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Biomedical subjects

Mark L Barr

Publications and source records attributed to Mark L Barr.

At least 19 recordsLinked to original sources
PubMed2006

Multicenter retrospective analysis of cardiovascular risk factors affecting long-term outcome of de novo cardiac transplant recipients.

BACKGROUND: Previous risk factor studies in cardiac transplant patients have analyzed pre-transplant risk factors as they relate to outcomes. This study is the first in-depth multicenter assessment of ongoing post-transplant risk factors in heart transplant patients and their impact on 5-year outcomes. METHODS: We reviewed 280 heart transplant patients who survived > 1 year for the impact of post-transplant risk factors (hyperlipidemia, hypertension, diabetes, body mass index [BMI] and renal dysfunction: 8 to 18 possible measurements over 5 years) on outcomes, including death, cardiac allograft vasculopathy (CAV) and non-fatal major adverse cardiac events (NF-MACE). RESULTS: Upon multivariate Cox regression analysis, significant findings were high total-cholesterol for NF-MACE (relative risk [RR] = 4.34, confidence interval [CI] 1.35 to 13.98, p = 0.01), presence of diabetes for NF-MACE (RR = 3.96, CI 1.24 to 12.65, p = 0.02) and high serum creatinine for graft death (RR = 1.59, CI 1.35 to 1.87, p < 0.001). No covariates were found to be significant for CAV. Other significant risk factors by univariate Cox regression models with time-dependent covariates included BMI > or = 33 for graft death. CONCLUSIONS: Post-transplant risk factors of hypercholesterolemia and diabetes are associated with NF-MACE, whereas high serum creatinine and BMI > or = 33 are associated with graft death. Risk factor modification, including direct therapy to minimize risk factors, should be considered.

Adult↗
PubMed2006

Transfer of regulatory T cells generated ex vivo modifies graft rejection through induction of tolerogenic CD4+CD25+ cells in the recipient.

Certain CD4+CD25+ T cells can induce and maintain T-cell non-responsiveness to donor alloantigens and have therapeutic potential in solid organ transplantation. Peripheral CD4+CD25- cells alloactivated with IL-2 and transforming growth factor beta (TGF-beta) ex vivo express the transcription factor FoxP3, and become potent antigen-specific CD4+CD25- suppressor cells. Here we report that the transfer of TGF-beta-induced regulatory CD4+ and CD8+ T cells (Tregs) co-incident with transplantation of a histoincompatible heart resulted in extended allograft survival. To account for this result, we injected non-transplanted mice with a single dose of CD4+ and CD8+ Tregs and transferred donor cells every 2 weeks to mimic the continuous stimulation of a transplant. We observed increased splenic CD4+CD25+ cells that were of recipient origin. These cells rendered the animals non-responsive to donor alloantigens by an antigen-specific and cytokine-dependent mechanism of action. Both the increased number of CD4+CD25+ cells and their tolerogenic effect were dependent on continued donor antigen boosting. Thus, Tregs generated ex vivo can act like a vaccine that generates host suppressor cells with the potential to protect MHC-mismatched organ grafts from rejection.

Animals↗
PubMed2005

The role of the hyaluronan receptor CD44 in mesenchymal stem cell migration in the extracellular matrix.

In a previous investigation, we demonstrated that mesenchymal stem cells (MSCs) actively migrated to cardiac allografts and contributed to graft fibrosis and, to a lesser extent, to myocardial regeneration. The cellular/molecular mechanism responsible for MSC migration, however, is poorly understood. This paper examines the role of CD44-hyaluronan interaction in MSC migration, using a rat MSC line Ap8c3 and mouse CD44-/- or CD44+/+ bone marrow stromal cells (BMSCs). Platelet-derived growth factor (PDGF) stimulation of MSC Ap8c3 cells significantly increased the levels of cell surface CD44 detected by flow cytometry. The CD44 standard isoform was predominantly expressed by Ap8c3 cells, accounting for 90% of the CD44 mRNA determined by quantitative real-time polymerase chain reaction. Mouse CD44-/- BMSCs bonded inefficiently to hyaluronic acid (HA), whereas CD44+/+ BMSC and MSC Ap8c3 adhered strongly to HA. Adhesions of MSC Ap8c3 cells to HA were suppressed by anti-CD44 antibody and by CD44 small interfering RNA (siRNA). HA coating of the migration chamber significantly promoted passage of CD44+/+ BMSC or Ap8c3 cells, but not CD44-/- BMSCs, through the insert membranes (p < .01). Migration of MSC Ap8c3 was significantly inhibited by anti-CD44 antibodies (p < .01) and to a lesser extent by CD44 siRNA (p = .05). The data indicate that MSC Ap8c3 cells, in response to PDGF stimulation, express high levels of CD44 standard (CD44s) isoform, which facilitates cell migration through interaction with extracellular HA. Such a migratory mechanism could be critical for recruitment of MSCs into wound sites for the proposition of tissue regeneration, as well as for migration of fibroblast progenitors to allografts in the development of graft fibrosis.

