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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Response of the fetal kidney to metabolic acidosis was studied in five fetal lambs, 115-125 days gestation, in order to evaluate the renal contribution to elimination of hydrogen ion during intra-uterine development. Experiments were conducted on healthy unanesthetized fetuses, intact in utero, with catheters implanted at hysterotomy into a fetal femoral artery and vein and into the bladder via the urachus, four or more days prior to the study. A metabolic acidosis was induced by infusion of isotonic lactic acid, 15 m mole/kg, intravenously over a period of 90 minutes. Serial arterial samples were taken and urine collected in fractions before, during and for three hours following the infusion, for measurements of pH, bicarbonate, lactate and electrolytes as well as urine output. During the infusion, urine pH fell from 6.65 to 6.25 and was 6.34 three hours later (Figs. 1 to 4, Tabs. III to IV). Lactic acid infusion caused a prompt increase in urine output from a mean rate of 0.12 to a maximum of 0.28 ml/kg/min at the end of the infusion, returning to control rates three hours later. Lactate excretion increased from 0.05 to a maximum of 4.6 mumole/kg/min at the end of infusion; titratable acid increased from 0.22 to a maximum of 4 muEq/kg/min; the rates of excretion of lactate and titratable acid were still higher than control at the end of three hours. Ammonia excretion increased from 0.21 to a maximum of 0.56 muEq/kg/min three hours after the end of infusion. The acid infusion caused a small but significant fall in excretion of bicarbonate. During the 90 minutes of infusion and over the following three hours, about 800 mumole lactate was excreted while net acid excretion over the same period was no more than half that amount. The diuresis was also accompanied by a net loss of sodium and chloride, the excretion of these ions increasing more than threefold following acid infusion; excretion of potassium decreased to one-third its rate prior to the infusion. During the 90 minutes of infusion, blood pH fell from 7.36 to 7.13, base deficit rose from 3.8 to 16.4 mEq/L and lactate rose from 2.2 to 14.8 mM/L; there was also a small but significant rise in both blood PCO2 and PO2 (Figs. 1 to 2, Tabs. I to II). During the following three hours of recovery, pH rose gradually to 7.29, base deficit and lactate fell to 7.4 mEq/L and 8.7 mM/L respectively. Since renal excretion of net acid and lactate was small, the decrease in blood base deficit and lactate levels during the recovery must therefore be mainly due to equilibration in various fetal compartments as well as placental transfer. These experiments indicate that, in the lamb fetus, intact in utero, the kidney although limited by immaturity of several mechanisms, is capable of responding to an acid load and thus can make a small contribution to fetal homeostasis. The increase in excretion of net acid is accompanied by loss of sodium and chloride in the urine.
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PMID:Renal response to acid loading in the developing lamb fetus, intact in utero. 0 Apr 79

Horse liver alcohol dehydrogenase was reacted with glyoxal at different pH values ranging from 6.0 to 9.0. At pH 9.0 the enzyme undergoes a rapid activation over the first minutes of reaction, followed by a decline of activity, which reaches 10% of that of the native enzyme. Chemical analysis of the inactivated enzyme after sodium borohydride reduction shows that 11 argi-ine and 11 lysine residues per mole are modified. At pH 7.7 the enzyme activity increases during the first hour of the reaction with glyoxal and then decreases slowly. Chemical analysis shows that 4 arginine and 3 lysine residues per mole are modified in the enzyme at the maximum of activation. At pH 7.0 the enzyme undergoes a 4-fold activation. Chemical analysis shows that in this activated enzyme 3 lysine and no arginine residues per mole have been modified. Steady-state kinetic analysis suggests that the activated enzyme is not subjected to substrate inhibition and that its Michaelis constant for ethanol is three times larger than that of the native enzyme. The possible role of arginine and lysine residues in the catalytic function of liver alcohol dehydrogenase is discussed.
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PMID:The reaction of horse-liver alcohol dehydrogenase with glyoxal. 0 Dec 46

The chemical composition of axoplasm extracted from the giant axon of Myxicola infundibulum has been analysed, and some of the factors which disperse its gel structure have been identified. 2. The axoplasm contains about 3-6% protein, and 0-12% lipid. It is isosmotic with sea water and has a pH near 7-0. 3. Inorganic ions in extracted axoplasm include: Na+, 13m-mole/kg wet wtl; K+, 280; Cl-, 24; Ca2+, 0-3; Mg2+, 3. 4. Free organic ions in axoplasm include: gly, 180 m-mole/kg wet st.; cysteic acid, 120; asp, 75; glu, 10; ala, 7; tau, 5; thr, 2; gln and ser, trace; homarine, 63; isethionate, 0. 5. The gel structure is dispersed by solutions containing 1--10 mM-Ca2+, because this ion activates an endogenous protease. The gel can also be dispersed without proteilysis by solutions containing 0-5 M-KCl, or 0-5 M guanidine hydrochloride, or 3-5 M urea, all of which break down neurofilaments. 6. It is argued that many aspects of the composition and dispersal properties of Myxicola axoplasm are similar to those in other axons.
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PMID:Axoplasm chemical composition in Myxicola and solubility properties of its structural proteins. 0 Dec 60

