Recent improvements in survival in primary systemic amyloidosis and the importance of an early mortality risk score

OBJECTIVE

To examine whether the outcome of patients with primary systemic amyloidosis (AL) has improved over time and to identify predictors of early mortality in patients with AL.

PATIENTS AND METHODS

We studied 2 separate cohorts of patients. The first cohort, consisting of 1998 patients with AL seen at Mayo Clinic between January 1977 and August 2006, was used to examine the trends in overall survival (OS) from diagnosis during this 30-year period. The second cohort, consisting of 313 patients seen between September 2006 and August 2009, was used to validate a model for predicting early mortality.

RESULTS

The 4-year OS from diagnosis improved during each decade of follow-up: 21%, 24%, and 33%, respectively, for the periods 1977-1986, 1987-1996, and 1997-2006 (P<.001). Within the last group (1997-2006), 4-year OS during 1997-1999, 2000-2002, and 2003-2006 was 28%, 30%, and 42%, respectively (P=.02). However, the 1-year mortality remained high during the 30-year period. A risk stratification score using cardiac troponin T, N-terminal probrain natriuretic peptide, and uric acid identified patients at risk of early mortality. The 1-year mortality with 0, 1, 2, or 3 risk factors was 19%, 37%, 61%, and 80%, respectively, in this training cohort of 459 patients. This was confirmed in a validation cohort of 313 patients.

CONCLUSION

Survival in AL has improved over time, with maximum improvement occurring in the past decade. However, early mortality remains high, and prospective identification of patients at risk of early mortality may allow development of risk-adapted strategies.

Prospective validation of a modified thrombolysis in myocardial infarction risk score in emergency department patients with chest pain and possible acute coronary syndrome

OBJECTIVES

This study attempted to prospectively validate a modified Thrombolysis In Myocardial Infarction (TIMI) risk score that classifies patients with either ST-segment deviation or cardiac troponin elevation as high risk. The objectives were to determine the ability of the modified score to risk-stratify emergency department (ED) patients with chest pain and to identify patients safe for early discharge.

METHODS

This was a prospective cohort study in an urban academic ED over a 9-month period. Patients over 24 years of age with a primary complaint of chest pain were enrolled. On-duty physicians completed standardized data collection forms prior to diagnostic testing. Cardiac troponin T-values of >99th percentile (> or =0.01 ng/mL) were considered elevated. The primary outcome was acute myocardial infarction (AMI), revascularization, or death within 30 days. The overall diagnostic accuracy of the risk scores was compared by generating receiver operating characteristic (ROC) curves and comparing the area under the curve. The performance of the risk scores at potential decision thresholds was assessed by calculating the sensitivity and specificity at each potential cut-point.

RESULTS

The study enrolled 1,017 patients with the following characteristics: mean (+/-SD) age 59.3 (+/-13.8) years, 60.6% male, 17.9% with a history of diabetes, and 22.4% with a history of myocardial infarction. A total of 117 (11.5%) experienced a cardiac event within 30 days (6.6% AMI, 8.9% revascularization, 0.2% death of cardiac or unknown cause). The modified TIMI risk score outperformed the original with regard to overall diagnostic accuracy (area under the ROC curve = 0.83 vs. 0.79; p = 0.030; absolute difference 0.037; 95% confidence interval [CI] = 0.004 to 0.071). The specificity of the modified score was lower at all cut-points of >0. Sensitivity and specificity at potential decision thresholds were: >0 = sensitivity 96.6%, specificity 23.7%; >1 = sensitivity 91.5%, specificity 54.2%; and >2 = sensitivity 80.3%, specificity 73.4%. The lowest cut-point (TIMI/modified TIMI >0) was the only cut-point to predict cardiac events with sufficient sensitivity to consider early discharge. The sensitivity and specificity of the modified and original TIMI risk scores at this cut-point were identical.

