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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The whole-cell configuration of the patch-clamp technique was used to record K+ currents from type I cells enzymatically dispersed from the neonatal rat carotid body. The current-voltage (I-V) relationship for the K+ currents showed a prominent, outward shoulder at test potentials of between +10 and +30 mV. 2. The shoulder of the I-V curve could be enhanced by raising extracellular Ca2+ concentration or by bath application of 5 microM-Bay K 8644. It could also be suppressed by bath application of 100 microM-Cd2+ or 5 microM-methoxyverapamil (D600), indicating that a large component of the K+ current in these cells was activated by an influx of Ca2+ through its own channels during cell depolarization. 3. Potassium currents were also reversibly suppressed by 8 nM-charybdotoxin but unaffected by 100 nM-apamin, suggesting that the Ca2(+)-dependent K+ current was carried through large or intermediate conductance Ca2(+)-activated K+ channels. 4. Lowering the pH of the bathing medium from 7.40 to 7.00 reversibly reduced the K+ current amplitudes, and suppressed the shoulder normally seen in the I-V relationship. This effect was enhanced in the presence of 5 microM-Bay K 8644 and abolished in the presence of 5 microM-D600. 5. It is concluded that the Ca2(+)-dependent K+ channels of type I carotid body cells are selectively suppressed by extracellular acidity. Possible mechanisms underlying this effect, and its role in excitation of the carotid body are discussed.
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PMID:Effect of lowered extracellular pH on Ca2(+)-dependent K+ currents in type I cells from the neonatal rat carotid body. 169 83

Calculus may be considered as an aggregate of calcified deposits or deposits that are going to calcify in the oral cavity. From a topographical point of view calculus is classified in supragingival and subgingival calculus. Calculus is composed by inorganic (70-80%) and organic (20-30%) components. Calculus results from calcification of plaque and epithelial cells exfoliated from oral mucosae. Calcification phenomena (carbonic acid theory) are caused by a rapid fall down of salivary acidity when saliva springs out gland ducts. In fact in the mouth there is a lower pressure of carbon dioxide than in the gland ducts. From this fact results that calcium bicarbonate (dissolvable) becomes calcium carbonate (undissolvable) that forms, starting from nucleating particles, calcium carbonate crystals. Then calculus is one of the most important cofactors in the etiology and pathogenesis of periodontal disease: a) it favors plaque growth and stabilizes it to dental and periodontal tissues; b) it favors retention of food debris and hinders dental cleaning; c) it has endotoxins and lets them free slowly; d) it hinders periodontal recovery. From this study it results that scaling and root planing are one of the first steps in periodontal therapy.
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PMID:[Tartar and periodontal disease--a cofactor in etiopathogenesis]. 186 21

The protein precursors of the schistosome eggshell are synthesized and packaged into secretory vesicles in the vitelline cells. These vesicles appear to contain an emulsion of eggshell precursor material. Evidence is presented to show that these secretory vesicles are acidic as in other systems and that this acidity stabilizes the emulsion and prevents the eggshell cross-linking reactions from occurring. Alkalinizing treatments trigger eggshell formation within the secretory vesicles as shown by (1) the induction of autofluorescence and (2) by electron microscopy which shows that the eggshell precursors have aggregated within the secretory vesicles into spherical particles bearing microspines. These aggregates formed in the secretory vesicles were isolated and shown to have the same protease resistance and amino acid composition as authentic eggshell. The calcium ionophore A23187 induces scattered autofluorescence in intact female worms which electron micrographs show to be due to exocytosis of eggshell material. Based on these observations we propose a model for the formation of schistosome eggshell and suggest that it may apply to all trematodes in which the eggshell precursors are present as stable emulsions in the secretory vesicles of the vitelline cells.
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PMID:Schistosoma mansoni: eggshell formation is regulated by pH and calcium. 191 44

