The role of landscape history and persistent biogeographical patterns in shaping the responses of Mediterranean land snail communities to recent fire disturbances

Aims To assess the impact of various fire regimes over the past 30 years on land snail communities and to analyse the role of recent landscape history and the influence of biogeography in shaping the response patterns of gastropod communities following disturbances by fire. Location South-eastern France (Provence) and Mediterranean region. Methods Stratified sampling within 12 sites was undertaken with regard to fire regime (i.e. number of fires, fire intervals and age of the last fire) occurring over the past 30 years. The study was complemented by a historical analysis using aerial photographs, old maps of vegetation cover and an analysis of the biogeographical composition of malacofaunas. Data were investigated using Correspondence Analysis and Sørensen coefficient of similarity. Results When a disturbance regime (land use or fire disturbances) has been maintained over decades or centuries, land snail communities appear highly modified and tend to be composed of only Mediterranean and xerophilous species. However, low fire regimes, since the 1970s, do not seem to greatly affect the composition of gastropod communities. Indeed, shade-loving, mesophilous and European range species persist even after successive fires within some sites. In addition, the malacofaunas have a higher component of European range species with increasing distance from the Mediterranean sea. Main conclusions Analysis of the response patterns of gastropod communities to fire shows a response to numerous different factors. The composition of current land snail communities is not only the result of (more or less) recent patterns of fire regimes but also of anthropogenic disturbances, of landscape changes over the last centuries and of subsequent structure of the pre-fire habitat, as well as of the influence of a biogeographical gradient. However, the response patterns observed and the persistence of pre-fire communities imply the presence of cryptic refuges located within burned areas.     

Distribution and Expression of Elicitin Genes in the Interspecific Hybrid Oomycete Phytophthora alni

Phytophthora alni subsp. alni, P. alni subsp. multiformis, and P. alni subsp. uniformis are responsible for alder disease in Europe. Class I and II elicitin gene patterns of P. alni subsp. alni, P. alni subsp. multiformis, P. alni subsp. uniformis, and the phylogenetically close species P. cambivora and P. fragariae were studied through mRNA sequencing and 3′ untranslated region (3′UTR)-specific PCRs and sequencing. The occurrence of multiple 3′UTR sequences in association with identical elicitin-encoding sequences in P. alni subsp. alni indicated duplication/recombination events. The mRNA pattern displayed by P. alni subsp. alni demonstrated that elicitin genes from all the parental genomes are actually expressed in this allopolyploid taxon. The complementary elicitin patterns resolved confirmed the possible involvement of P. alni subsp. multiformis and P. alni subsp. uniformis in the genesis of the hybrid species P. alni subsp. alni. The occurrence of multiple and common elicitin gene sequences throughout P. cambivora, P. fragariae, and P. alni sensu lato, not observed in other Phytophthora species, suggests that duplication of these genes occurred before the radiation of these species.     

Effect of nasal continuous or intermittent positive airway pressure on nonnutritive swallowing in the newborn lamb.

The present study was aimed at investigating the effects of nasal continuous positive airway pressure (nCPAP; 6 cmH2O) or intermittent positive pressure ventilation (nIPPV; 10/4 cmH2O) on nonnutritive swallowing (NNS) and on the coordination between NNS and phases of the respiratory cycle, while taking into account the potential effects of states of alertness. Twelve full-term lambs were chronically instrumented at 48 h after birth for polysomnographic recordings, including NNS, diaphragm electromyographic activity, respiratory movements, pulse oximetry, and states of alertness. Studies in control conditions, with nCPAP and nIPPV, were performed in random order in nonsedated lambs at 4, 5, and 6 days of life. Results demonstrate that nCPAP significantly decreased overall NNS frequency, more specifically isolated NNS during quiet sleep and bursts of NNS in active sleep. In comparison, the effects of nIPPV on NNS frequency were more variable, with an inhibition of NNS only in wakefulness and an increase in isolated NNS frequency in active sleep. In addition, neither nCPAP nor nIPPV disrupted the coordination between NNS and phases of the respiratory cycle. In conclusion, nCPAP inhibits NNS occurrence in newborn lambs. Clinical relevance of this novel finding is related to the importance of NNS for clearing the upper airways from secretions and gastric content frequently regurgitated in the neonatal period.     

Peptides as tools and drugs for immunotherapies.