Animals↗
PubMed2005

Transforming growth factor-beta/interleukin-2-induced regulatory CD4+ T cells prolong cardiac allograft survival in rats.

BACKGROUND: Treatment of naive CD4+ T cells in vitro with transforming growth factor-beta (TGF-beta) or TGF-beta/interleukin-2 (IL-2), combined with stimulation in a mixed lymphoid culture (MLC), has been shown to generate CD4+ CD25+ regulatory T cells. However, little is known about the effect of these regulatory T cells on cardiac allograft survival in vivo. METHODS: CD4+ CD25+ T cells were generated from Lewis (LEW) rat spleen through a primary MLC with TGF-beta (10 ng/ml) or TGF-beta/IL-2 (10 U/ml). The effect of adoptive transfer of the CD4+ CD25+ T cells (5.0 x 10(7)) was evaluated using an animal model of ACI rat cardiac allograft survival in LEW recipients. RESULTS: The MLC with TGF-beta or TGF-beta/IL-2 generated CD4+ CD25+ regulatory T cells, which suppressed the cytotoxic activity of LEW spleen T cells against irradiated ACI spleen cells in vitro. Adoptive transfer of the CD4+ CD25+ regulatory T cells intravenously to naive syngeneic recipients significantly prolonged the ACI cardiac allograft survival (N = 6, 13.5 +/- 3.4 days) compared with the control group (N = 6, 5.0 +/- 0.6 days). CONCLUSIONS: Intravenous administration of CD4+ CD25+ regulatory T cells, successfully generated by TGF-beta/IL-2 treatment, had a significant effect on cardiac allograft survival in this rat model. Adoptive transfer of regulatory T cells may represent a novel approach for preventing allograft rejection.

Animals↗
PubMed2005

Pleural space problems after living lobar transplantation.

BACKGROUND: We reviewed our experience with adult living lobar lung transplant (LL) recipients to assess whether size and shape mismatch of the donor organ to the recipient pre-disposes to the development of pleural space problems (PSP). METHODS: Eighty-seven LL were performed on 84 adult recipients from 1993 through 2003. Seventy-six patients had cystic fibrosis. Patient records were examined for PSP, defined as air leak or bronchopleural fistula for more than 7 days; pneumothorax, loculated pleural effusions, or empyema in 68 patients for which complete data were available. RESULTS: There were 24 PSP identified for an overall incidence of 35%. The most common PSP was air leak/bronchopleural fistula, accounting for 38% of PSP. The second most common PSP was loculated pleural effusion (21% of PSP). Empyema was uncommon (2 patients, 3% of total patients) in our series of patients despite the large population of cystic fibrosis patients. In 4 of these patients, computed tomography-guided drainage was used for loculated effusions after chest tube removal. Three LL patients underwent surgery for persistent air leak and required muscle flap repair. One of these required subsequent omental transfer. Two LL patients required decortication for empyema. Many patients with PSP could be managed without further surgical intervention (14/24 patients). Donor-recipient height mismatch was not significantly different between PSP and non-PSP patients (p = 0.53). CONCLUSIONS: The incidence of PSP in LL recipients is similar to that reported in the literature on cadaveric transplant recipients. The relatively small lobe in the potentially contaminated chest cavity of cystic fibrosis recipients does not significantly pre-dispose to development of empyema despite immunosuppression. Many PSP can be managed non-operatively, although early aggressive intervention for large air leaks and judicious chest tube management are essential for a good outcome.

Adult↗
PubMed2005

Contribution of mesenchymal progenitor cells to tissue repair in rat cardiac allografts undergoing chronic rejection.

