Atmospheric implications of large C2-C5 alkane emissions from the U.S. oil and gas industry

Emissions of C₂-C₅ alkanes from the U.S. oil and gas sector have changed rapidly over the last decade. We use a nested GEOS-Chem simulation driven by updated 2011NEI emissions with aircraft, surface and column observations to 1) examine spatial patterns in the emissions and observed atmospheric abundances of C₂-C₅ alkanes over the U.S., and 2) estimate the contribution of emissions from the U.S. oil and gas industry to these patterns. The oil and gas sector in the updated 2011NEI contributes over 80% of the total U.S. emissions of ethane (C₂H₆) and propane (C₃H₈), and emissions of these species are largest in the central U.S. Observed mixing ratios of C₂-C₅ alkanes show enhancements over the central U.S. below 2 km. A nested GEOS-Chem simulation underpredicts observed C₃H₈ mixing ratios in the boundary layer over several U.S. regions and the relative underprediction is not consistent, suggesting C₃H₈ emissions should receive more attention moving forward. Our decision to consider only C₄-C₅ alkane emissions as a single lumped species produces a geographic distribution similar to observations. Due to the increasing importance of oil and gas emissions in the U.S., we recommend continued support of existing long-term measurements of C₂-C₅ alkanes. We suggest additional monitoring of C₂-C₅ alkanes downwind of northeastern Colorado, Wyoming and western North Dakota to capture changes in these regions. The atmospheric chemistry modeling community should also evaluate whether chemical mechanisms that lump larger alkanes are sufficient to understand air quality issues in regions with large emissions of these species.

In situ analysis of mTORC1/2 and cellular metabolism-related proteins in human Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare progressive cystic lung disease with features of a low-grade neoplasm. It is primarily caused by mutations in TSC1 or TSC2 genes. Sirolimus, an inhibitor of mTOR complex 1 (mTORC1), slows down disease progression in some, but not all patients. Hitherto, other potential therapeutic targets such as mTOR complex 2 (mTORC2) and various metabolic pathways have not been investigated in human LAM tissues. The aim of this study was to assess activities of mTORC1, mTORC2 and various metabolic pathways in human LAM tissues through analysis of protein expression. Immunohistochemical analysis of p-S6 (mTORC1 downstream protein), Rictor (mTORC2 scaffold protein) as well as GLUT1, GAPDH, ATPB, GLS, MCT1, ACSS2 and CPT1A (metabolic pathway markers) were performed on lung tissue from 11 patients with sporadic LAM. Immunoreactivity was assessed in LAM cells with bronchial smooth muscle cells as controls. Expression of p-S6, Rictor, GAPDH, GLS, MCT1, ACSS2 and CPT1A was significantly higher in LAM cells than in bronchial smooth muscle cells (P<.01). No significant differences were found between LAM cells and normal bronchial smooth muscle cells in GLUT1 and ATPB expression. The results are uniquely derived from human tissue and indicate that, in addition to mTORC1, mTORC2 may also play an important role in the pathobiology of LAM. Furthermore, glutaminolysis, acetate utilization and fatty acid β-oxidation appear to be the preferred bioenergetic pathways in LAM cells. mTORC2 and these preferred bioenergetic pathways appear worthy of further study as they may represent possible therapeutic targets in the treatment of LAM.

Mayo clinic experience of lung transplantation in pulmonary lymphangioleiomyomatosis

OBJECTIVES

Lymphangioleiomyomatosis (LAM) is a rare, cystic lung disease that generally results in progressive decline in lung function. Despite advancement of pharmacological therapy for LAM, lung transplantation remains an important option for women with end-stage LAM.

METHODS

Patients with LAM undergoing lung transplantation at the Mayo Clinic campuses in Rochester, Minnesota and Jacksonville, Florida since 1995 were retrospectively reviewed.

RESULTS

Overall, 12 women underwent lung transplantation. Nine of 12 (75%) underwent double lung transplant. The mean age was 42 ± 8 years at the time of transplant. One patient (8%) had a chylothorax and 7 (58%) had recurrent pneumothoraces, 4 (33%) of which required pleurodesis. All had diffuse, cystic lung disease on chest CT consistent with LAM which was confirmed in the explant of all patients. The average length of ICU and hospital stays were 5 ± 4 and 19 ± 19 days, respectively. Mild to moderate anastomotic ischemia was evident in all patients but resolved with time. No patient was treated with sirolimus pre-transplant. Seven patients received sirolimus post-transplant; however, clinical benefit was documented in only 2 patients, 1 of which was treated for large retroperitoneal cysts with ureteral obstruction and another with persistent chylothorax and retroperitoneal lymphangioleimyomas. Five patients are deceased. The median survival by Kaplan-Meier analysis was 119 months with a median follow-up of 68 months (range 2-225 months).

CONCLUSIONS

Lung transplant remains a viable treatment for patients with end-stage LAM. The role of sirolimus peri-transplantation remains ill-defined.

