Dopamine (DA) is known as a primary regulator of prolactin secretion (PRL) and angiotensin II (Ang II) has been recognized as one brain inhibitory factor of this secretion. In this work, estrogen-primed or unprimed ovariectomized rats were submitted to the microinjection of saline or Ang II after previous microinjection of saline or of DA antagonist (haloperidol, sulpiride or SCH) both in the medial preoptic area (MPOA). Our study of these interactions has shown that 1) estrogen-induced PRL secretion is mediated by Ang II and DA actions in the MPOA, i.e. very high plasma PRL would be prevented by inhibitory action of Ang II, while very low levels would be prevented in part by stimulatory action of DA through D2 receptors, 2) the inhibitory action of Ang II depends on estrogen and is mediated in part by inhibitory action of DA through D1 receptors and in other part by inhibition of stimulatory action of DA through D2 receptors., C. M. Leite, G. J. R. Machado, R. C. M. Dornelles, C. R. Franci., and Obsahuje bibliografii a bibliografické poznámky
The effects of lyotropic (swelling) anions (Cl-, Br-, NO3- and I-) on contractile properties of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles were investigated in vitro at 20 °C and 35 °C. Isolated muscles bathed in anionic Tyrode solution were stimulated directly and isometric single twitches and fused tetanic contractions were recorded. In a Cl- Tyrode solution a decrease of the bathing temperature led to a cold potentiation of the twitch tension (Pt) in EDL muscles, however, to a cold depression in SOL muscles, in both muscles combined with a prolongation of contraction (CT) and half relaxation (HRT) times. The extent and order of the potentiating effect of lyotropic anions on the Pt, CT and HRT in EDL and SOL were quite similar and increased in the order: Cl-< Br- < NO3- < I-. Since the lyotropic anions did not influence tetanic tensions, the twitch-tetanus ratio (TTR) was increased in NO3- and I- solutions. All effects of the anions were rapidly and completely reversed in both muscles when the test solution was replaced by the normal one. The temperature decrease caused no significant alteration in the potentiation capacity of the anions or in the kinetics of their action and reversibility., Y. Wondmikun, T. Soukup, G. Asmussen., and Obsahuje bibliografii
Ligand-gated ionic channels are integral membrane proteins that enable rapid and selective ion fluxes across biological membranes. In excitable cells, their role is crucial for generation and propagation of electrical signals. This survey describes recent results from studies performed in the Department of Cellular Neurophysiology, Institute of Physiology ASCR, aimed at exploring the conformational dynamics of the acetylcholine, glutamate and vanilloid receptors during their activation, inactivation and desensitization. Distinct families of ion channels were selected to illustrate a rich
complexity of the functional states and conformational transitions these proteins undergo. Particular attention is focused on structure-function studies and allosteric modulation of their activity. Comprehension of the fundamental principles of mechanisms involved in the operation of ligand-gated ion channels at the cellular and molecular level is an essential prerequisite for gaining an insight into the pathogenesis of many psychiatric and neurological disorders and for efficient development of novel specifically targeted drugs.
Adenosine A3 receptor agonist N6-(3-iodobenzyl)adenosine-5’-N-methyluronamide (IB-MECA) has been tested from the point of view of potentiating the effects of hematopoietic growth factors interleukin-3 (IL-3), stem cell factor (SCF), granulocyte- macrophage colony-stimulating factor (GM-CSF), and granulocyte colony-stimulating factor (G-CSF) on the growth of hematopoietic progenitor cells for granulocytes and macrophages (GM-CFC) in suspension of normal mouse bone marrow cells in vitro. IB-MECA alone induced no GM-CFC growth. Significant elevation of numbers of GM-CFC evoked by the combinations of IB-MECA with IL-3, SCF, or GM-CSF as compared with these growth factors alone has been noted. Combinat ion of IB-MECA with G-CSF did not induce significantly higher numbers of GM-CFC in comparison with G-CSF alone. Joint action of three drugs, namely of IB-MECA + IL-3 + GM-CSF, produced significantly higher numbers of GM-CFC in comparison with the combinations of IB-MECA + IL-3, IB-MECA + GM-CSF, or IL-3 + GM-CSF. These results give evidence of a significant role of selective activation of adenosine A3 receptors in stimulation of the growth of granulocyte/macrophage hematopoietic progenitor cells., M. Hofer ... [et al.]., and Obsahuje seznam literatury
Ischemic preconditioning (IP) protects the heart against subsequent prolonged ischemia. Whether the β-adrenoceptor/adenylate cyclase pathway contributes to this cardioprotection is not yet fully known. Using enzyme catalytic cytochemistry we studied the adenylate cyclase activity and its distribution in the preconditioned rat heart. Adenylate cyclase activity was examined in Langendorff-perfused rat hearts subjected to the following conditions: control perfusion; 30 min regional ischemia; 5 min occlusion and 10 min reperfusion (IP); IP followed by ischemia. Ischemia-induced arrhythmias and the effect of ischemic preconditioning on the incidence of arrhythmias were analyzed. At the end of experiment the heart was shortly prefixed with glutaraldehyde. Tissue samples from the left ventricle were incubated in a medium containing the specific substate AMP-PNP for adenylate cyclase and then routinely processed for electron microscopy. Adenylate cyclase activity was cytochemically demonstrated in the sarcolemma and the junctional sarcoplasmic reliculum (JSR) in control hearts, while it was absent after test ischemia. The highest activity of the precipitate was observed after ischemic preconditioning. In the preconditioned hearts followed by test ischemia, adenylate cyclase activity in the precipitate was preserved in sarcolemma and even more in JSR. Protective effect of ischemic preconditioning was manifested by the suppression of severe arrhythmias. These rresults indicate the involvement of the adenylate cyclase system in mechanisms underlying ischemic preconditioning., Ľ. Okruhlicová, T. Ravingerová, D. Pancza, N. Tribulová, J. Styk, R. Štetka., and Obsahuje bibliografii
