PubMed Health⌕ Search

Biomedical subjects

G Boivin

Publications and source records attributed to G Boivin.

17 recordsLinked to original sources
PubMed1991

X-ray microanalysis of fluoride distribution in microfracture calluses in cancellous iliac bone from osteoporotic patients treated with fluoride and untreated.

Fluoride is able to augment cancellous bone mass in vertebral osteoporosis but is responsible for osteoarticular side effects in which microfractures are thought to be involved. During healing of these microfractures, a callus is formed all around the cancellous fracture line. Our hypothesis is that in fluoride-treated osteoporotic patients, calluses are bone sites where fluoride is focally deposited at a high concentration, and this could induce a local defect of calcification with a poor healing of microfractures. Our aim was to validate this hypothesis on several calluses following microfractures in undecalcified iliac cancellous bone from six women with osteoporosis (four fluoride treated and two untreated). Histologically normal iliac cancellous bone tissue, taken from a subject having neither fluoride treatment nor microfracture, was also examined. Selected areas, including new woven bone (calluses) and old lamellar bone, were carbon-coated and analyzed using an electron microprobe. Fluoride K alpha and calcium K alpha radiations were detected with wavelength and energy-dispersive spectrometers, respectively. In old lamellar bone at a distance from microfractures, the fluoride level was similar in normal and untreated osteoporotic patients but was slightly increased in treated osteoporotic patients. In untreated osteoporotic patients, the fluoride level was slightly higher (about 1.2 times) at the site of microfractures (lamellar and woven bone) than in lamellar bone far from such fractures, but fluoride was homogeneously distributed in lamellar and woven bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Fluoride-induced bone changes in lambs during and after exposure to sodium fluoride.

The evolution of bone changes induced by fluoride after the end of exposure was investigated in lambs. Sodium fluoride (NaF) was given orally at a dose of 3.5 mg/kg per day to 14 animals for 120 days. A group of 7 control and 7 treated lambs was slaughtered at the end of NaF administration (T120) and another group 120 days after the end of NaF exposure (T240). At T120, the bone fluoride content (BFC) was very significantly increased in treated animals. The histomorphometric analysis confirmed that fluoride induces an increase in bone formation (the osteoid perimeter and area were 3-fold and 4.5-fold higher respectively in treated than in control animals). The number of osteoblasts was significantly augmented. Serum osteocalcin level was twice as high in treated animals compared with controls. The bone formation rate at the tissue level (BFR) doubled after treatment, but the apposition rate (Aj.AR) was half that in the control group. The mineralization lag time (Mlt) was 120 days in treated animals compared with 42 days in controls. At T240, BFC had decreased by 50% compared with the level at T120, but it was still significantly higher than in controls. The osteoid and osteoblastic parameters were 2 and 1.3 times higher than in control animals. BFR remained significantly increased in treated animals, but Aj.AR and Mlt were similar in control and treated animals. In conclusion, after 4 months of NaF exposure fluoride induced an increase in osteoblast natality and bone formation at the tissue level, associated with a toxic effect at the individual cell level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effects of ossein-hydroxyapatite compound on ewe bone remodeling: biochemical and histomorphometric study.

Ossein-hydroxyapatite compound (OHC) is a protein-mineral complex derived from bovine bone. Its effects on bone remodeling were studied in old ewes which have seasonal variations in bone remodeling. Seven animals received 200 mg OHC/kg b.w./day for 90 days from July to September. The control group consisted of 7 untreated animals followed for the same period of time. OHC was administered through a fistula into the fourth stomach. A significant decrease of bone histomorphometric parameter values was noted in controls at the end of the experiment, due to seasonal variations: the cancellous eroded perimeter decreased by 45%, the osteoblastic perimeter by 60% and the bone formation rate at the cell level by 20%. In contrast, in the treated-group, these parameters tended to increase or did not change. In conclusion, counteracting the significant seasonal reduction of bone remodeling in ewes, OHC seems able to stimulate directly or indirectly bone metabolism, especially when osteoblast activity is reduced and may partly prevent the seasonal reduction of bone turnover.

Animals↗
PubMed1991

Dose effects on ewe bone remodeling of short-term sodium fluoride administration--a histomorphometric and biochemical study.

