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R J Mason

Publications and source records attributed to R J Mason.

At least 55 records · Page 3Linked to original sources
PubMed1999

Binding of rat and human surfactant proteins A and D to Aspergillus fumigatus conidia.

Surfactant proteins A (SP-A) and D (SP-D) are thought to play important roles in pulmonary host defense. We investigated the interactions of rat and human SP-A and SP-D with Aspergillus fumigatus conidia. Rat SP-D but not rat SP-A bound the conidia, and the binding was inhibited by EDTA, mannose, glucose, maltose, and inositol. Binding studies using a mutant recombinant rat SP-D with altered carbohydrate recognition but normal structural organization clearly established a role for the carbohydrate recognition domain in binding to conidia. However, neither rat SP-A nor SP-D increased the association of fluorescein isothiocyanate-labeled conidia with rat alveolar macrophages as determined by flow cytometry. Both human SP-A (isolated from normal and alveolar proteinosis lungs) and SP-D (recombinant protein and protein isolated from alveolar proteinosis lungs) bound the conidia. These data indicate that important differences exist between rat and human SP-A in binding to certain fungi. Human SP-A and SP-D binding to conidia was also examined in the presence of hydrophobic surfactant components (HSC), containing both the phospholipid and hydrophobic proteins of surfactant. We found that HSC inhibited but did not eliminate human SP-A binding to Aspergillus conidia. In contrast, the SP-D binding to conidia was unaffected by HSC. These findings indicate that SP-D plays a major role in the recognition of Aspergillus conidia in alveolar fluid.

Animals↗
PubMed1998

Regulatory mechanisms of surfactant secretion.

Surfactant secretion is a critical regulated process in the metabolism of pulmonary surfactant. Presumably, because this process is vital to the survival of the organism, there are several independent pathways for stimulating secretion which work through different cell surface receptors and signaling mechanisms. In addition, there is apparent homeostatic regulation in that two components of surfactant, namely SP-A and dipalmitoylphosphatidylcholine, can inhibit secretion. Although secretion of surfactant has been studied for over two decades, there remains some important issues to be resolved. In vivo secretion can be stimulated by hyperventilation or even a single large breath. However, we do not know the biochemical mechanism for this physiologically important form of stimulation. In vitro, we know many of the proximal events in signaling, but we do not know how the lamellar bodies move within a cell or the docking mechanism at the plasma membrane. Many investigators have demonstrated that SP-A will inhibit secretion in vitro, but the mechanism is not known. Finally, there is a route of secretion of SP-A independent of lamellar bodies, but we do not know details of this pathway nor its regulation.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

[Endoscopic intraluminal valvuloplasty--a therapy of the future for gastroesophageal reflux].

A new endoscopic intraluminal valvuloplasty is described. The procedure provides a simple, easy out-patient approach for antireflux surgery and is applicable to patients with early gastroesophageal reflux disease as an alternative to chronic life-long medical therapy. The feasibility, durability and efficacy of the procedure in baboons are reported.

Ambulatory Surgical Procedures↗
PubMed1998

Effects of soluble factors and extracellular matrix on DNA synthesis and surfactant gene expression in primary cultures of rat alveolar type II cells.

