Search PubMed⌕ Search

Biomedical subjects

C H Chang

Publications and source records attributed to C H Chang.

At least 775 records · Page 43Linked to original sources
PubMedDate not supplied

Idiopathic neonatal iron storage involving the liver, pancreas, heart, and endocrine and exocrine glands.

Autopsy studies of two infants, one a newborn, the other 4 months old, revealed massive amounts of iron in lysosomes of hepatocytes and pancreatic acinar cells. Iron, which had been transported across the placenta, accumulated in the same cell types as in adults with primary and secondary hemochromatosis. Hemosiderin was found in cardiac muscle cells, gastric and intestinal glands, and endocrine and exocrine organs including pituitary, thyroid, adrenals, islets of Langerhans, and sublingual and sweat glands. The liver was the most affected organ and the normal hepatic architecture was replaced by hepatocytes which were arranged in cluster, pseudoacinar structures, and multinucleated giant cells embedded in a collagen matrix. The islets of Langerhans were hyperplastic and hypertrophic. Ten similar cases, in five families, have been described; no patients liver longer than 4 months. Neonatal iron storage disease is clinically and pathologically distinct from Zellweger's cerebrohepatorenal syndrome and hypermethioninemia (tyrosinemia) neonatal diseases in which large stores of iron are present in hepatocytes. No abnormalities in serum iron, ferritin, or transferrin concentrations were detected in five parents of the affected children.

Cytoplasmic Granules↗
PubMedDate not supplied

Video-assisted endoscopic esophagectomy with stapled intrathoracic esophagogastric anastomosis.

Thoracic esophagus was usually removed through the transhiatal approach or via an open thoracotomy. The long incision and spreading of the ribs usually resulted in much pain and interference with chest wall mechanics. Today, with the development of a video-assisted endoscopic procedure, many intrathoracic lesions can be removed through small incision. Since March 1992 we have attempted 20 esophagectomies and reconstruction using a right thoracoscopic approach in 16 males and 4 females whose average age was 56 years. Indications for its use were esophageal cancer in 17 patients (squamous cell carcinoma in 12 patients, adenocarcinoma in 5) and caustic stenosis in 3. It is our impression that video-assisted endoscopic esophagectomy and reconstruction potentially causes less trauma, less postoperative discomfort, and a rapid functional recuperation. Our initial experiences showed that it is a feasible, effective procedure.

Adenocarcinoma↗
PubMedDate not supplied

Host recognition by the VirA, VirG two-component regulatory proteins of agrobacterium tumefaciens.

Agrobacterium tumefaciens contains about 25 vir genes localized on a 200-kb tumour-inducing (Ti) plasmid that direct a conjugation-like transfer of tumorigenic DNA from the bacterium to the nuclei of infected plant cells. These genes are strongly and coordinately induced during infection in response to three different classes of stimuli which are thought to be key chemical features of a typical wound site. These stimuli are (i) guaiacol and syringol derivatives such as acetosyringone, (ii) sugars such as glucose and glucuronic acid, and (iii) acidic pH. The sensing of these compounds is carried out by the VirA, VirG and ChvE proteins. VirA is a four-domain histidine protein kinase, while VirG is a transcriptional activator which is activated by VirA-mediated phosphorylation. ChvE is a chromosomally encoded periplasmic sugar binding protein which is required for sensing sugars but dispensable for sensing the other two stimuli. Here we will review the nature of these chemical stimuli, the structure and function of the three regulatory proteins, their similarity to sensors found in human and animal pathogens, the factors influencing their pool size, and their role in the host range of different strains of A. tumefaciens.

Agrobacterium tumefaciens↗
PubMedDate not supplied

Stresses at the cervical lesion of maxillary premolar--a finite element investigation.

