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Biomedical subjects

R Bouillon

Publications and source records attributed to R Bouillon.

At least 163 records · Page 9Linked to original sources
PubMed1996

Nonhypercalcemic vitamin D analogs: interactions with the vitamin D-binding protein.

The natural vitamin D hormone, 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3), not only regulates serum and bone calcium homeostasis but is probably also a paracrine factor in several cells and tissues including skin, immune system, placenta and brain, where it stimulates cell differentiation and inhibits cell proliferation. Several structural analogs of 1 alpha, 25-(OH)2D3 not only have superagonist activity but also display a selective action profile: indeed they maintain or have increased activity on cell differentiation/proliferation but also have substantially decreased calcemic activity when compared to 1 alpha,25-(OH)2D3. This decreased calcemic activity is partially due to mere pharmacological reasons: because of low binding affinity for the plasma vitamin D-binding protein, a more rapid extracellular metabolism and increased cellular uptake is possible when compared to 1 alpha,25-(OH)2D3. Their short extracellular half-life combined with comparable or enhanced transactivation potency together with analog-and cell-type-specific intracellular metabolism can probably explain why some analogs have a unique combination of superagonist activity and specific action profile with favorable dissociation of differentiation versus calcemic potency.

Animals↗
PubMed1996

Deficiency of the growth hormone-insulin-like growth factor-I axis potentially involved in age-related alterations in body composition.

Because the body composition effects of growth hormone and insulin-like growth factor-I (IGF-I) are opposite to those of advancing age, it has been hypothesized that the decreased activity of the growth hormone-IGF-I axis is partly responsible for the loss of bone and muscle mass that characterizes normal human aging. The aim of the present cross-sectional analysis was to test this hypothesis in a well-defined community-based sample of 245 healthy elderly women. Dual-energy X-ray absorptiometry was used to measure body composition. To establish the major determinants of total bone mineral content (TBBMC), we assessed the relationships between TBBMC and age, height, weight, body mass index, muscle strength and serum concentrations of IGF-I, calcidiol, calcitriol, parathyroid hormone and sex hormone-binding globulin. Total body lean mass (TBLM), an indication of muscle mass, was related to the following potential determinants: age, habitual physical activity and serum IGF-I. Multiple regression was used to adjust for potential confounders. A significant relationship between circulating IGF-I and TBLM was not apparent in this study. On the other hand, serum IGF-I was found to be an independent predictor of TBBMC, despite the inclusion of established determinants of bone mass. These findings suggest that the demineralization of the skeleton in aging women is in part due to a deficiency of the somatotrophic axis.

Absorptiometry, Photon↗
PubMed1996

[Study of neonatal malnutrition risk in the Zaire milieu].

This study is intended to assess neonatal risk of malnutrition owed to maternal energy intake lower than 2000 kcal/day among Zairian primiparae. Ninety-eight mother-neonate couples were classified according to the level of maternal energy intake. Neonatal albuminemia which previously showed itself as neonatal nutritional marker served for grouping neonates. Possibility of reaching optimal albuminemia value (29,34 g/l) was assessed according to different maternal energy profiles, using U-test and Chi 2. When maternal intake is lower than 2000 kcal/day, neonatal optimum is reached in 26% of cases; when maternal recommendation is lowered to 1675,21 kcal/day, neonatal optimum is reached in 63,43% of cases; with 2000 kcal/day as recommendation, this rate rises up to 71,4%. Under 2000 kcal/day neonatal risk of malnutrition is thus very high.

Democratic Republic of the Congo↗
PubMed1996

Aggressive pituitary macroadenoma: CT and MR appearances.

Two cases of aggressive pituitary macroadenoma (prolactinoma) with diffuse invasion of the skull base are described. Clinical signs usually appear late. CT shows the bone destruction, whereas MRI accurately delineates the extension of the tumor and involvement of the surrounding neurovascular structures. Histopathology and immunohistochemical staining are necessary for a definitive diagnosis differentiating prolactimonas from a wide range of skull base tumours and for deciding on additional therapy and prognosis. Aggressive pituitary macroadenoma is a large and diffuse tumor which is difficult to treat; therapy usually consists of extensive surgery, radiotherapy and pharmacotherapy with dopaminergic agents.

