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

The ratio of Cl- absorbed to HCO3- secreted by the in vitro small intestine of Amphiuma was measured using 36Cl and titration. The aim was to estimate the stoichiometry and thereby elucidate the underlying transport mechanisms. For every mole of HCO3- secreted 1.8 mol of Cl- underwent net absorption. Indirect measures of net Cl- absorption and HCO3- secretion were validated. Several known and putative Cl- transport inhibitors were examined for their ability to inhibit the anion transport events. Disulfonic stilbenes [4-acetamido-4'-isothiocyanostilbene-2',2'-disulfonic acid and 4,4'-diisothiocyano-2,2'-disulfonate stilbene (DIDS)] and the diuretics piretanide and furosemide inhibited the Cl- absorptive flux (JClm----s) and simultaneously the HCO3- secretory flux (JHCO3-). The diuretics acetazolamide and bumetanide also reduced JHCO3- and JClm----s, although the latter effect was not statistically significant. The ratio of inhibition, delta JClm----s/delta JHCO3-, varied from 1.2 to 1.8 for the different inhibitors. The presence of Cl(-)-HCO3- exchange at the serosal membrane was deduced from the reduction of JClm----s and JHCO3- by serosally added stilbenes, the reduction of Cl- absorption when serosal Cl- was replaced (reduced Cl(-)-Cl- exchange), inhibition of the secretory-to-mucosal Cl- flux by serosal stilbenes, and enhancement of JHCO3- when serosal medium HCO3- was elevated. Addition of DIDS to the mucosal medium did not alter the secretory flux. The observations are not consistent with one-for-one exchange of Cl- for HCO3- at the mucosal membrane. Other possible mechanisms including rheogenic Cl- uptake in parallel with electrodiffusional efflux of HCO3- are discussed. The observed coupling ratio is compatible with a one-for-one exchange of Cl- for HCO3- at the serosal membrane.
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PMID:Evidence against luminal one-for-one Cl(-)-HCO-3 exchange in urodele small intestine. 242 71

Bioactive cellulose derivatives have been synthesised by coupling enzymes/antibiotics on carboxymethyl cellulose acid chloride and cellulose carbonate. The effect of pH and temperature on the enzymatic activity of amyloglucosidase immobilised on cellulose carbonate was studied. Michaelis-Menten kinetics have been obeyed to the first degree of approximation despite the restricted mobility of the attached enzyme on the polymer support. Lineweaver-Burk plots for the amyloglucosidase immobilized on carboxymethyl cellulose acid chloride at ambient pH with cellulose carbonate at pH 8 have also been plotted. The Michaelis-Menten constant for the immobilized amyloglucosidase on cellulose carbonate at pH 8 was 9.1 mM, and the activation energy for starch hydrolysis was 21.8 kcals/mole.
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PMID:Biologically active polymer supports based on cellulosic derivatives: synthesis and kinetic study. 277 23

The urine composition of three rodent species, mole rat Spalax ehrenbergi, the golden hamster Mesocricetus auratus and the white rat Rattus norvegicus was studied. These three species represent different degrees of fossoriality. The results show that the urine of the species that show a higher degree of fossoriality, the mole rat and the hamster, contain high values of calcium and magnesium bicarbonates when compared with the white rat. From these results it may be assumed that the mole rat as well as the hamster can use the kidney as a pathway for releasing bicarbonate and carbonate. This mechanism may reduce the CO2 concentration in their hypercapnic environment.
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PMID:Urine analysis of three rodent species with emphasis on calcium and magnesium bicarbonate. 285 37

A new method of purification of rat liver L-threonine deaminase has been developed, and the results obtained are compared with values obtained by other authors. Some properties of this enzyme (pH optimum, temperature optimum, thermal stability, specificity, etc.) have been examined and we found that the enzyme is inhibited by carbonate ions, that L-cysteine (a competitive inhibitor) is also an inactivator of the enzyme and that it is bound to the enzyme in a ratio of 0.25 mole of cysteine per mole of enzyme, supporting the hypothesis that the enzyme consists of 4 subunits.
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PMID:Rat liver L-threonine deaminase: properties and purification. 392 53