OBJECTIVES: The objective of this study was to use a three-dimensional (3-D) finite element model to investigate normal stress distribution to substantiate the tooth flexure mechanism. The study also compared the changes in the stresses by different occlusal loading sites and directions. METHODS: The 3-D finite element analysis was used. A maxillary premolar was selected to construct the simulation model. The model was constructed step-by-step for convergence and validity. Seven load conditions for various load sites and different directions were simulated to the model. RESULTS: The maximal principal stress and minimal principal stress distributions developed within the structures of seven load conditions were output and their stress distributions on z-plane at the vertical midline were shown. The peak tensile stress of the cervical area for various load conditions were compared and listed. CONCLUSIONS: This study has shown that the presence of tensile stresses in the cervical region of a maxillary premolar by various loading sites and different directions. The results coincided with the stress-induced theory, hence sustaining it. The relationship of the affected factors of leverage to the development of cervical abfraction lesions, was explored.

Bicuspid↗
PubMedDate not supplied

A novel heterobifunctional linker for formyl to thiol coupling.

A maleimide hydrazide has been synthesized as a heterobifunctional cross-linking agent for thiol to formyl coupling. This linker has been applied to the coupling of the monoclonal antibody 17-1A, or an Fab' derived therefrom, to polyaldehyde dextran onto which the antineoplastic agent ellipticine has been attached. High binding avidities for the unshed antigen on the SW1116 colorectal tumor cell are retained in these drug-dextran-linker-antibody conjugates.

Antibodies, Monoclonal↗
PubMedDate not supplied

Conjugation and evaluation of 7E3 x P4B6, a chemically cross-linked bispecific F(ab')2 antibody which inhibits platelet aggregation and localizes tissue plasminogen activator to the platelet surface.

A bispecific F(ab')2 monoclonal antibody which recognizes both the platelet GPIIb/IIIa receptor and human tissue plasminogen activator was produced to target tPA to platelets for enhancement of thrombolysis. A stable, thioether-cross-linked bispecific F(ab')2 (7E3 X P4B6) combining the GPIIb/IIIa-specific monoclonal antibody 7E3, which inhibits platelet aggregation, and a nonneutralizing anti-tPA monoclonal antibody (P4B6) was produced. This was performed by coupling each of the parental Fab' moieties with the homobifunctional cross-linker bis(maleimido methyl) ether (BMME). 7E3 X P4B6 was sequentially purified using gel-filtration chromatography and hydrophobic interaction (HIC) HPLC. HIC was shown to completely resolve each of the parental F(ab')2 species from the bispecific one. 7E3 X P4B6 was shown to retain completely each of the parental immunoreactivities in GPIIb/IIIa and tPA binding EIA's. The bispecific antibody inhibited platelet aggregation in vitro at levels comparable to those for 7E3 Fab. Recruitment of tPA activity to washed human platelets was demonstrated using the S-2251 chromogenic substrate assay. 7E3 X P4B6 recruited 12-fold more tPA to the washed platelets than a mixture of the parental F(ab')2 molecules used as controls.

Antibodies, Monoclonal↗
PubMedDate not supplied

Aggregation response of human platelets stored at 22 C as platelet-rich plasma.

The aggregating response of human platelets stored at 22 C for 72 hours has been studied. Platelets were stored as platelet-rich plasma in order to maintain the plasma pH essentially constant. The response to ADP and collagen decreased with time, but the decrease was less with relatively high concentrations of the aggregating agents. The response to the ionophore A23187 was essentially unaltered during the storage period. Synergistic aggregation with combinations of ADP, collagen and ionophore A23187 was observed with platelets stored for 72 hours under conditions where singly each of the stimuli caused little or no effect. Stored platelets underwent reversible aggregation over a wide range of ADP concentrations but irreversible aggregation was observed in the presence of nonaggregating concentrations of collagen or ionophore A23187. The inhibition of aggregation by PGE1 or cyclic AMP was facilitated as a result of storage. It is suggested that the decreased response toward ADP and collagen reflects a reduced ability on the part of the platelets to mobilize calcium.

Adenosine Diphosphate↗