In cockroaches and certain other insects the concentration of trehalose in the hemolymph is increased by hypertrehalosemic hormone (HTH), a neuropeptide originating in the corpus cardiacum. A vital step in the action of HTH to promote conversion of glycogen stored in the fat body to trehalose is the activation of phosphorylase. The means by which HTH activates phosphorylase, with particular emphasis on its role in the regulation of intracellular calcium, is discussed. Additional information supporting the view that HTH stimulated synthesis of trehalose, and possibly its release from the trophocyte, is regulated by fatty acids and eicosanoids is presented., John E. Steele, and Lit
A possibility of using synthetic analogues of juvenile hormone (juvenoids) to disrupt imaginal diapause of the apple blossom weevil, Anthonomus pomorum females was demonstrated. Out of three preparations tested (methoprene, fenoxycarb and W-328) methoprene and fenoxycarb appeared to be effective. Sensitivity to juvenile hormone analogues develops early after imaginal emergence (even before the female starts to feed) and lasts throughout the whole aestivo-hibernation dormancy. Although the juvenoids could stimulate the onset of oogenesis at any time during diapause, the propensity of the ovaries to form normal eggs developed only during hibernation part of the dormancy; in earlier stages of diapause accumulation of yolk was observed but matured eggs were not produced. Methoprene treatment caused marked increase of locomotory activity accompanied with decrease of dry weight, increase of water content, depletion of trehalose resources, decrease of cold hardiness and, finally, 100% mortality within four weeks in the weevils treated during their feeding or aestivation stages. Although similar changes were observed in the treated pre-feeding weevils, they later recovered and survived until next spring without apparent loss of cold hardiness. A possibility of designing a control method based on this principle is discussed and the results of small-scale field trials that support its plausibility are reported.
Helicobacter pylori has been implicated in stimulation of immune system, development of autoimmune endocrinopathies as autoimmune thyroiditis (AT) and on other hand induction of immunosupresion activates gastric and extra-gastric diseases such as gastric ulcer or cancer. It causes persistent lifelong infection despite local and systemic immune response. Our results indicate that Helicobacter pylori might cause inhibition of the specific cellular immune response in Helicobacter pyloriinfected patients with or without autoimmune diseases such as AT. We cannot also declare the carcinogenic effect in oropharynx. However the association of any infection agents and cancerogenesis exists. The adherence of Helicobacter pylori expression and enlargement of benign lymphatic tissue and the high incidence of the DNA of Helicobacter pylori in laryngopharyngeal and oropharyngeal cancer is reality. LTT appears to be a good tool for detection of immune memory cellular response in patients with Helicobacter pylori infection and AT. All these complications of Helicobacter pylori infection can be abrogated by successful eradication of Helicobacter pylori., J. Astl, I. Šterzl., and Obsahuje bibliografii
Several deleterious effects may occur when intense and exhaustive exercise (IE) is not well-planned. This study aimed to investigate the effects of a short duration IE on body chemical composition and hypothalamic-pituitary-adrenal (HPA) axis. C57Bl/6 mice were distributed into four groups (10 mice per group): control (C-4D and C-10D), 4 days (E-4D), and 10 days of IE (E-10D). IE program consisted of a daily running session at 85 % of maximum speed until the animal reached exhaustion. Body weight as well as total body water, fat and protein content were determined from animal carcasses. HPA activation was assessed by plasma corticosterone levels measured by radioimmunoassay and the weight of both the adrenal glands and thymus were measured. Plasma corticosterone levels increased by 64 % in both the E-4D and E-10D groups. The weight of the adrenal glands augmented by 74 % and 45 %, at 4 and 10 days of IE, respectively, whereas thymus weight diminished by 15 % only in the E-10D group. The total carcass fat content decreased by 20 % only at 4 days IE, whereas protein content decreased by 20 % in both E-4D and E-10D groups. A relationship between corticosterone plasma levels and loss of body protein content in both E-4D and E-10D groups was observed (R2=0.999). We concluded that IE may be related to HPA axis activation associated with remodeling of body chemical composition in C57BL/6 mice., E. F. Rosa, G. A. Alves, J. Luz, S. M. A. Silva, D. Suchecki, J. B. Pesquero, J. Aboulafia, V. L. A. Nouailhetas., and Obsahuje bibliografii