Biomedical subjects

H C Chen

Publications and source records attributed to H C Chen.

At least 73 records · Page 4Linked to original sources

PubMed2001

Competitive exclusion of heterologous Campylobacter spp. in chicks.

Chicken and human isolates of Campylobacter jejuni were used to provide oral challenge of day-old broiler chicks. The isolation ratio of the competing challenge strains was monitored and varied, depending upon the isolates used. A PCR-restriction fragment length polymorphism assay of the flagellin gene (flaA) was used to discriminate between the chick-colonizing isolates. Our observations indicated that the selected C. jejuni colonizers dominated the niche provided by the chicken ceca. Chicken isolates from the flaA type 7 grouping generally had numerical superiority over the human isolates when they were administered in our 1-day-old chick model. Our results suggest that it is possible to use combinations of C. jejuni chicken isolates as a defined bacterial preparation for the competitive exclusion of human-pathogenic C. jejuni in poultry.

Animals↗

PubMed2001

Marek's disease virus (MDV) encodes an interleukin-8 homolog (vIL-8): characterization of the vIL-8 protein and a vIL-8 deletion mutant MDV.

Chemokines induce chemotaxis, cell migration, and inflammatory responses. We report the identification of an interleukin-8 (IL-8) homolog, termed vIL-8, encoded within the genome of Marek's disease virus (MDV). The 134-amino-acid vIL-8 shares closest homology to mammalian and avian IL-8, molecules representing the prototype CXC chemokine. The gene for vIL-8 consists of three exons which map to the BamHI-L fragment within the repeats flanking the unique long region of the MDV genome. A 0.7-kb transcript encoding vIL-8 was detected in an n-butyrate-treated, MDV-transformed T-lymphoblastoid cell line, MSB-1. This induction is essentially abolished by cycloheximide and herpesvirus DNA polymerase inhibitor phosphonoacetate, indicating that vIL-8 is expressed with true late (gamma2) kinetics. Baculovirus-expressed vIL-8 was found to be secreted into the medium and shown to be functional as a chemoattractant for chicken peripheral blood mononuclear cells but not for heterophils. To characterize the function of vIL-8 with respect to MDV infection in vivo, a recombinant MDV was constructed with a deletion of all three exons and a soluble-modified green fluorescent protein (smGFP) expression cassette inserted at the site of deletion. In two in vivo experiments, the vIL-8 deletion mutant (RB1BvIL-8DeltasmGFP) showed a decreased level of lytic infection in comparison to its parent virus, an equal-passage-level parent virus, and to another recombinant MDV containing the insertion of a GFP expression cassette at the nonessential US2 gene. RB1BvIL-8DeltasmGFP retained oncogenicity, albeit at a greatly reduced level. Nonetheless, we have been able to establish a lymphoblastoid cell line from an RB1BvIL-8DeltasmGFP-induced ovarian lymphoma (MDCC-UA20) and verify the presence of a latent MDV genome lacking vIL-8. Taken together, these data describe the identification and characterization of a chemokine homolog encoded within the MDV genome that is dispensable for transformation but may affect the level of MDV in vivo lytic infection.

Amino Acid Sequence↗

PubMed2001

Significance of salivary epidermal growth factor in peptic ulcer disease in hemodialysis patients.

BACKGROUND/AIMS: Hemodialysis (HD) patients are prone to developing peptic ulcers. However, of all the risk factors associated with peptic ulcers, none have been shown to be more prevalent in HD patients than in the general population. However, salivary epidermal growth factor (EGF) may play a role in peptic ulcer diseases. METHODS: Salivary EGF levels and bioactivities were assayed in 47 maintenance HD patients and 30 normal controls, and the molecular weights of EGF were assessed using high-performance liquid chromatography (HPLC). RESULTS: Salivary EGF levels were not different between both groups of subjects (4.2 +/- 0.34 vs. 5 +/- 0.54 ng/mg protein, NS), and HPLC revealed that salivary EGF in both groups had similar molecular weights. However, salivary EGF bioactivity was significantly depressed in the HD patients as compared to the normal controls (0.59 +/- 0.08 vs. 1.55 +/- 0.15 ng/mg protein, p < 0.01). Stepwise multiple regression showed that the low salivary EGF levels were associated with female gender (p < 0.05), while low salivary EGF bioactivity was associated with HD per se (p < 0.05). In the 22 HD patients who underwent gastric endoscopy, salivary EGF bioactivity was significantly lower in those with peptic ulcers than in those without (0.38 +/- 0.08 vs. 0.69 +/- 0.08 ng/mg protein, p < 0.05). CONCLUSION: Decreased salivary EGF bioactivity may contribute to peptic ulcer disease among maintenance HD patients.

