Evaluating the degree of weathering in landslide-prone soils in the humid tropics: The case of Limbe,SW Cameroon

This study analyses the behaviour and mobility of major and some trace elements during the physical and chemical development of landslide-prone soil profiles in Limbe, SW Cameroon. The soils result from in situ weathering of Tertiary basaltic and picrobasaltic rocks. Textural and chemical characterisations, together with two mass balance models are applied to understand the mobility and redistribution of elements during the weathering of pyroclastic cones and lava flows. Weathering indices are used to estimate the extent of weathering. The chemical composition of the samples is evaluated by Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP–OES) and their mineralogical composition by X-Ray Diffraction (XRD) analyses. It is observed that intensive weathering results in thick meta-stable soils in which significant loss of Ca, K, Mg, Na and Sr has taken place. There is a noticeable relative enrichment in all analysed trace elements (Ba, Zr, Y, Sc, V, Ni, and Co). Ti, Fe, Al, Mn, P and Ce tend to be leached in some horizons and concentrated in others. Zr, Ti, and Ce concentrations are greater in the soils than in the bedrock but show slight fluctuations in the soil and saprolites hence cannot be used as immobile elements for mass balance evaluations. Y increases progressively with advanced weathering. Major secondary mineral phases developed through weathering are a mixture of expanding (smectites) and non-expanding clays (kaolinite, halloysite and mica). The profiles show the presence of textural heterogeneities that can be exploited as slip surfaces. Data plotted in Si–Al–Fe diagram point out that the most advanced stage of weathering noted in these profiles is the kaolinisation stage.     

The calicheamicin gene cluster and its iterative type I enediyne PKS

The enediynes exemplify nature's ingenuity. We have cloned and characterized the biosynthetic locus coding for perhaps the most notorious member of the nonchromoprotein enediyne family, calicheamicin. This gene cluster contains an unusual polyketide synthase (PKS) that is demonstrated to be essential for enediyne biosynthesis. Comparison of the calicheamicin locus with the locus encoding the chromoprotein enediyne C-1027 reveals that the enediyne PKS is highly conserved among these distinct enediyne families. Contrary to previous hypotheses, this suggests that the chromoprotein and nonchromoprotein enediynes are generated by similar biosynthetic pathways.     

Human prion protein with valine 129 prevents expression of variant CJD phenotype

Variant Creutzfeldt-Jakob disease (vCJD) is a unique and highly distinctive clinicopathological and molecular phenotype of human prion disease associated with infection with bovine spongiform encephalopathy (BSE)-like prions. Here, we found that generation of this phenotype in transgenic mice required expression of human prion protein (PrP) with methionine 129. Expression of human PrP with valine 129 resulted in a distinct phenotype and, remarkably, persistence of a barrier to transmission of BSE-derived prions on subpassage. Polymorphic residue 129 of human PrP dictated propagation of distinct prion strains after BSE prion infection. Thus, primary and secondary human infection with BSE-derived prions may result in sporadic CJD-like or novel phenotypes in addition to vCJD, depending on the genotype of the prion source and the recipient.     

A cryptic subgroup of Anopheles gambiae is highly susceptible to human malaria parasites

Population subgroups of the African malaria vector Anopheles gambiae have not been comprehensively characterized owing to the lack of unbiased sampling methods. In the arid savanna zone of West Africa, where potential oviposition sites are scarce, widespread collection from larval pools in the peridomestic human habitat yielded a comprehensive genetic survey of local A. gambiae population subgroups, independent of adult resting behavior and ecological preference. A previously unknown subgroup of exophilic A. gambiae is sympatric with the known endophilic A. gambiae in this region. The exophilic subgroup is abundant, lacks differentiation into M and S molecular forms, and is highly susceptible to infection with wild Plasmodium falciparum. These findings might have implications for the epidemiology of malaria transmission and control.     

Composition of nutrients in the sclerotium of the mushroomPleurotus tuber regium

A tuberous sclerotium of the mushroomPleurotus tuber regium was analysed for proximate, amino acid and mineral content. The sclerotium had low protein, ether extract, amino acid and mineral content compared to the pileus of the same mushroom and similar mushrooms. Cystine, methionine, serine, arginine and lysine were exceptionally low. Because the sclerotium is milled with melon seeds in traditional preparation of a vegetable meat-substitute, nutrient intake of a human subject consuming 100 grams of the meat-substitute was compared to intake of one consuming 100 grams of stewed broiler meat. The meat-substitute provided more minerals than broiler meat but only a fraction (40–65%) of the amino acids of broiler meat.     

