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PubMed1985

Natriuretic effect of calcium antagonists.

Calcium antagonists differ from traditional vasodilators by increasing renal water and sodium excretion, although the various calcium antagonist compounds influence renal excretory functions to a different extent. Two important aspects of the renal response to calcium antagonists are discussed, as they still need clarification: (a) the mechanisms of the diuretic and natriuretic effect; (b) the duration of this effect. Various mechanisms and sites of action can be envisaged to account for the diuretic and natriuretic action of these compounds. The action may be due to (a) a change in glomerular filtration rate and/or renal blood flow; (b) interference with renin release; (c) interference with aldosterone secretion and/or aldosterone action on distal tubule; (d) interference with adrenergic sodium handling; (e) a direct tubular action. Although the mechanisms may be multiple, the last type of action is likely to be the most important one. Recent balance studies of our group show that, although the diuretic and natriuretic actions of calcium antagonists are displayed acutely on the first or second day of administration, a negative sodium balance is maintained for at least 1 week, and the diuretic and natriuretic effects of these compounds are not overcome by water- and sodium-retaining mechanisms, unless the doses given are too large.

Aldosterone↗
PubMed1986

Effect of omeprazole on gastric acid secretion by the rat isolated stomach.

The inhibitory effect of omeprazole has been investigated on the isolated gastric fundus from immature rats. Omeprazole (10(-7)-10(-5) M) inhibited basal acid secretion, conversely from H2-receptor antagonists, antimuscarinic compounds and calcium antagonists; the effect was mimicked only by KSCN (3 X 10(-4)-3 X 10(-2) M). Omeprazole (10(-6)-10(-5) M) caused an insurmountable antagonism of the hypersecretion induced by histamine and bethanechol, whereas it competitively antagonized the secretory response to isoprenaline and dibutyryl cAMP. Experiments carried out in low calcium media showed that calcium ions did not significantly affect the inhibitory potency of omeprazole when tested on basal acid secretion, whereas low calcium solutions enhanced the action of omeprazole against histamine-induced hypersecretion. The above data confirmed the potent antisecretory activity of omeprazole in different experimental conditions in which the common antisecretagogues are without effect and pointed out the novel site of action in the control of gastric acid secretion at intracellular level.

Animals↗
PubMed2006

Effect of blood contamination on retention characteristics of MTA when mixed with different liquids.

Simulated furcation perforations were repaired with and without blood contamination utilizing tooth-colored mineral trioxide aggregrate (MTA) mixed with either MTA liquid (sterile water), lidocaine, or saline. Samples underwent Instron testing at either 24 or 72 hours and at 7 days. Data were analyzed using a 3-way ANOVA and post-hoc testing using Turkey's true test for significance. All of the 72-hour samples displayed significantly greater resistance to displacement than the 24-hour samples. All of the 7-day samples displayed significantly greater resistance to displacement than the 24-hour and 72-hour samples. Non-contaminated samples displayed significantly greater resistance to displacement than their blood-contaminated counterparts at 7 days. Non-contaminated samples mixed with sterile water, lidocaine, or saline performed similarly at all time periods. Allowing tooth-colored MTA to set undisturbed for 72 hours or longer prior to placement of a coronal restoration may decrease the chance of MTA displacement in furcation perforation repairs.

Aluminum Compounds↗
PubMed2006

Antibacterial effect of two mineral trioxide aggregate (MTA) preparations against Enterococcus faecalis and Streptococcus sanguis in vitro.

