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Biomedical subjects

M F Chen

Publications and source records attributed to M F Chen.

At least 163 records · Page 9Linked to original sources
PubMed1997

Airway smooth muscle orientation in intraparenchymal airways.

Airway smooth muscle (ASM) shortening is the central event leading to bronchoconstriction. The degree to which airway narrowing occurs as a consequence of shortening is a function of both the mechanical properties of the airway wall as well as the orientation of the muscle fibers. Although the latter is theoretically important, it has not been systematically measured to date. The purpose of this study was to determine the angle of orientation of ASM (theta) in normal lungs by using a morphometric approach. We analyzed the airway tree of the left lower lobes of four cats and one human. All material was fixed with 10% buffered Formalin at a pressure of 25 cmH2O for 48 h. The fixed material was dissected along the airway tree to permit isolation of generations 4-18 in the cats and generations 5-22 in the human specimen. Each airway generation was individually embedded in paraffin. Five-micrometer-thick serial sections were cut parallel to the airway long axis and stained with hematoxylin-phloxine-saffron. Each block yielded three to five sections containing ASM. To determine theta, we measured the orientation of ASM nuclei relative to the transverse axis of the airway by using a digitizing tablet and a light microscope (x250) equipped with a drawing tube attachment. Inspection of the sections revealed extensive ASM crisscrossing without a homogeneous orientation. The theta was clustered between -20 degrees and 20 degrees in all airway generations and did not vary much between generations in any of the cats or in the human specimen. When theta was expressed without regard to sign, the mean values were 13.2 degrees in the cats and 13.1 degrees in the human. This magnitude of obliquity is not likely to result in physiologically important changes in airway length during bronchoconstriction.

Animals↗
PubMed1997

Percutaneous transvenous mitral balloon valvuloplasty alone in patients with combined aortic and mitral stenosis.

To investigate the feasibility of percutaneous transvenous balloon dilatation of the mitral valve in patients with combined aortic and mitral stenosis, 12 patients were studied by echocardiography and catheterization before and after mitral valvuloplasty. Aortic stenosis was defined from prevalvuloplasty catheterization study as a transaortic pressure gradient of more than 25 mm Hg. All 12 patients underwent transvenous balloon mitral valvuloplasty successfully. Immediately after the procedure, all patients experienced improvement in clinical symptoms and in hemodynamic variables. Mitral valve areas were significantly increased from 0.78 +/- 0.18 to 1.73 +/- 0.21 cm2 (P < 0.0001) by planimetry method. Cardiac output was significantly increased from 3.6 +/- 0.1 to 4.2 +/- 0.5 L/min (P = 0.01). Mean transaortic flow rate increased 33% (from 198 +/- 68 to 254 +/- 41 mL/s, P = 0.002). Mean pressure gradient across the aortic valve after mitral valvuloplasty was not significantly increased, from 34 +/- 7 to 37 +/- 13 mm Hg. Aortic valve areas, derived from the Gorlin formula, were significantly increased from 0.57 +/- 0.12 to 0.73 +/- 0.14 cm2 (P = 0.006) after mitral valvuloplasty. However, continuity equation-derived aortic valve area was independent of increasing flow rate after mitral valvuloplasty from 1.29 +/- 0.35 to 1.30 +/- 0.29 cm2. During follow-up with a mean of twenty four +/- fourteen months, 8 patients were in New York Heart association functional class I, 3 in class II, and 1 in class IV who received pericardiotomy owing to constrictive pericarditis without aortic valve replacement. In conclusion, mitral valvuloplasty alone may be safe and effective in alleviating symptoms in mitral stenosis patients with transaortic pressure gradient > 25 mm Hg. Continuity equation-derived aortic valve areas seem to be flow independent in evaluation of aortic stenosis and are important for decision making.

Adult↗
PubMed1997

Deleterious effect of tracheal obstruction on type II pneumocytes in fetal sheep.

It was previously shown that tracheal obstruction accelerated fetal lung growth and eventually reversed the pulmonary hypoplasia in experimental diaphragmatic hernia. We have successfully developed a reversible tracheal obstruction technique in fetal sheep using balloon occlusion and showed that 3 wk of obstruction induced significant lung growth of the same magnitude as the tracheal ligation. The purpose of this study was to examine the effects of 1 and 3 wk of tracheal occlusion on the alveolar cell population with specific attention to the type II pneumocytes. We first showed that 1 wk of occlusion induced a significant increase in lung weight and in alveolar surface area. We then used the surfactant protein C (SP-C) mRNA as a specific marker of differentiated type II pneumocytes. Total RNA was isolated from fetal sheep lung with or without tracheal occlusion, and Northern blots were hybridized with a cDNA probe specific for the sheep SP-C. The results show a dramatic decrease in SP-C mRNA expression (8.8-fold, p < 0.01). In situ hybridization showed a marked decrease in the density of cells expressing SP-C, as well as the amount of SP-C mRNA expressed by the cells. The effect was present as early as 1 wk of occlusion. The sparseness of type II pneumocytes was further confirmed by electron microscopy. We thus conclude that tracheal obstruction causes a profound decrease in the number of type II pneumocytes in the lungs. Given the crucial role of type II pneumocytes in surfactant production, we could speculate that, if tracheal occlusion is able to accelerate lung growth, the final product is probably surfactant-deficient.

