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H Fleisch

Publications and source records attributed to H Fleisch.

At least 37 records · Page 2Linked to original sources
PubMed1995

The diurnal rhythm of bone resorption in the rat. Effect of feeding habits and pharmacological inhibitors.

Prevention of low bone mass is important to reducing the incidence of osteoporotic fractures. This paper shows that, in rats, bone mass can be increased by feeding habits per se. Using six-hourly urinary excretion of [3H]tetracycline from prelabeled rats to monitor bone resorption, we previously found a peak of bone resorption following food administration. We now demonstrate that dividing the solid and liquid intake into portions blunts this peak and leads to a decrease in 24-h bone resorption to the level observed in thyroparathyroidectomized animals. Calcium balance increases and, when such feeding schedules are imposed for 30 d, bone mass increases. Dividing the intake is not effective in thyroparathyroidectomized animals, indicating the importance of PTH and/or calcitonin. Administration of calcitonin inhibits practically only the peak of bone resorption, suggesting that it is osteoclast mediated. In contrast, treatment with a bisphosphonate reduces basal bone resorption without a specific effect on the peak, indicating a fundamentally different mechanism of action. This is also supported by the finding that their combined effects are additive. Whether bone mass in humans is also under the control of dietary habits is not known. If so, an increased meal frequency may be used to prevent osteoporosis.

Animals↗
PubMed1994

Macrophage colony-stimulating factor restores bone resorption in op/op bone in vitro in conjunction with parathyroid hormone or 1,25-dihydroxyvitamin D3.

The in vivo administration of macrophage colony-stimulating factor (M-CSF) restores osteoclastogenesis and bone resorption in the op/op murine osteopetrosis. In vitro, exogenous M-CSF has been shown to be necessary for the generation of osteoclast-like cells in cocultures of hematopoietic and mesenchymal cells obtained from this mutant. In this study we investigated the capacity of M-CSF and other cytokines and hormones, alone or in combination, to induce bone resorption in explants of op/op metatarsals and metacarpals prelabeled with 45Ca. The effect on bone resorption was verified by counting the number of osteoclasts generated in the mineralized matrix. No osteoclast formation and no bone resorption were observed in the absence of M-CSF. M-CSF alone had only a slight effect at the high concentration of 10(4) units/ml. Addition of PTH or 1,25-(OH)2D3 together with M-CSF induced both osteoclastogenesis and bone resorption. The release of 45Ca was linear with time up to 15 days. PTH or 1,25-(OH)2D3 could not be substituted by TNF-alpha or IL-1, whereas IL-6 had a weak effect. M-CSF could not be replaced by GM-CSF. This study further emphasizes the role of M-CSF, PTH, and 1,25-(OH)2D3 in osteoclastogenesis.

Animals↗
PubMed1994

Evaluation of urinary pyridinium crosslink excretion as a marker of bone resorption in the rat.

The aim of this study was to evaluate the value of the urinary excretion of the pyridinium crosslinks, pyridinoline (Pyr) and deoxypyridinoline (D-Pyr), as markers of bone resorption in the rat. The excretion of the crosslinks was compared with that of urinary [3H]tetracycline ([3H]TC) excretion from chronically [3H]TC-prelabeled animals, a technique established to monitor bone resorption in the rat. Bone resorption was modulated by Ca restriction, infusion of PTH, thyroparathyroidectomy, and administration of different bisphosphonates. Furthermore, the urinary crosslinks were assessed in three different osteopetrotic mutations in the rat. We found a delayed response of Pyr and D-Pyr excretion to acute changes in bone resorption compared with [3H]TC excretion. This delay was 1 day after Ca restriction and longer after other treatments, such as PTH administration or bisphosphonate treatment, with which it was more than 3 weeks. In contrast, chronic states with stimulation or inhibition of bone resorption showed similar changes in excretion of the urinary crosslinks and [3H]TC, except after PTH administration. The excretion of the crosslinks was greatly reduced in osteopetrotic rats (op/op, tl/tl, and ia/ia) and increased to normal levels in tl/tl rats after stimulation of bone resorption by M-CSF administration. These results suggest that, in rats, urinary excretion of the pyridinium crosslinks reflects bone resorption in chronic but not always in acute conditions. The cause of this discrepancy is still unclear.

