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Biomedical subjects

F H Glorieux

Publications and source records attributed to F H Glorieux.

At least 19 recordsLinked to original sources
PubMed1992

Linkage mapping by simultaneous screening of multiple polymorphic loci using Alu oligonucleotide-directed PCR.

We present the use of our recently described multiple-loci polymorphic DNA markers ("alumorphs") for linkage mapping of the human genome. By using the polymerase chain reaction (PCR) with an Alu-specific primer we could reveal, in a single experiment, up to 20 genomic polymorphisms seen as the presence or absence of amplified DNA fragments originating from genomic segments flanked by Alu repeats. Using this approach we examined genomic DNA samples from two families with a history of pseudovitamin D-deficiency rickets (PDDR), an autosomal recessive disorder. An indication of linkage with the PDDR phenotype was found for one of the polymorphic bands, denoted 30A. A significant linkage [logarithm-of-odds (lod) score greater than 3.0] was obtained between this polymorphism and a number of chromosome 12q markers tightly linked to PDDR. The 30A band specifically hybridized to DNA digests from hybrid cell lines carrying a human chromosome 12, thus independently assigning the 30A marker to this chromosome. Since Alu elements are ubiquitous in human DNA, the use of alternative Alu-specific primers, which reveal different sets of Alu-flanked loci, should provide an efficient and rapid approach to human genetic mapping.

Base Sequence↗
PubMed1992

Defective bone formation by Hyp mouse bone cells transplanted into normal mice: evidence in favor of an intrinsic osteoblast defect.

The hypophosphatemic (Hyp) mouse is an animal model for human hypophosphatemic vitamin D-resistant rickets. We have reported that bone cells isolated from Hyp mice born to homozygous mutant females produce abnormal bone when transplanted into normal mice. To test whether an environmentally acquired defect of the mutant cells contributed to the impaired bone formation observed in transplants, periostea and osteoblasts from normal and Hyp littermates were transplanted intramuscularly into normal animals. To test more specifically for an hypophosphatemia-induced cell alteration before transplantation, bone cells isolated from phosphate-depleted normal mice were transplanted into normal animals. The bone nodules formed in 2 week transplants were characterized by measuring their osteoid thickness and volume. Impaired bone formation was evidenced in Hyp transplants compared to normal littermate transplants by increased osteoid thickness and volume. In contrast to cells from mutant mice, cells isolated from normal mice with comparable hypophosphatemia produced normal bone. These results indicate that the inability of Hyp osteoblasts to produce normal bone when placed in a normal environment is not the consequence of prior exposure to an altered environmental but likely of an intrinsic cellular abnormality. These observations add further support to the concept that the osteoblast is an important target for the Hyp mutation.

Animals↗
PubMed1992

Effect of dietary phosphate deprivation and supplementation of recipient mice on bone formation by transplanted cells from normal and X-linked hypophosphatemic mice.

The hypophosphatemic (Hyp) mouse is the murine homolog for human hypophosphatemic vitamin D-resistant rickets. We previously reported that bone cells isolated from normal and Hyp mice produced abnormal bone when transplanted intramuscularly into mutant mice. To assess the role of hypophosphatemia on bone formation in transplants, normal and Hyp mouse periostea were pair transplanted into control or phosphate (P)-supplemented Hyp mice and into control or P-deprived normal mice. The bone nodules formed in transplants after 2 weeks were characterized by measuring the thickness of the surrounding osteoid seams and the relative osteoid volume. P restriction in normal recipient mice impaired bone formation by transplanted normal cells and aggravated the defective bone formation by Hyp cells. The osteoid thickness and volume remained significantly higher in Hyp transplants than in normal cotransplants, however. P supplementation of Hyp recipient mice normalized bone formation by transplanted normal cells but not by Hyp cells. However, a marked decrease in osteoid thickness and volume was observed in Hyp transplants down to values observed in normal recipient mice. These results indicate that hypophosphatemia is not the only cause of abnormal bone formation in the Hyp mouse but that an osteoblast dysfunction contributes to the bone disease. These observations further support the concept that the osteoblast may be an important target for the Hyp mutation.

Animals↗
PubMed1992

Two hereditary defects related to vitamin D metabolism map to the same region of human chromosome 12q13-14.

