scholarly journals The exit of mouse oocytes from meiotic M-phase requires an intact spindle during intracellular calcium release

1995 ◽  
Vol 108 (1) ◽  
pp. 143-151 ◽  
Author(s):  
N.J. Winston ◽  
O. McGuinness ◽  
M.H. Johnson ◽  
B. Maro
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Calcium Transient ◽  
Oocyte Activation ◽  
High Concentration ◽  
Microtubule Inhibitor ◽  
Mouse Oocytes ◽  
M Phase ◽  
Single Spike ◽  
Calcium Spiking

To study the role of the metaphase spindle during the period of oocyte activation, mouse oocytes were fertilised or activated parthenogenetically in the presence or absence of the microtubule inhibitor nocodazole. In both cases, nocodazole caused the disappearance of the spindle and prevented the passage of the oocytes into interphase. However, the calcium spiking responses of the oocytes were not affected by nocodazole, being repetitive after fertilisation and a single spike after activation. If, after their activation or fertilisation in nocodazole, oocytes were later removed from the drug, only those that had been fertilised progressed into interphase. This progress was associated with continuing calcium spiking. Moreover, both the spiking and the progress to interphase could be blocked or reduced in incidence by removal of external calcium or addition of 5,5′-dimethyl BAPTA-AM. Oocytes that had been activated by ethanol in the presence of nocodazole and then removed from it, to allow re-formation of the spindle, only progressed into interphase if given a second exposure to ethanol, thereby eliciting a second calcium transient. These results show that exit from meiotic M-phase requires the simultaneous presence of a fully intact spindle during the release of calcium and that those factors leading to the degradation of cyclin B are only activated transiently. Since cyclin is being degraded continuously in the metaphase-II-arrested mouse oocyte and since this degradation is microtubule-dependent, these data suggest that the superimposition of a high concentration of intracellular calcium is required to tilt the equilibrium further in favour of cyclin degradation if exit from M-phase is to occur.

Caffeine attenuates contraction-induced diminutions of the intracellular calcium transient in mouse lumbrical muscle ex vivo

2019 ◽  
Vol 97 (5) ◽  
pp. 429-435 ◽  
Author(s):  
Ian C. Smith ◽  
Rene Vandenboom ◽  
A. Russell Tupling
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Ex Vivo ◽  
Calcium Transient ◽  
Calcium Transients ◽  
Inotropic Effects ◽  
Intracellular Calcium Transient ◽  
Lumbrical Muscle ◽  
Lumbrical Muscles

The amount of calcium released from the sarcoplasmic reticulum in skeletal muscle rapidly declines during repeated twitch contractions. In this study, we test the hypothesis that caffeine can mitigate these contraction-induced declines in calcium release. Lumbrical muscles were isolated from male C57BL/6 mice and loaded with the calcium-sensitive indicator, AM-furaptra. Muscles were then stimulated at 8 Hz for 2.0 s in the presence or absence of 0.5 mM caffeine, at either 30 °C or 37 °C. The amplitude and area of the furaptra-based intracellular calcium transients and force produced during twitch contractions were calculated. For each of these measures, the values for twitch 16 relative to twitch 1 were higher in the presence of caffeine than in the absence of caffeine at both temperatures. We conclude that caffeine can attenuate contraction-induced diminutions of calcium release during repeated twitch contractions, thereby contributing to the inotropic effects of caffeine.

Meiosis-associated calcium waves in ascidian oocytes are correlated with the position of the male centrosome

Zygote ◽  
2000 ◽  
Vol 8 (4) ◽  
pp. 285-293 ◽  
Author(s):  
Martin Wilding ◽  
Marcella Marino ◽  
Vincenzo Monfrecola ◽  
Brian Dale
Keyword(s):  
Intracellular Calcium ◽  
Calcium Release ◽  
Polar Body ◽  
Calcium Transients ◽  
Calcium Waves ◽  
Oocyte Activation ◽  
Animal Pole ◽  
Vegetal Pole ◽  
Sperm Penetration ◽  
Oocyte Cytoplasm

