Tissue response resulting from different force magnitudes combined with corticotomy in rats

Objectives:To evaluate the amount of hyalinization and root resorption after application of light and heavy forces during corticotomy-assisted tooth movement.Materials and Methods:Forty-eight male Wistar rats were used. Eight animals were the control group (day 0). The other 40 animals were randomly divided into two groups using the split-mouth technique: (1) corticotomy combined light force (CLF) and (2) corticotomy combined heavy force (CHF). Nickel-titanium closed coil springs that generated 10 g (light force) and 50 g (heavy force) were used for maxillary first molar movement. three-dimensional root volume was evaluated at 0, 14, and 28 days. Percent hyalinization was analyzed at 0, 3, 7, 14, 21, and 28 days by histomorphometric analysis.Results:The CHF group showed significantly lower cervical root volume than the CLF group at 28 days. Compared with day 0, the CHF group showed significantly less root volume in both distobuccal and distopalatal roots at 28 days. The hyalinization percentages in the CHF group were significantly higher than the CLF group at days 3 and 21.Conclusions:Heavy force combined with corticotomy produced more periodontal ligament hyalinization and root resorption than the light force combined with corticotomy.     

Irritant and repellent responses of Anopheles harrisoni and Anopheles minimus upon exposure to bifenthrin or deltamethrin using an excito-repellency system and a live host

Feeding responses of Anopheles harrisoni and An. minimus were evaluated following exposure to 2 pyrethroid insecticides, bifenthrin or deltamethrin, using an excito-repellency test system in the presence and absence of live host cues. The results demonstrated that contact irritancy was the primary action of bifenthrin or deltamethrin in both mosquito species. There was no noncontact repellency effect elicited by either insecticide. Anopheles minimus showed rapid escape response with high mortality rates following direct contact with deltamethrin in the absence of a host and delayed escape responses when a host was present. Similarly, exposure of An. minimus to bifenthrin also elicited a delayed escape response in the presence of a host but with lower mortality rates. In experiments using An. harrisoni, the presence or absence of a host had no significant effect on behavioral responses to either insecticide (P > 0.05). We conclude that deltamethrin elicited stronger irritant chemical effects than bifenthrin but that behavioral responses in vector populations are dampened in the presence of an available host. This information is useful for estimating probability of pathogen transmission when using irritant chemicals in proximity to a blood-meal source.     

Study of Pax6 mutant rat revealed the association between upper incisor formation and midface formation.

In this study, we investigated the process of supernumerary upper incisor formation in the Pax6 mutant rat, rSey(2)/rSey(2), which exhibits a facial cleft between the medial nasal and maxillary processes. Histological investigation and epithelial labeling studies of wild type rat embryos indicated that the upper incisor develops by fusion of two primary dental placodes (PDPs) in the medial nasal process with a contribution from the epithelium of the maxillary process. In the rSey(2)/rSey(2) embryo, both PDPs are formed but they stay apart, then subsequently these PDPs independently develop into upper incisor tooth buds. In order to examine if the failure of the two placodes to fuse is due to the cleft between the maxillary and medial nasal processes, maxillary and medial nasal process fusion was inhibited with a barrier in wild type embryos. This resulted in the maintenance of the two distinct PDPs. These results demonstrate that fusion of the facial processes reduces the number of odontogenic placodes and is required to assemble all components at one site for rat upper incisor formation. The results also provide further insight into the mechanism of supernumerary incisor formation in human cleft lip conditions.     

Genetic differentiation of Aedes aegypti mainland and island populations from southern Thailand

Isozymes of 5 wild-caught collections of Aedes aegypti were compared by using starch gel electrophoresis. All collections were collected from Surat-Thanee Province, southern Thailand, an area considered to be a hyperendemic zone for dengue virus. One collection was from Donsak Harbor, whereas the other 4 collections were from 4 districts of Samui Island. The percent polymorphic loci (24.2-33%) in the 4 island collections was lower than in the mainland collection (36.4%). This study revealed a large effective migration rate among all 5 collections. No fixed differences were detected. No significant differentiation was found among the 5 collections from Surat-Thanee Province.     

