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Biomedical subjects

R J Mason

Publications and source records attributed to R J Mason.

At least 37 records · Page 2Linked to original sources
PubMed2001

The appearance of a second genotype of Japanese encephalitis virus in the Australasian region.

In mid-January 2000, the reappearance of Japanese encephalitis (JE) virus activity in the Australasian region was first demonstrated by the isolation of JE virus from 3 sentinel pigs on Badu Island in the Torres Strait. Further evidence of JE virus activity was revealed through the isolation of JE virus from Culex gelidus mosquitoes collected on Badu Island and the detection of specific JE virus neutralizing antibodies in 3 pigs from Saint Pauls community on Moa Island. Nucleotide sequencing and phylogenetic analyses of the premembrane and envelope genes were performed which showed that both the pig and mosquito JE virus isolates (TS00 and TS4152, respectively) clustered in genotype I, along with northern Thai, Cambodian, and Korean isolates. All previous Australasian JE virus isolates belong to genotype II, along with Malaysian and Indonesian isolates. Therefore, for the first time, the appearance and transmission of a second genotype of JE virus in the Australasian region has been demonstrated.

Animals↗
PubMed2001

The crura and crura-sphincter pressure dynamics in patients with isolated upright and isolated supine reflux.

The reason why patients with isolated supine reflux do not reflux in the upright position and patients with isolated upright reflux do not reflux in the supine position is unknown. Our objective was to determine the characteristics of the crura, lower esophageal sphincter, crura-sphincter dynamics, and esophageal body on manometry, endoscopy, and X-ray in patients with isolated upright and isolated supine reflux. Eighty consecutive patients with isolated upright reflux were compared with 82 consecutive patients with isolated supine reflux. Manometrically there was no difference in lower esophageal sphincter characteristics and esophageal contractions between the two groups. The prevalence of a hiatal hernia on manometry was similar between upright and supine refluxers (88% vs 88%). Upright refluxers had shorter hiatal hernias [median (interquartile range) 1.1 (0.65-1.8) vs 1.2 (1-2.3), P < 0.046)]. The median crural pressure, crura-sphincter pressure gradient, and crura-sphincter pressure ratio in upright refluxers was 14.96 (9.5-21.27), 3.28 (1.7-12.2), and 1.33 (0.87-2.8) mm Hg, respectively. These values were significantly higher (P < 0.001) in supine refluxers at 21.43 (16.6-29.9), 10.66 (4.3-19.7), and 2.1 (1.3-4.2) mm Hg, respectively. We conclude that the significantly higher crural pressure in patients with supine reflux acts as a mechanical ring and as a physiologic protector against the unfolding of the sphincter in the postprandial and upright periods. Higher crura-sphincter pressure gradient and larger-size hiatal hernias in patients with supine reflux results in pressurization of the hernia sac and subsequent reflux when these patients are in a supine position.

Esophagus↗
PubMed2001

Laparoscopic ultrasonic epithelial ablation of the lower esophagus after nissen fundoplication in a porcine model: assessment of tissue damage and healing process.

A substantial population of patients with Barrett's esophagus has undergone antireflux surgery but still requires annual surveillance endoscopy. These patients would benefit from a definitive ablation of the Barrett's mucosa, which would remove the malignant potential of this disease. This study evaluates the efficacy of applying ultrasonic energy to remove the epithelium of the lower esophagus in a porcine model with prior Nissen fundoplication. Four Yakutan minipigs underwent laparoscopic Nissen fundoplication. After 2 weeks they underwent transgastric Cavitron ultrasonic surgical aspirator (CUSA; Valleylab, Boulder, CO) ablation of the lower esophageal epithelium. Healing of the mucosa was assessed by endoscopy at 2 weeks and pathological examination at 4 weeks after ablation. All pigs underwent successful laparoscopic Nissen fundoplication. Complete lower esophageal epithelial ablation was accomplished through the fundoplication in three animals. One pig developed a bezoar that prohibited ablation. At 2 weeks endoscopy showed patchy squamous epithelial regeneration, which was confirmed histologically. Esophageal specimens at 4 weeks showed complete regeneration of squamous epithelium with a partially healed small ulcer in one animal. No stricture formation was seen. We conclude that the CUSA technique can completely ablate Barrett's mucosa in the setting of a prior antireflux procedure. Healing with squamous mucosal regeneration is rapid and complete.

