Search PubMed⌕ Search

Biomedical subjects

C Y Chang

Publications and source records attributed to C Y Chang.

At least 199 records · Page 11Linked to original sources
PubMed1994

Crystallization and preliminary X-ray analysis of the monoclonal anti-tumor antibody BR96 and its complex with the Lewis Y determinant.

The monoclonal anti-tumor antibody BR96 binds a tetrasaccharide, Lewis y (Le(y)), in vitro and recognizes a Le(y)-bearing or Le(y)-related tumor-associated antigen in vivo. The Fab of the murine monoclonal antibody, mBR96 (IgG3, kappa), and the Fab' of its human chimera, cBR96 (IgG1, kappa), and their complexes with Le(y) have been screened for crystallization conditions. Crystals suitable for X-ray diffraction have been obtained for uncomplexed cBR96 Fab', cBR96 Fab' in complex with Le(y) and mBR96 Fab in complex with Le(y). The symmetry of the cBR96 Fab' crystals is consistent with space group P2(1)2(1)2, a = 61.1 A; b = 174.3 A; c = 45.6 A; the symmetry of the cBR96 Fab'-Le(y) complex crystals with space group P4(3)2(1)2 (or its enantiomorph), a = b = 82.2 A; c = 167.1 A and the symmetry of the mBR96 Fab-Le(y) complex crystals with space group P2(1)2(1)2(1), a = 69.4 A; b = 84.9 A; c = 86.8 A.

Animals↗
PubMed1994

Human mannose-binding protein carbohydrate recognition domain trimerizes through a triple alpha-helical coiled-coil.

Human mannose-binding protein is a hexamer of trimers with each subunit consisting of an amino-terminal region rich in cysteine, 19 collagen repeats, a 'neck', and a carbohydrate recognition domain that requires calcium to bind ligand. A 148-residue peptide, consisting of the 'neck' and carbohydrate recognition domains forms trimers in solution and in crystals. The structure of this trimeric peptide has been determined in two different crystal forms. The 'neck' forms a triple alpha-helical coiled-coil. Each alpha-helix interacts with a neighbouring carbohydrate recognition domain. The spatial arrangement of the carbohydrate recognition domains suggest how MBP trimers form the basic recognition unit for branched oligosaccharides on microorganisms.

Amino Acid Sequence↗
PubMed1994

A dominant mutation in the bacteriophage lambda S gene causes premature lysis and an absolute defective plating phenotype.

The S and R genes of the bacteriophage lambda are required for lysis of the host. R encodes 'endolysin', a soluble transglycosylase which accumulates in the cytoplasm during late protein synthesis. S encodes a 'holin', a small membrane protein which, at a precisely scheduled time, terminates the vegetative cycle by forming a lethal lesion in the membrane through which gpR gains access to the peptidoglycan. A missense allele of S, Ala52Gly, causes lysis to occur prematurely at about 19-20 min after induction of a lysogen, compared to 45 min for the wild type. This allele has a severe plaque-forming defect which appears to be entirely a consequence of the early lysis and resultant severe reduction in particle burst size. The early-lysis phenotype is dominant and is aggravated, in terms of an even more reduced burst size, at both 30 degrees C and 42 degrees C. The mutation maps in the middle of a putative membrane-spanning helical domain of S, near the sites of other S- mutations with recessive non-lytic phenotypes. The mutation has no effect on S-protein accumulation or on the ratio of S107 and S105 products in the membrane. The mutation appears to affect the intrinsic timing function by which the S protein controls the lysis schedule.

Alleles↗
PubMed1994

The transcription factor E2F-1 mediates the autoregulation of RB gene expression.

The retinoblastoma (RB) gene is the prototype tumor suppressor gene. Mutations in this gene are often associated with the occurrence of various tumors. Several mutations have been found in the promoter region of the gene, suggesting that inappropriate transcriptional regulation of the RB gene contributes to tumorigenesis. Sequence analysis of the RB promoter has revealed a potential E2F recognition site within a region critical for RB gene transcription. By using the cloned E2F-1 gene, here we report that (i) RB expression is negatively regulated by its own gene product, (ii) E2F-1 binds specifically to an E2F recognition sequence in the RB promoter and transactivates the RB promoter, (iii) overexpression of RB suppresses E2F-1-mediated stimulation of RB promoter activity, and (iv) the expression of the RB gene is paralleled by the expression of the E2F-1 gene during cell cycle progression. These results demonstrate that expression of RB is negatively autoregulated through E2F-1.

