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E Mack

Publications and source records attributed to E Mack.

At least 19 recordsLinked to original sources
PubMed1992

Volume-activated calcium uptake: its role in cell volume regulation of Madin-Darby canine kidney cells.

Immediately after osmotic swelling of Madin-Darby canine kidney (MDCK) cells, a transient (1-2 min) increase in Ca2+ influx and internal Ca2+ (Ca2+i) is observed. The normal Ca2+ influx appears to be mediated by the 3Na(+)-Ca2+ exchange system [Borle et al. Am. J. Physiol. 259 (Cell Physiol. 28): C19-C25, 1990], but the swelling-induced component is different in 1) Na+ dependence, 2) affinity for Ca2+, 3) inhibition by La3+, and 4) direction of net flux at low external Ca2+. Swelling appears to activate an uncoupled Ca2+ flow, perhaps through cation-nonspecific stretch-activated channels. The regulatory volume decrease (RVD) is dependent on the swelling-induced pulse of Ca2+ influx and associated rise in Ca2+i. Swelling also induces a biphasic change in membrane potential, a hyperpolarization followed by depolarization, reflecting sequential increases in K+ and Cl- permeabilities. The time dependence of the former corresponds closely with the transient peak in Ca2+i, but the latter does not. Ca2+i appears to have a direct activating effect on K+ channels but an indirect effect on Cl- channels, mediated via other Ca(2+)-triggered systems. The sequence of events following cell swelling appears to be transient increases in Ca2+ permeability, Ca2+ influx, Ca2+i, K+ permeability, followed by triggering of a mediating system that increases Cl- permeability. The net result is KCl, osmotic water loss, and volume adjustment.

Animals↗
PubMed1991

Drosophila snRNP associated protein P11 which specifically binds to heat shock puff 93D reveals strong homology with hnRNP core protein A1.

We have isolated cDNAs coding for a ribonucleoprotein of Drosophila melanogaster that is distinguished by its nearly exclusive presence at only one of the several heat shock puffs in polytene chromosomes of third instar larvae. We determined the nucleotide sequence and deduced the corresponding amino acid sequence. Its coding capacity for a 39 kDa protein is consistent with the size of the protein detected by the monoclonal antibody P11 used for expression cloning. Our results show that the P11 protein belongs to the category of hnRNP proteins of bipartite structure: the amino-terminal half contains two RNA binding domains and the carboxyterminal half is rich in glycine residues. Analysis of the genomic structure revealed two introns located within the coding portion of the gene and a third one in the 3'untranslated region. We detect two different polyadenylation sites as a result of alternative termination-polyadenylation. Its strong sequence homology with hnRNP A1 protein and its previously shown association with snRNP particles indicates that a typical hnRNP protein may also exist in a complex with snRNP particles. The P11 sequence corresponds to the Hrb87F sequence that was recently described by Haynes et al. (1) as hnRNP A related gene.

Amino Acid Sequence↗
PubMed1991

Actions of mercurials on cell volume regulation of dissociated MDCK cells.

The mercurial, p-chloromercuribenzoylsulfonate (PCMBS), blocks volume recovery of dissociated, osmotically swollen, Madin-Darby canine kidney cells (MDCK) and, at higher concentrations, induces substantial swelling. In the absence of Na+ the rate of volume recovery is, in contrast, substantially increased. PCMBS does not inhibit the "normal" volume-regulating pathways, K+ and Cl- conductances. Rather, its blocking action is due to substantial activation of Na+ and K+ permeabilities, especially the former. Consequently, the normal reshrinking mechanism, loss of KCl, is counterbalanced by PCMBS-induced gains of NaCl. In isotonic cells, PCMBS, at higher concentrations, induces cell swelling, indicating that Cl- permeability is also increased, a conclusion confirmed by direct measurement of 36Cl- fluxes. HgCl2 produces similar effects except that it is more potent and more rapid in its action. Activation of conductive ion permeabilities to Na+, K+, and Cl- are associated with appropriate changes in membrane potential. A small bumetanide-sensitive swelling component (Na(+)-Cl- cotransport) is activated by HgCl2 but not by PCMBS. Another effect is elevation of cytoplasmic Ca2+, apparently by mobilization from internal stores. Some of the functional sites (Na+ and K+) appear to be located externally, rapidly accessible to both HgCl2 and PCMBS, whereas others (Cl- and Ca2+) appear to be internal, rapidly accessible to the permeant HgCl2 but slowly to relatively impermeant PCMBS. In conclusion, the disturbances of volume regulation are largely due to the increases in conductive ion fluxes.

