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William H Barry

Publications and source records attributed to William H Barry.

14 recordsLinked to original sources
PubMed2006

CRYAB and HSPB2 deficiency increases myocyte mitochondrial permeability transition and mitochondrial calcium uptake.

Double knockout (DKO) of the small heat shock proteins CRYAB and HSPB2 increases necrosis and apoptosis induced by ischemia/reperfusion (I/R) in vitro, but the mechanisms involved are unknown. We examined [Ca2+]i during metabolic inhibition (MI) changes in [Ca2+]m induced by exposure to elevated [Ca2+]i, and whether mitochondria in isolated DKO ventricular myocytes (VM) are more susceptible than wild type (WT) to induction of the mitochondrial permeability transition (MPT). The rise in [Ca2+]i in DKO myocytes during metabolic inhibition (MI) was less than in WT, and ouabain caused a greater increase in [Ca2+]m in DKO than in WT. These findings suggested that Ca2+ uptake was increased in mitochondria in DKO myocytes. Measurements of Rhod 2 fluorescence during exposure of permeabilized VM to 1000 nM [Ca2+] for 5 min confirmed that DKO myocytes have enhanced mitochondrial Ca2+ uptake, and this difference between DKO and WT myocyte mitochondria was eliminated by inhibition of NO synthesis. MPT was induced more readily by ouabain, PAO, or TMRM in DKO myocytes than in WT. Thus, Ca2+ uptake by mitochondria is increased in DKO VM by a NO-dependent mechanism. This can predispose to the development of MPT, and increased VM injury during I/R. These findings indicate an important role of CRYAB and/or HSPB2 in mitochondrial function.

Animals↗
PubMed2006

Percutaneous coronary interventions with stents in cardiac transplant recipients.

BACKGROUND: Allograft coronary vasculopathy is a major cause of death beyond the first year after cardiac transplantation. The aim of this study was to review our experience with percutaneous coronary intervention (PCI) with stents in cardiac transplant recipients. METHODS: We identified patients who were treated with PCI using stents. Patient characteristics, procedure information and clinical outcomes were assessed for these patients by review of their medical records. We also compared results for those who had bare metal stents vs those who had drug-eluting stents. RESULTS: Forty patients from our program's 865 cardiac transplant recipients received a total of 78 coronary stents. There were 35 males (87.5%) and 5 females (12.5%). The indication for PCI was progressive asymptomatic coronary vasculopathy in 18 patients (45%), angina in 5 (12.5%), acute myocardial infarction (MI) in 4 (10%) and congestive heart failure (CHF) in 6 (15%). Primary success (<50% residual stenosis) was obtained in 71 (91%) of 78 stents. During the mean follow-up of 40.8 +/- 34.5 months, 6 patients died (15%) and 2 (5%) were re-transplanted. There was a lower rate of re-stenosis with drug-eluting stents (2 of 13, 15%) compared with bare metal stents (20 of 65, 31%), although this difference was not statistically significant (p = 0.27). CONCLUSIONS: In cardiac transplant recipients, PCI with stents can be performed with high rates of primary success. Restenosis rates are higher compared with PCI in native coronary arteries. A trend toward less restenosis with drug-eluting stents was observed, which needs to be confirmed in larger studies.

Angioplasty, Balloon, Coronary↗
PubMed2006

Na"Fuzzy space": does it exist, and is it important in ischemic injury?

Work is reviewed which provides evidence for the presence of a subsarcolemmal microdomain, in which the [Na(+)] is influenced by Na(+) influx via the Na(+) channel and the activity of the Na pump. The sarcolemma adjacent to this microdomain, which has been referred to as "Na(+) fuzzy space," appears to include Na-Ca exchangers, and thus alterations of [Na(+)] in this space may influence Ca(2+) influx and efflux, and thus Ca(2+) loading, more directly than do alterations of bulk cytoplasmic [Na(+)]. The degree of Ca(2+) loading is an important determinant of contractility in heart muscle, and therefore alterations in fuzzy space [Na(+)] may be important in mediating the positive inotropic effects of Na pump inhibitors, such as digitalis, and the negative inotropic effects of Na(+) channel blockers such as disopyramide. During ischemia, myocyte Ca(2+) overload can contribute to ATP depletion by activation of Ca(2+)-dependent ATPases and by induction of the mitochondrial permeability transition, and thus is an important contributor to myocyte dysfunction and injury. Hypoxia associated with ischemia can induce Na(+) influx via a persistent opening of the Na(+) channel. It is likely that this Na(+) influx elevates [Na(+)] in the fuzzy space, and thus increases Ca(2+) influx via Na-Ca exchange, and increases Ca(2+) loading. Inhibition of the persistent Na(+) current with a resulting decrease in Ca(2+) loading by drugs such as tetrodotoxin (TTX) and ranolazine may be a mechanism by which these agents produce a cardio-protective effect during ischemia.

