A selenium-induced peroxidation of glutathione in algae

Two unicellular marine algae cultured in media containing sodium selenite were examined for glutathione peroxidase activity. The 400 g supernatant from disrupted cells of both the green alga Dunaliella primolecta and the red alga Porphyridium cruentum were able to enhance both the H₂O₂ and the tert-butyl hydroperoxide dependent oxidation of glutathione. The glutathione peroxidation activity of D. primolecta was reduced only slightly by heating the 400 g supernatant, a 30% decrease in the rate with H₂O₂ and 10% decrease in the rate with t-BuOOH being observed. Heating caused the H₂O₂ dependent activity in P. cruentum to be reduced by only 30%, but the activity with t-BuOOH was reduced by 90%. Freezing decreased the t-BuOOH dependent activity of P. cruentum by 90%, but did not lower the t-BuOOH dependent activity of D. primolecta or the H₂O₂ dependent activity of either alga. It was concluded that the heat and cold stable, glutathione peroxidation was non-enzymatic in nature. A variety of small molecules (ascorbate, Cu(NO₃)₂, selenocystine, dimethyldiselenide and selenomethionine) were shown to be able to enhance the hydroperoxide dependent oxidation of glutathione in the assay system employed in this study. Such compounds could be responsible for the activity observed in algae. The heat and cold labile t-BuOOH reductase activity of P. cruentumwas possibly enzymatic, but was not attributable to the presence of glutathione-S-transferase. Both algae, when cultured in the presence of added selenite, displayed an approximate doubling of the non-enzymatic H₂O₂ and t-BuOOH dependent glutathione oxidase activities. The heat and cold labile t-BuOOH reductase activity of P. cruentum was unaltered when the alga was grown in the presence of added selenite. These observations are consistent with the hypothesis that selenium compounds present in the algae are responsible for the selenium induced glutathione peroxidation.     

Review article number 6 : Plant molluscicides

A review on the application of plant molluscicides in the control of schistosomiasis is presented. Laboratory bioassays are discussed, together with criteria for activity. An attempt has been made to provide a comprehensive list of known molluscicidal natural products.     

Zur Paarbildung der Uferschwalbe (Riparia riparia)

Zusammenfassung Uferschwalben kehren aus den afrikanischen Winterquartieren in Trupps beiderlei Geschlechts zurück. Erste Beringungsergebnisse belegen, daß zunächst mehrjährige, vermutlich untereinander bekannte Vögel eintreffen, die den Brutplatz aus vergangenen Brutperioden her kennen. Die Masse der später ankommenden Vögel dürfte weitgehend aus einjährigen oder ortsfremden Uferschwalben bestehen, die sich größtenteils erst während der Paarbildung persönlich kennenlernen. Der anfängliche Schwarmzusammenhalt der nacheinander eintreffenden Trupps führt zur Bildung von Subkolonien, die für Brutplätze ab einer bestimmten Größenordnung typisch sind. Uferschwalben- gründen nacheinander mehrere Reviere, d. h. sie besetzen Steilwandbereiche, in denen sie ausschließlich mit den Füßen eine Röhre oder Mulde graben, singen und Bogenflüge starten. Bis auf singende oder bekannte werden Artgenossen im Revier geduldet. Uferschwalben- suchen besetzte Reviere auf. Ohne Röhrenbindung verhalten sie sich still und unauffällig, ihre Grabungsaktivitäten sind von untergeordneter Bedeutung. Die Bindung an ein bestimmtes Revier entwickelt sich individuell verschieden und entscheidet über den Abschluß des Röhrenbaues (Herstellung der Nistkammer). Reviere ohne dauerhafte -Bindung werden von den aufgegeben. Aktivitäten, die auf wachsende Revierbindung eines hindeuten, sind: häufige oder/und länger dauernde Aufenthalte des in einem besetzten Revier und sporadisches Mitgraben; aggressives Verhalten gegenüber Artgenossen (i. d. R. fremde ), die im Revier landen wollen; gemeinschaftlicher, leiser Gesang von und im Röhrenbereich. Aktivitäten, die für eine vollzogene Paarbildung sprechen, sind: Fertigstellen der Röhre durch Grabung der Nestkammer; längere gemeinsame Aufenthalte innerhalb und außerhalb der Röhre; Voranfliegen des beim Röhrenanflug; Übernachten von und in der Röhre; Nestbau; ausdauernde Verfolgungsflüge während der Kopulationsphase. Die Paarbildung ist demnach ein individueller Prozeß, bei dem die Aktivitäten der im Revier als Werbung, die der als Revierwahl interpretiert werden.