4-Chloromercuribenzenesulfonate↗
PubMed1990

Volume-activated K+ and Cl- pathways of dissociated epithelial cells (MDCK): role of Ca2+.

Osmotic swelling of dissociated Madin-Darby canine kidney (MDCK) cells in NaCl medium is followed by shrinking (regulatory volume decrease, or RVD) or in KCl medium by secondary swelling. The cation ionophore gramicidin has little effect on volumes of isotonic cells but accelerates volume-activated changes in either medium. Immediately after hypotonic exposure, the membrane becomes transiently hyperpolarized followed by depolarization. The depolarization phase is diminished by the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). Swelling is also associated with an almost immediate increase in Ca2+ influx and elevation of cytoplasmic Ca2+ ([Ca2+]i) preceding RVD. In Ca2(+)-free medium, [Ca2+]i rapidly declines to a low level. Osmotic swelling, under these circumstances, is associated with a small transient increase in [Ca2+]i, but RVD or secondary swelling (in KCl) are minimal. Under these conditions, addition of gramicidin or the Ca2(+)-ionophore A23187 induces significant volume changes, although not as large as those found in the presence of Ca2+. Quinine inhibits RVD in the absence of gramicidin, but not in its presence; oligomycin C, DIDS, and trifluoperazine, on the other hand, inhibit in the presence of the ionophore. These findings suggest that in MDCK cells RVD involves activation of distinct conductive K+ and Cl- pathways which allow escape of KCl and osmotically obligated water and that activation of both pathways is associated with elevated [Ca2+]i derived largely from volume activation of a Ca2(+)-influx pathway.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Net efflux of chloride from cell suspensions measured with a K+ electrode.

Under appropriate conditions (presence of cation ionophores) net KCl efflux measured with a K+ electrode can be used to estimate conductive Cl- fluxes, a sensitive procedure that allows continuous recording. The procedure was tested in human red cells by demonstrating effects of ionophores and of an anion transport inhibitor, and in dissociated MDCK cells by demonstration of cAMP and volume-activated Cl- fluxes.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Dissolution of bile duct stones.

Mono-octanoin can be used either alone or as an adjunct to other techniques to dissolve cholesterol bile duct stones. This solvent can be administered through an existing T tube, through the nasobiliary route, or percutaneously through the liver. Unlike basket extraction, which requires a mature T-tube sinus tract, mono-octanoin can be used immediately postoperatively or for home dissolution therapy. The endoscopic extraction of bile duct stones has a 1 percent mortality rate and a 5 to 7 percent complication rate. Special mixtures of mono-octanoin, bile acids, and ethylene diaminetetraacetic acid (EDTA) are being evaluated to dissolve pigment stones. The use of methyl tert-butyl ether is still experimental but very effective. To be most successful, mono-octanoin treatment must be used in properly selected patients.

Bile Acids and Salts↗
PubMed1989

Small-bowel obstruction caused by heterotopic pancreas in an adult.

Aberrant pancreatic tissue has been found in several abdominal and intrathoracic locations, most frequently in the stomach or duodenum. Heterotopic pancreas in the jejunum or ileum is a rare, usually asymptomatic, incidental finding. A review of the English language literature since 1950 shows only one pediatric and one adult case of heterotopic pancreas causing small bowel intussusception. The authors report a case of ileo-ileal intussusception caused by a submucosal mass of aberrant pancreatic tissue that remained undetected during several diagnostic tests and two laparotomies.

