The four serotypes of dengue recognize the same putative receptors in Aedes aegypti midgut and Ae. albopictus cells

Background  

Dengue viruses (DENV) attach to the host cell surface and subsequently enter the cell by receptor-mediated endocytosis. Several primary and low affinity co-receptors for this flavivirus have been identified. However, the presence of these binding molecules on the cell surface does not necessarily render the cell susceptible to infection. Determination of which of them serve as bona fide receptors for this virus in the vector may be relevant to treating DENV infection and in designing control strategies.     

Flight behavior and phase polymorphism in the mosquito Aedes taeniorhynchus

Adults of Aedes taeniorhynchus, reared under two different population densities at 27° under LD 12:12, exhibit differences in their flight behavior. Adults reared under crowded conditions show a main flight peak on the day of emergence as compared to adults reared under non-crowded conditions, which do not. On the basis of their flight activity, these adults are designated as belonging to migrant and non-migrant phases. Adults from both these conditions did not show statistically significant differences in their morphological characteristics, percent glycogen and state of autogeny, but those belonging to migrant phase are much lighter in dry body weight and have lower percentages of lipid than those belonging to non-migrant phase. Analysis of these results and earlier work on this insect suggests that phase polymorphism in this insect is due to the plasticity in its ontogenetic potential.

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Fluggewohnheiten und phasenpolymorphismus bei der mücke Aedes taeniorhynchus

Zusammenfassung Erwachsene Aedes taeniorhynchus, die unter 27° und LD 12:12 bei zwei unterschiedlichen Populationsdichten aufgezogen wurden, weisen Unterschiede in ihrem Flugverhalten auf. Unter Gedrängebedingungen aufgewachsene Imagines zeigen am Schlupftage einen Hauptfluggipfel, nicht gedrängt aufgezogene dagegen nicht. Auf Grund ihrer Flugaktivität werden diese Adulten als Angehörige der migranten und der non-migranten Phase bezeichnet. Die unter diesen verschiedenen Bedingungen aufgezogenen Imagines weisen in ihren morphologischen Eigenschaften, dem prozentualen Glykogengehalt und im Autogeniezustand keine statistisch signifikanten Unterschiede auf, aber die zur Migrantenphase gehörenden haben ein viel geringeres Trockengewicht und geringere Prozentgehalte an Lipiden als die zur nonmigranten Phase zu rechnenden. Die Analyse dieser Ergebnisse und frühere Untersuchungen lassen vermuten, daß der Phasenpolymorphismus bei diesem Insekt eine Folge der Plastizität seines ontogenetischen Potentials ist.

     

Vitelline envelope genes of the yellow fever mosquito, Aedes aegypti

Vitelline envelope genes from the mosquito Aedes aegypti were analyzed with respect to their DNA sequences, genomic representation, temporal and spatial expression profiles and response to 20-hydroxyecdysone. Genomic clones of three vitelline envelope genes, 15a-1, 15a-2 and 15a-3 were isolated. Southern analysis indicates that all three genes are represented by a single copy in the genome. The deduced amino acid sequences of all three vitelline envelope genes contain a conserved region of 46 residues that overlaps with a region that is conserved in four Drosophila melanogaster vitelline envelope genes. DNA was sequenced flanking the 15a-1, 15a-2 and 15a-3 coding regions. A 360 bp sequence 5′ of the 15a-2 coding region was identified with 72% identity to a sequence upstream of the Ae. aegypti VgA1 vitellogenin gene. The temporal patterns of 15a-1, 15a-2 and 15a-3 expression, as determined by Northern analysis, were similar. The spatial patterns of expression, as determined by whole-mount in situ hybridization, differed between the three genes. 15a-1 and 15a-3 were only expressed in the middle and posterior regions of the follicle, while 15a-2 was also expressed at the anterior region. Vitelline envelope gene expression was higher in ovaries that were dissected at 0, 2 and 10 h following a blood meal and then incubated in vitro for 10 h in medium containing 10⁻⁵ M 20-hydroxyecdysone, compared to ovaries that were incubated without hormone.     

