BC-School of Pure and Applied Science

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Tryptophan Metabolism in Mice Infected with Schistosoma Mansoni
(Springer New York, 1991) Njagi, E.N.M.; Bender, D. A.
Biharzia due to infection with Schistosoma mansoni is a major and increasing problem in tropical countries, associated especially with irrigation schemes, which provide a habitat for the water snail which is the alternate host of the parasite. Infection results from bathing or other contact with water containing infected snails, which release large numbers of cer-cariae, the infectious form which penetrates human skin.
Phylogenetic analysis of the envelope HIV-1 type 1 isolates among Kenyan cohort
(American Society for Microbiology, 1999-05) Nyamache, A. K.; Muigai, A.W.T.; Khamadi, Samoel A.
In sub-Saharan Africa, where the effects of human immunodeficiency virus type 1 (HIV-1) have been most devastating, there are multiple subtypes of this virus. The distribution of different subtypes within African populations is generally not linked to particular risk behaviors. Thus, Africa is an ideal setting in which to examine the diversity and mixing of viruses from different subtypes on a population basis. In this setting, it is also possible to address whether infection with a particular subtype is associated with differences in disease stage. To address these questions, we analyzed the HIV-1 subtype, plasma viral loads, and CD4 lymphocyte levels in 320 women from Nairobi, Kenya. Subtype was determined by a combination of heteroduplex mobility assays and sequence analyses of envelope genes, using geographically diverse subtype reference sequences as well as envelope sequences of known subtype from Kenya. The distribution of subtypes in this population was as follows: subtype A, 225 (70.3%); subtype D, 65 (20.5%); subtype C, 22 (6.9%); and subtype G, 1 (0.3%). Intersubtype recombinant envelope genes were detected in 2.2% of the sequences analyzed. Given that the sequences analyzed represented only a small fraction of the proviral genome, this suggests that intersubtype recombinant viral genomes may be very common in Kenya and in other parts of Africa where there are multiple subtypes. The plasma viral RNA levels were highest in women infected with subtype C virus, and women infected with subtype C virus had significantly lower CD4 lymphocyte levels than women infected with the other subtypes. Together, these data suggest that women in Kenya who are infected with subtype C viruses are at more advanced stages of immunosuppression than women infected with subtype A or D. There are at least two models to explain the data from this cross-sectional study; one is that infection with subtype C is associated with a more rapid disease progression, and the second is that subtype C represents an older epidemic in Kenya. Discriminating between these possibilities in a longitudinal study will be important for increasing our understanding of the role of specific subtypes in the transmission and pathogenesis of HIV-1.
Enhancement of coffee quality in Kenya by prevention of mould current status and future outlook.
(Association Scientifique Internationale du Café, 2001-05) Gathaara, M. P. H.
A survey was conducted to find out the likely risk areas in the production chain namely, the primary and secondary processing facilities and in green coffee warehouses of the marketing body. Results indicated that there were conditions such as leaking roofs, crevices in the tools, and long storage periods that could favour growth of moulds. The recommended processing procedures, the survey, and the activities proposed as Kenya's contribution to the global project on coffee quality improvement thorough prevention of mould growth are described.
Effects of Climate and Human Activities on the Ecosystem of Lake Baringo, Kenya
(Springer Netherlands, 2002) Aloo, P. A.
Since the beginning of the last century, the Lake Baringo ecosystem has undergone several ecological changes. Most of the changes are a result of human activities within the catchment basin and changes in climatic conditions. Currently, the most significant limnological feature of the lake is its extreme turbidity with an average secchi disc reading of 9.5 cm. The lake water is brownish and muddy because of considerable siltation resulting from high rates of soil erosion caused by overgrazing by livestock and deforestation of the surrounding hills. Due to increased siltation, the bed of the lake in the open waters is virtually devoid of invertebrate life. Primary production in the open waters is very low as the only phytoplankton present are positively buoyant species such as Microcystis aeruginosa, Melosira granulata and Anabaena carcinalis. The depth of the lake has a significant effect on the transparency of the water (P<0.001), where transparency decrease with depth. Under normal conditions, Lake Baringo has low alkalinity, but with less rain, the lake has become more saline with an average conductivity of 660 μS cm−1 while the pH varies between 8.9 and 10.5. Five species of fish have been reported to occur in Lake Baringo: Oreochromis niloticus (Trewavas, 1983), Protopterus aethiopicus (Heckel, 1851), Glarias gariepinnus (Butchell, 1852), Barbus intermedius (Ruppell, 1836) and Labeo cylindricus (Peters, 1852). Presently, the species composition is dominated by Oreochromis (80.04%), Glarias (9.8%), and Protopterus (7.95%). Barbus rarely appear in the fisherman’s catches while Labeo has almost disappeared from the lake since the damming of the inflowing rivers which interfered with its breeding habits. Moreover statistical analysis has shown a significant relationship between fish yield and lake level changes (P<0.001).
