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J B Claiborne

Publications and source records attributed to J B Claiborne.

10 recordsLinked to original sources
PubMed2005

NHE3 in an ancestral vertebrate: primary sequence, distribution, localization, and function in gills.

In mammals, the Na+/H+ exchanger 3 (NHE3) is expressed with Na+/K+-ATPase in renal proximal tubules, where it secretes H+ and absorbs Na+ to maintain blood pH and volume. In elasmobranchs (sharks, skates, and stingrays), the gills are the dominant site of pH and osmoregulation. This study was conducted to determine whether epithelial NHE homologs exist in elasmobranchs and, if so, to localize their expression in gills and determine whether their expression is altered by environmental salinity or hypercapnia. Degenerate primers and RT-PCR were used to deduce partial sequences of mammalian NHE2 and NHE3 homologs from the gills of the euryhaline Atlantic stingray (Dasyatis sabina). Real-time PCR was then used to demonstrate that mRNA expression of the NHE3 homolog increased when stingrays were transferred to low salinities but not during hypercapnia. Expression of the NHE2 homolog did not change with either treatment. Rapid amplification of cDNA was then used to deduce the complete sequence of a putative NHE3. The 2,744-base pair cDNA includes a coding region for a 2,511-amino acid protein that is 70% identical to human NHE3 (SLC9A3). Antisera generated against the carboxyl tail of the putative stingray NHE3 labeled the apical membranes of Na+/K+-ATPase-rich epithelial cells, and acclimation to freshwater caused a redistribution of labeling in the gills. This study provides the first NHE3 cloned from an elasmobranch and is the first to demonstrate an increase in gill NHE3 expression during acclimation to low salinities, suggesting that NHE3 can absorb Na+ from ion-poor environments.

Amino Acid Sequence↗
PubMed2001

Expression of Na(+) / H(+) exchanger mRNA in the gills of the Atlantic hagfish (Myxine glutinosa) in response to metabolic acidosis.

Sodium/proton exchangers (NHE) are transmembrane proteins that facilitate the exchange of a Na(+) ion for a H(+) ion across cellular membranes. The NHE are present in the gills of fishes and are believed to function in acid-base regulation by driving the extrusion of protons across the branchial epithelium in exchange for Na(+) in the water. In this study, we have used reverse transcriptase-polymerase chain reaction (RT-PCR) to detect the presence of a branchial NHE in the gills of the Atlantic hagfish, Myxine glutinosa. The subsequent partial cDNA sequence shares homology with other vertebrate and invertebrate NHE isoforms. In addition, using semi-quantitative, multiplex RT-PCR we demonstrate that mRNA expression of hagfish gill NHE is upregulated following an induced metabolic acidosis. Expression was increased to 4.4 times basal levels at 2-h post-infusion and had decreased to 1.6 times basal by 6 h. Expression had returned to basal levels by 24-h post-infusion. The inference from this study is that a gill NHE which is potentially important in acid-base regulation has been present in the vertebrate lineage since before the divergence of the hagfishes from the main vertebrate line.

Acid-Base Equilibrium↗
PubMed1999

Immunolocalization of Na+/K(+)-ATPase in mitochondrion-rich cells of the atlantic hagfish (Myxine glutinosa) gill.

Using a monoclonal antibody for the alpha-subunit of the Na+/K(+)-ATPase, DASPEI (a vital mitochondria dye), and confocal laser scanning microscopy, the presence of Na+/K(+)-ATPase in mitochondrion-rich cells of the hagfish gill was confirmed. In addition, the level of Na+/K(+)-ATPase expression in the hagfish gill was compared to that of fishes with different osmoregulatory strategies (little skate, Raja erinacea and mummichog, Fundulus heteroclitus). Immunocytochemistry detected a high density of columnar cells expressing Na+/K(+)-ATPase in the afferent filamental epithelium. Positive cells were also found in the lamellar epithelium but at a much lower density. The distribution of DASPEI staining was similar to that of the Na+/K(+)-ATPase antibody, indicating that the enzyme is expressed in mitochondrion-rich cells. Immunoblot analysis confirmed the specificity of the antibody for the 97 kDa alpha-subunit of the enzyme. The immunoreactive band intensity for the Atlantic hagfish was similar to that of the little skate, but less than half that of the full-strength seawater mummichog. These results are discussed in relation to gill function in early craniates.