Animals↗
PubMed2001

Endoscopic antireflux procedures.

The pathophysiologic hallmark of gastroesophageal reflux disease is loss of the physical barrier at the gastroesophageal junction (GEJ). In recent years, endoscopic techniques that augment or enhance the barrier have emerged. The various techniques include the injection of polymers at the GEJ, delivery of radiofrequency energy to the cardia, and by simple suturing or plication the gastroesophageal junction endoscopically. Results show significant symptomatic improvement, reduction in antacid medication usage, improvement in patient satisfaction, and modest reductions in esophageal acid exposure. Safety, feasibility, and efficacy have been shown with these endoscopic techniques. Future refinements and improvements are expected in this emerging field.

Endoscopy↗
PubMed2000

A characterization of amiodarone-induced pulmonary toxicity in F344 rats and identification of surfactant protein-D as a potential biomarker for the development of the toxicity.

Amiodarone (AD) is gaining support as a first-line antiarrhythmic drug despite its potentially fatal pulmonary toxicity involving inflammation and fibrosis. The goals of this study were to characterize a rat model of AD-induced pulmonary toxicity (AIPT) and identify a serum biomarker to aid in the diagnosis of the onset of pulmonary toxicity. Male F344 rats were instilled intratracheally with AD (6.25 mg/kg with a 3.125 mg/ml solution) in sterile water or the sterile water vehicle on days 0 and 2, a protocol that led to the development of pulmonary fibrosis on day 28 in the AD-treated animals. Animals were killed on days 3, 5, 6, 7, or 10 and bronchoalveolar lavage (BAL) was performed. Recovery of alveolar macrophages and eosinophils was increased on days 3 and 5, while neutrophil recovery and albumin levels in the first BAL fraction were significantly elevated only on day 3. BAL cells recovered from AD-treated rats at day 3 produced more phorbol myristate acetate-stimulated luminol-dependent chemiluminescence (LDCL) over 20 min than BAL cells from control rats. Experiments using specific inhibitors implicated superoxide and nitric oxide in at least part of the LDCL response. Serum levels of surfactant protein-D (SP-D), a surfactant-associated protein, were increased concurrently with the inflammatory response in the lungs. These findings indicate that this model exhibits transient pulmonary inflammation and damage, with the potential for elevated oxidant production in the lungs and subsequent pulmonary fibrosis. Also, SP-D is proposed as a specific biomarker to monitor the onset of AIPT in this model.

Albumins↗
PubMed2000

Alveolar epithelial type II cell apoptosis in vivo during resolution of keratinocyte growth factor-induced hyperplasia in the rat.

Keratinocyte growth factor (KGF) induces rapid and transient hyperplasia of alveolar epithelial type II cells. We sought to determine components of the apoptotic process involved in the resolution of this hyperplasia and the fate of the apoptotic cells. Rats received intrabronchial instillation of 5 mg KGF/kg body weight or diluent. Lungs were fixed 1, 2, 3, 5, and 7 days later. Apoptosis was identified by TdT-mediated dUTP nick-end labeling (TUNEL), double-labeling for TUNEL and the type II cell marker MNF116, and electron microscopy. Fas, FasL, Bax, Bcl-2, and pro- and active caspase-3 were studied by immunohistochemistry. Changes were quantified by stereology. Cell type specificity was investigated by immunofluorescence double staining. Type II cells exhibited Fas, FasL, Bcl-2, and procaspase-3 irrespective of treatment and time. Immunoelectron microscopy revealed Fas at the apical type II cell membrane. Bax staining was prominent in controls (45-95% of type II cell surface fraction), markedly decreased during hyperplasia at days 2 (20-40%) and 3 (0-10%), and reappeared at day 7 (25-45%) when apoptosis was prominent. Remnants of apoptotic type II cells were incorporated in membrane-bound vacuoles of type II cell neighbors as well as alveolar macrophages. The results indicate that type II cells can enter the Fas/FasL/caspase-3 pathway regulated by Bax and Bcl-2. High Bcl-2:Bax levels favor type II cell survival and a low rate of apoptosis during hyperplasia. Low Bcl-2:Bax levels favor type II cell apoptosis during resolution. Because of time-dependent changes that occur within a short time, the KGF-treated rat lung provides a useful in vivo model to investigate apoptosis in the context of tissue remodeling and repair.

