Interest is growing in methods toKip1 . Adenovirally mediated ectopic overexpression of p27Kip1 in exponentially growing IGF-I transgenic satellite cells reversed the increase in cyclin Ecdk2 kinase activity, pRb phosphorylation, and cyclin A protein abundance, thereby implicating an important role for p27Kip1 in promoting satellite cell senescence. These observations provide a more complete dissection of molecular events by which increased local expression of a growth factor in mature skeletal muscle fibers extends replicative life span of primary stem cells than previously known.

To determine whether changes in glycogen synthase kinase-3beta (GSK-3beta) phosphorylation contribute to muscle hypertrophy, we delineated the effects of GSK-3beta activity on C(2)C(12) myotube size. We also examined possible insulin-like growth factor I (IGF-I) signaling of NFAT (nuclear factors of activated T cells)-inducible gene activity and possible modulation of NFAT activation by GSK-3beta. Application of IGF-I (250 ng/ml) or LiCl (10 mM) alone (i.e., both inhibit GSK-3beta activity) increased the area of C(2)C(12) myotubes by 80 and 85%, respectively. The application of IGF-I (250 ng/ml) elevated GSK-3beta phosphorylation and reduced GSK-3beta kinase activity by approximately 800% and approximately 25%, respectively. LY-294002 (100 microM) and wortmannin (150 microM), specific inhibitors of phosphatidylinositol 3'-kinase, attenuated IGF-I-induced GSK-3beta phosphorylation by 67 and 92%, respectively. IGF-I suppressed the kinase activity of GSK-3beta. IGF-I (250 ng/ml), but not LiCl (10 mM), induced an increase in NFAT-activated luciferase reporter activity. Cotransfection of a constitutively active GSK-3beta (cGSK-3beta) inhibited the induction by IGF-I of NFAT-inducible reporter activity. LiCl, which inhibits GSK-3beta, removed the block by cGSK-3beta on IGF-I-inducible NFAT-responsive reporter gene activity. These data suggest that the IGF-I-induced increase in skeletal myotube size is signaled, in part, through the inhibition of GSK-3beta.

The purpose of the current study was to examine IGFBP-3, -4, and -5 mRNA and protein expression levels as a function of muscle type, age, and regrowth from an immobilization-induced atrophy in Fischer 344 × Brown Norway rats. IGFBP-3 mRNA expression in the 4-mo-old animals was significantly higher in the red and white portions of the gastrocnemius muscle compared with the soleus muscle. However, there were no significant differences in IGFBP-3 mRNA expression among any of the muscle groups in the 30-mo-old animals. There were no significant differences in IGFBP-5 mRNA expression in any of the muscle groups, whereas in the 30-mo-old animals there was significantly less IGFBP-5 mRNA expression in the white gastrocnemius compared with the red gastrocnemius muscles. Although IGFBP-3 and -5 proteins were detected in the type I soleus muscle with Western blot analyses, no detection was observed in the type II red and white portions of the gastrocnemius muscle. Aging from adult (18 mo) to old animals (30 mo) was associated with decreases in IGFBP-3 mRNA and protein and IGFBP-5 protein only in the soleus muscle. After 10 days of recovery from 10 days of hindlimb immobilization, IGFBP-3 mRNA and protein increased in soleus muscles from young (4-mo) rats; however, only IGFBP-3 protein increased in the old (30-mo) rats. Whereas there were no changes in IGFBP-5 mRNA expression during recovery, IGFBP-5 protein in the 10-day-recovery soleus muscle did increase in the young, but not in the old, rats. Because one of the functions of IGFBPs is to modulate IGF-I action on muscle size and phenotype, it is hypothesized that IGFBP-3 and -5 proteins may have potential modulatory roles in type I fiber-dominated muscles, aging, and regrowth from atrophy.

Estrogen is a key regulator of vascular responses and angioadaptation in multiple organs and tissues, including brain. However, the consequences of a loss of ovarian steroid hormone secretion on the status of microvascular networks in brain and meninges are largely unknown. Here, using the perfused dura mater model coupled with high-resolution digital epifluorescence and laser scanning confocal microscopy and computer-assisted morphometric analysis, we demonstrate that cessation of ovarian hormone production causes dramatic vascular remodeling in meningeal microvascular networks characterized by a threefold decrease in microvessel density and capillary rarefaction and an almost fourfold increase in vascular permeability. These changes were accompanied by a significant decrease in angiopoietin-1 (Ang-1) expression and Ang-1/Tie-2 ratio (1.4-fold, P < 0.01, and 1.5-fold, P < 0.05, respectively) in ovariectomized animals compared with intact females, but no changes were detected in the expression of estrogen receptors (ER)-alpha and -beta. We conclude that estrogen-dependent control of Ang-1 expression plays an important role in stabilizing meningeal microvessel and maintaining healthy microvascular networks.

Summary The effect of cisapride pretreatment on gastric emptying in horses was determined by measuring serum concentrations of acetaminophen, a drug known to be readily absorbed in the small intestine but not in the stomach. The time to reach maximum serum acetaminophen concentrations (Tmax), the maximum serum concentrations (Cmax) and the area under the serum acetaminophen concentration vs. time curves (AUC) were compared among treatment groups. In the first part of the study, the effect of orally administered cisapride (0.1, 0.2 and 0.4 mg/kg bwt) on gastric emptying was examined in 6 normal fasted horses. In the second part of the study, gastric emptying in horses given endotoxin i.v. (n = 6) was compared to those that received cisapride per os prior to administration of endotoxin (n = 6) and those that received neither compound (n = 6). Cisapride did not alter gastric emptying in normal horses. Endotoxin caused a profound delay in gastric emptying and pretreatment with cisapride significantly attenuated this effect. It is concluded that cisapride may be useful as a prophylactic measure when administered prior to the development of endotoxaemia.