Laboratory And Field Studies On The Bionomics Of Culex Quinquefasciatus Say (Diptera: Culicidae) In Pulau Pinang, Malaysia

Kajian bionomik nyamuk Culex quinquefasciatus di dijalankan selama 14 bulan bermula dari Februari 2008 sehingga Mac 2009 di Pulau Pinang dengan menggunakan kaedah umpan kaki terdedah (bare-leg catch). The biting cycle and seasonal abundance of Culex quinquefasciatus mosquito were studied for 14 months from February 2008 to Mac 2009 in Penang using the bare-leg-catch technique

Effect of nutrient and density against the susceptibility status of Aedes aegypti and aedes albopictus towards diagnostic dose of malathion and permethrin

The knockdown 50% values (KT50) of Aedes aegypti and Aedes albopictus with variable nutrient and density conditions were determined based on World Health Organisation (WHO) Adult Bioassay standard protocol towards diagnostic dose of malathion (5%) and permethrin (0.75%) and the effect of nutrient and density on Aedes susceptibility status were investigated. Our results revealed that the susceptibility of these Aedes mosquitoes against malathion at F (4, 116) = 42.103, p<0.05 and permethrin at F (4, 121) = 45.138, p<0.05, gives the most delayed knockdown when fed with the optimum amount of nutrient which is 70mg compared with the lower amount of nutrient and the survival decreased once the nutrient amount was increased more than this amount. For density effect against Aedes susceptible status, at the highest density (600 larvae) examined, there was proportionally more larval mortality where the KT50 value was at the lowest value when compared with the optimal density which was between 150 to 250 larvae against malathion at F (6, 159) = 62.203, p<0.05 and permethrin at F (6, 148) = 57.431, p<0.05. However, the effect of nutrient and density factor of the different Aedes species significantly impacted their susceptibility to malathion and permethrin. The time required to knock down 50% (KT₅₀) of Ae. albopictus mosquitoes against the diagnostic dose of malathion as well as permethrin were relatively delayed compared to the values obtained by Ae. aegypti mosquitoes even though the environmental conditions were the same (p<0.05)

Effect of xenobiotic challenge on enzymatic activity of detoxification enzymes at different exposure periods in Aedes albopictus (skuse) (Diptera: Culicidae)

The xenobiotics including insecticides such as malathion and permethrin induce the activities of detoxification enzymes and potentially leading to the development of resistance. In this study, biochemical analysis was used to characterize the time-dependent malathion and permethrin induction profile of Glutathione S-transferase (GST), α-esterase (α-est), β-esterase (β-est), Cytochrome P450 (Cyt P450) and Acetylcholinesterase (AChE), enzymes which are known to contribute to metabolic resistance in Aedes albopictus. Time-dependent induction of early fourth instar larvae with the sub-lethal concentration (LC50) of malathion (0.099 mg/L) and permethrin (0.0023 mg/L) was done at 6, 12 and 24 hours to observe the effect on the enzymatic activity under toxicological challenges. Total protein content of larvae was most elevated when the larvae were exposed to both insecticides for 24 hours. The level of total enzyme activity and specific activity of GST, as well as Cyt P450 were found to be most elevated whereas the level of α-est and β-est total enzyme and specific activity were decreased at 24 hours of treatment with malathion. A different pattern was observed for permethrin induction whereby the total enzyme and specific activity of all enzymes except Cyt P450 were highly elevated upon 24 hours of acute exposure. The level of total enzyme activity and specific activity of almost all enzymes upon acute induction with malathion and permethrin were statistically significant (p˂0.05) when compared between the induced hours and to its susceptible strain. Conclusively, these findings indicate that the continuous and prolonged exposure to sub-lethal concentration of malathion and permethrin influenced the induction of GST, α-est, β-est, Cyt P450 as well as AChE enzymatic activities

Defence against Oxidative Stress and Insecticides in <em>Musca domestica</em>

This review is looking at the way Musca domestica defends itself against harmful molecules. One of the most notable enemies is against oxidative stress. Over the years there were reports that indicated the development of resistance on range of pesticides that are used against the flies. Researches have demonstrated that there are several functional protein molecules which contribute directly or indirectly as a response to oxidative stress and resistance against insecticides. As currently, the whole genome sequencing of the organisms has enabled future study to be conducted in evaluating the behaviour of the targeted protein/enzyme in response to oxidative stress and intake of insecticides in the flies

Expatriates' perception on factors affecting knowledge transfer between Asian expatriates and local employees

