Paracardial fat remodeling affects systemic metabolism through alcohol dehydrogenase 1

The relationship between adiposity and metabolic health is well established. However, very little is known about the fat depot, known as paracardial fat (pCF), located superior to and surrounding the heart. Here, we show that pCF remodels with aging and a high-fat diet and that the size and function of this depot are controlled by alcohol dehydrogenase 1 (ADH1), an enzyme that oxidizes retinol into retinaldehyde. Elderly individuals and individuals with obesity have low ADH1 expression in pCF, and in mice, genetic ablation of Adh1 is sufficient to drive pCF accumulation, dysfunction, and global impairments in metabolic flexibility. Metabolomics analysis revealed that pCF controlled the levels of circulating metabolites affecting fatty acid biosynthesis. Also, surgical removal of the pCF depot was sufficient to rescue the impairments in cardiometabolic flexibility and fitness observed in Adh1-deficient mice. Furthermore, treatment with retinaldehyde prevented pCF remodeling in these animals. Mechanistically, we found that the ADH1/retinaldehyde pathway works by driving PGC-1α nuclear translocation and promoting mitochondrial fusion and biogenesis in the pCF depot. Together, these data demonstrate that pCF is a critical regulator of cardiometabolic fitness and that retinaldehyde and its generating enzyme ADH1 act as critical regulators of adipocyte remodeling in the pCF depot.

Cellular Identification and Quantification of Senescence-Associated β-Galactosidase Activity In Vivo

Senescence-associated β-galactosidase (hereafter SA-β-gal) staining has now been employed for more than 20 years to identify the presence of senescent cells (Dimri et al., Proc Natl Acad Sci U S A 92:9363-9367, 1995). These cells, characterized by a permanent cell-cycle arrest (Hayflick and Moorhead, Exp Cell Res 25:585-621, 1961) and the production of a distinct secretory phenotype of cytokines, chemokines, and proteases (Coppe et al., PLoS Biol 6:2853-2868, 2008), have received much attention in recent years for their impacts on diverse biological processes. Here we describe a method to identify and quantify the specific cells that become senescent in vivo using transmission electron microscopy after SA-β-gal staining that can be used in countless scenarios.

[Difficulties in classifying body cavity fluids into transudate/ exudate depending on the various diagnostic criteria]

Disease processes may impair the production and reabsorption of fluid from in the body cavities, which results in its excessive accumulation.

AIM

The aim of the study was the evaluation of difficulties regarding the classification of fluids from the body cavities into transudate/exudate observing the following: Light's criteria, total fluid protein concentration, and total protein ratio (TP ratio) and lactate dehydrogenase ratio (LDH ratio).

MATERIALS AND METHODS

Retrospective analysis was conducted on pleural (N=314), peritoneal (N=114) and pericardial (N=10) fluids, which were tested for the total protein concentration and LDH activity both in fluid and serum and calculated on TP ratio and LDH ratio.

RESULTS

Based on the total protein concentration, 278 fluids from pleural cavity were classified as an exudate; 36 as a transudate. Applying the Light's criteria 240 fluids were classified as an exudate; the remaining 74 fluids were classified as a transudate. Based on TP and LDH ratios, 229 fluids from pleural cavity were classified as an exudate; 85 as a transudate. Depending on the total protein concentration, 35 fluids from the peritoneal cavity were classified as an exudate; 79 as a transudate. Applying the Light's criteria 54 fluids were classified as an exudate; the remaining 60 fluids were classified as a transudate. Based on TP and LDH ratios, 22 fluids from peritoneal cavity were classified as an exudate; 92 as a transudate. Analysis of pericardial fluids, depending on the total protein concentration classified 9 of them as an exudate and 1 as a transudate. The same results were obtained by applying Light's criteria. Based on TP and LDH ratios, 7 fluids from pericardial cavity were classified as an exudate; 3 - as a transudate.

CONCLUSIONS

Applying the Light's criteria or the total protein concentration in differential diagnostics of fluids from the body cavities resulted in qualification more of them as an exudates as compared to the analysis of the same fluids depending on the TP and LDH ratios. It can be assumed that some of the transudative/exudative fluids were incorrectly classified. Performed analysis suggest that more adequate criteria of the classification of fluids from the body cavities into transudate/exudate are of great importance.

Activity of MMP-9 after repair of abdominal wall defects with acellular and crosslinked bovine pericardium in rabbit

This study was undertaken for the identification of matrix metalloproteinases (MMPs) in extracts obtained from native, acellular and crosslinked bovine pericardium (in vitro), as well as in the plasma after implantation of these biomaterials in rabbits (in vivo). Native pericardium (NP) expressed a 72 kDa (MMP-2) band; whereas, in acellular pericardium (AP) two bands (10 kDa and 92 kDa) of MMPs were observed of which, 92 kDa band was very faint. AP crosslinked with glutaraldehyde did not show any gelatinase activity and thus reflects the creation of new additional chemical bonds between the collagen molecules which has been effectively removed. Gelatin zymography showed only one major band of 92 kDa in all the implanted and untreated rabbit plasma, but the relative amount of 92 kDa was 1-2 times higher in acellular bovine pericardium implanted rabbits as compared to crosslinked and native groups. In NP group, the 92 kDa band was the dullest among the three groups. This indicated that the level of MMP-9 corresponds to the degree of collagen degradation.

A dominant negative zebrafish Ahr2 partially protects developing zebrafish from dioxin toxicity

The toxicity by 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) is thought to be caused by activation of the aryl hydrocarbon receptor (AHR). However, our understanding of how AHR activation by TCDD leads to toxic effects is poor. Ideally we would like to manipulate AHR activity in specific tissues and at specific times. One route to this is expressing dominant negative AHRs (dnAHRs). This work describes the construction and characterization of dominant negative forms of the zebrafish Ahr2 in which the C-terminal transactivation domain was either removed, or replaced with the inhibitory domain from the Drosophila engrailed repressor protein. One of these dnAhr2s was selected for expression from the ubiquitously active e2fα promoter in transgenic zebrafish. We found that these transgenic zebrafish expressing dnAhr2 had reduced TCDD induction of the Ahr2 target gene cyp1a, as measured by 7-ethoxyresorufin-O-deethylase activity. Furthermore, the cardiotoxicity produced by TCDD, pericardial edema, heart malformation, and reduced blood flow, were all mitigated in the zebrafish expressing the dnAhr2. These results provide in vivo proof-of-principle results demonstrating the effectiveness of dnAHRs in manipulating AHR activity in vivo, and demonstrating that this approach can be a means for blocking TCDD toxicity.

Involvement of the MEKK1 signaling pathway in the regulation of epicardial cell behavior by hyaluronan

During embryonic development, cells comprising the outermost layer of the heart or epicardium play a critical role in the formation of the coronary vasculature. Thus, uncovering the molecular mechanisms that govern epicardial cell behavior is imperative to better understand the etiology of cardiovascular diseases. In this study, we investigated the function of hyaluronan (HA), a major component of the extracellular matrix, in the modulation of epicardial signaling. We show that stimulation of epicardial cells with high molecular weight HA (HMW-HA) promotes the association of MEKK1 with the HA receptor CD44 and induces MEKK1 phosphorylation. This leads to the activation of two distinct pathways, one ERK-dependent and another NFkappaB-dependent. Furthermore, HMW-HA stimulates epicardial cells to differentiate and invade, as suggested by increased vimentin expression and enhanced invasion through a collagen matrix. Blockade of CD44, transfection with a kinase-inactive MEKK1 construct or the use of ERK1/2 and NFkappaB inhibitors significantly abrogates the invasive response to HMW-HA. Together, these findings suggest an important role for HA in the regulation of epicardial cell fate via activation of MEKK1 signaling cascades.

Secretory type II phospholipase A2 is produced and secreted by epicardial adipose tissue and overexpressed in patients with coronary artery disease

CONTEXT

Epicardial adipose tissue (EAT) is a visceral adipose tissue in close contact with coronary vessels, the excess of which is associated with coronary artery disease (CAD).

OBJECTIVE

Our goal was to identify candidate molecule(s) characterizing EAT that could intervene in the pathogenesis of CAD.

