Xenogenic esophagus scaffolds fixed with several agents: comparative in vivo study of rejection and inflammation.

Most infants with long-gap esophageal atresia receive an esophageal replacement with tissue from stomach or colon, because the native esophagus is too short for true primary repair. Tissue-engineered esophageal conducts could present an attractive alternative. In this paper, circular decellularized porcine esophageal scaffold tissues were implanted subcutaneously into Sprague-Dawley rats. Depending on scaffold cross-linking with genipin, glutaraldehyde, and carbodiimide (untreated scaffolds : positive control; bovine pericardium : gold standard), the number of infiltrating fibroblasts, lymphocytes, macrophages, giant cells, and capillaries was determined to quantify the host response after 1, 9, and 30 days. Decellularized esophagus scaffolds were shown to maintain native matrix morphology and extracellular matrix composition. Typical inflammatory reactions were observed in all implants; however, the cellular infiltration was reduced in the genipin group. We conclude that genipin is the most efficient and best tolerated cross-linking agent to attenuate inflammation and to improve the integration of esophageal scaffolds into its surrounding tissue after implantation.

Malignant lymphoma of T-cell origin in a Humboldt penguin (Spheniscus humboldti) and a pink-backed pelican (Pelecanus rufescens).

Multicentric T-cell lymphomas were diagnosed in two birds from separate zoological collections: one in a 27-year-old female Humboldt penguin (Spheniscus humboldti) and the second in an adult pink-backed pelican (Pelecanus rufescens). The main clinical sign in the penguin was dysphagia caused by lymphoma formation in the esophagus. Besides the esophageal lymphoma, neoplastic lymphoid cells were observed in the adrenal glands, liver, kidneys, lung, proventriculus, and gizzard. The pelican was found dead without a clinical history. Neoplastic lymphoid cells were observed in the kidneys, liver, pancreas, spleen, ventriculus, and small intestine. Neoplastic cells of the penguin as well as of the pelican were immunoreactive to CD3 antigen, suggesting the lymphomas were of T-cell origin. In both cases, test results were negative for Marek's disease virus, avian leukosis virus, and reticuloendotheliosis virus. In the pelican, a skin melanoma was diagnosed on the left throat pouch in addition to the multicentric T-cell lymphoma.

Bone marrow-derived stem cells attenuate impaired contractility and enhance capillary density in a rabbit model of Doxorubicin-induced failing hearts.

BACKGROUND: There is a regenerative potential of bone marrow-derived stem cells (BMCs) in ischemic cardiomyopathy, but little is known of their effects in nonischemic cardiomyopathy. This study evaluates the effects of BMC transplantation on contractility and remote capillary density of doxorubicin-induced failing hearts. METHODS: Heart failure was induced in rabbits by doxorubicin (3 mg/kg; 6 weeks), followed by BMC transplantation (BMC group, 1.5-2.0 x 10(6) cells, n = 15), sham treatment (Medium group, n = 10), or no therapy (Dox group, n = 6). Healthy rabbits were used as controls (n = 10). Cells were transplanted locally into the left ventricle (LV). Four weeks later, contractility was assessed. Cross-sections of hearts were investigated by H&E, Picrosirius red stain, and immunohistologically (Troponin I, alpha-Actinin, Connexin43). Capillary density (CD31-antigen) was examined in the LV, septum, and right ventricle (RV). RESULTS: Global contractility was significantly higher in the BMC group versus Medium group (ejection fraction: 39.0 +/- 1.4% vs. 30.0 +/- 1.9%, p = 0.002, and fractional shortening: 22 +/- 0.8 vs. 19 +/- 0.6, p < 0.01). Hemodynamic measurements by Millar catheter (Millar Instruments, Houston, TX, USA) were also significantly improved. Capillary density increased in cell-treated hearts (LV: 55 +/- 2.2 vs. 42 +/- 2.0, p < 0.001, RV: 40 +/- 2.1 vs. 35 +/- 1.7, p = 0.065, and septum: 46 +/- 1.5 vs. 39 +/- 1.7, p = 0.005), when compared to the Medium group. The transplanted cells failed to express cardiac markers. The collagen content was reduced in BMC-treated rabbits. CONCLUSION: Despite local cell transplantation, autologous BMCs improve global contractility and enhance remote capillary density and collagen content in doxorubicin-induced cardiomyopathy. However, BMCs failed to transdifferentiate into new cardiomyocytes.

