School of Health Science and Technology
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Item Field Responses of Tsetse Flies (Glossinidae) and Other Diptera to Oils in Formulations of Deltamethrin(2003) Mireji, PO; Mabveni, AM; Dube, BN; Ogembo, JG; Matoka, CM; Mangwiro, TNCInvestigations were conducted to establish field responses of Glossina pallidipes, G. m. morsitans, muscoids and tabanids to castor, raw linseed, paraffin and chlorinated paraffin oils in deltamethrin suspension concentrate (sc) formulation, through randomised Latin square experiments. Tsetse landing responses on targets treated with 400 ml/m2 of any of the oils in 2 g/m2 deltamethrin formulation were significantly lower than on non-oil-containing deltamethrin formulations, for both G. pallidipes (F(4,32) = 4.855, P = 0.00357) and G. m. morsitans (F(4,32)=2.421, P = 0.06862). The landing response indices, relative to the control formulation without oil, were 0.60, 0.70, 0.61 and 0.41 in G. pallidipes and 0.92, 0.82, 0.75 and 0.42 in G. m. morsitans and for paraffin, chlorinated paraffin, castor and raw linseed oils respectively. Glossina pallidipes and G. m. morsitans landing responses were inversely proportional to raw linseed oil concentrations. None of the oils significantly affected muscoid (F(4/32) = 1.6959, P = 0.1753) or tabanid (F(4,32) = 1.7546, P = 0.1624) landing response, or tsetse fly resting persistence (F(4,32) = 0.9641, P = 0.4406) on the targets. The reduced tsetse fly response to targets treated with any of the oils can be attributed to adverse effect of the oil treatments on the tsetse fly olfactory responses to the targets. Since the oil formulations reduce target efficiency by reducing tsetse responses to the targets, application of the oil formulations on targets deployed in G. pallidipes and G. m. morsitans control programmes is not recommended.Item Gender differences in cardiovascular disease: The effects of estrogen(2005) Mbai, Fiona N; Hamilton, Karyn L; Knowlton, Anne AEstrogen and its therapeutic application in cardiovascular disease are highly controversial. There has been a paucity of basic research on estrogen and its molecular effects, which has weakened the underpinnings of clinical trials of estrogen treatment. In the past 10 years, much has been discovered about both the genomic and nongenomic effects of estrogen. The identification of at least three distinct receptors for estrogen, as well as the development of drugs with varying binding affinities for different receptors, has created exciting therapeutic possibilities.Item Differential induction of proteins in Anopheles gambiae sensu stricto (Diptera: Culicidae) larvae in response to heavy metal selection(2006) Mireji, Paul O; Keating, Joseph; Kenya, Eucharia; Mbogo, Charles; Nyambaka, Hudson; Osir, Ellie; Githure, John; Beier, JohnInvestigations were conducted to establish the magnitude and pattern of differential expression of proteins due to generational selection of third instar Anopheles gambiae s.s. Giles larvae by cadmium, copper and lead heavy metals, the three possible common urban pollutants. A susceptible strain of A. gambiae s.s. third instar larvae was separately placed under selection pressure with cadmium, copper and lead at LC30 and controls through five generations. First, third and fifth generation selection survivors were screened for differentially expressed proteins relative to non-exposed control by two-dimensional gel electrophoresis. Distribution patterns of the spots were analyzed by χ2 or Fishers' exact test and variations in expressions between and within generations by ANOVA. Most differentially expressed spots were acidic and of low molecular weight among all metals and generations. Type of heavy metal and generation were the main indicators of variations in differential expressions. Variation between generations was most significant among cadmium-selected populations of which the most number of spots were induced in the fifth generation. Most spots were induced in the copper-selected population in the third generation. The induced protein spots may be the products from respective genes that respond to heavy metals and counter their toxicity, thus building A. gambiae s.s. tolerance to these pollutants. The differential pattern and magnitude of expressed spots have potential application as molecular markers for assessment of anopheline adaptation status to heavy metals, and provide insight into the extent of environmental pollutionItem