Randall Packer | The George Washington University (original) (raw)

Papers by Randall Packer

American Journal of …, 2000

Increased systemic acid intake is associated with an increase in apical Na/H exchange in the rena... more Increased systemic acid intake is associated with an increase in apical Na/H exchange in the renal proximal tubule mediated by the type 3 Na/H exchanger (NHE3). Because NHE3 mediates both proton secretion and Na absorption, increased NHE3 activity could inappropriately perturb Na balance unless there are compensatory changes in Na handling. In this study, we use semiquantitative immunoblotting of rat kidneys to investigate whether acid loading is associated with compensatory decreases in the abundance of renal tubule Na transporters other than NHE3. Long-term (i.e., 7-day) acid loading with NH(4)Cl produced large decreases in the abundances of the thiazide-sensitive Na-Cl cotransporter (TSC/NCC) of the distal convoluted tubule and both the beta- and gamma-subunits of the amiloride-sensitive epithelial Na channel (ENaC) of the collecting duct. In addition, the renal cortical abundance of the proximal type 2 Na-dependent phosphate transporter (NaPi-2) was markedly decreased. In contra...

American Journal of …, 2000

Increased systemic acid intake is associated with an increase in apical Na/H exchange in the rena... more Increased systemic acid intake is associated with an increase in apical Na/H exchange in the renal proximal tubule mediated by the type 3 Na/H exchanger (NHE3). Because NHE3 mediates both proton secretion and Na absorption, increased NHE3 activity could inappropriately perturb Na balance unless there are compensatory changes in Na handling. In this study, we use semiquantitative immunoblotting of rat kidneys to investigate whether acid loading is associated with compensatory decreases in the abundance of renal tubule Na transporters other than NHE3. Long-term (i.e., 7-day) acid loading with NH(4)Cl produced large decreases in the abundances of the thiazide-sensitive Na-Cl cotransporter (TSC/NCC) of the distal convoluted tubule and both the beta- and gamma-subunits of the amiloride-sensitive epithelial Na channel (ENaC) of the collecting duct. In addition, the renal cortical abundance of the proximal type 2 Na-dependent phosphate transporter (NaPi-2) was markedly decreased. In contra...

Journal of the …, 1999

Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ... more Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ammonium accumulation mediated by active NH4+ absorption by the medullary thick ascending limb. To investigate whether alterations in the abundance of medullary thick ascending limb ion transporters, namely the apical Na+/K+(NH4+)/2Cl- -cotransporter (BSC-1), the apical Na+/H+ -exchanger (NHE3), and the Na+/K+ -ATPase alpha1-subunit, may be responsible in part for altered medullary ammonium accumulation, semiquantitative immunoblotting studies were performed using homogenates from the inner stripe of the rat renal outer medulla. After 7 d of NH4Cl (7.2 mmol/220 g body wt per d) loading (associated with increased medullary ammonium accumulation), neither BSC-1 nor Na+/K+ -ATPase protein expression was altered, but NHE3 protein abundance was significantly increased. On the other hand, both BSC-1 and Na+/K+ -ATPase protein abundance was increased significantly in rats fed NaHCO3 (7.2 mmol/2...

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Comparative biochemistry and physiology. Part D, Genomics & proteomics, Mar 1, 2018

In the face of ongoing climate change, it is imperative to understand better the effects of tempe... more In the face of ongoing climate change, it is imperative to understand better the effects of temperature on immune function in freshwater teleosts. It is unclear whether previously observed changes were caused by temperature per se. We studied changes in the gill transcriptome of fathead minnows (Pimephales promelas) at low temperature to understand better the effects of temperature on immune function. De novo assembly of the transcriptome using Trinity software resulted in 73,378 assembled contigs. Annotation using the Trinotate package yielded 58,952 Blastx hits (accessions). Expression of 194 unique mRNA transcripts changed in gill tissue of fathead minnows acclimatized to 5° compared to controls at 22 °C. At 5 °C mRNAs coding for proteins involved in innate immune responses were up-regulated. Those included proteins that block early-stage viral replication and macrophage activation. Expression of mRNAs coding for pro-inflammatory molecules and mucus secretion were also enhanced. ...

