Starfish oocytes of A. pectinifera reveal marked differences in sperm‐induced electrical and intracellular calcium changes during oocyte maturation and at fertilization

2021 ◽  
Author(s):  
Tatsuma Mohri ◽  
Keiichiro Kyozuka
Keyword(s):  
Intracellular Calcium ◽  
Oocyte Maturation

scholarly journals Mechanisms underlying oocyte activation and postovulatory ageing

Reproduction ◽  
2002 ◽  
pp. 745-754 ◽  
Author(s):  
RA Fissore ◽  
M Kurokawa ◽  
J Knott ◽  
M Zhang ◽  
J Smyth
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Intracellular Calcium ◽  
Oocyte Maturation ◽  
Abnormal Development ◽  
Oocyte Activation ◽  
Molecular Changes ◽  
Free Intracellular Calcium ◽  
Developmental Programme ◽  
Nuclear Modifications

Mammalian oocytes undergo significant growth during oogenesis and experience extensive cytoplasmic and nuclear modifications immediately before ovulation in a process commonly referred to as oocyte maturation. These changes are intended to maximize the developmental success after fertilization. Entry of a spermatozoon into the oocyte, which occurs a few hours after ovulation, initiates long-lasting oscillations in the free intracellular calcium ([Ca(2+)](i)) that are responsible for all events of oocyte activation and the initiation of the developmental programme that often culminates in the birth of young. Nevertheless, the cellular and molecular changes that occur during maturation to optimize development are transient, and exhibit rapid deterioration. Moreover, fertilization of oocytes after an extended residence in the oviduct (or in culture) initiates a different developmental programme, one that is characterized by fragmentation, programmed cell death, and abnormal development. Inasmuch as [Ca(2+)](i) oscillations can trigger both developmental programmes in mammalian oocytes, this review addresses one of the mechanism(s) possibly used by spermatozoa to initiate these persistent [Ca(2+)](i) responses, and the cellular and molecular changes that may underlie the postovulatory cellular fragmentation of ageing mammalian oocytes.

Cyclopiazonic acid induces accelerated progress of meiosis in pig oocytes

Zygote ◽  
1997 ◽  
Vol 5 (3) ◽  
pp. 193-205 ◽  
Author(s):  
Jaroslav Petr ◽  
Jirří Rozinek ◽  
František Jílek
Keyword(s):  
Intracellular Calcium ◽  
Oocyte Maturation ◽  
Ryanodine Receptors ◽  
Cyclopiazonic Acid ◽  
Cumulus Cells ◽  
Ruthenium Red ◽  
Sensitive Period ◽  
Calcium Deposits ◽  
Transient Elevation

SummaryIn mammalian oocytes, calcium plays an important role in the regulation of meiotic maturation. In our study, we used the mycotoxin cyclopiazonic acid (CPA), an inhibitor of calcium-dependent ATPases, to mobilise intracellular calcium deposits during in vitro maturation of pig oocytes. The CPA treatment of maturing oocytes significantly accelerated the progress of their maturation. Oocytes entered the CPA-sensitive period after 21 h of in vitro culture. A very short (5 min) exposure to CPA (100 mM) is sufficient to accelerate maturation and it seems that accelerated maturation can be triggered by a transient elevation of intracellular calcium levels. The effect of CPA is not mediated through the cumulus cells, because maturation is accelerated by CPA treatment even in oocytes devoid of cumulus cells. Culture of oocytes with the calcium channel blocker verapamil (concentrations ranging from 0.01 to 0.04 mM) blocked the progress of oocyte maturation beyond the stage of metaphase I. This block can be overcome by the mobilisation of intracellular calcium deposits after CPA treatment (100 nM). The microinjection of heparin (20 pl, 50.1 mg/;ml), the inhibitor of inositol triphosphate receptors, before CPA treatment prevented the acceleration of oocyte maturation. This indicates that CPA mobilises the release of calcium deposits through inositol trisphosphate receptors. On the other hand, the microinjection of procaine (20 pl, 200 nM) or the microinjection of ruthenium red (20 pl, 50 mM), both inhibitors of ryanodine receptors, did not prevent accelerated maturation in CPA-treated oocytes. If present in pig oocytes, ryanodine receptors evidently play no part in the liberation of calcium from intracellular stores after CPA treatment.

scholarly journals Functional reconstitutional of the human epidermal growth factor receptor system in Xenopus oocytes.