An immunohistochemical study of the role of matrix metalloproteinases and their tissue inhibitors in chronic mitral valvular disease (valvular endocardiosis) in dogs.

While the pathogenesis of chronic valvular disease (CVD) in dogs remains unclear, alterations in the activity of specific metalloproteinase enzymes and their inhibitors within the valve stroma are suspected of having a role. This study describes the immunohistochemical distribution pattern of matrix metalloproteinase (MMP) types 2, 9 and 14 and their tissue inhibitors, termed tissue inhibitors of metalloproteinase (TIMP), types 2 and 3, in normal canine mitral valves (MVs) (n=10) and in dogs with mild (n=7), moderate (n=14) and severe (n=9) CVD. In normal MVs, MMP-2 and -14, and TIMP-2 were expressed in isolated stromal cells. Tissue inhibitor of metalloproteinase-3 exhibited moderate intracellular and mild extracellular expression. With increasing severity of CVD, the expression of MMP-2 decreased. The number of stromal cells expressing MMP-14 increased, predominantly in the margins of the nodular lesions. Tissue inhibitor of metalloproteinase-2 and -3 expression increased both intra- and extracellularly. Matrix metalloproteinase-9 was not detected in normal or diseased valves. In conclusion, CVD was characterised by alterations in the distribution and intensity of valvular MMP and TIMP expression, suggesting that depressed catabolism and the accumulation of extracellular matrix components within affected valves contributes to their structural alteration and consequent loss of function.

Chronic endometritis in an Asian elephant (Elephas maximus).

A 48-yr-old female Asian elephant with a history of pododermatitis developed recurrent hematuria beginning in 2002. Transrectal ultrasonography and endoscopic examination in 2004 identified the uterus as the source of hematuria and excluded hemorrhagic cystitis. Treatment with Desloreline implants, antibiotics, and homeopathic drugs led to an improved general condition of the elephant. In July 2005, the elephant was suddenly found dead. During necropsy, the severely enlarged uterus contained about 250 L of purulent fluid, and histopathology revealed ulcerative suppurative endometritis with high numbers of Streptococcus equi ssp. zooepidemicus and Escherichia coli identified on aerobic culture. Additional findings at necropsy included: multifocal severe pododermatitis, uterine leiomyoma, and numerous large calcified areas of abdominal fat necrosis. Microbiologic culture of the pododermatitis lesion revealed the presence of Streptococcus agalactiae, Streptococcus equi ssp. zooepidemicus, Staphylococcus sp., Corynebacterium sp., and Entercoccus sp.

MSG1, a surface-localised protein of Mycoplasma suis is involved in the adhesion to erythrocytes.

Mycoplasma suis is a member of the group of uncultivable haemoplasmas which colonise erythrocytes of a wide range of vertebrates. Adhesion to erythrocytes is the crucial step in the unique haemoplasma life cycle. Due to the lack of a cultivation system, no adhesion structures have been identified so far. In order to determine potential adhesion molecules of M. suis, we screened genomic M. suis libraries. The protein MSG1 with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) similarity was identified. The encoding gene msg1 is 1011bp in size. The overall homology of the deduced amino acid sequence to GAPDHs of other pathogenic mycoplasmas ranged from 52.6% to 54.5%. Recombinant MSG1 expressed in Escherichia coli exhibited GAPDH activity. Immunoblot and immunoelectron microscopy analyses using antibodies against rMSG1 verified the membrane and surface localisation of native MSG1 in M. suis. Furthermore, we showed that rMSG1 binds to erythrocyte lysate in a dose-dependent manner. E. coli transformants which express MSG1 on their surface acquire the ability to adhere to porcine erythrocytes. This adhesion could be specifically and significantly inhibited by rMSG1 and antibodies to MSG1. In conclusion, our studies indicate that the membrane-associated MSG1 represents the first putative adhesion protein identified in the group of haemoplasmas.

First identification and functional characterization of an immunogenic protein in unculturable haemotrophic Mycoplasmas (Mycoplasma suis HspA1).

