RESUMEN
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Asunto(s)
Adulto , Masculino , Humanos , Traqueostomía , Estreptococos Viridans , Infecciones Estreptocócicas , Toracotomía , Derrame Pleural , Respiración Artificial , Drenaje , Desbridamiento , Mediastinitis , Intubación Intratraqueal , Angina de LudwigAsunto(s)
Calcio/fisiología , Proteínas Portadoras/fisiología , Músculos/fisiología , Neuronas/fisiología , Animales , Astrocitos/fisiología , Calcio/metabolismo , Proteínas Portadoras/metabolismo , Células Cultivadas , Femenino , Cinética , Músculo Liso Vascular/fisiología , Ratas , Ratas Endogámicas , Intercambiador de Sodio-Calcio , Sinaptosomas/fisiología , ThoracicaRESUMEN
Coupled Na+ exit/Ca2+ entry (Na/Ca exchange operating in the Ca2+ influx mode) was studied in giant barnacle muscle cells by measuring 22Na+ efflux and 45Ca2+ influx in internally perfused, ATP-fueled cells in which the Na+ pump was poisoned by 0.1 mM ouabain. Internal free Ca2+, [Ca2+]i, was controlled with a Ca-EGTA buffering system containing 8 mM EGTA and varying amounts of Ca2+. Ca2+ sequestration in internal stores was inhibited with caffeine and a mitochondrial uncoupler (FCCP). To maximize conditions for Ca2+ influx mode Na/Ca exchange, and to eliminate tracer Na/Na exchange, all of the external Na+ in the standard Na+ sea water (NaSW) was replaced by Tris or Li+ (Tris-SW or LiSW, respectively). In both Na-free solutions an external Ca2+ (Cao)-dependent Na+ efflux was observed when [Ca2+]i was increased above 10(-8) M; this efflux was half-maximally activated by [Ca2+]i = 0.3 microM (LiSW) to 0.7 microM (Tris-SW). The Cao-dependent Na+ efflux was half-maximally activated by [Ca2+]o = 2.0 mM in LiSW and 7.2 mM in Tris-SW; at saturating [Ca2+]o, [Ca2+]i, and [Na+]i the maximal (calculated) Cao-dependent Na+ efflux was approximately 75 pmol#cm2.s. This efflux was inhibited by external Na+ and La3+ with IC50's of approximately 125 and 0.4 mM, respectively. A Nai-dependent Ca2+ influx was also observed in Tris-SW. This Ca2+ influx also required [Ca2+]i greater than 10(-8) M. Internal Ca2+ activated a Nai-independent Ca2+ influx from LiSW (tracer Ca/Ca exchange), but in Tris-SW virtually all of the Cai-activated Ca2+ influx was Nai-dependent (Na/Ca exchange). Half-maximal activation was observed with [Na+]i = 30 mM. The fact that internal Ca2+ activates both a Cao-dependent Na+ efflux and a Nai-dependent Ca2+ influx in Tris-SW implies that these two fluxes are coupled; the activating (intracellular) Ca2+ does not appear to be transported by the exchanger. The maximal (calculated) Nai-dependent Ca2+ influx was -25 pmol/cm2.s. At various [Na+]i between 6 and 106 mM, the ratio of the Cao-dependent Na+ efflux to the Nai-dependent Ca2+ influx was 2.8-3.2:1 (mean = 3.1:1); this directly demonstrates that the stoichiometry (coupling ratio) of the Na/Ca exchange is 3:1. These observations on the coupling ratio and kinetics of the Na/Ca exchanger imply that in resting cells the exchanger turns over at a low rate because of the low [Ca2+]i; much of the Ca2+ extrusion at rest (approximately 1 pmol/cm2.s) is thus mediated by an ATP-driven Ca2+ pump.(ABSTRACT TRUNCATED AT 400 WORDS)
Asunto(s)
Calcio/farmacocinética , Músculos/metabolismo , Sodio/farmacocinética , Thoracica/metabolismo , Animales , Técnicas In Vitro , Músculos/citologíaRESUMEN
Spontaneous biliary-enteric fistula is almost always due to cholelithiasis or peptic ulcer disease; rarely is malignancy responsible. A patient with carcinoma of the pancreas who presented with gastrointestinal hemorrhage and pneumobilia due to a malignant cholecystoduodenal fistula is reported.
Asunto(s)
Fístula Biliar/etiología , Enfermedades Duodenales/etiología , Enfermedades de la Vesícula Biliar/etiología , Fístula Intestinal/etiología , Neoplasias Pancreáticas/complicaciones , Tomografía Computarizada por Rayos X , Adenocarcinoma/complicaciones , Adenocarcinoma/diagnóstico por imagen , Fístula Biliar/diagnóstico por imagen , Enfermedades Duodenales/diagnóstico por imagen , Enfermedades de la Vesícula Biliar/diagnóstico por imagen , Humanos , Fístula Intestinal/diagnóstico por imagen , Masculino , Persona de Mediana Edad , Neoplasias Pancreáticas/diagnóstico por imagenRESUMEN
Calcium-45 efflux was measured in squid axons whose internal solute concentration was controlled by internal dialysis. Most of the Ca efflux requires either external Na (Na-Ca exchange) or external Ca plus in alkali metal ion (Ca-Ca exchange; cf. Blaustein & Russell, 1975). Both Na-Ca and Ca-Ca exchange are apparently mediated by a single mechanism because both are inhibited by Sr and Mn, and because addition of Na to an external medium optimal for Ca-Ca exchange inhibits Ca efflux. The transport involves simultaneous (as opposed to sequential) ion counterflow because the fractional saturation by internal Ca (Cai) does not affect the external Na (Nao) activation kinetics; also, Nao promotes Ca efflux whether or not an alkali metal ion is present inside, whereas Ca-Ca exchange requires alkali metal ions both internally and externally (i.e., internal and external sites must be appropriately loaded simultaneously). ATP increases the affinity of the transport mechanism for both Cai and Nao, but it does not affect the maximal transport rate at saturating [Ca2+]i and [Na+]o; this suggest that ATP may be acting as a catalyst of modulator, and not as an energy source. Hill plots of the Nao activation data yield slopes congruent to 3 for both ATP-depleted and ATP-fueled axons, compatible with a 3 Na+-for-1 Ca2+ exchange. With this stoichiometry, the Na electrochemical gradient alone could provide sufficient energy to maintain ionized [Ca2+]i in the physiological range (about 10(-7) M).