We have used confocal microscopy to measure calcium waves and examine the distribution of tubulin in oocytes of the ascidian Ciona intestinalis during meiosis. We show that the fertilisation calcium wave in these oocytes originates in the vegetal pole. The sperm penetration site and female meiotic apparatus are found at opposite poles of the oocyte at fertilisation, confirming that C. intestinalis sperm enter in the vegetal pole of the oocyte. Following fertilisation, ascidian oocytes are characterised by repetitive calcium waves. Meiosis I-associated waves originate at the vegetal pole of the oocyte, and travel towards the animal pole. In contrast, the calcium waves during meiosis II initiate at the oocyte equator, and cross the oocyte cytoplasm perpendicular to the point of emission of the polar body. Immunolocalisation of tubulin during meiosis II reveals that the male centrosome is also located between animal and vegetal poles prior to initiation of the meiosis II-associated calcium waves, suggesting that the male centrosome influences the origin of these calcium transients. Ascidians are also characterised by an increase in sensitivity to intracellular calcium release after fertilisation. We show that this is not simply an effect of oocyte activation. The data strongly suggest a role for the male centrosome in controlling the mechanism and localisation of post-fertilisation intracellular calcium waves.

scholarly journals Air bubble contact with endothelial cells in vitro induces calcium influx and IP3-dependent release of calcium stores

2011 ◽  
Vol 301 (3) ◽  
pp. C679-C686 ◽  
Author(s):  
Peter Sobolewski ◽  
Judith Kandel ◽  
Alexandra L. Klinger ◽  
David M. Eckmann
Keyword(s):  
Endothelial Cells ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Transient Receptor Potential ◽  
Calcium Influx ◽  
Calcium Transient ◽  
Epifluorescence Microscopy ◽  
Transient Receptor Potential Vanilloid ◽  
Calcium Stores ◽  
Air Bubble

Gas embolism is a serious complication of decompression events and clinical procedures, but the mechanism of resulting injury remains unclear. Previous work has demonstrated that contact between air microbubbles and endothelial cells causes a rapid intracellular calcium transient and can lead to cell death. Here we examined the mechanism responsible for the calcium rise. Single air microbubbles (50–150 μm), trapped at the tip of a micropipette, were micromanipulated into contact with individual human umbilical vein endothelial cells (HUVECs) loaded with Fluo-4 (a fluorescent calcium indicator). Changes in intracellular calcium were then recorded via epifluorescence microscopy. First, we confirmed that HUVECs rapidly respond to air bubble contact with a calcium transient. Next, we examined the involvement of extracellular calcium influx by conducting experiments in low calcium buffer, which markedly attenuated the response, or by pretreating cells with stretch-activated channel blockers (gadolinium chloride or ruthenium red), which abolished the response. Finally, we tested the role of intracellular calcium release by pretreating cells with an inositol 1,4,5-trisphosphate (IP3) receptor blocker (xestospongin C) or phospholipase C inhibitor (neomycin sulfate), which eliminated the response in 64% and 67% of cases, respectively. Collectively, our results lead us to conclude that air bubble contact with endothelial cells causes an influx of calcium through a stretch-activated channel, such as a transient receptor potential vanilloid family member, triggering the release of calcium from intracellular stores via the IP3 pathway.

scholarly journals Intracellular calcium oscillations and activation in horse oocytes injected with stallion sperm extracts or spermatozoa

Reproduction ◽  
2003 ◽  
pp. 489-499 ◽  
Author(s):  
SJ Bedford ◽  
M Kurokawa ◽  
K Hinrichs ◽  
RA Fissore
Keyword(s):  
Embryonic Development ◽  
Intracellular Calcium ◽  
Intracytoplasmic Sperm Injection ◽  
Animal Species ◽  
Mammalian Species ◽  
Calcium Oscillations ◽  
Large Animal ◽  
Oocyte Activation ◽  
Mouse Oocytes ◽  
Species Specific

