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PubMed2002

Divalent cations reduce the electrogenic transport of monovalent cations across rumen epithelium.

The rumen epithelium of sheep and goats showed an increase in short circuit current ( Isc) and transepithelial conductance (gt) upon mucosal removal of divalent cations. A divalent-sensitive Isc and gt were present in Na+, K+ or Rb+ buffer, but nearly abolished in mucosal NMDG+ (N-methyl-D-glucamine) buffer. High K buffer, addition of BaCl2 or of ouabain on the serosal side also reduced or abolished the divalent-sensitive Isc. Mucosal Ca2+ was more potent in blocking Isc, but had the same potency as Mg2+ in blocking gt. A prolonged mucosal deprivation of Mg2+ ions increased gt, potential difference and basal as well as the Ca2+-sensitive Isc. Mucosal addition of Mg2+ had a smaller effect on gt after serosal preincubation with Ba. The data suggest that rumen epithelial cells exhibit an apical non-selective cation conductance, which permits the passage of monovalents in the mucosal absence of divalents. The development of a divalent-sensitive Isc in Na buffer requires Na+/K+ pumps and K+ recycling through Ba2+-sensitive K+ conductances on the basolateral side. This Isc is blocked by extracellular Ca2+ and both extracellular and intracellular Mg2+ ions. A prolonged deprivation of mucosal Mg2+ alone seems to affect intracellular Mg2+ in this Mg2+-absorbing tissue.

Animals↗
PubMed2001

Air insufflation: a useful adjunct to the single contrast barium enema for the evaluation of the rectum.

We examined whether insufflation of a small volume of air after a single-contrast barium enema would improve evaluation of the rectum. Eighty patients presenting for barium enema by single-contrast technique underwent examination of the colon including spot films with fluoroscopy and palpation during introduction of the barium and filled overhead views, using standard apparatus and technique. The examination was completed by draining barium from the rectum only, following which air in the barium enema bag was squeezed back into the rectum and three views of the rectum obtained (lateral, left posterior oblique, and frontal). Two reviewers then chose the best image of the rectum from each study with relevance to luminal distention and visibility of surface detail of the rectum. Following air insufflation, improved surface detail visualization was recognized by both reviewers in 69 (86%) patients and by one reviewer in 10 (12%) patients, a statistically significant observation (P < 0.0001). There was a trend towards improved rectal distention, recognized by both reviewers in 37 (46%) patients and by one reviewer in 18 cases (22%). In 25 (31%) patients neither reviewer recognized any improvement in rectal distention. Rectal abnormalities were identified in nine cases; there were two large carcinomas, two radiation strictures, two rectal fistulae, two small rectal polyps (5 and 7 mm), and one case of prolapsing rectal mucosa. All rectal abnormalities were visible on the air insufflation views. In the two cases of suspected rectal polyp and one of the cases of rectal fistula, the findings were not visible on the initial barium filled views. A normal rectum was observed in 71 cases. Follow-up of these 71 patients found no later evidence of any rectal abnormalities. Improved filling of the proximal colon following air insufflation was observed in 12 (15%) patients, an additional and unexpected benefit of this maneuver. Air insufflation is a simple addition to the SCBE study that improves visualization of the rectum.

Adult↗
PubMed2001

The role of mechanical bowel preparation for colonic resection and anastomosis: an experimental study.

BACKGROUND AND AIMS: To evaluate the effect of mechanical bowel preparation (MBP) on colonic resection and anastomosis. PATIENTS AND METHODS: Mongrel dogs were divided into two groups of 20 animals each. During the preoperative period (24 h) group A was not subjected to MBP, and group B was fasted and ingested 20 ml magnesium hydroxide plus 15 ml/kg 10% mannitol orally. All animals underwent segmental colectomy followed by end-to-end anastomosis. The survivors of both groups were reoperated upon on the 7th postoperative day. RESULTS: Mortality before reoperation was significantly higher in group A (45%) than in group B (10%; P<0.05). Upon reoperation on surviving animals the incidence of localized anastomotic leakage, leakage with peritonitis, and healed anastomoses was 72.72%, 9.09%, and 18.8% in group A, and 66.66%, 22.22%, and 11.11% in group B, respectively (P>0.05). Aerobic and anaerobic bacterial cultures showed similar growth in the two groups. CONCLUSION: We conclude that the omission of MBP increased the mortality due to early anastomotic leakage with peritonitis; MBP did not change the rate of localized anastomotic leakage, leakage with peritonitis, or intact anastomoses on the 7th day; no quantitative or qualitative differences were observed in the bacteria isolated from the two groups.