The antigenic structures of the haemotrophic Mycoplasma suis, an epicellular parasite of porcine erythrocytes, are largely unknown due to its unculturability. In this study, serological proteome and mass spectrometry analyses allowed the characterization of M. suis proteins targeted by the porcine antibody response: two proteins with characteristics of heat shock proteins, two proteins with characteristics of glycolytic enzymes, a RNA helicase- and an actin-like protein. The DnaK-like protein of M. suis (HspA1) was further analysed genetically and functionally. Its encoding gene (M. suis a1 gene) is 1.830 bp in size and corresponds to a 67 kDa protein. Immunoelectron microscopy verified the surface accessibility of HspA1 in M. suis. Recombinant HspA1 expressed in Escherichia coli demonstrated ATPase activity and antigenicity in experimentally infected pigs. In conclusion, this first identification and recombinant expression of an antigenic protein of M. suis provides the basis for the development of vaccines and new in vitro diagnostic assays.

Comparing the ultrastructural effects of two different cardiac preparation- and perfusion-techniques in a porcine model of extracorporal long-term preservation.

OBJECTIVE: In heart transplantation a well-preserved myocardial ultrastructure is an important precondition for functional regeneration. Aim of the study is to optimize the conditions in this new established model of extracorporeal cardiac perfusion. METHODS: (I) In six pigs, hearts were arrested with Bretschneider Histidine-Tryptophan-Ketoglutarate cardioplegia and cold ischemia, explanted and connected to a circulating constant pressure Langendorff system (80-90mmHg) and perfused with leukocyte depleted autologous blood. (II) Beating hearts of seven pigs were explanted and connected immediately to the Langendorff system (40-50mmHg). Myocardial biopsies (n=55) were taken in situ and during the following 12h of reperfusion, and were prepared for electron microscopy. RESULTS: Cardioplegia and hypothermia (group I) induced mitochondrial edema and myofibrillar degeneration in cardiomyocytes and severe endothelial edema. During 4h of reperfusion, mitochondrial edema, myofibrillar, and sarcolemmal damages in cardiomyocytes increased. Moderate endothelial degeneration, interstitial edema, and bleedings appeared. In contrast, in group II after 6h of reperfusion endothelia showed only mild alterations. Cardiomyocytes showed myofibrillary but not mitochondrial degeneration. Interstitial edema and bleedings were mild. CONCLUSION: Avoiding cardioplegia and hypothermia, and using lower perfusion pressure resulted in a better preservation of the ultrastructure in explanted hearts at the Langendorff system.

Serum cardiac troponin I and cardiac troponin T concentrations in dogs with gastric dilatation-volvulus.

OBJECTIVE: To determine whether serum concentrations of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) are increased in dogs with gastric dilatationvolvulus (GDV) and whether concentrations correlate with severity of ECG abnormalities or outcome. DESIGN: Prospective case series. ANIMALS: 85 dogs with GDV. PROCEDURE: Serum cTnl and cTnT concentrations were measured 12 to 24, 48, 72, and 96 hours after surgery. Dogs were grouped on the basis of severity of ECG abnormalities and outcome. RESULTS: cTnl and cTnT were detected in serum from 74 (87%) and 43 (51%) dogs, respectively. Concentrations were significantly different among groups when dogs were grouped on the basis of severity of ECG abnormalities (none or mild vs moderate vs severe). Dogs that died (n = 16) had significantly higher serum cTnI (24.9 ng/ml) and cTnT (0.18 ng/ml) concentrations than did dogs that survived (2.05 and < 0.01 ng/ml, respectively). Myocardial cell injury was confirmed at necropsy in 4 dogs with high serum cardiac troponin concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that concentrations of cTnI and cTnT suggestive of myocardial cell injury can commonly be found in serum from dogs with GDV and that serum cardiac troponin concentrations are associated with severity of ECG abnormalities and outcome.

First description of Mycobacterium heckeshornense infection in a feline immunodeficiency virus-positive cat.