Journal of the American Society of Nephrology Jasn, Feb 1, 1995

Journal of the American Society of Nephrology Jasn, May 1, 1999

Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ... more Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ammonium accumulation mediated by active NH 4 ϩ absorption by the medullary thick ascending limb. To investigate whether alterations in the abundance of medullary thick ascending limb ion transporters, namely the apical Na ϩ /K ϩ (NH 4 ϩ)/2Cl Ϫ-cotransporter (BSC-1), the apical Na ϩ /H ϩ-exchanger (NHE3), and the Na ϩ /K ϩ-ATPase ␣1-subunit, may be responsible in part for altered medullary ammonium accumulation, semiquantitative immunoblotting studies were performed using homogenates from the inner stripe of the rat renal outer medulla. After 7 d of NH 4 Cl (7.2 mmol/220 g body wt per d) loading (associated with increased medullary ammonium accumulation), neither BSC-1 nor Na ϩ /K ϩ-ATPase protein expression was altered, but NHE3 protein abundance was significantly increased. On

Journal of Experimental Biology, Apr 1, 1979

Brook trout (Sahelinus fontinalis Mitchill) with a chronically implanted dorsal aortic cannula we... more Brook trout (Sahelinus fontinalis Mitchill) with a chronically implanted dorsal aortic cannula were exposed to acidic environments. During exposure, trout developed severe metabolic acidosis as shown by decreases in standard plasma bicarbonate levels as well as negative base excess values. Reduced oxygen consumption seen in acidotic trout resulted from decreased gill oxygen transfer and reduced available blood oxygen capacity.

Journal of Experimental Biology, Apr 1, 1979

A nomogram is presented which allows the rapid assessment of acid-base status in brook trout (Sal... more A nomogram is presented which allows the rapid assessment of acid-base status in brook trout (SalveKnus fontinalis Mitchill) at 18 °C. Due to a P COt of 3-5-4*3 mmHg in the respirometer water, the fish from which data were obtained for determination of zero base excess values were suffering from slight respiratory acidosis. Trauma of surgery and anaesthetization as well as confinement in the respirometer might also have generated a slight metabolic acidosis. Base excess values for trout with a chronically implanted dorsal aortic cannula ranged from-3 to +3 m-equiv/1. Blood buffer values of <f[HCO 3-]/JpH = 7-5o±4'42 slykes and-dlog 10 P O oJdpH = 1-31 ±0-14 were found. Mean plasma protein concentration was 3-6 ±0-8 g/100 ml plasma and the buffering power of plasma was approximately 40% that of whole blood. Plasma proteins are more important blood buffers in fish than in humans. • A portion of this work was submitted as a thesis by A. L. Sunkin to George Washington University in partial fulfilment of the requirements for the M.Sc. degree.

Journal of the American Society of Nephrology : JASN, 1997

Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from gluc... more Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from glucocorticoid binding by an enzyme, 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2). To study the role of 11 beta-HSD2 in acid-base homeostasis, 11 beta-HSD2 activity was measured in rat IMCD-enriched cell suspensions. Homogenates of cell suspensions were incubated in buffers ranging in pH from 6.00 to 8.15 in the presence of 1 microCi of 3H-corticosterone (CS) and 400 microM NAD+. Enzyme activity was expressed as the amount of 3H-CS converted to 3H-11-dehydrocorticosterone (DHCS). IMCD 11 beta-HSD2 activity at pH 6.5 was 49% of activity at pH 7.5; 22.5 versus 11.0 fmol/microgram of protein per h. Experiments also were performed on intact cell suspensions at pH 7.5 and 6.5. There was a 42% inhibition in the IMCD cell suspension conversion rate of 3H-CS to 3H-11-DHCS at pH 6.5; 13.1 versus 7.6 fmol/microgram per h (P < 0.005). In cell suspensions at pH 7.5, 1-day acid loading c...

Contributions to nephrology, 1997

... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whor... more ... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whorwood CB, Valentino R, Burt D, Sheppard MC, Edwards CRW: 11-Beta-hydroxy-steroid dehydrogenase activity and gene expression in the hypertensive Bianchi-Milan rat. ...

