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Biomedical subjects

H Fleisch

Publications and source records attributed to H Fleisch.

At least 181 records · Page 10Linked to original sources
PubMed1978

The effects of diphosphonates on the growth and glycolysis of connective-tissue cells in culture.

1. The effects of two diphosphonates (compounds containing a P-C-P bond), disodium dichloromethanediphosphonate and disodium 1-hydroxyethane-1,1-diphosphonate, on the metabolism of cultured rat calvaria cells, rabbit ear cartilage cells and rat skin fibroblasts were investigated. 2. The diphosphonates had no effect on the growth of cartilage cells and on the exponential growth of the calvaria cells and the fibroblasts. However, dichloromethanediphosphonate stopped the growth of the calvaria cells and the fibroblasts after the beginning of confluence, whereas the untreated cells were still growing to a certain extent. This inhibition was dose-dependent. After the drug was withdrawn, the cells recovered slowly. 1-Hydroxyethane-1,1-diphosphonate had no detectable effect on the growth of any of the cell types studied. Both diphosphonates decreased the cloning efficiency of calvaria cells and fibroblasts. 3. The K+ content of cartilage, calvaria and skin cells was diminished only by the highest (0.25 mM) concentration of dichloromethanediphosphonate. 4. Radioactive dichloromethanediphosphonate and 1-hydroxyethane-1,1-diphosphonate were taken up linearly with time for at least 48 h by calvaria cells and fibroblasts. The diphosphonate concentration in the cells depended on its concentration in the medium. 5. Both diphosphonates, in a dose-dependent fashion, markedly inhibited glycolysis, dichloromethanediphosphonate being more effective than 1-hydroxyethane-1,1-diphosphonate, at drug doses that had no effect on cell growth or cellular K+ content. Calvaria cells were much more sensitive than cartilage cells. When cartilage cells were cultured in an N2 atmosphere, these effects on glucose and lactate metabolism disappeared. 6. As increased acid production appears to be associated with resorption of bone, this decrease in lactate may explain why diphosphonates are effective inhibitors of bone resorption in vivo.

Animals↗
PubMed1978

Stimulation of precipitation of calcium phosphate by matrix vesicles.

The ability of matrix vesicles isolated from the epiphysial growth plate of 6-week-old chicks to facilitate the precipitation of calcium phosphate was studied in vitro. The vesicles lowered the minimum concentration product [ca2+]X[p1] needed to induce crystal formation, thereby showing the vesicles are nucleators of crystallization. After freezing and thawing the vesicles at pH6.0, part but not all of this ability to nucleate disappeared. Freezing and thawing markedly decreased the Ca and Pi content of the vesicles, suggesting that part of the nucleating activity may have been due to mineral already present. After removal of the mineral the residual nucleating activity could be destroyed by extracting the vesicles with lipid solvents or by treatment with enzymes such as phosphoilipase C, neuraminidase or proteinase. Matrix vesicles obtained from chicks treated with 1-hydroxyethane-1, 1-diphosphonate, a compound that inhibits calcification in vivo, showed impaired nucleating activity, both before and after treatment at pH6.0. The vesicle preparation bound some diphosphonate in vitro, probably to the mineral present in the preparation, since no binding could be detected in vesicles preincubated at pH6.0. No difference was found in the nucleating activity of vesicles isolated from rachitic chicks which had or had not received cholacalciferol 48 h before death. These results suggest that matrix vesicles possess intrinsic nucleating activity that may be important in biological calcification.

Alkaline Phosphatase↗
PubMed1978

The influx of pyrophosphate ions into calvaria in vitro.

The flux of 32P-labeled inorganic pyrophosphate (PPi) into bone was studied in vitro using Ussing chamber techniques and calvaria from newborn rat pups. Because insignificant hydrolysis and backflux of PPi took place under experimental conditions, it was possible to study the penetration of bone membranes by PP1 unambiguously. At physiological concentrations, the influx was found to be linearly concentration dependent and to follow first order kinetics, apparently a simple diffusion process. In magnitude, the intrinsic constant for influx was found to be approximately one-half that of inorganic phosphate ions under comparable conditions.

Animals↗
PubMed1978

Regulation of the tubular transport of phosphate in the rat: role of parathyroid hormone and 1,25-dihydroxyvitamin D3.

The reduced capability of the tubular Pi transport to adapt to a high Pi diet in TPTX rats can be normalized by physiological doses of 1,25-(OH)2D3. This suggests that the chronic consequence of a lack of PTH could be due, at least in part, to the reduced production of 1,25-(OH)2D3. The mechanism of Pi adaptation appears to be the most important regulator of Pi excretion in the growing rats, since it can markedly alter the acute phosphaturic response to parathyroid hormone.

Animals↗
PubMed1978

Inhibitors and promoters of stone formation.

The understanding of the formation of urinary stones centers around three main mechanisms: the urinary concentration of stone-forming ions, the role of promoters, and the role of inhibitors of crystal formation and crystal aggregation. With respect to the promoting activity, lately emphasis has shifted from the role of the organic matrix to that of one salt inducing by epitaxy the precipitation of another salt. Among the inhibitors, it has become necessary to distinguish between those affecting crystal formation and those affecting crystal aggregation. For measuring the inhibitory activity, the various techniques and their relevance have been reviewed. It has been found that the main inhibitors for calcium phosphate and calcium oxalate precipitation are citrate, pyrophosphate, and perhaps magnesium. Those for calcium phosphate and calcium oxalate aggregation are glycosaminoglycans, pyrophosphate, and citrate. Among the synthetic inhibitors, the diphosphonates are the most powerful for both processes. The role and the therapeutic implications of these various concepts have been discussed.