Weight loss prior to lung transplantation is associated with improved survival

BACKGROUND

Obesity is associated with increased mortality after lung transplantation and is a relative contraindication to transplant. It is unknown whether weight reduction prior to transplantation ameliorates this risk. Our objective was to determine whether weight loss prior to lung transplantation improves survival.

METHODS

Our investigation was a two-center, retrospective cohort study of lung transplant recipients between January 1, 2000 and November 5, 2010. Change in weight, demographics, transplant details, lung allocation score, length of intensive care and mechanical ventilator days and graft and patient survival were abstracted. Wilcoxon's signed-rank test and the Cox proportional hazard model were used for analysis where appropriate.

RESULTS

Three hundred fifty-five patients (55% male, median age 59 years) satisfied inclusion and exclusion criteria. After adjusting for standard demographic and clinical measures, a 1-unit reduction in BMI pre-transplant was associated with a reduced risk of death with a hazard ratio 0.89 (95% confidence interval 0.82 to 0.96; p = 0.004). This survival benefit persisted in the group with baseline BMI ≥ 25 kg/m(2) (overweight and obese) and hazard ratio 0.85 (95% CI 0.77 to 0.95; p = 0.003), but not in those with a BMI ≤ 24.9 kg/m(2). The 1-unit reduction in BMI was also associated with a 6.1% decrease in median mechanical ventilator days (p = 0.02) and a trend toward decreased intensive care unit length of stay (p = 0.06).

CONCLUSIONS

A reduction in BMI prior to lung transplantation was associated with a reduction in the risk of death and mechanical ventilator days. A greater reduction in BMI was associated with a greater survival benefit.

An overview of immunosuppression in solid organ transplantation

Significant advancements in solid organ transplantation immunosuppressive medications and regimens have resulted in improved outcomes over the years. A multidrug approach involving medications with different mechanisms of action is commonly used. Induction therapy can involve the use of antibody agents or higher doses of medications used for maintenance therapy. A calcineurin inhibitor, an antiproliferative agent, and a corticosteroid commonly serve as the initial triple medication regimen. Due to the potential for nephrotoxicity with the use of calcineurin inhibitors and chronic conditions with the prolonged use of corticosteroids, various withdrawal strategies are used in practice. Antimicrobial agents are prescribed to provide prophylaxis against certain viral, fungal, and bacterial infections. Other concomitant medications in the regimens for patients who have undergone transplantation vary depending on patient-specific factors and conditions.

Lung deflation and oxygen pulse in COPD: results from the NETT randomized trial

BACKGROUND

In COPD patients, hyperinflation impairs cardiac function. We examined whether lung deflation improves oxygen pulse, a surrogate marker of stroke volume.

METHODS

In 129 NETT patients with cardiopulmonary exercise testing (CPET) and arterial blood gases (ABG substudy), hyperinflation was assessed with residual volume to total lung capacity ratio (RV/TLC), and cardiac function with oxygen pulse (O(2) pulse=VO(2)/HR) at baseline and 6 months. Medical and surgical patients were divided into "deflators" and "non-deflators" based on change in RV/TLC from baseline (∆RV/TLC). We defined deflation as the ∆RV/TLC experienced by 75% of surgical patients. We examined changes in O(2) pulse at peak and similar (iso-work) exercise. Findings were validated in 718 patients who underwent CPET without ABGs.

RESULTS

In the ABG substudy, surgical and medical deflators improved their RV/TLC and peak O(2) pulse (median ∆RV/TLC -18.0% vs. -9.3%, p=0.0003; median ∆O(2) pulse 13.6% vs. 1.8%, p=0.12). Surgical deflators also improved iso-work O(2) pulse (0.53 mL/beat, p=0.04 at 20 W). In the validation cohort, surgical deflators experienced a greater improvement in peak O(2) pulse than medical deflators (mean 18.9% vs. 1.1%). In surgical deflators improvements in O(2) pulse at rest and during unloaded pedaling (0.32 mL/beat, p<0.0001 and 0.47 mL/beat, p<0.0001, respectively) corresponded with significant reductions in HR and improvements in VO(2). On multivariate analysis, deflators were 88% more likely than non-deflators to have an improvement in O(2) pulse (OR 1.88, 95% CI 1.30-2.72, p=0.0008).

CONCLUSION

In COPD, decreased hyperinflation through lung volume reduction is associated with improved O(2) pulse.

Effects of administration of intravenous naloxone on gas exchange in brain-dead lung donors

OBJECTIVE

To observe the effect of naloxone on the lung function of potential lung transplant donors with neurogenic pulmonary edema.

DESIGN AND INTERVENTIONS

Donors aged 16 to 55 years without any factors to contraindicate lung donation (pneumonia, pulmonary contusion, etc) were included. Ventilator settings were standardized to a tidal volume of 10 to 12 mL/kg, an FIO2 of 0.40, and a respiratory rate that kept PCO2 between 35 and 45 mm Hg. Chest physiotherapy, nebulizer treatments, and frequent suctioning were undertaken. Baseline arterial blood gas analysis and an oxygen challenge were performed. The patients were then given 8 to 10 mg of naloxone. Oxygen challenges and arterial blood gas analyses were repeated every 4 to 6 hours. The data were analyzed by using a paired t test, and each patient served as his or her own control.

