Immune complex formation after xenotransplantation : evidence of type III as well as type II immune reactions provide clues to pathophysiology

Rejection of renal and cardiac xenografts is initiated when natural antibodies of the recipient bind to donor endothelium, activating complement on the surface of endothelial cells. Pulmonary xenotransplants, however, reveal less evidence of antibody binding and complement activation and, in contrast to other xenografts, fare worse when the complement of the graft recipient is depleted. Accordingly, we asked whether distinct immunochemical reactions might occur after xenotransplantation of the lung and what implications such reactions might have for pulmonary pathophysiology. Analysis of serum from baboons after transplantation with porcine lungs revealed complexes containing baboon IgM and porcine von Willebrand factor. The baboon IgM in these complexes was specific for Galalpha1-3Gal. Immune complexes were also seen, albeit to a lesser extent, in the serum of kidney and heart xenotransplant recipients. Deposits of porcine von Willebrand factor and baboon C3 were detected in livers and spleens of transplanted baboons. These results indicate pulmonary xenotransplantation eventuates in formation of immune complexes and in the deposition of those complexes at distant sites. Immune complex formation could explain the peculiar fate of xenoreactive antibodies after pulmonary xenotransplantation and might contribute to the pathophysiology of the lung and systemic changes not previously considered a complication of xenotransplantation.

The role of anti-Galalpha1-3Gal antibodies in acute vascular rejection and accommodation of xenografts

BACKGROUND

A major impediment to the transplanting of porcine organs into humans is the susceptibility of porcine organs to acute vascular rejection, which can destroy a vascularized xenograft over a period of hours to days. Acute vascular rejection of porcine-to-primate xenografts is thought to be triggered by binding of xenoreactive antibodies to the graft. We tested whether antibodies, binding to Galalpha1-3Gal epitopes in porcine tissue, initiate this phenomenon.

METHODS AND RESULTS

Specific depletion of anti-Galalpha1-3Gal antibodies from the blood of baboons, using extracorporeal perfusion of separated plasma through columns of Sepharose beads covalently linked to the antigenic trisaccharide, Galalpha1-3Galbeta1-4GlcAc, averted the development of acute vascular rejection in porcine organs transgenic for human decay-accelerating factor and CD59. More importantly, after immunodepletion was stopped and Gala1-3Gal antibodies were allowed to return, these same organs continued to function and remained pathologically normal and thus seemed to achieve a state of accommodation.

CONCLUSION

These results demonstrate that anti-Galalpha1-3Gal antibodies cause acute vascular rejection and suggest that depletion of these antibodies leads to accommodation of the donor cardiac xenograft and could supply an important model for additional study.

Tensile bond strength of resin-modified glass-ionomer cement to microabraded and silica-coated or tin-plated high noble ceramic alloy

PURPOSE

The purpose of this study was to evaluate the influence of alloy surface microabrasion, silica coating, or microabrasion plus tin plating on the tensile bond strengths between a resin-modified glass-ionomer luting cement and a high-noble alloy. Bond strength between the microabraded alloy specimens and conventional glass-ionomer cement or resin cement were included for comparison.

MATERIALS AND METHODS

One hundred twenty uniform size, disk-shaped specimens were cast in a noble metal alloy and divided into 6 groups (n = 10 pairs/group). The metal surfaces of the specimens in each group were treated and cemented as follows. Group 1: No surface treatment (as cast, control), cemented with a resin-modified glass-ionomer cement. Group 2: Microabrasion with 50-microm aluminum oxide particles, resin-modified glass-ionomer cement. Group 3: A laboratory microabrasion and silica coating system, resin-modified glass-ionomer cement. Group 4: Microabrasion and tin-plating, resin-modified glass-ionomer cement. Group 5: Microabrasion only, conventional glass-ionomer cement. Group 6: Microabrasion and tin-plating, conventional resin cement. The uniaxial tensile bond strength for each specimen pair was determined using an Instron Universal Testing Machine (Instron Corp, Canton, MA). Results were analyzed using a one-way analysis of variance (alpha = 0.05) and a Tukey post-hoc analysis.

