The Experts below are selected from a list of 1725 Experts worldwide ranked by ideXlab platform

Ann Marie Sastry - One of the best experts on this subject based on the ideXlab platform.

  • assessment of sperm chemokinesis with exposure to jelly coats of sea urchin eggs and resact a microfluidic experiment and numerical study
    The Journal of Experimental Biology, 2007
    Co-Authors: Munish Vishwas Inamdar, Taeyong Kim, Yao Kuang Chung, Alex Was, Xinran Xiang, Chiawei Wang, Shuichi Takayama, Christian M Lastoskie, Florence I M Thomas, Ann Marie Sastry
    Abstract:

    SUMMARY Specific peptides contained within the extracellular layer, or jelly coat, of a sea urchin egg have been hypothesized to play an important role in fertilization, though separate accounting of the effects of chemoattraction, chemokinesis, sperm agglomeration and the other possible roles of the jelly coat have not been reported. In the present study, we used a microfluidic device that allowed determination of the differences in the diffusion coefficients of sperm of the purple sea urchin Arbacia punctulata subjected to two chemoattractants, namely the jelly coat and resact. Our objectives were twofold: (1) to experimentally determine and compare the diffusion coefficients of Arbacia punctulata spermatozoa in seawater, jelly coat solution and resact solution; and (2) to determine the effect of sea urchin sperm diffusion coefficient and egg size on the sperm–egg collision frequency using stochastic simulations. Numerical values of the diffusion coefficients obtained by diffusing the spermatozoa in seawater, resact solution and jelly coat solution were used to quantify the chemotactic effect. This allowed direct incorporation of known enlargements of the egg, and altered sperm diffusion coefficients in the presence of chemoattractant, in the stochastic simulations. Simulation results showed that increase in diffusion coefficient values and egg diameter values increased the collision frequency. From the simulation results, we concluded that type of sperm, egg diameter and diffusion coefficient are significant factors in egg fertilization. Increasing the motility of sperm appears to be the prominent role of the jelly coat.

Paola Gianguzza - One of the best experts on this subject based on the ideXlab platform.

  • Role of two co-occurring Mediterranean sea urchins in the formation of barren from Cystoseira canopy
    Estuarine Coastal and Shelf Science, 2015
    Co-Authors: Davide Agnetta, Giulia Ceccherelli, Fabio Badalamenti, F. Di Trapani, Chiara Bonaviri, Paola Gianguzza
    Abstract:

    Abstract In the Mediterranean Sea the co-occurring sea urchins Paracentrotus lividus and Arbacia lixula are usually considered to share the same ecological role in the formation of barren from Cystoseira canopy. However, their foraging ability may vary due to feeding behavior and species-specific morphological traits. The relative effects of P. lividus and A. lixula on Cystoseira canopy was tested experimentally both in the laboratory, at a density of about 20 ind./m 2 , and in the field by gut content analysis. Field and laboratory results show that A. lixula is unable to affect Cystoseira spp. Furthermore, these results confirmed the great ability of P. lividus to consume Cystoseira canopy, thus supporting the evidence of the major role of this species in the creation of a barren state.

Joseph W Gorsuch - One of the best experts on this subject based on the ideXlab platform.

  • chronic toxicity of silver to the sea urchin Arbacia punctulata
    Environmental Toxicology and Chemistry, 2006
    Co-Authors: Timothy J. Ward, James R Kramer, Robert L Boeri, Joseph W Gorsuch
    Abstract:

    The chronic toxicity of silver to the seaurchin (Arbacia punctulata) was determined in 30%o salinity seawater during a three-part study: A fertilization test (1-h sperm exposure), a 48-h embryo test, and a 30-d adult test. Combined data from the three tests resulted in a lowest-observed-effect concentration of 19 μg/L, a no-observed-effect concentration of 8.6 μg/L, and a maximum acceptable toxicant concentration of 13 μg/L, based on measured concentrations of dissolved silver. The 96-h median effective concentration was 40 μg/L, and the acute to chronic toxicity ratio was 3.1. During the tests, measured concentrations of free ionic silver (Ag+) were only 0.0027 to 0.0046% of dissolved silver concentrations, as predicted by ion-speciation theory. Some measured Ag+ concentrations were lower than predicted, indicating the presence of other ligands in the seawater test media. These strong sulfide ligands were exuded by the exposed sea urchins into the seawater (where Ag-sulfide complexes formed) in amounts that increased in direct proportion to the silver concentration during the toxicity test. This suggests a toxicity-defense mechanism that functioned by modifying the chemistry of the surrounding external medium.

William Spindel - One of the best experts on this subject based on the ideXlab platform.

  • the inhibition of mitosis by deuterium
    Annals of the New York Academy of Sciences, 2006
    Co-Authors: Paul R. Gross, William Spindel
    Abstract:

    Investigations of the antimitotic action of heavy water were carried out. It was observed that, depending on the conditions of deuteration, cell division in eggs of the sea urchin Arbacia punctulata could be delayed or arrested reversibly. The universality of the antimitotic action of D/sub 2/0 is discussed. The five major types of proposals that were made to account for the biological effects of deuterium enrichment, and particularly for their interference with cell division, are outlined. (M.C.G.)

Benjamin U Kaupp - One of the best experts on this subject based on the ideXlab platform.

  • the signal flow and motor response controling chemotaxis of sea urchin sperm
    Nature Cell Biology, 2003
    Co-Authors: Benjamin U Kaupp, Johannes Solzin, Eilo Hildebrand, Joel E Brown, Annika Helbig, Volker Hagen
    Abstract:

    The signalling pathway and the behavioural strategy underlying chemotaxis of sperm are poorly understood. We have studied the cellular events and motor responses that mediate chemotaxis of sperm from the sea urchin Arbacia punctulata. Here we show that resact, a chemoattractant peptide, initiates a rapid and transient rise in the concentration of cyclic GMP, followed by a transient influx of Ca2+. The binding of a single resact molecule elicits a Ca2+ response, and 50–100 bound molecules saturate the response. The ability to register single molecules is reminiscent of the single-photon sensitivity of rod photoreceptors. Both resact and cyclic nucleotides cause a turn or brief tumbling in the swimming path of sperm. We conclude that a cGMP-mediated increase in the Ca2+ concentration induces the primary motor response of sperm to the chemoattractant.