Do Ogoyi

Determination of Heavy Metal Content in Water, Sediment and Microalgae from Lake Victoria, East Africa

Lake Victoria, which is the largest fresh water lake in Africa, represents a unique ecosystem that has the largest fresh water fishery in the continent. However, increased anthropogenic activities has increased the potential pollution of the lake especially the heavy metal pollutants which may be toxic to humans and aquatic fauna. There is need therefore for continuous monitoring of pollution levels in the lake. Samples of water, soil sediments and algae were collected in dry, long and short rainy periods of 2008 and analyzed for heavy metal by Atomic Absorption Spectrophotometry. The highest concentration of trace metals were found in sediment samples with Zn having the highest mean concentration values in both Winam (1.019 ppm) and Mwanza gulf (0.889 ppm). The mean concentration of Pb was higher in water samples from Winam gulf (0.823 ppm), while Hg in microalgae samples from Winam gulf had a mean concentration of 0.000148 ppm. The highest concentration of Zn (1.589 ppm) was determined in the sediment samples from Kirumba bay of the Mwanza gulf and the lowest was in sediments from Kishimba bay (0.327 ppm). Levels of trace metals in microalgae were not significant in different sites of the Mwanza Gulf. Like in the Mwanza gulf, levels of Zn was high in sediments from all the sites sampled in Winam Gulf, the highest recorded at Kisat. Pb levels were highest in the water samples from Hippo point, whereas concentration levels of Cd, Cr and Hg were lowest in all the four sites sampled. The maximum biomass of micro- algae occurred at Kisat during the short rain season (November-December) followed by Kamito in the same season.

FAT BODY TRIACYLGLYCEROL LIPASE IN SOLITARY AND GREGARIOUS PHASES OF SCHISTOCERCA GREGARIA (FORSKAL) (ORTHOPTERA: ACRIDIDAE)

The activities of the fat body triacylglycerol lipase were determined using 14C-trioleoylglycerol. Resting activities were estimated at 1.98 ± 0.24 and 1.95 ± 0.53 nmol free fatty acid (FFA)/hr/mg protein for gregarious and solitary locusts, respectively. Administration of adipokinetic hormone (AKH) I led to the activation of lipase with peak activities occurring after 30 min. In the solitary locusts, activities of 2.28 ± 0.16 and 2.30 ± 0.43 nmol FFA/hr/mg were obtained following administration of 10 and 2 pmol AKH I, respectively. In the gregarious locusts, enzyme activities of 3.17 ± 0.66 and 2.47 ± 0.39 nmol FFA/hr/mg were obtained after administration of 10 and 2 pmol AKH I, respectively. The Km values were estimated at 46.67 and 18.75 μM for gregarious and solitary locusts, respectively. Similarly, the Vmax values were estimated at 10.29 and 2.52 nmol/hr/mg for gregarious and solitary locusts, respectively. These results confirm phase-dependent differences in lipase properties with the gregarious form having a higher catalytic ability, but a lower affinity for the substrate than the solitary type.

Linkage and mapping analysis of a non-susceptibility gene to densovirus (nsd-2) in the silkworm, Bombyx mori.

Nonsusceptibility to Bombyx mori densovirus type 2 (BmDNV‐2) is controlled by a recessive non‐susceptibility gene, nsd‐2 (non‐susceptibility to DNV‐2) in B. mori. Taking advantage of a lack of crossing over in females, reciprocal backcrossed F1 (BF1) progeny were used for linkage analysis and mapping of nsd‐2 using silkworm strains C124 and 902, which are classified as being highly susceptible and non‐susceptible to DNV‐2, respectively. BF1 larvae were inoculated twice with DNV‐2 virus at the first and second instar stages. DNA was extracted from each of the surviving fifth instar larvae and analysed by RFLP inheritance patterns using probes specific to each of the 28 linkage groups of B. mori. Our results indicated that the non‐susceptibility gene was linked to linkage group 17, since all surviving larvae showed the homozygous profile of strain 902 in their genotype. The other linkage groups showed mixtures of heterozygous and homozygous genotypes, indicating an independent assortment. A linkage map of 30.6 cM was constructed for linkage group 17 with nsd‐2 mapped at 24.5 cM and three closely linked cDNA markers were identified.