Animals↗
PubMed2000

Visual identification of the cystic duct-CBD junction during laparoscopic cholecystectomy (visual cholangiography): an additional step for prevention of CBD injuries.

Despite advances in technical skills, common bile duct (CBD) injury during laparoscopic cholecystectomy is not an uncommon major complication. We describe a technical step that can be taken during the dissection of the triangle of Calot to allow the junction between the cystic duct and CBD to be clearly visualized. This is a safe and simple maneuver that mimics the one done in open surgery. Its routine application serves as an additional safety measure to prevent injury to the common bile duct.

Cholecystectomy, Laparoscopic↗
PubMed2000

Surfactant protein C expression in urethane-induced murine pulmonary tumors.

Mice injected with urethane develop tumors with distinct histological patterns, which are classified as solid, papillary, or a mixture of these two patterns within the same tumor. Most investigators agree that solid tumors arise from alveolar type II cells, but the cellular origin of papillary tumors is less certain, being attributed to either type II cells or nonciliated bronchiolar epithelial (Clara) cells. To characterize the state of differentiation of these tumors more precisely and to provide additional information on gene expression, we used immunocytochemistry and/or in situ hybridization to determine the cellular localization of surfactant-associated proteins A (SP-A), SP-B, SP-C, and SP-D; Clara cell-associated protein CC-10; and thyroid transcription factor-1. In normal mouse lung, the messenger RNAs (mRNAs) for SP-A, SP-B, and SP-D were expressed in both type II cells and Clara cells. SP-C mRNA, however, was expressed only in type II cells, and CC-10 expression of mRNA was restricted to Clara cells. All tumors examined, both solid and papillary, expressed SP-A, SP-B, SP-C, SP-D, and thyroid transcription factor-1, but not CC-10. However, SP-C expression was slightly diminished in larger (older) papillary tumors. These results demonstrate that urethane-induced murine lung tumors express the type II cell phenotype.

Adenoma↗
PubMed2000

Laparoscopic repair of chronic intrathoracic gastric volvulus.

BACKGROUND: Totally intrathoracic gastric volvulus is an uncommon presentation of hiatal hernia, in which the stomach undergoes organoaxial torsion predisposing the herniated stomach to strangulation and necrosis. This may occur as a surgical emergency, but some patients present with only chronic, non-specific symptoms and can be treated electively. The aim of this study is to describe a comprehensive approach to laparoscopic repair of chronic intrathoracic gastric volvulus and to critically assess the pre-operative work-up. METHODS: Eight patients (median age, 71 years) underwent complete laparoscopic repair of chronic intrathoracic gastric volvulus. Symptoms of epigastric pain and early satiety were universally present. Five patients had reflux symptoms. The diagnostic evaluation included a video esophagogram, upper endoscopy, 24-hour pH measurement, and esophageal manometry in all patients. Operative results and postoperative outcome were recorded and follow-up at 1 year included a barium swallow in all patients. RESULTS: All patients had documented intrathoracic stomach. Five of 8 patients had a structurally normal lower esophageal sphincter. All 4 patients with reflux esophagitis on upper endoscopy had a positive 24-hour pH study, and 2 of these patients had a structurally defective lower esophageal sphincter on manometry. None of the patients had preoperative evidence of esophageal shortening. All procedures were completed laparoscopically. The procedure included reduction of the stomach into the abdomen, primary closure of the diaphragmatic defect, and the construction of a short, floppy Nissen fundoplication. There were no major complications. One patient required repair of a trocar site hernia 6 months postoperatively. At 1-year follow-up, there were no radiologic recurrences of the volvulus. One patient complained of temporary swallowing discomfort and another had recurrent gastroesophageal reflux disease (GERD) symptoms caused by a breakdown of the wrap. All other patients remained asymptomatic during follow-up. CONCLUSIONS: The repair of chronic gastric volvulus can be accomplished successfully with a laparoscopic approach. A preoperative endoscopy and esophagogram are crucial to detect esophageal stricture or shortening, and manometry is needed to access esophageal motility; pH measurements do not affect operative strategy. The procedure should include a Nissen fundoplication to treat preoperative GERD, to prevent possible postoperative GERD, and to secure the stomach in the abdomen. The procedure is safe but technically challenging, requiring previous laparoscopic foregut surgical expertise.