Proliferation and differentiation of epithelial cells are thought to be regulated by soluble factors in extracellular fluid and insoluble components of the extracellular matrix. We have examined the combined effects of soluble factors and an extracellular matrix (EHS matrix) on DNA synthesis, cell proliferation, and surfactant protein gene expression in primary cultures of alveolar type II epithelial cells. Cells on EHS matrix cultured in DMEM containing insulin, cholera toxin, EGF, aFGF, 5% rat serum, and 15-fold concentrated bronchoalveolar lavage fluid (D-GM) formed larger aggregates than cells cultured on the same substratum in DMEM containing 5% rat serum (D-5). Cells cultured in D-GM on EHS matrix incorporated more [3H]-thymidine than cells on the same substratum in D-5, with an eight-fold increase seen on day 4 of culture. This increase in [3H]-thymidine incorporation was accompanied by a labeling index of greater than 65% of the cells. Cell counts showed that exposure of type II cells on EHS matrix to D-GM resulted in increased cell number on day 4 of culture. [3H]-thymidine autoradiography combined with immunostaining with anti-cytokeratin, anti-SP-A, and anti-vimentin antibodies demonstrated that the proliferating cells were epithelial cells that contained SP-A. Type II cells cultured on plastic in D-GM also showed increased [3H]-thymidine incorporation compared to cells cultured in D-5. The level of [3H]-thymidine incorporation by cells on plastic, however, was significantly less than that seen in cells cultured in the same medium on EHS matrix. Type II cells cultured on EHS matrix in D-GM had a decreased abundance of mRNAs for SP-A and SP-C than cells cultured on EHS matrix in D-5 as determined by Northern analysis. This inhibition was reversed by switching from D-GM to D-5 on day 4 and culturing the cells for an additional 4 days. In contrast, SP-B mRNA was increased in response to D-GM. This increase was not reversed by switching from D-GM to D-5 on day 4. These results suggest that the interaction of soluble factors and extracellular matrix components has a strong influence on type II cell proliferation, which were partially associated with the reversible inhibition of lung tissue-specific protein mRNAs. Their dynamic interplay among the type II cell, the extracellular matrix, and growth factors may determine multicellular functions and play an important role in normal lung development and in the repair of the lung epithelium following injury.

Animals↗
PubMed1998

Ultrasonic epithelial ablation of the lower esophagus without stricture formation. A new technique for Barrett's ablation.

BACKGROUND: The premalignant potential of Barrett's esophagus has stimulated efforts to find a way to ablate the columnar epithelium in order to reheal the area with squamous epithelium, thus obviating the cancer risk. This study describes and evaluates a new technique using ultrasonic energy to ablate the epithelium of the lower esophagus in a porcine model. METHODS: Eight young farm pigs were used to develop the technique of applying a laparoscopic Cavitron Ultrasonic Surgical Aspirator (CUSA) to the lower esophageal mucosa through an operating gastrostomy. A further 11 Yakutan minipigs then underwent CUSA epithelial ablation, followed by a laparoscopic Nissen fundoplication or postoperative acid suppression therapy. We then assessed the healing response in these subjects. RESULTS: Optimal CUSA energy settings enabled complete ablation of the squamous epithelium with preservation of the muscularis mucosa and submucosa. The integrity of the aspirated cells was sufficient for cytological analysis. Healing occurred by squamous regeneration without stricture formation. CONCLUSION: The CUSA technique holds promise for complete ablation of the Barrett's epithelium in a single setting. The unique tissue-selective nature of the ablative process allows complete mucosal reepithelialization without stricture formation.

Animals↗
PubMed1998

Esophagectomy for unsuccessful antireflux operations.

BACKGROUND: Primary antireflux surgery provides excellent symptom relief in most patients. Unfortunately, the results of redo surgery are less predictable. In these patients, esophageal injury from long-standing reflux of gastric contents and operative trauma from previous failed antireflux procedures results in progressive deterioration in esophageal propulsion, poor clearance of reflux episodes, mucosal damage, and, in some cases, stricture formation. For the past 16 years, we have selectively used esophageal resection and replacement instead of another reoperation in these challenging patients. METHODS: Seventeen patients with end-stage esophageal body dysfunction and one or more previously unsuccessful antireflux procedures underwent esophagectomy and reconstruction by colon interposition in 15 patients and jejunum interposition in 2 patients. The indications for esophagectomy rather than a redo antireflux procedure were a global loss of effective esophageal motility in 13 and a nondilatable stricture in four. Their outcome was compared with that of 32 patients with adequate motility and 18 with a similar global loss of motility who had a redo antireflux procedure. Perioperative complications after esophagectomy were recorded, and long-term outcome was assessed by means of a standardized questionnaire at a median of 7 years after the operation. RESULTS: Patients with profound esophageal body dysfunction who underwent esophageal resection had outcomes similar to those with normal motility who underwent a redo antireflux procedure. Those with profound esophageal motility dysfunction who underwent a redo antireflux procedure had a worse outcome than those who underwent resection. Esophageal resection and replacement was performed without mortality or graft failure. All patients who underwent resection stated that their preoperative symptoms were relieved completely (n = 6) or improved (n = 10). Thirteen patients (81%) were able to eat three meals a day, and 12 patients (75%) enjoyed an unrestricted diet. Two thirds of the patients were at or above their ideal body weight, and 88% were fully satisfied with the outcome of the procedure. CONCLUSION: Patients with end-stage esophageal body dysfunction who have had a previous unsuccessful antireflux procedure can be treated by esophageal resection with a high expectation of success.