Amino Acids↗
PubMed1994

Regulation of collagen type I and biglycan mRNA levels by hormones and growth factors in normal and immortalized osteoblastic cell lines.

Growth factors, such as transforming growth factor beta (TGF-beta) and insulin-like growth factors (IGF) I and II, have been shown to exert anabolic effects on bone cells in vitro. Hormones, such as PTH and probably insulin and growth hormone, were recently shown to stimulate bone formation in vivo as well. The aim of the present study was to assess by northern blots, which were quantitated by densitometry, the effects of these anabolic growth factors and hormones in two osteogenic cell populations: CRP 10/30 cells, a clonal cell population derived from primary rat calvarial cells, and IRC 10/30-myc cells, which were established from CRP 10/30 by immortalization. Transcripts for alpha 1(I) collagen, biglycan, osteonectin, osteopontin, and osteocalcin were detected in both cell populations, which is consistent with the phenotype expressed by mature osteoblasts. There were no difference in the basal expression of bone matrix mRNAs between the two cell populations. PTH increased alpha 1(I) collagen mRNA levels in both osteoblastic cells but had no effect on the biglycan transcripts. Neither insulin nor growth hormone affected mRNA levels of either matrix protein after 24 h exposure. All three growth factors, TGF-beta, IGF-I, and IGF-II, increased alpha 1(I) collagen transcripts in a time- and dose-dependent manner in both cell populations. Biglycan mRNA levels were enhanced in both osteoblastic lines only by IGF-I and IGF-II, but not TGF-beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Role of colony-stimulating factor-1 in bone metabolism.

Colony-stimulating factor-1 (CSF-1) is a cytokine required for proliferation, differentiation, activity, and survival of cells of the mononuclear phagocytic system. The growth factor is synthesized as a soluble, matrix, or membrane associated molecule. The specific functions of these forms are not clear. However, some data suggest a dependence of the development of various populations of tissue macrophages on the locally expressed and presented cytokine. Deficiency in CSF-1, as is the case in the murine mutant strain op/op, results in low numbers of macrophages and monocytes and, most striking, leads to osteopetrosis due to a virtual absence of osteoclasts. Using the op/op mutation as a model, CSF-1 was established as one of the growth factors for osteoclasts. The expression of CSF-1 receptors, encoded by the proto-oncogene c-fms, by osteoclast precursors and osteoclasts, suggested an effect of this cytokine not only during osteoclast formation but also on the mature cells. In fact, CSF-1 was shown to inhibit the resorbing activity, to stimulate migration, and to support survival of isolated osteoclasts in vitro. By these actions on cells of the osteoclast lineage, CSF-1 induces recruitment of new osteoclasts, leading to a net increase of bone resorption, and might govern the spatial distribution of resorption sites within the bone. During these processes, locally expressed and presented forms of the growth factor may play a crucial role, as will be discussed in this article.

Animals↗
PubMed1994

Dual-energy X-ray absorptiometry for measuring total bone mineral content in the rat: study of accuracy and precision.

Sequential studies of osteopenic bone disease in small animals require the availability of non-invasive, accurate and precise methods to assess bone mineral content (BMC) and bone mineral density (BMD). Dual-energy X-ray absorptiometry (DXA), which is currently used in humans for this purpose, can also be applied to small animals by means of adapted software. Precision and accuracy of DXA was evaluated in 10 rats weighing 50-265 g. The rats were anesthetized with a mixture of ketamine-xylazine administrated intraperitoneally. Each rat was scanned six times consecutively in the antero-posterior incidence after repositioning using the rat whole-body software for determination of whole-body BMC and BMD (Hologic QDR 1000, software version 5.52). Scan duration was 10-20 min depending on rat size. After the last measurement, rats were sacrificed and soft tissues were removed by dermestid beetles. Skeletons were then scanned in vitro (ultra high resolution software, version 4.47). Bones were subsequently ashed and dissolved in hydrochloric acid and total body calcium directly assayed by atomic absorption spectrophotometry (TBCa[chem]). Total body calcium was also calculated from the DXA whole-body in vivo measurement (TBCa[DXA]) and from the ultra high resolution measurement (TBCa[UH]) under the assumption that calcium accounts for 40.5% of the BMC expressed as hydroxyapatite. Precision error for whole-body BMC and BMD (mean +/- S.D.) was 1.3% and 1.5%, respectively. Simple regression analysis between TBCa[DXA] or TBCa[UH] and TBCa[chem] revealed tight correlations (n = 0.991 and 0.996, respectively), with slopes and intercepts which were significantly different from 1 and 0, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

Role of colony stimulating factor-1 in the establishment and regulation of tissue macrophages during postnatal development of the mouse.