Aged↗
PubMed2000

KGF regulates pulmonary epithelial proliferation and surfactant protein gene expression in adult rat lung.

Keratinocyte growth factor (KGF, FGF-7) is a potent mitogen for epithelial cells. We instilled recombinant human KGF to determine the effects of KGF on alveolar epithelial cells. Left lungs of adult rats were instilled intrabronchially with KGF (5 mg/kg) or normal saline. KGF instillation resulted in epithelial cell hyperplasia, and the alveolar bromodeoxyuridine (BrdU) labeling index peaked at 35% on day 2 after instillation. The mRNA levels for the surfactant proteins (SPs) SP-A, SP-B, and SP-D were increased in whole lung tissue on days 1 and 2 after KGF treatment and then returned to control levels on days 3-7. SP-C mRNA levels were increased on days 2-5 after KGF instillation. However, all surfactant protein mRNAs were reduced in type II cells isolated from rats instilled with KGF 2 or 3 days before isolation. These observations were confirmed by in situ hybridization. Instillation of KGF also increased the amount of SP-A and SP-D in lavage fluid. Transcripts for CC10, the 10-kDa Clara cell protein, were decreased. KGF increases the mRNA for the surfactant proteins per lung because of type II cell hyperplasia, but the mRNA per cell is slightly diminished as measured in isolated cells or estimated by in situ hybridization.

Age Factors↗
PubMed2000

Effect of adenovector-mediated gene transfer of keratinocyte growth factor on the proliferation of alveolar type II cells in vitro and in vivo.

Alveolar type II cell proliferation occurs after lung injury and is thought to minimize the subsequent fibrotic response. Keratinocyte growth factor (KGF) has been shown to be a potent growth factor for rat alveolar type II cells. In this study, we created a replication-deficient, recombinant human type 5 adenovirus vector expressing human KGF (Ad5-KGF) to produce alveolar type II cell hyperplasia in vivo. In rat type II cells in vitro, Ad5-KGF at a multiplicity of infection (MOI) of 2, 4, and 8 plaque-forming units (PFU)/cell increased thymidine incorporation 13.3-, 16.8-, and 20. 8-fold, respectively. The KGF concentration in the medium increased up to 26.0 +/- 1.0 ng/ ml. We then instilled 10(9) PFU of Ad5-KGF, Ad5-LacZ, or phosphate-buffered saline into Fischer 344 rats and analyzed the lungs 2, 3, 7, 14, 21, and 28 d later. Ad5-KGF produced extensive alveolar type II cell hyperplasia on Days 2, 3, and 7. Surfactant protein (SP)-A and SP-D in lavage and SP-D in serum increased more in the Ad5-KGF group than in the Ad5-LacZ and PBS groups on Days 2 and 3. KGF was readily detectable for up to 7 d in lavage fluid, although only a modest number of cells expressed KGF messenger RNA as detected by in situ hybridization. These data show that Ad5-KGF stimulates extensive alveolar type II cell proliferation in vivo.

Adenoviridae↗
PubMed2000

Arthroscopic ankle arthrodesis.

