An acid pH in the lumen of chloroplast thylakoids is necessary in order to derive the required amount of CO2 to account for the observed rates of carbon fixation. We point out that the endosymbiotic derivation of the chloroplast from a cyanobacterium would have resulted in the lumen of the thylakoid having an acid pH. The thylakoids of cyanobacteria are continuous with the plasma membrane, resulting in the lumen of the thylakoid being open to the outside of the cell. Endosymbiosis resulted in the cyanobacterium being taken up into a food vacuole of a protozoan. The vacuole would have had an acid pH, probably around pH 5, so the endosymbiotic bacterium would have been surrounded by an environment with an acidic pH. The lumen of the thylakoids would have been at an acid pH since they were open to the exterior of the cell, and to the contents of the vacuole. and R. E. Lee, P. Kugrens.
Acolpenteron australe sp. n. (Dactylogyridae, Dactylogyrinae) is described from ureters and renal tubules of Percichthys trucha (Cuvier et Valenciennes) (Perciformes, Percichthyidae) from Andean Patagonian lakes. The new species has a haptor with 14 hooks, with shanks comprised of two subunits. It has overlapped intercaecal gonads, male copulatory organ as a sclerotized tube with one counterclockwise coil and a J-shaped accessory piece. It differs from the other species of Acolpenteron by having a non-forked accessory piece. This is the first monogenean species described from a percichthyid host in South America.
The article deals with a research of acoustic emission induced by electromagnetic field. Experiments were focused on measurement of acoustic emission (sound waves) as a mechanical response to the excitation current. Surface displacement was detected by laser interferometer and arising surface waves were then observed. Maximal measured amplitude of mechanical displacement driven by excitation current with amplitude 120 mA is about 8 nm. and Článek se zabývá výzkumem akustické emise generované pomocí elektromagnetického pole. V experimentech se měří velikost mechanické odezvy akustické emise (mechanických vln) na budicí proud z generátoru. Výchylka povrchu byla snímána laserovým interferometrem, byla registrována přítomná povrchová vlna. Maximální amplituda výchylky je 8 nm při amplitudě budicího proudu 120 mA.
The effect of Cavalheiro's pilocarpine model of epileptogenesis upon conditioned taste aversion (CTA), an important example of nondeclarative memory, was studied in adult Long Evans rats. Deterioration of CTA was studied during the silent period between pilocarpine-induced status epilepticus (SE) and delayed spontaneous recurrent seizures. SE was elicited by i.p. injection of pilocarpine (320 mg/kg ) and interrupted after 2 hours by clonazepame (1 mg/kg i.p.). Peripheral cholinergic symptoms were suppressed by methylscopolamine (1 mg/kg i.p.), administered together with pilocarpine. CTA was formed against the salty taste of isotonic LiCl. In the experiment of CTA acquisition, the CTA was formed and tested during the silent period after SE. In the experiment of CTA retrieval, the CTA was acquired before SE and the retrieval itself was tested during the silent period. Retrieval of CTA acquired before SE was impaired more than the retrieval of CTA formed during the silent period. Our findings indicate that epileptic seizures can disrupt even non-declarative memory but that CTA formed by the damaged brain can use its better preserved parts for memory trace formation. Ketamine (50 mg/kg i.p.) applied 2 min after the onset of pilocarpine-induced status epilepticus protected memory deterioration., J. Šroubek, J. Hort, V. Komárek, M. Langmeier, G. Brožek., and Obsahuje bibliografii
Threshold intensities for epileptic phenomena induced by cortical stimulation were used for comparison of the action of GABA-B and GABA-A antagonists in rats with implanted electrodes. Both CGP 35348 (200 mg/kg i.p.) and bicuculline (4 mg/kg i.p.) significantly decreased thresholds for spike-and-wave afterdischarges and their motor counterpart (clonic seizures) whilst transition into the second, limbic type of afterdischarge as well as threshold for movements directly bound to stimulation remained uninfluenced by either drug., D. Živanović, K. Bernášková, Yu. Kaminskij, P. Mareš., and Obsahuje bibliografii
In chloroplasts of Spinacea oleracea L., Hg2+ ions interact with some sites in the photosynthetic electron transport chain: (l) with the intermediates Z+/D+ situated in the D1 and D2 proteins and with the manganese cluster in the oxygen evolving complex which are located on the donor side of photosystem (PS) 2, (2) with the chlorophyll a dimer in the core of PS1 (P700). P700 is oxidized in the dark by HgCl2. The Hg2+ ions form organometallic complexes with amino acids contained in chloroplast proteins. and F. Šeršeň, K. Král'ová, A. Bumbálová.
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
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