Biomedical subjects

W T Chen

Publications and source records attributed to W T Chen.

At least 91 records · Page 5Linked to original sources

PubMed1996

Clinical response of tuberculous pericarditis to medical treatment: a retrospective survey.

BACKGROUND: The prevalence of tuberculosis has declined with advanced antituberculous chemotherapy. However, the occurrence of subsequent constrictive pericarditis in tuberculosis has not reduced. Clinical progress of tuberculous pericarditis was investigated in patients receiving antituberculous chemotherapy. METHODS: Thirteen patients with tuberculous pericarditis (11 men and 2 women aged 14 to 86 years [mean 60.0 +/- 17.0]), treated initially with antituberculous medications were analyzed. All patients underwent pericardiocentesis on admission following echocardiography. RESULTS: Dyspnea was the most common clinical pictures. Bloody effusion fluids were noted in 10 patients. Moreover, the lymphocytic fluids were present in 78% of all patients. The neutrophilic fluids tended to have a bloody color, and there was progress to constrictive pericarditis even for those on anti-tuberculous chemotherapy. Five patients with subsequent constrictive pericarditis received pericardiectomy within 3.5 months of admission. Three of them received pericardiectomy later, despite pericardial window procedure. CONCLUSIONS: Follow-up by echocardiogram is necessary within three months after commencing medical treatment because of the high incidence of progression constrictive pericarditis despite aggressive medical treatment. Pericardiectomy seems to be the only solution to the catastrophic outcome of constrictive pericarditis.

Adolescent↗

PubMed1996

Heterogeneous clinical characteristics of identical twins concordant for systemic lupus erythematosus: a report of one pair of twins.

Lupus is a mysterious disease without definite etiology and pathogenesis. The heterogeneous clinical manifestation of systemic lupus erythematosus (SLE) increases the delay and difficulty of diagnosis and the complexity of pathogenesis. Even in twins with identical genome and similar environmental milieu, the incidence of concordance for SLE is not high. Identical twins, concordant for SLE with discordance to disease onset and expression, are reported. Besides genetics, multiple factors are responsible for the pathogenesis of SLE.

Adult↗

PubMed1995

Fractionation of fulvic acids: characteristics and complexation with copper.

Two fulvic acid samples isolated from Suwannee river (International Humic Substance Society) and Feeitsuey reservoir were subjected to gel filtration chromatography (GFC) for molecular size fractionation. The GFC-eluted samples were separated into three groups corresponding to the molecular weight ranges: < 220, 220-1000, and 1000-4000. Fluorescence quenching techniques were employed for determining the conditional stability coefficient and kinetic parameters of copper complexation with the three fractions of fulvic acids. Experimental conditions were pH 6, 5 x 10(-5)m total copper and 5 mg C litre(-1) of fulvic acids. The conditional stability coefficients of the fulvic acid fractions were in the order of 0.9-3.3 x 10(5)m(-1), and the forward and reverse rate constants were in the order of 6.9-12.4 x 10(3)m(-1) s(-1) and 3.5-8.0 x 10(-2) s(-1). Information could be useful in modelling copper transport in the hydrosphere.

Journal Article↗

PubMed1995

The value of ultrasound measurement of gallbladder wall thickness in predicting laparoscopic operability prior to cholecystectomy.

We prospectively analysed 51 consecutive cases who underwent laparoscopic cholecystectomy from June 1992 to February 1993. There were 35 cases of chronic cholecystitis and 16 cases of acute cholecystitis. All underwent pre-operative ultrasonography, complete blood cell count, liver function test and endoscopic retrograde cholangiopancreatography. Of those 44 had post-operative ultrasound within the first 2 d and again on the seventh day. In 35 cases of chronic cholecystitis, 31 of 32 cases with a pre-operative gallbladder (GB) wall thickness of less than 6 mm were successfully resected laparoscopically. All three cases with a GB wall thicker than 6 mm were converted to open cholecystectomy. In acute cholecystitis, the wall thickness of the laparoscopic cholecystectomy group ranged from 2 to 9 mm (average 4 mm) and the wall thickness of the conversion group was 4-7 mm (average 6 mm). Post-operative fluid accumulation was noted in 28 (63.6%) cases. There was no correlation between post-operative pyrexia, duration of post-operative pain, clinical complications and the presence of fluid accumulation in the GB fossa. However, of four cases with increasing fluid on the seventh day, three developed complications. We conclude that ultrasonography is valuable in chronic cholecystitis for selecting cases for laparoscopic cholecystectomy.