CONCLUSIONS

The modified TIMI risk score outperformed the original with regard to overall diagnostic accuracy. However, it had lower specificity at all cut-points of >0, suggesting suboptimal risk stratification in high-risk patients. It also lacked sufficient sensitivity and specificity to safely guide patient disposition. Both scores are insufficiently sensitive and specific to recommend as the sole means of determining disposition in ED chest pain patients.

Long-range fluorescence quenching by gold nanoparticles in a sandwich immunoassay for cardiac troponin T

We report the first homogeneous sandwich immunoassay with gold nanoparticles (AuNPs) as fluorescence quenchers. The sandwich assay is designed for the detection of the protein cardiac troponin T (cTnT) by its simultaneous interaction with two different antibodies, one attached to AuNPs and the other labeled with fluorescent dyes. We demonstrate the working principle of the assay and using time-resolved fluorescence spectroscopy, we determine the quenching efficiency of the gold nanoparticles. In spite of the relatively large separation distance between dye molecules and AuNPs, ranging from 3 to 22 nm, the AuNPs quench the fluorescence with efficiencies as high as 95%. A limit of detection of 0.02 nM (0.7 ng/mL) was obtained for cTnT, which is the lowest value reported for a homogeneous sandwich assay for cTnT. These results illustrate the use of metallic nanoparticles as fluorescence quenchers in immunoassays where the large biomolecules involved impose distances for which energy transfer between fluorophores would be inefficient.

A proteomics analysis of the effects of chronic hemiparetic stroke on troponin T expression in human vastus lateralis

Stroke disability is attributed to upper motor neuron deficits resulting from ischemic brain injury. We have developed proteome maps of the Vastus lateralis to examine the effects of ischemic brain injury on paretic skeletal muscle myofilament proteins. Proteomics analyses from seven hemiparetic stroke patients have detected a decrease of three troponin T isoforms in the paretic muscle suggesting that myosin-actin interactions may be attenuated. We propose that ischemic brain injury may prevent troponin T participation in complex formation thereby affecting the protein interactions associated with excitation-contraction coupling. We have also detected a novel skeletal troponin T isoform that has a C-terminal variation. Our data suggest that the decreased slow troponin T isoform pools in the paretic limb may contribute to the gait deficit after stroke. The complexity of the neurological deficit on Vastus lateralis is suggested by the multiple changes in proteins detected by our proteomics mapping.

Evidence for cardiomyocyte renewal in humans

It has been difficult to establish whether we are limited to the heart muscle cells we are born with or if cardiomyocytes are generated also later in life. We have taken advantage of the integration of carbon-14, generated by nuclear bomb tests during the Cold War, into DNA to establish the age of cardiomyocytes in humans. We report that cardiomyocytes renew, with a gradual decrease from 1% turning over annually at the age of 25 to 0.45% at the age of 75. Fewer than 50% of cardiomyocytes are exchanged during a normal life span. The capacity to generate cardiomyocytes in the adult human heart suggests that it may be rational to work toward the development of therapeutic strategies aimed at stimulating this process in cardiac pathologies.

Clinical correlation of multiple biomarkers for risk assessment in patients with acute coronary syndrome

OBJECTIVE

Biochemical markers are useful for the prediction of future cardiovascular events in patients with non-ST-segment elevation acute coronary syndrome (ACS). The independent as well as the combined prognostic value of elevated troponin-T, high-sensitivity C-reactive protein (hs-CRP), and N-terminal pro-brain natriuretic peptide (NT-pro-BNP) on the Thrombolysis In Myocardial Infarction (TIMI) risk score and on the short-term prognosis were evaluated in a cohort of ACS patients.

