Clinical utility of cardiac troponin I and cardiac troponin T measurements

The measurement of CK-MB remains the test of choice for confirmation or exclusion of AMI and probably will remain the test of choice for routine diagnosis in the near future. Nowadays determination of cardiac troponin T (cTnT) and cardiac troponin I (cTnI) as a method relatively expensive and time-consuming should be restricted to clinical settings that really require their high specificity.     

A new method of human cardiac troponin I and troponin T purification

Neurotrophins (NTFs) are a family of structurally related proteins with specific effects on the developing nervous system and a wide range of non-neuronal differentiating cells. To date, four NTFs have been characterized: nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4). To perform their biological effects, the NTFs must bind to appropriate receptors on the surface of responsive cells. High- and low-affinity receptors for NTFs have been identified. The high-affinity receptors are members of the trk protein tyrosine kinase receptor family. The low-affinity neurotrophin receptor gp75NTFR is a common receptor for all NTFs. Here we summarize some of our previous findings on the expression patterns of NGF, gp75NTFR, TrkB, and TrkC in the developing molar tooth of the rat. Both NGF and gp75NTFR are localized in dental epithelium and mesenchyme but often their expression patterns differ. Concomitant expression of NGF and gp75NTFR in mesenchyme is correlated with odontoblast differentiation. The trkB and trkC receptors show distinct cell-specific expression patterns in developing tooth, suggesting that other NTFs, apart from NGF, may be involved in odontogenesis. These data demonstrate that NTFs participate in the cascade of molecular events that direct tooth development, and support the notion that NTFs may have multiple and distinct roles in dental tissues.     

Assay of cardiac troponin T on Elecsys 2010: comparison with cardiac troponin I

Cardiac troponin T (troponin Tc) of second generation has been measured on the Boehringer Elecsys 2010 analyzer. Cardiac specificity has been studied in patients presenting a rhabdomyolysis syndrome and the results compared with those obtained for cardiac troponin I (troponin Ic) measured on the Dade-Behring Stratus analyzer. The results clearly demonstrated that both troponin Tc and Ic showed similar cardiac specificity. Moreover, troponin Tc and troponin Ic can be indifferently used for the biological diagnostic of myocardial infarction or to asses reperfusion after percutaneous transluminal coronary angioplasty for acute myocardial infarction. In renal disease, troponin Tc was upper the reference limit (0.10 microgram/l) in 25% of the patients studied (20 patients). By contrast, troponin Ic was upper the reference limit (0.6 microgram/l) in only one patient.     

Crystalloid versus cold blood cardioplegia and cardiac troponin I release

BACKGROUND: Cardiac troponin I (CTnI) has been shown to be a marker of myocardial injury. The aim of this study was to compare antegrade crystalloid cardioplegia with antegrade cold blood cardioplegia with warm reperfusion using CTnI release as the criteria for evaluating the adequacy of myocardial protection. METHODS AND RESULTS: Seventy patients were randomly assigned to receive crystalloid or blood cardioplegia. CTnI concentrations were measured in serial venous blood samples drawn just before cardiopulmonary bypass and after aortic unclamping at 6, 9, 12, and 24 hours and daily thereafter for 5 days. ANOVA with repeated measures was performed to test the effect of the type of cardioplegia on CTnI release. The total amount of CTnI released was higher in the crystalloid cardioplegia group than in the blood cardioplegia group (11.2 +/- 8.9 versus 7.8 +/- 8.6 micrograms, P < .02). CTnI concentration was significantly higher in the crystalloid group than in the blood group in the samples drawn at hours 9 and 12. Three patients in each group had ECG evidence of perioperative myocardial infarction. Eight patients in the crystalloid group and five patients in the blood group had CTnI evidence of perioperative myocardial infarction. CTnI release was significantly lower in patients requiring no electrical defibrillation after aortic unclamping. CONCLUSIONS: Cold blood cardioplegia followed by warm reperfusion is beneficial in an unselected group of patients with a preserved left ventricular function undergoing an elective first coronary artery bypass grafting. CTnI allowed the diagnosis of small perioperative necrotic myocardial areas. The need for electrical defibrillation after aortic unclamping was related to a higher release of CTnI. A further study is necessary to determine whether this technique was beneficial because of cold blood cardioplegia, warm reperfusion, or both.     