This paper aims to investigate the influence of individual factors (cultural intelligence and feedback seeking behavior) and social capital factors (shared vision and trust) on knowledge transfer between Asian expatriates and host country nationals (HCNs), as perceived by the former. This paper integrates the use of the Human Capital Theory, the Social Capital Theory, and the Anxiety and Uncertainty Management Theory to support the knowledge transfer framework between the two groups of human resources. Data were analyzed from a sample of 108 expatriates who are employed in multinational corporations and private companies in the area of Klang Valley, Malaysia. Results disclose that majority of these Asian expatriate are from South-East Asian and Far Eastern countries with a mean age of 39.6 years old, and have a moderate level of knowledge transfer and high levels of individual and social capital factors. Two factors were found as significant predictors of knowledge transfer, namely shared vision and cultural intelligence with a determination power of 23.6%

In Vivo Glutathione S-Transferases Superfamily Proteome Analysis: An Insight into <i>Aedes albopictus</i> Mosquitoes upon Acute Xenobiotic Challenges

In this study, the induction of glutathione S-transferase (GST) enzymatic activities in Aedes albopictus under 24 h of xenobiotic challenges was investigated. From LCMS analysis, 23 GST isoforms were identified under Delta, Epsilon, Sigma, Zeta, Omega, and Iota classes, together with one GSTX1-1 isoform, in both treated and untreated samples. Using STRING 11.5, the functional enrichment network of Gene Ontology (GO) analysis, the identified peptides were found to be involved in the glutathione metabolic biological process (GO:0006749, p-value: 1.93 × 10−29), and the molecular functions involved are due to glutathione transferase (GO:0016848, p-value: 2.92 × 10−8) aside from carbon-halide lyase activity (GO:004364, p-value: 1.21 × 10−31). The Protein-Protein Interaction (PPI) network (STRING 11.5) showed significant interactions within the GST superfamily and some of the GST classes interacted with other proteins among the input domain of the identified peptides (p-value −16). In TMT labeling for the quantification of peptide abundance, isoforms from Delta (GSTD1-2, GSTD1-3, GSTD1-4) and Epsilon (GSTE3-1, GSTE4-2) were found to be overexpressed (between 1.5-fold and 2-fold changes). In the PPI analysis, 12 common enriched pathways of Kyoto Encyclopedia of Genes and Genomes (KEGG) were found to be intercorrelated with the identified GSTs at PPI enrichment p-value −16. Overall, this study indicates that distinct GST enzymes, which were identified up to their specific protein isoforms, are involved in the metabolic mechanisms underlying xenobiotic stress

Relationship between the Floristic Composition and Soil Characteristics of a Tropical Rainforest (TRF)

Hutan Rimba Alam (HRA), Putrajaya is an urban forest which is the habitat for various tropical rainforest species. A field survey was undertaken to state the floristic composition, investigate the soil characteristics and identify the relationship between the recorded plant communities and soil characteristics. Six plots sized 10 &times; 10 m square were established in a lowland area of which 93 individual trees were identified. Moreover, the floristic composition revealed vascular tree communities consisting of 10 botanical families, 15 genera, and 27 species with Dipterocarpaceae as being predominant. Based on the important value index (IVI), Mangifera odorata (Anacardiaceae) was the highest (IVI = 68.80%). Furthermore, large trees such as Koompassia excelsa (Becc.) Taub. (Fabaceae) and Sandoricum koetjape (Burm.f.) Merr. (Meliaceae), with heights ranging from 17 m to 24 m, indicated that HRA is on the way to becoming a mature forest. The soil pH in all plots showed acidic properties, with a mean pH of 4.69 that is considered normal for tropical rainforests. The pH of the soils in HRA, Putrajaya had a positive correlation with the CEC and with nitrogen, but the value was low; however, the correlation was negative with C and P. The CEC had a relatively low correlation with C, N and P. Carbon had a very high correlation with N but low with P. Meanwhile, nitrogen had a very negatively low correlation with P. Extractable phosphorus exhibited a mean of 2.22 mg/kg which is normally used in plants for fruits, roots, and flower development. The present study revealed that plant communities in the urban forest in Putrajaya, meaning the diversity of the plant species belonging to a wide range of families, were established on acid soil, matching with the overall characteristics of tropical forest soils. With regard to the climate change context, which is leading to many altered ecosystems, the authors expect that the outputs of this research will be valued by decision makers for a better management of the forest