METHODS AND RESULTS

In an unselected, heterogeneous group of 80 patients with ACS (i.e., unstable angina [USA] or non-ST-elevation myocardial infarction [NSTEMI]), the levels of troponin-T, hs-CRP, and NT-pro-BNP were analyzed. The correlation between elevation of different biomarkers with TIMI risk score and their impact on 30-day major adverse cardiac events was sought. The levels of hs-CRP were significantly higher in patients who had angina as their predominant complaint (3.67 mg/dl vs. 1.67 mg/dl: p < 0.01), while levels of NT-pro-BNP was higher in those patients who had any element of heart failure at presentation (2616.39 pg/ml vs. 1068.3 pg/ml; p < 0.01). Troponin-T was highest in patients who had an element of both heart failure and angina at presentation (p < 0.01). The TIMI risk score expectedly had a positive and strong correlation with elevated troponin-T, but had no correlation with elevation of hs-CRP and NT-pro-BNP in isolation. However, when any two biomarkers were elevated, the patients were in the intermediate risk group as per TIMI risk score irrespective of troponin-T-elevation. When all the three biomarkers were elevated, the risk equaled the high-risk category of TIMI risk score. Elevated hs-CRP (3.40 mg/dl vs. 1.38 mg/dl; p < 0.001) and troponin-T (2.37 ng/ml vs. 1.23 ng/ml; p < 0.001) at baseline correlated independently with the occurrence of re-ischemia, while elevated NT-pro-BNP alone correlated significantly with the development of heart failure within 30 days of follow-up (4247.76 pg/ml vs. 1210.86 pg/ml; p < 0.01). The highest risk of death from any cardiovascular cause within 30 days of follow-up was significantly higher when all the three biomarkers were elevated.

CONCLUSION

The use of NT-pro-BNP, hs-CRP, and troponin-T in combination appears to add critical prognostic insight to the assessment of patients with ACS.

Myocardial damage in hair dye poisoning--an uncommon presentation

A 22-year-old female presented to us after consuming hair dye with features of angio-neurotic edema, asphyxia and irregular pulse. Serial ECGs revealed presence of ST segment elevation and T wave inversion in anterior chest leads. Strongly positive c-troponin-T test further confirmed the myocardial damage. This is a rare manifestation of para-phenylene diamine poisoning mentioned in literature. Patient also had elevated liver enzymes and oliguria.

Absolute quantification of cardiac troponin T by means of liquid chromatography/triple quadrupole tandem mass spectrometry

A liquid chromatography/tandem mass spectrometric method for absolute quantification of cardiac troponin T (cTnT) in mouse heart tissue is presented. Even in such a complex biological sample, the multiple reaction monitoring acquisition mode allowed the selective and sensitive determination of a specific peptide, obtained by cTnT enzymatic digestion. The concentration of this cTnT-specific peptide was considered as a representation of the concentration of its parent protein. Quantification was carried out by means of the matrix-matched calibration curve, constructed by adding the synthetic standard of the target peptide and another synthetic structurally analogous peptide as internal standard. Method identification limit and method quantification limit were estimated as 60 and 110 ng of cTnT per mg of total extracted proteins, respectively. The developed label-free approach has been applied for the absolute quantitation of cTnT because of its diagnostic and prognostic value as cardiac disease marker. However, the method could be of general application, since it requires only the synthesis of two suitable peptides, a protein tryptic cleavage product and an internal standard.

Calpain I inhibition prevents atrial structural remodeling in a canine model with atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is accompanied by atrial structural remodeling. Calpain activity is induced during AF. To test a causal relationship between calpain activation and atrial structural changes, N-acetyl-Leu-Leu-Met (ALLM), a calpain inhibitor, was utilized in a canine AF model.

METHODS

Fifteen dogs were randomly divided into 3 groups: sham-operated group, control group and calpain inhibitor group; each with 5 dogs. Sustained AF was induced by rapid right atrium pacing at 600 beats per minute for 3 weeks. ALLM was administered at a dosage of 1.0 mg x kg(-1) x d(-1) in the calpain inhibitor group. Three weeks later, the proteolysis, protein expression of TnT and myosin, calpain I localization and expression and structural changes were examined in left atrial free walls, right atrial free walls and the interatrial septum respectively. Atrial size and contractile function were also measured by echocardiography.

