scholarly journals Assessment of Intracellular Calcium and Plasmalemmal Membrane Potential in Cryopreserved Metaphase II Mouse Oocytes

2020 ◽  
Author(s):  
Omar Farhan Ammar ◽  
Therishnee Moodley
Keyword(s):  
Membrane Potential ◽  
Xenopus Oocytes ◽  
Channel Blocker ◽  
Oocyte Activation ◽  
Suitable Alternative ◽  
Human Oocytes ◽  
Mouse Oocytes ◽  
Failed Fertilization ◽  
Intracellular Ca

Abstract Objectives: Ca2+ is critical for normal oocyte activation and fertilization, and any alteration to the Ca2+ homeostasis may lead to failed fertilization or even cell death. It has been shown that intracellular Ca2+ is increased in bovine and human oocytes when cultured in vitro. Additionally, ATP sensitive potassium channels have been characterised recently in human and Xenopus oocytes Glibenclamide a KATP channel blocker was shown to protect human oocytes from Ca+2 overloading. None of these studies have been conducted in mouse oocytes to determine if they are a suitable alternative to human oocytes in the research setting. Thus, this research note aims to demonstrate if cryopreserved metaphase II (MII) mouse oocytes show similar Ca+2 and plasmalemmal membrane potential dynamics to those in human oocytes. Also, to show if glibenclamide influences Ca+2, and plasmalemmal membrane potential in cryopreserved metaphase II mouse oocytes. Results: our data did not show an increase in intracellular Ca2+ in untreated cryopreserved mouse oocytes loaded with Fluo-3 AM dye. However, an increase in the plasmalemmal membrane potential was noticed (hyperpolarization). Glibenclamide has shown no significant effect on Ca+2, mitochondrial and plasmalemmal membrane potential.

scholarly journals Assessment of Intracellular Calcium and Plasmalemmal Membrane Potential in Cryopreserved Metaphase II Mouse Oocytes

2020 ◽  
Author(s):  
Omar Farhan Ammar ◽  
Therishnee Moodley
Keyword(s):  
Membrane Potential ◽  
Xenopus Oocytes ◽  
Channel Blocker ◽  
Oocyte Activation ◽  
Human Oocytes ◽  
Mouse Oocytes ◽  
Failed Fertilization ◽  
Intracellular Ca ◽  
In Vitro Ageing

Abstract Objectives: Ca2+ is critical for normal oocyte activation and fertilization, and any alteration to the Ca2+ homeostasis may lead to failed fertilization or even cell death. It has been shown that intracellular Ca2+ is increased in bovine and human oocytes when cultured in vitro. Additionally, ATP sensitive potassium channels have been characterised recently in human and Xenopus oocytes. Glibenclamide a KATP channel blocker was shown to protect human oocytes from Ca+2 overloading via inhibition of plasmalemmal KATP channels. This research note aims to demonstrate the effects of oxidative stress and in vitro ageing on the intracellular Ca+2 and plasmalemmal membrane potential dynamics in cryopreserved metaphase II (MII) mouse oocytes. Also, this study aims to show if glibenclamide (a KATP channel blocker ) has a role in regulating intracellular Ca+2 and plasmalemmal membrane potential through KATP channels in cryopreserved metaphase II mouse oocytes.Results: our data did not show an increase in intracellular Ca2+ in untreated cryopreserved mouse oocytes loaded with Fluo-3 AM dye. However, an increase in the plasmalemmal membrane potential was noticed (hyperpolarization). Glibenclamide has shown no significant effect on Ca2+ and plasmalemmal membrane potential.

