Temporal patterns of diversification across global cichlid biodiversity (Acanthomorpha: Cichlidae).

The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini) and Cichlinae (Heroini) exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake). Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates.

Evaluation of DualMesh for repair of large hiatus hernia in a porcine model.

BACKGROUND: Prosthetic fascial grafts are frequently used for augmentation of cruroplasty in large hiatus hernia repair to decrease the chances of recurrence. Potential complications such as intraluminal erosion may be related to the constant movement of mesh and diaphragm over the outer surface of the esophagus. This study aimed to evaluate DualMesh for repair of large hiatal defects in a porcine model. METHODS: In this study, 18 Landrace x large white x Duroc crossbred pigs underwent either primary hiatal repair or tension-free prosthetic repair using DualMesh (80 x 50 mm or 80 x 100 mm). The animals were killed at 3 or 28 weeks for macroscopic and histologic evaluation of the hiatal region and gastroesophageal junction. RESULTS: All grafts had become encapsulated at 28 weeks, and the majority had filmy adhesions only to the visceral aspect. In all models, the esophagus moved freely over the cut edge of the prosthesis. No signs of intraluminal erosion were documented. At histologic examination, significant ingrowth was noted on the porous side of the mesh, whereas no defined mesothelial layer was identified on the capsule of the nonporous side. CONCLUSION: In this animal model of large hiatus hernia repair, DualMesh showed optimal characteristics in terms of host tissue incorporation on the porous side and absence of adhesions on the visceral side of the prosthesis. The absence of adhesions and intraluminal erosion in this study may provide reassurance to surgeons using mesh at the hiatus.

Rapid construction of a patient-specific torso model from 3D ultrasound for non-invasive imaging of cardiac electrophysiology.

One of the main limitations in using inverse methods for non-invasively imaging cardiac electrical activity in a clinical setting is the difficulty in readily obtaining high-quality data sets to reconstruct accurately a patient-specific geometric model of the heart and torso. This issue was addressed by investigation into the feasibility of using a pseudo-3D ultrasound system and a hand-held laser scanner to reconstruct such a model. This information was collected in under 20 min prior to a catheter ablation or pacemaker study in the electrophysiology laboratory. Using the models created from these data, different activation field maps were computed using several different inverse methods. These were independently validated by comparison of the earliest site of activation with the physical location of the pacing electrodes, as determined from orthogonal fluoroscopy images. With an estimated average geometric error of approximately 8 mm, it was also possible to reconstruct the site of initial activation to within 17.3 mm and obtain a quantitatively realistic activation sequence. The study demonstrates that it is possible rapidly to construct a geometric model that can then be used non-invasively to reconstruct an activation field map of the heart.

Thrombotic risk in patients with aortic bioprostheses.

Thrombosis of Mosaic aortic valve bioprostheses occurring at more than one month after surgery occurs in 0.8% (95% CI 0.33-1.67%) of patients. In the two cases reported here, each patient had risk factors for thrombus formation, namely severe left ventricular impairment in one patient, while the other patient was heterozygous for prothrombin variant G20210A. The cases were treated successfully, by thrombolytic therapy with streptokinase in the first case, and by repeat aortic valve replacement in the second case. Thrombosis of bioprosthetic valves in the aortic position is rare, and a period of anticoagulation postoperatively does not invariably protect against this serious complication. In conclusion, patients with risk factors for thrombus formation should be considered for long-term anticoagulation.

Comparison of the temperature profile and pathological effect at unipolar, bipolar and phased radiofrequency current configurations.

