Normalization of postinfarct biomechanics using a novel tissue-engineered angiogenic construct

BACKGROUND

Cell-mediated angiogenic therapy for ischemic heart disease has had disappointing results. The lack of clinical translatability may be secondary to cell death and systemic dispersion with cell injection. We propose a novel tissue-engineered therapy, whereby extracellular matrix scaffold seeded with endothelial progenitor cells (EPCs) can overcome these limitations using an environment in which the cells can thrive, enabling an insult-free myocardial cell delivery to normalize myocardial biomechanics.

METHODS AND RESULTS

EPCs were isolated from the long bones of Wistar rat bone marrow. The cells were cultured for 7 days in media or seeded at a density of 5 × 10(6) cells/cm(2) on a collagen/vitronectin matrix. Seeded EPCs underwent ex vivo modification with stromal cell-derived factor-1α (100 ng/mL) to potentiate angiogenic properties and enhance paracrine qualities before construct formation. Scanning electron microscopy and confocal imaging confirmed EPC-matrix adhesion. In vitro vasculogenic potential was assessed by quantifying EPC cell migration and vascular differentiation. There was a marked increase in vasculogenesis in vitro as measured by angiogenesis assay (8 versus 0 vessels/hpf; P=0.004). The construct was then implanted onto ischemic myocardium in a rat model of acute myocardial infarction. Confocal microscopy demonstrated a significant migration of EPCs from the construct to the myocardium, suggesting a direct angiogenic effect. Myocardial biomechanical properties were uniaxially quantified by elastic modulus at 5% to 20% strain. Myocardial elasticity normalized after implant of our tissue-engineered construct (239 kPa versus normal=193, P=0.1; versus infarct=304 kPa, P=0.01).

CONCLUSIONS

We demonstrate restoration and normalization of post-myocardial infarction ventricular biomechanics after therapy with an angiogenic tissue-engineered EPC construct.

Sustained release of engineered stromal cell-derived factor 1-α from injectable hydrogels effectively recruits endothelial progenitor cells and preserves ventricular function after myocardial infarction

BACKGROUND

Exogenously delivered chemokines have enabled neovasculogenic myocardial repair in models of ischemic cardiomyopathy; however, these molecules have short half-lives in vivo. In this study, we hypothesized that the sustained delivery of a synthetic analog of stromal cell-derived factor 1-α (engineered stromal cell-derived factor analog [ESA]) induces continuous homing of endothelial progenitor cells and improves left ventricular function in a rat model of myocardial infarction.

METHODS AND RESULTS

Our previously designed ESA peptide was synthesized by the addition of a fluorophore tag for tracking. Hyaluronic acid was chemically modified with hydroxyethyl methacrylate to form hydrolytically degradable hydrogels through free-radical-initiated crosslinking. ESA was encapsulated in hyaluronic acid hydrogels during gel formation, and then ESA release, along with gel degradation, was monitored for more than 4 weeks in vitro. Chemotactic properties of the eluted ESA were assessed at multiple time points using rat endothelial progenitor cells in a transwell migration assay. Finally, adult male Wistar rats (n=33) underwent permanent ligation of the left anterior descending (LAD) coronary artery, and 100 µL of saline, hydrogel alone, or hydrogel+25 µg ESA was injected into the borderzone. ESA fluorescence was monitored in animals for more than 4 weeks, after which vasculogenic, geometric, and functional parameters were assessed to determine the therapeutic benefit of each treatment group. ESA release was sustained for 4 weeks in vitro, remained active, and enhanced endothelial progenitor cell chemotaxis. In addition, ESA was detected in the rat heart >3 weeks when delivered within the hydrogels and significantly improved vascularity, ventricular geometry, ejection fraction, cardiac output, and contractility compared with controls.

CONCLUSIONS

We have developed a hydrogel delivery system that sustains the release of a bioactive endothelial progenitor cell chemokine during a 4-week period that preserves ventricular function in a rat model of myocardial infarction.

