Biomedical subjects

Y C Chang

Publications and source records attributed to Y C Chang.

At least 91 records · Page 5Linked to original sources

PubMed2000

Rapid separation of lysozyme from chicken egg white by reductants and thermal treatment.

Reductants (0.1-2.0% ascorbic acid, cysteine, or cystine and 0.04-1. 0% beta-mercaptoethanol) were added to 5-fold diluted, salted duck egg whites (commercially and laboratory prepared) and fresh egg whites (chicken and duck), and subsequently the mixtures were heated at 70 degrees C for 1-10 min. The maximal recovery and purification fold of lysozyme obtained from fresh chicken egg whites added with 1. 0% ascorbic acid were 78% and 2.4, respectively. Storage tests showed that the obtained lyophilized lysozyme powder after dialysis was stable when refrigerated at 4 degrees C for 3 months.

Animals↗

PubMed2000

New alkaloids from Annona purpurea.

Three new alkaloids, promucosine (1), romucosine F (2), and romucosine G (3), along with 28 known compounds, were isolated from the MeOH extract of stems of Annona purpurea. The structures of 1-3 were determined on the basis of spectral data and chemical evidence.

Alkaloids↗

PubMed2000

Butachlor, a suspected carcinogen, alters growth and transformation characteristics of mouse liver cells.

Butachlor is a widely used herbicide in Asia and South America. Previous investigations have indicated that it is a suspected carcinogen. To understand more about the biological effects of butachlor on cultured cells and the mechanism(s) of its carcinogenicity, we studied the alteration of the growth characteristics that was induced by butachlor in normal mouse liver cells (BNL CL2). This study demonstrates that butachlor decreases the population-doubling time of BNL CL2 cells, suggesting that it stimulates cell proliferation. To support this finding, a thymidine incorporation assay was conducted and a similar result that butachlor stimulates cell proliferation was elucidated. In addition, we show that butachlor increases the saturation density of the BNL CL2 cells. When combined with the tumor initiator N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), butachlor transforms cells efficiently, as demonstrated by loss of contact inhibition. These findings indicate that butachlor alters the growth characteristics of BNL CL2 cells and suggest that butachlor may induce malignant transformation through stimulation of cell proliferation, alteration of cell cycle regulation, and suppression of cell density-dependent inhibition of proliferation.

Acetanilides↗

PubMed2000

Expression of Bcl-2 inhibited Fas-mediated apoptosis in human hepatocellular carcinoma BEL-7404 cells.

Apoptosis plays an important role in embryonic development, tissue remodeling, immune regulation and tumor regression. Two groups of molecules (Bcl-2 family and "Death factor" family) are involved in regulating apoptosis. In order to know about the effect of Bcl-2 on apoptosis induced by Fas, a typical member of "Death factor" family, the transfection experiments with expression vectors pcDNA3-fl and pcDNA3-bcl-2 were performed in BEL-7404 cells, a human hepatocellular carcinoma cell line which expresses endogenous Fas, but not FasL and Bcl-2. The data showed that the expression of FasL in pcDNA3-fl transfected hepatoma cells obviously induced the apoptosis of the cells. However, the overexpression of Bcl-2 in pcDNA3-bcl-2 transfected 7404/b-16 cells counteracted pcDNA3-fl transient transfection mediated apoptosis. Further study by co-transfection experiments indicated that Bid but not Bax (both were pro-apoptotic proteins of Bcl-2 family) blocked the inhibitory effect of Bcl-2 on Fas-mediated apoptosis. These results suggested that Fas-mediated apoptosis in human hepatoma cells is possibly regulated by Bcl-2 family proteins via mitochondria pathway.

Apoptosis↗

PubMed2000

Identification of a pre-S2 mutant in hepatocytes expressing a novel marginal pattern of surface antigen in advanced diseases of chronic hepatitis B virus infection.