Coffee
(Taylor & Francis, 2005) Gathaara, M. P. H.; Njoroge, J. M.; Agwanda, C. O.; Kingori, P. N.; Karanja, A. M.
Information on the agronomy, trade, and future outlook of coffee is presented. Other subjects include: (1) historical background; (2) genetic resources; (3) breeding and selection; (4) breeding programmes; (5) field management; (6) diseases; (7) pests; (8) effects of consumer needs on adaptation; and (9) research and development organizations. The genus Coffea consists of more than 80 species. Coffea arabica is a native of Central Africa (Congo and Zaire). Coffea canephora (Robusta coffee) was introduced to India from Indonesia and Sri Lanka in the late 19th century when C. arabica started showing severe incidence of leaf rust. Coffea congensis, which has a compact bush habit and seeds of better quality, was introduced in India in the 1930s. At present, the Central Coffee Research Institute in Karnataka, India, has a collection of 18 species that belong to Coffea and the closely related genus Psilanthus. With an annual turnover of US$ 10 billion, coffee is the second most traded commodity after petroleum. Currently, world prices are under pressure by large quantities of poor quality coffees from countries such as Vietnam.
Human and natural impacts on forests along lower Tana river, Kenya: implications towards conservation and management of endemic primate species and their habitat
(Springer Netherlands, 2007) Oguge, N. O.; Moinde-Fockler, N. N.; Karere, G. M.; Otina, D.; Suleman, M. A.
Seventy-three forest patches were assessed to determine the effects of human and natural impact on native forests along the Lower Tana River flood plains in Kenya between January and March 2001. Seventeen of these forests were within the Tana River Primate National Reserve (TRPNR) while 56 were outside the protected area. Cultivation and dyke construction had the most devastating human impact, which involved partial or complete forest clearing resulting in further fragmentation of forest patches [Suleman MA, Wahungu GM, Mouria PK, Karere GM, Oguge N, Moinde NN (2001) Tana River primate census and forest evaluation. A report to Kenya Wildlife Services]. Natural impacts were either die back or flooding, which appeared to cause progressive degradation of forest structure and biodiversity. Overall, forest area in the Lower Tana significantly reduced by 34.5% (P < 0.001) over a 21-year period. Forest loss was greater outside the reserve (38%) than inside (29.2%) reiterating the significant role played by this protected area in habitat and species conservation. Continued forest loss increases extinction risks for the endemic primate species the Tana River Red Colobus (Procolobus rufomitratus) and the Crested Mangabey sub-species (Cercocebus galeritus galeritus). Initiation of community conservation programmes outside the reserve and introduction of sustainable micro-economic projects were recommended to enhance sustainable livelihoods and the environment.
Overview of principles and application of environmental risk assessment
(School of Environmental Studies and Human Science, Kenyatta University, 2007) Kenya, Eucharia.U.; Mwangi, E. M.
The Coffee Exporter's Guide - Third Edition
(International Trade Centre, 2011) Gathaara, M. P. H.
Guide providing information on trade practices relating to exporting coffee – presents an overview of the world coffee trade and markets; deals with international coffee contracts (Europe and United States), logistics, insurance, dispute resolution, futures markets, risk management and hedging, trade financing, and related management issues; covers coffee quality with a special emphasis on quality control aspects; outlines new trends in the coffee trade such as electronic commerce, niche markets, organic certification, fair trade labelling, and other sustainability schemes; highlights climate change and environmental issues relevant to the coffee industry; includes a list of frequently asked questions from coffee producers and the respective answers.