Adult↗
PubMed1995

Androgens and bone.

Androgen receptors are present at low densities in osteoblasts. Androgens are also metabolized in bone. (Non)aromatizable androgens probably induce proliferation of osteoblasts and differentiation. A direct effect of androgens on osteoclasts has not been demonstrated. Androgens may however inhibit bone resorption indirectly, by an inhibition of the recruitment of osteoclast precursors from bone marrow, by decreased secretion of interleukin-6 and/or prostaglandin E2, and/or by an increased sensitivity of marrow cells or osteoblasts for bone resorption stimulating factors such as PTH. The recent demonstration of androgen receptors in bone marrow stromal and osteoclast-like cells opens new perspectives in this respect. During puberty, androgens stimulate bone growth both directly and indirectly. Observations in androgen-resistant animals clearly demonstrated that the sexual dimorphism of bone depends on the presence of a functional androgen receptor. Optimal peak bone mass seems related to an appropriately timed androgen secretion. In adults, androgens are also involved in maintenance of the male skeleton. Androgen replacement may prevent further bone loss in hypogonadal men, however, it seems difficult to fully correct bone mass in these men.

Androgens↗
PubMed1995

Tumour-induced rickets: a case report and review of the literature.

UNLABELLED: Hypophosphataemic rickets was diagnosed in a 6-year-old boy with a negative family history. After 16 years of medical treatment he developed a malignant sarcoma of the right distal thigh. Removal of the tumour by high amputation of the leg resulted in disappearance of the phosphate leak. In spite of surgery and chemotherapy, the patient died due to extensive lung metastases. Retrospective analysis of the initial X-ray films showed a benign lesion on the lateral side of the right distal femur. This lesion is believed to be at the origin of the rickets. This is the first paediatric case reported with malignant degeneration of a benign tumour causing rickets. CONCLUSION: Patients with the classical hallmarks of X-linked, familial hypophosphataemic rickets but no affected family members should have a careful periodic search for a tumour, even years after onset of the disorder.

Child↗
PubMed1995

Vitamin D metabolites in childhood nephrotic syndrome.

We measured serum levels of total and ionised calcium, phosphate, intact parathyroid hormone, 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D] and the vitamin D binding protein (DBP) in 14 children with idiopathic nephrotic syndrome and 10 healthy, age-matched controls. In all nephrotics serum DBP levels were below the normal range. Serum 25(OH)D was below 7 ng/ml in 10 of 14 nephrotic children and in the low normal range in the remaining 4 patients. The average serum 1,25(OH)2D levels were lower in the nephrotic patients than in the controls. However, free 1,25(OH)2D levels were normal in the nephrotic patients. Both serum 25(OH)D and 1,25(OH)2D correlated positively with the concentration of DBP. There was a significant negative correlation between serum DBP levels and the urinary protein excretion and a significant positive correlation between the urinary excretions of DBP and albumin. From this study it can be concluded that the nephrotic child is capable of maintaining appropriate serum concentrations of free calcitriol despite important urinary losses of both substrate and bound calcitriol.

Adolescent↗
PubMed1995

Biological evaluation of epoxy analogs of 1 alpha,25-dihydroxyvitamin D3.