Journal of the American Society of Nephrology : JASN, 1995

Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organ... more Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organic anions (OA). Although citrate is the only OA previously identified as being excreted in appreciable amounts during base loading, citrate excretion accounts for only part of total OA excretion. The objectives of this study were to identify other OA excreted by rats and to see how their excretion changed in response to moderate (8 micro Eq/g per day) and heavy (30 micro Eq/g per day) loads of NaHCO3 and NH4Cl. Urinary OA were identified by high-performance liquid chromatography and were measured by enzymatic techniques as well. It was found that, in addition to citrate, significant quantities of alpha-ketoglutarate (alpha-KG) were excreted by base-loaded rats and that the excretion of citrate, alpha-KG, and succinate increased with base loading and decreased with acid loading. Citrate plus alpha-KG excretion rates were, respectively, two-thirds and one-third the rate of HCO3- excretion ...

Comparative Biochemistry and Physiology Part A: Physiology, 1971

ABSTRACT 1.1. In normal axolotl embryos (10 or 20°C) Na influx, net Na uptake and water content i... more ABSTRACT 1.1. In normal axolotl embryos (10 or 20°C) Na influx, net Na uptake and water content increased greatly before hatching.2.2. The rate of Na influx into normal larval axolotls was comparable to that of fish, but there were no cells in the gill similar to the Cl or “S” cell of fish gill.3.3. The swelling of fluid unbalanced embryos (ff) was especially severe at low (10°C) and high (28–30°C) temperatures.4.4. In 200 mOsm mannitol, ff embryos did not swell but survival was not enhanced.5.5. Injection or transplantation of normal tissues into ff embryos did not reduce the swelling.6.6. Due to a low influx rate, body Na content of ff embryos was reduced.

Comparative Biochemistry and Physiology Part A: Physiology, 1986

Crabs were acclimated to 20, 25 and 30°C and acid-base status was assessed by measuring hemolymph... more Crabs were acclimated to 20, 25 and 30°C and acid-base status was assessed by measuring hemolymph pH, pCO,, lactate and selected electrolyte concentrations. 2. Constant relative alkalinity of hemolymph was not maintained over the range of temperatures studied. As temperature increased, hemolymph pC0, and total CO2 content increased while hemolymph pH showed no significant change. 3. The results of this study are compared with findings of other investigators who studied acid-base balance in four other species of tropical terrestrial crabs. Of the five species compared, three appear not to maintain constant relative alkalinity

Physiological reviews, 1989

The American journal of physiology, 1989

The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed t... more The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed that water or solute fluxes across the PSE might result in changes in urine or medullary interstitial fluid composition. To study osmotic water and chloride permeabilities, the PSE was dissected from underlying medullary tissue and mounted in a small Ussing chamber. Osmotic water permeability was low (14.2 +/- 3.0 microns/s) and was unaffected by 100 nM vasopressin added to the basolateral surface. In contrast, the PSE showed a substantial chloride permeability of 3.1 +/- 0.4 x 10(-5) cm/s that decreased reversibly to 2.2 +/- 0.3 x 10(-5) cm/s (P less than 0.01) with vasopressin. Vasopressin also reversibly increased the transepithelial resistance of the PSE from 87 +/- 9 to 106 +/- 13 omega.cm2 (P less than 0.02). Apical bumetanide (10(-6) M) had no significant effect on PSE chloride permeability. The apparent Na-Cl permeability ratio (0.75 +/- 0.01) calculated from dilution potential me...

The American journal of physiology, 1990

The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the out... more The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the outer surface of the renal papilla and has an apical surface that faces the urinary space. We studied acid-base transport in this epithelium by dissecting it from the papilla, mounting it in a modified Ussing chamber, and following pH changes in the apical bathing solution. The experiments demonstrated that the PSE is capable of acidifying the apical solution at a substantial rate. The acidification rate was similar with 100% nitrogen and 100% oxygen (with and without 10 microM antimycin A), ruling out a dependence on oxidative metabolism. Addition of 1 mM iodoacetate decreased apical acidification by 55%, suggesting a dependence on glycolysis. The net rate of lactate secretion was only 17% of the total acid secretion rate, indicating that apical acidification was not directly caused by secretion of lactic acid alone. Removal of sodium or potassium from the apical solutions or the addition ...

