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Biomedical subjects

C M Chen

Publications and source records attributed to C M Chen.

At least 109 records · Page 6Linked to original sources
PubMed1999

Hepatitis C virus core protein enhances NF-kappaB signal pathway triggering by lymphotoxin-beta receptor ligand and tumor necrosis factor alpha.

Our previous study indicated that the core protein of hepatitis C virus (HCV) can associate with tumor necrosis factor receptor (TNFR)-related lymphotoxin-beta receptor (LT-betaR) and that this protein-protein interaction plays a modulatory effect on the cytolytic activity of recombinant form LT-betaR ligand (LT-alpha1beta2) but not tumor necrosis factor alpha (TNF-alpha) in certain cell types. Since both TNF-alpha/TNFR and LT-alpha1beta2/LT-betaR are also engaged in transcriptional activator NF-kappaB activation or c-Jun N-terminal kinase (JNK) activation, the biological effects of the HCV core protein on these regards were elucidated in this study. As demonstrated by the electrophoretic mobility shift assay, the expression of HCV core protein prolonged or enhanced the TNF-alpha or LT-alpha1beta2-induced NF-kappaB DNA-binding activity in HuH-7 and HeLa cells. The presence of HCV core protein in HeLa or HuH-7 cells with or without cytokine treatment also enhanced the NF-kappaB-dependent reporter plasmid activity, and this effect was more strongly seen with HuH-7 cells than with HeLa cells. Western blot analysis suggested that this modulation of the NF-kappaB activity by the HCV core protein was in part due to elevated or prolonged nuclear retention of p50 or p65 species of NF-kappaB in core protein-producing cells with or without cytokine treatment. Furthermore, the HCV core protein enhanced or prolonged the IkappaB-beta degradation triggering by TNF-alpha or LT-alpha1beta2 both in HeLa and HuH-7 cells. In contrast to that of IkappaB-beta, the increased degradation of IkappaB-alpha occurred only in LT-alpha1beta2-treated core-producing HeLa cells and not in TNF-alpha-treated cells. Therefore, the HCV core protein plays a modulatory effect on NF-kappaB activation triggering by both cytokines, though the mechanism of NF-kappaB activation, in particular the regulation of IkappaB degradation, is rather cell line and cytokine specific. Studies also suggested that the HCV core protein had no effect on TNF-alpha-stimulated JNK activity in both HeLa and HuH-7 cells. These findings, together with our previous study, strongly suggest that among three signaling pathways triggered by the TNF-alpha-related cytokines, the HCV core protein potentiates NF-kappaB activation in most cell types, which in turn may contribute to the chronically activated, persistent state of HCV-infected cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1999

Hepatitis C virus core protein interacts with cellular putative RNA helicase.

The nucleocapsid core protein of hepatitis C virus (HCV) has been shown to trans-act on several viral or cellular promoters. To get insight into the trans-action mechanism of HCV core protein, a yeast two-hybrid cloning system was used for identification of core protein-interacting cellular protein. One such cDNA clone encoding the DEAD box family of putative RNA helicase was obtained. This cellular putative RNA helicase, designated CAP-Rf, exhibits more than 95% amino acid sequence identity to other known RNA helicases including human DBX and DBY, mouse mDEAD3, and PL10, a family of proteins generally involved in translation, splicing, development, or cell growth. In vitro binding or in vivo coimmunoprecipitation studies demonstrated the direct interaction of the full-length/matured form and C-terminally truncated variants of HCV core protein with this targeted protein. Additionally, the protein's interaction domains were delineated at the N-terminal 40-amino-acid segment of the HCV core protein and the C-terminal tail of CAP-Rf, which encompassed its RNA-binding and ATP hydrolysis domains. Immunoblotting or indirect immunofluorescence analysis revealed that the endogenous CAP-Rf was mainly localized in the nucleus and to a lesser extent in the cytoplasm, and when fused with FLAG tag, it colocalized with the HCV core protein either in the cytoplasm or in the nucleus. Similar to other RNA helicases, this cellular RNA helicase has nucleoside triphosphatase-deoxynucleoside triphosphatase activity, but this activity is inhibited by various forms of homopolynucleotides and enhanced by the HCV core protein. Moreover, transient expression of HCV core protein in human hepatoma HuH-7 cells significantly potentiated the trans-activation effect of FLAG-tagged CAP-Rf or untagged CAP-Rf on the luciferase reporter plasmid activity. All together, our results indicate that CAP-Rf is involved in regulation of gene expression and that HCV core protein promotes the trans-activation ability of CAP-Rf, likely via the complex formation and the modulation of the ATPase-dATPase activity of CAP-Rf. These findings provide evidence that HCV may have evolved a distinct mechanism in alteration of host cellular gene expression regulation via the interaction of its nucleocapsid core protein and cellular putative RNA helicase known to participate in all aspects of cellular processes involving RNA metabolism. This feature of core protein may impart pleiotropic effects on host cells, which may partially account for its role in HCV pathogenesis.

