The sperm entry site during fertilization of the zebrafish egg: Localization of actin

1992 ◽  
Vol 32 (3) ◽  
pp. 217-228 ◽  
Author(s):  
Nathan H. Hart ◽  
Karen A. Becker ◽  
Joseph S. Wolenski
Keyword(s):  
Entry Site ◽  
Sperm Entry

scholarly journals Spatiotemporal Analysis of Ca2+ Waves in Relation to the Sperm Entry Site and Animal–Vegetal Axis during Ca2+ Oscillations in Fertilized Mouse Eggs

2000 ◽  
Vol 218 (2) ◽  
pp. 299-313 ◽  
Author(s):  
Ryusaku Deguchi ◽  
Hideki Shirakawa ◽  
Shoji Oda ◽  
Tatsuma Mohri ◽  
Shunichi Miyazaki
Keyword(s):  
Spatiotemporal Analysis ◽  
Entry Site ◽  
Sperm Entry ◽  
Mouse Eggs

scholarly journals Sperm entry induces polarity in fucoid zygotes

Development ◽  
2000 ◽  
Vol 127 (3) ◽  
pp. 493-501 ◽  
Author(s):  
W.E. Hable ◽  
D.L. Kropf
Keyword(s):  
Environmental Cues ◽  
Entry Site ◽  
Environmental Signals ◽  
Growth Axis ◽  
Low Sodium ◽  
Extrinsic Cues ◽  
Sperm Entry ◽  
Actin Patch ◽  
Adhesive Secretion ◽  
Lines Of Evidence

Fucoid zygotes establish a rhizoid-thallus growth axis in response to environmental signals; however, these extrinsic cues are not necessary for polarization, suggesting that zygotes may have inherent polarity. The hypothesis that sperm entry provides a default pathway for polarization of zygotes cultured in the absence of environmental signals was tested, and was supported by several lines of evidence. First, an F-actin patch, a cortical marker of the rhizoid pole, formed at the sperm entry site within minutes of fertilization. Second, the sperm entry site predicted the site of polar adhesive secretion (the first morphological manifestation of the rhizoid pole) and the position of rhizoid outgrowth. Third, when fertilization was restricted to one hemisphere of the egg, rhizoid outgrowth always occurred from that hemisphere. Fourth, delivery of sperm to one location within a population of eggs resulted in polarization of both adhesive secretion and rhizoid outgrowth toward the sperm source. Finally, induction of polyspermy using low sodium seawater increased the frequency of formation of two rhizoids. Sperm entry therefore provides an immediate default axis that can later be overridden by environmental cues.

scholarly journals An elevated free cytosolic Ca2+ wave follows fertilization in eggs of the frog, Xenopus laevis.

1985 ◽  
Vol 100 (4) ◽  
pp. 1325-1329 ◽  
Author(s):  
W B Busa ◽  
R Nuccitelli
Keyword(s):  
Protein Synthesis ◽  
Xenopus Laevis ◽  
Transient Increase ◽  
Cortical Granule ◽  
Entry Site ◽  
Cleavage Division ◽  
Present Evidence ◽  
Granule Exocytosis ◽  
Sperm Entry ◽  
Cortical Granule Exocytosis

The eggs of most or all animals are thought to be activated after fertilization by a transient increase in free cytosolic Ca2+ concentration ([Ca2+]i). We have applied Ca2+-selective microelectrodes to detect such an increase in fertilized eggs of the frog, Xenopus laevis. As observed with an electrode in the animal hemisphere, [Ca2+]i increased from 0.4 to 1.2 microM over the course of 2 min after fertilization, and returned to its original value during the next 10 min. No further changes in [Ca2+]i were detected through the first cleavage division. In eggs impaled with two Ca2+ electrodes, the Ca2+ pulse was observed to travel as a wave from the animal to the vegetal hemisphere, propagating at a rate of approximately 10 microns/s across the animal hemisphere. The apparent delay between the start of the fertilization potential and initiation of the Ca2+ wave at the sperm entry site as approximately 1 min. Through these observations describe only the behavior of subcortical [Ca2+]i, we suggest that our data represent the subcortical extension of the cortical Ca2+ wave thought to trigger cortical granule exocytosis, and we present evidence that both the timing and magnitude of the Ca2+ pulse we observed are consistent with this identity. This first quantification of subcortical [Ca2+]i during fertilization indicates that the Ca2+ transient is available to regulate processes (e.g., protein synthesis) in the subcortical cytosol.

scholarly journals Cytoplasmic streaming drifts the polarity cue and specifies the cell polarity in Caenorhabditis elegans zygotes

2019 ◽  
Author(s):  
Kenji Kimura ◽  
Akatsuki Kimura
Keyword(s):  
Caenorhabditis Elegans ◽  
Cell Polarity ◽  
Cytoplasmic Streaming ◽  
The Body ◽  
Cell Cortex ◽  
Spatial Cues ◽  
Entry Site ◽  
C Elegans ◽  
Sperm Entry ◽  
Anterior Posterior