Colony stimulating factor-1 (CSF-1) regulates the survival, proliferation and differentiation of mononuclear phagocytes. The osteopetrotic (op/op) mutant mouse is devoid of CSF-1 due to an inactivating mutation in the CSF-1 gene and is deficient in several mononuclear phagocyte subpopulations. To analyze more fully the requirement for CSF-1 in the establishment and maintenance of mononuclear phagocytes, the postnatal development of cells bearing the macrophage marker antigens F4/80 and MOMA-1, in op/op mice and their normal (+/op or +/+) littermates, were studied during the first three months of life. In normal mice, maximum expression of tissue F4/80+ cells was generally correlated with the period of maximum organogenesis and/or cell turnover. Depending on the tissue, the F4/80+ cell density either decreased, transiently increased or gradually increased with age. In op/op mice, tissues that normally contain F4/80+ cells could be classified into those in which F4/80+ cells were absent and those in which the F4/80+ cell densities were either reduced, normal or initially normal then subsequently reduced. To assess which F4/80+ populations were regulated by circulating CSF-1 in normal mice, op/op mice in which the circulating CSF-1 concentration was restored to above normal levels by daily subcutaneous injection of human recombinant CSF-1 from day 3 were analyzed. These studies suggest that circulating CSF-1 exclusively regulates both the F4/80+ cells in the liver, spleen and kidney and the MOMA-1+ metallophilic macrophages in the spleen. Macrophages of the dermis, bladder, bone marrow and salivary gland, together with a subpopulation in the gut, were partially restored by circulating CSF-1, whereas macrophages of the muscle, tendon, periosteum, synovial membrane, adrenals and the macrophages intimately associated with the epithelia of the digestive tract, were not corrected by restoration of circulating CSF-1, suggesting that they are exclusively locally regulated by this growth factor. Langerhans cells, bone marrow monocytes and macrophages of the thymus and lymph nodes were not significantly affected by circulating CSF-1 nor decreased in op/op mice, consistent with their regulation by other growth factors. These results indicate that important differences exist among mononuclear phagocytes in their dependency on CSF-1 and the way in which CSF-1 is presented to them. They also suggest that the prevalent role of CSF-1 is to influence organogenesis and tissue turnover by stimulating the production of tissue macrophages with local trophic and/or scavenger (physiological) functions. Macrophages involved in inflammatory and immune (pathological) responses appear to be dependent on other factors for their ontogenesis and function.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1993

Bisphosphonates in osteoporosis: an introduction.

The bisphosphonates are compounds characterized by a P-C-P bond. By substitution of the hydrogens on the carbon atom it is possible to synthesize a variety of bisphosphonates each with its own distinct physicochemical, pharmacological, and toxicological characteristics. The bisphosphonates investigated for use in bone disease have, in general the following properties: they bind strongly onto bone mineral, inhibit calcium phosphate crystal formation and dissolution, inhibit normal and ectopic mineralization (probably through a physicochemical inhibition of crystal growth), and inhibit bone resorption. The last effect is cell-mediated, the exact mechanism being unknown, and is exquisitely dependent upon bisphosphonates used. Various bisphosphonates have been investigated extensively in animals for a possible use in osteoporosis. They were found not only to increase the balance of calcium in normal rats but also to prevent various types of experimental osteoporosis, such as occurs after immobilization, ovariectomy, or administration of corticosteroids. the toxicity of these compounds is relatively low, probably because they are cleared rapidly from the plasma to be deposited preferentially in the bone, where they remain over a long time. In man, bisphosphonates are used successfully in diseases with increased bone turnover, such as Paget's disease and tumoral bone disease. Recently, a few have been investigated in osteoporosis. They were shown not only to inhibit bone loss but also to increase bone mass. The effect on the rate of fractures is not yet proven, but the first results look promising. Many issues as yet unsolved, will be essential for the choice of the best compound in osteoporosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

New bisphosphonates in osteoporosis.

