The sheep third ventricle: scanning electron microscopy of estrous, anestrous and estrogen-progesterone-treated anestrous ewes

Cells containing immunoreactive estrogen receptor-alpha in the human basal forebrain

The distribution of estrogen receptor protein-alpha (ER-alpha)-containing cells in the human hypothalamus and adjacent regions was studied using a monoclonal antibody (H222) raised against ER-alpha derived from MCF-7 human breast cancer cells. Reaction product was found in restricted populations of neurons and astrocyte-like cells. Neurons immunoreactive for ER-alpha were diffusely distributed within the basal forebrain and preoptic area, infundibular region, central hypothalamus, basal ganglia and amygdala. Immunoreactive astrocyte-like cells were noted within specific brain regions, including the lamina terminalis and subependymal peri-third-ventricular region. These data are consistent with the location of estrogen receptors in the basal forebrain of other species and the known effects of estrogens on the cellular functions of both neurons and supporting elements within the human hypothalamus and basal forebrain.

Scanning electron microscopy of central nervous system cerebrospinal-fluid-contacting surfaces: a bibliography (1963-1995)

This bibliography is compiled to assist in locating papers related to the application of scanning electron microscopy (SEM) to cerebrospinal-fluid-contacting surfaces in vertebrates. The use of SEM by neuroscientists has continued apace since the publication of the first bibliography in 1980. SEM studies now include more than 50 species of vertebrates and range from cyclostomes to humans; they encompass development from embryo to senescence and concern both normal and pathologic morphology. Although remarkable strides have been made toward a greater understanding of many aspects of the structure and function of cerebrospinal-fluid-contacting surfaces, many significant problems await the judicious application of scanning electron microscopy.

Fetal ependyma in sheep and goat. A scanning electron microscopy study

Morphology of the surface of apical membranes of ependymal cells has been studied in the whole ventricular system of the brain in goat and sheep fetuses using a scanning electron microscope. The surface structure of the ependymal lining surface in fetuses of small ruminants is very similar to that in adult animals. Supraependymal cells were found only in the lower part of the third cerebral ventricle in goat fetuses, but not in sheep fetuses. In small ruminants the ependymal surface is already regionally differentiated within the end of the first half of prenatal development. Fetal ependyma of goats and sheep, unlike the adult ependyma, is characterized by a high secretory activity, which is independent of sex or age of fetuses.

Ependyma of the goat. Part IV. Ependymal lining of the median eminence in goats under physiological and experimental conditions

The sexual differentiation of the ME ependymal lining surface structure has been proved in goats. Suitable hormonal preparations applied to females during anestrus induced on the median eminence the same picture as that during estrus. Only after gonadectomy in both the females and males there were dense macrophages-like SEC on the ME protruding from the deeper layers of the eminence. Their potential function is discussed.

Seasonal variations in the cerebrospinal fluid-contacting area of the pineal gland in the golden hamster (Mesocricetus auratus)

The cerebrospinal fluid-contacting area in the pineal recess of the golden hamster (Mesocricetus auratus) has been investigated light and electron microscopically. The results reveal that in this area the ventricular surface is composed of glial cell processes and protruding pinealocytes. The relative extent of these two components varies considerably and seems to be related to the season of the year: Morphometric analysis shows that in June, the mean size of the total cerebrospinal fluid-contracting area and, in addition, the relative extent of the area occupied by protruding pinealocytes is significantly larger than in November. The physiological significance of this finding remains to be determined.

The median eminence in normal, ovariectomized, and ovariectomized-estradiol-treated hamsters: an ultrastructural study

In an effort to define more clearly the effect various plasma concentrations of estrogen have on the morphology and function of tanycytes, the present investigation examined the median eminence (ME) of normally cycling, ovariectomized, and ovariectomized-estradiol-treated hamsters. In normally-cycling animals, when endogenous estrogen was at its highest level (day 4 or proestrus), numerous microappendages arose from the luminal surfaces of tanycytes located in the ventrolateral region of the ME. Large blebs (1.0-5.0-micrometers diameter), miniblebs (1.0-micrometer diameter), and microvilli dominated the surfaces of these cells. Large blebs appeared to have been formed by the coalescence of several miniblebs and were composed of cytoplasmic ground substance devoid of organelles. The peduncular shape of many of these blebs suggested their involvement in an apocrinelike secretion by the tanycyte. When endogenous estrogen levels were low (day 1 of the estrous cycle), the tanycytes of normally cycling hamsters possessed slightly fewer microappendages. Following ovariectomy, large blebs were nearly absent from the luminal surfaces of tanycytes, and the number of miniblebs and microvilli were also greatly reduced. Subcutaneous injections of 17-beta estradiol benzoate restored the large blebs to the tanycyte surface. The number and variety of tanycytic microappendages in these animals resembled those in normally cycling hamsters on day 4 of the estrous cycle. The present study demonstrates that tanycytes of the hamster ME are sensitive to estrogen and vary in their morphology in relation to the animal's reproductive status. These changes in tanycyte morphology can be correlated directly to functions of absorption (microvilli) and secretion (blebs). The sensitivity of tanycytes to estrogen suggests that these cells may also play a role in the hypophyseal-ovarian feedback mechanism.

The armadillo infundibulum: correlative histochemistry, scanning and transmission electron microscopy of the ventricular surface

The ependymal and supraependymal cells of the armadillo infundibulum (INF) were investigated by correlative histochemistry, scanning and transmission electron microscopy. Eighteen armadillos (8 adult females, 6 adult males, 2 immature females and 2 immature males) were examined. The following supraependymal elements were observed: (a) individual pleiomorphic cells made up of neurons, macrophages, and astrocytic-glial cells; (b) numerous spherical blebs of various sizes occurring singly or in clusters; (c) axons, traversing the surface alone or in association with macrophages and other SEC; (d) multicellular clusters containing SEC, macrophages, axons and other cell types. There were neurosecretory axons or blebs on and below the ependymal cell layer and a unique arrangement of multipolar cells and their processes, traversing the INF floor for several millimeters. The presence of neurosecretory axons at the INF ventricular surface, spherical blebs and SEC in contact with one another via long filaments or vast networks of smaller axons on the surface and numerous macrophages in close apposition to possible metabolic and transport sites give evidence of organized activity in a regulatory system.