Heavy metals in mosquito larval habitats in urban Kisumu and Malindi, Kenya, and their impact(2008) Mireji, PO; Keating, Joseph; Hassanali, Ahmed; Mbogo, Charles M; Nyambaka, Hudson; Kahindi, Samuel; Beierf, John CConcentrations and distribution of cadmium, chromium, copper, iron, lead, manganese and zinc in mosquito larval habitats in urban Kisumu and Malindi, Kenya and their effect on the presence of Anopheles gambiae, Aedes aegypti, Culex quinquefasciatus and Anopheles funestus larvae were investigated. Manganese and iron were the most prevalent heavy metals in water of larval habitats in urban Kisumu and Malindi, respectively. Iron was the most prevalent heavy metal in bottom sediments in larval habitats in both cities. The highest concentrations of all heavy metals, except cadmium and iron, were recorded in the poorly planned–well drained stratum in the two cities. All heavy metals were more concentrated in human-made than in natural larval habitats. Copper was positively associated with the presence of Ae. aegypti, and lead was associated with the presence of An. gambiae and Ae. aegypti in urban Kisumu. Absence of significant correlation between the other metals and mosquito species in both cities, despite relatively high concentrations, suggest that the local larval populations, including key malaria vectors have adapted to the detected levels of these metals.Item Effects of Dietary Decosahexaenoic Acid (DHA) on eNOS in Human Coronary Artery Endothelial Cells(2008) Stebbins, Charles L; Stice, James P; Hart, Michael; Mbai, Fiona N; Knowlton, Anne AEndothelial dysfunction occurs in heart disease and may reduce functional capacity via attenuations in peripheral blood flow. Dietary decosahexaenoic acid (DHA) may improve this dysfunction, but the mechanism is unknown. This study determined if DHA enhances expression and activity of eNOS in cultured human coronary artery endothelial cells (HCAEC). HCAEC from 4 donors were treated with 5 nM, 50 nM, or 1 μM DHA for 7 days to model chronic DHA exposure. A trend for increased expression of endothelial nitric oxide synthase (eNOS) and phospho-eNOS was observed with 5 and 50 nM DHA. DHA also enhanced expression of 2 proteins instrumental in activation of eNOS: phospho-Akt (5 and 50 nM) and HSP90 (50 nM and 1 μM). Vascular endothelial growth factor–induced activation of Akt increased NOx in treated (50 nM DHA) versus untreated HCAEC (9.2 ± 1.0 vs 3.3 ± 1.1 μmol/μg protein/μL). Findings suggest that DHA enhances eNOS and Akt activity, augments HSP90 expression, and increases NO bioavailability in response to Akt kinase activationItem Biological cost of tolerance to heavy metals in the mosquito Anopheles gambiae(2010) Mireji, PO; Keating, J; Hassanal, A; Mbogo, CM; Muturi, MN; Githure, JI; Beier, JCThe global rate of heavy metal pollution is rapidly increasing in various habitats. Anopheles malaria vector species (Diptera: Culicidae) appear to tolerate many aquatic habitats with metal pollutants, despite their normal proclivity for ‘clean’ water (i.e. low levels of organic matter). Investigations were conducted to establish whether there are biological costs for tolerance to heavy metals in Anopheles gambiae Giles sensu stricto and to assess the potential impact of heavy metal pollution on mosquito ecology. Anopheles gambiae s.s. were selected for cadmium, copper or lead tolerance through chronic exposure of immature stages to solutions of the metals for three successive generations. Biological costs were assessed in the fourth generation by horizontal life table analysis. Tolerance in larvae to cadmium (as cadmium chloride, CdCl2), copper [as copper II nitrate hydrate, Cu(NO3)2 2.5 H2O] and lead [as lead II nitrate, Pb(NO3)2], monitored by changes in LC50 concentrations of the metals, changed from 6.07 µg/L, 12.42 µg/L and 493.32 µg/L to 4.45 µg/L, 25.02 µg/L and 516.69 µg/L, respectively, after three generations of exposure. The metal-selected strains had a significantly lower magnitude of egg viability, larval and pupal survivorship, adult emergence, fecundity and net reproductive rate than the control strain. The population doubling times were significantly longer and the instantaneous birth rates lower in most metal-selected strains relative to the control strain. Our results suggest that although An. gambiae s.s. displays the potential to develop tolerance to heavy metals, particularly copper, this may occur at a significant biological cost, which can adversely affect its