The obvious socioeconomic advantages are quite dramatic, with early weight-bearing and AFO immobilization allowing patients an early return to work. Outpatient surgery is a cost-effective benefit. Patient satisfactions as well as comfort are greatly enhanced, requiring only oral pain medication. All patients have tolerated their postoperative regimen and same-day discharge. Arthroscopic subtalar arthrodesis is a technically demanding procedure that requires some rather advanced arthroscopic skills to perform. Joint access is tight, restricted, and requires small instrumentation. Deformities cannot be corrected; therefore, at this stage, a fusion in situ must be considered. The learning curve is certainly far steeper because of the smaller patient population available for enhancing surgical skills. Overall, this procedure has stood the test of time and follow-up. The results appear to be excellent in terms of patient satisfaction, fusion rate time until union, and postoperative morbidity. The recognition and enhancement of this technique as well as the development of more advanced technology will certainly allow this arthroscopic subtalar arthrodesis technique to mature even further over time.

Ankle Injuries↗
PubMed1999

Laparoscopic repair of perforated duodenal ulcers: outcome and efficacy in 30 consecutive patients.

HYPOTHESIS: Laparoscopic management of perforated duodenal ulcers is safe and effective. DESIGN: Prospective nonrandomized controlled trial. SETTING: Tertiary care academic center. PATIENTS AND METHODS: Between October 1993 and October 1997, 30 patients underwent laparoscopic Graham patch repair of perforated duodenal ulcers and 16 had an open repair. MAIN OUTCOME MEASURES: Morbidity, operating time, analgesic requirements, length of hospital stay, and time to return to work. RESULTS: There was no difference in morbidity between the 2 groups. Operating time was longer in the laparoscopy group (106 vs. 63 minutes; P = .001). Patients with shock on admission or symptoms for more than 24 hours had a higher conversion rate (P<.05). The laparoscopy group required fewer analgesics, had a shorter stay, and a quicker recovery. CONCLUSIONS: Laparoscopic repair for perforated ulcers is safe and maintains benefits of the minimally invasive approach. Laparoscopy is not beneficial in patients with shock.

Adult↗
PubMed1999

The pattern of esophageal acid exposure in gastroesophageal reflux disease influences the severity of the disease.

HYPOTHESIS: There is an independent association between the different patterns of esophageal acid exposure in gastroesophageal reflux disease and the severity of the disease. DESIGN: Case-comparison study. SETTING: Department of surgery at a university hospital. PATIENTS: A group of 401 patients with increased esophageal acid exposure divided into 4 groups according to the pattern of reflux: postprandial (n = 41), upright (n = 74), supine (n = 129), and bipositional (n = 157). MAIN OUTCOME MEASURES: The prevalence of mucosal injury and the status of the lower esophageal sphincter and esophageal motility were assessed in each group. RESULTS: The likelihood of having indicators of the severity of gastroesophageal reflux disease increases progressively from postprandial to upright, supine, and bipositional reflux. CONCLUSIONS: The pattern of esophageal acid exposure in gastroesophageal reflux disease is an objective predictor of the severity of disease and could be used for therapeutic decisions.

Case-Control Studies↗
PubMed1999

Is laparoscopic approach to lumbar spine fusion worthwhile?

BACKGROUND: Laparoscopic lumbar spine fusion has been recently described. The aim of this study is to evaluate the safety and efficacy of this procedure for single- and multiple-level degenerative disc disease. METHODS: Twenty-four consecutive laparoscopic interbody lumbar fusions were evaluated prospectively (18 single-level were compared with 6 multiple-level procedures). Results of the laparoscopic multiple-level procedures were further compared with 12 open multiple-level operations. RESULTS: Twenty procedures were completed laparoscopically. The conversions were related to iliac vein lacerations (3 cases) and a mesenteric tear. Single-level cases had lower morbidity (22% versus 83%), shorter hospital stay (2 versus 10 days), and higher fusion rate (88% versus 50%) than multiple-level procedures. Overall results in the latter group were worse than in the matched open group. CONCLUSIONS: Laparoscopic single-level fusion (L5-S1) is safe and carries the benefits of minimal access surgery. Morbidity after multiple level approach is high, and this procedure cannot be advocated at this time.

