Analytical determination of orthophosphate in water

Methods for orthophosphate determination and the problems of interferences are reviewed.An important group of methods utilizes the phosphomolybdate complex. The complexation step, the reduction step and the extraction step are treated separately and alternative procedures compared.Another group of methods uses ion association complexes; they are primarily used in physiology and not commonly used in water analyses today.Enzymatic methods for orthophosphate analysis in natural waters have been developed lately and are ready for application in selected waterbodies.Flame spectroscopic, fluorometric, gas chromatographic, ion exclusion chromatographic, inductively coupled plasma and other methods are also shortly presented.Radiobiological bioassays for orthophosphate are also available.In conclusion it was emphasized that the most common and reliable technique still is the molybdenum blue method as modified by Murphy & Riley (1962).The need for more specific and sensitive methods is particularly strong in investigations of phosphorus turnover and phosphorus limitation in natural waters. For these purposes the enzymatic phosphatase methods has advantages due to their specificity for orthophosphate and they might offer an alternative to the molybdenum blue method.     

Acute volume expansion as a physiological stimulus for the release of atrial natriuretic peptides in the rat

The concentration of immunoreactive atrial natriuretic peptide(s) (ANP) was measured in normovolemic conscious rats and 15 min after 10% and 20% blood volume expansion. A 20% blood volume expansion caused a 2-fold increase in plasma ANP. While plasma ANP increased linearly, atrial levels of ANP remained unaltered. The increase in plasma ANP parallelled increases of central blood volume and central venous pressure. It is concluded that acute blood volume expansion is a major physiological stimulus for the release of atrial natriuretic peptides into the circulation.     

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.     

Studies of the cellulolytic system of Trichoderma reesei QM 9414. Reaction specificity and thermodynamics of interactions of small substrates and ligands with the 1,4-beta-glucan cellobiohydrolase II

The 1,4-beta-glucan cellobiohydrolase II (CBH II) from Trichoderma reesei QM 9414 catalyses the hydrolysis of the 4-methylumbelliferyl beta-D-glycosides derived from cellotriose, cellotetraose and cellopentaose [MeUmb(Glc)n; n = 3 - 5]. The reaction has been followed by quantitative high-performance liquid chromatography. Specific activity for cellobiose removal at apparent substrate saturation were determined as (0.8 +/- 0.2) min-1 for MeUmb(Glc)3 and (9 +/- 2) min-1 for MeUmb(Glc)4. The enzyme showed a deviant specificity with MeUmb(Glc)5 as substrate. Two chromophoric products were formed simultaneously [MeUmb(Glc)3 and MeUmb(Glc)2] with turn-over numbers (17 +/- 4) min-1 and (21 +/- 6) min-1, respectively. Methylumbelliferyl beta-glucoside (MeUmbGlc) and the corresponding cellobioside [MeUmb(Glc)2] were used in equilibrium binding experiments. Both ligands yielded one binding site per molecule of Mr = 54000 upon forced flow dialysis (diafiltration). The association constants found were in fair agreement with those determined from MeUmb fluorescence quenching titrations. Quenching was total at all temperatures investigated for MeUmb(Glc)2, whereas for MeUmbGlc it increased from 80% to 100% between 2 degrees C and 20 degrees C. The association constants fitted linear van't Hoff plots in both cases. MeUmb(Glc)2 and MeUmbGlc were also used as indicator ligands to determine the association constants and thermodynamic parameters of several non-chromophoric ligands of CBH II. The binding of glucose increased the affinity for MeUmb(Glc)2 whereas it displaced MeUmbGlc from its complex. A putative binding site of the CBH II containing four subsites can be proposed. The thermodynamic data for methyl beta-D-glucopyranoside and cellobiose as ligands also point at an extended binding site.     

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.