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On pair-formation in the Sand Martin,Riparia riparia

Summary European Sand Martins arrive at their breeding sites in flocks of usually unmated and . Ringing results of a large population in NW-Germany and own observations indicate that the first flocks about a dozen individuals with an approximately balanced sex ratio appear at traditional breeding places and consist of older, experienced resident birds (presumably acquainted with one another). The birds arriving over the next several weeks are mainly first-year or non-resident individuals. The flocks arrive separately in areas with suitable sandcliffs, synchronize the pair-formation activities and avoid disturbances among paired and unpaired birds. This behaviour causes the formation of subcolonies, which are typical for all densely occupied breeding places. Each settles on a fixed area on the sandcliff (territory) in order to excavate a burrow, to sing the territory-song (fig. 2 b) and to perfor the territory-circle-flight (fig. 2 c, 4 a). Silent birds (normally ) are welcomed or tolerated by the resident . The sexes are monomorphic and therefore courtship displays of the are non-aggressive until establishment of pair-bonds. Only intruding singing or individually known neighbouring are driven away, usually at early stages of territory occupation. Unmated are normally shy and very sensitive to protracted disturbances. visit several occupied territories of the colony (fig. 1–3) in order to choose a burrow. leave territories which do not attract a . They settle new territories on the sandcliff, causing a surplus of burrows compared to breeding pairs in the colony. Activities which indicate the development of pair-bonds are: regular visits of a to a particular occupied territory with sporadic excavations by the ; aggressive activities of the towards other visitors usually , but sometimes at first even against the resident (i. e.: vocal threats, bill-gaping, pecking or pushing with the bill or vigorous face-to-face fights, fig. 3 b, 3 c). and sing the soft mating song at or in the burrow (fig. 1 c). Activities which indicate completed pair-bonds are: completion of the burrow by digging the nestchamber, predominantly done by the ; both birds staying together over long periods, both inside and outside the burrow; invitation-flight by the (fig. 4 b); and spending the night together in the burrow; beginning of nest-building, first only by the , then by both birds and finally only by the , accompanied by the (guarding-flight;, fig. 4c); mate-pursuit flights (sexual chases) during copulation phase, in which the singing pursues the silent , often accompanied by other (cp. fig. 4 d). Pair-formation in the Sand Martin occurs on individual territories and not, according toHickling (1959), within the flock.

     

Control of replication of FII plasmids: comparison of the basic replicons and of the copB systems of plasmids R100 and R1

The copy numbers of the FII plasmids R1 and R100 were determined in four different ways and found to be identical. Deletion of one of the copy number control genes, copB, together with its promoter gives rise to plasmid copy mutants with an increased copy number. The increase was found to be 8- and 3.5-fold for plasmids R1 and R100, respectively. These deletion derivatives were found to be extremely sensitive to the presence of CopB activity from their own parent plasmid but not to that of the other plasmid. Hence, the CopB protein and its target are plasmid-specific and not FII-group-specific. These results are consistent with the high degree of nonhomology between plasmids R1 and R100 in a 250-bp region covering the distal part of the copB gene and the repA promoter region, which contains the target for the CopB protein.     

Immunofluorescence staining of thin-filament sections not participating in actomyosin crossbridges: Studies by use of a monoclonal antibody specific to actin

Summary Monoclonal antibodies (mcab) were produced in vitro by fusing mouse X63-Ag8.653 plasmacytoma cells with spleen cells from a Balb/c mouse immunized with primary cultures of chick skeletal muscle (pmcc). After cloning on agar, stable clones were obtained, the antibodies of which stain specifically the I-band of myofibrils in the immunofluorescence (IF) procedure. For further characterization of these mcab their affinities to muscle proteins were tested by immunoblotting and by enzyme-linked immunosorbent assay (ELISA). Mcab specific for actin were revealed by these criteria. One of the anti-actin antibodies, mcab 647, reveals a variety of IF-staining patterns on myofibrils. On rest-length myofibrils the I-band is labeled only. However, at sarcomere lengths below 2 m, where the thin filaments meet in the middle of the A-band and form a region of double overlap, an additional fluorescent band appears in this position. The fluorescence intensity of this band is increased significantly in shorter sarcomeres. Finally, when the I-band has disappeared at a sarcomere length of 1.5 m, fluorescence is located exclusively in the middle of the A-band. These IF-staining patterns suggest that only those sections of the thin filament are stained that do not participate in actomyosin crossbridges.     

