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A M Kahn

Publications and source records attributed to A M Kahn.

13 recordsLinked to original sources
PubMed1992

Effects of serotonin on intracellular pH and contraction in vascular smooth muscle.

Serotonin (5-HT) and other contractile agonists stimulate Na(+)-H+ exchange in vascular smooth muscle. Since intracellular alkalinization, per se, stimulates contraction, we tested whether 5-HT-induced contraction was associated with an increased pHi. In HCO3(-)-free buffer (pHo 7.4), 5-HT (10(-5) M) increased pHi, as measured by 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein fluorescence, from 7.10 +/- 0.03 to 7.34 +/- 0.03 (p < 0.01) in primary cultures of canine femoral artery vascular smooth muscle cells grown to confluence in the presence of 10% fetal calf serum. In HCO3- buffer (24 mM, pHo 7.4), resting pHi was 7.26 +/- 0.04 (p < 0.01 versus HCO3(-)-free buffer) but was not altered by 5-HT. In both types of buffer, 5-HT stimulated 5-(N-ethyl-N-isopropyl)amiloride-sensitive 22Na+ uptake (Na(+)-H+ exchange). In HCO3- buffer and in Na(+)- and HCO3(-)-free buffer, 5-HT increased 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid-sensitive 36Cl- uptake, suggesting that 5-HT stimulated Na(+)-independent Cl(-)-HCO3- and Cl(-)-Cl- exchange activities, respectively. Individual vascular smooth muscle cells were then cultured on rat tail tendon collagen gels in the presence of 0.5% fetal calf serum, and cell length and pHi were measured by video and epifluorescence microscopy. 5-HT contracted cells in a dose-dependent, reversible, and ketanserin-inhibitable manner. These cells, like cells grown in 10% fetal calf serum, exhibited Na(+)-H+ and Na(+)-independent Cl(-)-HCO3- exchange. In HCO3- buffer, 5-HT contracted cells without an associated change in pHi. We concluded the following: 1) 5-HT stimulated both Na(+)-H+ and Na(+)-independent Cl(-)-HCO3- exchange activities in cultured vascular smooth muscle cells in parallel. 2) As a result of enhanced H+ and HCO3- efflux, pHi was not altered. 3) In the presence of HCO3-, 5-HT-induced contraction was not associated with a change in pHi.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1991

Na(+)-independent Cl(-)-HCO3- exchange in sarcolemmal vesicles from vascular smooth muscle.

Intracellular pH (pHin) affects vascular smooth muscle function, but the mechanisms that control pHin in this tissue are not well understood. These studies were performed to determine whether sarcolemmal vesicles from bovine superior mesenteric artery (SMA) contain a Na(+)-independent Cl(-)-HCO3- exchanger and, if so, to determine its sensitivity to membrane voltage and inhibitors. 36Cl- was taken up by vesicles into an osmotically active intravesicular space. In Na(+)-free media, an outwardly or inwardly directed HCO3- gradient stimulated 36Cl- transport in the opposite direction. An outwardly directed unlabeled Cl- gradient stimulated 36Cl- uptake by a mechanism that was inhibited by external HCO3-. HCO3- or Cl- gradient-stimulated 36Cl- uptake was not due to voltage coupling between ions. In the nominal absence of HCO3-, a threefold outwardly directed OH- gradient did not affect 36Cl- uptake. Total 36Cl- uptake was stimulated by an inside-positive voltage, but the HCO3- gradient-stimulated component of 36Cl- uptake was insensitive to a change in membrane voltage. Finally, HCO3- gradient-stimulated 36Cl- uptake was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and furosemide, with 50% inhibitory concentration values equalling approximately 1.0 and 0.5 mM, respectively. These data indicate that sarcolemmal vesicles from bovine SMA contain a Na(+)-independent Cl(-)-HCO3- exchanger. This transport system is probably electroneutral and is inhibitable by DIDS and furosemide. A conductive pathway for Cl- is present in the vesicles, but Cl(-)-OH- exchange activity was not observed.

Animals↗
PubMed1991

Effects of pHi on Na(+)-H+, Na(+)-dependent, and Na(+)-independent C1(-)-HCO3-exchangers in vascular smooth muscle.