With a multi-electrode catheter, phased radiofrequency (RF) delivers current between each electrode and a backplate as well as between adjacent electrodes. This study compared the tissue heating and lesion dimensions created by phased and standard RF. Ablation was performed on the in vivo thigh muscles in 5 pigs. Six lesions were created on each thigh muscle using phase angle 0 degrees RF, 127 degrees RF, 180 degrees RF with and without a backplate, and standard RF in bipolar and sequential unipolar configurations. Two plunge needles, each with 6 thermocouples 1 mm apart, were inserted into the tissue with one needle beside an electrode and the other midway between electrodes for tissue temperature measurement. The 0 degrees RF created lower tissue temperatures and smaller lesions between electrodes than those beside electrode. With 127 degrees and 180 degrees RF, tissue temperature and lesion dimensions between electrodes were similar to beside electrode, while the 127 degrees RF created higher tissue temperature and deeper lesions than 180 degrees RF (both with and without a backplate) at both sites. Standard RF bipolar ablation created similar tissue temperatures and lesion depths at both sites, but required greater power than the 127 degrees RF. Standard RF sequential unipolar ablation created only a slight temperature increase and no lesions between electrodes 3 and 4. As judged by tissue temperature, lesion depth and uniformity, and RF power requirement, 127 degrees RF may be a better energy configuration for linear ablation than the other RF modalities tested.

Opposite association of two PPARG variants with cancer: overrepresentation of H449H in endometrial carcinoma cases and underrepresentation of P12A in renal cell carcinoma cases.

Peroxisome proliferator activated receptor gamma (PPARgamma) is a nuclear hormone receptor that has been shown to regulate differentiation and cell growth. Studies of the differentiative effects of PPARgamma agonists on several cancer cell lines led to the hypothesis that dysfunction of PPARgamma contributes to tumorigenesis. These functional observations were strengthened by genetic evidence: somatic loss-of-function mutations in PPARG, encoding PPARgamma, in sporadic colorectal carcinomas and somatic translocation of PAX8 and PPARG in follicular thyroid carcinoma. Recently overrepresentation of the H449H variant was found in a cohort of American patients with glioblastoma multiforme. The glioblastoma multiforme data suggest that PPARG contributes common, low-penetrance alleles for cancer susceptibility. To test this hypothesis in a broader range of cancers we examined a series of carcinomas of the cervix, endometrium, ovary, prostate, and kidney for germline sequence variation in PPARG. In addition to the two common sequence variants, P12A and H449H, there were five other sequence variants. P12A alleles were underrepresented in renal cell carcinoma patients compared to country-of-origin race-matched controls (3.75% vs. 12.1%, P<0.04). In contrast, the H449H variant was overrepresented in individuals with endometrial carcinoma compared to controls (14.4% vs. 6.25%, P<0.02). These observations lend genetic evidence consistent with our hypothesis that PPARG serves as a common, low-penetrance susceptibility gene for cancers of several types, especially those epidemiologically associated with obesity and fat intake.

Purkinje and ventricular contributions to endocardial activation sequence in perfused rabbit right ventricle.

Interactions between peripheral conduction system and myocardial wave fronts control the ventricular endocardial activation sequence. To assess those interactions during sinus and paced ventricular beats, we recorded unipolar electrograms from 528 electrodes spaced 0.5 mm apart and placed over most of the perfused rabbit right ventricular free wall endocardium. Left ventricular contributions to electrograms were eliminated by cryoablating that tissue. Electrograms were systematically processed to identify fast (P) deflections separated by >2 ms from slow (V) deflections to measure P-V latencies. By using this criterion during sinus mapping (n = 5), we found P deflections in 22% of electrograms. They preceded V deflections at 91% of sites. Peripheral conduction system wave fronts preceded myocardial wave fronts by an overall P-V latency magnitude that measured 6.7 +/- 3.9 ms. During endocardial pacing (n = 8) at 500 ms cycle length, P deflections were identified on 15% of electrodes and preceded V deflections at only 38% of sites, and wave fronts were separated by a P-V latency magnitude of 5.6 +/- 2.3 ms. The findings were independent of apical, basal, or septal drive site. Modest changes in P-V latency accompanied cycle length accommodation to 125-ms pacing (6.8 +/- 2.6 ms), although more pronounced separation between wave fronts followed premature stimulation (11.7 +/- 10.4 ms). These results suggested peripheral conduction system and myocardial wave fronts became functionally more dissociated after premature stimulation. Furthermore, our analysis of the first ectopic beats that followed 12 of 24 premature stimuli revealed comparable separation between wave fronts (10.7 +/- 5.5 ms), suggesting the dissociation observed during the premature cycles persisted during the initiating cycles of the resulting arrhythmias.