Lipophorin as a yolk protein precursor in the mosquito, Aedes aegypti

We examined expression of the lipophorin (Lp) gene, lipophorin (Lp) synthesis and secretion in the mosquito fat body, as well as dynamic changes in levels of this lipoprotein in the hemolymph and ovaries, during the first vitellogenic cycle of females of the yellow fever mosquito, Aedes aegypti. Lipophorin was purified by potassium bromide (KBr) density gradient ultracentrifugation and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). Polyclonal antibodies were produced against individual Lp apoproteins, apolipoprotein-I (apoLp-I) and apolipoprotein-II (apoLp-II), with molecular weights of 240 and 75 kDa, respectively. We report here that in the mosquito A. aegypti, Lp was synthesized by the fat body, with a low level of the Lp gene expression and protein synthesis being maintained in pre- and postvitellogenic females. Following a blood meal, the Lp gene expression and protein synthesis were significantly upregulated. Our findings showed that the fat body levels of Lp mRNA and the rate of Lp secretion by this tissue reached their maximum at 18 h post-blood meal (PMB). 20-Hydroxyecdysone was responsible for an increase in the Lp gene expression and Lp protein synthesis in the mosquito fat body. Finally, the immunocytochemical localization of Lp showed that in vitellogenic female mosquitoes, this protein was accumulated by developing oocytes where it was deposited in yolk granules.     

Sensitivity of Aedes aegypti adults (Diptera: Culicidae) to the vapors of Eucalyptus essential oils

Vapors of essential oils extracted from various species of Eucalyptus (E. gunnii, E. tereticornis, E. grandis, E. camaldulensis, E. dunnii, E. cinerea, E. saligna, E. sideroxylon, E. globulus ssp. globulus, E. globulus ssp. maidenii, E. viminalis and the hybrids E. grandis × E. tereticornis and E. grandis × E. camaldulensis) and their major components were found to be toxic to Aedes aegypti adults, the yellow fever mosquito.An aliquot of each oil was placed in a cylindrical test chamber and the number of knocked-down mosquitoes was recorded as function of time. Knockdown time 50% was then calculated. Results showed that E. viminalis had the fastest knockdown time at of 4.2 min, on the same order as dichlorvos, a standard knockdown agent. A correlation was observed between the content of 1,8-cineole in the Eucalyptus essential oils and the corresponding toxic effect.The correlation between KT₅₀ values and calculated vapor pressures of the essential oil components showed that the fumigant activity of simple organic compounds in insects is correlated with their volatility.     

Factors affecting the production of glutamine in cultured mouse cells

Glutamine synthetase activity of NCTC clone 929 mouse cells (strain L) was studied as a function of the prior nutritional experience of the cells. Small enzyme increases were recorded in response to either glutamine depletion or chronic serum supplementation of the growth medium. Somewhat greater increases resulted from the administration of cortisol or certain other steroids, particularly if the hormone treatment was combined with glutamine withdrawal. High concentrations of glutamate in the medium did not augment the glutamine synthetase content of the cells and even caused an apparent decrease in it. The presence of glutamine in the culture medium resulted in a fairly rapid rate of disappearance of the glutamine synthetase of previously induced cells. The data suggest that glutamine and cortisol act independently on the cells in regulating the level of the enzyme.     