The antibacterial effects of gray-colored MTA (GMTA) and white-colored MTA (WMTA) against Enterococcus faecalis and Streptococcus sanguis were assessed in vitro using the tube dilution test. Broth tubes were prepared and divided into experimental and control groups. Aliquots of each of the tested microorganisms were taken from a stock culture and added to each experimental and positive control group. All groups were incubated at 37 degrees C and evaluated for turbidity at 0, 1, 24, 48, and 72-hour time periods. A direct correlation was found between GMTA and WMTA concentrations and their antibacterial effect. Tubes containing GMTA in concentrations of 50, 25, and 12.5 mg/ml did not show E. faecalis growth at any of the time periods tested whereas tubes containing WMTA showed E. faecalis growth at all concentrations and time periods tested. Statistically significant differences were found between tubes containing GMTA in concentrations of 50, 25 and 12.5 mg/ml and tubes containing similar concentrations of WMTA (p < 0.001). Tubes containing GMTA in concentrations of 50, 25, 12.5, 6.25, and 3.12 mg/ml and tubes containing WMTA in concentrations of 50, 25, and 12.5 mg/ml did not show S. sanguis growth at any of the time periods tested. Statistically significant differences were found between tubes containing GMTA in concentrations 6.25 and 3.12 mg/ml and tubes containing similar concentrations of WMTA (p < 0.001). It appears that the susceptibility of E. faecalis and S. sanguis to MTA differed and that GMTA requires lower concentrations than WMTA to exert the same antibacterial effect against each of the microorganisms tested.

Aluminum Compounds↗
PubMed2002

Microleakage of resected MTA.

Forty-six single rooted extracted human teeth were used in this study. After cleaning and shaping, twenty canals were randomly selected for obturation with MTA placed in an orthograde manor (Group 1). Another twenty roots were obturated with gutta-percha and Kerr EWT sealer, using warm vertical compaction (Group 2). The apical 3 mm of each root in both groups were resected at approximately 45 degrees to its long axis. The teeth were aged for 48 h in a humidor. The root-ends of the teeth in Group 2 were then prepared and received MTA as a root-end filling material to a depth of 3 mm. Six roots were used as positive and negative controls. The roots of all teeth were placed in contact with India ink for 48 h. The roots were split and examined for dye leakage. There was no discernible leakage in teeth with resected MTA or those with MTA placed as a retrograde root-end filling material. We found no significant difference in dye leakage between resected MTA (Group 1) and non-resected MTA (Group 2). Based on these results it appears that the resection of set MTA does not affect its sealing ability.

Aluminum Compounds↗
PubMed1985

Bactericidal properties of a new water disinfectant.

The N-chloramine compound 3-chloro-4,4-dimethyl-2-oxazolidinone (agent I) has been compared with calcium hypochlorite as to its efficacy as a bactericide for the treatment of water. The study included concentration, contact time, pH, temperature, and water quality as controlled variables. The species of bacteria tested were Staphylococcus aureus, Pseudomonas aeruginosa, and Shigella boydii. In general, for highly pure, demand-free water, calcium hypochlorite was the more rapid disinfectant at a given total chlorine concentration, although for water containing a controlled amount of organic load, agent I was the better disinfectant. The differences in efficacy of each of the two disinfectants can be attributed primarily to their different stabilities in water at various controlled conditions.

Bacteria↗
PubMed2003

Effects of LDL, cholesterol, and their oxidized forms on the precipitation kinetics of calcium phosphates.

BACKGROUND: LDL, cholesterol, and their oxidized forms are known cardiovascular risk factors and are often found in atherosclerotic lesions of various stages. Little is known, however, about whether they are directly involved in the formation of calcium phosphate compounds. METHODS: We used the pH-stat technique to follow the kinetics of calcium phosphate precipitation at pH 7.4, 37 degrees C, and ionic strength 0.150 mol/L, in the presence or absence of LDL, oxidized LDL, cholesterol, cholestane-3beta,5alpha,6beta-triol, and cholesteryl linoleate. The precipitates were characterized by x-ray diffraction, scanning and transmission electronic microscopy coupled with energy-dispersion x-ray analysis, and inductively coupled plasma atomic emission spectroscopy. RESULTS: Under the experimental conditions, LDL (14.8 and 43.1 mg/L protein) had no significant effect on the precipitation kinetics. Oxidized LDL (14.8 and 43.1 mg/L protein) prolonged the nucleation phase and diminished the amount of total precipitate, and both the extent of oxidation and the concentration of the protein affected the kinetics. Cholesterol microcrystals (71.4 and 143 mg/L) made the nucleation phase shorter (300 min vs 390 min for the control), and the precipitated particles had an organic core and a shell composed of calcium phosphates. L-alpha-Phosphatidylcholine vesicles (143 mg/L), cholesterol (71.4 mg/L)/phospholipid (143 mg/L) mixed vesicles, cholesteryl linoleate (143 mg/L), and cholestane-3beta,5alpha,6beta-triol (71.4 mg/L) prolonged the nucleation phase. CONCLUSIONS: LDL is not involved directly in the precipitation of calcium phosphates. Oxidized LDL inhibits both nucleation and crystal growth, possibly by attracting calcium ions in the solution and thus reducing supersaturation. Cholesterol microcrystals serve as seeds for the precipitation of hydroxyapatite, whereas L-alpha-phosphatidylcholine, cholesteryl linoleate, and cholestane-3beta,5alpha,6beta-triol exhibit inhibitive effects on the nucleation of calcium phosphates.

