Merkel cell carcinoma: squamous and atypical fibroxanthoma-like differentiation in successive local tumor recurrences

Merkel cell carcinoma (MCC) is a rare, frequently lethal, primary neuroendocrine carcinoma of the skin. Histopathologically, it appears as a dermal nodule of small, undifferentiated malignant cells. Historically, MCC was considered to be an eccrine carcinoma. Recognition of its neuroendocrine features later led to the hypothesis that it arose from Merkel cells in the skin, although recent evidence revisits the question of an epithelial origin. We present a case of MCC arising on the temple of a 78-year-old male, in association with an actinic keratosis. Three years later, a local tumor recurrence showed a mixed malignancy comprising small cell neuroendocrine and large cell squamoid components. A further recurrence at the site two years later, after local radiotherapy, revealed a bizarre pleomorphic large cell morphology with retention of immunohistochemical features of a neuroendocrine carcinoma. Evolution to a bizarre pleomorphic large cell neoplasm has been recorded in malignant tumors treated by radiotherapy, but is unique for MCC. The association of this MCC with an actinic keratosis and the development of squamoid differentiation in a local recurrence support the link between MCC and epithelial neoplasia. In addition, its evolution to an atypical fibroxanthoma-like morphology is of interest, because some view atypical fibroxanthomas as bizarre variants of squamous cell carcinoma.

Inappropriate shock therapy in a heart failure defibrillator

A 63-year-old male with dilated cardiomyopathy underwent implantation of a "heart failure" defibrillator capable of biventricular pacing. He received an inappropriate shock 5 hours after the procedure. Stored electrograms revealed that during each sinus beat the ventricular channel recorded up to three separate events. These resulted from far-field atrial sensing by the coronary venous lead, appropriate right ventricular sensing, then delayed left ventricular sensing (the result of left bundle branch block). As a consequence of far-field left atrial sensing the two subsequent ventricular electrograms fell within the VF zone. Following an atrial premature beat, VF detection criteria were satisfied and shock therapy delivered. Although coronary venous lead repositioning eliminated far-field atrial sensing, double counting of the widely split right and left ventricular electrograms still occurred during sinus rhythm. Shortening the programmed AV delay resulted in constant biventricular pacing with a single electrogram.

Neoadjuvant therapy for non-small cell lung cancer

Clinical trials evaluating neoadjuvant or preoperative therapy for locally advanced non-small cell lung cancer (NSCLC) have demonstrated the feasibility, tolerability and activity of this approach. Three randomized trials have reported improved survival in patients with stage III NSCLC treated with preoperative chemotherapy followed by surgical resection compared to surgery alone. Combinations of neoadjuvant chemotherapy plus thoracic radiotherapy have also been investigated, generally resulting in higher rates of pathologic response, but higher toxicity rates as well. The best approach to neoadjuvant therapy remains to be determined and may well be substage dependent. In bulky stage III NSCLC, the role of surgery itself remains unclear and is the subject of an ongoing intergroup trial in the US. Regardless, neoadjuvant therapy has emerged as an important paradigm for clinical research since it serves as an in vivo test of chemosensitivity in patients, and represents a 'window of opportunity' for testing new chemotherapeutic agents and novel strategies. Among the new chemotherapeutic agents being investigated in this setting is docetaxel, one of the most active agents in first- and second-line chemotherapy of NSCLC, and a potent radiosensitizer. Preliminary studies have confirmed the feasibility of integrating docetaxel into neoadjuvant treatment strategies and encouraging results have been reported.