DESIGN

An approach combining microarrays and bioinformatic sequence analysis tools for predicting secreted proteins (TargetP) was applied to paired biopsies of sc adipose tissue (SAT) and EAT, obtained from patients with or without CAD (NCAD). RESULTS were validated in three independent groups of subjects by quantitative RT-PCR, Western blot, immunohistochemistry, and explant secretion.

RESULTS

Secretory type II phospholipase A2 (sPLA2-IIA) ranked as the highest gene coding for potentially secreted proteins with the highest overexpression in EAT in both CAD and NCAD. Quantitative RT-PCR confirmed its increased expression in EAT (P < 0.01) as well as EAT from CAD as compared with NCAD (49.3 +/- 13 vs. 17.4 +/- 9.7 P < 0.01). sPLA2-IIA protein levels were higher in EAT than SAT (P < 0.001). EAT explants also showed significantly higher sPLA2-IIA secretion levels than SAT ones (4.37 +/- 2.7 vs. 0.67 +/- 0.28 ng/ml to 1 per gram tissue per 24 h, P < 0.03). sPLA2-IIA labeling was seen in the stroma vascular fraction between adipocytes and in connective capsules in EAT, with no immunostaining of the adipocytes. SAT was weakly labeled following the same process.

CONCLUSION

We have shown for the first time an increased expression of sPLA2-IIA in EAT in patients with CAD. sPLA2-IIA is a phospholipase, which has been shown to be an independent risk factor for CAD. These findings suggest that EAT has a potentially pathophysiological role in CAD.

Efficient in vivo catheter-based pericardial gene transfer mediated by adenoviral vectors

Adenoviral vectors are promising agents for a number of in vivo gene therapy applications including diseases of the heart and coronary vessels. Efficient intravascular gene transfer to specific sites has been achieved in occluded vessels, but otherwise is hampered by the effect of blood flow on localized vector uptake in the vessel wall. An alternative delivery approach to coronary arteries is the expression of diffusible gene products into the pericardial space surrounding the heart and coronary arteries. However, in vivo pericardial access is comparatively difficult and has been limited to surgical approaches. We hypothesized that efficient adenovirus-mediated gene expression in pericardial lining mesothelium could be achieved by transmyocardial vector delivery to the pericardium. To evaluate this concept, a hollow, helical-tipped penetrating catheter was used to deliver vector-containing fluid directly into the intrapericardial space. The catheter was introduced percutaneously in anesthetized mongrel dogs, advanced into the right ventricle, and the tip passed through the apical right ventricular myocardium under direct radiographic visualization until the open end of the catheter tip resided in the intrapericardial space. Adenoviral vectors expressing either nuclear-localizing beta-galactosidase, cytoplasmic luciferase, or secreted human alpha 1AT reporters (Av1nBg, Av1Lu, or Av1Aa, respectively) were instilled through the catheter into the intrapericardial space. Three days later the animals were sacrificed and reporter gene expression was evaluated in pericardium, epicardium, and multiple other tissues. In animals receiving Av1nBg, beta-galactosidase activity was evident in most of the pericardial lining endothelium, up to 100% in many areas. In animals receiving Av1Lu, luciferase reporter activity was abundant in pericardial tissues, but near-background levels were observed in other organs. In animals receiving Av1Aa, human alpha 1AT was abundant (16-29 mg/ml) in pericardial fluid, but was undetectable in serum. All animals tolerated the procedure well with no electrocardiographic changes and no clinical sequelae. These observations demonstrate highly efficient adenovirus vector delivery and gene transfer and expression in the pericardium and support the feasibility of localized gene therapy via catheter-based pericardial approaches. We suggest that the pericardial sac may serve as a sustained-release protein delivery system for the generation of desired gene products or their metabolites for diffusion into the epicardial region.

Role of activated CaMKII in abnormal calcium homeostasis and I(Na) remodeling after myocardial infarction: insights from mathematical modeling

Ca(2+)/calmodulin-dependent protein kinase II is a multifunctional serine/threonine kinase with diverse cardiac roles including regulation of excitation contraction, transcription, and apoptosis. Dynamic regulation of CaMKII activity occurs in cardiac disease and is linked to specific disease phenotypes through its effects on ion channels, transporters, transcription and cell death pathways. Recent mathematical models of the cardiomyocyte have incorporated limited elements of CaMKII signaling to advance our understanding of how CaMKII regulates cardiac contractility and excitability. Given the importance of CaMKII in cardiac disease, it is imperative that computer models evolve to capture the dynamic range of CaMKII activity. In this study, using mathematical modeling combined with biochemical and imaging techniques, we test the hypothesis that CaMKII signaling in the canine infarct border zone (BZ) contributes to impaired calcium homeostasis and electrical remodeling. We report that the level of CaMKII autophosphorylation is significantly increased in the BZ region. Computer simulations using an updated mathematical model of CaMKII signaling reproduce abnormal Ca(2+) transients and action potentials characteristic of the BZ. Our simulations show that CaMKII hyperactivity contributes to abnormal Ca(2+) homeostasis and reduced action potential upstroke velocity due to effects on I(Na) gating kinetics. In conclusion, we present a new mathematical tool for studying effects of CaMKII signaling on cardiac excitability and contractility over a dynamic range of kinase activities. Our experimental and theoretical findings establish abnormal CaMKII signaling as an important component of remodeling in the canine BZ.

Expression of adrenomedullin in human epicardial adipose tissue: role of coronary status

Epicardial white adipose tissue (eWAT) is in close contact with coronary vessels and therefore could alter coronary homeostasis. Adrenomedullin (AM) is a potent vasodilatator and antioxidative peptide which has been shown to play a cytoprotective role in experimental models of acute myocardial infarction. We studied, using immunohistochemistry and qRT-PCR, the expression of AM and its receptors calcitonin receptor-like receptor (CRLR), and receptor activity-modifying protein (RAMP)2 and -3 in paired biopsies of subcutaneous WAT (sWAT) and eWAT obtained from patients with coronary artery disease (CAD) or without CAD (NCAD). In eWAT obtained from NCAD or CAD patients, immunoreactivity for AM, CRLR, and RAMP2 and -3 was detected in blood vessel walls and isolated stromal cells close to adipocytes. Some of the AM positive stromal cells colocalized CD68 immunoreactivity. eWAT from CAD patients showed increased AM immunoreactivity and AM gene expression. CRLR mRNA levels were comparable in sWAT of both groups and decreased by 40-50% in eWAT, irrespectively of the coronary status. RAMP2 mRNA concentrations did not change while RAMP3 mRNA levels increased in sWAT from CAD patients. There was a positive linear relationship between eWAT 11beta-hydroxysteroid dehydrogenase type 1 mRNA (11beta-HSD-1, the enzyme that converts inactive to active glucocorticoids) and AM mRNA. In conclusion, we demonstrate that AM and its receptors are expressed in eWAT. Our data suggest that eWAT AM, which could originate from macrophages, is related to 11beta-HSD-1 expression. AM synthesis, which is increased in eWAT during chronic CAD in humans, can play a cardioprotective role.

Increased pericardial fluid level of matrix metalloproteinase-9 activity in patients with acute myocardial infarction: possible role in the development of cardiac rupture

BACKGROUND

In an animal model of acute myocardial infarction (AMI), deletion of matrix metalloproteinase (MMP)-9 results in suppression of the development of cardiac rupture. The present study sought to clarify how myocardial MMP-9 activity is related to the pathophysiologies of AMI and cardiac rupture in humans.

METHODS AND RESULTS

Levels of interleukin-8 (IL-8), polymorphonuclear leukocyte (PMN) elastase, monocyte chemotactic protein-1 (MCP-1) and MMP activity were measured in the pericardial fluid obtained from 28 patients with angina pectoris (AP group) and 16 patients with AMI (AMI group) undergoing cardiac surgery. In the AMI group, 5 were complicated with ventricular septal perforation (VSP) and the remaining 11 were not (non-VSP). Levels of IL-8, PMN elastase, MMP-2 and MMP-9 activity were all higher in the AMI group than in the AP group. In the AMI group, all levels other than MMP-2 activity were further elevated in cases with VSP compared with those in the non-VSP group. There was no significant difference in MCP-1 among the groups

CONCLUSIONS

Markers of neutrophil activation in the infarcted cardiac tissue seem to be elevated in AMI. Highly elevated levels of MMP-9 activity, which may be derived from neutrophils, and PMN elastase may be related to the pathophysiology of VSP or cardiac rupture in AMI.