RESULTS

Mean bond strength: Group 1: 3.6 (+/- 1.5) MPa. Group 2: 4.2 (+/-0.5) MPa. Group 3: 6.7 (+/- 0.9) MPa. Group 4: 10.6 (+/- 1.8) MPa. Group 5: 1.1 (+/- 0.4) MPa. Group 6: 14.6 (+/- 2.3) MPa. Group 6 was significantly stronger than Group 4. The bond strength of specimens cemented with the resin-modified glass-ionomer cement using microabrasion and tin-plating (Group 4) was significantly stronger than all other groups except the resin cement with microabrasion and tin-plating (Group 6).

CONCLUSION

Microabraded and tin-plated alloy specimens luted with the resin-modified glass-ionomer cement resulted in the greatest mean tensile strengths for the resin-modified glass-ionomer cement groups. This strength was 73% of the mean tensile strength of microabraded specimens luted with resin cement.

Evaluation of early postoperative results after bicaval versus standard cardiac transplantation and review of the literature

OBJECTIVE

Previous studies have been inconsistent in defining a clinical benefit to the bicaval cardiac transplantation technique relative to the standard technique, and many major centers have not adopted this newer approach. The purpose of this study was to determine whether clinically significant benefits support utilization of the bicaval technique.

METHODS

Sixty-eight consecutive adult patients undergoing a standard cardiac transplant were compared with 75 consecutive patients who underwent the bicaval technique during the period from 1991 to 1999. Etiology, recipient sex, recipient age, donor age, and pulmonary vascular resistance were similar between the two groups.

RESULTS

Cardiac index at 24 hours after operation was increased for the bicaval group relative to the standard group (3.15 +/- 0.7 vs 2.7 +/- 0.5 L/min/m(2), P <. 05). Inotropic requirements were significantly less, and there was significantly less tricuspid regurgitation in the bicaval group relative to the standard group. In addition, the bicaval group more frequently had a nonpaced normal sinus rhythm at 24 hours after operation (73.9% vs 50.7% [standard group], P =.025) and had fewer postoperative arrhythmias (29.3% vs 47.7% [standard group], P <.01). Finally, although mortality was similar for the two groups, length of postoperative hospitalization was longer for the standard group relative to the bicaval group (12.1 +/- 11 vs 20.4 +/- 12 days, P <. 001). Review of the literature identified reduced tricuspid regurgitation and improved rhythm as consistent benefits of the bicaval technique.

CONCLUSION

This review demonstrates a clinical benefit during the early postoperative period with bicaval cardiac transplantation (relative to standard) and encourages further utilization of this technique.

Beta(2)-adrenergic and several other G protein-coupled receptors in human atrial membranes activate both G(s) and G(i)

Cardiac G protein-coupled receptors that couple to Galpha(s) and stimulate cAMP formation (eg, beta-adrenergic, histamine, serotonin, and glucagon receptors) play a key role in cardiac inotropy. Recent studies in rodent cardiac myocytes and transfected cells have revealed that one of these receptors, the beta(2)-adrenergic receptor (AR), also couples to the inhibitory G protein Galpha(i) (activation of which inhibits cAMP formation). If beta(2)ARs could be shown to couple to Galpha(i) in the human heart, it would have important ramifications, because levels of Galpha(i) increase with age and in failing human heart. Therefore, we investigated whether beta(2)ARs in the human heart activate Galpha(i). By photoaffinity labeling human atrial membranes with [(32)P]azidoanilido-GTP, followed by immunoprecipitation with antibodies specific for Galpha(i), we found that Galpha(i) is activated by stimulation of beta(2)ARs but not of beta(1)ARs. In addition, we found that other Galpha(s)-coupled receptors also couple to Galpha(i), including histamine, serotonin, and glucagon. When coupling of these receptors to Galpha(i) is disrupted by pertussis toxin, their ability to stimulate adenylyl cyclase is enhanced. These data provide the first evidence that beta(2)AR and many other Galpha(s)-coupled receptors in human atrium also couple to Galpha(i) and that abolishing the coupling of these receptors to Galpha(i) increases the receptor-mediated adenylyl cyclase activity.