Cost-effectiveness of spinal cord stimulation in patients with intractable angina.

AIM: To review the cost of healthcare utilisation by patients suffering from intractable angina, unsuitable for coronary revascularisation, before and after treatment with spinal cord stimulation. METHODS: Data were collected for eight patients treated for intractable angina with spinal cord stimulation at Green Lane Hospital before April 1999. Information on consumption of specified medica resources for the twelve months preceding implantation, the implantation period, and the twelve months following implantation was collected. Where available, data were also collected for the eighteen months preceding and following treatment. RESULTS: In six patients successful permanent stimulation was established; in two it proved technically impossible to implant a stimulator. The six patients with successful stimulation spent fewer days in hospital (p=0.028) and consumed fewer resources (p=0.046) following implantation than in the period before implantation. The two patients for whom spinal cord stimulation was unsuccessful spent more days in hospital and consumed more resources in the twelve months following, than in the twelve months preceding attempted implantation. Extrapolation of data for all eight patients suggests that, on average, the cost of implanting a spinal cord stimulator will be recovered in approximately fifteen months. CONCLUSION: Spinal cord stimulation is a cost-effective treatment for intractable angina pectoris.

Reentry site during fibrillation induction in relation to defibrillation efficacy for different shock waveforms.

INTRODUCTION: Unsuccessful defibrillation shocks may reinitiate fibrillation by causing postshock reentry. METHODS AND RESULTS: To better understand why some waveforms are more efficacious for defibrillation, reentry was induced in six dogs with 1-, 2-, 4-, 8-, and 16-msec monophasic and 1/1- (both phases 1 msec) 2/2-, 4/4-, and 8/8-msec biphasic shocks. Reentry was initiated by 141+/-15 V shocks delivered from a defibrillator with a 150-microF capacitance during the vulnerable period of paced rhythm (183+/-12 msec after the last pacing stimulus). The shock potential gradient field was orthogonal to the dispersion of refractoriness. Activation was mapped with 121 electrodes covering 4 x 4 cm of the right ventricular epicardium, and potential gradient and degree of recovery of excitability were estimated at the sites of reentry. Defibrillation thresholds (DFTs) were estimated by an up-down protocol for the same nine waveforms in eight dogs internally and in nine other dogs externally. DFT voltages for the different waveforms were positively correlated with the magnitude of shock potential gradient and negatively correlated with the recovery interval at the site at which reentry was induced by the waveform during paced rhythm for both internal (DFT = 1719 + 64.5VV - 11.1RI; R2 = 0.93) and external defibrillation (DFT = 3445 + 150VV - 22RI; R2 = 0.93). CONCLUSION: The defibrillation waveforms with the lowest DFTs were those that induced reentry at sites of low shock potential gradient, indicating efficacious stimulation of myocardium. Additionally, the site of reentry induced by waveforms with the lowest DFTs was in myocardium that was more highly recovered just before the shock, perhaps because this high degree of recovery seldom occurs during defibrillation due to the rapid activation rate during fibrillation.

PTEN inhibits insulin-stimulated MEK/MAPK activation and cell growth by blocking IRS-1 phosphorylation and IRS-1/Grb-2/Sos complex formation in a breast cancer model.