Epidermal Growth Factor↗

PubMed2001

Differential effects of circulating IgA isolated from patients with IgA nephropathy on superoxide and fibronectin production of mesangial cells.

BACKGROUND: IgA nephropathy (IgAN) is characterized by predominant deposition of IgA in the glomerular mesangium. Serum IgA is often elevated in patients with IgAN, and it has been postulated that it is responsible for the mesangial lesions. However, the direct effect of circulating IgA on mesangial cells is not clear. METHODS: We investigated the effects of sera and IgA which were isolated from patients with IgAN on thymidine uptake, superoxide and fibronectin production and fibronectin mRNA expression of cultured rat mesangial cells, and we compared the findings to the effects of IgA isolated from patients with non-IgA mesangial proliferative glomerulonephritis (MsPGN) and normal controls. IgA was isolated with affinity chromatography using cyanogen bromide activated Sepharose 4B coupled to sheep antihuman IgA antiserum. RESULTS: Our results demonstrated that both sera and IgA from patients with IgAN dose-dependently increased mitogenesis of mesangial cells as measured by (3)H-labeled thymidine uptake. The thymidine uptake by sera and IgA isolated from patients with IgAN was significantly higher than that of sera and IgA isolated from patients with MsPGN and normal controls. Sera and IgA from patients with IgAN significantly enhanced superoxide and fibronectin production and fibronectin mRNA expression of mesangial cells. The superoxide and fibronectin production was also significantly higher as compared with patients with MsPGN and normal controls. CONCLUSIONS: Our results indicate that circulating IgA isolated from patients with IgAN is different from that of patients with MsPGN and normal controls and may potentially induce oxidative injury and production of extracellular matrix of glomerular mesangial cells in IgAN.

Adult↗

PubMed2001

Differential effects of FMLP-activated neutrophils from patients with IgA nephropathy enhanced endothelin 1 production of glomerular mesangial cells.

BACKGROUND: Neutrophil infiltration in the glomeruli is common in patients with IgA nephropathy (IgAN). The pathogenetic roles of the infiltrated neutrophils and their relationship with glomerular mesangial cells, however, are not clear. METHODS: We examined the effects of coculture with N-formyl-methionyl-leucyl-phenylalanine (FMLP) activated neutrophils on the viability, endothelin 1 (ET-1) production, and ET-1 mRNA expression of rat glomerular mesangial cells. Neutrophils were isolated from 15 IgAN patients, from 13 patients with non-IgA mesangial proliferative glomerulonephritis (MsPGN), and from 10 normal controls. RESULTS: The ET-1 production by mesangial cells was significantly higher after stimulation with FMLP-activated neutrophils from IgAN patients than that of MsPGN patients and normal controls, and this effect was significantly abolished by pretreating mesangial cells with superoxide dismutase and partly abolished by catalase. The ET-I mRNA expression of mesangial cells showed a parallel increase with ET-1 protein. The trypan blue exclusion test showed significant mesangial cell death after stimulation with FMLP-activated neutrophils as compared with quiescent neutrophils, and the cell death was also prevented by superoxide dismutase but not catalase. The FMLP-activated neutrophils from IgAN patients produced more superoxide than those of MsPGN patients and normal controls. CONCLUSION: The FMLP-activated neutrophils from patients with IgAN have differential effects in enhancing the cell death and the ET-1 production of glomerular mesangial cells through the release of superoxide.