Adult↗
PubMed1998

Pharyngeal swallowing disorders: selection for and outcome after myotomy.

OBJECTIVE: To develop selection criteria based on the mechanical properties of pharyngoesophageal swallowing that indicate when patients with pharyngeal dysphagia will benefit from a myotomy. SUMMARY BACKGROUND DATA: The pathophysiology of pharyngoesophageal swallowing disorders is complex. The disorder is of interest to several medical specialists (gastroenterologists, otorhinolaryngologists, general and thoracic surgeons), which contributes to confusion about the entity. The management is compounded because it is most frequently seen in the elderly, is often associated with generalized neuromuscular disease, and occurs with a high prevalence of concomitant disease. The selection of patients for myotomy is difficult and of major importance to the quality of life of the affected patients. METHOD: One hundred seven patients without a Zenker diverticulum but with pharyngeal dysphagia underwent a detailed manometric assessment of the upper esophageal sphincter (UES). Cricopharyngeal opening was identified by the presence of a subatmospheric pressure drop before bolus arrival. Impaired pharyngoesophageal segment compliance resulting in a resistance to pharyngoesophageal flow was determined by measuring the intrabolus pressure generated by a 5-ml liquid bolus. RESULTS: Thirty-one of 107 patients underwent a myotomy (29%). Both impaired sphincter opening and increased intrabolus pressure predicted a good outcome. CONCLUSION: Myotomy is beneficial in patients with pharyngeal swallowing disorders and manometric evidence of defective sphincter opening and increased intrabolus pressure.

Adult↗
PubMed1998

Dieulafoy's disease of the large and small bowel.

The Dieulafoy lesion is a rare cause of severe gastrointestinal hemorrhage. The lesion is usually located in the stomach, although it may occur anywhere in the gastrointestinal tract. We describe four patients with extragastric Dieulafoy's disease, in the duodenum (one), the proximal jejunum (two), and the left hemicolon (one). Diagnosis was made by endoscopy in all four and confirmed by histology in three. The pathology of the Dieulafoy lesion is essentially the same throughout the gastrointestinal tract. Endoscopic treatment by sclerotherapy combined with electrocoagulation was successful in the duodenal and colonic Dieulafoy lesions, but not in the jejunal lesions.

Adult↗
PubMed1998

Surfactant protein A and surfactant protein D in health and disease.

Surfactant protein (SP) A and SP-D are collagenous glycoproteins with multiple functions in the lung. Both of these proteins are calcium-dependent lectins and are structurally similar to mannose-binding protein and bovine conglutinin. Both form polyvalent multimeric structures for interactions with pathogens, cells, or other molecules. SP-A is an integral part of the surfactant system, binds phospholipids avidly, and is found in lamellar bodies and tubular myelin. Initially, most research interest focused on its role in surfactant homeostasis. Recently, more attention has been placed on the role of SP-A as a host defense molecule and its interactions with pathogens and phagocytic cells. SP-D is much less involved with the surfactant system. SP-D appears to be primarily a host defense molecule that binds surfactant phospholipids poorly and is not found in lamellar inclusion bodies or tubular myelin. Both SP-A and SP-D bind a wide spectrum of pathogens including viruses, bacteria, fungi, and pneumocystis. In addition, both molecules have been measured in the systemic circulation by immunologic methods and may be useful biomarkers of disease. The current challenges are characterization of the three-dimensional crystal structure of SP-A and SP-D, molecular cloning of their receptors, and determination of their precise physiological functions in vivo.