Adult↗

PubMed1994

A potential marker protease of invasiveness, seprase, is localized on invadopodia of human malignant melanoma cells.

Seprase, a large, gelatin-degrading membrane-protease complex, is expressed at the invasive front of malignant melanoma cells on invadopodia, and its surface expression contributes to the invasive phenotype. An in vitro assay was used to determine the matrix-degrading activity of four malignant human melanoma cell lines. The lines differ in matrix-degrading activity with LOX > RPM17951 > A375 > SKMEL28. The seprase and Gelatinase A activities of these cell lines were also investigated. Seprase and active gelatinase A are found in cell membranes of LOX and RPM17951 cells but not those of SKMEL28 cells. Experiments using anti-seprase monoclonal antibodies in conjunction with a cell fractionation technique indicate that seprase consists of M(r) 97,000 polypeptides and is enriched on the ventral membrane of LOX in contact with planar extracellular matrix substratum. Confocal microscopy further substantiates our biochemical findings that seprase, as well as Gelatinase A, is localized on invadopodia membranes with a 6-fold increase of seprase and 4-fold increase of Gelatinase A intensity over the level expressed on dorsal membranes. In addition, LOX cells expressing higher levels of seprase at the cell surface, as selected by fluorescence-activated cell sorting, are significantly more degradative than LOX cells with lower seprase expression. Taken together, our data show a concordance between seprase and Gelatinase A expression on the cell surface at invadopodia and the matrix-degrading activity of human malignant melanoma cells. Seprase and major secreted proteases may act in concert to degrade components of the extracellular matrix during invasion.

Biomarkers, Tumor↗

PubMed1994

Expression of tau exon 8 in different species.

A synthetic peptide corresponding to a region encoded by tau gene exon 8 was used to raise an antibody. The antibody, E8, was used to probe normal tau from different species and abnormal tau proteins from subjects with Alzheimer's disease. Immunoblotting and enzyme-linked immunosorbent assays demonstrated that only bovine tau reacted with the E8 antibody. The E8 immunoreactive tau isoform was estimated to represent less than 2% of the bovine tau. Our results indicate that bovine tau is unique in containing isoforms positive with E8, and that PHF formation does not require the presence of PHF-tau with exon 8.

Amino Acid Sequence↗

PubMed1994

Invadopodia promote proteolysis of a wide variety of extracellular matrix proteins.

Chicken embryo fibroblasts (CEF) transformed by Rous sarcoma virus invade the extracellular matrix (ECM) using plasma membrane protrusions, termed invadopodia, that contact and dissolve the matrix. Normal cells neither form invadopodia nor degrade the ECM. Here we show that cells expressing invadopodia degrade and enter into a fibronectin-rich matrix produced by normal fibroblasts. Within 6 h after seeding onto the matrix, the invasive cells create an area devoid of matrix fibrils surrounding the cell body. Proteolysis mediates this matrix clearing because sevenfold more radiolabeled matrix is released into the growth media by the transformed cells relative to the normal cells. In addition to this assembled matrix, transformed cells were grown on thin layers of purified ECM proteins, revealing that invadopodia can degrade fibronectin, collagen type I, collagen type IV, and laminin. A 160 kDa protease that is extracted from transformed cells by Triton X-114 partitions into the detergent phase and is prominent in ventral plasma membranes that contact the ECM suggesting that it is a membrane associated protease.