Gastroesophageal reflux as a reversible cause of allograft dysfunction after lung transplantation

Gastroesophageal reflux (GER) is increasingly recognized as contributing to a number of pulmonary disorders. The relationship of GER to pulmonary allograft dysfunction after lung transplantation is unknown. In this report, we describe a lung transplant recipient who developed an acute decline in pulmonary function several months after a retransplantation for chronic rejection. A pulmonary workup at that time, including bronchoscopy with biopsy, revealed bronchial inflammation with no allograft rejection or infection. Because of increasing GI symptoms after retransplantation, the patient also underwent additional testing, which revealed severe acid reflux. The treatment of this patient's acid reflux with Nissen fundoplication surgery resulted in a prompt and sustained improvement in his pulmonary function. We suggest that GER should be considered among the potential causes of allograft dysfunction after lung transplantation.

The role of antibodies in dysfunction of pig-to-baboon pulmonary transplants

OBJECTIVE

Pulmonary transplantation has become the preferred treatment for end-stage lung disease, but application of the procedure is limited because of a paucity of donors. One way to solve donor limitations is to use animal organs as a donor source or xenotransplantation. The current barrier to pulmonary xenotransplantation is the rapid failure of the pulmonary xenograft. Although antibodies are known to play a role in heart and kidney xenograft rejection, their involvement in lung dysfunction is less defined. This project was designed to define the role of antibodies in pulmonary graft rejection in a pig-to-baboon model.

METHODS

Orthotopic transgenic swine left lung transplants were performed in baboons depleted of antibodies by one of three techniques before transplantation: (1) ex vivo swine kidney perfusion, (2) total immunoglobulin-depleting column perfusion, and (3) ex vivo swine lung perfusion. Results were compared with those of transgenic swine lung transplants in unmodified baboons.

RESULTS

All three techniques of antibody removal resulted in depletion of xenoreactive antibodies. Only pretransplantation lung perfusion improved pulmonary xenograft function compared with lung transplantation in unmodified baboons.

CONCLUSIONS

The pathogenesis of pulmonary injury in a swine-to-primate transplant model is different from that in renal and cardiac xenografts. Depletion of antibodies alone does not have a beneficial effect and may actually be detrimental.

Significance of blood stream infection after lung transplantation: analysis in 176 consecutive patients

BACKGROUND

Although infection is a leading cause of death after lung transplantation, very little is known about the incidence, epidemiology, and clinical significance of bloodstream infections in lung transplant recipients.

METHODS

All blood cultures were reviewed in 176 consecutive lung transplant recipients over a 6-year period. Data were obtained from a prospectively collected microbiological database.

RESULTS

Bloodstream infection (BSI) occurred in 25% (44/176) of all lung transplant recipients over the 6-year study period. Staphylococcus aureus, Pseudomonas aeruginosa, and Candida species were the most common bloodstream isolates after lung transplantation. The epidemiology of posttransplant BSI, however, varied considerably between early and late posttransplant time periods and also differed between cystic fibrosis (CF) and non-CF patients. BSI infection after transplantation was associated with significantly worse survival by Kaplan-Meir analysis (P value log rank test=0.0001). In a multivariable logistic regression model, posttransplant BSI was a significant predictor of posttransplant death (odds ratio 5.62, CI 2.41-13.11, P=0.001), independent of other pre- and posttransplant factors.

CONCLUSIONS

Bloodstream infection represents a serious complication after lung transplantation, occurring more frequently than previously recognized, and independently contributing to posttransplant mortality.

Adult dogs receiving a rabies booster dose with a recombinant adenovirus expressing rabies virus glycoprotein develop high titers of neutralizing antibodies

Retired greyhound dogs, with low or absent antibody titers to rabies virus following previous vaccinations with commercially available vaccines, were immunized either subcutaneously or intramuscularly with a replication-defective recombinant adenovirus expressing the rabies virus glycoprotein termed Adrab.gp. Immunized animals developed high titers (geometric mean titers of 2630 and 5329) of viral neutralizing antibodies (VNA) against rabies virus by 10 days after vaccination. The antibody titers were even higher (geometric mean titers of 19349 and 122086) by 21 days after vaccination. The results indicate that the recombinant adenovirus expressing rabies virus glycoprotein is capable of inducing antibody immune responses in dogs and therefore may be developed as a rabies virus vaccine for dogs.