Nutritional Support in Acute Pancreatitis: An Update on Management Issues

About 20% of acute pancreatitis cases develop necrosis and have a high risk of inflammatory and infectious complications and a high mortality rate. Acute pancreatitis has a variety of causes and despite years of research its pathogenesis remains complex and obscure. Both local and systemic inflammatory responses play key roles in the pathophysiology of this disorder. Treatment plans continue to rely on supportive care without proven specific therapies. Pancreatic rest and use of total parenteral nutrition (TPN) were the gold standard for nutritional support of these challenging patients. Because numerous studies in other critically ill patients demonstrated benefits of enteral nutrition, recent investigations compared TPN to enteral nutrition in acute pancreatitis. These studies indicated that enteral nutrition delivered into the jejunum was tolerated well, even in patients with severe acute pancreatitis. "Mild'' cases of pancreatitis should improve and tolerate oral nutrition within a few days. In contrast, "severe'' cases of pancreatitis or those with a protracted clinical course require nutritional support to aid in preventing adverse effects of starvation and nutrient deficiencies. Current recommendations are to attempt enteral nutrition in patients with acute pancreatitis prior to instituting TPN. Further studies to determine optimal nutrient composition are warranted and should investigate the possibility of modulating the inflammatory response induced by pancreatitis to improve outcomes.

Minimal residual disease at the time of peripheral blood stem cell harvest in patients with advanced neuroblastoma

BACKGROUND

Despite treatment with high-dose myeloblative chemotherapy and peripheral blood stem cell (PBSC) rescue, a high proportion of children with neuroblastoma relapse and die. Re-infusion of PBSC contaminated with tumour at the time of autologous transplantation may play a significant role in this relapse. In this study the frequency of tumour contamination in PB from children with neuroblastoma has been investigated.

PROCEDURE

Minimal residual disease was measured using RT-PCR for tyrosine hydroxylase (TH) mRNA in PBSCs from patients with advanced neuroblastoma. PBSCs from 18 patients in complete clinical remission were studied.

RESULTS

Studies in other cancers have suggested minimal contamination of PBSCs with tumour cells; TH mRNA was detected by RT-PCR in 50% (9/18) of PBSC harvests. Seventy-seven percent (7/9) of patients with TH mRNA in PBSC died of disease compared to 44% (4/9) who were TH mRNA-negative.

CONCLUSIONS

Therefore, the presence of TH mRNA in PBSCs appeared to be associated with an unfavourable outcome, although this was not statistically significant. In summary, RT-PCR for TH mRNA is a sensitive method for the identification of tumour cells in PBSC harvest. The presence of TH mRNA in PBSC harvest may reflect disease status and be associated with an unfavourable outcome, although long-term clinical outcome studies in a larger patient cohort are required.

Molecular cytogenetic definition of 17q translocation breakpoints in neuroblastoma

BACKGROUND

Unbalanced translocations resulting in the gain of material from 17q are the most common chromosomal changes in neuroblastoma and are associated with poor patient survival, and are established indicators of bad prognosis.

PROCEDURE

We have used 13 fluorescent in situ hybridisation probes to map 17q translocation breakpoints in ten neuroblastoma cell lines and 21 primary tumours.

RESULTS

At least seven different breakpoints have been identified, all localised within the proximal half of 17q (53-68 cM, 17cen-17q22).

CONCLUSION

These results suggest that the dosage of a gene, or genes, in 17q22-qter is responsible for the clinical effects of 17q gain, rather than the disruption of a specific gene.

MYCN amplification and 17q in neuroblastoma: evidence for structural association

MYCN oncogene amplification in neuroblastoma is statistically associated with gain of chromosome segment 17q21-qter. In neuroblastoma cell lines and primary tumors with MYCN amplification in the form of homogeneously staining regions (hsrs), juxtaposition of chromosome 17 material with MYCN sequences has occasionally been reported, raising the possibility of a physical affinity between MYCN and chromosome arm 17q. We used FISH to test for association between chromosome 17 segments and MYCN in eight neuroblastoma cell lines and two neuroblastoma primary tumors known to include hsrs. Evidence of an association was found in the chromosomes of both primary tumors; in one, a MYCN hsr was inserted into a structurally abnormal chromosome 17, in the other, an hsr in 16p was shown to be flanked by 17 material. In cell line NCG, hsrs in 4q and 16p were flanked by 17q material. These observations confirm the juxtaposition of 17q material with MYCN sequences in some neuroblastomas, and imply that there may be a physical or functional relationship between these two features in MYCN amplified neuroblastoma.