Ethnobotanical survey and efficacy of antituberculosis medicinal plants around the Lake Victoria region of Kenya.
(IUCEA, 2012) Okemo, P. O.; Mariita, Richard M.; Orodho, John Aluko
In Africa, more than 70% of the people use ethnomedicine for their healthcare. With the emergence of new diseases and drug resistance to infections, traditional medicine should be given more attention in modern research and development. The aim of the study was to carry out an Ethnobotanical survey on the antimycobacterial plants used by the communities living around the Lake Victoria Basin of Kenya, and to screen their crude extracts against various mycobacteria strains. From the survey, 17 medicinal plants were collected. They were identified at the Department of Pharmacy and Complimentary Alternative Medicine, Kenyatta University, Nairobi, Kenya, in whose herbarium voucher specimens were deposited. Methanolic extracts from the plants were tested against four strains of Mycobacteria (Mycobacteria tuberculosis, M. kansasii, M. fortuitum, and M. smegmatis), which were obtained from Kenya Medical Research Institute (KEMRI), Nairobi, Kenya. A BACTEC MGIT 960 system was used to bioassay the extracts. All the plant extracts inhibited mycobacterial growth at 2.0 mg/mL. Aloe secundiflora gave strong antimycobacterial activity (zero GUs) against M. kansasii, at all concentrations used. Entada abysinnica was active (zero GUs at all concentrations used) against M. tuberculosis. Carissa edulis and Vernonia amygdalina were the most potent against M. smegmatis and M. fortuitum, completely inhibiting their growth (Zero GUs) at all concentrations used. Similarly, Toddalia asiatica had high inhibitory activity (Zero GUs) against M. tuberculosis and M. kansasii at all concentrations used. The results provide an indication that some of the tested plants may contain compounds that could be used against tuberculosis.
Essential Elements And Lead In Males Using Finger Nails And Scalp Hair: Influence Of Risk Factors On Levels Of Lead And Essential Elements In Finger Nails And Scalp Hair Of Males In Kenya
(LAP LAMBERT Academic Publishing, 2012-12-23) Ndiritu, J.; Murungi, J.; Wanjau, R. N.
A New Approach in Aflatoxin Management in Africa: Targeting Aflatoxin/Sterigmatocystin Biosynthesis in Aspergillus Species by RNA Silencing Technique
(INTECH, 2013) Alakonya, Amos Emitati; Monda, Ethel Oranga
Essential Elements in Watermelons Grown in Kenya
(LAP Lambert Academic Publishing, 2013-01-01) Wanjau, R. N.; Wanjau, R.; Murungi, J.
To be healthy and active, one requires food in adequate quantity, quality and variety to meet energy needs and nutrients. Watermelon has high content of water of about 93%. It is a rich source of essential minerals such as calcium, magnesium, phosphorous, potassium, sodium and smaller amounts of copper, iron, zinc and selenium. Watermelons have substantial amounts of boron, iodine, chromium, silicon and molybdenum. The levels of nutrients in different parts of the watermelons may be different. Different people consume different parts and varieties of watermelon and thus depending on the part/variety of watermelon consumed these people may get different nutrients and levels of the same. However, levels of nutrients in various parts/varieties of watermelon have not been documented.This study therefore determined the levels of Si, Ca, B, Mo, Cr and V in the four parts of Charleston grey, Crimson sweet and Sugar baby watermelons.
Copper Based Solar Cell Materials
(LAP LAMBERT Academic Publishing, 2013-01-15) Njoroge, W. K.; Karimi, P. M.; Keheze, F.M.
In this work, CuxOy and ZnO:Al thin films on plain glass substrates have been deposited as single thin films for property characterization by reactive DC Magnetron Sputtering and evaporation techniques using an Edward Auto 306 Magnetron Sputtering System respectively. A CuxOy-ZnO:Al p-n junction was fabricated by reactive DC magnetron sputtering and reactive thermal evaporation technique on a glass slide with silver as contacts. Transmittance and reflectance data in the range 300 nm-2500 nm were obtained using UV-VIS NIR Spectrophotometer Solid State 3700 DUV for all the thin films samples that were prepared. Transmittance values of above 70% for Copper Oxide and above 80 % for AZO were observed. The optical measurements were simulated using SCOUT 98 software to determine optical constants and optical bad gap of the thin films. Band gap values of 1.62 eV – 2.54 eV are observed for Copper Oxide and 3.18 eV - 3.42 eV for AZO. The surface sheet resistivities at room temperature of 298 K were found to vary with the deposition parameters and film thickness. Urbach energy for AZO was found to increase with doping levels from 2.08 × 10-4 to 2.18× 10-4 and varied between 0.6 ×10-4
Measurements and Evaluation of Radio Frequency radiation at cellular base stations.