SETTING

These interventions were performed on the 19 LifeQuest donors who met the set criteria from July 2002 to July 2004.

RESULTS

The PaO2 on the oxygen challenge immediately after administration of naloxone increased from 329 (SD 177) to 363 (SD 191) mm Hg, although the increase from baseline was not significant. The PaO2 from the second oxygen challenge (median time, 7 hours after administration of naloxone) increased to 413 (SD 177) mm Hg (P<.01).

Effects of Administration of Intravenous Naloxone on Gas Exchange in Brain-Dead Lung Donors

Objective

To observe the effect of naloxone on the lung function of potential lung transplant donors with neurogenic pulmonary edema.

Design and Interventions

Donors aged 16 to 55 years without any factors to contraindicate lung donation (pneumonia, pulmonary contusion, etc) were included. Ventilator settings were standardized to a tidal volume of 10 to 12 mL/kg, an FiO2 of 0.40, and a respiratory rate that kept PCO2 between 35 and 45 mm Hg. Chest physiotherapy, nebulizer treatments, and frequent suctioning were undertaken. Baseline arterial blood gas analysis and an oxygen challenge were performed. The patients were then given 8 to 10 mg of naloxone. Oxygen challenges and arterial blood gas analyses were repeated every 4 to 6 hours. The data were analyzed by using a paired t test, and each patient served as his or her own control.

Setting

These interventions were performed on the 19 LifeQuest donors who met the set criteria from July 2002 to July 2004.

Results

The PaO2 on the oxygen challenge immediately after administration of naloxone increased from 329 (SD 177) to 363 (SD 191) mm Hg, although the increase from baseline was not significant. The PaO2 from the second oxygen challenge (median time, 7 hours after administration of naloxone) increased to 413 (SD 177) mm Hg ( P < .01).

Safety of percutaneous dilatational tracheostomy with direct bronchoscopic guidance for solid organ allograft recipients

OBJECTIVE

To determine the safety of percutaneous dilatational tracheostomy (PDT) for solid organ allograft recipients, who have increased risks of bleeding and infection.

PARTICIPANTS AND METHODS

We reviewed the records of patients who underwent solid organ transplant between January 1, 2001, and September 30, 2005, followed by PDT (using the Ciaglia technique) with direct bronchoscopic guidance. We recorded comorbid conditions, number of days from intubation and transplant, positive end-expiratory pressures, ratios of PaO2 to fraction of inspired oxygen, coagulation study findings, complications, and procedure-related mortality rates.

RESULTS

Of the 51 patients in our study, 17 had undergone lung transplant; 32, liver transplant; and 2, kidney transplant. The median age was 55 years (range, 27-73), and 53% of patients were men. The median time from intubation to PDT was 10 days and from transplant to PDT, 22 days. The median ratio of PaO2 to fraction of inspired oxygen was 293, and the median positive end-expiratory pressure was 5 cm H2O. Twenty-one patients were receiving dialysis, and 11 were recovering from sepsis (of these, 8 were receiving vasopressors). Ten had coagulopathies (none of which were associated with bleeding complications). Complications were infrequent (7 periprocedural, 4 postprocedural) and included bleeding, bradycardia, hypotension, tracheal ring fracture, and cannula malfunction. Of the bleeding complications, only 2 were clinically remarkable and required removal of the tracheostomy or surgical revision. No infectious complications or procedure-related deaths were noted.

CONCLUSION

Percutaneous dilatational tracheostomy was tolerated well in recipients of solid organ allografts and had a relatively low risk of major complications and a low procedure-related mortality rate. This method should be considered an acceptable alternative to surgical tracheostomy.

Retrospective study of pulmonary function tests in patients presenting with isolated reduction in single-breath diffusion capacity: implications for the diagnosis of combined obstructive and restrictive lung disease

OBJECTIVE

To examine the frequency and spectrum of diseases associated with isolated reduction in the diffusing capacity of lung for carbon monoxide (D(Lco)).

PATIENTS AND METHODS

We retrospectively identified all potentially dyspneic patients who had pulmonary function tests (PFTs) performed at the Mayo Clinic in Jacksonville, Fla, between January 1, 1990, and June 30, 2000, that showed reduced D(Lco) (< 70% of predicted), normal lung volumes (total lung capacity and residual volume > 80% and < 120% of predicted, respectively), and airflow variables (forced expiratory volume in 1 second and forced vital capacity values > 80% of predicted and forced expiratory volume in 1 second/forced vital capacity ratio > 70% of predicted). Only patients who had also undergone chest computed tomography (CT) and echocardiography within 1 month of PFTs were studied.

