The protein dystrophin, normally found on the cytoplasmic surface of skeletal muscle cell membranes, is absent in patients with Duchenne muscular dystrophy as well as mdx (X-linked muscular ...dystrophy) mice. Although its primary structure has been determined, the precise functional role of dystrophin remains the subject of speculation. In the present study, we demonstrate that dystrophin-deficient muscle fibers of the mdx mouse exhibit an increased susceptibility to contraction-induced sarcolemmal rupture. The level of sarcolemmal damage is directly correlated with the magnitude of mechanical stress placed upon the membrane during contraction rather than the number of activations of the muscle. These findings strongly support the proposition that the primary function of dystrophin is to provide mechanical reinforcement to the sarcolemma and thereby protect it from the membrane stresses developed during muscle contraction. Furthermore, the methodology used in this study should prove useful in assessing the efficacy of dystrophin gene therapy in the mdx mouse.
Powerful masticatory muscles are found in most primates, including chimpanzees and gorillas, and were part of a prominent adaptation of Australopithecus and Paranthropus, extinct genera of the family ...Hominidae. In contrast, masticatory muscles are considerably smaller in both modern and fossil members of Homo. The evolving hominid masticatory apparatus-traceable to a Late Miocene, chimpanzee-like morphology-shifted towards a pattern of gracilization nearly simultaneously with accelerated encephalization in early Homo. Here, we show that the gene encoding the predominant myosin heavy chain (MYH) expressed in these muscles was inactivated by a frameshifting mutation after the lineages leading to humans and chimpanzees diverged. Loss of this protein isoform is associated with marked size reductions in individual muscle fibres and entire masticatory muscles. Using the coding sequence for the myosin rod domains as a molecular clock, we estimate that this mutation appeared approximately 2.4 million years ago, predating the appearance of modern human body size and emigration of Homo from Africa. This represents the first proteomic distinction between humans and chimpanzees that can be correlated with a traceable anatomic imprint in the fossil record.
Some studies report a high risk of death from intercurrent disease (DID) after postoperative radiotherapy (XRT) for non-small-cell lung cancer (NSCLC). This study determines the risk of DID after ...modern-technique postoperative XRT.
A total of 202 patients were treated with surgery and postoperative XRT for NSCLC. Most patients (97%) had pathologic stage II or III disease. Many patients (41%) had positive/close/uncertain resection margins. The median XRT dose was 55 Gy with fraction size of 1.8 to 2 Gy. The risk of DID was calculated actuarially and included patients who died of unknown/uncertain causes. Median follow-up was 24 months for all patients and 62 months for survivors.
A total of 25 patients (12.5%) died from intercurrent disease, 16 from confirmed noncancer causes and nine from unknown causes. The 4-year actuarial rate of DID was 13.5%. This is minimally increased compared with the expected rate for a matched population (approximately 10% at 4 years). On multivariate analysis, age and radiotherapy dose were borderline significant factors associated with a higher risk of DID (P =.06). The crude risk of DID for patients receiving less than 54 Gy was 2% (4-year actuarial risk 0%) versus 17% for XRT dose > or = 54 Gy. The 4-year actuarial overall survival was 34%; local control was 84%; and freedom from distant metastases was 37%.
Modern postoperative XRT for NSCLC does not excessively increase the risk of intercurrent deaths. Further study of postoperative XRT, particularly when using more sophisticated treatment planning and reasonable total doses, for carefully selected high-risk resected NSCLC is warranted.