Animals↗
PubMed1999

A mechanism for branchial acid excretion in marine fish: identification of multiple Na+/H+ antiporter (NHE) isoforms in gills of two seawater teleosts.

Both Na+/H+ exchange and the electrogenic extrusion of H+ via an H+-ATPase have been postulated to drive acid excretion across the branchial epithelium of fishes. While the H+-ATPase/Na+ channel system appears to be the predominant mechanism in some freshwater species, it may play a reduced role in seawater and brackish-water animals, where high external Na+ concentrations may thermodynamically favor Na+/H+ exchange driven by a Na+/H+ antiporter (NHE). In this study, we used molecular and immunological methods to assess the role of NHE isoforms in the branchial epithelium of the marine long-horned sculpin (Myoxocephalus octodecimspinosus) and the euryhaline killifish (Fundulus heteroclitus). Northern blot analysis of RNA probed with the human NHE-1 BamHI fragment suggested the presence of homologous gill NHE mRNA in sculpin. RT-PCR on gill RNA isolated from sculpin recovering from metabolic acidosis provided evidence for two distinct NHE isoforms; one with 76 % amino acid homology to mammalian NHE-2, and another 92 % homologous to trout erythrocytic beta-NHE. Killifish also have transcripts with 91 % homology to beta-NHE. Immunological detection using monoclonal antibodies for mammalian NHE-1 revealed a protein antigenically similar to this isoform in the gills of both species. Metabolic acidosis caused an approximately 30-fold decrease in expression of the NHE-1-like protein in sculpin. We speculate that beta-NHE in the gills plays the intracellular 'housekeeping' roles described for mammalian NHE-1. During systemic acidosis, apical gill NHE-2 (which is sensitive to external amiloride and low [Na+]) in parallel with a dramatic suppression of basolateral NHE-1 activity enhances net capdelta H+ transfers to the water.

Acidosis↗
PubMed1986

Acid-base regulation and ion transfers in the carp (Cyprinus carpio): pH compensation during graded long- and short-term environmental hypercapnia, and the effect of bicarbonate infusion.

To study both temporal and quantitative effects of hypercapnia on the extent of pH compensation in the arterial blood, specimens of carp (Cyprinus carpio) were exposed to a PCO2 of about 7.5 mmHg (1 mmHg = 133.3 Pa) (1% CO2) in the environmental water for several weeks, and a second group of animals was subjected to an environmental PCO2 of about 37 mmHg (5% CO2) for up to 96 h. A third series of experiments was designed to test the possibility that infusion of bicarbonate would increase the extent of plasma pH compensation. Dorsal aortic plasma pH, PCO2 and [HCO3-], as well as net transfer of HCO3- -equivalent ions, NH4+, Cl- and Na+, between fish and ambient water, were monitored throughout the experiments. Exposure to environmental PCO2 of 7.5 mmHg resulted in the expected respiratory acidosis with the associated drop in plasma pH, and subsequent compensatory plasma [HCO3-] increase. The compensatory increase of plasma bicarbonate during long-term hypercapnia continued during 19 days of exposure with plasma bicarbonate finally elevated from 13.0 mmoll-1 during control conditions to 25.9 mmoll-1 in hypercapnia, an increase equivalent to 80% plasma pH compensation. Exposure to 5% hypercapnia elicited much larger acid-base effects, which were compensated to a much lesser extent. Plasma pH recovered to only about 45% of the pH depression expected at constant bicarbonate concentration. At the end of the 96-h exposure period, plasma [HCO3-] was elevated by a factor of 2.5 to about 28.2 mmoll-1. The observed increase in plasma bicarbonate concentration during 5% hypercapnic exposure was attributable to net gain of bicarbonate equivalent ions from (or release of H+-equivalent ions to) the environmental water. Quantitatively, the gain of 15.6 mmol kg-1 was considerably larger than the amount required for compensation of the extracellular space, suggesting that acid-base relevant ions were transferred for compensation of the intracellular body compartments. The uptake of bicarbonate-equivalent ions from the water was accompanied by a net release of Cl-and, to a smaller extent, by a net uptake of Na+, suggesting a 75% contribution of the Cl-/HCO-3 exchange mechanism. Infusion of bicarbonate after 48 h of exposure to 7.5 mmHg PCo2 had only a transient effect on further pH compensation. The infused bicarbonate was lost to the ambient water, and pre-infusion levels of bicarbonate were reattained within 24 h. Repetition of the infusion did not result in a notable improvement of the acid-base status.(ABSTRACT TRUNCATED AT 400 WORDS)