1. The carbamate (HbCO(2)) concentration in oxygenated and deoxygenated human adult and foetal red blood cells was estimated at a constant pressure of carbon dioxide (P(CO2) = 40 mm Hg) and various pH values of the serum. The Donnan ratio for chloride and bicarbonate ions was used to calculate the bicarbonate concentration in the red cells. With this figure the carbamate concentration was calculated as follows:[HbCO(2)] = [Total CO(2)] - [HCO(-) (3)] - [dissolved CO(2)].2. At a given pH value in the red cell deoxygenated foetal red cells contain more HbCO(2) than deoxygenated adult ones. Upon oxygenation (at constant pH) HbCO(2) drops in both types of erythrocytes to lower values than in deoxygenated cells. The fraction of ;oxylabile carbamate' (-DeltaHbCO(2)/DeltaHbO(2)) at a red cell pH of 7.2 and a P(CO2) of 40 mm Hg is 0.117 in foetal and 0.081 in adult erythrocytes.3. From the fraction of moles carbamate formed per Hb monomer (moles CO(2)/mole Hb(i)) K'(c) and K'(z), the apparent carbamate equilibrium constants were calculated which can be used to estimate the carbamate concentration in normal adult and foetal blood.4. The first apparent dissociation constant of carbonic acid is significantly higher in oxygenated (-log(10)K'(1) = pK'(1) = 6.10) than in deoxygenated (pK'(1) = 6.12) adult red cells, whereas in foetal red cells the difference is smaller and statistically not significant.5. For a given set of physiological conditions in arterial and mixed venous blood in respect to oxygen saturation, P(CO2) and pH, the fractional contribution of carbamino compounds of haemoglobin to the amount of carbon dioxide which is exchanged during the respiratory cycle was computed on the basis of the present results and found to be 10.5% in adult and 19% in foetal blood.
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PMID:Carbamino compounds of haemoglobin in human adult and foetal blood. 464 57

1. The cyst wall of Colpoda steinii has been isolated and its chemical nature examined. It had a nitrogen content 13.9+/-0.2% (s.d.) and an ash 8.6+/-1.6% (s.d.). After lipid and hot-acid extraction there was a variable residual phosphorus of 0.19-0.64%. The protein nature, indicated by infrared and ultraviolet absorption, was confirmed when 100mug. of hydrolysed wall gave a ninhydrin colour equivalent to that given by 0.88-1.01mumoles of glycine. Hexosamine, hexose, pentose, lipid and dipicolinic acid were absent. 2. Paper chromatography of hydrolysates, besides showing the presence of the usual protein amino acids and three unidentified ninhydrin-reacting spots, indicated the presence of large amounts of glutamic acid. Estimated by chromatography, the amount present was 52.9+/-0.6 (s.d.) g./100g. of ash-free wall; manometric estimation of l-glutamic acid with l-glutamate 1-carboxy-lyase gave 46.5+/-0.9 (s.d.) g./100g. 3. Free carboxyl groups were estimated by titration as 0.159+/-0.011 (s.d.) mole/100g. and those present as amide as 0.154+/-0.004 (s.d.) mole/100g., and the total was compared with the dicarboxylic acid content 0.360+/-0.010 (s.d.) mole/100g. 4. After treatment with 98% formic acid 25-30% of the wall material could be extracted by 0.05m-sodium carbonate solution (extract 1); after treatment of the residue with performic acid a further 62-63% based on the original weight could be extracted by 0.05m-sodium carbonate (extract 2). 5. The average values found for the glutamic acid contents were 21.7g./100g. for extract 1 and 58.0g./100g. for extract 2. The cysteic acid content of whole oxidized wall was about 5.8g./100g. and of extract 2 also about 5.8g./100g. The glutamic acid and cysteic acid contents of the final residue were also investigated. 6. The significance of these extraction experiments in relation to the wall structure is discussed.
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PMID:The cyst wall of Colpoda steinii. A substance rich in glutamic acid residues. 495 13

1. Liquid-fed calves (aged 1(1/2)-4 months) examined more than five weeks after inserting a re-entrant fistula into the distal ileum, of normal sodium and potassium status and without abnormal gut infection, showed mean emergence rates from the ileum for sodium, potassium and water of 2.3 m-mole/hr, 0.38 m-mole/hr and 21 g/hr respectively after 16 hr fasting.2. Sodium and potassium emergence rates changed little when the residues from a milk or glucose-solution feed arrived at the distal ileum. When magnesium chloride was added to a glucose-solution feed an increase sometimes occurred but only in association with decreased small-intestine transit time.3. Widely differing sodium and potassium intakes had no appreciable direct effect on their emergence rates. Continued feeding of a diet deficient in either ion, however, altered the calf's metabolism and led to appropriate changes in the sodium/potassium ratio of ileal effluent. These changes were not simulated by injecting adrenal cortex hormones. The ratio also decreased when ileal effluent was allowed to discharge for several weeks without being returned to the colon. It was abnormally high in samples obtained less than five weeks after inserting cannulae.4. An increase in sodium and potassium emergence rates, which often occurred spontaneously at about 3 months of age, appeared to be due to infection and was usually prevented by giving aureomycin orally.5. Water emergence rate reflected changes in the emergence rates of osmotically effective constituents and isotonicity was maintained. In effluent after fasting, the cations involved were mainly sodium and potassium, and [Na] + [K] was approximately constant (mean 132 m-mole/l.). In effluent following feeds of milk or glucose, magnesium chloride solution, [Na] + [K] was depressed and [Na] + [K] + 1.5 [Mg] was approximately constant (mean 139 m-mole/l.). Magnesium behaved as it were mainly ionic. Calcium had no apparent osmotic effect and was probably insoluble.6. Bicarbonate was the major anion in ileal effluent after a milk feed with smaller amounts of chloride, phosphate and some other unknown anion(s).
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PMID:Mineral composition and rates of flow of effluent from the distal ileum of liquid-fed calves. 591 55