Expression of regulated cardiac troponin I in Escherichia coli

The study of the functional effects of troponin isoform changes would be greatly aided by the development of a strategy permitting protein engineering and mutational analysis. To assess the role of troponin isoforms in regulating myofibrillar ATPase activity, we have expressed rat cardiac troponin I (cTnI) in E. coli and purified the protein to near homogeneity. We utilized the inducible expression vector pGEX-KG to create a glutathione-S-transferase fusion protein which can be cleaved with thrombin. Approximately 6 mg of cTnI can be purified from 1 l of culture. Ca2+Mg2+ ATPase activity was measured using the bacterially synthesized cTnI and the remaining components of the regulated actomyosin complex (troponin T, troponin C, tropomyosin, actin, and myosin) purified to homogeneity from mammalian hearts. In the presence of free Ca2+ ranging from 10(-2) to 10(-8) M, bacterially synthesized cTnI exhibits specific activity similar to that observed for control cTnI isolated from rat hearts. The bacterially synthesized protein is capable of stoichiometric phosphorylation and demonstrates appropriately regulated specific activity. These results establish the feasibility of using bacterial expression to study functional consequences of changes in expression of troponin isoforms.     

Some theoretical issues confronting developmental psychologists.

A nagging persistent problem for developmental psychologists has always been the nativism-empiricism controversy. It is still with us today in almost every facet of developmental psychology. This issue is leading to an increasing "ecological" perspective in developmental psychology the end result of which is not clear yet. While Piagetian theory remains the reference point for much of cognitive developmental psychology, there has been a very marked decline in the degree to which many cognitive researchers subscribe to that theory. At the moment there is no grand integrative theory of cognitive development such Piaget's, much less of the field of developmental psychology as a whole. However, this may mean that the field as a whole is more open to different theoretical approaches. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Degradation of cardiac troponin I: implication for reliable immunodetection

We have analyzed by different immunological methods the proteolytic degradation of cardiac troponin I (cTnI) in human necrotic tissue and in serum. cTnI is susceptible to proteolysis, and its degradation leads to the appearance of a wide diversity of proteolytic peptides with different stabilities. N- and C-terminal regions were rapidly cleaved by proteases, whereas the fragment located between residues 30 and 110 demonstrated substantially higher stability, possibly because of its protection by TnC. We conclude that antibodies selected for cTnI sandwich immunoassays should preferentially recognize epitopes located in the region resistant to proteolysis. Such an approach can be helpful for a much needed standardization of cTnI immunoassays and can improve the sensitivity and reproducibility of cTnI assays.     

Phosphorylation-induced distance change in a cardiac muscle troponin I mutant

Phosphorylation of two adjacent serine residues in the unique N-terminal extension of cardiac muscle troponin I (cTnI) is known to decrease the Ca2+-sensitivity of cardiac myofilaments. To probe the structural significance of the N-terminal extension, we have constructed two cTnI mutants each containing a single cysteine: (1) a full-length cTnI mutant (S5C/C81I/C98S) and (2) a truncated cTnI mutant (S9C/C50I/C67S) in which the N-terminal 32 amino acid residues were deleted. We determined the apparent binding constants for the complex formation between IAANS-labeled cardiac troponin C (cTnC) and the two cTnI mutants. The affinities of the cTnC for the truncated cTnI mutant were: (1) 1.5 x 10(6) M(-1) in EGTA, (2) 28.9 x 10(6) M(-1) in Mg2+, and (3) 87.5 x 10(6) M(-1) in Mg2+ + Ca2+. These binding constants were approximately 1.4-fold smaller than the corresponding values obtained with the full-length cTnI mutant, suggesting a very small contribution of the N-terminal extension to the binding of cTnI to cTnC. Cys-5 in the full-length cTnI mutant was labeled with IAANS, and the distribution of the separation between this site and Trp-192 was determined by analysis of the efficiency of fluorescence resonance energy transfer from Trp-192 to IAANS. The following mean distances were obtained with the unphosphorylated full-length mutant: 44.4 A (cTnI alone), 48.3 A (cTnI + cTnC), 46.3 A (cTnI + cTnC in Mg2+), and 51.6 A (cTnI + cTnC in Mg2+ + Ca2+). The corresponding values of the mean distance determined with the phosphorylated full-length cTnI mutant were 35.8, 36.6, 34.8, and 37.3 A. The phosphorylation of cTnI reduced the half-width of the distribution from 9.5 to 3.7 A. Similar but less pronounced decreases of the half-widths were also observed with the phosphorylated cTnI complexed with cTnC in different ionic conditions. Thus, phosphorylation of cTnI resulted in a decrease of 9-12 A in the mean distance between the sites located at the N- and C-terminal portion of cTnI. Our results indicate that phosphorylation elicits a change in the conformation of cTnI which underlies the basis of the phosphorylation-induced modulation of cTnI activity.     