Adult↗
PubMed1988

Activation of K+ and Cl- channels by Ca2+ and cyclic AMP in dissociated kidney epithelial (MDCK) cells.

In dissociated MDCK cells, activators of the cyclic AMP system cause depolarization detectable by changes in fluorescence of the membrane potential sensitive dye bisoxonol. Addition of forskolin (60 microM), vasopressin (2 microM), 8-bromo-cyclic AMP (0.5 mM) or 1-epinephrine (10 microM) depolarized the cells substantially in low Cl- (5 mM) but had little effect in high Cl- (140 mM) solution. These results are consistent with cyclic AMP activation of Cl- channels. The Ca2+-ionophore ionomycin (1 microM) produced a rapid hyperpolarization in low and high Cl- solutions, consistent with K+ channel opening. Using a clonal subline, MDCK-14, the magnitude of the ionomycin hyperpolarization was roughly proportional to the concomitant rise in [Ca2+]i as measured with the intracellular Ca2+ probe indo-I. Both l-epinephrine and isoproterenol appeared to activate the Cl- channels. However only l-epinephrine produced a [Ca2+]i rise and a transient hyperpolarization (due to K+ channel opening), which preceded the depolarization due to Cl- channel opening. The l-epinephrine-induced [Ca2+]i response of the heterogeneous MDCK cell population but not of the clonal subline MDCK-14 was inhibited by removal of extracellular Ca2+. In the latter only the slow secondary phase of the [Ca2+]i rise was affected by Ca2+ removal. It is concluded that l-epinephrine activates K+ and Cl- channels in a sequential manner in MDCK cells by Ca2+ and cAMP signals, presumably via alpha- and beta-adrenergic receptors located on the same cell.

Animals↗
PubMed1987

Enhancement of conductive anion permeability in cultured cells by cetiedil.

Cetiedil, a drug that is reported to block K+-channels, substantially increases the conductive C1- permeability of Chinese hamster ovary (CHO) cells. The permeability was monitored by volume changes in cells treated with gramicidin to increase the cation permeability. Under this circumstance, increases in Cl- conductances result in volume changes detectable by electronic sizing, with the direction determined by the gradients of the permeating ions. In NaCl or KCl media, swelling occurs, but in N-methylglucamine chloride, shrinking. The increases in Cl- conductance could also be measured as an increased 36Cl- flux or by changes in membrane potential (measured by fluorescence of a potential-sensitive dye) toward the Cl- equilibrium potential. The effect of cetiedil was concentration dependent, with maximal effect at 50 microM. The anion specificity for the conductance was NO3- greater than Cl- = Br- much greater than SO4-2 or isethionate. A number of other drugs that influence transport activities had no effect on Cl- conductance. The cetiedil effect on Cl- conductance was observed in one other cell line, but was absent in several other cell types. The cetiedil-induced Cl- conductance in CHO cells appears to involve a different pathway than that induced by exposure to hypotonic medium.

Animals↗
PubMed1986

Voltage-dependent increase in ionized cytoplasmic calcium in the L6H9 muscle cell line detected with quin2.

The concentration of free Ca2+ ions in the cytoplasm ([Ca2+]i) is a key parameter in the function of muscle cells. This study describes the effect of membrane depolarization on [Ca2+]i in differentiating cells of the L6H9 line of rat skeletal muscle. [Ca2+]i was assessed using the fluorescent indicator quin2. In the presence of 1 mM extracellular Ca2+, [Ca2+]i averaged 250 nM. Replacement of extracellular Na+ with K+ resulted in cellular depolarization from -64 to -20 mV, measured with a fluorescent oxonol indicator. Depolarized cells showed a significant increase in [Ca2+]i, from 250 to 390 nM. The increase was prevented by nifedipine (5 microM) and was in great part dependent on the presence of extracellular Ca2+. A residual significant increase in [Ca2+]i was observed upon depolarization in Ca2+-free medium; this rise may be attributed to Ca2+ release from intracellular organelles. In the presence of extracellular Ca2+, replacement of extracellular Na+ by N-methylglucamine+ did not depolarize the cells, yet resulted in a significant increase in [Ca2+]i. This rise may be ascribed to inhibition or reversal of Na+/Ca2+ exchange activity due to the absence of extracellular Na+. The data are consistent with the presence of voltage-sensitive Ca2+ channels and Na+/Ca2+ antiporters at the cell surface, and of mechanisms of voltage-sensitive Ca2+ release from intracellular organelles.