We have localized the locus for the vitamin D receptor (VDR) responsible for hypocalcemic vitamin D-resistant rickets (HVDRR), close to the pseudovitamin D-deficient rickets (PDDR) locus, another disorder related to impaired vitamin D metabolism. PDDR (formerly vitamin D dependency type I, VDD1) was recently mapped to human chromosome 12q14 by linkage analysis. Here we report on the assignment of VDR to 12q13-14 by in situ hybridization and by linkage analysis. Linkage analysis between VDR, PDDR, and several RFLP markers show close linkage, with no recombination (theta = 0) between VDR and PDDR (Z = 1.94), a COL2A1 haplotype (Z = 4.03), ELA1 (Z = 0.98), and D12S15 (Z = 4.17). The analysis of extended haplotypes in one of the PDDR families provides evidence for recombination between VDR and PDDR and localizes VDR together with COL2A1 proximal to PDDR. Complete allelic association detected between VDR and COL2A1 loci on PDDR chromosomes and lower association between VDR and PDDR suggests a VDR location very close to COL2A1 and one more distant to PDDR. We propose the following order of loci: (VDR, COL2A1), (PDDR, ELA1, D12S15), D12S4, (D12S14, D12S17), D12S6. Thus, two clearly distinct loci involved in the control of vitamin D activity map close to each other in the region 12q13-14.

Chromosomes, Human, Pair 12↗
PubMed1992

Abnormal response of osteoblasts from Hyp mice to 1,25-dihydroxyvitamin D3.

To further explore the hypothesis of an osteoblast inappropriate response to 1,25-(OH)2D3 in hypophosphatemic vitamin D-resistant rickets (HYP), osteoblasts were isolated from Hyp mice, the animal model for human HYP, and their response to a physiologic dose of 1,25-(OH)2D3 (10(-10) M) was investigated with respect to alkaline phosphatase (ALP) activity and cell proliferation, and compared to that of normal osteoblasts. Cells in secondary culture were incubated for 72 h while in log phase, with or without 1,25-(OH)2D3, at various medium phosphate (P) concentrations ranging from 0.5 to 4.5 mM. Stimulation of ALP activity and inhibition of cell proliferation was induced by 10(-10)M 1,25-(OH)2D3 in normal cells exposed to medium P concentration corresponding to serum levels observed in normal mice (2.1-2.7 mM P). By contrast, Hyp cells failed to respond to 1,25-(OH)2D3 in that range of P concentrations. Stimulation of ALP activity and inhibition of proliferation of mutant cells were evident at higher medium P concentrations (over 3 mM). 1,25-(OH)2D3 at the supraphysiologic level of 10(-9)M had no consistent effect on ALP activity in normal and Hyp mouse osteoblasts, but inhibited cell proliferation in cultures of both genotypes at all P concentrations tested. These results indicate that extracellular P modulates the action of 1,25-(OH)2D3 on osteoblasts, and that this modulation was altered in osteoblasts from Hyp mice. The failure of Hyp cells to respond to a physiologic dose of 1,25-(OH)2D3 upon normal P concentration may reflect the abnormal response of bone to 1,25-(OH)2D3 observed in Hyp mice and HYP patients.

Alkaline Phosphatase↗
PubMed1992

Panostotic fibrous dysplasia. A new craniotubular dysplasia.

The authors describe the radiographic-scintigraphic features of an unusual craniotubular dysplasia characterized by diffuse osteopenia with bone expansion and a "ground glass" appearance, markedly increased skeletal turnover, myelofibrosis, hypophosphatemia, and pigmented "coast-of-Maine" patches. This syndrome, termed panostotic fibrous dysplasia, is distinct from previously reported disorders.

Adolescent↗
PubMed1992

Lumbar bone mineral content measured by dual energy X-ray absorptiometry in newborns and infants.

