The role of 20-hydroxyecdysone (20E) in the metamorphosis of the central nervous system was investigated by recording feeding, wandering and pupariation behaviour as the measures of hormonal effects on the neural tissues in the flesh fly Neobellieria (Sarcophaga) bullata. The minimum amount of food essential for the commitment to metamorphosis is rather small and constant and the larvae ingest it during the first 4 to12 h of the last instar. Underfed larvae maintain food appetency for a certain time and this period of hunger can be considerably shortened by the application of 20E. Application of 20E also significantly shortens or abolishes the intake of additional food offered to starving larvae. Thus 20E has an effect on neural mechanisms controlling both termination of the period of hunger and suppression of feeding behaviour. Application of 20E at any time during the wandering stage stimulates the precocious onset of pupariation. The central neurons controlling motor patterns of pupariation behaviour are committed to perform properly their programme some 15 h earlier than the larval integument is ready to transform into normal puparium. As a result of this temporal shift of tissue determination, some precociously formed puparia are not properly shaped despite the fact that the larva is exhibiting normal patterns of pupariation behaviour.
Numerous hypotheses have been proposed about the pathogenesis of the polycystic ovarian syndrome (PCOS). However, hormonal control of persistent follicles has not be enestablished. The objective of the present study was to compare the follicular structure and hormonal profiles of rats treated with the adrenocor ticotrophic hormone (ACTH) with two experimental models of PCOS. ACTH-treated animals were compared with those exposed to continuous light, those treated with estradiol valerate, and with control (in proestrous and diestrous). Serum hormone levels, histomorphometrical changes, and immunoexpression of vimentin, cytokeratins, cadherins, and proliferating cell nuclear antigen (PCNA) were examined. Treatment with ACTH resulted in an elevation of corticosterone secretion with LH reduction but without changes in ovarian morphology. Although stress (or ACTH) stimulation may be only one of pathophysiological mechanisms involved in follicular cystathogenesis in other species, we do not have important evidence to suppose that this would happen in rats., C. Bavaralle, N. R. Salvetti, G. A. Mira, J. A. Lorente, H. H. Ortega., and Obsahuje bibliografii a bibliografické odkazy
Certain liver metabolic diseases point to the presence of disturbances in glycogen deposition. Epinephrine raises the cAMP level that activates protein kinase A leading to the activation of phosphorylase and glycogen breakdown. In the present report, we sought to investigate whether NO is produced during adrenoceptor agonist-induced glycogenolysis in rat hepatocytes in cultures. Isolated glycogen rich rat hepatocytes in cultures were used. NO production (NO2-) was assessed under the effect of adrenergic agonists and adrenergic agonist/antagonist pairs, dibutyryl cyclic AMP sodium-potassium salt (db-cAMP), NO synthase (NOS) inhibitors Nω-nitro-L-arginine methyl ester (L-NAME), aminoguanidine (AG) and the NO donor S-nitroso-N-acetyl penicillamine (SNAP) . The inducible NO synthase (iNOS) mRNA was examined by the reverse transcription-polymerase chain reaction (RT-PCR). Glycogenolysis was quantified by glucose levels released into medium. The amount of glucose and NO2- released by hepatocytes was increased as a result of epinephrine, phenylephrine or db-cAMP treatments. The increase in glucose and NO2- released by epinephrine or phenylephrine was blocked or reduced by prazosin pretreatment and by NOS inhibitors aminoguanidine and L-NAME. iNOS gene expression was up-regulated by epinephrine. It can be concluded that glycogenolysis occurs through α adrenoceptor stimulation and a signaling cascade may involve NO production., J. Hodis, N. Kutinová-Canová, P. Potměšil, L. Kameníková, E. Kmoníčková, Z. Zídek, H. Farghali., and Obsahuje biblografii a bibliografické odkazy
A thermodynamical approach to the problem of star formation, presented in a previous paper, shows how, at least when the last stages of collapse are assumed as adiabatic, the characteristics of the outcomes depend on the initial conditions (thermal and rotational energies) and on the distribution of the angular momentum among the various parts of the system. In the case of a binary outcome, the distiribution can be profitably expressed in terms of two parameters, roughly corresponding to a) the spin ratio as function of the mass ratio and b) the fraction of a.m. involved in the orbital motion. A systematic exploration of these parameters allows us to analyze the different kinds of results. In this paper we present some preliminary results, assuming that both single and binary outcomes have an equilibrium Mc Laurin ellipsoidal shape, but not taking into account the possible formation of a system star+protoplanetary disc.
Photosystem 2 (PS 2) reaction centre can be considered as a water-plastoqninone oxido-reductase. Using four photons it transfers four electrons from two molecules of water to plastoquinone (PQ), producing the molecular oxygen and two molecules of double reduced PQ. PS 2 is the site of the antagonistic action of bicarbonate and formáte on PS 2 electron flow; incubation of isolated chloroplasts with formáte results in full inhibition of electron flow actívity, which can be restored by addition of bicarbonate. This bicarbonate effect is located at the Dl protein and affects the electron flow between the primary quinone and the PQ pool. Bicarbonate is probably involved in stabilizatíon of tíie semireduced secondary quinone Qb, and in the protonation reactions at this site. Under physiological conditions bicarbonate is boimd to thylakoid membranes. Addition of formáte to thylakoids appears to release CO2. The bicarbonate effect is not only observed in isolated chloroplasts, but also in intact organisms as green algae and leaves. Bicarbonate Controls PS 2 electron flow in order to cope with stress conditions leading to, for instance, photoinhibition or to the high rates of photorespiration.
