[The absorption of several calcium compounds from the gastro-intestinal tract and their effect on radioactive strontium uptake in rats].
Explore the source record for details and available documents.
Absorption↗
SEARCH · PubMed Health
Results for “Calcium Compounds”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
[Characteristics of the incorporation of phosphorus and calcium compounds in transplanted bones processed by different methods].
Explore the source record for details and available documents.
Animals↗
"Bilirubin-calcium compound" precipitation and the effect of bile salts on it. The pathogenesis of pigment gallstone.
Explore the source record for details and available documents.
Bile Acids and Salts↗
Physicochemical, pharmacological and pharmacokinetic study of a new GABAergic compound, calcium acetylhomotaurinate.
It has been shown that calcium acetylhomotaurinate (Ca AOTA; Meram Patent, France) decreased voluntary ethanol intake in rats (1); this was antagonized by bicuculline. Homotaurine did not have this effect. We thought this was due to a different blood-brain barrier crossing ability for the two drugs. The present study was, therefore, planned to confirm blood-barrier crossing by Ca AOTA and to study the drug's physicochemical and pharmacokinetic characteristics. Both in vitro and in vivo (i.p.) administration of Ca AOTA increased the accumulation of [3H] GABA in rat striatal synaptosomal preparations. The chemical study confirmed Ca AOTA's great stability in biological and hydrophilic media, excluding a "homotaurine-dispensing" effect. The molecule was totally dissociated in such media, but the absence of any detectable acid form at any pH indicates that ion pairs are formed to cross barriers, and/or that a carrier system is used. The pharmacokinetic study showed short half-lives (5 and 30 min for the distribution and elimination phases) and small distribution volumes. However, the elimination phase distribution volume was dose-dependent, a further argument for a carrier transport system. From the present study it appears that Ca AOTA is an extremely stable drug, totally dissociated in hydrophilic media, which acts centrally as a GABA agonist after crossing the blood-brain barrier. It is not a precursor of homotaurine and presumably crosses barriers with the help of a transporter.
Acamprosate↗
Preclinical efficacy evaluation of potential chemopreventive agents in animal carcinogenesis models: methods and results from the NCI Chemoprevention Drug Development Program.
In the NCI, Chemoprevention Branch drug development program, potential chemopreventive agents are evaluated for efficacy against chemical carcinogen-induced tumors in animal models. This paper summarizes the results of 144 agents in 352 tests using various animal efficacy models. Of these results, 146 were positive, representing 85 different agents. The target organs selected for the animals model are representative of high-incidence human cancers. The assays include inhibition of tumors induced by MNU in hamster trachea, DEN in hamster lung, AOM in rat colon (including inhibition of AOM-induced aberrant crypts), MAM in mouse colon, DMBA and MNU in rat mammary glands, DMBA promoted by TPA in mouse skin, and OH-BBN in mouse bladder. The agents tested may be classified into various pharmacological and chemical structural categories that are relevant to their chemopreventive potential. These categories include antiestrogens, antiinflammatories (e.g., NSAIDs), antioxidants, arachidonic acid metabolism inhibitors, GST and GSH enhancers, ODC inhibitors, protein kinase C inhibitors, retinoids and carotenoids, organosulfur compounds, calcium compounds, vitamin D3 and analogs, and phenolic compounds (e.g., flavonoids). The various categories of compounds have different spectra of efficacy in animal models. In hamster lung, GSH-enhancing agents and antioxidants appear to have high potential for inhibiting carcinogenesis. In the colon, NSAIDs and other antiinflammatory agents appear particularly promising. Likewise, NSAIDs are very active in mouse bladder. In rat mammary glands, retinoids and antiestrogens (as would be expected) are efficacious. Several of the chemicals evaluated also appear to be promising chemopreventive agents based on their activity in several of the animal models. Particularly, the ODC inhibitor DFMO was active in the colon, mammary glands, and bladder models, while the dithiolthione, oltipraz, was efficacious in all the models listed above (i.e., lung, colon, mammary glands, skin, and bladder).
Animals↗
Modulation of ileal calcium transport by phosphate-exchanging compounds.