Folate copolymer-mediated transfection of cultured cells

Poly(ethylene glycol) of various sizes was used as a molecular spacer to separate the cell-targeting ligand, folate, from the surface of poly-L-lysine. The resulting ternary macromolecule (pLys-PEG-folate) was investigated in various formulations for its ability to transfect reporter plasmids into receptor-bearing HeLa and IGROV cell lines. Formulations were optimized with respect to DNA content, +/- charge ratio, and the size and amount of PEG substitution off the pLys backbone. Transfection activity was highest 48 h after sample introduction, and PEG 3400 was determined to be the most favorable spacer size tested. pLys-PEG-folate:DNA transfection was also found to be both concentration dependent and saturable; plus, it was blocked by the addition of excess-free folate, indicative of a specific mechanism of uptake. Transfection activity was virtually identical for complexes formed in 10% serum-supplemented media, deionized water, or Hepes buffer. And, cell viability remained greater than 85% at the highest concentrations of pLys-PEG-folate:DNA complexes tested (4.8 microg/mL pLys 331 000; 12 microg/mL DNA). Taken together, these observations provide evidence that pLys-PEG-folate:DNA complexes are taken up specifically by the folate endocytosis pathway, and that the intramolecular spatial distance of the ligand from the pLys backbone dramatically influences transfection.     

A model of polymorphism with several seasons and several habitats, and its application to the mosquito Aedes aegypti

Polymorphism has been shown to be possible but unlikely with a different selection intensity in each of several niches, or with varying selection intensity during successive generations. We show that polymorphism is likely with the combination of several niches and several seasons. The model contains two seasons, three habitats, many generations per season, habitat selection, positive assortative mating, movement between habitats, and different fitnesses of each genotype in each habitat. It is a stepping stone model with differential migration of genotypes. It is applied to the polymorphism of the indoor and the outdoor genotypes of the yellow fever mosquito Aedes aegypti. Matrix methods and simple models of population genetics comprised the computer model. Polymorphism is likely with most reasonable values of the parameters. Fitnesses and rate of movement are the most important parameters influencing the character and likelihood of polymorphism; habitat selection and positive assortative mating have much less effect. The model indicates that polymorphism of A. aegypti in east Africa results from: (1) the presence of a dry season when breeding occurs only in the human habitat; (2) greater fitness of the indoor ecotype in the human habitat and of the outdoor ecotype in the natural habitat; and (3) less than random movement between human and natural habitats.     

Evaluation of an experimental product based on Bacillus thuringiensis sorovar. israelensis against Aedes aegypti larvae (Diptera:Culicidae)

The larvicidal activity of an experimental formulation of Bacillus thuringiensis israelensis (Bti) against Aedes aegypti larvae was evaluated under laboratory and simulated field conditions (SFC). Samples of technical powder (TP) were assayed to establish the LC₅₀ and the potency of the product. The larvicidal activity of the TP and the tablet (T) were evaluated under SFC to assess the efficacy and the residual activity, measured against Ae. aegypti larvae. Either a T or 250 mg of TP were added to 50 L of water in plastic containers. Containers were exposed to sunlight or kept in the shade. Results showed a LC₅₀ of 0.26 mg/L and a potency of 750 ITU/mg. In spite of differences in the toxicity amongst TP and T samples, all of them killed 98–100% of the larvae and the mortality remained high for six months, in the shade. The replacement of 20% or 60% of the water volume did not affect the activity of the product. Seasonal differences influenced the persistence of the product in containers exposed to sunlight. Both formulations showed an excellent performance, especially when kept in the shade. The Bti tablet evaluated in this study is potentially very useful in programs to control dengue vectors.     

Factors affecting the photokilling of cultured Chinese hamster cells by phthalocyanines

Chloroaluminum phthalocyanine (CAPC) was recently shown to sensitize the inactivation of cultured Chinese hamster cells by visible light. Several factors affecting the photodynamic action of CAPC have been defined in the present study. Thus the photosensitized inactivation of Chinese hamster cells is not affected by superoxide dismutase, suggesting that O-2 radicals are not involved in the process. Postillumination treatments with D2O or heat (42 degrees C, 90 min) enhanced CAPC-induced photosensitivity, indicating the existence of a repair mechanism for photodamage. Preillumination treatments with sodium salicylate and 5-bromodeoxyuridine also enhanced photosensitivity. The later observation suggests that CAPC-induced DNA damage is potentially lethal. However, 3-aminobenzamide, a potent inhibitor of poly(ADP-ribose) synthesis which is involved in repair of DNA strand breakage, had no effect on the photosensitivity. Photosensitized inactivation by CAPC is dependent on the pH value of the medium during irradiation. Thus, in the range of pH values 6-8, the sensitivity was increased at the lower values.     

