Hypoxia caused a progressive cytochalasin B-inhibitable increase in the rate of 3-O-methylglucose transport in rat epitrochlearis muscles to a level approximately six-fold above basal. Muscle ATP concentration was well maintained during hypoxia, and increased glucose transport activity was still present after 15 min of reoxygenation despite repletion of phosphocreatine. However, the increase in glucose transport activity completely reversed during a 180-min-long recovery in oxygenated medium. In perfused rat hindlimb muscles, hypoxia caused an increase in glucose transporters in the plasma membrane, suggesting that glucose transporter translocation plays a role in the stimulation of glucose transport by hypoxia. The maximal effects of hypoxia and insulin on glucose transport activity were additive, whereas the effects of exercise and hypoxia were not, providing evidence suggesting that hypoxia and exercise stimulate glucose transport by the same mechanism. Caffeine, at a concentration too low to cause muscle contraction or an increase in glucose transport by itself, markedly potentiated the effect of a submaximal hypoxic stimulus on sugar transport. Dantrolene significantly inhibited the hypoxia-induced increase in 3-O-methylglucose transport. These effects of caffeine and dantrolene suggest that Ca2+ plays a role in the stimulation of glucose transport by hypoxia.

Skeletal muscle surface membrane is constituted by the PM domain and its specialized deep invaginations known as TTs. We have shown previously that insulin induces a rapid translocation of GLUT4s from an IM pool to the PM in rat skeletal muscle (6). In this study, we have investigated the possibility that insulin also stimulates the translocation of GLUT4 proteins to TTs, which constitute the largest area of the cell surface envelope. PM, TTs, and IM components of control and insulinized skeletal muscle were isolated by subcellular fractionation. The TTs then were purified further by removing vesicles of SR origin by using a Ca-loading procedure. Ca-loading resulted in a five- to sevenfold increase in the purification of TTs in the unloaded fraction relative to the loaded fraction, assessed by immunoblotting with an anti-DHP-receptor monoclonal antibody. In contrast, estimation of the content of Ca(2+)-ATPase protein (a marker of SR) with a specific polyclonal antibody revealed that most, if not all, SR vesicles were recovered in the Ca-loaded fraction. Western blotting with an anti-COOH-terminal GLUT4 protein polyclonal antibody revealed that acute insulin injection in vivo (30 min) increased the content of GLUT4 (by 90%) in isolated PMs and markedly enhanced (by 180%) GLUT4 content in purified TTs. Importantly, these insulin-dependent changes in GLUT4 content of PM and purified TTs were seen in the absence of changes in the alpha 1-subunit of the Na(+)-K(+)-ATPase, a surface membrane marker.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitors of HIV protease have been shown to have antiapoptotic effects in vitro, yet whether these effects are seen in vivo remains controversial. In this study, we have evaluated the impact of the HIV protease inhibitor (PI) nelfinavir, boosted with ritonavir, in models of nonviral disease associated with excessive apoptosis. In mice with Fas-induced fatal hepatitis, Staphylococcal enterotoxin B-induced shock, and middle cerebral artery occlusion-induced stroke, we demonstrate that PIs significantly reduce apoptosis and improve histology, function, and/or behavioral recovery in each of these models. Further, we demonstrate that both in vitro and in vivo, PIs block apoptosis through the preservation of mitochondrial integrity and that in vitro PIs act to prevent pore function of the adenine nucleotide translocator (ANT) subunit of the mitochondrial permeability transition pore complex.

Background and Purpose-Previous studies have reported a low, Ϸ1% to 3%, rate of detection of occult atrial fibrillation (AF) with Holter monitor in patients with acute stroke. Furthermore, at least one study has reported that Holter monitoring could not always corroborate initial electrocardiographic (ECG) detection of AF suggesting underestimation of AF by Holter. We compare the detection of new-onset AF by serial ECG assessments and Holter after acute ischemic stroke. Methods-One hundred forty-four patients with ischemic stroke admitted to a stroke unit were studied. The number of ECGs conducted within the first 3 days up to the detection of AF as well as the time interval for Holter "hookup" and subsequent reporting of AF was documented. Results-ECGs were performed in 143 patients with a baseline of 10 (7%) patients having a history of AF. Serial ECGs detected 15 new AF cases in Ͻ2 days of admission, thereby increasing the total number of known AF cases to 25 (17.5%), a 2.6-fold increased realization of AF (Pϭ0.011). Holter was also completed in 12 of 15 new cases of AF but surprisingly identified AF in only 50% (6 of 12). Holter monitoring was performed in 126 cases and in this subgroup, there was no statistically significant difference in the rate of AF detection with ECG or Holter. Conclusions-Serial ECG assessments within the first 72 hours of an acute stroke significantly improve detection of AF.The discordance regarding the corroboration of AF by Holter in ECG-positive patients with AF supports previous observations and suggests a high incidence of paroxysmal AF as a cause of ischemic stroke.