Serum levels of cardiac troponin I and troponin T in estimating myocardial infarct size soon after reperfusion

BACKGROUND: Cardiac troponin I (TnI) and troponin T (TnT) are highly specific myocardial markers. OBJECTIVE: To determine whether their serum levels can be used to estimate myocardial infarct size soon after reperfusion. METHODS: We measured the serum levels of TnI, TnT, and creatine kinase every 3 h, and the serum cardiac myosin light chain I (MLCI) every 24 h, in 42 patients with acute myocardial infarction in whom reperfusion therapy had successfully been performed. We calculated the severity of regional hypokinesis by analyzing the follow-up ventriculograms with the centerline method. RESULTS: The time from reperfusion to the peak level for TnI was 6.1 +/- 3.5 h, significantly shorter than those for creatine kinase (7.5 +/- 4.1 h) and MLCI (55 +/- 28 h). The time to peak level for TnT (6.8 +/- 4.0 h) differed significantly from that for MLCI but not from that for creatine kinase. There was a significant correlation between the peak levels of TnI and TnT (r = 0.86). The peak TnI and TnT levels were correlated well to the peak creatine kinase level (r = 0.67 and 0.69, respectively), total creatine kinase release (r = 0.66 and 0.66), and the peak MLCI level (r = 0.71 and 0.80). We observed excellent correlations between the peak levels of TnI and TnT, and regional hypokinesis (r = -0.84 and -0.85, respectively). These were comparable to the correlations between regional hypokinesis and the peak creatine kinase level (r = 0.75), total creatine kinase release (r = -0.72), and the peak MLCI level (r = -0.76). CONCLUSIONS: These results suggest that the peak serum levels of TnI and TnT in patients with successful reperfusion are accurate and early indices of infarct size.     

Stepwise subunit interaction changes by mono- and bisphosphorylation of cardiac troponin I

Four phosphorylation degrees of cardiac troponin I (cTnI) have been characterized, namely, a dephospho, a bisphospho, and two monophospho states. Here we describe for the first time a role of the monophosphorylated forms. We have investigated the interaction between the cardiac troponin subunits dependent on the phosphorylation state of cTnI by surface plasmon resonance (SPR) spectroscopy. The monophosphorylated forms were generated by mutating each of the two serine residues, located in human cTnI at positions 22 and 23, to alanine. Association and dissociation rate constants of binary (cTnI-cTnT and cTnI-cTnC) and ternary (cTnI/cTnC complex-cTnT) complexes were determined. Mono- and consecutive bisphosphorylation of cTnI gradually reduces the affinity to cTnC and cTnT by lowering the association rate constants; the dissociation rate constants remain unchanged. Phosphorylation also affects formation of the ternary complexes; however, in this instance, association rate constants are constant, and dissociation rate constants are enhanced. A model of cardiac troponin is presented describing an induction of distinct conformational changes by mono- and bisphosphorylation of cTnI.     

Differential reactivity of cardiac and skeletal muscle from various species in a cardiac troponin I immunoassay