Although playing an important role in shaping the environment, the mechanisms responsible for runoff initiation and yield in arid and semiarid regions are not yet fully explored. With infiltration-excess overland flow, known also as Hortonian overland flow (HOF) taking place in these areas, the uppermost surface 'skin' plays a cardinal role in runoff initiation and yield. Over large areas, this skin is composed of biocrusts, a variety of autotrophs (principally cyanobacteria, green algae, lichens, mosses) accompanied by heterotrophs (such as fungi, bacteria, archaea), which may largely dictate the infiltration capability of the surface. With most biocrust organisms being capable of excreting extracellular polymeric substances (EPS or exopolymers), and growing evidence pointing to the capability of certain EPS to partially seal the surface, EPS may play a cardinal role in hindering infiltration and triggering HOF. Yet, despite this logic thread, great controversy still exists regarding the main mechanisms responsible for runoff generation (runoff initiation and yield). Elucidation of the possible role played by EPS in runoff generation is the focus of the current review.
Primary amoebic meningoencephalitis (PAM) was induced in mice by intranasal inoculation of Naegleria fowleri (Singh et Das, 1970) to study the role of the blood vessels and lungs in the early and later stages in this disease. Upon culturing blood and lung tissue obtained at 24-, 36-, 48-, 72-, 96-, and 120-hour time periods, it was found that amoebae grew only from blood and lung tissue obtained at the 96 and 120 hour time periods. Paraffin sections of the head revealed small foci of acute inflammation and amoebae within the olfactory bulb of the central nervous system (CNS) at 24 hours. Amoebae were not observed within blood vessels of the CNS until 96 and 120 hours. Also, amoebae were observed within the connective tissue surrounding blood vessels and sutures of the skull, bone marrow, and venous sinusoids between the skull bone tables at 96 and 120 hours. No amoebae or acute inflammatory reactions were observed in the lung sections from any time period and indirect immunofluorescence microscopy was negative for N. fowleri. This study provides evidence that neither blood vessels nor lungs provide routes for N. fowleri to the CNS during the early stages of PAM and that amoebae enter veins of the CNS and bone marrow during later stages of the disease.
Carbon dioxide interacts both with reactive nitrogen species and reactive oxygen species. In the presence of superoxide, NO reacts to form peroxynitrite that reacts with CO2 to give nitrosoperoxycarbonate. This compound rearranges to nitrocarbonate which is prone to further reactions. In an aqueous environment, the most probable reaction is hydrolysis producing carbonate and nitrate. Thus the net effect of CO2 is scavenging of peroxynitrite and prevention of nitration and oxidative damage. However, in a nonpolar environment of membranes, nitrocarbonate undergoes other reactions leading to nitration of proteins and oxidative damage. When NO reacts with oxygen in the absence of superoxide, a nitrating species N2O3 is formed. CO2 interacts with N2O3 to produce a nitrosyl compound that, under physiological pH, is hydrolyzed to nitrous and carbonic acid. In this way, CO2 also prevents nitration reactions. CO2 protects superoxide dismutase against oxidative damage induced by hydrogen peroxide. However, in this reaction carbonate radicals are formed which can propagate the oxidative damage. It was found that hypercapnia in vivo protects against the damaging effects of ischemia or hypoxia. Several mechanisms have been suggested to explain the protective role of CO2 in vivo. The most significant appears to be stabilization of the iron-transferrin complex which prevents the involvement of iron ions in the initiation of free radical reactions., A. Veselá, J. Wilhelm., and Obsahuje bibliografii
Chronic heart failure has become a significant health problem. Cardiac surgery has an important role in the treatment of patients with heart failure. There are traditional surgical techniques in cardiac surgery – coronary revascularization, valve surgery, ventricular reconstructive surgery as well as new surgical techniques – cardiac support device (CorCap), mechanical circulatory support and resynchronization therapy. Cardiac surgery has a definitive role in the treatment algorithm for chronic heart failure., J. Pirk., and Obsahuje seznam literatury
To evaluate the role of chloride in the pathogenesis of salt-dependent deoxycorticosterone (DOC) hypertension, we studied young Wistar rats chronically loaded with sodium bicarbonate (NaHCO3) or sodium chloride (NaCl) which were administered either in the diet or in the drinking fluid. Selective sodium loading (without chloride) increased blood pressure (BP) in DOC-treated animals only if NaHCO3 was provided in the diet. In contrast, no significant blood pressure changes were induced by DOC treatment in rats drinking NaHCO3 solution. Hypernatremia and high plasma osmolality occurred only in rats drinking NaCl or NaHCO3 solutions. Compared to great volume expansion in NaCl-loaded DOC-treated rats, the degree of extracellular fluid volume expansion (namely of its interstitial fraction) was substantially lower in both NaHCO3-loaded groups in which significant hypokalemia was observed. NaHCO3-drinking rats without significant blood pressure response to DOC treatment represented the only experimental group in which blood volume was not expanded. In conclusion, our data confirm previous observations that NaHCO3 loading is less potent in eliciting DOC hypertension than NaCl loading, but blood pressure rise in rats fed NaHCO3 diet clearly demonstrated that selective sodium loading could potentiate the development of DOC hypertension if NaHCO3 is offered within the appropriate dietary regimen. The reasons for the failure of NaHCO3-drinking rats to elevate blood pressure in response to chronic mineralocorticoid treatment are not obvious. However, the absence of a significant plasma volume expansion together with hypernatremia and increased plasma osmolality suggest a considerable degree of dehydration in these animals which fail to increase their fluid consumption compared to water drinking rats.