Nephrolithiasis is a heterogeneous disorder, with varying chemical composition and pathophysiologic background. Although kidney stones are generally composed of calcium oxalate or calcium phosphate, they may also consist of uric acid, magnesium-ammonium phosphate, or cystine. Stones develop from a wide variety of metabolic or environmental disturbances, including varying forms of hypercalciuria, hypocitraturia, undue urinary acidity, hyperuricosuria, hyperoxaluria, infection with urease-producing organisms, and cystinuria. The cause of stone formation may be ascertained in most patients using the reliable diagnostic protocols that are available for the identification of these disturbances. Effective medical treatments, capable of correcting underlying derangements, have been formulated. They include sodium cellulose phosphate, thiazide, and orthophosphate for hypercalciuric nephrolithiasis; potassium citrate for hypocitraturic calcium nephrolithiasis; acetohydroxamic acid for infection stones; and D-penicillamine and alpha-mercaptopropionylglycine for cystinuria. Using these treatments, new stone formation can now be prevented in most patients.
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PMID:Etiology and treatment of urolithiasis. 196 46

1. Single-chain toxin is enzymatically converted into two-chain isotoxins which differ from the precursor by their higher pharmacological activity, acidity and hydrophilicity. The interchain disulfide bridge and the disulfide loop within fragment C have been located at the amino acid level. 2. Independent of the enzymes used, the nicking sites are positioned within a region spanning no more than 17 amino acids. The N- and C-termini of the primary gene product are preserved in the two-chain toxin. The chains have been separated by isoelectric focussing and can be reconstituted to functionally intact toxin. 3. Light chain inhibits neurotransmitter release on different systems. First, permeabilized bovine adrenal chromaffin cells and rat pheochromocytoma (PC 12) cells release catecholamines when exposed to micromolar [Ca2+]. Inhibition is achieved with light chain or reduced two-chain toxin, but not with single-chain toxin or heavy chain. Washing away the light chain does not restitute the Ca2(+)-evoked release. The light chains of tetanus and botulinum A toxin act in a apparently similar, however not identical manner. Second, light but not heavy chain inhibits the release of acetylcholine when injected into Aplysia neurones. 4. The pharmacology of heavy chain is quite different. Ganglioside binding is mediated by its fragment C moiety, and modulated by the adjoining beta 2 piece and by light chain. Heavy chain and to a lesser degree its N-terminal beta 2-fragment promote the loss of calcein from liposomes indicating pore formation. Its C-terminal fragment C is inactive in this respect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chains and fragments of tetanus toxin, and their contribution to toxicity. 207 46

An acidic intravenous source of phosphorus (Addiphos) was compared with dipotassium hydrogen phosphate in 25 preterm infants to study acid-base state. Eight infants were given either Addiphos or dipotassium hydrogen phosphate alternately for 48 hour periods and similar amounts of calcium and phosphorus were delivered. There were no significant differences in calcium and phosphorus intake, calcium and phosphate plasma concentrations, or acid-base state between study periods on the two solutions. Seventeen infants were given the two solutions alternately for 72 hour periods; Addiphos was used to increase the amounts of calcium and phosphorus being delivered. Calcium and phosphorus intake was decreased on dipotassium hydrogen phosphate, but Addiphos significantly increased calcium and phosphorus intake and plasma calcium and phosphate concentrations. It also lowered the pH of the urine and raised the titratable acidity. Acid-base state, however, was not significantly different. It is therefore possible to increase intake of calcium and phosphorus in preterm infants without causing a significant metabolic acidosis.
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PMID:Acid-base state of the preterm infant and the formulation of intravenous feeding solutions. 211 Aug 4

