Fabrication of coupled graphene-nanotube quantum devices.

We report on the fabrication and characterization of all-carbon hybrid quantum devices based on graphene and single-walled carbon nanotubes. We discuss both carbon nanotube quantum dot devices with graphene charge detectors and nanotube quantum dots with graphene leads. The devices are fabricated by chemical vapor deposition growth of carbon nanotubes and subsequent structuring of mechanically exfoliated graphene. We study the detection of individual charging events in the carbon nanotube quantum dot by a nearby graphene nanoribbon and show that they lead to changes of up to 20% of the conductance maxima in the graphene nanoribbon, acting as a well performing charge detector. Moreover, we discuss an electrically coupled graphene-nanotube junction, which exhibits a tunneling barrier with tunneling rates in the low GHz regime. This allows us to observe Coulomb blockade on a carbon nanotube quantum dot with graphene source and drain leads.

Electronic excited states in bilayer graphene double quantum dots.

We report tunneling spectroscopy experiments on a bilayer graphene double quantum dot device that can be tuned by all-graphene lateral gates. The diameter of the two quantum dots are around 50 nm and the constrictions acting as tunneling barriers are 30 nm in width. The double quantum dot features additional energies on the order of 20 meV. Charge stability diagrams allow us to study the tunable interdot coupling energy as well as the spectrum of the electronic excited states on a number of individual triple points over a large energy range. The obtained constant level spacing of 1.75 meV over a wide energy range is in good agreement with the expected single-particle energy spacing in bilayer graphene quantum dots. Finally, we investigate the evolution of the electronic excited states in a parallel magnetic field.

The impact of pharmacogenomic factors on acute persistent rejection in adult lung transplant patients.

Persistent rejection in the face of treatment and multiple episodes of rejection are associated with the development of chronic rejection and graft loss in solid organ transplantation. The factors that create an environment for rejection that persists in the face of treatment are as yet not understood. The objective of this study was to evaluate the risk factors, including human multidrug resistance gene (MDR1), cytochrome P4503A5 (CYP3A5) and cytokine gene polymorphisms, associated with acute persistent rejection (APR) in lung transplant patients. One hundred and twenty-five adult lung transplant patients were studied. MDR1 G2677T, C3435T and CYP3A5 polymorphisms were assessed by direct sequencing of the polymorphic region in patient DNA. Cytokine genotyping for five cytokines was performed using the polymerase chain reaction-sequence specific primers (PCR-SSP) technique. Multivariate regression analysis was used to identify the predictors of acute persistent rejection. The dependent variable was the presence or absence of acute persistent rejection based on lung biopsies during the first postoperative year. The independent variables were MDR1 G2677T and C3435T, CYP4503A5 and cytokine polymorphisms, survival status, age, gender, survival days and HLA mismatches. The MDR1 C3435T polymorphism and age were independently associated with acute persistent rejection (p = 0.025, odds ratio = 0.29, 95% CI 0.1-0.86 and p = 0.016, odds ratio = 0.94, 95% CI 0.89-0.98, respectively). For the MDR1 C3435T polymorphism, 72% of patients with the C allele had acute persistent rejection in comparison to 52% for TT patients (p = 0.04). For age, a significant difference was found between the nonrejection group and the rejection group (mean+/-S.D. 52.1+/-11.2 vs. 44.4+/-12.3, p = 0.01). This is the first report of the association of a drug disposition genotype with drug-resistant acute rejection in organ transplant patients. The major predictor of acute persistent rejection in the first postoperative year for lung transplant patients was the MDR1 C3435T genotype. This association could be due to drug resistance, altered drug disposition or other immunologic effects associated with P-glycoprotein (P-gp) function. Future prospective treatment algorithms should be developed that will incorporate the knowledge of gene polymorphisms into treatment regimens to improve the outcome following lung transplantation.

Preservation of post-transplant lung function with aerosol cyclosporin.

