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Y K Chen

Publications and source records attributed to Y K Chen.

At least 37 records · Page 2Linked to original sources
PubMed2000

Immunohistochemical expression of inducible nitric oxide synthase in DMBA-induced hamster buccal pouch carcinogenesis.

Nitric oxide (NO) plays a key role in the processes of inflammation and carcinogenesis. Three isoforms of NO synthase have been identified: endothelial nitric oxide synthase (NOS), neuronal NOS, and inducible NOS (iNOS). The purpose of this study was to investigate the characteristics of iNOS in 7, 12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Thirty outbred young (6-week-old) male Syrian golden hamsters were randomly divided into three groups: DMBA (0.5%) painted group (n=10); mineral oil-treated group (n=10); and non-treated group (n=10). The average number of iNOS positive foci per section in the DMBA-treated group was approximately 12.2+/-4.7. Both cytoplasmic and nuclear stainings were observed in the DMBA-treated pouch keratinocytes. No iNOS activity could be detected in the untreated or mineral oil-treated pouches. In conclusion, this study has demonstrated that iNOS is expressed in DMBA-induced hamster pouch carcinomas. This finding suggests that iNOS expression may be associated with the development of chemically induced oral carcinomas.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2000

Glandular odontogenic cyst: a case report.

Glandular odontogenic cyst (GOC) is an extremely rare lesion occurring in the jawbones. Sialo-odontogenic cyst was first described as a multicystic lesion resembling a botryoid odontogenic cyst (BOC) or a central mucoepidermoid carcinoma by Padayachee in 1987. In 1988, Gardner used the term "glandular odontogenic cyst" and considered it as a histologic variant of BOC. Most authors agreed that GOC was odontogenic because of the concurrent ball-like epithelial structure, ameloblastoma, squamous odontogenic tumor-like proliferation in its wall, or hyaline bodies in the epithelium lining. Recently, immunohistochemical studies of the cytokeratin profiles have also supported this concept. Its aggressive behavior and the recurrent tendency make it important. A new case of GOC in a 59-year-old male presented as a multilocular radiolucency in the anterior region of the mandible, invading the marrow space by epithelial islands is described with other clinicopathologic features and the literature is briefly discussed.

Humans↗
PubMed1999

Structure and genomic organization of porcine RACK1 gene.

The cDNA encoding porcine RACK1 protein was isolated from porcine spleen cDNA library. The deduced protein sequence of porcine RACK1 cDNA shows that it contains 317 amino acid residues, and shares nearly 100% identity with its vertebrate counterparts. Noticeably, the RACK1 protein was differentially expressed in various porcine tissues. High expression of RACK1 protein was observed in the tissues including thymus, pituitary, spleen and liver, whereas there was no detectable expression in muscle. The genomic DNA of porcine RACK1 with approximate 7.5 kb was constructed by both polymerase chain reaction amplification and genomic library screening. It consists of eight exons intervened by seven introns, and most of the intron/exon splice sites conform to the GT/AG rule. The promoter region contains functional serum response element, YY1-like binding site and AP1 site, which is supported by the finding that the expression of RACK1 gene in cultured porcine ST cells has a serum response as well as a TPA response.

Amino Acid Sequence↗
PubMed1999

Placental glutathione S-transferase isoenzyme expression during promotion of two-stage hamster cheek-pouch carcinogenesis.

