Tulane Virus as a Potential Surrogate To Mimic Norovirus Behavior in Oysters

Oyster contamination by noroviruses is an important health and economic problem. The present study aimed to compare the behaviors of Norwalk virus (the prototype genogroup I norovirus) and two culturable viruses: Tulane virus and mengovirus. After bioaccumulation, tissue distributions were quite similar for Norwalk virus and Tulane virus, with the majority of viral particles detected in digestive tissues, while mengovirus was detected in large amounts in the gills and mantle as well as in digestive tissues. The levels of persistence of all three viruses over 8 days were comparable, but clear differences were observed over longer periods, with Norwalk and Tulane viruses displaying rather similar half-lives, unlike mengovirus, which was cleared more rapidly. These results indicate that Tulane virus may be a good surrogate for studying norovirus behavior in oysters, and they confirm the prolonged persistence of Norwalk virus in oyster tissues.     

Diarylquinolines target subunit c of mycobacterial ATP synthase

The diarylquinoline R207910 (TMC207) is a promising candidate in clinical development for the treatment of tuberculosis. Though R207910-resistant mycobacteria bear mutations in ATP synthase, the compound's precise target is not known. Here we establish by genetic, biochemical and binding assays that the oligomeric subunit c (AtpE) of ATP synthase is the target of R207910. Thus targeting energy metabolism is a new, promising approach for antibacterial drug discovery.     

Stimulated growth rate by restriction of P availability at moderate salinity but insensitive to P availability at high salinity in Crithmum maritimum

The halophyte Crithmum maritimum thrives in cracks of calcareous rocks or cliffs at seashores, a situation which associates limited phosphorus availability and high salinity. In order to understand the common patterns of colonization and zonation of this species, seedlings were cultivated for 34 d in inert sandy soil irrigated with a nutrient solution containing or not phosphorus at moderate (50 mM) or high (250 mM) NaCl level. Net assimilation rate and consequently relative growth rate increased in response to P deprivation at moderate saline level, but not at high salinity level. Parallelly, CO2 fixation rate, rubisco capacity, transpiration rate and stomatal conductance were diminished by P deprivation at moderate NaCl level. Intercellular CO2 concentration was therefore not affected. Chlororophyll fluorescence analysis revealed that photosynthetic systems were insensitive to change in P availability at moderate salinity level: neither pigment content, nor effective and maximum quantum yield, photochemical and non photochemical quenching, and electron transport rate were affected by P deprivation. On the contrary, at high salinity level when net photosynthesis, rubisco capacity and the quantum yields of PS2 were severely affected, P deprivation strongly augmented electron transport rate. Stomatal aperture and more modest increase in net photosynthesis, rubisco capacity, photosystem II effective quantum yield and photochemical quenching accompanied this response. This study shows the tolerance of C. maritimum to the phosphorus deprivation combined to moderate or to high saline level which may explain the common patterns of colonization and zonation of this species.     

Relative growth and reproductive cycle of the date mussel Lithophaga lithophaga (Linnaeus, 1758) sampled from the Bizerte Bay (Northern Tunisia)

Relative growth and the reproductive cycle of the date mussel Lithophaga lithophaga were studied from September 2002 to October 2003 in the Bizerte Bay (Northern Tunisia). Relationships between shell length and shell width, shell height as well as volume-related variables (shell dry weight, soft tissues dry weight and total wet weight) showed negative allometries in both sexes except for shell width in males (isometry) and shell height in both sexes (positive allometry). The sex ratio was unbalanced, within the length range of 6–48 mm, 49.43 % of the animals were males, 24.39 % females and 26.17 % sexually undifferentiated; within the length range of 49–92 mm, the respective values were 41.19, 52.7 and 6.1 %. Histological investigations as well as analyses of the condition index and the gonadosomatic index (CI and GSI) revealed the presence of a single reproductive cycle per year. Spawning occurred at the end of August and early September and was associated with a decrease in seawater temperature and salinity. A resting phase occurred in winter, coinciding with the lowest water temperatures. Histological examinations of the gonads of a total of 130 specimens revealed only two cases of hermaphroditism. The present study constitutes a useful baseline for a sustainable management of local wild stocks of L. lithophaga.     