RESULTS

Of the 38,095 patients who underwent PFTs during the study period, 179 (0.47%; 95% confidence interval [CI], 0.40%-0.54%) had isolated D(Lco) abnormalities. The 27 patients (15.1%; 95% CI, 10.2%-21.2%) who had also undergone chest CT and echocardiography within 1 month of PFTs form the study cohort reported herein. Their mean D(Lco) was 50% +/- 15% (95% CI, 45%-56%) with average normal pulse oxygen saturation at rest and mild hypoxemia with activity. Thirteen of the 27 patients (48%; 95% CI, 28.7%-68.1%) had underlying emphysema evident on CT. Eleven of these 13 patients had emphysema associated with a restrictive lung process. The 14 patients without emphysema had interstitial lung disease, pulmonary vascular disease, and other isolated findings. Six patients with combined emphysema and idiopathic pulmonary fibrosis accounted for the largest percentage (22%) of patients with Isolated D(Lco) reduction. The mean +/- SD smoking history of the 27 patients in the study cohort was 36 +/- 33 pack-years (range, 0-116 pack-years).

CONCLUSION

Dyspneic patients with respiratory symptoms and normal lung volumes and airflows associated with Isolated reduction in D(Lco) should be evaluated for underlying diseases such as emphysema, with or without a concomitant restrictive process, and pulmonary vascular disease.

Pathophysiology and classification of emphysema

Current research is providing new understanding in the pathophysiology of emphysema, and this knowledge will be translated in finding better modalities of therapy for patients currently affected by COPD. The single best effort that can alter the course of COPD is promoting policies to remove smoking as an available option to young people, before they become addicted and thus prey of tobacco-producing companies. Landmark studies like NETT and the GOLD initiative are providing tool classify emphysema in the context of physiological criteria and possible therapeutic alternatives.

Atelectasis--an unusual and late complication of lung transplant

We report a previously unrecognized late complication of allograft lung transplantation - persistent recurrent atelectasis of the transplanted lung. The patient developed sudden, severe respiratory distress about 2 yr after a right lung transplant, because of acute atelectasis of her transplanted lung. Multiple transbronchial biopsies at the time revealed minimal inflammation and no evidence of rejection. She was treated with surfactant replacement therapy, and her collapsed lung fully expanded following surfactant installation. To eliminate the possibility of acquired deficiency of surfactant lipids or proteins, ultrastructural examination and immunostains for surfactant proteins were performed in a transbronchial lung biopsy. No deficiency of surfactant lipids or proteins was found. On ultrastructural examination of the lung biopsy, the number of Type II cells per alveolus and the number of lamellar bodies per square micron of Type II cell cross-sectional area was increased compared with an age-matched control. We conclude that synthesis of surfactant lipids and proteins was unimpaired and because of the patient's response to surfactant replacement therapy, that the increase in number of lamellar bodies could reflect a compensatory mechanism for a surfactant functional defect. The patient later developed breast carcinoma to which she succumbed. We raise the possibility that the functional surfactant defect is a hitherto unrecognized non-metastatic manifestation of malignancy.

Endoluminal graft repair for abdominal aortic aneurysms in high-risk patients and octogenarians: is it better than open repair?

OBJECTIVE

To analyze the short-term and midterm results of open and endoluminal repair of abdominal aortic aneurysms (AAA) in a large single-center series and specifically in octogenarians.

METHODS

Between January 1997 and October 2000, 470 consecutive patients underwent elective repair of AAA. Conventional open repair (COR) was performed in 210 patients and endoluminal graft (ELG) repair in 260 patients. Ninety of the patients were 80 years of age or older; of these, 38 underwent COR and 52 ELG repair.

RESULTS

Patient characteristics and risk factors were similar for both the entire series and the subgroup of patients 80 years or older. The overall complication rate was reduced by 70% or more in the ELG versus the COR groups. The postoperative death rate was similar for the COR and ELG groups in the entire series and lower (but not significantly) in the ELG 80 years or older subgroup versus the COR group. The 36-month rates of freedom from endoleaks, surgical conversion, and secondary intervention were 81%, 98.2%, and 88%, respectively.

CONCLUSION

The short-term and midterm results of AAA repair by COR or ELG are similar. The death rate associated with this new technique is low and comparable, whereas the complication rate associated with COR in all patients and those 80 years or older in particular is greater and more serious than ELG repair. Long-term results will establish the role of ELG repair of AAA, especially in elderly and high-risk patients.

The use of endoscopic argon plasma coagulation in airway complications after solid organ transplantation

The objective of the study was to describe a safe and effective treatment option for endobronchial complications after solid organ transplantation. A retrospective analysis was performed in a tertiary-care university hospital. The use of bronchoscopic argon plasma coagulation (APC) for the treatment of endobronchial lesions was studied in five solid organ transplant recipients. Four patients presented with variable degrees of endobronchial obstruction, and one patient presented with massive hemoptysis. Two of the patients with endobronchial obstruction were double lung transplant recipients who developed anastomotic strictures. The strictures were opened with endobronchial stents but became obstructed again by inflammatory granulation tissue overgrowth through the stent mesh. APC was used to maintain airway patency. One kidney transplant recipient developed pulmonary zygomycosis with secondary obstruction of the left main bronchus because of granulation tissue growth through endobronchial stents. Airway patency was reestablished with several treatments with APC. Another kidney transplant recipient developed subglottic and tracheal papillomatosis that was effectively removed with APC. A heart transplant recipient was referred with recurrent massive hemoptysis refractory to bronchial artery embolization. The bleeding was caused by hemorrhagic polypoid lesions, which were completely ablated by APC. Bronchoscopic use of the argon plasma coagulator is a safe and simple technique that can be used effectively to treat endobronchial pathology in solid organ transplant patients.