Factors affecting the growth characteristics of alginate-entrapped Chlorella

Previous studies have shown that growth of immobilized Chlorella emersonii is restricted to the periphery of calcium alginate gel beads. Results presented here show that CO₂, the growth-limiting factor, is responsible for this zonation. Light intensity (6–30 klx), though not saturating for photosynthesis, is not responsible for the effect. High concentrations of CO₂ (≈ 2%) were necessary to produce alginate beads containing high cell stocking densities without acute cell zonation. These findings are discussed in the context of other work on immobilized algal cells.     

The inactivation of acetylcholinesterase by alpha-terthienyl and ultraviolet light Studies in vitro and in larvae of the mosquito Aedes aegypti

Acetylcholinesterase (EC 3.1.1.7) was inactivated photochemically in solution, in the presence of dissolved terthiophene sensitizers. Alpha-terthienyl (2,2′:5,2″-terthiophene) and its isomers 3,2′:5′,2″- and 3,2′:5′,3″-terthiophenes showed very similar sensitizing properties. With all three terthiophenes, the photosensitization was completely suppressed under anaerobic conditions, and therefore the inactivation process required the presence of oxygen. The enzyme was inactivated in vivo when fourth instar larvae of the mosquito Aedes aegypti were treated with alpha-terthienyl in the presence of long-wavelength ultraviolet light. No inactivation was observed when the organisms were treated with the ultraviolet light alone, with the chemical alone, or with a previously irradiated sample of the chemical. This paper represents the first example of acetylcholinesterase inactivation in vivo by a photoactive insecticide.     

Factors affecting the breeding success of the grey heron ( Ardea cinerea) in northern Poland

The aim of this study was to estimate the importance of factors affecting the breeding success of the grey heron (Ardea cinerea) in three colonies in the northern Poland (Mosty, Kiersity and Kty Rybackie), differentiated in population size, habitat type and feeding areas used by birds. The highest mean number of fledglings (39–51 days old) per nest in 2000–2002 combined was recorded at Kty Rybackie (3.2±0.91 SD). Lower values were recorded at Kiersity (2.5±1.11) and Mosty (2.8±1.20). Breeding success increased with the size of the heronry (r₇=0.77, P<0.05) and was the highest in the biggest, at Kty Rybackie (716–879 nests). In the studied colonies, the number of feeding visits was the most important factor affecting breeding success. At Kty Rybackie and Kiersity, chick mortality significantly decreased with increasing numbers of feeding visits per nest. The highest breeding success was recorded in the colonies with feeding areas situated nearby (Kty Rybackie and Mosty). Siblicide was also a very important reason of chick mortality in those colonies (54% and 32% chicks died in nests where sibling aggression was observed). Other factors, independent of the level of feeding, like predation, human disturbance, weather condition and experience of parent birds, seem to be of negligible importance.Communicated by F. Bairlein     

Transient expression of the Drosophila melanogaster cinnabar gene rescues eye color in the white eye (WE) strain of Aedes aegypti

The lack of eye pigment in the Aedes aegypti WE (white eye) colony was confirmed to be due to a mutation in the kynurenine hydroxylase gene, which catalyzes one of the steps in the metabolic synthesis of ommochrome eye pigments. Partial restoration of eye color (orange to red phenotype) in pupae and adults occurred in both sexes when first or second instar larvae were reared in water containing 3-hydroxykynurenine, the metabolic product of the enzyme kynurenine hydroxylase. No eye color restoration was observed when larvae were reared in water containing kynurenine sulfate, the precursor of 3-hydroxykynurenine in the ommochrome synthesis pathway. In addition, a plasmid clone containing the wild type Drosophila melanogaster gene encoding kynurenine hydroxylase, cinnabar (cn), was also able to complement the kynurenine hydroxylase mutation when it was injected into embryos of the A. aegypti WE strain. The ability to complement this A. aegypti mutant with the transiently expressed D. melanogaster cinnabar gene supports the value of this gene as a transformation reporter for use with A. aegypti WE and possibly other Diptera with null mutations in the kynurenine hydroxylase gene.     

