scholarly journals The Cortical Changes on Fertilization of the Sea-Urchin Egg

1955 ◽  
Vol 32 (3) ◽  
pp. 451-467
Author(s):  
H. KACSER
Keyword(s):  
Calcium Ions ◽  
Sea Urchins ◽  
Critical Role ◽  
Psammechinus Miliaris ◽  
Sea Urchin Egg ◽  
Dark Ground ◽  
Artificial Activation ◽  
Kinetics Of ◽  
Cortical Change

The kinetics of the dark ground cortical change in fertilized sea urchins has been analysed. In normal eggs of Psammechinus miliaris the change appears to obey an autocatalytic mechanism. The evidence from artificial activation suggests that the initiation of the response is caused by a relatively unspecific event. The critical role of calcium is considered in relation to the evidence from eggs fertilized in capillary tubes. This suggests that calcium ions are not concerned with the initiation but with the propagation of the response. The primary change in activation may consist of an increase in permeability at the site of initiation.

scholarly journals Participation of the Lys313-Ile333 Sequence of the Purinergic P2X4 Receptor in Agonist Binding and Transduction of Signals to the Channel Gate

2006 ◽  
Vol 281 (43) ◽  
pp. 32649-32659 ◽  
Author(s):  
Zonghe Yan ◽  
Zhaodong Liang ◽  
Tomas Obsil ◽  
Stanko S. Stojilkovic
Keyword(s):  
Transmembrane Domain ◽  
Critical Role ◽  
Receptor Function ◽  
Agonist Binding ◽  
Channel Opening ◽  
Channel Gate ◽  
Agonist Concentration ◽  
Opening And Closing ◽  
Kinetics Of

To study the roles of the Lys313-Ile333 ectodomain sequence of the rat P2X4 receptor in ATP binding and transduction of signals to the channel gate, the conserved Lys313, Tyr315, Gly316, Ike317, Arg318, Asp320, Val323, Lys329, Phe330, and Ile333 residues were mutated. Current recordings were done on lifted cells and ATP was applied using an ultrafast solution-switching system. The rates of wild type channel opening and closing in the presence of ATP, but not the rate of washout-induced closing, were dependent on agonist concentration. All mutants other than I317A were expressed in the plasma membrane at comparable levels. The majority of mutants showed significant changes in the peak amplitude of responses and the EC50 values for ATP. When stimulated with the supramaximal (1.4 mm) ATP concentration, mutants also differed in the kinetics of their activation, deactivation, and/or desensitization. The results suggest a critical role of the Lys313 residue in receptor function other than coordination of the phosphate group of ATP and possible contribution of the Tyr315 residue to the agonist binding module. The pattern of changes of receptor function by mutation of other residues was consistent with the operation of the Gly316-Ile333 sequence as a signal transduction module between the ligand binding domain and the channel gate in the second transmembrane domain.

scholarly journals The Critical Role of Carbon in the Chemical Delithiation Kinetics of LiFePO4

2020 ◽  
Vol 167 (7) ◽  
pp. 070538 ◽  
Author(s):  
Montserrat Galceran ◽  
Abdelbast Guerfi ◽  
Michel Armand ◽  
Karim Zaghib ◽  
Montse Casas-Cabanas
Keyword(s):  
Critical Role ◽  
Kinetics Of

scholarly journals Arrhythmogenic and antiarrhythmic actions of late sustained sodium current in the adult human heart

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anh Tuan Ton ◽  
William Nguyen ◽  
Katrina Sweat ◽  
Yannick Miron ◽  
Eduardo Hernandez ◽  
...  
Keyword(s):  
Human Heart ◽  
Ex Vivo ◽  
Sodium Current ◽  
Critical Role ◽  
Anemonia Sulcata ◽  
Effective Therapeutic Strategy ◽  
Kinetics Of ◽  
Selective Blocker ◽  
Antiarrhythmic Actions