Peptides are essential tools for discovery and pre-clinical and pharmaceutical development of viral and cancer vaccines ('active immunotherapies') as well as for therapeutic antibodies ('passive immunotherapies'). They help to trigger and analyze immune responses at a molecular level (B-cell, T-helper and CTL epitopes). They contribute largely to the design of new vaccine candidates and to the generation of monoclonal antibodies. They are also valuable analytical reference compounds for the structural characterisation by liquid chromatography and mass spectrometry of recombinant proteins used as biopharmaceuticals. As for other therapeutic applications, formulation, solubilisation, batch consistency and stability, issues have to be addressed to allow the pre-clinical and clinical development of this class of compounds as immunotherapeutic drugs. In the present review, three case studies dealing with (i) the design and the characterisation of Respiratory Syntycial Virus subunit vaccines, (ii) peptide-based melanoma vaccines, and (iii) therapeutic monoclonal antibodies, all investigated in clinical trials, are reported and discussed.     

Rotavirus Infection Reduces Sucrase-Isomaltase Expression in Human Intestinal Epithelial Cells by Perturbing Protein Targeting and Organization of Microvillar Cytoskeleton

Rotavirus infection is the most common cause of severe infantile gastroenteritis worldwide. These viruses infect mature enterocytes of the small intestine and cause structural and functional damage, including a reduction in disaccharidase activity. It was previously hypothesized that reduced disaccharidase activity resulted from the destruction of rotavirus-infected enterocytes at the villus tips. However, this pathophysiological model cannot explain situations in which low disaccharidase activity is observed when rotavirus-infected intestine exhibits few, if any, histopathologic changes. In a previous study, we demonstrated that the simian rotavirus strain RRV replicated in and was released from human enterocyte-like Caco-2 cells without cell destruction (N. Jourdan, M. Maurice, D. Delautier, A. M. Quero, A. L. Servin, and G. Trugnan, J. Virol. 71:8268–8278, 1997). In the present study, to reinvestigate disaccharidase expression during rotavirus infection, we studied sucrase-isomaltase (SI) in RRV-infected Caco-2 cells. We showed that SI activity and apical expression were specifically and selectively decreased by RRV infection without apparent cell destruction. Using pulse-chase experiments and cell surface biotinylation, we demonstrated that RRV infection did not affect SI biosynthesis, maturation, or stability but induced the blockade of SI transport to the brush border. Using confocal laser scanning microscopy, we showed that RRV infection induces important alterations of the cytoskeleton that correlate with decreased SI apical surface expression. These results lead us to propose an alternate model to explain the pathophysiology associated with rotavirus infection.     

The supply of regeneration micro-sites and segregation of tree species in a hardwood/boreal forest transition zone

We examine the role that demand for, and supply of, micro-sites for seedling regeneration plays in preserving segregation of species into boreal and hardwood communities in the Lake Superior region of northern Ontario. The sensitivity of tree seedlings of the two dominant species in each community to micro-environmental variations was measured in transitional zones, where all species were present, and these responses compared to the availability of micro-sites in adjacent 'pure' communities. Acer saccharum Marsh seedlings exhibited the largest ecological amplitude, and were found growing on the deepest litter layers and where the greatest mass of hardwood litter had accumulated. Abies balsamea (L.) Mill., Picea glauca (Moench) Voss, and Betula alleghaniensis Britton seedlings were found growing where hardwood litter layers were thinnest, more moss was present, and light levels were higher, all conditions most frequent in the boreal community. The results imply that Acer should regenerate well in both community types, while the other three species should regenerate well only in boreal communities. The abruptness of the hardwood/boreal community boundary in this area is explained by the abrupt population boundary of Acer saccharum , the potential regional dominant; this is tentatively attributed to temperature limitation on this species at its northern range limit.     

Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish

We have cloned agroup of cDNAs that encodes the skeletal ryanodine receptor isoform(RyR1) of fish from a blue marlin extraocular muscle library. The cDNAsencode a protein of 5,081 amino acids with a calculated molecular massof 576,302 Da. The deduced amino acid sequence shows strong sequenceidentity to previously characterized RyR1 isoforms. An RNA probederived from a clone of the full-length marlin RyR1 isoform hybridizesto RNA preparations from extraocular muscle and slow-twitch skeletalmuscle but not to RNA preparations from fast-twitch skeletal or cardiacmuscle. We have also isolated a partial RyR clone from marlin andtoadfish fast-twitch muscles that shares 80% sequence identity withthe corresponding region of the full-length RyR1 isoform, and a RNAprobe derived from this clone hybridizes to RNA preparations fromfast-twitch muscle but not to slow-twitch muscle preparations. Westernblot analysis of slow-twitch muscles in fish indicates the presence ofonly a single high-molecular-mass RyR proteincorresponding to RyR1. [³H]ryanodine bindingassays revealed the fish slow-twitch muscle RyR1 had a greatersensitivity for Ca²⁺ than thefast-twitch muscle RyR1. The results indicate that, in fish muscle,fiber type-specific RyR1 isoforms are expressed and the two proteinsare physiologically distinct.