Amino Acid Sequence↗
PubMed1999

Wingless transduction by the Frizzled and Frizzled2 proteins of Drosophila.

Wingless (Wg) protein is a founding member of the Wnt family of secreted proteins which have profound organizing roles in animal development. Two members of the Frizzled (Fz) family of seven-pass transmembrane proteins, Drosophila Fz and Fz2, can bind Wg and are candidate Wg receptors. However, null mutations of the fz gene have little effect on Wg signal transduction and the lack of mutations in the fz2 gene has thus far prevented a rigorous examination of its role in vivo. Here we describe the isolation of an amber mutation of fz2 which truncates the coding sequence just after the amino-terminal extracellular domain and behaves genetically as a loss-of-function allele. Using this mutation, we show that Wg signal transduction is abolished in virtually all cells lacking both Fz and Fz2 activity in embryos as well as in the wing imaginal disc. We also show that Fz and Fz2 are functionally redundant: the presence of either protein is sufficient to confer Wg transducing activity on most or all cells throughout development. These results extend prior evidence of a ligand-receptor relationship between Wnt and Frizzled proteins and suggest that Fz and Fz2 are the primary receptors for Wg in Drosophila.

Alleles↗
PubMed1999

Dominant effects of RET receptor misexpression and ligand-independent RET signaling on ureteric bud development.

During kidney development, factors from the metanephric mesenchyme induce the growth and repeated branching of the ureteric bud, which gives rise to the collecting duct system and also induces nephrogenesis. One signaling pathway known to be required for this process includes the receptor tyrosine kinase RET and co-receptor GFR(&agr;)-1, which are expressed in the ureteric bud, and the secreted ligand GDNF produced in the mesenchyme. To examine the role of RET signaling in ureteric bud morphogenesis, we produced transgenic mice in which the pattern of RET expression was altered, or in which a ligand-independent form of RET kinase was expressed. The Hoxb7 promoter was used to express RET throughout the ureteric bud branches, in contrast to its normal expression only at the bud tips. This caused a variable inhibition of ureteric bud growth and branching reminiscent of, but less severe than, the RET knockout phenotype. Manipulation of the level of GDNF, in vitro or in vivo, suggested that this defect was due to insufficient rather than excessive RET signaling. We propose that RET receptors expressed ectopically on ureteric bud trunk cells sequester GDNF, reducing its availability to the normal target cells at the bud tips. When crossed to RET knockout mice, the Hoxb7/RET transgene, which encoded the RET9 isoform, supported normal kidney development in some RET-/- animals, indicating that the other major isoform, RET51, is not required in this organ. Expression of a Hoxb7/RET-PTC2 transgene, encoding a ligand-independent form of RET kinase, caused the development of abnormal nodules, outside the kidney or at its periphery, containing branched epithelial tubules apparently formed by deregulated growth of the ureteric bud. This suggests that RET signaling is not only necessary but is sufficient to induce ureteric bud growth, and that the orderly, centripetal growth of the bud tips is controlled by the spatially and temporally regulated expression of GDNF and RET.

Animals↗
PubMed1999

Treatment of large skeletal defects in the lower extremities using double-strut, free vascularized fibular bone grafting.

