1,720,997 research outputs found
Na-ca Exchange And Ca Fluxes During Contraction And Relaxation In Mammalian Ventricular Muscle
No full textThere are four cellular Ca transport systems which compete to remove Ca from the myoplasm in mammalian ventricular myocytes. These are 1) the SR Ca-ATPase, 2) the sarcolemmal Na-Ca exchange, 3) the sarcolemmal Ca-ATPase and 4) the mitochondrial Ca uniporter. Using multiple experimental approaches we have evaluated the dynamic interaction of these systems during the normal cardiac contraction-relaxation cycle. The SR Ca-ATPase and Na-Ca exchange are clearly the most important, quantitatively; however, the relative roles vary in a species-dependent manner. In particular, the SR is much more strongly dominant in rat ventricular myocytes, where ~ 92% of Ca removal is via SR Ca-ATPase and only 7% via Na-Ca exchange during a twitch. In other species (rabbit, ferret, cat, and guinea pig) the balance is more in the range of 70% SR Ca-ATPase and 25-30% Na-Ca exchange. Ferret ventricular myocytes also exhibit an unusually strong sarcolemmal Ca-ATPase. During the steady state the same amount of Ca must leave the cell as enters over a cardiac cycle. This implies that 25-30% of the Ca required to activate contraction must enter the cell, and experiments demonstrate that this amount of Ca may be supplied by the L-type Ca current.779430442Bers, D.M., (1991) Excitation-Contraction Coupling and Cardiac Contractile Force, pp. 1-258. , (Single author monograph.) Kluwer Academic Press. Dordrecht, NetherlandsSutko, J.L., Willerson, J.T., Ryanodine alteration of the contractile state of rat ventricular myocardium. Comparison with dog, cat and rabbit ventricular tissues (1980) Circ. Res., 46, pp. 332-343Bers, D.M., Ca influx and SR Ca release in cardiac muscle activation during postrest recovery (1985) Am. J. Physiol., 248, pp. H366-H381Bers, D.M., Mechanisms contributing to the cardiac inotropic effect of Na-pump inhibition and reduction of extracellular Na (1987) J. Gen. Physiol., 90, pp. 479-504Bers, D.M., Christensen, D.M., Nguyen, T.X., Can Ca entry via Na-Ca exchange directly activate cardiac muscle contraction? (1988) J. Mol. Cell. Cardiol., 20, pp. 405-414Beuckelmann, D.J., Wier, W.G., Mechanism of release of calcium from sarcoplasmic reticulum of guinea pig cardiac cells (1988) J. Physiol., 405, pp. 233-255Fabiato, A., Time and calcium dependence of activation and inactivation of calcium-induced release of calcium from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell (1985) J. Gen. Physiol., 85, pp. 247-290Leblanc, N., Hume, J.R., Sodium current-induced release of calcium from cardiac sarcoplasmic reticulum (1990) Science, 248, pp. 372-376Levi, A.J., Spitzer, K.W., Kohmoto, O., Bridge, J.H.B., Depolarization-induced Ca entry via Na-Ca exchange triggers SR release in guinea pig cardiac myocytes (1994) Am. J. Physiol., 266, pp. H1422-H1433Kohmoto, O., Levi, A.J., Bridge, J.H.B., Relation between reverse sodium-calcium exchange and sarcoplasmic reticulum calcium release in guinea pig ventricular cells (1994) Circ. Res., 74, pp. 550-554Bassani, R.A., Bassani, J.W.M., Bers, D.M., Mitochondrial and sarcolemmal Ca transport can reduce [Ca]i during caffeine contractures in rabbit cardiac myocytes (1992) J. Physiol., 453, pp. 591-608Bassani, J.W.M., Bassani, R.A., Bers, D.M., Relaxation in rabbit and rat cardiac cells: Species-dependent differences in cellular mechanisms (1994) J. Physiol., 