Pneumomediastinum and subcutaneous emphysema from pacemaker placement

Percutaneous insertion of permanent pacemaker leads through the subclavian vein is an alternative to the cephalic vein approach. A rare occurrence and successful conservative management of extensive pneumomediastinum and subcutaneous emphysema without concomitant pneumothorax resulting from permanent transvenous pacemaker insertion in an 80-year-old man with syncope and arrhythmia is reported.

Loss-of-function mutations reveal that the Drosophila nautilus gene is not essential for embryonic myogenesis or viability

nautilus (nau), the single Drosophila member of the bHLH-containing myogenic regulatory family of genes, is expressed in a subset of muscle precursors and differentiated fibers. It is capable of inducing muscle-specific transcription as well as myogenic transformation, and plays a role in the differentiation of a subset of muscle precursors into mature muscle fibers. In previous studies, the nau zygotic loss-of-function phenotype was determined using genetic deficiencies in which the gene is deleted. We note that this genetic loss-of-function phenotype differs from the loss-of-function phenotype determined using RNA interference (L. Misquitta and B. M. Paterson, 1999, Proc. Natl. Acad. Sci. USA 96, 1451-1456). The present study re-examines this loss-of-function phenotype using EMS-induced mutations that specifically alter the nau gene, and extends the genetic analysis to include the loss of both maternal and zygotic nau function. In brief, embryos lacking nau both maternally and zygotically are missing a distinct subset of muscle fibers, consistent with its apparent expression in a subset of muscle fibers. The muscle loss is tolerated, however, such that the loss of nau both maternally and zygotically does not result in lethality at any stage of development.

Outcome of bedside percutaneous tracheostomy with bronchoscopic guidance

OBJECTIVE

To determine the morbidity and mortality of percutaneous dilational tracheostomy with bronchoscopic guidance when performed by medical intensivists.

DESIGN

A retrospective analysis.

SETTING

A tertiary care university hospital.

PATIENTS

Fifty consecutive patients who underwent percutaneous dilational tracheostomy for prolonged mechanical ventilation.

INTERVENTION

Bedside percutaneous dilational tracheostomy with bronchoscopic guidance.

RESULTS

Seventeen women and 33 men with a mean age of 62 +/- 17 years. Operative mortality was 0 with four (8%) operative complications. Complications included one posterior tracheal abrasion, one anterior tracheal laceration, one episode of endobronchial hemorrhage requiring bronchoscopy, and one pneumothorax. Thirty-day mortality was 28% and overall mortality was 40%. All deaths were related to the patients' underlying disease.

CONCLUSIONS

Percutaneous dilational tracheostomy with bronchoscopic guidance is a safe procedure when performed by experienced medical intensive care personnel in tertiary care institutions. Bronchoscopy helps to reduce the risk of major complications and aids in the management of minor complications.

Formation of supported membranes from vesicles

Using a combination of the quartz crystal microbalance and surface plasmon resonance techniques, we have studied the spontaneous formation of supported lipid bilayers from small (approximately 25 nm) unilamellar vesicles. Together these experimental methods measure the amount of lipid adsorbed on the surface and the amount of water trapped by the lipid. With this approach, we have, for the first time, been able to observe in detail the progression from the adsorption of intact vesicles to rupture and bilayer formation. Monte Carlo simulations reproduce the data.

Risk analysis for thoracoscopic lung volume reduction: a multi-institutional experience

OBJECTIVE

Most reports of thoracoscopic lung volume reduction (TLVR) are relatively small and early experiences from a single institution, factors which limit both the statistical validity and the applicability to the population at large. In order to address these shortcomings we undertook an analysis of the TLVR experience at five separate institutions to assess operative morbidity and identify predictors of mortality.

METHODS

Questionnaires were sent to four groups of surgical investigators at five institutions actively performing TLVR. Data was requested regarding preoperative, operative and postoperative parameters. Twenty-five potential predictors of mortality were analyzed and seven proved to be at least marginally significant (P<0.10). These parameters were entered into a stepwise logistic regression analysis to identify independent predictors.

RESULTS

The 682 patients (415 males, 267 females, mean age 64.0 years) underwent unilateral (410) or bilateral (272) TLVRs. Overall, operative mortality was 6% with half of the deaths resulting from respiratory causes. The remaining patients were discharged to home (88%), a rehabilitation facility (4%) or a ventilator facility (2%). There were 25 perioperative factors chosen representing clinically important indices such as spirometry, oxygenation, functional status, clinical and demographic variables. Univariate analysis identified seven variables as predictors of mortality (P<0.10) and these were entered into a stepwise logistic regression analysis. Only age, 6-min walk, gender (male 8%, female 3% mortality) and the procedure performed (unilateral 4.6%, bilateral 8%) were independent predictors while preoperative steroid therapy, preoperative oxygen administration, and time since smoking cessation dropped out of the model. The specific institution, learning curve (early vs. late experience), type of lung disease, spirometric indices and predicted maximum VO(2) were not significant predictors.