AbstractLate sodium current (late INa) inhibition has been proposed to suppress the incidence of arrhythmias generated by pathological states or induced by drugs. However, the role of late INa in the human heart is still poorly understood. We therefore investigated the role of this conductance in arrhythmias using adult primary cardiomyocytes and tissues from donor hearts. Potentiation of late INa with ATX-II (anemonia sulcata toxin II) and E-4031 (selective blocker of the hERG channel) slowed the kinetics of action potential repolarization, impaired Ca2+ homeostasis, increased contractility, and increased the manifestation of arrhythmia markers. These effects could be reversed by late INa inhibitors, ranolazine and GS-967. We also report that atrial tissues from donor hearts affected by atrial fibrillation exhibit arrhythmia markers in the absence of drug treatment and inhibition of late INa with GS-967 leads to a significant reduction in arrhythmic behaviour. These findings reveal a critical role for the late INa in cardiac arrhythmias and suggest that inhibition of this conductance could provide an effective therapeutic strategy. Finally, this study highlights the utility of human ex-vivo heart models for advancing cardiac translational sciences.

Oocyte activation: fundamental and clinical aspects

2020 ◽  
Vol 19 (5) ◽  
pp. 77-85
Author(s):  
Yu.Yu. Gromenko ◽  
◽  
E.F. Galimova ◽  
D.D. Gromenko ◽  
K.Sh. Galimov ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Calcium Ions ◽  
Therapeutic Option ◽  
Clinical Aspects ◽  
Oocyte Activation ◽  
Molecular Events ◽  
General Aspects ◽  
Artificial Activation ◽  
Main Factor

Fertilization and embryogenesis in mammals are initiated by a series of molecular events called ‘oocyte activation.’ This process includes a number of specific fluctuations of calcium ions in the cell with the involvement of specific phospholipase C ζ (PLCζ), an enzyme of spermatozoa introduced into the ooplasm during gamete fusion and recognized as the main factor responsible for inducing oocyte activation. Substantial biochemical and clinical evidence supports the role of PLCζ in this fundamental process, which is very important for the diagnosis and treatment of infertility. This literature review aims to provide some insight in the structure, mechanism of action, and regulation of PLCζ activity in healthy individuals and people with pathological conditions. Oocyte activation deficiency is associated with abnormalities in the structure, expression, and location of this enzyme in spermatozoa. Artificial activation of oocytes using ionophores, which is the only therapeutic option currently available for patients with its insufficiency, is being debated, especially in terms of its potential epigenetic effects on the embryo. Therefore, interest towards the development of human recombinant PLCζ as an alternative treatment is understandable. Researchers are currently discussing the possibility of diagnostic and clinical application of this enzyme to overcome male infertility associated with oocyte activation deficiency, as well as general aspects of this pathology. Key words: oocyte activation, infertility, calcium ions, phospholipase C ζ

scholarly journals The Block to Polyspermy in Sturgeon and Trout with Special Reference to the Role of Cortical Granules (Alveoli)

Development ◽  
1961 ◽  
Vol 9 (1) ◽  
pp. 173-190
Author(s):  
A. S. Ginsburg
Keyword(s):  
Sea Urchins ◽  
Morphological Changes ◽  
Cortical Layer ◽  
Vitelline Membrane ◽  
Cortical Granules ◽  
Sea Urchin Egg ◽  
Protective Reaction ◽  
Fertilization Membrane ◽  
The Subject

When a monospermic egg is fertilized, the attachment of the fertilizing spermatozoon to the egg surface provokes a protective reaction that prevents all ut one spermatozoon from entering the egg; this is the block to polyspermy. The nature of the defence mechanism against polyspermy has been the subject of many investigations, performed mainly on the eggs of sea urchins. It was established that on fertilization of the sea-urchin egg a cortical reaction takes place consisting of morphological changes in the cortical layer, spreading in wave-like fashion from the point of the spermatozoon attachment over the whole egg surface: the light scattering and the intensity of birefringence undergo changes; extrusion of mucopolysaccharide granules takes place, accompanied by the separation of the vitelline membrane and its transformation into the fertilization membrane; the perivitelline space appears and the hyaline layer is then formed at the egg surface (see Runnström, 1952; Rothschild, 1956; Allen, 1958).

