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Biomedical subjects

C Kindermans

Publications and source records attributed to C Kindermans.

At least 19 recordsLinked to original sources
PubMed2001

beta(1)-adrenergic antagonists improve sleep and behavioural disturbances in a circadian disorder, Smith-Magenis syndrome.

Smith-Magenis syndrome (SMS) is a clinically recognisable contiguous gene syndrome ascribed to interstitial deletions of chromosome 17p11.2. Patients have a phase shift of their circadian rhythm of melatonin with a paradoxical diurnal secretion of the hormone. Serum melatonin levels and day-night behaviour were studied in nine SMS children (aged 4 to 17 years) given acebutolol, a selective beta(1)-adrenergic antagonist (10 mg/kg early in the morning). Cardiac examination, serum melatonin, motor activity recordings, and sleep diaries were monitored before and after drug administration. The present study shows that a single morning dose of acebutolol suppressed the inappropriate secretion of melatonin in SMS. A significant improvement of inappropriate behaviour with increased concentration, delayed sleep onset, increased hours of sleep, and delayed waking were also noted. These results suggest that beta(1)-adrenergic antagonists help to manage hyperactivity, enhance cognitive performance, and reduce sleep disorders in SMS.

Acebutolol↗
PubMed2001

Vitamin D status and redefining serum parathyroid hormone reference range in the elderly.

Subclinical vitamin D insufficiency is characterized by mild secondary hyperparathyroidism and enhanced risk of osteoporotic fracture. However, although low levels of 25-hydroxyvitamin D (25OHD) are common in otherwise normal elderly people, vitamin D status has not generally been taken into account in the previously published reference values for serum PTH. We measured fasting morning serum (obtained from April through June) PTH, total calcium, albumin, phosphate, creatinine, bone markers, and 25OHD in 280 healthy subjects (140 men and 140 women), aged 60-79 yr. Serum PTH was measured by means of 2 immunoradiometric assays, the Allegro intact PTH assay (Nichols Institute Diagnostics) and the new CAP assay (Scantibodies Laboratory, Inc.). We found a high prevalence (167 of 280; 59.6%) of low 25OHD (< or =30 nmol/L) in these otherwise healthy individuals. The PTH concentrations (95% confidence interval) obtained in the whole group of 280 subjects ranged from 13-64 ng/L for the Allegro assay and from 10-44 ng/L for the CAP assay. In the subjects with a serum 25OHD concentration greater than 30 nmol/L, values for both PTH assays were lower, 10-46 and 9-34 ng/L for the Allegro and the CAP assays, respectively. By using these values as a reference range, approximately 25% of the subjects with a serum 25OHD level of 30 nmol/L or less had a high serum PTH level (whatever the assay), reflecting secondary hyperparathyroidism. This might be missed if the reference PTH values are those obtained in the entire group, as is usually done. These results strongly suggest that vitamin D status should be taken into account when establishing reference values for serum PTH in elderly subjects.

Aged↗
PubMed2000

Differences in the capacity of several biochemical bone markers to assess high bone turnover in early menopause and response to alendronate therapy.

