The Functional Anatomy of the Echinoderm Spermatozoon and its Interaction with the Egg at Fertilization

Summers, Robert G.; Hylander, Bonnie L.; Colwin, Laura Hunter; Colwin, Arthur L.

doi:10.1093/icb/15.3.523

Cited by 106 publications

(55 citation statements)

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“…19). This specialization of the periacrosomal material at the base of the acrosome has been reported in other echinoderms (Hagiwara et al, 1967;Mabuchi and Mabuchi, 1973;Tilney et al> 1973;Summers et al, 1975;Hylander and Summers, 1975;Colwin et al) 1975).…”

Section: Spermatozoon (Figs 17-19)supporting

confidence: 81%

Ultrastructural Observations on the Spermatogenesis of the Brittle-Star Amphipholis Kochii Lutken (Echinodermata : Ophiuroidea)

Yamashita¹,

Iwata²

1983

Publ. SMBL

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Section: Spermatozoon (Figs 17-19)supporting

confidence: 81%

Ultrastructural Observations on the Spermatogenesis of the Brittle-Star Amphipholis Kochii Lutken (Echinodermata : Ophiuroidea)

Yamashita¹,

Iwata²

1983

Publ. SMBL

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“…What is interesting is that polymerization occurred only from the center of the cup in relation to some filamentous material which was more electron dense than the material in the rest of the cup. I speculated that these dense filaments (core filaments) might nucleate the assembly of the actin, a conjecture originally proposed by Colwin et al (2) and Summers et al (15).…”

mentioning

confidence: 95%

Polymerization of actin. V. A new organelle, the actomere, that initates the assembly of actin filaments in Thyone sperm

Lg¹

1978

The Journal of Cell Biology

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Between the acrosomal vacuole and the nucleus is a cup of amorphous material (profilactin) which is transformed into filaments during the acrosomal reaction. In the center of this cup in untreated Thyone sperm is a dense material which I refer to as the actomere; it is composed of 20-25 filaments embedded in a dense matrix. To visualize the substructure of the actomere, the profilactin around it must be removed. This is achieved either by demembranating the sperm with Triton X-100 and then raising the pH to 8.0, or by adding ionophores to intact sperm at pH 8.0. Under these conditions, the actomere remains as a unit while the rest of the profilactin is solubilized or polymerized. When demembranated sperm are incubated under conditions in which the actin should polymerize, filaments grow from the end of the actomere: the actomere thus appears to behave as a nucleating body. This observation is strengthened by experiments in which untreated sperm are incubated in seawater or isotonic NaC1 at pH 7.0 and the ionophore X537A is added; in this case, only a partial polymerization of the actin occurs and the acrosomal vacuole does not fuse with the cell surface. The actin filaments that do form, however, are attached to the apical end of the actomere. In fact, the elongating filaments push their way into and frequently through the acrosomal vacuole. Thus, it appears that the sperm organizes the actin filaments by controlling their nucleation. My model is that the cell controls the amount of unbound actin such that it is slightly above the critical concentration for polymerization. Then, spontaneous nucleation is unfavored and polymerization would proceed from existing nuclei such as the actomere.KEY WORDS actin polymerization sperm nucleation 9 acrosome reaction actomere One of the most fascinating aspects in the assembly of structural proteins such as microtubules and actin filaments in cells is the control of their distribution, for ultimately the factors involved in this control regulate motility, cell shape, intracellular transport, and secretion. Although many actin filaments appear randomly distributed in cells or in large regions of cells, actin filaments are often seen attached to specific regions of the cell, i.e., to the "Z" line in skeletal muscle, to the dense bodies in smooth muscle, and to membranes in many nonmuscle ceils. Whether this attachment occurs because these sites nucleate the J. CELL BIOLOGY 9 The Rockefeller University Press 9 0021-9525/78/0501-055151.00 551

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“…The acrosome reaction of sea urchin spermatozoa is characterized by a sequence of events that include fusion of the acrosomal membrane with the plasma membrane, exocytosis of the acrosomal vacuole and polymerization of G-actin to form the acrosomal filament (Dan, 1967; Summers, Hylander, Colwin & Colwin, 1975). In many invertebrate spermatozoa, the membrane events are known to occur concomitantly with actin polymerization, and the acrosome reaction can be assessed by the presence of an extended filament (Tilney, Hatano, Ishikawa & Mooseker, 1973).…”

Section: Introductionmentioning

confidence: 99%

Effects of putative protease inhibitors on the acrosome reaction of sea urchin spermatozoa

Hyne¹,

Garbers²

1982

Reproduction

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The Functional Anatomy of the Echinoderm Spermatozoon and its Interaction with the Egg at Fertilization

Cited by 106 publications

References 0 publications

Ultrastructural Observations on the Spermatogenesis of the Brittle-Star Amphipholis Kochii Lutken (Echinodermata : Ophiuroidea)

Ultrastructural Observations on the Spermatogenesis of the Brittle-Star Amphipholis Kochii Lutken (Echinodermata : Ophiuroidea)

Polymerization of actin. V. A new organelle, the actomere, that initates the assembly of actin filaments in Thyone sperm

Effects of putative protease inhibitors on the acrosome reaction of sea urchin spermatozoa

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