CONCLUSION

This experience suggests that unilateral and bilateral lung volume reduction procedure can be performed with acceptable morbidity and mortality. Although age, gender, exercise capacity and the procedure performed are all independent predictors of mortality, the risk of operative death did not appear excessive in this fragile patient subset.

Pulmonary alveolar proteinosis in association with household exposure to fibrous insulation material

We report the case of a 35-year-old woman who developed pulmonary alveolar proteinosis requiring multiple lavage treatments, in association with household exposure to ventilation system dust comprised at least partially by a cellulose fire-resistant fibrous insulation material. Scanning electron microscopy with energy-dispersive x-ray analysis documented the presence of spectral peaks consistent with the insulation material in transbronchial biopsy tissue. The patient showed symptomatic improvement once exposure to the insulation material had ceased. We believe that this case demonstrates an unusual association with pulmonary alveolar proteinosis. This case emphasizes the broad differential diagnosis for this histologic injury pattern and the need to thoroughly investigate environmental exposures in patients with unexplained pulmonary disease.

Comparison of clinical results for unilateral and bilateral thoracoscopic lung volume reduction

BACKGROUND

It is widely believed that bilateral thoracoscopic lung volume reduction (BTLVR) yields superior results when compared with unilateral thoracoscopic lung volume reduction (UTLVR) with regard to spirometry, functional capacity, oxygenation and quality of life results.

METHODS

To address these issues, we compared the results of patients undergoing UTLVR (N = 338 patients) and BTLVR (N = 344 patients) from 1993 to 1998 at five institutions. Follow-up data were available on 671 patients (98.4%) between 6 and 12 months after surgery, and a patient self-assessment was obtained at a mean of 24 months.

RESULTS

It was found that BTLVR provides superior improvement in measured postoperative percent change in FEV1 (L) (UTLVR 23.3% +/- 55.3 vs BTLVR 33% +/- 41, p = 0.04), FVC(L) (10.5% +/- 31.6 vs 20.3% +/- 34.3, p = 0.002) and RV(L) (-13% +/- -22 vs -22% +/- 17.9, p = 0.015). BTLVR also provides a slight improvement over UTLVR in patient's perception regarding improved quality of life (UTLVR 79% vs BTLVR 88%, p = 0.03) and dyspnea relief (71% vs 61%, p = 0.03). There was no difference in mean changes in PO2 (mm Hg) (UTLV 4.5 +/- 12.3 vs BTLVR 4.9 +/- 13.3, p = NS), 6-minute walk (UTLVR 26% +/- 66.1 vs BTLVR 31% +/- 59.6, p = NS) or decreased oxygen utilization (UTLVR 78% vs BTLVR 74%, p = NS).

CONCLUSIONS

These data suggest that both UTLVR and BTLVR yield significant improvement, but the results of BTLVR seem to be superior with regard to spirometry, lung volumes, and quality of life.

Long-term survival after thoracoscopic lung volume reduction: a multiinstitutional review

BACKGROUND

It has been suggested that bilateral thoracoscopic lung volume reduction (BTLVR) yields significantly better long-term survival than unilateral thoracoscopic lung volume reduction (UTLVR).

METHODS

All perioperative data were collected at the time of the procedure. Follow-up data were obtained during office visits or by telephone.

RESULTS

A total of 673 patients underwent thoracoscopic LVR: 343 had either simultaneous or staged BTLVR and 330, UTLVR. As of July 1998, follow-up was available on 667 (99%) of the 673 patients with a mean follow-up of 24.3 months. The patients in the BTLVR group were significantly younger (62.6+/-8.0 years versus 65.4+/-8.1 years; p < 0.0001), had a higher preoperative arterial oxygen tension (69.7+/-12 mm Hg versus 65.3+/-11 mm Hg; p < 0.0001), and had a superior preoperative 6-minute walk performance (279.9+/-93.6 m [933+/-312 feet] versus 244.5+/-101.4 m [815+/-338 feet] p < 0.0001). There was no difference in the operative mortality rate between the two groups (UTLVR, 5.1%, and BTLVR, 7%). Actuarial survival rates for the UTLVR group at 1 year, 2 years, and 3 years were 86%, 75%, and 69%, respectively versus 90%, 81%, and 74%, respectively, for the BTLVR group (p = not significant).

CONCLUSIONS

Contrary to previous reports, survival after BTLVR was not superior to that after UTLVR even though the former group appeared to have a lower risk preoperatively because of younger age, higher arterial oxygen tension, more advantageous anatomy, and better functional status. Despite thoracoscopic LVR, the actuarial mortality rate approached 30% at 3 years, and this calls into question whether this procedure offers any survival advantage to patients with end-stage emphysema.