We measured bone mineral density (BMD), four markers of bone formation [bone alkaline phosphatase (bAP), osteocalcin (Oc), N- and C-terminal propeptide of type I procollagen (PINP and PICP respectively)] and five markers of bone resorption [serum C-terminal telopeptide of type I collagen (CTx), urinary CTx, N-terminal cross-linked telopeptide (NTx), free and total deoxypyridinoline (fDpd and tDpd respectively)] in 28 healthy premenopausal women (45.7 +/- 3.0 years), 15 early (< 7 years) healthy menopausal women (53.8 +/- 3.1 years) and 20 osteoporotic women (65.3 +/- 8.2 years). Bone markers and BMD were also measured in the osteoporotic women 4.1 +/- 0.2 and 12.6 +/- 1.2 months after the beginning of alendronate therapy (Fosamax, 10 mg/day) respectively (BMD in 16/20). We calculated the intra-individual coefficient of variation (iCV) and the least significant change (LSC) for each bone marker from a subset of 9 healthy premenopausal women (32 +/- 5 years) who had a first and a second morning void urine collection (FMV and SMV respectively) and a blood sample on 4 nonconsecutive days (mean interval 14 +/- 3 days). None of the bone markers was correlated with BMD (except p = 0.043 between serum Oc and hip BMD). All markers, except fDpd, were increased significantly in early menopausal women when compared with the premenopausal group. Serum CTx presented the highest increase at menopause (+67.8%) and identified the highest rate (11/15) of early menopausal women with bone turnover above the premenopausal range. The iCVs for bone formation markers (7.2-14.4%) were lower than those for bone resorption markers (14.6-22.3%). The iCVs obtained on FMV and SMV were not different. The decrease after 4 months of alendronate was significant for each bone marker but variable from one marker to another. Serum CTx showed the largest decrease (70.8%) and identified the highest number of biologically responding patients (change > LSC; n = 17/20). A significant change in serum CTx after 4 months of alendronate was the best predictor of a significant gain in spine BMD (i.e., > or = 27 mg/cm2) after 1 year of therapy, allowing 15 of 16 patients (94%) to be classified correctly (one false-positive). Urinary NTx/Cr was the second best predictor. Despite a moderately high iCV (20.6%), serum CTx appeared the most effective of the markers tested and could be of interest for the detection of high bone turnover and the longitudinal monitoring of alendronate therapy in the individual patient. It must be stressed that serum PINP and urinary NTx and tDpd compared very similarly with serum CTx for monitoring alendronate therapy.

Adult↗
PubMed2000

Hyperparathyroidism: the limits of surgery in cases of bone or cardiovascular involvement.

In primary hyperparathyroidism (PHPT), asymptomatic bone disease can be detected by bone densitometry. The bone mineral density is about 10% lower than normal control values, especially in the cortical radius. Without parathyroidectomy, bone mineral density is frequently stable, but a few patients, mostly postmenopausal women, have a significant decrease. Histology shows maintenance of trabecular connectivity but with an increase in cortical porosity. After parathyroidectomy, bone mineral density increases, particularly at the lumbar spine and femoral neck, and the benefit persists after 10 years. The fracture risk is controversial but risk of trabecular bone fracture may be higher than that for controls. The impact of PHPT on survival is also controversial, but highest quartile of serum calcium, osteoporosis, old age, and low lean mass are each associated with a death risk. There is also a debate about the criteria for distinguishing between asymptomatic and symptomatic PHPT and about the bone mineral density threshold that should be used as a basis to recommend surgery. The rate of progression of PHPT is slow but in some cases bone loss progresses, justifying bone mineral density follow-up. The frequency of inadequate follow-up and the cost of nonoperative follow-up are in favor of recommending surgery. With broader indications for surgery, it is mandatory to improve the biochemical diagnosis of PHPT.

Bone Density↗
PubMed2000

Effects on bone metabolism of one year recombinant human growth hormone administration to children with juvenile chronic arthritis undergoing chronic steroid therapy.

OBJECTIVE: To study the effects on bone metabolism of treatment with recombinant human growth hormone (rhGH) in children with juvenile chronic arthritis (JCA) who are undergoing treatment with glucocorticoids (GC) and have severe bone lesions. METHODS: We assessed the effects of rhGH treatment (1.4 U/kg/week) on bone metabolism markers and bone density measured during a one year treatment course in 14 patients with systemic forms of JCA undergoing longterm GC treatment. RESULT: All patients at inclusion showed severe bone demineralization (mean bone density: -3.7 standard deviation score for chronological age). Compared to pretreatment values, bone formation markers (blood levels of osteocalcin and C-terminal propeptide of type 1 procollagen) and bone resorption markers (urinary hydroxyproline, pyridinoline, and deoxypyridinoline levels) increased significantly during treatment and returned to pretreatment values after discontinuation of rhGH. We observed that plasma level of osteocalcin was the best predictive variable of growth response to rhGH treatment in these patients. CONCLUSION: The results reflect an increase in bone turnover in these patients. Despite these biochemical changes no improvement of bone density was observed during the one year treatment. Treatment of longer duration is necessary to evaluate the curative effects of GH.

Adolescent↗
PubMed1999

Bsm I polymorphism in the vitamin D receptor gene is related to bone collagen turnover in healthy infants.