Animals↗
PubMed2005

Difference in propagation of Ca2+ release in atrial and ventricular myocytes.

Intracellular [Ca2+] ([Ca2+]i) was imaged in atrial and ventricular rat myocytes by means of a high-speed Nipkow confocal microscope. Atrial myocytes with an absent t-tubule system on 8-di- ANEPPS staining showed an initial rise in Ca2+ at the periphery of the cell, which propagated to the interior of the cell. Ventricular myocytes showed a uniform rise in [Ca2+]i after electrical stimulation, consistent with a prominent t-tubular network. In atrial myocytes, there was a much shorter time between the peak of the [Ca2+]i transient and the peak contraction as compared to ventricular myocytes. A regional release of Ca2+ induced by an exposure of one end of the myocyte to caffeine with a rapid solution switcher resulted in a uniform propagation of Ca2+ down the length of the cell in atrial myocytes, but we found no propagation in ventricular myocytes. A staining with rhodamine 123 indicated a much greater density of mitochondria in ventricular myocytes than in atrial myocytes. Thus the atrial myocytes display a lack of "local control" of Ca2+ release, with propagation after the Ca2+ release at the periphery induced by stimulation or at one end of the cell induced by exposure to caffeine. Ventricular myocytes showed the presence of local control, as indicated by an absence of the propagation of a local caffeine-induced Ca2+ transient. We suggest that this finding, as well as a reduced delay between the peak of the [Ca2+]i transient and the peak shortening in atrial myocytes, could be due in part to reduced Ca2+ buffering provided by mitochondria in atrial myocytes as opposed to ventricular myocytes.

Animals↗
PubMed2005

Propagation of Ca2+ release in cardiac myocytes: role of mitochondria.

Factors contributing to "local control" of Ca2+ release in cardiac myocytes are incompletely understood. We induced local release of Ca2+ by regional exposure of mouse atrial and ventricular myocytes to 10mM caffeine for 500 ms using a rapid solution switcher. Propagation of Ca2+ release was imaged by means of a Nipkow confocal microscope, and fluo-3. Under physiologic conditions, a local release of Ca2+ propagated in atrial myocytes, not in ventricular myocytes. Inhibition of SR Ca2+ uptake (500 nM thapsigargin), and of Ca2+ extrusion via Na/Ca exchange (5mM Ni2+), did not result in propagation in ventricular myocytes. The density of mitochondria was greater in ventricular than in atrial myocytes, although the abundance of ryanodine receptors and myofilaments was similar. Partial inhibition of Ca2+ uptake via the mitochondrial Ca2+ uniporter (5 microM Ru360) caused an increase in the [Ca2+]i transient in paced ventricular myocytes, and consistently resulted in propagation of Ca2+ release. This effect of Ru360 did not appear to be due to altered SR Ca2+ content. These data indicate that Ca2+ uptake via the mitochondrial uniporter occurs on a beat-to-beat basis, and may contribute to local control of Ca2+ release. Propagation of Ca2+ release in atrial myocytes may result in part from the relatively low density of mitochondria present.

Animals↗
PubMed2005

Relative abundance of alpha2 Na(+) pump isoform influences Na(+)-Ca(2+) exchanger currents and Ca(2+) transients in mouse ventricular myocytes.