17q gain in neuroblastoma predicts adverse clinical outcome. U.K. Cancer Cytogenetics Group and the U.K. Children's Cancer Study Group

BACKGROUND

It is now recognized that gain of chromosome 17 material is the most frequent genetic abnormality of neuroblastoma cells. Several studies have linked 17q gain with known adverse prognostic factors: patient age >1 year, advanced stage disease, deletion of chromosome arm 1 p, and amplification of the MYCN oncogene. We sought to further investigate the clinical and prognostic associations of chromosome 17 status in relation to other well-established predictive factors.

PROCEDURE

In a collaborative study by UK cytogenetics centres, we compiled a series of 104 neuroblastoma tumours for which the status of chromosome 17 was confidently defined by cytogenetics, metaphase or interphase FISH, or CGH analysis. The results were correlated with data on 1p and MYCN, and with centrally collated clinical and survival information.

RESULTS

Gain of 17q (i.e., unbalanced gain of segment 17q21-qter) was found in 66.3% of tumours, while 33.7% showed a '17q normal' status (i.e., no gain at all, or gain of whole chromosome 17 relative to ploidy). Gain of 17q was strongly associated with advanced stage disease, patient age >1 year, 1p deletion, and MYCN amplification (all P< 0.01). In univariate analysis, 17q gain was a significant predictor of adverse outcome (projected 5 year relapse-free survival 15.6% compared to 75.2% in cases lacking this feature in tumour cells; (P < 0.0001). In multivariate analysis, 17q gain was more strongly associated with adverse outcome than was either stage (Stage 4 vs other combined) or 1p status.

CONCLUSION

We conclude that gain of chromosome segment 17q21-qter is of great biological and clinical importance in neuroblastoma, and that its detection at diagnosis should be a priority.

Non-specific antiviral activity of antisense molecules targeted to the E1 region of human papillomavirus

Antisense phosphorothioate oligonucleotides (ODN1 0x5 OMe) directed against the E1 start region of human papillomavirus 11 (HPV11) can inhibit papillomavirus induced growth of implanted human foreskin in a mouse xenograft model. Administration of a mismatch control oligonucleotide (ODN9 0x5 OMe), in which guanine was replaced with adenine in the same model, had no effect on papilloma induced growth. However, the apparent antiviral activity of ODN1 0x5 OMe was also shown in a lethal mouse cytomegalovirus (CMV) model, in which the oligonucleotides are not expected to have antisense activity. To understand the mechanisms of action of these oligonucleotides, a mismatch oligonucleotide (ODN61 0x5 OMe) was prepared which retained the CpG motifs of ODN1 0x5 OMe. This was tested in the mouse xenograft model and shown to have moderate inhibitory activity. As a definitive experiment, a comparison was made between the efficacy of the active oligonucleotide ODN1 0x5 OMe against two papilloma viruses HPV11 and HPV40. Both these viruses cause benign genital warts, but differ by four bases in their E1 sequence that was the target for ODN1 0x5 OMe. Papillomavirus induced growth in the mouse xenograft model was inhibited by ODN1 0x5 OMe in both cases, suggesting that oligonucleotide molecules have a non-specific antiviral activity that is not directly related to their antisense sequence.

Novel translocation of the BCL10 gene in a case of mucosa associated lymphoid tissue lymphoma

Interest has focused on a recently identified gene, BCL10, thought to play an important role in the genesis of extranodal, marginal zone (MALT) lymphomas. This gene belongs to a family containing caspase recruitment domains (CARD), that are involved in the apoptotic pathway. Translocations of the BCL10 gene to the immunoglobulin heavy chain locus at 14q32 have been described. We report herein a case of MALT lymphoma showing t(1; 2)(p22; p12). The translocation was shown to involve the BCL10 gene and the immunoglobulin kappa light chain locus by fluorescence in situ hybridization.