Scrub typhus reemergence in the Maldives

In summer 2002, an outbreak of febrile illness began in the Maldives in the Indian Ocean. Through April 2003, officials recorded 168 cases with 10 deaths. The Armed Forces Research Institute of Medical Sciences in Bangkok confirmed Orientia tsutsugamushi and conducted a joint investigation with the Ministry of Health, Maldives. These cases of scrub typhus were the first in the Maldives since World War II.     

Meconial peritrophic matrix structure, formation, and meconial degeneration in mosquito pupae/pharate adults: histological and ultrastructural aspects

The noncellular peritrophic matrix (PM) that forms around the food bolus in the midgut of many arthropod species may influence the fate of ingested microbes. In mosquitoes, PMs have been identified in the pupal as well as larval and adult stages. In pupae, the PMs surround the meconium, the sloughed larval midgut epithelium. Meconial PM1 (MPM1) forms early in the pupal stadium, and a second meconial PM (MPM2) sometimes forms around the time of adult emergence. A recent study suggests that MPMs contribute to the sterilization of the adult midgut by sequestering microorganisms ingested during the larval stage, which, along with remaining meconial material, are egested after adult emergence. We have compared MPM1 formation and patterns of meconial degeneration in representative species in five mosquito genera and identified a temporal association between MPM1 formation, meconial degeneration, and apolysis. Ultrastructural study of MPM1 and MPM2 in Aedes aegypti (L.) revealed that MPM1 seems to be structurally different from either the larval or adult PMs, whereas MPM2 more closely resembles PM formed around a bloodmeal in adult females. Our results are consistent with the microbial sequestration role.     

Dispersal of the dengue vector Aedes aegypti within and between rural communities

Knowledge of mosquito dispersal is critical for vector-borne disease control and prevention strategies and for understanding population structure and pathogen dissemination. We determined Aedes aegypti flight range and dispersal patterns from 21 mark-release-recapture experiments conducted over 11 years (1991-2002) in Puerto Rico and Thailand. Dispersal was compared by release location, sex, age, season, and village. For all experiments, the majority of mosquitoes were collected from their release house or adjacent house. Inter-village movement was detected rarely, with a few mosquitoes moving a maximum of 512 meters from one Thai village to the next. Average dispersal distances were similar for males and females and females released indoors versus outdoors. The movement of Ae. aegypti was not influenced by season or age, but differed by village. Results demonstrate that adult Ae. aegypti disperse relatively short distances, suggesting that people rather than mosquitoes are the primary mode of dengue virus dissemination within and among communities.     

Production of antibodies by single DNA immunization: comparison of various immunization routes

DNA immunization is a recent vaccination method that induces humoral and cellular immune responses in a range of hosts. Different immunization routes induce a different degree of the immune response. In the present report, we demonstrate that multiple intramuscular immunizations of plasmid DNA encoding various leukocyte surface molecules induced a specific antibody response. In contrast, a single intramuscular immunization could not induce antibody production. To study the induction of antibody response after a single immunization of plasmid DNA, mice were single-dose intramuscularly, intraperitoneally, intravenously and intrasplenically immunized, simultaneously, with the same preparation of plasmid DNA encoding CD147 membrane protein. We observed that only the intrasplenic route induced specific antibody production. The induction of antibody by intrasplenic immunization was confirmed by using plasmid DNA encoding CD54 molecule. By this single-dose DNA intrasplenic immunization, the generated antibodies could be detected in mice up to 6 months. These results suggest that the injected DNA is expressing the relevant protein antigen in the spleen for several months after injection. Our results demonstrate that direct immunization of antigen-encoding DNA into the spleen is a more effective method for induction of antibody production. This finding may support future investigations of DNA vaccination strategies that specifically promote the uptake of plasmid by splenocytes. Intrasplenic immunization may also be helpful in the understanding of the early events of the immune response to DNA vaccine and be useful as an effective route for the induction of immune responses.