Effect of insecticide resistance on development, longevity and reproduction of field or laboratory selected Aedes aegypti populations

Aedes aegypti dispersion is the major reason for the increase in dengue transmission in South America. In Brazil, control of this mosquito strongly relies on the use of pyrethroids and organophosphates against adults and larvae, respectively. In consequence, many Ae. aegypti field populations are resistant to these compounds. Resistance has a significant adaptive value in the presence of insecticide treatment. However some selected mechanisms can influence important biological processes, leading to a high fitness cost in the absence of insecticide pressure. We investigated the dynamics of insecticide resistance and its potential fitness cost in five field populations and in a lineage selected for deltamethrin resistance in the laboratory, for nine generations. For all populations the life-trait parameters investigated were larval development, sex ratio, adult longevity, relative amount of ingested blood, rate of ovipositing females, size of egglaying and eggs viability. In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level. In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control. Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost.     

Effects of chronic caloric restriction on kidney and heart redox status and antioxidant enzyme activities in Wistar rats

Caloric restriction (CR) has been associated with health benefits and these effects have been attributed, in part, to modulation of oxidative status by CR; however, data are still controversial. Here, we investigate the effects of seventeen weeks of chronic CR on parameters of oxidative damage/modification of proteins and on antioxidant enzyme activities in cardiac and kidney tissues. Our results demonstrate that CR induced an increase in protein carbonylation in the heart without changing the content of sulfhydryl groups or the activities of superoxide dismutase and catalase (CAT). Moreover, CR caused an increase in CAT activity in kidney, without changing other parameters. Protein carbonylation has been associated with oxidative damage and functional impairment; however, we cannot exclude the possibility that, under our conditions, this alteration indicates a different functional meaning in the heart tissue. In addition, we reinforce the idea that CR can increase CAT activity in the kidney. [BMB Reports 2012; 45(11): 671-676]     

Advantages of q-PCR as a method of screening for gene targeting in mammalian cells using conventional and whole BAC-based constructs

We evaluate here the use of real-time quantitative PCR (q-PCR) as a method for screening for homologous recombinants generated in mammalian cells from either conventional gene-targeting constructs or whole BAC-based constructs. Using gene-targeted events at different loci, we show that q-PCR is a highly sensitive and accurate method for screening for conventional gene targeting that can reduce the number of clones requiring follow-up screening by Southern blotting. We further compared q-PCR to fluorescent in situ hybridization (FISH) for the detection of gene-targeting events using full-length BAC-based constructs designed to introduce mutations either into one gene or simultaneously into two adjacent genes. We find that although BAC-based constructs appeared to have high rates of homologous recombination when evaluated by FISH, screening by FISH was prone to false positives that were detected by q-PCR. Our results demonstrate the utility of q-PCR as a screening tool for gene targeting and further highlight potential problems with the use of whole BAC-based constructs for homologous recombination.     

Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.     

Cloning and genomic organization of the mouse gene slc23a1 encoding a vitamin C transporter.

Vitamin C is known to exist in particularly high concentrations in brain tissue, and its free radical scavenging function is thought to represent a major antioxidative defense system. We have cloned, sequenced and analyzed the genomic structure of a mouse sodium-dependent vitamin C transporter gene, Slc23a1 (also known as Svct2). The mouse Slc23a1 cDNA is 6.4 kb long and was cloned directly from a mouse brain RNA preparation. Hybridization screening of a mouse genomic BAC library identified BAC 53L21 which contains at least the entire coding sequence of the mouse Slc23a1 gene. Determination of the exon-intron structure of the gene revealed 17 exons ranging from 58 bp to 4407 bp extending over 50 kb of the mouse genome, with the translation start codon located in exon 3. Its 1944 nucleotide open reading frame encodes a polypeptide of 647 aa, which is highly similar to rat and human orthologs. The mouse gene was assigned to chromosome 2qG2 by fluorescence in situ hybridization analysis. Expression of this gene was demonstrated in a wide range of tissues, with especially high levels in brain. Neurodegenerative diseases with an established role for oxidative stress in the cytoplasm may therefore be conditions of SLC23A1 dysfunction. Key words: gene structure; Vitamin C; transporter; oxidative stress     

Leptin and prolactin, but not corticosterone, modulate body weight and thyroid function in protein-malnourished lactating rats.

To understand the role of hormonal changes in the lower food ingestion and body weight in protein-restricted lactating rats as well as the higher serum T (3), higher deiodination, iodide and T (3) milk transfer, we measured maternal serum prolactin, leptin, TSH and corticosterone, which are hormones that could influence those parameters. After birth, dams were separated into: control-fed with a 23 % protein diet (n = 12) and PR (protein-restricted)-fed with an 8 % protein diet (n = 12). At the 4 (th) and 21 (st) day of lactation, half of the animals in each group were sacrificed. PR dams presented hyperleptinemia (day 4: + 20 %; day 21: + 19 %; p < 0.05) and hypoprolactinemia (day 4: - 85 %; day 21: - 92 %; p < 0.05), which could help explain the lower food consumption and body weight in lactating PR rats since leptin is anorexigenic and prolactin is orexigenic. Also, this hyperleptinemia could contribute for the increase in serum T (3) of PR dams, since leptin stimulates T (3) production, especially acting on deiodinases. Serum corticosterone was not different between PR and C groups, and TSH was lower only at the end of lactation. Thus, we suggest that both leptin and prolactin could play an important role in the body weight and thyroid hormone changes observed in protein-malnourished lactating rats.     

Subtle changes in elevation shift bat‐assemblage structure in Central Amazonia

The distribution patterns of animal species at local scales have been explained by direct influences of vegetation structure, topography, food distribution, and availability. However, these variables can also interact and operate indirectly on the distribution of species. Here, we examined the direct and indirect effects of food availability (fruits and insects), vegetation clutter, and elevation in structuring phyllostomid bat assemblages in a continuous terra firme forest in Central Amazonia. Bats were captured in 49 plots over 25‐km² of continuous forest. We captured 1138 bats belonging to 52 species with 7056 net*hours of effort. Terrain elevation was the strongest predictor of species and guild compositions, and of bat abundance. However, changes in elevation were associated with changes in vegetation clutter, and availability of fruits and insects consumed by bats, which are likely to have had direct effects on bat assemblages. Frugivorous bat composition was more influenced by availability of food‐providing plants, while gleaning‐animalivore composition was more influenced by the structural complexity of the vegetation. Although probably not causal, terrain elevation may be a reliable predictor of bat‐assemblage structure at local scales in other regions. In situations where it is not possible to collect local variables, terrain elevation can substitute other variables, such as vegetation structure, and availability of fruits and insects.