This article reports on the use of double-strut, free vascularized fibular grafts to treat six patients with infected nonunion or traumatic bone loss in the femur or tibia after prolonged treatment and multiple operations. The defects were 6-13 cm long. Five patients achieved solid union within 6 months, and one patient required additional cancellous grafting to achieve union at the distal end of the fibula. One patient experienced a stress fracture due to strenuous exercise, and union was achieved 3 months after reapplying an external fixator. Although three patients had some restricted knee motion, all patients had a satisfactory outcome in regard to walking, and no limb-length discrepancies were noted in any patient.

Adult↗
PubMed1999

Salmonella infection in total hip replacement--report of successful reimplantation and review of the literature.

A case of Salmonella enteritidis group C infection following total hip replacement was treated by resectional arthroplasty and appropriate antibiotics. Total hip replacement with reimplantation of an antibiotic-impregnated cemented hip prosthesis was performed five months later. The postoperative course was smooth and hip function was good, without any sign of infection recurrence throughout 10 years of follow-up. The treatment protocol and clinical results are discussed along with a review of the literature.

Arthroplasty, Replacement, Hip↗
PubMed1999

Usefulness of molecular testing in Huntington's disease.

BACKGROUND: Uncertainty in diagnosing Huntington's disease (HD) may occur in the absence of a family history or typical movement disorders. HD is characterized by a progressive disturbance of typical movement disorders (i.e., chorea, athetosis), psychiatric symptoms (i.e., depression, insomnia, anxiety, suspiciousness), and cognitive deterioration, in the absence of a dominant family history of similar disorders. Often, some of these symptoms are missing, which makes the diagnosis difficult. In recent years molecular testing has become the gold standard for diagnosing HD. Diagnostic accuracy for HD on genetic screening of patients and their families is important. We evaluated a polymerase chain reaction (PCR) technique for the detection of CAG trinucleotide repeats in the Huntington IT15 gene on chromosome 4 for the diagnosis of HD. METHODS: A segment of the Huntington gene was amplified by PCR using the primers HD-1 and HD-3 flanking the CAG repeat sequence. Genomic PCR was performed on DNA extracted from the peripheral leukocytes of 12 patients from three unrelated families. One family had no documented history of movement or mental disorders, while the other two did. These two, therefore, required pre-symptomatic testing and exclusion of diagnosis in a seemingly symptomatic case. RESULTS: We successfully identified four subjects with expansion of CAG trinucleotide repeats in Huntington gene IT15 on chromosome 4. Movement disorder was present in three of these subjects. One was the sister of subject 4, who was asymptomatic. A sister of subject 9 was ruled out from having HD by PCR despite having depression symptoms, which are frequently seen in HD patients. CONCLUSIONS: Genetic testing is of prime importance in the establishment of an accurate diagnosis of Huntington's disease, especially in "sporadic" cases and presymptomatic family members, and for the exclusion of HD in family members with equivocal symptoms.

Adult↗
PubMed1999

Analysis of prognostic factors in Chinese women with breast cancer in southern Taiwan.

BACKGROUND: We conducted a retrospective review of all early-stage breast cancer patients treated at the Veterans General Hospital-Kaohsiung to determine overall and disease-free survival rates, and to evaluate prognostic factors for these outcomes. METHODS: During the period of October, 1990, to December, 1997, 332 patients with early-stage breast cancer were treated at our institution. Cox's multivariate regression analysis was used to select prognostic factors significant for overall survival and disease-free survival. RESULTS: The survival rate for breast cancer patients was 88.35% at five years. Prognostic factors predicting breast cancer mortality included poorly differentiated histologic grade, four or more lymph nodes positive for metastasis and negative progesterone-receptor status. For disease recurrence, prognostic factors included positive nodes, aneuploidy and poorly differentiated histologic grading. CONCLUSIONS: We conclude that a combination of lymph node status, DNA ploidy, histologic grading and progesterone-receptor status help to evaluate the possible outcomes for patients with breast cancer and to plan for optimal therapy.

Adult↗
PubMed1999

Protective effects of partially purified antigens of Actinobacillus pleuropneumoniae on experimentally infected mice.