Continuous flow left ventricular assist device implant significantly improves pulmonary hypertension, right ventricular contractility, and tricuspid valve competence

BACKGROUND

Continuous flow left ventricular assist devices (CF LVAD) are being implanted with increasing frequency for end-stage heart failure. At the time of LVAD implant, a large proportion of patients have pulmonary hypertension, right ventricular (RV) dysfunction, and tricuspid regurgitation (TR). RV dysfunction and TR can exacerbate renal dysfunction, hepatic dysfunction, coagulopathy, edema, and even prohibit isolated LVAD implant. Repairing TR mandates increased cardiopulmonary bypass time and bicaval cannulation, which should be reserved for the time of orthotopic heart transplantation. We hypothesized that CF LVAD implant would improve pulmonary artery pressures, enhance RV function, and minimize TR, obviating need for surgical tricuspid repair.

METHODS

One hundred fourteen continuous flow LVADs implanted from 2005 through 2011 at a single center, with medical management of functional TR, were retrospectively analyzed. Pulmonary artery pressures were measured immediately prior to and following LVAD implant. RV function and TR were graded according to standard echocardiographic criteria, prior to, immediately following, and long-term following LVAD.

RESULTS

There was a significant improvement in post-VAD mean pulmonary arterial pressures (26.6 ± 4.9 vs. 30.2 ± 7.4 mmHg, p = 0.008) with equivalent loading pressures (CVP = 12.0 ± 4.0 vs. 12.1 ± 5.1 p = NS). RV function significantly improved, as noted by right ventricular stroke work index (7.04 ± 2.60 vs. 6.05 ± 2.54, p = 0.02). There was an immediate improvement in TR grade and RV function following LVAD implant, which was sustained long term.

CONCLUSION

Continuous flow LVAD implant improves pulmonary hypertension, RV function, and tricuspid regurgitation. TR may be managed nonoperatively during CF LVAD implant.

Assessing the reach of nicotine replacement therapy as a preventive public health measure

INTRODUCTION

Access to Nicotine Replacement Therapy (NRT) is a key public health intervention to reduce smoking. We assessed prevalence and correlates of use of NRT in Ontario, where NRT is available without prescription.

METHODS

Participants were a representative sample of 2262 adult smokers in the Ontario Tobacco Survey cohort. Prospectively measured use of NRT over a 6-month period was reported in relation to smoking behaviour and history, attempts to quit, receipt of other supports for cessation supports and attitudes toward NRT.

RESULTS

Overall, 11% of smokers used NRT over the six-month follow-up period. Prevalence was 25% among the 27% of smokers matching clinical guidelines that recommend NRT as a therapeutic option, and low among smokers not trying to quit.

CONCLUSION

With increasing accessibility of NRT, further surveillance and research are warranted to determine the impact of the reach and benefits of NRT, considering both the general and targeted smoking populations.

Rehabilitation outcomes of stroke patients treated with multi-modal endovascular reperfusion therapy

AIM

The aim of this study was to investigate the influence of multi-modal endovascular reperfusion therapy (MMRT) on functional outcomes following rehabilitation.

METHODS

Data from 14 MMRT-treated patients were analyzed and compared to MMRT-ineligible, age and stroke severity-matched patients treated at the same Neurological and Rehabilitation departments. Neurological evaluation was assessed with the NIH stroke scale (NIHSS). Activity of daily living was measured using the FIMTM instrument. Functional outcome was measured using the modified Rankin scale (mRS).

RESULTS

The baseline characteristics of both groups were similar. NIHSS scores were lower in the MMRT group and they had slightly better functional and rehabilitation scores on admission to rehabilitation. At the end of rehabilitation, more MMRT-treated patients reached functional independence (mRS≤2; 50% vs. 7% respectively P=0.03). FIM scores were also higher in the MMRT group (mean score 93.3 vs. 87.7, respectively) but the difference did not reach significance. The delta in FIM and NIHSS scores obtained during rehabilitation did not significantly differ between the groups. MMRT remained a significant modifier of good outcome after regression analysis (OR 21.5 95% CI 1.1-410).

