Faculty of Applied Science and Technology

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    Glutathione S-Transferases: α-Naphthyl Acetate Activity and Possible Role in Insecticide Resistance
    (1995) Lalah, Joseph O; Chien, Cheng-I; Motoyama, Naoki; Dauterman, Walter C
    Rat liver and house fly, Musca domestica L., glutathione S-transferases were purified by affinity chromatography and chromatofocusing. The specific activity with α-naphthyl acetate (a substrate, for general esterase activity) was determined. Some of the esterase activity that is normally assayed for resistance is apparently caused by the activity of the glutathione S-transferase.
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    The Persistence and Fate of Malathion Residues in Stored Beans (Phaseolus vulgaris) and Maize (Zea mays)
    (1996) Lalah, Joseph O; Wandiga, Shem O
    Two experimental models simulating the traditional storage conditions prevalent in Kenya, i.e. the open basket model and the modern wooden box model, were used to study the rate of dissipation and fate of malathion residues in maize grains and beans stored for periods of up to one year at ambient temperatures averaging 23°C. The grain samples were initially treated with 10·36 mg kg−1 of radiolabelled malathion dust prior to storage and portions analysed at regular intervals for malathion, malaoxon and the transformation products isomalathion, malathion α-monocarboxylic acid and malathion β-monocarboxylic acid using a combination of chromatographic, radioisotopic and mass-spectrometric techniques. The findings showed a gradual penetration of malathion into the grains in amounts which were slightly higher in maize than in beans irrespective of the method of storage. After 51 weeks of storage, 34–60% of the initial residues persisted in all the grains. The total residual levels were slightly higher in beans than in maize irrespective of the storage methods though the persistence was a little higher in the wooden box than in the open basket. The rates of dissipation of the pesticide from the grains decreased with storage time and followed a biphasic pattern. Applying first-order reaction kinetics, the following half-lives were obtained: maize grains stored in open basket: 194 days; maize grains stored in closed wooden box: 261 days; beans stored in open basket: 259 days; beans stored in closed wooden box: 405 days. Beans stored in the wooden box had higher levels of bound residues than those sampled from the open basket. This trend was similar in maize grains although the concentrations were lower. The analysis of malathion metabolites confirmed the degradation trend of the residues.
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    The metabolism and distribution of [14C‐phenyl]‐ethyl parathion in a tropical soil under field conditions
    (1999) Lalah, Joseph O; Wandiga, Shem O
    The persistence, distribution and metabolism of [l4C‐phenyl]‐ethyl parathion applied to soil columns in an agricultural farm were investigated under tropical field conditions. Volatilization, soil microbial activity, moisture levels and pH were found to influence the persistence, distribution and metabolism of this pesticide in the soil. There was rapid distribution of the pesticide in the soil matrix with time resulting in high levels of bound residues which reduced the overall rate of disappearance of parathion residues from the soil. The soil was slightly acidic but the metabolites, paraoxon, p‐nitrophenol and p‐aminophenol were detected in the soil extracts 7 days after pesticide application. After 72 days, 43.7% of the applied pesticide remained in soil composed of 18.9% extractable and 24.8% bound residues. A mechanism for the metabolism of ethyl parathion in this soil is given.
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    Regioselective Synthesis of a Branched Isomer of Nonylphenol, 4-(3′,6′-Dimethyl-3′-heptyl)phenol, and Determination of its Important Environmental Properties
    (2001) Lalah, Joseph O; Schramm, Karl-Werner; Lenoir, Dieter; Henkelmann, Bernhard; Hertkorn, Norbert; Kettrup, Antonius; Günther, Klaus
    A method for the synthesis of a pure nonylphenol isomer, 4-(3′,6′-dimethyl-3′-heptyl)phenol, by Friedel–Crafts reaction between anisole and 3-bromo-3,6-dimethylheptane that gives a 47.3 % overall yield is reported. The reactions were followed by GC-MS, and the chemical structures are in agreement with the NMR and IR spectra. The log Kow value for this compound, its water solubility, vapor pressure, and Henry's Law constant were also determined. These physicochemical properties were required for prediction of the compound's behavior in aquatic ecosystems.
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    The effect of boiling on the removal of persistent malathion residues from stored grains
    (Elsevier, 2002) Lalah, Joseph O; Wandiga, Shem O
    This study aimed at finding the fate of malathion in maize grains and beans stored in a tropical laboratory for 12 months at temperatures of 20–24°C, relative humidity of 42–80% and grain moisture contents of 11.7–12.5% in maize grains and 14.1–15.3% in beans. Malathion and its degradation products malaoxon, malathion α-monocarboxylic acid and β-monocarboxylic acid were found in stored maize grains and beans treated with a mixture of pure radiolabelled malathion and 2% malathion dust after 12 months of storage. A significant percentage of these residues were removed from the grains by cooking in boiling water. Though malathion and its polar metabolites, malathion α- and malathion β-monocarboxylic acids were completely eliminated by boiling, malaoxon was still detected in quite high quantities in the solvent extracts of cooked beans and maize. Addition of NaCl to the grains increased the rate of removal of the residues from both maize grains and beans by boiling water. The data obtained clearly showed a distinction in persistence, distribution and metabolism of malathion between the two types of crop, indicating also that more adverse windy, humid and hot tropical conditions contributed to higher rates of metabolism and loss of the pesticide from the grains. The accuracy and ease of using radiolabelled malathion in investigating its fate and behaviour in the two matrices is shown in this study.