RESULTS

Long-term rapid atrial pacing induced marked structural changes such as enlarged atrial volume, myolysis, degradation of TnT and myosin, accumulation of glycogen and changes in mitochondrial shape and size, which were paralleled by an increase in calpain activity. The positive correlation between calpain activity and the degree of myolysis (r(s) = 0.90 961, P < 0.0001) was demonstrated. In addition to structural abnormalities, pacing-induced atrial contractile dysfunction was observed in this study. The pacing-induced atrial structural alterations and loss of contractility were partially prevented by the calpain inhibitor ALLM.

CONCLUSIONS

Activation of calpain represents key features in the progression towards overt structural remodeling. Calpain inhibitor, ALLM, suppressed the increased calpain activity and reversed structural remodeling caused by sustained atrial fibrillation in the present model. Calpain inhibition may therefore provide a possibility for therapeutic intervention in AF.

Rapid diagnosis of myocardial injury with troponin T and CK-MB relative index

BACKGROUND

Current hospital practice involves protracted observation of chest-pain patients to rule out myocardial infarction. Concurrent measurement of multiple biomarkers may increase sensitivity and make rapid diagnosis feasible.

OBJECTIVE

We sought to determine the optimal biomarker strategy for highly sensitive, early diagnosis of myocardial injury.

STUDY DESIGN

A prospective evaluation of 171 acute coronary syndrome patients admitted to a single university medical center was performed. Blood tests for creatine kinase (CK), CK myocardial band isoenzyme (CK-MB), and troponin T were obtained at 0, 3, 6, 8, and 16 hours after presentation to the emergency department. Myocardial injury was defined as a troponin T level of >or=0.03 ng/mL.

RESULTS

Troponin T had sensitivities of 79.7%, 95.7%, and 98.4% at the time of initial presentation, 3 and 6 hours after presentation, respectively. Using a combination of troponin T and CK-MB relative index, sensitivity on presentation was increased to 90.6%. The sensitivity was improved to 97.9% and 100% at 3 and 6 hours, respectively.

CONCLUSION

This study demonstrates that the diagnosis of myocardial injury can be accurately excluded within 6 hours of admission with high sensitivity using troponin T. The combination of troponin T and CK-MB relative index provided the largest improvement in diagnostic sensitivity at patient arrival. These results support the feasibility of rapid, efficient triage for the emergent presentation of patients with chest pain.

Oxidative stress during coronary artery bypass operations: importance of surgical trauma and drug treatment

OBJECTIVE

To investigate oxidative stress and myocardial injury at different stages of coronary artery bypass grafting (CABG).

DESIGN

Twenty patients underwent CABG with use of cardiopulmonary bypass (CPB) and with intermittent sampling of plasma and urine. Main markers were: 8-iso-PGF2alpha (oxidative stress); troponin T (myocardial injury); and 15-keto-dihydro-PGF2alpha and hsCRP (inflammation).

RESULTS

Plasma 8-iso-PGF2alpha increased after start of surgery, but there was no further rise during CPB or after aortic cross-clamp release and no significant myocardial arterio-venous differences. An increase in troponin T was seen early after the operation, but no relationship was established between 8-iso-PGF2alpha and troponin T. 8-iso-PGF2alpha levels were elevated by preoperative withdrawal of acetylsalicylic acid (ASA) but reduced by intraoperative use of heparin. 15-keto-dihydro-PGF2alpha was elevated during operation and hsCRP following operation.

CONCLUSIONS

In the present study oxidative stress was multifactorial in origin with main impacts from surgical trauma, less from CPB and little if any from myocardial ischemia-reperfusion events. In addition, cardiovascular drugs in common use like ASA and heparin seemed to influence the pro- and antioxidant balance, a finding that has to be confirmed in future studies.