Animals↗

PubMed1994

Membrane proteases as potential diagnostic and therapeutic targets for breast malignancy.

Metastasizing cancer cells can invade the extracellular matrix using plasma membrane protrusions, termed invadopodia, that contact and dissolve the matrix. Various membrane associated proteases localized on the invadopodial membranes are responsible for the extracellular matrix degradation. Work from our laboratory shows that secreted proteases including Gelatinase A, and high molecular weight integral membrane proteases are associated with cell surface invadopodia. Three cell types, including chicken embryonic cells transformed by Rous sarcoma virus, human malignant melanoma cell line LOX, and human breast carcinoma cell line MDA-MB-231, retain the invasive phenotype in vitro, express invadopodia, degrade and enter into a fibronectin-rich collagenous matrix. We suggest that invadopodium-associated proteases are ideal targets for the diagnosis and treatment of cancer as their presence in association with primary tumors may signal increased metastatic potential. An approach toward the development of new prognostic markers for breast malignancy involved production of monoclonal antibodies directed against membrane proteases in a mixture of glycoproteins. Double immunofluorescent technique using a known invadopodium marker is designed to select specific monoclonal antibodies colocalizing at the invasion front, on invadopodia of cancer cells. Membrane protease accessibility at the cell surface can therefore be exploited for therapeutic advances by the development of specific antibodies and inhibitors that block their activities, and by the use of monoclonal antibodies to target cytotoxic molecules to micrometastases. Also, this same accessibility may potentially be used to detect surface proteases on micrometastases or to detect components shed by micrometastases in serum.

Antigens, Neoplasm↗

PubMed1993

Binding and localization of M(r) 72,000 matrix metalloproteinase at cell surface invadopodia.

Degradation (turnover) of collagenous matrix occurs on the surface of specialized membrane extensions termed "invadopodia," which are sites of cell invasion into the extracellular matrix. Here we show the localization of the M(r) 72,000 type IV collagenase of the matrix metalloproteinase family at invadopodia. When added exogenously, latent M(r) 72,000 collagenase binds to invadopodia of chicken embryo fibroblasts transformed by Rous sarcoma virus, whereupon the bound collagenase loses its propeptide. The collagenase binds to a component contained within the detergent extract of transformed cells, and increased levels of the active M(r) 62,000 form of the collagenase are seen here. Such an association is not detected in the detergent extract derived from normal cells. Using a recently developed cell fractionation procedure to collect cell surfaces enriched in invadopodia, we show that the M(r) 72,000 collagenase associates with the invadopodial fraction and active forms of the enzyme become immobilized on the collagenous surface. Thus, invadopodia direct intense localized degradation of the extracellular matrix by concentrating active membrane-associated collagenases at sites of cellular invasion.

Amino Acid Sequence↗

PubMed1993

Protease production by cultured microglia: substrate gel analysis and immobilized matrix degradation.

The production of collagen-degrading proteases by cultured neonatal rat microglia was examined using an immobilized fibronectin-gelatin matrix coupled to a fluorescent marker and by substrate gel analysis. When microglia were plated onto the surface of the matrix and incubated under resting (nonstimulated) conditions, a small but visible amount of immobilized matrix was degraded. Treatment with lipopolysaccharide (LPS) or interleukin-1 (IL-1) significantly increased the number of microglia demonstrating substrate degradation. Substrate-SDS polyacrylamide gel electrophoresis of samples of supernatants from untreated cultured microglia indicated the presence of a 72 and a 92 kD metalloproteinase with characteristics corresponding to collagenases. Supernatants from untreated astrocyte cultures were shown to have primarily a 72 kD metalloproteinase. Proteinase activity increased on stimulation of the microglia with LPS and IL-1 in a dose-dependent fashion. These results indicate that cultured microglia release active proteases capable of degrading the extracellular matrix in a localized region. The production of proteases by activated microglia may have important physiological and pathophysiological consequences within the restricted extracellular matrix of the CNS.

