Ovipositional Behavior of <i>Anopheles gambiae</i> Mosquitoes

Mosquito eggs laid within two hours are necessary for transgenic (injection) studies, because mosquito eggs become hard after that period. Thus, in order to have eggs available within this two-hour window, it is important for transgenic studies to understand the ovipositional behavior of <i>Anopheles gambiae s.s.</i>. In the present study, the ovipositional behavior of <i>An. gambiae s.s.</i> (Kisumu) was investigated in several different conditions: age of mosquitoes, time post blood meal to access oviposition substrate, and light conditions. Two groups of mosquitoes, 3–5 day old and 9–11 day old mosquitoes were blood-fed. For those mosquito groups, an oviposition dish was set either at 48 hours or 72 hours after the blood meal either in a light condition or in an artificial dark condition. The number of laid eggs was compared among different conditions. The 3–5 day old mosquitoes apparently produced a higher number of eggs than 9–11 day old ones, while there was no significant difference between the 2 groups. The number of laid eggs per one surviving blood-fed mosquito in the dark condition was significantly higher than that in the light condition (<i>p</i> = 0.03). Providing an oviposition dish at 72 hours after blood meal resulted in a significantly higher number of laid eggs per one surviving blood-fed mosquito compared to providing an oviposition dish at 48 hours after blood meal (<i>p</i> = 0.03). In conclusion, the optimal condition to have readily available egg supply in the present study for transgenic analysis was as follows: 3–5 days old mosquitoes with an oviposition dish placed at 72 hours after the blood meal in a dark environment.

Ovipositional Behavior of <i>Anopheles gambiae</i> Mosquitoes

Mosquito eggs laid within two hours are necessary for transgenic (injection) studies, because mosquito eggs become hard after that period. Thus, in order to have eggs available within this two-hour window, it is important to understand the ovipositional behavior of <i>Anopheles gambiae s.s.</i>. In the present study, the ovipositional behavior of <i>An. gambiae s.s.</i> (Kisumu) was investigated in several different conditions: age of mosquitoes, time post blood meal to access oviposition substrate, and light conditions. Two groups of mosquitoes, 3–5 days old and 9–11 days old were blood-fed. For those mosquito groups, an oviposition dish was set either at 48 hours or 72 hours after the blood meal either in a light condition or in an artificial dark condition. The number of laid eggs was compared among the different conditions. The 3–5 day-old mosquitoes apparently produced a higher number of eggs than 9–11 day-old mosquitoes, while there was no significant difference between the two groups. The number of laid eggs per one surviving blood-fed mosquito in the dark condition was significantly higher than that in the light condition (<i>p</i> = 0.03). Providing an oviposition dish at 72 hours after blood meal resulted in a significantly higher number of laid eggs per one surviving blood-fed mosquito than at 48 hours after blood meal (<i>p</i> = 0.03). In conclusion, the optimal condition to have readily available egg supply for transgenic analysis was as follows: 3–5 day-old mosquitoes with an oviposition dish placed at 72 hours after the blood meal in a dark environment.

Schistosome eggs have a direct role in the induction of basophils capable of a high level of IL-4 production: Comparative study of single- and bisexual infection of Schistosoma mansoni in vivo

Immunobiological roles of schistosome eggs during murine experimental infection were investigated with special reference to the induction of basophilic leukocytes. After single- or bisexual infection with <I>Schistosoma mansoni</I> in BALB⁄c mice, splenomegaly and liver granulomas were observed only in bisexual infection in parallel with deposition of mature parasite eggs. Comparison of the kinetics of basophil response revealed a marked increase in number in the bone marrow of mice with bisexual infection at the 7<SUP>th</SUP> week post infection as opposed to a marginal increase in single- sex infections. In the spleen, bimodal response was observed in the basophil responses; a small but repeatable peak at the 4<SUP>th</SUP> week after infection, increasing again at the 8<SUP>th</SUP> week, which corresponded to the initiation and maturation of parasite eggs in the affected organs of infected mice. The same time course was observed for IL-4 production by the splenocytes from mice of bisexual infection. To obtain more concrete evidence of the role of eggs in the induction of basophils, we tested using the intravenous egg injection model. Injection of eggs induced basophilia, and it was accompanied by the up-regulation of IL-4 production in splenocytes from the 8<SUP>th</SUP> day. Basophils induced in this model showed a high level of IL-4 production confirmed by flow cytometry, while faint levels of IL-4 production were observed for CD4<SUP>+</SUP> T cells at this time point. In addition, we demonstrate that egg deposition is the trigger of basophil induction and activation in the murine experimental model of <I>S. mansoni</I> infection, which might play an essential role in the initiation of Th1⁄2 conversion during the course of <I>S. mansoni</I> infection <I>in vivo</I>.