Animals↗
PubMed1994

Macrophages in degradation of collagen/hydroxylapatite(CHA), beta-tricalcium phosphate ceramics (TCP) artificial bone graft. An in vivo study.

The macrophages mediated biodegradation of two biomaterials, collagen/hydroxylapatite (CHA) and beta-tricalcium phosphate ceramics (TCP), was studied in 24 male Kunming mice and 20 male C57BL/6 mice with histopathologic, histochemical and ultrastructural observation. It was demonstrated that macrophages infiltrated after CHA, TCP were implanted. The macrophages could be differentiated from fibroblasts and the other infiltrated cells for special cellular profile and strong acid phosphatase activity. Morphologically, monocyte-macrophages and infused multinuclear giant cell degraded CHA and TCP by phagocytosis and extracellular resorption. The carbonic anhydrase activity of macrophages was demonstrated by histochemical technique. It suggested that macrophages secreted H+ and accomplished the decalcification of calcium phosphate compound of CHA and TCP. We conclude that macrophages are the main mediating cells which degraded CHA and TCP intracellularly and extracellularly.

Animals↗
PubMed1994

[Drug resistance and plasmid analysis in Pseudomonas aeruginosa].

One hundred and ninety seven strains of Pseudomonas aeruginosa were isolated from urine (59 strains), wound pus (60 strains), sputum (30 strains), stool (30 strains) and eye discharge (18 strains) at Kaohsiung medical College Hospital. These strains were serotyped with antisera against O antigens and tested with twelve different antimicrobial agents. The results showed that the most frequently isolated strains were serotype E (41.1%), followed by serotype B (20.3%), serotype F (10.7%) and serotype L (9.1%). In in vitro susceptibility testing, all isolated strains were resistant to chloramphenicol and tetracycline. Otherwise, these isolates were highly susceptible to ceftazidime (95.4%), enoxacin (89.3%) and piperacillin (87.8%). The isolates from urine exhibited more multiple drug resistance patterns than those of other specimens. When plasmid content was analysed from pseudomonas aeruginosa, only 15.2% (30/197) of isolates carried plasmids. By conjugation, transformation and mobilization experiments, it was shown that 13.3% (4/30) of plasmid carrying strains contained R plasmids.

Chloramphenicol↗
PubMed1994

Computed tomography evaluation of chronic paranasal sinusitis.

BACKGROUND: Although chronic paranasal sinusitis has been recognized and diagnosed more frequently in recent years, it is still one of the most frequently overlooked disease and a significant source of morbidity and economic loss. Therefore, a further detailed analysis of its clinical pictures and computed tomographic (CT) presentations is necessary for better understanding. METHODS: We collected 230 cases in recent two years and studied their CT manifestations. RESULTS: The pathological changes of sinusitis on CT were classified into four groups: mucosal thickening, mucosal thickening combined with fluid level, fluid level only, and total sinus opacification, in increasing frequency. Maxillary sinus was the most commonly involved sinus. Focal high density areas were noted in 17 sinuses. Ten of them were operated and revealed only thick mucous without evidence of calcification or fungal infection. There was no correlation between the disease duration and the number of sinuses involved. CONCLUSIONS: CT is the image modality of choice in evaluating patients with chronic paranasal sinusitis.

Adolescent↗
PubMed1993

26-10 Fab-digoxin complex: affinity and specificity due to surface complementarity.

We have determined the three-dimensional structures of the antigen-binding fragment of the anti-digoxin monoclonal antibody 26-10 in the uncomplexed state at 2.7 A resolution and as a complex with digoxin at 2.5 A resolution. Neither the antibody nor digoxin undergoes any significant conformational changes upon forming the complex. Digoxin interacts primarily with the antibody heavy chain and is oriented such that the carbohydrate groups are exposed to solvent and the lactone ring is buried in a deep pocket at the bottom of the combining site. Despite extensive interactions between antibody and antigen, no hydrogen bonds or salt links are formed between 26-10 and digoxin. Thus the 26-10-digoxin complex is unique among the known three-dimensional structures of antibody-antigen complexes in that specificity and high affinity arise primarily from shape complementarity.

Amino Acid Sequence↗
PubMed1993

Synthesis of two bacteriophage lambda S proteins in an in vivo system.

