PLCζ, a sperm-specific PLC and its potential role in fertilization

2007 ◽  
Vol 74 ◽  
pp. 23-36 ◽  
Author(s):  
Christopher M. Saunders ◽  
Karl Swann ◽  
F. Anthony Lai
Keyword(s):  
Intracellular Calcium ◽  
Membrane Fusion ◽  
Causative Agent ◽  
Calcium Concentration ◽  
Potential Role ◽  
Vital Role ◽  
The Other ◽  
Sperm Protein ◽  
Dramatic Rise ◽  
The Moment

A dramatic rise in intracellular calcium plays a vital role at the moment of fertilization, eliciting the resumption of meiosis and the initiation of embryo development. In mammals, the rise takes the form of oscillations in calcium concentration within the egg, driven by an elevation in inositol trisphosphate. The causative agent of these oscillations is proposed to be a recently described phosphoinositide-specific phospholipase C, PLCζ, a soluble sperm protein that is delivered into the egg following membrane fusion. In the present review, we examine some of the distinctive structural and functional characteristics of this crucial enzyme that sets it apart from the other known forms of mammalian PLC.

Cadmium block of isometric contractions of isolated bullfrog atrial cells

1991 ◽  
Vol 260 (2) ◽  
pp. C249-C258 ◽  
Author(s):  
N. Shepherd ◽  
F. Kavaler ◽  
W. Spielman
Keyword(s):  
Latent Period ◽  
Intracellular Calcium ◽  
Calcium Concentration ◽  
The Other ◽  
Isometric Contractions ◽  
Force Of Contraction ◽  
Twitch Force ◽  
Atrial Cells ◽  
Concentration Changes ◽  
Single Field

We studied the effect of cadmium, verapamil, and quinacrine on the force of contraction (Fp) of isolated, single, field-stimulated bullfrog atrial cells. All agents were applied or removed rapidly (t1/2 approximately 15 ms) to minimize intracellular concentration changes other than intracellular calcium concentration. Two components of twitch force were observed, one blocked by micromolar Cd2+ and the other by millimolar Cd2+. The two contributed about equally to the activation of the twitch. The "cadmium-sensitive" portion of force (that affected by [Cd] less than or equal to 100 microM) had a K1/2 approximately 1 microM, was identical in magnitude to, and not additive with, a "verapamil-sensitive" (10 microM) component of force, was most strongly affected by 50-ms pulses of Cd2+ when they were applied in the mechanical latent period, and was potentiated by catecholamines. The cadmium-insensitive portion of force was abolished by the removal of extracellular calcium and was greatly potentiated by quinacrine (3 or 10 microM), a blocker of Na-Ca exchange. The results are consistent with the idea that activating calcium enters the cell via both an inactivating cadmium-sensitive L-type channel and a noninactivating cadmium-insensitive mechanism that is not Na-Ca exchange and leaves the cell via Na-Ca exchange.

Modification of intracellular calcium concentration in cardiomyocytes by inhibition of sarcolemmal Na+/H+ exchanger

2006 ◽  
Vol 291 (6) ◽  
pp. H2790-H2800 ◽  
Author(s):  
Harjot K. Saini ◽  
Naranjan S. Dhalla
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Extracellular Ph ◽  
The Other ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Rat Cardiomyocytes ◽  
Intracellular Ca ◽  
Isolated Rat

Although the Na+/H+ exchanger (NHE) is considered to be involved in regulation of intracellular Ca2+ concentration ([Ca2+]i) through the Na+/Ca2+ exchanger, the exact mechanisms of its participation in Ca2+ handling by cardiomyocytes are not fully understood. Isolated rat cardiomyocytes were treated with or without agents that are known to modify Ca2+ movements in cardiomyocytes and exposed to an NHE inhibitor, 5-( N-methyl- N-isobutyl)amiloride (MIA). [Ca2+]i in cardiomyocytes was measured spectrofluorometrically with fura 2-AM in the absence or presence of KCl, a depolarizing agent. MIA increased basal [Ca2+]i and augmented the KCl-induced increase in [Ca2+]i in a concentration-dependent manner. The MIA-induced increase in basal [Ca2+]i was unaffected by extracellular Ca2+, antagonists of the sarcolemmal (SL) L-type Ca2+ channel, and inhibitors of the SL Na+/Ca2+ exchanger, SL Ca2+ pump ATPase and mitochondrial Ca2+ uptake. However, the MIA-induced increase in basal [Ca2+]i was attenuated by inhibitors of SL Na+-K+-ATPase and sarcoplasmic reticulum (SR) Ca2+ transport. On the other hand, the MIA-mediated augmentation of the KCl response was dependent on extracellular Ca2+ concentration and attenuated by agents that inhibit SL L-type Ca2+ channels, the SL Na+/Ca2+ exchanger, SL Na+-K+-ATPase, and SR Ca2+ release channels and the SR Ca2+ pump. However, the effect of MIA on the KCl-induced increase in [Ca2+]i remained unaffected by treatment with inhibitors of SL Ca2+ pump ATPase and mitochondrial Ca2+ uptake. MIA and a decrease in extracellular pH lowered intracellular pH and increased basal [Ca2+]i, whereas a decrease in extracellular pH, in contrast to MIA, depressed the KCl-induced increase in [Ca2+]i in cardiomyocytes. These results suggest that NHE may be involved in regulation of [Ca2+]i and that MIA-induced increases in basal [Ca2+]i, as well as augmentation of the KCl-induced increase in [Ca2+]i, in cardiomyocytes are regulated differentially.