The early effects of two doses of sodium fluoride (NaF) on bone remodeling was studied in 14 ewes divided into two groups. Group I received orally 1 mg NaF/kg/day and group II received a five-fold greater dose. No calcium supplement was given. Transiliac bone biopsies and blood samples were taken before treatment (T0) and after 45 (T45) days of treatment. Bone fluoride content significantly increased in group II. In both groups, a significant decrease of serum calcium and phosphorus, and a slight but nonsignificant augmentation in serum parathyroid hormone were noted. Osteoid perimeter and area were significantly increased. The osteoid width significantly increased in both groups, but was twice higher in group II than I. At T45, the osteoblast perimeter increased in both groups. Osteoid perimeter was significantly correlated with serum osteocalcin values (r = 0.74; p less than 0.001) and bone fluoride content (r = 0.64; p less than 0.01). The bone formation rate at tissue level tended to increase in both groups. Concerning the apposition rate, a decrease was noted which was 1.5-fold higher in group II than in I. The increased formation period resulted from a prolonged inactive period in group II. These results point out a stimulatory effect of fluoride on the birth rate of osteoblasts. However, fluoride prolonged the lifespan of osteoblasts that had reduced activity.

Animals↗
PubMed1991

Azinphos-methyl residues in apples and spatial distribution of fluorescein in vase-shaped apple trees.

Vase-shaped standard apple trees cv. McIntosh were sprayed with azinphos-methyl at pink, pink and 1st cover and 1st cover only. Residue analyses by gas chromatography revealed detectable residues on foliage until mid summer. At harvest, negligible residue levels were found on the peel and the whole apple. On four trees, fluorescein was sprayed in the same manner as the insecticide and maximum levels of the dye were detected on the outside lower canopy along the row. Minimal concentration of fluorescein was detected on the inner upper canopy away from the direction of the row.

Aerosols↗
PubMed1990

Skeletal fluorosis: histomorphometric findings.

Histomorphometric analysis of undecalcified sections was performed in transiliac biopsy cores taken from 29 patients (16 men, 13 women, aged 51 +/- 17 years) suffering from skeletal fluorosis due to chronic exposure to fluoride. The origin of the exposure, known in 20 patients, was either by water (endemic or sporadic), or industrial, or in a few cases iatrogenic. Measured on calcified bone using a specific ion electrode, bone fluoride content was significantly high in each specimen (mean +/- SD: 0.79 +/- 0.36% of bone ash) as compared to control values (less than 0.10%). The radiologically evident osteosclerosis observed in each patient was confirmed by the significant increase of cancellous bone volume (40.1 +/- 11.2 vs. 19.0 +/- 2.8% in controls, p less than 0.0001). There were significant increases in cortical width (1292 +/- 395 vs. 934 +/- 173 microns, p less than 0.0001) and porosity (14.4 +/- 6.4 vs. 6.5 +/- 1.7%, p less than 0.002), but without reduction of cortical bone mass. Osteoid parameters were significantly increased in fluorotic patients. The increase in cancellous osteoid perimeter was almost threefold greater than that noted in cancellous eroded perimeter. The fluorotic group had a greater number of osteoblasts than controls, with a very high proportion of flat osteoblasts. In 15 patients doubly labeled with tetracycline, the mineral apposition rate was significantly decreased, while mineralization lag time significantly increased. Bone formation rate and adjusted apposition rate were significantly decreased in skeletal fluorosis. Cancellous wall width was normal in fluorosis but the formation period and active formation period were significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Localization of endogenous osteocalcin in neonatal rat bone and its absence in articular cartilage: effect of warfarin treatment.