Nutritional evaluation of pigeon pea meal

Mineral, amino acid and fatty acid composition of pigeon pea meal were determined by analysis, while with chick essays, availability (true digestibility) of minerals and amino acids in the meal were estimated. Gross energy, metabolizable energy and true protein digestibility experiments were also conducted. Pigeon pea meal had a very high content of potassium, high content of potassium, high content of phosphorus, moderate content of calcium and magnesium and low content of iron, zinc, copper and manganese. Average availability of minerals was 58.09%. Amino acid content was low, especially cystine and methionine. Amino acid availability was 82.32%, lower than amino acid availability of soybean meal (>90%). Pigeon pea lipids were predominantly saturated fatty acids (69.04%) with low content of unsaturated fatty acids (30.69%) and a total absence of linolenic acid. Metabolizable energy content (N-corrected) was 11.08 MJ/kg in raw pigeon pea and 12.03 MJ/kg in toasted pigeon pea meal.     

Quercetin exhibits a specific fluorescence in cellular milieu: a valuable tool for the study of its intracellular distribution

The elaboration of novel techniques for flavonoid intracellular tracing would elucidate the compounds' absorption and bioavailability and assist molecular and pharmacological approaches, as they are promising candidates for drug development. This study exploited the properties of quercetin (3,3',4',5,7-pentahydroxyflavone), found in high concentrations in the majority of edible plants. Through the use of UV-vis spectroscopy, confocal microscopy, and HPLC-ESI-MS, native quercetin, at physiologically relevant concentrations, was found to exhibit a specific fluorescence (488 nmex/500-540 nmem) upon internalization. This fluorescence shift is due to a non-covalent binding to intracellular targets (probably proteins) and compatible with the settings applied in confocal microscopy. This property provides a valuable, selective alternative technique for quercetin tracing in cellular systems, permitting the quantitative evaluation of its transit at pharmacologically relevant concentrations and the validation of a number of already described molecular functions.     

Antimicrobial resistance and virulence profile of enterococci isolated from poultry and cattle sources in Nigeria

This study investigated the occurrence, antimicrobial resistance and virulence of Enterococcus from poultry and cattle farms. Three hundred and ninety samples: cloacal/rectal swabs (n?=?260) and manure (n?=?130] were processed for recovery of Enterococcus species. Standard bacteriological methods were used to isolate, identify and characterize Enterococcus species for antimicrobial susceptibility and expression of virulence traits. Detection of antibiotic resistance and virulence genes was carried out by polymerase chain reaction. Enterococcus was recovered from 167 (42.8%) of the 390 samples tested with a predominance of Enterococcus faecium (27.7%). Other species detected were Enterococcus gallinarum, Enterococcus faecalis, Enterococcus hirae, Enterococcus raffinosus, Enterococcus avium, Enterococcus casseliflavus, Enterococcus mundtii and Enterococcus durans. All the isolates tested were susceptible to vancomycin, but resistance to tetracycline, erythromycin, ampicillin and gentamicin was also observed among 61.0, 61.0, 45.1 and 32.7% of the isolates, respectively. Sixty (53.1%) of the isolates were multidrug resistant presenting as 24 different resistance patterns with resistance to gentamicin-erythromycin-streptomycin-tetracycline (CN-ERY-STR-TET) being the most common (n?=?11) pattern. In addition to expression of virulence traits (haemolysin, gelatinase, biofilm production), antibiotic resistance (tetK, tetL, tetM, tetO and ermB) and virulence (asa1, gelE, cylA) genes were detected among the isolates. Also, in vitro transfer of resistance determinants was observed among 75% of the isolates tested. Our data revealed poultry, cattle and manure in this area are hosts to varying Enterococcus species harbouring virulence and resistance determinants that can be transferred to other organisms and also are important for causing nosocomial infection.     

Evaluation of mosquito fish Gambusia holbrooki (Girard) as a partial and complete pellet replacement for juvenile barramundi Lates calcarifer (Bloch)

Barramundi (Lates calcarifer, Bloch) fed live mosquito fish (Gambusia holbrooki, Girard) exhibited faster growth and a better food conversion ratio (on a dry‐weight basis) than those fed an iso‐calorific ration of commercial barramundi pellets and a 50:50 ration of mosquito fish and pellets. The improved performance of barramundi fed mosquito fish was attributed to their higher protein content, higher protein to energy ratio and lower carbohydrate content. The essential amino acid indices and fatty acid profiles of the two diets were similar, suggesting that imbalances or deficiencies in these nutrients were not the limiting factor to the slower growth of barramundi fed on pellets. The use of mosquito fish as barramundi food offers a potential use of this noxious species and may allow barramundi to be cultured without the use of conventional fish meal.