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Speract induces calcium oscillations in the sperm tail.

Wood CD, Darszon A, Whitaker M - J. Cell Biol. (2003)

Bottom Line: These data point to a model in which a messenger generated periodically in the tail diffuses to the head.Sperm are highly polarized cells.Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

View Article: PubMed Central - PubMed

Affiliation: School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, NE2 4HH, UK.

ABSTRACT
Sea urchin sperm motility is modulated by sperm-activating peptides. One such peptide, speract, induces changes in intracellular free calcium concentration ([Ca2+]i). High resolution imaging of single sperm reveals that speract-induced changes in [Ca2+]i have a complex spatiotemporal structure. [Ca2+]i increases arise in the tail as periodic oscillations; [Ca2+]i increases in the sperm head lag those in the tail and appear to result from the summation of the tail signal transduction events. The period depends on speract concentration. Infrequent spontaneous [Ca2+]i transients were also seen in the tail of unstimulated sperm, again with the head lagging the tail. Speract-induced fluctuations were sensitive to membrane potential and calcium channel blockers, and were potentiated by niflumic acid, an anion channel blocker. 3-isobutyl-1-methylxanthine, which potentiates the cGMP/cAMP-signaling pathways, abolished the [Ca2+]i fluctuations in the tail, leading to a very delayed and sustained [Ca2+]i increase in the head. These data point to a model in which a messenger generated periodically in the tail diffuses to the head. Sperm are highly polarized cells. Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

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Typical response of a field of sperm to addition of speract to a final concentration of 125 nM. (A) Fluo-4 fluorescence immediately before speract addition. (B) Fluo-4 fluorescence 4 s after speract addition. Images extracted from a time series acquired at 40 frames per second with 25-ms individual frame exposure time. (C) Ratio increases in Fluo-4 fluorescence across whole field. Upper trace (black), response to addition of 125 nM speract at t = 0. Lower trace (red), fluorescence from control field with no speract addition. Both traces have been corrected for the effects of fluorophore bleaching. Data acquired at 40 frames per second with 25-ms individual frame exposure time.
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fig1: Typical response of a field of sperm to addition of speract to a final concentration of 125 nM. (A) Fluo-4 fluorescence immediately before speract addition. (B) Fluo-4 fluorescence 4 s after speract addition. Images extracted from a time series acquired at 40 frames per second with 25-ms individual frame exposure time. (C) Ratio increases in Fluo-4 fluorescence across whole field. Upper trace (black), response to addition of 125 nM speract at t = 0. Lower trace (red), fluorescence from control field with no speract addition. Both traces have been corrected for the effects of fluorophore bleaching. Data acquired at 40 frames per second with 25-ms individual frame exposure time.

Mentions: Saturating concentrations of speract (∼100 nM) induce an approximately fivefold transient increase in [Ca2+]i in Fura-2– or Fluo-3–loaded S. purpuratus sea urchin sperm bulk suspensions (Cook and Babcock, 1993a,b). From these previous studies, it was determined that [Ca2+]i elevates with a time to half-height (t1/2) of ∼0.4 s and relaxes almost to the basal level with a t1/2 of ∼25 s (Schackmann and Chock, 1986; Babcock et al., 1992; Nishigaki et al., 2001). To study the spatial distribution of this transient within single sperm, a system has been developed for measuring, continuously and at relatively high sampling frequencies (40 frames.s−1), spatially resolved [Ca2+]i changes (see Materials and methods and Fig. 1) . This approach yields data consistent with the changes in calcium that have been measured in sperm populations, yet has uncovered a temporal and spatial structure to sperm calcium signals that was not predicted and is only apparent at the single-cell level.


Speract induces calcium oscillations in the sperm tail.

Wood CD, Darszon A, Whitaker M - J. Cell Biol. (2003)

Typical response of a field of sperm to addition of speract to a final concentration of 125 nM. (A) Fluo-4 fluorescence immediately before speract addition. (B) Fluo-4 fluorescence 4 s after speract addition. Images extracted from a time series acquired at 40 frames per second with 25-ms individual frame exposure time. (C) Ratio increases in Fluo-4 fluorescence across whole field. Upper trace (black), response to addition of 125 nM speract at t = 0. Lower trace (red), fluorescence from control field with no speract addition. Both traces have been corrected for the effects of fluorophore bleaching. Data acquired at 40 frames per second with 25-ms individual frame exposure time.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172867&req=5

fig1: Typical response of a field of sperm to addition of speract to a final concentration of 125 nM. (A) Fluo-4 fluorescence immediately before speract addition. (B) Fluo-4 fluorescence 4 s after speract addition. Images extracted from a time series acquired at 40 frames per second with 25-ms individual frame exposure time. (C) Ratio increases in Fluo-4 fluorescence across whole field. Upper trace (black), response to addition of 125 nM speract at t = 0. Lower trace (red), fluorescence from control field with no speract addition. Both traces have been corrected for the effects of fluorophore bleaching. Data acquired at 40 frames per second with 25-ms individual frame exposure time.
Mentions: Saturating concentrations of speract (∼100 nM) induce an approximately fivefold transient increase in [Ca2+]i in Fura-2– or Fluo-3–loaded S. purpuratus sea urchin sperm bulk suspensions (Cook and Babcock, 1993a,b). From these previous studies, it was determined that [Ca2+]i elevates with a time to half-height (t1/2) of ∼0.4 s and relaxes almost to the basal level with a t1/2 of ∼25 s (Schackmann and Chock, 1986; Babcock et al., 1992; Nishigaki et al., 2001). To study the spatial distribution of this transient within single sperm, a system has been developed for measuring, continuously and at relatively high sampling frequencies (40 frames.s−1), spatially resolved [Ca2+]i changes (see Materials and methods and Fig. 1) . This approach yields data consistent with the changes in calcium that have been measured in sperm populations, yet has uncovered a temporal and spatial structure to sperm calcium signals that was not predicted and is only apparent at the single-cell level.

Bottom Line: These data point to a model in which a messenger generated periodically in the tail diffuses to the head.Sperm are highly polarized cells.Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

View Article: PubMed Central - PubMed

Affiliation: School of Cell and Molecular Biosciences, University of Newcastle upon Tyne, NE2 4HH, UK.

ABSTRACT
Sea urchin sperm motility is modulated by sperm-activating peptides. One such peptide, speract, induces changes in intracellular free calcium concentration ([Ca2+]i). High resolution imaging of single sperm reveals that speract-induced changes in [Ca2+]i have a complex spatiotemporal structure. [Ca2+]i increases arise in the tail as periodic oscillations; [Ca2+]i increases in the sperm head lag those in the tail and appear to result from the summation of the tail signal transduction events. The period depends on speract concentration. Infrequent spontaneous [Ca2+]i transients were also seen in the tail of unstimulated sperm, again with the head lagging the tail. Speract-induced fluctuations were sensitive to membrane potential and calcium channel blockers, and were potentiated by niflumic acid, an anion channel blocker. 3-isobutyl-1-methylxanthine, which potentiates the cGMP/cAMP-signaling pathways, abolished the [Ca2+]i fluctuations in the tail, leading to a very delayed and sustained [Ca2+]i increase in the head. These data point to a model in which a messenger generated periodically in the tail diffuses to the head. Sperm are highly polarized cells. Our results indicate that a clear understanding of the link between [Ca2+]i and sperm motility will only be gained by analysis of [Ca2+]i signals at the level of the single sperm.

Show MeSH
Related in: MedlinePlus