Airway Obstruction↗
PubMed1997

Gabexate mesilate improves pancreatic microcirculation and reduces lung edema in a rat model of acute pancreatitis.

We evaluated the effects of a protease inhibitor on the progression of acute pancreatitis in rats. The model was selected and modified to mimic an intermediate stage of the disease. The degree of microcirculatory derangement in the pancrease and of lung edema was determined to assess the effects of gabexate mesilate (ethyl-4-(6-guanidinohexanoyloxy) benzoate methane sulfonate), a synthetic antiprotease, in acute pancreatitis. Male Sprague-Dawley rats (225-275 g) were used. Experimental pancreatitis was established by four intramuscular injections of cerulein (50 micrograms/kg) at 1 hour intervals. Lipopolysaccharide (10 mg/kg) was injected intraperitoneally as an acute septic challenge. Gabexate mesilate was infused intravenously 6 hours after the initiation of induction of acute pancreatitis at doses of 0.01, 0.1, 1, or 10 mg/kg/h. Microcirculatory changes in the pancreas were studied using in vivo microscopy. All animals survived until the end of the experiments. Gabexate mesilate significantly improved pathologic criteria and decreased serum lipase levels at doses of 1 and 10 mg/kg/h. It significantly lessened the severity of lung edema and improved the microcirculatory environment in the pancreas by increasing flow velocity and reducing leukocyte sticking. These results indicate the beneficial effects of gabexate mesilate on pancreatic microcirculation and lung edema in the progression of acute pancreatitis with septic challenge in rats.

Acute Disease↗
PubMed1997

Role of hepatic resection in surgery for bilateral intrahepatic stones.

BACKGROUND: Hepatic resection is the treatment of choice for unilateral intrahepatic stones. The availability of the flexible choledochoscope has greatly changed the management of intrahepatic stones. Little has been reported regarding hepatic resection for bilateral intrahepatic stones. METHODS: Fifty-nine (15.1 per cent) of 392 patients with bilateral intrahepatic stones underwent hepatic resection. The indications and results were reported. Surgical outcome and long-term follow-up were analysed, and results were compared with those in patients not undergoing hepatectomy. RESULTS: Fifty-nine patients underwent hepatic resection because of destruction of the left liver by repeated infection (n = 40), multiple cholangitic liver abscesses (n = 18) or associated intrahepatic cholangiocarcinoma (n = 1). The hospital mortality rate was 1.7 per cent. The majority of complications were wound infection (9 per cent), haematobilia (5 per cent) and biliary fistula (3 per cent). The incidence of residual stones after surgery was 60 per cent. One year after postoperative choledochoscopic stone extraction, the rate of complete stone clearance was 84 per cent. In patients who did not have hepatectomy the respective rates were 90.1 and 52.9 per cent. The recurrence rate for stones in the hepatectomy and no-hepatectomy groups was 12 and 33.0 per cent respectively. CONCLUSIONS: Compared with patients not undergoing hepatectomy, those having hepatic resection had similar operative risks, fewer residual stones and a low incidence of recurrent stones (P < 0.05).

Adult↗
PubMed1996

New form of bone dysplasia with multiple fractures associated with monosomy X.

We report on the clinical, radiologic, and pathologic findings in a 20-week-old fetus with monosomy X and severe hydrops associated with fetal dwarfism. The fetus presented with osteoporosis, bent bones, multiple fractures, and distinctive symmetric submetaphyseal transverse bone interruptions or pseudofractures. We excluded by radiologic and histopathologic examination the diagnoses of osteogenesis imperfecta, hypophosphatasia, campomelic dysplasia, achondrogenesis, hypochondrogenesis, and other types of bone dysplasia. To our knowledge, this is a previously undescribed bone dysplasia associated with monosomy X. This bone dysplasia may be inherited as an X-linked recessive disorder.

Bone Diseases, Developmental↗
PubMed1996

Changes of left ventricular function after percutaneous balloon mitral valvuloplasty in mitral stenosis with impaired left ventricular performance.

