Effects of pH on calcium transport in turtle bladder

Unidirectional 45Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (JnetCa) was secretory (serosa to mucosa) and was 388.3 +/- 84.5 pmol.mg-1.h-1 (n = 20, P less than 0.001). Ouabain (5 X 10(-4) M) reversed JnetCa to an absorptive flux (serosal minus mucosal flux = -195.8 +/- 41.3 pmol.mg-1.h-1; n = 20, P less than 0.001). Amiloride (1 X 10(-5) M) reduced both fluxes such that JnetCa was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, JnetCa decreased to approximately one-third of control value but remained secretory (138.4 +/- 54.3 pmol.mg-1.h-1; n = 9, P less than 0.025). When ouabain was added under short-circuit conditions, JnetCa was similar in magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue 45Ca content was approximately equal to 30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca2+-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na+-K+-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.

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Effects of pH on apical calcium entry and active calcium transport in rabbit cortical collecting system

AJP Renal Physiology ◽

10.1152/ajprenal.1994.266.4.f620 ◽

1994 ◽

Vol 266 (4) ◽

pp. F620-F627 ◽

Cited By ~ 14

Author(s):

R. J. Bindels ◽

A. Hartog ◽

S. L. Abrahamse ◽

C. H. Van Os

Keyword(s):

Calcium Transport ◽

Apical Membrane ◽

Channel Blockers ◽

Intracellular Acidification ◽

Apical Side ◽

Collecting Ducts ◽

Effects Of Ph ◽

Active Calcium ◽

Permeable Supports ◽

Collecting System

Rabbit connecting tubules and cortical collecting ducts were isolated by immunodissection and cultured on permeable supports. The monolayers actively transported Ca2+ with a net transcellular rate of 92 +/- 3 nmol.h-1.cm-2. Methoxyverapamil, felodipine, diltiazem, omega-conotoxin GVIA, and omega-agatoxin IVA when added to the apical side had no effect on Ca2+ absorption. Neither hyperpolarization nor depolarization of the apical membrane affected Ca2+ transport rates significantly. Stepwise lowering of the apical pH (pHa) from 8.0 to 5.6 gradually inhibited Ca2+ transport from 88 +/- 5 to 7 +/- 2 nmol.h-1.cm-2. Measuring the intracellular pH (pHi) with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein revealed that lowering the pHa from 8.0 to 5.6 decreased pHi from 7.8 to 6.7. To determine whether inhibition of Ca2+ absorption results from intracellular acidification, pHi was lowered using an NH4Cl pulse while extracellular pH was kept constant. Intracellular acidification from 7.4 +/- 0.2 to 6.9 +/- 0.1 reduced Ca2+ absorption by 26 +/- 6% only. In addition, lowering of the basolateral pH to 6.2 resulted in a pHi of 6.8 +/- 0.1, without affecting Ca2+ absorption rates. In conclusion, the basal Ca2+ influx mechanism in the apical membrane is most likely a voltage-independent Ca2+ transporter, insensitive to Ca2+ channel blockers, but strongly inhibited by apical acidification.

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Ca++-ATPase activity in the hepatopancreas cells of Oniscus asellus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100124501 ◽

1992 ◽

Vol 50 (1) ◽

pp. 820-821

Author(s):

G.M. Vernon ◽

A. Surace ◽

R. Witkus

Keyword(s):

B Cells ◽

Epithelial Cell ◽

Atpase Activity ◽

Calcium Transport ◽

Carcinus Maenas ◽

Cell Types ◽

Molt Cycle ◽

Copper And Zinc

The hepatopancreas consists of a pair of bilobed tubules comprised of two epithelial cell types. S cells are absorptive and accumulate metals such as copper and zinc. Ca++ concentrations vary between the S and B cells and during the molt cycle. Roer and Dillaman implicated Ca++-ATPase in calcium transport during molting in Carcinus maenas. This study was undertaken to compare the localization of Ca++-ATPase activity in the S and B cells during intermolt.

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Immunogold localization of calmodulin in root caps of the maize Cultivar Merit

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160923 ◽

1990 ◽

Vol 48 (3) ◽

pp. 674-675

Author(s):

P.T. Nguyen ◽

C. Uphoff ◽

C.L. Stinemetz

Keyword(s):

Calcium Binding ◽

Calcium Transport ◽

Primary Role ◽

Immunogold Localization ◽

Root Tips ◽

Electrical Currents ◽

Considerable Evidence ◽

Maize Cultivar ◽

Gravity Response ◽

Induced Changes

Considerable evidence suggest that the calcium-binding protein calmodulin (CaM) may mediate calcium action and/or transport important in the gravity response of plants. Calmodulin is present in both shoots and roots and is capable of regulating calcium transport in plant vesicles. In roots calmodulin is concentrated in the tip, the gravisensing region of the root; and is reported to be closely associated with amyloplasts, organelles suggested to play a primary role in gravi-perception. Inhibitors of CaM such as chlorpromazine, calmidazolium, and compound 48/80 interfere with the gravitropic response of both snoots and roots. The magnitude of the inhibition corresponded well with the extent to which the drug binds to endogenous CaM. Compound 48/80 and calmidazolium block gravi-induced changes in electrical currents across root tips, a phenomenon thought to be associated with the sensing of the gravity stimulus.In this study, we have investigated the subcellular distribution of CaM in graviresponsive and non-graviresponsive root caps of the maize cultivar Merit.

