Adaptation to hypoxia is beneficial in cardiovascular pathology related to NO shortage or overproduction. However, the question about the influence of adaptation to hypoxia on NO metabolism has remained open. The present work was aimed at the relationship between processes of NO production and storage during adaptation to hypoxia and the possible protective significance of these processes. Rats were adapted to intermittent hypobaric hypoxia in an altitude chamber. NO production was determined by plasma nitrite/nitrate level. Vascular NO stores were evaluated by relaxation of the isolated aorta to diethyldithiocarbamate. Experimental myocardial infarction was used as a model of NO overproduction; stroke-prone spontaneously hypertensive rats (SHR-SP) were used as a model of NO shortage. During adaptation to hypoxia, the plasma nitrite/nitrate level progressively increased and was correlated with the increase in NO stores. Adaptation to hypoxia prevented the excessive endothelium-dependent relaxation and hypotension characteristic for myocardial infarction. At the same time, the adaptation attenuated the increase in blood pressure and prevented the impairment of endothelium-dependent relaxation in SHR-SP. The data suggest that NO stores induced by adaptation to hypoxia can either bind excessive NO to protect the organism against NO overproduction or provide a NO reserve to be used in NO deficiency., E. B. Manukhina, S. Yu. Mashina, B. V. Smirin, N. P. Lyamina, V. N. Senchikhin, A. F. Vanin, I. Yu. Malyshev., and Obsahuje bibliografii
The present study was performed to evaluate the role of neuronal nitric oxide synthase (nNOS)-derived nitric oxide (NO) during the developmental phase of hypertension in transgenic rats harboring the mouse Ren-2 renin gene (TGR). The first aim of the present study was to examine nNOS mRNA expression in the renal cortex and to assess the renal functional responses to intrarenal nNOS inhibition by S-methyl-L-thiocitrulline (L-SMTC) in heterozygous TGR and in age-matched transgene-negative Hannover Sprague-Dawley rats (HanSD). The second aim was to evaluate the role of the renal sympathetic nerves in mediating the renal functional responses to intrarenal nNOS inhibition. Thus, we also evaluated the effects of intrarenal L-SMTC administration in acutely denervated TGR and HanSD. Expression of nNOS mRNA in the renal cortex was significantly increased in TGR compared with HanSD. Intrarenal administration of L-SMTC decreased the glomerular filtration rate (GFR), renal plasma flow (RPF) and sodium excretion and increased renal vascular resistance (RVR) in HanSD. In contrast, intrarenal inhibition of nNOS by L-SMTC did not alter GFR, RPF or RVR and elicited a marked increase in sodium excretion in TGR. This effect of intrarenal L-SMTC was not observed in acutely denervated TGR. These results suggest that during the developmental phase of hypertension TGR exhibit an impaired renal vascular responsiveness to nNOS derived NO or an impaired ability to release NO by nNOS despite enhanced expression of nNOS mRNA in the renal cortex. In addition, the data indicate that nNOS-derived NO increases tubular sodium reabsorption in TGR and that the renal nerves play an important modulatory role in this process., L. Červenka, H. J. Kramer, J. Malý, I. Vaněčková, A. Bäcker, D. Bokemeyer, M. Bader, D. Ganten, K. D. Mitchell., and Obsahuje bibliografii
It has been suggested that increase in acute nitric oxide (NO) or cyclic guanosine monophosphate production may be involved in cardioprotection induced by chronic hypoxia (CH). We studied the effect of NO donor molsi domine and phosphodiesterase type 5 inhibitor sildenafil on myocardial ischemia/reperfusion (I/R) injury in rats adapted to CH. Male Wistar rats were exposed to continuous hypoxia in a normobaric chamber (10 % O 2 , 4 weeks). Rats received either saline, mol sidomine (10 mg/kg body weight, i.v.) or sildenafil (0.7 mg/kg body weight, i.v.) 30 min before ischemia. Control rats were kept under normoxia and treated in a corresponding manner. Adaptation to CH increased the myocardial ischemic tolerance. Acute treat ment with either molsidomine or sildenafil significantly reduced infarct size in normoxic rats and further enhanced cardioprotection induced by CH. However, the cardioprotective effect of CH on I/R injury was not additive to the cardioprotection provided b y the drugs., P. Alánová, F. Kolář, B. Ošťádal, J. Neckář., and Obsahuje bibliografii
Properties of the Frőhlich model of collective oscillations of polar molecules (such as proteins) residing inside, or in the plasma membrane, of bio\-logical cells, receiving energy from intracellular metabolic sources and giving it off to surroundings, are studied. The exchange mechanisms with the heat bath can be linear and non-linear. Particular attention is given to condensation of energy in the lowest-frequency (fundamental) mode. Occurrence of this phenomenon, which is of importance for generation of electromagnetic fields by the cells as well as for other functions, presupposes that the non-linear interaction coefficient exceeds certain limit; if it is too small, the incoming energy is distributed to all modes. This can happen e.g. in the context of cancerous conditions due to perturbation of high static electric fields around mitochondria which are necessary support for non-linear behaviour. On the contrary, if interaction with the heat bath is too high, the oscillator system leaks energy to surroundings and must be pumped heavily to attain condensation.