AbstractCell polarisation is required to define body axes during development. The position of spatial cues for polarisation is critical to direct the body axes. In Caenorhabditis elegans zygotes, the sperm-derived pronucleus/centrosome complex (SPCC) serves as the spatial cue to specify the anterior–posterior axis. Approximately 30 minutes after fertilisation, the contractility of the cell cortex is relaxed near the SPCC, which is the earliest sign of polarisation and called symmetry breaking (SB). It is unclear how the position of SPCC at SB is determined after fertilisation. Here, we show that SPCC drifts dynamically through the cell-wide flow of the cytoplasm, called meiotic cytoplasmic streaming. This flow occasionally brings SPCC to the opposite side of the sperm entry site before SB. Our results demonstrate that cytoplasmic flow determines stochastically the position of the spatial cue of the body axis, even in an organism like C. elegans for which development is stereotyped.

scholarly journals Sperm Receptivity in Sea Urchin Oocytes and Eggs

1985 ◽  
Vol 118 (1) ◽  
pp. 85-97 ◽  
Author(s):  
BRIAN DALE
Keyword(s):  
Experimental Data ◽  
Sea Urchin ◽  
Resting Potential ◽  
Entry Site ◽  
Sea Urchin Eggs ◽  
Interaction Sites ◽  
Sperm Entry ◽  
Electrophysiological Method ◽  
Cytoplasmic Maturation ◽  
Two Parameters

An electrophysiological method for studying the receptivity to spermatozoa of sea urchin eggs and oocytes is described. Pairs of adjacent oocytes and eggs, with intact jelly layers, were impaled and simultaneously exposed to a known concentration of spermatozoa. Two parameters were studied. The time from insemination to the first successful collision (as indicated by a step depolarization across the egg plasma membrane) and the total number of successful collisions. Sperm densities of 107ml−1 were used, which ensured almost immediate interaction between several thousand spermatozoa and each female gamete. In all cases, under control conditions, the oocyte was more receptive to spermatozoa than was the egg, giving rise to the first electrical event at about 5 s post-insemination, compared to about 13 s for the egg. In addition, whereas 10–15 spermatozoa usually entered the oocyte, only one entered the egg. The low receptivity of eggs appears to be independent of resting potential. Cytoplasmically immature eggs or mature eggs briefly exposed to nicotine, strychnine, choline or Tris tend to be polyspermic and have comparable receptivity to oocytes. The data suggest that there are limited number of viable interaction sites on the oocyte surface and that during cytoplasmic maturation these sites are rendered less receptive. In the mature egg there may be one preferential sperm entry site. This hypothesis is consistent with the experimental data and would explain why sea urchin eggs are usually monospermic at high sperm densities.

Histology of the vertebral artery–dural junction: relevance to posterolateral approaches to the skull base

2019 ◽  
pp. 1-6
Author(s):  
Robert C. Rennert ◽  
Martin P. Powers ◽  
Jeffrey A. Steinberg ◽  
Takanori Fukushima ◽  
John D. Day ◽  
...  
Keyword(s):  
Connective Tissue ◽  
Vertebral Artery ◽  
Skull Base ◽  
Histological Analysis ◽  
Foramen Magnum ◽  
Entry Site ◽  
Microsurgical Technique ◽  
Vessel Injury ◽  
Far Lateral ◽  
Clear Delineation

OBJECTIVEThe far-lateral and extreme-lateral infrajugular transcondylar–transtubercular exposure (ELITE) and extreme-lateral transcondylar transodontoid (ELTO) approaches provide access to lesions of the foramen magnum, inferolateral to mid-clivus, and ventral pons and medulla. A subset of pathologies in this region require manipulation of the vertebral artery (VA)–dural interface. Although a cuff of dura is commonly left on the VA to avoid vessel injury during these approaches, there are varying descriptions of the degree of VA-dural separation that is safely achievable. In this paper the authors provide a detailed histological analysis of the VA-dural junction to guide microsurgical technique for posterolateral skull base approaches.METHODSAn ELITE approach was performed on 6 preserved adult cadaveric specimens. The VA-dural entry site was resected, processed for histological analysis, and qualitatively assessed by a neuropathologist.RESULTSHistological analysis demonstrated a clear delineation between the intima and media of the VA in all specimens. No clear plane was identified between the connective tissue of the dura and the connective tissue of the VA adventitia.CONCLUSIONSThe VA forms a contiguous plane with the connective tissue of the dura at its dural entry site. When performing posterolateral skull base approaches requiring manipulation of the VA-dural interface, maintenance of a dural cuff on the VA is critical to minimize the risk of vascular injury.

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