The effects of 2-butoxyethanol (2-BE) on poly(ADP-ribosyl)ation were studied in Syrian hamster embryo (SHE) cells by measuring the cellular concentrations of the polymer poly(ADP-ribose) (pADPr) and of NAD+, the substrate of poly(ADP-ribose) polymerase (PARP). As biotransformation pathways of ethylene glycol ethers involve NAD+-dehydrogenases, it was hypothesized that 2-BE could reduce poly(ADP-ribosyl)ation by consuming NAD+. As a result DNA repair could be altered, which would explain that 2-BE had been shown to potentiate the effects of clastogenic substances such as methyl-methanesulfonate (MMS). In this study, the effects of 2-BE on MMS-induced pADPr metabolism were analyzed. The results indicated that: (i) 2-BE (5 mM) by itself did not influence significantly pADPr or NAD+ levels. (ii) 2-BE inhibited pADPr synthesis in MMS (0.2 mM)-pretreated cells, without any change in NAD+ concentrations. (iii) MMS treatment, which rapidly increased pADPr levels, also affected the poly(ADP-ribosyl)ation system as a secondary effect by damaging cell structures. Membrane permeabilization, which occurred at concentrations >1 mM MMS, led to a dramatic leakage of cellular NAD+ resulting in a strong reduction in pADPr levels. (iv) A bleomycin pulse (100 microM) applied after MMS and/or 2-BE treatment confirmed that 2-BE reduced poly(ADP-ribosyl)ation capacities of MMS-treated cells, though the glycol ether had no effect alone. This study confirmed that the inhibition of pADPr synthesis could be responsible for the synergistic effects of 2-BE with genotoxic substances. The mechanism of this inhibition cannot be explained by a lack of NAD+ at the concentrations of 2-BE tested.     

Mutations in the cardiac troponin I gene associated with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM), the most common cause of sudden death in the young, is an autosomal dominant disease characterized by ventricular hypertrophy accompanied by myofibrillar disarrays. Linkage studies and candidate-gene approaches have demonstrated that about half of the patients have mutations in one of six disease genes: cardiac beta-myosin heavy chain (c beta MHC), cardiac troponin T (cTnT), alpha-tropomyosin (alpha TM), cardiac myosin binding protein C (cMBPC), ventricular myosin essential light chain (vMLC1) and ventricular myosin regulatory light chain (vMLC2) genes. Other disease genes remain unknown. Because all the known disease genes encode major contractile elements in cardiac muscle, we have systematically characterized the cardiac sarcomere genes, including cardiac troponin I (cTnI), cardiac actin (cACT) and cardiac troponin C (cTnC) in 184 unrelated patients with HCM and found mutations in the cTnI gene in several patients. Family studies showed that an Arg145Gly mutation was linked to HCM and a Lys206Gln mutation had occurred de novo, thus strongly suggesting that cTnI is the seventh HCM gene.     

Role of cardiac troponin I in the evaluation of myocardial injury

Congenital fibrosarcoma is a rare soft tissue sarcoma. A 22-year-old woman in the 22nd week of her first pregnancy underwent sonographic examination, which revealed a soft tissue swelling of the fetus's left thigh. The pregnancy was terminated, and congenital fibrosarcoma was diagnosed by pathologic examination. To our knowledge, this is the first published report of the intrauterine sonographic observation of this tumor in a fetal extremity.     

Cardiac troponin I phosphorylation increases the rate of cardiac muscle relaxation

Cardiac troponin (Tn) I (CTnI), compared with skeletal TnI, contains extra amino acids (32 to 33) at its amino terminus, including two adjacent serine residues. These two serine residues are believed to be phosphorylated by protein kinase A (PKA) upon stimulation of the heart by beta-agonists. In this study, we found that phosphorylation of a cardiac skinned muscle preparation by PKA, mainly at CTnI, results in a decrease in the Ca2+ sensitivity of muscle contraction. The pCa50 decreased by approximately 0.27 +/- 0.06 pCa units upon phosphorylation. To study cardiac muscle relaxation, we used diazo-2, a photolabile Ca2+ chelator with a low Ca2+ affinity in its intact form that is converted to a high-affinity form after photolysis. We found that the rate of cardiac muscle relaxation increased from a time of half-relaxation (t1/2) = 110 +/- 10 milliseconds to t1/2 = 70 +/- 8 milliseconds after CTnI phosphorylation. This result demonstrates that CTnI phosphorylation can be linked with the increased rate of muscle relaxation in a relatively intact muscle preparation. Since CTnI phosphorylation has been shown previously to affect the Ca2+ affinity and Ca2+ off-rate of CTnC in vitro, it is likely that the faster relaxation seen here reflects faster dissociation of Ca2+ from cardiac TnC (CTnC). Model calculations show that increased dissociation of Ca2+ from CTnC, coupled with the faster uptake of Ca2+ by the sarcoplasmic reticulum stimulated by PKA phosphorylation of phospholamban, can account for the faster relaxation seen in the inotropic response of the heart to catecholamines.     