We examined the vitamin D receptor genotypes (BB, Bb and bb) defined by the Bsml restriction endonuclease in relation to biochemical indices of bone metabolism in healthy Caucasian infants. We measured the serum concentrations of the carboxy-terminal propeptide of type I procollagen (PICP) and the urinary excretion of total pyridinoline, free, total and bound deoxypyridinoline, the type I collagen N-terminal and C-terminal cross-linked telopeptides. The concentrations of the urinary indices are expressed relative to creatinine. Subjects with BB genotype had the highest mean concentrations of free, total and bound deoxypyridinoline and of the N-terminal cross-linked telopeptide (PANOVA = 0.0016, 0.0004, 0.0002 and 0.0053, respectively). BB boys had a higher excretion of the C-terminal cross-linked telopeptide than the other genotypes (PANOVA = 0.0253). In a subgroup of homozygotes aged 10 (1) months, BB subjects had the highest levels of the C-terminal cross-linked telopeptide (p=0.03), and of total deoxypyridinoline (p=0.02) and pyridinoline (p=0.06) concentrations. No significant association between the vitamin D receptor genotype and PICP was found. These data suggest that there may be a contribution of the vitamin D receptor genotype to skeletal metabolism in early childhood.

Bone and Bones↗
PubMed1999

Bone markers in clinical practice.

Although biologic indices of bone turnover are widely accepted as research tools in population-based studies, their clinical utility in the management of the individual patient remains controversial. Their main limitation for a routine clinical use is related to an important biologic variability, which means that large variations (ie, in response to therapy) are needed to consider a difference between two measurements as reflecting a significant biologic change. To date, the most valuable bone markers are serum osteocalcin, bone-specific alkaline phosphatase, and the N-terminal propeptide of type 1 procollagen for bone formation and urinary measurements of the phenazopyridine crosslinks and related telopeptides for bone resorption. New serum assays for both C-telopeptide and N-telopeptide of type 1 collagen seem promising but need extensive validation. Although bone markers provide little information in the diagnosis of osteoporosis, strong evidence now shows that they can predict, albeit imperfectly, the rate of bone loss in menopausal women and the response to some antiresorptive therapies. In some populations, increased bone turnover has been shown to be a strong predictor of fracture risk, independently and to the same extent as low bone density. Whether bone markers are used to monitor the efficacy of (or compliance with) a specific treatment or to identify patients at risk for osteoporosis and thus to target preventive therapy, cost-benefit analysis, and evaluation of the potential improvement in patient outcome are clearly needed before these parameters may be universally accepted as tools to optimize patient care.

Alkaline Phosphatase↗
PubMed1997

Diagnostic and therapeutic aspects of calciotropic hormones.

The measurement of calciotropic hormones may be useful in metabolic bone disease. Assays of intact parathyroid hormone are essential to differentiate between primary hyperparathyroidism and nonparathyroid-mediated hypercalcemia. Vitamin D status is best assessed by measuring serum 25(OH)D. Concentrations of calciotropic hormones should be measured in osteoporotic patients if the degree of osteopenia does not correlate with the risk factors. The decrease in circulating parathyroid hormone in osteoporotic patients treated with vitamin D reflects the success of the vitamin D treatment. Parathyroid hormone is also a potential anabolic agent.

Bone Diseases, Metabolic↗
PubMed1997

Bone mineral density and metabolism in children with congenital hypothyroidism after prolonged L-thyroxine therapy.

The effect of long-term L-thyroxine (LT4) replacement therapy on bone mineral density and on biochemical markers of bone turnover were studied in children with congenital hypothyroidism (CH). Forty-four children and adolescents (mean age 8.5 +/- 3.5 years) with primary CH who began LT4 replacement therapy within the first month of life were studied. Bone mineral density (BMD) of the lumbar vertebrae and the upper femoral bone was measured by dual energy X-ray absorptiometry. Serum osteocalcin (OC) and bone alkaline phosphatase were measured as markers of bone formation and urinary deoxypyridinoline was taken as a marker of bone resorption. Bone mineral densities of CH children were not different from those in age-matched controls. The biochemical markers of bone turnover were normal except for the serum OC levels which were found to be higher than in controls and positively correlated with the free thyroid hormone levels (for FT4 r = 0.42, p = 0.02). Eight CH children demonstrated low BMD values (below -1 SDS) at -2 +/- 0.7 SDS for the lumbar spine and -1.6 +/- 0.5 SDS for the femoral site. These eight children showed lower mean weight (p < 0.05) and their dietary calcium intake tended to be less (p <0.06) than that seen in the normal BMD group. In conclusion, our results show that LT4 replacement therapy for 8 years is not detrimental to the skeletal mineralization of CH children. As in a healthy population, weight and current intake of calcium seem to be major determinants of bone density. Dietary recommendations, especially when calcium intake is below the recommended dietary allowance, may have to be reconsidered.

