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Biomedical subjects

Z Chang

Publications and source records attributed to Z Chang.

At least 73 records · Page 4Linked to original sources
PubMed1995

[Treatment of burned joints and functional recovery].

From 1979 to 1990, 33 operations on 29 patients with joint burn were performed by early debridement and primary repair with myocutaneous flaps. As a result, 29 wounds healed by first intention. The healing rate of early operations performed within 10 days postburn was 95.2%, and that of the late operations delayed more than 10 days post-burn was only 75.0%. 31 among 33 joints (93.9%) recovered full range of movement, while the other 2 joints ended with only slight limitation of function. We suggest that the early debridement and primary repair with myocutaneous flap is the best choice for treatment of burned bone and joints.

Adolescent↗
PubMed1994

The immunodominant 38-kDa lipoprotein antigen of Mycobacterium tuberculosis is a phosphate-binding protein.

Several antigens of Mycobacterium tuberculosis have been identified by monoclonal antibodies and are being exploited in the development of improved vaccines and diagnostic reagents, but none has been linked to a specific function. Herein we report that the 38-kDa extracellular lipoprotein antigen, the most potent immunogen of the mycobacteria, is a phosphate-binding protein with features very similar to those of the well characterized periplasmic phosphate-binding protein of Escherichia coli which serves as an initial receptor for active transport. This is also the first report definitively linking a function of a binding protein anchored to a membrane and found in other than Gram-negative bacteria.

Amino Acid Sequence↗
PubMed1994

Crystallization and preliminary X-ray crystallographic analysis of the 38-kDa immunodominant antigen of Mycobacterium tuberculosis.

The 38-kDa lipoprotein is one of the most potent cell surface immunogens of Mycobacterium tuberculosis in antibody-and T cell-mediated reactions. Using a pure recombinant form of the protein, we have recently shown that it binds phosphate much like that of the phosphate-binding protein (M(r) = 34.4 kDa) that is localized in the periplasm of Escherichia coli and is involved as an initial receptor for active transport of phosphate. The purified 38-kDa protein has been crystallized in 2 forms that are suitable for high-resolution structural analyses. One form belongs to the monoclinic space group P2(1) with unit cell dimensions of a = 67.42 A, b = 113.38 A, c = 42.68 A, and beta = 108.53 degrees. The other is of orthorhombic space group P2(1)2(1)2 with a = 125.46 A, b = 72.27 A, and c = 73.43 A. Both crystal forms diffract to about 2 A resolution on a fine focus rotating anode.

Antigens, Bacterial↗
PubMed1993

Transrectal ultrasound-guided percutaneous radical cryosurgical ablation of the prostate.

BACKGROUND: The two major treatments for prostate cancer, radical prostatectomy and radiation therapy, are associated with considerable morbidity and variable results. This article presents the preliminary results using percutaneous radical cryosurgical ablation under ultrasound guidance to treat prostate cancer. METHODS: The patient group consisted of all patients with localized prostate cancer who underwent cryosurgery between June 1, 1990 and May 1, 1992. Patients in Group 1 were treated by freezing of the tumor with two cryoprobes placed multiple times. Group 2 patients were treated by freezing of the tumor with five cryoprobes placed simultaneously. Cryoprobes (3 mm in diameter) were placed percutaneously with a transperineal approach. Cryoprobe placement and freezing were monitored using the transrectal ultrasound. RESULTS: Of the 55 patients (68 procedures) undergoing treatment, 23 have 3 months of follow-up with associated biopsy (Group 1, 8 patients; Group 2, 15 patients). In Group 1, three (37.5%) patients had residual disease. In Group 2, one (6.7%) patient had residual disease, whereas 14 (93.3%) patients did not. Combining both groups, 19 (82.6%) patients had no residual disease, whereas 4 (17.4%) patients had positive results on postoperative biopsy. Complications included rectal freezing, urethrorectal fistula, sloughing urethral tissue, impotence, perineal ecchymosis, penile edema, and ileus. CONCLUSIONS: Preliminary results indicate that percutaneous transperineal ultrasound-guided prostate cryosurgery may be an effective treatment for prostate cancer with minimal associated morbidity.

Biomarkers, Tumor↗
PubMed1993

The Drosophila neuralized gene encodes a C3HC4 zinc finger.

The neurogenic genes of Drosophila are required for cell-cell communication that determines the choice between neuronal and epidermal cell fate. Here we report the molecular characterization of the neurogenic gene neuralized (neu) and show that it encodes a protein containing a C3HC4 zinc finger DNA-binding motif. This motif has been previously characterized in a variety of regulatory proteins, including transcription factors, locus-specific Drosophila chromosomal proteins, and oncoproteins. These results suggest a nuclear function for neu in the cell-cell signalling process responsible for inhibiting neuronal determination.

Amino Acid Sequence↗
PubMed1993

Molecular and genetic characterization of the Drosophila tartan gene.

Here we report the discovery and characterization of the Drosophila tartan gene. tartan is transcribed in an unusual embryonic pattern of intersecting stripes which are generated in response to the anterior-posterior and dorsal-ventral regulatory systems. tartan encodes a putative transmembrane protein containing extracellular leucine-rich repeats characteristic of numerous cell surface receptors and adhesion proteins. Its expression is correlated with aspects of segmentation and neurogenesis, including the formation of neuroblasts, sensory mother cells, and peripheral nerves. Mutants homozygous for a recessive lethal tartan loss-function allele exhibit defects in the position and number of cells within peripheral sense organs, the routing of peripheral nerves, and the organization of commissures within the central nervous system. Mutants are also defective in muscle organization. These results suggest that tartan is required for cell surface interactions important for normal organization of epidermal and subepidermal structures.

Amino Acid Sequence↗
PubMed1992

Refined 2.5 A structure of murine adenosine deaminase at pH 6.0.

The X-ray structure of murine adenosine deaminase complexed with the transition-state analogue 6-hydroxyl-1,6-dihydropurine ribonucleoside has been determined from a single crystal grown at pH 4.2 and transferred to mother liquor of increasing pH up to a final pH of 6.0 prior to data collection. The structure has been refined to 2.5 A to a final crystallographic R-factor of 20% using phases from the previously refined 2.4 A structure at pH 4.2. Kinetic measurements show that the enzyme is only 20% active at pH 4.2 whereas it is fully active between pH 6.0 and pH 8.5. The refined structures at either pH are essentially the same. Consideration of the pKa values of the key catalytic residues and the mechanism proposed on the basis of the structure suggests that the ionization state of these residues is largely responsible for the pH dependence on activity.

Adenosine Deaminase↗
PubMed1992

Probing protein stability with unnatural amino acids.

Unnatural amino acid mutagenesis, in combination with molecular modeling and simulation techniques, was used to probe the effect of side chain structure on protein stability. Specific replacements at position 133 in T4 lysozyme included (i) leucine (wt), norvaline, ethylglycine, and alanine to measure the cost of stepwise removal of methyl groups from the hydrophobic core, (ii) norvaline and O-methyl serine to evaluate the effects of side chain solvation, and (iii) leucine, S,S-2-amino-4-methylhexanoic acid, and S-2-amino-3-cyclopentylpropanoic acid to measure the influence of packing density and side chain conformational entropy on protein stability. All of these factors (hydrophobicity, packing, conformational entropy, and cavity formation) significantly influence protein stability and must be considered when analyzing any structural change to proteins.

Amino Acids↗