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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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Speract-induced increases in [Ca2+]i are dependent on [Ca2+]e in a dose-dependent manner. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity after addition of speract to a final concentration of 1 nM (Fmax) and the initial fluorescence intensity value (F0). Fmax/F0 is presented as the average of all sperm heads analyzed (total number of sperm heads at each [Ca2+]e shown in brackets). Error bars represent ± SEM. (B) Typical responses in individual sperm heads at different [Ca2+]e. F/F0 shown over time after addition of speract to a final concentration of 1 nM (indicated by arrow) and data represented as a five-point rolling average. Images acquired at 10 frames per second with 100-ms individual frame exposure time. One-tailed t test (comparison to prior [Ca2+]e) **, P < 0.01; *, P < 0.05.
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fig5: Speract-induced increases in [Ca2+]i are dependent on [Ca2+]e in a dose-dependent manner. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity after addition of speract to a final concentration of 1 nM (Fmax) and the initial fluorescence intensity value (F0). Fmax/F0 is presented as the average of all sperm heads analyzed (total number of sperm heads at each [Ca2+]e shown in brackets). Error bars represent ± SEM. (B) Typical responses in individual sperm heads at different [Ca2+]e. F/F0 shown over time after addition of speract to a final concentration of 1 nM (indicated by arrow) and data represented as a five-point rolling average. Images acquired at 10 frames per second with 100-ms individual frame exposure time. One-tailed t test (comparison to prior [Ca2+]e) **, P < 0.01; *, P < 0.05.

Mentions: The spontaneous and speract-induced [Ca2+]i increases and fluctuations are completely dependent on extracellular Ca2+ ([Ca2+]e). Fig. 5 shows how as [Ca2+]e decreases, the amplitude of both the tonic response and of the fluctuations in [Ca2+]i induced by 1 nM speract become smaller. At 500 μM [Ca2+]e, both the tonic and phasic responses are lost. The effect of reduction of [Ca2+]e on the tonic response agrees with previous studies performed on sperm populations (Schackmann and Chock, 1986; Cook et al., 1994), and our results clearly indicate that Ca2+ influx is a major contributor to both the tonic and phasic responses.


Speract induces calcium oscillations in the sperm tail.

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

Speract-induced increases in [Ca2+]i are dependent on [Ca2+]e in a dose-dependent manner. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity after addition of speract to a final concentration of 1 nM (Fmax) and the initial fluorescence intensity value (F0). Fmax/F0 is presented as the average of all sperm heads analyzed (total number of sperm heads at each [Ca2+]e shown in brackets). Error bars represent ± SEM. (B) Typical responses in individual sperm heads at different [Ca2+]e. F/F0 shown over time after addition of speract to a final concentration of 1 nM (indicated by arrow) and data represented as a five-point rolling average. Images acquired at 10 frames per second with 100-ms individual frame exposure time. One-tailed t test (comparison to prior [Ca2+]e) **, P < 0.01; *, P < 0.05.
© Copyright Policy
Related In: Results  -  Collection

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

fig5: Speract-induced increases in [Ca2+]i are dependent on [Ca2+]e in a dose-dependent manner. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity after addition of speract to a final concentration of 1 nM (Fmax) and the initial fluorescence intensity value (F0). Fmax/F0 is presented as the average of all sperm heads analyzed (total number of sperm heads at each [Ca2+]e shown in brackets). Error bars represent ± SEM. (B) Typical responses in individual sperm heads at different [Ca2+]e. F/F0 shown over time after addition of speract to a final concentration of 1 nM (indicated by arrow) and data represented as a five-point rolling average. Images acquired at 10 frames per second with 100-ms individual frame exposure time. One-tailed t test (comparison to prior [Ca2+]e) **, P < 0.01; *, P < 0.05.
Mentions: The spontaneous and speract-induced [Ca2+]i increases and fluctuations are completely dependent on extracellular Ca2+ ([Ca2+]e). Fig. 5 shows how as [Ca2+]e decreases, the amplitude of both the tonic response and of the fluctuations in [Ca2+]i induced by 1 nM speract become smaller. At 500 μM [Ca2+]e, both the tonic and phasic responses are lost. The effect of reduction of [Ca2+]e on the tonic response agrees with previous studies performed on sperm populations (Schackmann and Chock, 1986; Cook et al., 1994), and our results clearly indicate that Ca2+ influx is a major contributor to both the tonic and phasic responses.

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