     

Pitfalls in the Dextran-coated charcoal assay of estrogen receptors in breast cancer tissue

This study investigated the influence of the degree of concentration of breast tumor cytosols on the apparent estrogen receptor content as measured by the Dextran-charcoal assay. It was found that the dilution of cytosols to 1-2 mg protein/ml frequently but not always causes highly underestimated receptor concentrations. This could not be explained by the protein loss through adsorption to the charcoal. The effect was also studied in the presence of gelatin, sodium molybdate or with limited trypsinization of the incubation mixture. Addition of 1 mg/ml gelatin in the Dextran-charcoal suspension was very useful in most cases in preventing dilution induced losses in receptor sites. Both trypsinization and addition of sodium molybdate produced increases in receptor concentrations that were not as susceptible to inactivation through dilution of the cytosol. These data suggest that the observed high variability in the dilution induced receptor losses can be explained by receptor heterogeneity: some receptor form(s) are either readily absorbed to or "stripped" by the charcoal particles. As a conclusion we recommend that in order to optimize the estrogen receptor assay as regards both binding sites and affinities the cytosol concentrations should be maintained as high as possible and a protein expander be included in the Dextran-charcoal suspension. Though sodium molybdate frequently gives considerable increases in estrogen binding sites it occasionally has an opposite effect. For this reason we hesitate to recommend its use in routine assays of estrogen receptors.     

Organization of early region 1B of human adenovirus type 2: identification of four differentially spliced mRNAs.

The mRNAs from early region 1B of adenovirus type 2 have been studied by Northern blot, S1 nuclease, and cDNA analysis. Two novel mRNAs, designated 14S and 14.5S, have been observed in addition to the previously identified 9S, 13S, and 22S mRNAs. They are 1.26 and 1.31 kilobases long and differ from the 13S and 22S mRNAs in being composed of three exons instead of two. Their two terminal exons are the same as those present in the 13S mRNA, whereas the middle exon is unique to each of the two novel mRNA species. The structures of the 14S and 14.5S mRNAs allow the prediction of their coding capacities: both mRNA species, like the 22S and 13S mRNAs, contain an uninterrupted translational reading frame encoding a 21,000-molecular-weight (21K) polypeptide. The 14S mRNA can, in addition, encode a 16.5K polypeptide which shares N-terminal and C-terminal sequences with the 55K polypeptide, known to be encoded by the 22S mRNA. The 14.5S mRNA species encodes a hypothetical 9.2K polypeptide which has the same N terminus as the 55K polypeptide but a unique C terminus. The two mRNAs differ in their kinetics of appearance; the 14.5S mRNA is preferentially expressed late after infection in contrast to the 14S mRNA, which is present in approximately equal amounts early and late after infection. Taken together with previously published information the results suggest that early region 1B of adenovirus type 2 encodes five proteins in addition to virion polypeptide IX. These have predicted molecular weights of 55,000, 21,000, 16,500, 9,200, and 8,100.     

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.     

Nuclease S1-sensitive sites in multigene families: human U2 small nuclear RNA genes.

We show here that human U2 small nuclear RNA genes contain a 'strong nuclease S1 cleavage site' (SNS1 site), a sequence that is very sensitive to digestion by nuclease S1. This site is located 0.50-0.65 kb downstream of the U2 RNA coding region. It comprises a 0.15-kb region in which (dC-dT)n:(dA-dG)n co-polymeric stretches represent greater than 90% of the sequence. Nuclease S1 is able to excise unit length repeats of the human U2 RNA genes both from cloned fragments and total human genomic DNA. The precise locations of the cleavage sites are dependent on the superhelicity of the substrate DNA. In negatively supercoiled substrates, cleavages are distributed over the entire 0.15-kb region, but in linearized substrates, they occur within a more limited region, mainly at the boundary of the SNS1 site closest to the human U2 RNA coding region. Nuclease S1 cleavage of negatively supercoiled substrates occurs at pHs as high as 7.0; in contrast, cleavage of linearized substrates requires a pH less than 5.0, indicating that supercoiling contributes to the sensitivity of this site. Mung bean nuclease gives results similar to that observed with nuclease S1.