1990 ◽  
Vol 111 (4) ◽  
pp. 1661-1671 ◽  
Author(s):  
L K Opresko ◽  
H S Wiley
Keyword(s):  
Tyrosine Kinase ◽  
Intracellular Calcium ◽  
Oocyte Maturation ◽  
Mammalian Cells ◽  
Xenopus Oocytes ◽  
Kinase Activity ◽  
Egf Receptor ◽  
Biological Activities ◽  
Tyrosine Kinase Activity ◽  
Receptor System

We have expressed the human EGF receptor (hEGF-R) in Xenopus oocytes by injecting mRNA synthesized in vitro using SP6 vectors containing receptor cDNAs. Each oocyte could express over 1 x 10(10) receptors of a single affinity class and these were able to bind and rapidly internalize EGF. Occupancy resulted in receptor tyrosine autophosphorylation, downregulation, and release of intracellular calcium. Occupied receptors also rapidly induced meiotic maturation in stage VI oocytes. Receptors lacking tyrosine kinase activity bound EGF normally, but did not downregulate or induce any biological responses. The rate of oocyte maturation was proportional to hEGF-R occupancy and was significantly faster than progesterone-induced maturation at nanomolar EGF concentrations. Mutant hEGF-R truncated at residue 973 displayed identical phenotypes in both mammalian cells and oocytes in that they were defective in their ability to release intracellular calcium, undergo ligand induced internalization and receptor downregulation. However, these receptors were fully capable of inducing oocyte maturation. The remarkable retention of specific biological activities of different hEGF-R in the context of oocytes suggests that this receptor system interacts with generally available cellular components that have been conserved during evolution. In addition, it suggests that cell surface tyrosine kinase activity may play an important role in regulating resumption of the cell cycle.

scholarly journals 280 EFFECTS OF β-ENDORPHIN AND NALOXONE ON INTRACELLULAR CALCIUM LEVELS IN CUMULUS CELLS OF EQUINE OOCYTES

2005 ◽  
Vol 17 (2) ◽  
pp. 290
Author(s):  
T. De Santis ◽  
M.E. Dell'Aquila ◽  
F. Maritato ◽  
V. Casavola ◽  
P. Minoia
Keyword(s):  
Intracellular Calcium ◽  
Opioid Receptor ◽  
Oocyte Maturation ◽  
Single Cells ◽  
Cumulus Cells ◽  
High Concentration ◽  
Before And After ◽  
Different Seasons ◽  
Μ Opioid Receptor ◽  
Μ Receptor

Changes in intracellular calcium levels in the cumulus oocyte complex (COC) have a crucial role in oocyte maturation. In previous studies we demonstrated that the μ-opioid receptor is expressed in the bovine COC and participates in the signaling associated with oocyte maturation, by inducing an intracellular calcium increase (Dell'Aquila ME et al. 2002 Mol. Reprod. Dev. 63, 210–222). In this work we evaluated modifications of intracellular calcium induced by β-endorphin (β-end) or Naloxone (Nx) in cumulus cells of equine oocytes in relation to the time of the year and cumulus morphology at retrieval. Cumulus cells, isolated by mechanical treatment from compact (Cp, n = 120) or expanded (Exp, n = 120) COCs, recovered from the ovaries of slaughtered mares (follicles <20 mm in diameter) during anestrus, breeding season, spring transition, and autumnal transition, were cultured for 24 h and loaded with 5 μM Fura2-AM for microspectrofluorometric measurements of cytoplasmic ionized calcium (Dell'Aquila et al., 2002). The changes in β-end (30 μM)- or Nx (1mM and 10 μM)-induced calcium concentration were calculated in single cells (n = 194) and are expressed as Δ fluorescence (Fmaximal effect – Fbaseline) before and after 1-min perfusion with the drugs. The use of 1 mM Nx induced a significant increase of intracellular calcium levels in cumulus cells of oocytes recovered in all periods of the year in both Cp and Exp (P < 0.01). The addition of 10 μM Nx or 30 μM β-end significantly increased intracellular calcium only in cumulus cells from oocytes recovered in anestrus (P < 0.05). These results confirm previous observations, carried out on bovine oocytes, in which Nx behaved as a μ-receptor agonist when used at high concentration (Dell'Aquila et al. 2002). The effects of β-end and Nx may be explained in terms of a binding of the two subtances at the μ-receptor with consequent intracellular calcium increases due to extracellular calcium entry or depletion of intracellular stores. These findings could be related to differential espression and/or activation status of the μ-opioid receptor in COCs retrieved in different seasons. These substances can be used to modulate intracellular calcium in the equine COCs, and consequent effects on the stimulation/inhibition of oocyte maturation in this species need to be further investigated. This work was supported by Grant MIUR COFIN PRIN 2003.