In oocytes from all mammalian species studied to date, fertilization by a spermatozoon induces intracellular calcium ([Ca(2+)](i)) oscillations that are crucial for appropriate oocyte activation and embryonic development. Such patterns are species-specific and have not yet been elucidated in horses; it is also not known whether equine oocytes respond with transient [Ca(2+)](i) oscillations when fertilized or treated with parthenogenetic agents. Therefore, the aims of this study were: (i) to characterize the activity of equine sperm extracts microinjected into mouse oocytes; (ii) to ascertain in horse oocytes the [Ca(2+)](i)-releasing activity and activating capacity of equine sperm extracts corresponding to the activity present in a single stallion spermatozoon; and (iii) to determine whether equine oocytes respond with [Ca(2+)](i) transients and activation when fertilized using the intracytoplasmic sperm injection (ICSI) procedure. The results of this study indicate that equine sperm extracts are able to induce [Ca(2+)](i) oscillations, activation and embryo development in mouse oocytes. Furthermore, in horse oocytes, injection of sperm extracts induced persistent [Ca(2+)](i) oscillations that lasted for >60 min and initiated oocyte activation. Nevertheless, injection of a single stallion spermatozoon did not consistently initiate [Ca(2+)](i) oscillations in horse oocytes. It is concluded that stallion sperm extracts can efficiently induce [Ca(2+)](i) responses and parthenogenesis in horse oocytes, and can be used to elucidate the signalling mechanism of fertilization in horses. Conversely, the inconsistent [Ca(2+)](i) responses obtained with sperm injection in horse oocytes may explain, at least in part, the low developmental success obtained using ICSI in large animal species.

Soluble extracts from ascidian spermatozoa trigger intracellular calcium release independently of the activation of the ADP ribose channel

Zygote ◽  
1998 ◽  
Vol 6 (2) ◽  
pp. 149-154 ◽  
Author(s):  
Martin Wilding ◽  
Brian Dale
Keyword(s):  
Nitric Oxide ◽  
Plasma Membrane ◽  
Intracellular Calcium ◽  
Metabolic Pathway ◽  
Metabolic Pathways ◽  
Calcium Release ◽  
Ciona Intestinalis ◽  
Calcium Transient ◽  
Calcium Oscillations ◽  
Repetitive Pattern

We have injected soluble extracts of sperm from the ascidian Ciona intestinalis into oocytes of the same species to test whether these extracts can mimic the events of fertilisation. Injection of ascidian sperm extracts leads, after a delay of approximately 60 s, to a large calcium transient and repetitive pattern of calcium oscillations, mimicking the normal fertilisation response. The response was concentration-independent, suggesting a stimulatory mechanism in triggering the fertilisation response. We tested the pathway of calcium release in ascidian oocytes after injection of sperm extracts by preinjection of calcium release inhibitors. The data demonstrate that dual pathways to calcium release act at fertilisation in ascidians, as in other species. C. intestinalis oocytes are characterised by a nion channel in the plasma membrane that is gated uniquely by ADP ribose. We show that this channel is not gated by the injection of ascidian sperm extracts. Our data suggest that one metabolic pathway triggered by sperm, the release of nitric oxide, is not stimulated by sperm extracts and that several metabolic pathways are stimulated at fertilisation by more than one factor within sperm.

scholarly journals Calcium- and voltage-activated plateau currents of cardiac Purkinje fibers.

1987 ◽  
Vol 89 (6) ◽  
pp. 921-958 ◽  
Author(s):  
J L Kenyon ◽  
J L Sutko
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Intracellular Calcium ◽  
Potassium Current ◽  
Calcium Release ◽  
Outward Current ◽  
Calcium Transient ◽  
Chloride Ions ◽  
Purkinje Fibers ◽  
Cardiac Purkinje Fibers ◽  
Sarcoplasmic Reticulum Calcium

We have used the two-microelectrode voltage-clamp technique to investigate the components of membrane current that contribute to the formation of the early part of the plateau phase of the action potential of calf cardiac Purkinje fibers. 3,4-Diaminopyridine (50 microM) reduced the net transient outward current elicited by depolarizations to potentials positive to -30 mV but had no consistent effect on contraction. We attribute this effect to the blockade of a voltage-activated transient potassium current component. Ryanodine (1 microM), an inhibitor of sarcoplasmic reticulum calcium release and intracellular calcium oscillations in Purkinje fibers (Sutko, J.L., and J.L. Kenyon. 1983. Journal of General Physiology. 82:385-404), had complex effects on membrane currents as it abolished phasic contractions. At early times during a depolarization (5-30 ms), ryanodine reduced the net outward current. We attribute this effect to the loss of a component of calcium-activated potassium current caused by the inhibition of sarcoplasmic reticulum calcium release and the intracellular calcium transient. At later times during a depolarization (50-200 ms), ryanodine increased the net outward current. This effect was not seen in low-sodium solutions and we could not observe a reversal potential over a voltage range of -100 to +75 mV. These data suggest that the effect of ryanodine on the late membrane current is attributable to the loss of sodium-calcium exchange current caused by the inhibition of sarcoplasmic reticulum calcium release and the intracellular calcium transient. Neither effect of ryanodine was dependent on chloride ions, which suggests that chloride ions do not carry the ryanodine-sensitive current components. Strontium (2.7 mM replacing calcium) and caffeine (10 mM), two other treatments that interfere with sarcoplasmic reticulum function, had effects in common with ryanodine. This supports the hypothesis that the effects of ryanodine may be attributed to the inhibition of sarcoplasmic reticulum calcium release.

