Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Proximal duodenum was perfused with various solutions and mucosal permeability assessed by measuring the clearance of 51Cr labelled ethylenediaminetetra-acetate (EDTA) from blood-to-intestinal lumen in anaesthetized rats. Net flux of fluid was determined by measurement of effluent weight changes. Perfusion of duodenum with 50 mM NaCl significantly increased fluid absorption but had no effect on EDTA clearance. EDTA clearance was unaffected by perfusion with 400 mM or 800 mM mannitol. Perfusion with 400 mM NaCl induced a sustained fluid secretion and a small but irregular increase (40%) in EDTA clearance. A significant 3.6-fold increase in clearance was obtained in response to perfusion of duodenum with deionized water. Similarly, perfusion with either 20 mM HCl or 50 mM ethyleneglycol-bis-(beta-amino-ethylether)-N,N'-tetraacetic acid (EGTA) significantly increased the EDTA clearance 3.3-fold and 2-fold respectively. Perfusion with a hypotonic HCl-solution (10 mM HCl + 40 mM NaCl) increased fluid absorption and the EDTA clearance. It is concluded that no positive linear relationship exists between luminal osmolality and 51Cr-EDTA movement across the mucosa. It is postulated that high luminal acidity or extreme hypotonicity increase the EDTA clearance by widening of and/or disruption of intercellular junctional structure.
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PMID:Characterization of 51Cr-EDTA as a marker of duodenal mucosal permeability. 195 98

Chemical and biological similarities of plutonium(IV) and iron(III) suggested that octadentate ligands containing hydroxamate or catecholate functional groups, which are found in microbial iron chelating agents (siderophores), would be effective and relatively selective complexing agents for actinide(IV) ions. However, their usefulness for in vivo chelation of actinide(IV) is limited, because catechol and hydroxamate are such weak acids that the potential for octadentate binding of actinide(IV) cannot be achieved at physiological pH. The structurally similar monoprotic and more acidic 1-hydroxy-2(1H)-pyridinone (1,2-HOPO) group was, therefore, incorporated into multidentate ligands. Treatment of 1,2-dihydro-1-hydroxy-2-oxopyridine-6-carboxylic acid (5) with phosgene in THF solution gives the active ester poly[1,2-dihydro-1,2-dioxopyridine-6-carboxylate], which upon treatment with excess anhydrous dimethylamine gave a 60% yield of N,N-dimethyl-1,2-dihydro-1-hydroxy-2-oxopyridine-6-carboxamide (6). A similarly reactive intermediate was prepared from 5 and an equimolar amount of phosgene in N,N-dimethylacetamide. Combined in situ with 1,3-propanediamine, benzylamine, spermine, spermidine, 1,3,5-tris(aminomethyl)benzene, or desferrioxamine B and excess triethylamine, the latter intermediate gave the corresponding amides in isolated yields ranging from 16% to 60%. The free ligands, their Zn(II) complexes, and the ferric complex of 3,4,3-LIHOPO were administered to mice [30 mumol/kg intraperitoneally 1 h after Pu(IV)-238 citrate, kill at 24 h]. Net Pu removal [Pu excretion (treated)-PU excretion (control)], expressed as percent of injected Pu, was as follows: Na salts and Zn(II) complexes, respectively, of 3-LIHOPO (54, 56), 3,4-LIHOPO (58, 60), 3,4,3-LIHOPO (73, 76); Na salts of MEHOPO (46), DFO-HOPO (78); Fe(III) complex of 3,4,3-LIHOPO (79). DFO-HOPO and 3,4,3-LIHOPO and its Zn(II) and Fe(III) complexes promoted significantly more Pu excretion than CaNa3-DTPA (61% of injected Pu). Preliminary findings on the acute toxicity of the poly(HOPO) ligands and HOPO monomers are presented in an appendix. The biological data indicate strongly that the aqueous solubility and relatively high acidity of the octadentate HOPO ligands, 3,4,3-LIHOPO and DFO-HOPO allow them to form complete eight-coordinate complexes with Pu(IV) ion.
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PMID:Specific sequestering agents for the actinides. 16. Synthesis and initial biological testing of polydentate oxohydroxypyridinecarboxylate ligands. 282 83

