See AIDS.参阅AIDS。...[继续阅读]

    See AIDS.参阅AIDS。...[继续阅读]

    A membrane-bound sac in theanterior head region of a spermatozoon.In amammalian sperm it usually forms a cap overthe nucleus. It contains enzymes that are re-leased on contact with the egg at fertilization,as part of the ACROSOME REACTION.Theenzymes break...[继续阅读]

    The process by which asperm penetrates the wall of an egg duringfertilization. Contact with an egg of the samespecies triggers a series of events,includingthe release of lytic enzymes from the ACRO-SOME. These enzymes break down the outerlayer of the egg,...[继续阅读]

    See corticotropin.参阅corticotropin。...[继续阅读]

    A protein that is a major constituentof the cytoskeleton and of muscle. It is themost abundant protein inside eukaryote cells,accounting for 1-5% of total protein.Actin exists as globular monomers (G-actin),which assemble into long filamentous poly-mers (...[继续阅读]

    Proteins that bindto actin filaments-either in muscle to regu-late contraction,or as components of the cy-toskeleton.In skeletal muscle they include TR-OPOMYOSIN and TROPONINS,and addi-tionally CALDESMON in smooth muscle. Allwork essentially by altering t...[继续阅读]

    Proteins thatform cross-links between actin filaments inthe cytoskeleton. Each cross-linking proteinmolecule has two actin-binding sites,andcan bind two actin filaments.With shortlinkers,such as fimbrin molecules,the actinfilaments form parallel bundles;l...[继续阅读]

    Adiverse group of Gram-positive bacteria char-acterized by a filamentous,often branchinggrowth form that resembles the mycelium of afungus. They are numerous in the topsoil andare important in soil fertility. Some can causeinfections in animals and humans...[继续阅读]

    The transitory change inelectrical potential that occurs across themembrane of a nerve or muscle fiber duringthe passage of a nervous impulse. The actionpotential is an ALL-OR-NONE event,and isindependent of the strength of the stimuluseliciting the impul...[继续阅读]