Bisphosphonates are non-biodegradable compounds characterized by a phosphorus-carbon-phosphorus bond. By substituting the hydrogens on the carbon atom, a variety of bisphosphonates can be synthesized, each with distinct physical-chemical, biologic, therapeutic, and toxicologic characteristics. Bisphosphonates have in general a strong affinity to calcium phosphates, both in vitro and in vivo. They inhibit bone resorption through a cellular mechanism that is not yet completely understood. When given in large amounts, some bisphosphonates can inhibit normal and ectopic mineralization through a physical-chemical mechanism. The main difference among the various compounds appears to be their potency in inhibiting bone resorption, which can vary from 1 to 10,000. The potential efficacy of bisphosphonates in osteoporosis has been investigated extensively in animals. In the growing rat, they induce an increase in intestinal absorption and body retention of calcium. Various types of experimental osteoporosis, such as induced by immobilization, ovariectomy, administration of corticosteroids, or low calcium diet, can be prevented. Bisphosphonates are rapidly cleared from plasma, with 20%-60% deposited in bone and the remainder excreted in the urine. The half-life in bone is, however, very long. The toxicity of bisphosphonates is low, probably because of their rapid plasma and soft tissue clearance. It varies greatly from compound to compound. Bisphosphonates are used successfully in diseases with increased bone turnover, such as Paget's disease of bone, tumoral bone disease, and recently, osteoporosis. Most results in osteoporosis have been obtained with etidronate and pamidronate. Both of these compounds, as well as other bisphosphonates, such as tiludronate, alendronate, and clodronate, inhibit bone loss and sometimes even increase bone mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Resorption↗
PubMed1993

Expression of tissue transglutaminase in skeletal tissues correlates with events of terminal differentiation of chondrocytes.

Calcifying cartilages show a restricted expression of tissue transglutaminase. Immunostaining of newborn rat paw bones reveals expression only in the epiphyseal growth plate. Tissue transglutaminase appears first intracellularly in the proliferation/maturation zone and remains until calcification of the tissue in the lower hypertrophic zone. Externalization occurs before mineralization. Subsequently, the enzyme is present in the interterritorial matrix during provisional calcification and in the calcified cartilage cores of bone trabeculae. In trachea, mineralization occurring with maturation in the center of the cartilage is accompanied by expression of tissue transglutaminase at the border of the hydroxyapatite deposits. Transglutaminase activity also shows a restricted distribution in cartilage, similar to the one observed for tissue transglutaminase protein. Analysis of tissue homogenates showed that the enzyme is present in growth plate cartilage, but not in articular cartilage, and recognizes a limited set of substrate proteins. Osteonectin is coexpressed with tissue transglutaminase both in the growth plate and in calcifying tracheal cartilage and is a specific substrate for tissue transglutaminase in vitro. Tissue transglutaminase expression in skeletal tissues is strictly regulated, correlates with chondrocyte differentiation, precedes cartilage calcification, and could lead to cross-linking of the mineralizing matrix.

Animals↗
PubMed1993

Bisphosphonates act on rat bone resorption through the mediation of osteoblasts.

Bisphosphonates are generally considered to act on bone resorption by binding to bone mineral and subsequently inhibiting the activity of the osteoclasts which ingest them. This has been supported by the fact that bisphosphonates adsorbed on mineralized tissue inhibit the resorbing activity of isolated osteoclasts in vitro. However, the effectiveness of different bisphosphonates determined in this system does not reflect their relative potencies in vivo. Employing the well-described isolated osteoclast resorption pit assay, with ivory as the resorption substrate, we show here that this lack of correlation prevails only when the bisphosphonates are added to the mineral before addition of osteoclasts, but not when the cells are treated for a short time (5 min) before allowing them to adhere onto ivory. By using this approach with five different bisphosphonates, a stringent correlation of relative potencies was obtained with those found, both in the rat and in the human, in vivo. Furthermore, by using an osteoblastic cell line (CRP 10/30) which is a powerful promoter of osteoclastic resorption in vitro, we obtained evidence that the inhibitory effect of bisphosphonates was the result of an action on osteoblasts rather than on osteoclasts. Thus, in experiments in which the osteoblastic cells were pretreated for 5 min with bisphosphonates and then cocultured with osteoclasts, inhibition of osteoclastic resorbing activity was obtained. Moreover, it was found that this treatment resulted in a decrease of the stimulatory effect found in CRP 10/30-conditioned medium. In conclusion the present study shows that part of the osteoclast inhibiting action of the bisphosphonates is mediated through an action on osteoblasts.