CONCLUSION

MMRT-treated patients have better chances of attaining independence after rehabilitation therapy. However, the additional improvements gained while in active rehabilitation were independent of reperfusion status.

Multimodal reperfusion therapy for large hemispheric infarcts in octogenarians: is good outcome a realistic goal?

BACKGROUND AND PURPOSE

MMRT may be beneficial in a subset of patients with large hemispheric stroke who cannot be treated with systemic thrombolysis. Because most previous studies only included relatively young patients, the outcome of very old patients given MMRT remains unknown.

MATERIALS AND METHODS

Consecutive patients with large hemispheric stroke treated with MMRT and admitted to intensive care were included. We compared neurologic and functional outcomes between patients younger and older than 80 years.

RESULTS

We included 14 patients older than 80 years and compared them with 66 patients who were younger than 80. Cerebrovascular risk factor profile, admission NIHSS scores, stroke etiology and pathogenesis, and procedure-related variables did not differ between the groups except for a higher prevalence of smoking in younger patients. Excellent target vessel recanalization (Thrombolysis in Myocardial Infarction score of 3) and good outcome at 90 days (modified Rankin Score ≤ 2) were more common in younger patients (45% versus 14%, P = .047, and 41% versus 0%, P = .008, respectively). In contrast, mortality rates were higher in octogenarians (43% versus 17%, respectively).

CONCLUSIONS

In this study, very old patients had higher chances of mortality and a very low probability of achieving functional independence even after MMRT. Further prospective studies are needed to examine the futility of MMRT in the very old.

Visual failure and recovery after thrombosis of a giant carotid ophthalmic aneurysm following vascular bypass and carotid artery ligation

Thrombosis via Hunterian ligation, with or without high-flow bypass, is the definitive treatment for unclippable giant aneurysms; however, secondary deterioration may occur. We present a 67-year-old woman with an unclippable giant (33mm) carotid ophthalmic aneurysm. High-flow external carotid artery to middle cerebral artery bypass and proximal cervical internal carotid artery Hunterian ligation achieved complete thrombosis. Subsequent expansion of the thrombosed aneurysm created mass effect with hydrocephalus, leading to marked cognitive and visual decline. Aneurysmal decompression led to improved vision and near-normal neurological function.

Stromal cell-derived factor-1alpha activation of tissue-engineered endothelial progenitor cell matrix enhances ventricular function after myocardial infarction by inducing neovasculogenesis

BACKGROUND

Myocardial ischemia causes cardiomyocyte death, adverse ventricular remodeling, and ventricular dysfunction. Endothelial progenitor cells (EPCs) have been shown to ameliorate this process, particularly when activated with stromal cell-derived factor-1α (SDF), known to be the most potent EPC chemokine. We hypothesized that implantation of a tissue-engineered extracellular matrix (ECM) scaffold seeded with EPCs primed with SDF could induce borderzone neovasculogenesis, prevent adverse geometric remodeling, and preserve ventricular function after myocardial infarction.