Post-lung transplant use of aerosol cyclosporin (ACsA) is considered by examining the relationship between deposited aerosol dose and effect. In a sub-study of placebo controlled trials of ACsA as a rejection prophylaxis, 15 drug subjects received aerosol dose quantification tests to gage their ability to effectively deposit the nebulised drug in their transplanted lung(s). A total of seven placebo subjects received mock deposition tests. The deposited doses and mock doses were compared to changes in the forced expiratory volume in one second, at six time points during the 2-yr trial period (ACsA was started within 6 weeks post-transplant). Linear relationships were demonstrated between deposited dose and improvement in lung function in the drug subjects at all intervals. Mock dose data from placebo subjects did not demonstrate similar correlation. Based on these results, subjects were grouped by dose and compared. Subjects depositing > or = 5 mg of the drug in the periphery of their transplant(s) had improving pulmonary function on average. Low-dose and placebo subjects demonstrated declines, more A2-A4 rejection events in the latter portion of the trial, and more chronic rejection beyond the end of the trial. A dose-to-effect relationship is demonstrated for aerosol cyclosporin in terms of pulmonary function and biopsy proven rejection.

Aerosol cyclosporin therapy in lung transplant recipients with bronchiolitis obliterans.

The majority of patients who develop bronchiolitis obliterans, after lung transplantation, die within 2-3 yrs after onset since treatment with conventional immunosuppression is typically ineffective. A case/control study was conducted in lung transplant recipients with biopsy-documented bronchiolitis obliterans to determine whether aerosol cyclosporin use contributed to increased survival. The cases comprised 39 transplant recipients who received open-label aerosol cyclosporin treatment in addition to conventional immunosuppression. The controls were transplant recipients treated with conventional immunosuppression alone. There were 51 controls from the University of Pittsburgh Medical Center and 100 from a large multicentric database (Novartis Lung Transplant Database). Forced expiratory volume in one second expressed as a percentage of the predicted value was an independent predictor of survival in all patients with bronchiolitis obliterans. Cox proportional-hazards analysis revealed a survival advantage for aerosol cyclosporin cases compared to the Pittsburgh control group. A survival advantage was also seen when comparing study cases to multicentric controls. Aerosol cyclosporin, given with conventional immunosuppression to lung transplant recipients with bronchiolitis obliterans, provides a survival advantage over conventional therapy alone.

Improving drug delivery from medical nebulizers: the effects of increased nebulizer flow rates and reservoirs.

Drug delivery from jet nebulizers can be considered in terms of the dose inhaled and the respirability of that dose. It is proposed that dose respirability and dose per breath can be controlled through specification of the driving gas flowrate, and that the dose inhaled per breath can also be increased through the use of nebulizer reservoirs. When a Hudson Micromist nebulizer was used and assessments of respirability were made utilizing phase Doppler interferometry, it was noted that the portion of the spray mass in droplet sizes of

The epidemiology of parainfluenza virus infection in lung transplant recipients.

Human parainfluenza virus (HPIV) is a common cause of seasonal respiratory tract infections. However, little is known about the clinical presentation and impact of HPIV infections in lung transplant recipients. We reviewed HPIV infections at the University of Pittsburgh Medical Center. From January 1990 through May 2000, 32 cases of HPIV infection were identified. HPIV infection was found in 24 lung transplant recipients (75%), all of whom were included in the study group. Diagnosis was established at a median of 2.1 years after transplantation (range, 0.6-5 years). Presenting symptoms included cough (17 patients), shortness of breath (16), and temperature elevation (4). Respiratory failure occurred in 5 patients (21%). The HPIV serotypes were HPIV-1 (7 patients), HPIV-2 (2), and HPIV-3 (15 [63%]). Twenty-two patients underwent transbronchial biopsy, and 18 (82%) showed signs of acute allograft rejection. Seven patients (32%) subsequently were found to have bronchiolitis obliterans.

Neutrophils, unopposed neutrophil elastase, and alpha1-antiprotease defenses following human lung transplantation.

