Kurze Mitteilungen

Ohne Zusammenfassung     

Erhoehter Virusbefall in den Randreihen von Kartoffelbestaenden als Folge des Flugverhaltens der Vektoren

Zusammenfassung Versuchsparzellen von Ackersegen-Kartoffeln in Nord- und Mitteldeutschland wurden durch wöchentliche Insektizidbehandlungen während der gesamten Vegetationsperiode 1956 frei von Blattlauskolonien gehalten. Prüfung des Nachbaus auf Virusverseuchung 1957 ergab, daß die Bestände 1956 dennoch Virusinfektionen erhalten hatten, daß der Grad der Verseuchung mit der örtlichen Flugintensität der Vektoren (Myzus persicae Sulz.) in enger Beziehung stand und daß dabei die Randreihen bedeutend mehr Infektionen aufwiesen als die Mitte der Bestände. Diese Befunde werden mit dem Flug- und Wirtswahlverhalten der geflügelten Vektoren interpretiert.

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Summary In the course of comparative investigations of the significance of the infestation flight of Aphis fabae Scop. on the distribution of virus diseases, the virus infection which is frequently different on the edges and in the centre of virus diseased potato fields, has been analysed in the potato degeneration area (i.e. where seed potatoes cannot be grown year after year due to the high incidence of virus) of Middle Germany (Quedlinburg) and in the seed growing area of Northern Germany (Groß-Lüsewitz, Mecklenburg). In 1956 a nearly square plot of 500 healthy Ackersegen plants was kept free from apterae (aphids) by a weekly treatment with insecticides (Wofatox spray) and in 1957 the following generation (from 5 by 5 tubers taken separatedly from each bush) was tested for virus infection. The infection was found to be by 12 times more frequent in the degeneration area than in the seed production district. This can only have been due to the visits of alate vectors, especially Myzus persicae Sulz., the infestation flight of which was 29 times greater in Middle than in Northern Germany. In both places the virus infestation in the test plots was observed to decrease quickly from edge to centre. At Quedlinburg the third row showed barely one half of the infestation of the edge and the 5th row only one third of the infestation of the outer rows. At Groß-Lüsewitz it dropped to a tenth in the second row. This phenomenon is due to the nature of the infestation flight of the vectors, which glide extremely near to the ground. The flight is stopped at the bordering rows because of the density of the crop, effecting a far higher infestation rate here than in the centre, where it penetrates only very sparsely. This was evident from an experiment on planting times, described by v. Bernuth 1948: The later the potatoes grow up, the smaller is the virus infestation quotient edge to centre, for when the plants are all small the whole crop is equally exposed to the infestation flight of the vectors, which begins by the end of June.From this experience the demand of agricultural practice for the earliest possible planting and quickest possible covering of the ground by crop is be easily unterstood.

     

Spirulina raphidioides n. sp. und Bemerkungen über ähnliche Planktonalgen

Zusammenfassung Spirulina raphidioides n. sp. ist trotz ihrer geringen Dimensionen sicher als mehrzellig erkennbar. Es besteht die Möglichkeit der Verwechslung mit der einzelligenDactylococcopsis, doch sind die ähnlichenDactylococcopsis-Arten offenbar verkannteAnkistrodesmus-Arten.-Die Trichome erfahren nach Erreichen einer gewissen, geringen Länge eine Querteilung.-Durch starken mechanischen Druck läßt sich das Trichom in seine Einzelzellen zerlegen, wobei das Centroplasma an den zerrissenen Querwänden austritt.     

Resistenzuntersuchungen vor allem über Kienzopf und Schütte an der Kiefer

Ohne ZusammenfassungMit 5 TextabbildungenNach einem Vortrag, gehalten auf der Arbeitstagung für forstliche Samen-Plantagen vom 24.–26. Okt. 1955 in Waldsieversdorf.     

Sucrose to starch: a transition in molecular plant physiology.

The major flux in potato tuber carbon metabolism is the conversion of sucrose through hexose phosphates to starch. The enzymes that mediate this pathway are well characterized, the genes that encode them have been cloned and transgenic plants have been generated. These transgenic studies have confirmed hypotheses based on more indirect methods, but they have also generated new challenges by highlighting the enormous flexibility and complexity inherent in plant metabolism. The investigation of the sucrose-to-starch transition in potato tubers is an excellent example of how the discipline of molecular plant physiology is evolving at both the scientific and technical levels.     

Estimating Trends in the Proportion of Transmitted and Acquired HIV Drug Resistance in a Long Term Observational Cohort in Germany

Objective

We assessed trends in the proportion of transmitted (TDR) and acquired (ADR) HIV drug resistance and associated mutations between 2001 and 2011 in the German ClinSurv-HIV Drug Resistance Study.