表面分析法标准化

表面分析法标准化是一个迅速发展的学科,随着各种表面分析法在冶金工业中的应用,其标准化越来越引起重视。介绍了表面分析法标准化现状,系统而全面地探讨了六种表面分析法标准化发展趋势,对我国钢铁工业分析测试与标准化制修订有一定指导意义。     

Public land and natural resource issues confronting animal scientists and livestock producers

Livestock producers using public lands in the West were once concerned primarily with efficient systems for livestock production. Historically, this concept began in 1934 with the passage of the Taylor Grazing Act. Management activities on public lands continued to focus on sustainable livestock production until the 1970s, when the public began to demand enforcement of the Multiple Use Act and the National Environmental Policy Act. During this time, species listing under the Endangered Species Act became more active. Unfortunately, so many species are listed or are being considered for listing that it becomes impossible to develop biological information on causative factors for listing or recovery plans for each one. Peer-reviewed science that addresses management needs is often unavailable, and articles from the gray literature have been used in management plans for both threatened and endangered species and for public land. Personal biases of both scientists and land managers can influence the development of land management plans, especially in cases in which scientific information is minimal. The Land Grant System is well positioned to develop research applicable for public lands. Animal scientists need to be involved in interdisciplinary teams. Livestock producers need to overcome the stigma that livestock grazing is not a sustainable use. Rangeland in poor condition, whether public or private, should be improved if livestock managers are to change the public perception that grazing degrades rangeland. To accomplish this, education and peer pressure should be used. Another approach needed is activism on the part of producers and animal scientists. The public is demanding a voice in public land management. Working groups seem to be the emerging pathway to cooperatively develop management plans.     

Prognostic role of troponin T versus troponin I in unstable angina pectoris for cardiac events with meta-analysis comparing published studies

Controversy exists as to the clinical roles and relative specificities of cardiac troponin T or I in patients with unstable angina pectoris (UAP). We measured troponin T and I levels on admission in 123 patients with UAP. Of the 107 patients with normal creatine kinase during the first 24 hours, troponin T and I were elevated in 14 and 13 patients, respectively. At 30 days, 5 of 14 patients (36%) with elevated troponin T and 3 of 93 patients (3.2%) with normal troponin T had acute myocardial infarction (odds ratio [OR], 16.7; 95% confidence interval [CI] 3.4 to 81.5; p <0.001). Of 13 patients with elevated troponin I, 5 patients (39%) and 3 of 94 patients (3.2%) with normal troponin I had acute myocardial infarction (odds ratio, 21.7; 95% CI 4.3 to 110; p <0.001). No deaths occurred within 30 days. Both markers demonstrated equivalent sensitivity (63%) and specificities (troponin T: 91%; troponin I: 92%) for myocardial infarction. Meta-analysis of 12 published troponin T and 9 troponin I studies in patients with UAP produced risk ratios of 4.2 (95% CI 2.7 to 6.4, p <0.001) for troponin I compared with 2.7 (95% CI 2.1 to 3.4, p <0.001) for troponin T. Comparison of the sensitivities and specificities of both markers using summary receiver operating characteristic curves showed no significant difference in their abilities to predict acute myocardial infarction and cardiac death. Troponin T and I show similar prognostic significance for acute myocardial infarction or death in the same patients with UAP. The 2 markers are equally sensitive and specific, as confirmed by meta-analysis, and this supports a role in risk stratification.     

Assessment of left ventricular function using serum cardiac troponin I measurements following myocardial infarction

The FhuA protein of Escherichia coli K-12 transports ferrichrome and the structurally related antibiotic albomycin across the outer membrane and serves as a receptor for the phages T1, T5, and phi 80 and for colicin M. In this paper, we show that chimeric proteins consisting of the central part of FhuA and the N- and C-terminal parts of FhuE (coprogen receptor) or the N- and/or C-terminal parts of FoxA (ferrioxamine B receptor), function as ferrichrome transport proteins. Although the hybrid proteins contained the previously identified gating loop of FhuA, which is the principal binding site of the phages T5, T1, and phi 80, only the hybrid protein consisting of the N-terminal third of FoxA and the C-terminal two thirds of FhuA conferred weak phage sensitivity to cells. Apparently, the gating loop is essential, but not sufficient for wild-type levels of ferrichrome transport and for phage sensitivity. The properties of FhuA-FoxA hybrids suggest different regions of the two receptors for ferric siderophore uptake.