Contributions to nephrology, 1991

The American journal of physiology, 1992

To study mechanisms involved in renal glutamate dehydrogenase (GDH) regulation in response to sys... more To study mechanisms involved in renal glutamate dehydrogenase (GDH) regulation in response to systemic acid loading, we have measured blood pH, ammonium excretion, renal GDH mRNA levels, and GDH activity in rats. Acid intake (0.28 M NH4Cl in drinking water for 3 days) increased GDH mRNA levels in the renal cortex, but had no effect in the outer stripe of the outer medulla, inner stripe of the outer medulla, or the inner medulla. Rats were subjected to a step change in acid intake by alkali loading for 3 days (7.2 meq NaHCO3 per day in food slurry) and shifting to acid loading for up to 7 days (7.2 meq NH4Cl in food slurry). Ammonium excretion rose rapidly, increasing by 14-fold in the first 24-h period and 38-fold in the second 24-h period. Cortical GDH mRNA levels were increased relative to alkali-loaded values by 3.7-fold in 24 h, 4.3-fold in 4 days, but only 2.2-fold in 7 days. GDH activity was unchanged after 24 h of acid intake, but was significantly increased after 48 h. We co...

Comparative Biochemistry and Physiology Part A: Physiology, 1977

The tunicate Molgula munlmt~msis is an estuarine animal lacking protonephridia and tubular excret... more The tunicate Molgula munlmt~msis is an estuarine animal lacking protonephridia and tubular excretory organs but possessing a well-developed renal sac thought to be the primary osmoregulatory organ. 2. Animals were acclimated to three different salinities (271 mM Na+, 218 mM Na+ and 125 mM Na+). after which sodium and potassium levels were measured in plasma and renal sac fluid. The results indicate regulation of the sodium and potassium content of renal sac fluid, but not plasma. 3. Transmission electron microscopy reveals that the renal sac epithelium possesses structural features known to be associated in other animals with ion secretion and/or osmoregulation.

American Journal of …, 2000

Increased systemic acid intake is associated with an increase in apical Na/H exchange in the rena... more Increased systemic acid intake is associated with an increase in apical Na/H exchange in the renal proximal tubule mediated by the type 3 Na/H exchanger (NHE3). Because NHE3 mediates both proton secretion and Na absorption, increased NHE3 activity could inappropriately perturb Na balance unless there are compensatory changes in Na handling. In this study, we use semiquantitative immunoblotting of rat kidneys to investigate whether acid loading is associated with compensatory decreases in the abundance of renal tubule Na transporters other than NHE3. Long-term (i.e., 7-day) acid loading with NH(4)Cl produced large decreases in the abundances of the thiazide-sensitive Na-Cl cotransporter (TSC/NCC) of the distal convoluted tubule and both the beta- and gamma-subunits of the amiloride-sensitive epithelial Na channel (ENaC) of the collecting duct. In addition, the renal cortical abundance of the proximal type 2 Na-dependent phosphate transporter (NaPi-2) was markedly decreased. In contra...

American Journal of …, 2000

Increased systemic acid intake is associated with an increase in apical Na/H exchange in the rena... more Increased systemic acid intake is associated with an increase in apical Na/H exchange in the renal proximal tubule mediated by the type 3 Na/H exchanger (NHE3). Because NHE3 mediates both proton secretion and Na absorption, increased NHE3 activity could inappropriately perturb Na balance unless there are compensatory changes in Na handling. In this study, we use semiquantitative immunoblotting of rat kidneys to investigate whether acid loading is associated with compensatory decreases in the abundance of renal tubule Na transporters other than NHE3. Long-term (i.e., 7-day) acid loading with NH(4)Cl produced large decreases in the abundances of the thiazide-sensitive Na-Cl cotransporter (TSC/NCC) of the distal convoluted tubule and both the beta- and gamma-subunits of the amiloride-sensitive epithelial Na channel (ENaC) of the collecting duct. In addition, the renal cortical abundance of the proximal type 2 Na-dependent phosphate transporter (NaPi-2) was markedly decreased. In contra...