Calcium Phosphates↗
PubMed2003

[Calcimimmetic and calcilytics: new perspectives of correction of abnormal parathormone (PTH) secretion].

Treatment of excessive secretion of parathyroid hormone (PTH) in primary hyperparathyroidism (I degree HPT) as well as in secondary hyperparathyroidism (II degree HPT) in chronic renal insufficiency is symptomatic, short-term acting and far from expectations. Recognition of properties of calcium receptor (CaR) expressed on parathyroid principal cell membranes created possibilities to explore new compounds that could alter directly PTH secretion and provide a novel therapy for direct correction of increased secretion of the hormone in these disorders. Ligands that activate this receptor and inhibit PTH secretion are called calcimimetics. Recently clinical trials with NPS R-568, a calcimimetic of the Ist generation, and AMG 073, a representative of calcimimetics of IInd generation, were completed. Calcimimetics, taken orally, effectively lower increased secretion of PTH and hypercalcemia in I degree HPT, by "pharmacologic parathyroidectomy". Such compounds are also safe and effective in dialysed patients with II degree HPT in chronic renal insufficiency: they decrease PTH plasma level and prevent parathyroid cell hyperplasia. The other compounds, called calcilytics and represented by NPS 2143, inhibit CaR resulting therefore in increase of PTH secretion. Administration of calcilytics would provide a valuable alternative to inhibit progression of osteoporosis. Subcutaneous, pulsative low doses of recombinant PTH (ALX1-11) administration induces increase of bone formation. Such an effect to some extent was obtained by transient increase of endogenous PTH secretion induced by oral administration of calcilytic NPS 2143 to osteopenic ovariectomized rats, especially if it was accompanied by supplementation of estrogens.

Aniline Compounds↗
PubMed2005

Localisation, function and composition of primary Ca(2+) spark discharge region in isolated smooth muscle cells from guinea-pig mesenteric arteries.

Smooth muscle cells (SMCs) contain numerous calcium release domains, grouped into regions discharging as a single unit. Laser scanning confocal microscopy, voltage clamp and immunocytochemistry of single SMCs from small mesenteric arteries of guinea-pig were used to study the localisation, function and macromolecular composition of such calcium discharge regions (CDRs). Use of the Ca(2+)-sensitive fluorescent dye fluo-3 or fluo-4 with BODIPY TR-X ryanodine (BTR), a fluorescent derivative of ryanodine, showed spontaneous Ca(2+) sparks originating from regions stained by BTR, located immediately under the plasma membrane, in the arch formed by the sarcoplasmic reticulum surrounding the nucleus. Membrane depolarisation or application of noradrenaline or alpha,beta-methylene ATP, a P2X purinoceptor agonist, elicited Ca(2+) sparks from the same, spontaneous Ca(2+) spark-discharging region. The most active (primary) CDR accounted for nearly 60% of spontaneous transient outward currents at -40 mV and these were of significantly higher amplitude than the ones discharged by secondary CDRs. Immunocytochemical staining for type 1 IP(3) receptors, BK(Ca) channels, P2X(1) purinoceptors or alpha(1) adrenoceptors revealed their juxtaposition with BTR staining at the location typical of the primary CDR. These data suggest the existence of a primary calcium discharge region in SMCs; its position can be predicted from the cell's structure, it acts as a key region for the regulation of membrane potential via Ca(2+) sparks and is a potential link between the external, neurohumoral and the cell's internal, calcium signalling system.