ecological fitness.Item Expression of metallothionein and [alpha]-tubulin in heavy metal-tolerant(2010) Mireji, PO; Keating, J; Hassanali, A; Impoinvil, DE; Mbogo, CM; Muturi, MN; Nyambaka, H; Kenya, EU; Githure, JI; Beier, JCItem Expression of metallothionein and α-tubulin in heavy metal-tolerant Anopheles gambiae sensu stricto (Diptera: Culicidae)(2010) Mireji, Paul O; Keating, Joseph; Hassanali, Ahmed; Impoinvil, Daniel E; Mbogo, Charles M; Muturi, Martha N; Nyambaka, Hudson; Kenya, Eucharia U; Githure, John I; Beier, John CAnopheles mosquitoes have been shown to adapt to heavy metals in their natural habitats. In this study we explored the possibility of using Anopheles gambiae sensu stricto as bio-reporters for environmental heavy metal pollution through expressions of their metal-responsive metallothionein and α-tubulin genes. The study was undertaken with third instar larvae after selection by cadmium, copper, or lead at LC30 through five successive generations. Expression levels were determined in the 5th generation by semi-quantitative RT-PCR on the experimental and control populations. The data were analyzed using one-way ANOVA. The highest metallothionein (F3, 11=4.574, P=0.038) and α-tubulin (F3, 11=12.961, P=0.002) responses were observed in cadmium-tolerant treatments. There was significantly higher expression of metallothionein in cadmium or copper treatments relative to the control (P=0.012), and in cadmium than in lead treatments (P=0.044). Expressions of α-tubulin were significantly higher in cadmium than in control treatments (P=0.008). These results demonstrate the capacity of An. gambiae s.s. to develop tolerance to increased levels of heavy metal challenge. The results also confirm the potential of heavy metal-responsive genes in mosquitoes as possible bio-indicators of heavy metal environmental pollution. How the tolerance and expressions relate to An. gambiae s.s. fitness and vectorial capacity in the environment remains to be elucidated.Item Impact of aging vs. estrogen loss on cardiac gene expression: estrogen replacement and inflammation(2011) Pechenino, Angela S; Lin, Li; Mbai, Fiona N; Lee, Alison R; He, Xian-Min; Stallone, John N; Knowlton, AADespite an abundance of evidence to the contrary from animal studies, large clinical trials on humans have shown that estrogen administered to postmenopausal women increases the risk of cardiovascular disease. However, timing may be everything, as estrogen is often administered immediately after ovariectomy (Ovx) in animal studies, while estrogen administration in human studies occurred many years postmenopause. This study investigates the discrepancy by administering 17β-estradiol (E2) in a slow-release capsule to Norway Brown rats both immediately following Ovx and 9 wk post-Ovx (Late), and studying differences in gene expression between these two groups compared with age-matched Ovx and sham-operated animals. Two different types of microarray were used to analyze the left ventricles from these groups: an Affymetrix array (n = 3/group) and an inflammatory cytokines and receptors PCR array (n = 4/group). Key genes were analyzed by Western blotting. Ovx without replacement led to an increase in caspase 3, caspase 9, calpain 2, matrix metalloproteinase (MMP)9, and TNF-α. Caspase 6, STAT3, and CD11b increased in the Late group, while tissue inhibitor of metalloproteinase 2, MMP14, and collagen I α1 were decreased. MADD and fibronectin were increased in both Ovx and Late. TNF-α and inducible nitric oxide synthase (iNOS) protein levels increased with Late replacement. Many of these changes were prevented by early E2 replacement. These findings suggest that increased expression of inflammatory genes, such as TNF-α and iNOS, may be involved in some of the deleterious effects of delayed E2 administration seen in human studiesItem Deciphering the reproductive protein-protein interaction network in Anopheles gambiae with Drosophila melanogaster as a framework(2011) Achinko, Daniel; Mireji, Paul O; Catteruccia, Flaminia; Masiga, DanProtein-protein interactions (PPIs) are the most fundamental biological processes at the molecular level. The experimental methods for testing PPIs are time-consuming and are limited by analogs for many reactions. As a result, a computational model is necessary to predict PPIs and to explore the consequences of signal alterations in biological pathways. Reproductive control of the vector Anopheles gambiae using transgenic techniques poses a