Influence of panel-reactive antibodies on posttransplant outcomes in lung transplant recipients

BACKGROUND

Panel-reactive antibody (PRA) is used to estimate the degree of humoral sensitization in the recipient before transplantation. Although pretransplant sensitization is associated with increased complications in other solid organ transplant recipients, less is known about the outcome of sensitized lung transplant recipients. Therefore, we sought to determine the impact of elevated pretransplant PRA on clinical outcomes after lung transplantation.

METHODS

The records of the first 200 lung transplant operations performed at Duke University Medical Center were reviewed. The outcomes of sensitized patients, PRA greater than 10% before transplantation (n = 18), were compared with the outcomes of nonsensitized patients.

RESULTS

Sensitized patients experienced a significantly greater number of median ventilator days posttransplant (9 +/- 8) as compared with nonsensitized recipients (1 +/- 11; p = 0.0008). There were no significant differences between the number of episodes of acute rejection; however, there was a significantly increased incidence of bronchiolitis obliterans syndrome occurring in untreated sensitized recipients (56%) versus nonsensitized (23%; p = 0.044). In addition, there was a trend towards decreased survival in the sensitized recipients, with a 2-year survival of 58% in sensitized recipients as compared with 73% in the nonsensitized patients (p = 0.31).

CONCLUSIONS

Sensitized lung transplant recipients experience more acute and chronic complications after transplantation. These patients probably warrant alternative management strategies.

Systemic effects of an intraosseous injection of 2% lidocaine with 1:100,000 epinephrine

The effect of a mandibular intraosseous injection of 2% lidocaine with 1:100,000 epinephrine on the heart rate and blood pressure of 20 volunteer patients was examined. Changes in blood pressure from preoperative levels were minimal and did not vary significantly at any time of measurement. The only statistically significant change in heart rate occurred immediately after the intraosseous injection (an increase of 12 beats per minute). In young healthy adults, the intraosseous injection of 1.5 mL of 2% lidocaine with 1:100,000 epinephrine resulted in a slight transient elevation in heart rate but had no significant effect on systolic or diastolic blood pressure.

Causes of failure among cuspal-coverage amalgam restorations: a clinical survey

BACKGROUND

Investigations of cuspal-coverage amalgam restorations suggest that tooth fracture is the leading cause of failure, while for Class I and II restorations, the leading cause is caries. In this study, the authors evaluated the causes of failure for a large number of cuspal-coverage restorations.

METHODS

The causes of failure for 706 cuspal-coverage amalgam restorations were determined through the use of a questionnaire. Dentists from a variety of dental schools; Army, Navy, Air Force, Public Health and Veterans Affairs dental clinics; and private practice were asked to record pertinent information regarding patients and restoration failures from choices provided on a survey form.

RESULTS

The survey documented 706 failed restorations. Mandibular first molars accounted for 36.25 percent of all failures. The majority of failures were caused by fractured teeth (24.3 percent), caries (20 percent) and fractured restorations (17.1 percent). Among all of the failed restorations, 82.15 percent were restorable, 9.35 percent were repairable and 8.50 percent were nonrestorable. Among the fractured teeth, 80 percent were restorable, 14.5 percent were nonrestorable and 5.5 percent were repairable. Among the carious teeth, 84 percent were restorable, 8 percent were nonrestorable and 8 percent were repairable. A chi 2 analysis revealed that tooth fracture was more likely to be associated with nonrestorability than either caries (chi 2 = 5.013, P < .05) or restoration fracture (chi 2 = 6.202, P < .05).

CONCLUSIONS

The leading cause of failure among the 706 restorations was tooth fracture, which resulted in significantly greater numbers of nonrestorable teeth than either caries or fractured restorations.

CLINICAL IMPLICATIONS

Tooth fracture creates a greater risk of nonrestorability than any other cause of failure. Replacement or coverage of fracture-prone cusps is likely to improve the life expectancy of complex amalgam restorations.

Respiratory viral infections in lung transplant recipients: radiologic findings with clinical correlation

PURPOSE

To evaluate radiologic finding of respiratory viral infection in lung transplant recipients with clinical correlation.