Cardiac biomarkers and survival in haemodialysis patients

BACKGROUND

In dialysis patients, cardiac troponin T (cTNT) is often elevated despite the absence of acute myocardial ischaemia, and amino-terminal pro-B-natriuretic peptide (NT-proBNP) is markedly higher compared to non-haemodialysis patients. In a longitudinal observation, we evaluated the association of cTNT and NT-proBNP on cardiovascular morbidity and mortality in haemodialysis patients with and without fluid overload.

MATERIALS AND METHODS

Plasma cTNT levels of 134 haemodialysis patients were measured before and after a dialysis session by 3rd generation electro-chemoluminiscence immunoassay. NT-proBNP was determined using a polyclonal antibody recognizing the N-terminal fragment of BNP (Elecsys autoanalyzer 2010, Roche Diagnostics, Mannheim, Germany). Volume status was determined by a clinical score system. Cardiovascular morbidity and mortality were assessed over a follow-up period of 36 months.

RESULTS

Plasma cTNT > 0.03 ng mL(-1) was found in 39.6% of all patients. Patients with hypervolaemia had significantly higher cTNT levels compared to euvolaemic patients (median 0.054 ng mL(-1), interquartile range 0.019-0.153 vs. 0.005 ng mL(-1), < 0.001-0.034; P < 0.001). All haemodialysis patients had excessively high levels of NT-proBNP (median 4524; interquartile range 2000-10 250 pg mL(-1)), and NT-proBNP was significantly higher in hypervolaemic haemodialysis patients (11 988, 5307-19 242) compared to euvolaemic haemodialysis patients (3247, 1619-5574); P < 0.001. Receiver operator curves showed a threshold of cTNT > 0.026 ng mL(-1) and NT-proBNP > 5300 pg mL(-1) as predictors of hypervolaemia. Asymptomatic chronic haemodialysis patients with cTNT > 0.026 ng mL(-1) and NT-proBNP > 5300 pg mL(-1) were more likely to die due to cardiac events in the follow-up period. Multivariate analysis documented that elevated cTNT and NT-proBNP levels were highly predictive for cardiovascular events.

CONCLUSIONS

Plasma levels of cTNT are elevated in approximately 40% and NT-proBNP levels in 100% of asymptomatic chronic haemodialysis patients. Both parameters depend on volume status. Increased NT-proBNP and cTNT are strongly associated with adverse outcome in end-stage renal disease patients undergoing haemodialysis, and are a useful tool for risk stratification in chronic haemodialysis patients.

Surface plasmon resonance immunosensor for human cardiac troponin T based on self-assembled monolayer

The cardiac troponin T (cTnT) is specific biomarker important for trials of acute myocardial infarctions (AMI). In this paper, a SPR sensor in real time to detect the biomarker was developed on a commercially available surface plasmon resonance AUTOLAB SPIRIT. The cTnT receptor molecule was covalently immobilized on a gold substrate via a self-assembled monolayer (SAM) of thiols by using cysteamine-coupling chemistry. This biosensor presented a linear response range for cTnT between 0.05 and 4.5 ng/mL (r=0.997, p<<0.01) with a good reproducibility (CV=4.4%). The effect of the cysteamine (CYS) concentrations on the SAM coated gold sensor was studied as a function of the amount of the immobilized cTnT monoclonal antibodies. Analysis using serum samples undiluted was carried out at room temperature showing a well agreement with the ECLIA methods and the sensor surface could be regenerated by using a solution of 1% (w/v) sodium dodecyl sulphate (SDS) without losing the sensor immunoreactivity. These studies open new perspectives of using SAM to develop regenerable immunosensor with a good reproducibility allowing its use in the clinical applications.

Impact of Repeated Prolonged Exercise Bouts on Cardiac Function and Biomarkers

PURPOSE

The present study examined the impact of repeated bouts of prolonged (< 60 min) exercise on left ventricular function and cardiac biomarkers.

