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At least 343 records · Page 19Linked to original sources

Novel point mutation in the cardiac transcription factor CSX/NKX2.5 associated with congenital heart disease.

The homeobox transcription factor CSX/NKX2.5, which is a vertebrate homologue of the Drosophila gene tinman, is essential for cardiac development. It is expressed in the early cardiac mesoderm and in heart muscle lineage throughout life. Homozygous deletion of CSX/NKX2.5 causes early embryonic lethality in mice because cardiac development is arrested at the linear heart tube stage. Heterozygous mutation of human CSX/NKX2.5 has been associated with various congenital heart diseases such as atrial septal defect (ASD), ventricular septal defect, tetralogy of Fallot, and tricuspid valve abnormalities, including Ebstein's anomaly. Additionally, CSX/NKX2.5 mutation causes atrioventricular (AV) conduction block with or without associated congenital heart diseases. Ten different heterozygous mutations have been already reported and a new point mutation, which is a C-to-A transition (Cys264ter) at nucleotide 901 of CSX/NKX2.5, results in the production of a truncated protein occurring COOH-terminal to the homeodomain of CSX/NKX2.5. The mutation was found in a patient with familial ASD and first-degree AV block; 4 members from 3 generations had secundum-type ASD and first-degree AV block.

Cysteine↗

Three zebrafish MEF2 genes delineate somitic and cardiac muscle development in wild-type and mutant embryos.

The zebrafish is an important experimental system for vertebrate embryology, and is well suited to the molecular analysis of muscle development. Transcription factors, such as the MEF2s, regulate skeletal and cardiac muscle-specific genes during development. We report the identification of three zebrafish MEF2 genes which, like their mammalian counterparts, encode factors that function as DNA-binding transcriptional activators of muscle specific promoters. The pattern of MEF2 expression in zebrafish defines discrete cell populations in the developing somites and heart and has mechanistic implications for developmental regulation of the MEF2 genes, when compared with other species. Alteration of MEF2 expression in two mutants affecting somitogenesis provides insight into the control of muscle formation in the embryo.

Amino Acid Sequence↗

Developmental changes in rat cardiac DNA, RNA and protein tissue base: implications for the interpretation of changes in gene expression.

During cardiac development the expression levels of many genes change as determined by Northern blot, dot blot, RNase protection, quantitative RT-PCR. Western blot or immunoprecipitation analyses. It is not always realized that the total amount of RNA or protein per gram of heart, dubbed tissue base, may change significantly during development as well. If this would be the case, this has to be taken into account. So far, the (changing) tissue base has not been established during cardiac development. To this end developmental profiles of cardiac DNA, RNA and protein concentration were determined in rats ranging in age from embryonic day 13 until neonatal day 121. The profiles show significant development changes in each parameter, that closely match the distinct growth phases of the developing heart and provide the parameters that are essential for an adequate interpretation of changes in the amount of a distinct mRNA and/or protein. In a comparison between in situ hybridization and Northern blot analysis it is demonstrated that the same developmental profile leads to an almost opposite conclusion depending on whether or not the changing tissue base is taken into account. These findings are of great interest for studies aimed at unravelling the molecular mechanisms underlying the regulation of gene expression during cardiac development.

Age Factors↗

[Arrhythmias and cardiac electrophysiology: main developments in 2005].

Cardiac electrophysiology laboratories deal with a wide range of pathological conditions, diagnostic techniques, and treatments. Since a huge quantity of material has been published in recent months, this article will be limited to discussion of the most significant developments in the prognostic evaluation of arrhythmias, hereditary disease, syncope, atrial fibrillation, implantable cardioverter-defibrillators, cardiac resynchronization therapy, and catheter ablation. Even within these areas, discussion will be restricted to specific concrete topics and to a limited number of publications that were judged to have important implications for clinical practice. Our principal aim was to provide clinical cardiologists with an overview of the latest developments in cardiac electrophysiology.

Arrhythmias, Cardiac↗

[Use of transesophageal electrostimulation of the atrium and nitroglycerin test in the evaluation of the degree of risk of the development of cardiac complications after reconstructive surgery in patients with Leriche's syndrome].

