Search PubMed⌕ Search

Biomedical subjects

D Epel

Publications and source records attributed to D Epel.

At least 73 records · Page 4Linked to original sources
PubMed1976

The glutathione thiol-disulfide status in the sea urchin egg during fertilization and the first cell division cycle.

The intracellular levels of GSH, GSSG, and protein-glutathione disulfide (protein-SSG) have been measured in the eggs and developing embryos of the sea urchins Lytechinus pictus and Stronglyocentrotus purpuratus. Total cellular glutathione is maintained in a very highly reduced state during these initial stages of development. Thus for unfertilized eggs of L. pictus the results (mumol/g dry weight) were 11 +/- 1 for GSH, 0.02 +/- 0.01 for GSSG, and 0.07 +/- 0.02 for protein-SSG. No significant change in these values was observed upon fertilization of the eggs or during the first cell division cycle. The values obtained with S. purpuratus were somewhat greater, but were also found to exhibit no significant variations upon fertilization or cell division. These observations indicate that changes in the total cellular glutathione thiol-disulfide status are not involved in the control mechanisms which operate during fertilization of the first cell division cycle in the sea urchin egg.

Animals↗
PubMed1976

Scanning electron microscope studies of sea urchin fertilization. I. Eggs with vitelline layers.

The surface coats of sea urchin eggs and the events of fertilization which take place on these surfaces were examined with the scanning electron microscope (SEM). Gametes of Stronglyocentrotus purpuratus and Lytechinus pictus were considered in detail; eggs of seven other echinoids were examined for comparative purposes. Jelly coats, preserved by varying the pH of fixation, were found to vary in morphology and solubility properties between species. The vitelline layers of the nine echinoids are characterized by arrays of projections which are impressions of cytoplasmic microvilli in the vitelline layer. After sperm bind to the egg surface via the acrosomal process, fine filaments, apparently an egg response to insemination, further connect some sperm heads and tails to the egg. The cortical reactions spread out as a wave from where the fertilizing sperm fused with the egg; separation of the vitelline layer proceeds as a smooth wave from S. purpuratus eggs and as a series of localized separations in L. pictus eggs. The fertilization membranes of S. purpuratus and Allocentrotus fragilis zygotes are expanded replicas of their respective vitelline layers, suggesting that fertilization membranes are formed by an unfolding of the vitelline layer.

Animals↗
PubMed1976

Fertilization acid of sea urchin eggs is not a consequence of cortical granule exocytosis.

Sea urchin eggs treated with 10 mM NHC1 release a "fertilization acid" although cortical granule exocytosis does not take place. If the eggs are inseminated following ammonia activation, the cortical reaction occurs and a fertilization membrane elevates in the absence of detectable acid release. Examination by electron microscopy of eggs fixed between ammonia activation and insemination confirms the presence of intact granules. Thus, the fertilization acid is not caused by the release of the cortical granules. Ammonia treatment of fertilized eggs stimulates further release of acid. The release of acid can occur repeatedly in ammonia activated eggs if they are washed into normal seawater between successive ammonia treatments. Our results suggest that the release of fertilization acid is related to some metabolic process which can be turned "on or off".

Ammonia↗
PubMed1975

Polyspermy block of Spisula eggs is prevented by cytochalasin B.

The eggs of the surf clam Spisula solidissima have a built-in mechanism that prevents polyspermy: the eggs show a 70 percent decrease in sperm receptivity 5 seconds after fertilization, and become completely resistant to sperm by 15 seconds. When the outer egg coat (vitelline layer) was removed, there was no change in fertilizability or the timing of the block to polyspermy. This suggests that the alteration occurs in or at the plasma membrane. Such changes in the egg surface were sensitive to low concentrations of cytochalasin B.

Animals↗
PubMed1975

Relationship between release of surface proteins and metabolic activation of sea urchin eggs at fertilization.

Macromolecular components are released from sea urchin eggs when their metabolism is activated at fertilization or by incubation in ammonia. When the released material is dialyzed, concentrated, and added back to partially activated eggs the rate of protein synthesis is suppressed to the level of the unactivated egg. The surface proteins of the unfertilized eggs can be labeled with 125I by a lactoperoxidase procedure. When fertilized or activated with various parthenogenetic agents, 15-25% of the total labeled protein is released; most of the label is associated with a 150,000-dalton glycoprotein. The extent of metabolic activation, as assessed by measuring increased protein synthesis, is correlated with the amount of surface label released. Several other proteins are released during activation but are not labeled by the lactoperoxidase procedure in the intact cell. We have not yet identified which of these components is responsible for suppressing protein synthesis, nor do we know if any of the other metabolic changes of fertilization such as K+ conductance and DNA synthesis are also suppressed. We suggest that these released components are surface molecules involved in maintaining the low metabolic state occurring at the end of oogenesis and that removal of these components during fertilization results in the release of the suppression of the egg.

Ammonia↗