Animals↗
PubMed1998

Hepatocyte growth factor and keratinocyte growth factor in the pulmonary edema fluid of patients with acute lung injury. Biologic and clinical significance.

Hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) are among the most potent mitogens identified for alveolar type II epithelial cells and may have other important functions in repair of the alveolar epithelium in acute lung injury (ALI). However, neither growth factor has been identified in the distal air spaces or plasma of patients with ALI. The goals of this study were to determine: (1) whether HGF and KGF are present in pulmonary edema fluid from patients with ALI and control patients with hydrostatic pulmonary edema; (2) whether HGF and KGF are biologically active in pulmonary edema; and (3) whether HGF or KGF levels are associated with clinical outcome. Pulmonary edema and plasma samples were obtained within 48 h of onset of acute pulmonary edema requiring mechanical ventilation in 26 patients with ALI and 11 control patients with hydrostatic edema. HGF and KGF concentrations were measured with enzyme-linked immunosorbent assays (ELISAs). The median (25th to 75th percentiles) concentration of HGF in pulmonary edema fluid was 21.4 (8.3 to 41.3) ng/ml in ALI and 6.6 (4.8 to 11.4) ng/ml in hydrostatic edema fluid (p < 0.01). The HGF concentration was 7-fold higher in the edema fluid than in the plasma of patients with ALI. In contrast, KGF was detected in low concentrations in edema fluid of patients with ALI and hydrostatic pulmonary edema; the concentration of KGF did not differ in ALI edema (0.6 [0.3 to 2.1] ng/ml) and hydrostatic edema fluid (0.2 [0.0 to 2.6] ng/ml) (p = NS). HGF and KGF were partly purified from four edema-fluid samples by heparin-Sepharose chromatography. Partly purified edema fluids were potent stimuli of DNA synthesis in cultured rat type II alveolar cells; addition of neutralizing antibodies to HGF and KGF attenuated this increase in DNA synthesis by 66% and 53%, respectively. Interestingly, higher edema-fluid levels of HGF were associated with higher mortality in patients with ALI. These novel results show that HGF and KGF are active in the alveolar space early in ALI, probably mediating early events in lung repair, and that increased levels of HGF in edema fluid may have prognostic value early in ALI.

Adolescent↗
PubMed1998

KGF increases SP-A and SP-D mRNA levels and secretion in cultured rat alveolar type II cells.

Studies of secretion of surfactant proteins by alveolar type II cells have been limited because the expression of the genes for these proteins decreases rapidly in primary culture. We developed a culture system to investigate the regulation of lipid and protein secretion by alveolar type II cells and the genes involved in these processes. Rat type II cells were plated on membrane inserts coated with rat-tail collagen in medium containing 10% fetal bovine serum (FBS) for 1 d before being changed to medium containing 5 ng/ml keratinocyte growth factor (KGF) and 2% serum for 3 d and to medium with 5% Engelbreth-Holm-Swarm tumor matrix (EHS) but without serum for 2 d. From this time forward, the cells were placed on a rocking platform and cultured with 0.4 ml medium on the apical surface at the air-liquid interface (A/L) in four different, serum-free media: basal Dulbecco's modified Eagle's medium (DMEM)/F12 medium (DF12), basal medium plus EHS (DF12/EHS), basal medium plus KGF (DF12/KGF), and basal medium plus EHS and KGF (DF12/EHS/KGF). Cells cultured in DF12 and DF12/EHS assumed an attenuated, flattened morphology, whereas those in DF12/KGF and DF12/EHS/KGF were more cuboidal, contained numerous lamellar bodies, and had apical microvilli. Cells cultured in DF12 and DF12/EHS produced a relatively weak signal for the surfactant protein mRNAs (surfactant proteins [SP]-A, SP-B, SP-C, and SP-D, respectively), and secretion of SP-A and SP-D remained low. In contrast, cells maintained for 3 d at A/L and cultured in the presence of KGF showed strong signals for SP-A, SP-B, and SP-D mRNAs, and secreted SP-A, SP-D, and lysozyme into the apical medium. The combination of 12-O-tetradecanoyl-phorbol-11-acetate (TPA) and terbutaline stimulated secretion of [3H]phosphatidylcholine ([3H]PC), SP-A, and lysozyme, but not SP-D. This primary culture system should prove useful for mechanistic studies of the secretion of SP-A, SP-D, and surfactant lipids.

