Functional properties of photosynthetic apparatus in three <Emphasis Type="Italic">Fucus</Emphasis> species inhabiting the White Sea: Effect of dehydration

Three species of Fucus inhabiting different zones at the littoral and sublittoral of the White Sea (F. vesiculosus L., F. serratus L., and F. distichus L.) were compared with regard to performance of the photosynthetic apparatus (PSA) and PSA changes upon prolonged desiccation of algae. The content of chlorophyll a and the total content of carotenoids were significantly higher in F. serratus than in F. vesiculosus. The potential quantum yield (F _v/F _m) of photosystem II (PSII) was 0.69–0.74 in all species. The highest effective quantum yield of PSII (Y _II) was observed in F. vesiculosus plants inhabiting zones with the most intense insolation. The ratio of non-photochemical quenching to photochemical quenching (qN/qP) increased with the depth of algal habitats in the row from F. vesiculosus to F. serratus. The fluorescence parameters F. serratus deviated during desiccation from their normal values and did not recover upon the subsequent return to water. By contrast, the fluorescence parameters of F. vesiculosus and F. distichus recovered gradually after the return of algae from air to sea water. It is supposed that F. serratus plants, unlike other species, are characterized by comparatively low physiological plasticity.     

Unusual polypeptide synthesis in the kinetoplast-mitochondria from Leishmania tarentolae. Identification of individual de novo translation products.

The de novo synthesis of cytochrome c oxidase subunits I, II (COI and COII), and apocytochrome b (Cyb) was investigated in kinetoplast-mitochondria of Leishmania. The organelles were isolated after breaking whole cells with nitrogen cavitation. Individual COI, COII, and Cyb polypeptides were identified by fractionation of the kinetoplast membranes, labeled with [(35)S]methionine and cysteine, using two-dimensional (9 versus 14% and 20 versus 11%) denaturing gel electrophoresis. The reaction did not require exogenous energy sources or amino acids. On the contrary, the presence of amino acids other than methionine somewhat inhibited the labeling reaction probably by competing with the uptake of labeled amino acids. The synthesis reaction was insensitive to 100 microg/ml chloramphenicol, gentamycin, paromomycin, lincomycin, hygromycin, and tetracycline, as well as cycloheximide. The process showed a linear increase in the amount of synthesized polypeptides during the first 2 h of incubation, followed by a slower accumulation of products for up to 4 h. The de novo synthesized polypeptides were stable for several additional hours. Their assembly into respiratory complexes, investigated using two-dimensional Blue Native/N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine-SDS gels, began early during the incubation and continued throughout the course of the synthesis. This work represents the first unequivocal identification of the polypeptide synthesis in kinetoplasts.     

Simple method for fractionation of <Emphasis Type="Italic">Parmelia sulcata</Emphasis> lichen thalli

Three fractions were isolated from Parmelia sulcata lichen thalli: mycobiont-enriched fraction, highly purified preparation of Trebouxia sp. alga, and a photobiont-enriched fraction, in which the fungal component and symbiotic relations between the bionts were retained. The ratio between the fungal and algal components in all fractions was estimated from the photosynthesis/respiration and chlorophyll/dry weight ratios. Simple methods for lichen thallus fractionation are suggested to study symbiotic relationships of bionts.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 306–310.Original Russian Text Copyright © 2005 by Maslov, Pavlova.This revised version was published online in April 2005 with a corrected cover date.     

Immature stages of <Emphasis Type="Italic">Molipteryx fuliginosa</Emphasis> (Uhler) (Heteroptera,Coreidae) in the South of the Russian Far East

The morphology of the egg and the I-V-instar nymphs of Molipteryx fuliginosa (Uhler) was studied based on the observations made under near-natural conditions in Primorskii Territory since the emergence of over-wintered adults till the appearance of adults of the new generation, including egg production, maturation and molt at each nymphal instar. The egg and the nymphal instars are described and the distinguishing characters of Molipteryx fuliginosa and Coreus marginatus (Linnaeus) are given.     

Nitrate uptake by isolated bionts of the lichen <Emphasis Type="Italic">Parmelia sulcata</Emphasis>

It was found that bionts isolated from the lichen Parmelia sulcata Taylor had a marked difference with respect to nitrate assimilation. Isolated and purified photobiont, the green alga Trebouxia sp. showed no ability of nitrate absorption. Mycobiont and thallus fragments containing both bionts absorbed nitrate. Illumination had no essential influence on the rate of nitrate uptake. The respiratory inhibitor sodium azide decreased the rate of nitrate uptake by 80–100%, whereas the photosynthetic inhibitor dichlorophenyldimethylurea did not reduce it. Using mass-spectroscopic technique, it was shown that, in the intact thallus, nitrate was first absorbed by the mycobiont, and only later appeared in the photobiont. Probably such nutritional difference between bionts serves as one of the mechanisms by which the host fungi control the associated green algae and support their symbiosis.     