scholarly journals The cytosolic sperm factor that triggers Ca2+ oscillations and egg activation in mammals is a novel phospholipase C: PLCζ

Reproduction ◽  
2004 ◽  
Vol 127 (4) ◽  
pp. 431-439 ◽  
Author(s):  
K Swann ◽  
M G Larman ◽  
C M Saunders ◽  
F A Lai
Keyword(s):  
Membrane Fusion ◽  
Phospholipase C ◽  
Potential Role ◽  
Egg Activation ◽  
Specific Factor ◽  
Sperm Protein ◽  
Protein Factor ◽  
Inositol 1,4,5 Trisphosphate ◽  
Intracellular Ca ◽  
Sperm Factor

When sperm activate eggs at fertilization the signal for activation involves increases in the intracellular free Ca2+concentration. In mammals the Ca2+changes at fertilization consist of intracellular Ca2+oscillations that are driven by the generation of inositol 1,4,5-trisphosphate (InsP3). It is not established how sperm trigger the increases in InsP3and Ca2+at fertilization. One theory suggests that sperm initiate signals to activate the egg by introducing a specific factor into the egg cytoplasm after membrane fusion. This theory has been mainly based upon the observation that injecting a cytosolic sperm protein factor into eggs can trigger the same pattern of Ca2+oscillations induced by the sperm. We have recently shown that this soluble sperm factor protein is a novel form of phospholipase C (PLC), and it is referred to as PLCζ(zeta). We describe the evidence that led to the identification of PLCζ and discuss the issues relating to its potential role in fertilization.

The Final ‘Thank You’

Derrida Today ◽  
2010 ◽  
Vol 3 (1) ◽  
pp. 21-36
Author(s):  
Grant Farred
Keyword(s):  
South Africa ◽  
South African ◽  
Jacques Derrida ◽  
Political Transition ◽  
The Other ◽  
World Cup ◽  
The Core ◽  
Nelson Mandela ◽  
Black President ◽  
The Moment

‘The Final “Thank You”’ uses the work of Jacques Derrida and Friedrich Nietzsche to think the occasion of the 1995 rugby World Cup, hosted by the newly democratic South Africa. This paper deploys Nietzsche's Zarathustra to critique how a figure such as Nelson Mandela is understood as a ‘Superman’ or an ‘Overhuman’ in the moment of political transition. The philosophical focus of the paper, however, turns on the ‘thank yous’ exchanged by the white South African rugby captain, François Pienaar, and the black president at the event of the Springbok victory. It is the value, and the proximity and negation, of the ‘thank yous’ – the relation of one to the other – that constitutes the core of the article. 1

Macaronics as What Eludes Translation

Paragraph ◽  
2015 ◽  
Vol 38 (2) ◽  
pp. 214-230
Author(s):  
Haun Saussy
Keyword(s):  
Print Culture ◽  
The Other ◽  
Digital Code ◽  
Avant Garde ◽  
The Moment

‘Translation’ is one of our all-purpose metaphors for almost any kind of mediation or connection: we ask of a principle how it ‘translates’ into practice, we announce initiatives to ‘translate’ the genome into predictions, and so forth. But the metaphor of translation — of the discovery of equivalents and their mutual substitution — so attracts our attention that we forget the other kinds of inter-linguistic contact, such as transcription, mimicry, borrowing or calque. In a curious echo of the macaronic writings of the era of the dawn of print, the twentieth century's avant-garde, already foreseeing the end of print culture, experimented with hybrid languages. Their untranslatability under the usual definitions of ‘translation’ suggests a revival of this avant-garde practice, as the mainstream aesthetic of the moment invests in ‘convergence’ and the subsumption of all media into digital code.

Covid-19 – rumours and facts in media

2020 ◽  
Vol 11 (SPL1) ◽  
pp. 171-174
Author(s):  
Tarare Toshida ◽  
Chaple Jagruti
Keyword(s):  
Social Media ◽  
Preventive Measures ◽  
Vital Role ◽  
The Other ◽  
Sources Of Information ◽  
Other Hand ◽  
Corona Virus ◽  
The People ◽  
The World

The covid-19 resulted in broad range of spread throughout the world in which India has also became a prey of it and in this situation the means of media is extensively inϑluencing the mentality of the people. Media always played a role of loop between society and sources of information. In this epidemic also media is playing a vital role in shaping the reaction in ϑirst place for both good and ill by providing important facts regarding symptoms of Corona virus, preventive measures against the virus and also how to deal with any suspect of disease to overcome covid-19. On the other hand, there are endless people who spread endless rumours overs social media and are adversely affecting life of people but we always count on media because they provide us with valuable answers to our questions, facts and everything in need. Media always remains on top of the line when it comes to stop the out spread of rumours which are surely dangerous kind of information for society. So on our side we should react fairly and maturely to handle the situation to keep it in the favour of humanity and help government not only to ϑight this pandemic but also the info emic.

