An analysis of apoptotic and autophagic genes in novel Drosophila models of Parkinson disease

Parkinson disease (PD) is the most common neurodegenerative movement disorder in humans and is strongly associated with the selective loss of dopaminergic (DA) neurons. The clinical features include motor dysfunction, resting tremor and in some cases non-motor features such as autonomic, cognitive and psychiatric disorders. The neuropathologic hallmarks are Lewy bodies and Lewy neurites in surviving neurons which are composed of proteinaceous inclusions comprised of α-synuclein, ubiquitin and other proteins. Pathological mechanisms implicated in PD include aberrant protein aggregation, mitochondrial dysfunction, oxidative stress, and failed cellular processes such as apoptosis, autophagy, proteasomal pathway, and several cellular stressors. To analyse the implication and contribution of some of these cellular processes, we altered the expression of the; classical apoptotic genes namely Buffy and Debcl; autophagy genes Atg6 and Pi3K59F; the antiapoptotic transmembrane Bax inhibitor-1 containing motif (TMBIM) family Bax inhibitor-1, Lifeguard and GHITM; mitochondrial genes such as HtrA2, MICU1, porin/VDAC, Pink1 and parkin; and an increased disease risk gene pyridoxal kinase in DA neurons and in the developing eye. We show that the altered expression of key genes can either be detrimental or beneficial to the health of DA neurons as determined by lifespan and locomotor function, in addition to supportive results obtained from biometric analysis of phenotypes from the neuron rich eye. We found that the overexpression of Buffy, the sole pro-survival Bcl-2 homologue in Drosophila could suppress the loss of function-induced phenotypes

Expression of Bcl-2 homologues in the α-synuclein-induced Parkinson disease model in Drosophila

In Parkinson disease (PD), the age-dependent degeneration of dopaminergic neurons (DA) and loss of locomotor function have been shown to be correlated with prominent mitochondrial abnormalities and dysfunction. A number of genes are associated with inherited forms of PD and most of these genes encode protein products that interact with components of the mitochondria. The pro-survival Bcl-2 proteins are reputed to be the guardians of the mitochondria, an organelle central to the process of cell death in all animals. Drosophila melanogaster possess two mitochondria localized Bcl-2-like proteins encoded by debel, which promotes cell death, and Buffy, which is pro-cell survival. The Bcl-2 proteins have been shown to have a dual role in the control of cell death and subsequent engulfment of cellular components (autophagy). In the α-synuclein-induced Drosophila model of PD, Buffy and debel were overexpressed in the DA neurons and developing eye using the UAS-GAL4 system of directed gene expression. Longevity and climbing ability of these flies were influenced by these two Bcl-2 genes: debel enhances the severity of the α-synuclein-induced age-dependent loss of climbing ability. On the other hand, Buffy suppresses the α-synuclein-induced PD-like phenotypes. When overexpressed in the developing neurons of the eye, a similar trend was observed with Buffy suppressing the eye defects. Taken together, these results suggest a protective role for Buffy, especially under α-synuclein-induced protein toxicity

New records of Anopheles arabiensis breeding on the Mount Kenya highlands indicate indigenous malaria transmission

BACKGROUND: Malaria cases on the highlands west of Mount Kenya have been noticed since 10 – 20 years ago. It was not clear whether these cases were introduced from the nearby lowland or resulted from local transmission because of no record of vector mosquitoes on the highlands. Determination of presence and abundance of malaria vector is vital for effective control and epidemic risk assessment of malaria among both local residents and tourists. METHODS: A survey on 31 aquatic sites for the malaria-vector mosquitoes was carried out along the primary road on the highlands around Mount Kenya and the nearby Mwea lowland during April 13 to June 28, 2005. Anopheline larvae were collected and reared into adults for morphological and molecular species identification. In addition, 31 families at three locations of the highlands were surveyed using a questionnaire about their history of malaria cases during the past five to 20 years. RESULTS: Specimens of Anopheles arabiensis were molecularly identified in Karatina and Naro Moru on the highlands at elevations of 1,720 – 1,921 m above sea level. This species was also the only malaria vector found in the Mwea lowland. Malaria cases were recorded in the two highland locations in the past 10 years with a trend of increasing. CONCLUSION: Local malaria transmission on the Mount Kenya highlands is possible due to the presence of An. arabiensis. Land use pattern and land cover might be the key factors affecting the vector population dynamics and the highland malaria transmission in the region

Characterization of potential larval habitats for Anopheles mosquitoes in relation to urban land-use in Malindi, Kenya

BACKGROUND: This study characterized Anopheles mosquito larval habitats in relation to ecological attributes about the habitat and community-level drainage potential, and investigated whether agricultural activities within or around urban households increased the probability of water body occurrence. Malindi, a city on the coast of Kenya, was mapped using global positioning system (GPS) technology, and a geographic information system (GIS) was used to overlay a measured grid, which served as a sampling frame. Grid cells were stratified according to the level of drainage in the area, and 50 cells were randomly selected for the study. Cross-sectional household and entomological surveys were conducted during November and December 2002 within the 50 grid cells. Chi-square analysis was used to test whether water bodies differed fundamentally between well and poorly drained areas, and multi-level logistic regression was used to test whether household-level agricultural activity increased the probability of water body occurrence in the grid cell. RESULTS: Interviews were conducted with one adult in 629 households. A total of 29 water bodies were identified within the sampled areas. This study found that characteristics of water bodies were fundamentally the same in well and poorly drained areas. This study also demonstrated that household-level urban agriculture was not associated with the occurrence of water bodies in the grid cell, after controlling for potential confounders associated with distance to the city center, drainage, access to resources, and population density. CONCLUSIONS: Household-level urban agricultural activity may be less important than the other types of human perturbation in terms of mosquito larval habitat creation. The fact that many larvae were coming from few sites, and few sites in general were found under relatively dry conditions suggests that mosquito habitat reduction is a reasonable and attainable goal in Malindi