Immunocytochemistry after cryoultramicrotomy was used to localize endogenous osteocalcin in bone (calvaria, femoral diaphysis) and epiphyseal femoral cartilage from 8-day-old rats treated (or mot) for 7 days with warfarin. Ultrathin frozen sections were incubated with goat antiserum against rat osteocalcin at high dilutions (2 x 10(-4) to 2 x 10(-6). In calvaria and femur of untreated rats, endogenous osteocalcin was observed in osteoblasts (cytoplasm and nucleus) and in the collagenous matrix. Osteocalcin appeared progressively in osteoblasts and bone matrix in the mineralization front, then increased in the regions of extended calcification. Osteocalcin was also detected in osteocytes but was not as abundant as in osteoblasts. In bone samples of warfarin-treated rats, endogenous osteocalcin was only detected in bone matrix but not in osteoblasts. Furthermore, osteocalcin was only observed if antiserum was not very dilute (2 x 10(-2). In cartilage (hypertrophied and degenerative zones), osteocalcin was not observed in matrix and chondrocytes. However, it was found in the vicinity of matrix vesicles at the initial loci of calcification. Osteocalcin was never detected in the cartilage of warfarin-treated rats. Our results provide ultrastructural immunocytological evidence for the localization of endogenous osteocalcin in osteoblasts, the presence of osteocalcin in bone matrix and a direct gradient between the presence of osteocalcin and the calcification process. Osteocalcin is absent from cartilage, except possibly close to calcifying matrix vesicles. Warfarin inhibits the formation of osteocalcin.

Animals↗
PubMed1990

Comparison between radial bone mineral density measured by single photon absorptiometry and histomorphometric bone mass parameters measured on iliac crest biopsies.

Bone mineral density (BMD) measured by single photon absorptiometry (SPA) with a Moolsgard 1100 device on the distal and proximal part of the radius was compared with histomorphometric parameters measured on iliac crest biopsies in 37 patients suffering from various bone disorders. In the whole population, a good correlation was observed between the cancellous bone volume (Cn-BV/TV) measured on iliac crest biopsies and BMD from both the proximal part of the radius (r = 0.76, p less than 0.001) and the distal part of the radius (r = 0.73, p less than 0.001). Significant, although weaker correlations, were also found between the cortical width and the BMD from the distal part (r = 0.37, p less than 0.001) and the proximal part (r = 0.44, p less than 0.001) of the radius. In the 14 untreated osteoporotic patients, only a significant Spearman correlation was observed between the iliac Cn-BV/TV and the proximal radial BMD (r' = 0.69, p less than 0.05). It is thus not clear, whether radial proximal BMD correctly indicates cortical bone density in osteoporotic patients or not. The large internal variability of each of the two investigated methods and the small group of osteoporotic patients might explain the lack of correlation between the two methods in this group.

Absorptiometry, Photon↗
PubMed1990

[Effects of 1,25 dihydroxyvitamin d3 on the morphology and alkaline phosphatase activity of ROS 17/2,8 osteoblastic cells: influence of time and dose].

Osteosarcoma-derived osteoblastic cells were exposed to 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) either to 0.001-1,000 nmol.l-1 for 4 days or to 10 nmol.-1 for 1-21 days. Between 0.01 and 10 nmol.l-1, a dose-dependent increase in alkaline phosphatase (AP) activity was found, which rose to a maximum level at 10 nmol.l-1 (+55%). At higher doses (100 and 1,000 nmol.l-1), 1,25(OH)2D3 induced a decrease in AP activity of 40%. After 1 day at 10 nmol.l-1 a slight increase in AP activity was noted (+20%) which augmented with the duration of exposure. This stimulatory effect was highest after 8 days (+130%). In contrast, after 15 and 21 days, AP activity decreased by 30%. Under 1,25(OH)2D3, microtubules were observed mainly in the perinuclear region.

Alkaline Phosphatase↗
PubMed1979

The mineralization processes in teleost fish scales.

In Teleost fish scales, growth and mineralization are continuous. Different mineralization processes can be distinguished. The external layer of the scale is the first to be mineralized and may be classified as the initial calcifying structure of the scale. The initial calcification loci are matrix vesicles of cellular origin always observed during the formation of this layer. This mineralization process takes place progressively, closely following the elaboration of the organic matrix in the scale periphery. The outer limiting and internal layers of the scale are developed after the external layer has been formed. A mineral substance is deposited without the mediation of matrix vesicles, but in contact with the previously mineralized external layer. This type of mineralization is called subsequential. However, the mineralization of the outer limiting layer closely follows the secretion of a collagen-free organic matrix and is thus different from the mineralization of the internal layer in which the calcification front remains remote from the collagen matrix surface and corresponds to a delayed mineralization process. The isolated calcifications (Mandl's corpuscles) which develop in the unmineralized laminae of the internal layer are mineralized in the absence of matrix vesicles and without making contact with a pre-existing calcified tissue, probably by a heterogeneous nucleation of the collagen fibrils.