The pathophysiological role of mechanical and myocardial factors for impairment of left ventricular performance in mitral stenosis is still not clear. To investigate this controversy, 27 patients of mitral stenosis with left ventricular ejection fraction < 50% were studied. Patients were divided into two groups: Group 1: 20 patients, left ventricular ejection fraction improved to > 50% after valvuloplasty, and Group 2: 7 patients, left ventricular ejection fraction still < 50% after valvuloplasty. The clinical and hemodynamic characteristics were comparable for the two groups before valvuloplasty. Follow-up catheterization done one week later showed similar changes in mitral valve area, cardiac index, pulmonary pressure, left ventricular end-diastolic volume index and systemic vascular resistance between the two groups. However, left ventricular end-systolic volume was significantly decreased after valvuloplasty in Group 1 but not in Group 2, resulting in significantly higher ejection fraction in Group 1 than in Group 2. Postoperatively, regional wall motion scores were lower in Group 1 than in Group 2 (2.0 +/- 0.6 vs. 2.7 +/- 0.5 at the anterolateral wall, P = 0.002; 1.9 +/- 0.6 vs. 2.9 +/- 0.4 at the posterobasal wall, P = 0.0003). Most of our mitral stenosis patients with impaired left ventricular ejection fraction showed improvement after mitral valvuloplasty had released the mechanical obstruction. However, in some patients, impaired ejection fraction persisted after valvuloplasty, suggesting the mechanism of myocardial failure. Thus, both myocardial and mechanical factors play important roles in the pathogenesis of left ventricular ejection performance impairment.

Adult↗
PubMed1996

Excessive papillary muscle traction and dilated mitral annulus in mitral valve prolapse without mitral regurgitation.

This study demonstrated excessive papillary muscle displacement during peak systole but normal mitral annulus function during the cardiac cycle in patients with mitral valve prolapse and no mitral regurgitation. The excessive papillary muscle displacement may play an important role in the pathogenesis of the superior displacement of mitral leaflets in patients with mitral valve prolapse.

Adolescent↗
PubMed1996

Usefulness of transdermal scopolamine for vasovagal syncope.

We studied short-term effectiveness of transdermal scopolamine in a group of patients with unexplained syncope provoked during head-up tilt testing. This double-blind randomized trial of transdermal scopolamine demonstrated no significant effect of preventing vasovagal syncope.

Administration, Cutaneous↗
PubMed1996

Primary carcinoma of the gallbladder in Taiwan.

To define more precisely the prognostic index for patients with primary carcinoma of the gallbladder in Taiwan, we retrospectively reviewed the data of 74 patients with gallbladder carcinoma treated over a period of 15 years, from 1979 to 1993. Of these patients, 75% had Nevin stage V gallbladder cancer. The most common presenting complaint was abdominal pain, followed by jaundice, fever, and nausea and vomiting. Accurate preoperative diagnosis was made in 29.7% of the patients. Ultrasonography and computed tomography had a diagnostic accuracy of 34.0% and 40.9%, respectively. The most common histologic type was adenocarcinoma. Liver was the organ most commonly invaded (51.9%) by direct extension and/or metastases, followed by regional lymph nodes (38.5%). The overall 5-year survival rate was 4.1%. Age, sex, white cell count, hemoglobulin, SGOT, SGPT, total bilirubin, alkaline phosphatase, and cholelithiasis were not significant prognostic factors. Patients with cancers confined in the gallbladder wall (stages I, II, III) had a better (P < 0.05) cumulative survival rate than did those with regional lymph nodes and distant metastases. Cholecystectomy or extended surgery had a better survival rate than did palliative surgery, but there was no significant difference between cholecystectomy and extended surgery. High index of suspicion of the disease and earlier surgical treatment may improve patient survival.

Adult↗
PubMed1996

Excessive myocardial contraction in vasovagal syncope demonstrated by echocardiography during head-up tilt test.