Membrane potential controls calcium entry into descending vasa recta pericytes

2002 ◽  
Vol 283 (4) ◽  
pp. R949-R957 ◽  
Author(s):  
Zhong Zhang ◽  
Kristie Rhinehart ◽  
Thomas L. Pallone
Keyword(s):  
Membrane Potential ◽  
Channel Blocker ◽  
Calcium Entry ◽  
Ang Ii ◽  
Channel Blockade ◽  
Voltage Gated ◽  
Vasa Recta ◽  
Intracellular Ca ◽  
Bayk 8644

We tested the hypothesis that constriction of descending vasa recta (DVR) is mediated by voltage-gated calcium entry. K+ channel blockade with BaCl2 (1 mM) or TEACl (30 mM) depolarized DVR smooth muscle/pericytes and constricted in vitro-perfused vessels. Pericyte depolarization by 100 mM extracellular KCl constricted DVR and increased pericyte intracellular Ca2+ ([Ca2+]i). The KATP channel opener pinacidil (10−7-10−4 M) hyperpolarized resting pericytes, repolarized pericytes previously depolarized by ANG II (10−8 M), and vasodilated DVR. The DVR vasodilator bradykinin (10−7 M) also reversed ANG II depolarization. The L-type Ca2+ channel blocker diltiazem vasodilated ANG II (10−8 M)- or KCl (100 mM)-preconstricted DVR, and the L-type agonist BayK 8644 constricted DVR. The plateau phase of the pericyte [Ca2+]i response to ANG II was inhibited by diltiazem. These data support the conclusion that DVR vasoreactivity is controlled through variation of membrane potential and voltage-gated Ca2+ entry into the pericyte cytoplasm.

Nuclear envelope removal/maintenance determines the structural and functional remodelling of embryonic red blood cell nuclei in activated mouse oocytes

Zygote ◽  
1998 ◽  
Vol 6 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Daniel Szöllösi ◽  
Renata Czołowska ◽  
Ewa Borsuk ◽  
Maria S. Szöllösi ◽  
Pascale Debey
Keyword(s):  
Nuclear Envelope ◽  
Transcriptional Activity ◽  
Chromatin Condensation ◽  
Oocyte Activation ◽  
Cell Nuclei ◽  
Nuclear Envelope Breakdown ◽  
Mouse Oocytes ◽  
Female Pronucleus ◽  
Mouse Fetuses

SummaryNuclei of embryonic red blood cells (e-RBC) from 12-day mouse fetuses are arrested in Go phase of the cell cycle and have low transcriptional activity. These nuclei were transferred with help of polyethylene glycol (PEG)-mediated fusion to parthenogenetically activated mouse oocytes and heterokaryons were analysed for nuclear structure and transcriptional activity. If fusion proceeded 25–45 min after oocyte activation, e-RBC nuclei were induced to nuclear envelope breakdown and partial chromatin condensation, followed by formation of nuclei structurally identical with pronuclei. These ‘pronuclei’, similar to egg (female) pronuclei, remained transcriptionally silent over several hours of in vitro culture. If fusion was performed 1 h or later (up to 7 h) after activation, the nuclear envelope of e-RBC nuclei remained intact and nuclear remodelling was less spectacular (slight chromatin decondensation, formation of nucleolus precursor bodies). These nuclei, however, reinforced polymerase-II-dependent transcription within a few hours of in vitro culture. Our present experiments, together with our previous work, demonstrate that nuclear envelope breakdown/maintenance are critical events for nuclear remodelling in activated mouse oocytes and that somatic dormant nuclei can be stimulated to renew transcription at a time when the female pronucleus remains transcriptionally silent.

238 CAFFEINE PREVENTS A LOSS OF CALCIUM OSCILLATORY RESPONSE ASSOCIATED WITH POSTOVULATORY AGING OF MOUSE OOCYTES

2009 ◽  
Vol 21 (1) ◽  
pp. 217
Author(s):  
T. Wakai ◽  
N. Zhang ◽  
R. A. Fissore
Keyword(s):  
Subsequent Development ◽  
Oocyte Quality ◽  
Developmental Competence ◽  
Oscillatory Activity ◽  
Strontium Chloride ◽  
Oocyte Activation ◽  
Mouse Oocytes ◽  
Oocyte Aging ◽  
Postovulatory Aging

