Because the function and mechanisms of sleep are partially clear, here we applied a meta-analysis to address the issue whether sleep function includes antioxidative properties in mice and rats. Given the expansion of the knowledge in the sleep field, it is indeed ambitious to describe all mammals, or other animals, in which sleep shows an antioxidant function. However, in this paper we reviewed the current understanding from basic studies in two species to drive the hypothesis that sleep is a dynamic-resting state with antioxidative properties. We performed a systematic review of articles cited in Medline, Scopus, and Web of Science until March 2015 using the following search terms: Sleep or sleep deprivation and oxidative stress, lipid peroxidation, glutathione, nitric oxide, catalase or superoxide dismutase. We found a total of 266 studies. After inclusion and exclusion criteria, 44 articles were included, which are presented and discussed in this study. The complex relationship between sleep duration and oxidative stress is discussed. Further studies should consider molecular and genetic approaches to determine whether disrupted sleep promotes oxidative stress.

The acrosome reaction (AR), necessary for fertilization in many species, requires an increase in intracellular Ca(2+) ([Ca(2+)](i)). In sea urchin sperm, the AR is triggered by an egg-jelly factor: the associated [Ca(2+)](i) elevation lasts minutes and involves two Ca(2+) permeable channels. Both the opening of the second channel and the onset of the AR occur approximately 5 s after treatment with egg factor, suggesting that these events are linked. In agreement, removal of Ca(2+) from sea water or addition of Ca(2+) channel blockers at the time when opening of the second channel is first detected inhibits AR and causes a "rapid" (t(1/2) = 3--15 s) decrease in [Ca(2+)](i) and partial inhibition of the intracellular pH change associated with the AR. Simultaneous addition of NH(4)Cl and either EGTA, Co(2+), or Ni(2+) 5 s after egg factor prevents the partial inhibition of the evoked pH(i) change observed but does not reverse AR inhibition. Therefore, the sustained increase in [Ca(2+)](i) caused by the second Ca(2+) channel is needed for the sperm AR. Experiments with agents that induce capacitative Ca(2+) uptake (thapsigargin and cyclopiazonic acid) suggest that the second channel opened during the AR could be a store-operated Ca(2+) channel.

Functional evidence indicates that voltage-dependent Ca 2+ (Ca v ) channels participate in sea urchin sperm motility and the acrosome reaction (AR), however, their molecular identity remains unknown. We have identified transcripts for two Ca 2+ channel a1 subunits in sea urchin testis similar in sequence to Ca v 1.2 and Ca v 2.3. Antibodies against rat Ca v 1.2 and Ca v 2.3 channels differentially label proteins in the flagella and acrosome of mature sea urchin sperm. The Ca v channel antagonists nifedipine and nimodipine, which inhibit the AR, diminish the intracellular Ca 2+ elevation induced by a K + -induced depolarization in valinomycin-treated sperm. These findings reveal that Ca v 1.2 and Ca v 2.3 channels could participate in motility and/or the AR in sea urchin sperm.

The sperm‐activating peptide speract and fucose‐sulphate glycoconjugate (FSG) are sea urchin egg‐envelope components that modulate sperm ion permeability. They influence motility and induce acrosomal reaction (AR), respectively. A fluorescent Na+‐sensitive dye (Na+‐binding benzofuran isophthalate, SBFI) was used to determine how these egg envelope components influence sperm Na+ permeability. [Ca2+]i and pHi were also measured to correlate their changes in response to speract and FSG with those observed in [Na+]i. SBFI determinations indicate that the resting [Na+]i is 20 ± 8 mm in sea urchin sperm. Saturating levels of speract increased [Na+]i by ≈15 mm, while similar levels of FSG caused a further elevation of ≈30 mm. The kinetics of the [Na+]i, [Ca2+]i and pHi changes induced by saturating levels of speract were faster than those induced by FSG. Both egg ligands appeared to activate more than one Na+ transport system. Nifedipine, Ni2+ and TEA+ inhibited the ionic changes and the AR induced by FSG but, importantly, did not alter those caused by speract. Thus, there are differences in some of the ionic transport mechanisms that operate in the speract and FSG responses. ZD2788, a blocker of hyperpolarization and cyclic‐nucleotide‐gated (HCN) channels such as SpHCN present in sea urchin sperm, did not decrease the speract‐induced [Na+]i increase, but slowed its kinetics. Therefore, SpHCN does not play a major role in the uptake of Na+ triggered by this decapeptide. KB‐R7943, an inhibitor of Na+/Ca2+ exchangers, decreased the resting [Na+]i and did not change significantly the speract‐induced [Ca2+]i increase, but slowed its recovery.

Acrosome reaction inactivation (ARI) is a process that renders sperm irreversibly refractory to the egg jelly (the natural inducer of the acrosome reaction, AR). This process triggered by the egg jelly, is associated with an increase in [Ca2+]i. However, we show here that a rise in [Ca2+]i alone is not sufficient to induce ARI, since artificially increasing [Ca2+]i with either an ionophore or rising external pH, does not trigger ARI. Contrary to the AR which strictly requires Ca2+, ARI can be triggered almost equally well by Sr2+. On the other hand, Mn2+ inhibits ARI and, as we showed earlier, does not affect AR. These observations indicate that the mechanisms involved in ARI differ from those leading to AR. In addition, we report here that high external pH (a non-physiological inducer of AR) triggers the AR in previously inactivated sperm by opening the same Ca2+ channels activated by the egg jelly. Considering that the opening of Ca2+ channels is one of the earliest responses triggered by the egg jelly and that ARI requires the egg jelly receptor to be activated, we have concluded that ARI involves the uncoupling between the egg jelly receptor and Ca2+ channels. Furthermore, intracellular pH (pHi) determinations, in the presence or absence of ionomycin to substitute for the uncoupled Ca2+ channels, indicate that pHi regulation is also impaired in inactivated sperm. In conclusion, ARI is a manifestation of the uncoupling of the egg jelly receptor from the different ion transport systems required for the acrosome reaction.