Neutrophils are sequestered in the newly transplanted lung after reperfusion or with infection, rejection, and chronic graft dysfunction. Because unopposed (free) neutrophil elastase (NE) released into bronchoalveolar secretions may injure the lung allograft and impair bacterial clearance, we assessed total neutrophil numbers, myeloperoxidase activity as an index of neutrophil influx and degranulation, alpha1-antiprotease (alpha1-AP) concentrations, and unopposed NE activity in bronchoalveolar secretions from lung transplant recipients. Unopposed NE activity was present in bronchoalveolar lavage fluid (BALF) from recipients transplanted for emphysema associated with alpha1-AP deficiency as well as recipients without such deficiency (171 of 2,137 BALF; 8%). Ten of 17 (59%) recipients with alpha1-AP deficiency who were followed for at least 1 yr after transplant with multiple surveillance and diagnostic bronchoscopies had at least one BALF containing unopposed NE, usually associated with the presence of > or = 10(5) colony forming units/ml BALF of aerobic bacteria. In contrast, 19 of 58 (33%) with emphysema not associated with alpha1-AP deficiency, 8 of 32 (25%) recipients with cystic fibrosis (CF), 6 of 16 (38%) with idiopathic pulmonary fibrosis (IPF), and 11 of 36 (31%) with other indications for transplant had unopposed NE in BALF. alpha1-AP levels were significantly elevated in the early posttransplant time period and could be augmented considerably in alpha1-AP-deficient recipients with episodes of infection or rejection. Our findings indicate that unopposed NE activity can be found in both alpha1-AP-deficient and alpha1-AP-sufficient recipients after transplantation, usually in association with endobronchial bacterial infection.

Rejection after organ transplantation: a historical review.

Progress toward understanding the biochemical basis of human individuality spans centuries, but tissue rejection remains the primary clinical challenge of organ transplantation. This article highlights the chronology of scientific discoveries made in the quest to overcome the rejection associated with transplantation. The purposes of this review are to raise clinicians' awareness of the advances in surgery, genetics, immunology, and immunosuppression that have contributed to the current knowledge of tissue rejection and to indicate potential new directions in this challenging field.

Balloon dilation and endobronchial stent placement for bronchial strictures after lung transplantation.

PURPOSE: To evaluate the effect of balloon dilation and endobronchial stent placement for bronchial fibrous stenoses and bronchomalacia after lung transplantation. MATERIALS AND METHODS: Bronchial dilation and/or stent placement was performed on 25 lung transplant recipients. Indications included severe dyspnea with postobstructive pneumonia (n = 24) and respiratory failure (n = 1). All patients underwent pulmonary function testing (PFT) before and after bronchial dilation, the results of which were evaluated for changes. A total of 63 procedures were performed between February 1996 and December 1998. Thirty-five lesions were treated (18 were due to bronchomalacia, 17 were due to fibrosis). Areas treated included the left mainstem bronchus (n = 11), bronchus intermedius (n = 10), right mainstem bronchus (n = 7), left upper lobe bronchus (n = 4), right lower lobe bronchus (n = 2), and right middle lobe bronchus (n = 1). Bronchoscopic and/or bronchographic follow-up ranged from 1 to 34 months (mean, 15 months). RESULTS: Six-month primary patency of stents placed for bronchomalacia was 71% (10 of 14), with three of the four occlusions caused by mechanical failure of Palmaz stents in the mainstem bronchi. Six-month primary patency for treatment of fibrous strictures was 29%. Secondary patency at 1 year was 100% for both bronchomalacia and fibrous strictures. After treatment, there was a significant improvement in mean PFT results (P = .01-.0001). There was one acute complication, obstruction of the left lower lobe bronchus by a Wallstent treated by dilating a hole in the side of the stent. CONCLUSIONS: Balloon dilation and stent placement are safe and effective for bronchial strictures and bronchomalacia after lung transplantation, resulting in significant improvement in PFT results. However, there is almost universal restenosis in patients treated for fibrous strictures necessitating reintervention for prolonged patency.

Soluble donor HLA class I and beta 2m-free heavy chain in serum of lung transplant recipients: steady-state levels and increases in patients with recurrent CMV infection, acute rejection episodes, and poor outcome.

