High frequency of-β-hexosaminidase deficiency in lymphoblastoid cell lines

The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome.Four lines were deficient in total β-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical β-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease.The possible mechanisms explaining the high frequency of β-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.     

Sequences homologous to Tc(s) transposable elements ofCaenorhabditis elegans are widely distributed in the phylum nematoda

Summary To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements fromCaenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found inCaenorhabditis and inTeratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and inBursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited toC. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history.     

DNA sequence analysis of the lamB gene from Klebsiella pneumoniae: implications for the topology and the pore functions in maltoporin.

Summary We have determined the sequence of the lamB gene from Klebsiella pneumoniae. It encodes the precursor to the LamB protein, a 429 amino acid polypeptide with maltoporin function. Comparison with the Escherichia coli LamB protein reveals a high degree of homology, with 325 residues strictly identical. The N-terminal third of the protein is the most conserved part of the molecule (1 change in the signal sequence, and 13 changes up to residue 146 of the mature protein). Differences between the two mature proteins are clustered mainly in six regions comprising residues 145–167, 173–187, 197–226, 237–300, 311–329, and 367–387 (K. pneumoniae LamB sequence). The most important changes were found in regions predicted by the two-dimensional model of LamB folding to form loops on the cell surface. In vivo maltose and maltodextrin transport properties of E. coli K 12 and K. pneumoniae strains were identical. However, none of the E. coli K12 LamB-specific phages was able to plaque onto K. pneumoniae. Native K. pneumoniae LamB protein forms highly stable trimers. The protein could be purified by affinity chromatography on starch-Sepharose as efficiently as the E. coli K12 LamB protein, indicating a conservation of the binding site for dextrins. However, none of the monoclonal antibodies directed against native E. coli K12 LamB protein recognized native purified K. pneumoniae LamB protein. These data indicate that most of the variability occurs within exposed regions of the protein and provide additional support for the proposed model of LamB folding. The fact that the N-terminal third of the protein is highly conserved is in agreement with the idea that it is part of, or constitutes, the pore domain located within the transmembranous channel and that it is not accessible from the cell surface.     

The impact of CO2 emission scenarios and nutrient enrichment on a common coral reef macroalga is modified by temporal effects

Future coral reefs are expected to be subject to higher pCO₂ and temperature due to anthropogenic greenhouse gas emissions. Such global stressors are often paired with local stressors thereby potentially modifying the response of organisms. Benthic macroalgae are strong competitors to corals and are assumed to do well under future conditions. The present study aimed to assess the impact of past and future CO₂ emission scenarios as well as nutrient enrichment on the growth, productivity, pigment, and tissue nutrient content of the common tropical brown alga Chnoospora implexa. Two experiments were conducted to assess the differential impacts of the manipulated conditions in winter and spring. Chnoospora implexa's growth rate averaged over winter and spring declined with increasing pCO₂ and temperature. Furthermore, nutrient enrichment did not affect growth. Highest growth was observed under spring pre‐industrial (PI) conditions, while slightly reduced growth was observed under winter A1FI (“business‐as‐usual”) scenarios. Productivity was not a good proxy for growth, as net O₂ flux increased under A1FI conditions. Nutrient enrichment, whilst not affecting growth, led to luxury nutrient uptake that was greater in winter than in spring. The findings suggest that in contrast with previous work, C. implexa is not likely to show enhanced growth under future conditions in isolation or in conjunction with nutrient enrichment. Instead, the results suggest that greatest growth rates for this species appear to be a feature of the PI past, with A1FI winter conditions leading to potential decreases in the abundance of this species from present day levels.     

Targeting head and neck tumoral stem cells: From biological aspects to therapeutic perspectives

Head and neck squamous cell cancer(HNSCC) is the sixth most common cancer in the world. Effective therapeutic modalities such as surgery, radiation, chemotherapy and combinations of each are used in the management of the disease. In most cases, treatment fails to obtain total cancer cure. In recent years, it appears that one of the key determinants of treatment failure may be the presence of cancer stem cells(CSCs) that escape currently available therapies. CSCs form a small portion of the total tumor burden but may play a disproportionately important role in determining outcomes. CSCs have stem features such as self-renewal, high migration capacity, drug resistance, high proliferation abilities. A large body of evidence points to the fact that CSCs are particularly resistant to radiotherapy and chemotherapy. In HNSCC, CSCs have been increasingly shown to have an integral role in tumor initiation, disease progression, metastasis and treatment resistance. In the light of such observations, the present review summarizes biological characteristics of CSCs in HNSCC, outlines targeted strategies for the successful eradication of CSCs in HNSCC including targeting the self-renewal controlling pathways, blocking epithelial mesenchymal transition, niche targeting, immunotherapy approaches and highlights the need to better understand CSCs biology for new treatments modalities.     

First Insights into the Genetic Diversity of the Pinewood Nematode in Its Native Area Using New Polymorphic Microsatellite Loci

The pinewood nematode, Bursaphelenchus xylophilus, native to North America, is the causative agent of pine wilt disease and among the most important invasive forest pests in the East-Asian countries, such as Japan and China. Since 1999, it has been found in Europe in the Iberian Peninsula, where it also causes significant damage. In a previous study, 94 pairs of microsatellite primers have been identified in silico in the pinewood nematode genome. In the present study, specific PCR amplifications and polymorphism tests to validate these loci were performed and 17 microsatellite loci that were suitable for routine analysis of B. xylophilus genetic diversity were selected. The polymorphism of these markers was evaluated on nematodes from four field origins and one laboratory collection strain, all originate from the native area. The number of alleles and the expected heterozygosity varied between 2 and 11 and between 0.039 and 0.777, respectively. First insights into the population genetic structure of B. xylophilus were obtained using clustering and multivariate methods on the genotypes obtained from the field samples. The results showed that the pinewood nematode genetic diversity is spatially structured at the scale of the pine tree and probably at larger scales. The role of dispersal by the insect vector versus human activities in shaping this structure is discussed.     

Identification of low frequency knockout mutants in Dictyostelium discoideum created by single or double homologous recombination

Generation and characterization of knockout clones is a widely used approach to evaluate the specific function of a gene product in Dictyostelium discoideum. The mutant clones are generally obtained by double homologous recombination in the target gene. A frequent limitation to obtaining mutants is the low frequency of homologous recombination. Here we present an easy method to identify rare mutants, based on PCR analysis of pools of clones. This method also allows the isolation of functional knockout mutants created by a single homologous recombination event, which can be more frequent than a double recombination event.