Animals↗
PubMed2002

2-Aminoethoxydiphenyl borate inhibits phototransduction and blocks voltage-gated potassium channels in Limulus ventral photoreceptors.

2-Aminoethoxydiphenyl borate (2-APB) is a membrane-permeable modulator that inhibits the activation of inositol (1,4,5) trisphosphate (InsP(3)) receptors, store operated channels (SOCs) and TRP channels in cells that utilize the phosphoinositide cascade for cellular signaling. In Limulus ventral photoreceptors, light-induced calcium release via the phosphoinositide cascade is thought to activate the photocurrent. Injection of either exogenous InsP(3) or calcium ions can therefore mimic excitation by light. One hundred micromolar 2-APB reversibly inhibited the photocurrent of ventral photoreceptors in a concentration-dependent manner, acting on at least two processes thought to mediate the visual cascade. 2-APB reversibly inhibited both light and InsP(3)-induced calcium release, consistent with its role as an inhibitor of the InsP(3) receptor. In addition, 2-APB reversibly inhibited the activation of depolarizing current flow through the plasma membrane caused by pulsed pressure injection of calcium ions into the light-sensitive lobe of the photoreceptor. We also found that 100 micro M 2-APB reversibly inhibited both transient and sustained voltage-activated potassium current during depolarizing steps. 2-APB has previously been shown to block phototransduction in Drosophila photoreceptors. The lack of specificity of the action of 2-APB in Limulus indicates that this blockade need not necessarily arise from inhibition of InsP(3)-induced calcium release.

Animals↗
PubMed1990

Calcium carbonate gel therapy for hydrofluoric acid burns of the hand.

Hydrofluoric acid is used extensively as an industrial cleaning agent for metals and glass. Many workers are injured by cutaneous contact of the acid with exposed skin surfaces, particularly hands. Hydrofluoric acid burns are characterized by delayed onset of symptomatology with skin ulceration, and severe pain may be of extended duration. Treatment of hydrofluoric acid burns traditionally has consisted of local infiltration or intraarterial injections of calcium solutions. These injections are painful and frequently require retreatment. A new treatment utilizing a topical gel of calcium carbonate is described. Nine patients have been treated for hydrofluoric acid burns of the hand with calcium carbonate gel applied topically and covered with occlusive glove dressings. A gel slurry is compounded from calcium carbonate tablets and K-Y Jelly. Fingernails of the affected fingers are removed if a subungual burn is obvious. The gel is put into a surgeon's glove and placed over the burned hand. The patient replaces the glove and slurry every 4 hours for 24 hours. After the first day, the glove is discontinued unless there is resumption of painful symptoms. Full range of motion is encouraged during this interval. The calcium carbonate gel technique was successfully utilized in nine patients with no further need for injection therapy. In these patients, pain relief was obtained within 4 hours of treatment, with no further progression of skin ulceration. No reconstructive procedures were required in any patient, and only one patient did not return to full-duty work within 1 week. There were no long-term sequelae from burns treated with this topical therapy, except one patient, who presenting 24 hours after the burn, developed a digital tip neuroma that was excised.

Adult↗
PubMed1983

Calcium secretion from the feline pancreas. Influence of hormonal and cholinergic secretagogues and of serum calcium.

The influences of secretagogues and of elevated serum calcium concentrations on the calcium secretion from the cat pancreas have been studied in vivo. During a high and constant fluid secretion rate evoked by a background infusion of secretin, additional infusions of both cholecystokinin-pancreozymin and urecholine led to a dose-dependent increase in calcium secretion in pancreatic juice parallel to the rise of protein. The amount of calcium in pancreatic juice associated to 1 mg protein (18.3 nmol/mg protein) calculated from regression analysis was independent of dose or kind of stimulus used. The protein-independent pancreatic juice calcium fraction was 0.184 mM in normocalcemia. During an episode of hypercalcemia produced by an intravenous calcium infusion, the protein-independent calcium fraction was increased and correlated linearly to the serum calcium concentration. We conclude that pancreatic juice calcium consists of two major fractions, one being associated with the enzyme protein and stimulated by secretagogues, and the other being protein independent and directly dependent on the extracellular calcium concentration.

Animals↗