Numerous studies have demonstrated that postovulatory aging of oocytes prior to fertilization has detrimental effects on oocyte quality and developmental competence. Oocyte aging is accompanied by abnormal oocyte activation and subsequent development, suggesting a disruption of Ca2+ oscillations after fertilization. The inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) in mammals is responsible for the majority of Ca2+ release during fertilization (Miyazaki S et al. 1993 Dev. Biol.). Previously, we reported that phosphorylation of IP3R1 at an MPM-2 epitope may play an important role in facilitating the induction of Ca2+ oscillations at the MII stage (Lee B et al. 2006 Development), indicating that IP3R1 phosphorylation may be a good indicator of the health of the oocyte. However, few studies have investigated the alteration of the Ca2+ signaling and IP3R1 function associated with oocyte aging. On the other hand, a previous report showed that caffeine increased MPF activity and suppressed fragmentation after parthenogenetic activation of aged oocytes (Kikuchi K et al. 2000 Biol. Reprod.). Therefore, the purpose of the present study was to examine whether and how Ca2+ oscillatory activity changes during oocyte aging and to test if caffeine prevents the negative effects of oocyte aging. MII mouse oocytes were collected 14 h after hCG injection and cultured in vitro for 8, 24 or 48 h with or without caffeine (5 or 10 mm). Oocyte quality was assessed by the occurrence of spontaneous fragmentation, monitoring of Ca2+ oscillations after exposure to 10 mm strontium chloride, Western blot analysis of IP3R1 phosphorylation and immunostaining of IP3R1. In oocytes in vitro aged for 8 h, the duration of the first Ca2+ rise was significantly decreased compared with fresh MII oocytes, although this reduction was not observed in MII oocytes treated with 5 mm caffeine. The phosphorylation of IP3R1 at the MPM-2 epitope was slightly decreased during oocyte aging in both caffeine and noncaffeine treatment. Importantly, whereas IP3R1 in MII oocytes treated for 8 h with 5 mm caffeine displayed the typical cortical cluster organization, IP3R1 in aged oocytes without caffeine became dispersed in the cytoplasm. In addition, caffeine significantly suppressed the spontaneous fragmentation that is normally observed by 48 h of in vitro culture. These results suggest that the Ca2+ oscillatory activity is compromised during oocyte aging and caffeine prevents the loss of integrity of Ca2+ signaling possibly by keeping the cortical distribution of IP3R1.

Evidence that signal transduction for osmoreception is mediated by stretch-activated ion channels in tilapia

2003 ◽  
Vol 284 (5) ◽  
pp. C1290-C1296 ◽  
Author(s):  
A. P. Seale ◽  
N. H. Richman ◽  
T. Hirano ◽  
I. Cooke ◽  
E. G. Grau
Keyword(s):  
Ion Channels ◽  
Channel Blocker ◽  
Oreochromis Mossambicus ◽  
Cell Swelling ◽  
Simultaneous Measurements ◽  
Perfusion Chamber ◽  
Intracellular Ca ◽  
Stretch Activated Ion Channels

Prolactin (PRL) plays a central role in the freshwater osmoregulation of teleost fish, including the tilapia ( Oreochromis mossambicus). Consistent with this action, PRL release from the tilapia pituitary increases as extracellular osmolality is reduced both in vitro and in vivo. Dispersed tilapia PRL cells were incubated in a perfusion chamber that allowed simultaneous measurements of cell volume and PRL release. Intracellular Ca2+ concentrations were measured from fura 2-loaded PRL cells treated in a similar way. Gadolinium (Gd3+), known to block stretch-activated cation channels, inhibited hyposmotically induced PRL release in a dose-related manner without preventing cell swelling. Nifedipine, an L-type Ca2+ channel blocker, did not prevent the increase in PRL release during hyposmotic stimulation. A high, depolarizing concentration of KCl induced a transient and marked increase of intracellular Ca2+ and release of PRL but did not prevent the rise in intracellular Ca2+ and PRL release evoked by exposure to hyposmotic medium. These findings suggest that a decrease in extracellular osmolality stimulates PRL release through the opening of stretch-activated ion channels, which allow extracellular Ca2+ to enter the cell when it swells.