A 13-year-old cat was presented to the veterinary clinic with poor condition, vomiting and a reduced appetite. A painful abdomen was diagnosed because of tension and defence reactions on palpation. Diagnostic laparotomy showed a thickening of the colon and caecal intestinal wall. Histopathological investigation of intestinal biopsies revealed focal severe granulomatous inflammation with numerous acid-fast bacilli in the tela submucosa. The complete blood count test showed a severe lymphopenia and anaemia, and the cat tested positive for feline immunodeficiency virus (FIV) antibodies by enzyme-linked immunosorbent assay. The cat was euthanased and necropsied. Multifocal granulomatous nodules were present in the intestines, liver and kidneys. The gastric lymph node was markedly enlarged and showed a caseous cut surface. Histopathology revealed a systemic mycobacteriosis affecting intestine, lymph nodes, liver and kidneys. The mycobacterial strain was cultured and determined by its unique 16S rRNA gene sequence as Mycobacterium heckeshornense. This is the first reported case of M heckeshornense in a cat. It was suspected that the disseminated mycobacteriosis was supported by the FIV infection.

The reverse remodeling effect of mesenchymal stem cells is independent from the site of epimyocardial cell transplantation.

OBJECTIVE: The transplantation of mesenchymal stem cells (MSCs) represents a promising approach for treating the ischemic and the nonischemic diseased heart. The positive effects of transplanting these cells could be shown, but the exact mechanisms remain unknown. We evaluated whether the injection site affects the improvement in left ventricular (LV) ejection fraction (EF) and angiogenesis in doxorubicin (Dox)-induced failing hearts. METHODS: Heart failure was induced in New Zealand white rabbits by doxorubicin treatment, followed by right ventricular MSC transplantation (RV-MSC, n = 6), LV MSC transplantation (LV-MSC, n = 6), sham treatment (sham group, n = 6), or no therapy (Dox group, n = 5). Healthy rabbits were used as control group (n = 8). Cells were isolated after bone marrow aspiration and transplanted locally into the ventricular myocardium. After 4 weeks, cardiac function and capillary density (CD31 staining) were measured. RESULTS: The transplantation of MSCs increased the EF significantly (LV-MSC, 39.0% ± 1.4%, and RV-MSC, 39.2% ± 2.6%, vs sham group, 29.8% ± 3.7%; P < 0.001), without significance between the MSC groups (P = 0.858). Neither the evidence of a transdifferentiation nor any signs of cell engraftment of transplanted cells could be found. The capillary density (capillaries/high-power field) increased in both MSC groups compared with the sham group (LV-MSC by 8.3% ± 3.4%; and RV-MSC, 8.1% ± 2.2%; P < 0.05), without significance between the two MSC groups (P = 0.927). CONCLUSIONS: Injection of autologous MSCs in doxorubicin-induced cardiomyopathic rabbit hearts improves EF and enhances angiogenesis. Despite local application, we observed global effects on heart function and capillary density without significant difference between right and LV injection. The paracrine mechanism might be one possible explanation for these findings.

Pathology, protein expression and signaling in myxomatous mitral valve degeneration: comparison of dogs and humans.

Myxomatous degenerative mitral valve disease (MMVD) is a common heart disease in dogs. Although several morphological similarities occur between human and canine MMVD differences exist. However, in advanced stages the accumulation of proteoglycans is the main finding in both species. The extracellular matrix (ECM) in normal canine and human mitral valves is similar. In MMVD of both species proteoglycans is the major alteration, although specific changes in collagen distribution exists. The valvular expression pattern of matrix metalloproteinases (MMPs) and of their inhibitors (TIMPs) differs, in part, between dogs and humans. The MMPs and TIMPs expression patterns are similar in normal canine and human mitral valves, but they are quite different during degenerative progression. Valve endothelial cells (VEC) and interstitial cells (VIC) are phenotypically transformed in canine and human MMVD. Inflammation is an unlikely cause of valve degeneration in humans and dogs. There are several lines of evidence suggesting that transforming growth factor ß1 (TGF ß1) and serotonin signaling may mediate valve degeneration in humans and dogs. Although human and canine MMVD share structural similarities, there are some differences in ECM changes, enzyme expression and cell transformation, which may reflect a varied pathogenesis of these diseases.

Morphological respiratory diffusion capacity of the lungs of ball pythons (Python regius).

