Study of possible involvement of MEK mitogen-activated protein kinase and TGF-β receptor in planarian regeneration processes using pharmacological inhibition analysis

Possible involvement of MEK mitogen-activated protein kinase and TGF-β receptor in the processes of regeneration and morphogenesis in freshwater planarian flatworms Schmidtea mediterranea was studied using a pharmacological inhibitor analysis. It was found that pharmacological inhibitors of these kinases significantly inhibit the regeneration of the head end of the animals and that this effect is realized due to inhibition of proliferative activity of neoblasts, planarian stem cells. It is shown that that the inhibition of the studied protein kinases in regenerating planarians markedly disturbs stem cell differentiation and morphogenesis.     

The changing of cell-free DNA properties of peripheral blood and TCR-mutant cell frequency in individuals exposed to ionizing radiation

Some properties of the cell-free DNA (cfDNA) of peripheral blood plasma were assessed in 153 employees of atomic industry enterprises. The contents of ribosomal repeat (rDNA) and its concentration in plasma increased in cfDNA of the group of persons in comparison with non-irradiated individuals. The contents of satellite III in cfDNA of donors and of irradiated persons do not differ and less than in DNA nucleus. The correlation between cumulative dose of radiation, contents of rDNA in cfDNA and the frequency of lymphocytes bearing mutations at T-cell receptor (TCR) locus was obtained. The definition of three indications in irradiated persons: the contents of ribosomal genes in cfDNA, TCR-mutant cell frequency and concentration of ribosomal genes in blood plasma--may be useful for revealing individuals in organism of which an intensive cell apoptosis takes place and there is an increased probability of carcinogenesis and of progress of disease of immune system.     

Genotypic structure of a natural daphnia population based on the phenotypic responce on change in the amount of food

Natural populations of Daphnia are genetically heterogeneous with regard to phenotypic response to modification in the food quantity (a set of metric quantitative traits). In the majority of the traits, three genetically determined response types to the environmental factor studied have been detected: arithmetic means decrease (R1), increase (R2) or remain constant (St) as a result of a decrease in the food quantity. This phenotypic response was shown to occur in the whole set of the metric traits studied, irrespective of physiological specialization. The problems of assessment of genetic population structure based on phenotypic response of the individuals reflected in quantitative traits are discussed.     

Involvement of neuropeptide mechanisms in the integration of heterotopic dentate fascia grafts and recipient brain

Embryonic dentate fascia was grafted into the somatosensory neocortex of adult rats. Nine months post-grafting, the ultrastructural and morphometric analysis of the giant synapses established between the grafted granular neurons and inappropriate targets in the recipient brain was performed. As compared to the intact synaptic endings in the control hippocampus, differences were found in both the number and distribution of large dense-core synaptic vesicles, which store the neuropeptide co-transmitters. The peptidergic vesicle proportion (of total vesicle pool) within the ectopic giant synapses was 5.8 +/- 0.6% (versus 3.3 +/- 0.6% in the control). Clusters of large dense-core vesicles near the active zones of aberrant connections were observed almost 7.9 times more frequently than that of normal contacts. These data provide evidence that neuropeptide transmitters are critical for the maintenance of synaptic connections between the heterotopic dentate grafts and host brain.     

Role of cannabinoid receptors in regulation of cardiac tolerance to ischemia and reperfusion

Coronary artery occlusion (45 min) and reperfusion (2 h) were modeled in vivo in anesthetized artificially ventilated Wistar rats. Total ischemia (45 min) and reperfusion (30 min) of the isolated rat heart were performed in vitro. The selective agonist of cannabinoid (CB) receptors HU-210 was injected intravenously at a dose of 0.1 mg/kg 15 min prior to the coronary artery ligation. The selective CB1 antagonist SR141716A and the selective CB2 antagonist SR144528 were injected intravenously 25 min prior to ischemia. In vitro, HU-210 and SR141716A were added to the perfusion solution at the final concentrations of 0.1 μM prior to total ischemia. Preliminary injection of HU-210 reduced the infarct size-to-area at risk (IS/AAR) ratio in vivo. This cardioprotective effect was completely abolished by SR141716A but remained after SR144528 injection. Both antagonists had no effect on the IS/AAR ratio. Preliminary injection of the K_ATP channel blocker glibenclamide did not abolish the cardioprotective effect of HU-210. The addition of HU-210 prior to ischemia reduced the creatine phosphokinase (CPK) level in the coronary effluent and decreased left ventricular developed pressure. SR141716A alone had no effect on cardiac contractility and CPK levels. These results suggest that cardiac CB1 receptor activation increases cardiac tolerance to ischemia-reperfusion and has a negative effect on the cardiac pump function. Endogenous cannabinoids are not involved in the regulation of cardiac contractility and tolerance to ischemia and reperfusion. ATP-sensitive k_ATP-channels are not involved in the mechanism of the cardioprotective effect of HU-210.     

Significance of cardiac cannabinoid receptors in regulation of cardiac rhythm,myocardial contractility,and electrophysiologic processes in heart

Intravenous administration of cannabinoid (CB) receptor agonists (HU-210, 0.1 mg/kg; ACPA, 0.125 mg/kg; methanandamide, 2.5 mg/kg; and anandamide, 2.5 mg/kg) induced bradycardia in chloralose-anesthetized rats irrespective of the solubilization method. Methanandamide, HU-210, and ACPA had no effect on the electrophysiological activity of the heart, while anandamide increased the duration of the QRS complex. The negative chronotropic effect of HU-210 was due to CB1 receptor activation since it was not observed after CB1 receptor blockade by SR141716A (1 mg/kg intravenously) but was present after pretreatment with CB2 receptor antagonist SR144528 (1 mg/kg intravenously). CB receptor antagonists SR141716A and SR144528 had no effect on cardiac rhythm or ECG indices. Hence, in the intact heart, endogenous CB receptor agonists are not involved in the regulation of cardiac rhythm and electrophysiological processes. The chronotropic effect of CBs was independent of the autonomic nervous system because it remained significant after autonomic ganglion blockade by hexamethonium (1 mg/kg intravenously). CB receptor activation by HU-210 (0.1 and 1 μM) in vitro decreased the rate and force of isolated heart contractions, the rates of contraction and relaxation, and end diastolic pressure. The negative chronotropic effect of HU-210 was less pronounced in vitro than in vivo. The maximum inotropic effect of HU-210 was reached at the concentration of 0.1 μM.     

Estimation of seasonal dynamics of number and age structure of South Baikal natural population of <Emphasis Type=Italic>Epischura baicalensis</Emphasis> sars using ANOVA

The seasonal dynamics of number and age structure of natural population of Epischura baicalensis Sars, 1900 (Copepoda, Calanoida) from South Baikal was studied using the materials of ten-day sampling of zooplankton samples in the water layer of 0–250 min 2001–2004. Using ANOVA we determined the statistical significance of seasonal changes in number and ratio of nauplius larvae, copepodid larvae, and adults. The method of sampling reduction was used to identify the three phases of population cycle: growth, peak, and depression of number, corresponding to three biological seasons. The importance of the obtained data is discussed considering the regulating mechanisms for numbers of population of E. baicalensis