Effects of a botanical larvicide derived from Azadirachta indica (the neem tree) on oviposition behaviour in Anopheles gambiae s.s. mosquitoes

More focus is given to mosquito larval control due to the necessity to use several control techniques together in integrated vector management programmes. Botanical products are thought to be able to provide effective, sustainable and cheap mosquito larval control tools. However, bio-larvicides like Azadirachta indica (neem) could repel adult mosquitoes from laying their eggs in the treated larval habitats. In this study the response of Anopheles gambiae s.s. mosquitoes towards varying doses of crude aqueous neem extracts was examined. Non-choice oviposition tests were used to measure the proportion of mosquitoes laying on the first or second night, or not laying at all, when compared to the control. For each individual mosquito, the number of eggs laid and/or retained in the ovary was counted to determine the relationship between wing length and egg production. Larger female mosquitoes produced larger egg batches. The results show that at a dose of 0.1 g/l, a concentration previously found to be effective at controlling mosquito larvae, the oviposition behaviour of adult female mosquitoes was not significantly affected. The results indicate that the mosquitoes would expose progeny to this neem control tool, making the use of these simple neem wood extracts effective and potentially sustainable

Influence of age and previous diet of Anopheles gambiae on the infectivity of natural Plasmodium falciparum gametocytes from human volunteers

The effect of age and dietary factors of Anopheles gambiae (Diptera: Culicidae) on the infectivity of natural Plasmodium falciparum parasites was studied. Mosquitoes of various ages (1–3, 4–7 and 8–11 day old) and those fed blood (either single or double meals) and sugar meals were experimentally co-infected with P. falciparum gametocytes obtained from different naturally infected human volunteers. On day 7, midguts were examined for oocyst infection to determine whether mosquito age or diets have significant effects on parasite infectivity. The age of the mosquitoes did not significantly influence the oocyst infection rates (χ(2) = 48.32, df = 40, P = 0.172) or oocyst load (# of oocysts/midgut) (P = 0.14) observed. Oocyst load between groups was not significantly different. Similarly, the type of diet (either blood or sugar) did not influence oocyst infection rates (χ(2) = 16.52, df = 19, P = 0.622). However, an increase in oocyst infection rates resulted after previous feeding on double blood meals (35%) compared to single blood meals (25%), with comparable oocyst load. These observations are in agreement with those reported in previous studies suggesting that increased mosquito nutritional reserves resulting from increased dietary resources is favorable for malaria infectivity. This field-based study indicates that vector competence of An. gambiae to natural P. falciparum parasites does not vary with age and that nutritional resources acquired prior to an infectious blood meal plays a crucial role in mosquito-parasite relationships. Abbreviation: / oocyst load: number of oocysts per midgut oocyst infection rates: percent of midguts with oocyst

Daily oviposition patterns of the African malaria mosquito Anopheles gambiae Giles (Diptera: Culicidae) on different types of aqueous substrates

BACKGROUND: Anopheles gambiae Giles is the most important vector of human malaria in sub-Saharan Africa. Knowledge of the factors that influence its daily oviposition pattern is crucial if field interventions targeting gravid females are to be successful. This laboratory study investigated the effect of oviposition substrate and time of blood feeding on daily oviposition patterns of An. gambiae mosquitoes. METHODS: Greenhouse-reared gravid and hypergravid (delayed oviposition onset) An. gambiae sensu stricto and wild-caught An. gambiae sensu lato were exposed to three types of substrates in choice and no-choice cage bioassays: water from a predominantly anopheline colonised ground pool (anopheline habitat water), swamp water mainly colonised by culicine larvae (culicine habitat water) and distilled water. The daily oviposition pattern and the number of eggs oviposited on each substrate during the entire egg-laying period were determined. The results were subjected to analysis of variance using the General Linear Model (GLM) procedure. RESULTS: The main oviposition time for greenhouse-reared An. gambiae s.s. was between 19:00 and 20:00 hrs, approximately one hour after sunset. Wild-caught gravid An. gambiae s.l. displayed two distinct peak oviposition times between 19:00 and 20:00 hrs and between 22:00 and 23:00 hrs, respectively. During these times, both greenhouse-reared and wild-caught mosquitoes significantly (P < 0.05) preferred anopheline habitat water to the culicine one. Peak oviposition activity was not delayed when the mosquitoes were exposed to the less preferred oviposition substrate (culicine habitat water). However, culicine water influenced negatively (P < 0.05) not only the number of eggs oviposited by the mosquitoes during peak oviposition time but also the overall number of gravid mosquitoes that laid their eggs on it. The differences in mosquito feeding times did not affect the daily oviposition patterns displayed. CONCLUSION: This study shows that the peak oviposition time of An. gambiae s.l. may be regulated by the light-dark cycle rather than oviposition habitat characteristics or feeding times. However, the number of eggs laid by the female mosquito during the peak oviposition time is affected by the suitability of the habitat