scholarly journals Spindle function in Xenopus oocytes involves possible nanodomain calcium signaling

2016 ◽  
Vol 27 (21) ◽  
pp. 3273-3283 ◽  
Author(s):  
Ruizhen Li ◽  
Julie Leblanc ◽  
Kevin He ◽  
X. Johné Liu
Keyword(s):  
Calcium Signaling ◽  
Intracellular Calcium ◽  
Oocyte Maturation ◽  
Polar Body ◽  
Calcium Transients ◽  
Meiotic Spindle ◽  
First Polar Body ◽  
Spindle Microtubules ◽  
Spindle Function

Intracellular calcium transients are a universal phenomenon at fertilization and are required for egg activation, but the exact role of Ca2+ in second-polar-body emission remains unknown. On the other hand, similar calcium transients have not been demonstrated during oocyte maturation, and yet, manipulating intracellular calcium levels interferes with first-polar-body emission in mice and frogs. To determine the precise role of calcium signaling in polar body formation, we used live-cell imaging coupled with temporally precise intracellular calcium buffering. We found that BAPTA-based calcium chelators cause immediate depolymerization of spindle microtubules in meiosis I and meiosis II. Surprisingly, EGTA at similar or higher intracellular concentrations had no effect on spindle function or polar body emission. Using two calcium probes containing permutated GFP and the calcium sensor calmodulin (Lck-GCaMP3 and GCaMP3), we demonstrated enrichment of the probes at the spindle but failed to detect calcium increase during oocyte maturation at the spindle or elsewhere. Finally, endogenous calmodulin was found to colocalize with spindle microtubules throughout all stages of meiosis. Our results—most important, the different sensitivities of the spindle to BAPTA and EGTA—suggest that meiotic spindle function in frog oocytes requires highly localized, or nanodomain, calcium signaling.

Ultra-Rapid Freezing of Isolated Skeletal Muscle Fibers

1977 ◽  
Vol 35 ◽  
pp. 576-577
Author(s):  
Joachim R. Sommer ◽  
Nancy R. Wallace
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Granular Material ◽  
Nuclear Envelope ◽  
Intracellular Calcium ◽  
Ruthenium Red ◽  
Threshold Concentration ◽  
Rapid Freezing ◽  
Frog Skeletal Muscle ◽  
Electrical Isolation

After Howell (1) had shown that ruthenium red treatment of fixed frog skeletal muscle caused collapse of the intermediate cisternae of the sarcoplasmic reticulum (SR), forming a pentalaminate structure by obi iterating the SR lumen, we demonstrated that the phenomenon involves the entire SR including the nuclear envelope and that it also occurs after treatment with other cations, including calcium (2,3,4).From these observations we have formulated a hypothesis which states that intracellular calcium taken up by the SR at the end of contraction causes the M rete to collapse at a certain threshold concentration as the first step in a subsequent centrifugal zippering of the free SR toward the junctional SR (JSR). This would cause a) bulk transport of SR contents, such as calcium and granular material (4) into the JSR and, b) electrical isolation of the free SR from the JSR.

Sign in / Sign up

Export Citation Format

Share Document