Proteasome degradation of GRK2 during ischemia and ventricular tachyarrhythmias in a canine model of myocardial infarction

Arrhythmia-prone subepicardial border zone (EBZ) tissue demonstrates decreased G protein receptor kinase 2 (GRK2) activity and increased sensitivity to isoproterenol 6–24 h after coronary artery ligation (CAL) in the dog. With the use of a semiquantitative immunofluorescence technique, the relative fluorescence intensity (RF) of GRK2 in EBZ decreased to 24% of that in a remote site (RS) ( P < 0.01, n = 30 cells from 3 dogs), whereas GRK5 RF did not change. Confocal studies of cardiac tissue from transgenic mice overexpressing GRK2 validated the use of a semilogarithmic relationship between RF and GRK2 activity. As shown with the use of quantitative real-time RT-PCR, both GRK2 and GRK5 mRNA were not decreased at 24 h in EBZ ( n = 6 dogs) relative to RS control, indicating that the decrease of GRK2 in the EBZ is likely due to posttranscriptional degradation following CAL. Pretreatment of six dogs with the selective proteasome inhibitor bortezomib provided 100% (EBZ) and 50% (infarct) protection against loss of GRK2 at 24 h. There was an absence of rapid (>300 beats/min) and very rapid (>360 beats/min) ventricular triplets that are highly predictive of sudden cardiac death during ECG monitoring in the bortezomib-pretreated animals in contrast to nonpretreated infarcted animals. We have demonstrated that the dramatic decrease in GRK2 in cardiac ischemic tissue can be largely blocked by prior proteasome blockade and that this is associated with significant cardioprotection against malignant ventricular tachyarrhythmias.

Distribution and function of biogenic amines in the heart of Nautilus pompilius L. (Cephalopoda, Tetrabranchiata)

Biogenic amines (serotonin and catecholamines), play an important role in the control of the blood flow not only in vertebrates, but also in invertebrates such as cephalopods. In contrast to the well investigated hearts of the a 'modern', coleoid cephalopods, the innervation of the heart of the archaic Nautilus pompilius L. has not been studied in detail. In this study the distribution and effects of biogenic amines in the Nautilus heart were investigated. Serotonin and catecholamines were visualised by the glyxoylic acid induced fluorescence. High performance liquid chromatotography analysis was performed to discriminate between the catecholamines, which showed a high content of noradrenaline in the 4 auricles, the aorta and the ventricle, whereas the ventricle showed a high dopamine content. Adrenaline was found at a very low concentration in the ventricle. Serotonin and dopamine were also immunohistochemically localised to larger nerves and throughout the heart, respectively. In organ bath experiments, the auricles showed little spontaneous activity. After adding serotonin, they displayed rhythmical contractions, which were accelerated dose-dependently by noradrenaline. In summary, these data suggest an important role for biogenic amines in the control of the heart of Nautilus pompilius L., with serotonin possibly stimulating excitatory nerve fibres, whereas noradrenaline is likely to influence the muscle contraction itself.

Nitrogen oxide blockade does not aggravate the endothelin-1-induced myocardial ischemia and release of purine metabolites from the dog heart

Increased intrapericardial levels of endothelin-1 (ET-1) induce myocardial ischemia and concomitant release of the purine metabolites adenosine (ADO), inosine (INO) and hypoxanthine (HXA) into the pericardial fluid. However, the potential modulatory role of nitrogen monoxide in compensating the ET-1-induced ischemic stress is not fully elucidated. The pericardial elevations of purine metabolite concentrations in the pericardial fluid after ET-1 administration (150 pmol/kg intrapericardially) were measured in the in situ dog heart with (n = 6) or without (n = 5) systemic nitrogen monoxide synthase blockade (30 mg/kg (G)-nitro-L-arginine methyl ester, followed by 6 mg/min intravenously). After control sampling, three consecutive pericardial infusate samples (ET1, ET2, ET3) were obtained for purine metabolite determinations (high-performance liquid chromatography-ultraviolet). It was found that intrapericardial ET-1 elevated the pericardial purine metabolite concentrations significantly in both groups. No significant differences were detected between the control and (G)-nitro-L-arginine methyl ester-treated groups in ischemic changes of pericardial ADOmax (+3.27 +/- 1.13 microM versus +1.84 +/- 0.56 microM), INOmax (+15.21 +/- 2.3 microM versus +12.09 +/- 4.04 microM) and HXAmax (+16.34 +/- 2.98 microM versus +17.09 +/- 5.22 microM) levels and in the maximal ST elevations (0.43 +/- 0.05 mV versus 0.61 +/- 0.08 mV). The hemodynamic variables did not change with ET-1 administration. In conclusion, systemic nitrogen monoxide synthase blockade does not aggravate the ET-1-induced acute myocardial ischemia and the release of purine metabolites, suggesting that endogenous nitrogen monoxide is not a supplementary factor to purine metabolites in this type of coronary adaptive responses.

Transforming growth factor-β induces loss of epithelial character and smooth muscle cell differentiation in epicardial cells

During embryogenesis, epicardial cells undergo epithelial-mesenchymal transformation (EMT), invade the myocardium, and differentiate into components of the coronary vasculature, including smooth muscle cells. We tested the hypothesis that transforming growth factor-beta (TGFbeta) stimulates EMT and smooth muscle differentiation of epicardial cells. In epicardial explants, TGFbeta1 and TGFbeta2 induce loss of epithelial morphology, cytokeratin, and membrane-associated Zonula Occludens-1 and increase the smooth muscle markers calponin and caldesmon. Inhibition of activin receptor-like kinase (ALK) 5 blocks these effects, whereas constitutively active (ca) ALK5 increases cell invasion by 42%. Overexpression of Smad 3 did not mimic the effects of caALK5. Inhibition of p160 rho kinase or p38 MAP kinase prevented the loss of epithelial morphology in response to TGFbeta, whereas only inhibition of p160 rho kinase blocked TGFbeta-stimulated caldesmon expression. These data demonstrate that TGFbeta stimulates loss of epithelial character and smooth muscle differentiation in epicardial cells by means of a mechanism that requires ALK5 and p160 rho kinase.

MAP kinase activation in avian cardiovascular development

Signaling pathways mediated by receptor tyrosine kinases (RTK) and mitogen-activated protein kinase (MAPK) activation have multiple functions in the developing cardiovascular system. The localization of diphosphorylated extracellular signal regulated kinase (dp-ERK) was monitored as an indicator of MAPK activation in the forming heart and vasculature of avian embryos. Sustained dp-ERK expression was observed in vascular endothelial cells of embryonic and extraembryonic origins. Although dp-ERK was not detected during early cardiac lineage induction, MAPK activation was observed in the epicardial, endocardial, and myocardial compartments during heart chamber formation. Endocardial expression of dp-ERK in the valve primordia and heart chambers may reflect differential cell growth associated with RTK signaling in the heart. dp-ERK localization in the epicardium, subepicardial fibroblasts, myocardial fibroblasts, and coronary vessels is consistent with MAPK activation in epicardial-derived cell lineages. The complex temporal-spatial regulation of dp-ERK in the heart supports diverse regulatory functions for RTK signaling in different cell populations, including the endocardium, myocardium, and epicardial-derived cells during cardiac organogenesis.

Endomyocardial nitric oxide synthase and the hemodynamic phenotypes of human dilated cardiomyopathy and of athlete's heart

OBJECTIVE

In dilated cardiomyopathy and in athlete's heart, progressive LV dilatation is accompanied by rightward displacement of the diastolic LV pressure-volume relation. In dilated cardiomyopathy, an increase in diastolic LV stiffness can limit this rightward displacement thereby decreasing LV systolic performance. Because nitric oxide (NO) reduces diastolic LV stiffness, the present study relates diastolic LV stiffness and LV systolic performance to intensity of endomyocardial NO synthase (NOS) gene expression in dilated cardiomyopathy and in athlete's heart.