Dual energy X-ray absorptiometry (DXA), a non-invasive method for measuring small amounts of mineral, was used to assess the bone mineral content (BMC) and bone mineral density (BMD) of the lumbar spine (5 vertebrae) in 57 newborns (on day 1-2) and 22 infants (1-24 months of age). A modified high-resolution program (Hologic) allowed us to assess BMC and BMD with a precision higher than 2.4% and 1.5%, respectively. In newborns, BMC and BMD correlated positively with birth weight, body area, length and gestational age: r = 0.73, 0.71, 0.63 and 0.60, respectively, for BMC; and r = 0.59, 0.58, 0.54 and 0.53, respectively, for BMD. In infants, both BMC and BMD were highly correlated with weight, age, length and body area over two years (r = 0.94 or better in each instance). The data provide normal values for lumbar spine BMC and BMD in newborns (gestational age 31-40) and infants up to two years of age; DXA appears to be an excellent and safe tool for pediatric bone mineral measurements.

Absorptiometry, Photon↗
PubMed1992

Dual energy x-ray absorptiometry measurement of bone mineral content in newborns: validation of the technique.

To evaluate the applicability of dual energy x-ray bone absorptiometry in newborns, precision and accuracy of the method was tested for very small quantities of mineral ranging from less than 0.5 g to about 4 g of hydroxyapatite using a Hologic QDR 1000 instrument. For six femurs excised from preterm stillborns, the mean precision for bone mineral content (BMC) and bone mineral density (BMD) was 1.2 and 0.8%, respectively. Accuracy based on ash weight indicated a mean overestimation of about 7%. In vivo, the precision was assessed by measuring lumbar spine BMC and BMD (L1 to L5) two or three times in 10 newborns (gestational age, 33 to 40 wk). The mean coefficients of variation were 2.40 and 1.55% for BMC and BMD, respectively. Lumbar spine BMC and BMD were also measured once in 30 full-term infants. Values ranged from 1.17 to 3.90 g for BMC and from 0.192 to 0.356 g/cm2 for BMD. The present study shows that dual energy x-ray absorptiometry provides a valuable new tool for the assessment and management of BMC in low birth weight infants and neonates in general.

Absorptiometry, Photon↗
PubMed1991

In vivo osteogenic activity of isolated human bone cells.

Human bone cells were obtained as the outgrowth from cancellous bone fragments pretreated with collagenase and DNase. The osteogenic potential of cells in primary culture was assessed upon intramuscular transplantation into young mice pretreated with cortisone. Transplants were recovered after 2 weeks and examined by light microscopy. Of 34 transplants, 6 showed evidence of osteogenesis and 12 the production of unmineralized matrix. Only cells were observed in the other transplants. In an attempt to find a biochemical marker for osteogenic cells we have assayed medium osteocalcin and alkaline phosphatase activity levels in cultures before transplantation. No correlation was found between the level of expression of the two osteoblast markers and the osteogenic potential of the cells.

Adolescent↗
PubMed1991

Phospholipid changes in the bones of the hypophosphatemic mouse.

The mineral and lipid composition of the bones of 35 day old hypophosphatemic (Hyp/Y) and control (+/Y) mice were compared in order to test the hypothesis that phosphate status has an effect on the complexed acidic phospholipid content of developing bones. The Hyp/Y bones were found to be rachitic and osteomalacic, having significantly reduced mineral content. That mineral was shown by X-ray diffraction to consist of larger/more perfect crystals than that in +/Y animals, indicating either a preference for crystal growth rather than new mineral deposition, or an increased mineral turnover. The increased crystal perfection was confirmed by chemical analyses which showed an increased calcium to phosphorus ratio in the Hyp/Y bones. The bones of Hyp/Y animals had significantly reduced complexed acidic phospholipid contents relative to those of control animals. Since these complexes are believed to play a role in vitro and in vivo mineral deposition, it is suggested that the deficiency of these complexes contributes to the mineralization defect. The magnitude of the complexed acidic phospholipid deficiency in the Hyp/Y animals indicates the importance of phosphate for the formation of these lipids. Although the proportion of phosphatidylserine and phosphatidylinositol and lysophospholipids tended to be reduced in the Hyp/Y bones, the absence of other statistically significant phospholipid abnormalities in the bones and brains of these animals suggests that the lipid defect is not systemic, but is associated with a decrease in phosphate at the site of bone formation.

Animals↗
PubMed1991

Dynamic histomorphometric evaluation of human fetal bone formation.