Absorptiometry, Photon↗
PubMed1997

Procollagen propeptide and pyridinium cross-links as markers of type I collagen turnover: sex- and age-related changes in healthy children.

The correlations among age, gender, body size parameters, and type I collagen metabolism were evaluated in 183 healthy infants, aged 8.5-27.5 months. Collagen formation was assessed by measuring serum type I collagen carboxy-terminal propeptide, and degradation was determined by urinary pyridinoline and deoxypyridinoline (measured by high performance liquid chromatography) and cross-linked N- and C-terminal telopeptides of type I collagen (measured by NTx and CrossLaps assays). A new RIA specific for deoxypyridinoline was also evaluated. The results provide reference values at 10 months and 2 yr of age, including cross-linked C-terminal telopeptides (1492 +/- 685 and 1510 +/- 446 in boys; 1705 +/- 612 and 1849 +/- 611 micrograms/mmol creatinine in girls; mean +/- 1 SD). There was a good correlation between the high performance liquid chromatography and RIA data for deoxypyridinoline, showing that the RIA method is suitable for use in healthy children. Some correlations were found among peptide-bound cross-links, serum type I collagen carboxy-terminal propeptide, and the anthropometric parameters, suggesting that these peptides reflect bone resorption and also overall body type I collagen. Finally, there were age- and sex-related differences in the urinary excretion of the collagen degradation markers, suggesting that, unlike boys, girls maintain a high degree of collagen degradation up to the age of 24 months despite a decrease in their rate of collagen formation.

Aging↗
PubMed1994

Glomerular response to acute protein load is not blunted by high-protein diet or nephron reduction.

Inulin clearance (CIn) was measured in the presence of varying degrees of renal excision (NX, 0-85% of renal mass by weight), in anesthetized rats fed on high-protein (HP, 30%), median-protein (MP, 10%), or low-protein (LP, 7%) diets, before and during amino acid (AA) infusion or before and after an intragastric protein load. CIn was higher in rats fed HP than in rats fed LP in controls (3.4 vs. 2.1 ml/min) and in rats with NX up to 70% after feeding for 3 wk (1.4 vs. 0.7 ml/min) or 4 days (1.5 vs. 1.1 ml/min). The difference decreased from 0% to 70% NX, and disappeared when NX exceeded 70%. Acute AA infusion and intragastric loads always increased CIn with wide individual variations. The increase was greater in rats fed HP than in rats fed MP and LP (+1.4 vs. 0.8 and 1.1 ml/min for 0% NX), diminished with greater NX (0.7 vs. 0.2 and 0.4 ml/min for 70% NX), and was very small for NX above 70%. However, when expressed as the percent of baseline values, the mean CIn increment after acute stimulation remained constant (30-45%), regardless of renal ablation and of diet. Thus preexisting hyperfiltration resulting from diet or from renal ablation does not suppress the glomerular response to an acute protein load, and acute loads afford no advantages over baseline glomerular filtration rate (GFR) measurements. By contrast, chronic protein feeding increases GFR only when nephron loss is not too severe.

Amino Acids↗
PubMed1993

Water-balance hormones during long-term follow-up of oral dDAVP treatment in diabetes insipidus.

