Myosin heavy chain (MHC) isoforms alpha and beta have intrinsically different ATP hydrolysis activities (ATPase) and therefore cross-bridge cycling rates in solution. There is considerable evidence ...of altered MHC expression in rodent cardiac disease models; however, the effect of incremental beta-MHC expression over a wide range on the rate of high-strain, isometric cross-bridge cycling is yet to be ascertained. We treated male rats with 6-propyl-2-thiouracil (PTU; 0.8 g/l in drinking water) for short intervals (6, 11, 16, and 21 days) to generate cardiac MHC patterns in transition from predominantly alpha-MHC to predominantly beta-MHC. Steady-state calcium-dependent tension development and tension-dependent ATP consumption (tension cost; proportional to cross-bridge cycling) were measured in chemically permeabilized (skinned) right ventricular muscles at 20 degrees C. To assess dynamic cross-bridge cycling kinetics, the rate of force redevelopment (ktr) was determined after rapid release-restretch of fully activated muscles. MHC isoform content in each experimental muscle was measured by SDS-PAGE and densitometry. alpha-MHC content decreased significantly and progressively with length of PTU treatment 68 +/- 5%, 58 +/- 4%, 37 +/- 4%, and 27 +/- 6% for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA). Tension cost decreased, linearly, with decreased alpha-MHC content 6.7 +/- 0.4, 5.6 +/- 0.5, 4.0 +/- 0.4, and 3.9 +/- 0.3 ATPase/tension for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA). Likewise, ktr was significantly and progressively depressed with length of PTU treatment 11.1 +/- 0.6, 9.1 +/- 0.5, 8.2 +/- 0.7, and 6.2 +/- 0.3 s(-1) for 6, 11, 16, and 21 days, respectively; P < 0.05 (ANOVA) Thus cross-bridge cycling, under high strain, for alpha-MHC is three times higher than for beta-MHC. Furthermore, under isometric conditions, alpha-MHC and beta-MHC cross bridges hydrolyze ATP independently of one another.
Center for Cardiovascular Research,Physiology, Biophysics and Medicine, University of Illinois at Chicago, Chicago, Illinois 60612
Submitted 21 January 2004
; accepted in final form 2 March 2004
...Cardiac disease in diabetes presents as impaired left ventricular contraction and relaxation; however, the mechanisms underlying contractile protein dysfunction during the progression of disease are unknown. Accordingly, we assessed Ca 2+ -dependent tension development and tension-dependent ATP consumption (tension cost) in a rat model early (6 wk) and late (12 wk) after the onset of diabetes (50 mg/kg iv streptozotocin) using mechanical force- and enzyme-coupled UV absorbance measurements. Myofilament Ca 2+ sensitivity and maximal tension were unchanged between groups at either time point. Cross-bridge cycling rate was significantly decreased in diabetes, as indexed by tension cost (early control 5.4 ± 0.4 and early diabetes 4.2 ± 0.3; and late control 6.0 ± 0.2 and late diabetes 4.2 ± 0.2; P < 0.05). Because rodent models of cardiac disease are confounded by altered myosin isoform distribution, myosin content was determined by SDS-PAGE and densitometry. The cardiac content of -myosin in diabetes was decreased to 41% ± 4.1 at 6 wk and 32.5% ± 2.9 at 12 wk of diabetes (early control 77.8% ± 3.3 and late control 73.6% ± 2.5). Separate control experiments demonstrated a linear decrease in tension cost with decreased -myosin content. Given this, the depression of tension cost in this rodent model of diabetes could be fully explained by the altered myosin isoform distribution.
cross-bridge cycling; cardiac energetics
Address for reprint requests and other correspondence: P. P. de Tombe, Dept. of Physiology and Biophysics, Univ. of Illinois at Chicago, 835 S. Wolcott (M/C 901), Chicago, IL 60612 (E-mail: pdetombe{at}uic.edu ).