BACKGROUND: Mesenchymal progenitor cells (MPC) have recently been demonstrated to actively migrate into cardiac allografts during chronic rejection. This study examines the role of MPC in tissue repair of heart allografts in a rat model of chronic rejection. METHODS: The potential of a rat MPC line (Ap8c3) to differentiate to myofibroblasts and cardiomyocytes was studied in differentiation cultures. Ap8c3 cells tagged with an enhanced green fluorescent protein (eGFP) reporter gene were engrafted into Fischer 344 (F344) recipients of Lewis (LEW) cardiac allografts. Development of intragraft MPC into scar-forming fibroblasts and cardiomyocytes was studied using immunohistochemistry. RESULTS: Ap8c3 cells contain fibroblast progenitors (FP) positive for P07 antibody. Transforming growth factor (TGF)-beta stimulation promoted FP to terminally differentiate into myofibroblasts, which express alpha-smooth muscle actin (alphaSMA). In cardiac differentiation culture, Ap8c3 cells were induced by 5-azatiditin (5-aza) to form tropomyosin+ myotubes, and to express mRNA encoding for cardiac troponin I (TnI) and alpha-myosin heavy chain (alphaMHC). Transfusion of eGFP+ Ap8c3 cells to F344 recipients resulted in migration of eGFP(+) cells into LEW heart allografts, as well as homing of the eGFP+ MPC to bone marrow. The majority of eGFP+ cells in the heart allografts appeared to be vimentin-expressing fibroblasts. Foci of eGFP+ myocardium were also detected in all heart allografts, with eGFP+ cardiomyocytes representing 4.8 +/- 1.2% of the allografted eGFP+ cells. CONCLUSIONS: The data suggest that rat MPC participate in tissue repair in heart allografts by giving rise to scar-forming myofibroblasts and cardiomyocytes.

Animals↗
PubMed2005

Long-term pulmonary function after living-donor lobar lung transplantation in adults.

BACKGROUND: Living-donor lobar lung transplantation was developed as an alternative to cadaveric transplantation. However, whether two pulmonary lobes provide comparable intermediate and long-term pulmonary function to full-sized bilateral cadaveric grafts in adults is unknown. METHODS: An analysis of the pulmonary functions of 59 bilateral lobar and 43 bilateral cadaveric adult lung transplant recipients who survived more than 3 months after transplantation was performed. RESULTS: Mean follow-up was 3.8 +/- 2.8 years. In lobar recipients, mean percent predicted forced vital capacity and forced expiratory volume in 1 second improved between 1 and 6 months after transplantation (42.5% +/- 13.4% and 46.9% +/- 14.0% at 1 month versus 63.6% +/- 14.1% and 64.5% +/- 13.7% at 6 months; p < 0.001 and <0.001, respectively). In cadaveric recipients, mean percent predicted forced vital capacity improved after transplantation (54.3% +/- 14.5% at 1 month versus 74.2% +/- 21.3% at 12 months; p < 0.01). As compared with the cadaveric group, mean percent predicted forced vital capacity and forced expiratory volume in 1 second were lower 1 and 3 months after transplantation in the lobar recipients (p = 0.001 at both times); however, by 6 months after transplantation, these values were comparable and remained so throughout the follow-up period. In a subset of lobar and cadaveric recipients, maximal exercise, heart rate, peak oxygen consumption, anaerobic oxygen consumption threshold, and ability to maintain oxygen saturation were also comparable. CONCLUSIONS: In those adult recipients surviving more than 3 months after transplantation, lobar lung transplantation provides comparable intermediate and long-term pulmonary function and exercise capacity to bilateral cadaveric lung transplantation.

Actuarial Analysis↗
PubMed2005

The ethics of living donor lung transplantation.

