A nested multivariate chemometrics based calibration strategy for direct trace biometal analysis in soft tissue utilizing Energy Dispersive X-Ray Fluorescence (EDXRF) and scattering spectrometry.

Compton scatter-modulated fluorescence and multivariate chemometric (artificial neural network (ANN) and principal component regression (PCR)) calibration strategy was explored for direct rapid trace biometals (Mn, Fe, Cu, Zn, Se) analysis in "complex" matrices (model soft tissues). This involved spectral feature selection (multiple fluorescence signatures) normalized to or in conjunction with Compton scatter. ANN model resulted in more accurate trace biometal determination (R2>0.9) compared to PCR. Hybrid nested (ANN and PCR) approach led to optimized accurate biometals' concentrations in Oyster tissue (≤ ± 10%).

Helminth parasites in the intestinal tract of indigenous poultry in parts of Kenya.

A study was carried out on 456 indigenous poultry intestinal specimens from various towns in Kenya to determine the occurrence and distribution of helminth parasites in the intestinal tract of the birds. Of the specimens examined, 414 had parasites whereas the remaining 42 had none, which is an infection rate of 90.78%. The main species of helminths found in the intestines were Raillietina sp. (47.53%), Heterakis gallinarum (21.33%), Ascaridia galli (10.03%), Strongyloides avium (9.96%), Choanotaenia infundibulum (4.61%), Cotugnia digonopora (3.6%), Capillaria sp. (1.5%), Trichostrongylus tenius (1.04%) and Syngamus trachea (0.40%). Most helminths were present in both the mid- and hindguts. Syngamus trachea and C. digonopora were only found in the foregut and midgut, respectively. Although chickens from which the specimens were collected appeard healthy, the high prevalence of helminthiasis observed shows the poor level of helminth infection control practiced by the indigenous poultry keepers in the country, which might affect the health status of the birds and their growth rates. Poultry keepers should be encouraged to prevent, control and treat such cases.

Fine structure of the nephron in the euryhaline teleost, Oreochromis niloticus.

Ultrastructural studies were carried out on the nephron of a euryhaline teleost, Oreochromis niloticus. The nephron consisted of a renal corpuscle, neck segment, bisegmental proximal tubule and a distal tubule. Renal corpuscles displayed a trilaminate structure of fenestrated endothelium, triple layered basement membrane and a highly branched podocyte layer. Neck segments consisted of low cuboidal cells with apical cilia and few vacuoles. Proximal tubules were made up columnar cells with apical brush border. The initial part of the proximal tubule (PI) was characterized by a well developed endocytic apparatus which was absent in the next part (PII). Distal segments comprised of low columnar cells with scanty or no microvilli and an extensive system of basolateral membrane infoldings associated with mitochondria. These findings have been discussed in relation to renal function in fresh water euryhaline teleosts.

Routine oxygen consumption in different sizes of a tilapia, Oreochromis niloticus (Trewavas) using the closed chamber respiratory method.

Routine oxygen consumption (Vo2) measurements on 54 specimens (0.055-190.4 g) of a tilapia, Oreochromis niloticus (Trewavas) were carried out using two different types of closed respirometers: a modified cuvette for fish weighing 0.055-0.91 g and ordinary closed chamber respirometer for fish weighing more than 1 g. Vo2 values over the weight range studied had a scaling value of 0.743 which relates closely to the values for the gill respiratory surface area and morphometric oxygen diffusing capacity of O. niloticus in a previous study /13/. This shows that a close relationship exists between changes in structural parameters involved in oxygen uptake and the routine metabolism of O. niloticus with development. The values for routine Vo2 of 1.38 and 7.65 ml/h for 10 g and 100 g fish, respectively (calculated from the regression equation) show that O. niloticus is a moderately active fish.

Morphometry of the kidneys of fresh water percoid and ostariophysian teleosts.

Kidneys of four fresh water teleost species representing percormorpha (Oreochromis niloticus and Micropterus salmoides) and Ostariophysi (Cyprinus carpio and Clarias mossambicus) were studied for quantitative structural characteristics using tissues fixed by perfusion. The renosomatic index (weight of kidney/weight of fish) was higher in the ostariophysian than percoid fish (p < 0.05) but values of volume of nephronic tissue/body weight were not significantly different. Results obtained by point counting morphometry showed that the kidneys of the percoid species were made up of 56.85-64.4% nephronic tissue, 30.45-32.47% blood vessels, 2.84-8.20% ureter and ureteral ducts and 2.07-2.48% connective tissue. The kidneys of the osariophysian species comprised of 35.27-36.71% nephronic tissue, 27.86-29.29% blood vessels, 1.59-4.20% ureter and its ducts, 29.07-29.51% interstitial cells and 2.70-3.60% connective tissue. The mean values for the volume proportions of the components of nephronic tissue were not significantly different in the percoids and ostariophysians and they were; renal corpuscles 3.84-6.54%, neck segments 0.50-1.11%, proximal segments 67.17-69.72%, distal segments 18.16-20.55%, and collecting tubule-collecting duct (CT-CD) system 5.66-7.41%. These results show that the quantitative structural characteristics of the kidneys of fresh water species from different orders are quite similar and emphasise the all persuasive influence of the environment on renal structure and function in teleosts.

Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): a fish living on the edge.

Spermatogenesis in Lake Magadi tilapia (Alcolapia grahami), a cichlid fish endemic to the highly alkaline and saline Lake Magadi in Kenya, was evaluated using light and transmission electron microscopy. Spermatogenesis, typified by its three major phases (spermatocytogenesis, meiosis and spermiogenesis), was demonstrated by the presence of maturational spermatogenic cells namely spermatogonia, spermatocytes, spermatids and spermatozoa. Primary spermatogonia, the largest of all the germ cells, underwent a series of mitotic divisions producing primary spermatocytes, which then entered two consecutive meiotic divisions to produce secondary spermatocytes and spermatids. Spermatids, in turn, passed through three structurally distinct developmental stages typical of type-I spermiogenesis to yield typical primitive anacrosomal spermatozoa of the externally fertilizing type (aquasperm). The spermatozoon of this fish exhibited a spheroidal head with the nucleus containing highly electron-dense chromatin globules, a midpiece containing ten ovoid mitochondria arranged in two rows and a flagellum formed by the typical 9 + 2 microtubule axoneme. In addition, the midpiece, with no cytoplasmic sheath, appeared to end blindly distally in a lobe-like pattern around the flagellum; a feature that was unique and considered adaptive for the spermatozoon of this species to the harsh external environment. These observations show that the testis of A. grahami often undergoes active spermatogenesis despite the harsh environmental conditions to which it is exposed on a daily basis within the lake. Further, the spermiogenic features and spermatozoal ultrastructure appear to be characteristic of Cichlidae and, therefore, may be of phylogenetic significance.

Animal health problems attributed to environmental contamination in lake Nakuru National Park, Kenya: a case study on heavy metal poisoning in the Waterbuck Kobus ellipsiprymnus defassa (Ruppel 1835).

A study was conducted in which samples of soil, forage, as well as serum, bone, kidney, and liver of waterbuck were collected from Lake Nakuru National Park. The objective was to determine the ecosystem health status in order to establish the causes of animal health problems previously recorded in some sections of the Park. Trace element analysis in serum indicated occurrence of copper (Cu) deficiency in the north and eastern sections of the Park where mean values were marginal (range: 0.36-0.81, mean: 0.62 mg/l) compared to concentrations recorded in the western part of the Park (range: 0.69-1.48, mean: 1.22 mg/l). Bone analysis on dry matter basis (DM) indicated higher (p < 0.01) levels of cadmium (Cd, 0.437 mg/kg), fluoride (F, 3178 mg/kg), and lead (Pb, 20.62 mg/kg) in animals from the east compared to those from the west (0.002, 1492, 4.87 mg/kg, respectively), suggesting heavy exposure. In addition, samples from the east had much lower than normal calcium (Ca)-to-phosphorus (P) ratios (mean: 1.9:1) compared to those recorded in the west (2.2:1), suggesting poor bone mineralization. There was a higher concentration of Cd in the kidney (16.24 mg/kg, p < 0.05) and Pb in the liver (58.3 mg/kg, p < 0.01) in animals from the east compared to those in the west (12.92 and 36.2 mg/kg, respectively), but the converse was true of Cu. The liver Cu status was better in animals from the west with, concentrations (mean: 21.7 mg/kg) being about twice those recorded in the east (11.9 mg/kg DM). Forage analysis revealed prospects of Ca, P, and Cu deficiencies in the entire Park. However, in the northeastern section of the Park (measuring 50 ha) where waterbuck residence times are high, forage concentrations of Cd (0.31 mg/kg DM), molybdenum (Mo, 7.20 mg/kg DM), Pb (2.88 mg/kg DM), and zinc (Zn, 126 mg/kg DM) were an order of magnitude greater (p < 0.01) than the levels recorded in the rest of the Park (ranges: 0.133-0.165, 3.69-5.61, 0.485-0.621, 11.6-17.4 mg/kg DM, respectively). These disparities were attributed to a higher soil concentration of Cd (2.77 mg/kg DM), Pb (85.1 mg/k DM) and Zn (1414 mg/kg DM) in this section compared to the rest of the Park (ranges: 0.10-0.15, 5.02-6.26, 1.49-5.44 mg/kg DM, respectively), and strongly suggest heavy metal contamination as the source of animal health problems in the Park.