SUMMARYOcean acidification is predicted to have significant effects on benthic calcifying invertebrates, in particular on their early developmental stages. Echinoderm larvae could be particularly vulnerable to decreased pH, with major consequences for adult populations. The objective of this study was to understand how ocean acidification would affect the initial life stages of the sea urchin Paracentrotus lividus, a common species that is widely distributed in the Mediterranean Sea and the NE Atlantic. The effects of decreased pH (elevated P CO2 ) were investigated through physiological and molecular analyses on both embryonic and larval stages. Eggs and larvae were reared in Mediterranean seawater at six pH levels, i.e. pH T 8.1, 7.9, 7.7, 7.5, 7.25 and 7.0. Fertilization success, survival, growth and calcification rates were monitored over a 3day period. The expression of genes coding for key proteins involved in development and biomineralization was also monitored. Paracentrotus lividus appears to be extremely resistant to low pH, with no effect on fertilization success or larval survival. Larval growth was slowed when exposed to low pH but with no direct impact on relative larval morphology or calcification down to pH T 7.25. Consequently, at a given time, larvae exposed to low pH were present at a normal but delayed larval stage. More surprisingly, candidate genes involved in development and biomineralization were upregulated by factors of up to 26 at low pH. Our results revealed plasticity at the gene expression level that allows a normal, but delayed, development under low pH conditions.

Reproducible and nondegradative preparation of sulfated molecules exhibiting diverse biological properties requires caring out sulfation reactions under ready controlled mild conditions. Although, to date, sulfur trioxide is the most used sulfation agent, its highly acid character has brought its use in association with different nitrogen bases as sulfur trioxide−nitrogen base complexes and/or by introduction of basic solvents as pyridine. We have applied sulfur trioxide and other sulfation agents including protocols for the synthesis of biologically active sulfated polysaccharides and demonstrated that these agents provoke cleavage of glycosidic bonds and other acid labile functions as amides, esters and even ethers. These facts prompted us to develop new reaction conditions for a general and nondestructive sulfation protocol. Our approach consists of the introduction of 2-methyl-2-butene as an acid scavenger of neutral character. Application of the method leads to an efficient, reproducible, and controlled synthesis of acid labile dextran derivatives well-known to be active in tissue repair and recently proposed for example as a new therapeutic agent for prion diseases. A novel 1H NMR structural analysis of this kind of macromolecules is presented. This method offers a new advance for more efficient synthesis of biologically active sulfated macromolecules.

1.60 and N ‫؍‬ 230d 1.75 , respectively, for TEP occurring in water masses with short (i.e., <40 days) and long (i.e., >40 days) residence times. These two relationships imply that viral abundance decreases with TEP size, and they indicate that water residence time influences viral density and virus-bacterium interactions within aggregates. Our data suggest that the fraction of viruses attached to TEP is highest in areas characterized by a low renewal rate of the water mass and can constitute at times a significant fraction of total virus abundance. Due to the small distance between viruses and hosts on TEP, these particles may be hot spots for viral infection.

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Burn-related skin fibrosis leads to loss of tissue function and hypertrophic scar formation with damaging consequences for the patient. There is therefore a great need for an efficient agent to treat burned skin. We report that ReGeneraTing Agent (RGTA) reduces burn-induced skin alteration. The tissue-regenerating effect of RGTA OTR4120 was evaluated after 1-6 days and after 10 months in a rat skin burn model. This effect was also examined in vitro using fibroblasts isolated from control and 6-day-old burned skins. We measured production of dermal collagen I, III, and V and activities of metalloproteinases 2 and 9 (MMP-2 and MMP-9). Ratio of collagen III over collagen I production increased 6 days after the burn, because of a decrease in collagen I production. After 10 months, ratio of collagen III over collagen I in burn sites was still increased compared with control skin, because of an increase in collagen III production. Both abnormalities were corrected by OTR4120. OTR4120 increased pro-and active MMP-2 and MMP-9, compared with healthy and burned controls and therefore accelerated remodeling. Similar data were obtained with cultured fibroblasts from healthy and burned skins. OTR4120 enhanced healing in short-and long-term after burns, reducing the formation of fibrotic tissue, and then represents a potential agent to improve burned skin healing.

The emergence of ocean acidification as a significant threat to calcifying organisms in marine ecosystems creates a pressing need to understand the physiological and molecular mechanisms by which calcification is affected by environmental parameters. We report here, for the first time, changes in gene expression induced by variations in pH/pCO2 in the widespread and abundant coccolithophore Emiliania huxleyi. Batch cultures were subjected to increased partial pressure of CO2 (pCO2; i.e. decreased pH), and the changes in expression of four functional gene classes directly or indirectly related to calcification were investigated. Increased pCO2 did not affect the calcification rate and only carbonic anhydrase transcripts exhibited a significant down-regulation. Our observation that elevated pCO2 induces only limited changes in the transcription of several transporters of calcium and bicarbonate gives new significant elements to understand cellular mechanisms underlying the early response of E. huxleyi to CO2-driven ocean acidification.

Nonhealing wounds remain a major health problem whose treatment is challenging and costly. Treatments based on cells or growth factors are still not very effective. We developed an entirely novel strategy consisting in treatment of the wound-tissue matrix with biopolymers engineered to mimic heparan sulfates called OTR4120. This compound was dextran polymer with sulfated and carboxymethyl groupments. After binding to matrix proteins, the heparan-sulfate-mimicking polymer protects the microenvironment, maintaining the normal production of signals and growth factors needed for healing to occur. Here, we show that a specific biopolymer accelerates ulcer closure and improves re-epithelialization and dermal-matrix-component remodeling. OTR4120 treatment was associated with faster maturation of epidermal structures, most notably regarding the number of epithelial-cell layers, and with an appearance that more closely resembled normal skin. Treatment had also a main effect on collagen I and III expression. Necrotic skin ulcers induced in mice with doxorubicin recovered normal collagen levels and organization, with no evidence of fibrosis. Thus, appropriate polymer-based matrix therapy is a valid and simple alternative to regenerative medicine.

The study site located in the northwestern Mediterranean Sea was visited nine times in [2005][2006] to collect water samples from the epipelagic (5 m), mesopelagic (200 m, 600 m), and bathypelagic (1000 m, 2000 m) zones. The relative abundance of Bacteria, Crenarchaea, and Euryarchaea was determined by catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH). Apparent richness (total number of phylotypes detected) and community composition (different phylotypes detected) of Bacteria and Archaea were assessed by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified fragments of the 16S ribosomal ribonucleic acid (rRNA) gene followed by sequencing and phylogenetic analysis of selected phylotypes. The relative abundance of Crenarchaea and Euryarchaea in the epipelagic zone increased as stratification decreased. Apparent bacterial richness increased with decreasing stratification in the mesopelagic and bathypelagic zones. Deep vertical mixing at the study site represented the beginning of a seasonal succession. The effects of this succession were detectable throughout the water column and led to distinct prokaryotic communities in different depth layers during the stratified period. The seasonal variability in the relative abundance of Bacteria, as well as apparent prokaryotic richness and community composition, was comparable between the different depth layers. This suggests that prokaryotic communities of the dark ocean can be as dynamic as those found at the surface.