Alendronate↗
PubMed1992

Detection of transcripts for the receptor for macrophage colony-stimulating factor, c-fms, in murine osteoclasts.

Macrophage colony-stimulating factor (M-CSF), whose action is restricted to the cell populations of the mononuclear phagocyte system, has recently been found to be required for osteoclastogenesis and bone resorption. To investigate the cells involved in the action of M-CSF in these processes, expression of c-fms mRNA, encoding the M-CSF receptor, was studied by in situ hybridization. Paws from murine embryos and newborn mice, tibiae from 2-day-old animals, as well as isolated osteoclasts, were hybridized with a c-fms-specific RNA probe. In bone, c-fms mRNA was detected only in cells at the late stages of osteoclastogenesis and in mature osteoclasts. The findings strengthen the relation between osteoclasts and the mononuclear phagocyte system. Furthermore, they suggest that M-CSF acts directly on osteoclast precursors and on mature osteoclasts during osteoclastogenesis.

Animals↗
PubMed1992

Expression of collagen, osteocalcin, and bone alkaline phosphatase in a mineralizing rat osteoblastic cell culture.

Rat calvaria bone cells isolated by collagenase digestion form a bone-like matrix which mineralizes in vitro in the presence of beta-glycerophosphate, in less than 2 weeks. The purpose of this work was to investigate, in this mineralizing rat osteoblastic cell culture, the synthesis of collagen, osteocalcin, and bone alkaline phosphatase (ALP). The results obtained indicate (1) After 15 days in culture, the extracellular-matrix contains collagen type I, V, and to some extent type III. Metabolic labeling at day 14, during the phase of nodules mineralization as well as new nodules formation, shows that collagen types I and type V are synthesized; (2) During the phase of cell growth, no osteocalcin could be detected in the medium, however, at the point of nodule formation, the osteocalcin level reached values of 3.55 +/- 1.39 ng/ml, followed by a 30-fold increase after nodules became mineralized. At day 14, after metabolic labeling, de novo synthesized osteocalcin was chromatographed on an immunoadsorbing column. With urea-SDS PAGE the apparent molecular weight was determined to be 9,000 daltons. (3) Specific activity of ALP was found to be 10 nmol/min/mg of proteins at cell confluence. At day 15, when nodules are mineralized, this activity was increased by 40-fold. The Michaelis constant was 1.58 10(-3) M/L. ALP was inhibited by L-homoarginine and levamisole but not by L-phenylalanine. ALP was shown to be heat sensitive at 56 degrees C with two slopes of inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1992

Effect of Pasteurella multocida toxin on bone resorption in vitro.

Pasteurella multocida toxin (PMT), which is the primary etiologic factor in the pathogenesis of progressive atrophic rhinitis in pigs, was found to stimulate bone resorption in vitro. This stimulation was observed both in cultures of murine calvaria by measuring the release of calcium and of the lysosomal enzyme beta-glucuronidase and in murine long bone cultures by measuring the release of calcium. Both systems showed the same dose response curve, with the maximal effect at a concentration of 5 ng/ml. The effect on calvaria was studied in more detail. PMT increased bone resorption 24 h after its addition and always had to be present to express an effect. Calcitonin was able to inhibit this increase of resorption completely, and inhibitors of prostaglandin synthesis suppressed it partially. Although the data show an effect of PMT on bone tissue, the results do not exclude an action on cells in the nasal cavity, which could indirectly stimulate bone resorption.

Animals↗