Non-linear correlation between nerve terminal parameters and muscle fibre diameter of exercised mice during aging

The effect of exercise on morphological age changes in endplate parameters and their relation to muscle fibre diameter was studied in male [C57B1/6J] mice. Animals [N = 60; half of them served as controls] aged 12, 18 and 24 months at sacrifice, were treadmill exercised for two months for 1 h/day at velocities up to 30 m/min. The area [A], perimeter [P], nerve longitudinal extent length [E] and fibre diameter [FD] from camera lucida drawings of extensor digitorum longus zinc iodide osmium-stained nerve terminals were measured. Non-linear regression and multivariate analysis were used to study the inter-relationships among these parameters under aging and exercise conditions. At 12 months E was strongly correlated with FD, but the correlation badly deteriorated with aging, and exercise did not improve it. At all ages A was not correlated with FD during aging alone, but with exercise the correlation improved, especially at 18 months [r2 = 0.73]. The ratio E/FD was not correlated with the other endplate parameters except in exercised animals, in whom E/FD showed a high correlation with A, especially at age 12 months [r2 = 0.72]. FD showed a high correlation with P/A at 12 months of age, but exercise decreased this correlation at all ages. Multivariate analysis showed no significant relationship between FD and nerve terminal parameters at any age in control animals, but in exercised animals a close relationship appeared, given by the equation: FD = 18.75 + 0.025A - 0.08E + 0.01P with P < 0.01 and r2 = 0.34. The discovery of a non-linear relationship between FD and nerve terminal parameters makes possible a further analysis of the effects of exercise on morphological age changes at the neuromuscular junction

Effect of acute lead treatment on the in vivo thrombosis in mouse cerebral microvessels under hydrated and dehydrated conditions

Effect of water deprivation for 24 h on blood parameters and platelet aggregation in pial arterioles of lead-treated mice was investigated. Exposure to lead was made by intraperitoneal injections for 24 h of lead acetate dissolved in a 5% glucose solution vehicle. Three doses of lead were used, a low dose of 0.1 mg/kg, intermediate dose of 0.5 mg/kg and a high dose of 1.0 mg/kg. Adult male mice were divided into four groups of 10 each. Platelet aggregation in pial microvessels was induced photochemically, in vivo, in anaesthetized [urethane, 1 - 2 mg/g, i.p] animals by activation of circulating sodium fluorescein [0.1 mL of 5% solution /25g, i.v.] with an intense mercury light. The time required for the first platelet aggregate to appear in pial arterioles was significantly [P < 0.05] shorter [166 +/- 27, 154 +/- 58, 218 +/- 68 sec; in low, intermediate and high doses of lead, respectively] than in control [276 +/- 63 sec]. Dehydration significantly reduced both the time requied for the first platelet aggregate [61 +/- 21 vs 125 +/- 31 sec] and the time to full occlusion [134 +/- 18 vs 239 +/- 68 sec, lead-treated vs control, P < 0.05].Blood data of dehydrated mice confirmed haemoconcentration and lead treatment did not have any influence, except haemoglobin and haematocrit in the high dose group which showed significant differences from those of control [P < 0.05]. These data revealed that lead can cause cerebrovascular thrombosis after 24 h of exposure and its effect can be enhanced under water deprivation conditions