By the method of transesophageal electrostimulation of the left auricle, 98 patients with Leriche's syndrome were examined. Of them in 51, the coronary disease was revealed. The degree of ischemic changes in the terminal part of the ventricular complex were defined by the rate of stimulation, depth of the ST segment shift, and duration of ischemic depression. The nitroglycerin test permitted to evaluate the anti-ischemic effect of the drug, quality and effectiveness of the preoperative preparation. In patients with negative or doubtful anti-ischemic effect, the risk of the development of cardiac complications increases.

Atrial Function↗

Purification and characterization of a high-molecular-weight protein induced in rat serum during the development of cardiac hypertrophy.

A relatively high-molecular-weight polypeptide was found in rat serum within 6 h after aortic constriction in experimental animals. This polypeptide persists for about 7 days of the postoperative period and disappears at later stage of hypertrophy (40%). Further, fractionation and purification of this protein through DEAE-Sepharose and gel filtration chromatography have revealed that this protein is a single polypeptide and its relative molecular weight is 135 kDa. Immunoprecipitation and immunofluorescence microscopic analysis have indicated the presence of the above polypeptide in the nuclear fraction of heart cells. Studies on phosphorylation in vitro have revealed that this protein is a phosphoprotein. DNase I sensitivity and hybridization using a muscle specific gene probe have indicated the involvement of this protein in template associated changes in heart nuclei. Further the possibility of this protein being synthesized by heart cells indicates that this protein could traverse back and forth between heart cells and the extracellular fluid, suggesting an autocrine/paracrine role for this protein during the development of cardiac hypertrophy.

Animals↗

Mannheimer Lecture. The quintessence of the making of the heart.

In my Mannheimer lecture, designed to meet the needs of a mainly clinical audience, I present aspects of cardiac development that link basic science to clinically relevant problems. During development of the cardiac tube, and its subsequent changes as a dextrally looped structure, which is still connected to the dorsal body wall by a venous and an arterial pole, there are basic requirements. These consist of the development of myocardium, endocardium and the interposed cardiac jelly from the cardiogenic plates. In this primitive heart tube, septation and valvar formation then take place to convert it into a four-chambered heart. I demonstrate that the refining of the above events cannot take place without the addition of extracardiac populations of cells. These are presented as the "quintessence of heart development", and consist of cells derived from the neural crest, along with epicardially derived cells. Without these contributions, the embryos uniformly die of cardiac insufficiency. Important contributions are made by the cells derived from the neural crest to septation and the formation of the arterial valves, and possibly in differentiation of the central conduction system. The epicardially derived cells are essential for formation of the interstitial fibroblasts and the myocardium, as well as the coronary vascular system. I conclude by discussing specific malformations of the heart that might be linked to these extracardiac contributions.

Animals↗

The frequency and pattern of cardiotoxicity observed with capecitabine used in conjunction with oxaliplatin in patients treated for advanced colorectal cancer (CRC).

We examined the cardiotoxicity in 153 patients treated with capecitabine and oxaliplatin in two prospective trials for advanced colorectal cancer. Ten patients (6.5%) developed cardiac events. One patient (0.7%) had sudden death, one patient developed cardiac failure with raised troponin I while another developed ventricular tachycardia (VT). The remaining seven patients (4.6%) experienced angina and three of the seven patients had raised troponin I, one of which developed ventricular fibrillation. Eight events occurred within cycle 1 (median cycle 1 day 10). Four patients with angina and one patient with VT recovered on stopping capecitabine, four patients required additional medical management and the remaining patient died suddenly at home. Patients with ischaemic heart disease appeared to be at increased risk. Physicians and patients need to be aware of these complications, so that prompt discontinuation of treatment and appropriate interventions may be instituted.

Adult↗

Catecholamines and development of cardiac pacemaking: an intrinsically intimate relationship.

