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Biomedical subjects

S W Chang

Publications and source records attributed to S W Chang.

98 records · Page 6Linked to original sources
PubMedDate not supplied

Bacterial toxin-induced pulmonary epithelial cytotoxicity and the protective effect of dibutyryl-cAMP.

Bacterial infection is the most common cause of the adult respiratory distress syndrome which, in turn is associated with endothelial capillary permeability and alveolar oedema. Previously, we have demonstrated the direct cytotoxicity of the bacterial toxins Pseudomonas aeruginosa exotoxin A (Exo A) and Salmonella enteritidis lipopolysaccharide (LPS) on pulmonary endothelial cells. The purpose of this study was to investigate the effect of Exo A and LPS on pulmonary epithelial cells in vitro. We also tested the protective effect of dibutyryl cyclic adenosine monophosphate (db-cAMP) on Exo A-induced cytotoxicity. In cultured rat alveolar epithelial cells (RAEC) Exo A caused cytotoxicity as measured by 51Cr release from these cells. LPS did not injure RAEC's. Pretreatment of RAEC with db-cAMP (1 mM) attenuated Exo A induced cytotoxicity. We conclude that (1) Exo A directly injures epithelial lung cells and may contribute to lung injury in cases of bacterial infection; (2) db-cAMP protects alveolar epithelial cells against Exo A-induced cytotoxicity and (3) alveolar epithelial cells in this model are resistant to LPS induced injury.

ADP Ribose Transferases↗
PubMedDate not supplied

Effects of contact lenses on corneal endothelium - a morphological and functional study.

PURPOSE: To study the corneal endothelial morphological changes and endothelial barrier function in contact lens wearers. METHODS: Specular microscopy and anterior segment fluorophotometry were performed on 116 controls (group 1) and 76 daily wear soft contact lens wearers. Group 2 patients (n = 34) had been wearing contact lenses for less than 5 years and group 3 (n = 42) for more than 5 years. The relationship of corneal thickness, endothelial cell density, hexagonal cell percentage, coefficient of variation in cell area, corneal autofluorescence and corneal endothelial permeability to the contact lens wear duration was studied. RESULTS: The average corneal thickness of contact lens wearers did not differ significantly from controls (0.533 +/- 0.031, 0.538 +/- 0.044, 0.532 +/- 0.031 mm for groups 1, 2 and 3, respectively; p = 0.89). However, there was a significant tendency toward corneal thinning with a longer history of contact lens wear (r = -0.31, p = 0.002 in groups 2 and 3). The percentage of hexagonal cells decreased with both increasing hours of contact lens wear per day (r = -0.36, p < 0.001) and the duration of contact lens wear in years (r = -0.33, p < 0.001), but there was no significant change in endothelial cell density in contact lens wearers. The coefficient of variation in cell size correlated more closely with increased hours of contact lens wear per day (r = 0.35, p = 0.002) than with the duration of contact lens wear in years (r = 0.12; p = 0.31). In the functional study, corneal autofluorescence increased in contact lens wearers (5.13 +/- 0.71 ng/ml in group 1, 6.45 +/- 2.03 ng/ml in group 2 and 7.21 +/- 1.51 ng/ml in group 3, respectively, p < 0.001) and the mean endothelial permeability decreased in contact lens wearers (3.89 +/- 0.95 x10(-4)/cm in group 1, 2.71 +/- 0.73 x 10(-4)/cm in group 2 and 2.95 +/- 0.91 x 10(-4)/cm in group 3, respectively, p = 0.003). CONCLUSIONS: Daily wear soft contact lenses caused morphological changes in the corneal endothelium. With an increasing span of contact lens wear, there was a significantly increased variation in cell size, a decreased hexagonal cell percentage, an evident intercellular dark area and rosette formation. The corneal autofluorescence increased and the overall endothelial permeability decreased as a consequence of contact lens wear. Contact lens wear also caused corneal thinning, and the cornea became thinner with increasing duration of contact lens wear.

Adult↗
PubMedDate not supplied

Corneal autofluorescence and epithelial barrier function in diabetic patients.