373 OOCYTE-ACTIVATING CAPACITY OF BOVINE SPERMATOGENIC CELLS AND ACTIVATION PROTOCOLS FOR INTRACYTOPLASMIC INJECTION OF BOVINE ROUND SPERMATIDS

2007 ◽  
Vol 19 (1) ◽  
pp. 302
Author(s):  
C. Kani ◽  
M. Takenaka ◽  
T. Muneto ◽  
M. Yamamoto ◽  
T. Horiuchi
Keyword(s):  
Germ Line ◽  
Oocyte Activation ◽  
Spermatogenic Cells ◽  
Blastocyst Development ◽  
Chi Square ◽  
Mouse Oocytes ◽  
Intracytoplasmic Injection ◽  
Bovine Oocytes ◽  
Activation Capacity

In vitro spermatogenesis can be applied to generate spermatids or spermatozoa and produce a genetically modified male germ line. Intracytoplasmic injection of the spermatids or spermatozoa is an important technique for effective production of offspring. The objective of this study is to evaluate oocyte-activation capacity of bovine spermatids or spermatozoa and to determine the effective activation treatment for in vitro development of bovine oocytes injected with round spermatids. Cryopreserved testicular spermatogenic cells and cauda epididymal spermatozoa obtained from a 1-year-old Japanese bull were used. In the first experiment, we injected bovine round (ROS) and elongated (ELS) spermatids, or testicular (TES) and cauda epididymal (CES) spermatozoa into mouse oocytes to examine their oocyte-activating capacity. The presence of pronuclei within whole-mounted oocytes was observed 4 h after injection. In the second experiment, we injected similar spermatids and spermatozoa into bovine oocytes without additional activation, and examined cleavage and blastocyst development. In the third experiment, bovine oocytes injected with ROS were activated with 7% ethanol or 5 �M ionomycin for 5 min (1 � Et or 1 � Iono) immediately after injection; some were further activated repeatedly at 3 h after injection (2 � Et or 2 � Iono), and some of these were subjected to 1.9 mM 6-dimethylaminopurine (DMAP) for 3 h after the second activation (2 � Et + DMAP or 2 � Iono + DMAP). Data were analyzed by the chi-square test in all experiments. The vast majority of bovine ROS failed to activate mouse oocytes (activation rate 10%). Activation rates of mouse oocytes injected with bovine ELS, TES, and CES were 61%, 75%, and 91%, respectively. The results suggest that oocyte-activation capacity is acquired during transformation from ROS to ELS. Cleavage and blastocyst rates of bovine oocytes injected with CES (59% and 19%, respectively) were significantly higher (P < 0.05) than the rates obtained with injections of TES (37% and 9%) and ROS (5% and 0%) without additional activation. However, cleavage and blastocyst rates of bovine oocytes injected with ROS in the groups of 2 � Et + DMAP (80% and 19%) and 2 � Iono + DMAP (76% and 19%) were significantly higher (P < 0.05) than those in the groups of 1 � and 2 � Et (37% and 2%, 59% and 4%), 1 � and 2 � Iono (10% and 7%, 22% and 4%), or those receiving a sham injection and activated with 2 � Iono + DMAP (43% and 4%). These results demonstrate that intracytoplasmic injection of ROS with repeated Et or Iono activation followed by DMAP treatment is more efficient than single or double Et or Iono activation.