METHODS

Microtip LV pressures, conductance-catheter or angiographic LV volumes, echocardiographic LV wall thicknesses and snap-frozen LV endomyocardial biopsies were obtained in 33 patients with dilated cardiomyopathy and in three professional cyclists referred for sustained ventricular tachycardia. Intensity of LV endomyocardial inducible NOS (NOS2) and constitutive NOS (NOS3) gene expression was determined using quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Dilated cardiomyopathy patients with higher diastolic LV stiffness-modulus and lower LV stroke work had lower NOS2 and NOS3 gene expression at any given level of LV end-diastolic wall stress. The intensity of NOS2 and NOS3 gene expression observed in athlete's heart was similar to dilated cardiomyopathy with low LV diastolic stiffness-modulus and preserved LV stroke work.

CONCLUSIONS

High LV endomyocardial NOS gene expression is observed in athlete's heart and in dilated cardiomyopathy with low diastolic LV stiffness and preserved LV stroke work. Favourable effects on the hemodynamic phenotype of high LV endomyocardial NOS gene expression could result from a NO-mediated decrease in diastolic LV stiffness and a concomitant rise in LV preload reserve.

Gelatinases in soft tissue biomaterials. Analysis of different crosslinking agents

Chemical modification of pericardium-based cardiac valves tends to reduce the relatively high degree of biodegradation and calcification of the implanted bioprostheses. We analysed the tissue properties of pericardium from young calves and pigs after crosslinking with different agents (glutaraldehyde. diphenylphosphorylazide (DDPA), 1-ethyl-3,3-dimethyl-aminopropyl-carbodiimide (EDAC)) and when exposed to anticalcification treatments (chloroform/methanol or ethanol) prior to glutaraldehyde (GA) crosslinking. Protein extraction after tissue homogenisation in the presence of detergents showed that crosslinking using GA or DPPA was much more effective. The amounts of protein extracted from these two groups of chemically modified pericardium were significantly lower: the other modified tissues presented only a slight reduction when compared with untreated tissue. Matrix metalloproteinases- (MMP) 2 and 9 were detected in native pericardium from calf and pig by zymography. While the MMP-9/MMP-2 activity ratio was close to 1 in pig pericardium, it was 8.5-fold higher in bovine tissue. Crosslinking with GA and with DPPA almost completely abolished gelatinase activities, even when equal amounts of solubilised protein were loaded onto the zymograms. Anticalcification treatments followed by GA crosslinking or treatment with EDAC were not as effective in reducing gelatinase activities; but, interestingly, a relative reduction of MMP-9 versus MMP-2 was detected. The presence of these gelatinase activities in pericardium may contribute to the in vivo degradability of pericardium-based cardiac valves.

Aspirin prevents Escherichia coli lipopolysaccharide- and Staphylococcus aureus-induced downregulation of endothelial nitric oxide synthase expression in guinea pig pericardial tissue

The aim was to analyze whether pericardial tissue expresses endothelial NO synthase (eNOS) protein and to determine the presence of cytosolic proteins that bind to eNOS mRNA. The effect of aspirin on the above-mentioned parameters was also analyzed. eNOS protein was expressed in pericardial tissue from male guinea pigs. Escherichia coli lipopolysaccharide (LPS, 10 microgram/mL) and Staphylococcus aureus endotoxin (SA, 10 microgram/mL) reduced eNOS protein expression and shortened the half-life of the eNOS messenger. Under basal conditions, cytosolic extracts from pericardial samples bound to the 3'-untranslated region (3'-UTR) of eNOS mRNA, which was enhanced by LPS and SA. Proteinase K fully prevented the binding of cytosolic pericardial extracts to 3'-UTR of eNOS mRNA, suggesting the involvement of proteins that were further characterized as 60- and 51-kDa proteins. Aspirin (1 to 10 mmol/L) restored eNOS expression in either LPS- and SA-stimulated pericardial samples and reduced the binding activity of the pericardial cytosolic proteins to 3'-UTR of eNOS mRNA. Indomethacin also reduced the downregulation of eNOS by LPS and diminished the binding activity of the cytosolic proteins, although higher doses of indomethacin than of aspirin were needed to improve these parameters. In conclusion, eNOS protein is expressed in guinea pig pericardial tissue. LPS and SA stimulate the binding activity of pericardial cytosolic proteins to 3'-UTR of eNOS mRNA and reduce eNOS protein expression. High doses of aspirin and indomethacin protect eNOS protein expression and reduce the binding activity of the cytosolic proteins to 3'-UTR of eNOS mRNA, suggesting an inverse association between the presence of these cytosolic proteins and eNOS expression.

Ethanol-induced reduction in myocardial oxygen consumption can be attenuated by inhibiting guanylyl cyclase

We tested the hypothesis that low-dose ethanol-induced reductions in myocardial metabolism were related to increased cyclic guanosine monophosphate (GMP). Anesthetized open chest rabbits were divided into four groups: control (Ringers lactate and vehicle), ETOH (250 mg/kg i.v. ethanol and vehicle), ODQ (Ringers lactate and 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ 10(-4) M ), and ETOH-ODQ (ethanol and ODQ). ODQ, a soluble guanylyl cyclase inhibitor, or vehicle was applied topically to the epicardium for 15 min, while either Ringers lactate or ethanol was administered intravenously. Oxygen consumption (VO2 ) in both the subepicardium (EPI) and subendocardium (ENDO) was determined from coronary blood flow (radioactive microspheres) and O2 extraction (microspectrophotometry). Cyclic GMP was determined by radioimmunoassay. ETOH significantly decreased VO2 in the subepicardium (9.2 +/- 1.0-5.6 +/- 0.7 ml O2 /min/100 g) and subendocardium (9.7 +/- 0.8-7.1 +/- 0.8) and increased cyclic GMP in the subepicardium (10.2 +/- 1.7-13.8 +/- 0.8 pmol/g) and subendocardium (11.0 +/- 0.5-13.7 +/- 0.9). With ODQ, there was no significant change in the subepicardial (9.5 +/- 1.3) or subendocardial (9.0 +/- 0.9) VO2. However, ODQ caused a significant increase in both wall thickening (12.9 +/- 0.9-17.2 +/- 1.2%) and maximal rate of change in wall thickness (10.8 +/- 0.9-16.3 +/- 1.9 mm/s) and decreased subepicardium (8.3 +/- 1.3) and subendocardium (7.8 +/- 1.2) cyclic GMP. The ETOH-ODQ group had cyclic GMP (subepicardium 9.0 +/- 1.8, subendocardium 8.6 +/- 2.4) and VO2 (subepicardium 7.9 +/- 0.5, subendocardium 8.4 +/- 0.4) values similar to control. Thus, the ethanol-induced rise in cyclic GMP was associated with a decrease in myocardial O2 consumption. When this rise was blocked with a soluble guanylyl cyclase inhibitor, the reduction in metabolic demand was also eliminated. This demonstrated that the alcohol-induced reduction in myocardial metabolism was related to increased cyclic GMP and suggests a novel mechanism for the effect of ethanol.

Detection of inducible nitric oxide synthase- and nitrotyrosine-positive cells in the lesions of pericarditis induced by porcine enterovirus serotype 3 infection

The expression of inducible nitric oxide synthase (iNOS), an enzyme that produces nitric oxide, was examined in the hearts of pigs infected with porcine enterovirus serotype 3 (PEV3). Piglets orally infected with PEV3 developed tremors and paralysis 3-7 days post-infection. Affected animals had pericarditis and myocarditis. There were fibrin and inflammatory cell infiltrates (macrophages and neutrophils) in the pericardial sac and myocardium. Immunohistochemically, the majority of inflammatory cells in the pericardial sac were positive for iNOS and nitrotyrosine, an end product of nitric oxide. These results suggest that iNOS is upregulated in the pericardial lesion, and that increased nitric oxide production plays an important role in the development of PEV3-induced pericarditis and myocarditis.

