Browsing by Author "Hassanali, A."

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    Biochemical changes in developing embryos of Schistocerca gregaria (orthoptera: acrididae) induced by pheromone produced by ovipositing gregarious females.
    (Cambridge University Press, 2015) Khamis, Fathiya M.; Mireji, Paul O.; Osir, E. O.; Imbuga, M.O.; Hassanali, A.
    Trans-generational transfer of gregarious-phase traits in the desert locust Schistocerca gregaria (Forska°l, 1775) is mediated by primer gregarizing pheromonal signals produced by ovipositing females that experience crowding. We monitored time-course proteomic events in eggs from solitary-reared locusts that had been exposed for 1, 3, 5, 7, 10 and 12 days to different levels of the sand-associated gregarizing signal originating from 0, 3, 5 or 10 ovipositions by crowd-reared females. Evidence for the phase transition was sought by comparing the protein patterns of embryos thus exposed with those from crowd-reared (gregarious) controls; this comparison was continued until the stage of the first instars. Expressed proteins were analysed by two-dimensional protein gel electrophoresis, and patterns from the different treatments within stages were compared by profile matching and x 2 analyses. Eggs derived from crowd- and solitary-reared females showed essentially similar protein patterns at early stages of embryogenesis; however, mature stages (particularly, days 10 and 12) and hatchlings demonstrated significantly different patterns. Protein patterns of eggs from solitary-reared females that were incubated in sand contaminated with the pheromonal signal and of the hatchlings that emerged were similar to those derived from gregarious females and dependent on the level of the pheromone to which the embryos had been exposed. The results confirm the gregarizing effect of the signal and constitute a useful basis for unravelling the mechanism of the signalling cascades associated with gene expressions triggered by the pheromone.
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    Constituents of Commiphora Rostrata and Some of their Analogues as Maize Weevil, Sitophilus Zeamais Repellents
    (Cambridge University Press, 1992-10-01) Hassanali, A.; Lwande, W.; Mcdowell, P. G.; Moreka, L.; Nokoe, S. K.; Waterman, P. G.
    The major alkanone constituents of the resin of Commiphora rostrata, 2-decanone and 2-undecanone, and a series of structural analogues were bioassayed for their repellency against the maize weevil, Sitophilus zeamais in olfactometric assays. All the aliphatic ketones and aldehydes showed comparable or greater activity than the synthetic commercial insect repellent N, N-diethyl toluamide (DEET). In the 2-alkanone series the C-8 and C-9 compounds demonstrated significantly higher activity than their shorter- and longer-chained congeners. Analogues differing in the relative positions of the carbonyl group, including aldehydes, showed a variable pattern of repellency. Alkanols appeared to be mildly attractive to the weevil. The results support our previous suggestion that the resin constituents may play an allomonal role in the ecosystem where the plant thrives.
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    Larvicidal activity of Kotschya uguenensis plant powders and methanol extracts against Anopheles gambiae s.s. larvae in the laboratory and in simulated ponds
    (2013-02) Innocent, E.; Nkunya, M. H. H.; Hassanali, A.
    Polar constituents of Kotschya uguenensis Verdc. (Fabaceae) do not exhibit acute toxicity but cause growth disruption of Anopheles gambiae s.s. Gile (Diptera: Culicidae) larvae with eventual death. Time-course larvicidal effects of powders of root and stem barks and their crude methanol extracts in form of emulsions were compared in the laboratory and in artificial semi-field ponds. Kotschya uguenensis powders of root and stem barks and emulsions of their crude methanol extracts were assayed against A. gambiae s.s according to protocols of WHO 1996 & 2005. All formulations were equally effective under laboratory conditions giving 100% larval mortality within three days at a dose of 50 μg/ml of the extracts or concentrations of powders corresponding to the same level of extractable material. Under semi-field conditions, suspensions of the powder materials appeared to perform better than emulsions of methanol extracts. Time taken to give 80% mortality (LT80) of larvae and pupa at 0.1% w/v was 6.06 days for powders of root bark and 5.60 days for powders of stem bark. The LT80 for the root bark extract at 200 μg/ml was 8.28 days while that for the stem bark methanol extract was 12.47 days. No residual effects of the test materials on the larvae or pupae were evident in semi-field ponds 14 days after the re-introduction of the test materials. Our results suggest that, for the control of anophelines in the field, a weekly application of appropriate amounts of powders of K. uguenensis may be effective.
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    Molecular Identification and Antibiotic Susceptibility Patterns of Bacterial Isolates from Urine Samples of African Buffalo, Eland and Cattle
    (International Journal of Applied Biology, 2021-07-03) Musonye, H. A.; Njeru, E. M.; Hassanali, A.; Langata, L. M.; Nonoh, J.