Ranitidine bismuth citrate can help to overcome Helicobacter pylori resistance to clarithromycin in vivo

BACKGROUND

Helicobacter pylori eradication usually fails when clarithromycin is used against resistant strains.

OBJECTIVE

The objective of this study was to test whether the apparent synergy found in vitro between ranitidine bismuth citrate (RBC) and clarithromycin also exists in vivo against resistant strains.

METHODS

H. pylori was cultured and clarithromycin susceptibility was determined before and after treatment, from duodenal ulcer patients receiving RBC and clarithromycin or omeprazole and clarithromycin for 2 weeks in a multicenter randomized clinical trial.

RESULTS

The overall eradication rate was 88.7% in the RBC group (71 patients) and 52.7% in the omeprazole group (74 patients). The demographic characteristics of the two groups were not different. Clarithromycin-resistant strains were isolated in 22 cases (15.1%). A difference between the eradication rates of susceptible and resistant strains was found in the omeprazole group but not in the RBC group. After treatment, resistance to clarithromycin developed in three of the seven strains (42.3%) cultured from the patients of the RBC group, compared with 11 of the 26 strains (42%) of the omeprazole group. That is, clarithromycin-resistant strains were found in 6% and 27% in the RBC group and the omeprazole group, respectively, on considering the global results.

CONCLUSION

A synergy between RBC and clarithromycin may exist in vivo and, while clarithromycin resistance is increasing, it is an argument for using RBC in triple therapies.

Autonomic dysfunction secondary to intracerebral hemorrhage

IMPLICATIONS

We report a case of autonomic dysfunction secondary to intracranial hemorrhage. The patient had periodical episodes of hypertension, tachycardia, tachypnea, and diaphoresis that responded dramatically to Thorazine, but not to conventional measures.

Inhibition of nitric oxide synthase enhances the myocardial toxicity of phenylpropanolamine

OBJECTIVE

To investigate the direct and indirect effects of the anorexic agent phenylpropanolamine (PPA) on the heart and to determine whether nitric oxide deficiency exacerbates the myocardial toxicity of PPA.

DESIGN

Dose response effects using sequential drug administration.

SETTING

Animal research laboratory of a large tertiary academic medical center.

SUBJECTS

Isolated hearts (n = 8) from male Sprague-Dawley rats weighing 300-400 g.

INTERVENTIONS

Measurement of heart rate, maximal change in pressure over time (dP/dtmax), -dP/dtmax, and coronary blood flow in isolated hearts perfused on a Langendorff apparatus. PPA was infused through the aortic cannula at 0.05, 0.125, 0.25, 0.5, and 1.25 mmol/L before and after inhibition of nitric oxide synthesis with N-nitro-L-arginine methyl ester (L-NAME).

RESULTS

PPA had little effect on myocardial contractility of normal hearts until the highest dose of PPA (1.25 mmol/L). However, after L-NAME, PPA significantly depressed contractility at a dose of 0.25 mmol/L. PPA had no significant effects on coronary blood flow. PPA failed to induce arrhythmias in normal hearts. However, after L-NAME, PPA induced ventricular fibrillation in 50% of the hearts.

CONCLUSION

PPA causes myocardial contractile depression without altering global coronary artery blood flow. Inhibition of nitric oxide synthesis sensitizes the heart to the myocardial depressant effects of PPA and increases the risk for ventricular fibrillation.

A multifilamented electrode in the middle cardiac vein reduces energy requirements for defibrillation in the pig

OBJECTIVE

To compare the defibrillation efficacy of a novel lead system placed in the middle cardiac vein with a conventional non-thoracotomy lead system.

