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

The Streptomyces populations inhabiting five acidic forest soils were examined. It was found that lowering the pH of a medium selective for streptomycetes (starch-casein agar) to the pH of the particular soil horizon being plated influenced both the total numbers and types of streptomycetes that were isolated from the soils examined in this study. On the acidified medium both the numbers of streptomycetes and the percentage of total bacteria on the plates represented by streptomycetes increased (as compared with the same medium with a pH of 7.2). These differences were greatest on the isolations from the most acid soils. The largest concentrations of streptomycetes were found in the surface horizon (0 to 15 cm) and the litter layer immediately over the surface mineral horizon. Acidity tolerance tests demonstrated that random samplings of isolates contained acidophilic, neutrophilic, and acidoduric strains, with the largest numbers of acidophiles being found on the acidified media from the most acid soils. There were no differences between overall utilization of selected carbohydrates among the isolates taken from either the neutral or acidic media, although a larger proportion of the acid media isolates produced acid from the carbohydrates. Evidence is presented which indicates that different types of streptomycetes were isolated on the acid media, and possible reasons for the presence of these acid-tolerant populations are discussed.
Appl Environ Microbiol 1976 Sep
PMID:Influences of soil acidity on Streptomyces populations inhabiting forest soils. 1 Aug 35

A method of continuous gastric perfusion with "artificial gastric juice" was used in a study of individual factors (intragastric pressure, pH, and pepsin) known to participate in the pathogenesis of peptic ulcers. This method allowed change of only one factor at a time, while the other two remained constant. The gastric mucosa of normal rats, fasted for 48 hr, was found to be resistant to the ulcerogenic effects of artificial gastric juice perfused through the stomach for 6 hr without increasing the intragastric pressure. Perfusion of hydrochloric acid (pH 1.3) under increasing pressure produced ulceration of the corpus as well as forestomach portion of the stomach. The degree of gastric ulceration paralleled increases in intragastric pressure, acidity, and pepsin proteolytic activity. Inhibition of pepsin activity by a pepsin inhibitor protected the gastric mucosa even at the very low pH of 1.3. These results demonstrate that under the experimental conditions used, hydrochloric acid alone in the absence of pepsin does not produce ulceration of the rat stomach.
Gastroenterology 1977 Sep
PMID:Role of intragastric pressure, pH, and pepsin in gastric ulceration in the rat. 1 34

For comparative studies on the esterase activities of thrombin and trypsin N(alpha)-arylsulfonyl-L-arginine methyl esters were synthetised containing in aromatic ring substituents of different polar nature, size and hydrophobicity. The kinetics of their hydrolysis by thrombin and trypsin were measured. Values of Km and kcat in steady-state conditions were determined. It was shown, that thrombin-catalysed hydrolysis was more sensitive than that of trypsin to the nature of substituents of arylsulfonyl group and determined by their polar and steric effects. A line correlation between specificity constants (kcat/Km) and sigma and Es of substituents were demonstrated. The difference in reactivity of compounds under investigation is suggested to depend on alterations of stability of hydrogen bond between arylsulfonylamide nitrogen atom of substrate and the active center of the enzyme due to changes in the acidity of the arylsulfonylamide group affected by substituent of the benzene ring.
Biokhimiia 1977 Sep
PMID:[Dependence of thrombin- and trypsin-catalyzed hydrolysis of N-alpha-arylsulfonyl-L-arginine methyl esters on the structure of acylamide part of substrates]. 2 Sep 97

Endocrine cells of the gastric fundal and pyloric mucosa in patients suffering from gastric and duodenal ulcers with different gastric juice acidity, were studied. At hyperacid ulcers, the number of argyrhilic endocrine cells of gastric fundus was increased to 218 +/- 21.1 as compared with the normal acidity 164 +/- 14.8, while it was decreased to 97 +/- 15.1 as compared with hypoacidity. Argentaffinic cells were found in patients with hypo- and unacid gastric juice only. The electron microscopy revealed six types of endocrine cells (A-like, ECL, G, D, D1, EC). The ultrastructural changes of A-like, ECL, and G cells in patients with hyperacid gastric juice indicated their high functional activity. A balance seems to exist between activating and inhibiting systems of the endocrine apparatus of gastric mucosa which accounts for the hyperacidity of the gastric juice.
Fiziol Zh SSSR Im I M Sechenova 1978 Sep
PMID:[Endocrine apparatus of human gastric mucosa]. 3 Jun 54