Administration, Oral↗
PubMed2005

Expression of the human erythroid Rh glycoprotein (RhAG) enhances both NH3 and NH4+ transport in HeLa cells.

The erythroid Rh-associated glycoprotein (RhAG) is strictly required for the expression of the Rh blood group antigens carried by Rh (D,CE) proteins. A biological function for RhAG in ammonium transport has been suggested by its ability to improve survival of an ammonium-uptake-deficient yeast. We investigated the function of RhAG by studying the entry of NH3/NH4+ in HeLa cells transiently expressing the green fluorescent protein (GFP)-RhAG fusion protein and using a fluorescent proton probe to measure intracellular pH (pHi). Under experimental conditions that reduce the intrinsic Na/H exchanger activity, exposure of control cells to a 10 mM NH4Cl- containing solution induces the classic pHi response profile of cells having a high permeability to NH3 (PNH3) but relatively low permeability to NH4+ (PNH4). In contrast, under the same conditions, the pHi profile of cells expressing RhAG clearly indicated an increased PNH4, as evidenced by secondary reacidification during NH4Cl exposure and a pHi undershoot below the initial resting value upon its removal. Measurements of pHi during methylammonium exposure showed that RhAG expression enhances the influx of both the unprotonated and ionic forms of methylammonium. Using a mathematical model to adjust passive permeabilities for a fit to the pHi profiles, we found that RhAG expression resulted in a threefold increase of PNH4 and a twofold increase of PNH3. Our results are the first evidence that the human erythroid RhAG increases the transport of both NH3 and NH4+.

Ammonia↗
PubMed2000

Role of potassium channels in the control of renin secretion from isolated perfused rat kidneys.

This study aimed to assess the relevance of specific potassium channels, such as inwardly or outwardly rectifying and calcium-regulated potassium channels, to the control of renin secretion. For this purpose we examined the effects of the K+ channel blockers 4-aminopyridine (1 mmol/l), barium (100 micromol/l), tetraethylammonium (2 mmol/l) and apamin (200 nmol/l) on basal renin secretion, on renin secretion stimulated by isoproterenol (10 nmol/l) and on the inhibition of renin secretion by angiotensin II (100-300 pmol/l) in the isolated rat kidney perfused at constant pressure. Whilst all four K+ channel blockers increased renal vascular resistance, only 4-aminopyridine and barium attenuated isoproterenol-stimulated renin secretion in an additive fashion and augmented the inhibitory effect of angiotensin II. These effects of K+ channel blockers were not changed by the L-type calcium channel blocker amlodipine (5 pmol/l), indicating that their effects on renin secretion are not due to voltage-operated calcium influx. Our data, moreover, suggest that potassium efflux from renal juxtaglomerular cells is not important for the inhibitory action of angiotensin II on renin secretion. As a consequence it appears that the membrane potential of renal juxtaglomerular cells per se is relevant to renin secretion such that membrane depolarization inhibits the exocytosis of renin whilst hyperpolarization favors renin secretion. By their activity, potassium channels can contribute to membrane hyperpolarization and thus facilitate renin secretion.

4-Aminopyridine↗
PubMed1998

Possible Ca2+-dependent mechanism of apical outer hair cell modulation within the cochlea of the guinea pig.

Calcium ions were precipitated with potassium antimonate after injection of the inorganic calcium channel blocker MnCl2 or the inorganic potassium channel blockers BaCl2 or CsCl into the perilymph of the scala vestibuli of the guinea pig. The spatial distribution of the formed histochemical reaction products within the organ of Corti was studied by energy-filtering transmission-electron microscopy. Compared with untreated control ears, the number of the formed precipitates drastically increased at the extracellular side of the lamina reticularis after application of the various inorganic channel blockers. The apical side of the outer hair cells and the intervening Deiter cells were covered by a thick layer of calcium precipitates, whereas the number of histochemical reaction products was clearly reduced in the nearby acellular tectorial membrane. The high calcium content within the formed reaction products at the lamina reticularis could be demonstrated by elemental mapping and by electron energy-loss spectroscopy. To ascertain the alterations in the amounts of the calcium precipitates within the tectorial membrane after application of the various inorganic channel blockers, the precipitate densities were determined semiquantitatively by an image processing system and the values obtained compared with those of untreated control specimens. The observed histochemical results are in good agreement with published electrophysiological findings concerning the spatial distribution of ion channels located at the apical outer hair cell membrane. The detected alterations in the spatial distribution of calcium precipitates might correspond to calcium-dependent processes involved in outer hair cell modulation.