We determined the concentration of donor sHLA/beta(2)m and total beta(2)m-free heavy chain (HC) in the serum of lung transplant recipients with ELISA assays. While we were unable to detect specific donor beta(2)m-free HCs due to a lack of available antibodies, we could determine if events that led to an increase in the release of beta(2)m-free HC also led to an increase in the release of donor sHLA/beta(2)m, particularly the 36 kDa, proteolytically cleaved form. We found that lung transplants constituitively release donor sHLA/beta(2)m at ng/ml levels. The levels (both of donor sHLA/beta(2)m and total beta(2)m-free HC) were significantly increased in CMV-sero-negative recipients (but not in CMV-sero-positive recipients) at the onset of post-transplant CMV disease. Acute rejection episodes were also associated with an increased release of donor sHLA/beta(2)m, but not of beta(2)m-free HC. However, in patients with particularly poor outcome (i.e., graft loss within 1 year) there was a significant release of beta(2)m-free HC. Analysis of one such patient showed a predominance of 36 kDa forms of donor-sHLA/beta(2)m. Our data are consistent with the hypothesis that the metalloproteinase that cleaves beta(2)m-free HC is active during uncontrolled CMV infection and acute rejection. However, recall responses to CMV and controlled immune responses to donor may result in little or no activation of sHLA class I release.

Empyema complicating successful lung transplantation.

OBJECTIVE: To assess the prevalence and etiology of empyema complicating successful lung transplantation. DESIGN: Retrospective review. SETTING: University medical center transplant service. PATIENTS: All recipients (n = 392) of single-lung, double-lung, and heart-lung transplantation between May 1984 and April 1997. RESULTS: Of the 392 transplant recipients, empyema was documented in 14 patients (3.6%) at a mean time (+/- SD) of 46 days after transplantation (range, 14 to 167 days). Of these 14 recipients with empyema, 4 recipients (28.6%) died of infectious complications related to empyema. Empyema was seen secondary to Gram-positive, Gram-negative, and saprophytic organisms; however, there was no predominance of a particular organism recovered from the empyemic fluid (chi2 = 0.53; p = 0.75). The development of empyema was not related to whether the transplant was performed secondary to a septic or nonseptic lung disorder (chi2 = 1.06; p = 0.67), nor was it related to the type of transplant procedure performed (ie, single-lung, double-lung, or heart-lung allografts; chi2 = 4.39; p = 0.30). CONCLUSION: Empyema, a relatively uncommon complication of lung transplantation, is not related to the type of allograft received or to whether the recipient had a septic or a nonseptic lung disorder. If empyema does occur, the mortality associated with this infection is substantial.

Lung transplantation for end-stage pulmonary sarcoidosis.

BACKGROUND: Sarcoidosis is a multi-system granulomatous disease which can cause significant pulmonary morbidity and occasionally be fatal. The long term benefit of lung transplantation for this disorder are unknown. METHODS: A retrospective review was made of nine single lung transplant procedures performed at the University of Pittsburgh between March 1991 and March 1995 in patients with end-stage lung disease secondary to sarcoidosis. Two contemporaneous groups of recipients receiving transplants for COPD (n = 30) and inflammatory lung disease (n = 13) served as control groups. Surviving recipients underwent sequential surveillance bronchoscopy with transbronchial biopsy. RESULTS: All recipients survived beyond post-operative day (POD) 30, with 5 recipients currently alive. One year survival for this group was 6/9 (67%). Eight of the 9 sarcoidosis recipients had sequential lung biopsy procedures. Five of these 8 recipients (62.5%) had recurrence of granulomata in the lung allograft with the mean time to diagnosis of recurrent sarcoidosis being POD 224.2 +/- 291.3 (range POD 21-719). None of these 5 recipients had radiographic evidence or clinical symptoms related to granulomatous inflammation in the allograft. Pre-operative and post-operative spirometric values were available on 8 recipients. Vital capacity significantly improved in all recipients from 1.54 +/- 0.43 litres to 2.55 +/- 0.63 litres by POD 180 and was maintained through the fourth postoperative year (p < 0.05 Wilcoxon Signed Rank). Spirometric values were also compared before and after transplantation in the 5 recipients with granulomata in the allograft. Vital capacity significantly improved in these 5 recipients from 1.53 +/- 0.48 litres to 2.71 +/- 0.71 litres by POD 180 and was maintained throughout the first postoperative year (p < 0.05, Wilcoxon Signed Rank). The prevalence of high grade acute cellular rejection [ACR (histologic grades III and IV)] did not differ from that seen in a contemporaneous group of 30 single lung recipients who received allografts for COPD (p < 0.05 Mann-Whitney U), nor when compared to a group of 13 single lung recipients who received allografts for immunologically mediated lung disease (p < 0.05 Mann-Whitney U). The prevalence of chronic rejection (histologic obliterative bronchiolitis [OB]) in the sarcoidosis recipients was 4/8 (50%). In the controls with COPD recipients the prevalence of OB was 10/30 (33.3%), and in the 13 controls with immunologic disease it was 6/13 (46.2%). There was no significant difference in the prevalence of OB between the sarcoidosis recipients and controls. When analyzed to the fifth year after transplantation, freedom from the development of OB also failed to differ between these 3 groups (p = 0.25, Logrank, Mantel-Cox). CONCLUSIONS: Although granulomatous inflammation in the lung allograft is common following transplantation for sarcoidosis, it is not clinically or radiographically relevant. In addition, the prevalence of high grade ACR and histologic OB is no different when compared to other single lung recipients. For these reasons lung transplantation is a viable alternative for end-stage lung disease secondary to sarcoidosis.