This study aims at a functional and morphological characterization of the lung of a boid snake. In particular, we were interested to see if the python's lungs are designed with excess capacity as compared to resting and working oxygen demands. Therefore, the morphological respiratory diffusion capacity of ball pythons (Python regius) was examined following a stereological, hierarchically nested approach. The volume of the respiratory exchange tissue was determined using computed tomography. Tissue compartments were quantified using stereological methods on light microscopic images. The tissue diffusion barrier for oxygen transport was characterized and measured using transmission electron micrographs. We found a significant negative correlation between body mass and the volume of respiratory tissue; the lungs of larger snakes had relatively less respiratory tissue. Therefore, mass-specific respiratory tissue was calculated to exclude effects of body mass. The volume of the lung that contains parenchyma was 11.9±5.0mm(3)g(-1). The volume fraction, i.e., the actual pulmonary exchange tissue per lung parenchyma, was 63.22±7.3%; the total respiratory surface was, on average, 0.214±0.129m(2); it was significantly negatively correlated to body mass, with larger snakes having proportionally smaller respiratory surfaces. For the air-blood barrier, a harmonic mean of 0.78±0.05µm was found, with the epithelial layer representing the thickest part of the barrier. Based on these findings, a median diffusion capacity of the tissue barrier ( [Formula: see text] ) of 0.69±0.38ml O(2)min(-1)mmHg(-1) was calculated. Based on published values for blood oxygen concentration, a total oxygen uptake capacity of 61.16mlO(2)min(-1)kg(-1) can be assumed. This value exceeds the maximum demand for oxygen in ball pythons by a factor of 12. We conclude that healthy individuals of P. regius possess a considerable spare capacity for tissue oxygen exchange.

Crimping may affect the durability of transcatheter valves: an experimental analysis.

BACKGROUND: Transcatheter aortic valve implantation has gained widespread acceptance to treat elderly high-risk patients with aortic stenosis. We used a subcutaneous rat model to evaluate whether crimping may affect valve long-term durability. METHODS: Standard Sapien transcatheter valves (Edwards Lifesciences, Irvine, CA) were crimped for different durations (1 hour, 1 day, 1 month) and uncrimped, and leaflet pieces as well as control tissue (Perimount Magna, Edwards) were then implanted subcutaneously in 15 male weanling Sprague-Dawley rats for 12 weeks. Grade of calcification was measured by freeze-dried mass and van Kossa staining. Histologic and electron microscopic examination were performed to investigate potential leaflet-fragmentation caused by crimping. RESULTS: There were no differences in calcification among the groups. The calcium carbonate concentrations in all samples ranged from 0.1 to 100 mg/g dry weight. Leaflet morphology, however, differed from no fragmentation (control group) to highly fragmented tissue (1-month crimped). These differences reached statistical significance between crimped and non-crimped leaflets (p<0.003). CONCLUSIONS: Transcatheter valve crimping does not necessarily affect leaflet calcification. However, the structural changes of the leaflets that were caused by crimping may have clinical significance. Duration of crimping should be as short as possible, and very tight crimping to small diameters should be avoided.

Histomorphological findings and expression of matrix metalloproteinases and their tissue specific inhibitors (TIMPs) in normal tricuspid valves and in chronic tricuspid valvular disease in dogs.

The histomorphological findings and immunohistochemical expression of matrix metalloproteinases (MMPs-1, 2, 9 and 14) and their tissue inhibitors (TIMPs-2, 3 and 4) are reported in the parietal (pTV) and septal leaflets (sTV) of the tricuspid valves in normal dogs and dogs with chronic valvular disease (CVD). The layers of the normal sTV were not as well defined as in the pTV and the spongiosa of the sTV contained abundant mucopolysaccharides (MPS) and adipocytes. In CVD, there was expansion of the spongiosa of the pTV due to deposition of MPS, leading to formation of nodules along the free edge. In CVD, there was fibrosis of the atrialis of the sTV and formation of nodular deposits of MPS in the spongiosa and ventricularis, mainly affecting the proximal and middle parts of the leaflet. In dogs with normal pTV and sTV, MMPs-1 and 14 and TIMPs-2, 3 and 4 were expressed, while MMPs-2 and 9 were absent. In mild CVD, expression of MMPs-2, 9 and 14 were increased in the pTV, whereas small foci within the spongiosa contained MMP-9 and TIMP-3 positive cells. In advanced CVD, MMP-14 also was increased in the pTV. In mild CVD, there was increased expression of MMPs-1 and 2 and TIMP-2, but decreased expression of TIMP-4, in the sTV. Small foci with expression of MMP-14 and TIMPs-2, 3 and 4 were also present in the sTV in mild CVD. In advanced CVD, there was increased expression of MMPs-2 and 9 and TIMP-2 in the sTV. In CVD there is upregulation of various MMPs in the pTV, whereas there is a complex alteration in expression of MMPs and TIMPs in the sTV.

