Showing papers by "Shinji Kasai published in 2007"
TL;DR: This is the first time in mosquitoes that P450 monooxygenase involvement in pyrethroid resistance has been isolated and studied without the confounding effects of kdr .
69 citations
TL;DR: B. quintana started proliferation in body lice 4 days after ingestion and was constantly excreted in the feces for at least 3 weeks, creating an explosive multiplication rate and active excretion that could be related to epidemics of trench fever in developed countries.
Abstract: Although body louse is a well-known vector of trench fever, the growth kinetics of Bartonella quintana in body lice has not been fully understood. We performed a quantitative analysis of bacterial multiplication rate. B. quintana started proliferation in body lice 4 days after ingestion and was constantly excreted in the feces for at least 3 weeks. The number of bacteria in feces reached the maximum 10(7)/louse per day on Day 15. The doubling time of B. quintana estimated from logistic regression formula was 21.3 hours. Scanning electron microscopy showed the presence of bacterial masses in feces. Immunofluorescent study using specific monoclonal antibody confirmed identification of B. quintana. Such an explosive multiplication rate and active excretion of B. quintana from the body lice could be related to epidemics of trench fever in developed countries.
37 citations
TL;DR: The insect growth regulators diflubenzuron and pyriproxyfen were found to be sufficiently effective enough to control Culex larvae present, but decreased sensitivities to these insecticides were slightly detected in some colonies of Cx.
Abstract: Culex pipiens complex is the significant vector mosquito of West Nile virus. To take stock of the current situation of insecticide susceptibilities and design an ideal mosquito control strategy, we collected Culex pipiens pallens Coquillet, Culex pipiens form molestus Forskal, and Culex quinquefasciatus Say from fields in Japan and conducted bioassays for five larvicides (fenitrothion, temephos, etofenprox, diflubenzuron, and pyriproxyfen) by using a larval dipping method. Among five insecticides tested, obvious reduced susceptibilities were observed for etofenprox, which is the only pyrethroid compound registered as a larvicide in Japan. Twenty-two of 56 colonies exhibited a >10% survival rate at the etofenprox concentration of 5.7 microg/ml, which is a 10 times higher concentration of the working solution. The LC50 of a colony collected from Fukuoka prefecture for etofenprox exceeded 60 microg/ml (resistance ratio >2,307), and this colony also exhibited cross-resistance to other pyrethroids, permethrin (299-fold) and phenothrin (1,200-fold). The insect growth regulators diflubenzuron and pyriproxyfen were found to be sufficiently effective enough to control Culex larvae present, but decreased sensitivities to these insecticides were slightly detected in some colonies of Cx. p. form molestus collected from urban areas. Several etofenprox-resistant colonies of Cx. p. form molestus exhibited simultaneously decreased susceptibilities to other insecticides, including temephos, diflubenzuron, and pyriproxyfen.
31 citations
TL;DR: Two cDNA sequences encoding Drosophila Ace-orthologous and -paralogous acetylcholinesterase precursors, respectively, were identified from the body louse and the potential significance of the AP-AChE isoform in Pediculus human lice in association with the efficacy of AChE-targeting pediculicides was suggested.
Abstract: Two cDNA sequences encoding Drosophila Ace-orthologous and -paralogous acetylcholinesterase precursors (AO- and AP-AChE precursors, respectively), were identified from the body louse, Pediculus humanus humanus L. In vitro inhibition studies with an insecticide-susceptible body louse strain exhibited a simplex inhibitory response of AChE. The I50 values of fenitroxon and carbaryl were estimated to be 2.2 and 1.9 microM for the susceptible lice, respectively. The mRNA level of AP-AChE gene was 3.1- and 9.3-fold higher than that of AO-AChE gene in the abdomen and the combined parts of the head and thorax, respectively, suggesting, due to its abundance, the potential significance of the AP-AChE isoform in Pediculus human lice in association with the efficacy of AChE-targeting pediculicides.
21 citations
TL;DR: Results show that p-Ace is better as an insecticidal target because of its abundant transcripts in nervous tissue, and the roles of o-Aces, which is present ubiquitously without secretion into the hemolymph in insects, are discussed.
Abstract: Recent studies have revealed that non-Cyclorrhapha insects possess two acetylcholinesterases (AChEs): Drosophila Ace-orthologous (o-Ace) and -paralogous (p-Ace) forms. In these insects, p-Ace is considered as a neural target of insecticides because mutations conferring insecticide insensitivity have been consistently identified in equivalent forms from various insects. To clarify the functional differentiation between the two AChE isoforms, we characterized the expression of two AChE genes in nerve cell-rich and -poor tissues of German cockroaches. The two AChE genes were expressed at comparable levels in both the nerve cord and head. Two AChE isoforms with mutually discriminatory fenitroxon sensitivities were exhibited in the nerve cord, indicating that o-Ace and p-Ace function in the neurons. p-Ace was mainly expressed in the nerve cord and head, while o-Ace was ubiquitously expressed at a comparable level. Moreover, o-Ace transcripts as well as AChE activity were detected in the fat body where no nervous tissue is observed. No AChE activity was detected in the hemolymph. These results show that p-Ace is better as an insecticidal target because of its abundant transcripts in nervous tissue. In addition, the roles of o-Ace, which is present ubiquitously without secretion into the hemolymph in insects, are discussed.
10 citations