Adult↗

PubMed2001

Effects of task goal and personal preference on seated reaching kinematics after stroke.

BACKGROUND AND PURPOSE: Current theories of motor control in rehabilitation focus on how the nervous system responds to many types of external and internal constraints to execute motor behavior to accomplish a task. However, the dynamic interplay between these 2 constraints remains unclear. This study examined the impact of some aspects of internal and external constraints on motor performance in persons with stroke. METHODS: Twenty-seven persons with stroke used the uninvolved arms to perform an upper-extremity reaching task under 4 experimental conditions, formed by the crossing of functional goals and personal preferences. For the higher level of a functional goal, subjects took a drink from a can of beverage. For the lower level of a functional goal, subjects brought the can to the mouth without drinking. The level of personal preferences was determined, by interview, by the degree of predilection for particular beverages. RESULTS: Significant and large effects of functional goals and personal preference were found in the variables of movement time and reaction time. However, the data trend of the 4 testing conditions varied according to presence of visuospatial neglect and side of lesion. CONCLUSIONS: Offering choices for the treatment activities and incorporating functional goals to therapeutic tasks might enhance response rate or movement efficiency, depending on the side of the lesion and presence of visuospatial neglect. The findings suggest that the consideration of the neglect phenomenon is a necessity when rehabilitative treatment planning incorporates constraint factors.

Aged↗

PubMed2001

Lexical activation during the recognition of Chinese characters: evidence against early phonological activation.

In two primed-naming experiments involving Chinese character recognition, one with native Mandarin-speaking subjects and another with native Cantonese-speaking subjects, we varied both the stimulus onset asynchrony (SOA) and the prime-target similarity along various lexical dimensions. Across both experiments, the results were as follows: (1) Relatively strong and reliable semantic priming appeared very early across various SOAs, and its onset was not affected by meaning precision, (2) either homophonic priming had negligible effects on target naming or the effects appeared relatively late (only at 57 msec), and (3) graphic inhibition was found across different SOAs. Since the same set of stimuli and procedure were adopted as those in the study of Perfetti and Tan (1998), the present findings raise questions about the reliability and validity of the results from their study that have been used to support the notion that phonology is a constitutive element of character recognition and precedes meaning access in the identification process. Instead, the present results suggest that phonology is optional for accessing meaning in Chinese character recognition among skilled adult readers.

Adult↗

PubMed2001

Reconstruction of the voice after laryngectomy.

Voice reconstruction and rehabilitation are important for quality of life for patients after surgical ablation of tumors in the larynx or pharynx. In addition to the esophageal voice, the artificial larynx, and external voice devices, the following procedures have been developed: (1) after laryngectomy with preservation of pharynx, neoglottis or TEP can be performed; (2) after laryngopharyngectomy a forearm flap with TEP, or a jejunal transfer with TEP or voice tube shunt can be selected; and (3) after laryngopharyngoesophagectomy, either pharyngogastrotomy with TEP, or colon segment interposition with TEP can be employed. The voice tube shunt is improving, and allograft transplantation is currently under investigation.

Esophagus↗

PubMed2001

Mandibular reconstruction with fibula osteoseptocutaneous free flap and osseointegrated dental implants.

The fibula osteoseptocutaneous free flap is ideal for reconstruction of composite mandible defects. Osseointegration is possible and advantageous. Primary osseointegration of dental implants is a safe and reliable procedure in selected groups of patients, promoting early total oral rehabilitation with restoration of both function and cosmesis. Further studies are necessary to assess the specific indications for osseointegration teeth in patients with malignant tumors and in those patients who have received radiation therapy.

Adult↗

PubMed2001

Esophageal cancer after endoscopic injection sclerotherapy for esophageal varices.