1. The effect of acute alterations of plasma sodium concentration (PNa) on renal sodium excretion (UNaV) was investigated by three types of experiments on anaesthetized dogs: (a) A local increase in PNa at one kidney was produced by infusion of hypertonic saline directly into its artery while systemic levels of PNa were stabilized by haemodialysis. (b) Systemic levels of PNa were lowered by exchange transfusion of blood for an equal volume of salt-free dextran-in-dextrose solution. The results were contrasted with those observed after similar exchanges, but using dextran-in-saline solution. (c) The level of PNa was altered by varying the sodium concentration of a saline solution infused at a fixed rate either intravenously or into one renal artery. 2. All three types of experiment suggest a dependence of UNaV on PNa Analysis demonstrated that this relationship was not due to contemporary changes in: packed cell volume; plasma solids concentration; plasma potassium concentration; blood pressure or plasma hydrogen ion concentration. The distribution of these variables did not change with PNa except for plasma hydrogen ion concentration. Moreover, the relationship persisted when data were selected to exclude clearance periods in which the value for any variable had shifted past the group mean obtained before PNa was altered. 3. The fall in UNaV at low levels of PNa could be attributed to a fall in glomerular filtration rate (GFR), but the progressive rise in UNaV seen as PNa exceeded 150 m-mole 1(-1) occurred despite a fall in GFR and no apparent change in the mean filtered load of sodium. These results suggest that the increased sodium excretion accompanying raised levels of PNa is due to reduced tubular re-absorption of sodium.
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PMID:Plasma sodium concentration and sodium excretion in the anaesthetized dog. 0 71

Preparations of the melanotropic-lipolytic peptide IIF from bovine choroid plexus contain 3% Ca, 1% Mg and less than 0.1% Na and K. Ca and Mg were removed by gel filtration on Sephadex G-10 in 1 N acetic acid. Capacity of the resulting cation-free peptide to bind Ca++, Mg++, Na+ and K+ was examined with the method of Hummel and Dreyer (Biochim. Biophys. Acta 63: 530-532, 1962). Peptide IIF bound a maximum of 3.7 to 4.4 mEq of Ca++, Mg++, Na+ or K+ per g of peptide. For each cation, linear Scatchard plot indicated one class of binding site. Association constants (liters per mole) were Ca++, 4.3 X 10(4); Mg++, 3.6 X 10(4); Na+, 4.8 X 10(2), K+, 1.9 X 10(2). Competitive binding experiments showed that all four cations occupied the same class of binding site.
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PMID:Cation-binding property of choroid plexus peptide IIF. 0 98

(-)-3/-Norepinephrine (3H-NE) binding to the microsomal fraction of the rabbit aorta has been studied. Binding appears to increase linearly with time up to at least 30 min, shows no evidence of stereoselectivity and may be inhibited only by compounds possessing the catechol or 3-methoxy-4hydroxyphenyl moieties, with the latter being 100-fold less effective. 3H-NE binding is saturable with a Km of 8.5 X 10(-8) M and V max of 28 pmoles/mg protein. A Hill plot indicates that binding is noncooperative whereas a Scatchard plot suggests that two sites may be present. Binding does not appear to require physiological concentrations of Ca2+ or Mg2+ and is inhibited significantly by EDTA and sodium metabisulfite. In addition, binding is markedly enhanced by low and high pH values. This binding is also inhibited by sodium metabisulfite which suggests that an oxidized form of the catecholamine is the active binding species. Experiments with several group specific reagents indicate that binding may require a free sulfhydryl group but not a carboxyl function. The binding process requires an energy of activation of 14.8 kcal/mole whose magnitude may be partly explained, with the aid of optical rotatory dispersion spectra, by a non-stereoslective conformational change in protein structure induced by the amine. The characteristics of the 3H-NE binding sites observed in the microsomal fractional of the rabbit aorta appear to be different from those expected if binding were to the adrenoreceptors. A possible mechanism for catecholamine binding to free sulfhydryl groups on protein is presented.
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PMID:A kinetic analysis of a catechol-specific binding site in the microsomal fraction from the rabbit aorta. 0 20