serious challenge. To meet this challenge, it would help to define the biological network involving the male accessory gland (MAG) proteins responsible for successful formation of the mating plug [1]. This plug forms in the male and is transferred to the female during mating, hence initiating the PPIs in both sexes. As is the case in Drosophila melanogaster, a close relative of A. gambiae, some MAG proteins responsible for the formation of the mating plug have been shown to alter the post-mating behavior of females.Item Life stage and tissue speciation of cathepsin B (AGAP004533) derives different functional properties in the G3 strain of the mosquito Anopheles gambiae(2012) Achinko, Daniel; Masiga, Dan; Mireji, Paul O; Catteruccia, FlaminiaCathepsin B is a lysosomal papain-like cysteine peptidase that is expressed in all tissues and functions primarily as an exopeptidase through its carboxydipeptidyl activity. Together with other cathepsins, it is involved in the degradation of proteins, proenzyme activation, antigen processing, metabolism and apoptosis. AGAP004533 is a cathepsin B peptidase of 337 amino acids known to be found on the mating plug. This plug is known to be produced in the male Anopheles gambiae mosquito and transferred to the female during mating [1]. The female digests this plug in 24 h. The protein is expressed in all life stages of the mosquito and in all tissues of the adult. We cloned and sequenced the protein in the larvae and pupae stages and all reproductive tissues (spermatheca, atria and ovary of the female; testes and male accessory glands (MAGs) of the male) of the G3 mosquito strain. These sequences were analysed with Geneious 5.5.5 and cLc workbench 6.6.1 software. Within the coding sequence, two single mutations at C584T (juvenile stages) and nucleotide A14T (ovary) were identified. The latter translates into a glutamine for leucine (Q6L), which causes the loss of the signal peptide due to loss of five amino acids at the N-terminal region of the protein sequence, meanwhile the former translates into an alanine for valine (A195V). Both mutations cause structural modifications within the secondary structure of the protein that eventually affect its 3D conformation. The sequences in the artria and spermatheca showed insertion of a cytosine at nucleotide 1010, which translates to a proline for a leucine (P337L) substitution, and hence loss of the stop codon at amino acid 338. This loss causes an extension of 14 amino acids at the carboxylic end of the protein, resulting in secondary structure modification. The sequence for the testes appeared transposed, and hence was not considered in the analysis. All the sequences translated on the same frame except for that of the ovary, which translated on a different frame. Protein BLAST of these sequences at NCBI using the blosum62 matrix, identified with AGAP004533 of Anopheles gambiae alongside other mosquito species, although that of the artria and spermatheca also identified with species of distant taxa such as Manduca sexta (FM957999.1) and Gallus gallus (NM205371.1). This relation was due to the amino acid extensions at the carboxylic end relating to parasite killing in the former, and embryonic apoptosis in the latter. Transcription factor predictions on all sequences identified equal binding sites (T00821, T00752), and that of the male accessory glands identified an extra binding site (T00360) known in humans as a bifunctional protein nuclear cytoplasmic O-N-acetylglucosaminidase and acetyltransferase. This site also has alternative splicing functions, which could be important for the variations observed in this gene. Sequence variations of this protein in the different stages and tissues of the mosquitoes may also be highly related to their functions and relative positions in the same or different biological processes within the various tissues. In-depth analysis of the reproductive role of AGAP004533 will help in reproductive control of the vectorItem Changes in genotypes of Plasmodium falciparum human malaria parasite following withdrawal of chloroquine in Tiwi, Kenya(Elsevier, 2012) Mang’era, Clarence M.; Mbai, Fiona N; Omedo, Irene A; Mireji, Paul O; Omar, Sabah AChloroquine (CQ) drug was withdrawn in 1998 as a first-line treatment of uncomplicated malaria in Kenya. This was in response to resistance to the drug in Plasmodium falciparum malaria parasite. Investigations were conducted to determine prevalence of CQ resistance genotypes in the