In the mouse, genetic reduction in the Na(+), K(+)-ATPase alpha1 or alpha2 isoforms results in different functional phenotypes: heterozygous alpha2 isolated hearts are hypercontractile, whereas heterozygous alpha1 hearts are hypocontractile. We examined Na(+)/Ca(2+) exchange (NCX) currents in voltage clamped myocytes (pipette [Na(+)]=15 mM) induced by abrupt removal of extracellular Na(+). In wild-type (WT) myocytes, peak exchanger currents were 0.59+/-0.04 pA/pF (mean+/-S.E.M., n=10). In alpha1(+/-) myocytes (alpha2 isoform increased by 54%), NCX current was reduced to 0.33+/-0.05 (n=9, P<0.001) indicating a lower subsarcolemmal [Na(+)]. In alpha2(+/-) myocytes (alpha2 isoform reduced by 54%), the NCX current was increased to 0.89+/-0.11 (n=8, P=0.03). The peak sarcolemmal Na(+) pump currents activated by abrupt increase in [K(+)](o) to 4 mM in voltage clamped myocytes in which the Na(+) pump had been completely inhibited for 5 min by exposure to 0 [K(+)](o) were similar in alpha1(+/-) (0.86+/-0.12, n=10) and alpha2(+/-) myocytes (0.94+/-0.08 pA/pF, n=16), and were slightly but insignificantly reduced relative to WT (1.03+/-0.05, n=24). The fluo-3 [Ca(2+)](i) transient (F/F(o)) in WT myocytes paced at 0.5 Hz was 2.18+/-0.09, n=34, was increased in alpha2(+/-) myocytes (F/F(o)=2.56+/-0.14, n=24, P=0.02), and was decreased in alpha1(+/-) myocytes (F/F(o)=1.93+/-0.08, n=28, P<0.05). Thus the alpha2 isoform rather than the alpha1 appears to influence Na(+)/Ca(2+) exchanger currents [Ca(2+)](i) transients, and contractility. This finding is consistent with the proposal that alpha2 isoform of the Na pump preferentially alters [Na(+)] in a subsarcolemmal micro-domain adjacent to Na(+)/Ca(2+) exchanger molecules and SR Ca(2+) release sites.

Animals↗
PubMed2004

A beneficial role of cardiac P2X4 receptors in heart failure: rescue of the calsequestrin overexpression model of cardiomyopathy.

The P2X4 purinergic receptor (P2X4R) is a ligand-gated ion channel. Its activation by extracellular ATP results in Ca2+ influx. Transgenic cardiac overexpression of the human P2X4 receptor showed an in vitro phenotype of enhanced basal contractility. The objective here was to determine the in vivo cardiac physiological role of this receptor. Specifically, we tested the hypothesis that this receptor plays an important role in modulating heart failure progression. Transgenic cardiac overexpression of canine calsequestrin (CSQ) showed hypertrophy, heart failure, and premature death. Crossing the P2X4R mouse with the CSQ mouse more than doubled the lifespan (182 +/- 91 days for the binary CSQ/P2X4R mouse, n = 35) of the CSQ mouse (71.3 +/- 25.4 days, n = 50, P < 0.0001). The prolonged survival in the binary CSQ/P2X4R mouse was associated with an improved left ventricular weight-to-body weight ratio and a restored beta-adrenergic responsiveness. The beneficial phenotype of the binary mouse was not associated with any downregulation of the CSQ level but correlated with improved left ventricular developed pressure and +/-dP/dt. The enhanced cardiac performance was manifested in young binary animals and persisted in older animals. The increased contractility likely underlies the survival benefit from P2X4 receptor overexpression. An increased expression or activation of this receptor may represent a new approach in the therapy of heart failure.

Animals↗
PubMed2003

Saxitoxin blocks L-type ICa.

Saxitoxin (STX) and tetrodotoxin (TTX) are frequently used to selectively block sodium channels. In this study, we provide evidence that commercial STX also inhibits L-type Ca2+ currents (I(Ca,L)) in adult mouse ventricular myocytes (VMs) and tsA-201 cells that were transiently cotransfected with three calcium channel subunits. We measured inhibition of sodium currents (INa) in mouse VMs, of I(Ca,L) in mouse VM and tsA-201 cells, and intracellular calcium concentration ([Ca2+]i) transients in single mouse VMs. STX or TTX was abruptly applied before the test voltage pulse using a rapid solution switcher device. STX (10 microM; Calbiochem) and TTX (60 microM; Sigma-Aldrich) completely blocked INa in mouse VMs. However, STX at 10 microM also reduced I(Ca,L) in mouse VM by 39% (P < 0.0001; n = 14), whereas TTX at 60 microM had no effect on I(Ca,L). STX (10 microM; Calbiochem) reduced the amplitude of the [Ca2+]i transients in mouse VMs by 36% (P < 0.0001; n = 10). In contrast, TTX (60 microM; Sigma-Aldrich) only reduced the amplitude of the [Ca2+]i transients by 9% (P = 0.003; n = 5). STX (10 microM) obtained from Sigma-Aldrich showed a similar inhibitory effect on I(Ca,L) (33%) (P < 0.0001; n = 5) in mouse VMs. STX (Calbiochem) inhibited the calcium currents of tsA-201 cells in a dose-dependent manner. This inhibition was voltage-independent. The current-voltage relationship of calcium currents in tsA-201 cells was not altered by STX. These results indicate that STX partially blocks L-type Ca2+ channels and thus provide further evidence that its effects are not specific for Na+ channels.