Mannitol might inhibit paracellular reabsorption of water and sodium chloride in the proximal tubules by reducing the osmotic driving force. We examined this hypothesis in anesthetized dogs. Bicarbonate reabsorption was kept constant by sodium bicarbonate infusion, and transcellular sodium chloride reabsorption was inhibited by ethacrynic acid. The glomerular filtration rate (GFR) was varied by altering renal perfusion pressure. Mannitol infusion reduced sodium chloride reabsorption from 62 +/- 5% to 33 +/- 5% of the filtered load. The calculated increase in reabsorbate osmolality, averaging 82 +/- 6 mOsm/kg H2O, was due to sodium bicarbonate and equalled the increase in plasma osmolality. Mannitol concentration averaged 81 +/- 7 mM in plasma and 101 +/- 12 mM in urine. A linear relationship between reabsorption and GFR (glomerulo-tubular balance) was maintained over the same range of GFR before and after mannitol infusion. Mannitol infusion reduced sodium chloride reabsorption from 2.6 to 1.4 moles for each mole of sodium bicarbonate reabsorbed. During mannitol infusion, acetazolamide inhibited sodium bicarbonate reabsorption as in control experiments, but reduced sodium chloride reabsorption less. We conclude that reduced water reabsorption increases sodium bicarbonate concentration in the paracellular fluid as much as mannitol concentration is raised in the plasma and glomerular filtrate. Along the proximal tubules, net osmotic force is progressively reduced as mannitol concentration rises, accounting for reduced water and sodium chloride reabsorption.
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PMID:Mechanism of osmotic diuresis. 626 98

Periodate treatments of apo human serum transferrin (HST), and apo chicken ovotransferrin (COT) were previously reported to cause a rapid loss of Fe+3 binding capacity, with a loss of 3 to 5 tyrosine residues [P. AZARI AND J. L. PHILLIPS (1970) Arch. Biochem. Biophys. 138, 32-38; K. F. GEOGHEGAN, J. L. DALLAS, AND R. E. FEENEY (1980) J. Biol. Chem. 255, 11429-11434]. The effects of periodate and hydrogen peroxide on human lactotransferrin (HLT), HST, and COT have been compared. All three apotransferrins were rapidly inactivated and lost approximately 4 to 5 tyrosine residues by 5 mM periodate treatment; their iron complexes had little or no inactivation and losses of approximately 1 to 2 tyrosine residues. All three iron transferrins were highly resistant to inactivation by 5 mM periodate in bicarbonate, with or without the addition of phosphate, while in phosphate (with ambient carbonate) Fe2HLT was highly resistant, Fe2COT slightly less resistant, and Fe2HST much less resistant. Similar oxidations of methionines to the sulfoxides were found in both the apo and iron forms. After 150 min of 5 mM periodate treatment HST lost approximately 3 (apo 3.1, iron 2.8) of 9, HLT approximately 3 (apo 2.6, iron 2.9) of 6, and COT approximately 7 (apo 7.2, iron 7.2) of 11 methionines per mole of protein. In the presence of 8 M urea HST had essentially all of its methionine residues oxidized by periodate, but only lost part of its activity on renaturation. Treatment of all apo transferrins with 300 mM hydrogen peroxide resulted in little or no losses (less than 10%) in activity. HST lost approximately one-third of its methionines and no tyrosines during the 300 mM hydrogen peroxide treatment. Therefore the essentiality of tyrosines for all three transferrins was confirmed and the nonessentiality of methionines was demonstrated.
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PMID:Comparative oxidations of tyrosines and methionines in transferrins: human serum transferrin, human lactotransferrin, and chicken ovotransferrin. 631 90

The interaction between bovine lactoferrin (bLf) and ascorbate (Asc) was investigated through malondialdehyde (MAD) formation in a solution containing DNA, bleomycin (BLM), and Fe2+ or Asc. The inhibition by bLf on MDA formation in the presence of Asc was not changed even by adding carbonate or oxalate ions to the solution. The percentage inhibition by the hydrolysates of bLf treated with pepsin, trypsin, and both enzymes on MDA formation was almost the same as that by the untreated bLf in the presence of Asc. The inhibition of MDA formation also occurred with the filtrate obtained from a solution containing bLf and Asc, but not with that from a solution of bovine serum albumin and Asc. The interaction of bLf and Asc was observed by gel filtration in a Sephadex G75 column. The binding amount of Asc was estimated to be 87 mol per mole of bLf.
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PMID:Interaction of lactoferrin with ascorbate and the relationship with bleomycin-dependent DNA damage. 753 54


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