Unopposed neutrophil elastase in bronchoalveolar lavage from transplant recipients with cystic fibrosis.

Large numbers of neutrophils with unopposed neutrophil elastase (NE) proteolytic activity are found in lower respiratory tract secretions from most patients with advanced cystic fibrosis (CF). To determine whether antielastase defenses may be overwhelmed in epithelial lining fluid after lung transplantation, we measured NE activity (cleavage of the specific substrate, MeO-Suc-Ala-Ala-Pro-Val-pNA) in bronchoalveolar lavage fluids (BALF) obtained for surveillance or diagnostic purposes at various intervals (1 mo to 7 yr after transplantation) from 52 recipients who had undergone double or bilateral lung transplantation for end-stage CF. Unopposed NE activity was found in BALF from 14 recipients, most of whom also had >= 10(5) colony forming units (cfu) of Pseudomonas aeruginosa in BALF. Ten of the 14 recipients with unopposed NE in bronchoalveolar lavage (BAL) had developed obliterative bronchiolitis (OB), but only 8 of the 38 subjects without unopposed NE activity had OB (p = 0. 002; Fisher exact test). We conclude that antiprotease defenses in lower respiratory tract secretions of CF patients receiving lung allografts are sufficient in the majority of patients to prevent unopposed NE activity. However, the presence of unopposed NE activity in BAL from lung allografts of patients with CF is associated with progressive, irreversible OB and graft failure.

Clinical significance of cytomegalovirus-specific T helper responses and cytokine production in lung transplant recipients.

Cytomegalovirus (CMV) disease continues to be a major problem for lung transplant recipients. In CMV-seropositive individuals, we detected two types of CMV-specific responses: a self-restricted response stimulated by soluble CMV antigen (sCMV-Ag) and a non-self-restricted response induced by CMV-infected cells (cCMV-Ag). Lung transplant recipients who develop the CMV-specific self-restricted T helper response have a low risk of recurrent CMV disease. In contrast, during CMV disease, lung transplant recipients exhibit only the non-self-restricted T helper responses. We characterized the T cell activation and the kinetics of cytokine production of sorted CD4+ and CD8+ T cells from PBLs of CMV seropositive donors. The two types of CMV antigens induced cytokine production in both T cell subsets. We also performed competitive RT-PCR for Granzyme B (GB) in BAL cells of lung transplant recipients prior to, during and following CMV disease. CMV disease was associated with increase in GB gene expression when was accompanied by acute cellular rejection while it remained low in patients with CMV disease that did not have a complicated course. In summary, CMV-activated T cells within the allograft may produce inflammatory cytokines and effector molecules that may promote allograft rejection.