Sexual Differences In Synaptogenesis In The Suprachiasmatic Nucleus Of The Rat Brain

1. A literature review of the effects of perinatal sex steroids on the development of the brain is presented. It can be shown that the hormones can modify the morphology of discrete areas of the brain. 2. It was concluded that there was a lack of information about how soon these morphological changes appeared. 3. It was therefore decided to study the effects of sex and perinatal hormonal levels on synaptogenesis in a discrete area of the brain. 4. The Suprachiasmatic Nucleus (SON) was chosen for anatomical convenience and because of its role in the photocontrol of ovulation. 5. In this thesis I describe synaptogenesis in the suprachiasmatic nucleus of rats of both sexes ranging from prenatal (20 days of gestation) to adult and in neonatally androgenised females. Preliminary results from neonatally castrated males are also included. 6. Synaptogenesis was studied using morphometric analysis of electron micrographs. It was found that the rate of development of synapses was similar in the SCN of both sexes, but that absolute values in males were higher than in females. Male type development cannot be mimicked by neonatal androgenization but initial results suggest that femal type development can be induced by neonatal castration. 7. My results suggest that both prenatal and postnatal androgens are essential to normal male development

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Frutexites-like structures formed by iron oxidizing biofilms in the continental subsurface (Äspö Hard Rock Laboratory, Sweden)

Stromatolitic iron-rich structures have been reported from many ancient environments and are often described as Frutexites, a cryptic microfossil. Although microbial formation of such structures is likely, a clear relation to a microbial precursor is lacking so far. Here we report recent iron oxidizing biofilms which resemble the ancient Frutexites structures. The living Frutexites-like biofilms were sampled at 160 m depth in the Äspö Hard Rock Laboratory in Sweden. Investigations using microscopy, 454 pyrosequencing, FISH, Raman spectroscopy, biomarker and trace element analysis allowed a detailed view of the structural components of the mineralized biofilm. The most abundant bacterial groups were involved in nitrogen and iron cycling. Furthermore, Archaea are widely distributed in the Frutexites-like biofilm, even though their functional role remains unclear. Biomarker analysis revealed abundant sterols in the biofilm most likely from algal and fungal origins. Our results indicate that the Frutexites-like biofilm was built up by a complex microbial community. The functional role of each community member in the formation of the dendritic structures, as well as their potential relation to fossil Frutexites remains under investigation.Open-Access-Publikationsfonds 201