1 Center for Cardiovascular Research, Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, and 2 Department of Cardiology, Jeroen Bosch Hospital, ...'s-Hertogenbosch, The Netherlands
Submitted 18 December 2006
; accepted in final form 14 March 2007
The cellular mechanisms underlying the development of congestive heart failure (HF) are not well understood. Accordingly, we studied myocardial function in isolated right ventricular trabeculae from rats in which HF was induced by left ventricular myocardial infarction (MI). Both early-stage (12 wk post-MI; E-pMI) and late, end-stage HF (28 wk post-Mi; L-pMI) were studied. HF was associated with decreased sarcoplasmic reticulum Ca 2+ ATPase protein levels (28% E-pMI; 52% L-pMI). HF affected neither sodium/calcium exchange, ryanodine receptor, nor phospholamban protein levels. Twitch force at saturating extracellular Ca 2+ was depressed in HF (30% E-pMI; 38% L-pMI), concomitant with a marked increase in sensitivity of twitch force toward extracellular Ca 2+ (26% E-pMI; 68% L-pMI). Ca 2+ -saturated myofilament force development in skinned trabeculae was unchanged in E-pMI but significantly depressed in L-pMI (45%). Tension-dependent ATP hydrolysis rate was depressed in L-pMI (49%), but not in E-pMI. Our results suggest a hierarchy of cellular events during the development of HF, starting with altered calcium homeostasis during the early phase followed by myofilament dysfunction at end-stage HF.
myofibrillar proteins; cross-bridges; sarcomere mechanics; laser diffraction; calcium; myosin ATPase; myofilaments
Address for reprint requests and other correspondence: P. P. de Tombe, Dept. of Physiology and Biophysics MC901, Center for Cardiovascular Research, Univ. of Illinois at Chicago, 835 S. Wolcott Ave., Chicago, IL 60612 USA (e-mail: pdetombe{at}uic.edu )
Background and purpose:
The histamine H
4
receptor is widely expressed in cells of immune origin and has been shown to play a role in a variety of inflammatory processes mediated by histamine. In ...this report, we describe the
in vitro
and
in vivo
anti‐inflammatory properties of a potent histamine H
4
receptor antagonist, A‐940894 (4‐piperazin‐1‐yl‐6,7‐dihydro‐5H‐benzo6,7cyclohepta1,2‐dpyrimidin‐2‐ylamine).
Experimental approach:
We have analysed the pharmacological profile of A‐940894 at mouse native, rat recombinant and human recombinant and native, histamine H
4
receptors by radioligand binding, calcium mobilization, mast cell shape change, eosinophil chemotaxis assays and in the mouse model of zymosan‐induced peritonitis.
Key results:
A‐940894 potently binds to both human and rat histamine H
4
receptors and exhibits considerably lower affinity for the human histamine H
1
, H
2
or H
3
receptors. It potently blocked histamine‐evoked calcium mobilization in the fluorometric imaging plate reader assays and inhibited histamine‐induced shape change of mouse bone marrow‐derived mast cells and chemotaxis of human eosinophils
in vitro
. In a mouse mast cell‐dependent model of zymosan‐induced peritonitis, A‐940894 significantly blocked neutrophil influx and reduced intraperitoneal prostaglandin D
2
levels. Finally, A‐940894 has good pharmacokinetic properties, including half‐life and oral bioavailability in rats and mice.
Conclusions and Implications:
These data suggest that A‐940894 is a potent and selective histamine H
4
receptor antagonist with pharmacokinetic properties suitable for long‐term
in vivo
testing and could serve as a useful tool for the further characterization of histamine H
4
receptor pharmacology.