Chronic administration of an organophosphorus insecticide to rats alters cholinergic muscarinic receptors in the pancreas

Male rats were treated for 10 days with the organophosphorus insecticide, acetylcholinesterase inhibitor, O,O-diethyl S-[2-(ethylthio)ethyl]phosphorodithioate (disulfoton, 2 mg/kg/day by gavage). At the end of the treatment, binding of [³H]quinuclidinyl benzilate ([³H]QNB) to cholinergic muscarinic receptors and cholinesterase (ChE) activity were assayed in the pancreas. Functional activity of pancreatic muscarinic receptor was investigated by determining carbachol-stimulated secretion of α-amylase in vitro. ChE activity and [³H]QNB binding were significantly decreased in the pancreas from disulfoton-treated rats. The alteration of [³H]QNB binding was due to a decrease in muscarinic receptor density with no change in the affinity. Basal secretion of amylase from pancreas in vitro was not altered, but carbachol-stimulated secretion was decreased. The effect appeared to be specific since pancreozymin was able to induce the same amylase release from pancreases of control and treated rats. The results suggest that repeated exposures to sublethal doses of an organophosphorus insecticide lead to a biochemical and functional alteration of cholinergic muscarinic receptors in the pancreas.     

Temporal Distribution of [3H]-Imipramine Binding in Rat Brain Regions is Not Changed by Chronic Methamphetamine

Specific binding of [³H]-imipramine in the rat suprachiasmatic nuclei, occipital cortex and caudate putamen underwent significant and replicable changes throughout 24 hr under a light-dark cycle or under constant conditions. Daily variations were also found in the medial and dorsal raphe nuclei and the lateral hypothalamus. Methamphetamine, a psychoactive drug with marked effect on circadian rhythms in physiological and hormonal parameters and adrenergic receptors, did not have any significant effect on imipramine binding rhythms in eight discrete brain regions. Thus a drug known to reduce serotoninergic neurotransmission did not change characteristics of the modulatory binding site related to serotonin uptake.     

Preparative Electrophoresis of Isotopically Labeled L-Cell Interferons

The preparative method of polyacrylamide gel electrophoresis was adapted for purification and characterization of isotopically labeled L-cell interferons. Re-covery of interferon activity was quantitative, and purification and resolution were comparable to those obtained by analytical polyacrylamide gel electrophoresis. Ultimate specific activities attainable ranged from 2 x 10(6) to 3 x 10(6) international units per mg of protein.     

Der Einfluß von Elektrolyten auf Chloroplasten beim Gefrieren und Trocknen

Summary The effect of freezing, desiccation and various electrolytes on photophosphorylation, electron transport and some enzyme reactions of isolated spinach chloroplasts has been investigated. Freezing of broken chloroplasts took place at-25°C for 3 hrs; desiccation was performed at +2°C in vacuo over CaCl₂ for 3 hrs. The influence of various electrolytes during freezing or drying or during incubation of thylakoids or stroma enzymes for 3 hrs at +2°C in electrolyte solutions was determined. After treatment, the activities of a number of enzymes and enzyme systems were measured under normal conditions, e. g. in the absence of elevated electrolyte levels in a reaction medium which contained only the substrates and cofactors which are necessary for the respective enzyme reactions.Only photophosphorylation and electron transport were affected by freezing, desiccation and high concentrations of electrolytes; various soluble enzymes investigated here were not inactivated under the same conditions. In general, mild dehydration and lower concentrations of electrolytes resulted in an irreversible inactivation of ATP synthesis but did not impair ferricyanide reduction. With increasing dehydration or at higher concentrations of electrolytes the Hill reaction was also inhibited. In a certain range of dehydration and electrolyte concentration uncoupling of photophosphorylation from electron transport took place. Sugar protects the sensitive structures against the deleterious effect of both dehydration and high concentration of electrolytes.Various electrolytes affected thylakoid membranes differently. Inactivation of the membranes increased with increasing ion radius and decreasing hydration envelope of univalent or divalent cations. Divalent cations were more destructive than univalent cations. Anions did not follow these rules. Within a group of similar anions (halides or organic anions) effectivity decreased with increasing hydration envelope. On a molar basis, polyvalent anions were less effective than univalent anions. Inactivation by anions followed Hofmeister's series in seversed order. However, exceptions were observed and it appears that various ions affect the membrane in a specific manner.Inactivation of photophosphorylation and electron transport due to freezing or desiccation is identical to that due to high concentrations of electrolytes. This suggests that during dehydration due to freezing or drying the concentration of electrolytes in the remaining solution is responsible for the inactivation of the sensitive membranes.     

Flavonglykoside in Blüten vonPaeonia arborea undPaeonia suffruticosa

Summary Three glycosides have been isolated fromPaeonia arborea: kaempferol-3--glucoside-7--glucoside (Paeonoside), apigenin-7--glucoside, and apigenin-7-rhamnoglucoside (Rhoifolin).Paeonia suffruticosa also contains these three compounds but its main glycoside is kaempferol-3--glucoside (astragalin), which is present inPaeonia arborea only in traces.