A generation ago, a melding of imagination and experimental evidence led to the hypothesis that catecholamines were essential in establishing basal cardiac pacemaking rhythm. Subsequent discoveries of depolarizing "pacemaker" currents and viable adult catecholamine-deficient animals raised serious doubts about the necessity of catecholamines in pacemaking. However, the findings that catecholamines are produced in pacemaking regions prior to innervation, and that they are required for embryonic survival during a defined "critical period" of embryonic development have revitalized the original hypothesis. Recent results have further suggested that intrinsic cardiac adrenergic cells can differentiate into pacemaking myocytes, and that protein kinase A, a prominent downstream mediator of beta-adrenergic signaling, is required for pacemaking activity. Here, we discuss how catecholamines and the intrinsic cardiac adrenergic cells that produce them may influence ontological development of cardiac pacemaking.

Animals↗

Cardiotrophin-1 and the role of gp130-dependent signaling pathways in cardiac growth and development.

The reactivation of an embryonic pattern of gene expression is a central feature common to virtually all forms of cardiac hypertrophy. Unraveling the regulatory mechanisms, growth factors and cytokines controlling gene expression and cell fate during cardiac development may therefore have implications for our understanding of cardiac hypertrophy in the adult. Along this line, a cDNA expression library was established from an embryonic stem cell-based in vitro model of cardiogenesis, and screened for clones that would induce an increase in cell size in cultured cardiomyocytes. This experimental strategy resulted in the isolation of a novel cytokine, cardiotrophin-1 (CT-1), that activates several features of cardiomyocyte hypertrophy in vitro, including sarcomeric organization and embryonic gene expression. CT-1 displays structural similarities to the interleukin (IL)-6 related cytokines. Furthermore, receptor binding studies and functional studies reveal that CT-1 shares the signal transducing receptor components gp130 and LIFR with the previously identified members of the IL-6 cytokine family. CT-1 rapidly activates gp130 and LIFR tyrosine phosphorylation in cultured cardiac myocytes. The growth promoting effects of CT-1 therefore indicate that signaling pathways emanating from gp130 and LIFR are coupled to cardiomyocyte hypertrophy. In support of this notion, the simultaneous overexpression of IL-6 and the IL-6 receptor in transgenic mice has been shown to result in a constitutive tyrosine phosphorylation of gp130 in the myocardium and cardiac hypertrophy. The striking phenotype of gp130 null-mutant mice, generated by homologous recombination, implies gp130 in cardiac development as well: mutant mice exhibit severe ventricular hypoplasia, suggesting a role for gp130-dependent signaling pathways in the expansion of the compact layer of the ventricular myocardium. CT-1 is expressed at high levels in the myocardium during the course of cardiogenesis, and promotes the proliferation and survival of embryonic cardiomyocytes. CT-1 may therefore represent a candidate cytokine to activate gp130 during cardiac development. In summary, cytokines signaling through gp130 are emerging as potent regulators of embryonic heart development and adult cardiac hypertrophy.

Animals↗

Temperature-dependent development of cardiac activity in unrestrained larvae of the minnow Phoxinus phoxinus.

The minnow (Phoxinus phoxinus) was raised up to the stage of swim bladder inflation at temperatures between 10 degrees C and 25 degrees C, and the time of development significantly decreased at higher temperatures. Accordingly, initiation of cardiac activity was observed at day 2 in 25 degrees C animals and at day 4 in 12.5 degrees C animals. Only a minor increase in body mass was observed during the incubation period, and, at the end of the incubation period, animals raised at 25 degrees C did not have a significantly lower body mass compared with animals raised at 15 degrees C. Metabolic activity, determined as the rate of oxygen consumption of a larva, increased from 3.3 to 19.5 nmol/h during development at 15 degrees C and from 5.6 to 47.6 nmol/h during development at 25 degrees C. Heart rate showed a clear correlation to developmental stage as well as to developmental temperature, but at the onset of cardiac activity, diastolic ventricular volume and also stroke volume were higher at the lower temperatures. Furthermore, stroke volume increased with development, except for the group incubated at 12.5 degrees C, in which stroke volume decreased with development. Initial cardiac output showed no correlation to incubation temperature. Although metabolic activity increased severalfold during development from egg to the stage of swim bladder inflation at 15 degrees C and at 25 degrees C, weight-specific cardiac output increased only by approximately 40% with proceeding development. At 12.5 degrees C, cardiac output remained almost constant until opening of the swim bladder. The data support the notion that oxygen transport is not the major function of the circulatory system at this stage of development. The changes in heart rate with temperature appear to be due to the intrinsic properties of the pacemaker; there was no indication for a regulated response.