Calcium transport in the ileal-ligated loop was studied in the adult rat in the presence of either phosphate alone or phosphate-binding compounds, namely either hydroxylated or aminated substances. Sorbitol or creatine (50 mM) added to a 10-mM CaCl2 solution, which was instilled into ileal loop, markedly enhanced calcium transport, as determined by 45Ca radioactivity appearing in plasma and from 45Ca radioactivity disappearing from the loop. The presence of both compounds maintained Ca soluble in an instilled solution at a constant concentration, whereas with a control solution the Ca concentration progressively decreased towards zero after an incubation period of 60 min. Phosphate, which was either simultaneously added with sorbitol or creatine or which was present as sorbitol or creatine phosphate, led to an equally marked decrease in calcium transport. Calcium transfer was even more reduced when phosphate alone was present with calcium in the ileal loop, in the absence of sorbitol. Similar to the above phosphate-binding compounds, adenosine and its constitutive component, ribose, increased calcium transfer, whereas adenine, the other constitutive component of adenosine, was ineffective. Guanosine was twice more active than adenosine in stimulating ileal calcium transport. Interestingly, the structure of guanosine allows the binding of two phosphates, with one binding site being on the ribose and the other on the guanine base moiety. Thus guanosine is capable of binding a greater amount of phosphate than the two other aminated compounds examined, namely adenosine and alanine, when transphosphorylation from ATP is studied with intestinal microvilli preparations.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine↗
Calcium metabolism in bone disease: effects of treatment with microcrystalline calcium hydroxyapatite compound and dihydrotachysterol.
Microcrystalline calcium hydroxyapatite compound (MCHC) was given orally together with small doses of dihydrotachysterol (DHT) to a number of patients with osteogenesis imperfecta (OI). Serial calcium and phosphate balances in three patients representing wide variations in severity of OI are presented over periods from eight months to two years. The combination of MCHC and DHT resulted in an immediate positive calcium balance which was maintained throughout the period of assessment in 2 cases. However, no radiological improvement could be demonstrated. Substituting calcium gluconate for MCHC resulted in a reduction of positive balance. No adverse effects were noted. The reasons why MCHC with DHT should result in increased calcium retention are discussed. This combination of MCHC and DHT could be of benefit in many common situations of bone demineralization, such as osteoporosis.
Administration, Oral↗
Clinical utility of the alizarin red S stain on permanent preparations to detect calcium-containing compounds in synovial fluid.
The alizarin red S stain for permanent cytologic preparations is a valuable test that is complementary to compensated polarized light microscopic examination to detect calcium crystals. Alizarin red S has the greatest sensitivity for detection of calcium pyrophosphate crystals because crystals are stained regardless of how weakly or strongly birefringent they may be. Alizarin red S stain does not distinguish between amorphous types of calcium compounds; therefore, the different types of calcium compounds can be distinguished only when typical crystal morphologic features are present. Diagnostic importance can be attached to intracellular material that is stainable. In contrast, the diagnostic value of stainable, amorphous, extracellular material is unreliable because it is difficult to distinguish this extracellular material from contaminants frequently found in clinical specimens. Alizarin red S does not stain monosodium urate or corticosteroid crystals. Air-dried cytospin smears are helpful because they may frequently demonstrate more crystals than the wet-mount preparation. Furthermore, special stains can be performed subsequently on air-dried cytospin smears if necessary.
Anthraquinones↗
Adsorption of selected organic compounds onto calcium fluoride.
Selected organic compounds adsorb onto CaF2 and can be revealed by staining methods. The possible influence of CaF2 coated with organic compounds on the dissolution rate is discussed.
Absorption↗
Analysis of pH variation of various calcium hydroxide compounds in vitro.
Among the reasons for the use of calcium hydroxide products, there is their alkalinity. Variations in the alkalinity of six commonly used calcium hydroxide compounds were studied in vitro at different time intervals. All these compounds rendered the saline solution strongly alkaline. Dycal, Life, Nucap and Reocap, had a weaker effect as compared with Contrasil and to Pulpdent paste. Such differences in the pH values were accompanied by differences in calcium loss, as revealed by scanning electron microscopy. Differences in the alkaline pH values and calcium losses among these calcium hydroxide compounds may account for their different clinical effectiveness in vivo.
Calcium Hydroxide↗
Calcium antagonism and structure-affinity relationships of terfenadine, a histamine H1 antagonist, and some related compounds.