The equine endometrosis: new insights into the pathogenesis.

This paper describes the histomorphological and immunohistochemical characterisation of phenotypic variations of endometrosis as well as potential etiological factors which may influence disease progression. In total, 779 endometrial biopsies were examined. These biopsies were taken in the breeding and non-breeding season (n=509), on defined days during the estrous cycle (n=70) and before and after experimentally induced bacterial endometritis (n=200). In addition to conventional histopathology, selected biopsies were investigated using alcianblue staining as well as immunohistochemical methods for the detection of steroid hormone receptors, Ki-67-antigen, vimentin, desmin, fibronectin, smooth-muscle-alpha-actin and laminin. The equine endometrosis can be divided into a destructive and a non-destructive form. Based on the morphology of the stromal cells involved, an active or inactive state can be distinguished in fibrotic foci. In all types of endometrosis, fibrotic stromal cells show a distinctly reduced expression of steroid hormone receptors in comparison to the intact stroma, indicating their dedifferentiation. However, the steroid hormone receptor expression of involved glandular epithelia seems to depend on the activity of the fibrosis. These results suggest an independency of all fibrotic foci from the hormonal control mechanism of the uterus. The characteristical features of destructive endometrosis are a large number of smooth-muscle-alpha-actin containing myofibroblasts, a pronounced epithelial vimentin expression, excessive extracellular matrix accumulation and a progressive alteration of the basal lamina. Furthermore, the frequently seen cystic glandular dilatation and mechanical destruction of the uterine glands may occur due to the contractibility of the myofibroblasts involved. As shown in this study, a simultaneous endometritis can cause a temporary activation of fibrotic stromal cells. However, cyclic and seasonal endocrine changes seem to have no effects on progression of the disease. It can be concluded that the various types of endometrosis represent different stages in the fibrotic process, possibly leading to the destruction of the glands and subsequently resulting in the development of a stromal fibrosis.

Immunohistochemical characterization of the extracellular matrix in normal mitral valves and in chronic valve disease (endocardiosis) in dogs.

This study aimed to characterize the composition and distribution of the extracellular matrix (ECM) components in normal canine mitral valves (MV) and in chronic heart valve disease (CVD). MV of 50 dogs (normal (n=9), mild (n=13), moderate (n=17), severe (n=11) CVD) were investigated macroscopically, histologically (H.-E., picrosirius red) and immunohistochemically (collagen I, III, IV, V, VI, elastin, laminin, fibronectin, heparan sulphate). In normal MV, ECM components were expressed in a typical layered pattern. In mild CVD, basement membrane components (laminin, collagen IV, fibronectin) were increased. Advanced CVD was characterized by myxomatous nodular lesions displaying a marginal and a central region comprised mainly of collagen I, VI and fibronectin in the former and collagen I and III in the latter. Collagen IV and laminin appeared multifocally in marked CVD. In conclusion, not only an accumulation of proteoglycans, but also a distinctly altered expression of basement membrane components, and collagens characterizes CVD.

Functional, metabolic, and morphological aspects of continuous, normothermic heart preservation: effects of different preparation and perfusion techniques.