We reported two cases of squamous cell carcinoma of the esophagus following endoscopic injection sclerotherapy (EIS) for esophageal varices. Both patients were cigarette smokers and had a long history of alcohol abuse. HBsAg and Anti-HCV were negative, and Anti-HBs was positive in one of the patients. They were diagnosed as alcoholic cirrhosis with esophageal varices and received EIS treatment. Sotradecol was utilized as the sclerosant with a mean total volume of around 30 ml. Patients developed dysphagia at 5 and 48 months following EIS, respectively. Endoscopic examination showed stenosis and ulcerative mass at the lower portion of the esophagus. Biopsy revealed well- to moderately differentiated squamous cell carcinoma of the esophagus. We conclude that endoscopic follow-up is essential and carcinoma of the esophagus should be included in the differential diagnosis for esophageal ulceration and dysphagia following EIS, particularly in those patients with risk factors for developing esophageal carcinoma.

Adult↗

PubMed2001

Persistent hyperendemicity of hepatitis C virus infection in Taiwan: the important role of iatrogenic risk factors.

The purpose of this study was to investigate determinants of endemic hepatitis C virus (HCV) infection within communities in Taiwan. A two-phase study, including a seroprevalence survey and a prevalent case-control study at the first phase, which has been published previously, and a follow-up seroconversion determination and an incident case-control study during the second phase, was carried out to evaluate correlates of persistent endemic HCV infection. At the first phase, a total of 12,021 men and 1,819 women who were 30-64 years old and living in seven townships in Taiwan were tested for the seroprevalence of antibodies to HCV (anti-HCV). In addition, a prevalent case-control study involving 272 HCV-positive cases and 282 seronegative controls identified from the anti-HCV testing was conducted to investigate risk factors associated with HCV prevalence. During the second phase, a total of 2,728 men and 834 women who were seronegative at recruitment participated in the 1-year prospective study on anti-HCV seroconversion. Subsequently, an incident case-control study based on 39 seroconverters and 81 persistently seronegative controls were carried out to elucidate determinants of HCV seroconvertion. Antibodies to HCV were tested by the second-generation enzyme immunoassay. Information on risk factors of HCV infection was collected from subject interviews. The prevalence of anti-HCV consistently increased with age (range 2.9-5.4%), whereas no apparent age trend was observed for anti-HCV seroconversion rate (range 0.9-1.7%). A striking geographical variation in seroprevalence and seroconversion rates of anti-HCV was observed in the study townships. Furthermore, a significant geographical correlation between HCV seroprevalence and seroconversion rates was noted (r = 0.962, P = 0.001). From the results of both prevalent and incident case-control comparisons, medical injections were found to be the main mode to sustain the persistent endemic state of HCV infection within a community (odds ratios for prevalent and incident case-control studies were 2.5 (95% CI = 1.7-3.6) and 3.1 (95% CI = 1.4-7.1), respectively. The data indicate that the basis for HCV transmission has already been existed in study areas and the iatrogenic risk factor tended to be the major determinant for sustaining persistent endemicity within a community.

Adult↗

PubMed2001

Replantation of the thumb, especially avulsion.

In replantation for avulsion amputation of the thumb, high survival rate of replanted digits depends on good debridement, good arterial repair with vein grafts or neurovascular bundles, and good coverage, with loose closure of the wound. The functional success depends on liberal use of nerve and tendon grafts or transfer; subsequent procedures, such as tenolysis and opponensplasty; and backup procedures for cases with severe soft tissue avulsion or long ischemic periods. All thumb amputations should be explored in the operating room for evaluation of replantability. If it is still questionable, an experienced microsurgeon should be consulted to choose between replantation and an alternative reconstructive procedure.

Adolescent↗

PubMed2001

[Expression of the gE gene of pseudorabies virus in insect cells].

In order to develop a simple and safe test for the detection of vaccinated as well as wild type Pseudorabies virus (PRV) infected pigs, the modified gE gene of PRV Ea strain, obtained by cutting the 5' UTR using PCR and DNA recombinant technique, was inserted into baculovirus expression vector pFastBac 1, resulting the trans-position plamid pFE1.75. After homologous recombination, recombinant baculovirus rvBacE1.75 was gained and high level expression of glycoprotein E (gE) was observed after the infection of rvBacE1.75 to Tn-5B1-4 cells. The expression product was 80-88 kD and was specific to antisera against PRV Ea strain by Western-blotting. Purified recombinant proteins were used as an antigen in Latex Agglutination Test(gE-LAT) and the test was specific, sensitive, safe and simple.