METHODS AND RESULTS

Lewis rats (n=82) underwent left anterior descending artery ligation to induce myocardial infarction. EPCs were isolated, characterized, and cultured on a vitronectin/collagen scaffold and primed with SDF to generate the activated EPC matrix (EPCM). EPCM was sutured to the anterolateral left ventricular wall, which included the region of ischemia. Control animals received sutures but no EPCM. Additional groups underwent application of the ECM alone, ECM primed with SDF (ECM+SDF), and ECM seeded with EPCs but not primed with SDF (ECM+SDF). At 4 weeks, borderzone myocardial tissue demonstrated increased levels of vascular endothelial growth factor in the EPCM group. When compared to controls, Vessel density as assessed by immunohistochemical microscopy was significantly increased in the EPCM group (4.1 versus 6.2 vessels/high-powered field; P<0.001), and microvascular perfusion measured by lectin microangiography was enhanced 4-fold (0.7% versus 2.7% vessel volume/section volume; P=0.04). Comparisons to additional groups also showed a significantly improved vasculogenic response in the EPCM group. Ventricular geometry and scar fraction assessed by digital planimetric analysis of sectioned hearts exhibited significantly preserved left ventricular internal diameter (9.7 mm versus 8.6 mm; P=0.005) and decreased infarct scar formation expressed as percent of total section area (16% versus 7%; P=0.002) when compared with all other groups. In addition, EPCM animals showed a significant preservation of function as measured by echocardiography, pressure-volume conductance, and Doppler flow.

CONCLUSIONS

Extracellular matrix seeded with EPCs primed with SDF induces borderzone neovasculogenesis, attenuates adverse ventricular remodeling, and preserves ventricular function after myocardial infarction.

Acute myocardial rescue with endogenous endothelial progenitor cell therapy

PURPOSE

Post-myocardial infarction heart failure is a major health concern with limited therapy. Molecular revascularisation utilising granulocyte-macrophage colony stimulating factor (GMCSF) mediated endothelial progenitor cell (EPC) upregulation and stromal cell derived factor-1α (SDF) mediated myocardial EPC chemokinesis, may prevent myocardial loss and adverse remodelling. Vasculogenesis, viability, and haemodynamic improvements following therapy were investigated.

PROCEDURES

Lewis rats (n=91) underwent LAD ligation and received either intramyocardial SDF and subcutaneous GMCSF or saline injections at the time of infarction. Molecular and haemodynamic assessments were performed at pre-determined time points following ligation.

FINDINGS

SDF/GMCSF therapy upregulated EPC density as shown by flow cytometry (0.12±0.02% vs. 0.06±0.01% circulating lymphocytes, p=0.005), 48hours following infarction. A marked increase in perfusion was evident eight weeks after therapy, utilising confocal angiography (5.02±1.7×10(-2)μm(3)blood/μm(3)myocardial tissue vs. 2.03±0.710(-2)μm(3)blood/μm(3)myocardial tissue, p=0.00004). Planimetric analysis demonstrated preservation of wall thickness (0.98±0.09mm vs. 0.67±0.06mm, p=0.003) and ventricular diameter (7.81±0.99mm vs. 9.41±1.1mm, p=0.03). Improved haemodynamic function was evidenced by echocardiography and PV analysis (ejection fraction: 56.4±18.1% vs. 25.3±15.6%, p=0.001; pre-load adjusted maximal power: 6.6±2.6mW/μl(2) vs. 2.7±1.4mW/μl(2), p=0.01).

CONCLUSION

Neovasculogenic therapy with GMCSF-mediated EPC upregulation and SDF-mediated EPC chemokinesis maybe an effective therapy for infarct modulation and preservation of myocardial function following acute myocardial infarction.

Convexity properties of products of random nonnegative matrices

Consider a sequence of N x N random nonnegative matrices in which each element depends on a vector u of parameters. The nth partial product is the random matrix formed by multiplying, from right to left, the first n of these random matrices in order. Under certain conditions, the elements of the nth partial product grow asymptotically exponentially as n increases, and the logarithms of the discrete long-run growth rates are convex functions of u. These conditions are met by some models in statistical mechanics and demography. Consequently, the Helmholtz free energy is concave and the population growth rate is convex in these models.

Food webs and the dimensionality of trophic niche space

If the trophic niche of a kind of organism is a connected region in niche space, then it is possible for trophic niche overlaps to be described in a one-dimensional niche space if and only if the trophic niche overlap graph is an interval graph. An analysis of 30 food webs, using the combinatorial theory of interval graphs, suggests that a niche space of dimension 1 suffices, with unexpectedly high frequency and perhaps always, to describe the trophic niche overlaps implied by real food webs in single habitats. Consequently, real food webs fall in a small subset of the set of mathematically possible food webs. That real food webs are compatible with one-dimensional trophic niche spaces, more often than can be explained by chance alone, has not been noticed previously.

