Spatio-temporal variations in biological performances and summer mortality of the Pacific oyster Crassostrea gigas in Normandy (France)

Mortality and biological performances of half-grown Crassostrea gigas were studied from spring 2000 to autumn 2001 at six instrumented stations located in two areas (Gefosse and Grandcamp) of the Bay of Veys (Normandy). Shell and meat growth, condition indexes and a macroscopic maturity index were determined on oysters deployed at the six stations in order to assess spatial variability in the influence of environmental conditions. In addition, histological and biochemical analyses were performed in order to determine the sex and establish the reproductive cycle (at all six sites) and the biochemical composition (at four stations). The data set including monthly mean temperatures and data provided by examination of 2,837 oysters were analysed by Principal Component Analysis and a Hierarchical Ascending Clustering which resulted in the formation of four clusters. The highest station on the shoreline belonged to a cluster characterized notably by low total weight due to a short immersion/feeding period, whereas all other stations belonged to another single cluster. Nevertheless, various biological differences were found between these stations, e.g. the reproductive cycle was generally synchronized throughout the bay but some differences relative to spawning occurrence were observed. In 2000, oyster mortality was higher at Gefosse than at Grandcamp, the latter being a more marine area. In 2001, oyster mortalities were significantly higher and all stations were strongly affected. In the Bay of Veys, oyster biological performances and mortality thus showed spatio-temporal variations which were worthy to be discussed.     

A novel polymorphism in the coding sequence of the human RET proto-oncogene

A novel polymorphism in the coding sequence of the human RET proto-oncogene is described. The RET proto-oncogene maps to chromosome 10q11.2, and is involved in multiple endocrine neoplasia (MEN 2A, MEN 2B), familial medullary thyroid carcinoma and Hirschsprung's disease.     

Neural processes underlying conscious perception: Experimental findings and a global neuronal workspace framework

One striking property of perception is that it can be achieved in two seemingly different ways: either consciously or non-consciously. What distinguishes these two types of processing at the neural level? So far, empirical findings suggest that conscious perception is associated with an increase in activity at the sensory level, the specific involvement of a fronto-parietal network and an increase in long-distance functional connectivity and synchrony within a broad network of areas. We interpret these data in the framework of the global neuronal workspace model which proposes that the neural basis of conscious access is a sudden self-amplifying process leading to a global brain-scale pattern of activity. In contradiction with several theories which assume that there is a continuum of perception, associated with a gradual change in the intensity of brain activation, the model predicts a sharp non-linear transition between non-conscious and conscious processing.     

Characterization of double minute chromosomes’ DNA content in a human high grade astrocytoma cell line by using comparative genomic hybridization and fluorescence in situ hybridization

The presence of double minute chromosomes (dmin) in cancer cells is known to be correlated with gene amplifications. In human high grade astrocytomas or glioblastomas, about 50% of cytogenetically characterized cases display dmin. G5 is a cell line which has been established from a human glioblastoma containing multiple dmin. In order to identify the DNA content of these dmin, three techniques were successively used: conventional cytogenetic analysis, comparative genomic hybridization (CGH), and fluorescent in situ hybridization (FISH). The karyotype of G5 cells showed numerical chromosome changes (hypertriploidy), several marker chromosomes, and multiple dmin. CGH experiments detected two strong DNA amplification areas located in 9p21-22 and 9p24, as well as an underrepresentation of chromosomes 6, 10, 11, 13, 14, and 18q. By using FISH with a chromosome 9-specific painting probe to metaphase chromosomes of the G5 cell line, dmin were shown to contain DNA sequences originating from chromosome 9. This study demonstrates the usefulness of a combination of classical karyotyping, CGH, and FISH to identify the chromosomal origin of amplified DNA sequences in dmin. Received: 30 October 1994 / Revised: 25 February 1996     

A human RNA polymerase II subunit is encoded by a recently generated multigene family

Background  

The sequences encoding the yeast RNA polymerase II (RPB) subunits are single copy genes.     

Underwater wingbeats extend depth and duration of plunge dives in northern gannets Morus bassanus

Plunge-diving is a specialised hunting tactic used by some avian predators to overcome the high buoyancy encountered near the water surface and surprise prey. However, plunge-diving is effective only to a certain depth; to access deeper prey, birds need to use an additional method of propulsion, e.g. wings or feet. We used miniature accelerometers to record the details of the aerial and underwater phases of plunge dives by northern gannets Morus bassanus . Birds never reached depths >11  m using the momentum of the aerial part of the plunge dive and had to flap their wings underwater to gain additional depth. A biomechanical model demonstrates that little additional depth can be obtained from momentum alone when initiating a plunge from heights >40  m. Thus, the additional energy required to attain greater starting heights is not rewarded by reaching significantly greater depths. However, by using their wings underwater, gannets were able to more than double the depth attained (up to 24  m). It appears that prey may be captured by surprise in the first 10  m of the water column, whereas wing-propelled pursuit is required to catch prey at deeper depths, a strategy likely to be used only for prey of sufficient profitability to justify the cost of flapping the gannet's large wings underwater. Our study demonstrates the importance of understanding the constraints placed on predators by the physical environment when interpreting predator-prey interactions.     

Effects of deferasirox and deferiprone on cellular iron load in the human hepatoma cell line HepaRG

Two oral chelators, CP20 (deferiprone) and ICL670 (deferasirox), have been synthesized for the purpose of treating iron overload diseases, especially thalassemias. Given their antiproliferative effects resulting from the essential role played by iron in cell processes, such compounds might also be useful as anticancer agents. In the present study, we tested the impact of these two iron chelators on iron metabolism, in the HepaRG cell line which allowed us to study proliferating and differentiated hepatocytes. ICL670 uptake was greater than the CP20 uptake. The iron depletion induced by ICL670 in differentiated cells increased soluble transferrin receptor expression, decreased intracellular ferritin expression, inhibited ⁵⁵Fe (III) uptake, and reduced the hepatocyte concentration of the labile iron pool. In contrast, CP20 induced an unexpected slight increase in intracellular ferritin, which was amplified by iron-treated chelator exposure. CP20 also promoted Fe(III) uptake in differentiated HepaRG cells, thus leading to an increase of both the labile pool and storage forms of iron evaluated by calcein fluorescence and Perls staining, respectively. In acellular conditions, compared to CP20, iron removing ability from the calcein-Fe(III) complex was 40 times higher for ICL670. On the whole, biological responses of HepaRG cells to ICL670 treatment were characteristic of expected iron depletion. In contrast, the effects of CP20 suggest the potential involvement of this compound in the iron uptake from the external medium into the hepatocytes from the HepaRG cell line, therefore acting like a siderophore in this cell model.