Animals↗

PubMed2001

Sequential changes of gastric hyperplastic polyps following endoscopic ligation.

BACKGROUND: Endoscopic ligation has been extensively applied in the management of esophageal and gastric varices with or without bleeding. The varices are automatically eradicated through the use of ligation. However, whether avascular necrosis will occur in a gastrointestinal polyp when the base is ligated remains unclear. The aims of this pilot study were to investigate the sequential changes of gastric hyperplastic polyps following endoscopic detachable snare ligation and to determine the possibility of induction of avascular necrosis in these lesions following ligation. METHODS: Eleven patients with eighteen gastric hyperplastic polyps were treated with endoscopic detachable-snare ligation. The polyps were observed for 5 minutes and biopsies were then conducted. At 14 days after endoscopic ligation, follow-up endoscopies were performed to assess the outcome of the strangulated polyps. RESULTS: After being strangulated by the detachable snares, a majority of the polyps immediately congested (94%), and then developed cyanotic change (89%) approximately 4 minutes later. Pathological examination revealed severe venous congestion in the lamina propria of the strangulated polyps. On follow-up endoscopy 2 weeks later, all the snares had dropped off, and avascular necrosis occurred in sixteen polyps (89%). All of the polyps with avascular necrosis were detected to have developed cyanotic changes in initial endoscopy. No complications occurred during or following the ligation procedure. CONCLUSIONS: Most gastric hyperplastic polyps develop avascular necrosis following ligation by detachable snare. Cyanotic change is an important predictor of the outcomes of the lesions following endoscopic ligation. The application of this ligation technique in treatment of bleeding or non-bleeding gastrointestinal polyps deserves further investigation.

Adolescent↗

PubMed2000

[Influence of IFN-alpha and IFN-alpha combined with GM-CSF on expression of the genes related to cell apoptosis of MNCs from bone marrow in CML patients].

OBJECTIVE: To investigate the effects of interferon-alpha(IFN-alpha) and IFN-alpha combined with granulocytic macrophage colony-stimulating factor(GM-CSF) on expression of bcr-abl, bcl-2 and c-myc genes in the mononuclear cells(MNCs) from bone marrow(BM) of the patients with chronic myelogenous leukemia at chronic phase(CML-CP). METHODS: The MNCs were collected from bone marrow of 14 CML-CP patients by centrifugalization in lymphocyte-separation medium, and cultivated in the medium with IFN-alpha and IFN-alpha plus GM-CSF for 24 hours. The expression levels of bcr-abl, bcl-2, c-myc and beta-actin were detected by using relatively quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and optical density scanning technology for the amplified fragments. The statistical differences between each inducing experimental group and the control were analyzed by t-test in pairs. RESULTS: Both IFN-alpha (200 U.ml-1) and IFN-alpha combined with GM-CSF (10 ng.ml-1) significantly inhibited bcr-abl gene expression, meanwhile IFN-alpha partially suppressed c-myc and bcl-2 gene expression, and GM-CSF significantly inhibited bcl-2 gene expression but partially upregulated bcr-abl and c-myc gene expression levels on the basis of IFN-alpha effects. CONCLUSIONS: Both IFN-alpha and IFN-alpha plus GM-CSF can inhibit the expression of anti-apoptosis gene such as bcr-abl and bcl-2, and regulate the expression of c-myc. It is the possible mechanism of IFN-alpha therapy or combined therapy on CML at chronic phase that the malignant clone expansion is inhibited by promoting apoptotic cell death.

Bone Marrow Cells↗

PubMed2000

Tyrosine kinases and gastric cancer.