Three different models of protection experiments in mice using partially purified Actinobacillus pleuropneumoniae antigens such as crude culture supernatant extract (CCSE) and partially purified cell extract (PPCE) were attempted. Biochemical analysis showed that these two immunogens had protein concentration of 0.17-0.2 mg/mL and pentose concentration of 0.012-0.014 mg/mL. In the first model intranasal (IN) vaccination with different doses (from 0.01-10 IN-LD50) against IN challenge with the dose of 20 IN-LD50 containing 1.2 x 10(9) colony forming unit (CFU)/50 microL showed that only those with the dose more than 1 IN-LD50 had slight protection in terms of survival index (SI). In the second model of protection experiment, in which subcutaneous vaccination (s.c.) with the immunogens plus soybean oil against IN challenge with 10 IN-LD50 containing 6 x 10(8) CFU/50 microL, showed that formalin-killed bacteria (bacterin) and CCSE plus PPCE had only a slight protection whereas vaccination with CCSE or PPCE immunogen alone had no protection. In the third model of protection experiment, in which the intramuscular (i.m.) vaccination with the immunogens plus aluminum hydroxide [Al(OH3)] gel against intraperitoneal (i.p.) challenge with the dose of either 2 or 6 i.p.-LD50 containing 1.2-3.6 x 10(8) CFU/0.5 mL of 0.3% mucin saline showed highly effective.

Actinobacillus Infections↗
PubMed1998

Requirement of the mouse I-mfa gene for placental development and skeletal patterning.

The bHLH-repressor protein I-mfa binds to MyoD family members, inhibits their activity, and blocks their nuclear import and binding to DNA. In situ hybridization analysis demonstrated that mouse I-mfa was highly expressed in extraembryonic lineages, in the sclerotome, and subsequently within mesenchymal precursors of the axial and appendicular skeleton, before chondrogenesis occurs. Targeted deletion of I-mfa in a C57Bl/6 background resulted in embryonic lethality around E10.5, associated with a placental defect and a markedly reduced number of trophoblast giant cells. Overexpression of I-mfa in rat trophoblast (Rcho-1) stem cells induced differentiation into trophoblast giant cells. I-mfa interacted with the bHLH protein Mash2, a negative regulator of trophoblast giant cell formation, and inhibited its transcriptional activity in cell culture. In contrast, I-mfa did not interfere with the activity of the bHLH protein Hand1, a positive regulator of giant cell differentiation. Interestingly, I-mfa-null embryos on a 129/Sv background had no placental defect, generally survived to adulthood, and exhibited delayed caudal neural tube closure and skeletal patterning defects that included fusions of ribs, vertebral bodies and abnormal formation of spinous processes. Our results indicate that I-mfa plays an important role in trophoblast and chondrogenic differentiation by negatively regulating a subset of lineage-restricted bHLH proteins.

Animals↗
PubMed1998

Use of nonautologous microencapsulated fibroblasts in growth hormone gene therapy to improve growth of midget swine.

The aim of the present study was to investigate the expression activity, both in vitro and in vivo, of the porcine growth hormone complementary DNA (pGH cDNA) in porcine fetal fibroblast (PFF) cells. The pGH gene had been constructed inside the bicistronic retroviral vector PSN and subsequently transfected into PFF cells further encapsulated with immunoprotective microcapsules. This would provide a way to evaluate the improvement in growth performance of Tao-Yuan swine by the use of nonautologous microencapsulated fibroblasts carrying the pGH cDNA via the technique of somatic gene therapy. Results from Southern blot analysis confirmed that the full length of the pGH cDNA was completely integrated into the genome of the PFF cells after they had been infected one to four times using a PSN retroviral vector. Moreover, Northern blot analysis showed that high transcription activity was present in clones infected twice, and exogenous pGH secretion was found when the pGH-infected PFF had been further cultured for 48 hr in vitro and subjected to immunoblot assay. Encapsulation of the pGH-PFF with an alginate-poly-L-lysine-alginate membrane did not show any deterioration in their proliferation and survival both in vitro and in vivo. The pGH gene in encapsulated recombinant fibroblasts was fully expressed after it had been transplanted into the peritoneal cavity of the Tao-Yuan swine, and reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed on the microcapsules retrieved 1 month later. The feasibility of pGH gene therapy to improve midget Tao-Yuan swine growth enhancement is further supported by the fact that transplantation of the encapsulated recombinant fibroblast cells resulted in a much more significant increase in weight gain than in those swine in either the age-matched untreated control group or in those that had been transplanted with uncapsulated recombinant PFF cells (10.56 +/- 1.01 kg versus 6.95 +/- 0.94 and 5.27 +/- 1.30 kg; p < 0.05). These experimental data suggest that growth hormone gene therapy did provide an alternative approach for growth improvement in midget Tao-Yuan swine.

