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Details Title: Fertilization mechanisms Description: 4.19.07 Total Flash Cards: 21 Created: 04/23/2007 18:43:18	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term what are the necessary aspects of an egg? Definition perivitelline space, zona pellucida, 1rst polar body, metaphase II spindle, cumulus oophoros, corona radiata Term How does the oocyte complete maturation and ovulation? Definition Resumption of meiosis begins within the ovarian follicle in response to the LH surge, Expansion of the cumulus oophorus Due to secretion of hyaluronic acid by the cumulus cells, Extrusion of the first polar body, Formation of the metaphase II spindle, Ovulation of metaphase II-arrested egg, fertalization or death Term How does the sperm mature? Definition Begins within the epididymis; Sperm surface acquires new proteins from epididymal secretions; Gradual development of progressive motility during sperm transit from caput to corpus to cauda epididymis; Transit time for sperm in the human epididymis is ~80-90 days Term what is capacitation? Definition Development of the “capacity” to fertilize an egg Term where does C normally occur? Definition Normally occurs within the female reproductive tract: endocervix, uterus, Fallopian tube Term what changes occur during C? Definition Involves many changes in the sperm: Loss of cholesterol from sperm plasma membrane ; Changes in the surface charge of proteins; Movements of sperm surface proteins and lipids; Changes in ion conductance; Changes in phosphorylation of sperm proteins; Development of hyperactivated motility Term what are the 2 sperm enzymes involved in capacitation? Definition Two sperm enzymes are involved in capacitation: “soluble” adenylyl cyclase (sAC) - activated by bicarbonate and calcium, Protein kinase A (PKA; cAMP-dependent protein kinase) Term what is the sperm's path to the egg? Definition Ectocervix; Endocervix; Uterine cavity; Fallopian tube Term must sperm be hyperactivated? Definition it sure helps Term what are the 5 steps to fertalization? Definition 1. arrival, 2. specific binding, 3. induction of acrosome reaction, 4. ZP penetration, 5. membrane recognition and Egg Activation. Term what is the penetration of cumulus cell layer? Definition Assisted by hyaluronidase activity associated with the sperm head Assisted by sperm motility May be a “group effort” - many sperm providing enzyme activity to help each other dissolve the hyaluronic acid matrix Term what is the sperm-ZP interaction? Definition Initiated by binding of an unidentified sperm surface receptor to carbohydrate residues expressed on the zona pellucida (ZP) glycoproteins Binding to the ZP causes the induction of acrosomal exocytosis Secondary binding of the inner acrosomal membrane to the ZP occurs after acrosomal exocytosis Term what is acrosomal exocytosis? Definition Complex receptor-mediated signaling event that results in calcium release within the sperm Fusion of sperm plasma membrane with the outer acrosomal membrane Release of acrosomal contents that include enzymes that help to digest the ZP Term what is ZP3? Definition ZP3 binds a sperm surface receptor (R) and produces two separate intracellular signals 1. Activation of a cation channel (C) produces a depolarizing current which causes activation of a T-type Ca2+ channel (T) 2. ZP3 activates a pH regulator via Gi-class G proteins (G), resulting in a transient alkalinization of internal pH. Transient Ca2+ and pH elevations synergistically promote a sustained Ca2+ elevation, leading to acrosomal exocytosis Term what is penetration of the ZP? Definition Requires motile force generated by flagellar movement Requires enzymatic hydrolysis by acrosomal proteases linked to the inner acrosomal matrix Angiotensin converting enzyme (ACE) releases GPI-linked proteins from the sperm surface and inner acrosomal matrix TESP5 - testis serine protease 5 PH-20 - hyaluronidase Term what is sperm-egg plasma membrane binding? Definition Sperm components: Izumo***, Cyritestin, CRISP1, Fertilin (?) Egg components: CD9***, GPI-linked protein(s), integrin (?) Term what is egg activation? Definition the process by which the sperm and egg interacting together become a 2-cell embryo capable of full term development. Egg activation begins with sperm-egg plasma membrane interactions. Term what are egg activation events? Definition Increase in intracellular calcium followed by repetitive calcium oscillations Cortical granule exocytosis Zona pellucida block to polyspermy Sperm head decondensation Resumption of the cell cycle Completion of meiosis with 2nd polar body emission Formation of male and female pronuclei Cleavage to the 2-cell stage Term what happens during Fertilization-induced calcium oscillations? Definition A hallmark of the initiation of egg activation in all mammalian species (calcium changes occur in all species) , Calcium release is triggered by phospholipase C (PLC) activity Term what does Cortical granule exocytosis results in? Definition the zona pellucida block to polyspermy Term what are the biochemical changes to the block of polyspermy? Definition ZP3 will no longer bind sperm or induce acrosomal exocytosis ZP2 is proteolytically cleaved and will no longer bind acrosome-reacted sperm