The aim of the present study was to investigate the hormonal control of water-balance in children with diabetes insipidus and to assess safety and efficacy of long-term treatment with oral dDAVP. Plasma atrial natriuretic peptide, plasma renin activity, aldosterone, plasma and urinary cyclic 3'5'-guanosine monophosphate and urinary prostaglandin E2 were measured in eight patients (aged 3-21 y) with central diabetes insipidus. At baseline, 12 h after the last dDAVP dose, patients had hypotonic polyuria but normal plasma sodium concentrations and plasma osmolality relative to a control group. The mean plasma atrial natriuretic peptide concentration in patients (26.2 +/- 2.6 pg/ml) tended to be lower than in controls (36.5 +/- 8.2 pg/ml, mean +/- SEM), although the difference was not significant. Plasma cyclic 3'5' guanosine monophosphate was higher in controls (6.0 +/- 0.6 pmol/ml, mean +/- SEM) than in patients (3.8 +/- 0.3 pmol/ml). Aldosterone, plasma renin activity, urinary cyclic guanosine monophosphate and urinary prostaglandin E2 were similar in the two groups. During 3 h following dDAVP administration, atrial natriuretic peptide levels did not change in patients but decreased significantly in controls to 23.0 +/- 4.0 pg/ml. No adverse reactions, or circulating antibodies against dDAVP, were observed after 3.5 years of oral dDAVP treatment. The average oral dDAVP dosage was similar after 1 and 3.5 years of treatment (906 +/- 406 micrograms/24 h, mean +/- SD). Water-balance is not detectably different from normal in correctly treated diabetes insipidus patients in terms of plasma atrial natriuretic peptide, plasma renin activity and aldosterone levels. Long-term oral dDAVP treatment is safe and efficacious.

Administration, Oral↗
PubMed1992

Evaluation of capillaries for ionized calcium measurements.

Commercially available capillaries containing calcium-titrated heparinate as an anticoagulant designed specifically for ionized calcium measurements in blood were tested with four serum pools with ionized calcium concentrations adjusted to 0.75, 1.25, 1.50 and 2.50 mmol/L. Although this is the best available anticoagulant for this purpose, the use of these capillaries induced a +/- 1% alteration of the original concentration around the titration level and changes of -2 to +10% at pathological values. The amount of heparinate released exceeded the recommended limit of 50 IU/mL of specimen with some variability (6% to 20%). Increasing the amount of anticoagulant with the objective of avoiding magnetic mixing did not seem to be a valid approach. Finally, Radiometer, IL and AVL capillaries gave the best available and acceptable results in terms of alterations in ionized calcium.

Blood Specimen Collection↗
PubMed1991

Preanalytical errors in ionized calcium measurements induced by the use of liquid heparin.

The use of heparin in a liquid form to measure ionized calcium (Ca++) in plasma or whole blood can induce preanalytical errors by dilution and by changing the original Ca++ value by binding or by re-equilibration with calcium in the anticoagulant solution. To quantify these errors, Ca++ was measured on serum pools under different sampling conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested. Syringes were rinsed with saline to yield pure dilution effects, with sodium heparinate to study binding and with calcium-titrated heparinate to evaluate 'calcium-distortion'. Detailed tables provide percentage error values for all sampling conditions. Dilution errors could reach -5% and binding was always important (-14 to -50%). Distortion was minimal around 1.25 mmol/L but could reach -4% for high and +8% for low Ca++ values. Errors increased when syringes were not filled to their nominal volume, especially with small-sized specimens.

Anticoagulants↗
PubMed1991

In vitro evaluation of a heparinized blood sampler for ionized calcium measurement.

When ionized calcium measurements are needed urgently blood has to be sampled with an anticoagulant to allow rapid specimen processing. Heparinate salts cause a decrease in ionized calcium by binding which is clinically significant when the concentration exceeds 15 IU/mL of whole blood. The use of an anticoagulant in an aqueous state induces 'solution-dilution' errors. To avoid these two types of error the use of calcium-titrated sodium heparinate in a dry state has been proposed. However, in this situation the actual calcium concentration could be modified if its value were different from the titration level. This possibility has been studied using a commercially available sampler (Radiometer B-129). When the sampler was used as recommended, errors were non-significant around 1.25 mmol/L. There was a +3% increase for low (0.75 mmol/L) values and a -2% decrease for high (2.50 mmol/L) values. Incomplete syringe filling increased these errors.

Calcium↗
PubMed1991

Use of calcium-titrated sodium heparinate for ionized calcium determination on plasma and whole blood (heparinized blood sampler B-129 Radiometer).

We report modifications of ionized calcium as observed on specimens collected in a commercially available sampling device (Radiometer B-129). When the sampler is used as recommended, errors are non-significant around 1.25 mmol l-1. There is a +3% increase for low (0.75 mmol l-1) values and a -2% decrease for high (2.50 mmol l-1) values. Incomplete syringe-filling increases these errors.

Blood Specimen Collection↗