A comparison of the elastic properties of human choroid and sclera.

Multiple strips of choroid (56) and sclera (64) from eight pairs of human eye-bank eyes were subjected to simple tension in a test apparatus to determine the rigidity (modulus of elasticity) of these tissues. The modulus of elasticity of the chorodial complex (choroid-Bruch's membrane-pigment epithelium) was significantly greater in posteriorly located samples than in anteriorly located ones (7.5 +/- 7.0 vs. 2.2 +/- 1.5 x 10(5) N m-2, mean +/- S.D.). The modulus of elasticity for the complex averaged across all locations was 6.0 +/- 2.8 x 10(5) N m-2 and the average stress at failure was 3.3 +/- 1.3 x 10(5) N m-2. The modulus of elasticity for scleral strips also varied with location and averaged 2.9 +/- 1.4 x 10(6) N m-2 for anterior sclera and 1.8 +/- 1.1 x 10(6) N m-2 for posterior sclera at stress levels ranging from 20- to 260 x 10(4) N m-2. There was a significant correlation of scleral stiffness with age (P less than 0.05, r = 0.80). The elastic properties of the choroidal complex may be relevant to the pathogenesis of a variety of ocular diseases, including macular degeneration, angioid streaks, choroidal folds, and choroidal ruptures.

The ethanol sensitivity of calcium taken up by a depolarization-dependent process in mouse strains DBA and C57BL.

In vitro effects of ethanol on calcium taken up by synaptosomes were examined in two strains of mice, C57BL and DBA, that exhibit marked differences in alcohol sensitivity and preference. There were no significant strain differences in basal or depolarization-dependent synaptosomal calcium levels. Ethanol did not reduce the basal calcium level but instead reduced depolarization-dependent calcium levels with the same potency in both strains. These results do not support a role for changes of calcium levels as the basis for differences in ethanol sensitivity in these mouse strains.

Cortical beta-adrenergic subsensitivity after desmethylimipramine may depend on the passage of time rather than daily treatment.

Earlier data from our laboratory indicated that the effects of antidepressants on dopamine autoreceptors are dependent on the passage of time rather than repeated treatment. The present study inquired whether the same might be true of cortical beta-adrenergic receptors. Our findings indicate that beta-adrenergic subsensitivity is obtained whether rats were treated with desmethylimipramine daily for 17 days or only on day 1 and day 17. These data suggest that antidepressant-induced changes in beta-receptor sensitivity may, like those in dopamine autoreceptors, also depend on the passage of time.