Intracellular calcium handling heterogeneities in intact guinea pig hearts

2004 ◽  
Vol 286 (2) ◽  
pp. H648-H656 ◽  
Author(s):  
Rodolphe P. Katra ◽  
Etienne Pruvot ◽  
Kenneth R. Laurita
Keyword(s):  
Guinea Pig ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Optical Mapping ◽  
Contractile Function ◽  
Calcium Transient ◽  
Calcium Transients ◽  
Calcium Handling ◽  
Excitation Light ◽  
Intact Heart

Regional heterogeneities of ventricular repolarizing currents and their role in arrhythmogenesis have received much attention; however, relatively little is known regarding heterogeneities of intracellular calcium handling. Because repolarization properties and contractile function are heterogeneous from base to apex of the intact heart, we hypothesize that calcium handling is also heterogeneous from base to apex. To test this hypothesis, we developed a novel ratiometric optical mapping system capable of measuring calcium fluorescence of indo-1 at two separate wavelengths from 256 sites simultaneously. With the use of intact Langendorff-perfused guinea pig hearts, ratiometric calcium transients were recorded under normal conditions and during administration of known inotropic agents. Ratiometric calcium transients were insensitive to changes in excitation light intensity and fluorescence over time. Under control conditions, calcium transient amplitude near the apex was significantly larger (60%, P < 0.01) compared with the base. In contrast, calcium transient duration was significantly longer (7.5%, P < 0.03) near the base compared with the apex. During isoproterenol (0.05 μM) and verapamil (2.5 μM) administration, ratiometric calcium transients accurately reflected changes in contractile function, and, the direction of base-to-apex heterogeneities remained unchanged compared with control. Ratiometric optical mapping techniques can be used to accurately quantify heterogeneities of calcium handling in the intact heart. Significant heterogeneities of calcium release and sequestration exist from base to apex of the intact heart. These heterogeneities are consistent with base-to-apex heterogeneities of contraction observed in the intact heart and may play a role in arrhythmogenesis under abnormal conditions.

Fertilisation and thimerosal stimulate similar calcium spiking patterns in mouse oocytes but by separate mechanisms

Development ◽  
1993 ◽  
Vol 119 (1) ◽  
pp. 179-189 ◽  
Author(s):  
T.R. Cheek ◽  
O.M. McGuinness ◽  
C. Vincent ◽  
R.B. Moreton ◽  
M.J. Berridge ◽  
...  
Keyword(s):  
Divalent Cation ◽  
Meiotic Spindle ◽  
Oocyte Activation ◽  
Fura 2 ◽  
Mouse Oocytes ◽  
Calcium Spiking ◽  
Quench Analysis

Exposure of freshly ovulated mouse oocytes to a fertilising spermatozoon, thimerosal, Sr2+ or acetylcholine induced similar Ca2+ spiking responses. We propose that each of the four agents reduces the threshold for Ca2+ release from internal stores, but by different mechanisms. All agents except thimerosal stimulated oocyte activation, but thimerosal caused dissassembly of the meiotic spindle and thus prevented progress into interphase. Dithiothreitol (DTT) completely blocked and reversed the spiking responses induced by thimerosal, but facilitated and accelerated those induced by spermatozoa, Sr2+ and acetylcholine. The stimulatory effect of DTT was not simply a consequence of progress into interphase, but was attributable, at least in part, to an enhancement of divalent cation entry, as measured by Mn2+ quench analysis of fura-2 in both fertilised and unfertilised oocytes. Possible mechanisms by which DTT might achieve its effects are discussed.

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