Dose-dependent behavioral response of the mosquito Aedes albopictus to floral odorous compounds.

The value of using plant volatiles as attractants for trapping and spatial repellents to protect hosts against mosquitoes has been widely recognized. The current study characterized behavioral responses of Aedes albopictus (Skuse) (Diptera: Culicidae) to different concentrations, ranging from 6 to 96%, of several common floral odorous compounds, including linalool, geraniol, citronellal, eugenol, anisaldehyde, and citral, using a wind tunnel olfactometer system. The results indicated that female mosquitoes reacted differently to different concentrations of the tested compounds, and the reactions also were different when those chemicals were tested alone or in the presence of human host odor. When tested alone, anisaldehyde was attractive at all tested concentrations, eugenol was attractive only at concentrations of 48-96%, while citronellal, linalool, citral, and geraniol were attractive at lower concentrations and repellent at higher concentrations. When tested in the presence of a human host, all compounds except for anisaldehyde at all tested concentrations showed host-seeking inhibition to certain degrees. Based on the results, it was concluded that anisaldehyde was effective in attracting Ae. albopictus when used alone but could also remarkably inhibit the host-seeking ability at a concentration of 96%, while citral, geraniol, linalool, citronellal, and eugenol are suitable as spatial repellents.

Behavior of solid carbon sources for biological denitrification in groundwater remediation.

The present study was conducted to compare the behavior of wheat straw, sawdust and biodegradable plastic (BP) as potential carbon sources for denitrification in groundwater remediation. The results showed that a greater amount of nitrogen compounds were released from wheat straw and sawdust than from BP in leaching experiments. In batch experiments, BP showed higher nitrate removal efficiency and longer service life than wheat straw and sawdust, which illustrated that BP is the most appropriate carbon source for stimulation of denitrification activity. In column experiments, BP was able to support complete denitrification at influent nitrate concentrations of 50, 60, 70, 80, and 90 mg NO(3)(-)-N/L, showing corresponding denitrification rates of 0.12, 0.14, 0.17, 0.19, and 0.22 mg NO(3)(-)-N.L(-1).d(-1).g(-1), respectively. These findings indicate that BP is applicable for use as a carbon source for nitrate-polluted groundwater remediation.

Preliminary analysis of several attractants and spatial repellents for the mosquito, Aedes albopictus using an olfactometer.

Mosquito attractants and spatial repellents hold great promise in controlling mosquito pests. In assessing the effectiveness of mosquito attractants and repellents, a good olfactometer system, and optimized testing conditions, are essential. In this research, we demonstrated the usefulness of an olfactometer system, and optimized testing conditions for Aedes albopictus (Diptera: Culicidae). We found no significant difference in the biting activity of the insect between 8:00 and 22:00. Furthermore, 5-10 day old mosquitoes were relatively strongly attracted, with bloodsucking rate 75.8%. The random capture rate (entered trap in absence of odor) was less than 20% for the 20-40 tested insects. Capture rates and systematic errors increased as the number of testing insects increased. Wind speed affected the capture rate significantly, whereas variations in temperature between 25-28°C did not result in significant difference. The wind speed of 0.2 m/s exhibited a higher capture rate, which was significantly different from those at either 0.1 m/s or 0.4 m/s (P < 0.05). At the wind speed of 0.2 m/s, time durations within the first 8 minutes correlated positively with capture rates (r(2) = 0.997), but further increase in time duration to 10 minutes did not result in further increase in capture rates. One percent of L-lactic acid in dichloromethane resulted in a consistently higher capture rate (43.8%) than that from a human odor (31.2%). Under our testing conditions, eugenol, anisaldehyde, geraniol, citronellal, citral, and linalool all exhibited some inhibition effect on mosquitoes to successfully trace human odor or 1% of L-lactic acid in dichloromethane. The results of these two tests indicate that the L-lactic acid/dichloromethane mixture may be used as an effective attractant to evaluate the effect of possible spatial repellents on Ae. albopictus.

Host-seeking and blood-feeding behavior of Aedes albopictus (Diptera: Culicidae) exposed to vapors of geraniol, citral, citronellal, eugenol, or anisaldehyde.