Calcium channel affinity of terfenadine and its optical isomers was determined by the displacement of [3H]nitrendipine on rat cerebral cortex membranes. Terfenadine showed a pKd of 6.36 +/- 0.03 whereas its R(+)-isomer (VUF4567) had a pKd value of 6.39 +/- 0.03 and the S(-)-isomer (VUF4568) had a pKd of 6.40 +/- 0.04. The same affinity between the enantiomers suggests that the binding domain on the membrane is not sterically restricted towards the part of the molecule in which the chiral centre is present. The characteristics of terfenadine in regulating [3H]nitrendipine binding were similar to those of some other diphenyl-alkylamine type calcium antagonists. It allosterically altered the binding affinity for nitrendipine and acted at the same site linked to the calcium channel as gallopamil. A structure-affinity relationship among a group of terfenadine analogues is discussed.
Animals↗
Differential influence of various calcium-modulating compounds on ouabain intoxication in isolated rat left atria.
Various calcium-modulating compounds were tested with respect to their protective action against cardiac glycoside toxicity. At the concentrations applied, control force of contraction was reduced by nifedipine and verapamil and slightly attenuated by flunarizine, R 56865, and cimetidine, while it was strongly enhanced by Bay K 8644. The positive inotropic response to ouabain (stimulation rate: 1 Hz) was impaired by nifedipine and verapamil. The increment in contractile force induced by Bay K 8644 was not enhanced by ouabain. The increase in diastolic tension during toxic conditions of ouabain (stimulation rate: 3 Hz) was attenuated by nifedipine, verapamil, bepridil, flunarizine, cimetidine, phenytoin, and R 56865 but not by diltiazem, amiodarone, and amiloride. K loss was prevented by nifedipine, verapamil, diltiazem, bepridil, flunarizine, cimetidine, phenytoin, and R 56865. The increase in cellular Na content was inhibited by R 56865 only. Ca gain was prevented by verapamil, bepridil, flunarizine, R 56865, and cimetidine but not by nifedipine, diltiazem, phenytoin, amiodarone, and amiloride. Ionic deterioration was enhanced by Bay K 8644. These results suggest that pretreatment with various calcium-modulating compounds protects against mechanical and ionic changes during ouabain intoxication induced by Na-Ca overload through different mechanisms.
3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
Calcium and phospholipid-dependent protein kinase activity in mouse epidermis cytosol. Stimulation by complete and incomplete tumor promoters and inhibition by various compounds.
Calcium- and phospholipid-dependent protein kinase (Ca, PL-PK) activity is detectable in mouse epidermis cytosol. It can be stimulated in vitro by complete and incomplete tumor promoters (12-0-tetradecanoylphorbol-13-acetate (TPA) and 12-0-retinoylphorbol-13-acetate (RPA], respectively. Effective inhibition of the enzyme activity is achieved with quercetin and phloretin, whereas the lipoxygenase and cyclooxygenase inhibitors nordihydroguaiaretic acid (NDGA) and esculetin show just weak or no inhibition. Quercetin inhibits the lipoxygenase and cyclooxygenase equally well as the Ca, PL-PK, whereas the strong Ca, PL-PK inhibitor phloretin is absolutely ineffective in inhibiting the lipoxygenase/cyclooxygenase. The application of these inhibitors in differentiating tumor promoter induced effects in vivo is proposed.
Animals↗
Macrophages in degradation of calcium phosphate compound artificial bone: an in vitro study.
The isolated mice peritoneal macrophages in degradation of calcium phosphate compound artificial bone--collagen/hydroxylapatite (CHA), hydroxylapatite (HA), beta-tricalcium phosphate (TCP) ceramics, have been studied by use of both Ca++, P concentration assay in cultured supernatant and scanning electron microscopy (SEM). The solubility of Ca++, composition of materials increased more significantly when macrophages were inoculated than when macrophages were not seeded (P < 0.001), and it was shown that the ground materials were wrapped and phagocytized or resorbed extracellularly by macrophages under SEM, suggesting that macrophages could mediate the degradation of calcium phosphate compound artificial bone by phagocytizing and/or degrading extracellularly.
Animals↗
Effect of dietary calcium on the colonic luminal environment.