476, pp. 279-293Bassani, R.A., Bassani, J.W.M., Bers, D.M., Relaxation in ferret ventricular myocytes: Unusual interplay among calcium transport systems (1994) J. Physiol., 476, pp. 295-308Bers, D.M., Bridge, J.H.B., Relaxation of rabbit ventricular muscle by Na-Ca exchange and sarcoplasmic reticulum Ca-pump: Ryanodine and voltage sensitivity (1989) Circ. Res., 65, pp. 334-342Bridge, J.H.B., Relationships between the sarcoplasmic reticulum and transarcolemmal Ca transport revealed by rapidly cooling rabbit ventricular muscle (1986) J. Gen. Physiol., 88, pp. 437-473Bers, D.M., Bridge, J.H.B., Spitzer, K.W., Intracellular Ca transients during rapid cooling contractures in guinea-pig ventricular myocytes (1989) J. Physiol., 417, pp. 537-553Bers, D.M., Lederer, W.J., Berlin, J.R., Intracellular Ca transients in rat cardiac myocytes: Role of Na/Ca exchange in excitation-contraction coupling (1990) Am. J. Physiol., 258, pp. C944-C954Hryshko, L.V., Stiffel, V.M., Bers, D.M., Rapid cooling contractures as an index of SR Ca content in rabbit ventricular myocyte (1989) Am. J. Physiol., 257, pp. H1369-H1377Hove-Madsen, L., Bers, D.M., SR Ca uptake and thapsigargin sensitivity in permeabilized rabbit and rat ventricular myocytes (1993) Cir. Res., 73, pp. 820-828Bassani, J.W.M., Bassani, R.A., Bers, D.M., Twitch-dependent SR Ca accumulation and release in rabbit ventricular myocytes (1993) Am. J. Physiol., 265, pp. C533-C540Bassani, R.A., Bers, D.M., Rate of diastolic Ca release from the sarcoplasmic reticulum of intact rabbit and rat ventricular myocytes (1995) Biophys. J., 68, pp. 2015-2022Bassani, J.W.M., Yuan, W., Bers, D.M., Fractional SR Ca release is altered by trigger Ca and SR Ca content in cardiac myocytes (1995) Am. J. Physiol., 268, pp. 1313-1319Gatto, C., Milanick, M.A., Inhibition of the red blood cell calcium pump by eosin and other fluorescein analogues (1993) Am. J. Physiol., 264, pp. C1577-C1586Gatto, C., Hale, C.C., Milanick, M.A., Eosin, a potent inhibitor of the plasma membrane Ca pump, does not inhibit the cardiac Na-Ca exchanger (1995) Biochemistry, 34, pp. 965-972Bassani, R.A., Bassani, J.W.M., Bers, D.M., Relaxation in ferret ventricular myocytes: Role of the sarcolemmal Ca ATPase (1995) Pflüg. Arch., 430, pp. 573-579Hove-Madsen, L., Bers, D.M., Passive Ca buffering and SR Ca uptake in permeabilized rabbit ventricular myocytes (1993) Am. J. Physiol., 264, pp. C677-C686Negretti, N., O'Neill, S.C., Eisner, D.A., The relative contributions of different intracellular and sarcolemmal systems to relaxation in rat ventricular myocytes (1993) Cardiovasc. Res., 27, pp. 1826-1830Crespo, L.M., Grantham, C.J., Cannell, M.B., Kinetics, stoichiometry and role of the Na-Ca exchange mechanism in isolated cardiac myocytes (1990) Nature, 345, pp. 618-621Puglisi, J.L., Bassani, R.A., Bassani, J.W.M., Amin, J.N., Bers, D.M., Temperature and the relative contributions of Ca transport systems in cardiac myocyte relaxation (1996) Am. J. Physiol., , In pressDelbridge, L.M., Bassani, J.W.M., Bers, D.M., Steady-state twitch Ca fluxes and cytosolic Ca buffering in rabbit ventricular myocytes (1996) Am. J. Physiol., 39, pp. C192-C199Fabiato, A., Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum (1983) Am. J. Physiol., 245, pp. C1-C1
Temperature And Relative Contributions Of Ca Transport Systems In Cardiac Myocyte Relaxation