METHODS

Ten athletes completed a 15.3-mile hill run on three consecutive days and were assessed before, immediately after, 1 h after, and 20 h after each bout. Six of the athletes completed a fourth bout. Left ventricular (LV) function was examined echocardiographically using two-dimensional M-mode, Doppler, and flow propagation velocity (Vp). Venous blood samples were analyzed for cardiac biomarkers including cardiac troponin T (cTnT).

RESULTS

Ejection fraction (EF) significantly decreased (P = 0.027) after the third exercise bout compared with baseline (mean +/- SD: 56.3 +/- 4.4 vs 51.3 +/- 5.9%), accompanied by a nonsignificant decrease in systolic blood pressure/end systolic volume (SBP/ESV) ratio. A sustained depression in systolic function 20 h after bout 3 also persisted in the subset who completed a fourth bout, yet this did not reach clinical levels. Significant (P < 0.01) reductions in early to late diastolic filling (E:A) ratio pre-to post-bout 1 (mean +/- SD: 1.9 +/- 0.5 vs 1.4 +/- 0.3) and pre- to post-bout 3(2.0 +/- 0.5 vs 1.3 +/- 0.4) normalized after each 20-h recovery period. A similar pattern of change was observed in Vp. Cardiac troponin T was elevated in four individuals 1 h after bout 1 (range: 0.013-0.125 microg.L(-1)) but was undetectable thereafter except in one athlete.

CONCLUSION

Repeated bouts of prolonged exercise induce short-term reductions in diastolic filling and a cumulative decrease in systolic function, yet these alterations seem to have minimal clinical or functional impact. Elevated cTnT after the initial bout, but not thereafter, may represent an adaptive response to prolonged exercise.

Redefining Risk in Acute Coronary Syndromes Using Molecular Medicine

Acute coronary syndromes represent a complex phenotype involving the interplay of many elements. The risk of developing an acute coronary syndrome and related complications has been defined by variables such as age, diabetes, smoking history, serum creatine phosphokinase, or electrocardiographic findings. However, in the past 5 years the wide-scale acceptance of a protein--troponin--has changed the diagnostic profile. With advances in molecular medicine, this protein is a segue to a panel of molecular assays that will improve screening and tailored intervention. We expound upon some of these factors and the potential they may carry in changing clinical medicine.

Mass spectrometric approaches for elucidation of antigenantibody recognition structures in molecular immunology

Mass spectrometric approaches have recently gained increasing access to molecular immunology and several methods have been developed that enable detailed chemical structure identification of antigen-antibody interactions. Selective proteolytic digestion and MS-peptide mapping (epitope excision) has been successfully employed for epitope identification of protein antigens. In addition, "affinity proteomics" using partial epitope excision has been developed as an approach with unprecedented selectivity for direct protein identification from biological material. The potential of these methods is illustrated by the elucidation of a beta-amyloid plaque-specific epitope recognized by therapeutic antibodies from transgenic mouse models of Alzheimer's disease. Using an immobilized antigen and antibody-proteolytic digestion and analysis by high resolution Fourier transform ion cyclotron resonance mass spectrometry has lead to a new approach for the identification of antibody paratope structures (paratope-excision; "parex-prot"). In this method, high resolution MS-peptide data at the low ppm level are required for direct identification of paratopes using protein databases. Mass spectrometric epitope mapping and determination of "molecular antibody-recognition signatures" offer high potential, especially for the development of new molecular diagnostics and the evaluation of new vaccine lead structures.

Results from a multicenter evaluation of the 4th generation Elecsys Troponin T assay

BACKGROUND AND OBJECTIVE

Discrepancies between serum and heparin plasma samples have been described for many commercial troponin assays including the cardiac troponin T (cTnT) assay. Using the current 3rd generation Elecsys Troponin T immunoassay, heparin plasma cannot be recommended for the determination of cTnT due to systematic lower test results caused by a direct interference of the immunoassay by heparin. The purpose of the multicenter study was to evaluate the analytical performance of an improved 4th generation Elecsys Troponin T immunoassay with a special focus on the comparability of cTnT results determined in heparin plasma and serum.