153 Fertilisation of Cattle Oocytes is Linked to Novel Waves of a Ca2+ Fluorophore in Cumulus Cells

2018 ◽  
Vol 30 (1) ◽  
pp. 216
Author(s):  
H. J. McLennan ◽  
M. L. Sutton-McDowall ◽  
S. Heng ◽  
J. G. Thompson
Keyword(s):  
Xenopus Oocytes ◽  
Cumulus Cells ◽  
Time Lapse ◽  
Molecular Probes ◽  
Vitelline Membrane ◽  
Oocyte Activation ◽  
Sperm Binding ◽  
Significant Difference ◽  
The Media

During fertilization, multiple intracellular calcium (Ca2+) oscillations are initiated after sperm binding to the oocyte vitelline membrane. This Ca2+ signalling has been extensively studied in denuded mouse and Xenopus oocytes but minimally studied in larger mammals. Cows in particular are unusual, as the few studies on oocyte activation have observed fewer Ca2+ oscillations during fertilisation compared with mice. Furthermore, cattle intracytoplasmic sperm injection (ICSI) is inefficient, despite parthenogenetic activation occurring readily. We hypothesise that cumulus cells are important for cattle oocyte activation at fertilisation. Here, we assessed the behaviour of Ca2+oscillations in fertilising intact cattle cumulus–oocyte complexes (COC). Abattoir-derived cattle COC were matured and fertilised in vitro using Bovine Vitro Media Suite (IVF Vet Solutions). The COC were stained 3.5 h after insemination with the Ca2+ fluorescent probe Fluo4AM (5 μM, Molecular Probes Inc., Eugene, OR, USA) for 30 min, washed, and imaged every 5 min for 6 h in a Fluoview FV10i incubating time-lapse confocal microscope (Olympus) before being returned to culture. Embryo development was assessed at Day 8 to confirm fertilisation. Fluo4AM fluorescence intensity was assessed using FIJI ImageJ. Mean relative intensity over time was graphed for specific regions of interest and the area under graphs was calculated to quantify differences for comparison using a Mann-Whitney Test (mean ± SEM). Experiment 1 (4 reps of 10 COC) compared confirmed fertilised v. uninseminated; experiment 2 (2 reps of 10 COC) compared inseminated COC ± 10 μM BAPTA-AM (Ca2+ chelator, Sigma-Aldrich, St. Louis, MO, USA). There were distinct coordinated waves of differing Fluo4AM intensity in both the oocyte and the cumulus cells surrounding the confirmed fertilised oocytes. This contrasted to the random uncoordinated flashes of Fluo4AM fluorescence in the cumulus cells of the uninseminated oocytes. The fluorescence pattern in +BAPTA-AM COC matched the random flashes observed in the uninseminated group of experiment 1. The fluorescence in the media surrounding the COC immediately following the Fluo4AM waves spiked and then plateaued at a higher level of fluorescence. This was quantified by assessing the area under the graph for 1 h of the plateau following the fluorescence spike. There were no differences between confirmed fertilised (346.4 ± 41.62) and uninseminated groups (239.8 ± 32.08; P > 0.05), but this was affected by differences in cumulus dispersal due to the presence or absence of sperm. Experiment 2 used BAPTA-AM to block oocyte activation with sperm present in both groups and showed a significant difference between the fluorescence increase in the media of the 2 groups (–BAPTA-AM: 311.2 ± 31.57, +BAPTA-AM: 201.4 ± 26.59; P < 0.03). Although the physiological significance has yet to be determined, we have observed a novel Ca2+ wave in the cumulus cells that could be linked to oocyte activation in cattle. There was a significant increase in Fluo4AM fluorescence in the media surrounding the COC, which may indicate cumulus cells are releasing Ca2+ at the time of oocyte activation.

scholarly journals The Persistence-Inducing Toxin HokB Forms Dynamic Pores That Cause ATP Leakage

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Dorien Wilmaerts ◽  
Mariam Bayoumi ◽  
Liselot Dewachter ◽  
Wouter Knapen ◽  
Jacek T. Mika ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Lipid Bilayers ◽  
Channel Blocker ◽  
Clinical Importance ◽  
Chronic Infections ◽  
Persister Cells ◽  
Bacterial Populations ◽  
Content Type ◽  
Intracellular Atp