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    The bioaccumulation and fate of a branched 14C-p-nonylphenol isomer in Lymnaea stagnalis L.
    (2003) Lalah, Joseph O.; Behechti, Akbar; Severin, Gabriele F; Lenoir, Dieter; Günther, Klaus; Kettrup, Antonius; Schramm, Karl-Werner
    A single branched isomer of p-nonylphenol, 4(3′,6′-dimethyl-3′-heptyl)-phenol, previously identified by gas chromatography-mass spectrometry as one of the major constituent isomers in p-nonylphenol (constituting approximately 10% of all its isomers), was synthesized and used in studies of its bioaccumulation and excretion in the hermophroditic pond snail Lymnaea stagnalis L. Branched isomers of nonylphenol are perceived to have more estrogenlike toxicity than the straight-chain isomers in addition to being more resistant to biodegradation in the environment. With an average static exposure concentration of 104 μg/L (range: 92–116 μg/L) in water at 19°C for 8 d, the uptake of the compound was found to be fairly rapid, reaching a peak concentration of 23,548 μg/kg of whole tissue wet weight after 5 d and a peak bioaccumulation factor (BAFw) of 242 (5,562, based on lipid weight) after 3 d. The uptake data fitted into a logarithmic expression C(t) = 5,231 ln(t) + 11,956, where C(t) is the amount of residues accumulated in whole tissue in micrograms per kilogram tissue wet weight after a period of time, t, and t is the period of exposure in days. By determination of the excretion of 14C-residues released in water and in feces, an average loss of 96% of the accumulated residues was achieved after 22 d of continuous exposure to clean water. By first-order kinetics analysis of the excretion data, an average half-life of excretion of 4.9 d was obtained. By high-performance liquid chromatography and gas-liquid chromatography-mass spectrometry, a catechol metabolite, 4(3′,6′-dimethyl-3′-heptyl)-catechol, was detected in tissue extracts (after hydrolysis with β-glucuronidase) and in feces, in addition to the parent isomer, suggesting that the isomer may have been metabolized by glucuronic acid conjugation and hydroxylation at the ortho position of its phenolic ring.
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    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, TNC
    Investigations 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.
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    Gender differences in cardiovascular disease: The effects of estrogen
    (2005) Mbai, Fiona N; Hamilton, Karyn L; Knowlton, Anne A
    Estrogen 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.
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    Polynuclear aromatic compounds in kerosene, diesel and unmodified sunflower oil and in respective engine exhaust particulate emissions
    (2005) Lalah, Joseph O; Kaigwara, Peter N
    Polynuclear aromatic compounds (PAC) were characterized in diesel fuel, kerosene fuel and unmodified sunflower oil as well as in their respective engine exhaust particulates. Diesel fuel was found to contain high amounts of different PAC, up to a total concentration of 14,740 ppm, including carbazole and dibenzothiophene, which are known carcinogens. Kerosene fuel was also found to contain high amounts of different PAC, up to a total concentration of 10,930 ppm, consisting mainly of lower molecular weight (MW) naphthalene and its alkyl derivatives, but no PAC component peaks were detected in the unmodified sunflower oil. Engine exhaust particulates sampled from a modified one-cylinder diesel engine running on diesel, kerosene and unmodified sunflower oil, respectively, were found to contain significantly high concentrations of different PAC, including many of the carcinogenic ones, in the soluble organic fraction (SOF). PAC concentrations detected at the exhaust outlet indicated that most of the PAC that were present in diesel and kerosene fuels before the test runs got completely burnt out during combustion in the engine whereas some new ones were also formed. The difference between the character and composition of PAC present in the fuels and those emitted in the exhaust particulates indicated that exhaust PAC were predominantly combustion generated. High amounts of PAC, up to totals of 52,900 and 4830 µg m−3 of burnt fuel, in diesel and kerosene exhaust particulates, respectively, were detected in the dilution tunnel when the exhaust emissions were mixed with atmospheric air. Significant amounts of PAC were also emitted when the engine was run on unmodified sunflower oil with a total concentration of 17,070 µg m−3 of burnt fuel detected in the dilution tunnel. High proportions of the combustion-generated PAC determined when the engine was run on diesel, kerosene and unmodified sunflower, respectively, consisted of nitrogen-containing PAC (PANH) and sulphur-containing PAC (PASH).
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    Astronomy in the cultural heritage of African societies
    (2006) Baki, Paul
    The African perspectives of astronomy are explored from the point of view of using indigenous knowledge of the night sky for purposes of addressing local challenges such as food insecurity and periodic natural weather phenomena such as droughts and floods. The local ethnic groups use stellar positions, and plant and animal behaviour changes for purposes of forecasting the weather and climate for the coming seasons. These traditional indicators give rise to an interdisciplinary discourse that could benefit the community in environmental protection measures and boost the tourism industry in some countries in Africa
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    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, John
    Investigations 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 pollution
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    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 C
    Concentrations 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.