Animals↗
PubMed1998

Trafficking of newly synthesized surfactant protein A in isolated rat alveolar type II cells.

We examined the synthesis, transport, and localization of surfactant protein A (SP-A) in primary cultures of alveolar type II cells. In type II cells maintained in culture for 6 h, 39% of the SP-A pool detected with an enzyme-linked immunosorbent assay (ELISA) was found in lamellar bodies (LBs). After 24 h in culture, 53% of the cellular SP-A pool was found in LBs. The absolute amount of SP-A in the LB compartment was almost identical at 6 and 24 h of culture. In contrast to the results obtained with ELISA, 35S labeling of newly synthesized SP-A revealed that less than 7% of the cellular SP-A pool was in LBs at either 6 or 24 h of culture. In the 6-h cultures, 17% of the total (i.e., cells and media) [35S]SP-A pool was extracellular. In the 24-h cultures, 70% of the [35S]SP-A pool was extracellular. The secretion of [35S]SP-A was blocked by brefeldin A at all times. When medium containing newly secreted [35S]SP-A was incubated with alveolar type II cells maintained in culture for 24 h, the protein was taken up and incorporated into the LB fraction. More than 80% of the internalized SP-A was associated with the LB compartment after a 6 h incubation. The uptake of [35S]SP-A was blocked at 4 degrees C and was promoted by addition of unlabeled SP-A at 37 degrees C. These findings support a pathway of extracellular routing of SP-A prior to its accumulation in LBs in cultured type II cells.

Animals↗
PubMed1998

A 50-kDa variant form of human surfactant protein D.

The dominant form of human surfactant protein D (SP-D) is a multimeric collagenous glycoprotein composed of monomeric subunits that have a molecular mass of 43 kDa under reducing conditions. However, in evaluating monoclonal antibodies to human SP-D, an additional monomeric subunit was identified with a reduced molecular mass of 50 kDa. This 50-kDa variant was detected in approximately half of the samples evaluated and was found in lavage fluid from normal subjects, patients with alveolar proteinosis or idiopathic pulmonary fibrosis and in amniotic fluid. This 50-kDa variant had the same amino-terminal sequence, amino acid composition and apparent size of the carboxy-terminal collagenase-resistant fragment (20 kDa) as the 43-kDa subunit. The major difference was in the amino-terminal portion of the molecule and was due to altered glycosylation, as determined by carbohydrate staining, chemical deglycosylation, treatment with N-glycanase and neuraminidase and reduced signals for threonine at positions 5, 9 and 10 during amino-terminal sequencing. After gel filtration chromatography, the 50-kDa form was not present in the high molecular weight fraction, which is commonly used in purification of SP-D, but was found only in the smaller molecular weight fraction of monomers and trimers of SP-D. In conclusion, the 50 kDa-form of surfactant protein D is produced by post-translational glycosylation and does not form higher ordered oligomers, but its precise physiological function remains to be determined.

Amino Acids↗