A novel protein that binds juvenile hormone esterase in fat body tissue and pericardial cells of the tobacco hornworm Manduca sexta L

Juvenile hormone esterase degrades juvenile hormone, which acts in conjunction with ecdysteroids to control gene expression in insects. Circulating juvenile hormone esterase is removed from insect blood by pericardial cells and degraded in lysosomes. In experiments designed to characterize proteins involved in the degradation of juvenile hormone esterase, a pericardial cell cDNA phage display library derived from the tobacco hornworm moth Manduca sexta L. was constructed and screened for proteins that bind juvenile hormone esterase. A 732-base pair cDNA encoding a novel 29-kDa protein (P29) was isolated. Western and Northern analyses indicated that P29 is present in both pericardial cell and fat body tissues and is expressed in each larval instar. In immunoprecipitation experiments, P29 bound injected recombinant juvenile hormone esterase taken up by pericardial cells and native M. sexta juvenile hormone esterase in fat body tissue, where the enzyme is synthesized. Binding assays showed that P29 bound juvenile hormone esterase more strongly than it did a mutant form of the enzyme with mutations that perturb lysosomal targeting. Based on these data, we propose that P29 functions in pericardial cells to facilitate lysosomal degradation of juvenile hormone esterase.

Effects of double cross-linking technique on the enzymatic degradation and calcification of bovine pericardia

The strength, resorption rates, and biocompatibility of collagenous biomaterials are profoundly influenced by the method of cross-linking. The in vitro and in vivo calcification and enzymatic degradation of bovine pericardia (BP) after a series of surface modifications were studied as a function of exposure time. Collagenase degradations of modified BP were monitored by scanning electron microscopy and tensile strength measurements. Bovine pericardium was modified by a combination of different tissue fixatives such as glutaraldehyde (GA), carbodiimide (EDC), diisocyanate (HMDIC), and polyethylene glycol (PEG). GA-PEG-EDC-PEG and GA-PEG-HMDIC-PEG combination treated BP retained maximum stability in collagenase digestion compared to GATBP. In vitro calcification studies and in vivo rat subcutaneous implantations of modified pericardium have shown substantial reduction in the calcification of double cross-linked BP with PEG modification. Further, the biocompatibility aspects of pericardial tissues were established by platelet adhesion and octane contact angle. It seems that cross-links involving amino and carboxyl residues may provide new ways of controlling biodegradation and calcification.

Heterogeneous transmural gene expression of calcium-handling proteins and natriuretic peptides in the failing human heart

OBJECTIVE

Human heart failure is associated with a disturbed intracellular calcium (Ca2+) homeostasis. In this regard, ventricular wall stress is considered to be a determinant for expression of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a). In the present study, we analyzed the transmural protein and/or mRNA levels of SERCA2a, other Ca(2+)-handling proteins, and of atrial and brain natriuretic peptides (ANP and BNP) in the human heart.

METHODS

Subepicardial (epi), midmyocardial (mid), and subendocardial (endo) sections of the left ventricular free wall from end-stage failing (n = 17) and nonfailing (n = 5) human hearts were analyzed by Western blot for immunoreactive protein levels of SERCA2a, phospholamban (PLN), and calsequestrin (CS). Subepi- and subendocardial sections were analyzed by Northern blot for steady-state mRNA levels of SERCA2a, Na(+)-Ca2+ exchanger (NCX1), ANP, and BNP.

RESULTS

SERCA2a protein and mRNA levels were reduced by 40 +/- 5% (P < 0.01) and 25 +/- 7% (P < 0.05) in endo compared to epi in the failing heart and by 27 +/- 14% and 16 +/- 12% (non-significant) in the nonfailing heart, respectively. PLN protein levels were reduced by 23 +/- 6% (P < 0.05) in endo compared to epi in the failing heart and by 17 +/- 25% (non-significant) in the nonfailing heart, whereas CS protein levels and NCX1 mRNA levels were similar across the left ventricular wall. Strikingly, in the failing heart, both BNP and ANP mRNA levels were upregulated predominantly in endo.

CONCLUSIONS

In the failing human heart, SERCA2a and PLN, as well as natriuretic peptides but not CS and NCX1 are differentially expressed across the left ventricular wall, implicating (1) different susceptibility of subendocardium and subepicardium to factors affecting expression of these proteins and (2) differences in regulation of the distinct calcium-cycling proteins.

Endocardial versus epicardial differences of sarcoplasmic reticulum Ca2+-ATPase gene expression in the canine failing myocardium

It is unknown whether the transmural heterogeneity of sarcoplasmic reticulum (SR) Ca2+-ATPase gene expression is present within the left ventricular (LV) wall. Moreover, the changes of transmural distribution have not been examined in the failing hearts. We thus quantified steady-state mRNA abundance of SR Ca2+ regulatory proteins by Northern blot analysis in both subendocardial and subepicardial LV layers from normal and rapid pacing-induced heart failure (HF) dog hearts. For normal LV, Ca2+-ATPase mRNA abundance (normalized to glyceraldehyde-3-phosphate dehydrogenase [GAPDH] mRNA) was significantly reduced in the subendocardium, whereas calsequestrin mRNA abundance was comparable between the two layers. For HF LV, Ca2+-ATPase mRNA abundance in the subendocardium was also reduced compared to the subepicardium. However, the endocardium to epicardium ratio was comparable between control and HF (0.62 +/- 0.08 vs. 0.65 +/- 0.07; p = NS). Therefore, the transmural gradient of this gene was constant in both control and HF. Even though the data on the transmural heterogeneity of protein level is not available, the subendocardium contained significantly less Ca2+-ATPase mRNA, which might contribute, at least in part, to the transmural gradients of biochemical and mechanical function.

Adenosine mediates sustained adrenergic desensitization in the rat heart via activation of protein kinase C

Adenosine attenuates the myocardial metabolic and contractile responses induced by ss-adrenergic stimulation. Our study was conducted to investigate the longevity of this antiadrenergic action after adenosine exposure. Adenosine (33 micromol/L) was infused into isolated perfused rat hearts for 1, 5, 30, or 60 minutes, and the adrenergic responsiveness (AR) to isoproterenol (10(-8) mol/L) was determined at the end of each infusion period and during a 45-minute adenosine washout period. Interstitial levels of adenosine, as determined from epicardial surface transudates, returned to preinfusion levels within 10 minutes of washout. The duration of adenosine infusion had no effect on the extent of attenuation of AR at the end of the infusion. Whereas AR returned to preadenosine levels with washout of shorter adenosine infusions (1 and 5 minutes), there was a slow and incomplete recovery of AR after the longer exposures (30 and 60 minutes) to adenosine. The magnitude of this persistent antiadrenergic effect (PAE) of adenosine at 15 minutes of washout was proportional to the epicardial concentration of adenosine during infusion of the nucleoside. Infusion of adenosine either with the nonselective adenosine receptor antagonist 8-p-sulfophenyl theophylline or with the selective A1-receptor antagonist 1,3-dipropyl, 8-cyclopentylxanthine, abolished the PAE during the washout period. In addition, the PAE could be demonstrated only with the selective A1-receptor agonist 2-chloro-N6-cyclopentyladenosine and not with the selective A3-receptor agonist 4-aminobenzyl-5'-N methylcarboxamido-adenosine. When the protein kinase C (PKC) inhibitor chelerythrine was coadministered with adenosine, the PAE of adenosine was not apparent during adenosine washout. A 30-minute infusion of phenylephrine, an alpha-adrenergic agonist that enhances PKC activity, produced a PAE that lasted for up to 30 minutes of washout. This effect was prevented by the coinfusion of chelerythrine. Thus, it is concluded that the PAE of adenosine is determined by the myocardial concentration of this nucleoside and is manifested when myocardial concentrations of adenosine returned to baseline levels. Moreover, a 5-minute duration of adenosine exposure is required for the expression of the PAE. This latter effect seems to be dependent on adenosine-induced PKC activation via A1-receptors.