Animals↗
PubMed1978

Mineral substance of bone tissue and of experimental cutaneous calcinosis in rats: chemical analysis and ESR study.

The evolution of the mineral constituents of subcutaneous calcinosis induced in rats by topical calciphylaxis was studied by the method of quantitative chemical analysis, and after treatment with excited gases by electron spin resonance (ESR) analysis. Chemical data show that the genesis of the subcutaneous calcinosis does not significantly alter the concentration of Ca, P, F, CO3, Mg, and Fe in the mineral phase of the femoral bone of calciphylactic rats. In the calcinosis an important increase of the fluoride concentration is noticed in function of the time after challenging. There is also a high concentration of Mg2+ ions in the early stages of the experimental calcification. Iron injected for the challenging is continuously present in the calciphylactic tissue after this treatment. This suggests that subcutaneous calcinosis might be a means of fixing certain heavy metal ions. After treatment with excited gases, the proportions of the trapped CO33- and O3- radicals are of the same order of magnitude in calciphylactic tissue after 12 days and observations in bone mineral. These suggest that after 12 days the mineral of the calciphylactic tissue has a crystalline state close to that of bone.

Animals↗
PubMed1978

Effects of hormones on osteocyte function and perilacunar wall structure.

Microradiographical and ultrastructural aspects of periosteocytic lacunae are determined by osteocytic activity, lacunar modeling and perilacunar miniremodeling in particular. The miniremodeling activity is constituted by two alternating processes: osteolysis and osteoplasis. Modifications of lacunar shape and size and of perilacunar wall ultrastructure, caused by a direct or indirect effect of certain hormones on osteocytic activity, were observed. The lacunar modeling alterations, particularly in cases of VDH or PTH deficiency, result in an irreversible impaired calcification of the lacunar walls and consequently, mottled lacunae. The alterations of periosteocytic osteolysis are characterized by an increase in number of enlarged lacunae and/or by increased magnitude of this lacunar enlargement. Usually observed as an effect of PTH and VDH, these alterations can also be induced by GC, T4, PG. On the other hand, CT causes a decrease in periosteocytic osteolysis. Periosteocytic osteoplasis is characterized by perilacunar bone formation of various aspects and is known to be stimulated by CT. The osteocytic response to hormones is a function of concentration and not of time; it is transient and not integrative. It can be concluded that none of the perilacunar wall modifications observed is characteristic of any particular hormonal effect or metabolic bone disease.

Calcitonin↗
PubMedDate not supplied

[Cutaneous calcinosis induced by topical calciphylaxis in rats. I. Ultrastructural aspcts].

Skin calcification induced by topical calciphylaxis was provoked by a subcutaneous injection of iron chloride in rats previously sensitized by D.H.T. and studied by electron microscope. The evolution of the calciphylatic response can be resumed as follows: -- early appearance of numberous granules in the mitochondria of the cells of the connective tissue; their inorganic nature was revealed by microincineration and it is highly probable that they are a reserve of mineral ions; -- between the 6 hr, and the 18 hr, stages the interfibrillar matrix contained rounded vesicular structures, enclosed by a triple mambrane, which must surely be of cellular origin; they progressively incorporated more and more mineral particles which confirm their primordial role in the initial phases of mineralization; -- from the 14 hr. stage onward, mineral rodlets composed of chains of little dots appeared in the intercellular matrix and then on the collagen fibrils, probably in contact with the mucopolysaccharides; -- starting at the 24 hr, stage, the mineralization progressed without a vesicular intermediary forming increasingly dense and widespread plaques; the presence of needles of homogenous aspect indicated the appearance of a crystalline mineral deposit; an intrafibrillar mineral deposit becomes visible later. These results are compared with those obtained previously in other studies of experimental or pathological calcinosis and of mineralization of skeletal tissues.

Animals↗