I – V characteristics and electrical conductivity of synthetic melanin

I – V characteristics for synthetic melanin were investigated at – 10 and 25°C. It was found that the Ohm law is valid for low voltages whereas the Child law holds for higher ones. Furthermore, the steady state electrical conductivity was estimated. The change of activation energy from 0.76 eV for low temperatures to 1.58 eV was noticeable near 0°C.     

Effect of angiotensin II on protein phosphorylation in PC12 cell line

Two subtypes of angiotensin II receptors have been characterised so far: AT1 and AT2. In PC12W pheochromocytoma cells, only AT2 receptors have been found (acting probably through G1 proteins or via G protein-independent mechanism). Here, dynamic changes in phosphorylation pattern in PC12W cells upon induction of angiotensin II and under influence of redox agents were investigated. PC12W pheochromocytoma cell line was preincubated with angiotensin II, then incubated with redox agents. After lysis the cells were subjected to Western-Blotting technique with antiphosphotyrosine and anti-ERK2 antibodies, as well as phosphotyrosine phosphatases and kinases activity was measured. Angiotensin II through its AT2 receptor induced dephosphorylation of tyrosines of the proteins in the range of 60 to 150 kD in PC12W cells. The obtained phosphorylation pattern suggests that AT2 receptors may act comparably to leukocyte CD45 receptor pathway. Treatment of PC12W cells with H2O2 resulted in significant decrease in phosphotyrosine phosphatases activity. It could be assumed that signal transduction based on protein phosphorylation might be controlled by cellular redox mechanisms.     

Analysis of glycogen structure in rat hepatocytes using cytochemical and FRET methods

Using cytochemical and FRET (Forster, Resonance Energy Transfer) methods, the glycogen structure in rat hepatocytes was investigated during fasting and at different time intervals after per os glucose administration to animals. Hepatocytes on slides were stained with fluorescent PAS-reaction. Staining the slides with ethidium bromide-SO2 (EtBr-SO2) for 40 min revealed a labile glycogen fraction (LE), and the subsequent staining the same samples with auramine-SO2 (Au-SO2) for 50 min showed a stable glycogen fraction (SF) in the cells. The total glycogen content (LF and SF) in the hepatocytes at different stages of refeeding was determined by means of cytofluorimetry, and then efficiency of FRET was measured in the same cells. Registration of FRET in several areas of the cells was carried out on a laser scanning confocal microscope Leica TCS SP5 with application of FRET AB (Acceptor Photobleaching) procedure. In this procedure, auramine served as a donor (D) and ethidium bromide was an acceptor (A). It was shown that the efficiency of FRET varied from 10 to 14 % during refeeding, while the glycogen structure had a marked influence on the value of this parameter. FRET efficiency was shown to correlate with the ratio A/D in the cells of hungry rats and at the early stages after glucose administration to animals, which reflected the degree of filling of the external tiers of glycogen molecules of glucose residues. At later stages, this correlation was either less pronounced or absent. It was found that the FRET efficiency can vary by 3-4 times at the same value of A/D. Since the probability of energy transfer from D to A is proportional to 1/R6, where R is a distance between D and A, such variations of the FRET efficiency indicate that the glycogen molecules possess a labile structure in which the chain of glucose residues can deviate from its axis by a distance of about half their diameter.     

Longitudinal oxygen gradients in cerebra micro vessels in acute anaemia in rats

Using a fine-tip oxygen microelectrodes the longitudinal gradients of oxygen tension (pO2) have been studied in small arterioles (with lumen diameter in control of 5 +/- 20 microm) and in capillaries of the rat brain cortex during stepwise decrease of the blood haemoglobin concentration [Hb] from control [Hb]--14.4 +/- 0.3 g/dl to 10.1 +/- 0.2 g/dl (step 1), 7.0 +/- 0.2 g/dl (step 2) and 3.7 +/- 0.2 g/dl (step 3). All data are presented as "mean +/- standard error". Oxygen tension was measured in arteriolar segments in two locations distanced deltaL = 265 +/- 34 microm, n = 30. Mean diameter of studied arterioles was 10.7 +/- 0.5 microm, n = 71. Length of studied capillary segments was about deltaL = 201 +/- 45 Mm, n = 18. The measured longitudinal pO2 gradient (deltapO2/deltaL) in arterioles amounted 0.03 +/- 0.01 mmHg/microm, n = 15 in control; 0.06 +/- 0.01 mmHg/microm, n = 16 (step 1); 0.07 +/- +/- 0.01 mmHg/microm, n = 14 (step 2); 0.1 +/- 0.01 mmHg/microm, n = 30 (step 3). In the capillaries, the deltapO2/deltaL amounted to: 0.07 +/- 0.01 mmHg/microm, n = 17 (control); 0.09 +/- 0.02 mmHg/microm, n = 16 (step 1); 0.08 +/- 0.01 mmHg/microm, n = 15 (step 2); 0.1 +/- 0.02 mmHg/microm, n = 18 (step 3). An over threefold decrease in the system blood oxygen capacity did not result in significant changes (p > 0.05) of the deltapO2/deltaL in capillaries that might result in relatively homogeneous oxygen flux from blood to tissue in acute anaemia. The longitudinal gradients of blood O2 saturation (deltaSO2/deltaL) in studied arterioles and capillaries were obtained using oxygen dissociation curve (ODC) of haemoglobin in the system blood. The gradients deltaSO2/deltaL in capillaries was shown to be threefold higher than the corresponding gradients in arterioles. The data show that anatomic capillaries are the main source of oxygen to brain tissue as in control and in hypoxic conditions. Sufficient oxygen delivery to brain tissue in acute anaemia is maintained by compensatory mechanisms of cardiovascular and respiratory systems. The data presented are the first measurements of the longitudinal pO, gradients in capillaries and minute cortical arterioles at acute anaemia.     