(2013-12-18) Mwaura, Ng' ang' a Francis; Munji, M. K.; Nderu, J. N.
The World Health Organization (WHO), International Commission on Non-ionizing Radiation Protection (ICNIRP) has stated that continuous exposure to Radio Frequency Radiation (RF) beyond certain levels could cause health consequences such as cancer, congenital anomalies, epilepsy, and persistent headache and may destroy reproductive organs etc. In this regard and following the proliferation of cellular base stations across Kenya this study was carried out to determine and evaluate the levels of RF radiation that a typical person would be exposed to in a given enviromnent in Kenya. This study measured radio frequency radiation levels at 16 selected cellular base station transmitters within Nairobi, Kenya. The results were evaluated against the recommended levels set by ICNIRP. Detailed measurements of power density of the radio frequency radiation were performed over the cellular frequency bands GSM 900, GSM 1800 and UMTS 2100, which are the frequency bands in which the cellular transmitters in Kenya operate. Measurements were taken at the point perceived to have high population density near the base stations paying more attention to the direction of maximum radiation of antennas used. The highest levels at each point of measurements were recorded and evaluated against the ICNIRP exposure guidelines. ICNIRP 1998 specifies a maximum non-occupational exposure limit of 4.5W/m2 at GSM 900 Band, 9W/m2 at GSM1800 frequency band and 10W/m2 at UMTS 2100 frequency band. Based on our measurements from 16 selected cellular base stations within Nairobi and its environs the worst case of RF exposure at GSM 900 was 0.080W/m2 from an indoor micro base station situated in Sarit Centre. This value is 1.7% of the ICNIRP maximum public exposure (MPE) limits at the frequency band. The highest level at Sarit Centre was attributed to the close proximity of the radiating antenna to the point of measurement and the electromagnetic waves may have been scattered by walls and other obstacles thus creating high radiation levels away from the base station antennas. At GSM 1800 band, the worst RF exposure recorded was 0.325W/m2 from the base station at Sarit Centre .This value is 3.6% of the ICNIRP MPE limits in this frequency band. The highest RF exposure at UMTS 2100 recorded was 7.06mW/m2 recorded at t"anindoor site 016 (Tuskys Supermarket) in Nairobi CBD. This value is only 0.07% of the' ICNIRP MPE limit at the frequency band in consideration. The study reveals that the radiation exposure levels in Nairobi and environs emitted by the four main mobile phones operators i.e. Safaricom, Airtel, Orange and Essar are several orders of magnitude below the maximum permitted limits.
Enhanced Utilization of Biotechnology Research and Development Innovations in Eastern and Central Africa for Agro-ecological Intensification
(Springer International Publishing, 2014) Matheka, J. M.; Masiga, C.W.; Mugoya, C.; Ali, R.; Mohamed, A.; Osama, S.; Ngugi, A.; Kiambi, D.; De Villiers, S.; Ngugi, K.; Niyibigira, T.; Tesfamichel, A.; Machuka, J.; Oduor, R.; Runo, Steven; Adam, R.; Bedada, L.; Seth, M.; Kuria, E.; Ndirigwe, J.; Ndolo, P.; Muthamia, Z.; Nasona, B.; Ntimpirangeza, M.
The Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) through its Agrobiodiversity and Biotechnology Programme is enhancing the utilization of biotechnology research and development innovations in Eastern and Central Africa (ECA). We present successes in the application of biotechnology to enhance the productivity of cassava, sweet potato, banana, maize and sorghum in ECA. These products—drought tolerant maize, sorghum resistant to striga, as well as the technology for producing and distributing disease free planting materials of cassava, sweet potato and banana to farmers—are central for the agro-ecological intensification of farming systems in the central African highlands
Innovative but Not Feasible: Green Water Saving Schemes at the Crossroad in Semi-Arid Lands
(Organisation for Social Science Research in Eastern and Southern Africa (OSSREA), 2014) Obando, Joy Apiyo; Shisanya, C.A.; Cush, Ngonzo Luwesi
A Comparative Study of Modified and Unmodified Algae (Pediastrum boryanum) for Removal of Lead, Cadmium and Copper in Contaminated Water
(INTECH, 2017) Joseph, John Okapes; Mwangi, Isaac W.; Swaleh, Sauda; Wanjau, Ruth N.; Ram, Manohar; Ngila, Jane Catherine
The presence of heavy metals in water is of concern due to the risk toxicity. Thus there is need for their removal for the safety of consumers. Methods applied for removal of heavy metals include adsorption, membrane filtration and co-precipitation. However, studies have revealed adsorption is highly effective technique. Most adsorbents are expensive or require extensive processing before use and hence need to explore for possible sources of inexpensive adsorbents. This research work investigated the use an algal biomass (pediastrum boryanum) as an adsorbent for removal of Lead, Cadmium and Copper in waste water in its raw and modified forms. The samples were characterized with FTIR and was confirmed a successful modification with tetramethylethlynediamine (TMEDA). Sorption parameters were optimized and the material was finally applied on real water samples. It was found that the sorption was best at lower pH values (4.2-6.8). Sorption kinetics was very high as more that 90% of the metals were removed from the solution within 30 minutes. The adsorption of copper fitted into the Langmuir adsorption isotherm indicating a monolayer binding mechanism. Cadmium and lead fiĴed best the Freundlich adsorption mechanism. Sorption of lead and cadmium was of pseudo-second order kinetics, confirming a multisite interaction whereas copper was pseudoȬfirst order indicating a single site adsorption. The adsorption capacity did not improve upon modification but the stability of the material was improved and secondary pollution of leaching colour was alleviated. This implies that the modified material is suitable for application on the removal of metals from water.
Bioassay-Guided Isolation of Active Phytochemicals Against Tuta absoluta (Meyrick) from Turraea floribunda and Caesalpinia welwitschiana
(Springer, 2020) Ehawa, Flaure Rosette Essoung; Mohamed, Samira Abuelgasim; Hassanali, Ahmed; Chhabra, Sumesh Chander
Tuta absoluta Meyrick is now one of the most harmful insect pests of Solanaceae in various parts of the world. Synthetic pesticides are the most used, current control method, but are associated with several problems including the development of resistance and negative ecological effects. These led to the search for more eco-friendly methods of controlling the pest, such as a search for phytochemicals that show subtle anti-pest properties. In the present study, the effects of the constituents of methanolic extracts associated with Turraea floribunda and T. nilotica leaves (Meliaceae) and those of Caesalpinia welwitschiana and C. bonduc roots (Fabaceae-Caesalpiniaceae) were evaluated on second instar larvae of T. absoluta. The extract from T. floribunda leaves was the most active (LD50 = 587.0 ng/μl), followed by C. welwitschiana (LD50 = 779.1 ng/μl). Bioassay-guided isolation of active compounds from these active extracts, using column chromatographic and preparative HPLC, led to the identification of twenty-two compounds. Their structures were established using spectroscopic techniques, including MS, 1 and 2D-NMR, and also by comparison with reported data. The methanolic leaf extract of T. floribunda yielded ten compounds (β-sistosterol, stigmasterol, ursolic acid, betulinic acid, a mixture of β-sistosterol-3-O-β-D-glucopyranoside and stigmastreol-3-O-β-D-gluco pyranoside, fridelin, lupeol, 11-epi-21-hydroxytoonacilide and 11β, 12α-diacetoxycedrelone). The methanolic roots extract of C. welwitschiana afforded twelve constituents, including apigenin, luteolin, afzelin, quercitrin, epiafzelechin-3-O-gallate, Kaempferol 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside, Kaempferol, dipteryxic acid, neocaesalpin L, rutin, methyl gallate, and galic acid. Some of the isolates were tested on T. absoluta eggs. They showed varying levels of ovicidal effect, with quercitrin being the most active constituent at 81%. The results of the study showed potential of the phytochemicals of these plants in the management of T. absoluta.