The acid--forming, acid--neutralizing functions of the stomach, morphological state of its walls and level of histamine in the blood were studied in control rats and in rats subjected to continuous histamine administration. In the latter, intensive elevation of intragastric acidity in empty stomach, an increase in the histamine contents in the blood, and distrophic processes in the wall of stomach occurred. The functional--morphological data obtained suggest remarkable adaptational abilities of the stomach.
Fiziol Zh SSSR Im I M Sechenova 1978 Sep
PMID:[Gastric secretion in rats during long-term histamine administration]. 3 Jun 55

Gastric secretion and fasting plasma gastrin levels were investigated in 26 patients with bilharzial hepatic fibrosis and 26 controls. The groups did not differ in their basal secretion. When stimulated by intravenous infusion of histamine the maximal acid output in patients with bilharzial hepatic fibrosis was significantly less than in the control group. This was unlikely to be a result of neutralisation by reflux of alkaline duodenal contents as the volumes of reflux were not different from control subjects, but was compatible with a true reduction in gastric secretion as assessed by two-component hypothesis. Neither the lowered gastric acidity nor the liver damage in patients with bilharzial hepatic fibrosis correlated with circulating gastrin. The fasting levels of plasma gastrin in these patients were not different from controls. As in other liver diseases the cause of diminished gastric secretion remains unclear.
Gut 1978 Sep
PMID:Gastric secretion and basal gastrin concentration in bilharzial hepatic fibrosis. 3 Jun 81

1. The Na current threshold in sheep cardiac Purkinje fibres and in frog atrium is shifted in a positive direction by protons and Ca2+ ions. The titration curves for Purkinje fibres are consistent with a surface potential of -18 mV at pH 7.4 and 1.8 mM-Ca. 2. In Purkinje fibres, the pacemaker K current activation curve, s infinity, is shifted in a positive direction by Ca2+ ions. The results are consistent with a surface potential of -16 mV in normal physiological solutions. 3. The results on s inifinity during pH changes are unexpected. As also shown by Van Bogaert, Vereecke & Carmeliet (1975) the voltage shifts are usually in the opposite direction to that expected from titration of external surface negative charges. 4. Acid solutions reduce the magnitude of iK2 when fully activated. Alkalinity has little effect on iK2. 5. Acidification and alkalinization are both capable of arresting spontaneous activity in Purkinje fibres. The effects of acidity are usually irreversible. The effects of alkalinity are reversible.
J Physiol 1978 Sep
PMID:Displacement of activator thresholds in cardiac muscle by protons and calcium ions. 3 63

There is a paucity of information regarding excretion of contaminants in human milk, due to experimental difficulties and until recently a general lack of interest. Because of the high fat content of milk and as its acidity is higher than that of plasma, nearly all liposoluble and basic agents consumed by the mother will be excreted in the milk. Distinction must be made between, on the one hand drugs and social toxicants such as smoking and alcohol, whose intake can be stopped or limited during pregnancy and lactation, and ecological toxicants present in a polluted environment to which the mother is exposed. Cases have occurred of heavy prenatal and postnatal intoxication of infants with hexachlorobenzene in Turkey and methylmercury in Iraq due to consumption of fungicide-treated seed wheat by pregnant and lactating mothers. Recent attention has been concentrated on contamination of milk with organochlorine compounds such as DDT and PCB's, that are found in many parts of the world. The heaviest contamination with DDT has been found in Guatemala, resulting in suckling infants consuming many times the Acceptable Daily Intake of this compound proposed by WHO, with unknown future effects.
Acta Paediatr Scand 1978 Sep
PMID:Contaminants in human milk. 8 Sep 16

The experimental relation between adrenergic nervous system and ulcus has been studied. Administration of adrenaline to rats did not induce any ulcers, or showed any noteworthy modification in the studied pH, acidity and peptic activity of gastric content parameters. The number of ulcers induced by the Shay method, acidity and peptic activity decreased after beta receptor blockage. Ko-592 did not induce any significant change on these parameters when the animals were subjected to stress conditions by restraint. Beta receptors discretely participate in ulcer pathology.
Rev Esp Fisiol 1976 Sep
PMID:[Modifications induced through beta receptors in adrenergic nervous system and gastric ulcers (author's transl)]. 13 31

The effects of solid non-nutritive diet on pylorus-ligation ulcers were tested. An experimental group of 16 rats received a bulky mixture of silica and methylcellulose during 48 hr prior to ligation. Control rats were food deprived for the same period of time. A multivariate analysis of variance was applied to nine measures of the study. It was found that rumenal ulceration and total acidity were lower in experimental animals than in controls. This finding confirms a previous observation indicating that the physical property of diet has antiulcerogenic effects.
Physiol Behav 1977 Sep
PMID:Ulcer reduction by non-nutritive bulk in pylorus ligated rats. 20 62


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