Gonadotrophin levels and morphological testicular features in rats after different doses of the phytoestrogen coumestrol.

INTRODUCTION: Phytoestrogens are a wide variety of chemical compounds, mainly isoflavonoids, from a vegetable source. Their name makes reference to their ability to induce estrogenic responses in mammals. Coumestrol is a phytoestrogen that can be found in high concentrations in the dietary elements of cattle. Some endocrine alterations have been reported for cows and ewes after ingestion of vegetables with high concentrations of coumestrol. However, these studies have been made mainly in females. OBJECTIVE: To analyze some features of the masculine endocrine response in rats after several doses of the phytoestrogen coumestrol. DESIGN: Adult male rats were injected with several doses of coumestrol. Plasma gonadotrophins (LH/FSH) and testosterone levels were assessed. In addition, morphology of the testicles was analyzed. SETTING: Experiments were done in the facilities of the neurosciences area at the University. RESULTS: No significant changes were observed in gonadotrophin levels after the administration of coumestrol. Testosterone levels showed a significant decrease with the higher doses. Morphological analysis showed an inhibitory effect on spermatogenesis expressed mainly in the right testicle. Testicular volume decreased and the tubular area increased significantly after coumestrol treatment. CONCLUSIONS: These results suggest that the endocrine effect of coumestrol is mainly expressed in peripheral targets in male rats. In addition, the possible mediation of estrogen beta receptors is discussed.

Expression of a human polyomavirus oncoprotein and tumour suppressor proteins in medulloblastomas.

AIMS: Although the aetiology of medulloblastoma remains elusive, several lines of evidence suggest an association with the human neurotropic polyomavirus JC and its oncoprotein T antigen. The tumour forming properties of JC virus T antigen are the result, at least in part, of its ability to bind and inactivate tumour suppressor/cell cycle regulatory proteins, such as p53 and the retinoblastoma family of proteins. METHODS: To examine potential relations between these factors, immunohistochemistry was used to determine associations between the T antigen and the expression of p53 and the retinoblastoma proteins pRb, p107, and Rb2/p130 in eight medulloblastomas. RESULTS: Only the three medulloblastomas with T antigen expression also showed nuclear positivity with antibodies to p53. Although immunohistochemistry detected nuclear labelling for pRb in five of the cases, the three that were positive for T antigen showed the highest pRb labelling. The retinoblastoma related proteins p107 and Rb2/p130 were also immunopositive in most T antigen positive medulloblastomas. Double label immunohistochemistry also demonstrated p53 and pRb positivity in the same cells that were T antigen positive. CONCLUSIONS: These correlations suggest that associations between T antigen and p53 and/or T antigen and pRb occur in some of these tumours. These data provide indirect evidence that JC virus, acting through T antigen, might be involved in the formation and progression of medulloblastoma.

Oxidative damage to mitochondrial DNA and activity of mitochondrial enzymes in chronic active lesions of multiple sclerosis.

Soluble products of activated immune cells include reactive oxygen species (ROS) and nitric oxide (NO) with a high potential to induce biochemical modifications and degenerative changes in areas of inflammation in the central nervous system (CNS). Previously, we demonstrated an increased production of ROS by activated mononuclear cells (MNC) of patients with multiple sclerosis (MS) compared to those of controls, and development of oxidative damage to total DNA in association with inflammation in chronic active plaques. The current study aimed to determine whether mitochondrial (mt)DNA is affected by oxidative damage, and whether oxidative damage to mitochondrial macromolecules (including mtDNA) is associated with a decline in the activity of mitochondrial enzyme complexes. Using molecular and biochemical methods we demonstrate a trend for impaired NADH dehydrogenase (DH) activity and a possible compensatory increase in complex IV activity in association with oxidative damage to mtDNA in chronic active plaques. Immunohistochemistry confirms the increase of oxidative damage to DNA predominantly located in the cytoplasmic compartment of cells in chronic active plaques. These observations suggest that oxidative damage to macromolecules develops in association with inflammation in the CNS, and may contribute to a decline of energy metabolism in affected cells. As observed in neurodegenerative diseases of non-inflammatory origin, decreased ATP synthesis can ultimately lead to cell death or degeneration. Therefore, elucidation of this pathway in MS deserves further studies which may identify neuroprotective strategies to prevent tissue degeneration and the associated clinical disability.

Role of HIV-1 Tat and CC chemokine MIP-1alpha in the pathogenesis of HIV associated central nervous system disorders.

Two syndromes affecting cognitive and motor function in the setting of AIDS have been described as HIV encephalopathy (HIVE) and progressive multifocal leukoencephalopathy (PML). HIVE is characterized by the presence of microglial nodules with accompanying astrocytosis. PML is a fatal demyelinating disease of the white matter induced by the human papovavirus JCV which causes cytolytic destruction of glial cells. In addition to the effect of HIV-1 induced immune suppression, HIV may act directly as a co-factor for stimulation of JCV replication in AIDS patients, in part due to Tat-induced activation of JCV gene transcription. Since Tat has been implicated in CNS pathogenesis, we examined its localization in CNS specimens from HIV infected patients with HIVE and PML as well as controls. Based on the observation of CC chemokine induction in monocytes by Tat, we also examined the cellular localization of the CC chemokine Macrophage Inflammatory Protein-1alpha (MIP-1alpha) and its cognate receptor CCR-5 in these samples. In HIVE, Tat was primarily localized in astrocytes and microglia, within the nodular lesions. In PML, a marked increase in the number of Tat positive astrocytes was observed. In both HIVE and PML, prominent expression of MIP-1alpha and CCR-5 was found within areas containing histopathological lesions. CCR-5 positivity of microglia was localized primarily to nodular lesions in HIVE. In PML, increased numbers of cells with monocyte/microglial morphology were observed relative to HIVE. The increased MIP-1 alpha positivity, and potentially other chemokines, may contribute to the pathogenesis of PML in the setting of HIV infection. Tat may play an important role in the pathogenesis of both HIV associated CNS disease states, acting indirectly through cytokine and chemokine dysregulation.