The tumour suppressor gene PTEN encodes a dual-specificity phosphatase that recognizes protein substrates and phosphatidylinositol-3,4,5-triphosphate. PTEN seems to play multiple roles in tumour suppression and the blockade of phosphoinositide-3-kinase signalling is important for its growth suppressive effects, although precise mechanisms are not fully understood. In this study, we show that PTEN plays a unique role in the insulin-signalling pathway in a breast cancer model. Ectopic expression of wild-type PTEN in MCF-7 epithelial breast cancer cells resulted in universal inhibition of Akt phosphorylation in response to stimulation by diverse growth factors and selective inhibition of MEK/extracellular signal-regulated kinase (ERK) phosphorylation stimulated by insulin or insulin-like growth factor 1 (IGF-1). The latter was accompanied by a decrease in the phosphorylation of insulin receptor substrate 1 (IRS-1) and the association of IRS-1 with Grb2/Sos, without affecting the phosphorylation status of the insulin receptor and Shc, nor Shc/Grb2 complex formation. The MEK inhibitor, PD980059, but not the PI3K inhibitor, wortmannin, abolished the effect of PTEN on insulin-stimulated cell growth. Without addition of insulin, wortmannin reduced PTEN-mediated growth suppression, whereas PD980059 had little effect, suggesting that PTEN suppresses insulin-stimulated cell growth by blocking the mitogen-activated protein kinase (MAPK) pathway. Furthermore, PD980059 treatment led to the downregulation of cyclin D1 and the suppression of cell cycle progression. Our data suggest that PTEN blocks MAPK phosphorylation in response to insulin stimulation by inhibiting the phosphorylation of IRS-1 and IRS-1/Grb2/Sos complex formation, which leads to downregulation of cyclin D1, inhibition of cell cycle progression and suppression of cell growth.

Improvement of defibrillation efficacy and quantification of activation patterns during ventricular fibrillation in a canine heart failure model.

BACKGROUND: Little is known about the effects of heart failure (HF) on the defibrillation threshold (DFT) and the characteristics of activation during ventricular fibrillation (VF). METHODS AND RESULTS: HF was induced by rapid right ventricular (RV) pacing for at least 3 weeks in 6 dogs. Another 6 dogs served as controls. Catheter defibrillation electrodes were placed in the RV apex, the superior vena cava, and the great cardiac vein (CV). An active can coupled to the superior vena cava electrode served as the return for the RV and CV electrodes. DFTs were determined before and during HF for a shock through the RV electrode with and without a smaller auxiliary shock through the CV electrode. VF activation patterns were recorded in HF and control animals from 21x24 unipolar electrodes spaced 2 mm apart on the ventricular epicardium. Using these recordings, we computed a number of quantitative VF descriptors. DFT was unchanged in the control dogs. DFT energy was increased 79% and 180% (with and without auxiliary shock, respectively) in HF compared with control dogs. During but not before HF, DFT energy was significantly lowered (21%) by addition of the auxiliary shock. The VF descriptors revealed marked VF differences between HF and control dogs. The differences suggest decreased excitability and an increased refractory period during HF. Most, but not all, descriptors indicate that VF was less complex during HF, suggesting that VF complexity is multifactorial and cannot be expressed by a scalar quantity. CONCLUSIONS: HF increases the DFT. This is partially reversed by an auxiliary shock. HF markedly changes VF activation patterns.

Transient ectopic expression of PTEN in thyroid cancer cell lines induces cell cycle arrest and cell type-dependent cell death.

The tumour suppressor gene PTEN/MMAC1/TEP1 has been implicated in a variety of human cancers and several inherited hamartoma tumour syndromes, including Cowden syndrome, which has a high risk of breast and thyroid cancer. We have previously reported that overexpression of PTEN in MCF-7 breast cancer cells induces cell cycle arrest and apoptosis. In this study, we analysed PTEN status at both the structural and expression levels and explored PTEN's growth-suppressive effects on thyroid. We found that 1 of 10 thyroid cancer lines [follicular thyroid carcinoma FTC-133] had hemizygous deletion and a splice variant IVS4--19G-->A in the remaining allele. Four lines, including FTC-133, express PTEN mRNA at low levels. In general, PTEN protein levels correlated with mRNA levels, except for NPA87, which has low levels of transcript and relatively high levels of PTEN protein. Transient expression of PTEN in seven thyroid cancer cell lines resulted in G(1) arrest in two well differentiated papillary thyroid cancer lines (PTCs) and both G(1) arrest and cell death in the remaining five lines, including three FTCs, one poorly differentiated PTC and one undifferentiated thyroid cancer. The level of phosphorylated Akt was inversely correlated with the endogenous level of PTEN protein and overexpression of PTEN-blocked Akt phosphorylation in all cells analysed. Our results suggest that downregulation of PTEN expression at the mRNA level plays a role in PTEN inactivation in thyroid cancer and PTEN exerts its tumour-suppressive effect on thyroid cancer through the inhibition of cell cycle progression alone or both cell cycle progression and cell death.