    Presence of antibiotic resistant bacteria in natural environment is an escalating risk of serious implication on human and animal health. Livestock and wildlife have been long recognized as reservoirs for antibiotic resistant bacteria. Nonetheless, there is limited knowledge regarding the potential of livestock and wildlife urine to act as transmission corridor for the spread of antibiotic resistant bacteria. The present study aimed at evaluating antibiotic susceptibility patterns and molecular identification of bacteria isolated from livestock and wildlife urine samples. A total of 19 different bacteria isolated from urine samples of African buffalo, eland and cattle were subjected to antibiotic susceptibility test. The isolates showed diverse susceptibility patterns against co-trimoxazole, tetracycline, amoxycillin, ciprofloxacin, streptomycin, nalidixic acid, chloramphenicol and gentamicin. Of the tested isolates, 73.7 % were exhibited resistance while 31.6 % were intermediate to the range of antibiotics tested. High resistance prevalence to amoxicillin (58%), tetracycline (26 %) and cotrimoxazole (11%) by the tested bacteria was observed. This study reveals the bacteria associated with African buffalo, eland and cattle urine as potential candidates for antibiotic resistance. This information demonstrates the need for measures to be adopted to limit the presence of antibiotic resistant bacteria in wildlife and livestock reservoirs.
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    Repellency of Tsetse-refractory Waterbuck (Kobus defassa) Body Odour to Glossina pallidipes (Diptera: Glossinidae): Assessment of Relative Contribution of Different Classes and Individual Constituents.
    (Elsevier, 2015) Bett, M. K.; Saini, R. K.; Hassanali, A.
    Our earlier studies on the comparative behavioural responses of caged savanna tsetse (Glossina morsitans morsitans and Glossina pallidipes) on a preferred host (ox) and a non-host (waterbuck) suggested the presence of allomonal constituents on the latter. Follow up comparison of the compositions of odours of waterbuck with those of ox and buffalo led to the identification of a series of compounds (15) specific to waterbuck, including straight chain carboxylic acid (C5-C10), phenols (guaiacol and carvacrol), 2-alkanone homologues (C8-C12), geranylacetone and δ-octalactone. Behavioural studies in a windtunnel in the laboratory suggested that G. m. morsitans was repelled by a synthetic blend of waterbuck-specific constituents. In the present study, the effects of different blends of these compounds on catches of mixed sexes of G. pallidipes in attractant-baited NG2G traps were evaluated in the field. Each multicomponent class of constituents (acids, ketones and phenols) was found to reduce fly catches, but a 14-component blend of all these compounds was more effective (reduced catches by 79-85%), indicating that each of these classes of compounds contributes incrementally to the repellency of the waterbuck odour. However, subtractive assays showed some redundancy within each class of compounds, with some even demonstrating attractive properties. Addition of (RS)-δ-octalactone to the 14-component significantly increased the repellency of the resulting blend. A 5-component blend of compounds selected on the basis of their relative performance in subtractive assays (δ-octalactone, guaiacol, geranylacetone, hexanoic and pentanoic acid) showed substantial reduction in fly catches (84%) relative to the baited control. In separate sets of experiments involving an ox tethered in the middle of an incomplete ring of electric screens in the presence or absence of 15-component or 5-component blends, comparable levels in the reduction of fed flies (94 and 96%, respectively) were obtained with the two blends. The chemo-ecological significance and practical implication of these results are highlighted.
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    Semi-field evaluation of the effects of sub-lethal doses of pesticides, with and without adult Schistocerca gregaria pheromone, on hoppers
    (Wiley, 2016) Magzoub, B.; Hassanali, A.; Korena, H.; Widaatalla, A.
    Previously, we reported a chain of effects induced by phenylacetonitrile, the gregarious-phase adult cohesion pheromone of the desert locust, Schistocerca gregaria (Forsk al) (Orthoptera: Acrididae), on conspecific hoppers. Specifically, the nymphs became hyperactive and displayed high levels of intraspecific predation, as surviving individuals gradually shifted to the solitary phase. The findings suggested that the pheromone could induce a significant level ofmortality of the nymphs and predispose them to greater sensitivity to lower doses of insecticides. In this study, we compared the effects of the pheromone and various doses of three pesticides (fipronil, malathion, and carbosulfan) to pheromone-exposed and unexposed crowd-reared hoppers in semi-field enclosures. The pheromone on its own displayed a high level of cumulative mortality of the nymphs (89%). Although combinations with fractional pesticide doses gave control efficiencies that were, in most cases, higher than with individual pesticides, pheromonal and pesticidal effects were only partially complementary, probably because of the feeding-deterrent effects of the pesticides and the resulting reduction in cannibalism. However, our results demonstrate the possibility of significantly reducing the levels of pesticides used in hopper control and, thus, their negative environmental effects