The biological activity of 16-epoxy side-chain analogs of 1 alpha,25-dihydroxyvitamin D3, (1 alpha,25(OH)2D3) was evaluated in vitro and in vivo. Compared to 1 alpha,25(0H)2D3, all analogs had lower affinities for the pig duodenal vitamin D receptor and also for the human serum vitamin D binding protein. The in vitro effects on cell proliferation or differentiation of human promyeloid leukemia (induction of superoxide production in HL-60 cells), human osteosarcoma MG-63 cells (osteocalcin secretion), or human breast cancer cells (incorporation of thymidine in MCF-7 cells), was markedly inhibited by several epoxy analogs, compared to 1 alpha,25(OH)2D3, but the rank order of their activity widely varied among different cancer cells. The most potent analogs (24S,25S-24-hydroxy-25,26-epoxy-22-ene-1 alpha-OHD3, 25,26-epoxy-23-yne-1 alpha-OHD3, and 25,26-epoxy-23-yne-20-epi-1 alpha-OHD3 or compounds, 16, 5, and 7, respectively) were equipotent (16 and 5) or 30-fold (compound 7 on MG-63 cells) to 40-fold (compound 7 on MCF-7 cells) more active than 1 alpha,25-(OH)2D3. These analogs were nevertheless poorly antirachitic (< 3%) when tested in vitamin D-deficient chicks (using serum and bone calcium, serum osteocalcin and duodenal calbindin D-28K, as end points). Compound 7 was also 100-fold more active than 1 alpha,25-(OH)2D3 in inhibition of proliferation of human foreskin keratinocytes. Some epoxy analogs of 1 alpha,25-(OH)2D3 thus display interesting dissociations between their receptor affinity and their potency to induce cell differentiation, whereas their effect on cell proliferation/differentiation exceed their calcemic effects more than 100- to 1000-fold.

Animals↗
PubMed1995

Antagonistic activity of 24-oxa-analogs of vitamin D.

24-Oxa-vitamin D3 (24-oxa-D3) and 24-oxa-1 alpha-hydroxyvitamin D3 were designed as possible inhibitors of the vitamin D metabolic activation pathway. Their affinity for the vitamin D receptor (from pig intestine) and human vitamin binding protein were reduced, and their potency to induce cell differentiation of human leukemia cells (HL 60) or osteosarcoma cells (MG 63) was markedly reduced (19% and 3%, respectively), in comparison with calcitriol. A single or chronic injection of 24-oxa-D3 had no biological activity, whereas chronic administration of 24-oxa-1 alpha-hydroxy-D3 showed weak agonist activity in rachitic chicks. When the 24-oxa-D3 was given prior to a single injection of vitamin D3, lower values of serum calcium (64% of the value obtained in vitamin D-treated animals), osteocalcin (52%), 25-(OH)D3 (45%) and duodenal calbindin-D 28K (9.4%) were found. When given chronically in a 100-fold more excess no clear antagonistic effects were observed. 24-Oxa-D3 is thus a new metabolic weak antagonist of vitamin D3, but adding a hydroxyl group at C-1 creates a weak agonist.

Animals↗
PubMed1995

Prevention of murine experimental allergic encephalomyelitis: cooperative effects of cyclosporine and 1 alpha, 25-(OH)2D3.

The hormone 1 alpha, 25-dihydroxyvitamin D3 (1,25(OH)2D3) has immune modulatory activities in vitro and in vivo, and can prevent or delay the onset of experimental or spontaneous autoimmune diseases. At therapeutical doses, however, hypercalcemic side effects are found. The present experiments examined the effects of combined treatment with subtherapeutic doses of cyclosporine A (CsA) and 1,25(OH)2D3 on the evolution of experimental autoimmune encephalomyelitis (EAE) in SJL mice. 1,25(OH)2D3 at 5 micrograms/kg body weight (given by i.p. injection every 2 days) prevented the appearance of paralysis in 70% of the treated mice. The treatment with 1,25(OH)2D3 at 2 micrograms/kg/2 days alone had less substantial protective effects (22% disease-free animals versus 5% in the control group). However, when this subtherapeutic dose was associated to treatment with a daily dose of CsA (2 or 5 mg/kg/day), which by itself was subtherapeutic (24 and 50% disease-free animals, respectively), the association of both drugs led to near-total protection (86% disease-free animals when combined with the highest dose of CsA). When an alternate day administration schedule (CsA at 10 mg/kg and 1,25(OH)2D3 at 2 micrograms/kg, each given on alternate days from day -3 to +19 after disease induction) was used, all treated mice were completely protected clinically and histologically. The two drugs also showed additive effects on serum osteocalcin and urinary calcium and desoxypyridinoline excretion, but not on serum calcium concentration. Our experiments demonstrate that 1,25(OH)2D3 might be a potential dose-reducing agent for CsA in immunosuppressive therapy.