Corneal autofluorescence and corneal epithelial barrier function of 146 diabetic patients and 121 controls were examined using anterior segment fluorophotometry. Corneal autofluorescence in diabetic patients was significantly higher when compared with that of controls (14.6 +/- 3.7 vs. 10.9 +/- 2.7 ng/ml, p < 0.001), and was increased in patients with more severe diabetic retinopathy (r = 0.23, p = 0.005), higher postprandial blood glucose level (r = 0.25, p = 0.009), and higher glycosylated hemoglobin (r = 0.21, p = 0.047). No correlation existed between corneal autofluorescence and the duration of diabetes mellitus. The corneal fluorescein concentration 45 min after topical application of 20 microliters of 2% sodium fluorescein was also significantly higher in diabetics than in controls (1,373.2 +/- 1,081.5 vs. 363.0 +/- 308.3 ng/ml, p < 0.001). No correlation existed with postprandial blood sugar (r = -0.19, p = 0.056) nor with glycosylated hemoglobin (r = -0.13, p = 0.20). The corneas in diabetics became more hypesthetic with longer duration of diabetes mellitus (r = -0.19, p = 0.02), although the mean corneal sensitivity threshold was not statistically higher in the diabetic group (p = 0.57). There was no correlation of the epithelial barrier function with the duration of diabetes (r = -0.07, p = 0.38), the severity of diabetic retinopathy (r = 0.07, p = 0.38), and the corneal sensitivity threshold (r = -0.06, p = 0.43).

Aged↗
PubMedDate not supplied

Absorption of rectally administered phenytoin: a pilot study.

OBJECTIVE: To test the hypothesis that rectally administered phenytoin is absorbed in healthy volunteers. DESIGN: This single-center, open-label crossover pilot study compared rectal absorption with intravenous administration of phenytoin injectable solution (7 mg/kg) in healthy volunteers. Twelve serial blood samples were taken from each volunteer beginning at time zero until 36 hours following administration. These were analyzed for presence of phenytoin by immunoassay. SETTING: The study took place at St. Paul's Hospital, a tertiary care center. PARTICIPANTS: Funding permitted for a sample size of five healthy participants, two men and three women, aged 21-45 years. Selection was by volunteer sample. Inclusion criteria were as follows: no known medical conditions, not receiving medication, no history of adverse drug reactions or allergies, not known to be pregnant, and normal liver function as determined per study protocol. MAIN OUTCOME MEASURES: Signs of absorption as indicated by presence of phenytoin in blood samples, maximum concentrations (Cmax), time to Cmax (tmax), AUC, and apparent bioavailability. RESULTS: Maximum mean concentrations of 2.4+/-1.1 mg/L (mean +/- SD) following rectal administration and 11.2+/-1.6 mg/L following intravenous administration were achieved during the first one to two hours (tmax in both treatment arms). Mean apparent bioavailability of the rectally administered phenytoin was 24.4+/-13.4% (15.8-44.1%). CONCLUSIONS: Results from this pilot study demonstrate that rectal absorption of phenytoin begins within 30 minutes following single-dose administration and was reported by four out of five volunteers to be the preferred route. Further studies are required before extrapolation can be made to the patient population.

Administration, Rectal↗
PubMedDate not supplied

Effects of cis-diamminedichloroplatinum (CDDP) and cis-diammine (1,1-cyclobutanedicarboxylate) platinum (CBDCA) on thermotolerance development and thermosensitivity of the thermotolerant cells.

The interactive effects of combined treatment with heat and CDDP (0.5 micrograms/ml) or CBDCA (10 micrograms/ml) were examined on the surviving fractions of V-79 cells. Both CDDP and CBDCA treatment induced a slight enhancement in thermosensitivity of thermotolerant cells. The development of thermotolerance during step-up heating was partially inhibited by simultaneous treatment with CDDP or CBDCA throughout the heating process. Simultaneous heat treatment at 42 degrees C with either drug showed marked interactive effect and inhibited the thermotolerance developed during 42 degrees C heating.

Animals↗