Propyl-methylenedioxyindene (pr-MDI; 30 mg/kg, i.p.), an intracellular calcium antagonist, significantly reduced the number and size of erosions per stomach induced by cold-restraint stress by 69% and 86%, respectively. Our previous findings indicate that the antiulcer activity of pr-MDI is highly correlated with its inhibitory effect on gastric motor activity. Since central TRH is suggested as the brain mediator responsible for cold-restraint stress gastric ulcers in rats, the inhibitory action of pr-MDI was evaluated in the TRH-induced gastric lesion model. Pr-MDI (30 mg/kg) did not reduce the gastric erosions induced by intracisternal administration of 100ng RX77368, a stable thyrotropin-releasing hormone (TRH) analogue, even though it abolished the RX77368-induced stimulation of gastric emptying, gastric acidity, and acid output. Since pr-MDI (30 mg/kg, i.p.) significantly inhibited the stimulation of gastric motility by both cold-restraint stress and TRH, but only cold-restraint stress-induced gastric erosions were effectively reduced by the drug, the present findings suggest a possible dissociation between the ulcerogenic mechanisms of cold-restraint stress and intracisternal administration of TRH.
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PMID:Antiulcer activity of the calcium antagonist propyl-methylenedioxyindene. IV. Effects on gastric lesions in rats induced by cold-restraint stress and thyrotropin-releasing hormone. 212 9

This histopathological study investigated the pulp reaction to a restoration system employing a posterior composite resin with or without the pulp protection of visible light curing calcium hydroxide composition and alpha-TCP cement lining to dentin. Black's class V cavities were prepared in 120 adult dog teeth. They were then extracted for histological examination. As a result of this study, their lining materials were found to be effective in pulp protection. To understand the pathological finding, the pH values of "Fulfil", "Universal bond", "VLC Dycal" and "Vitacemen Type II" were measured. The pH levels of "Fulfil" and "Universal Bond" were mildly acidic (4.79-5.18) before polymerization, with no subsequent changes. "VLC Dycal" was initially a strongly alkaline (11.75) and remained this condition. "Vitacemen Type II" was initially acidic (3.78), but eventually reached the milder acidity of 5.12 after 24 hours.
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PMID:Histo-pathological study of pulp response to a composite resin restoration with two lining materials. 213 52

Hippocampal neurons are extremely sensitive to ischemic injury; two plausible mechanisms have been implicated in mediating such damage. The first involves overexposure of neurons to excitatory N-methyl-D-aspartate (NMDA) receptor agonists, which mobilize damaging concentrations of intracellular calcium; the second involves the generation of damaging tissue acidosis. A recent report shows that exposure to pH 6.6 can block NMDA-induced calcium currents in hippocampal neurons. This suggests that moderate acidity might protect against NMDA-mediated neurotoxicity and ischemic injury in vivo. We have observed such projection in vitro using primary hippocampal cultures. At an extracellular pH of 7.4, 6 h of glucose-free anoxia caused delayed and profound damage to neurons which was partially attenuated by the NMDA receptor antagonist, 2-amino-5-phosphonovaleric acid (APV). Dropping the pH to 6.5 provided virtually complete protection against this insult. Thus, acidosis need not be viewed exclusively as a damaging component of ischemic insults.
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PMID:Mild acidosis protects hippocampal neurons from injury induced by oxygen and glucose deprivation. 215 91

Eighteen different infants' drinks from five manufacturers were examined for their carbohydrate, calcium, phosphorus and acid contents, and their attack on tooth mineral. Seven of the drinks were compared with nine varieties of adults' soft drinks, and demineralization was studied with and without the presence of a cariogenic oral streptococcus. The influence of the acids already in the drinks in dissolving Ca and P outstripped that of any acid generated in these studies in vitro by microbial fermentation of the sugars they contained, giving an indication of their relative erosiveness rather than their cariogenic action. Various other features of the drinks relevant to dental health were identified. Titratable acid was a better guide than pH to their dental properties. Although there were considerable differences between the various infants' drinks, taken as a group, their acidity levels and demineralizing powers were generally lower than those of the adults' drinks.
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PMID:Potential dental effects of infants' fruit drinks studied in vitro. 240 Jul 65


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