Animals↗
PubMed1998

Gas-phase postderivatization following solid-phase microextraction for determining acidic herbicides in water.

This study analyzes acidic herbicides from an aqueous sample by developing a methylated postderivatization on the fiber following solid-phase microextration (SPME) with diazomethane gas procedure combined with GC/MS. Analysis results indicate that a silica fiber coated with polyacrylate (PA) yields a higher extraction efficiency than that obtained with poly(dimethylsiloxane) (PDMS) using the SPME technique. Detection limits are achieved at the level of 10-30 ng/L. Linearity is obtained over a wide range, with precision below 12% RSD. In addition, the significant reduction in extraction efficiency is attributed to the concentration of humic acids exceeding 5 mg/L. Various degradation compounds of acidic herbicides in basic solution are also detected, including 2,4-dichlorophenol, 2,4,5-trichlorophenol, 4-chloro-3-methylphenol, pentachlorinated biphenyl, and tetrachlorinated biphenyl. Moreover, the amount of pentachlorinated biphenyl and tetrachlorinated biphenyl increases over time.

Gas Chromatography-Mass Spectrometry↗
PubMed1998

Enhanced cervical MRI in identifying intracranial dural arteriovenous fistulae with spinal perimedullary venous drainage.

Diagnosis of an intracranial dural arteriovenous fistula (DAVF) with spinal perimedullary venous drainage is challenging because the presenting symptoms are usually related to dysfunction of the spine, not of the brain. Repeated spinal angiograms are usually performed before the diagnosis is finally made by cerebral angiography. We report two cases of intracranial DAVFs with spinal perimedullary venous drainage. In both cases contrast-enhanced cervical MRI demonstrated dilated lower brainstem and upper spinal veins, which, we believe, is a good indicator of the existence of such drainage. We suggest that, in cases with perimedullary serpentine enhancement on thoracic or lumbar MR images, additional Gd-enhanced cervical spinal MR imaging should be performed. The simple process of tracing the veins upwards may avoid a lot of unnecessary examinations and delay in the diagnosis.

Adult↗
PubMed1998

Interaction of DNA-binding proteins with the 5'-flanking region of a cytokinin-responsive cucumber hydroxypyruvate reductase gene.

Transcription of the cucumber hpr-A gene is responsive to cytokinin and light. To investigate the molecular basis for transcriptional regulation by cytokinin, we have identified DNA sequences and proteins that may be involved in the regulation of hpr-A gene expression. Transient expression assays in etiolated cucumber cotyledons indicate that the 315 bp fragment (-382 to -67) contains sequences necessary for cytokinin responsiveness of the luciferase reporter gene. Band shift assays detected cytokinin-enhanced and -reduced protein binding sites in a 97 bp fragment (-382 to -285) upstream of the hpr-A gene. DNase I footprinting identified two protein-protected sites, a 15 bp sequence, 5'-AAATGACGAAAATGC-3', that contains an as-1 TGACG motif found in other plant promoters, and a 13 bp sequence, 5'-AAGATTGATTGAG-3', of unknown function. Two-dimensional band shift analysis of the cytokinin-responsive DNA protein complex revealed the presence of six DNA protein interactions. Band shift assays showed that cytokinin and light have different effects on the interaction of nuclear proteins to the 97 bp fragment of the hpr-A gene. These data suggest that cytokinin and light do not share identical signal transduction pathways in regulating hpr-A gene expression.

Alcohol Oxidoreductases↗
PubMed1998

The effects of projection geometry and trabecular texture on estimated fractal dimensions in two alveolar bone models.

