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Aging is a process which operates at many levels of physiological, genetic and molecular organization and leads inevitably to death. Brain macroscopic changes by MRI investigation during aging were observed in humans and dogs but chimpanzees did not display significant changes. This suggestion led to the statement that brain aging is different in various species. Although human brain changes, e.g. β-amyloid storage, neurofibrillary tangle formation, lipofuscin, are relatively well known, we are still looking for a suitable animal model to study the mechanisms of aging and neurodegenerative diseases. Therefore, this paper presents a comparative analysis of the changes described in the brains of senile dog, horse and gorilla. In addition we present the latest, non-invasive methods that can be applied in the diagnosis of old age in mammals. Our considerations have shown that the best animal model for further studies and observations on aging is the dog.

The purpose of this study was to determine whether hippocampus and cerebral cortex fatty acids (FA) composition can be altered as a result of n-3 enriched diet, or modifications in FA can affect the age-related histological changes in these brain tissues. The study was performed on eighteen rats which were fed control (CD) or fish oil supplemented diet (FOD) for 12 months. We investigated the n-3 and n-6 brain FA profile by gas-chromatography analysis. Histomorphometry included the measurement of the quantity of pyramidal cells in the cerebral cortex (layer II-III) and in the hippocampal formation (CA1, CA3 and DG). The number of apoptotic cells (neuron and glial cells) was also calculated separately in three hippocampal areas and in the pyramidal cerebral cortex layer. Rats fed supplemented diet showed a significantly poorer content of the arachidonic acid (AA, 20:4n6) in all brain regions when compared to the control group. Furthermore, the level of the docosahexaenoic acid (DHA, 22:6n3) was significantly higher in the cerebral cortex in fish oil fed rats vs. the control group. The neurons of the pyramidal cortex showed significant changes in cell density in control animals when compared to the group of fish oil fed rats. Furthermore, the number of positive apoptotic cells was significantly higher in the CA1 area and cerebral pyramidal layer in rats fed control diet. Following dietary n-3 fatty acids supplementation, the increase in DHA content in the cerebral cortex resulted in consequential changes in histology of this tissue. The results obtained indicate that dietary intake of fish n-3 fatty acids may reduce the risk of age-related brain impairments.

Endogenous development of a pure strain of Eimeria media and of a precocious line derived from this strain was studied in specific pathogen-free (SPF) rabbits. Endogenous development of the parental strain comprised three generations and the gamogony began 76 h post-inoculation (pi). Two types of meronts were observed in each generation. The type A meronts gave rise to large, polynucleated merozoites present in low numbers. Multiplication was carried out by endomerogony. Within type B meronts, merozoites arose from ectomerogony. These were slender and more numerous than those of type A. The sporozoite refractile body was divided and distributed into the first and second generation merozoites but not into the third. The endogenous development of the precocious line was similar to that of the parental strain except that no refractile body was observed and the last merogony was absent. Gamogony appeared 60 h pi.