Storm Water Drainage Systems’ Effectiveness and Adequacy in Managing Storm Water Discharge in Kisii Municipality, Kenya

Urbanization and increased developments have put pressure on important infrastructure like storm water drainage networks, often resulting to flash floods and blockage of drainage structures. This study assessed the effectiveness and adequacy of storm water drainage systems (channels) in Kisii municipality, in collecting and discharging storm water. The study areas for drainage networks were selected purposively based on the drainages type (concrete, earth and grass lined). Discharge was calculated based on the amount of rainfall, duration of rain, land use and slope of the study area. Land use maps and drainage network were generated in Personal Computer Storm Water Management Model (PCSWMM) using satellite maps and digital elevation models respectively. The effectiveness was established by routing runoff water in the PCSWMM. Surcharged culverts and joints indicated inefficient storm water drainage systems, resulting to ponding and flooding. Results from this study indicated that there were instabilities in conduits and surcharge in nodes. Surcharging of nodes was experienced for up to 22 hours at Daraja Mbili while ponding in Mwembe lasted for up to 22 hours. The level of surcharge and flooding on Rivers was experienced within 15 minutes of a rainfall in Nyanchwa sub catchment

Development of Mathematical Models for Estimation of the Quantity of Biomass Residues

Abstract Biomass residues derived from agricultural and forest-based operations and processes i

Short CommunicationsStrength Properties and Groups of Major Commercial Timbers Grown in Kenya

The strength properties (based on two physical and four mechanical parameters) were assessed for 49 timber species grown in Kenya based on small clear specimens. Data on mean values were computed from which other statistical information on minimum, mean and maximum strength values were generated. The relationships between physical and selected mechanical properties were also analysed using regression analysis. The species were further classified into four strength groups based on a method developed in Australia but modified to fit the major uses of timber in Kenya. The results confirmed the influence of moisture content and specific gravity on strength properties. There was an observed increase in specific gravity and mechanical strength properties on drying, a fact which favours the use of dry timber. The results also confirmed that both specific gravity and stiffness are useful in predicting strength properties of timber. However, the moderate values of R2 obtained for several relationships reflect clear variation between species due to various factors and the need for applying allowances (Safety factors) when applying the regression models generated. The strength groups developed revealed that most species in Kenya are suitable for heavy engineering works and building construction. The system of grouping developed is suitable where machine grading is not yet in use on a meaningful scale. Discovery and Innovation Vol. 13 no. 3/4 December (2001) pp. 144-149 KEY WORDS: strength properties, commercial timber, physical and mechanical properties Résumé Les propriétés de résistance, basées sur deux paramètres physiques et quatre mécaniques ont été évaluées pour 49 espèces de bois cultivées au Kenya sur des petits spécimens. Les données sur des valeurs moyennes ont été saisies et elles ont servi à générer d'autres informations statistiques comme la résistance minimale, moyenne, maximale. Des rapports entre propriétés physiques et mécaniques retenues pour l'étude ont été également calculés par analyse de régression. Les espèces ont été ensuite classées dans quatre groupes de résistance basée sur une méthode développée en Australie mais modifiée pour l'adapter aux utilisations principales du bois au Kenya. Les résultats ont confirmé l'influence de l'humidité et de la densité spécifique sur des propriétés de résistance. On a observé une augmentation de densité spécifique et de propriétés mécaniques de résistance résultant du séchage, un fait qui plaide en faveur de l'utilisation du bois sec. Les résultats ont également confirmé que la densité et la rigidité étaient des paramètres utiles pour la prédiction des propriétés de résistance du bois. Cependant les valeurs modérées de R2 obtenues pour plusieurs rapports reflètent une nette variation entre les espèces, résultant de divers facteurs, d'où besoin est d'appliquer des marges de sécurité lors de l'application des modèles de régression générés. Les groupes de résistance mis sur pied ont révélé que la plupart des espèces au Kenya sont bien indiquées pour les travaux d'ingénierie lourde et la construction de bâtiments. Le système de groupements développés convient dans les lieux où les appareils d'étalonnage sont peu utilisés ou ne le sont pas du tout. Mots-clés: propriétés de résistance, bois commercial, propriétés physiques et propriétés mécaniques sélectionnée