Journal of the …, 1999

Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ... more Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ammonium accumulation mediated by active NH4+ absorption by the medullary thick ascending limb. To investigate whether alterations in the abundance of medullary thick ascending limb ion transporters, namely the apical Na+/K+(NH4+)/2Cl- -cotransporter (BSC-1), the apical Na+/H+ -exchanger (NHE3), and the Na+/K+ -ATPase alpha1-subunit, may be responsible in part for altered medullary ammonium accumulation, semiquantitative immunoblotting studies were performed using homogenates from the inner stripe of the rat renal outer medulla. After 7 d of NH4Cl (7.2 mmol/220 g body wt per d) loading (associated with increased medullary ammonium accumulation), neither BSC-1 nor Na+/K+ -ATPase protein expression was altered, but NHE3 protein abundance was significantly increased. On the other hand, both BSC-1 and Na+/K+ -ATPase protein abundance was increased significantly in rats fed NaHCO3 (7.2 mmol/2...

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

Comparative biochemistry and physiology. Part D, Genomics & proteomics, Mar 1, 2018

In the face of ongoing climate change, it is imperative to understand better the effects of tempe... more In the face of ongoing climate change, it is imperative to understand better the effects of temperature on immune function in freshwater teleosts. It is unclear whether previously observed changes were caused by temperature per se. We studied changes in the gill transcriptome of fathead minnows (Pimephales promelas) at low temperature to understand better the effects of temperature on immune function. De novo assembly of the transcriptome using Trinity software resulted in 73,378 assembled contigs. Annotation using the Trinotate package yielded 58,952 Blastx hits (accessions). Expression of 194 unique mRNA transcripts changed in gill tissue of fathead minnows acclimatized to 5° compared to controls at 22 °C. At 5 °C mRNAs coding for proteins involved in innate immune responses were up-regulated. Those included proteins that block early-stage viral replication and macrophage activation. Expression of mRNAs coding for pro-inflammatory molecules and mucus secretion were also enhanced. ...

Journal of the American Society of Nephrology Jasn, Feb 1, 1995

Journal of the American Society of Nephrology Jasn, May 1, 1999

Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ... more Changes in ammonium excretion with acid/base perturbations are dependent on changes in medullary ammonium accumulation mediated by active NH 4 ϩ absorption by the medullary thick ascending limb. To investigate whether alterations in the abundance of medullary thick ascending limb ion transporters, namely the apical Na ϩ /K ϩ (NH 4 ϩ)/2Cl Ϫ-cotransporter (BSC-1), the apical Na ϩ /H ϩ-exchanger (NHE3), and the Na ϩ /K ϩ-ATPase ␣1-subunit, may be responsible in part for altered medullary ammonium accumulation, semiquantitative immunoblotting studies were performed using homogenates from the inner stripe of the rat renal outer medulla. After 7 d of NH 4 Cl (7.2 mmol/220 g body wt per d) loading (associated with increased medullary ammonium accumulation), neither BSC-1 nor Na ϩ /K ϩ-ATPase protein expression was altered, but NHE3 protein abundance was significantly increased. On

Journal of Experimental Biology, Apr 1, 1979

Brook trout (Sahelinus fontinalis Mitchill) with a chronically implanted dorsal aortic cannula we... more Brook trout (Sahelinus fontinalis Mitchill) with a chronically implanted dorsal aortic cannula were exposed to acidic environments. During exposure, trout developed severe metabolic acidosis as shown by decreases in standard plasma bicarbonate levels as well as negative base excess values. Reduced oxygen consumption seen in acidotic trout resulted from decreased gill oxygen transfer and reduced available blood oxygen capacity.

Journal of Experimental Biology, Apr 1, 1979

A nomogram is presented which allows the rapid assessment of acid-base status in brook trout (Sal... more A nomogram is presented which allows the rapid assessment of acid-base status in brook trout (SalveKnus fontinalis Mitchill) at 18 °C. Due to a P COt of 3-5-4*3 mmHg in the respirometer water, the fish from which data were obtained for determination of zero base excess values were suffering from slight respiratory acidosis. Trauma of surgery and anaesthetization as well as confinement in the respirometer might also have generated a slight metabolic acidosis. Base excess values for trout with a chronically implanted dorsal aortic cannula ranged from-3 to +3 m-equiv/1. Blood buffer values of <f[HCO 3-]/JpH = 7-5o±4'42 slykes and-dlog 10 P O oJdpH = 1-31 ±0-14 were found. Mean plasma protein concentration was 3-6 ±0-8 g/100 ml plasma and the buffering power of plasma was approximately 40% that of whole blood. Plasma proteins are more important blood buffers in fish than in humans. • A portion of this work was submitted as a thesis by A. L. Sunkin to George Washington University in partial fulfilment of the requirements for the M.Sc. degree.

