Caecal ligation and puncture induced sepsis in the rat results in increased brain water content and perimicrovessel oedema.

To investigate brain water content and ultrastructure in a rat caecal ligation and puncture (CLP) model of sepsis, adult male Wistar rats were assigned to one of the following experimental groups: CLP, Un-operated or Sham. CLP was performed under anaesthesia, Sham rats were exposed to anaesthesia, laparotomy and caecal mobilisation and Un-operated rats did not experience anaesthesia or surgery. CLP and Sham rats were sacrificed 18-20 h following recovery from surgery and Un-operated rats were sacrificed at the same time. Frontal cortex samples (CLP n = 9; Un-operated n = 10; Sham n = 8) were taken immediately post mortem and their water content determined using gravimetry. Similar samples were taken from other rats (CLP n = 8; Un-operated n = 8; Sham n = 8), processed for electron microscopy and subjected to morphometric analysis. There was significantly more brain water in CLP than Un-operated (P < 0.01) and Sham (P < 0.05) rats. Electron microscopy revealed significantly more peri-microvessel oedema in CLP than Un-operated (P < 0.001) and Sham rats (P < 0.05). Microvessel endothelial cell lumen cross-sectional area was significantly smaller in CLP than Un-operated (P < 0.001) and Sham (P < 0.05) rats and microvessel endothelial cell cross-sectional area was significantly smaller in CLP than Un-operated (P < 0.05) rats. Significantly more endothelial cell cytoplasmic area was occupied by mitochondria in CLP than Un-operated (P < 0.05) and Sham (P < 0.05) rats. However, experimental group did not affect the number of mitochondria present in endothelial cell profiles, or their cross-sectional area. Therefore, sepsis-induced cerebral oedema involves an increase in and a redistribution of brain water, together with ultrastructural changes to cerebral microvessels and adjacent tissue.

Role of aquaporin-4 in the development of brain oedema in liver failure.

BACKGROUND & AIMS: Liver failure is associated with progressive cytotoxic brain oedema (astrocyte swelling), which underlies hepatic encephalopathy (HE). Ammonia and superimposed inflammation are key synergistic factors in HE, but the mechanism(s) involved remain unknown. We aimed to determine whether aquaporin-4 (AQP4), an astrocyte endfeet bi-directional water channel, is associated with the brain oedema of HE. METHOD: Rats (n=60) received sham-operation (sham), 5 days hyperammonaemia-inducing diet (HD), galactosamine (GALN) induced acute liver failure (ALF), 4 weeks bile duct-ligation (BDL) induced cirrhosis, or caecal ligation and puncture (CLP), a 24h model of bacterial peritonitis. Rats from every group (except CLP) were randomised to receive intraperitoneal injections of lipopolysaccharide (LPS; 1mg/kg) or saline, prior to termination 3h later. Brain water, AQP4 protein expression (western blot) and AQP4 localisation by immunogold electron microscopy were investigated. RESULTS: Significant hyperammonaemia was observed in saline-injected BDL (p<0.05), GALN (p<0.01), and HD (p<0.01), compared to sham rats. LPS injection did not affect arterial ammonia or plasma biochemistry in any of the treatment groups. Increased brain water was observed in saline-injected GALN (p<0.05), HD (p<0.01), and CLP (p<0.001) compared to sham rats. Brain water was numerically increased in BDL rats, but this failed to reach significance (p=0.09). LPS treatment further increased oedema significantly in all treatment groups (p<0.05, respectively). AQP4 expression was significantly increased in saline-injected BDL (p<0.05), but not other treatment groups, compared to sham rats. Membrane polarisation was maintained in BDL rats. CONCLUSION: The results suggest that AQP4 is not directly associated with the development of brain oedema in liver failure, hyperammonaemia, or sepsis. In cirrhosis, there is increased AQP4 protein expression, but membrane polarisation, is maintained, possibly in a compensatory attempt to limit severe brain oedema.

Adrenergic agents modify cerebral edema and microvessel ultrastructure in porcine sepsis.

OBJECTIVE: To investigate the effects of adrenergic agents on the cerebral response to sepsis. DESIGN: Prospective, randomized, controlled, experimental animal study. SETTING: Medical school research laboratories. SUBJECTS: Twenty-eight middle white pigs (25-30 kg). INTERVENTIONS: Pigs were anesthetized, mechanically ventilated, and randomly assigned to one of the following groups: cecal peritonitis (n = 5), cecal peritonitis with dopexamine (n = 5), cecal peritonitis with dopexamine and the beta2-adrenergic receptor antagonist ICI 118,551 (n = 4), cecal peritonitis with methoxamine (n = 5), cecal peritonitis with dopexamine and methoxamine (n = 4), and sham-operated (n = 5). Sham-operated pigs were killed after laparotomy, and pigs with cecal peritonitis were killed 8 hrs after its induction. Samples of frontal cerebral cortex were taken immediately after death, processed for light and electron microscopy, and then subjected to morphometric analysis. MEASUREMENTS AND MAIN RESULTS: There was significantly more (p <.0005) cerebral perimicrovessel edema in pigs with cecal peritonitis (80.2 microm2 +/- 5.3 sem) than in sham-operated pigs (26.2 microm2 +/- 2.7 sem) and significantly less (p <.0005) perimicrovessel edema in dopexamine-treated pigs with cecal peritonitis (39.8 microm2 +/- 5.5 sem) than in pigs with cecal peritonitis alone (80.2 microm2 +/- 5.3 sem). There was no significant difference between the amount of perimicrovessel edema in pigs with cecal peritonitis treated with dopexamine plus ICI118,551 and pigs with cecal peritonitis alone. The mean cerebral microvessel endothelial cell cross-sectional area in methoxamine-treated pigs with cecal peritonitis (26.3 microm2 +/- 2.6 sem) was significantly greater than that in pigs with cecal peritonitis alone (16.3 microm2 +/- 2.1 sem, p =.008) or in sham-operated pigs (12.3 microm2 +/- 1.3 sem, p =.0005). CONCLUSIONS: Dopexamine protects against cerebral edema formation in sepsis by stimulation of beta2-adrenergic receptors, whereas the alpha1 adrenoceptor agonist methoxamine induces cerebral microvessel endothelial cell swelling.

The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles.

The purpose of this study was to measure the relative contributions of 4 hip and thigh muscles while performing squats at 3 depths. Ten experienced lifters performed randomized trials of squats at partial, parallel, and full depths, using 100-125% of body weight as resistance. Electromyographic (EMG) surface electrodes were placed on the vastus medialis (VMO), the vastus lateralis, (VL), the biceps femoris (BF), and the gluteus maximus (GM). EMG data were quantified by integration and expressed as a percentage of the total electrical activity of the 4 muscles. Analysis of variance (ANOVA) and Tukey post hoc tests indicated a significant difference (p < 0.001*, p = 0.056**) in the relative contribution of the GM during the concentric phases among the partial- (16.9%*), parallel- (28.0%**), and full-depth (35.4%*) squats. There were no significant differences between the relative contributions of the BF, the VMO, and the VL at different squatting depths during this phase. The results suggest that the GM, rather than the BF, the VMO, or the VL, becomes more active in concentric contraction as squat depth increases.