Animals↗
PubMed2003

Intracellular Na+ regulation in cardiac myocytes.

Intracellular [Na+] ([Na+]i) is regulated in cardiac myocytes by a balance of Na+ influx and efflux mechanisms. In the normal cell there is a large steady state electrochemical gradient favoring Na+ influx. This potential energy is used by numerous transport mechanisms, including Na+ channels and transporters which couple Na+ influx to either co- or counter-transport of other ions and solutes. Six sarcolemmal Na+ influx pathways are discussed in relatively quantitative terms: Na+ channels, Na+/Ca2+ exchange, Na+/H+ exchange, Na+/Mg2+ exchange, Na+/HCO3- cotransport and Na+/K+/2Cl- cotransport. Under normal conditions Na+/Ca2+ exchange and Na+ channels are the dominant Na+ influx pathways, but other transporters may become increasingly important during altered conditions (e.g. acidosis or cell volume stress). Mitochondria also exhibit Na+/Ca2+ antiporter and Na+/H+ exchange activity that are important in mitochondrial function. These coupled fluxes of Na+ with Ca2+, H+ and HCO3- make the detailed understanding of [Na+]i regulation pivotal to the understanding of both cardiac excitation-contraction coupling and pH regulation. The Na+/K+-ATPase is the main route for Na+ extrusion from cells and [Na+]i is a primary regulator under physiological conditions. [Na+]i is higher in rat than rabbit ventricular myocytes and the reason appears to be higher Na+ influx in rat with a consequent rise in Na+/K+-ATPase activity (rather than lower Na+/K+-ATPase function in rat). This has direct functional consequences. There may also be subcellular [Na+]i gradients locally in ventricular myocytes and this may also have important functional implications. Thus, the balance of Na+ fluxes in heart cells may be complex, but myocyte Na+ regulation is functionally important and merits focused attention as in this issue.

Animals↗
PubMed2003

Elective coronary angiography and percutaneous coronary intervention during uninterrupted warfarin therapy.

The management of patients anticoagulated with warfarin and referred for coronary angiography presents a substantial challenge to the physician who must minimize risks of periprocedural hemorrhage and thromboembolism. The aim of this study was to evaluate the feasibility and safety of performing diagnostic coronary angiography and percutaneous coronary intervention during uninterrupted warfarin therapy. Patients treated with warfarin were prospectively identified and enrolled in the study. Nineteen diagnostic cardiac catheterizations and six percutaneous coronary interventions were performed in 23 patients. The mean international normalized ratio was 2.4 +/- 0.5 (range, 1.8-3.5). Hemostasis was achieved with AngioSeal following 21 procedures and with Perclose following 4 procedures. No patient experienced a predefined endpoint. Specifically, no patient experienced procedure-related myocardial infarction, major or minor bleeding. We conclude that cardiac catheterization and percutaneous coronary intervention may be considered in the setting of uninterrupted warfarin therapy.

Aged↗
PubMed2003

Comparison of sarcoplasmic reticulum Ca2+-ATPase function in human, dog, rabbit, and mouse ventricular myocytes.

It has been reported that sarcoplasmic reticulum (SR) Ca(2+) uptake is more rapid in rat than rabbit ventricular myocytes, but little information is available on the relative SR Ca(2+) uptake activity in others species, including humans. We induced Ca(2+) transients with a short caffeine pulse protocol (rapid solution switcher, 10 mM caffeine, 100 ms) in single ventricular myocytes voltage clamped (-80 mV) with pipettes containing 100 microM fluo-3 and nominal 0 Ca(2+), in 0 Na(+)(o)/0 Ca(2+)(o) solution to inhibit Na/Ca exchange. SR in non-paced human, dog, rabbit, and mouse ventricular myocytes could be readily loaded with Ca(2+) under our experimental conditions with a pipette [Ca(2+)] = 100 nM. Resting [Ca(2+)](i) was similar in four types of ventricular myocytes. Activation of the Ca(2+)-release channel with a 100-ms caffeine pulse produced a rise in [caffeine](i) to slightly above 2 mM, the threshold for caffeine activation of Ca(2+) release. This caused a similar initial rate of rise and peak [Ca(2+)](i) in the four types of ventricular myocytes. However, there were significant differences in the duration of the plateau (top 10%) [Ca(2+)](i) transients and the time constant of the [Ca(2+)](i) decline (reflecting activity of the SR Ca(2+)-ATPase), with values for human > dog > rabbit > mouse. In paced myocytes under physiologic conditions, SR Ca(2+) content was greater in mouse than in rabbit myocytes, while peak I(Ca,L) was smaller in mouse. These findings confirm substantial species difference in SR Ca(2+)-ATPase activity, and suggest that the smaller the animal and the more rapid the heart rate, greater the activity of the SR Ca(2+)-ATPase. In addition, it appears that substantial species differences exist in the degree of SR Ca(2+) loading and I(Ca,L) under physiologic conditions.