Lipophorin and apolipophorin-III in solitary and gregarious phases of Schistocerca gregaria

Abstract Lipophorin was isolated from the hemolymph by KBr density gradient ultracentrifugation. Apolipophorin-III (apoLp-III) was isolated from low-density lipophorin (LDLp). High-density lipophorin (HDLp) (Mr ∼-620,000) consisted of two apoproteins, apoLp-I (Mr ∼-224,000) and apoLp-II (Mr ∼-81,000). Isolated apoLp-III (Mr ∼-20,000) had two isoforms in non-denaturing gels. Injection of adipokinetic hormone-I resulted in the formation of LDLp in both locust phases. Lipid content of HDLp was estimated at 48.4% and 51.8% for solitary and gregarious locusts, respectively. In LDLp, lipids constituted 59.8% and 57.1% for gregarious and solitary locusts, respectively. The results suggest that the gregarious locusts were more efficient in the conversion of HDLp to LDLp.

Effects of heavy metal pollution on ω3 polyunsaturated fatty acids levels in tilapia fish from Winam Gulf of Lake Victoria

Winam Gulf is facing major pollution threats from anthropogenic input of pollutants such as heavy metals and agrochemical residues. This has deleterious effects on flora and fauna in the lake and consequently the quality of omega - 3 polyunsaturated fatty acids (PUFAs) which have numerous health benefits in humans. In addition, heavy metal bioac- cumulation in fish poses a threat to human health. The major objective of the study was to establish whether there is a cor- relation between the heavy metal pollutants and the levels of omega - 3 PUFAs in fish. Levels of heavy metals - lead, cadmium, Zinc and chromium in sediments, water, and tilapia from selected sites in Winam Gulf were investigated. They were analyzed using Atomic Absorption Spectrophotometer. Fish muscles were further analyzed for omega -3 PUFAs us- ing gas chromatography. Sediment samples accumulated the highest levels of heavy metals ranging from below detection limit to as high as 277 mg/kg on dry weight basis. Zinc levels in fish muscles were the highest whereas cadmium was the lowest. Heavy metal levels in water were found to be lowest compared to sediments and fish. Omega-3 PUFAs, particu- larly alpha-linolenic, eicosapentaenoic, docosapentaenoic and docosahexaenoic acids were in substantial amounts in fish. Oil contents were in the range of (2.47- 3.87) %. There was no clear link observed between the levels of heavy metals and omega-3 PUFAs in fish although the fish muscles showed presence of these metals.

Characterization of protective antigens from the midgut of Amblyomma variegatum ticks

Separation of midgut membrane proteins from the tick,Ambylomma variegatum, using a non-ionic detergent (TritonX-114), resulted in two protein fractions, namely DET (detergent) and AQ (aqueous). In immunoblotting analysis with polyclonal antibodies against these fractions, 4 proteins (Mr ∼27,000, 67,000, 86,000 and 95,000,)and 2 proteins (Mr ∼54,000 and 67,000) were detected in the DET and AQ fractions, respectively. Three of the DET fraction proteins Mr∼27,000, 67,000 and 95,000 were glycosylated since they bound to the lectin, concanavalin A. In 2-dimensional gel electrophoresis, the AQ and DET fraction proteins were found to be acidic in nature. In a series of bioassay experiments, rabbits were first immunised with both DET and AQ fractions and then infested with ticks. The egg batch weights of these ticks were reduced by 50% compared to control ticks. Furthermore, there was a significant reduction in the hatchability of eggs laid by ticks fed on rabbits previously immunised with both DET (14%) and AQ (33%) fractions. Based on the egg hatchability, there productive capacity of ticks was reduced by 77 and 48% by DET and AQ fractions, respectively.

Variation in lipophorin titres during development in solitarious and gregarious schistocerca gregaria (Forskål) (orthoptera: acrididae)