Direct medical cost of chronic obstructive pulmonary disease in the U.S.A.

The aim of this study was to estimate the direct medical costs of chronic obstructive pulmonary disease (COPD) in the United States using a public-payor perspective. Cost estimates were derived separately for 10 components of care using national survey databases and valued using Medicare and Medicaid reimbursement rates. COPD affects 15 million people in the U.S.A. and the total annual U.S. payment for care is $6.6 billion. Approximately one-third ($2.3 billion) is due to the cost of long-term oxygen therapy, one-quarter is attributed to hospitalizations and inpatient physician services ($1.9 billion), and one-seventh ($942 million) is due to nursing home stays. Other annual costs are outpatient physician visits ($480 million), prescription medications ($462 million), home healthcare ($309 million), emergency department visits ($148 million), outpatient diagnostic procedures ($55 million) and hospice care ($28 million). The cost of COPD is therefore considerable. The significant expenditure for long-term oxygen therapy indicates that disease severity is a major driver of costs. However, the cost of hospitalizations, nursing home stays, emergency department and physician visits are not insignificant.

Reduction of atrial defibrillation threshold with an interatrial septal electrode.

BACKGROUND: The standard lead configuration for internal atrial defibrillation consists of a shock between electrodes in the right atrial appendage (RAA) and coronary sinus (CS). We tested the hypothesis that the atrial defibrillation threshold (ADFT) of this RAA-->CS configuration would be lowered with use of an additional electrode at the atrial septum (SP). METHODS AND RESULTS: Sustained atrial fibrillation was induced in 8 closed-chest sheep with burst pacing and continuous pericardial infusion of acetyl-ss-methylcholine. Defibrillation electrodes were situated in the RAA, CS, pulmonary artery (PA), low right atrium (LRA), and across the SP. ADFTs of RAA-->CS and 4 other lead configurations were determined in random order by use of a multiple-reversal protocol. Biphasic waveforms of 3/1-ms duration were used for all single and sequential shocks. The ADFT delivered energies for the single-shock configurations were 1.27+/-0.67 J for RAA-->CS and 0. 86+/-0.59 J for RAA+CS-->SP; the ADFTs for the sequential-shock configurations were 0.39+/-0.18 J for RAA-->SP/CS-->SP, 1.16+/-0.72 J for CS-->SP/RAA-->SP, and 0.68+/-0.46 J for RAA-->CS/LRA-->PA. Except for CS-->SP/RAA-->SP versus RAA-->CS and RAA-->CS/LRA-->PA versus RAA+CS-->SP, the ADFT delivered energies of all of the configurations were significantly different from each other (P:<0. 05). CONCLUSIONS: The ADFT of the standard RAA-->CS configuration is markedly reduced with an additional electrode at the atrial SP.

Signal averaging in Wolff-Parkinson-White syndrome: evidence that fractionated activation is not necessary for body surface high-frequency potentials.