The effects of electrolytes on the self-association of the antihistaminic drugs, tripelennamine hydrochloride, thenyldiamine hydrochloride, pyrilamine maleate, pheniramine maleate, chlorpheniramine maleate, and brompheniramine maleate, in aqueous solution were examined by light-scattering from tripelennamine bydrochloride and thenyldiamine hydrochloride in 0.154 mole of sodium chloride/kg and 0.150 mole of sodium maleate/kg indicated a micellar pattern of aggregation. Higher aggregation numbers and lower CMC's were determined in the presence of the maleate ion. No significant discontinuity in the concentration dependence of the light scattering of the remaining compounds in either of the two electrolytes was evident, and the aggregation of these compounds was treated using a stepwise association model. Values of the association constants and the limiting number of associating species were, in general, increased by the addition of electrolyte in the order water less than sodium chloride less than sodium maleate. An apparently nonmicellar pattern of aggregation could be induced by chemically changing the counterion from chloride to maleate.
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PMID:Aggregation of antihistamines in aqueous solution: effect of counterions on self-association of pyridine derivatives. 0 28

The structure of polyguanylic acid (poly G) at neutral pH has been studied by optical and calorimetrical methods. It can be shown that diverging from earlier findings Poly G reversibly undergoes a cooperative thermal transition. Thermal denaturation curves are recorded at 253 nm as a function of the sodium ion concentration. The denaturation enthalpy of poly G in dilute aqueous solution is determined to 2.2 kcal/mole g. It is concluded, that the part of the ordered poly G structure, which gives rise to a temperature dependent cooperative transition, arises from stacking interactions of adjacent bases in the single strand.
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PMID:A calorimetric study of polyguanylic acid at neutral pH. 1 20

The alkaline phosphatase (orthophosphoric monoester phosphydrolase, EC 3.1.3.1) of Bacillus licheniformis MC14 was studied in an attempt to determine the number of subunits contained in the 120,000-molecular-weight native enzyme. Two moles of arginine was liberated per mole of native enzyme by carboxypeptidases A and B in the presence of sodium dodecyl sulfate. The effect on the native enzyme of progressively lowering the solvent buffer pH was monitored by determining the molecular weight by sedimentation equilibrium analysis, the sedimentation coefficient, the frictional coefficient, and the percent alpha-helix content of the enzyme. The alkaline phosphatase dissociates into two subunits around pH 4. At pH 2.8 a further decrease in S value, but no change in molecular weight, is observed, indicating a change in conformation. The frictional coefficients and percent alpha-helix content agree with this interpretation. A subunit molecular weight of 59,000 was calculated from sodium dodecyl sulfate gels.
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PMID:Subunits of the alkaline phosphatase of Bacillus licheniformis: chemical, physicochemical, and dissociation studies. 1 Feb 80

The defect in urinary acidification induced by amphotericin B (AMB) was further characterized in turtle bladder. Since AMB has been shown to increase the hydrogen ion (H+) permeability of this epithelium in the absence of exogenous bicarbonate ions (HCO3-), we explored the permeability characteristics in the presence of imposed bicarbonate ion gradients, comparable to those occurring in vivo. With mucosal (M) pH lowered to the point of zero net hydrogen ion secretion, the transepithelial flow of bicarbonate ions (JHCO3) from serosa (S) to M was 0.91 +/- .06 y mole/hr in response to a 20 mM HCO3- gradient. After AMB addition to M, back diffusion of hydrogen ions from M to S (-JH) increased from zero to 0.36+/-0.05 micronmole/hr, whereas bicarbonate ion transport from S to M (JHCO3) failed to increase (0.91+/-0.06 before and 0.82+/-0.09 micronmole/hr after AMB). In contrast to M addition, S addition of AMB had no effect on either -JH or JHCO3. The defect in urinary acidification induced by AMB is characterized by a large increase in the permeability for hydrogen ions rather than that for bicarbonate ions and depends on direct exposure of the luminal cell membrane to AMB. The permeability increase is cation selective, not only for hydrogen ions but also, as shown previously, for potassium ions, and to a lesser extent, for sodium ions. The results are consistent with the formation by AMB of aqueous half pores in the luminal membrane. Although the passive permeabilities for bicarbonate and chloride ions are not affected primarily, they may increase after prolonged exposure, probably as a results of paracellular leaks that are not specific for AMB.
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PMID:Acidifying defect induced by amphotericin B: comparison of bicarbonate and hydrogen ion permeabilities. 1 60


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