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Biomedical subjects

H Fleisch

Publications and source records attributed to H Fleisch.

At least 217 records · Page 12Linked to original sources
PubMed1976

Tubular adaptation of inorganic phosphate (Pi) transport in response to variations in dietary Pi in rats.

The renal response to variations in the dietary intake of inorganic phosphate (Pi) has been studied in intact and thyroparathyroidectomized (TPTX) rats. The results show that the renal tubule can markedly vary its capacity to transport Pi according to homeostatic requirements: the lower the prior dietary intake, the higher the capacity of the tubule to reabsorb Pi. This adaptive response also occurs in TPTX rats. It is observed as early as three days after varying the dietary intake of Pi. This diet-induced difference in the tubular transport capacity for Pi can be seen in the presence of identical plasma Ca and urinary pH and also during marked expansion of extracellular volume. Comparison between Pi intake and thyroparathyroidectomy indicates that the fractional excretion of Pi measured at similar [Pi] Pl. can vary more than 100 times according to the prior dietary intake, whereas the removal of the thyroparathyroid glands brings about only a change of 2-4 times in this parameter. Free-flow micropunctures done in sham-operated rats pair-fed diets containing either 0.2 or 1.8 g/100 g P show a difference in Pi handling along the early proximal and distal tubule. However the most striking alteration seems to take place along the terminal nephron where an apparent net secretion of Pi would occur in the rats fed the high Pi diet. In conclusion the renal tubule adapts its transport capacity for Pi according to the supply of Pi in the diet. This involves a PTH-independent mechanism of great adaptive capability.

Administration, Oral↗
PubMed1976

Role of matrix vesicles in calcification.

The role of matrix vesicles in the calcification process was investigated in vitro. Isolated vesicles were unable to transport calcium actively. The ATPase activity was not stimulated by calcium in the presence of an optimal magnesium concentration. At a physiological substrate concentration of pyrophosphate, the pyrophosphatase had a pH optimum around 7.0. The vesicles nucleated calcium phosphate precipitation independently of the presence of hydrolyzable phosphate compounds. It is suggested that vesicles induce calcification by nucleating calcium phosphate precipitation and through the local destruction of pyrophosphate, a crystallization inhibitor.

Biological Transport, Active↗
PubMed1975

The comparative effects of vitamin d deficiency and ethane-1-hydroxy-1,1-diphosphonate administration on the histology and glycolysis of chick epiphyseal and articular cartilage.

A comparison has been made between the effect of a vitamin D--deficient diet and treatment with disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on the morphology of chick epiphyseal cartilage and on the production of lactate in vitro by epiphyseal and articular cartilage. The cell populations in the growth plate were different following the two treatments. Vitamin D deficiency was characterized by an increase in proliferating cells, with a relative paucity of hypertrophic cells; EHDP treatment was characterized by an increase in hypertrophic cells. When similar cell types were compared, neither treatment changed lactate production from the control value. This stresses the need to correlate the morphology of cell types with their metabolic function. The present results indicate that the major effect of vitamin D deficiency in the chick is to block the differentiation of proliferating to hypertrophic cells. In contrast, EHDP may act by inhibiting calcification directly. Even though EHDP at the doses used is known to interfere with the production of 1,25-dihydroxycholecalciferol there is no block to cell differentiation under EHDP similar to that seen in dietary deficiency of vitamin D.

Animals↗
PubMed1975

Quantitative determination of ethane-1-hydroxy-1,1-diphosphonate in urine and plasma.

A technique has been developed to measure the diphosphonate ethane-1-hydroxy-1, 1-diphosphonate (EHDP) quantitatively in 5 ml of urine or 2 ml of plasma. The procedure is based on a coprecipitation of EHDP with calcium phosphate, elimination of inorganic phosphate as an insoluble triethylamine-phosphomolybdate complex, decomposition of the P-C-P bond with ultraviolet light and spectrophotometric determination of the inorganic phosphate released. A trace amount of [14C] EHDP is used to correct for losses. The method appears specific for the diphosphonate, exhibits quantitative recoveries, and has a mean coefficient of variation of 3.7% for urine and 7.3% for plasma. The limit of detection is in the order of 2.5 mumol/1 in 5 ml urine and 0.5 mumol/1 in 2 ml of plasma.

Chemical Precipitation↗
PubMed1975

[Treatment of Paget's disease with phosphonates].

A group of 22 patients with Paget's disease of bone was treated with a diphosphonate (sodium etidronate; EHDP), a stable synthetic analogue of inorganic pyrophosphate. This substance was given during 3 months at the dose of 20 mg/kg body weight per day, and proved effective by reducing the raised urinary excretion of total hydroxyproline and by lowering the concentration of serum alcaline phosphatase. It also improved the disease-related osteo-articular pain in 60% of the patients. A rise in serum phosphate under EHDP therapy is due to the increase in renal tubular reabsorption of phosphate. Bone histology showed regression of disease activity and the appearance of lamellar structure in newly formed bone. Because of a transient increase of the amount of uncalcified osteoid, it is advisable to give the diphosphonate in courses not over 3 months or at a reduced daily dose.