The levels of lipophorin, the principal insect haemolymph lipoprotein, were estimated during the development of solitary and gregarious phases of Schistocerca gregaria using single radial immunodiffusion. In the gregarious phase, lipophorin titres ranged from 6.69 ± 0.57 mg/ml in the 3rd nymphal instar to 14.42 ± 2.04 mg/ml in mature adults. The titres in the solitary phase were 3.33 ± 0.59 mg/ml in the 3rd nymphal instar and 8.44 + 0.67 mg/ml in mature adults. Peak lipophorin titres occurred in mature adults (14.42 ± 2.04 mg/ml) and 5th nymphal instar (8.75 ± 0.25 mg/ml) for gregarious and solitary locusts, respectively. Gregarious locusts had significantly (P < 0.05) higher lipophorin titres than their solitary counterparts during the 3rd and 4th nymphal instars as well as in the adult stage (P < 0.01). Estimation of the haemolymph protein levels over the same period showed a general increase from the 3rd nymphal instar to mature adult stage in both phases. It is proposed that the higher lipophorin titre in gregarious locusts is a physiological adaptation that ensures high lipid reserves that are necessary to cope with the high metabolic requirements of this phase.RésuméLes taux de lipophorine, la principale lipoprotéine de l’hémolymphe des insectes, ont été estimés pendant le développement des phases solitaires et grégaires de Schistocerca gregaria à l’aide de l’immunodiffusion radiale simple. Chez la phase grégaire, les teneurs en lipophorine sont comprises entre 6.69 ±0.57 mg/ml pour le 3eme Stade juvénile et 14.42 + 2.04 mg/ml pour les adultes matures. Chez la phase solitaire, les teneurs sont de 3.33 ± 0.59 mg/ml pour le 3ème stade juvénile et de 8.44 ± 0.67mg/ml pour les adultes matures. Les teneurs les plus élevées en lipophorine sont rencontrées sur les adultes matures (14.42 + 2.04 mg/ml) et le 5ème stade juvenile (8.75 + 0.25 mg/ml) pour les criquets grégaires et solitaires, respectivement.Les criquets grégaires ont des teneurs significativement plus élevées (P < 0.05) que leurs homologues solitaires pendant les Stades juvéniles 3 et 4, de même que chez le stade adulte (P < 0.01). Pendant la même période, pour les deux phases, l’estimation des teneurs en protéines de l’hémolymphe montre un accroissement général lorsque l’on passe du 3ème stade juvénile au stade adulte. Les plus fortes teneurs en lipophorine chez les criquets grégaires seraient une adaptation physiologique leur permettant de disposer d’importantes réserves lipidiques nécessaires à leurs fortes exigences métaboliques.

Lipophorin of the larval stalk borer, Busseola Fusca : Purification and properties

Lipophorin was isolated from the stalk borer, Busseola fusca, larvae by ultracentrifugation in a KBr density-gradient. The lipophorin ( Mr ~ 700,000) is a high density lipoprotein (density = 1.13 g/ml) composed of 46% lipids and 4% carbohydrates. It consists of two apoproteins, apolipophorin-I (apoLp-I, Mr ~ 210,000) and apolipophorin-II (apoLp-II, Mr ~78,000). Both apoproteins are glycosylated as shown by periodate Schiff reagent staining and binding to the lectin, concanavalin A. Amino acid composition analysis of lipophorin showed predominance of aspartate (13%), glutamate (9%) and glycine (9%).In an immunoblotting experiment, both apoproteins showed immunoreactivity with antiserum to B. fusca lipophorin and no cross-reactivity occurred with any other haemolvmph proteins. Immunodiffusion studies with the same antibodies showed cross-reactivity with haemolymph derived from other Lepidoptera and not from Orthoptera, Dictyoptera or Diptera.RésuméUne lipophorine a été isolée des larves de Busseola fusca, par ultracentrifugation avec gradient de densité. La lipophorine dont le poids moléculaire est d’environ ~700,000 est une lipoprotéine de densité élevée (1.13 mg/ml) composée de 46% de lipides et de 4% de glucides. La lipophorine comporte 2 apoprotéines: l’apolipophorine-I (apoLp-I, de poids moléculaire environ ~210,000) et l’apolipophorine-II (apoLp-II, de poids moléculaire ~78,000). Les deux apoprotéines sont glycosylées comme le démontre la coloration au réactif du périodate de Schiff (PAS). La présence de manose comportant des chaines d’oligosaccharides a été établie par la réaction d’attachement de la lipophorine à la concanavaline-A sur colonne de sépharose. L’analyse de la composition en acides aminés de la lipophorine montre une prédominance d’aspartate (13%), de glutamate (9%) et de glycine (9%). Au cours de tests d’immunoblotting, les antisera des deux apoprotéines de la lipophorine ont réagi avec les anticorps. Nos résultats suggèrent également que les lipophorines d’insectes du même ordre développeraient une cross réaction.