Animals↗
PubMed1983

Differential sensitivity to angiotensin II in pregnant rabbits.

Threshold concentrations for angiotensin II and barium chloride were determined in the perfused hind limb of the nonpregnant, pseudopregnant, and pregnant rabbit. The threshold concentration for these vasoconstrictors was defined as the amount of drug per milliliter of hind limb blood flow which would increase hind limb blood pressure by 4 mm Hg. There was no difference in the mean angiotensin II threshold concentration between the nonpregnant and pseudopregnant rabbits. The angiotensin II dose for the pregnant rabbits was double that of the first two groups. There was no significant difference in the mean barium chloride threshold concentration between the three groups. This difference in the pregnant angiotensin II threshold concentration with no difference in barium chloride threshold concentration indicates a change in vascular sensitivity which is dependent upon a specific angiotensin II-receptor interaction and is not inherent in the contractile response of the vessel, nor is it mimicked by pseudopregnancy.

Angiotensin II↗
PubMed1986

High-performance liquid chromatography and ultraviolet spectrophotometry for quantitation of tryptophan in barytic hydrolysates.

A procedure for quantitation of tryptophan in feedstuffs is described. It is based on barytic hydrolysis of material at 125 degrees C for 16 h, acidification of hydrolysate to pH 3 with HCl, high-performance liquid chromatography on Nova Pak C18 (Waters Assoc.), and spectrophotometric determination of tryptophan at 280 nm. The recovery of tryptophan from lysozyme added to samples ranges from 98.7 to 100%.

Barium↗
PubMed1986

Identification of tyrosine O-sulfate in proteins by reverse-phase high-performance liquid chromatography: use of base hydrolysis combined with precolumn derivatization using phenyl isothiocyanate.

A procedure has been developed for the analysis of tyrosine O-sulfate in proteins. Samples are subjected to base hydrolysis with Ba(OH)2, neutralized with sulfuric acid, and the majority of other amino acids removed by chromatography on Dowex AG 50 X 8. The average recovery of tyrosine O-sulfate from these procedures was 43%. Tyrosine O-sulfate was identified by reverse-phase HPLC as the phenylthiocarbamyl derivative following precolumn derivatization with phenyl isothiocyanate. The method has been applied to bovine fibrinogen giving a tyrosine O-sulfate content ranging from 0.59 to 1.23 mol/mol. These procedures were also shown to be suitable for the analysis of the incorporation of [35S]sulfate into tyrosine O-sulfate residues in proteins by intact cells.

Animals↗
PubMed1988

Removal of dodecyl sulfate from protein solution.

Sodium dodecyl sulfate is one of the most widely used detergents. But, there is no good method to remove dodecyl sulfate (DS) from a small volume of protein solution. We showed that (a) DS in protein solution was removed by the addition of potassium salts with high recovery of protein, and (b) the method was useful before tryptic digestion of protein.

Barium↗
PubMed1992

Identification of muscarinic acetylcholine receptors in isolated canine lingual epithelia via voltage clamp measurements.

Acetylcholine (ACh), muscarine and methacholine all decreased the short-circuit current (Isc) measured across isolated canine lingual epithelia bathed in symmetrical solutions of Krebs-Henseleit buffer when added to the serosal, but not mucosal, solutions. Atropine inhibited the ACh-induced decrease in Isc whereas serosal solutions of 1 mM hexamethonium or 1 mM nicotine did not. Addition of a membrane-permeable analogue of cAMP also reduced Isc and, in the presence of this analogue, the decrease in Isc produced by ACh was markedly reduced. These data suggested the presence of muscarinic acetylcholine receptors in the serosal membranes of isolated canine lingual epithelia. The decrease in Isc induced by ACh may involve the inhibition of Ba(2+)-inhibitable K+ currents, as the addition of 100 microM BaCl2 to the serosal solution inhibited Isc and also completely inhibited the response produced by ACh. These findings suggest that responses of sensory fibres in lingual epithelia elicited by ACh may involve an interaction of ACh with epithelial cells rather than a direct interaction of ACh with receptors on sensory nerves.

Acetylcholine↗
PubMed1981

Ion transport through hemocyanin channels in oxidized cholesterol artificial bilayer membranes.

Incorporation of molluscan hemocyanins, obtained either from the blood of Megatura crenulata or Paludina vivipara, into oxidized-cholesterol black lipid films results in the formation of ionic channels. Channel conductance depends on the type of electrolyte present, ranging in our experiments from about 20 to 500 pS. It rises in a non-linear way as the salt concentration is increased, showing a saturation effect. An observed pH dependence of channel conductance suggests that there is a negative fixed charge associated with the pore. We discuss a model based on a simplified form of the Gouy-Chapman theory of the electrified double layer to explain the experimental results.