Adult↗
PubMed1999

Keratinocyte growth factor-induced hyperplasia of rat alveolar type II cells in vivo is resolved by differentiation into type I cells and by apoptosis.

Keratinocyte growth factor (KGF) is a potent mitogen of alveolar epithelial type II cells (AEII). AEII hyperplasia is resolved within several days following intratracheal instillation of KGF by unknown mechanism(s). AEII hyperplasia was induced in rat lungs by intrabronchial instillation of 5 mg recombinant human (rh)KGF x kg body weight(-1) or an equivalent amount of diluent. Epithelial architecture, cell proliferation, transformation of AEII into type I cells (AEI) and apoptosis were investigated by means of immunohistochemistry, stereology, double immunofluorescence microscopy, electron microscopy and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL) technique in lungs fixed 1, 2, 3 and 7 days after treatment. After 1 day of rhKGF instillation, an increase was observed in the nuclear antigen Ki-67, a proliferation marker detected by the antibody MIB-5-expressing surfactant protein (SP)-B, -C, -D-positive AEII. The incidence of mitosis was increased by day 2, resulting in AEII micropapillae with intense basolateral expression of the exon 6 containing isoform (v6) of CD446 (CD44v6), a marker for AEII. By day 3, monolayers of AEII exhibiting lateral CD44v6 covered 45% of the alveolar surface. After 7 days, there were numerous intermediate AEII/AEI cells characterized by a flat elongated shape, staining for SP-D, apical appearance of AEI marker Lycopersicon esculentum lectin and lateral staining for AEII marker CD44v6. Increased numbers of TUNEL-positive epithelial cells were seen at days 2-7. In conclusion, restoration of normal alveolar epithelium after instillation of recombinant human keratinocyte growth factor is accomplished by terminal differentiation and apoptosis of hyperplastic alveolar epithelial type II cells in vivo.

Animals↗
PubMed1999

Laparoscopic management of benign solid and cystic lesions of the liver.

OBJECTIVE: The authors present their experience in the laparoscopic management of benign liver disease. The aim of the study is to analyze technical feasibility and evaluate immediate and long-term outcome. SUMMARY BACKGROUND DATA: Indications for the laparoscopic management of varied abdominal conditions have evolved. Although the minimally invasive treatment of liver cysts has been reported, the laparoscopic approach to other liver lesions remains undefined. METHODS: Between September 1990 and October 1997, 43 patients underwent laparoscopic liver surgery. There were two groups of benign lesions: cysts (n = 31) and solid tumors (n = 12). Indications were solitary giant liver cysts (n = 16), polycystic liver disease (n = 9), hydatid cyst (n = 6), focal nodular hyperplasia (n = 3), and adenoma (n = 9). Only solid tumors, hydatid cysts, and patients with polycystic disease and large dominant cysts located in anterior liver segments were included. All giant solitary liver cysts were considered for laparoscopy. Patients with cholangitis, cirrhosis, and significant cardiac disease were excluded. Data were collected prospectively. RESULTS: The procedures were completed laparoscopically in 40 patients. Median size was 4 cm for solid nodules and 14 cm for solitary liver cysts. Conversion occurred in three patients (7%), for bleeding (n = 2) and impingement of a solid tumor on the inferior vena cava (n = 1). The median operative time was 179 minutes. All solitary liver cysts were fenestrated in less than 1 hour. There were no deaths. Complications occurred in 6 cases (14.1%). Two hemorrhagic and two infectious complications were noted after management of hydatid cysts. There were no complications after resection of solid tumors. Three patients received transfusions (7%). The median length of stay was 4.7 days. Median follow-up was 30 months. There was no recurrence of solitary liver or hydatid cysts. One patient with polycystic disease had symptomatic recurrent cysts at 6 months requiring laparotomy. CONCLUSION: Laparoscopic liver surgery can be accomplished safely in selected patients with small benign solid tumors located in the anterior liver segments and giant solitary cysts. The laparoscopic management of polycystic liver disease should be reserved for patients with a limited number of large, anteriorly located cysts. Hydatid disease is best treated through an open approach.

Adult↗