Animals↗

PubMed1993

Nuclear proteins of the bovine esophageal epithelium. I. Monoclonal antibody W2 specifically reacts with condensed nuclei of differentiated superficial cells.

Cells from three layers of the bovine esophageal epithelium, representing different stages of differentiation, were dissociated and separated by Percoll gradient centrifugation into fractions of small, medium and large sizes. A majority of the large cells possessed condensed nuclei, a characteristic feature of terminal differentiation of the superficial epithelium. The small cells resembled the proliferate cells of the basal layer. In vitro culture of the esophageal epithelial cells resulted in proliferation of the small cells, colony formation, and, in some cases, differentiation into cells with condensed nuclei. Nuclei, or nuclear subfractions derived from cells of the different layers, were used as immunogens for the generation of hybridomas secreting monoclonal antibodies that bound specifically to different regions of the esophageal tissue. One such antibody, designated W2, labeled the condensed nuclei from the superficial layer of stratified esophageal and corneal epithelia in situ, as well as the large cells from esophageal culture in vitro. Thus, the expression of the W2 antigen may be associated with the process of nuclear condensation during epithelial differentiation. Immunoisolation of the target antigen of W2 from extracts of large cells of the bovine esophagus yielded a band of M(r) approximately 33,000 on nonreducing polyacrylamide gels. This band dissociated into two polypeptides, of M(r) approximately 22,000 and approximately 11,000, upon treatment with dithiothreitol. Amino acid sequence analysis of the larger polypeptide showed extensive homology to a group of small calcium-binding proteins, including two helix-turn-helix motifs designated as the EF-hand, characteristic of the configuration of the metal-ion coordinating ligands of the calcium-binding site. Similarly, the sequence at the amino terminus of the polypeptide of approximately 11,000 indicated that it was the light chain counterpart of the same calcium-binding protein complex.

Amino Acid Sequence↗

PubMed1993

Proteases of cell adhesion proteins in cancer.

Neoplastic cells elaborate a vast array of proteases that enable them to proteolytically digest underlying adhesion molecules. In doing this, the tumor cell disrupts the adhesive interactions holding it in place so it is free to degrade and migrate through the basement membrane and interstitial stroma resulting in invasion and ultimately metastasis. Invasive cells elaborate specialized membrane protrusions, invadopodia, that actively degrade the underlying substratum. Evidence indicates that integral membrane proteases and receptors for secreted proteases are present on these surface protrusions. All the major classes of secreted proteases are reported to associate with the plasma membrane. Interactions between proteases occurring at the plasma membrane may result in proenzyme activation. It is possible that various proteases in close proximity to each other on the plasma membrane could interact in a proteolytic cascade resulting in in vivo activation, and the subsequent degradation of adhesion proteins.

Animals↗

PubMed1992

Evaluation of vitamin D-binding protein and vitamin D metabolite loss in children on continuous ambulatory peritoneal dialysis.

We measured the serum concentration of vitamin D-binding protein (DBP) in children with chronic renal failure (CRF). We also evaluated the relationships between the peritoneal loss of vitamin D metabolites, DBP and albumin in nine children on continuous ambulatory peritoneal dialysis (CAPD). The serum levels of DBP in children with CRF were significantly higher than in normal children. The mean serum DBP level in CRF children undergoing CAPD was slightly lower than in CRF patients who were not on dialysis. In patients on CAPD, the peritoneal loss of 25-hydroxyvitamin D (25OHD) showed a significant positive correlation with the DBP concentration in the dialysate (r = 0.855, P less than 0.005). In contrast, the peritoneal loss of 1,25-dihydroxyvitamin D (1,25(OH)2D) showed a significant correlation with the loss of albumin in the dialysate (r = 0.779, P less than 0.01). The synthesis of 1,25(OH)2D3 is reduced in advanced renal failure, and the peritoneal losses of the active vitamin D sterols in patients on CAPD may aggravate this deficiency. We recommend that supplementation of active form of vitamin D, such as 1 alpha-hydroxyvitamin D3 or 1,25(OH)2D3, is important in CAPD patients, particularly those with elevated peritoneal loss of DBP and/or albumin.