Animals↗
PubMed1978

Uptake by bone of pyrophosphate, diphosphonates and their technetium derivatives.

1. The uptake of inorganic pyrophosphate (PPi) from blood to bone was investigated in the rat in vivo. 2. PPi is taken up by the bone, where it appears both as PPi and as inorganic orthophosphate (Pi). The latter is due at least partly to local hydrolysis. 3. The fraction of injected PPi taken up by bone, measured as total PPi, was in the same range as that of technetium-tin-PPi, diphosphonates, technetium-tin-ethane-1-hydroxy-1,1-diphosphonate and Pi, but lower than that of calcium. 4. The plasma half-life of PPi is in the same order of magnitude as that of technetium-tin-PPi, diphosphonates, technetium-tin-ethane-1-hydroxy-1,1-diphosphonate, Pi and calcium. 5. PPi, diphosphonates and their technetium complexes are only partly ultrafiltrable in plasma. 6. It appears that the technetium complexes behave in a similar fashion to free PPi or diphosphonate.

Animals↗
PubMed1978

Biochemical and clinical effects of ethane-1-hydroxy-1,1-diphosphonate in calcium nephrolithiasis.

1. The short- and longer-term effects of ethane-1-hydroxy-1,1-diphosphonate (EHDP), an inhibitor of crystal growth and potential preventive agent against urinary tract stones in man, have been studied. 2. Measurement of urinary excretion of EHDP was used to define the best dosage regimen. When 4.4 mmol of EHDP mmol of EHDP was given in four divided doses the murinary concentration of EHDP achieved was high enough (10-5 mol/1) to inhibit the crystallization of calcium crystals throughout the day. 3. Nine patients with recurrent calcium stones were given this dose of EHDP daily for 12 months and seven were then studied for a further 12 months under placebo. During treatment with EHDP, inhibitory activity in urine towards precipitation of calcium phosphate was restored from low values to greatly above normal. This could be accounted for by the inhibitory effect of EHDP itself, coupled with an increase in urinary inorganic pyrophosphate. After stopping EHDP the excretion of EHDP rapidly fell to undetectable levels but the excretion of pryophosphate remained elevated throughout the 12 months of placebo treatment. EHDP also induced a rise in plasma phosphate and an increase in the urinary excretion of oxalic acid and uric acid, but these changes were all fully reversible when EHDP was stopped. 4. The average rate of stone formation per patient per year decreased from 2.4 to 0.2 during treatment with EHDP and remained low during the following 24 months. However, the dose needed for this effect is known to affect bone turnover and mineralization.

Adult↗
PubMed1978

Aerobic glycolysis in bone: lactic acid production by rat calvaria cells in culture.

Considerable data have been accumulated on aerobic glycolysis of intact bone preparations. To test whether aerobic glycolysis is a feature of the bone cells themselves or of the localized conditions within an intact bone, cells isolated from rat calvaria were cultured and the effect of several factors on lactate production was determined. These cells drastically decreased lactate production when the pH in the culture medium was lowered, changing from 100 to 20 percent for a pH shift from 7.4 to 6.75. L-lactate inhibited its own formation by 40 percent at 20 mM. Parathyroid hormone (PTH) (820 U/mg) at a concentration ranging from 0.2 to 5.0 U/ml stimulated slightly the lactate production in a log-linear response, the ratio treated over control changing from 1.1 to 1.3. The maximal stimulation is observed at pH 7.0. Isolated cells respond qualitatively the same as did intact calvaria. Quantitatively, there were significant differences: notably, a smaller response to parathyroid hormone and a higher sensitivity to lowered pH.

Aerobiosis↗
PubMed1977

The effect of pyrophosphate and diphosphonates on calcium transport in red cells.

The effect of 0.5 mM pyrophosphate (PPi), disodium ethane-4-hydroxy-1,1-diphosphonate (EHDP) and disodium dichloromethane diphosphonate (Cl2MDP) on the ATP-dependent Ca2+ extrusion from the human red cell ghosts was studied. PPi and Cl2MDP had no effect, when introduced into the cells or added outside to the medium. EHDP slightly increased the calcium concentration in the released cells and slightly decreased the rate constant of the calcium transport, having opposite effects when it was inside or outside the cells. PPi and the 2 diphosphonates were not found to move easily across the red cell membrane.

Biological Transport, Active↗
PubMed1977

Aggregation of calcium oxalate crystals: effect of urine and various inhibitors.

The influence of various factors on aggregation of calcium oxalate crystals in vitro was determined. Aggregation was assessed by filtering the crystal suspension and measuring the flow rate through a filter. 10% urine completely inhibited aggregation. Orthophosphate and magnesium at concentrations occuring in urine had no effect. Citrate had no effect at 10(-4) M ,but did inhibit at 10(-3) M. The latter effect is probably due to calcium binding. Pyrophosphate and disodium dichioromethylene diphosphonate (C12MDP) inhibited strongly at 10(-4) M, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) at 10(-5) M, whereas pentanemonophosphonate had no effect. Uromucoid also did not show any inhibitory activity. Studies by means of heat inactivation, ultrafiltration and fractionation on DEAE-cellulose and gel-filtration indicated that the inhibitory activity was heterogenous and that the major part was larger than 10 000 daltons.

Calcium↗