METHODS

In eight pigs (weighing 35-71 kg), an electrode was advanced transvenously to the right ventricular apex (RV), with the proximal electrode in the superior caval vein (SCV). Middle cardiac vein (MCV) angiography was used to delineate the anatomy before a three electrode system (length 2 x 25 mm + 1 x 50 mm) was positioned in the vein. An active housing (AH) electrode was implanted in the left pectoral region. Ventricular fibrillation was induced and biphasic shocks were delivered by an external defibrillator. The defibrillation threshold was measured and the electrode configurations randomised to: RV-->AH, RV+MCV-->AH, MCV-->AH, and RV-->SCV+AH.

RESULTS

For these configurations, mean (SD) defibrillation thresholds were 27.3 (9.6) J, 11.9 (2.9) J, 15.2 (4.3) J, and 21.8 (9.3) J, respectively. Both electrode configurations incorporating the MCV had defibrillation thresholds that were significantly less than those observed with the RV-->AH (p < 0.001) and RV-->SCV+AH (p < 0.05) configurations. Necropsy dissection showed that the MCV drained into the coronary sinus at a location close to its orifice (mean distance = 2.7 (2.2) mm). The MCV bifurcated into two main branches that drained the right and left ventricles, the left branch being the dominant vessel in the majority (6/7) of cases.

CONCLUSIONS

Placement of specialised defibrillation electrodes within the middle cardiac vein provides more effective defibrillation than a conventional tight ventricular lead.

Maternal undernutrition during the preimplantation period of rat development causes blastocyst abnormalities and programming of postnatal hypertension

Epidemiological studies have indicated that susceptibility of human adults to hypertension and cardiovascular disease may result from intrauterine growth restriction and low birth weight induced by maternal undernutrition. Although the ‘foetal origins of adult disease’ hypothesis has significant relevance to preventative healthcare, the origin and biological mechanisms of foetal programming are largely unknown. Here, we investigate the origin, embryonic phenotype and potential maternal mechanisms of programming within an established rat model. Maternal low protein diet (LPD) fed during only the preimplantation period of development (0-4.25 days after mating), before return to control diet for the remainder of gestation, induced programming of altered birthweight, postnatal growth rate, hypertension and organ/body-weight ratios in either male or female offspring at up to 12 weeks of age. Preimplantation embryos collected from dams after 0–4.25 days of maternal LPD displayed significantly reduced cell numbers, first within the inner cell mass (ICM; early blastocyst), and later within both ICM and trophectoderm lineages (mid/late blastocyst), apparently induced by a slower rate of cellular proliferation rather than by increased apoptosis. The LPD regimen significantly reduced insulin and essential amino acid levels, and increased glucose levels within maternal serum by day 4 of development. Our data indicate that long-term programming of postnatal growth and physiology can be induced irreversibly during the preimplantation period of development by maternal protein undernutrition. Further, we propose that the mildly hyperglycaemic and amino acid-depleted maternal environment generated by undernutrition may act as an early mechanism of programming and initiate conditions of ‘metabolic stress’, restricting early embryonic proliferation and the generation of appropriately sized stem-cell lineages.

Radiofrequency ablation of idiopathic left ventricular tachycardia at the site of earliest activation as determined by noncontact mapping

INTRODUCTION

The most effective method for guiding radiofrequency (RF) ablation of idiopathic left ventricular tachycardia (ILVT) has yet to be determined. We investigated the use of noncontact mapping in five patients with this condition.

METHODS AND RESULTS

The multielectrode array was positioned in the left ventricular apex via the retrograde approach. Isopotential color maps of ILVT were examined to determine the site of earliest endocardial activation. The ablation catheter was steered to the target site using the locator signal. Pace mapping was performed and contact electrograms examined for diastolic potentials. RF energy was applied to the target site. Sustained ventricular tachycardia was induced in 2 patients and nonsustained ventricular tachycardia in 3. The site of earliest activation was at the apical septum in 3, the inferior apex in 1, and the base of the inferior wall in 1. Mean timing was 21 +/- 10 msec before onset of the surface QRS. Diastolic activity was visualized with noncontact mapping at the base of the septum in 1 patient. A Purkinje potential was seen at the ablation site in only 1 patient. No diastolic activity was seen in the remaining 3 patients. Tachycardia was successfully terminated in all 5 patients with a median of four RF applications. No patient suffered a recurrence after 9.6 +/- 4.7 months of follow-up.