Dietary supplementation with calcium may prevent the development of colorectal cancer. This mechanism may be related to fatty acid and bile salt chelation in the small bowel forming non-toxic calcium-soap compounds. Calcium may also act locally or systemically on the colonic mucosa. Faecal concentrations of free fatty acids and free bile acids were measured in 17 Sprague-Dawley rats (weighing 472 (39 g)) whose daily calcium intake had been trebled by enriching the chow and adding calcium lactate (24 g/l) to the drinking water. Mean (SEM) faecal concentrations of free bile acids were 33% less than in 19 controls (1.23 (0.15) v 1.82 (0.20) mg/g; p less than 0.001), whereas free fatty acid concentrations were 117% higher (14.68 (3.59) v 6.76 (2.41) mg/g; p less than 0.02). The 'direct' effect of calcium was assessed by organ culture of rat colonic explants in three different concentrations of calcium. Crypt cell production rate (measured by a stathmokinetic technique), which was (mean (SEM)) 4.80 (0.23) cells/crypt/h in control medium (Ca2+ = 2.14 mmol/l), fell by 43% when calcium concentration was doubled (p less than 0.05) and by a further 43% when the concentration was trebled (p less than 0.02). Calcium binds free fatty acids but not free bile acids intraluminally. Calcium has a direct antitropic action on colonic crypts.
Animals↗
Interactions between calcium channel compounds and adenosine systems in brain of rat.
A number of organic ligands of calcium channels were investigated for possible actions on several aspects of adenosine systems in the cerebral cortex of rat. The principle findings of the present study were that a number of antagonists of calcium channels and the agonist compound Bay K 8644 inhibited binding to adenosine receptors, binding to nucleoside transporters, and the accumulation of [3H]adenosine with a low microM potency. 2-Nitrophenyl dihydropyridine derivatives were more potent than 3-nitrophenyl dihydropyridine or non-dihydropyridine ligands of calcium channels at inhibiting binding to adenosine receptors. Dihydropyridine ligands of calcium channels were more potent than non-dihydropyridine ligands of calcium channel in inhibiting the binding of [3H]nitrobenzylthioinosine to cortical membranes or inhibiting the accumulation of [3H]adenosine into synaptoneurosomes. However, unlike the case of adenosine receptors, no distinction between 2-nitrophenyl and 3-nitrophenyl dihydropyridine derivatives was observed. In addition, the non-dihydropyridine ligand of calcium channels, diltiazem was a weak inhibitor of the accumulation of [3H]adenosine. These results demonstrate that organic ligands of calcium channels, particularly dihydropyridine compounds, can interact with several aspects of adenosine systems.
Adenosine↗
Accumulation of technetium-99m methylene diphosphonate. Conditions affecting adsorption to hydroxyapatite.
Experiments were carried out to explore the mechanism of technetium-99m methylene diphosphonate (99mTc-MDP) adsorption with various calcium compounds including hydroxyapatite powder. 99mTc-MDP adsorption to hydroxyapatite was markedly inhibited by the addition of either pyrophosphate or methylene diphosphonate (MDP). Moreover, adsorbed 99mTc-MDP was partly removed by rinsing with pyrophosphate solution. Adsorption was pH-dependent and was inhibited by univalent cations, adenosine triphosphate solution, and guanosine triphosphate. Adsorption was most apparent to hydroxyapatite and calcium pyrophosphate and was less marked for the other calcium compounds tested. It is suggested that 99mTc-MDP adsorption is affected by the hydroxyapatite crystalline structure and environmental factors such as pH and the presence of phosphates, calcium compounds, and various cations.
Adsorption↗
Extracellular effect of calcium on compound 48/80 stimulated mast cells.
The effects of changes in the extracellular concentration of calcium on activation of rat mast cells by compound 48/80 were studied. The intracellular exchangeable Ca2+ pools at various concentrations of extracellular Ca2+ were determined by equilibration of the cells with 45Ca2+. The cells stimulated by compound 48/80 in the presence of 2.5 microM and 1.6 mM extracellular Ca2+ released comparable amounts of histamine. However, the intracellular Ca2+ pool was doubled in 2.5 microM Ca2+ and was increased sixfold in 1.6 mM Ca2+. In 14.4 mM extracellular Ca2+, there was neither release of histamine nor uptake of Ca2+ which suggested an impairment in activation. The kinetics of Ca2+ influx in the presence of 2.5 microM Ca2+ did not reveal intracellular mobilization of calcium. The cells activated in 1.6 mM Ca2+ at 0 degrees C when allowed to stand in 14.4 mM extracellular Ca2+ released decreased amounts of histamine upon warming to 37 degrees C. The inhibition of the release progressively increased with time of standing at 0 degrees C. The decrease in histamine release was not seen with the cells standing in 1.6 mM Ca2+ at 0 degrees C. The effect of 14.4 mM Ca2+ added prior to tha challenge with compound 48/80 did not depend on the time of incubation. The data presented in this paper suggest that the high concentration of Ca2+ inhibits the histamine release from mast cells by interfering with membrane-associated phenomena.
Animals↗