BACKGROUND AND AIMS: The expression of hepatitis B viral (HBV) antigens in liver tissue reflects the replicative status of chronic HBV infection. We have previously recognized a novel marginal pattern of hepatitis B surface antigen (HBsAg) in hepatocytes, which usually clusters in groups and emerges at the late non-replicative phase. This study was designed to investigate whether the marginal-type HBsAg represented the gene product of a specific HBV-surface mutant. METHODS: Microdissection of cirrhotic nodules homogeneously expressing marginal HBsAg was performed on two of 12 resected livers from HBsAg-seropositive patients with hepatocellular carcinoma. The gene presumably encoding marginal HBsAg was polymerase chain reaction (PCR)-cloned, sequenced and analysed. In vitro transfection and expression of the cloned surface mutant plasmids were performed on the Huh7 cell line to illustrate intrahepatic HBsAg expression. RESULTS: Immunohistochemical staining revealed that the marginal HBsAg was positive for pre-S1 and thus contained large surface proteins. The PCR cloning and sequencing of the genes presumably encoding marginal-type HBsAg in both cases revealed the same deletion at the 5' terminus (nt 2-55) of pre-S2. A point mutation on the small-surface (S) antigen was also found in one case. The pre-S2 deletion sequence and the mutation sites of the S gene coincide with human lymphocyte antigen-restricted T- and/or B-cell epitopes. In vitro transfection of the mutant plasmid revealed a blot-like retention or accumulation of HBsAg in the cytoplasm or at the periphery of hepatocytes, accompanied by a decreased secretion of HBsAg in the culture supernatant, mimicking intrahepatic expression. CONCLUSION: A natural pre-S2 deletion mutant was identified in hepatocytes expressing a novel marginal pattern of HBsAg, which probably contains mutant, large, surface proteins. The biological significance of the pre-S2 deletion mutant should be interesting in view of the clustering proliferation of hepatocytes expressing marginal HBsAg.

Female↗

PubMed2000

Carbon urea breath test is not as accurate as endoscopy to detect Helicobacter pylori after gastrectomy.

BACKGROUND: This study was conducted to determine (1) whether Helicobacter pylori infection decreases in conjunction with time elapsed after gastrectomy and (2) the diagnostic efficacy of (13)C urea breath test (UBT) for H pylori in patients after gastrectomy. METHODS: From January 1997 to June 1998, 86 patients who had undergone gastrectomy and 180 patients with dyspepsia without gastrectomy were enrolled. A UBT for the analysis of excess (13)CO(2)/(12)CO(2) ratio (ECR) was obtained for each patient. Each patient also underwent endoscopy to obtain gastric biopsies for histology and H pylori culture. The presence of H pylori by either histology or culture served as the standard to test the efficacy of UBT. The 86 patients with a prior gastrectomy were categorized into 3 subgroups (I, less than 1 year; II, 1 to 3 years; III, greater than 3 years), according to the interval between surgery and UBT. The initial H pylori status of these 86 patients was determined by histologic evaluation of the resected stomach. RESULTS: At trial initiation, the postgastrectomy group had a lower H pylori infection rate (52.3%) as compared with the dyspeptic control group (80%). The initial H pylori status among subgroups I, II, and III was similar. There was a trend for the presence of H pylori in the stomach to decrease with increasing time elapsed after surgery (I to III: 68.8%, 48.3%, 36%, respectively; p < 0.05). The maximum UBT sensitivity and specificity achieved were 82.2% and 87.8% in the gastrectomy group and 97.2% and 96.3% in the dyspeptic group, with cutoff points of 2.5 and 4.0, respectively. CONCLUSION: The prevalence of H pylori diminishes with time elapsed after gastrectomy. UBT for detection of H pylori is more effective in patients without prior gastrectomy than in patients who have undergone gastrectomy and is less effective than endoscopy for patients who have had a gastrectomy.

Biopsy↗

PubMed2000

Cytotoxicity evaluation of perforation repair materials on human periodontal ligament cells in vitro.