Adult↗
PubMed1975

[Paget's deforming osteodysttophy].

The present clinical aspects of Paget's osteodystrophy are reviewed. The nosological definition, localiztion, natural course and signs are described and the recent description of "rheumatoid manifestations" in Paget's disease by FRANCK et al. is mentioned. The same authors revealed a positive correlation between the grade of extenstion of Paget's disease in the whole skeleton and the concentration values for alkaline phosphatase and uric acid in the serum. Among the complications of Paget's disease the orthopedic, neurological, haemodynamic, oncologic, hematological and dermatological are reviewed X-ray of the involved skeleton, which in most cases is diagnostic, may be supported by isotope scanning with 18F or 87mSr and bone biopsy for establishment of diagnosis. Current drug therapy is confined to diphosphonate and calcitonin. The antibiotic mithramycin, which is cytotoxic, reduces bone turnover and may improve the course in Paget's disease. However, toxic side effects on kidney, liver and hemopoiesis do not allow its further therapeutic use in this disease. A case is described which demonstrates that a spontaneous or traumatic fracture in the area of osteodystrophy exhibits almost the same potential for conso lidation as normal bone tissue following both conservative and osteosynthetic treatment of the fracture. In a further instance corrective osteotomy with osteosynthesis (plate) because of serious varisation and antecurvature of the femur due to Paget's disease were performed sucessfully without assisting drug therapy. A third patient displayed extensive osteodystrophy of the whole pelvic skeleton, which was discovered by X-ray as rehabilitation following CVA failed to progress due to severe bilateral reduction of hip joint function. In view of the age and general status of the patient and the absence of pain, no medication or surgical therapy was performed in this case.

Aged↗
PubMed1975

Renal secretion of diphosphonates in rats.

Diphosphonates, characterized by a P--C--P bond, are relatively new experimental drugs used for the treatment of myositis ossificans, dental calculus, nephrolithiasis and Paget's disease. These compounds are not metabolized and the fraction which is not taken up by the skeleton is excreted unchanged in the urine. In the present study, the renal clearances of two 14C-labelled diphosphonates, disodium ethane-1-hydroxy-1,1-diphosphonate (CEHDP) and disodium dichloromethylene diphosphonate (CC12MDP) have been measured in conscious rats. The clearances have been found to be higher than the glomerular filtration rate (GFR), Cdiphosphonate/GFR being about 1.5. This observation indicates net tubular secretion of both drugs. High plasma concentration of EHDP or Cl2MDP significantly depressed CEHDP, whereas CEHDP was not influenced by varying urine pH, by infusing NH4Cl or NaHCO3, or by simultaneous administration of high doses of para-aminohippurate (PAH), probenecid, N-methylnicotinamide or Ca-EDTA. High plasma concentration of inorganic phosphate depressed CEHDP and also depressed the in vitro ultrafiltrability of EHDP. In conclusion, these results provide evidence of an active renal transport of diphosphonates which appears distinct from the mechanisms handling organic acids, organic bases and EDTA in the rat kidney.

Aminohippuric Acids↗
PubMed1975

Purification and heterogeneity of inorganic pyrophosphatase of pig scapula cartilage.

Inorganic pyrophosphatase (pyrophosphate phosphohydrolase; EC 3.6.1.1) was purified from pig scapula cartilage by fractionation with N-cetylpyridinium chloride and (NH4)2SO4, followed by ion-exchange and gel-filtration chromatography. Enzyme preparations of high purity were obtained, with specific activities (100-400 units/mg) higher than those previously described for mammalian pyrophosphatases. The enzyme activity could be separated into several subfractions on ion-exchange columns.

Alkaline Phosphatase↗
PubMed1975

Properties of inorganic pyrophosphatase of pig scapula cartilage.

The properties of a highly purified inorganic pyrophosphatase (pyrophosphate phosphohydrolase; EC 3.6.1.1) from pig scapula cartilage were studied. The enzyme had a molecular weight of 66 000 and a pH optimum of 7-8. It was markedly activated by magnesium, but not, or only to a much smaller degree, by other metal ions. PP1 was the only substrate found and had a Km value of 11 muM. The enzyme was not inhibited by phosphate and other inhibitors of alkaline phosphatase such as CN- minus, amino acids and theophylline; it was slightly inhibited by tartrate, formaldehyde and ammonium molybdate and strongly inhibited by F- minus, Ca2+ and other metal ions. The properties of the enzyme in the presence of concentrations of PP1 present in plasma (3.5 muM) were similar to those found at higher (2 mM) concentrations of PP1. The diphosphonates ethane-1-hydroxy-1,1-diphosphonate and dichloromethylenediphosphonate inhibited the enzyme in the presence of low PP1 concentrations. The characteristics of this enzyme are therefore similar to pyrophosphatases from other sources, such as from yeast and erythrocytes, and do not support a specific role of this enzyme in the calcification process.