Predictive validity and measurement issues in documenting quit intentions in population surveillance studies

INTRODUCTION

Discrete classification of smokers by intention to quit is desirable in many public health and clinical settings.

METHODS

Two methodological studies examine measurement properties of measures of discrete-time intention to quit smoking used in population-based tobacco surveillance surveys: an ecological comparison of rates of positive intention in relation to the form of measure used and a prospective analysis examining predictive validity of self-reported quit intentions using multiple possible points of dichotomization of an ordinal measure of intention to quit. The prospective analysis used a repeated measures design and follow-up to 1 year for 2,047 smokers in the Ontario Tobacco Survey cohort.

RESULTS

The estimated percent of smokers intending to quit was significantly higher using the Stages of Change intention measure, relative to another single question measure. Significant dose-response effects were found. The sooner one intended to quit the more likely one was to make an attempt or achieve at least 30 days abstinence in the next 6 months. Intending to quit in a month or later was not associated with cessation during follow-up among respondents without prior attempts. Examination of cutpoints revealed no value, which maximized both positive and negative prediction. Regardless of quit attempt history, greatest predictive validity was found where respondents stated that they had no intention at all.

DISCUSSION

Measures of intentions quit smoking in specific time periods and expressed as dichotomies have limited psychometric properties but utility in applied research. Our findings suggest a possible measurement effect warranting caution in comparisons across studies.

Risk score derived from pre-operative data analysis predicts the need for biventricular mechanical circulatory support

BACKGROUND

Right ventricular (RV) failure after left ventricular assist device (LVAD) placement is a serious complication and is difficult to predict. In the era of destination therapy and the total artificial heart, predicting post-LVAD RV failure requiring mechanical support is extremely important.

METHODS

We reviewed patient characteristics, laboratory values and hemodynamic data from 266 patients who underwent LVAD placement at the University of Pennsylvania from April 1995 to June 2007.

RESULTS

Of 266 LVAD recipients, 99 required RV assist device (BiVAD) placement (37%). We compared 36 parameters between LVAD (n = 167) and BiVAD patients (n = 99) to determine pre-operative risk factors for RV assist device (RVAD) need. By univariate analysis, 23 variables showed statistically significant differences between the two groups (p < or = 0.05). By multivariate logistic regression, cardiac index < or =2.2 liters/min/m(2) (odds ratio [OR] 5.7), RV stroke work index < or =0.25 mm Hg . liter/m(2) (OR 5.1), severe pre-operative RV dysfunction (OR 5.0), pre-operative creatinine > or =1.9 mg/dl (OR 4.8), previous cardiac surgery (OR 4.5) and systolic blood pressure < or =96 mm Hg (OR 2.9) were the best predictors of RVAD need.

CONCLUSIONS

The most significant predictors for RVAD need were cardiac index, RV stroke work index, severe pre-operative RV dysfunction, creatinine, previous cardiac surgery and systolic blood pressure. Using these data, we constructed an algorithm that can predict which LVAD patients will require RVAD with >80% sensitivity and specificity.

Modeling the population dynamics of a cuckoo-host association and the evolution of host defenses

Cuckoo parasitism in Nagano Prefecture in Japan has shown dramatic changes in the parasitism rate, host usage by the cuckoo, and defensive behavior of hosts during the past 60 yr. To gain insights into these phenomena, we model the population dynamics of a cuckoo-host association together with the population genetics of a rejecter gene in the host population. Analysis shows that both the dynamical change in the host-parasite association and the establishment of the host's counteradaptation crucially depend on the product of two factors, the carrying capacity of the host and cuckoo's searching efficiency. When the product is less than a critical value, the host population cannot evolve a counteradaptation even if parasitized by the cuckoo. Hence, the lack of counteradaptation does not necessarily imply that the host population only recently has become parasitized. As the product becomes larger, the rejection behavior will be eventually established at higher levels in the host population In this case, the spreading of rejection behavior is very fast, which suggests that the cuckoo-host association reaches an equilibrium state within a relatively short period. These results make possible new interpretations of several circumstances reported about cuckoo-host associations.

