Microsatellite gene diversity in coconut (Cocos nucifera L.) accessions resistants to lethal yellowing disease

One of the problems faced in coconut cultivation is the lethal yellowing disease. Experimental trials, conducted in endemic region, showed that the Vanuatu Tall and Sri-Lanka Green Dwarf genotypes weretolerant while the West African Tall appeared susceptible to the lethal yellowing disease. Genetic differences between these tolerant genotypes and the susceptible ones were evaluated using twelvemicrosatellite markers. This work aimed to use identified materials as reference to select suitable parents for gene mapping studies. A total of 58 alleles were detected at the 12 microsatellite loci. Thenumber of alleles varied from 3 to 7, with an average of 4.83 alleles. The Fst index revealed that 59.70% of the total allele variability explained differences between the three accessions. Genotypes of WestAfrican Tall, susceptible to the lethal yellowing disease, were less genetically clustered to the genotypes of the two tolerant accessions. This differentiation was based on specific alleles and frequency variation of shared allele in the three accessions. This molecular typology was useful as reference for large molecular screening of coconut genetic resources and the identification of suitableparents for the development of mapping populations for tagging the lethal yellowing resistance genes

Evaluation of some basic traits of a promising coconut hybrid: Sri Lankan green dwarf crossed to Vanuatu tall (sgd x vtt)

The Lethal Yellowing Disease locally referred to as the “Cape St Paul Wilt Disease” is the single most important disease that has devastated several hectares of coconut plantations in Ghana. Two decades of coconut screening for tolerant planting material has identified the Sri LankanGreen Dwarf crossed Vanuatu Tall (SGD x VTT) coconut hybrid as the most promising planting material in the context of disease. To provide farmers with planting material that has high disease tolerance and also good agronomic characteristics, the study compared some basic traits ofthe coconut hybrid with other important coconut varieties with the objective of determining the suitability of the SGD x VTT as alternative planting material to revamp the coconut industry in Ghana. Mean sample size of 25 palms per coconut variety under the study was analyzed using two sample t-test procedure. The study indicated that the yield performance of the SGD x VTT coconut hybrid was better than the tall coconut types including the local West African Tall (WAT) and compared favourably with the Malayan Yellow Dwarf crossed Vanuatu Tall (MYD x VTT) coconut hybrid. The good agronomic characteristics of the SGD x VTT coupled with itshigh resistance to the CSPWD proved its suitability as alternative planting material to revamp the coconut industry in Ghana

Initiation of human colon cancer cell proliferation by trypsin acting at protease-activated receptor-2

The protease-activated receptor-2 (PAR-2) is a G protein-coupled receptor that is cleaved and activated by trypsin. We investigated the expression of PAR-2 and the role of trypsin in cell proliferation in human colon cancer cell lines. A total of 10 cell lines were tested for expression of PAR-2 mRNA by Northern blot and RT-PCR. PAR-2 protein was detected by immunofluorescence. Trypsin and the peptide agonist SLIGKV (AP2) were tested for their ability to induce calcium mobilization and to promote cell proliferation on serum-deprived cells. PAR-2 mRNA was detected by Northern blot analysis in 6 out of 10 cell lines [HT-29, Cl.19A, Caco-2, SW480, HCT-8 and T84]. Other cell lines expressed low levels of transcripts, which were detected only by RT-PCR. Further results were obtained with HT-29 cells: (1) PAR-2 protein is expressed at the cell surface; (2) an increase in intracellular calcium concentration was observed upon trypsin (1–100 nM) or AP2 (10–100 μM) challenges; (3) cells grown in serum-deprived media supplemented with trypsin (0.1–1 nM) or AP2 (1–300 μM) exhibited important mitogenic responses (3-fold increase of cell number). Proliferative effects of trypsin or AP2 were also observed in other cell lines expressing PAR-2. These data show that subnanomolar concentrations of trypsin, acting at PAR-2, promoted the proliferation of human colon cancer cells. The results of this study indicate that trypsin could be considered as a growth factor and unravel a new mechanism whereby serine proteases control colon tumours. © 2001 Cancer Research Campaign http://www.bjcancer.co

Observation of the inverse spin Hall effect in silicon

The spin–orbit interaction in a solid couples the spin of an electron to its momentum. This coupling gives rise to mutual conversion between spin and charge currents: the direct and inverse spin Hall effects. The spin Hall effects have been observed in metals and semiconductors. However, the spin/charge conversion has not been realized in one of the most fundamental semiconductors, silicon, where accessing the spin Hall effects has been believed to be difficult because of its very weak spin–orbit interaction. Here we report observation of the inverse spin Hall effect in silicon at room temperature. The spin/charge current conversion efficiency, the spin Hall angle, is obtained as 0.0001 for a p-type silicon film. In spite of the small spin Hall angle, we found a clear electric voltage due to the inverse spin Hall effect in the p-Si film, demonstrating that silicon can be used as a spin-current detector

The Importance of the Stem Cell Marker Prominin-1/CD133 in the Uptake of Transferrin and in Iron Metabolism in Human Colon Cancer Caco-2 Cells

As the pentaspan stem cell marker CD133 was shown to bind cholesterol and to localize in plasma membrane protrusions, we investigated a possible function for CD133 in endocytosis. Using the CD133 siRNA knockdown strategy and non-differentiated human colon cancer Caco-2 cells that constitutively over-expressed CD133, we provide for the first time direct evidence for a role of CD133 in the intracellular accumulation of fluorescently labeled extracellular compounds. Assessed using AC133 monoclonal antibody, CD133 knockdown was shown to improve Alexa488-transferrin (Tf) uptake in Caco-2 cells but had no impact on FITC-dextran or FITC-cholera-toxin. Absence of effect of the CD133 knockdown on Tf recycling established a role for CD133 in inhibiting Tf endocytosis rather than in stimulating Tf exocytosis. Use of previously identified inhibitors of known endocytic pathways and the positive impact of CD133 knockdown on cellular uptake of clathrin-endocytosed synthetic lipid nanocapsules supported that CD133 impact on endocytosis was primarily ascribed to the clathrin pathway. Also, cholesterol extraction with methyl-β-cyclodextrine up regulated Tf uptake at greater intensity in the CD133high situation than in the CD133low situation, thus suggesting a role for cholesterol in the inhibitory effect of CD133 on endocytosis. Interestingly, cell treatment with the AC133 antibody down regulated Tf uptake, thus demonstrating that direct extracellular binding to CD133 could affect endocytosis. Moreover, flow cytometry and confocal microscopy established that down regulation of CD133 improved the accessibility to the TfR from the extracellular space, providing a mechanism by which CD133 inhibited Tf uptake. As Tf is involved in supplying iron to the cell, effects of iron supplementation and deprivation on CD133/AC133 expression were investigated. Both demonstrated a dose-dependent down regulation here discussed to the light of transcriptional and post-transciptional effects. Taken together, these data extend our knowledge of the function of CD133 and underline the interest of further exploring the CD133-Tf-iron network

Studies on the biology of the leafhopper, Nzinga palmivora Wilson n.sp. (Homoptera: Cicadellida: Typhlocybinae) in Ghana

No Abstract. Ghana Journal of Agricultural Science No. 1, 2005: 199-20

Reduction of spread of Cape St Paul wilt disease (CSPWD) of coconut by insecticidal hot-fogging and removal of diseased palms

No Abstract. Ghana Journal of Agricultural Science No. 1, 2005: 193-19