Amino Acids↗
PubMed1975

Stimulation of calcium absorption and apparent increased intestinal 1,25-dihydroxycholecalciferol in rats treated with low doses of ethane-1-hydroxy-1,1-diphosphonate.

1. Ligated intestinal segments from rats treated with disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) at the daily dose of 16 mumol (identical to 1 mg of phosphorus)/kg subcutaneously for 7 days show an increased rate of calcium absorption. 2. This dose of EHDP enhances the intestinal accumulation of a vitamin D3 metabolite with the chromatographic characteristics of 1,25-dihydroxycholecalciferol.

Animals↗
PubMed1975

Secretion of inorganic phosphate in the rat nephron.

1. The existence of tubular secretion of inorganic phosphate (Pi) in the mammalian kidney has been investigated by studying the renal response of rats infused with sodium phosphate by three different techniques. 2. Clearance studies indicate that, in anaesthetized rats, the net tubular reabsorption decreases markedly in response to Pi infusion. In conscious rats, the clearance of Pi slightly exceeded that of inulin at high plasma Pi concentration. 3. Free-flow micropuncture in control rats showed a net tubular reabsorption of Pi along the proximal tubule, and probably between the end of the distal tubule and the ureteral urine. In phosphate-loaded rats, whether receiving parathyroid hormone or not, an apparent net secretion of Pi was observed between the end of the distal tubule and the reteral urine. In the phosphate-loaded group receiving parthyroid hormone, net secretion was also observed very early in the proximal tubule followed by a predominant reabsorption along this segment. Thus the early proximal tubule and probably also the terminal nephron can be the site of either net reabsorption or net secretion. 4. Microperfusions of proximal tubules show a fall in the specific radioactivity of the perfused radioactive Pi solution, indicating entry of Pi into the lumen.

Anesthesia, Intravenous↗
PubMed1975

Pyrophosphate and diphosphonates in skeletal metabolism. Physiological, clinical and therapeutic aspects.

Pyrophosphate and diphosphonates produce striking results on calcium metabolism in experimental animals and man. Compounds containing P-O-P- bonds (e.g. inorganic pyrophosphate [PP-ii1 or P-C-P bonds (diphosponates) inhibit both the formation and dissolution of calcium phosphate crystals in vitro. PP-i may have a physiological function in regulating calcification and bone turnover, and obnormalities in its metabolism may occur in some human diseases notably hypophosphatasia and pseudogout. Diphosphonates inhibit ectopic calcification, and slow down resorption and bone turnover in several experimental systems in vivo. They have helped in studies of various aspects of the regulation of calcium metabolism. The diphosphonate, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) has been shown in clinical studies to be effective against ectopic calcification particularly in myositis ossificans progressiva and in disorders of increased bone resorption such as Paget's diseases and some types of osteoporosis. -99mTechnetium complexes of EHDP, PP-i and other polyphosphates have also recently been used successfully as bone scanning agents.

Animals↗
PubMed1975

Effects of a diphophonate on calcium metabolism in calcium-deprived rats.

Calcium metabolism was studied in growing rats, submitted to calcium deprivation ofvarious intensity. A decreased intake resulted in decreased net absorption of calcium(V'na), no change in bone formation (V'o+), and an increase in bone resorption (V'o -). In animals given dichloromethylene disphosphate (Cl'2MDP), a compoundknown to inhibit bone resorption, V'o+ was less than in the controls but again the same at all calcium intakes; V'na was below V'o+, V'o- still increased as the calcium intake was reduced. The various kinetic parameters in rats receiving Cl'2MDPwere indistinguishable from published data in parathyroidectomized (PTX) animals, yetblood calcium was low in PTX rats but normal in Cl'2MDP-atreated rats. It appears that the rat has an efficient mechanism for increasing bone resorption which is not inhibited by Cl'2MDP and does not require parathyroid hormone.

Animals↗
PubMed1975

Action of 1,25-dihydroxyvitamin D3 and a diphosphonate on calcium metabolism in rats.

The effect of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) on Ca balance, 45Ca kinetics, and bone morphology has been studied in control rats and rats given disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP), 10 mg P/kg sc per day. This large dose of EHDP is known to inhibit bone mineralization and intestinal calcium absorption and to depress the endogenous production of 1,25-(OH)2D3. In conctrol rats, 1,25-(OH)2D3 increased intestinal calcium absorption. However, in contrast to the enhanced calcium absorption that results from an augmentation of dietary calcium, the 1,25(OH)2D3-induced augmentation of calcium absorption does not lead to a rise in calcium retention, the intestinal effect being matched by an increased excretion of urinary calcium. The EHDP-induced decrease of intestinal calcium absorption could be completely prevented by the concomitant administration of 1,25-(OH)2D3 but not the inhibition of bone mineralization. Therefore, in contrast to the impairment of calcium absorption, that of bone mineralization brought about by large doses of EHDP cannot be merely attributed to a decreased production of 1,25-(OH)2D3.

Animals↗