MATERIALS AND METHODS

Over 5 years, 21 episodes of respiratory viral infection (parainfluenza [n = 9], respiratory syncytial virus [n = 8], adenovirus [n = 5], influenza [n = 2]) were diagnosed 6-727 days (mean, 270 days) after lung transplantation in 20 recipients. Chest radiographs, computed tomographic (CT) images, and clinical records were reviewed.

RESULTS

Sixteen episodes of respiratory viral infection were diagnosed in patients with symptoms of lower respiratory tract infection or acute allograft dysfunction; five were diagnosed in asymptomatic patients. Chest radiographs were abnormal in 11 (52%) episodes; findings included heterogeneous or homogeneous opacities and masslike consolidation. All patients with radiographic abnormalities were symptomatic. Chest radiographs were unchanged from baseline in 10 (48%) episodes; in one, CT revealed findings not depicted at radiography. Adenoviral infection (n = 5) was typically symptomatic, was associated with new radiographic abnormalities, and was rapidly lethal (n = 4). Infection with parainfluenza and/or respiratory syncytial virus was commonly asymptomatic and was not associated with radiographic abnormalities; affected patients had good outcomes.

CONCLUSION

Respiratory viral infections are important causes of morbidity and mortality in lung transplant recipients. Radiographic abnormalities in patients with respiratory viral infections were usually accompanied by symptoms of lower respiratory tract infection. Adenoviral infection was frequently accompanied by progressive pulmonary opacity and fatal outcome.

Right ventricular dysfunction after cardiac transplantation: primarily related to status of donor heart

BACKGROUND

It is unclear whether right ventricular dysfunction after transplantation is due to donor brain death-related myocardial injury or recipient pulmonary hypertension.

METHODS

A canine donor model of brain death and a monocrotaline pyrrole-induced chronic pulmonary hypertension recipient model were established, and used for 30 orthotopic bicaval cardiac transplantations divided into three groups: Controls (group A, normal donor/recipient), group B (brain-dead donors/normal recipient), and group C (normal donor/recipients with pulmonary hypertension). Right ventricular function was measured before transplant and brain death, 4 hours after brain death, and after transplant (1 hour off bypass) by load-independent means plotting stroke work versus end-diastolic volume during caval occlusion. Right ventricular total power and pulmonary vascular impedance were determined by Fourier analysis.

RESULTS

In comparison to the control group right ventricular preload-recruitable stroke work and total power decreased significantly after brain death and transplant in group B (from 22.7 x 10(3) erg (+/-1.2) at baseline to 15.6 x 10(3) (+/-0.9) after brain death and to 11.3 x 10(3) (+/-0.9) after transplant). In group C there was a significant increase in pulmonary artery pressure, impedance, right ventricular preload-recruitable stroke work, total power after transplant.

CONCLUSIONS

Normal donor hearts adapt acutely to the recipient's elevated pulmonary vascular resistance by increasing right ventricular power output and contractility. Brain death caused significant right ventricular dysfunction and power loss, which further deteriorated after graft preservation and transplantation. The effects of donor brain death on myocardial function contribute to right ventricular dysfunction after cardiac transplantation.

Effect of saliva contamination on the bond of dentin to resin-modified glass-ionomer cement

This in vitro study compared the shear bond strength of a resin-modified glass-ionomer restorative material (Fuji II LC) bonded to saliva-contaminated dentin versus non-contaminated dentin. Seventy-five extracted human molar teeth were randomly divided into five groups of 15 samples each. The dentin was treated with 10% polyacrylic acid for 20 seconds, rinsed, and dried. The acid-treated dentin surfaces in Groups 1-4 were contaminated with saliva. In Group 1, the saliva was air thinned. In Groups 2-4, saliva was dried completely with compressed air. The saliva-contaminated dentin in Group 3 was rinsed and dried. The saliva-contaminated dentin in Group 4 was rinsed, dried, treated with 10% polyacrylic acid, and dried. Specimens in Group 5 received no contamination. The resin-modified glass-ionomer cement restorative material was mixed and applied to the dentin surfaces. Following placement of the restorative material and 7 days of storage, the specimens were thermo-cycled 300 times. Using the Instron Universal Testing Machine, a shear force was applied to the restorative material. Shear bond strength values were compared among the groups using a one-way ANOVA and Student-Neuman-Keuls Multiple Range Test (alpha = 0.05). The non-contaminated specimens (Group 5) were significantly stronger than the contaminated specimens (Groups 1-4). There were no significant differences in bond strength among the groups containing contaminated specimens. Salivary contamination occurring after dentin etching significantly reduced the bond strength of the resin-modified glass-ionomer restorative material to dentin. Neither rinsing nor rinsing and re-etching resulted in bond strengths as great as to non-contaminated dentin.