Occurrence and distribution of Organochlorine Pesticide Residues in Water and Sediments of Earthen Fish Ponds in South Western Kenya

Persistent organochlorine residues in the environment are a threat to ecological health of aquatic organisms and pose a health risk to both animals and human consumers. Organochlorine pesticides were determined in water and sediments collected during wet and dry season from selected riverine and earthen fish pond sites in high altitude catchment areas within Kuja River (Kenya) between August 2016–May, 2017. Analysis of DDT and metabolites, Hexachlorocyclohexanes (HCHs) isomers and cyclodienes using a gas chromatograph (GC), and electron capture detector (ECD), confirmed using GC - Mass Spectrometry (MS). Mean (± Standard error) results of DDTs, cyclodienes and HCHs in pond waters were:- below detection level (BDL) to 0.27±0.03µg/L, BDL to 0.11±0.00µg/L, and 4.39±1.01µg/L respectively; and BDL to 0.23±0.01µg/L, 1.20±0.005µg/L, and 1.71±0.02µg/L in river water respectively. Sediment mean OCPs contents were significantly (p<0.05) higher for Dieldrin (3.043±0.43µg/kg), Endrin (2.56±0.460µg/kg), Heptachlor (3.61±0.02µg/kg) DDT (2.97±1.32µg/kg), Endosulfan (6.31.27±1.051µg/kg), Methoxychlor (2.15±1.641µg/kg) and Lindane (2.96±1.32µg/kg), respectively. A longitudinal spatial distribution pattern was noted for both water and sediment OCPs contents, demonstrating that cyclodienes are predominant contaminants in point and non-point sources in water courses. The study recommends continuous monitoring of OCPs in upstream catchment areas for informed management and policy decisions on pesticide use. Keywords: Kuja-Migori River; Organic contaminants; Organochlorine Pesticide

Deciphering the targets of retroviral protease inhibitors in Plasmodium berghei.

Retroviral protease inhibitors (RPIs) such as lopinavir (LP) and saquinavir (SQ) are active against Plasmodium parasites. However, the exact molecular target(s) for these RPIs in the Plasmodium parasites remains poorly understood. We hypothesised that LP and SQ suppress parasite growth through inhibition of aspartyl proteases. Using reverse genetics approach, we embarked on separately generating knockout (KO) parasite lines lacking Plasmepsin 4 (PM4), PM7, PM8, or DNA damage-inducible protein 1 (Ddi1) in the rodent malaria parasite Plasmodium berghei ANKA. We then tested the suppressive profiles of the LP/Ritonavir (LP/RT) and SQ/RT as well as antimalarials; Amodiaquine (AQ) and Piperaquine (PQ) against the KO parasites in the standard 4-day suppressive test. The Ddi1 gene proved refractory to deletion suggesting that the gene is essential for the growth of the asexual blood stage parasites. Our results revealed that deletion of PM4 significantly reduces normal parasite growth rate phenotype (P = 0.003). Unlike PM4_KO parasites which were less susceptible to LP and SQ (P = 0.036, P = 0.030), the suppressive profiles for PM7_KO and PM8_KO parasites were comparable to those for the WT parasites. This finding suggests a potential role of PM4 in the LP and SQ action. On further analysis, modelling and molecular docking studies revealed that both LP and SQ displayed high binding affinities (-6.3 kcal/mol to -10.3 kcal/mol) towards the Plasmodium aspartyl proteases. We concluded that PM4 plays a vital role in assuring asexual stage parasite fitness and might be mediating LP and SQ action. The essential nature of the Ddi1 gene warrants further studies to evaluate its role in the parasite asexual blood stage growth as well as a possible target for the RPIs

Prevalence of mutations in the cysteine desulfurase IscS (Pfnfs1) gene in recurrent Plasmodium falciparum infections following artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) treatment in Matayos, Western Kenya