Deficient tryptophan catabolism along the kynurenine pathway reveals that the epididymis is in a unique tolerogenic state

Indoleamine 2,3-dioxygenase (IDO) is the first and rate-limiting enzyme of tryptophan catabolism through the kynurenine pathway. Intriguingly, IDO is constitutively and highly expressed in the mammalian epididymis in contrast to most other tissues where IDO is induced by proinflammatory cytokines, such as interferons. To gain insight into the role of IDO in the physiology of the mammalian epididymis, we studied both wild type and Ido1(-/-)-deficient mice. In the caput epididymis of Ido1(-/-) animals, the lack of IDO activity was not compensated by other tryptophan-catabolizing enzymes and led to the loss of kynurenine production. The absence of IDO generated an inflammatory state in the caput epididymis as revealed by an increased accumulation of various inflammation markers. The absence of IDO also increased the tryptophan content of the caput epididymis and generated a parallel increase in caput epididymal protein content as a consequence of deficient proteasomal activity. Surprisingly, the lack of IDO expression had no noticeable impact on overall male fertility but did induce highly significant increases in both the number and the percentage of abnormal spermatozoa. These changes coincided with a significant decrease in white blood cell count in epididymal fluid compared with wild type mice. These data provide support for IDO playing a hitherto unsuspected role in sperm quality control in the epididymis involving the ubiquitination of defective spermatozoa and their subsequent removal.     

Death Receptor-Induced Apoptosis Signalling Regulation by Ezrin Is Cell Type Dependent and Occurs in a DISC-Independent Manner in Colon Cancer Cells

Ezrin belongs to the ERM (ezrin-radixin-moesin) protein family and has been demonstrated to regulate early steps of Fas receptor signalling in lymphoid cells, but its contribution to TRAIL-induced cell death regulation in adherent cancer cells remains unknown. In this study we report that regulation of FasL and TRAIL-induced cell death by ezrin is cell type dependant. Ezrin is a positive regulator of apoptosis in T-lymphoma cell line Jurkat, but a negative regulator in colon cancer cells. Using ezrin phosphorylation or actin-binding mutants, we provide evidence that negative regulation of death receptor-induced apoptosis by ezrin occurs in a cytoskeleton- and DISC-independent manner, in colon cancer cells. Remarkably, inhibition of apoptosis induced by these ligands was found to be tightly associated with regulation of ezrin phosphorylation on serine 66, the tumor suppressor gene WWOX and activation of PKA. Deficiency in WWOX expression in the liver cancer SK-HEP1 or the pancreatic Mia PaCa-2 cell lines as well as WWOX silencing or modulation of PKA activation by pharmacological regulators, in the colon cancer cell line SW480, abrogated regulation of TRAIL signalling by ezrin. Altogether our results show that death receptor pro-apoptotic signalling regulation by ezrin can occur downstream of the DISC in colon cancer cells.     

How does iron deficiency disrupt the electron flow in photosystem I of lettuce leaves?

The changes observed photosystem I activity of lettuce plants exposed to iron deficiency were investigated. Photooxidation/reduction kinetics of P700 monitored as ΔA₈₂₀ in the presence and absence of electron transport inhibitors and acceptors demonstrated that deprivation in iron decreased the population of active photo-oxidizable P700. In the complete absence of iron, the addition of plant inhibitors (DCMU and MV) could not recover the full PSI activity owing to the abolition of a part of P700 centers. In leaves with total iron deprivation (0 μM Fe), only 15% of photo-oxidizable P700 remained. In addition, iron deficiency appeared to affect the pool size of NADP⁺ as shown by the decline in the magnitude of the first phase of the photooxidation kinetics of P700 by FR-light. Concomitantly, chlorophyll content gradually declined with the iron concentration added to culture medium. In addition, pronounced changes were found in chlorophyll fluorescence spectra. Also, the global fluorescence intensity was affected. The above changes led to an increased rate of cyclic electron transport around PSI mainly supported by stromal reductants.     

Unexpected mosaic distribution of two hybridizing sibling lineages in the teleplanically dispersing snail Stramonita haemastoma suggests unusual postglacial redistribution or cryptic invasion

Molecular approaches have proven efficient to identify cryptic lineages within single taxonomic entities. Sometimes these cryptic lineages maybe previously unreported or unknown invasive taxa. The genetic structure of the marine gastropod Stramonita haemastoma has been examined in the Western Mediterranean and North‐Eastern Atlantic populations with mtDNA COI sequences and three newly developed microsatellite markers. We identified two cryptic lineages, differentially fixed for alternative mtDNA COI haplogroups and significantly differentiated at microsatellite loci. The mosaic distribution of the two lineages is unusual for a warm‐temperate marine invertebrate with a teleplanic larval stage. The Atlantic lineage was unexpectedly observed as a patch enclosed in the north of the Western Mediterranean Sea between eastern Spain and the French Riviera, and the Mediterranean lineage was found in Macronesian Islands. Although cyto‐nuclear disequilibrium is globally maintained, asymmetric introgression occurs in the Spanish region where the two lineages co‐occur in a hybrid zone. A first interpretation of our results is mito‐nuclear discordance in a stable postglacial hybrid zone. Under this hypothesis, though, the location of genetic discontinuities would be unusual among planktonic dispersers. An alternative interpretation is that the Atlantic lineage, also found in Senegal and Venezuela, has been introduced by human activities in the Mediterranean area and is introgressing Mediterranean genes during its propagation, as theoretically expected. This second hypothesis would add an additional example to the growing list of cryptic marine invasions revealed by molecular studies.