A constant awareness of the risk to the living donors must be maintained with any living donor organ transplantation program, and comprehensive short- and long-term follow-up should be strongly encouraged to maintain the viability of these potentially life-saving procedures. There has been no perioperative or long-term mortality following lobectomy for living lobar lung transplantation, and perioperative risks associated with donor lobectomy seem to be similar to those seen with standard lung resections. These risks might increase, however, if the procedure is offered on an occasional basis and not within a well-established program. The long-term outcomes and functional effects of lobar donation raise important questions that are unanswered. This has proved difficult to follow closely, because of the fact that many donors live far from the transplant medical center and are reluctant to return for routine follow-up evaluation. The death of a recipient can further exacerbate this situation, because there is reluctance to insist on further routine examinations for a grieving donor. Prospective donors must be informed of the morbidity associated with lobectomy and the potential for mortality, and for potential negative recipient outcomes in regard to life expectancy and quality of life after transplantation. Although cadaveric transplantation must be considered because of the risk to the donors, living lobar lung transplantation should continue to be used under properly selected circumstances. The results reported by the authors' group and others are important if this procedure is to be considered as an option at more pulmonary transplant centers in view of the institutional, regional, and international differences in the philosophic and ethical acceptance of the use of living organ donors for transplantation. The integration of ethical discussion into topics that are relevant and of interest to thoracic surgeons, such as living lung donation, is a recent and welcome event. Many of the clinical situations that thoracic surgeons deal with on a daily basis have important and complex ethical implications, and there has been little training to deal effectively with these issues. This is changing as invited discussions on ethically compelling topics are finding their way into journals and the programs of national meetings. What may be of more importance, however, is the development of an ethics curriculum for those training in the specialty. The core curriculum recommended by the Thoracic Surgical Directors Association (which represents the leadership of the 89 approved residency training programs in the United States) has one lecture pertaining to ethics out of the several hundred offerings in its requisite curriculum. It is hoped that this will change in the near future.

Ethics, Clinical↗
PubMed2005

Thoracic organ transplantation in the United States, 1994-2003.

Using OPTN/SRTR data, this article reviews the state of thoracic organ transplantation in 2003 and the previous decade. Time spent on the heart waiting list has increased significantly over the last decade. The percentage of patients awaiting heart transplantation for >2 years increased from 23% in 1994 to 49% by 2003. However, there has been a general decline in heart waiting list death rates over the decade. In 2003, the lung transplant waiting list reached a record high of 3,836 registrants, up slightly from 2002 and more than threefold since 1994. One-year patient survival for those receiving lungs in 2002 was 82%, a statistically significant improvement from 2001 (78%). The number of patients awaiting a heart-lung transplant, declining since 1998, reached 189 in 2003. Adjusted patient survival for heart-lung recipients is consistently worse than the corresponding rate for isolated lung recipients, primarily due to worse outcomes for heart-lung recipients with congenital heart disease. A new lung allocation system, approved in June 2004, derives from the survival benefit of transplantation with consideration of urgency based on waiting list survival, instead of being based solely on waiting time. A goal of the policy is to minimize deaths on the waiting list.

Female↗
PubMed2004

Potential role for antiangiogenic proteins in the myocardial infarction repair process.

OBJECTIVE: Although angiogenic proteins have been identified as positive modulators of myocardial revascularization following acute myocardial infarction, little if anything is known regarding the role that antiangiogenic proteins have in myocardial revascularization. We explored the temporospatial distribution of endothelial-monocyte activating polypeptide (EMAP) II to determine whether antiangiogenic proteins have a role in the repair of myocardial tissue following infarction. METHODS: A rat model of myocardial infarction was utilized to examine EMAP II distribution (in situ hybridization) and protein expression (Western analysis) over a 6-week period. RESULTS: At baseline, EMAP II protein and mRNA are minimally expressed with transcription products localizing predominately to the perivascular stroma region in the normal rat myocardium. Six hours following myocardial infarction, EMAP II changes its distribution from the perivascular stroma to an invading inflammatory cell population. This is associated with a 2-fold (P < 0.0009) increase in EMAP II protein and its transcription primarily localized to the infarct region. EMAP II protein expression remains elevated throughout the weeks following the infarction with transcription limited to the infarct region and a notable decrease in EMAP II transcription products noted in the viable vasculature surrounding the infarct zone. Six weeks following myocardial infarction, EMAP II protein is elevated above control, changes its location of transcription from the inflammatory cell population to that of the fibroblasts located in the relative avascular scar tissue, and has resumed its perivascular stromal distribution in the viable periinfarct tissue. CONCLUSIONS: Thus, the temporospatial distribution of this antiangiogenic protein suggests that negative vascular modulators may have a function in the revascularization process following acute myocardial infarction.

Angiogenesis Inhibitors↗
PubMed2004

A decade of living lobar lung transplantation: recipient outcomes.

