, obesity was studied in a total of 1028 boys and girls in age-strata 6-8, 8-10, 10-12 years, selected at random from school classes. Participation rate was about 70%. Non-participants did not differ from participants in comparisons of school records of height and weight. Furthermore, information on birth weight, parents' height and weight was collected, as well as reported problems of obesity in grandparents. The results show a high prevalence of pronounced obesity in these children. BMIs were strongly correlated between the children and both parents. Furthermore, grandparents' obesity problems were related to the BMI of parents, and also to obesity indices in the children. Birth weights were related to current BMI of the children (in girls only for the youngest age-group), and to their mothers' BMI. It was concluded that obesity is prevalent in this area and can be traced through three generations, and seems to be discoverable already at birth. Energy intake is high and physical activity level is low in these children. However, statistical analyses suggest that familial factors exert a greater impact than environmental factors on the BMI of the children. These results, as well as the wide-spread, consistent familial clustering of obesity, traceable already at birth, suggest influence of strong genetic traits for obesity in this population.

Adolescent↗