Cuspal reinforcement in endodontically treated molars

This in vitro study compared the ability of horizontal pins and a dental adhesive to reinforce the facial cusps of endodontically treated mandibular molars. Seventy-two mandibular molars were divided into six groups and mounted in acrylic blocks (n = 12). In Groups 1-5 standardized endodontic access and instrumentation in the coronal one-third of each root canal were completed. In Groups 1-4 the lingual cusps were reduced, leaving the buccal cusps intact. The facial cusps of the teeth in each group received one of the following modes of reinforcement: Group 1--no reinforcement; Group 2--dentin adhesive (Amalgambond Plus); Group 3--two horizontal TMS Minim pins; Group 4--two horizontal TMS Minim pins and Amalgambond Plus. Teeth in Group 5 were prepared for and restored with a complete cuspal coverage amalgam restoration using four vertical TMS Minim pins. Group 6 consisted of intact natural teeth. Using an Instron Universal Testing Machine, the lingual slope of the facial cusp of each specimen was loaded to failure using a compressive force applied at an angle 60 degrees to the long axis of the tooth. The mean fracture strengths for all groups were analyzed using a one-way ANOVA and Student-Newman-Keuls multiple range test (alpha = 0.05). Fracture patterns and modes of failure were also evaluated.

RESULTS

The intact teeth (Group 6) were significantly more fracture resistant than all other groups, with the exception of Group 4 (combination of pins and adhesive). Group 1 (non-reinforced teeth) was significantly weaker than all other groups. Groups 2-4 (specimens with reinforced cusps) were not significantly different from each other. The use of horizontal pins or a combination of horizontal pins plus dentin adhesive for cuspal reinforcement resulted in significantly more teeth demonstrating favorable fracture patterns than did the use of adhesives alone.

CONCLUSION

The buccal cusps of endodontically treated mandibular molars reinforced with a combination of horizontal pins and dentin adhesive were not significantly weaker than intact teeth. Of the restored teeth, those which had buccal cusps reinforced with horizontal pins and those treated with complete cuspal coverage amalgam restorations exhibited the most favorable restorative prognosis following cusp fracture.

Cystic fibrosis: usefulness of thoracic CT in the examination of patients before lung transplantation

PURPOSE

To evaluate the usefulness of thoracic computed tomography (CT) in the pre-lung transplantation examination of patients with cystic fibrosis (CF).

MATERIALS AND METHODS

Fifty-six patients (age range, 12-42 years) with CF were evaluated for possible lung transplantation from 1991 to 1997. Twenty-six of these patients underwent bilateral lung transplantation, 19 were awaiting transplantation at the time of the study, seven died before transplantation, and four were excluded for psychosocial concerns. Preoperative chest radiographic and CT findings were reviewed and correlated with clinical, operative, and pathology records.

RESULTS

In seven patients, discrete, 1-2-cm pulmonary nodules were detected at CT. Five of these patients underwent transplantation; the nodules were found to be mucous impactions. No malignancy was found in any of the patients who underwent transplantation. Pretransplantation sputum cultures grew Aspergillus fumigatus in seven patients, none of whom had radiologic findings suggestive of Aspergillus infection. Radiographic or CT findings were suggestive of mycetoma in five cases, but no such tumors were found at transplantation. The accuracies of chest radiography and CT for the detection of pleural disease in 48 hemithoraces were 81% (n = 39) and 69% (n = 33), respectively. The radiologic findings of pleural thickening did not influence the surgical approach in any patient.

