Biomedical subjects

C H Chang

Publications and source records attributed to C H Chang.

At least 127 records · Page 7Linked to original sources

PubMed1999

Automatic finite element mesh generation for maxillary second premolar.

Developing three dimensional finite element mesh models for irregular geometric objects requires a large amount of manual efforts, hence limiting the three dimensional approach for dental structure analyses. An automatic procedure which can be used to generate a three dimensional finite element mesh for the maxillary second premolar was developed in this study. Firstly, a embedded second premolar was sliced and scanned parallel to the occlusal surface. A self-developed image processing system was employed to detect the boundaries of different materials within each section. An automatic mesh generation program was used on these boundaries to create tetrahedral elements based on moving nodes of uniform cube approach. Six mesh models of the second premolar with different element sizes using linear and quadratic elements were analyzed. Strain energy and von Mises stresses were reviewed for convergence in the crown regions.

Algorithms↗

PubMed1999

Tuberculous pseudoaneurysm of the femoral artery: a case report.

Pseudoaneurysm of the femoral artery is an extremely rare complication of tuberculosis. We present a case of tuberculous femoral pseudoaneurysm that was successfully treated with resection, direct anastomosis, and postoperative antituberculous chemotherapy.

Aged↗

PubMed1999

In vivo screening of haloalkane dehalogenase mutants.

Haloalkane dehalogenase (Dh1A) from Xanthobacter autotrophicus GJ10 catalyzes the dehalogenation of short chain primary alkyl halides. Due to the high Km and low turnover, wild type Dh1A is not optimal for applications in bioremediation. We have developed an in vivo screen, based on a colorimetric pH indicator, to identify Dh1A mutant with improved catalytic activity. After screening 50,000 colonies, we identified a Dh1A mutant with a lower pH optimum. Sequence analysis of the mutant revealed a single substitution, alanine 149 to threonine, which is located close to the active site of Dh1A. Replacement of alanine 149 via site-directed mutagenesis with threonine, serine or cysteine retained the mutant phenotype. Other substitutions at position 149 show little or no activity.

Escherichia coli↗

PubMed1999

Emphysema surgery--loop ligation approach.

OBJECTIVES: To demonstrate the efficacy of using thoracoscopic endoloop ligation of bullae in patients with bullous emphysema. METHODS: From 1992 to 1997, 93 advanced age (mean age, 66 years) and oxygen dependency patients underwent thoracoscopic procedure using endoloop ligation for treatment of bullous emphysema. Clinical data were collected from chart review. Thoracoscopic loop ligation of bulla was carried out under general anesthesia with double lumen endotracheal tube and single lung ventilation. RESULTS: Eighty-two patients (88%) exhibited subjective improvement in their symptom status at 3-month follow-up (from grade 2 or 3 to grade 1 or 2) according to the modified Medical Research Council dyspnea scale. The mean duration of chest drainage was 7.5 days (range, 4-19 days). Average hospital stay was 9.5 (range, 5-26) days. There was no post-operative death. A comparison of pre-operative and post-operative functional evaluation was available in 27 patients who showed an average increase in FEV1 (from 0.89 to 1.12 l) and declined in residual volume after operation. Complications include persistent airleak over 10 days in nine patients (9.7%), wound infection in three patients and localized empyema in five patients. There was no recurrent after a mean follow-up of 37 months. CONCLUSION: Thoracoscopic loop ligation of bulla has proven to be a safe, reliable and cost effective means of technique for bullous emphysema.

Aged↗

PubMed1999

Blunt trauma with flail chest and penetrating aortic injury.

Blunt chest trauma with flail chest is common. The mortality attributes initially to the associated pulmonary contusion, massive hemothorax and later to the occurrence of adult respiratory distress syndrome. We report a case of flail chest with segmental fractures near the costovertebral junction and delayed hemothorax attacked 14 h later. The final diagnosis of the penetrating aortic injury by detached rib fragment was appreciated by aortogram. Unfortunately, active aortic hemorrhage made prompt thoracotomy in vain for life salvage.

Accidental Falls↗

PubMed1999

A novel role for the major histocompatibility complex class II transactivator CIITA in the repression of IL-4 production.

Class II transactivator (CIITA) is known as a coactivator for MHC class II gene expression in antigen-presenting cells. Surprisingly, when CIITA-/- CD4 T cells were stimulated in the presence of IL-12, they produced not only IFNgamma but also high levels of IL-4. The IL-4 production is due to the accumulation of IL-4 gene transcripts in Th1 cells. This transcriptional control is observed in T cells differentiating to the Th1 but not Th2 lineage, consistent with induction of expression of the CIITA gene in T cells by IFNgamma. Thus, in addition to its role in transactivation of genes involved in antigen presentation, CIITA plays a critical role during the T cell differentiation by negatively regulating the IL-4 gene transcription.

Animals↗

PubMed1999