parasites in Tiwi, a malaria endemic town in Kenya, before and about a decade after the withdrawal of the drug. Blood samples were collected and spotted on filter papers in 1999 and 2008 from 75 and 77 out-patients respectively with uncomplicated malaria. The sampling was conducted using finger pricking technique. DNA was extracted from individual spots in the papers and screened for the presence of P. falciparum chloroquine resistance transporter (Pfcrt) and multi drug resistance (Pfmdr-1) markers using nested PCR. Nature of mutations (haplotypes) in the Pfcrt and Pfmdr-1 markers in the samples were confirmed using dot blot hybridization technique. Changes in pattern of CQ resistance in the parasite samples in 1999 and 2008 were assessed by Chi Square test. There was a significant (P < 0.05) reduction in CQ resistant genotypes of the parasite between 1999 and 2008. Pfmdr and Pfcrt CQ resistant genotypes in 2008 reduced to 54.10 and 63.64% respectively, from 75.39 and 88.0% respectively in 1999. This reduction was accompanied by emergence of Pfcrt specific CQ sensitive (IEK) and intermediate/partially CQ resistant (MET) haplotypes. Results suggest significant reversal of the phenotype of the parasite from chloroquine resistant to wild/sensitive type. The novel haplotypes indicates transitional phase of the parasite to the wild type. Current prevalence of chloroquine resistant genotype is definitely above the threshold for efficacious re-introduction of chloroquine for treatment of malaria in Tiwi.Item A Venue-Based Approach to Reaching MSM, IDUs and the General Population with VCT: A Three Study Site in Kenya(2012) Singh, Kavita; Brodish, Paul; Mbai, Fiona N; Kingola, Nzioki; Rinyuri, Agnes; Njeru, Carol; Mureithi, Patrick; Sambisa, William; Weir, SharonA venue-based HIV prevention study which included Voluntary Counseling and Testing (VCT) was conducted in three diverse areas of Kenya—Malindi, Nanyuki and Rachounyo. Aims of the study were to: (1) assess the acceptability of VCT for the general population, men who have sex with men (MSM), and injecting drug users (IDUs) within the context of a venue-based approach; (2) determine if there were differences between those agreeing and not agreeing to testing; and (3) study factors associated with being HIV positive. Approximately 98% of IDUs and 97% of MSM agreed to VCT, providing evidence that populations with little access to services and whose behaviors are stigmatized and often considered illegal in their countries can be reached with needed HIV prevention services. Acceptability of VCT in the general population ranged from 60% in Malindi to 48% in Nanyuki. There were a few significant differences between those accepting and declining testing. Notably in Rachuonyo and Malindi those reporting multiple partners were more likely to accept testing. There was also evidence that riskier sexual behavior was associated with being HIV positive for both men in Rachounyo and women in Malindi. Overall HIV prevalence was higher among the individuals in this study compared to individuals sampled in the 2008–2009 Kenya Demographic and Health Survey, indicating the method is an appropriate means to reach the highest risk individuals including stigmatized populations.Item Reply to “Letter to the Editor: ‘Understanding the WHI gap’(2012) Pechenino, Angela S; Lee, Alison R; Lin, Li; Mbai, Fiona N; Stallone, John N; Knowlton, AAThis is a reply in response to Drs. Kerber's and Turner's commentary about our article (10) in Physiological Genomics. We thank Kerber and Turner for their enthusiastic response to our article and are pleased that they found it useful in their practice (10). However, we would like to point out that the link between estrogen therapy postmenopause and a decrease in dementia in older women is tenuous at best. Few studies indicate definitively that hormone replacement therapy (HRT) results in a decrease in dementia, and most only point toward a possibility that has yet to be realized (5). Basic studies in rodent models suggest that estrogen replacement can reduce brain injury in models of stroke, but more work is needed before taking these findings to the clinical setting (1). Additionally, the Women's Health Initiative (WHI) and the Million Woman Study indicate that breast cancer risk increases significantly when women are put on HRT, specifically with estrogen and progesterone taken in combination, a finding that should limit the use of HRT to those women who do not already