METHODS AND RESULTS

The multicenter evaluation was performed in 10 clinical laboratories according to a standardized protocol (Roche Diagnostics, Penzberg, Germany, Study No. B05P008). The Elecsys Troponin T immunoassay was performed on the Modular Analytics E170 and Elecsys 2010 systems. Intraassay imprecision (n = 21) and total imprecision (2 runs/d, 10 days, triplicate measurements) were evaluated using 2 commercial controls (Roche Diagnostics) and 6 different serum pools (cTnT: 0.0140 - 4.102 microg/L). Intraassay CVs ranged from 0.73 to 3.22%. Total imprecision CVs ranged from 3.61 to 35.45% (cTnT < 0.1 microg/L) and 1.82 to 9.09% (cTnT > 0.1 microg/L), respectively. The cut-off for myocardial necrosis was determined to be 0.03 microg/L using the 10% total imprecision CV criteria. Linearity was assessed by serial dilutions of 6 different serum samples using cTnT negative serum pools. Linearity was proven up to 21.3 microg/L (recoveries: 90% - 110%). Regression data of all comparison studies were calculated according to the method of Passing and Bablok. The method comparison between the 4th generation and the commercially available cTnT immunoassay showed highly similar results across the whole measuring range (0.01 - 25.0 microg/L): y = 1.024x -0.001, r = 0.998; n = 988. Using the commercially available cTnT reagent, the serum to heparin plasma comparison yielded a systematic bias to approximately 8% lower cTnT results in heparin plasma. However, suitable comparability was obtained using the 4th generation Elecsys cTnT assay. The regression analysis (serum vs. heparin plasma) across the studied measuring range (cTnT: 0.01 - 14 microg/L) yielded the following equation: y = 0.975x + 0.001; r = 0.986; n = 403. However, rare individual serum to matched heparin plasma samples still yielded poor comparability (deviation > 20%) using the 4th generation Elecsys Troponin T immunoassay.

CONCLUSION

Our data confirm an excellent analytical performance of the improved troponin T immunoassay. Most importantly, no systematic bias between cTnT results determined in serum and heparin plasma was observed from data obtained in 7 evaluation sites. The performance of the 4th generation Elecsys Troponin T assay is therefore comparable to other commercially available troponin immunoassays. Further studies are necessary to investigate the cause of poor comparability of cTnT results in rare individual serum to matched heparin plasma samples.

Differentiation of rhabdomyosarcoma cell lines using retinoic acid

BACKGROUND

Rhabdomyosarcoma (RMS) is the most frequent sporadic soft tissue sarcoma of childhood and adolescence. The overall 5-year survival rate for patients with RMS is 70% with the use of surgery, radiation, and chemotherapy. Novel therapeutic approaches are necessary to improve on these outcomes particularly among the more aggressive alveolar RMS (ARMS) and late stages of disease, where 5-year survival is less than 20%. Retinoids have been successfully used in the treatment of acute promyelocytic leukemia (APML) and neuroblastoma.

PURPOSE

However, analysis of retinoids as a differentiating agent for RMS has been incomplete. This work examined the ability of retinoic acid (RA) to promote differentiation of RMS cell lines by examining the expression of myogenic proteins in five RMS cell lines in response to All-trans Retinoic Acid (ATRA) or 9-cis retinoic acid (CRA).

RESULTS

Analysis of growth curves indicates that both retinoids suppress cell growth of Rh4 and Rh28. RD cells only responded to-CRA whereas Rh30 and Rh18 did not respond. Following treatment with ATRA FACS analysis showed an altered cell cycle with the same pattern as the growth curves. ATRA altered cellular morphology of two cell lines, Rh4 and Rh28, and induced Troponin T expression in these cells suggesting a differentiating effect.