Myocardial effects of cyclic AMP phosphodiesterase inhibition are dampened in thyroxine-induced cardiac hypertrophy

We tested the hypothesis that the increase in myocardial O2 consumption (MVO2) and myocardial wall thickening in response to milrinone would not be limited by thyroxine (T4)-induced (0.5 mg/kg for 16 days) cardiac hypertrophy. Anesthetized open-chest New Zealand white rabbits were divided into four groups: control vehicle (CV, n = 5), control milrinone (CM, n = 8), T4 vehicle (T4V, n = 7), and T4 milrinone (T4M, n = 9). Vehicle or milrinone (10(-3) M) were topically applied to the left ventricular epicardium for 15 min. Coronary blood flow (radioactive microspheres) and O2 extraction (microspectrophotometry) were used to determine O2 consumption. Cyclic AMP levels were determined by radioimmunoassay. T4 increased the heart weight to body weight ratio from 2.6 +/- 0.1 to 3.1 +/- 0.1 (g/kg). T4 rabbits had significantly higher baseline heart rates, blood pressures, and dP/dtmax and both subepicardial (EPI) and subendocardial (ENDO) blood flows. Topical application of milrinone did not have significant hemodynamic effects in either group. Baseline cyclic AMP levels (pmol/g) in the EPI and ENDO myocytes were comparable between control and T4 rabbits (CVEPI = 599 +/- 34, CVENDO = 532 +/- 26, T4VEPI = 656 +/- 42, T4VENDO = 657 +/- 17). Milrinone increased cyclic AMP in all groups although the increases were less in the T4 rabbits (CMEPI = 742 +/- 115, CMENDO = 698 +/- 101, T4MEPI = 742 +/- 103, T4MENDO = 690 +/- 55). Baseline MVO2 (ml O2/min/100 g) was significantly higher in T4 rabbits than controls (T4VEPI = 17.7 +/- 3.5 vs CVEPI = 8.5 +/- 1.5, T4VENDO = 17.2 +/- 3.2 vs CVENDO = 9.2 +/- 1.5). Significant increases in MVO2 were noted with the addition of milrinone in control (CMEPI = 14.8 +/- 3.0, CMENDO = 13.5 +/- 1.6) and T4 (T4MEPI = 25.5 +/- 3.4, T4MENDO = 22.0 +/- 3.3) rabbits; however, the percentage increase in MVO2 was significantly greater in controls (CEPI = 73%, CENDO = 47%) than T4 (T4,EPI = 44%, T4,ENDO = 28%). Thus, although the cyclic AMP phosphodiesterase activity was comparable between T4 rabbit hearts and controls, the metabolic effects and cyclic AMP effects of milrinone were dampened in this form of hypertrophy.

Presence of immunoreactive endothelin-1 and atrial natriuretic peptide in human pericardial fluid

This study was undertaken to characterize endothelin-1 (ET-1) and atrial natriuretic peptide (ANP) concentrations in human pericardial fluid, blood plasma, right atrial appendage and papillary muscle by use of specific radioimmunoassays. In patients undergoing cardiac surgery (n=16) pericardial fluid mean immunoreactive (ir-) ET-1 and ir-ANP levels were 36-fold and 4-fold higher than corresponding plasma levels, respectively. In high performance liquid chromatography (HPLC) pericardial fluid ir-ET-1 was indistinguishable from human ET-1[1-21] and the majority of pericardial fluid ir-ANP coeluted with human ANP[99-126]. Atrial tissue ir-ET-1 and ir-ANP concentrations were 17-fold and 870-fold higher than in ventricular tissue. Our present study demonstrated for the first time the presence of ir-ET-1 in the pericardial fluid in humans. Human pericardial fluid contained far the highest concentrations of ET-1 among all biological fluids tested thus far. The functions of pericardial fluid ET-1 and ANP on cardiac performance and coronary vascular tone require further investigations.

Characterization and stimuli for production of pericardial fluid atrial natriuretic peptide in dogs

Recently high immunoreactive atrial natriuretic peptide (ir-ANP) levels have been found in the pericardial fluid of patients undergoing cardiac surgery. The present study was designed to characterize pericardial fluid ANP in anesthetized dogs. Pericardial fluid ir-ANP levels were 3.4-fold higher than plasma levels and the molecular form, revealed by high performance liquid chromatography, was indistinguishable from ANP[99-126]. Elimination of [125I]ANP was 5-fold slower in the pericardial space than in plasma. Activity of the major ANP degrading enzyme, neutral endopeptidase (NEP, EC 3.4.24.11), was 15-times higher in the pericardial fluid than in plasma. Right atrial balloon distension and rapid right ventricular pacing induced maximally 2.3-fold and 1.5-fold increases of pericardial fluid ir-ANP, respectively. Pericardial fluid ir-ANP concentrations and right atrial pressure values showed significant correlation during the stimuli. Our present results show that high concentrations of ir-ANP can be found in the dog pericardial fluid even under unstimulated conditions. Slow elimination of ANP from the pericardial fluid compartment may contribute to the high peptide levels. However this slow elimination cannot be attributed to a lower NEP activity. High basal levels of ANP in the pericardial fluid could be further increased by atrial balloon stretch and rapid ventricular pacing. The increase of pericardial fluid ir-ANP appeared to be a stretch-dependent response. ANP released into the pericardial fluid may be involved in the regulation of cardiac function and coronary vascular tone.

Pericardial trauma and adhesions in relation to reoperative cardiac surgery

In an attempt to appreciate the changes that favour adhesion formation we compared the morphological and fibrinolytic changes that occur in human primary and reoperative pericardium. Ten patients undergoing primary elective open heart surgery and ten undergoing first time reoperative open heart surgery were studied. Pericardial samples were taken at four time points. At 0 (time A) and 30 (time B) minutes from the time of pericardiotomy (before the commencement of CPB), 30-50 minutes (time C) after the commencement of CPB, and then finally 10 minutes (time D) after the patient had been rewarmed. The fibrinolytic activity, as measured by the plasminogen activating activity (PAA), in the pericardial samples of the ten primary cases was compared with that in 5 of the reoperative cases. For the primary group, the PAA after 30 minutes of exposure (median 6.65 IU/cm2, range 3.85-11.89 IU/cm2, p = 0.14, n = 10) was not significantly reduced when compared to the initial activity (median 8.74 IU/cm2, range 2.22-17.68 IU/cm2, n = 10). After 30-50 minutes CPB the PAA was significantly reduced (median 3.93 IU/cm2, range 1.5-13.24 IU/cm2, p = 0.028, n = 10) and still reduced after rewarming for 10 minutes (median 3.12 IU/cm2, range 0.88-19.93 IU/cm2, p = 0.047, n = 10). The simultaneous plasma tissue-type plasminogen activator activity showed a significant (p < 0.05) increase after 30-50 minutes bypass with a later decline. The changes in the reoperative pericardial PAA were similar. In addition, the degree of PAA in reoperative pericardium was consistently lower than that observed in primary tissue. The extent of primary pericardial mesothelial damage at times B, C, and D compared with that at time A showed a significant (p < 0.01 for times B, C, and D) increase. Similarly there was a significant worsening of the degree of inflammation. Compared with primary pericardium, the reoperative samples showed a significant (p < 0.01 for times A, B, and C) preponderance of damaged mesothelium at the earlier stages of the operation. It appears that, following the initial bypass surgery, the processes that cause pericardial and mesothelial healing with recovery of PAA compete with those leading to pericardial adhesions and fibrosis. The histological and biochemical outcome seen in reoperative pericardium is the result of these competitive actions.

Detection of remnant proteolytic activities in unimplanted glutaraldehyde-treated bovine pericardium and explanted cardiac bioprostheses

The presence and activity of proteolytic enzymes has been investigated in vitro on soluble and insoluble preparations obtained from both unimplanted and implanted glutaraldehyde-treated bovine parietal pericardium. Using detection by colorimetric techniques, soluble preparations were shown to hydrolyze enzyme substrates that are characteristic for trypsin-like proteases, cathepsin-like proteases, and collagenase. As detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in gradient gels and gel filtration on Sepharose CL-6B, insoluble (pellet) preparations degraded denatured type I collagen in a time-dependent pattern, producing low-molecular-weight fragments. These activities were partially inhibited by phenylmethylsulfonyl fluoride, N-ethyl maleimide, soybean trypsin inhibitor, para-chloromercuribenzoic acid, or ethylenediaminetetraacetic acid, suggesting the presence of a heterogeneous enzymatic mixture. Insoluble preparations incubated with pure pericardial dermatan sulfate proteoglycan detached the glycosaminoglycan chains from their core protein carrier, producing a digestion pattern similar to Cathepsin C. These findings demonstrate the presence of active proteases in glutaraldehyde-fixed bovine pericardium per se and in explanted pericardial bioprosthetic cardiac valves, an additional factor that might contribute to intrinsic extracellular matrix degeneration in pericardial bioprosthetic devices.