It is commonly assumed that the presence of high frequency components in body surface potentials implies that fractionated activation fronts, caused by heterogeneously viable tissue, are present in the heart. However, it is possible that non-fractionated activation fronts can also give rise to high frequency surface potentials and that the relative amount of high frequency power is related to the complexity of the activation sequence. In a test of this idea, averaged body surface potentials were recorded during the entire QRS complex of nine Wolff-Parkinson-White (WPW) patients in situations in which fractionated activation fronts should not have been present, but which represent increasing degrees of complexity of ventricular activation: (1) postoperative ectopic pacing from subepicardial wires placed during surgery, when a single coherent activation front was present throughout most of the QRS; (2) Preoperative preexcited rhythm, when a single coherent activation front was present for one portion of the QRS (the delta wave); and (3) postoperative normal rhythm, when two or more activation fronts were present in the ventricles throughout most of the QRS. For comparison, averaged body surface potentials were also analyzed during the last 40 ms of the QRS complex and the ST segment of 14 postinfarction patients with chronic ventricular tachycardia. In the patients with WPW syndrome, relatively high frequency content increased (attenuation -36.7 vs -27.2 vs -18.3 dB) and QRS width decreased (160.7 vs 125.9 vs 94.1 ms) significantly from paced to preoperative to postoperative beats. Significant high frequency content was present in all cases, showing that coherent activation fronts can give rise to high frequencies. Interestingly, the postoperative QRS of WPW patients contained a larger proportion of high frequency power than did the late potentials of the patients with ventricular tachycardia. Thus, while the presence of late fractionated body surface potentials may be a marker for ventricular tachycardia, these potentials by themselves do not necessarily signify that the underlying cardiac activation giving rise to these signals is fractionated.

A telemetry system for the study of spontaneous cardiac arrhythmias.

The characteristics of spontaneous cardiac arrhythmias leading to sudden cardiac death are largely unknown. To study arrhythmias in animal models, an eight-channel implantable radio telemetry system has been developed to record continuously cardiac electrograms over a period of weeks to months, with maintenance restricted to changing batteries. The inputs are connected in a unipolar manner. Each channel has a gain of fifty and is AC coupled, band limited to 0.07-260 Hz. The signals are digitized with 12 bits resolution at 1000 samples/s. The amplifiers, analog-to-digital converter, and control logic are packaged in an implantable unit. An umbilical cable is passed through the skin to an external backpack unit for power and data transmission. A custom serial interface card, a PC/104 form factor 25-MHz 80386-based single-board computer with a PCMCIA wireless local area network (WLAN) card, and battery power supply make up the backpack. Data are read into the parallel port of the computer, buffered, then transmitted over the WLAN to the laboratory network where it can be analyzed and archived. Approximately 12 h of 14,000 bytes/s data can be collected with each set of batteries. The system is suitable for continuous monitoring of animal models of spontaneous arrhythmias and sudden cardiac death.

Three-dimensional mapping of spontaneous ventricular arrhythmias in a canine thrombotic coronary occlusion model.

INTRODUCTION: Ventricular tachycardia (VT) and ventricular fibrillation (VF) induced by thrombotic coronary occlusion were mapped in three dimensions in ten dogs. METHODS AND RESULTS: Thrombotic occlusion was induced using a wire to deliver current to the proximal left circumflex artery (LCX). In nine dogs, nonsustained VT (NSVT) arose from numerous focal sites. Sustained VT was initiated in six dogs (VT group) by a focus near or in the ischemic region. VT was maintained by a focus in the ischemic border in three dogs and by macroreentry that involved both the ischemic and nonischemic regions in the other three dogs. In five dogs, VT degenerated into VF due to intramural reentry in different locations. Mean total activation time (AT), the time for activation to traverse the ventricles, for a sinus beat when LCX current was first applied was 40 +/- 4 msec. In the four dogs in which VT occurred 3 to 7 minutes after total occlusion, sinus AT increased to 98 to 146 msec just before VT. Sinus AT in the four dogs without VT was always <98 msec. Mean AT of the first ten cycles of VT was significantly longer in those VTs that degenerated into VF (169 +/- 29 msec) than in those that did not (81 +/- 12 msec). CONCLUSION: Thrombotic LCX occlusion induced NSVT in 90%, VT in 60%, and VF in 50% of dogs. Focal mechanisms caused most NSVTs and VT initiation. VT was maintained by a focus near or in the ischemic region or by macroreentry involving both the ischemic and nonischemic regions. AT identified animals in which VT occurred soon after LCX occlusion and in which VT progressed to VF.