Adolescent↗

PubMed1992

Membrane proteases: roles in tissue remodeling and tumour invasion.

The coordinated control of extracellular matrix degradation on the cell surface involves three crucial elements: secreted proteases and their inhibitors, surface protease receptors and integral membrane proteases. The roles that each of these elements play in cell surface proteolysis are described. The localization of proteases to the cell surface, protease activation, and regulation of cell surface proteolysis by protease inhibitors are key issues for elucidating the role of membrane proteases in tissue remodeling and tumour invasion.

Animals↗

PubMed1992

Tyrosine phosphorylation of membrane proteins mediates cellular invasion by transformed cells.

Tyrosine phosphorylation of membrane-associated proteins is involved at two distinct sites of contact between cells and the extracellular matrix: adhesion plaques (cell adhesion and de-adhesion) and invadopodia (invasion into the extracellular matrix). Adhesion plaques from chicken embryonic fibroblasts or from cells transformed by Rous sarcoma virus contain low levels of tyrosine-phosphorylated proteins (YPPs) which were below the level of detection in 0.5-microns thin, frozen sections. In contrast, intense localization of YPPs was observed at invadopodia of transformed cells at sites of degradation and invasion into the fibronectin-coated gelatin substratum, but not in membrane extensions free of contact with the extracellular matrix. Local extracellular matrix degradation and formation of invadopodia were blocked by genistein, an inhibitor of tyrosine-specific kinases, but cells remained attached to the substratum and retained their free-membrane extensions. Invadopodia reduced or lost YPP labeling after treatment of the cells with genistein, but adhesion plaques retained YPP labeling. The plasma membrane contact fractions of normal and transformed cells have been isolated form cells grown on gelatin cross-linked substratum using a novel fractionation scheme, and analyzed by immunoblotting. Four major YPPs (150, 130, 81, and 77 kD) characterize invadopodial membranes in contact with the matrix, and are probably responsible for the intense YPP labeling associated with invadopodia extending into sites of matrix degradation. YPP150 may be an invadopodal-specific YPP since it is approximately 3.6-fold enriched in the invasive contact fraction relative to the cell body fraction and is not observed in normal contacts. YPP130 is enriched in transformed cell contacts but may also be present in normal contacts. The two major YPPs of normal contacts (130 and 71 kD) are much lower in abundance than the major tyrosine-phosphorylated bands associated with invadopodial membranes, and likely represent major adhesion plaque YPPs. YPP150, paxillin, and tensin appear to be enriched in the cell contact fractions containing adhesion plaques and invadopodia relative to the cell body fraction, but are also present in the soluble supernate fraction. However, vinculin, talin, and alpha-actinin that are localized at invadopodia, are equally concentrated in cell bodies and cell contacts as is the membrane-adhesion receptor beta 1 integrin. Thus, tyrosine phosphorylation of the membrane-bound proteins may contribute to the cytoskeletal and plasma membrane events leading to the formation and function of invadopodia that contact and proteolytically degrade the extracellular matrix; we have identified several candidate YPPs that may participate in the regulation of these processes.

Actins↗

PubMed1992

High copy number of the pUC plasmid results from a Rom/Rop-suppressible point mutation in RNA II.

The plasmids pUC18 and pUC19 are pBR322 derivatives that replicate at a copy number several fold higher than the parent during growth of Escherichia coli at 37 degrees C. We show here that the high copy number of pUC plasmids results from a single point mutation in the replication primer, RNA II, and that the phenotypic effects of this mutation can be suppressed by the Rom (RNA one modulator)/Rop protein or by lowering the growth temperature to 30 degrees C. The mutation's effects are enhanced by cell growth at 42 degrees C, at which copy number is further increased. During normal cell growth, the pUC mutation does not affect the length or function of RNA I, the antisense repressor of plasmid DNA replication, but may, as computer analysis suggests, alter the secondary structure of pUC RNA II. We suggest that the pUC mutation impedes interactions between the repressor and the primer by producing a temperature-dependent alteration of the RNA II conformation. The Rom/Rop protein may either promote normal folding of the mutated RNA II or, alternatively, may enable the interaction of sub-optimally folded RNA II with the repressor.