Characterization of paraoxonase activity in pericardial fluid: usefulness as a marker of coronary disease

In this study, the presence of paraoxonase activity in pericardial fluid was demonstrated. A comparison of some properties, such as optimum pH, stability versus pH, heat inactivation, effect of inhibitors, isoelectric point and kinetic parameters (Km and Vmax), between plasma and pericardial fluid paraoxonase was made. The properties studied were practically identical. The enzyme activity in pericardial fluid was tested as a marker in the postmortem diagnosis of myocardial infarction. The paraoxonase activity in the myocardial infarction group (47 cases) was lower than in the control group (40 cases), but the difference was not significant.

Effects of metallic ions and diphosphonates on inhibition of pericardial bioprosthetic tissue calcification and associated alkaline phosphatase activity

This study focused on the association of extrinsic alkaline phosphatase (AP) activity with both early and advanced calcification of glutaraldehyde-pretreated bovine pericardial bioprosthetic (GPBP) tissue, and the inhibition of both calcification and AP activity by pre-incubation in diphosphonates (sodium-ethanehydroxydiphosphonate [NaEHDP], aminopropanehydroxydiphosphonate [APD]) and metallic salts (FeCl3, Ga(NO3)3, AICI3). GPBP specimens were implanted subcutaneously in 3 wk old male rats after pre-incubation. Following explantation of the tissue at 72 h and 21 d, calcification was assessed morphologically by light microscopy and chemically by atomic adsorption spectroscopy for calcium content and by molybdate complexation for phosphorus. AP activity was characterized by enzymatic hydrolysis of paranitrophenyl phosphate and by histochemical studies. In both control and pretreated groups, AP levels were greater in 72 h explants than 21 d retrievals, which demonstrated extensive calcification in control explants. All pre-incubations that resulted in inhibition of calcification after 21 d, except for APD, were associated with 72 h AP content which was lower than control specimens. The typical time of initiation of calcification was 72 h, as determined by previous studies with this model system. Covalently bound APD inhibited calcification. Increased AP activity in the APD group may be due to the toxicity of this agent with resultant acute inflammation, or other incompletely understood effects of diphosphonates on calcification and AP. Furthermore, EHDP and Ga3+ incubations were also associated with decreased GPBP AP at 72 h compared to control, but were not effective for inhibiting calcification after 21 d. We concluded that inhibition of peak GPBP AP activity is not necessarily associated with the prevention of GPBP mineralization.

Necropsy study of association between sudden death and cardiac enzymes

AIMS

To determine if cardiac enzymes measured at necropsy could be used to predict early myocardial infarction.

METHODS

Cardiac enzyme activities were measured in body fluids at necropsy. Coroners' necropsies were grouped by gross and microscopic findings into cases of definite myocardial infarction, cases with occlusive coronary artery atheroma but no identifiable myocardial infarction, and non-cardiac cases. Pericardial fluid, peripheral venous blood, and blood from the right atrium were collected. Total creatine phosphokinase, creatine phosphokinase isoenzymes, aspartate aminotransferase and hydroxybutarate dehydrogenase activities were measured and the results analysed by logistic regression.

RESULTS

The values of creatine phosphokinase and its isoenzymes were raised in those who had died of cardiac disease and were most discriminatory. Cases of early myocardial infarction without evidence of infarction on routine histological examination could be identified from enzyme activities.

CONCLUSIONS

Measurement of cardiac enzymes in blood and pericardial fluid at necropsy can provide valuable additional information in cases of sudden death as a result of myocardial ischaemia which have occurred before macroscopic or microscopic evidence of myocardial infarction.

Differences in myosin isoform expression in the subepicardial and subendocardial myocardium during cardiac hypertrophy in the rat

We have investigated myosin isoform expression during progressive cardiac hypertrophy and the development of congestive heart failure in young male rats. Cardiac enlargement was produced by placing a constricting band (0.024-inch diameter) around the ascending aorta of 25-day-old animals, which resulted in progressively increased stenosis as the rat matured. A 57% and 77% cardiac hypertrophy was observed at 2 and 8 weeks, respectively, with signs of congestive failure at the latter time point. Myosin isoform expression was examined in the subendocardial and subepicardial myocardium of the left ventricle and the free wall of the right ventricle by use of native gel electrophoresis. The percentage of the V3 isoform increased dramatically in both ventricles. In the subendocardial myocardium of the left ventricle, expression of the V3 isoform increased (p less than or equal to 0.05) relative to the subepicardial myocardium at 2, 4, and 8 weeks (17.1% vs. 10.2%, 29.4% vs. 18%, and 46.6% vs. 36.2%). In addition to regional differences within a given transmural segment, we also observed a high degree of heterogeneity in myosin isoform expression throughout a given layer (particularly the subendocardial myocardium) when small (less than or equal to 10-15 mg) adjacent samples were examined. This variability illustrated a potential danger in interpretation of gel results obtained from a single small tissue sample. Thus, cardiac hypertrophy produced by pressure overload in 25-day-old rats resulted in significantly increased V3 myosin in both the left and right ventricles. Furthermore, within the hypertrophied left ventricle, the subendocardial myocardium contained a significantly greater percentage of V3 myosin than the subepicardial myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline phosphatase activity of glutaraldehyde-treated bovine pericardium used in bioprosthetic cardiac valves

Bioprosthetic valves fail frequently because of pathological mineralization, a process that begins in cell remnants of the glutaraldehyde (GLUT) fixed tissue. Other pathological cardiovascular calcification and physiological mineralization in skeletal/dental tissues are both largely initiated in cell-derived membranous structures (often called "matrix vesicles"), and the enzyme alkaline phosphatase (AP) likely has an important function in the pathogenesis of mineral nucleation. This study tested the hypothesis that AP might also be present in and contribute to calcification of bioprosthetic valves. AP activity of fresh and GLUT-treated bovine pericardium was measured by the conversion of p-nitrophenyl phosphate to p-nitrophenol. Following 24 hours in 0.6% HEPES-buffered GLUT and storage for 2 weeks in 0.2% GLUT, considerable AP hydrolytic activity remained in GLUT-treated tissue relative to that of fresh tissue (Vmax, 24 vs. 45 mumol reaction product/min/mg tissue protein, respectively), although binding was somewhat reduced (Km, 1.9 X 10(3) vs. 1.4 X 10(3) microM substrate, respectively). Enzyme reaction product was demonstrated in both fixed and fresh tissue by light microscopic histochemical studies, confirming the biochemical results. Reaction product was noted along membranes of vascular endothelial cells and interstitial fibroblasts, the sites of early calcific deposits in bioprosthetic valves, by ultrastructural examination of GLUT-treated tissue. We conclude that GLUT-treated bovine pericardium retains much of the hydrolytic activity of AP, an enzyme associated with normal skeletal and pathological cardiovascular and noncardiovascular mineralization, and suggest that further examination of the mechanistic role of this enzyme may stimulate new approaches for slowing or preventing calcification of bioprosthetic tissue.