We have evaluated dynamic and static parameters of bone formation in femoral metaphyses collected from two human fetuses at 19 weeks of gestation. Tetracycline was administered to the mother at set intervals (2-5-2 day schedule) before interruption of pregnancy. Labels were distinct and sharply linear, suggesting a well organized calcification front at this early stage of mineralization. Mineral apposition rate (MAR) was fastest (4.1 +/- 0.3 microns/d) in the periosteal (Ps) envelope, and about half that value in the endosteal envelopes (endocortical: 2.5 +/- 0.1, cancellous 2.1 +/- 0.1 microns/d). Because cellular activities may vary throughout the metaphyseal area, sections were arbitrarily separated in 0.75 mm layers starting from the growth plate. Three measured parameters decreased rapidly with increasing distance from the physis: Ps MAR: 4.9 to 2.3 microns/d, trabecular osteoid thickness: 5.9 to 1.2 microns, and cartilage volume (CgV/TV): 5.4% to 1.2%. Others did not vary significantly along the metaphysis. Comparison of several static parameters with those measured in five autopsy specimens from full-term infants showed that bone and cartilage volume, and trabecular thickness increased while osteoid thickness and parameters of resorption decreased in the second half of the gestation period. The study indicates that fetal bone matrix mineralization is already highly organized at mid-gestation, and validates the use of histomorphometry to assess bone maturation during early skeletal development.

Bone Development↗
PubMed1990

Calcitriol treatment in vitamin D-dependent and vitamin D-resistant rickets.

Use of 1,25(OH)2D3 (calcitriol) can be of benefit in the treatment of two hereditary types of rickets and osteomalacia, vitamin D dependency type I (VDD1) and X-linked hypophosphatemic vitamin D-resistant rickets (HPDR). VDD1 is due to inadequate activation of 25(OH)D to 1,25(OH)2D, leading to very low circulating levels of 1,25(OH)2D in plasma; the basic abnormality appears to be an alteration in renal 1 alpha-hydroxylase activity. In VDD1, replacement therapy with calcitriol results in complete correction of the abnormal phenotype. By contrast, in HPDR, plasma levels of 25(OH)D and 1,25(OH)2D are in the normal range, although it has been demonstrated that the ability of patients to produce 1,25(OH)2D under conditions of stress is impaired. When started early in life, the use of phosphate salts in HPDR generally results in healing of rickets, normal growth, and correction of lower limb deformities. However, osteomalacia is not corrected by treatment with phosphate, either alone or in combination with vitamin D. By pharmacologically increasing the level of 1,25(OH)2D3 in these patients, there is often a dramatic improvement in the appearance of the trabecular surface, leading to correction of the osteomalacic component of HPDR; in addition, the secondary hyperparathyroidism observed in previous patients treated with phosphate and vitamin D is easier to control. Closed medical follow-up allows the prevention of renal damage that could result from long-term administration of calcitriol.

Calcitriol↗
PubMed1990

Cultured osteoblasts from normal and hypophosphatemic mice: calcitriol receptors and biological response to the hormone.

The content and affinity of calcitriol receptors were analyzed in cultured osteoblasts from normal and hypophosphatemic mice. Hypertonic cell extracts were prepared by sonication followed by centrifugation at 200,000 g x 30 min. Analysis, at saturating levels of labeled 1,25(OH)2D3, revealed that binding of the hormone was dependent on the density of the cells plated and on the length of time in culture. It reached a maximum at 5 days of culture when 1.0 x 10(6) cells were plated. Under those conditions the binding capacity of Hyp osteoblasts was 6306 +/- 1267 sites/ng protein (mean +/- SEM) not different from N cells (7594 +/- 1713). The dissociation constant (Kd) was 18.3 +/- 5.4 and 20.0 +/- 5.7 pM for mutant and normal mouse osteoblasts respectively (NS). In both genotypes, a single peak for specific binding, migrating at approximately 3.0-3.5 S was observed by sucrose gradient centrifugation. 25-hydroxycholecalciferol-24-hydroxylase (24-OHase) was induced at 1 and 10 nM 1,25(OH)2D3 in a dose-dependent fashion. However, the induction was higher in mutant than in normal cells when the medium contained 1 mM and 2 mM phosphate salts. The difference vanished when cells were incubated in the presence of 3 and 4 mM phosphate salts. The effect of calcitriol on cultured osteoblasts was also analyzed in terms of collagen synthesis and alkaline phosphatase activity. In the range of 10(-10) M to 10(-7) M, 1,25(OH)2D3 was found to inhibit collagen synthesis in a dose-dependent fashion. At physiological levels, 1,25(OH)2D3 (10(-11)M-10(-10)M), stimulated alkaline phosphatase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

Role of the source of phosphate salt in improving the mineral balance of parenterally fed low birth weight infants.