Summary Use of human acellular dermal matrix (ADM) during prosthetic breast reconstruction has increased. Several ADM products are available produced by differing manufacturing techniques. It is not ...known if outcomes vary with different products. This study reports the complication prevalence following use of a tutoplast-derived ADM (T-ADM) in prosthetic breast reconstruction. We performed a retrospective chart review of 203 patients (mean follow-up times 12.2 months) who underwent mastectomy and immediate prosthetic breast reconstruction utilizing T-ADM, recording demographic data, surgical indications and complication (infection, seroma, hematoma, wound healing exceeding three weeks and reconstruction failure). During a four-year period, 348 breast reconstructions were performed Complications occurred in 16.4% of reconstructed breasts. Infection occurred in 6.6% of breast reconstructions (3.7% – major infection, requiring intravenous antibiotics and 2.9% minor infection, requiring oral antibiotics only). Seromas occurred in 3.4% and reconstruction failure occurred in 0.6% of breast reconstructions. Analysis suggested that complication prevalence was significantly higher in patients with a BMI >30 ( p = 0.03). The complication profile following T-ADM use is this series is comparable to that reported for with other ADM products. T-ADM appears to be a safe and acceptable option for use in ADM-assisted breast reconstruction.
BACKGROUND:Patients undergoing mastectomy and prosthetic breast reconstruction have significant acute postsurgical pain, routinely mandating inpatient hospitalization. Liposomal bupivacaine (LB) ...(Exparel; Pacira Pharmaceuticals, Inc., Parsippany, N.J.) has been shown to be a safe and effective pain reliever in the immediate postoperative period and may be advantageous for use in mastectomy and breast reconstruction patients.
METHODS:Retrospective review of 90 immediate implant-based breast reconstruction patient charts was completed. Patients were separated into 3 groups of 30 consecutively treated patients who received 1 of 3 pain treatment modalitiesintravenous/oral narcotic pain control (control), bupivacaine pain pump, or LB injection. Length of hospital stay, patient-reported Visual Analog Scale (VAS) pain scores, postoperative patient-controlled analgesia usage, and nausea-related medication use were abstracted and subjected to analysis of variance and multiple linear-regression analysis, as appropriate.
RESULTS:Subjects were well-matched for age (P = 0.24) regardless of pain-control modality. Roughly half (53%) of control and pain pump–treated subjects had bilateral procedures, as opposed to 80% of LB subjects. Mean length of stay for LB subjects was significantly less than control (1.5 days vs 2.00 days; P = 0.016). LB subjects reported significantly lower VAS pain scores at 4, 8, 12, 16, and 24 hours compared with pain pump and control (P < 0.01). There were no adverse events in the LB group.
CONCLUSION:Use of LB in this group of immediate breast reconstruction patients was associated with decreased patient VAS pain scores in the immediate postoperative period compared with bupivacaine pain pump and intravenous/oral narcotic pain management and reduced inpatient length of stay.
Center for Cardiovascular Research, 1 Department of Physiology and Biophysics, Department of Medicine; and 2 Section of Cardiology, University of Illinois, Chicago, Illinois
Submitted 26 May 2006
; ...accepted in final form 28 June 2006
It is currently unclear whether left ventricular (LV) myofilament function is depressed in experimental LV hypertrophy (LVH) or congestive heart failure (CHF). To address this issue, we studied pressure overload-induced LV hypertrophy (POLVH) and myocardial infarction-elicited congestive heart failure (MICHF) in rats. LV myocytes were isolated from control, POLVH, and MICHF hearts by mechanical homogenization, skinned with Triton, and attached to micropipettes that projected from a sensitive force transducer and high-speed motor. A subset of cells was treated with either unphosphorylated, recombinant cardiac troponin (cTn) or cTn purified from either control or failing ventricles. LV myofilament function was characterized by the force-Ca 2+ relation yielding Ca 2+ -saturated maximal force (F max ), myofilament Ca 2+ sensitivity (EC 50 ), and cooperativity (Hill coefficient, n H ) parameters. POLVH was associated with a 35% reduction in F max and 36% increase in EC 50 . Similarly, MICHF resulted in a 42% reduction in F max and a 30% increase in EC 50 . Incorporation of recombinant cTn or purified control cTn into failing cells restored myofilament Ca 2+ sensitivity toward levels observed in control cells. In contrast, integration of cTn purified from failing ventricles into control myocytes increased EC 50 to levels observed in failing myocytes. The F max parameter was not markedly affected by troponin exchange. cTnI phosphorylation was increased in both POLVH and MICHF left ventricles. We conclude that depressed myofilament Ca 2+ sensitivity in experimental LVH and CHF is due, in part, to a decreased functional role of cTn that likely involves augmented phosphorylation of cTnI.