Air Sacs↗

Premature death and age-related cardiac dysfunction in male eNOS-knockout mice.

The aims of our study were to determine mortality, and age- and genotype-related cardiac phenotype in endothelial nitric oxide synthase (NOS) knockout (-/-) and wild-type (+/+) mice. Male and female (-/-) and male and female (+/+) conscious mice were studied at different ages by echocardiography and tail-cuff blood pressure (BP) measurement. Only 50% male (-/-) mice lived longer than 21 months whereas 89% (+/+) mice were still alive after 24 months (P < 0.005). There was little mortality in female mice of either genotype. Both (-/-) and (+/+) male mice have normal cardiac dimensions and function at 5.5 months. However, (-/-) mice developed cardiac dilation and dysfunction at 21 months as evidenced by a significant increase (P < 0.05) in left ventricular (LV) end-diastolic diameter from 2.69 +/- 0.13 to 3.13 +/- 0.09 mm, LV end-systolic diameter from 1.28 +/- 0.11 to 1.86 +/- 0.12 mm, LV end-diastolic cavity volume from 21 +/- 2.8 to 31 +/- 2.5 microl and LV mass from 19 +/- 2.5 to 27 +/- 1.9 mg/10 g and a significant decrease (P < 0.05) in ejection fraction (from 65 +/- 3.3% to 41 +/- 4.6%), shortening fraction (from 53 +/- 2.2% to 41 +/- 3.4%), LV posterior wall thickening (from 27 +/- 2% to 12 +/- 4%) and septum thickening (from 27 +/- 2% to 12 +/- 4%) compared with those at 5.5 months. There was a clear increase in cardiac weight and cardiac dilation by hematoxylin and eosin in male (-/-) mice at 21 months. BP in male (-/-) mice fell with the cardiac dysfunction, whereas female (-/-) mice were hypertensive even at 21 months. The level of mRNA for neuronal NOS and inducible NOS was greater in all females compared to males. These results indicate that male (-/-) mice have a significantly shorter lifespan than (+/+) or female mice, and male (-/-) mice develop cardiac dysfunction with age.

Aging↗

Role of Na+-Ca2+ exchange in the development of cardiac abnormalities due to calcium paradox.

Reperfusion of rat heart with Ca2+-containing medium for 1 to 10 min after a 5 min perfusion with Ca2+-free medium resulted in a generalized disruption of myocardial ultrastructure including swelling of sarcoplasmic reticulum and mitochondria, depletion of creatine phosphate and adenosine triphosphate stores, reduction of the microsomal but augmentation of the mitochondrial Ca2+ uptake activities and elevation of the cardiac Na+ as well as Ca2+ contents. These hearts developed contracture and were unable to generate contractile force. Lowering the concentration of Na+ from 145 to 35 mmol l-1 in the medium during Ca2+-free perfusion was observed to markedly reduce or prevent the reperfusion induced changes in myocardium. On the other hand, lowering the concentration of Na+ in the medium during the reperfusion phase following a 5 min perfusion with Ca2+-free medium enhanced the rate of depletion of the high energy phosphate stores and the rate of elevation of myocardial Ca2+ contents but markedly depressed the rise in Na+ contents. These results suggest that Ca2+-paradoxical changes in myocardium occur as a consequence of the intracellular Ca2+ overload in which Ca2+ entry through Na+-Ca2+ exchange mechanism at the cell membrane may be an important contributory factor.

Animals↗

Rate of tension development in cardiac muscle varies with level of activator calcium.