OBJECTIVES: To study the effects of trabecular texture and projection geometry on estimates of fractal dimensions from simulated alveolar bone. METHODS: Two models, one scale-variant and the other relatively scale-invariant, were used. Projections of 2-D slices through both the models were calculated, a uniform series of projections computed for the angular orientations between (0 degree and 180 degrees). Results of the 128 stacked projections are the projection of the 3-D object from different angles. Power spectra were produced by calculating the squared magnitude from the data and plotted as the logarithm of the power against the logarithm of the frequency, to give the fractal dimension. RESULTS: In the scale-variant model, the alveolar trabecular texture produced with a relatively thicker cylindrical diameter yielded a smaller fractal dimension (t = 8.44, P = 0.00). Linear regression analysis showed that the correlation between projection angle and the resulting fractal dimension was low for both the thicker cylinder (r = 0.02, P = 0.82), and for thinner cylinder (r = 0.02, P = 0.84). The scale-invariant model, also yielded a relatively smaller estimated fractal dimension (t = 7.23, P = 0.00). However, the correlation between projection angle and the resulting estimate of the fractal dimension was found to be low for both trabecular configurations (r = 0.10, P = 0.29 and r = 0.07, P = 0.45 respectively). CONCLUSIONS: Fractal dimensions increased when the diameter of the simulated cylindrical trabeculae decreased irrespective of the differences in self-similarity. The degree to which they varied with projection angle was relatively less for the scale-invariant (self-similar) model. However, fractal dimensions changed significantly with projection geometry.

Alveolar Process↗
PubMed1998

The selective antianginal effect without changing blood pressure of butylidenephthalide in conscious rats.

Synthetic butylidenephthalide (Bdph), 60 mg/kg per os (p.o.) given 3 h prior to injection of pituitrin (4 U/kg, i.v.), significantly prevented T-wave lowering on lead II electrocardiograph in unanesthetized rats. The effective dose, 60 mg/kg, was about 1/56th of the median lethal dose (LD50, p.o.) in rats. However, Bdph (60 mg/kg, p.o.) did not affect systolic pressure and heart rate in unanesthetized rats. Therefore, Bdph, found in the rhizome of Ligusticum chuaxiong Hort. (L. wallichii Franch., Umbelliferae), appears to have selective antianginal effect without changing blood pressure and heart rate.

Angina Pectoris↗
PubMed1998

The benefit and risk of postmastectomy radiation therapy in patients with high-risk breast cancer.

To evaluate the efficacy of postmastectomy radiation therapy (PMRT) for prophylaxis against locoregional recurrence in high-risk breast cancer patients, and the rate of complication associated with such treatment, we retrospectively reviewed 79 breast cancers in 78 patients, who were given therapy (PMRT) between April 1990 and March 1995. Radiation doses were 46-50 Gy in 2-Gy fractions. High-risk factors included primary tumor (> or = 5 cm) in 19 (24.1%) patients, positive axillary lymph nodes (> or = 4) in 56 (70.9%) patients, positive or close (< or = 2 mm) surgical margins in 14 (17.7%) patients, and central or inner quadrant tumor with positive axillary nodes and lymphovascular invasion in seven (8.9%) patients. Adjuvant chemotherapy was also given to 69 of 78 (88.5%), patients and hormonal therapy to 41 of 78 (53.7%) patients. The median follow-up time was 25 months (range, 7-66 months) after mastectomy. Our study revealed that locoregional failure as the first site of failure occurred in only one of 78 (1.3%) patients. Relapse-free survival at 3 years was 67.7% [95% confidence interval (CI), 52.0-81.3], and overall survival was 76.9% (95% CI, 63.3-90.6). The incidence of radiological evidence of lung fibrosis increased significantly in patients whose internal mammary chain was included in the radiation field. The occurrence of lung fibrosis can be reduced by changing radiation treatment technique and keeping central lung distance (CLD) of tangential field to < or = 2.8 cm in tangential field technique or < or = 1.4 cm in tangential with a separate internal mammary field technique. We concluded that the risk of locoregional recurrence in high-risk breast cancer patients can be much reduced by PMRT. With careful selection of radiation treatment fields, radiotherapy technique, and limitation of CLD to < or = 2.8 cm in tangential technique or < or = 1.4 cm in separate technique, the risk of symptomatic radiation pneumonitis is minimal. PMRT should be recommended for breast cancer patients who are at high risk for locoregional recurrence.

Adult↗