In view of the data indicating that insulin can modify penetration of some drugs across cell membranes and tissue barriers, particularly the blood-brain barrier, the aim of the present study was to evaluate the effect of insulin on both the anticonvulsant activity and the brain concentration of carbamazepine in mice suffering from seizures induced by maximal electroshock. The antiepileptic drug was administered per os in single doses either alone or in combination with insulin given as single intraperitoneal injections. To assess the anticonvulsant activity of carbamazepine the ED50 values were calculated. The results indicate that insulin given in doses up to 2 units/kg did not affect the convulsive threshold, whereas insulin applied at 2 units/kg led to a significant reduction in the anticonvulsant activity of carbamazepine, as judged by an increase in the ED50 value from 16.2 to 41.3 mg/kg. This effect was accompanied by the marked reduction in both the brain and blood concentrations of the drug. It is likely, therefore, that the inhibitory activity of insulin on the anticonvulsive function of carbamazepine is related not only to the effect of the former on the blood-brain transport of the latter, but also to insulin-induced modulation of the serum concentration of the drug.
This review presents studies of the induction of meiosis undertaken on the ciliate Paramecium, a unicellular model eukaryotic organism. Meiosis in Paramecium, preceding the process of fertilization, appears in starved cells after passing a defined number of divisions (cell generations), starting from the last fertilization. Investigations were performed on clones of cells entering autogamy, a self-fertilization process. Genetic as well as epigenetic factors, i.e. endo- and exogenous factors, affecting the induction of meiosis and changing the duration of the interautogamous interval (IAI), were analyzed. The results show that: (1) Meiosis induction is controlled genetically by the somatic macronucleus. However, besides the nuclear factors, the cytoplasmic protein immaturin also affects this process (HAGA & HIWATASHI 1981); (2) Epigenetic factors, such as non-genetically disturbed cytoskeleton structures and changes in the cell architecture observed in doublet Paramecium cells, exert internal mechanical stress (INGBER 2003), which constitutes the endogenous impulse accelerating meiosis; (3) Mild osmotic stress, acting as an exogenous factor, can initiate the specific MAP kinases signaling pathway resulting in earlier meiosis induction, as in other unicellular eukaryotes (SEET & PAWSON 2004).
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