Gonadal hormone regulation of glial fibrillary acidic protein immunoreactivity and glial ultrastructure in the rat neuroendocrine hypothalamus

The influence of gonadal steroids on the ultrastructure of glial cells and on the immunoreactivity for the specific astrocytic marker glial fibrillary acidic protein (GFAP) has been assessed in the neuroendocrine hypothalamus. The following parameters were analyzed in the arcuate nucleus of adult female rats: the number and the surface density of cells immunoreactive for GFAP, the number of glial profiles showing bundles of glial filaments, the size of the bundles of glial filaments, and the proportion of neuronal perikaryal membrane apposed by glial processes. These parameters were studied during the different phases of the estrous cycle, after ovariectomy, and after the administration of estradiol or progesterone to ovariectomized rats. No significant differences were detected in the number of GFAP-immunoreactive cells among the different experimental groups. The surface density of GFAP-immunoreactive material, the number of glial profiles in the neuropil, and the proportion of neuronal perikaryal membrane covered by glia were increased in the afternoon of proestrus and in the morning of estrus compared with other phases of the estrous cycle or to ovariectomized rats and showed a rapid (5 h) and reversible increase in ovariectomized rats injected with 17β estradiol, with a maximal effect by 24 h after the administration of the hormone. In contrast, the size of the bundles of glial filaments was decreased in the afternoon of proestrus, in the morning of estrus, and by the administration of estradiol to ovariectomized rats. The parameters studied were not affected by the administration of progesterone. However, progesterone (300 μg/rat) blocked the effects of 17β estradiol (1, 10, and 300 μg). The results suggest that glial cells may be actively involved in the modulation of neuroendocrine events by the hypothalamus. © 1994 Wiley-Liss, Inc.     

Sugar intake, serum insulin and platelet adhesiveness in men with and without peripheral vascular disease

Both the level of serum insulin and the adhesiveness of platelets are correlated with sucrose intake in men with peripheral vascular disease. These correlations do not exist in men who have no signs or symptoms of the disease, or of predisposing conditions such as hypertension.     

Placenta and myometrial block

The fluorescent dye method of Mashima and Csapo was employed in a study of the propagated activity of the pregnant rabbit uterus.Mechanical activity induced by stimulating one end of an 8 cm. long uterine strip was well conducted along the entire length of the postpartum uterine strip. This is evidence of propagation. The extent of activity was dependent on the strength and duration of electrical stimulation, as characteristic of excitable tissues.The uterus in early pregnancy (before implantation) showed activity strictly restricted to the stimulated portion, due to a uniform block exerted on the entire length of the uterine horn. In the late pregnant uterus the block was no longer uniform but it was restricted to the placental portion of the uterine wall. The interplacental regions and the nonpregnant horn of the pregnant uterus did propagate the wave of activity to some extent. This segmental distribution of propagating and nonpropagating regions, in the pregnant uterus, results in functional inhomogeneity.Functional inhomogeneity is characteristic of the rabbit uterus in late pregnancy; the pregnant horn becomes fully propagating and of uniform activity after the placenta is born, or if placental function is suspended before term.