CONCLUSION

Thoracic CT has little utility in the routine pre-lung transplantation examination of patients with CF.

Comparison of direct aortic and femoral cannulation for port-access cardiac operations

BACKGROUND

Differences in outcome after direct aortic cannulation (AORT) in the chest versus standard femoral arterial cannulation (FEM) have not been defined for minimally invasive cardiac operations utilizing the port-access approach.

METHODS

A retrospective study was performed of 165 patients undergoing port-access cardiac mitral valve operation (n = 126) or coronary artery bypass grafting (n = 39). In 113 patients, FEM was used, while in 52 patients, AORT was accomplished through a port in the first intercostal space.

RESULTS

AORT eliminated endoaortic balloon clamp migration (0/36 [0%] vs. 17/95 [18%]), and groin wound or femoral arterial complications (0/52 [0%] vs. 11/113 [10%]) without changing procedure times (363+/-55 vs. 355+/-70 minutes). Complications attributable to AORT were injury to the right internal mammary artery and aortic cannulation site bleeding in 1 patient each.

CONCLUSIONS

Direct aortic cannulation is technically easy, allows use of an endoaortic clamp, and avoids aorto-iliac arterial disease, the groin incision, and possible femoral arterial injury associated with femoral arterial cannulation. Direct arterial cannulation should expand the pool of patients eligible for port-access operation, and may become the standard for port-access procedures.

Mini-circuit cardiopulmonary bypass with vacuum assisted venous drainage: feasibility of an asanguineous prime in the neonate

Conventional cardiopulmonary bypass (CPB) in neonates results in increased transfusion requirements and hemodilution. There has been little advancement in CPB for the neonatal population. There is evidence that increased priming volumes and blood product transfusion enhances inflammatory response to CPB and increases myocardial and pulmonary dysfunction. We have devised a miniaturized CPB circuit that utilizes vacuum-assisted venous drainage (VAVD) in an effort to decrease priming volume and avoid transfusion requirements. The purpose of this study was to evaluate the safety and efficacy of this miniaturized CPB system and determine the feasibility of an asanguineous prime. Ten 1-week-old piglets were randomized to five mini- and five conventional CPB pump circuits. Subjects were supported with CPB at 100 ml/kg/min, cooled to 28 degrees C, exposed to 10 min aortic crossclamp with cardioplegic arrest, rewarmed to 37 degrees C, weaned from bypass, and subjected to modified-ultrafiltration (MUF) for approximately 10 min. This method was chosen to simulate a situation with all the elements of clinical CPB. Blood transfusion trigger was a hematocrit <15 on CPB. Serum samples were obtained pre-CPB, at 15 min of CPB onset, immediately post-CPB completion, and immediately post-MUF. Indices of hemolysis (SGOT, LDH), production of inflammatory mediators (interleukin (IL)-8, tumor necrosis factor-alpha (TNFalpha)), and physiologic parameters of inflammation were measured. The overall blood requirement was significantly less in the mini-circuit compared to conventional CPB (47.0+/-5.8 ml vs 314.2+/-31.6 ml; p < 0.0001). The only significant blood requirement in the mini-circuit was to replace the volume removed for samples. During the study, mean arterial pressure (MAP) (p = 0.004), static pulmonary compliance (p = 0.04), platelets (p = 0.0003), and white blood cells (p = 0.003) significantly decreased across the groups. Lung water content (p = 0.02), TNFalpha levels (p = 0.05), and SGOT (p = 0.009) increased significantly during the study, across the groups. Among all parameters tested, except for blood requirement and hematocrit post-CPB, there were no significant differences between the two circuits. VAVD makes asanguineous prime in neonates feasible. When used in this study to miniaturize a conventional-CPB circuit, VAVD with a reconfigured neonatal CPB console and circuit resulted in no detrimental effects, and allowed for markedly decreased priming volumes and blood transfusion requirements.