Abstract Background Malaria remains a public health concern globally. Resistance to anti-malarial drugs has consistently threatened the gains in controlling the malaria parasites. Currently, artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) are the treatment regimens against Plasmodium falciparum infections in many African countries, including Kenya. Recurrent infections have been reported in patients treated with AL or DP, suggesting the possibility of reinfection or parasite recrudescence associated with the development of resistance against the two therapies. The Plasmodium falciparum cysteine desulfurase IscS (Pfnfs1) K65 selection marker has previously been associated with decreased lumefantrine susceptibility. This study evaluated the frequency of the Pfnfs1 K65 resistance marker and associated K65Q resistant allele in recurrent infections collected from P. falciparum-infected individuals living in Matayos, Busia County, in western Kenya. Methods Archived dried blood spots (DBS) of patients with recurrent malaria infection on clinical follow-up days after treatment with either AL or DP were used in the study. After extraction of genomic DNA, PCR amplification and sequencing analysis were employed to determine the frequencies of the Pfnfs1 K65 resistance marker and K65Q mutant allele in the recurrent infections. Plasmodium falciparum msp1 and P. falciparum msp2 genetic markers were used to distinguish recrudescent infections from new infections. Results The K65 wild-type allele was detected at a frequency of 41% while the K65Q mutant allele was detected at a frequency of 22% in the recurrent samples. 58% of the samples containing the K65 wild-type allele were AL treated samples and while 42% were DP treated samples. 79% of the samples with the K65Q mutation were AL treated samples and 21% were DP treated samples. The K65 wild-type allele was detected in three recrudescent infections (100%) identified from the AL treated samples. The K65 wild-type allele was detected in two recrudescent DP treated samples (67%) while the K65Q mutant allele was identified in one DP treated (33%) recrudescent sample. Conclusions The data demonstrate a higher frequency of the K65 resistance marker in patients with recurrent infection during the study period. The study underscores the need for consistent monitoring of molecular markers of resistance in regions of high malaria transmission

Deletion of the PM4 gene significantly attenuates the growth of asexual parasites.

<p><b>(A).</b> Box plots are showing the percentage parasitaemia in mice infected with the PM4_KO, PM7_KO or PM8_KO parasite line relative to the wild-type (WT) parasite line as measured on day four post parasite inoculation in the standard 4-day suppressive test. <b>(B).</b> Violin plots are showing the distribution of the parasites in mice infected with the PM4_KO, PM7_KO or PM8_KO parasite line relative to the wild-type (WT) parasite line as measured in the standard 4-day suppressive test. The PM4_KO parasites acquired a reduced growth rate phenotype (<i>P</i> = 0. 0.003), while the PM7_KO and PM8_KO parasites lines attained an increased growth rate phenotype.</p

Deciphering the targets of retroviral protease inhibitors in <i>Plasmodium berghei</i> - Fig 1

<p><b>PCR genotyping of the knockout (KO) parasites; (A) PM4_KO, (B) PM7_KO, (C) PM8_KO, and the wild-type (WT) control lines.</b> The PCR amplification used three sets of primer pairs; QCR2/GW2 to confirm the presence of the vector, GT/GW1 or GT/GW2 to verify integration of the vector into the parasite genome and QCR1/QCR2 to confirm deletion of the specific genes. The QCR1, QCR2 and GT1 are vector specific primers while GW2 and GW1 primers are standard primers.</p

Deciphering the targets of retroviral protease inhibitors in <i>Plasmodium berghei</i> - Fig 5

<p>(A) The crystallographic structure of PM4 protein in complex with the lopinavir as visualized using PyMOL. (B) 2D LP-PM4 interaction diagram with the oxygen atoms shown in red, nitrogen atoms shown in blue while hydrogen bonds are shown as olive green dotted line. The interaction plots were generated using <a href="https://www.ebi.ac.uk/thornton-srv/software/LigPlus/download.html" target="_blank">LigPlot+</a>.</p