Significance of ATP-sensitive K(+)-channel in the mechanism of antiarrhythmic and cardioprotective effect of adaptation to intermittent hypobaric hypoxia

Adult male Wistar rats were exposed to intermittent hypobaric hypoxia (5000 m, 6 h/day, 6 weeks). It has been found that such mode of adaptation increased cardiac tolerance to arrhythmogenic action of a 45-min coronary artery occlusion but did not change an infarct size/area at risk (IS/AAR) ratio. In a separate series, rats were exposed to stronger intermittent hypobaric hypoxia (7000 m, 8 h/day, 6 weeks) and subjected to 20-min coronary artery occlusion and 3-h reperfusion on the day after the last hypoxic exposure. It has been established that in this case adaptation decreased the IS/AAR ratio, increased cardiac tolerance to arrhythmogenic action of reperfusion but had no effect on the incidence of ventricular arrhythmias occurred during ischemic period. We found that cardioprotective and antiarrhythmic effect of adaptation to the "altitudes" of 7000 m and antiarrhythmic effect of adaptation to the "altitude" of 5000 m is mediated via K(ATP)-channel activation.     

Role of delta opioid receptors and their ligands in the development of adaptive heart protection against arrhythmogenesis

It has been found that stimulation of delta-1 opioid receptors by intravenous administration of DPDPE (0.5 mg/kg) decreases the incidence of ischemic and reperfusion-induced arrhythmias and also increases myocardial tolerance to the arrhythmogenic action of epinephrine in rats. Pretreatment with a selective delta-2 agonist, DSLET, had no antiarrhythmic effect. The inhibition of the enzymatic breakdown of endogenous enkephalins by intravenous administration of acetorphan decreased the incidence of epinephrine-induced arrhythmias. Pretreatment with a selective delta opioid receptor antagonist, ICI-174.868, completely abolished this antiarrhythmic effect. Adaptation of rats to repeated immobilization stress during 12 days increased myocardial tolerance to the arrhythmogenic action of coronary artery occlusion (10 min) and reperfusion (10 min). Pretreatment with a selective delta opioid receptor antagonist, TIPP(Psy), did not abolish the antiarrhythmic effect of adaptation to immobilization stress. It seems that endogenous agonists of delta opioid receptors are not involved in the antiarrhythmic effect resulting from adaptation to stress.     

Stimulation of μ- and δ-Opiate Receptors and Tolerance of Isolated Heart to Oxidative Stress: the Role of NO-Synthase

Preliminary intravenous injection of -opiate receptor (OR) agonists DSLET (0.1 mg/kg) or DTLET (0.1 mg/kg) increased tolerance of isolated perfused myocardium to damage by oxidative stress simulated in vivo with FeSO₄ + ascorbic acid. This manifested itself by a decreased level of creatine phosphokinase (CPK) in the perfusate flowing out of the heart during the oxidative exposure. The preliminary systemic injection of -agonists DAMGO (0.1 mg/kg) or DALDA (0.1 mg/kg) failed to affect the release of CPK from the myocardium. The cardioprotective effect of the -agonist DSLET was completely abolished by preliminary intravenous injection of the -OR antagonist ICI 174,864 (2.5 mg/kg). The intravenous injection of the NO-synthase inhibitor L-NAME (50 mg/kg) also completely abolished the cardioprotective effect of -OR stimulation. The preliminary injection of DSLET but not of DAMGO prevented an increase in the level of diene conjugates and a decrease in the activity of superoxide dismutase (SOD) in the isolated myocardium tissue. Thus, the in vivo stimulation of -OR increased the tolerance of the heart to oxidative stress through activation of NO-synthase and SOD.     

Interactions of peripheral mu-opioid receptors and K(ATP)-channels in regulation of cardiac electrical stability in ischemia,reperfusion, and postinfarction cardiosclerosis

It has been shown that mu-opioid receptor stimulation by intravenous administration of the selective mu receptor agonist DALDA in a dose of 0.1 mg/kg prevented ischemic and reperfusion arrhythmias in rats subjected to coronary artery occlusion (10 min) and reperfusion (10 min), and also increased the ventricular fibrillation threshold in rats with postinfarction cardiac fibrosis. These effects were abolished by pre-treatment with the selective mu receptor antagonist CTAP in a dose of 0.5 mg/kg or by prior injection of the opioid receptor antagonist naloxone methiodide (2 mg/kg) which does not penetrate the blood-braib barrier. Both antagonists by themselves had no effect on the incidence of occlusion or reperfusion-induced arrhythmias or on the ventricular fibrillation threshold. Pre-treatment with ATP-sensitive K+ channel (KATP channel) blocker glibenclamide in a dose of 0.3 mg/kg completely abolished the antiarrhythmic effect of DALDA. We believe that DALDA prevents occurrence of electrical instability during ischemia and reperfusion and increases the ventricular fibrillation threshold in rats with postinfarction cardiac fibrosis via stimulation of peripheral mu-opioid receptor which appear to be coupled to the KATP channel.