Wolffia arrhiza (L.) Wimm. plants precultivated under different radiation conditions were exposed to UV-B at low or strong "white" irradiance. Photosynthetíc electron transport (Hill actívity) was more damaged by UV-B under 6 W m"^ than at 15 W m‘2 supplemental "white light" (WR). The inhibitory effect was more pronounced using red radiation (RR) precultivated plants compared to precultívatíon at blue radiation (BR) or WR. Hill reaction in RR grown W. arrhiza with a high growth rate was more affected by UV-B - in comiection with DCMU and 1,5- diphenyl carbazide - than of plants with a low growth rate. No effect was observed using plants precultivated at BR or WR.
Most studies of responses of insects to elevated carbon dioxide have been made using short-term exposures to treated food plants and have involved measurements of responses in growth, reproduction, food consumption and efficiencies of conversion at specific stages in the life cycle. These will be reviewed in the light of longer-term studies recently published where whole generations have been reared in chambers with simultaneous treatment of plants and where insects have been free to select their food and microenvironment. Factors such as seasonal change in plants, choice of food plant, mode of feeding, timing of exposure, temperature, the role of natural enemies are considered and the whole placed in the context of other aspects of climate change.
It is concluded that in studies to date, the only feeding guild in which some species have shown increases in population density in elevated carbon dioxide are the phloem feeders. Chewing insects (both free-living,and mining) generally have shown no change or reduction in abundance, though relative abundance may be greatly affected. Compensatory feeding is common in these groups., John B. Whittaker, and Lit
The presence of insulin resistance is frequently found in essential hypertension. There are, however, only sparse data with respect to the potential presence of insulin resistance in patients with secondary hypertension. We have therefore undertaken a study to reveal the potential occurrence of insulin resistance in primary hyperaldosteronism (PH). The hyperinsulinemic euglycemic clamp technique together with the evaluation of insulin receptor characteristics were used to study insulin resistance in 12 patients with PH. The measured parameters were compared to normal values in control subjects. We have found a significantly lower glucose disposal rate (M, m mol/kg/min) (18.7± 6 vs. 29.3± 4), decreased tissue insulin sensitivity index (M/I, m mol/kg/min per mU/l x100) (23.7± 9.8 vs. 37.5± 11.6) and also lower metabolic clearance rate of glucose (MCRg, ml/kg/min) (3.8± 1.5 vs. 7.0± 1.1) in patients with primary hyperaldosteronism. The insulin receptor characteristics on erythrocytes did not differ in primary hyperaldosteronism as compared to control healthy subjects. We thus conclude that insulin resistance is also present in secondary forms of hypertension (primary hyperaldosteronism) which indicates the heterogeneity of impaired insulin action in patients with arterial hypertension., J. Widimský Jr., G. Šindelka, T. Haas, M. Prázný, J. Hilgertová, J. Škrha., and Obsahuje bibliografii
The aim of the study was to evaluate skin microvascular reactivity (MVR) and possible influencing factors (fibrinolysis, oxidative stress, and endothelial function) in patients with Cushing’s syndrome. Twenty-nine patients with active Cushing’s syndrome (ten of them also examined after a successful operation) and 16 control subjects were studied. Skin MVR was measured by laser Doppler flowmetry during post-occlusive (PORH) and thermal hyperemia (TH). Malondialdehyde and Cu,Zn-superoxide dismutase were used as markers of oxidative stress. Fibrinolysis was estimated by tissue plasminogen activator (tPA) and its inhibitor (PAI-1). N-acetyl-β-glucosaminidase, E-selectin, P-selectin, and ICAM-1 were used as markers of endothelial function. Oxidative stress and endothelial dysfunction was present in patients with hypercortisolism, however, increased concentration of ICAM-1 was also found in patients after the operation as compared to controls (290.8±74.2 vs. 210.9±56.3 ng.ml-1, p<0.05). Maximal perfusion was significantly lower in patients with arterial hypertension during PORH and TH (36.3±13.0 vs. 63.3±32.4 PU, p<0.01, and 90.4±36.6 vs. 159.2±95.3 PU, p<0.05, respectively ) and similarly the velocity of perfusion increase during PORH and TH was lower (3.2±1.5 vs. 5.2±3.4 PU.s-1, p<0.05, and 0.95±0.6 vs. 1.8±1.1 PU.s-1, p<0.05, respectively). The most pronounced impairment of microvascular reactivity was present in patients with combination of arterial hypertension and diabetes mellitus., M. Prázný, J. Ježková, E. Horová, V. Lazárová, V. Hána, J. Kvasnička, L. Pecen, J. Marek, J. Škrha, M. Kršek., and Obsahuje bibliografii a bibliografické odkazy