Perforation of a tooth structure resulting in communication of the pulp space with periodontium occasionally occurs during endodontic therapy. For the best prognosis, the perforation area must be sealed as soon as possible. Because these materials will be in direct contact with periodontal tissues, their cytotoxic potential must be evaluated before clinical use. The purpose of this study was to determine the cytocompatibility of three perforation repair materials (amalgam, resin, and glass ionomer). Cultured human periodontal ligament (PDL) cells were used to evaluate the cellular response resulting from these materials by cell viability and proliferation assays. Twenty-seven 5 x 4 mm cylinders of each material were fabricated for this study. All tested materials were cytotoxic to human PDL cells. Both types of material and time affected cell viability and proliferation. Resin exhibited the most cytotoxic effects followed by glass ionomer and amalgam during a 14-day incubation period. Amalgam and glass ionomer slightly inhibited cell viability and growth in the first 24 hr, compared with the control. Amalgam or glass ionomer may initially react more favorably to PDL cells than resin. The present model of cultured human PDL cells is simple, relatively cheap, and easily established and propagated under standardized conditions in any laboratory. Furthermore, this method allows long-term observation of human cellular reactions and thus might be a preliminary screening test for initial biocompatibility of dental materials.

Analysis of Variance↗

PubMed2000

Cytotoxic and nongenotoxic effects of phenolic compounds in human pulp cell cultures.

Phenolic compounds are widely used in clinical dentistry as sedatives for the dental pulp, as disinfectants for caries, and as root canal medications. The pathobiological effects of various phenolic compounds on human dental pulp fibroblasts were investigated with Hoechst 33258 fluorescence assay and DNA precipitation assay. All phenolic compounds showed cytotoxicity in Hoechst 33258 fluorescence assay by inhibiting cellular DNA in a concentration-dependent manner. The 50% inhibition concentrations required to decrease the cellular DNA contents by guaiacol, phenol, eugenol, and thymol were 9.8, 4.5, 0.9, and 0.5 mM, respectively. However these phenolic compounds did not cause DNA single-strand breaks in cultured human pulp fibroblasts. These results indicate that phenolic compounds are cytotoxic agents but are without genotoxic effects on human pulp fibroblasts in vitro. However care should be taken to reduce the possibility of pulpal as well as periapical irritations from inadvertent extrusion of these substances in clinical usage.

Bisbenzimidazole↗

PubMed2000

Neurocognitive attention and behavior outcome of school-age children with a history of febrile convulsions: a population study.

PURPOSE: A prospective population-based case-control study was performed to ascertain whether febrile convulsion (FC) in early childhood is associated with neurocognitive attention deficits in school age. METHODS: A total of 103 children, confirmed to have FC by age 3 years from a population survey of 4,340 live-birth newborns in Tainan City, Taiwan, was followed up until at least age 6 years. An achievement test, behavioral ratings, and computerized neurocognitive battery assessing various subcomponents of attention were given to 87 FC children (FC group) and 87 randomly selected population-matched control (CC group). RESULTS: Compared with the CC group, the FC group did not have scholastic performance or behavioral outcome disadvantage. Overall FC group performance was distinguished by significantly higher scores in the achievement test and fewer missing errors (p < 0.005) and commission errors (p < 0. 05), less variability in reaction time (p < 0.005), and a nonsignificant trend of impulsivity. Attention performance of the FC and CC groups were comparable. Within the FC group, age at onset, complex FC, recurrence of FC, development of unprovoked seizures, or prior use of phenobarbital had no adverse effects on neurocognitive attention outcome. CONCLUSIONS: This population study suggests that FC in early childhood does not have adverse effects on behavior, scholastic performance, and neurocognitive attention. On the contrary, the FC group demonstrated significantly better control of distractibility and attention at school age.

Achievement↗

PubMed2000

Properties of various Rho1 mutant alleles of Cryptococcus neoformans.

The RHO1 homologue of Cryptococcus neoformans complemented Saccharomyces cerevisiae rho1 mutations. The results of overexpression and site-specific mutagenesis of CnRHO1 in C. neoformans and S. cerevisiae indicated that although CnRHO1 could functionally substitute for the RHO1 gene of S. cerevisiae, mutants of cnrho1 manifested unique features in certain aspects.

Alleles↗

PubMed2000

Characterization of the distal tail fiber locus and determination of the receptor for phage AR1, which specifically infects Escherichia coli O157:H7.