CONCLUSIONS

These studies suggest that retinoids are effective inducers of growth arrest and differentiation in some RMS cell lines, and offer a basis for further in vivo testing in mice of ATRA as a potential approach to ARMS treatment.

Effects of acetate-free double-chamber hemodiafiltration and standard dialysis on systemic hemodynamics and troponin T levels

Using acetate as a buffer during hemodialysis is recognized to predispose to intradialytic hypotension; however, bicarbonate-based dialysis is not acetate free. Paired hemodiafiltration (PHF) is a novel online acetate-free technique. We investigated whether PHF is capable of abrogating the changes in systemic hemodynamics and troponin T (cTnT) seen with conventional hemodialysis. Twelve patients entered a randomized crossover study. Blood pressure (BP) and a full range of hemodynamic variables were measured throughout PHF and standard dialysis using continuous pulse wave analysis. We also measured predialysis cTnT in 54 stable and unstable dialysis patients. BP was lower during PHF but without increased instability. Stoke volume and cardiac output declined progressively during both treatments but to a much lesser extent during PHF (p = 0.003, p < 0.0001 respectively), whereas peripheral resistance rose to a larger degree during hemodialysis (p < 0.0001). cTnT levels were lower before PHF as compared with hemodialysis (p = 0.023), with levels falling after PHF and rising after hemodialysis (p < 0.0001). In the supplementary patient group, predialysis median serum cTnT was higher in the unstable patients (p = 0.0001). This study demonstrates that PHF (without exposure to acetate) is associated with less deterioration in systemic hemodynamics, maintenance of BP, and less suppression of myocardial contractility as compared with bicarbonate dialysis.

Porcine cardiac myocyte power output is increased after chronic exercise training

Chronic exercise training increases the functional capacity of the heart, perhaps by increased myocyte contractile function, as has been observed in rodent exercise models. We examined whether cardiac myocyte function is enhanced after chronic exercise training in Yucatan miniature swine, whose heart characteristics are similar to humans. Animals were designated as either sedentary (Sed), i.e., cage confined, or exercise trained (Ex), i.e., underwent 16-20 wk of progressive treadmill training. Exercise training efficacy was shown with significantly increased heart weight-to-body weight ratios, skeletal muscle citrate synthase activity, and exercise tolerance. Force-velocity properties were measured by attaching skinned cardiac myocytes between a force transducer and position motor, and shortening velocities were measured over a range of loads during maximal Ca2+ activation. Myocytes (n = 9) from nine Ex pigs had comparable force production but a approximately 30% increase in peak power output compared with myocytes (n = 8) from eight Sed. Interestingly, Ex myofibrillar samples also had higher baseline PKA-induced phosphorylation levels of cardiac troponin I, which may contribute to the increase in power. Overall, these results suggest that enhanced power-generating capacity of porcine cardiac myofibrils contributes to improved cardiac function after chronic exercise training.

Troponin as a marker of myocardiac damage in drug-induced cardiotoxicity

Cardiac troponins T and I (cTnT and cTnI) are becoming the serum biomarkers of choice for monitoring potential drug-induced myocardial injury in both clinical and preclinical studies. The utility of cardiac troponins has been mainly demonstrated following the administration of antineoplastic drugs and beta-sympathomimetics, although the routine use of these markers in the monitoring in patients who received anthracyclines therapy is far from settled. Unlike the previous markers, which suffered from numerous shortages, the main advantages of cardiac troponins are their high specificity and sensitivity, wide diagnostic window and the possibility to use commercially available assays in clinical settings as well as in a broad range of laboratory animals. Nevertheless, in spite of vigorous research in this area, a number of questions are still unanswered and these are discussed in this review. The main problems seem to be the lack of standardisation of variety of troponin immunoassays, the assessment of suitable cutoff for drug-induced cardiotoxicity and determination of critical diagnostic window related to the optimal timing of sample collection, which may be drug-dependent.