Method

The German ClinSurv-HIV Drug Resistance Study is a subset of the German ClinSurv-HIV Cohort. For the ClinSurv-HIV Drug Resistance Study all available sequences isolated from patients in five study centres of the long term observational ClinSurv-HIV Cohort were included. TDR was estimated using the first viral sequence of antiretroviral treatment (ART) naïve patients. One HIV sequence/patient/year of ART experienced patients was considered to estimate the proportion of ADR. Trends in the proportion of HIV drug resistance were calculated by logistic regression.

Results

9,528 patients were included into the analysis. HIV-sequences of antiretroviral naïve and treatment experienced patients were available from 34% (3,267/9,528) of patients. The proportion of TDR over time was stable at 10.4% (95% CI 9.1–11.8; p _{for trend} = 0.6; 2001–2011). The proportion of ADR among all treated patients was 16%, whereas it was high among those with available HIV genotypic resistance test (64%; 1,310/2,049 sequences; 95% CI 62–66) but declined significantly over time (OR 0.8; 95% CI 0.77–0.83; p _{for trend}<0.001; 2001–2011). Viral load monitoring subsequent to resistance testing was performed in the majority of treated patients (96%) and most of them (67%) were treated successfully.

Conclusions

The proportion of TDR was stable in this study population. ADR declined significantly over time. This decline might have been influenced by broader resistance testing, resistance test guided therapy and the availability of more therapeutic options and not by a decline in the proportion of TDR within the study population.     

Effect of poly(ethylene glycol) on phospholipid hydration and polarity of the external phase

The hydration properties of phosphatidylcholine (PC)/water dispersions on the addition of poly(ethylene glycol) were studied by means of ²H-NMR. The quadrupole splittings and their temperature dependences correspond to measurements of PC/water dispersions at low water content. It is concluded that the bound water is partly extracted by poly(ethylene glycol) but the binding properties of the water in the inner hydration shell of about five water molecules are not changed. The ability of some phospholipid/water dispersions to undergo phase transitions to nonlamellar structures upon dehydration is discussed. Dipalmitoylphosphatidylcholine (DPPC) and egg phosphatidylcholine do not form nonlamellar structures on addition of purified poly(ethylene glycol), as was demonstrated by means of ³¹P-NMR. Poly(ethylene glycol) decreases the polarity of the aqueous phase and the partition of hydrophobic molecules between the membrane and the external phase is changed. This was demonstrated using the excimer fluorescence of pyrene in a ghost suspension. It is suggested that the changes in polarity and hydration on the addition of poly(ethylene glycol) can contribute to the alterations in the membrane surface observed under conditions of membrane contact and fusion.     

Mutual predation between and cannibalism within several freshwater gammarids: Dikerogammarus villosus versus one native and three invasives

Dikerogammarus villosus, a Ponto-Caspian species, is known to be a particularly successful invader, and is currently the prevailing invasive gammarid in Southern German large waters. Field observations suggest that D. villosus has replaced the native G. pulex and the invasive D. haemobaphes, also a Ponto-Caspian species, in some reaches of the German Danube. Dikerogammarus villosus is also believed to be the reason why Echinogammarus berilloni, a Mediterranean species, and Dikerogammarus bispinosus, a further Ponto-Caspian gammaridean species, could not build significant populations in Southern German rivers. Because intraguild predation (IGP) is regarded as a major force leading to species displacements, we hypothesized that superiority in predation by D. villosus is responsible for the disappearance or limited occurrence of several native and invasive gammarideans in many reaches of Southern German waters. To test this hypothesis, we conducted a series of laboratory IGP experiments with 1:1 combinations in which D. villosus was allowed to prey on other gammarids and vice versa. We also studied the extent of cannibalism within species. Dikerogammarus villosus was a stronger predator than G. pulex and E. berilloni. However, D. villosus was not stronger in predation than its relatives D. haemobaphes and D. bispinosus, although results with the combinations of D. villosus and D. bispinosus were less conclusive, especially in the female–female combination. Cannibalism rate was high in D. haemobaphes compared with other species. We conclude that superiority in IGP experiments could explain the disappearance of G. pulex and the missing or limited occurrence of E. berilloni since the arrival of D. villosus in Southern German rivers. However, the results of IGP experiments do not explain why D. haemobaphes was displaced by D. villosus in many places and why D. bispinosus could not build significant populations in Southern German waters. Possibly specific combinations between mutual predation and cannibalism or factors other than predation could have affected displacement and occurrence patterns of Dikerogammarus species in Southern German waters.