The aim of the study was to evaluate the impact of simulated acute hyperglycemia (HG) on PI3K/Akt signaling in preconditioned and non -preconditioned isolated rat hearts perfused with Krebs -Henseleit solution containing normal (11 mmol/l) or elevated (22 mmol/l) glucose subjected to ischemia -reperfusion. Ischemic preconditioning (IP) was induced by two 5 -min cycle s of coronary occlusion followed by 5 -min reperfusion. Protein levels of Akt, phosphorylated (activated) Akt (P-Akt), as well as contents of BAX protein were assayed (Western blotting) in cytosolic fraction of myocardial tissue samples taken prior to and a fter 30 -min global ischemia and 40- min reperfusion. In “normoglycemic ” conditions (NG), IP significantly increased P -Akt at the end of long -term ischemia, while reperfusion led to its decrease together with the decline of BAX levels as compared to non- pre conditioned hearts. On the contrary, under HG conditions, P -Akt tended to decline in IP - hearts after long -term ischemia, and it was significantly higher after reperfusion than in non -preconditioned controls . No significant influence of IP on BAX levels at the end of I/R was observed under HG conditions . It seems that high glucose may influence IP -induced activation of Akt and its downstream targets, as well as maintain persistent Akt activity that may be detrimental for the heart under above conditions., M. Zálešák, P. Blažíček, I. Gablovský, V. Ledvényiová, M. Barteková, A. Ziegelhöffer, T. Ravingerová., and Obsahuje bibliografii
We investigated and evaluated post-irradiation survival in cyclooxygenase-2-deficient (COX-2 KO) mice. Thirty-day survival following exposure of COX-2 KO mice to a lethal dose of 8.5 Gy of γ-rays was observed to be statistically significantly lower in both males and females, as well as when the sexes were merged, in comparisons with their wild-type counterparts. These findings were related to the previous observations concerning the detrimental influence of the COX-2 genetic disruption on hematopoiesis in sublethally irradiated mice. Deteriorated postirradiation survival of COX-2 KO mice confirmed the previously anticipated conclusion regarding negative influence of the antiinflammatory action of COX-2 deficiency under the conditions of exposure of the animals to ionizing radiation., M. Hofer, Z. Hoferová, A. Gruzdev, L. Dušek, M. Falk., and Obsahuje bibliografii
Resistance to vitamin D has been known for decades as vitamin D resistant rickets, caused by mutations of the gene encoding for vitamin D receptor (VDR). Findings of extra-skeletal effects of vitamin D and learning of the molecular mechanisms used by its biologically active metabolite calcitriol revealed other ways leading to its impaired sensitivity. Calcitriol takes advantage of both genomic and non-genomic mechanisms through its binding to vitamin D receptor, located not only in the cell nuclei but also in a perinuclear space. On the genomic level the complex of calcitriol bound to VDR binds to the DNA responsive elements of the controlled gene in concert with another nuclear receptor, retinoid X receptor, and expression of the VDR itself is controlled by its own ligand. These elements were found not only in the promotor region, but are scattered over the gene DNA. The gene expression includes a number of nuclear transcription factors which interact with the responsive elements and with each other and learning how they operate would further contribute to revealing causes of the impaired vitamin D sensitivity. Finally, the examples of major disorders are provided, associated with impairment of the vitamin D function and its receptor., L. Máčová, M. Bičíková, R. Hampl., and Obsahuje bibliografii
Fatty liver disease associated with obesity is an important medical problem and the mechanisms for lipid accumulation in hepatocytes are not fully elucidated yet. Recent findings indicate that mitochondria play an importan t role in this process. Our data on hepatocytes in which mitochondria are in contact with other cytosolic structures importan t for their function, extend observations obtained on isolated mitochondria and confirm inhibition of Complex I activity in hepatocytes isolated from rats fed by high fat diet (HFD) compared with controls fed by standard diet (STD). Furthermore we have found that HFD- hepatocytes are more sensitive to the peroxidative stress because under these conditions also Complex II activity is disturbed. Therefore in HFD animals decrease of Complex I activity cannot be compensated by Complex II substrates as in STD hepatocytes. Our data thus indicates that combination of HFD and peroxidative stress potentiates HFD damaging effect of mitochondria because both branches of the respiratory chain (NADH- and flavoprotein-dependent) are disturbed., T. Garnol ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
The electrical properties of the supported lipid bilayer membrane (s-BLM) of egg phosphatidylcholine (PC) selfassembled on agar surface were examined. To characterize the insulating properties of s-BLMs, electrochemical impedance spectroscopy (EIS) was used. The analysis of impedance spectra in terms of an equivalent circuit of agar/electrolyte and agar/s-BLM/electrolyte in the frequency range of 0.1 Hz-10 kHz was performed. The high-density lipoproteins (HDL)/s-BLM interaction in the concentration range from 20 μg/ml to 80 μg/ml of HDL was investigated. It is evident that treatment of s-BLM with HDL resulted in an increase of the lipid film resistance and a decrease of membrane capacitance., M. Legiň, G. Laputková, J. Sabo, L. Vojčíková., and Obsahuje bibliografii