Animals↗
PubMed1986

Osmotic activation of the Na+/H+ antiport in protein kinase C-depleted lymphocytes.

The Na+/H+ antiport of rat thymic lymphocytes is activated when protein kinase C is stimulated by phorbol esters. A similar activation of the antiport is obtained when the cells are treated with hypertonic solutions. We tested the possibility that protein kinase C also mediates the osmotic activation of Na+/H+ exchange. Protein kinase C was depleted by preincubation of thymocytes for 24 hr in the presence of high concentrations of phorbol ester. Disappearance of the enzyme was assessed by direct measurement of phosphotransferase activity, and by the loss of biological responses to phorbol esters. The Na+/H+ antiport in protein kinase C-depleted cells was not stimulated by addition of phorbol ester, but responded normally to hypertonic treatment. The results indicate that the osmotic activation of countertransport does not require stimulation of protein kinase C.

Amiloride↗
PubMed1986

Regulation of amino acid uptake by phorbol esters and hypertonic solutions in rat thymocytes.

Growth factors, mitogens, and malignant transformation can alter the rate of amino acid uptake in mammalian cells. It has been suggested that the effects of these stimuli on proliferation are mediated by activation of Na+/H+ exchange. In lymphocytes, Na+/H+ exchange can also be activated by phorbol esters and by hypertonic media. To determine the relationship between the cation antiport and amino acid transport, we tested the effects of these agents on the uptake of alpha-aminoisobutyric acid (AIB), methyl-AIB, proline, and leucine in rat thymocytes. Both 12-O-tetradecanoylphorbol-13-acetate (TPA) and hypertonicity stimulated amino acid uptake through system A (AIB, proline, and methyl-AIB). In addition, TPA, but not hypertonicity, also elevated leucine uptake. The stimulation of the Na+ -dependent system A was not due to an increased inward electrochemical Na+ gradient. The effects of TPA and hypertonic treatment were not identical: Stimulation of AIB uptake by TPA was observed within minutes, whereas at least 1 hr was required for the effect of hypertonicity to become noticeable. Moreover, stimulation by hypertonicity but not that by TPA, was partially inhibited by cycloheximide, suggesting a role of protein synthesis. That stimulation of Na+/H+ exchange does not mediate the effects on amino acid transport is suggested by two findings: 1) the stimulation of AIB uptake was not prevented by concentrations of amiloride or of 5-(N,N-disubstituted) amiloride analogs that completely inhibit the Na+/H+ antiport and 2) conditions that mimic the effect of the antiport, namely, increasing [Na+]i or raising pHi failed to stimulate amino acid uptake. Thus, in lymphocytes, activation of Na+/H+ exchange and stimulation of amino acid transport are not casually related.

Amino Acids↗
PubMed1985

Bromo-A23187: a nonfluorescent calcium ionophore for use with fluorescent probes.

4-Bromo-A23187, a halogenated analog of the widely studied divalent cation ionophore A23187, is a nonfluorescent Ca2+ ionophore suitable for use in the calibration of cytoplasmic free Ca2+ by fluorescent probes. Br-A23187 is shown to saturate Ca2+ sites in quin-2-loaded rat thymic lymphocytes in a manner essentially identical to ionomycin.

Aminoquinolines↗