CONCLUSION

By identifying the precise site of earliest activation during ILVT, noncontact mapping has been shown to be an effective and safe method for guiding RF ablation.

N;-3 and n;-6 polyunsaturated fatty acids induce cytostasis in human urothelial cells independent of p53 gene function

The role of long-chain polyunsaturated fatty acids (PUFA) in the etiopathology and treatment of cancer is poorly understood. We have studied the effects of n;-3 and n;-6 PUFA on the proliferation and survival of normal human uroepithelial (NHU) cells, cells with disabled p53 function after stable transfection with the human papillomavirus 16 (HPV16) E6 gene (HU-E6), and p53-disabled cells that had passed through crisis and acquired karyotypic abnormalities (HU-E6P). The n;-3 and n;-6 PUFA had distinct reversible antiproliferative and irreversible cytostatic effects according to concentration and exposure time. The reversible antiproliferative effect was partly due to the production of lipoxygenase metabolites. NHU and HU-E6 cells were equally sensitive to n;-3 and n;-6 PUFA, but HU-E6P cells were more resistant to both the antiproliferative and cytostatic effects. Cytostatic concentrations of n;-3 and n;-6 PUFA did not induce apoptosis, but caused permanent growth arrest ("interphase" or "reproductive" cell death) and mRNA levels for genes involved in cell cycle control (p21, p16, p27, cdk1, cdk2, and cdk4) were not altered. Neither n;-3 nor n;-6 PUFA promoted acquisition of karyotypic abnormalities in HU-E6 cells, suggesting that n;-3 and n;-6 PUFA do not cause genotoxic damage. In conclusion, our studies show that the antiproliferative and cytostatic effects of n;-3 and n;-6 PUFA are not dependent on p53 function and, further, that transformation results in a loss of sensitivity to n;-3 and n;-6 PUFA-mediated growth inhibition.

Comparison of minimally invasive esophagectomy with transthoracic and transhiatal esophagectomy

HYPOTHESIS

Minimally invasive esophagectomy can be performed as safely as conventional esophagectomy and has distinct perioperative outcome advantages.

DESIGN

A retrospective comparison of 3 methods of esophagectomy: minimally invasive, transthoracic, and blunt transhiatal.

SETTING

University medical center.

PATIENTS

Eighteen consecutive patients underwent combined thoracoscopic and laparoscopic esophagectomy from October 9, 1998, through January 19, 2000. These patients were compared with 16 patients who underwent transthoracic esophagectomy and 20 patients who underwent blunt transhiatal esophagectomy from June 1, 1993, through August 5, 1998.

MAIN OUTCOME MEASURES

Operative time, amount of blood loss, number of operative transfusions, length of intensive care and hospital stays, complications, and mortality.

RESULTS

Patients who had minimally invasive esophagectomy had shorter operative times, less blood loss, fewer transfusions, and shortened intensive care unit and hospital courses than patients who underwent transthoracic or blunt transhiatal esophagectomy. There was no significant difference in the incidence of anastomotic leak or respiratory complications among the 3 groups.

CONCLUSION

Minimally invasive esophagectomy is safe and provides clinical advantages compared with transthoracic and blunt transhiatal esophagectomy.