ABSTRACTBacterial populations harbor a small fraction of cells that display transient multidrug tolerance. These so-called persister cells are extremely difficult to eradicate and contribute to the recalcitrance of chronic infections. Several signaling pathways leading to persistence have been identified. However, it is poorly understood how the effectors of these pathways function at the molecular level. In a previous study, we reported that the conserved GTPase Obg induces persistence inEscherichia colivia transcriptional upregulation of the toxin HokB. In the present study, we demonstrate that HokB inserts in the cytoplasmic membrane where it forms pores. The pore-forming capacity of the HokB peptide is demonstrated byin vitroconductance measurements on synthetic and natural lipid bilayers, revealing an asymmetrical conductance profile. Pore formation is directly linked to persistence and results in leakage of intracellular ATP. HokB-induced persistence is strongly impeded in the presence of a channel blocker, thereby providing a direct link between pore functioning and persistence. Furthermore, the activity of HokB pores is sensitive to the membrane potential. This sensitivity presumably results from the formation of either intermediate or mature pore types depending on the membrane potential. Taken together, these results provide a detailed view on the mechanistic basis of persister formation through the effector HokB.IMPORTANCEThere is increasing awareness of the clinical importance of persistence. Indeed, persistence is linked to the recalcitrance of chronic infections, and evidence is accumulating that persister cells constitute a pool of viable cells from which resistant mutants can emerge. Unfortunately, persistence is a poorly understood process at the mechanistic level. In this study, we unraveled the pore-forming activity of HokB inE. coliand discovered that these pores lead to leakage of intracellular ATP, which is correlated with the induction of persistence. Moreover, we established a link between persistence and pore activity, as the number of HokB-induced persister cells was strongly reduced using a channel blocker. The latter opens opportunities to reduce the number of persister cells in a clinical setting.

Chemical activation in Rhinella arenarum oocytes: effect of dehydroleucodine (DhL) and its hydrogenated derivative (2H-DhL)

Zygote ◽  
2014 ◽  
Vol 23 (6) ◽  
pp. 924-932
Author(s):  
M.F. Medina ◽  
M.I. Bühler ◽  
G. Sánchez-Toranzo
Keyword(s):  
Mechanism Of Action ◽  
Chemical Activation ◽  
Dependent Manner ◽  
Oocyte Activation ◽  
Parthenogenetic Activation ◽  
Intracellular Ca ◽  
Rhinella Arenarum ◽  
Dose Dependent ◽  
Maturation Promoting Factor

SummaryMature oocytes are arrested in metaphase II due to the presence of high levels of active maturation promoting factor (MPF). After fertilization, active MPF levels decline abruptly, enabling oocytes to complete meiosis II. One of the first and universal events of oocyte activation is an increase in cytosolic Ca2+ that would be responsible for MPF inactivation. Mature oocytes can also be activated by parthenogenetic activation. The aims of this work are to test the ability of dehydroleucodine (DhL) and its hydrogenated derivative 11,13-dihydro-dehydroleucodine (2H-DhL) to induce chemical activation in amphibian oocytes and to study the participation of calcium in the process. Results indicated that DhL and 2H-DhL induced oocyte activation in a dose-dependent manner. After 90 min of treatment, DhL 36 μM was able to induce 95% activation, while 2H-DhL 36 μM was less active, with only 40% activation. Our results suggest that DhL induced the inhibition of MPF activity, probably by an increase in intracellular Ca2+ concentration. Extracellular Ca2+ would not be significant, although Ca2+ release from intracellular stores is critical. In this sense, IP3Rs and RyRs were involved in the Ca2+ transient induced by lactones. In this species, RyRs appears to be the largest contributor to Ca2+ release in DhL-induced activation. Although more studies are needed on the mechanism of action through which these lactones induce oocyte activation in Rhinella arenarum, the results of this research provide interesting perspectives for the use of these lactones as chemical activators in in vitro fertilization and cloning.

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