Phage AR1 is similar to phage T4 in several essential genes but differs in host range. AR1 infects various isolates of Escherichia coli O157:H7 but does not infect K-12 strains that are commonly infected by T4. We report here the determinants that confer this infection specificity. In T-even phages, gp37 and gp38 are components of the tail fiber that are critical for phage-host interaction. The counterparts in AR1 may be similarly important and, therefore, were characterized. The AR1 gp37 has a sequence that differs totally from those of T2 and T4, except for a short stretch at the N terminus. The gp38 sequence, however, has some conservation between AR1 and T2 but not between AR1 and T4. The sequences that are most closely related to the AR1 gp37 and gp38 are those of phage Ac3 in the T2 family. To identify the AR1-specific receptor, E. coli O157:H7 was mutated by Tn10 insertion and selected for an AR1-resistant phenotype. A mutant so obtained has an insertion occurring at ompC that encodes an outer membrane porin. To confirm the role of OmpC in the AR1 infection, homologous replacement was used to create an ompC disruption mutant (RM). When RM was complemented with OmpC originated from an O157:H7 strain, but not from K-12, its AR1 susceptibility was fully restored. Our results suggest that the host specificity of AR1 is mediated at least in part through the OmpC molecule.

Bacteriophages↗

PubMed2000

Mapping of the Cryptococcus neoformans MATalpha locus: presence of mating type-specific mitogen-activated protein kinase cascade homologs.

In this study we investigated the relationship between the MATalpha locus of Cryptococcus neoformans and several MATalpha-specific mitogen-activated protein (MAP) kinase signal transduction cascade genes, including STE12alpha, STE11alpha, and STE20alpha. To resolve the location of the genes, we screened a cosmid library of the MATalpha strain B-4500 (JEC21), which was chosen for the C. neoformans genome project. We isolated several overlapping cosmids spanning a region of about 71 kb covering the entire MATalpha locus. It was found that STE12alpha, STE11alpha, and STE20alpha are imbedded within the locus rather than closely linked to the locus. Furthermore, three copies of MFalpha, the mating type alpha-pheromone gene, a MATalpha-specific myosin gene, and a pheromone receptor (CPRalpha) were identified within the locus. We created a physical map, based on the restriction enzyme BamHI, and identified both borders of the MATalpha locus. The MATalpha locus of C. neoformans is approximately 50 kb in size and is one of the largest mating type loci reported among fungi with a one-locus, two-allele mating system.

Chemoreceptor Cells↗

PubMed2000

Detection of human cytomegalovirus retinitis and monitoring of ganciclovir treatment using conjunctival swab with polymerase chain reaction in AIDS patients.

This report studies the accuracy of conjunctival swab polymerase chain reaction (CS-PCR) for the diagnosis of human cytomegalovirus retinitis (HCMV) in AIDS patients. PCR and virus culture were used for the detection of HCMV in conjunctival swab, serum, and urine specimens from 38 AIDS patients between April 1996 and April 1998. The clinical utility of the identification of HCMV retinitis by these 6 different methods was demonstrated by their prediction power to estimate AIDS patients at risk of contracting HCMV retinitis. The sensitivity, specificity, positive predictive value, and negative predictive value of CS-PCR for the detection of HCMV retinitis were 91.5%, 80.9%, 60.8%, and 92.7%, respectively; for serum PCR were 74.3%, 81.7%, 57.2%, and 90.3%; for urine PCR were 100%, 17.3%, 20.4%, and 100%; for conjunctival swab culture were 22.7%, 100%, 100%, and 86%; for serum culture were 27.3%, 98.1%, 75%, and 86.4%; and for urine culture were 90.9%, 44.2%, 25.6%, and 95.8%.

AIDS-Related Opportunistic Infections↗

PubMed2000

Molecular cloning and characterization of rpbA encoding RNA polymerase II largest subunit from a filamentous fungus, Aspergillus oryzae.

We have cloned rpbA encoding the RNA polymerase II largest subunit (polIIL) from a filamentous fungus, Aspergillus oryzae. The rpbA product included eight highly conserved regions and the carboxyl-terminal domain (CTD). A. oryzae polIIL CTD with 184 amino acids was composed of 25 CTD consensus repeats, which was a similar number to those of lower eukaryotes. The amino acids in each repeat of A. oryzae polIIL, however, conformed less to the CTD consensus than those of polIILs from other lower eukaryotes.