Objective: To provide further information addressing the etiology, optimal hormonal management and surgical management in catamenial pneumothorax (CP). Methods: We retrospectively analyzed records of ...all female patients operated on for spontaneous pneumothorax at a university hospital between January 1993 and March 2002. Results: In eight of 24 patients, pneumothoraces were timed with menses. In all, the right side was involved. Seven patients were on hormonal medications pre-operatively and six post-operatively. All six patients taking estrogen/progesterone replacement had recurrences pre-operatively and two of three had recurrences post-operatively while on these medications. No patient suffered a pneumothorax either pre- or post-operatively while taking a gonadotropin releasing hormone agonist (two and three patients, respectively). Intraoperative findings included diaphragmatic implants 5 diaphragmatic fenestrations 4, apical blebs 2 and visceral pleural implants 2. All pathology was specifically addressed at the time of surgery. Pleural space management included mechanical pleurodesis in seven and pleurectomy with talc insufflation in 1. Follow-up ranged from 27 to 63 months with a mean of 48 months. Three patients developed post-operative recurrences. One was managed without intervention and two required additional procedures. Conclusion: Catamenial pneumothorax is under appreciated, representing up to one-third of women with spontaneous pneumothorax. Hormonal agents that allow for menses are ineffective. Gonadotropin releasing hormone agonists should be considered as part of the pre-operative or post-operative management in high risk patients. Our findings suggest that an additional intervention to augment pleural symphysis at the level of the diaphragm should be performed.
Although single-cell RNA sequencing studies have begun to provide compendia of cell expression profiles
, it has been difficult to systematically identify and localize all molecular cell types in ...individual organs to create a full molecular cell atlas. Here, using droplet- and plate-based single-cell RNA sequencing of approximately 75,000 human cells across all lung tissue compartments and circulating blood, combined with a multi-pronged cell annotation approach, we create an extensive cell atlas of the human lung. We define the gene expression profiles and anatomical locations of 58 cell populations in the human lung, including 41 out of 45 previously known cell types and 14 previously unknown ones. This comprehensive molecular atlas identifies the biochemical functions of lung cells and the transcription factors and markers for making and monitoring them; defines the cell targets of circulating hormones and predicts local signalling interactions and immune cell homing; and identifies cell types that are directly affected by lung disease genes and respiratory viruses. By comparing human and mouse data, we identified 17 molecular cell types that have been gained or lost during lung evolution and others with substantially altered expression profiles, revealing extensive plasticity of cell types and cell-type-specific gene expression during organ evolution including expression switches between cell types. This atlas provides the molecular foundation for investigating how lung cell identities, functions and interactions are achieved in development and tissue engineering and altered in disease and evolution.
Metabolic reprogramming of the tumor microenvironment is recognized as a cancer hallmark. To identify new molecular processes associated with tumor metabolism, we analyzed the transcriptome of bulk ...and flow-sorted human primary non-small cell lung cancer (NSCLC) together with
FDG-PET scans, which provide a clinical measure of glucose uptake. Tumors with higher glucose uptake were functionally enriched for molecular processes associated with invasion in adenocarcinoma and cell growth in squamous cell carcinoma (SCC). Next, we identified genes correlated to glucose uptake that were predominately overexpressed in a single cell-type comprising the tumor microenvironment. For SCC, most of these genes were expressed by malignant cells, whereas in adenocarcinoma, they were predominately expressed by stromal cells, particularly cancer-associated fibroblasts (CAF). Among these adenocarcinoma genes correlated to glucose uptake, we focused on glutamine-fructose-6-phosphate transaminase 2 (
), which codes for the glutamine-fructose-6-phosphate aminotransferase 2 (GFAT2), a rate-limiting enzyme of the hexosamine biosynthesis pathway (HBP), which is responsible for glycosylation.
was predictive of glucose uptake independent of GLUT1, the primary glucose transporter, and was prognostically significant at both gene and protein level. We confirmed that normal fibroblasts transformed to CAF-like cells, following TGFβ treatment, upregulated HBP genes, including
, with less change in genes driving glycolysis, pentose phosphate pathway, and TCA cycle. Our work provides new evidence of histology-specific tumor stromal properties associated with glucose uptake in NSCLC and identifies
as a critical regulator of tumor metabolic reprogramming in adenocarcinoma.
These findings implicate the hexosamine biosynthesis pathway as a potential new therapeutic target in lung adenocarcinoma.
.