Animals↗
PubMed1990

Polarized 86Rb+ effluxes in primary cultures of rabbit kidney proximal cells: role of calcium and hypotonicity.

Isolated proximal cells from rabbit kidney were seeded on collagen-coated permeable supports. After 8 days, the cultured cells became organized as a confluent monolayer. The proximal origin of the monolayer was confirmed by enzymatic, immunological, electrical and electron microscopical studies. The epithelia exhibited a morphological polarity that allowed for measurements of effluxes across the apical or the basolateral membranes. 86Rb was used as an isotopic tracer to indicate potassium movements. The 86Rb+ efflux across the basolateral face was 1.93-times that across the apical face, and both effluxes were pH dependent. Apical and basolateral 86Rb+ effluxes increased when the Ca2+ ionophore ionomycin (3 microM) was applied and when monolayers were exposed to a hypotonic medium. A pharmacological study revealed that BaCl2 (5 mM), tetraethylammonium (TEA, 20 mM) and Leiurus quinquestriatus hebraeus scorpion venom (from which charybdotoxin is extracted) abolished both ionomycin and hypotonically-stimulated effluxes, whereas apamin had no significant effect on the hypotonically-stimulated 86Rb+ efflux. This stimulated efflux was also abolished when monolayers were preincubated with pertussis toxin, but did not decrease in a Ca2(+)-free medium.

Animals↗
PubMed1991

Regulatory volume decrease in small intestinal crypts is inhibited by K+ and Cl- channel blockers.

Total crypt volume has been estimated by analysis of photographic images of intact viable crypts isolated from guinea-pig small intestine. Exposing these crypts to a hypotonic medium, led to transient swelling followed by regulatory volume decrease (RVD) in 12-20 min. RVD was blocked by inhibitors of K+ and Cl- conductance, suggesting that it occurs by activation of K+ and Cl- permeability pathways and loss of these ions.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1992

Different patterns of cell volume regulation in hyposmotic media between attached and suspended HeLa cells.

Both attached and suspended HeLa cells swelled in a medium of a hypotonic osmolality of 235 mosmol/kg H2O. When the osmolality was further decreased to 166 mosmol/kg H2O, attached cells instantly swelled and then rapidly lost water and K+, followed by slow gains of them. Suspended cells instantly swelled and then K+ loss and regulatory volume decrease (RVD) occurred. Neither 0.1 mM ouabain nor 10 mM TEA changed the water loss of attached cells, whereas ouabain inhibited RVD of suspended cells. Quinine (1 mM) inhibited water losses from both cells and comparison of the losses implies stronger activation of K+ channel in attached cells than in suspended cells. Omission of medium Ca2+ or addition of 10 mM BaCl2 inhibited RVD in part. These results suggest that hyposmotic stress induces net water loss from attached cells, associated with K+ release through the Ca(2+)-dependent K+ channel. Suspended cells osmotically swell, followed by RVD with K+ and Na+ releases through the K+ channel and Na(+)-pump, respectively. The different patterns of volume changes may relate to the difference of activity or time of activation of the K+ channel between both cells.

Barium↗
PubMed1995

Effect of protein synthesis inhibitors on synexin levels and secretory response in bovine adrenal medullary chromaffin cells.

The effects of the protein synthesis inhibitors actinomycin D and cycloheximide on the cellular content of the calcium binding protein synexin, and on the secretory response of cultured bovine adrenal medullary chromaffin cells were determined. Both protein synthesis inhibitors produced a slow decrease in the cellular synexin content. The synexin level was reduced by 50% after 133 h of incubation in the presence of 2 micrograms/ml actinomycin D or 5 micrograms/ml cycloheximide. However, this was partly due to an artefactual stabilization of synexin, since metabolic labelling of synexin with [35S]methionine showed that the half-time of degradation was only 40 h. The secretory response of chromaffin cells was quickly diminished in the presence of protein synthesis inhibitors. Catecholamine secretion induced by membrane depolarization or barium stimulation of intact cells, or by calcium stimulation of digitonin-permeabilized cells was decreased by 77-82% after 24 h of incubation in the presence of 5 micrograms/ml cycloheximide. These results suggest that, in addition to synexin, at least one or more proteins with a shorter half-time of degradation than synexin are involved in the secretory response of adrenal chromaffin cells.

Adrenal Medulla↗