Amino Acids↗
PubMed1995

Differentiation induction of human leukemia cells (HL60) by a combination of 1,25-dihydroxyvitamin D3 and retinoic acid (all trans or 9-cis).

1,25(OH)2D3 and two stereoisomers of retinoic acid, all trans and 9-cis retinoic acid, are regulators of cell proliferation and differentiation. The aim of this study was to evaluate the effects of a combination of 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) on proliferation and cell differentiation of the human promyelocytic leukemia cell line HL60, and to test the reversibility of the induced differentiation. Cell proliferation was inhibited as expected by 1,25(OH)2D3 and all trans retinoic acid alone (IC50 of cell survival was 4 x 10(-7) M, 9 x 10(-6) M and 9 x 10(-7) M for 1,25(OH)2D3, all trans and 9-cis retinoic acid, respectively). Combination of 1,25(OH)2D3 and either form of retinoic acid resulted in a partially additive decrease in cell proliferation. 1,25(OH)2D3 induced a monocytic differentiation (100% CD14+ cells with 10(-7) M 1,25(OH)2D3), while retinoic acid led to a predominantly granulocytic differentiation (36 and 42% CD67+ cells with 10(-6) M all trans and 9-cis retinoic acid, respectively). Additive effects on differentiation were observed upon combination of subtherapeutical doses of the drugs, achieving a mainly monocytic population, demonstrating the dominant role of 1,25(OH)2D3 in determining the direction of differentiation. The effects on proliferation and differentiation of the solitary drugs were reversible, while the proliferation arrest and differentiation induced by the combination persisted and even progressed after withdrawal of the drugs. We conclude that 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) exert additive effects on inhibition of proliferation and induction of cell differentiation of HL60 cells, leading to a persistent differentiation, even after drug withdrawal.

Antigens, CD↗
PubMed1995

Crystallization and X-ray investigation of vitamin D-binding protein from human serum. Identification of the crystal content.

Vitamin D-binding protein (DBP), a multifunctional, highly polymorphic glycoprotein responsible for the transport of vitamin D and for sequestering extracellular actin, was isolated from human serum and crystallized using vapour diffusion methods. The crystals were grown from 7.5% v/v polyethylene glycol 400 and 0.1 M acetate buffer at pH 4.6. These crystals show diffraction patterns consistent with the tetragonal space groups P4(1) and P4(3) with unit cell dimensions a = b = 135.5(4) A and c = 75.9(4) A. They diffract to 2.3 A. Using polyacrylamide gel electrophoresis it was shown that according to their electrophoretic mobility the O-glycosylated isoforms, with a terminal sialic acid residue, are absent in the crystals.

Crystallization↗
PubMed1995

Propofol anesthesia does not inhibit stimulation of cortisol synthesis.

Recent data suggest a negative effect of propofol anesthesia on cortisol secretion. The present study was designed to evaluate the effect of propofol anesthesia on the steroidogenic potential of the adrenal glands. The response of cortisol secretion to stimulation with an adrenocorticotropic hormone (ACTH) analog during intravenous anesthesia with propofol has not been reported before. The response of the secretion of cortisol, 11-deoxycortisol, and 17 alpha-hydroxyprogesterone to tetracosactide stimulation was compared in patients anesthetized with propofol-nitrous oxide (n = 10) or thiopental-isoflurane-nitrous oxide (n = 10) and in normal volunteers (n = 10). The response to tetracosactide was similar in all three groups. An adequate increase in cortisol plasma concentration (more than 7.25 micrograms/dL) was obtained in all subjects except one volunteer. The increase in the plasma concentration of the cortisol precursors was also similar. We were unable to detect any influence of propofol anesthesia on the synthesis of cortisol in response to tetracosactide stimulation.

