Biomedical subjects

M R Adler

Publications and source records attributed to M R Adler.

3 recordsLinked to original sources

PubMed1999

Extracellular ATP stimulates volume decrease in Necturus red blood cells.

This study examined whether extracellular ATP stimulates regulatory volume decrease (RVD) in Necturus maculosus (mudpuppy) red blood cells (RBCs). The hemolytic index (a measure of osmotic fragility) decreased with extracellular ATP (50 microM). In contrast, the ATP scavenger hexokinase (2.5 U/ml, 1 mM glucose) increased osmotic fragility. In addition, the ATP-dependent K+ channel antagonist glibenclamide (100 microM) increased the hemolytic index, and this inhibition was reversed with ATP (50 microM). We also measured cell volume recovery in response to hypotonic shock electronically with a Coulter counter. Extracellular ATP (50 microM) enhanced cell volume decrease in a hypotonic (0.5x) Ringer solution. In contrast, hexokinase (2.5 U/ml) and apyrase (an ATP diphosphohydrolase, 2.5 U/ml) inhibited cell volume recovery. The inhibitory effect of hexokinase was reversed with the Ca2+ ionophore A-23187 (1 microM); it also was reversed with the cationophore gramicidin (5 microM in a choline-Ringer solution), indicating that ATP was linked to K+ efflux. In addition, glibenclamide (100 microM) and gadolinium (10 microM) inhibited cell volume decrease, and the effect of these agents was reversed with ATP (50 microM) and A-23187 (1 microM). Using the whole cell patch-clamp technique, we found that ATP (50 microM) stimulated a whole cell current under isosmotic conditions. In addition, apyrase (2.5 U/ml), glibenclamide (100 microM), and gadolinium (10 microM) inhibited whole cell currents that were activated during hypotonic swelling. The inhibitory effect of apyrase was reversed with the nonhydrolyzable analog adenosine 5'-O-(3-thiotriphosphate) (50 microM), and the effect of glibenclamide or gadolinium was reversed with ATP (50 microM). Finally, anionic whole cell currents were activated with hypotonic swelling when ATP was the only significant charge carrier, suggesting that increases in cell volume led to ATP efflux through a conductive pathway. Taken together, these results indicate that extracellular ATP stimulated cell volume decrease via a Ca2+-dependent step that led to K+ efflux.

Adenosine Triphosphate↗

PubMed1998

Protein kinase C and regulatory volume decrease in mudpuppy red blood cells.

This study examined whether protein kinase C (PKC) stimulates K+ efflux during regulatory volume decrease (RVD) in Necturus maculosus (mudpuppy) red blood cells (RBCs). The limit of osmotic fragility increased with the general protein kinase inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7, 10 micrometer), but not with the cyclic nucleotide-dependent kinase antagonists N-(2'-guanidinoethyl)-5-isoquinolinesulfonamide (HA-1004, 10 micrometer) and N-2-(methylamino)ethyl-5-isoquinoline-sulfonamide (H-8, 5 micrometer). Consistent with these results, osmotic fragility also increased with the PKC antagonists bisindolylmaleimide I (GF-109203X or bis I, 100 nm), bisindolylmaleimide II (bis II, 100 nm), and chelerythrine (10 micrometer). The effect of these three antagonists and H-7 was reversed with gramicidin (5 micrometer in a choline Ringer), indicating PKC was linked to K+ efflux (gramicidin is a cationophore that was used to ensure a high K+ permeability). We also measured cell volume recovery from hypotonic shock (0.5x Ringer) with a Coulter counter and estimated cell volume from the hematocrit. The percent RVD compared to control decreased with H-7 (10 micrometer), sphingosine (100 nm), chelerythrine (10 micrometer), bis I (100 nm), and bis II (100 nm), but not with HA-1004 (10 micrometer) nor H-8 (5 micrometer). Inhibition of RVD by H-7, chelerythrine, bis I, and bis II was reversed with gramicidin (5 micrometer). Furthermore, using the patch clamp technique, we found H-7 (10 micrometer) reduced a whole cell conductance that was activated during cell swelling. In addition, a conductance responsible for K+ efflux during cell swelling was inhibited by bis I (100 nm) and bis II (100 nm). These results indicate that a conductive pathway mediating K+ loss during RVD is regulated, at least in part, by protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1995

The effects on professional practices of a three-day course on breastfeeding.

This study assessed reported changes in clinical breastfeeding support practices following a three-day (approximately 24 hour) course. The course, presented at the Catholic University in Santiago, Chile, included the physiology of lactation and lactational infertility, related policy, clinical skills, the Lactational Amenorrhea Method (LAM), and program-related findings. A questionnaire was sent to all participants and an additional systematic sample was telephoned to assure a statistically valid sample. Sixty-nine percent of respondents reported changes in clinical practices resulting from attendance at the course. The results support the concept, now being advanced by the Baby-Friendly Hospital Initiative, that an 18-24 hour course can change clinical practices.

Breast Feeding↗