No full textThe relative contributions of the different Ca transport systems involved in cardiac relaxation were evaluated at 25 and 35°C in isolated rabbit, ferret, and cat ventricular myocytes during twitches, caffeine-induced contractures in normal Tyrode solution, and caffeine-induced contractures in Na- and Ca-free solution. The time course of intracellular [Ca] decline during these contractions in rabbit ventricular myocytes allowed estimates of the relative contributions of the sarcoplasmic reticulum (SR) Ca pump, Na/Ca exchange, sarcolemmal Ca pump, and the mitochondrial calcium uniporter (with the latter two considered together as 'slow mechanisms'). The percent contributions of the SR Ca pump, the Na/Ca exchange, and the slow mechanisms were 70, 27, and 3% at 25°C and 74, 23, and 3% at 35°C. Warming from 25 to 35°C decreases twitch contractions in rabbit and ferret myocytes and caffeine-induced contractures in normal Tyrode solution and Na- and Ca-free solution in all species. In contrast, in cat myocytes warming increased twitches, possibly because of a stronger effect of temperature on Ca influx. We conclude that increased temperature accelerates all of the Ca transport systems involved in relaxation. Despite large changes in each Ca transport system with warming, the relative contributions during relaxation remain similar at physiological temperature.2705 39-5H1772H1778Bassani, J.W.M., Bassani, R.A., Bers, D.M., Relaxation in rabbit and rat cardiac cells: Species-dependent differences in cellular mechanisms (1994) J. Physiol. Lond., 476, pp. 279-293Bassani, J.W.M., Yuan, W., Bers, D.M., Fractional SR Ca release is regulated by trigger Ca and SR Ca content in cardiac myocytes (1995) Am. J. Physiol., 268, pp. C1313-C1329. , Cell Physiol. 37Bassani, R.A., Bassani, J.W.M., Bers, D.M., Relaxation in ferret ventricular myocytes: Role of the sarcolemmal Ca ATPase (1995) Pfluegers Arch., 430, pp. 573-578Bassani, R.A., Bassani, J.W.M., Bers, D.M., Relaxation in ferret ventricular myocytes: Unusual interplay among calcium transport systems (1994) J. Physiol. Lond., 476, pp. 295-308Bassani, R.A., Bassani, J.W.M., Bers, D.M., Mitochondrial and sarcolemmal Ca2+ transport reduce [Ca]1 during caffeine contractures in rabbit cardiac myocytes (1992) J. Physiol. Lond., 453, pp. 591-608Bers, D.M., (1991) Excitation-Contraction Coupling and Cardiac Contractile Force, p. 258. , Dordrecht, The Netherlands: Kluwer AcademicBers, D.M., Berlin, J.R., The kinetics of [Ca]1 decline in cardiac myocytes depends on peak [Ca]i (1995) Am. J. Physiol., 268, pp. C271-C277. , Cell Physiol. 37Bers, D.M., Bridge, J.H.B., Relaxation of rabbit ventricular muscle by Na-Ca exchange and sarcoplasmic reticulum calcium pump. Eyanodine and voltage sensitivity (1989) Circ. Res., 65, pp. 334-342Bers, D.M., Bridge, J.H.B., Spitzer, K.W., Intracellular Ca2+ transients during rapid cooling contractures in guinea-pig ventricular myocytes (1989) J. Physiol. Lond., 417, pp. 537-553Bersohn, M.M., Vemuri, R., Schuil, D.W., Weiss, R.S., Philipson, K.D., Effect of temperature on sodium-calcium exchange in sarcolemma from mammalian and amphibian hearts (1991) Biochim. Biophys. Acta, 1062, pp. 19-23Blinks, J.R., Koch-Weser, J., Physical factors in the analysis of the action of drugs on myocardial contractility (1963) Pharmacol. Rev., 15, pp. 531-599Briggs, G.M., Bers, D.M., Role of calcium current in hypothermie inotropy in myocytes isolated from rabbit ventricles (1990) Biophys. J, 57, p. 346Cavalié, A., McDonald, T.F., Pelzer, D., Trautwein, W., Temperature-induced