Objectives: Vascularized, pedicled tissue flaps are often used for cardiothoracic surgical problems complicated by factors that adversely affect healing, such as previous irradiation, established ...infection, or steroid use. We reviewed our experience with use of the omentum in these situations to provide a yardstick against which results with other vascularized flaps (specifically muscle flaps) could be compared. Methods: A retrospective review was undertaken of 85 consecutive patients in whom omentum was used in the chest. In 47 patients (group I), use of omentum was prophylactic to aid in the healing of closures or anastomoses considered to be at high risk for failure. In 32 patients (group II), omentum was used in the treatment of problems complicated by established infection. In 6 patients (group III), omentum was used for coverage of prosthetic chest wall replacements after extensive chest wall resection. Results: Overall, omental transposition was successful in its prophylactic or therapeutic purpose in 88% of these difficult cases (75/85). Success with omentum was achieved for 89% of patients (42/47) in group I, 91% of patients (29/32) in group II, and 67% of patients (4/6) in group III. Three patients (3.5%) had complications of omental mobilization. Four patients (4.7%) died after the operation as a result of failure of the omentum to manage the problem for which it was used. Conclusions: Results with omental transposition compare favorably with published series of similarly challenging cases managed with muscle transposition. Complications of omental mobilization are rare. We believe that its unique properties render the omentum an excellent choice of vascularized pedicle in the management of the most complex cardiothoracic surgical problems.
J Thorac Cardiovasc Surg 2003;125:526-32
Objectives: Our objectives were to delineate the clinicopathologic characteristics of adrenocorticotropin-secreting bronchopulmonary carcinoid tumors causing Cushing's syndrome and to derive from ...these findings a rational approach to diagnosis and surgical management of this unusual condition.
Methods: We conducted a retrospective, chart-review analysis of seven consecutive patients treated at the Massachusetts General Hospital over a 16-year period.
Results: The patients uniformly had symptoms of marked hypercortisolism, and the underlying lung lesions remained clinically occult for a mean of 24 months. Standard endocrine testing was misleading in 83% of patients, reinforcing the need for an alternative diagnostic strategy based on petrosal sinus catheterization and computed tomography of the chest. Although 72% of the tumors were typical carcinoids by standard criteria, 57% demonstrated microscopic evidence of local invasiveness, and 43% were associated with mediastinal lymph node metastases. Eighty-six percent of patients have been cured by pulmonary resection a mean of 59 months after the operation, but 50% of these required a second operation for resection of involved lymph nodes after an initial relapse.
Conclusions: These data suggest that adrenocorticotropin-secreting bronchopulmonary carcinoid tumors represent a distinct, more aggressive subtype of the usual, typical carcinoid. The high rate of lymphatic and local spread demands a surgical approach consisting of anatomic resection and routine mediastinal lymph node dissection. (J Thorac Cardiovasc Surg 1997;114:367-75)
The X chromosome-linked muscular dystrophic (mdx) mouse lacks the subsarcolemmal protein dystrophin and thus represents a genetic homologue of human Duchenne muscular dystrophy. The present study ...examined alterations in diaphragm contractile properties and myosin heavy chain (MHC) expression in young (3-4 mo) and old (22-24 mo) control and mdx mice. In young mdx mice, maximum isometric tension (Po) was reduced to 50% of control values. An increase in fibers coexpressing types I (slow) and IIa MHC as well as regenerating fibers expressing embryonic MHC occurred, whereas IIx/b fibers were decreased. In the old mdx group, Po underwent a further reduction to 25% of control, and there was a slowing of twitch kinetics along with markedly increased diaphragm endurance. These changes were associated with an approximate sevenfold increase in type I MHC fibers and virtual elimination of the IIx/b fiber population; there was no detectable embryonic MHC expression. We conclude that the mdx diaphragm responds to progressive muscle degeneration with transition to a slower phenotype associated with reduced power output and augmented muscle endurance. In the setting of progressive muscle fiber destruction, these changes may help preserve contractile function and promote greater survival of remaining muscle fibers by decreasing cellular energy requirements.
PDF