Bacteriophage lambda has two genes which are essential for lysis: R, a gene encoding a 158-amino-acid (aa) transglycosylase that attacks the peptidoglycan, and S, a gene encoding two inner-membrane-associating proteins, designated S105 and S107 for their predicted lengths in aa residues. S105 and S107 are thought to have opposing roles in lysis, with the former acting as the lethal lysis effector and the latter as a lysis inhibitor. Here, we used a T7-polymerase-mediated expression system to show that S105 and S107 are synthesized at a constant ratio of about 2.5:1 throughout the period leading up to lysis, indicating that lysis scheduling does not require a translationally controlled switch from inhibitor (S107) to effector (S105) synthesis. However, evidence is presented that the mRNA sequences immediately 5' to the ribosome-binding site (RBS) of the S gene are required for the rather limited translation, but not the stability, of the S mRNA. No difference could be found in the pattern of ternary complex formation over the two S start codons in in vitro toe-printing assays with the wild-type mRNA and with mRNA deleted of the upstream sequences. Nevertheless, these results may suggest a role for translational control in S gene expression, if not in its temporal regulation or in the partition between S105 and S107 production.

Amino Acid Sequence↗
PubMed1993

Coexistence of calcific tendinitis and rotator cuff tear: an arthrographic study.

A prospective evaluation of the coexistence of calcific tendinitis and tear of the rotator cuff demonstrated by arthrography was made in patients presenting with shoulder pain. Patients were X-rayed using conventional views and impingement views. Eighty-one patients (mean age 61.2 years) with calcific tendinitis underwent arthrography. Arthrography showed 22 partial or complete tears of the rotator cuff. A small rather than a large amount of calcification was more likely to be associated with a rotator cuff tear (p = 0.005). The coexistence of calcific tendinitis with rotator cuff tear is not uncommon, especially in older age groups.

Calcinosis↗
PubMed1993

An ultrastructural observation of macrophages in rabbits' radius callus.

The ultrastructure of macrophages in rabbits' radius callus at the 14th and 31st day after fracture had been observed in the study. It was found that macrophages mostly appeared in the early stage callus where there were inflammation, clot, and bone chips. Commonly seen macrophages were active phagocytes with single nucleus, but they could evolve to form multinuclear macrophages or fuse into foreign body giant cells. We are therefore led to conclude that the functions performed by macrophages in healing callus are to phagocytize and digest damaged cellular fragments, small bone chips, clot and foreign body; to disrupt larger dead bone matrix extracellularly and to resorb them by microvilli-like processes on the surface of foreign body giant cells.

Animals↗
PubMed1993

De Vega's semicircular annuloplasty for tricuspid valve regurgitation.

Moderate to severe functional tricuspid regurgitation was found in 26% of cardiac surgical patients with mitral or aortic valvular disease at Tri-Service General Hospital in Taiwan. Almost all patients were able to receive de Vega's annuloplasties. After a mean follow-up period of 20 months, none of the 63 patients had moderate or severe tricuspid regurgitation. There was no heart block or right atrial thrombosis; the single late death was not related to the heart disease. De Vega's tricuspid annuloplasty is considered to be a safe, effective, and durable procedure in the treatment of functional tricuspid regurgitation. Compared with tricuspid valve replacement and other types of annuloplasty, the de Vega is the first choice here.

Adolescent↗
PubMed1993

Expression of a retinoblastoma transgene results in dwarf mice.

Introduction of the normal retinoblastoma gene (RB) into different tumor cells possessing inactivated RB genes suppresses their tumorigenicity in nude mice. These results suggest that RB replacement is a potential strategy for developing future clinical treatments of cancer. In a transgenic mouse model, we found that the quantity of RB protein in a given cell may play an important role in dictating its effect. Four founder mice containing 1-7 copies of a human RB cDNA transgene under the transcriptional control of the human RB promoter were generated. Most of the transgenic mice were smaller than nontransgenic littermates. This effect was found as early as embryonic day 15. The degree of dwarfism correlated roughly with the copy number of the transgene and the corresponding level of RB protein. The expression pattern of the transgene products was similar to that of the endogenous mouse RB gene with regard to tissue and temporal distribution. Transferring the transgene to RB deficient mice, which are nonviable, resulted in the development of normal, healthy mice, indicating that the human RB gene can functionally complement the mouse homolog. These studies demonstrate that the effect of RB on overall mouse development is closely dependent upon its dosage.

3T3 Cells↗
PubMed1993

Characterization of R plasmids from Shigella sonnei in Taiwan.