Journal of the American Society of Nephrology : JASN, 1997

Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from gluc... more Mineralocorticoid receptors in the inner medullary collecting duct (IMCD) are protected from glucocorticoid binding by an enzyme, 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2). To study the role of 11 beta-HSD2 in acid-base homeostasis, 11 beta-HSD2 activity was measured in rat IMCD-enriched cell suspensions. Homogenates of cell suspensions were incubated in buffers ranging in pH from 6.00 to 8.15 in the presence of 1 microCi of 3H-corticosterone (CS) and 400 microM NAD+. Enzyme activity was expressed as the amount of 3H-CS converted to 3H-11-dehydrocorticosterone (DHCS). IMCD 11 beta-HSD2 activity at pH 6.5 was 49% of activity at pH 7.5; 22.5 versus 11.0 fmol/microgram of protein per h. Experiments also were performed on intact cell suspensions at pH 7.5 and 6.5. There was a 42% inhibition in the IMCD cell suspension conversion rate of 3H-CS to 3H-11-DHCS at pH 6.5; 13.1 versus 7.6 fmol/microgram per h (P < 0.005). In cell suspensions at pH 7.5, 1-day acid loading c...

Contributions to nephrology, 1997

... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whor... more ... Endo-crinology 1993; 132: 2614-2621. Nolan/Knepper/Packer 60 Page 73. ... 16 Stewart PM, Whorwood CB, Valentino R, Burt D, Sheppard MC, Edwards CRW: 11-Beta-hydroxy-steroid dehydrogenase activity and gene expression in the hypertensive Bianchi-Milan rat. ...

Journal of the American Society of Nephrology : JASN, 1995

Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organ... more Animals eating a base-loaded or base-forming diet excrete urine containing large amounts of organic anions (OA). Although citrate is the only OA previously identified as being excreted in appreciable amounts during base loading, citrate excretion accounts for only part of total OA excretion. The objectives of this study were to identify other OA excreted by rats and to see how their excretion changed in response to moderate (8 micro Eq/g per day) and heavy (30 micro Eq/g per day) loads of NaHCO3 and NH4Cl. Urinary OA were identified by high-performance liquid chromatography and were measured by enzymatic techniques as well. It was found that, in addition to citrate, significant quantities of alpha-ketoglutarate (alpha-KG) were excreted by base-loaded rats and that the excretion of citrate, alpha-KG, and succinate increased with base loading and decreased with acid loading. Citrate plus alpha-KG excretion rates were, respectively, two-thirds and one-third the rate of HCO3- excretion ...

Comparative Biochemistry and Physiology Part A: Physiology, 1971

ABSTRACT 1.1. In normal axolotl embryos (10 or 20°C) Na influx, net Na uptake and water content i... more ABSTRACT 1.1. In normal axolotl embryos (10 or 20°C) Na influx, net Na uptake and water content increased greatly before hatching.2.2. The rate of Na influx into normal larval axolotls was comparable to that of fish, but there were no cells in the gill similar to the Cl or “S” cell of fish gill.3.3. The swelling of fluid unbalanced embryos (ff) was especially severe at low (10°C) and high (28–30°C) temperatures.4.4. In 200 mOsm mannitol, ff embryos did not swell but survival was not enhanced.5.5. Injection or transplantation of normal tissues into ff embryos did not reduce the swelling.6.6. Due to a low influx rate, body Na content of ff embryos was reduced.