Because the monobasic potassium phosphate salt (monobasic) improves the solubility of calcium and phosphorus in amino acid plus dextrose solutions, compared with the current mixtures of monobasic plus dibasic salts (dibasic), we tested the bioavailability and clinical effects of monobasic in 16 parenterally fed low birth weight infants at standard (n = 8) and high levels (n = 8) of mineral intakes. A constant infusion of macronutrients and vitamin D was provided in a crossover design of two four-day periods. With standard intakes of calcium (35 mg/kg/day, 0.9 mmol/kg/day) and phosphorus (30 mg/kg/day, 1 mmol/kg/day), there was no difference between monobasic and dibasic regimens on balance data or plasma biochemical monitoring (calcium, phosphorus, pH, carbon dioxide pressure, base excess, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D). With the use of the monobasic regimen, the mineral intakes were doubled without precipitation in the infusate: calcium, 70 mg/kg/day (1.8 mmol/kg/day), and phosphorus, 55 mg/kg/day (1.7 mmol/kg/day). This led to increased apparent retention of both calcium (63 +/- 5 mg/kg/day, 1.58 +/- 0.12 mmol/kg/day) and phosphorus (52 +/- 4 mg/kg/day, 1.67 +/- 0.14 mmol/kg/day) compared with that for standard levels of mineral intake. The improvement of calcium-phosphorus balance was accompanied by more severe calciuria (9 +/- 2 mg/kg/day, 0.2 +/- 0.05 mmol/kg/day) and by metabolic compensation for an increased acid load. In addition to the possibility of exceeding the buffering capacity of the infant, this relative acidosis could also be evidence of improved bone mineralization.

Amino Acids↗
PubMed1990

Mapping autosomal recessive vitamin D dependency type I to chromosome 12q14 by linkage analysis.

Linkage analysis in French-Canadian families with vitamin D dependency type I (VDD1) demonstrated that the gene responsible for the disease is linked to polymorphic RFLP markers in the 12q14 region. We studied 76 subjects in 14 sibships which included 17 affected individuals and 17 obligate heterozygotes. Significant results for linkage were obtained with the D12S17 locus at the male recombination fraction (theta m) .018 (Z[theta m theta f] = 3.20) and with D126 at (theta m = .025 (Z[theta m theta f] = 3.07). Multipoint linkage analysis and studies of haplotypes and recombinants strongly suggest the localization of the VDD1 locus between the collagen type II alpha 1 (COL2A1) locus and clustered loci D12S14, D12S17, and D12S6, which segregate as a three-marker haplotype. Linkage disequilibrium between VDD1 and this three-marker haplotype supports the notion of a founder effect in the studied population. The current status of the localization of the disease allows for carrier detection in the families at risk.

Chromosome Banding↗
PubMed1988

Mineralization in osteoblast cultures: a light and electron microscopic study.

Osteoblasts isolated mechanically from newborn mouse calvaria produced a calcified matrix when cultured in the presence of 10 mM beta-glycerophosphate or 3 mM inorganic phosphate. The uncalcified matrix revealed numerous matrix vesicles scattered among collagen fibrils. The calcified matrix showed mineralized collagen fibrils and calcified nodules whose underlying organic matrix was detected after decalcification. These structures resembled those described in fetal and woven bone. In partially decalcified areas, calcification was shown to spread out from these structures along collagen fibrils. Alkaline phosphatase activity was found associated with the plasma membrane and matrix vesicles. X-ray diffraction analysis demonstrated that the mineral phase deposited in culture was hydroxyapatite. These observations which demonstrate that the isolated cells elaborate in culture a mineralized matrix with chemical and ultrastructural properties of woven bone further support the osteoblastic nature of the cells.

Alkaline Phosphatase↗