OBJECTIVE: Living lobar lung transplantation was developed as a procedure for patients considered too ill to await cadaveric transplantation. METHODS: One hundred twenty-eight living lobar lung transplantations were performed in 123 patients between 1993 and 2003. Eighty-four patients were adults (age, 27 +/- 7.7 years), and 39 were pediatric patients (age, 13.9 +/- 2.9 years). RESULTS: The primary indication for transplantation was cystic fibrosis (84%). At the time of transplantation, 67.5% of patients were hospitalized, and 17.9% were intubated. One-, 3-, and 5-year actuarial survival among living lobar recipients was 70%, 54%, and 45%, respectively. There was no difference in actuarial survival between adult and pediatric living lobar recipients (P =.65). There were 63 deaths among living lobar recipients, with infection being the predominant cause (53.4%), followed by obliterative bronchiolitis (12.7%) and primary graft dysfunction (7.9%). The overall incidence of acute rejection was 0.8 episodes per patient. Seventy-eight percent of rejection episodes were unilateral. Age, sex, indication, donor relationship, preoperative hospitalization status, use of preoperative steroids, and HLA-A, HLA-B, and HLA-DR typing did not influence survival. However, patients on ventilators preoperatively had significantly worse outcomes (odds ratio, 3.06, P =.03; Kaplan-Meier P =.002), and those undergoing retransplantation had an increased risk of death (odds ratio, 2.50). CONCLUSION: These results support the continued use of living lobar lung transplantation in patients deemed unable to await a cadaveric transplantation. We consider patients undergoing retransplantations and intubated patients to be at significantly high risk because of the poor outcomes in these populations.

Adolescent↗
PubMed2004

Neochordal repair of the posterior mitral leaflet.

BACKGROUND: Myxomatous mitral valve insufficiency is traditionally repaired by posterior leaflet quadrangular resection and reconstruction. A simplified repair technique without leaflet resection is described, and our initial experience is reviewed. METHODS: Thirty-nine consecutive patients with significant mitral regurgitation underwent repair since January 2000 by placement of expanded polytetrafluoroethylene sutures between the leading (coapting) edge of the posterior leaflet and the corresponding papillary muscle. An annuloplasty ring was placed, and no leaflet tissue was resected. Patient medical records were obtained and retrospectively reviewed. RESULTS: Twenty-five men and 14 women (median age, 61 years; range, 40-88 years) had their mitral valve repaired by a variety of surgical approaches, including robotic (18 patients), right thoracotomy (6 patients), and sternal (15 patients). Three patients have required valve replacement: 1 at the initial operation, 1 because of dehiscence of the annuloplasty ring, and 1 after subsequent rupture of a previously normal native chorda. At follow-up (median, 12 months), 92% (33/36) of the remaining patients had an intact mitral repair with no to mild regurgitation, 8.3% (3/36) of patients had moderate regurgitation, and 92% of all patients (36/39) were in New York Heart Association class I. There were no deaths. CONCLUSIONS: Myxomatous mitral regurgitation due to posterior leaflet insufficiency can be repaired without leaflet resection by placement of neochordae. This repair technique is effective and is readily accomplished by traditional and minimally invasive surgical approaches.

Adult↗
PubMed2004

Living lobar lung transplantation.