Comparative Biochemistry and Physiology Part A: Physiology, 1986

Crabs were acclimated to 20, 25 and 30°C and acid-base status was assessed by measuring hemolymph... more Crabs were acclimated to 20, 25 and 30°C and acid-base status was assessed by measuring hemolymph pH, pCO,, lactate and selected electrolyte concentrations. 2. Constant relative alkalinity of hemolymph was not maintained over the range of temperatures studied. As temperature increased, hemolymph pC0, and total CO2 content increased while hemolymph pH showed no significant change. 3. The results of this study are compared with findings of other investigators who studied acid-base balance in four other species of tropical terrestrial crabs. Of the five species compared, three appear not to maintain constant relative alkalinity

Physiological reviews, 1989

The American journal of physiology, 1989

The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed t... more The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed that water or solute fluxes across the PSE might result in changes in urine or medullary interstitial fluid composition. To study osmotic water and chloride permeabilities, the PSE was dissected from underlying medullary tissue and mounted in a small Ussing chamber. Osmotic water permeability was low (14.2 +/- 3.0 microns/s) and was unaffected by 100 nM vasopressin added to the basolateral surface. In contrast, the PSE showed a substantial chloride permeability of 3.1 +/- 0.4 x 10(-5) cm/s that decreased reversibly to 2.2 +/- 0.3 x 10(-5) cm/s (P less than 0.01) with vasopressin. Vasopressin also reversibly increased the transepithelial resistance of the PSE from 87 +/- 9 to 106 +/- 13 omega.cm2 (P less than 0.02). Apical bumetanide (10(-6) M) had no significant effect on PSE chloride permeability. The apparent Na-Cl permeability ratio (0.75 +/- 0.01) calculated from dilution potential me...

The American journal of physiology, 1990

The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the out... more The rabbit papillary surface epithelium (PSE) is a simple cuboidal epithelium that covers the outer surface of the renal papilla and has an apical surface that faces the urinary space. We studied acid-base transport in this epithelium by dissecting it from the papilla, mounting it in a modified Ussing chamber, and following pH changes in the apical bathing solution. The experiments demonstrated that the PSE is capable of acidifying the apical solution at a substantial rate. The acidification rate was similar with 100% nitrogen and 100% oxygen (with and without 10 microM antimycin A), ruling out a dependence on oxidative metabolism. Addition of 1 mM iodoacetate decreased apical acidification by 55%, suggesting a dependence on glycolysis. The net rate of lactate secretion was only 17% of the total acid secretion rate, indicating that apical acidification was not directly caused by secretion of lactic acid alone. Removal of sodium or potassium from the apical solutions or the addition ...

Contributions to nephrology, 1991

The American journal of physiology, 1992

To study mechanisms involved in renal glutamate dehydrogenase (GDH) regulation in response to sys... more To study mechanisms involved in renal glutamate dehydrogenase (GDH) regulation in response to systemic acid loading, we have measured blood pH, ammonium excretion, renal GDH mRNA levels, and GDH activity in rats. Acid intake (0.28 M NH4Cl in drinking water for 3 days) increased GDH mRNA levels in the renal cortex, but had no effect in the outer stripe of the outer medulla, inner stripe of the outer medulla, or the inner medulla. Rats were subjected to a step change in acid intake by alkali loading for 3 days (7.2 meq NaHCO3 per day in food slurry) and shifting to acid loading for up to 7 days (7.2 meq NH4Cl in food slurry). Ammonium excretion rose rapidly, increasing by 14-fold in the first 24-h period and 38-fold in the second 24-h period. Cortical GDH mRNA levels were increased relative to alkali-loaded values by 3.7-fold in 24 h, 4.3-fold in 4 days, but only 2.2-fold in 7 days. GDH activity was unchanged after 24 h of acid intake, but was significantly increased after 48 h. We co...

Comparative Biochemistry and Physiology Part A: Physiology, 1977

The tunicate Molgula munlmt~msis is an estuarine animal lacking protonephridia and tubular excret... more The tunicate Molgula munlmt~msis is an estuarine animal lacking protonephridia and tubular excretory organs but possessing a well-developed renal sac thought to be the primary osmoregulatory organ. 2. Animals were acclimated to three different salinities (271 mM Na+, 218 mM Na+ and 125 mM Na+). after which sodium and potassium levels were measured in plasma and renal sac fluid. The results indicate regulation of the sodium and potassium content of renal sac fluid, but not plasma. 3. Transmission electron microscopy reveals that the renal sac epithelium possesses structural features known to be associated in other animals with ion secretion and/or osmoregulation.