The mechanisms that control intracellular pH (pHi) in vascular smooth muscle are not fully understood. We reported that pHi in primary cultured vascular smooth muscle cells from canine femoral artery is 7.26, a value maintained via HCO3- influx by the Na(+)-dependent C1(-)-HCO3-exchanger but not via H+ efflux by the Na(+)-H+ exchanger [A. M. Kahn, E. J. Cragoe, Jr., J. C. Allen, R. D. Halligan, and H. Shelat. Am. J. Physiol 259 (Cell Physiol. 28): C134-C143, 1990]. To explain these findings, in the present study, we determined the pHi activity profile of these two transport systems. Although both were active at acidic pHi, Na(+)-H+ exchange activity was very low at and above pHi 7.0, while Na(+)-dependent C1(-)-HCO3-exchange activity maintained near-maximal activity up to pHi 7.26 but fell to undetectable levels by pHi 7.4. A Na(+)-independent C1(-)-HCO3-exchanger was present, which mediated HCO3-efflux after an acute alkaline load. The activity of this system was negligible at pHi 7.2 and was stimulated at alkaline pHi. In conclusion, the pHi of these vascular smooth muscle cells at rest is maintained via HCO3-influx by the Na(+)-dependent C1(-)-HCO3-exchanger. After acute acidic or alkaline loads, correction of pHi is mediated by activation of the normally quiescent Na(+)-H+ and Na(+)-independent C1(-)-HCO3-exchangers, respectively. All three acid-base transport systems have pHi set points that protect the cell from overcorrecting pHi after a disturbance in either direction.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1990

Na(+)-H+ and Na(+)-dependent Cl(-)-HCO3- exchange control pHi in vascular smooth muscle.

The mechanisms that control intracellular pH (pHi) in vascular smooth muscle are not fully understood. These studies were performed to determine the identity and relative importance of the sarcolemmal transport systems that mediate net acid efflux in primary cultured vascular smooth muscle cells from canine femoral artery. In HEPES- or HCO3(-)-buffered physiological salt solution (HEPES-PSS, HCO3(-)-PSS), recovery from an acute acid load was totally dependent on external Na+. 5-[N-ethyl-N-isopropyl]amiloride (EIPA, 50 microM) inhibited pHi recovery 100 and 68% in HEPES-PSS and HCO3(-)-PSS, respectively. EIPA-insensitive pHi recovery in HCO3(-)-PSS was inhibited 48% by 4,4'-diisothyocyanostilbene-2,2'-disulfonic acid (DIDS). An outwardly directed H+ gradient stimulated amiloride-sensitive 22Na+ uptake, and an inwardly directed HCO3- gradient stimulated amiloride-insensitive 22Na+ uptake. The latter was inhibited by DIDS or prior depletion of cell Cl-. In HEPES-PSS, resting pHi was 7.17 +/- 0.03, was not affected by DIDS, but was lowered by EIPA or by removing extracellular Na+. In HCO3(-)-PSS, resting pHi was 7.25 +/- 0.02 (P less than 0.05) and was not affected by EIPA. Removing extracellular Na+ in the presence of EIPA decreased pHi in HCO3(-)-PSS but not in HEPES-PSS. DIDS lowered resting pHi in HCO3(-)-PSS, after which EIPA further lowered pHi. We conclude that acid efflux from these cells is mediated by a Na(+)-H+ exchanger and a Na(+)-dependent Cl(-)-HCO3- exchanger. In HEPES-PSS, acid efflux via the Na(+)-H+ exchanger maintains resting pHi. In HCO3(-)-PSS, additional acid efflux via the Na(+)-dependent Cl(-)-HCO3- exchanger results in a higher pHi. Although the Na(+)-H+ exchanger is primarily responsible for acid efflux after an acute acid load, the Na(+)-dependent Cl(-)-HCO3- exchanger is responsible for acid efflux under physiological conditions.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1988

Sodium-lithium exchange in sarcolemmal vesicles from canine superior mesenteric artery.

Exchange of intracellular sodium for extracellular lithium readily occurs in vascular smooth muscle, but the mechanism of this exchange is not known. These studies examined whether a sodium-lithium countertransport system was present in the cell membrane of vascular smooth muscle. A sarcolemmal-enriched vesicle preparation was obtained from canine superior mesenteric artery via a magnesium aggregation and differential centrifugation technique. An outwardly directed gradient for lithium stimulated 22Na uptake by the vesicles, and an inwardly directed gradient for lithium stimulated 22Na efflux. These effects were not due to an alteration in membrane potential, and sodium uptake was not stimulated by lithium in the absence of a gradient for lithium. The lithium gradient-stimulated component of sodium uptake was not affected by a change in membrane potential and was insensitive to ouabain. Both sodium-lithium exchange and sodium-proton exchange in sarcolemmal-enriched vesicles were inhibited by two compounds that inhibit the sodium-lithium countertransport system in red cells, phloretin and quinidine. Ethylisopropylamiloride also inhibited both sodium-lithium exchange and sodium-proton exchange in the vesicles. In support of the possibility that sarcolemmal sodium-lithium exchange and sodium-proton exchange are mediated by a single cation exchange mechanism with affinity for sodium, lithium, and protons, we found that an inwardly directed sodium or lithium gradient stimulated proton efflux, and that the stimulation of sodium efflux by external lithium or protons was not additive. It is concluded from these studies that sarcolemmal vesicles from canine superior mesenteric artery contain an electroneutral, phloretin, quinidine, and ethylisopropylamiloride inhibitable sodium-lithium exchange transport system.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1987

Difference between human red blood cell Na+-Li+ countertransport and renal Na+-H+ exchange.