Continuous blood perfusion of donor hearts for transplantation has been the focus of an increasing amount of research, but the optimal preparation and perfusion techniques have not been clearly defined. Therefore, we investigated the effectiveness of different preservation strategies using continuous, normothermic heart perfusion after donor heart harvesting. Hearts of 12 pigs were randomly assigned to two groups receiving a constant pressure perfusion in a modified Langendorff system after different preparation techniques. In Group 1, six hearts were arrested with Bretschneider HTK cardioplegia (4 degrees C) and then reperfused with a circulating pressure of 80 to 90 mmHg using leukocyte depleted autologous blood. In Group 2, beating hearts of six pigs were explanted while being perfused, without cardioplegic arrest. Post-harvesting perfusion was similar to Group 1 except for a lower circulating pressure (40-50 mm Hg). At different time points (baseline and 1, 6, and 12 h after reperfusion), myocardial biopsies were taken, and contractility was assessed by measuring the maximum rate of left ventricular pressure rise (Deltap/Deltat (max)). Adenosine triphosphate (ATP) concentration was measured in all biopsies using a bioluminescence technique. Additionally, ultrastructural alterations were investigated using electron microscopy. Hypothermic cardioplegia and a higher reperfusion pressure (Group 1) were associated with an earlier and sharper decline in contractile function and intracellular ATP concentration. Ultrastructural alterations in Group 1 appeared earlier and were more distinctive than in Group 2. Endothelial ultrastructure, in particular, was better preserved in Group 2. Significant alterations were present in both groups after 12 h of perfusion but were more severe in Group 1. Blood perfusion provides protection against severe ischemic damage for a limited time. The use of a lower perfusion pressure, as well as avoiding cardioplegia and hypothermia, led to significantly better and longer preservation of perfused hearts.

Magnetic resonance imaging findings in histologically confirmed Pug dog encephalitis.

The purpose of the study was to describe magnetic resonance (MR) imaging features of histologically confirmed necrotizing encephalitis in four Pugs and to compare those findings with MR imaging characteristics of necrotizing encephalitis in other breeds. All dogs had the following common findings: lesions restricted to the forebrain, both cerebral hemispheres diffusely but asymmetrically affected, lesions affected gray and white matter resulting in loss of distinction between both, most severe lesions in occipital and parietal lobes, lesions were irregularly T2-hyperintense and T1-isointense to slightly T1-hypointense, and no cavitation. There were various degrees of contrast enhancement of brain and leptomeninges. Asymmetry of lateral ventricles and midline shift was seen in one dog each. Two dogs had brain herniation, which may have contributed to the progression of neurologic signs. Hyperintensity on T2-weighted and fluid attenuated inversion recovery images in the hippocampus and piriform lobe was consistent with excitotoxic edema, whereas similar imaging features in other forebrain areas corresponded to areas of inflammation or liquefaction on histopathology. In comparison with necrotizing encephalitis in other canine breeds, Pug dog encephalitis has some unique MR imaging features. Therefore, these characteristics cannot be applied to other breeds, nor should imaging features of necrotizing encephalitis of other canine breeds be used for interpretation of MR images in Pug dogs.

Endocardial laser ablation for the treatment of atrial fibrillation in an acute sheep model.

BACKGROUND: The purpose of this study was to test the feasibility, effectiveness, and safety of the use of a new laser energy catheter for linear endocardial ablation in an acute sheep model. METHODS: Bipolar pacing electrodes were positioned on the left atrial appendage (LAA) and the pulmonary veins (PVs). Laser ablation within the left atrium was performed around the LAA and PVs in six sheep. The temperature in the esophagus was measured continuously during ablation. The animals were weaned from cardiopulmonary bypass (CPB) and were sacrificed two hours after ablation. The heart, lungs, and esophagus were retrieved for histological examination. RESULTS: Aortic cross clamp time was 26.2 +/- 6.1 minutes and CPB time was 81 +/- 29 minutes. Electrical isolation of the LAA and PVs was confirmed in all sheep. On histological analysis, there was an extensive transmural alteration of the left atrial tissue including vascular lesions, myocardial degeneration, and necrosis, and epi- and endocardial necrosis. In six out of six cases, extensive lesions of the esophagus (muscular layer) were also found. Significant changes in esophageal temperature were observed, reaching up to 70 degrees C. The epithelial layer of the esophagus was not affected by the laser energy, but mild focal degeneration of the subepithelial connective tissue was observed in all sheep. There were no injuries to the circumflex coronary artery. CONCLUSIONS: Laser is an effective tool in endocardial ablation, resulting in electrical isolation and transmurality. Future studies should more completely assess the safety of laser ablation, especially with regards to the nearby esophagus, as well as examine the results of epicardial application.