Identification of antigens on porcine pulmonary microvascular endothelial cells recognized by human xenoreactive natural antibodies

Transplantation of organs between species is prevented in part by humoral immune responses triggered by xenoreactive natural antibodies. Although the immune barrier to xenotransplantation of the lung is thought to be qualitatively and quantitatively different than the immune barrier to xenotransplantation of the kidney or heart, the antibody-antigen reactions responsible for rejection of pulmonary xenografts have not been characterized. To begin to address this issue for porcine lungs transplanted into humans, we analyzed the porcine pulmonary endothelial antigens recognized by human xenoreactive natural antibodies. Human and baboon natural antibodies recognized glycoprotein and glycolipid antigens isolated from the membranes of porcine pulmonary microvascular endothelial cells. The antigens included the integrin chains alpha1, alpha2, alpha3, alpha5, alpha(v), beta1, beta 3, the von Willebrand Factor, and fibronectin. These glycoproteins seemed to be recognized by the same antibodies that bind to porcine kidney or cardiac xenografts. Natural antibodies also recognized at least four glycolipids containing from one to five sugar residues, although at a lower level per unit number of cells than glycoprotein antigens. The epitope recognized by natural antibodies was predominantly Gal alpha1-3Gal, a structure expressed by lower mammals but not by humans and baboons. The antigens recognized by human antibodies in the porcine lung may provide insight into the pathogenesis of the rejection reaction. Moreover, the similarity of porcine lung antigens to porcine kidney and heart antigens suggests that differences in the rejection reactions between these organs reflects the distinct responses of the organs to humoral immunity.

Rabbit antithymocyte globulin decreases acute rejection after lung transplantation: results of a randomized, prospective study

STUDY OBJECTIVES

The efficacy of antithymocyte induction therapy in lung transplantation is controversial, and its use varies from center to center. We hypothesized that rabbit antithymocyte globulin (RATG) induction therapy would decrease acute rejection after lung transplantation, and we designed a single-center, randomized, prospective study to test this hypothesis.

DESIGN

A total of 44 single or bilateral adult lung transplant recipients were randomly assigned to receive either RATG induction therapy (dosage, 1.5 mg/kg/d for 3 days) at the time of transplantation, along with conventional immunosuppression (cyclosporine, azathioprine, and prednisone), or conventional immunosuppression alone with no induction therapy.

RESULTS

Although a similar number of biopsies were performed in each group, the number of patients experiencing biopsy-proven grade II or greater acute rejection was significantly reduced in the group receiving RATG induction therapy (23% incidence), as compared to the patients treated with conventional immunosuppression alone (55% incidence; p = 0.03). In addition, there was a nonsignificant reduction in the incidence of bronchiolitis obliterans syndrome at the conclusion of the study in patients who received RATG induction (20%), as compared to patients in the control group (38%). The incidence of posttransplant infections and malignancies were similar between the two groups.

CONCLUSION

Induction therapy with RATG significantly reduces the incidence of acute allograft rejection after lung transplantation.

Molecular and functional mechanisms of right ventricular adaptation in chronic pulmonary hypertension

BACKGROUND

Chronic pulmonary hypertension can lead to compensatory changes in the right ventricle. In this study, the adaptive mechanisms of the right ventricle in the setting of pulmonary hypertension were assessed at the molecular and functional level using a canine model of monocrotaline pyrrole-induced pulmonary hypertension.

METHODS

Animals underwent pulmonary artery catheterization to measure pulmonary hemodynamics before and 8 weeks after an injection of monocrotaline pyrrole, 3 mg/kg (n = 8) or placebo (n = 8) (controls). Systolic function was assessed with load-insensitive means (preload-recruitable stroke work). Myocardial biopsy specimens were collected to analyze membrane alpha1- and beta-adrenergic receptor density and adenylate cyclase activity.

RESULTS

Eight weeks after injection, significant increases in pulmonary hemodynamic indices were noted in monocrotaline-injected dogs. Significant increases in right ventricular preload-recruitable stroke work were also observed in these animals compared with controls and occurred in association with significant increases in right ventricular alpha1- and beta-adrenergic receptor density and isoproterenol hydrochloride-stimulated adenylate cyclase activity. No significant differences in basal adenylate cyclase activity in the right ventricle were noted between the two groups.

CONCLUSIONS

These data suggest that alterations in right ventricular function in the setting of chronic pulmonary hypertension may partially be due to changes in myocardial adrenergic receptor signaling.