Current status of thoracoscopic lung volume reduction

Surgical therapy has recently been reintroduced for the treatment of emphysema, and a number of investigators have used video-assisted thoracic surgical (VATS) techniques to accomplish lung volume reduction. The published reports differ with regard to patient selection, preoperative preparation, operative approach, and surgical technique. The results of these reports are reviewed and compared. Thoracoscopic lung volume reduction appears to be a useful part of the surgeon's armamentarium in managing patients with severe pulmonary emphysema.

Endovascular stent grafts for aneurysmal and occlusive vascular disease

BACKGROUND

This report details our initial experience with two types of endovascular grafts- one for the treatment of infrarenal abdominal aortic aneurysms and the other for the treatment of iliac artery occlusive disease.

METHODS

An abdominal aortic aneurysm was repaired in 34 patients using 3 different types of Ancure endografts (Menlo Park, California). Control patients (n = 9) had a standard aneurysm repair. Patients with chronic lower extremity ischemia (n = 7) secondary to iliac artery occlusive disease were treated with a Hemobahn endograft (W. L. Gore & Associates, Flagstaff, Arizona).

RESULTS

Ancure graft deployment was achieved in 33 of 34 (97.1%) patients. Perioperative mortality for the Ancure and control group patients was 2.9% and 0%, respectively. Periprosthetic leaks were identified within 48 hours of deployment in 6 (18.2%) Ancure graft patients. All but 2 of the leaks resolved on serial follow-up. Additional endovascular procedures were required in 11 (32.4%) Ancure graft patients at the initial procedure or during follow-up to correct graft or arterial stenoses. Patients treated with an endovascular graft had significantly less blood loss and shorter hospital stays than control group patients. For Hemobahn patients, the technical success for graft deployment was 100%. There were no perioperative deaths. The ankle/brachial index increased from a mean of 0.52 preoperatively to 0.86 postoperatively (P = 0.004). One patient required a Wallstent in follow-up to correct a graft wrinkle. Angiography at 6 months demonstrated mild intimal hyperplasia in the stent graft in 5 of 6 patients.

CONCLUSIONS

These early results support the potential for endovascular grafts in the treatment of aneurysmal and occlusive vascular disease. Further modifications in the devices and deployment techniques are necessary to reduce the incidence of periprosthetic leaks, graft limb stenoses, and intimal hyperplasia.

A role for nautilus in the differentiation of muscle precursors

In the Drosophila embryo, nautilus is expressed in a subset of muscle precursors and differentiated fibers and is capable of inducing muscle-specific transcription, as well as myogenic transformation. In this study, we examine the consequences of nautilus loss-of-function on the development of the somatic musculature. Genetic and molecular characterization of two overlapping deficiencies, Df(3R)nau-9 and Df(3R)nau-11a4, revealed that both of these deficiencies remove the nautilus gene without affecting a common lethal complementation group. Individuals transheterozygous for these deficiencies survive to adulthood, indicating that nautilus is not an essential gene. These embryos are, however, missing a subset of muscle fibers, providing evidence that (1) some muscle loss can be tolerated throughout larval development and (2) nautilus does play a role in muscle development. Examination of muscle precursors in these embryos revealed that nautilus is not required for the formation of muscle precursors, but rather plays a role in their differentiation into mature muscle fibers. Thus, we suggest that nautilus functions in a subset of muscle precursors to implement their specific differentiation programs.

Surface specific kinetics of lipid vesicle adsorption measured with a quartz crystal microbalance

We have measured the kinetics of adsorption of small (12.5-nm radius) unilamellar vesicles onto SiO2, oxidized gold, and a self-assembled monolayer of methyl-terminated thiols, using a quartz crystal microbalance (QCM). Simultaneous measurements of the shift in resonant frequency and the change in energy dissipation as a function of time provide a simple way of characterizing the adsorption process. The measured parameters correspond, respectively, to adsorbed mass and to the mechanical properties of the adsorbed layer as it is formed. The adsorption kinetics are surface specific; different surfaces cause monolayer, bilayer, and intact vesicle adsorption. The formation of a lipid bilayer on SiO2 is a two-phase process in which adsorption of a layer of intact vesicles precedes the formation of the bilayer. This is, to our knowledge, the first direct evidence of intact vesicles as a precursor to bilayer formation on a planar substrate. On an oxidized gold surface, the vesicles adsorb intact. The intact adsorption of such small vesicles has not previously been demonstrated. Based on these results, we discuss the capacity of QCM measurements to provide information about the kinetics of formation and the properties of adsorbed layers.

