The biology and t heories of aging.

Aging is a natural, time-dependent process characterized by irreversible changes in the molecules, cells, tissues, and organs. It occurs as a result of cumulative damage at different levels of the organization, in particular by damaging proteins and DNA. There is no single definition, nor a unique attitude about when and how age arises and what are its causes. The process is extremely complex and most likely a consequence of the effects of different mechanisms (not only genetic but also acquired) that lead to disrupt homeostasis, reduce stress resistance and the more frequent occurrence of the disease. There are many classifications of theories about aging and they often contradict one another. No one theory is sufficiently able to explain the process of aging. The aim of this work is to analyze the different aspects, main characteristics of the aging, individual differences in the speed of this process and theories about the mechanisms of aging.

Impact of the toxicity of Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju on laboratory rats in vivo.

In vivo laboratory studies of toxicity were performed on Wistar rats using a methanol extract produced by the natural population of Cylindrospermopsis raciborskii (abundance of 2.13 × 105 trichomes mL-1) collected at Aleksandrovac Lake (Serbia). HPLC analysis showed that the extract contains 6.65 µg cylindrospermopsin (CYN) mg-1. The rats were killed 24 or 72 h after a single intraperitoneal injection of C. raciborskii extract in concentrations of 1500, 3000, 6000 and 12,000 µg kg-1 body weight (bw) and an equivalent amount of CYN as present in the highest dose of the extract (79.80 µg CYN kg-1 bw). The genotoxic effect on the livers treated with C. raciborskii was evaluated using comet assay and potential induction of oxidative stress as the toxicity mechanism associated with the presence of CYN in extract. The results from the analyses of DNA damage in the comet tail length, tail moment and percentage of DNA in the tail in the liver indicated that administration of extract and CYN present statistically significant difference when compared with the negative control group. Although an increase in the frequency of selected parameters induced by the CYN was observed in the liver, this damage was less than the damage resulting from the administration of the highest dose of extract. The changes in the biochemical parameters of the hepatic damage showed that the application of single doses of the extract and CYN did not cause serious liver damage in rats. The extract and CYN significantly increased oxidative stress in rats' liver after a single exposure.