A constant awareness of the risk to the living donors must be maintained with any live-donor organ transplantation program, and comprehensive short- and long-term follow-up should be strongly encouraged to maintain the viability of these potentially life-saving programs. There has been no perioperative or long-term mortality following lobectomy for living lobar lung transplantation, and in the authors' series the perioperative risks associated with donor lobectomy are similar to those seen with standard lung resection. These risks might increase if the procedure were offered on an occasional basis and not within a well-established program. Further long-term outcome data, similar to data for live-donor renal and liver transplantation, are needed. Therefore, the authors still favor performing living lobar lung transplantation only for the patient with a clinically deteriorating condition. They believe that prospective donors should be informed of the morbidity associated with donor lobectomy and the potential for mortality, as well of potential recipient outcomes in regard to life expectancy and quality of life after transplantation. A major question regarding lobar lung transplantation that has been unanswered during the last decade has been defining when a potential recipient is too ill to justify placing two healthy donors at risk of donor lobectomy. Recipient age, gender, indication for primary transplant, prehospitalization status, preoperative steroid usage, relationship of donor to recipient, and the presence or absence of rejection episodes postoperatively do not seem to influence overall mortality. Patients receiving mechanical ventilation preoperatively and those undergoing retransplantation after either a previous cadaveric or lobar lung transplantation have significantly elevated odds ratios for postoperative death. The authors therefore recommend caution in these subgroups of patients. This experience is similar to the cadaveric experience in which intubated patients have higher I-year mortalities and patients undergoing retransplantation have decreased 3- and 5-year survival. A similar experience with a smaller number of lobar transplants has been reported by the Washington University group. Despite the high-risk patient population, this alternative procedure has been life saving in severely ill patients who would die or become unsuitable recipients before a cadaveric organ becomes available. Although cadaveric transplantation is preferable because of the risk to the donors, living lobar lung transplantation should continue to be used under properly selected circumstances. Although there have been no deaths in the donor cohort, a risk of death between 0.5% and 1% should be quoted pending further data. These encouraging results are important if this procedure is to be considered as an option at more pulmonary transplant centers in view of the institutional, regional, and intra- and international differences in the philosophical and ethical acceptance of the use of organs from live donors for transplantation.

Adult↗
PubMed2004

Thoracic organ transplantation.

This article presents an overview of factors associated with thoracic transplantation outcomes over the past decade and provides valuable information regarding the heart, lung, and heart-lung waiting lists and thoracic organ transplant recipients. Waiting list and post-transplant information is used to assess the importance of patient demographics, risk factors, and primary cardiopulmonary disease on outcomes. The time that the typical listed patient has been waiting for a heart, lung, or heart-lung transplant has markedly increased over the past decade, while the number of transplants performed has declined slightly and survival after transplant has plateaued. Waiting list mortality, however, appears to be declining for each organ and for most diseases and high-severity subgroups, perhaps in response to recent changes in organ allocation algorithms. Based on perceived inequity in organ access and in response to a mandate from Health Resources and Services Administration, the lung transplant community is developing a lung allocation system designed to minimize deaths on the waiting list while maximizing the benefit of transplant by incorporating post-transplant survival and quality of life into the algorithm. Areas where improved data collection could inform evolving organ allocation and candidate selection policies are emphasized.

Algorithms↗
PubMed2004

Surrogate markers and risk factors for chronic lung allograft dysfunction.

Obliterative bronchiolitis (OB) is the histologic correlate of chronic allograft dysfunction in pulmonary transplantation. The histologic diagnosis of OB is challenging, therefore a physiologic definition, bronchiolitis obliterans syndrome (BOS) based on pulmonary function tests has been used as a surrogate marker for OB for the last decade. BOS has proven to be the best available surrogate marker for OB and is predictive of the ultimate endpoints of graft and patient survival. Multiple other clinical markers have been reported and proposed as alternates for or complements to BOS grade, but all need further evaluation and validation in large, prospective clinical trials. Lastly, given the early occurrence and high incidence of chronic allograft dysfunction, the easily measurable endpoint of BOS grade, and our lack of understanding of ways to prevent or alter the course of BOS, lung transplant recipients represent an ideal population for clinical trials targeting prevention and treatment of chronic allograft dysfunction.

Adult↗
PubMed2004

A decade of living lobar lung transplantation: perioperative complications after 253 donor lobectomies.

Living lobar lung transplantation places two donors at risk for each recipient. We examined the perioperative outcomes associated with the 253 donor lobectomies performed at our institution during our first decade of living lobar lung transplantation. There have been no perioperative or long-term deaths. 80.2% of donors (n = 203) had no perioperative complications, while fifty (19.8%) had one or more complication. The incidence of intraoperative complications was 3.6%. Complications requiring reoperation occurred in 3.2% of donors. 15.0% of donors had other perioperative complications; the most serious were two donors who developed pulmonary artery thrombosis, while the most common was the need for an additional thoracostomy tube or a thoracostomy tube for >/=14 d for persistent air leaks and/or drainage. Right-sided donors were more likely to have a perioperative complication than left-sided donors (odd ratio 2.02, p = 0.04), probably secondary to right lower and middle lobe anatomy. This experience has shown donor lobectomy to be associated with a relatively low morbidity and no mortality, and is important if this procedure is to be considered an option at more pulmonary transplant centers, given continued organ shortages and differences in philosophical and ethical acceptance of live

Adult↗