Simultaneous frequency and dissipation factor QCM measurements of biomolecular adsorption and cell adhesion

We have measured the energy dissipation of the quartz crystal microbalance (QCM), operating in the liquid phase, when mono- or multi-layers of biomolecules and biofilms form on the QCM electrode (with a time resolution of ca. 1 s). Examples are taken from protein adsorption, lipid vesicle adsorption and cell adhesion studies. Our results show that even very thin (a few nm) biofilms dissipate a significant amount of energy owing to the QCM oscillation. Various mechanisms for this energy dissipation are discussed. Three main contributions to the measured increase in energy dissipation are considered. (i) A viscoelastic porous structure (the biofilm) that is strained during oscillation, (ii) trapped liquid that moves between or in and out of the pores due to the deformation of the film and (iii) the load from the bulk liquid which increases the strain of the film. These mechanisms are, in reality, not entirely separable, rather, they constitute an effective viscoelastic load. The biofilms can therefore not be considered rigidly coupled to the QCM oscillation. It is further shown theoretically that viscoelastic layers with thicknesses comparable to the biofilms studied in this work can induce energy dissipation of the same magnitude as the measured ones.

Mixed (neutrophil-rich) interstitial pneumonitis in biopsy specimens of lung allografts: a clinicopathologic evaluation

STUDY OBJECTIVES

Mixed interstitial pneumonitis (MIP), defined herein as a diffuse neutrophil-rich inflammatory infiltrate within the interstitial tissues, is an uncommon finding that is not a standard manifestation of acute or chronic rejection. This study examines the clinical significance of MIP in lung allograft recipients at St. Louis University Hospital.

DESIGN

We retrospectively reviewed surgical pathology reports from a selected 50-month period, and identified MIP reported in 13 transbronchial biopsy specimens in lung transplant recipients, representing 4.7% of all lung allograft biopsy specimens seen during this 4-year period. Biopsy specimens with MIP were examined to confirm the presence of a neutrophil-rich interstitial infiltrate and other associated histopathologic findings. The culture results, cytopathologic findings, and clinical charts of the affected patients were also reviewed.

MEASUREMENTS AND RESULTS

The detection of MIP at some point in a patient's posttransplant course was found to be associated with a significantly shorter (p < 0.01) survival, when compared to lung allograft recipients who did not show this finding. A total of seven lung allograft recipients (23% of total) showed MIP at some point in their posttransplant course. Four of the seven (57%) were actively smoking following lung transplantation, compared to 0 of 22 patients who did not show MIP. Six of the 13 MIP biopsy specimens were associated with positive cultures. In no case did MIP coexist with the conventional histologic patterns of acute or chronic rejection. MIP also did not correlate with levels of immunosuppressive therapy or with the incidence of rejection at other times in the patients' posttransplant courses.

CONCLUSIONS

We found no evidence that MIP represents an unusual form of acute or chronic rejection. Instead, it appears to represent a response to acute injury, similar to other injury patterns (hyaline membranes, organizing pneumonia) in transplant recipients. Exposure to tobacco smoke is likely to have played a role in the development of MIP in at least some cases. Because patients with MIP had a significantly shorter posttransplant survival, MIP may usefully identify lung allograft recipients at risk for an adverse outcome.

Drosophila myogenesis and insights into the role of nautilus

Several aspects of muscle development appear to be conserved between Drosophila and vertebrate organisms. Among these is the conservation of genes that are critical to the myogenic process, including transcription factors such as nautilus. From a simplistic point of view, Drosophila therefore seems to be a useful organism for the identification of molecules that are essential for myogenesis in both Drosophila and in other species. nautilus, the focal point of this review, appears to be involved in the specification and/or differentiation of a specific subset of muscle founder cells. As with several of its vertebrate and invertebrate counterparts, it is capable of inducing a myogenic program of differentiation reminiscent of that of somatic muscle precursors when expressed in other cell types. We therefore favor the model that nautilus implements the specific differentiation program of these founder cells, rather than their specification. Further analyses are necessary to establish the validity of this working hypothesis. Studies have revealed a critical role for Pax-3 in specifying a particular subset of myogenic cells, the progenitors of the limb muscles. These myogenic cells migrate from the somite into the periphery of the organism, where they differentiate. These myoblasts do not express MyoD or myf5 until they have arrived at their destination and begin the morphologic process of myogenesis (Bober et al., 1994; Goulding et al., 1994; Williams and Ordahl, 1994). They then begin to express these genes, possibly to put the myogenic plan into action. Thus, as with nautilus, MyoD and myf5 may be necessary for the manifestation of a muscle-specific commitment that has already occurred. By comparison with vertebrates, it was anticipated that the single Drosophila gene would serve the purpose of all four vertebrate genes. However, its restricted pattern of expression and apparent loss-of-function phenotype are inconsistent with this expectation. It remains to be determined whether nautilus functions in a manner similar to just one of the vertebrate genes. Since the myf5- and MyoD-expressing myoblasts are proliferative, the loss of one cell type appears to be compensated by proliferation of the remaining cell type. This apparent plasticity may obscure differences in mutant phenotype resulting from the loss of particular cells that express each of these genes. In Drosophila, by comparison, nautilus-expressing cells committed to the myogenic program undergo few, if any, additional cell divisions, and thus no other cells are available to compensate for the loss of nautilus. Therefore, the apparent differences between the Drosophila nautilus gene and its vertebrate counterparts may reflect, at least in part, differences in the developmental systems rather than differences in the function of the genes themselves.