left ventricle; troponin; phosphorylation; cardiac disease
Address for reprint requests and other correspondence: P. P. de Tombe, Dept. of Physiology & Biophysics, Univ. of Illinois at Chicago, 835 S. Wolcott (M/C 901), Chicago, IL 60612 (email: pdetombe{at}uic.edu )
Myofilament dysfunction is a common point of convergence for many forms of heart failure. Recently, we showed that cardiac overexpression of PKC epsilon initially depresses myofilament activity and ...then leads to a progression of changes characteristic of human heart failure. Here, we examined the effects of PKC epsilon on contractile reserve, Starling mechanism, and myofilament activation in this model of end-stage dilated cardiomyopathy. Pressure-volume loop analysis and echocardiography showed that the PKC epsilon mice have markedly compromised systolic function and increased end-diastolic volumes. Dobutamine challenge resulted in a small increase in contractility in PKC epsilon mice but failed to enhance cardiac output. The PKC epsilon mice showed a normal length-dependent tension development in skinned cardiac muscle preparations, although Frank-Starling mechanism appeared to be compromised in the intact animal. Simultaneous measurement of tension and ATPase demonstrated that the maximum tension and ATPase were markedly lower in the PKC epsilon mice at any length or Ca2+ concentration. However, the tension cost was also lower indicating less energy expenditure. We conclude 1) that prolonged overexpression of PKC epsilon ultimately leads to a dilated cardiomyopathy marked by exhausted contractile reserve, 2) that PKC epsilon does not compromise the Frank-Starling mechanism at the myofilament level, and 3) that the Starling curve excursion is limited by the inotropic state of the heart. These results reflect the significance of the primary myofilament contractilopathy induced by phosphorylation and imply a role for PKC epsilon-mediated phosphorylation in myofilament physiology and the pathophysiology of decompensated cardiac failure.
Myosin heavy chain (MHC) isoforms alpha and beta have intrinsically different ATP hydrolysis activities (ATPase) and therefore cross-bridge cycling rates in solution. There is considerable evidence ...of altered MHC expression in rodent cardiac disease models; however, the effect of incremental beta-MHC expression over a wide range on the rate of high-strain, isometric cross-bridge cycling is yet to be ascertained. We treated male rats with 6-propyl-2-thiouracil (PTU; 0.8 g/l in drinking water) for short intervals (6, 11, 16, and 21 days) to generate cardiac MHC patterns in transition from predominantly alpha-MHC to predominantly beta-MHC. Steady-state calcium-dependent tension development and tension-dependent ATP consumption (tension cost; proportional to cross-bridge cycling) were measured in chemically permeabilized (skinned) right ventricular muscles at 20 degrees C. To assess dynamic cross-bridge cycling kinetics, the rate of force redevelopment (ktr) was determined after rapid release-restretch of fully activated muscles. MHC isoform content in each experimental muscle was measured by SDS-PAGE and densitometry. Alpha-MHC content decreased significantly and progressively with length of PTU treatment 68 +/- 5%, 58 +/- 4%, 37 +/- 4%, and 27 +/- 6% for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA). Tension cost decreased, linearly, with decreased alpha-MHC content 6.7 +/- 0.4, 5.6 +/- 0.5, 4.0 +/- 0.4, and 3.9 +/- 0.3 ATPase/tension for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA). Likewise, ktr was significantly and progressively depressed with length of PTU treatment 11.1 +/- 0.6, 9.1 +/- 0.5, 8.2 +/- 0.7, and 6.2 +/- 0.3 s-1 for 6, 11, 16, and 21 days, respectively; P < 0.05 (ANOVA) Thus cross-bridge cycling, under high strain, for alpha-MHC is three times higher than for beta-MHC. Furthermore, under isometric conditions, alpha-MHC and beta-MHC cross bridges hydrolyze ATP independently of one another. PUBLICATION ABSTRACT
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