17-alpha-Hydroxyprogesterone↗
PubMed1995

Immunomodulatory effects of 1,25-dihydroxyvitamin D3.

The activated form of vitamin D, 1,25-dihydroxyvitamin D3, has not only a central role in bone and calcium metabolism, but also has important general effects on cell proliferation and differentiation. Moreover, 1,25-dihydroxyvitamin D3 behaves as a paracrine factor in the immune system as it can be produced by monocytes and has potent actions on all the cellular components of the immune defence system. In recent years, this new physiological role has been studied intensively both in terms of research and with the purpose of exploiting this action in a (pre)clinical setting. Indeed, through chemical alterations of the parent molecule, new substances have been created, called vitamin D analogues. Some of these molecules share the immunological effects of the mother compound, but have decreased effects on calcium and bone metabolism. This makes them potentially useful in clinical practice as immunomodulatory drugs. In the present review, we summarize the data on the in-vitro immune effects of 1,25-dihydroxyvitamin D3 and its analogues and demonstrate that these compounds have clear in-vivo immune modulating properties in the prevention of spontaneous and allergic autoimmune diseases and in the prevention of graft rejection.

Adjuvants, Immunologic↗
PubMed1995

Increased and decreased relative risk for non-insulin-dependent diabetes mellitus conferred by HLA class II and by CD4 alleles.

Non-insulin-dependent diabetes mellitus has been recognized to be heterogeneous in etiology, with multiple subgroups. Several genes or chromosomal regions have been implicated in the development of the disease. In this study the association of HLA class II alleles and genotypes and the association of CD4 and CD3 polymorphisms were assessed in a large number of Belgian non-insulin-dependent diabetes mellitus patients. Furthermore, the importance of the DQ alpha 1Arg52/DQ alpha 1Arg52 and the DQ beta 1Asp57/DQ beta 1Asp57 genotypes and the combination of both genotypes were examined. Our results show that in the HLA class II genes only the DQ alpha 1Arg52+/DQ alpha 1Arg52+ genotype was significantly associated with non-insulin-dependent diabetes mellitus compared with controls (p = 0.011, RR = 2.02). We also observed that the frequency of the CD4*A4/*A8 genotype and the CD4*A7 allele was significantly increased and decreased respectively in non-insulin-dependent diabetes mellitus patients as compared with the controls (p = 0.018, RR = 2.16 and p = 0.0003, RR = 0.49 respectively). These results therefore suggest that HLA class II and CD4 genes might independently contribute to the susceptibility for non-insulin-dependent diabetes mellitus and that these alleles and genotypes might identify subgroups of patients with different susceptibilities.

Adult↗
PubMed1995

Umbilical cord osteocalcin in normal pregnancies and pregnancies complicated by fetal growth retardation or diabetes mellitus.

A homologous radioimmunoassay for human osteocalcin was used to measure cord serum osteocalcin concentrations in normal pregnancies and in pregnancies complicated by intrauterine growth retardation (IUGR) and diabetes. The mean osteocalcin concentrations in term newborns (100-110 micrograms/l) were comparable with levels that we previously measured in pubertal children. There was a small increase in mean osteocalcin concentrations during the third trimester of fetal life, with the maximum at 35 weeks; between weeks 36 and 41, the osteocalcin levels dropped by 13%. Osteocalcin was 20% lower in IUGR neonates than in age- or weight-matched newborns. The newborns of diabetic mothers had markedly lower osteocalcin concentrations than the weight-matched neonates, and 16 of the 19 samples were more than 1 SD below the mean of the gestational-age osteocalcin regression curve. Cord serum osteocalcin appears to be a useful parameter in studying normal and abnormal fetal mineralization.

Female↗