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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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The magnitude of the tonic calcium increase and the frequency of the phasic calcium fluctuations are dependent on the concentration of speract. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity post-speract addition (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 speract concentration shown in brackets). Error bars indicate ± SEM. At concentrations of speract above and including 100 pM, only those sperm heads that showed a response to speract were analyzed. At concentrations of speract below and including 10 pM, and in control analyses, sperm heads were chosen at random. (B) Changes in [Ca2+]i were determined for individual flagella by ratioing their fluorescence (F) against their initial fluorescence (F0). The number of fluctuations occurring after speract addition was determined by including all excursions whose increase from trough to peak was >20% of the trough value. Data are presented as the average number of fluctuations occurring in 10 s post-speract addition per flagellum. Number of flagella analyzed indicated in brackets. Error bars represent ± SEM.
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fig4: The magnitude of the tonic calcium increase and the frequency of the phasic calcium fluctuations are dependent on the concentration of speract. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity post-speract addition (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 speract concentration shown in brackets). Error bars indicate ± SEM. At concentrations of speract above and including 100 pM, only those sperm heads that showed a response to speract were analyzed. At concentrations of speract below and including 10 pM, and in control analyses, sperm heads were chosen at random. (B) Changes in [Ca2+]i were determined for individual flagella by ratioing their fluorescence (F) against their initial fluorescence (F0). The number of fluctuations occurring after speract addition was determined by including all excursions whose increase from trough to peak was >20% of the trough value. Data are presented as the average number of fluctuations occurring in 10 s post-speract addition per flagellum. Number of flagella analyzed indicated in brackets. Error bars represent ± SEM.

Mentions: Single-cell analysis (Fig. 2 B) reveals that the speract response consists of at least two superimposed patterns of calcium increase. A sustained tonic increase occurs both in the flagella and the head cytoplasmic region. In addition, speract induces phasic [Ca2+]i fluctuations superimposed on the tonic response both in the flagella and the head. The speract-induced fluctuations are smaller (Table I) and more frequent (between 10 and 20 in the first 10-s post-speract addition; Fig. 4) than the spontaneous fluctuations (1–5 over a 10-s period; n = 34). The [Ca2+]i fluctuations in the head region were less pronounced relative to the tonic response than those in the flagella, suggesting that the head may integrate the flagellar changes. There are clear indications that the flagellar responses are correlated with the head responses, and precede them (see following section).


Speract induces calcium oscillations in the sperm tail.

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

The magnitude of the tonic calcium increase and the frequency of the phasic calcium fluctuations are dependent on the concentration of speract. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity post-speract addition (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 speract concentration shown in brackets). Error bars indicate ± SEM. At concentrations of speract above and including 100 pM, only those sperm heads that showed a response to speract were analyzed. At concentrations of speract below and including 10 pM, and in control analyses, sperm heads were chosen at random. (B) Changes in [Ca2+]i were determined for individual flagella by ratioing their fluorescence (F) against their initial fluorescence (F0). The number of fluctuations occurring after speract addition was determined by including all excursions whose increase from trough to peak was >20% of the trough value. Data are presented as the average number of fluctuations occurring in 10 s post-speract addition per flagellum. Number of flagella analyzed indicated in brackets. Error bars represent ± SEM.
© Copyright Policy
Related In: Results  -  Collection

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

fig4: The magnitude of the tonic calcium increase and the frequency of the phasic calcium fluctuations are dependent on the concentration of speract. (A) For each sperm head, the ratio increase in [Ca2+]i was determined from the maximum fluorescence intensity post-speract addition (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 speract concentration shown in brackets). Error bars indicate ± SEM. At concentrations of speract above and including 100 pM, only those sperm heads that showed a response to speract were analyzed. At concentrations of speract below and including 10 pM, and in control analyses, sperm heads were chosen at random. (B) Changes in [Ca2+]i were determined for individual flagella by ratioing their fluorescence (F) against their initial fluorescence (F0). The number of fluctuations occurring after speract addition was determined by including all excursions whose increase from trough to peak was >20% of the trough value. Data are presented as the average number of fluctuations occurring in 10 s post-speract addition per flagellum. Number of flagella analyzed indicated in brackets. Error bars represent ± SEM.
Mentions: Single-cell analysis (Fig. 2 B) reveals that the speract response consists of at least two superimposed patterns of calcium increase. A sustained tonic increase occurs both in the flagella and the head cytoplasmic region. In addition, speract induces phasic [Ca2+]i fluctuations superimposed on the tonic response both in the flagella and the head. The speract-induced fluctuations are smaller (Table I) and more frequent (between 10 and 20 in the first 10-s post-speract addition; Fig. 4) than the spontaneous fluctuations (1–5 over a 10-s period; n = 34). The [Ca2+]i fluctuations in the head region were less pronounced relative to the tonic response than those in the flagella, suggesting that the head may integrate the flagellar changes. There are clear indications that the flagellar responses are correlated with the head responses, and precede them (see following section).

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