Computational and experimental studies of the strength of full-scale samples of pipes with defects "metal loss" and "dent with groove"

2020 ◽  
Vol 10 (3) ◽  
pp. 226-233
Author(s):  
Dmitry A. Neganov ◽  
◽  
Victor M. Varshitsky ◽  
Andrey A. Belkin ◽  
◽  
...  
Keyword(s):  
Internal Pressure ◽  
Experimental Studies ◽  
Full Scale ◽  
The Other ◽  
Metal Loss ◽  
Calculation Methods ◽  
Reliable Operation ◽  
Sufficient Stability ◽  
Comparative Results ◽  
The Moment

The article contains the comparative results of the experimental and calculated research of the strength of a pipeline with such defects as “metal loss” and “dent with groove”. Two coils with diameter of 820 mm and the thickness of 9 mm of 19G steel were used for full-scale pipe sample production. One of the coils was intentionally damaged by machining, which resulted in “metal loss” defect, the other one was dented (by press machine) and got groove mark (by chisel). The testing of pipe samples was performed by applying static internal pressure to the moment of collapse. The calculation of deterioration pressure was carried out with the use of national and foreign methodical approaches. The calculated values of collapsing pressure for the pipe with loss of metal mainly coincided with the calculation experiment results based on Russian method and ASME B31G. In case of pipe with dent and groove the calculated value of collapsing pressure demonstrated greater coincidence with Russian method and to a lesser extent with API 579/ASME FFS-1. In whole, all calculation methods demonstrate sufficient stability of results, which provides reliable operation of pipelines with defects.

scholarly journals Orientia tsutsugamushi Inhibits Apoptosis of Macrophages by Retarding Intracellular Calcium Release

2002 ◽  
Vol 70 (8) ◽  
pp. 4692-4696 ◽  
Author(s):  
Mee-Kyung Kim ◽  
Seung-Yong Seong ◽  
Ju-Young Seoh ◽  
Tae-Hee Han ◽  
Hyeon-Je Song ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Calcium Release ◽  
Cytosolic Calcium ◽  
Orientia Tsutsugamushi ◽  
Cytosolic Calcium Concentration ◽  
Infected Cells ◽  
Intracellular Calcium Release ◽  
Calcium Redistribution ◽  
In Cells

ABSTRACT Orientia tsutsugamushi shows both pro- and antiapoptotic activities in infected vertebrate cells. Apoptosis of THP-1 cells induced by beauvericin was inhibited by O. tsutsugamushi infection. Beauvericin-induced calcium redistribution was significantly reduced and retarded in cells infected with O. tsutsugamushi. Antiapoptotic activities of O. tsutsugamushi in infected cells are most probably due to inhibition of the increase in the cytosolic calcium concentration.

scholarly journals Regulation of membrane fusion by the membrane-proximal coil of the t-SNARE during zippering of SNAREpins

2002 ◽  
Vol 158 (5) ◽  
pp. 929-940 ◽  
Author(s):  
Thomas J. Melia ◽  
Thomas Weber ◽  
James A. McNew ◽  
Lillian E. Fisher ◽  
Robert J. Johnston ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Fusion Proteins ◽  
The Other ◽  
Proximal Portion ◽  
Intrinsic State ◽  
Temporal Control ◽  
Helical Bundle ◽  
Proximal Half

We utilize structurally targeted peptides to identify a “tC fusion switch” inherent to the coil domains of the neuronal t-SNARE that pairs with the cognate v-SNARE. The tC fusion switch is located in the membrane-proximal portion of the t-SNARE and controls the rate at which the helical bundle that forms the SNAREpin can zip up to drive bilayer fusion. When the fusion switch is “off” (the intrinsic state of the t-SNARE), zippering of the helices from their membrane-distal ends is impeded and fusion is slow. When the tC fusion switch is “on,” fusion is much faster. The tC fusion switch can be thrown by a peptide that corresponds to the membrane-proximal half of the cognate v-SNARE, and binds reversibly to the cognate region of the t-SNARE. This structures the coil in the membrane-proximal domain of the t-SNARE and accelerates fusion, implying that the intrinsically unstable coil in that region is a natural impediment to the completion of zippering, and thus, fusion. Proteins that stabilize or destabilize one or the other state of the tC fusion switch would exert fine temporal control over the rate of fusion after SNAREs have already partly zippered up.

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