Follicle development, blood feeding, digestion and egg maturation in diapausing mosquitoes, Culiseta inornata

Female Culiseta inornata (Williston) caught at Edmonton, Canada, in September and October were nulliparous, had small ovarian follicles and did not take blood meals in nature. Most newly collected females did feed on the author in the laboratory, but the blood meals were small and ejected prematurely, there was no trypsin activity and no egg maturation. In some females that were kept for 7 days at 16 hr daylength and 20°, follicle growth and yolk deposition occurred, and in such females, blood feeding was followed by egg maturation. Follicle development also occurred in females that had been kept for 2–3 months at 12 hr daylength and 5°, and although blood feeding rates were low, trypsin activity and egg maturation were observed in all blood-fed females. Ovarian diapause in C. inornata may be considered terminated when the ratio of the length of a typical follicle to the length of its germarium has reached 2.0.

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Zusammenfassung In Zentral-Alberta (Kanada) erscheinen die diapausierenden Weibchen von Culiseta inornata (Williston), die Überwinterungsform, im August. Weibchen, die im September gesammelt wurden, legten keine Eier, hatten kleine Eifollikel und nahmen im Freien keine Blutnahrung auf. Die meisten frisch gesammelten Weibchen saugten im Laboratorium Blut am Autor, doch war die Blutmenge gering und wurde bald wieder ausgestossen. Es wurde keine Trypsinaktivität und keine Eireifung festgestellt. Bei einigen Weibchen, die während 7 Tagen bei einer Photoperiode von 16 Stunden und 20° gehalten wurden, kam es zu Follikelwachstum und Dotterablagerung. Bei diesen Weibchen folgte Eireifung auf die Blutaufnahme. Follikelentwicklung setzte auch ein bei Weibchen, die für 2–3 Monate bei 12 Stunden-Tag und 5° gehalten worden waren. Obwohl die Blutaufnahme gering war, wurde Trypsinaktivität und Eireifung bei allen blutgefütterten Weibchen beobachtet. Die Ovarialdiapause bei C. inornata kann als beendet betracht werden, wenn das Verhältnis der Länge eines typischen Follikels zur Länge seines Germarium 2.0 erreicht hat.

     

Modeling and dynamic simulation of a two-stage pre-denitrification MBBR system under increasing organic loading rates

Bioprocess and Biosystems Engineering - Biofilm-based wastewater treatment systems have become attractive due to their numerous advantages when compared to other suspended growth processes....     

The emergence of rabbit haemorrhagic disease virus: will a non-pathogenic strain protect the UK?

Rabbit haemorrhagic disease virus emerged in China in 1984, and has killed hundreds of millions of wild rabbits in Australia and Europe. In the UK there appears to be an endemic non-pathogenic strain, with high levels of seroprevalence being recorded, in the absence of associated mortality. Using a seasonal, age-structured model we examine the hypothesis that differences in rabbit population demography differentially affect the basic reproductive rates (R(0)) of the pathogenic and non-pathogenic strains, leading to each dominating in some populations and not others. The strain with the higher R(0) excluded the other, with the dynamics depending upon the ratio of the two R(0) values. When the non-pathogenic strain dominated, the pathogenic strain caused only transient mortality, although this could be significant when the two R(0) values were similar. When the pathogenic strain dominated, repeated epidemics led to host eradication. Seroprevalence data suggest that the non-pathogenic strain may be protecting some, but not all UK populations, with half being 'at risk' from invasion by the pathogenic strain and a fifth prone to significant transient mortality. We identify key questions for empirical research to test this prediction.     

Pyridoxamine protects intestinal epithelium from ionizing radiation-induced apoptosis

Reactive oxygen species (ROS) and reactive carbonyl species (RCS) are the major causes of biological tissue damage during exposure to ionizing radiation (IR). The existing strategies to protect normal tissues from the detrimental effects of IR suffer from several shortcomings including highly toxic side effects, unfavorable administration routes, and low efficacy. These shortcomings emphasize a need for radioprotective treatments that combine effectiveness with safety and ease of use. In this paper, we demonstrate that pyridoxamine, a ROS and RCS scavenger with a very favorable safety profile, can inhibit IR-induced gastrointestinal epithelial apoptosis in cell culture and in an animal model. Pyridoxamine was more effective at protecting from radiation-induced apoptosis than amifostine, a synthetic thiol compound and the only FDA-approved radioprotector. We suggest that pyridoxamine has potential as an effective and safe radioprotective agent.     

Affinities of the nucleocapsid protein for variants of SL3 RNA in HIV-1

Efficient packaging of genomic RNA into new HIV-1 virus particles requires that nucleocapsid domains of precursor proteins bind the SL3 tetraloop (G317-G-A-G320) from the 5'-untranslated region. This paper presents the affinities of 35 RNA variants of SL3 for the mature 55mer NC protein, as measured by fluorescence quenching of tryptophan-37 in the protein by nucleobases. The 1:1 complexes that form in 0.2 M NaCl have dissociation constants ranging from 8 nM (GGUG) to 20 microM (GAUA). The highly conserved (GGAG) sequence for the wild type is not the most stable (K(d) = 28 nM), suggesting that other selective pressures beyond the stability of the complex must be satisfied. The leading requirement for strong interaction is for G320, followed closely by G318. Replacing either with U, A, or C reduces affinity by a factor of 15-120. NC-domains from multiple proteins combine to recognize unpaired G(2)-loci, where two guanines are in close proximity. We have previously measured affinities of the NC protein for the important stem-loops of the major packaging domain [Shubsda, M. F., Paoletti, A. C., Hudson, B. S., and Borer, P. N. (2002) Biochemistry 41, 5276-82]. Comparison with the present work shows that the nature of the stem also modulates NC-RNA interactions. Placing the G(2)-loci from the apical SL2 or SL1 loops on the SL3 stem increases affinity by a factor of 2-3, while placing the SL4 loop on the SL3 stem reduces affinity 50-fold. These results are interesting in the context of RNA-protein interaction, as well as for the discovery of antiNC agents for AIDS therapy.     

Disease invasion: impacts on biodiversity and human health

An introduction to the theme issue that includes papers that identify how, where and why infectious diseases in wildlife emerge, while also addressing their possible conservation impacts.