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    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 A
    Endothelial 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 activation
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    Seasonal variability of persistent organochlorine pesticide residues in marine fish along the Indian Ocean coast of Kenya
    (Taylor & Francis, 2008-05-01) Lalah, Joseph O.; Barasa, M. W.; Wandiga, S. O.
    The adsorption behaviour of DDT in a tropical silt-clay soil from Kenya showed that addition of increasing metal ion concentrations from 10 to 100 lg/g of soil, reduced the % DDT adsorption in the soil by factors ranging from 6.1% to 15.4% depending on the type of metal ion. The inhibition of adsorption by metal ions was most observed in the lower ranges of metal ion concentrations in soil, i.e. up to 100 lg/g, beyond which additional increase in metal ion concentration did not result in any further increase in % adsorption. In the standard adsorption test procedure with different soil samples saturated with 100 lg/g of metal ions, the rate of adsorption of the pesticide varied with the type of metal ion and the equilibrium maximum adsorption of DDT was lowered with addition of metal ions, with the % adsorption of 78.4% (control) being reduced to lower values in the range of 67%–77.4%, depending on the type of metal ion. The data for control and samples fitted well into the Freundlich adsorption model and showed that addition of metal ions lowered the Kf values compared with control. The results suggested that in the natural soil–water environments where there was no disturbance, aggregation of humic substances-pesticide molecule complexes altered the observed lowering of adsorption caused by inhibition by metal ions, and enhanced binding to solid soil phase occurred instead. In the leaching experiments, DDT was found to leach more extensively in soils with lower %OC
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    Anthropogenic Sources of Heavy Metals in the Indian Ocean Coast of Kenya
    (Springer Science+Business Media, LLC, 2008-11-28) Lalah, Joseph O.
    Water and surface sediment samples from Rivers Sabaki, Ramisi and Vevesi that flow into the Indian Ocean coast of Kenya were analysed for heavy metals. The sediment concentrations of exchangeable cations (in μg/g) for Co, Cu, Mn, Ni, Pb, Sn and Zn ranged from 0.10 to 506.75 (for Mn at Sabaki), constituting between 2% and 20% of the total metal concentrations obtained by digestion with strong acid. Cu, Mn, Ni, Pb and Zn were more leachable with 0.1 N HCl. The total dissolved metal in water and the total sediment concentrations for Ag, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sn and Zn are given in the text. For dissolved metals, the metal/Mn ratios indicated higher concentrations of Ag in Sabaki River, Cd in Ramisi, Ni in Sabaki and Pb in Ramisi, respectively. In sediments, the metal/Mn ratios showed higher enrichment of Ag in Ramisi, Cd in Sabaki and Vevesi, and Zn in Sabaki, respectively. Enrichment factors showed elevated levels of Cd, Pb and Zn in sediment in River Sabaki and River Vevesi that were due to anthropogenic inputs through Athi River. The total dissolved metal concentration ranges for the three rivers were comparable with those ranges reported in rivers in South Africa but the sediment concentrations were below those of rivers in Europe and Asia where anthropogenic addition of some of the toxic elements such as Cu, Pb and Cd is evidently higher.
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    Spartial and Seasonal Variations in Concentrations of Polycyclic Aromatic Hydrocarbons in Water and Sediment of Kisumu City Bay of Winam Gulf, Lake Victoria-Kenya
    (2009) Kwach, Bowa O; Lalah, Joseph O; Wandiga, O. Shem
    Seasonal and offshore concentration variations for selected sixteen priority pollutant polycyclic aromatic hydrocarbons (PAHs) in surface sediments and water of Car Wash and Kisat areas of Winam Gulf, Lake Victoria, have been investigated. PAHs concentrations in sediments and water range from 0.4 to 31.95 μg/g dry weight and 3.32 to 55.8 μg/L, respectively. Statistical analysis of the PAHs concentrations showed that the most contaminated samples are found during rainy season (April, 2006), 5 m offshore for sediments and 10 m offshore for water. Dry season (October, 2005) generally recorded lower concentrations. The variations showed significant difference (p ≤ 0.05) with season and distance of sampling from the shore.
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    The dissipation of hexazinone in tropical soils under semi-controlled field conditions in Kenya
    (2009) Lalah, Joseph O; Muendo, Bonface M.; Getenga, Zachary M
    The dissipation of hexazinone (Velpar) in two tropical soil types in Kenya was studied under field and semi-controlled conditions for a period of 84 days. The dissipation was found to be very rapid and this could be attributed to adverse weather conditions including high initial rainfall as well as to low soil-organic-matter content, volatilization, surface run-off and biodegradation. The DT50 values of dissipation obtained by first order kinetics were 20 days and 21.3 days in clay and loam soil types, respectively. The influence of bargasse compost (1000 μg/g dry soil) was also studied and was found to enhance dissipation to some extent, giving DT50 values of 18 days and 18.3 days in clay and loam soil types, respectively.