transitory and steady-state changes in the calcium current of guinea pig ventricular myocytes (1985) Pfluegers Arch., 405, pp. 294-296Chapman, R.A., Sodium/calcium exchange and intracellular calcium buffering in ferret myocardium: An ion-sensitive microelectrode study (1986) J. Physiol. Lond., 373, pp. 163-179Debetto, P., Cusinato, F., Luciani, S., Temperature dependence of Na+/Ca2+ exchange activity in beef-heart sarcolemmal vesicles and proteoliposomes (1990) Arch. Biochem. Biophys., 278, pp. 205-210Delbridge, L.M., Bassani, J.W.M., Bers, D.M., Steadystate twitch Ca fluxes and cytosolic Ca buffering in rabbit ventricular myocytes (1996) Am. J. Physiol., 270, pp. C192-C199. , Cell Physiol. 39Grynkiewicz, G., Poenie, M., Tsien, R.Y., A new generation of Ca2+ indicators with greatly improved fluorescence properties (1985) J. Biol. Chem., 250, pp. 3440-3450Harrison, S.M., Bers, D.M., Influence of temperature on the calcium sensitivity of the myofilaments of skinned ventricular muscle from the rabbit (1989) J. Gen. Physiol., 93, pp. 411-428Hove-Madsen, L., Bers, D.M., Passive Ca buffering and SR Ca uptake in permeabilized rabbit ventricular myocytes (1993) Am. J. Physiol., 264, pp. C677-C686. , Cell Physiol. 33Hryshko, L.V., Stiffel, V.M., Bers, D.M., Rapid cooling contractures as an index of sarcoplasmic reticulum calcium content in rabbit ventricular myocytes (1989) Am. J. Physiol., 257, pp. H1369-H1377. , Heart Circ. Physiol. 26Kimura, J., Miyamae, S., Noma, A., Identification of sodium-calcium exchange current in single ventricular cells of guinea-pig (1987) J. Physiol. Lond., 384, pp. 199-222Kruta, V., Sur l'activité rythmique du muscle cardiaque. II. Variations, en fonction de la température, des relations entre la réponse mécanique et le rythme (1938) Arch. Int. Physiol., 47, pp. 35-62Lipp, P., Pott, L., Callewaert, G., Carmeliet, E., Simultaneous recording of indo-1 fluorescence and Na+/Ca2+ exchange current reveals two components of Ca2+ release from sarcoplasmic retieulum of cardiac atrial myocytes (1990) FEBS Lett., 275, pp. 181-184Mattiazzi, A.R., Nilsson, E., The influence of temperature on time course of the mechanical activity in rabbit papillary muscle (1976) Acta Physiol. Scand., 97, pp. 310-318Negretti, N., O'Neill, S.C., Eisner, D.A., The relative contributions of different intracellular and sarcolemmal systems to relaxation in rat ventricular myocytes (1993) Cardiouasc. Res., 27, pp. 1826-1830Niggli, E., Lederer, W.J., Activation of Na-Ca exchange current by photolysis of "caged calcium" (1993) Biophys. J, 65, pp. 882-891Shattock, M.J., Bers, D.M., Inotropic response to hypothermia and the temperature-dependence of ryanodine action in isolated rabbit and rat ventricular muscle: Implications for the excitation-contraction coupling (1987) Circ. Res., 61, pp. 761-771Shikegawa, M., Finegan, J.M., Katz, A.M., Calcium transport ATPase of canine cardiac sarcoplasmic reticulum (1976) J. Biol. Chem., 251, pp. 6894-6900Sitsapesan, R., Montgomery, R.A., MacLeod, K.T., Williams, A.J., Sheep cardiac sarcoplasmic reticulum calcium-release channels: Modification of conductance and gating by temperature (1991) J. Physiol. Lond., 434, pp. 469-488Zhou, Z., Lipsius, S.L., Na+-Ca2+ exchange current in latent pacemaker cells isolated from cat right atrium (1993) J. Physiol. Lond., 466, pp. 263-28
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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