Effect of exogenous N-stearoylethanolamine on fatty acid composition of individual phospholipids in the isolated rat heart under postischemic reperfusion

Changes of the individual phospholipid fatty acid composition under the normothermal short-time ischemia with following reperfusion were investigated. Modification of the phospholipid fatty acid (FA) composition under ischemia-reperfusion didn't bear total character and was more manifested in cardiolipin (CL) and phosphatidylethanolamine (PE). The decrease of short chain FA in these phospholipids (more than by 50%) was observed. The amount of unsaturated FA included in CL increased and whole the saturated ones decreased. This caused the rise of the unsaturation index. The selective type of the changes suggested that they had an adaptive character. The addition of the N-stearoilethanolamine (NSE) into the perfusion solution caused a normalization of saturated and unsaturated FA relative amount, as well as of omega-3 and omega-9 FA level in CL. The modification of the FA composition of phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidylinositol (PI) was also found. The quantity of arachidonic acid in PC increased by 26% and the amount of stearinic acid enhanced in PS. The labeled N-([1-(14)C]-palmitoil)-ethanolamine was found in different lipid classes of the rat organs immediately 5 min following intraperitoneal injection. Approximately 1/3 of all incorporated label accumulated in the phospholipid fraction, and more than 50% of the labels were found in CL.     

Enhancement of luminol-dependent chemiluminescence in an aqueous NaCl/H2O2 solution by argon

It was found that the bubbling of argon through NaCl/H2O2 aqueous solutions results in the development of intense sustained luminol-dependent chemiluminescence. Bubbling of nitrogen and air through similar solutions does not result in such effect. The relationship between argon-supported chemiluminescence and initial concentrations of NaCl and H2O2 is characterized by threshold effects. In NaCl/H2O2 solutions blown with argon, hypochlorite was found, indicating that argon intensifies the reaction of chloride oxidation with H2O2. It is suggested that the enhancement of this reaction in aqueous solutions saturated with argon is related to specific changes in the properties of water, which is a highly nonequilibrium system. Possible consequences of relatively high concentrations of argon in the atmosphere for the chemical processes that occur in aqueous systems and, in particular, living systems are discussed.     

Computerized methods for therapy and rehabilitation of patients suffering dizziness and balance disorder

A new computerized method is proposed for correction and inhibition of unfavorable illusory (vertigo), vestibular-oculomotor (nystagmus), and vestibular-postural (balance) responses. This method allows to teach the subject to block generalization of an afferent signal to effector mechanisms of the central nervous system by developing a fixational reflex, utilizing a delayed biofeedback. Three variant ofthis method were employed, depending on the kind of stimulation programs aimed at inducing abnormal responses of a certain sensory modality (visual, vestibular or combined). The study involved 36 subjects divided into 3 equal groups one of which had been taught by a visual or vestibular technique, and the last one by a combined. Each group included approximately equal numbers of subjects with vestibulopathies of an organic (peripheral or central) or psychogenic origin. It was demonstrated that the method proposed allows, with the help of computerized stimulation programs, to provoce abnormal illusory and vestibular-optooculomotor responses in the subject, and inhibit them with the help of development of a fixational reflex. Patients were taught using three various variants of the method. A subsequent comparative analysis of results obtained has shown dependence of their effectiveness on the level of disturbance in the vestibular system: the visual variant of correction was the most effective for subjects with peripheral vestibulopathia; for subjects with central vestibulopathia, the vestibular variant was more effective; the combined variant of correction was the most effective for subjects with psychogenic vestibulopathia.     

Compensatory hypertension and fetal heart remodeling: from adaptation to pathology

Left ventricular (LV) isovolumetric relaxation time (IRT), shape and LV wall movement uniformity were assessed in 102 appropriate for gestational age (AGA) human fetuses and 36 fetuses with intrauterine growth retardation (IUGR). In 28 AGA newborns and 26 IUGR infants rennin and angiotensin 1 concentrations were assessed in umbilical cord blood by radioimmunoassay. Systolic blood pressure (BP) was also measured in these infants. The IRT in IUGR fetuses was more (50.9+/-8.6 ms) than in the AGA fetuses (42.8+/-6.7 ms, p < 0.01). The mean BP in the IUGR newborns was greater (76+/-5 mm Hg vs 60+/-6 mm Hg, p < 0.01) than in the AGA fetuses. Rennin and angiotensin 1 concentrations were 1.61- and 1.56-fold greater in the blood of the IUGR newborns than in the AGA infants. A chronic hypertension in placenta perfusion increase in the IUGR fetuses was proposed. The changes in LV shape and uniformity of wall movement (remodeling) are considered to be the result of chronic increase in afterload. Rennin-angiotensin activation and LV remodeling as an adaptive reactions of antenatal period could promote the arterial hypertension development in later life.     

How does environment modify the spatial structure of Dictyostelium discoideum population

The transformation of the spatial structure of a Dictyostelium discoideum population in response to environmental changes induced by this population was investigated. A comparative analysis of the spatial and temporal characteristics of the D. discoideum colony is given for two cases: (a) when the colony is cultivated on a bacterial lawn, i.e. under conditions close to natural, and (b) in the absence of the bacterial lawn when the colony grows on the nutrient substrate enriched with folic acid. It is shown that the environmental changes induced by cell metabolism modify the spatial structure of the D. discoideum population first, the rate of population propagation falls drastically, which correlates with a decrease in the substrate pH; second, the spatial redistribution of the D. discoideum cell density correlates with the redistribution of folic acid in the substrate. The mechanism of the environment impact on the D. discoideum colony transformation is discussed.