Animals↗
PubMed2003

Ca2+ sparks induced by Na/Ca exchange.

Whether Ca(2+) influx on the Na/Ca exchanger (NCX) can trigger elementary sarcoplasmic reticulum (SR) Ca(2+) release events (Ca(2+) sparks) is controversial. We imaged [Ca(2+)](i) (Nipkow confocal microscope and fluo-3) in left ventricular myocytes isolated from wild type (WT) and transgenic (TG) mice overexpressing NCX 2.5-fold. Sudden activation of Ca(2+) influx via NCX induced by abrupt exposure to "0" [Na(+)](o)/normal [Ca(2+)](o) solution by means of a rapid solution switcher-induced Ca(2+) sparks in NCX TG myocytes in 425+/-17 ms, n=21. The diameter and amplitude (F/F(0)) of these sparks (2.74+/-0.14 microm, F/F(0)=2.16+/-0.06, n=18) were similar to those induced by field stimulation of myocytes in the presence of 20 microM nifedipine (2.70+/-0.10 microm, F/F(0)=1.98+/-0.08, n=17). In WT myocytes no Ca(2+) sparks were observed within the first 600 ms after abrupt removal of extracellular Na. In parallel experiments, voltage clamp current measurements (-80 mV) showed that the Na/Ca exchange current (I(NCX)) began within 60 ms of activation of the switcher, and peaked at 312+/-57 pA in TG myocytes within 300-500 ms. I(Ca,L) in 20 microM nifedipine was 10.3+/-4.3 pA, n=7. These results indicate that Ca(2+) entering the myocyte via NCX can cause Ca(2+) sparks which are similar to those elicited by electrical stimulation. However, Ca(2+) influx on NCX is much less efficient in inducing Ca(2+) sparks than Ca(2+) influx via I(Ca,L).

Animals↗
PubMed2003

Effects of FK506 on [Ca2+]i differ in mouse and rabbit ventricular myocytes.

FK506 binding proteins (FKBPs 12 and 12.6) interact with ryanodine receptor (RyR) and modulate its functions. FK506 binds to and reverses effects of FKBP on RyR, thus increasing RyR sensitivity to Ca2+, decreasing RyR cooperativity, and increasing RyR open probability. FK506 would thus be expected to have an effect on excitation-contraction coupling, but which of these FK506 effects predominates and how the [Ca2+]i transient would be altered are difficult to predict. FK506 has been reported to increase the [Ca2+]i transient in rat myocytes, but effects in other species have not been described. We compared the effects of FK506 on [Ca2+]i transients, L-type Ca2+ channel and Na/Ca exchange currents, membrane potential, and sarcoplasmic reticulum (SR) Ca2+ content in adult mouse and rabbit ventricular myocytes (VM). FK506 (10 microM) increased the [Ca2+]i transient in mouse VM (656 +/- 116 to 945 +/- 144 nM, p < 0.001) but decreased the amplitude of [Ca2+]i transients in rabbit VM (627 +/- 61 to 401 +/- 37 nM, p < 0.001). Similar effects were observed with rapamycin. The effects of FK506 and rapamycin on [Ca2+]i transients in VM of both species were reversible upon washout. FK506 did not alter SR Ca2+ content in mouse VM (0.79 +/- 0.1 versus 0.78 +/- 0.1 pC/pF) but reduced the SR Ca2+ content in rabbit VM (0.43 +/- 0.05 versus 0.30 +/- 0.04 pC/pF, P < 0.05) [pC = the integral (pA. s) of the caffeine-induced inward I(Na/Ca) normalized by cell capacitance (pF)]. FK506 had no effects on membrane potential, I(Ca,L) and outward I(Na/Ca) in either mouse or rabbit VM. These results indicate that alteration of the functions of RyR by FK506-mediated dissociation of FKBP from RyR has different species-dependent effects on SR Ca2+ load and thus [Ca2+]i transients. This difference may result from the fact that [Na+]i is low in rabbit myocytes, allowing extrusion by Na+/Ca2+ exchange of Ca2+ released by FK506-induced dissociation of FKBP12.6 from SR RyR.

Animals↗