The influence of olfactory and visual stimuli on the mating behaviour of Theresimima ampellophaga males was investigated in the field. A female model attached to a pheromone source significantly increased the number of males contacting and showing copulatory responses compared to their reaction to a pheromone stimulus alone. The pheromone stimulus was the primary factor releasing male copulatory behaviour, independent of the spatial arrangement of olfactory and visual cues. The role of the visual cues decreased with increasing distance between visual and olfactory cues. The reaction of males to pairs of models with different characteristics of conspecific females, in combination with a pheromone source placed 2 cm upwind from the center of the line between each pair of models, was compared. The size and shape of the female seemed not to be important, while the colour, posture, sex and species belongings significantly influenced the male's mating reaction.
We studied the response of several parameters related to oxidative stress in the liver of aging rats. Male Wistar rats aged 1.5, 3, 18 and 24 months were used. Livers showed an increase in superoxide anion (O2-) concentration at 1.5 and 18 months of age compared to the 3-month-old group; a decrease in superoxide dismutase (SOD) was seen at 1.5 months and catalase concentrations remained unaltered throughout the aging process. Nitric oxide (NO) progressively declined with age; a significant decrease was particularly apparent at 18 and 24 months of age. Thiobarbituric acid reactive substances (TBARS) decreased significantly at 1.5 months, whereas it increased at 18 and 24 months of age. Concentrations of prostaglandin E2 (PGE2), and adenine nucleotides, and their metabolites, remained unchanged throughout the aging process. Although the mitochondrial damage caused by oxidative stress can result in reduced ATP production and compromised cell function, our results on adenosine nucleotides and their metabolites support the notion that the integrity of mitochondria and enzymatic activity remain mostly unchanged with aging. In conclusion, we observed a significant decrease in the levels of NO in the older groups of rats and hence in its antioxidant activity. This could explain the observed increase in lipid peroxides which suggests an important role for NO in oxidative stress in the liver of older rats., F. Mármol ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
The ability of activity modulators of ornithine transcarbamoylase (OCT) from the liver of the thresher shark Alopias vulpinus to stabilize the enzyme against thermal denaturation was investigated in the tri-buffer at pH 7.8, at temperatures ranging from 60 to 70 °C, in the presence of polyhydroxylic molecules such as glycerol and sugars. The study indicated that in the presence of 0.5 M sugars and 1.6 M glycerol in the preincubation medium the OCT activity increases. When trehalose is introduced directly in the reaction mixture in a range of concentration of 0.25-0.5 M, the activity is lower than that with maltose, glycerol and buffer alone. Kinetic data for carbamoyl phosphate and ornithine with and without maltose and glycerol are similar, whereas trehalose increases the kinetic values. Arrhenius plots show an increase of activation energy due to trehalose, whereas values obtained with maltose and glycerol are similar to the control
Remodeled pulmonary arteries return to normal structural conditions after the increase in pulmonary artery flow resistance is reversed. We studied whether proteolysis of extracellular matrix proteins and apoptosis occur during reversal of remodeling produced by chronic hypoxia in the rat. Main pulmonary arteries were removed at different times during a 10-day period of exposure to 10% O2 and 14 days after return to air. Content and rates of degradation of collagen and elastin as well as immunoreactive collagenase in tissue and isolated mast cells were measured. Immunoblots for collagenase and tissue inhibitor of metalloproteinases (TIMP) were performed. Apoptosis was assessed by cleavage of DNA and TUNEL assay. Excess collagen and elastin present at 10 days of hypoxia decreased to near normal levels after 3-5 days of air. Transient increases in collagenolytic and elastolytic enzyme activities accompanied the rapid decrease in matrix proteins. Mast cells containing collagenase accumulated in remodeled pulmonary arteries, and the active form of collagenase appeared at the time of peak proteolytic activity. TIMP increased during remodeling. Apoptosis was maximal 3 days after return to air. Our results suggest that activation of enzymes, which degrade matrix proteins, and apoptosis play a role in resolution of vascular remodeling., D. J. Riley, S. Thakker-Varia, F. J. Wilson, G. J. Poiani, C. A. Tozzi., and Obsahuje bibliografii
Image de-noising is a traditional task related to linear and non-linear 2D filtering methods. The artificial neural network (ANN) can be also used as a kind of a sophisticated non-linear filter on local pixel neighborhood (3x3). The disadvantage of linear systems and neural networks is their sensitivity to impulse (isolated) noise. That is why the median and the other rank based filters are better in this case. The opposite situation is in the case of Gaussian noise when the mean filtering has higher value of signal / noise ratio (SNR) than the median filter. The first aim of our paper is to define k-robustness of local de-noising. Then it is easy to build up a new class of k-robust de-noising systems consisting of input frame, robust preprocessing, ANN and robust postprocessing. Implementation details related to signal processing and learning are also included. The third aim of our paper is to learn 1-robust and 2-robust systems to have maximum possible SNR for Gaussian noise on real MR image of human brain.