Mineralocorticoid plays a role in urinary acidification and acid-base balance, but the response of the inner medulla to aldosterone has not been elucidated. A model of selective aldosterone deficiency (SAD) with hyperkalemia and hyperchloremic metabolic acidosis was employed to assess segmental acidification by measuring in situ pH, titratable acidity (TA) and total ammonia (Am). Hydrogen ion secretion was also examined as a function of the increment in in situ PCO2 in the collecting duct during bicarbonate loading. SAD rats were compared to ADX controls that received adrenalectomy and chronic replacement of gluco- and mineralocorticoid and to rats with chronic metabolic acidosis induced by oral NH4Cl (CMA). Both fractional and absolute delivery of Am to the loop of Henle was lower in SAD vs. CMA rats (1.34 to 3.63 mM, P less than 0.01). Delivery of Am to the base and tip collecting duct (BCD and TCD) was also markedly lower in SAD (1.50 vs. 0.52 and 1.77 vs. 0.47 mM, respectively, P less than 0.01). Net addition of Am and net acid between BCD and TCD, observed in CMA rats, was not observed in SAD despite equivalent degrees of systemic metabolic acidosis. Similarly, the concentration gradient favoring transfer of NH3 between loop of Henle and CD was reduced in SAD. During bicarbonate loading the increment in PCO2 at BCD, TCD and in final urine was significantly lower in SAD rats than in adrenal intact bicarbonate-loaded rats. Therefore, the acidification defect in this model of SAD appears to be a result of a decrease in ammonia production and delivery to the loop of Henle, impaired transfer from loop to collecting duct and reduction in the rate of H+ secretion by the collecting duct.
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PMID:Effect of selective aldosterone deficiency on acidification in nephron segments of the rat inner medulla. 318 58

The effect of three aminoglycosides, gentamicin, netilmicin and amikacin, on renal acid excretion was studied in rats treated with doses equivalent to 10 times those used clinically. The gentamicin and amikacin groups showed a marked decrease (P less than 0.05), in glomerular filtration rate (GFR), U/P inulin ratio and renal plasma flow (RPF), while in the normal acid-base state. Under acidotic conditions, only gentamicin promoted significant alterations in GFR and RPF. Net acid excretion as measured by the acid balance (BH) was calculated as the sum of ammonium excretion (NH4+) and titratable acidity (AT) minus the amount of excreted bicarbonate (CHCO3-). Under normal conditions, netilmicin promoted a considerable fall in both NH4+ and AT, which led to a significant decrease in BH, whereas no changes were observed in these parameters with the other two drugs. In contrast, during acute metabolic acidosis, all tested antibiotics promoted a marked fall in BH, particularly due to a significant decrease in NH4+ and AT. These data suggest that the effects of aminoglycoside treatment during acute metabolic acidosis in clinical practice deserve further study in view of possible deleterious effects on the clinical state.
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PMID:Aminoglycosides and renal acid excretion. 359 8

Annual applications of (NH4)2SO4, NH4NO3 and urea on a Solonetzic soil at 112 kg N/ha for 10 consecutive years reduced pH levels from 5.6 for the check to 4.4, 4.9 and 5.3, respectively for (NH4)2SO4, NH4NO3 and urea. (NH4)2SO4 generated twice as much exchange acidity as NH4NO3 and four times as much as urea. Net extractable cations leached from the Ap horizon closely approximated the amount of exchange acidity generated by (NH4)2SO4 and NH4NO3 fertilizers. The levels of soil extractable Al and Mn were greatly enhanced by (NH4)2SO4 as were plant contents. Similar acidifying effects to that produced by the (NH4)2SO4 occurred when NH4NO3 was applied at 300 kg N/ha annually for 12 consecutive years in another field experiment on the same soil. Liming samples of the field (NH4)2SO4 acidified soils in the greenhouse, significantly increased yields and lowered the Al and Mn contents of the plants to normal levels.
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PMID:Acidification of a Solonetzic soil by nitrogenous fertilizers. 629 69