manifest a high risk for breast cancer (2, 9). In contrast to chronic estrogen replacement, there is a small, but growing, literature supporting a role for a protective role of estrogen in acute injury (11–13). We and others have found that treatment with a high concentration of 17β-estradiol at the time of injury can greatly reduce inflammation and apoptosis (3, 4, 6, 14). Such limited use of E2 will not increase the risk of cancer but does have the possibility of greatly reducing tissue injury. We feel that a more promising area for the treatment of postmenopausal symptoms comes from the selective estrogen receptor modulators (SERMs). For example, raloxifene improved verbal memory in postmenopausal women when given over a period of 5 yr.(7) In contrast tamoxifen, a SERM that is primarily an estrogen antagonist, was associated with poorer performance on letter fluency and manual dexterity in women with breast cancer compared with untreated controls (8). Many SERMs have been synthesized, and some may have the positive, protective effects of estrogen without promoting cell proliferation and cancer. More work will be needed identifying the specific effects of these compounds before this type of treatment can be applied in the clinic to ameliorate aging-associated changes such as cardiovascular disease and dementiaItem Rapid Activation of Nuclear Factor-κB by 17β-Estradiol and Selective Estrogen Receptor Modulators: Pathways Mediating Cellular Protection(2012) Stice, James P; Mbai, Fiona N; Chen, Le; Knowlton, Anne A17 β -estradiol (E2) treatment activates a set of protective response that have been found to protect cells from injury and more importantly to significantly abate the injuries associated with trauma- hemorrhage in vivo . Rapid NF κ B activation has been found to be an important signaling step in E2 mediated protection in cell culture, in vivo ischemia and trauma-hemorrhage. In the current study, we investigated the signaling cascades linking E2 signaling with NF κ B activation and the protective response, and compared them with the effects of two selective estrogen receptor modulators (SERMs), raloxifene and tamoxifen. Two candidate pathways, mitogen activated protein kinases (MAPK), and phosphatidylinositol-3-kinase (PI3-K) were studied. Selective inhibitors were used to identify each pathway's contribution to NF κ B activation. Treatment of HCAECs with E2 activated PI3-K/Akt, p38, and JNK, all of which activated ERK 1/2 followed by NF κ B activation. The combined activation of Akt, p38 and JNK was essential to activate NF κ B. The two SERMs activated PI3-K and p38, which then phosphorylated ERK 1/2 and activated NF κ B independent of the JNK pathway. NFkB activation by these compounds protected cells from hypoxia/reoxygenation injury. However, E2, unlike either SERM, led to modest increases in apoptosis through the JNK pathway. SERM treatment led to increased expression of the protective proteins, Mn-superoxide dismutase and endothelial nitric oxide synthase, that was not seen with E2. These results provide new insight into the pathways activating NFkB by E2 and SERMS and demonstrate that SERMs may have greater protective benefits than E2 in adult endothelial cells and potentially in vivo , as wellItem Juvenile hormone and insulin suppress lipolysis between periods of lactation during tsetse fly pregnancy(Elsevier, 2013) Baumann, Aaron A; Benoit, Joshua B; Michalkova, Veronika; Mireji, Paul O; Attardo, Geoffrey M; Moulton, John K; Wilson, Thomas G; Aksoy, SerapTsetse flies are viviparous insects that nurture a single intrauterine progeny per gonotrophic cycle. The developing larva is nourished by the lipid-rich, milk-like secretions from a modified female accessory gland (milk gland). An essential feature of the lactation process involves lipid mobilization for incorporation into the milk. In this study, we examined roles for juvenile hormone (JH) and insulin/IGF-like (IIS) signaling pathways during tsetse pregnancy. In particular, we examined the roles for these pathways in regulating lipid homeostasis during transitions between non-lactating (dry) and lactating periods. The dry period occurs over the course of oogenesis and embryogenesis, while the lactation period spans intrauterine larvigenesis. Genes involved in the JH and IIS pathways were upregulated during dry periods, correlating with lipid accumulation between bouts of lactation. RNAi suppression of Forkhead Box Sub Group O (FOXO) expression impaired