In skeletal muscle, the rate of transition from weakly bound to force-generating crossbridge states increases as calcium concentration is increased. To examine possible calcium sensitivity of this transition in cardiac muscle, we determined the kinetics of isometric tension development during steady activation in detergent-permeabilized rat ventricular trabeculae (n = 7) over a range of calcium concentrations. Force-generating crossbridges in activated trabeculae were disrupted by a brief, rapid release and restretch equivalent to 20% muscle length (15 degrees C), which resulted in a subsequent phase of tension redevelopment that was well fit by a monoexponential function (rate constant, ktr). Sarcomere length was monitored by laser diffraction and held constant during tension redevelopment by an iterative adaptive feedback control system. The ktr increased from 3.6 +/- 0.8 s-1 at the lowest calcium concentration studied (pCa 5.9) to 9.5 +/- 1.3 s-1 during maximal activation (pCa 4.5). The relationship between relative ktr and relative tension was approximately linear over a wide range of [Ca2+] (r2 = .94). This result differs quantitatively from results in skeletal muscle, in which ktr is sensitive to [Ca2+] primarily at higher activation levels. This observation is also inconsistent with a recent suggestion that the rate of force development in living myocardium is independent of the activation level. Our results in skinned myocardium can be explained by a model in which calcium is a graded regulator of both the extent and rate of binding of force-generating crossbridges to the thin filament.

Animals↗

Fast-track failure after cardiac surgery: development of a prediction model.

OBJECTIVE: Risk factors for unsuccessful fast-tracking of cardiac surgery patients have not been collectively defined in the literature. The aim of this study was to determine risk factors for fast-track failure and incorporate them into a predictive fast-track failure score. DESIGN: Prospective observational study. SETTING: Cardiothoracic Department of St Mary's Hospital, London. PATIENTS: Data were collected from April 2003 to April 2005 including 1,084 patients undergoing heart surgery who were admitted into the fast-track unit. INTERVENTIONS: Multifactorial logistic regression was used to develop a propensity score for estimating the likelihood of fast-track failure. MEASUREMENTS AND MAIN RESULTS: One hundred and sixty-nine patients failed fast-track management (15.6%). Independent predictors for fast-track failure were impaired left ventricular function with or without recent acute coronary syndrome (odds ratios 2.89 and 1.65 respectively), re-do operation (one, two, or more vs. none, odds ratio 1.75, 7.98), extracardiac arteriopathy (odds ratio 2.63), preoperative intra-aortic balloon pump (odds ratio 3.09), raised serum creatinine in micromol/L (120-150, >150 vs. <120, odds ratio 1.57, 11.24), and nonelective (odds ratio 3.43) and complex surgery (odds ratio 2.70). Model validation showed very good discrimination (area under the curve = 0.815) and calibration (ĉ statistic = 8.527, p = .129). CONCLUSIONS: The fast-track failure score incorporates several preoperative factors and has been successfully internally validated; after undergoing external validation and possible recalibration it may be used as a tool to facilitate planning and flow of cardiac surgery patients, based on the predicted probability of failure. Application of this score may limit fast-track failure rates and help to reduce morbidity and cost.

Aged↗

Risk of aortic aneurysm surgery as assessed by preoperative gated heart pool scan.

Gated heart pool scan measuring left ventricular ejection fraction (LVEF) was performed preoperatively in 72 patients presenting for elective repair of abdominal aortic aneurysm. Patients with a positive cardiac history were more likely to have a LVEF of less than or equal to 45 per cent (P less than 0.001). The operative mortality rate was 4 per cent. Each of three patients who died had a LVEF less than or equal to 35 per cent and developed cardiac failure which led to renal failure. Five other patients developed cardiac failure manifested by acute pulmonary oedema during the early postoperative period. There was no statistically significant association between a positive cardiac history and the occurrence of postoperative cardiac failure or death. However, patients with a LVEF of less than or equal to 45 per cent were more likely to develop postoperative cardiac failure (P = 0.004) while patients with a LVEF of less than or equal to 35 per cent had a greater chance of dying (P less than 0.001). No patient died with a LVEF greater than 35 per cent. Preoperative evaluation of LVEF can select patients at high risk of cardiac death from repair of abdominal aortic aneurysm. Such patients could be followed conservatively if they remain asymptomatic and the aneurysm does not enlarge. If operation is considered mandatory, patients with a low LVEF should receive intensive perioperative monitoring with enhancement of ventricular performance.

Adult↗