Carcinoma of the stomach is one of the most prevalent cancer types in the world today. Two major forms of gastric cancer are distinguished according to their morphological and clinicopathological classifications (well differentiated/intestinal type and poorly differentiated/diffuse type), characteristics that could also be attributed to the altered expression of different types of oncogenes or tumor suppressor genes. Significant differences exist for gastric cancer incidence comparing people of different ethnic origins, implicating various genetic and epigenetic factors for gastric oncogenesis. There are only a limited number of molecular markers available for gastric cancer detection and prognostic evaluation, among which are tyrosine kinases. There is convincing evidence that tyrosine kinases are involved in oncogenesis and disease progression for many human cancers. Amplifications of certain tyrosine kinases (c-met, k-sam and erbB2/neu) have been associated with human gastric cancer progression. Alternatively spliced transcripts and enhanced protein-expression levels for some of these tyrosine kinases are correlated with clinical outcomes for gastric cancer patients. With advent of high throughput techniques, it is now possible to detect nearly all expressed tyrosine kinases in a single screen. This increases the chance to identify additional tyrosine kinases as predictive markers for gastric cancers. In this article, we will first review the literature data concerning certain tyrosine kinases implicated in gastric carcinogenesis and then summarize more recent work which provide comprehensive tyrosine kinase profiles for gastric cancer specimens and cell lines. Two new gastric cancer molecular markers (tie-1 and mkk4) have been identified through the use of these profiles and demonstrated effective as clinical prognostic indicators.

Humans↗

PubMed2000

Altering expression of alpha3beta1 integrin on podocytes of human and rats with diabetes.

The adhesion molecule integrin alpha3beta1 is the major receptor of podocyte to the glomerular capillary basement membrane (GBM). Since progressive alteration of the glomerular extracellular matrix (ECM) compartment leading to GBM thickening is common in diabetic nephropathy, we investigated the cellular distribution of alpha3beta1 integrin in podocytes of patients with diabetic nephropathy and streptozotocin-induced diabetic rats, and we evaluated the effects of high glucose on the cultured rat podocytes. Both human and rat kidneys were stained using the immunoelectron microscopy and immunoperoxidase technique with mouse monoclonal antibodies to human integrin alpha3 subunit. The results showed that both the number of immunogold particles and the staining of integrin alpha3 subunit on podocytes were weaker in patients with diabetic nephropathy than those of control kidneys. The staining of alpha3 on podocytes in the poorly-controlled diabetic rats was also weaker after one and three months of hyperglycemia. However, the staining was identical to controls in rats with only one week of hyperglycemia. High glucose (25 mM) but not streptozotocin in vitro suppressed the alpha3 expression of cultured rat podocytes. Our results demonstrated that the expression of integrin alpha3beta1 on podocytes was suppressed in both human and rats with diabetes, possibly due to the effects of hyperglycemia, and the suppression became more severe with the duration of diabetes.

Adult↗

PubMed2000

Taxol reduces cytosolic E-cadherin and beta-catenin levels in nasopharyngeal carcinoma cell line TW-039: cross-talk between the microtubule- and actin-based cytoskeletons.

Taxol affects microtubule dynamics by promoting microtubule assembly. To obtain a better insight into possible cross-talk between the microtubule- and actin-based cytoskeletons, we studied the short-term effects of Taxol treatment on the expression of actin and the E-cadherin/catenin complex in the nasopharyngeal carcinoma cell line TW-039 using immunofluorescence, immunoprecipitation, and immunoblotting methods. Morphologic changes in actin filaments, including ventral actin clumps and perijunctional actin blebs, were seen at Taxol concentrations > or =1 microM. Levels of detergent-soluble E-cadherin fell to 53% or 58% compared to controls in cells treated, respectively, with 1 or 5 microM Taxol, while levels of detergent-soluble beta-catenin fell to 76% or 74%. Levels of the detergent-soluble pool of alpha- and gamma-catenin and the detergent-insoluble pool of the E-cadherin/catenin complex were unchanged by Taxol treatment and no significant difference was seen in the levels of adenomatous polyposis coli or glycogen synthase-3beta or tyrosine phosphorylation patterns. These results suggest that modulation of microtubule dynamics by Taxol may have effects on the expression of actin and the cytosolic E-cadherin and beta-catenin in nasopharyngeal carcinoma cells through pathways not involving the phosphorylation of beta-catenin.

Actins↗