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Effect of pH and inhibitors on beta-amyloid fibril assembly

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166221 ◽

1996 ◽

Vol 54 ◽

pp. 752-753

Author(s):

Beverly E. Maleeff ◽

Timothy K. Hart ◽

Stephen J. Wood ◽

Ronald Wetzel

Keyword(s):

Amyloid Fibril ◽

Peptide Fragment ◽

Hydrophobic Peptides ◽

Amyloid Fibril Formation ◽

Effects Of Ph ◽

Severity Of The Disease ◽

Kinetics Of ◽

The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

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Effects of pH on proton transport by vacuolar pumps from maize roots

Physiologia Plantarum ◽

10.1034/j.1399-3054.1992.860109.x ◽

1992 ◽

Vol 86 (1) ◽

pp. 63-70 ◽

Cited By ~ 1

Author(s):

David Brauer ◽

DeNea Conner ◽

Shu-I Tu

Keyword(s):

Proton Transport ◽

Maize Roots ◽

Effects Of Ph

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DIP quality influenced by process water quality

TAPPI Journal ◽

10.32964/tj13.9.51 ◽

2014 ◽

Vol 13 (9) ◽

pp. 51-60

Author(s):

DENNIS VOSS ◽

HANS-JOACHIM PUTZ ◽

SAMUEL SCHABEL

Keyword(s):

Water Quality ◽

Surface Tension ◽

Ph Value ◽

Water Hardness ◽

Process Water ◽

Test Results ◽

Negative Effects ◽

Water Parameters ◽

Effects Of Ph ◽

Contamination Levels

The need for deinking mills to reduce their fresh water consumption has resulted in higher loads of various contaminants in the process water. Lower recovered paper quality also leads to higher contamination levels in the mills. This higher load has an influence on achievable target brightness. The objective of the work was to determine and explain the main reasons for relatively poor deinked pulp quality or poor deinking potential based on the influence of recovered paper composition and process water quality. The process water parameters significantly affect the deinking potential of recovered paper. The test results showed the negative effects of increased water hardness. For standard recovered paper mixtures, flotation selectivity is higher with increasing flotation pH-value. Good results were realized for standard recovered paper with low hardness, low surface tension, and high pH-value. The results for recovered paper containing flexo newsprint could be slightly improved with low hardness, low surface tension, and low pH-value. The results of the test program using design of experiments showed interacting effects of pH-value and surface tension on luminosity and flotation selectivity.

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In vivo Production of Soluble Inorganic Pyrophosphatases in Two Strains of Vibrio cholerae

Bangladesh Journal of Microbiology ◽

10.3329/bjm.v24i1.1235 ◽

1970 ◽

Vol 24 (1) ◽

pp. 38-41

Author(s):

Taslima Taher Lina ◽

Mohammad Ilias

Keyword(s):

Vibrio Cholerae ◽

Specific Activity ◽

Experimental Conditions ◽

Environmental Strain ◽

Cell Extracts ◽

Atcc Strain ◽

The Family ◽

Effects Of Ph ◽

Vibrio Cholerae O1

The in vivo production of soluble inorganic pyrophosphatases (PPases) was investigated in two strains, namely, Vibrio cholerae EM 004 (environmental strain) and Vibrio cholerae O1 757 (ATCC strain). V. cholerae is known to contain both family I and family II PPase coding sequences. The production of family I and family II PPases were determined by measuring the enzyme activity in cell extracts. The effects of pH, temperature, salinity of the growth medium on the production of soluble PPases were studied. In case of family I PPase, V. cholerae EM 004 gave the highest specific activity at pH 9.0, with 2% NaCl + 0.011% NaF and at 37°C. The strain V. cholerae O1 757 gave the highest specific activity at pH 9.0, with media containing 0% NaCl and at 37°C. On the other hand, under all the conditions family II PPase did not give any significant specific activity, suggesting that the family II PPase was not produced in vivo in either strains of V. cholerae under different experimental conditions. Keywords: Vibrio cholerae, Pyrophosphatases (PPases), Specific activityDOI: http://dx.doi.org/10.3329/bjm.v24i1.1235 Bangladesh J Microbiol, Volume 24, Number 1, June 2007, pp 38-41

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