Bacterial Proteins↗

PubMed1992

Radial keratotomy. II. Role of the myofibroblast in corneal wound contraction.

The cellular mechanism of corneal wound contraction after radial keratotomy (RK) was studied in a feline eye model. A total of 10 cat eyes were evaluated at various times from 0-30 days after surgery. Changes in the distribution of intracellular filamentous actin, nonmuscle myosin, alpha-actinin, surface membrane alpha 5 beta 1 integrin, and extracellular fibronectin were studied using immunofluorescence and laser confocal and electron microscopy. From day 3-7, staining for fibronectin increased along the wound margin. By day 7, keratocytes adjacent to the wound margin showed increased f-actin staining with intense staining for fibronectin compared with normal keratocytes. Myosin and alpha 5 beta 1 integrin expression was very weak at this time; alpha-actinin was not found. By day 14, fibroblasts within the wound formed f-actin microfilament bundles (stress fibers) which colocalized with fibronectin. Wound-healing fibroblasts also stained positively for alpha 5 beta 1 integrin, myosin, and alpha-actinin (the latter two were colocalized). The presence of myosin and alpha-actinin in the wound fibroblasts and the re-organization of f-actin into stress fibers by day 14 correlated with the development of wound contraction. A comparison of the cellular distribution of actin, myosin, and alpha-actinin with alpha 5 beta 1 integrin 14 days after injury suggested that integrin was localized along stress fiber bundles during wound contraction. The data from this study suggest that modulation of wound gape during healing of RK wounds may involve transformation of the corneal keratocyte to a myofibroblast-like cell and the subsequent formation of intracellular stress fibers composed of f-actin, nonmuscle myosin, and alpha-actinin. Based on the colocalization of fibronectin filaments and f-actin filaments and the unique distribution of alpha 5 beta 1 integrin, these findings support the hypothesis that the tension within the wound is generated by the formation of intracellular stress fibers and the interactions between stress fibers and the extracellular matrix, mediated by specific membrane receptor molecules.

Animals↗

PubMed1991

Decreased size of peritoneal macrophage during peritonitis in continuous ambulatory peritoneal dialysis patients.

From January 1987 to July 1988, 30 patients suffering from end-stage renal disease were treated with continuous ambulatory peritonitis dialysis (CAPD) therapy. Serial cell number, size and cycle of the peritoneal macrophage (PM) in these patients were measured before and during episodes of peritonitis from the time they started CAPD therapy. Patients with peritonitis were divided into high peritonitis occurrence (HPOG) and low peritonitis occurrence (LPOG) groups. Both before and during occurrence of peritonitis, there were no significant differences in the number of PM cells in the dialysate taken from patients in the HPOG and LPOG. When peritonitis occurred, the size and cell cycle S/Go-G1 ratio decreased about 3 days after the onset of peritonitis. It progressed to the lowest level 7-10 days later, then progressively recovered. However, the dialysate PM cells from the HPOG took a much longer time to recover to the preperitonitis size. When dialysate PM cells from patients without peritonitis were put into the dialysate of HPOG patients on day 10 of peritonitis and incubated for 24 h, an obvious decrease in cell size could be identified. On the other hand, when the PM cells from HPOG patients with peritonitis on day 10 were incubated 24 h with the dialysate from patients without peritonitis, there were obvious increases in cell size. These results suggest there may be a substance (or substances) in the peritonitis dialysate, which contribute(s) to the shrinkage of PM cell size.

Adolescent↗