Plasmids of 70MDa from 6 Shigella sonnei isolates originating in Kaohsiung, Taiwan were found. All of them encoded resistance to chloramphenicol and tetracycline. These plasmids belonged to the H II incompatibility group. The fertility inhibition property of plasmids was the fi- type. Restriction endonuclease analysis revealed the six plasmids all had identical restriction patterns with BamH I, Hind III and Nru I. All six plasmids carried the type I chloramphenicol acetyltransferase gene and the class B tetracycline resistance gene as determined by Southern hybridization with DNA probes of various antimicrobial resistance genes. The results demonstrated that S. sonnei isolates harboured the same R plasmid.

Chloramphenicol O-Acetyltransferase↗
PubMed1993

Quantitative effects of the retinoblastoma gene on mouse development and tissue-specific tumorigenesis.

Models for studying the quantitative effects of RB protein in development and in tumorigenesis have been constructed. By crossing transgenic mice carrying the human Rb gene with mice heterozygous for the normal mouse Rb gene, we have generated mice that contain varying copies of the human Rb transgene and express varying amounts of human RB protein. Herein, we show that different amounts of RB protein are required to rescue two different phenotypes resulting from Rb deficiency: death during fetal development and susceptibility to cancer. Normal fetal development seems to depend on expression of critical amounts of RB protein, > or = 50% of the amount in wild-type mice. Adult mice, even if they overexpress RB protein, are prone to cancer if their cells express from only one Rb gene allele. Mice expressing small amounts of RB protein from different Rb alleles, however, are protected from cancer. Tumor suppression in cancer-prone cells, therefore, rather than depending on an absolute amount of RB protein, more directly depends on having redundancy in the Rb gene, assuring that at least one copy of a gene encoding functional RB protein is always available.

Animals↗
PubMed1993

[Characterization of trimethoprim resistance in Shigella].

Ninety-seven Shigella strains from 1982 to 1987 were isolated. When these isolates were tested with minimal inhibitory concentrations of trimethoprim, twenty-two were found to be resistant. Among these, 10 were found to be S. flexneri, and 12 to be S. sonnei. In addition, all of these 22 isolates were found to have multiple drug resistance. In order to determine the type of dihydrofolate reductase (DHFR) genes in these 22 trimethoprim-resistant isolates, colony hybridization with probes representing types I, II, III and V DHFR, were used. The results revealed the presence of type I DHFR gene in all of these isolates. Further southern hybridization indicated that the type I DHFR gene was located on plasmids. In order to determine whether a trimethoprim resistant gene existed as a functional transposable element in these isolates, we used a specific probe to detect the prevalence of Tn7. However, no positive hybridization was found. The relationship between the trimethoprim resistant gene and integron is characterized by the fact that the integrase gene, in our study, was frequently found in all of the 22 resistant isolates. These results indicate that trimethoprim resistant genes might transfer among bacteria via site-specific integration.

Serotyping↗
PubMed1993

[MRI of postmortem brains].

We studied 18 formalin-fixed brains using MRI, and correlated our data with subsequent gross and microscopic examinations. 9 of our patients died from brain diseases (stroke due to infarction 4, stroke due to hemorrhage 1, encephalitis 2, head injury 1, brain tumor 1). 9 of our patients died from non-CNS diseases (stomach cancer 1, colon cancer 1, liver cirrhosis 1, myocardial infarction 2, trauma 4). In MRI of postmortem brain, T1WI and T 2WI was able to clearly show the myelination process of brainstem, basal ganglia, internal capsule and optic radiation in a 2 months-old-boy. The findings were similar to MRI of live infants. In normal adult postmortem brains, the T1WI showed a relatively low signal intensity of white matter as compared to gray matter. The pictures were similar to proton density images, not T1WI of normal adult brains. The reason why the signal intensity of the white matter was lower than the gray matter may have been due to lysis of lipid of myelin sheath in the formalin solution. Postmortem MRI was able to detect the periventricular hyperintensity (corresponding to arteriosclerotic encephalopathy) and subcortical hyperintensity spots (which corresponding to the widening of the Virchow-Robin perivascular space because of arteriosclerosis) in the brains of our elderly patients. Postmortem MRI detected the intracerebral hemorrhage, which appeared as a dark signal in both short and long TR images. However, MRI did not show blood in the ventricles, sulci, or superficial hemorrhages in the cortex of brain. Brain edema was revealed in the postmortem MRI and appeared as low signal intensity in T1WI and hyperintensity in T2WI. It was associated with a significant mass effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