Amino Acid Sequence↗

PubMed2000

Gamma knife radiosurgery as a primary treatment for prolactinomas.

OBJECT: The purpose of this study was to estimate the efficacy of gamma knife radiosurgery (GKS) in controlling tumor growth and endocrinopathy associated with prolactinomas. METHODS: Between 1993 and 1997, 164 of 469 patients with pituitary adenomas treated by GKS harbored prolactinomas. The dose to the tumor margin ranged from 9 to 35 Gy (mean 31.2 Gy), and the visual pathways were exposed to a dose of less than 10 Gy. The mean tumor diameter was 13.4 mm. The mean follow-up time for 128 cases was 33.2 months (range 6-72 months). Tumor control was observed in all but two patients who underwent surgery 18 and 36 months, respectively, after GKS. Clinical cure was achieved in 67 cases. Clinical improvement was noted with a decrease in the hyperprolactinemia after GKS. Nonetheless, in 31 (29%) of 108 patients who were followed for more than 2 years no improvement in serum prolactin levels was demonstrated, although this could be normalized by bromocriptine administration after treatment. Nine infertile women became pregnant 2 to 13 months after GKS and all gave birth to normal children. There was no visual deterioration related to GKS. Five women experienced premature menopause. In these patients there was subtotal disappearance of the tumor and an empty sella developed. CONCLUSIONS: Gamma knife radiosurgery as a primary treatment for prolactinomas can be safe and effective both for controlling tumor growth and for normalization of prolactin hypersecretion. A higher margin dose (> or = 30 Gy) seemed to be associated with a better clinical outcome. Gamma knife radiosurgery may make prolactinomas more sensitive to the bromocriptine.

Humans↗

PubMed2000

Right-sided pleural effusion in spontaneous esophageal perforation.

Spontaneous esophageal perforation (Boerhaave's syndrome) is a rare clinical entity in which overindulgence in a large meal precedes vomiting and chest pain. Early diagnosis and aggressive management are keys to minimizing the morbidity and mortality. We report an unusual presentation of this already uncommon occurrence in a 33-year-old female. She presented to the Emergency Department with severe chest pain following vomiting with hematemesis after a large meal. The initial chest radiograph showed up nothing in particular. Dyspnea developed two days later, and a right-sided pleural effusion was seen on chest x-ray. Panendoscopy was highly suggestive of Boerhaave's syndrome. She underwent emergency operation. After three months of hospital care, she was discharged in relatively good condition. This case of right-sided pleural effusion extends the reported description of Boerhaave's syndrome.

Adult↗

PubMed2000

Swyer-James syndrome complicated by lung abscess.

Swyer-James syndrome, a rare disease with unilateral hyperlucent lung due to bronchiolitis obliterans and pulmonary artery hypoplasia, generally develops after lower respiratory tract infection during early childhood. Invasive procedures, including bronchoscopy and angiography, are often necessary for a definitive diagnosis. We report a 17-year-old man admitted because of cystic bronchiectasis complicated by lung abscess. Chest roentgenography showed the typical findings of Swyer-James syndrome. Noninvasive magnetic resonance angiography was used to confirm hypoplasia of the right pulmonary artery. The patient received antibiotic therapy, underwent a right lower lobectomy for the lung abscess, and recovered.

Adolescent↗

PubMed2000

Endometrial stromal sarcoma of the vagina.

Endometrial stromal sarcoma is a rare tumor and has unique histopathologic features. Most tumors of this kind occur in the uterus; thus, the vagina is an extremely rare site. A 34-year-old woman presented with endometrial stromal sarcoma arising in the vagina. No correlative endometriosis was found. Because of the uncommon location, this tumor was differentiated from other more common neoplasms of the vagina, particularly embryonal rhabdomyosarcoma and other smooth muscle tumors. Although the pathogenesis of endometrial stromal tumors remains controversial, the most common theory of its origin is heterotopic Müllerian tissue such as endometriosis tissue. Primitive cells of the pelvis and retroperitoneum are an alternative possible origin for the tumor if endometriosis is not present. According to the literature, the tumor has a fairly good prognosis compared with other vaginal sarcomas. Surgery combined with adjuvant radiotherapy appears to be an adequate treatment.

Adult↗