Acid-Base Equilibrium↗
PubMed1984

Transepithelial potential measurements in the isolated, perfused head of a marine teleost.

The transepithelial potential (TEP) across the gills of a seawater teleost, the long-horned sculpin (Myoxocephalus octodecimspinosus), was measured both in vivo and utilizing an isolated, perfused head preparation (IPHP). The TEP of the IPHP was compared to that of the whole animal while in normal seawater and Na- or Cl-free seawater. The TEP or the IPHP in seawater was similar to that measured in vivo (+7.7 versus +7.2 mV, respectively). Na-free seawater induced a depolarization of both the IPHP and the intact fish, while Cl-free seawater hyperpolarized the TEP in vivo. The positive TEP of the sculpin, measured both in vivo and in vitro, is indicative of a transbranchial Na+ to Cl- permeability ratio greater than unity. The IPHP of the sculpin exhibits differential ion permeabilities similar to that of the whole animal. TEP comparisons described here should be applied to other IPHP systems now in use.

Animals↗
PubMed1983

Haemodynamic effects of adrenaline on the isolated, perfused head of the dogfish 'pup' (Squalus acanthias).

The isolated, perfused head of the dogfish 'pup' (Squalus acanthias) maintained pressure:flow relationships near to those described for the in vivo adult for at least 3 h when perfused at a constant rate. The addition of 3% polyvinylpyrrolidone reversibly increased branchial resistance, and the postbranchial outflow (arterial + venous) equalled the inflow. 10(-5) M adrenaline reversibly reduced gill resistance (in some cases after a transient increase in resistance) and stimulated perfusate outflow from the dorsal aorta, at the expense of flow from the cephalic and branchial venous system. Phentolamine did not alter the effect of adrenaline on pressure and flow pattern; addition of propranolol inhibited both adrenaline effects and resulted in a slight increase in afferent pressure, indicating that alpha-adrenergic receptors are present, but that the dominant haemodynamic effects are mediated via beta-adrenergic receptors. The isolated, perfused 'pup' head may provide a vehicle for investigation of transport phenomena in the elasmobranch branchial epithelium.

Animals↗
PubMed1982

H-FLUX: an interactive program for the analysis of acid-base efflux.

H-FLUX is an interactive computer program designated to facilitate the calculation of acid or base efflux from a tissue or organism into the surrounding media. It will accept data derived from different experimental protocols and allows for a high level of experimental flexibility. An example calculation of acid efflux from the marine fish Opsanus beta is given.

Acid-Base Equilibrium↗
PubMedDate not supplied

A minicomputer program for rapid graphical and statistical analysis of laboratory data.

The utility of a FORTRAN program package, which enables the scientific investigator to make a rapid assessment of laboratory data is described. Data are submitted from the keyboard or specified disk files in the form of coordinate pairs. The program includes routines for plotting values as a series of X-Y pairs on the computer video monitor or for comparing the X and Y arrays via paired differences and Student's t-test. A least squares linear regression of plotted data may also be called. Data modification, curve fitting, and I/O are easily handled in either single pair or column format. Examples of both statistical and graphical data analysis are presented.

Computers↗