Reduction in defibrillation threshold using an auxiliary shock delivered in the middle cardiac vein

Defibrillation in the middle cardiac vein (MCV) has been shown to reduce ventricular defibrillation thresholds (DFTs). Low amplitude auxiliary shock (AS) from an electrode sutured to the left ventricle at thoracotomy have also been shown to reduce DFT if delivered immediately prior to a biphasic shock (between the ventricular RV and superior vena caval (SVC) electrodes). This study investigates the impact on DFT of an AS shock from a transvenously placed MCV lead system. A standard defibrillation electrode was positioned in the RV in eight anesthetized pigs (35-43 kg). A 50 x 1.8-mm electrode was inserted in the MCV through an 8 Fr angioplasty guide catheter. A 150-V (leading edge) monophasic AS was delivered (95 microF capacitor) from the MCV-->Can with three different pulse widths (3, 5, 7 ms). A primary biphasic shock (PS) (95 microF capacitor, phase 1: 44% tilt, 1.6-ms extension and phase 2: 2.5-ms fixed duration) was delivered from the RV-->Can +/- AS. The four configurations were randomized and DFTs (PS + AS) assessed using a modified binary search. Ventricular fibrillation (VF) was induced with 60 Hz AC followed 10 seconds later by the test shock. The DFTs were compared using repeated measures analysis of variance (ANOVA). All configurations incorporating AS produced significant (P < 0.05) reduction in the DFT compared to no AS (13.8 +/- 7.4 J). There was no difference in the efficacy of differing pulse widths (P > 0.05); 3 ms (11.0 +/- 5.4 J), 5 ms (11.5 +/- 6.0), and 7 ms (10.6 +/- 5.3 J). In conclusion, delivering an AS from a transvenous lead system deployed in the MCV reduces the DFT by 23% compared to a conventional RV-->Can shock alone.

Electrophysiological mapping and ablation of intra-atrial reentry tachycardia after Fontan surgery with the use of a noncontact mapping system

BACKGROUND

Atrial tachyarrhythmias are a complication of Fontan surgery. Conventional electrophysiological mapping and ablation techniques are limited by the complex anatomic and surgical substrate and a high arrhythmia recurrence rate. This study investigates the use of noncontact mapping to identify arrhythmia circuits and guide ablation in Fontan patients.

METHODS AND RESULTS

Eleven arrhythmias were recorded in 6 patients. Noncontact mapping improved recognition of the anatomic and surgical substrate and identified exit sites from zones of slow conduction in all clinical arrhythmias. Radiofrequency linear lesions were targeted across these critical zones in 5 patients. One patient underwent surgical cryotherapy. Although immediate success was achieved in 3 of 5 patients with radiofrequency ablation, 2 patients had a recurrence after a mean of 6.4 months of follow-up. The patient who underwent cryoablation remains free of arrhythmias.

CONCLUSIONS

Noncontact mapping can identify arrhythmia circuits in the Fontan atrium and guide placement of ablation lesions. Arrhythmia recurrence is high, possibly because of inadequate lesion creation rather than inaccurate mapping and lesion targeting.

Practical issues in 'writing up' a research thesis

Beginning to 'write up' your research thesis can seem a daunting prospect. While the experience can be stressful, with careful planning, the process can be managed effectively, and prove both rewarding and pleasurable. Paula Roberts offers a practical guide to managing the process of writing-up. Three distinct phases are discussed: the input phase of planning the write-up; the process phase of writing-up; and the output phase ofpreparing the finished document for submission.

Cardiovascular effects of carnosine

Carnosine (beta-alanyl-L-histidine) is an endogenous dipeptide found in various cells at millimolar concentration with its specific function(s) largely unknown. Our interests in therapeutic peptides led to the discovery that carnosine dramatically increases contractility when perfused into isolated rat hearts. Carnosine's effects are not mediated by histaminic or beta-adrenergic receptors or by increasing cyclic AMP, but carnosine does cause a rise in myoplasmic Ca(2+) concentration. In chemically skinned cardiac cells, carnosine releases calcium, produces contracture, and alters the contractile protein's tension response to calcium. Carnosine also acts directly on the ryanodine receptor calcium release channel producing large increases in open state probability and dwelltime. In this manuscript, we will review studies which provide a basis for considering carnosine a modulator of calcium-regulated proteins in cardiac muscle cells and consequently an important determinant of contractility and cardiac function.