Early planned institution of biventricular mechanical circulatory support results in improved outcomes compared with delayed conversion of a left ventricular assist device to a biventricular assist device

OBJECTIVE

It is generally accepted that patients who require biventricular assist device support have poorer outcomes than those requiring isolated left ventricular assist device support. However, it is unknown how the timing of biventricular assist device insertion affects outcomes. We hypothesized that planned biventricular assist device insertion improves survival compared with delayed conversion of left ventricular assist device support to biventricular assist device support.

METHODS

We reviewed and compared outcomes of 266 patients undergoing left ventricular assist device or biventricular assist device placement at the University of Pennsylvania from April 1995 to June 2007. We subdivided patients receiving biventricular assist devices into planned biventricular assist device (P-BiVAD) and delayed biventricular assist device (D-BiVAD) groups based on the timing of right ventricular assist device insertion. We defined the D-BiVAD group as any failure of isolated left ventricular assist device support.

RESULTS

Of 266 patients who received left ventricular assist devices, 99 (37%) required biventricular assist device support. We compared preoperative characteristics, successful bridging to transplantation, survival to hospital discharge, and Kaplan-Meier 1-year survival between the P-BiVAD (n = 71) and D-BiVAD (n = 28) groups. Preoperative comparison showed that patients who ultimately require biventricular support have similar preoperative status. Left ventricular assist device (n = 167) outcomes in all categories exceeded both P-BiVAD and D-BiVAD group outcomes. Furthermore, patients in the P-BiVAD group had superior survival to discharge than patients in the D-BiVAD group (51% vs 29%, P < .05). One-year and long-term Kaplan-Meier survival distribution confirmed this finding. There was also a trend toward improved bridging to transplantation in the P-BiVAD (n = 55) versus D-BiVAD (n = 22) groups (65% vs 45%, P = .10).

CONCLUSION

When patients at high risk for failure of isolated left ventricular assist device support are identified, proceeding directly to biventricular assist device implantation is advised because early institution of biventricular support results in dramatic improvement in survival.

Transmyocardial revascularization to enhance myocardial vasculogenesis and hemodynamic function

OBJECTIVE

A significant number of patients have coronary artery disease that is not amenable to traditional revascularization. Prospective, randomized clinical trials have demonstrated therapeutic benefits with transmyocardial laser revascularization in this cohort. The molecular mechanisms underlying this therapy, however, are poorly understood. The focus of this study was evaluation of the proposed vasculogenic mechanisms involved in transmyocardial laser revascularization.

METHODS

Male Yorkshire pigs (30-35 kg, n = 25) underwent left thoracotomy and placement of ameroid constrictors around the proximal left circumflex coronary artery. During the next 4 weeks, a well-defined region of myocardial ischemia developed, and the animals underwent a redo left thoracotomy. The animals were randomly assigned to sham treatment (thoracotomy only, control, n = 11) or transmyocardial laser revascularization of hibernating myocardium with a holmium:yttrium-aluminum-garnet laser (n = 14). After an additional 4 weeks, the animals underwent median sternotomy, echocardiographic analysis of wall motion, and hemodynamic analysis with an ascending aortic flow probe and pulmonary artery catheter. The hearts were explanted for molecular analysis.

