Obtention de cristaux de carbonate de calcium in vitro à partir de protéines isolées du manteau de Pinctada margaritifera

International audienc

Spermatozoa motility in bivalves: Signaling, flagellar beating behavior, and energetics

WOS:000476579700004Though bivalve mollusks are keystone species and major species groups in aquaculture production worldwide, gamete biology is still largely unknown. This review aims to provide a synthesis of current knowledge in the field of sperm biology, including spermatozoa motility, flagellar beating, and energy metabolism; and to illustrate cellular signaling controlling spermatozoa motility initiation in bivalves. Serotonin (5-HT) induces hyper-motility in spermatozoa via a 5-HT receptor, suggesting a serotoninergic system in the male reproductive tract that might regulate sperm physiology. Acidic pH and high concentration of K+ are inhibitory factors of spermatozoa motility in the testis. Motility is initiated at spawning by a Na+-dependent alkalization of intracellular pH mediated by a Na+/H+ exchanger. Increase of 5-HT in the testis and decrease of extracellular K+ when sperm is released in seawater induce hyperpolarization of spermatozoa membrane potential mediated by K+ efflux and associated with an increase in intracellular Ca2+ via opening of voltage-dependent Ca2+ channels under alkaline conditions. These events activate dynein ATPases and Ca2+/calmodulin-dependent proteins resulting in flagellar beating. It may be possible that 5-HT is also involved in intracellular CAMP rise controlling cAMP-dependent protein kinase phosphorylation in the flagellum. Once motility is triggered, flagellum beats in asymmetric wave pattern leading to circular trajectories of spermatozoa. Three different flagellar wave characteristics are reported, including "full", "twitching", and "declining" propagation of wave, which are described and illustrated in the present review. Mitochondrial respiration, ATP content, and metabolic pathways producing ATP in bivalve spermatozoa are discussed. Energy metabolism of Pacific oyster spermatozoa differs from previously studied marine species since oxidative phosphorylation synthetizes a stable level of ATP throughout 24-h motility period and the end of movement is not explained by a low intracellular ATP content, revealing different strategy to improve oocyte fertilization success. Finally, our review highlights physiological mechanisms that require further researches and points out some advantages of bivalve spermatozoa to extend knowledge on mechanisms of motility

Quality assessment of cryopreserved black-lip pearl oyster Pinctada margaritifera spermatozoa

High quality of sperm is essential to a high fertilization rate, especially post- cryopreservation. Assessment of sperm integrity, motility and energy reserves before cryopreservation is necessary for selection of milt with optimal fertilizing potential. We describe the effect of cryopreservation on the quality of black-lip pearl oyster, Pinctada margaritifera var. cumingii sperm. Evaluated quality indices of fresh and frozen/thawed P. margaritifera spermatozoa, included morphology, ultrastructure and motility characteristics relative to the energy content (ATP) and its capacity to be sustained by mitochondrial respiration. Morphology and ultrastructure were quantitatively evaluated using images obtained by optical microscopy assisted by the Image J software and TEM, respectively. Sperm motility was assessed using Image J software combined with a computer assisted sperm analysis plugin adapted for assessing P. margaritifera spermatozoa. Other sperm quality parameters evaluated included O2 consumption, ATP content, and creatine kinase activity. Frozen/thawed spermatozoa exhibited damage to the head but retained a compact spherical shape. Sperm motility indicators showed a significant decrease in quality resulting from the freeze/thaw process. The percent of motile cells was 54% compared to 84% in fresh sperm, O2 consumption was 4.8 compared to 44 nanomol min−1, ATP content was 0.72 nmol/109 spermatozoa in the activating medium compared to 4.54 nmol/109 spermatozoa, and creatine kinase activity was 9.06 × 10−5 IU mg−1 protein compared to 12.5 × 10−5 IU mg−1 protein. The cryopreservation protocol allowed obtaining an acceptable motility rate after thawing, confirming the predictive value of sperm motility measurements before cryopreservation in terms of their ability to withstand freezing process

Screening of bioactive compounds in proliferative macroalgae from French Polynesia: a sustainable approach

International audienc

Evaluation of cytotoxicity of various common French polynesian vascular plants extracts on murin melanomas cells

International audienc

Study of total phenolic content, anti-radical and anti-oxidant activities of two French Polynesian endemic plants : Vaccinium cereum and Pipturus argenteus

International audienc

Hatchery-scale trials using cryopreserved spermatozoa of black-lip pearl oyster,

Cryopreservation is a valuable tool for genetic improvement programs. Several bivalve mollusc species have already been the subject of such programs and the Tahitian black pearl oyster industry is now planning the development of selective breeding for desirable traits in Pinctada margaritifera. The ability to cryopreserve spermatozoa would, therefore, offer significant benefits to the cultured black pearl industry. Spermatozoa were cryopreserved with cryoprotectant agent (CPA) 0.7 M trehalose in 0.8 M Me2SO and a two-step freezing process was used: straws were first maintained in nitrogen vapour for 10 minutes, then directly plunged into liquid nitrogen and stored for one week before use. The viability of thawed sperm was 23% lower than that of fresh sperm. When using thawed sperm, therefore, a higher sperm/egg ratio of 100 000:1 was required to reach 80% oocyte fertilization, compared with 100:1 for fresh sperm. Nevertheless, this first demonstration of cryopreserved sperm fertility in black pearl oyster confirms the hatchery applicability of the cryopreservation technique defined here. Monitoring for larval viability during the first 23 days of life revealed no significant differences between the progeny produced with cryopreserved sperm and that produced using fresh sperm

Evaluation of the tyrosinase inhibition activity of different varieties of breadfruit trees, Artocarpus altilis (Parkinson) Fosb. from French Polynesia

International audienc

Potential of tropical macroalgae from French Polynesia for biotechnological applications

WOS:000489922500001International audienceExtracts from 26 marine macroalgal species (11 Phaeophyceae, 7 Chlorophyta, and 8 Rhodophyta) sampled from the lagoons of Tahiti, Moorea, and Tubuai (French Polynesia) were tested for several biological activities. The red macroalga Amansia rhodantha exhibited the strongest antioxidant activities using four complementary methodologies (total phenolic content, 2,2-diphenyl-1-picrylhydrazyl, ferric reducing antioxidant power assay, and oxygen radical absorbance capacity assay). Therefore, the major metabolites of A. rhodantha were isolated and their structures identified. Some brown algae, especially species of the family Dictyotaceae like Padina boryana and Dictyota hamifera, showed cytotoxic activities against murine melanoma cells. Caulerpa chemnitzia extract demonstrated also a strong alpha-glucosidase inhibition (83.8% at 10 mu g mL(-1)) and Asparagopsis taxiformis extract a high acetylcholinesterase inhibition (71.3% at 100 mu g mL(-1)). Lastly, several Polynesian seaweeds demonstrated quorum-sensing inhibition for Vibrio harveyi. These results suggested that some seaweeds from French Polynesia have a great biotechnological potential for future applications in aquaculture, health, or cosmetic industries

Glass thickness for windows

The choice of glass thickness for windows has always been one of conventional practice. This digest presents information regarding glass strength and wind pressure characteristics. It is now possible to incorporate this information in an improved procedure for determining appropriate glass thicknesses for windows of different sizes subjected to different wind pressures.Aussi disponible en fran\ue7ais : \uc9paisseur du verre destin\ue9 aux fen\ueatresPeer reviewed: NoNRC publication: Ye