The purpose of this study was to gain insight into the mechanism of vasovagal syncope and to test the efficacy of theophylline to prevent syncope. Twenty-six patients with vasovagal syncope underwent two-dimensional echocardiography and theophylline test during head-up tilt test. A standard parasternal short-axis view of echocardiography at the level of the papillary muscle was recorded to measure fraction shorting of the left ventricle, and left ventricular end-diastolic and end-systolic dimensions. Heart rate, blood pressure, and symptoms were recorded. There were three groups; Group 1: no syncope with and without isoproterenol (n = 5); Group 2: syncope only after the infusion of isoproterenol (n = 16); Group 3: syncope without isoproterenol (n = 5). Groups 2 and 3 proceeded to theophylline injection (250 mg). The study showed that the 80 degrees tilt induced an increase in heart rate of 6.6 +/- 4.0, 12.4 +/- 6.6, and 25.4 +/- 4.5 beats/min in Groups 1, 2, and 3, respectively (p < 0.05 in Groups 1 and 2, p < 0.05 in Groups 1 and 3). The addition of isoproterenol during posture change from supine to an 80 degrees tilt made the significant change of fractional shortening from 0.4 +/- 5% to 6 +/- 13% in Group 2 (p = 0.05), compared with no significant change in Group 1. There were no significant differences in left ventricular end-diastolic dimension and end-systolic dimension in each group between baseline and isoproterenol infusion during posture change. Vasovagal syncope was associated with vigorous myocardial contraction, rather than with contraction against an empty left ventricle. The acute loading of theophylline was not effective in preventing vasovagal syncope.

Adrenergic beta-Agonists↗
PubMed1996

The endothelium-dependent response of human hepatic artery after preservation with the UW solution.

The University of Wisconsin's (UW) solution has been used commonly for current liver transplantation. However, its effect on the vascular endothelium remains unclear. Experiments were designed to study the effects. Human hepatic arteries harvested from patients with hepatocellular carcinoma undergoing liver resection were preserved in 4 degree C physiological solution (group 1, the content showed on the text) and UW solution (group 2) for 1 hr. Segments of preserved and control (group 3) hepatic arteries were suspended in organ chamber to measure the isometric force. The relaxations to acetylcholine (ACH) and adenosine diphosphate in segments of hepatic artery with endothelium were significantly greater than those segments without endothelium. The maximal relaxation to ACH in arterial segments with endothelium of group 2 was significantly different from those of group 1 and 3 (group 1 to group 3, 82 +/- 2%, 57 +/- 6%, and 83 +/- 4% of the initial tension contracted by neoepinephrine (3 X 10-7 mole/l, P < 0.05). The maximal relaxation to adenosine diphosphate was similar to the response to ACH. Perfusate hypoxia (oxygen tension 30 +/- 5 mmHG) caused endothelium-dependent contraction of the arterial segments (group 1 to group 3, 233 +/- 32%, 276 +/- 35%, and 251 +/- 40% of the initial tension, P < 0.05). Endothelium-independent relaxation and contraction of human hepatic artery to sodium nitroprusside and norepinephrine were not altered by UW solution. In summary, the impaired endothelium-dependent relaxation by UW solution and prominent endothelium-dependent contraction to hypoxia of human hepatic artery would favor vasospasm and thrombus formation after liver transplantation.

Adenosine↗
PubMed1996

The effect of gabexate mesilate on pancreatic and hepatic microcirculation in acute experimental pancreatitis in rats.

Microcirculatory derangements are important early features in many organs during the process of acute pancreatitis. However, dynamic evaluation of these factors has been difficult. Antiprotease has long been used for the treatment of acute pancreatitis, although its effects and mechanism have not been fully elucidated. The involvement of proteases and microcirculatory derangement early in the course of acute pancreatitis are the main concern of this study. A severe acute pancreatitis model in male Sprague-Dawley rats (225-275 g) was established by adding caerulein (15 microg/kg/ hr) in intravenous infusion fluid and intraductal injection of 0.1 ml glycodeoxycholic acid (5 mM). Gabexate mesilate [GM; ethyl-4-(6-guanidinohexanoyloxy)benzoate methanesulfonate], a synthetic antiprotease, was infused intravenously in doses of 0.01, 0.1, 1, and 10 mg as a therapeutic intervention in this model. Pathology hematocrit, serum amylase level, and glutamic-oxaloacetic transaminase (GOT) levels were used to confirm the severity of disease and effect of therapy. In vivo microscopic technique was used as a investigating tool in this study of microcirculatory derangement in pancreas and liver, 8 hr after induction of acute pancreatitis. GM can significantly improve pathologic criteria and changes of serum amylase levels in the range of 1-10 mg/kg/hr. The severity of changes of hematocrit and GOT was significantly lessened with GM in the range of 0.1-10 mg/kg/hr. This agent also could improve the microcirculatory environment in pancreas and liver after induction of acute pancreatitis according to the parameters, such as flow velocity and rolling leukocyte phenomenon, in the range of 1-10 mg/kg/hr. According to our observation, severity of hyperpermeability had not changed with the treatment of GM. These results indicated the beneficial effects of GM on pancreatic and hepatic microcirculation early in the course of acute pancreatitis. The beneficial effects were noted in serum parameters and hematocrit. The importance of protease activation and remote organ dysfunction is emphasized in the course of acute pancreatitis from this study.

Acute Disease↗