Macromolecules containing four sulfonated catecholy (2,3-dihydroxybenzoyl) groups are effective for decorporation of newly acquired Pu(IV). However, multiple injections in mice and single injections in dogs of 30 mumole/kg of 3,4,3-LICAM(S), the most effective sulfonated poly(catechoylamide) ligand, indicated that it would be toxic, so the ligand structure was modified. Each ligand was injected into mice (30 mumole/kg, intraperitoneally) 1 hr after an intravenous injection of 238Pu(IV) citrate, and mice were killed 24 hr after the Pu injection. Excreta and tissues were analyzed for Pu. (a) The number of catechoyl groups per molecule was reduced to suppress affinity for Fe(III). Net excretion (treated - control) of 55% of the injected Pu was promoted by tetrameric 3,4,3-LICAM(S), 51% by trimeric 3,4-LICAM(S), 22% by dimeric 2-LICAM(S), and 7.4% by the monomer, Tiron. (b) A mesitylene platform was substituted for the linear backbone. Net Pu excretion promoted by MECAM(S), a structurally less flexible trimer, was only 26%, and excretion was delayed. (c) A carboxyl substituent on the catechoyl groups reduced the acidity and hydrophilicity of the ligands. Tetrameric 3,4,3-LICAM(C) promoted 63% net Pu excretion, and one-third of that was fecal. The Pu contents of liver and skeleton were 33 and 44% of their respective 1-hr control values--compared to 51 and 44%, respectively, for CaNa3-DTPA. Mice given 30 mumole/kg of 3,4,3-LICAM(C) 20 times in 4 weeks showed no ill effects. (d) Large N-terminal alkane substituents added to 3,4,3-LICAM(C) increased ligand lipophilicity, hindered Pu chelation, and delayed excretion.
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PMID:Specific sequestering agents for the actinides: 10. Enhancement of 238Pu elimination from mice by poly(catechoylamide) ligands. 654 38

The STP-C488 oncogene of herpesvirus saimiri has transforming activity independent of the rest of the viral genome. Three distinct structural regions can be predicted from the STP-C488 sequence: an acidic amino terminal domain, a collagen domain, and a hydrophobic carboxyl-terminal domain. To study the importance and functional roles of these regions, 25 different mutant forms of STP-C488 were generated. Net negative charge in the 17 amino acid amino-terminal domain was found to be important for protein structure and transformation. Increasing the net negative charge decreased electrophoretic mobility and decreasing net negative charge increased electrophoretic mobility. The three glutamic acid residues and overall acidity in this region were found to be necessary to retain potent transforming activity. Interruption of the 18 collagen-like repeats in the central region also interrupted transforming activity. The hydrophobic region at the carboxyl terminus was found to be important for membrane localization. The acidic amino-terminal domain is likely to be the catalytic or ligand binding site of STP-C488.
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PMID:Distinct functional domains of STP-C488 of herpesvirus saimiri. 794 43

Net transepithelial transport (and cellular accumulation) of the dipeptide glycylsarcosine (Gly-Sar), across the apical membrane of human intestinal Caco-2 epithelia, is driven by a proton gradient (Na(+)-free conditions) and displays saturation kinetics (Km 17.4 +/- 5.1 mM, Vmax of 92.8 +/- 15.6 nmol.cm-2.h-1). Net Gly-Sar transport is associated with the stimulation of an inward short-circuit current (Isc). This dipeptide-stimulated Isc is observed in both Na(+)-containing and Na(+)-free conditions, is stimulated by apical acidity, and displays saturation kinetics (in Na(+)-free media at apical pH 6.0, Km of 13.6 +/- 4.5 mM and a Vmax of 284.1 +/- 39.3 nmol.cm-2.h-1). The maximal capacities of Gly-Sar transport and Isc suggest a dipeptide/proton stoichiometry greater than unity (1:3).
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PMID:Transepithelial dipeptide (glycylsarcosine) transport across epithelial monolayers of human Caco-2 cells is rheogenic. 827 76