Factors affecting facultative polygyny and breeding results in the Great Reed Warbler (Acrocephalus arundinaceus)

Summary In a population of Great Reed Warbler (42–53 stationary males) the sex ratio was balanced and occurence of polygynous males (on average 15 % of the males) was more or less compensated by respective number of unmated males. Prospective polygynists arrived earlier in spring on average than monogamists, and got the first female quicker. Their territories were larger (statistically insignificant) and more often situated close to good foraging grounds. The reeds around primary female nests were on average thicker (and taller) and not so dense as in the case of monogamous, secondary and tertiary females. The intensity of nestling feeding (no. of visits per nestling per hour) was higher in the nests of monogamous females, than in primary females, and lowest in secondary and tertiary females nests. Nestlings in secondary and tertiary female broods were on average lighter than in monogamous and primary female broods. The male helped feed nestlings in secondary female nest only exceptionally. In monogamous situation their share in feeding was ca. 50%, and less so in primary female nests. Production of fledglings per female was highest in primary females and lowest in secondary and tertiary females, mainly due to the high starvation rate in the nests of secondary and tertiary females. Generally, collected data strongly suggest that female choice is determined by territory quality, and polygyny threshold hypothesis cannot be rejected. The deception hypothesis cannot be rejected as well in some observed special situations (disruptive territories or polyterritoriality; four cases).

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Voraussetzungen für fakultative Polygynie beim Drosselrohrsänger (Acrocephalus arundinaceus)

Zusammenfassung Das Geschlechterverhältnis in der untersuchten Drosselrohrsänger-Population von 42 bis 53 war ausgeglichen. Das Auftreten polygyner (durchschnittlich 15 % der ) wurde mehr oder weniger durch eine entsprechende Anzahl unverpaarter kompensiert. Prospektiv polygyne kamen durchschnittlich früher an als monogame und waren schneller verpaart. Ihre Reviere waren (statistisch nicht signifikant) größer und lagen näher zu günstigen Nahrungsgebieten. Das Schilf in der Nähe der Nester von Erst- war durchschnittlich dicker (und höher) als und nicht so dicht wie bei Einzel- oder Zweit- und Dritt- . Die Fütterungsfrequenz der Nestlinge (Anzahl der Besuche beider Altvögel mit Futter pro Nestling pro Stunde) war bei Nestern von Einzel- höher als bei Erst- und am niedrigsten bei Nestern von Zweit- und Dritt-. Nestlinge von Zweit- und Dritt- waren durchschnittlich leichter als solche von Einzel-und Erst- . halfen nur ausnahmsweise bei der Fütterung von Nestlingen von Zweit- . Bei monogamen Paaren beteiligten sich die ungefähr zur Hälfte an der Fütterung der Nestlinge, bei Nestern von Erst- in geringerem Umfang. Der Ausfliegeerfolg war am höchsten beim Erst- und am niedrigsten bei Zweit- und Dritt- , hauptsächlich bedingt durch Verhungern der Nestlinge. Allgemein legen die Daten nahe, da\ die die nach der Revierqualität auswählen und daß das Polygynieschwellenmodell vonOrians undVerner nicht abgelehnt werden kann. Einige Beobachtungen stützen die Hypothese, daß in bestimmten Situationen (unübersichtliche Reviere, Polyterritorialität) durch Täuschung polygyn werden.