Exploiting Arbuscular Mycorrhizal Fungi-Rhizobia-Legume Symbiosis to Increase Smallholder Farmers’ Crop Production and Resilience Under a Changing Climate
(Springer, 2020) Njeru, Ezekiel Mugendi; Muthini, Morris; Muindi, Mercy Martha; Ombori, Omwoyo; Nchore, Shem Bonuke; Runo, Steve; Maingi, John M.
Beneficial soil microbiota, such as arbuscular mycorrhizal fungi (AMF) and rhizobia, provide essential agroecosystem services in smallholder farming systems. Such microorganisms have great potential to promote crop production and resilience under a changing climate in sub-Saharan Africa. However, their function is affected by agronomic management practices, crop genotype and soil quality, among other factors. In this work, we sought to determine the effect of soil quality and crop genotype on nodulation, percentage mycorrhizal colonization and growth of maize and cowpea crops. Soil samples were obtained from ten smallholder farms with known management history in Embu and Kitui counties of Kenya and analysed for physicochemical parameters. Greenhouse bioassays were then carried out, where the samples were put in sterilized pots in four replicates and maintained in a completely randomized design. Four cowpea and maize genotypes (locally grown landraces and recommended genotypes from Kenya Agricultural and Livestock Research Organization) were grown in pots for 40 days. After harvesting, nodulation in the case of cowpea, shoot dry weights and mycorrhizal root colonization were determined. Remarkably, cowpea genotypes differed significantly (p < 0.0001) in nodule number. The locally cultivated landrace (C2) recorded the lowest nodulation with 30.4 nodules plant−1, compared to the open pollinated varieties (OPVs): C1, 39.15; C3, 43.70; and C4, 40.6 nodules plant−1. Among the maize genotypes, the locally cultivated landrace (M3) recorded a significantly (p = 0.008) higher percentage of mycorrhizal root colonization (68.9%) compared to the OPVs: M1 58.1% and M2 65.3%, while the hybrid (M4) had the lowest root colonization of 57.8%. Soil characteristics influenced nodulation and mycorrhizal colonization, where soil P was positively correlated to cowpea nodulation. Soil organic matter, nitrogen, pH and calcium positively correlated with AMF maize root colonization. Our results demonstrate the strong effect of soil quality and crop genotype on AMF-rhizobia-legume symbiosis, which affects overall crop growth and production. These factors should therefore be critically considered during the development of efficient low-cost inocula for enhanced smallholder farmers’ crop production.
A Mathematical Model for Pressure Distribution in a Bounded Oil ReservoirSubject to Single-Edged and Bottom Constant Pressure
(IOSR Journal of Mathematics, 2020) Mutili, Peter Mutisya; Adewole, Stephen Ezizanami; Awuor, Kennedy Otieno; Oyoo, Daniel Okang‟a
Well test analysis of a horizontal well is complex and difficult to interpret. Most horizontal well mathematical models assume that horizontal wells are perfectly horizontal and are parallel to the top and bottom boundaries of the reservoir. As part of effort towards correct horizontal well test analysis, the purpose of this study is to develop a mathematical model using source and Green’s functions for a horizontal well completed in an oil reservoir at late time flow period, where the reservoir is bounded by an edge and bottom constant pressure boundaries. The purpose of the derivation is to understand the effects of well completion, well design and reservoir parameters on pressure and pressure derivative behavior of the well at late flow time, when all these external boundaries are presumed to have been felt. If the model is applied for well test analysis therefore information like reservoir natural permeability distribution, actual external boundary types and even the well completion performance will be decidable easily.Dimensionless variables were used to derive throughout the derivations. Results of the derivation show that the dimensionless pressure and dimensionless pressure derivatives increase with increase in dimensionless well length. This means that higher well productivity is achievable with extended well length when the reservoir is surrounded partially by constant pressure boundaries. Furthermore, the models show that higher directional permeabilities would also encourage higher well productivity at late flow time. The dimensionless pressure derivative will, as a result of a constant dimensionless pressure, potentially collapse gradually to zero at the moment the dimensionless pressure begins to exhibit a constant trend. Finally, the dimensionless pressure and dimensionless pressure derivatives vary inversely with the reservoir dimensionless width at late flow time.

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