Tobacco (Nicotiana tabacum L., cv. 'Coker 319') plants were grown for 28 days in flowing nutrient culture containing either 1.0 mM NO3- or 1.0 mM NH4+ as the nitrogen source in a complete nutrient solution. Acidities of the solutions were controlled at pH 6.0 or 4.0 for each nitrogen source. Plants were sampled at intervals of 6 to 8 days for determination of dry matter and nitrogen accumulation. Specific rates of NO3- or NH4+ uptake (rate of uptake per unit root mass) were calculated from these data. Net photosynthetic rates per unit leaf area were measured on attached leaves by infrared gas analysis. When NO3- [correction of NO-] was the sole nitrogen source, root growth and nitrogen uptake rate were unaffected by pH of the solution, and photosynthetic activity of leaves and accumulation of dry matter and nitrogen in the whole plant were similar. When NH4+ was the nitrogen source, photosynthetic rate of leaves and accumulation of dry matter and nitrogen in the whole plant were not statistically different from NO3(-) -fed plants when acidity of the solution was controlled at pH 6.0. When acidity for NH4(+) -fed plants was increased to pH 4.0, however, specific rate of NH4+ uptake decreased by about 50% within the first 6 days of treatment. The effect of acidity on root function was associated with a decreased rate of accumulation of nitrogen in shoots that was accompanied by a rapid cessation of leaf development between days 6 and 13. The decline in leaf growth rate of NH4(+) -fed plants at pH 4.0 was followed by reductions in photosynthetic rate per unit leaf area. These responses of NH4(+) -fed plants to increased root-zone acidity are characteristic of the sequence of responses that occur during onset of nitrogen stress.
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PMID:Effects of root-zone acidity on utilization of nitrate and ammonium in tobacco plants. 1153 85

To determine if the daily pattern of NO3- and NH4+ uptake is affected by acidity or NO3- : NH4+ ratio of the nutrient solution, non-nodulated soybean plants (Glycine max) were exposed for 21 days to replenished, complete nutrient solutions at pH 6.0, 5.5, 5.0, and 4.5 which contained either 1.0 mM NH4+, 1.0 mM NO3- [correction of NO3+], 0.67 mM NH4+ plus 0.33 mM NO3- (2:1 NH4+ : NO3-) [correction of (2:1 NH3+ : NO4-)], or 0.33 mM NH4+ plus 0.67 mM NO3- (1:2 NH4+ : NO3-). Net uptake rates of NH4+ and NO3- were measured daily by ion chromatography as depletion from the replenished solutions. When NH4+ and NO3- were supplied together, cumulative uptake of total nitrogen was not affected by pH or solution NH4+ : NO3- ratio. The cumulative proportion of nitrogen absorbed as NH4+ decreased with increasing acidity; however, the proportional uptake of NH4+ and NO3- was not constant, but varied day-to-day. This day-to-day variation in relative proportions of NH4+ and NO3- absorbed when NH4+ : NO3- ratio and pH of solution were constant indicates that the regulatory mechanism is not directly competitive. Regardless of the effect of pH on cumulative uptake of NH4+, the specific nitrogen uptake rates from mixed and from individual NH4+ and NO3- sources oscillated between maxima and minima at each pH with average periodicities similar to the expected interval of leaf emergence.
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PMID:Cyclic variations in nitrogen uptake rate of soybean plants: effects of pH and mixed nitrogen sources. 1153 44


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