Several laboratories have reported that the activities of sodium-lithium countertransport are increased in red blood cells from patients with essential hypertension. Based on the many similarities between this transport system and the renal sodium-proton exchanger, a hypothesis has been put forth in the literature that increased red blood cell sodium-lithium countertransport activity may be a marker for increased sodium-proton exchange activity in the renal proximal tubule. The present studies were designed to test the hypothesis that sodium-lithium countertransport in red blood cells from humans or rabbits is mediated by the same transport mechanism that mediates sodium-proton exchange in the renal brush border from those species. Similar to what has been reported for the rabbit, the present studies show that an amiloride-sensitive sodium-proton exchanger is present in human renal brush border vesicles. However, Na+-Li+ countertransport in human and rabbit red blood cells, assayed under several different conditions, was not inhibited by amiloride. In agreement with what has been reported for humans, the present studies show that extracellular proton-stimulated sodium efflux is inhibited by amiloride in rabbit red blood cells. These data demonstrate a difference (amiloride sensitivity) between the red blood cell sodium-lithium countertransporter and the renal brush border sodium-proton exchanger in humans and rabbits. These experiments detract from the hypothesis that increased red blood cell sodium-lithium countertransport activity in patients with essential hypertension is a marker for increased sodium-proton exchange activity in the renal brush border.

Amiloride↗
PubMed1979

Burn wound biopsy. Multiple uses in patient management.

It is often exceedingly difficult to initially evaluate the depth of a burn wound and thus inaugurate appropriate definitive therapy. The clinical picture of the burn would may not always correlate with the true histologic depth of the injury. For this reason we have undertaken a program of obtaining punch biopsies of burn wounds in patients where the depth of the burn wound is equivocal. In such cases the biopsy has proven to be useful in guiding subsequent therapy. In addition to establishing the anatomic depth of injury, there are several other valuable uses of burn wound biopsies. The other uses are: diagnosis of invasive infection, quantitative bacterial culture, medical-legal values, psychological values and forensic utility.

Biopsy↗
PubMed1978

Diagnostic value of ascitic fluid lactic dehydrogenase, protein, and WBC levels.

Three characteristics of an exudate, ie, an ascitic fluid lactic dehydrogenase (LDH) level of greater than 400 Sigma units (SU), an ascitic fluid-serum LDH ratio of greater than 0.6, and an ascitic fluid-serum protein ratio of greater than 0.5, were studied in a prospective fashion to determine their usefulness in the differential diagnosis of ascites. The ascitic fluid LDH level did not exceed 400 SU in any patient with uncomplicated chronic liver disease, whereas in patients with malignant, tuberculous, or pancreatic ascites it exceeded 500 SU in 12/19 patients. The finding of two of the three characteristics indicated a nonhepatic cause for the ascites whereas the absence of all three strongly suggested uncomplicated liver disease as the sole cause. The ascitic fluid WBC count was also useful in that values exceeded 500/cu mm in bacterial and tuberculous peritonitis whereas it was low (297 +/- 49/cu mm) in chronic liver disease.

Ascites↗
PubMedDate not supplied

Treatment for depigmentation resulting from burn injuries.

A new surgical technique to "repigment" skin that has been depigmented by deep partial-thickness burn injuries has been developed and proven to be successful. Partial-thickness burn injuries frequently heal with pigmentary changes. Occasionally, permanent depigmentation is observed, especially in areas such as the hands and fingers. This article reports our surgical technique and our success in using it to treat depigmentation after burn injuries. This new technique consists of superficial dermabrasion of the depigmented region, followed by transplantation of melanocytes via epithelial grafts. With this technique, 15 separate surgical procedures have been performed on 11 patients. The follow-up period for these patients has ranged from 0.5 months to 94 months, with an average of 14 months. The skin-graft take has been excellent in all patients. The color match ranges from good to excellent. No complications have been observed, and this procedure has consistently and reliably improved the disfigurement from depigmentation after these burn injuries.

Adult↗
PubMedDate not supplied

Relationship between nurses' opinions about mental illness and experience.

To examine the effect of long-term experience on a psychiatric ward on nurses' opinions about mental illness, experimental groups of nursing students (N = 11) and experienced psychiatric nurses (N = 8) and a control group of medical-surgical nurses (N = 8) were compared along the five dimensions of the Opinions about Mental Illness Scale. The medical-surgical and psychiatric nurses were matched for age and education. The experienced psychiatric nurses were found to hold significantly more authoritarian opinions about mental illness; they adhered less to a belief in interpersonal etiology than the other two groups. Compared to the nursing students, the psychiatric nurses held significantly more socially restrictive opinions about mental illness; they adhered less to current mental health ideology. However, age could not be ruled out as a variable in the latter two opinions. Factors which may contribute to opinion change in psychiatric nurses are discussed.

Adult↗