Previous studies using dissociated cell cultures of fetal rat brain have revealed considerable regional diversity as well as sex steroid-independent sex differences in developmental schedules of ...dopaminergic neurons. Because these phenomena might be related to glial heterogeneity, cultures of dissociated male and female diencephalon, mesencephalon, and rhombencephalon of gestational day 14 rats were investigated with respect to the development of astrocytic markers. Cultures were incubated for 3-8 days in vitro (DIV) in serum-supplemented or serum-free medium. Vimentin and glial fibrillary acidic protein (GFAP) were quantified by counting of immunolabeled cells and immunoblotting. Vimentin and GFAP content rose from DIV 3 to 6 in all cultures. Regional variation of vimentin content was low, but large differences occurred in amounts of GFAP. GFAP reached high levels in rhombencephalon, especially when supplemented with serum, but remained very low or not detectable in mesencephalon. Simultaneous immunostaining for both cytoskeletal proteins revealed the presence of large numbers of vimentin single-labeled and small numbers of vimentin/GFAP double-labeled cells. Numbers of cells expressing GFAP showed similar regional variations as GFAP contents in both serum-free and serum-supplemented medium. They rose steeply from DIV 3 to 8 in rhomb- and diencephalon but not in mesencephalon. Transiently, female diencephalic cultures contained slightly more GFAP-immunoreactive cells than male cultures. The results thus demonstrate considerable regional heterogeneity of astrocytic maturation. However, neither the regional nor the sex differences show a consistent correlation with previous data on development of dopaminergic and other monoaminergic neurons in vitro. It seems likely that the dependence of neurons on glial environment for realization of an inherent developmental program varies among neuronal phenotypes.
Sexual dimorphisms of the rat brain are generally believed to be brought about by the presence of testosterone during a critical period starting at embryonic day (ED) 17/18. In contrast, sex ...differences of diencephalic and mesencephalic dopaminergic neurons were observed to develop in cell cultures raised from ED 14 rat brains. This was interpreted as evidence indicating that sexual differentiation of certain neural systems may occur independently of gonadal hormones. To substantiate this claim, it was felt necessary to examine the rat embryo for clues to a possible existence of sex differences in hormonal environment prior to ED 17. Morphometry was applied to compare the development of male and female Wolffian and Müllerian ducts, both primary targets of hormones secreted from the male gonad. Diameters of serially cross-sectioned Wolffian and Müllerian ducts were measured in rats of ED 15.0 to ED 16.5. Females had thicker Müllerian ducts from ED 15.5 on. The first step of differentiation in males was the widening of the lumen and a slight increase of the outer diameter of the Wolffian duct at ED 16.0. The size differences of both ducts were most obvious in the vicinity of the lower half of the gonad. Except in Wolffian ducts of ED 16.5, sex differences were absent in the caudal parts of the ducts. It appears that gonadal androgen and Müllerian inhibiting substance do not affect the development of their classical target organs prior to ED 16.0 and ED 15.5, respectively. Furthermore, the first effects are paracrine in nature. There is no evidence for sex differences in systemic androgen environment until ED 16.5.
The expression of the synaptic vesicle antigens synaptophysin (SY) and synaptoporin (SO) was studied in the rat striatum, which contains a nearly homogeneous population of GABAergic neurons. In situ ...hybridization revealed high levels of SY transcripts in the striatal anlage from embryonic day (E) 14 until birth. In contrast, SO hydridization signals were low, and no immunoreactive cell bodies were detected at these stages of development. At E 14, SY-immunoreactivity was restricted to perikarya. In later prenatal stages of development SY-immunoreactivity appeared in puncta (identified as terminals containing immunostained synaptic vesicles), fibers, thick fiber bundles and 'patches'. In postnatal and adult animals, perikarya of striatal neurons exhibited immunoreaction for SO; ultrastructurally SO antigen was found in the Golgi apparatus and in multivesicular bodies. SO-positive boutons were rare in the striatum. In the neuropil, numerous presynaptic terminals positive for SY were observed. Our data indicate that the expression of synaptic vesicle proteins in GABAergic neurons of the striatum is developmentally regulated. Whereas SY is prevalent during embryonic development, SO is the major synaptic vesicle antigen expressed postnatally by striatal neurons which project to the globus pallidus and the substantia nigra. In contrast synapses of striatal afferents (predominantly from cortex, thalamus and substantia nigra) contain SY.
The following conclusions which show the importance of time of medical treatment resulted from the examination of 288 testicular biopsies (including 46 controls) by statistical analysis in ...correlation to age. 1. There is no difference in the number of spermatogonia per tubule cross section of descended and undescended testes in children from birth to 2 years of age. 2. The number of spermtogonia in descended testes is not different in children from birth to 2 years in comparison to children aged 2-6 years. 3. A statistically significant decrease of spermatogonia takes place in the undescended testes of children from 2-6 years in comparison to children from birth to 2 years. 4. The difference in the number of spermatogonia of descended and undescended testes increases in children above the age of 2. It must be concluded from this study that the pathological alterations of the germinative epithelium increase in children beyond the age of 2. Assuming that pathological alterations of the germinative epithelium are caused by the dystopy of the testes, medical treatment should be carried out before the child is more than 2 years old.
PDF