Phosphatase enzyme activity is retained in glutaraldehyde treated bioprosthetic heart valves

Calcification of bioprosthetic valves, which frequently causes their failure, begins in cell remnants analogous to matrix vesicles of physiologic mineralization. Because the enzyme alkaline phosphatase (AP) is important in normal skeletal mineralization, the authors hypothesized that AP also might be present in bioprosthetic valve tissue and thereby contribute to calcification. AP activity of fresh and glutaraldehyde (GLUT) treated bovine pericardium was measured by the conversion of p-nitrophenyl phosphate to p-nitrophenol. After 24 hrs in 0.6% HEPES buffered GLUT and storage for 2 weeks in 0.2% GLUT, considerable AP hydrolytic activity remained relative to that of fresh tissue (Vmax: 24 vs 45 microM reaction product/min/mg tissue protein, respectively), although binding was moderately reduced (KM: 1900 vs 1400 microM substrate, respectively). Light microscopic histochemistry suggested cell oriented AP activity. Ultrastructural examination of GLUT treated tissue demonstrated reaction product along membranes of vascular endothelial cells and fibroblasts, the sites of early calcific deposits in bioprosthetic valves. Thus, AP hydrolytic activity is largely preserved following GLUT treatment of bovine pericardium. These results indicate that the widely held view that GLUT eliminates all metabolic activities of bioprosthetic tissue is inaccurate and suggests that examination of the role of AP and other phosphatases may stimulate approaches for inhibiting calcification.

Adenosine's role in regulating basal coronary arteriolar tone

This study examined the role of adenosine in regulating coronary arteriolar tone under basal conditions in the normal coronary circulation. Measurements of hemodynamics and flow (microspheres) were made in eight closed-chest, sedated pigs at 1) control and 2) after 10 min of infusion of adenosine deaminase (ADA, 10 U X kg-1 X min-1) into the left anterior descending (LAD) coronary artery. Heart rate was held constant by atrial pacing. Transmural flow in the distal LAD zone did not change versus control (1.81 +/- 0.36) with ADA (1.78 +/- 0.46). However, in comparison with control the distal LAD:circumflex zone transmural flow ratio (0.96 +/- 0.04) declined (P less than 0.01) during ADA infusion (0.93 +/- 0.04). Similarly, the distal LAD:circumflex zone transmural flow resistance ratio increased significantly (P less than 0.01) versus control (1.04 +/- 0.05) in response to intracoronary ADA infusion (1.08 +/- 0.04). Regional myocardial oxygen consumption in the distal LAD zone did not change versus control (16.9 +/- 3.3 3.3 ml X min-1 X 100 g-1) during ADA (16.9 +/- 4.5). Additional studies in 15 open-chest swine given intracoronary infusion of ADA demonstrated that 1) the enzyme penetrates the interstitial fluid (ISF) and 2) attains ISF levels which are adequate to reduce basal adenosine concentration 10 fold even if substantial increase in adenosine production occurs in response to ADA. Thus, since destruction of adenosine by ADA caused only very modest relative reduction in regional flow, it is likely that the nucleoside plays only a limited role in regulation of arteriolar tone under basal conditions in the normal coronary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

The biochemical changes in pericardial fluid after death. An investigation of the relationship between the time since death and the rise or fall in electrolyte and enzyme concentrations and their possible usefulness in determining the time of death

This paper reports the biochemical changes that occur in pericardial fluid after death. Significant changes in relation to the time since death occurred in potassium, sodium, phosphate, protein and several commonly measured enzymes. The variation in individual results at similar times since death would limit the use of pericardial fluid biochemistry in determining the time of death.

Postmortem diagnosis of myocardial disease by enzyme analysis of pericardial fluid

The authors measured the activities of CK, LDH, and their isoenzymes in pericardial fluid to determine their usefulness in evaluating acute myocardial injury. Their prospective study reveals that these enzymes significantly are elevated in cardiac deaths in contrast to fatalities from noncardiac causes. Also, a group of healthy individuals who were victims of violent deaths and died from extracardiac injuries had enzyme elevations greater than those found in acute cardiac deaths, suggesting catecholamine-mediated myocardial injury (stress cardiomyopathy) as part of the physiologic response to trauma. Measurements of cardiac enzymes in pericardial fluid may prove useful in establishing the postmortem diagnosis of acute myocardial injury in instances when such injury is suspected but cannot be established by ordinary histologic methods. Studies such as this may help in defining the participation of myocardial injury as one of the lethal mechanisms in various causes of death.

Reversible, highly localized alterations in fatty acid metabolism in the chronically ischemic canine myocardium

Acute myocardial ischemia is accompanied by a marked decrease in the oxidation of fatty acids. Whether similar changes occur during chronic ischemia was studied in 13 beagles. In 10 dogs, an ameroid constrictor was implanted about the left circumflex artery; 3 others served as sham-operated controls. Mitochondrial and peroxisomal fatty acid oxidation of (1-14C)oleate were measured and compared in affected (posterobasal left ventricular endocardial [posterior LV endo]) and unaffected (anteroapical LV epicardial [anterior LV epi]) tissues of control and experimental dogs. Five experimental and 3 control dogs were killed after 3 weeks. The posterior LV endo sections of experimental dogs at 3 weeks showed increased fatty acid oxidation due to peroxisomal (KCN-insensitive) beta oxidation (p less than 0.01). The anterior LV epi sections showed no difference in fatty acid oxidation between sham-operated and experimental dogs. Five dogs were studied after 3 months; fatty acid oxidation of the posterior LV endo section was normal. Thus, under a slowly evolving state of myocardial ischemia, highly localized and reversible adaptive changes in fatty acid oxidation occur that enable the affected tissue to cope with a fatty acid load. When collateralization is accomplished, fatty acid metabolism reverts to normal.

Ischemia-induced alterations in myocardial (Na+ + K+)-ATPase and cardiac glycoside binding

The effects of ischemia on the canine myocardial (Na+ + K+)-ATPase complex were examined in terms of alterations in cardiac glycoside binding and enzymatic activity. Ability of the myocardial cell to bind tritiated ouabain in vivo was assessed after 1, 2, and 6 h of coronary occlusion followed by 45 min of reperfusion, and correlated with measurements of in vitro (Na+ + K+)-ATPase activity and in vitro [3H]ouabain binding after similar periods of ischemia. Regional blood flow alterations during occlusion and reperfusion were simultaneously determined utilizing 15 mum radioactive microspheres to determine the degree to which altered binding of ouabain might be flow related. Anterior wall infarction was produced in 34 dogs by snaring of confluent branches of the left coronary system. Epicardial electrograms delineated ischemic and border zone areas. Coronary reperfusion after 2 and 6 h of occlusion was associated with impaired reflow of blood and markedly impaired uptake of [3H]ouabain in ischemic myocardium. In both groups, in vivo [3H]ouabain binding by ischemic tissue was reduced out of proportion to the reduction in flow. Despite near-complete restoration of flow in seven dogs occluded for 1 h and reperfused, [3H]ouabain remained significantly reduced to 58 +/- 9% of nonischemic uptake in subendocardial layers of the central zone of ischemia. Thus, when coronary flow was restored to areas of myocardium rendered acutely ischemia for 1 or more hours, ischemic zones demonstrated progressively diminished ability to bind ouabain. To determine whether ischemia-induced alteration in myocardial (Na+ + K+)-ATPase might underlie these changes, (Na+ + K+)-ATPase activity and [3H]ouabain binding were measured in microsomal fractions from ischemic myocardium after 1, 2, and 6 h of coronary occlusion. In animals occluded for 6 h, (Na+ + K+)-ATPase activity was significantly reduced by 40% in epicardial and by 35% in endocardial layers compared with nonischemic myocardium. Comparable reductions in in vitro [3H]ouabain binding were also demonstrated. Reperfusion for 45 min after occlusion for 6 h resulted in no significant restoration of enzyme activity when compared to the nonreperfused animals. In six animals occluded for 2 h, a time at which myocardial creatine phosphokinase activity remains unchanged, (Na+ + K+)-ATPase activity was reduced by 25% compared with nonischemic enzyme activity. In five dogs occluded for 1 h, (Na+ + K+)-ATPase activity in ischemic myocardium was unchanged from control levels. We conclude that reduced regional myocardial blood flow, local alterations in cellular milieu, and altered glycoside-binding properties of (Na+ + K+)-ATPase all participate in the reduction of cardiac glycoside binding observed after reperfusion of ischemic myocardium. In addition, after 2 or more hours of severe ischemia, myocardial (Na+ + K+)-ATPase catalytic activity is significantly reduced despite incubation in the presence of optimal substrate concentrations.