The changes of the host-seeking and blood-feeding behavior of Aedes albopictus (Skuse) (Diptera: Culicidae) surviving in a space containing vapors of the spatial repellents geraniol, eugenol, citral, anisaldehyde, or citronellal were evaluated using an arm-in-cage test and a bioassay of bloodmeals on a shaved mouse. The mosquitoes surviving concentrations of geraniol, citral, eugenol, or anisaldehyde at 0.013, 0.025, 0.050, 0.100, and 0.250 microg/cm3 for 24 and 48 h all showed different degrees of reduction in host-seeking ability. After 48 h of exposure to 0.250 microg/cm3 geraniol, almost 100% of the mosquitoes lost their host-seeking ability. The next most potent spatial repellent, anisaldehyde, stopped host seeking by > 85.5%. Citronellal did not result in a significant reduction in the host-seeking ability at any concentration level after either 24 or 48 h of treatment. We also found that reduction of host-seeking ability recovered after various times. The longest recovery time (144 h) was observed for geraniol after 24 h at 0.250 microg/cm3. In the study, geraniol, eugenol, and citral all significantly affected the activation and orientation stages of the blood-feeding behavior. However, only anisaldehyde significantly interrupted the normal blood-feeding of mosquitoes in all stages of behavior. These initial laboratory results clearly showed that anisaldehyde and geraniol could be promising spatial repellents against Ae. albopictus that they could play a major role in new repellent technology.

Limitations of allotopic expression of mitochondrial genes in mammalian cells.

The possibility of expressing mitochondrial DNA-coded genes in the nuclear-cytoplasmic compartment provides an attractive system for genetic treatment of mitochondrial disorders associated with mitochondrial DNA mutations. In theory, by recoding mitochondrial genes to adapt them to the universal genetic code and by adding a DNA sequence coding for a mitochondrial-targeting sequence, one could achieve correct localization of the gene product. Such transfer has occurred in nature, and certain species of algae and plants express a number of polypeptides that are commonly coded by mtDNA in the nuclear-cytoplasmic compartment. In the present study, allotopic expression of three different mtDNA-coded polypeptides (ATPase8, apocytochrome b, and ND4) into COS-7 and HeLa cells was analyzed. Among these, only ATPase8 was correctly expressed and localized to mitochondria. The full-length, as well as truncated forms, of apocytochrome b and ND4 decorated the periphery of mitochondria, but also aggregated in fiber-like structures containing tubulin and in some cases also vimentin. The addition of a hydrophilic tail (EGFP) to the C terminus of these polypeptides did not change their localization. Overexpression of molecular chaperones also did not have a significant effect in preventing aggregations. Allotopic expression of apocytochrome b and ND4 induced a loss of mitochondrial membrane potential in transfected cells, which can lead to cell death. Our observations suggest that only a subset of mitochondrial genes can be replaced allotopically. Analyses of the hydrophobic patterns of different polypeptides suggest that hydrophobicity of the N-terminal segment is the main determinant for the importability of peptides into mammalian mitochondria.

Human mitochondrial DNA with large deletions repopulates organelles faster than full-length genomes under relaxed copy number control.

Partially-deleted mitochondrial DNA (DeltamtDNA) accumulates during aging of postmitotic tissues. This accumulation has been linked to decreased metabolic activity, increased reactive oxygen species formation and the aging process. Taking advantage of cell lines with heteroplasmic mtDNA mutations, we showed that, after severe mtDNA depletion, organelles are quickly and predominantly repopulated with DeltamtDNA, whereas repopulation with the wild-type counterpart is slower. This behavior was not observed for full-length genomes with pathogenic point mutations. The faster repopulation of smaller molecules was supported by metabolic labeling of mtDNA with [3H]thymidine during relaxed copy number control conditions. We also showed that hybrid cells containing two defective mtDNA haplotypes tend to retain the smaller one as they adjust their normal mtDNA copy number. Taken together, our results indicate that, under relaxed copy number control, DeltamtDNAs repopulate mitochondria more efficiently than full-length genomes.