William R Eckberg

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Egg activation in all animals evidently requires the synthesis of inositol 1,4,5-trisphosphate (InsP(3)) from phosphatidylinositol 4,5-bisphosphate (PIP(2)) by phospholipase C (PLC). Depending on the organism, InsP(3) elicits either calcium oscillations or a single wave, which in turn initiates development. A soluble component in boar sperm that activates(More)
Intracellular calcium release from the endoplasmic reticulum is a hallmark at egg activation of both vertebrates and invertebrates. This fertilization-associated calcium release results from generation of the second messenger inositol 1,4,5-trisphosphate (IP(3)) by one or more phospholipases C (PLC). We characterized Chaetopterus PLCbeta and gamma by(More)
Transient waves of Ca2+ release cross-fertilizing deuterostome eggs from the point of sperm entry to its antipode and provide much of the activating stimulus for the egg. Based on several indirect lines of experimental evidence, it was proposed that protostome eggs are activated by a prolonged uptake of Ca2+ from the medium due to sperm-induced membrane(More)
We report that protein kinase C (PKC) plays a regulatory role in early cleavage in Chaetopterus eggs. Using Western blotting, we assayed the expression patterns of conventional PKCs (cPKC), novel PKCs (nPKC), and atypical PKCs (aPKC). During early development after fertilization, PKC protein levels varied independently by isoform. PKC protein expression(More)
Others have reported that microinjection of inositol 1,4,5-trisphosphate (InsP3) releases stored intracellular Ca2+ and causes fertilization envelope elevation, part of the activation process normally initiated by fertilization in deuterostome eggs. In the protostome, Spisula solidissima, germinal vesicle breakdown (GVBD) is the first visible response of(More)
Binding of estrogen to its receptor (ER) activates early genes that drive responsive cells through the proliferative phase. Earlier studies to evaluate the expression of protooncogenes, growth factors, growth factor receptor and steroid hormone receptor gene activities in the rat uterine system indicated complex pathways that involve significant 'crosstalk'(More)
The human breast cancer cell lines MCF-7 (ER positive), ZR 75-1 (ER positive) and MDA-MB 231 (ER negative) form solid tumors within one week following inoculation into athymic nude mice. Tumor formation by MCF-7 and ZR 75-1 cells was dependent upon estrogen, whereas MDA-MB 231 cells formed tumors in ovariectomized mice with or without supplemental estrogen.(More)
PTPH1 is a human protein-tyrosine phosphatase with homology to the band 4.1 superfamily of cytoskeleton-associated proteins. Here, we report the purification and biochemical characterization of this enzyme from baculovirus-infected insect cells. The purified protein exhibited an apparent M(r) of 120,000 on SDS gels. The native enzyme dephosphorylated both(More)
Increases in the intracellular free calcium concentration are of great importance to the initiation of development in deuterostomes. Their involvement has not yet been clearly defined in protostomes. We used endogenous ligands (IP3, cADPR, ryanodine and NAADP) and pharmacological agents (thapsigargin [Tg], thimerosal, caffeine and heparin) to study smooth(More)
Changes in protein tyrosine phosphorylation are an essential aspect of egg activation after fertilization. Such changes result from the net contributions of both tyrosine kinases and phosphatases (PTP). This study was conducted to determine what role(s) PTP may have in egg activation. We identified four novel PTP in Chaetopterus pergamentaceus oocytes,(More)