RESULTS

Molecular analysis demonstrated statistically significant increases in the proangiogenic proteins nuclear factor kappaB (42 +/- 27 intensity units vs 591 +/- 383 intensity units, P = .03) and angiopoietin 1 (0 +/- 0 intensity units vs 241 +/- 87 intensity units, P = .003) relative to sham control values with transmyocardial laser revascularization within the ischemic myocardium. There were also increases in vasculogenesis (18.8 +/- 8.7 vessels/high-power field vs 31.4 +/- 10.2 vessels/high-power field, P = .02), and perfusion (0.028 +/- 0.009 microm3 blood/microm3 tissue vs 0.044 +/- 0.004 microm3 blood/microm3 tissue, P = .01). Enhanced myocardial viability was demonstrated by increased myofilament density (40.7 +/- 8.5 cardiomyocytes/high-power field vs 50.8 +/- 7.5 cardiomyocytes/high-power field, P = .03). Regional myocardial function within the treated territory demonstrated augmented contractility. Global hemodynamic function was significantly improved relative to the control group with transmyocardial laser revascularization (cardiac output 2.1 +/- 0.2 L/min vs 2.7 +/- 0.2 L/min, P = .007, mixed venous oxygen saturation 64.7% +/- 3.6% vs 76.1% +/- 3.4%, P = .008).

CONCLUSION

Transmyocardial laser revascularization with the holmium-YAG laser enhances perfusion, with resultant improvement in myocardial contractility.

Ischemic heart failure enhances endogenous myocardial apelin and APJ receptor expression

Apelin interacts with the APJ receptor to enhance inotropy. In heart failure, apelin-APJ coupling may provide a means of enhancing myocardial function. The alterations in apelin and APJ receptor concentrations with ischemic cardiomyopathy are poorly understood. We investigated the compensatory changes in endogenous apelin and APJ levels in the setting of ischemic cardiomyopathy.Male, Lewis rats underwent LAD ligation and progressed into heart failure over 6 weeks. Corresponding animals underwent sham thoracotomy as control. Six weeks after initial surgery, the animals underwent hemodynamic functional analysis in the presence of exogenous apelin-13 infusion and the hearts were explanted for western blot and enzyme immunoassay analysis. Western blot analysis of myocardial APJ concentration demonstrated increased APJ receptor protein levels with heart failure (1890750+/-133500 vs. 901600+/-143120 intensity units, n=8, p=0.00001). Total apelin protein levels increased with ischemic heart failure as demonstrated by enzyme immunoassay (12.0+/-4.6 vs. 1.0+/-1.2 ng/ml, n=5, p=0.006) and western blot (1579400+/-477733 vs. 943000+/-157600 intensity units, n=10, p=0.008). Infusion of apelin-13 significantly enhanced myocardial function in sham and failing hearts. We conclude that total myocardial apelin and APJ receptor levels increase in compensation for ischemic cardiomyopathy.

Domestic dogs and cats as sources of Trypanosoma cruzi infection in rural northwestern Argentina

The reservoir capacity of domestic cats and dogs for Trypanosoma cruzi infection and the host-feeding patterns of domestic Triatoma infestans were assessed longitudinally in 2 infested rural villages in north-western Argentina. A total of 86 dogs and 38 cats was repeatedly examined for T. cruzi infection by serology and/or xenodiagnosis. The composite prevalence of infection in dogs (60%), but not in cats, increased significantly with age and with the domiciliary density of infected T. infestans. Dogs and cats had similarly high forces of infection, prevalence of infectious hosts (41-42%), and infectiousness to bugs at a wide range of infected bug densities. The infectiousness to bugs of seropositive dogs declined significantly with increasing dog age and was highly aggregated. Individual dog infectiousness to bugs was significantly autocorrelated over time. Domestic T. infestans fed on dogs showed higher infection prevalence (49%) than those fed on cats (39%), humans (38%) or chickens (29%) among 1085 bugs examined. The basic reproduction number of T. cruzi in dogs was at least 8.2. Both cats and dogs are epidemiologically important sources of infection for bugs and householders, dogs nearly 3 times more than cats.