scholarly journals The Central Role of the F-Actin Surface in Myosin Force Generation

Biology ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1221
Author(s):  
Matthew H. Doran ◽  
William Lehman
Keyword(s):  
Critical Role ◽  
Structural Features ◽  
Force Generation ◽  
Actin Binding ◽  
Myosin Isoforms ◽  
Thin Filaments ◽  
Cellular Processes ◽  
Muscle Myosin ◽  
Kinetics Of

Actin is one of the most abundant and versatile proteins in eukaryotic cells. As discussed in many contributions to this Special Issue, its transition from a monomeric G-actin to a filamentous F-actin form plays a critical role in a variety of cellular processes, including control of cell shape and cell motility. Once polymerized from G-actin, F-actin forms the central core of muscle-thin filaments and acts as molecular tracks for myosin-based motor activity. The ATP-dependent cross-bridge cycle of myosin attachment and detachment drives the sliding of myosin thick filaments past thin filaments in muscle and the translocation of cargo in somatic cells. The variation in actin function is dependent on the variation in muscle and non-muscle myosin isoform behavior as well as interactions with a plethora of additional actin-binding proteins. Extensive work has been devoted to defining the kinetics of actin-based force generation powered by the ATPase activity of myosin. In addition, over the past decade, cryo-electron microscopy has revealed the atomic-evel details of the binding of myosin isoforms on the F-actin surface. Most accounts of the structural interactions between myosin and actin are described from the perspective of the myosin molecule. Here, we discuss myosin-binding to actin as viewed from the actin surface. We then describe conserved structural features of actin required for the binding of all or most myosin isoforms while also noting specific interactions unique to myosin isoforms.

Critical role of elemental copper for enhancing conversion kinetics of sulphur cathodes in rechargeable magnesium batteries

2019 ◽  
Vol 484 ◽  
pp. 933-940 ◽  
Author(s):  
Boeun Lee ◽  
Jihwan Choi ◽  
Subin Na ◽  
Dong-Joo Yoo ◽  
Jong Hak Kim ◽  
...  
Keyword(s):  
Critical Role ◽  
Elemental Copper ◽  
Magnesium Batteries ◽  
Kinetics Of ◽  
Rechargeable Magnesium Batteries

scholarly journals Glass ionomer bone cements based on magnesium-containing bioactive glasses

2019 ◽  
Vol 5 (1) ◽  
pp. 1-12
Author(s):  
Roland Wetzel ◽  
Leena Hupa ◽  
Delia S. Brauer
Keyword(s):  
Calcium Ions ◽  
Mechanical Stability ◽  
Critical Role ◽  
Bone Cements ◽  
Glass Ionomer Cements ◽  
Magnesium Ions ◽  
Glass Ionomer ◽  
Acid Attack ◽  
Ion Release

Abstract Glass ionomer cements (GIC) are used in restorative dentistry and their properties (low heat during setting, adhesion to mineralised tissue and surgical metals) make them of great interest for bone applications.However, dental GIC are based on aluminium-containing glasses, and the resulting release of aluminium ions from the cements needs to be avoided for applications as bone cements. Replacing aluminium ions in glasses for use in glass ionomer cements is challenging, as aluminium ions play a critical role in the required glass degradation by acid attack as well as in GIC mechanical stability. Magnesium ions have been used as an alternative for aluminium in the glass component, but so far no systematic study has looked into the actual role of magnesium ions. The aim of the present study is therefore the systematic comparison of the effect of magnesium ions compared to calcium ions in GIC glasses. It is shown that by partially substituting MgO for CaO in simple SiO2-CaO-CaF2 glasses, ion release from the glass and, subsequently, GIC setting behaviour can be adjusted. Magnesium ions act as typical network modifiers here but owing to their larger field strength compared to calcium ions reduce ion release from the glasses significantly. By choosing an optimum ratio of magnesium and calcium ions in the glass, GIC setting and subsequently compressive strength can be controlled.

Sign in / Sign up

Export Citation Format

Share Document