lipolysis during tsetse lactation and reduced fecundity. Similar reduction of the JH receptor Methoprene tolerant (Met), but not its paralog germ cell expressed (gce), reduced lipid accumulation during dry periods, indicating functional divergence between Met and gce during tsetse reproduction. Reduced lipid levels following Met knockdown led to impaired fecundity due to inadequate fat reserves at the initiation of milk production. Both the application of the JH analog (JHA) methoprene and injection of insulin into lactating females increased stored lipids by suppressing lipolysis and reduced transcripts of lactation-specific genes, leading to elevated rates of larval abortion. To our knowledge, this study is the first to address the molecular physiology of JH and IIS in a viviparous insect, and specifically to provide a role for JH signaling through Met in the regulation of lipid metabolism during insect lactation.Item RESEARCH Open Access Sex-specific induction of CYP6 cytochrome P450 genes in cadmium and lead tolerant Anopheles gambiae(2013) Musasia, Fauzia K; Isaac, Alfred O; Masiga, Daniel K; Omedo, Irene A; Ochieng, Richard; Mireji, Paul O; Mwakubambanya, RamadhanBackground: Anopheles gambiae, one of the main Afro-tropical mosquito vector of malaria, has adapted to heavy metals in its natural habitat, and developed resistance to most conventional insecticides. Investigations were conducted to establish an association between tolerance to cadmium or lead-heavy metals, and expression of specific genes for cytochrome p450 enzymes associated with pyrethroid resistance in the mosquito. Methods: Juvenile aquatic stages of the mosquito were selected for tolerance to cadmiun or lead through chronic exposure of the stages to maximum acceptable toxicant concentrations (MATCs) of the metals. Using real-time quantitative polymerase chain reaction (qPCR), three replicates each of male or female cadmium or lead-tolerant individuals and relevant controls were separately screened for expression of CYP6M2 , CYP6P3 and CYP6Z1 genes. The variance in expression levels of the genes amongst the treatments was compared by ANOVA statistical tool. Results: Expressions of all the genes were significantly lower (P <0.05) in females than in males. Within gender, there 1.3 - 2.3 or 3.1-4.2-fold reduction in expression of the genes in cadmium or lead selected than respective control populations. Expression of all the classes of gene was elevated in cadmium selected female populations relative to their respective controls. Conclusion: These findings suggest that tolerance to cadmium or lead in the mosquito can influence response in cytochrome p450 genes associated with metabolism of pyrethroids in the mosquito in a sex-specific manner. This can, in turn, affect sensitivity of the mosquito to pyrethroids and other xenobiotics associated with these genes, with potential implications in mosquito vector control operations.Item In vitro Anti-plasmodial Activity of Rubia cordifolia, Harrizonia abyssinica, Leucas calostachys Olive and Sanchus schweinfurthii Medicinal Plants.(2013) Nyambati, GK; Lagat, ZO; Maranga, RO; Samuel, M; Ozwara, HPlasmodium falciparum is becoming increasingly resistant to conventional antimalaria drugs. Rapid increase of parasite resistant strains, resistance of the vector to insecticides and the difficulty in creating efficient vaccines has lead to an urgent need for new anti-malarial drugs. To determine anti-plasmodial activity of Rubia cordifolia, Harrizonia abyssinica, Sachus schweinfurthii and Leucas calostachys Olive plants. Aqueous and methanolic crude extracts were prepared from R. cordifolia, H. abyssinica, S. schweinfurthii and L. calostachys plants. The extracts were then prepared into appropriate concentrations for anti-plasmodial activities. In vitro anti-plamsodial activities of herbal drugs were analysed according to the methods of Tona et al., 1999. Methanolic extracts were more efficacious than aqueous extracts. S. schweinfurthii and L. calostachys had IC50 (Inhibition Concentration) of between 1.10μg/ml and 3.45μg/ml and had highest parasite inhibition ranging between 3.5% and 5.2%. R. cardifolia and H. abyssinica had IC50 of between 1.5μg/ml and 3.0μg/ml and it had moderate parasitaemia ranging between 5.20% and 7.22%. Vernonia lasiopa and Erythrina abysinnica had insufficient yields. S. schweinfurthii and L. calostachys had the highest parasite inhibition while R. cardifolia and H. abyssinica had moderate inhibition