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One of the hypotheses on the origin of Alzheimer's disease (AD) stems from a close relation between a re-activation of a cell-cycle in post-mitotic neurons and a neural cells death observed in pathologically affected parts of AD brains. In the normal, healthy brain almost all neural cells are terminally differentiated and "locked" in the GO phase of the cell-cycle. For these cells, the consequence of the re-entry to the cell-cycle is targeting them towards cellular divisions and turning on the apoptotic pathway. We used an RNA interference (RNAi) methodology in neural cells to switch-off genes for two cyclin- dependent kinases 4 and 6 (cdk4, cdk6), which control the activation of the initial steps of the cell-cycle. As a result, some evidences are delivered that silencing these genes, which are expressed during cell proliferation but inhibited at mature neurons, prevents the stimulation of apoptotic pathways in the neural cells cultured in a oxidative stress conditions and may have a neuroprotective effect. We demonstrate that down-regulation of genes important in the G1 phase of the cell-cycle may play the protective function on the neuronal cells, and can be considered as the promising approach for the potential gene therapy of neurodegenerative diseases.
The global adaptive convergence of subterranean mammals currently involves 3 orders: rodents, insectivores and marsupials. These include 11 families, 50 genera, and several hundreds of species. This global evolutionary process followed the stepwise climatic cooling and drought followed by biotic extinction in the transition from the middle Eocene to the early Oligocene, a period of 10 million years (35-45 Ma = million years ago), of profound change in earth geology, climate and biota. The earth changed from the Mesozoic "hot house" to the Neogene (Miocene to Present) "cold house", ie from a warm, equable, mostly subtropical world that persisted from the Mesozoic to the beginning of the present glaciated world. The ecological theater of open country biotas, that opened up progressively in the Cenozoic following the Eocene-Oligocene transition, was associated with increasing aridity, colder climate, and terrestrialism. This climatic change set the stage for a rapid evolutionary play of recurrent adaptive radiations of unrelated mammals on all continents into the subterranean ecotope. The subterranean ecotope is relatively simple, stable, specialised, low or medium in productivity, predictable and discontinuous. Its major evolutionary determinants are specialization, competition and isolation. This ecotope involves the herbivorous (rodents) and insectivorous (insectivores and marsupials) niches. All subterranean mammals share molecular and organismal convergent adaptations to their common unique ecology. By contrast, they display divergent adaptations to their separated niches of herbivory and insectivory and to their different phylogenies. The remarkable adaptive evolution of subterranean mammals involves adaptive structural and functional progression and regression. It is one of the most dramatic examples of global convergent evolution due to underground ecological constraints, at both the molecular and organismal levels of evolutionary theory.
We demonstrated that a quickly growing hamster skin melanoma developed a tumor after autologous implantation into the anterior chamber of the eye. Tumor cells were seen invading all the surrounding tissues, including the iris, ciliary body, choroid and cornea. Histological examination confirmed the presence of numerous blood vessels of large diameter. Their walls were very thin, thus only the endothelium could be identified using light microscopy. Macrophages, microemboli and extravasations were present within the tumor mass.
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