Glutathione S-transferases (GSTs) are the products of a multigene family. A well-established function of GSTs is to metabolize carcinogens by catalysing the conjugation of electrophilic substrates to glutathione. Whether placental GST (GST-P) is expressed during the promotion of two-stage hamster buccal-pouch mucosa (HBPM) carcinogenesis was investigated here, using 7,12-dimethylbenz[a]anthracene (DMBA) as the initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as the promoter. Cytoplasmic and nuclear staining for GST-P was seen in pouches treated with DMBA for 4 or 16 weeks, as well as in those treated with DMBA for 4 weeks and then TPA for 12 weeks. No GST-P positivity was seen in any pouches treated with only TPA or with mineral oil for either 4 or 16 weeks. The average number of GST-P-stained foci in the groups treated with DMBA for 16 weeks (246 +/- 96; mean +/- SD) or DMBA for 4 weeks followed by TPA for 12 weeks (186 +/- 67) was significantly higher than in pouches treated with only DMBA for 4 weeks (97 +/- 24). These results demonstrate that TPA alone is not sufficient for GST-P expression in hamster buccal pouch mucosa. However, after being initiated with DMBA, then promoted with TPA, GST-P activity is induced in hamster buccal pouch mucosa during squamous-cell carcinogenesis. This underpins the suggestion that GST-P may play an important part during the promotion stage of oral carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Successful reversal of Barrett's esophagus with multipolar electrocoagulation despite inadequate acid suppression.

BACKGROUND: Barrett's epithelium is a risk factor for esophageal cancer. In this study we attempted to reverse Barrett's epithelium in an acid-reduced environment by using multipolar electrocoagulation. METHODS: All patients had specialized columnar epithelium of at least 2 cm in length. Patients with dysplasia on successive screening examinations were excluded. Esophageal motility and 24-hour pH studies were performed before therapy and at 9 and 18 weeks. All patients received lansoprazole 30 mg twice a day regardless of pH study results. Multipolar electrocoagulation was applied to one side of the esophagus (2 to 3 cm per session) with the contralateral side serving as control. Biopsies were obtained from each 2 cm length at each endoscopy and reviewed by a single, blinded pathologist. At the 9-week evaluation of the treatment side, all patients elected to undergo multipolar electrocoagulation therapy for the control side. RESULTS: Twenty-seven patients completed the study: 21 men and 6 women, ages 33 to 81 years, length of specialized columnar epithelium 2 to 10 cm. Endoscopy at the 18-week follow-up showed normal mucosa (n = 16), residual small (< 3 mm) islands or tongue-shaped extensions of apparent specialized columnar epithelium (n = 7), untreated distal strips (< 5 mm) of apparent specialized columnar epithelium at the gastroesophageal junction (n = 3), and persistent specialized columnar epithelium (n = 1). Histologically, only 5 of 27 patients had residual specialized columnar epithelium at week 18. Of 16 patients with a normal endoscopic appearance, one still had specialized columnar epithelium on biopsy. While on lansoprazole, pH studies were normal in 15 of 26 patients at 9 weeks. Of 22 patients with histologic evidence of specialized columnar epithelium reversal, 10 had persistently abnormal 24-hour pH studies (pH < 4, 6.1% to 33.7% of total time). Four of five patients with residual specialized columnar epithelium on biopsy had persistent reflux. Side effects of multipolar electrocoagulation were transient, and treatment did not adversely alter motility patterns. CONCLUSIONS: Multipolar electrocoagulation therapy can induce re-epithelialization with normal squamous mucosa in most patients with specialized columnar epithelium and does not adversely affect esophageal motility. Adequate acid suppression is not mandatory for therapy to be effective in the short term.

Adult↗
PubMed1999

Impact of flumazenil on recovery after outpatient endoscopy: a placebo-controlled trial.

BACKGROUND: Flumazenil is an imidazobenzodiazepine that blocks the central effects of benzodiazepines by competitive interaction at the receptor level. In this study we assessed the impact of flumazenil use on postsedation observation time in outpatients undergoing endoscopy. METHODS: Sixty outpatients received midazolam for conscious sedation and were randomized after endoscopy to receive intravenous flumazenil (0.1 mg/mL) or placebo until awake or a total of 10 mL was given. All patients were assessed using various psychomotor and cognitive tests at baseline and at 5, 15, 30, 45 and 60 minutes after flumazenil or placebo was administered. RESULTS: The two groups were similar in age, gender, midazolam dose (mg/kg), vital signs, and baseline parameters. The average dose of flumazenil given was 0.41 mg. Sedation scores returned to presedation levels earlier in the flumazenil group, with significant differences compared to placebo at 5 minutes (84.6% vs. 24.2%), 15 minutes (88. 5% vs. 57.6%) and 30 minutes (96.2% vs. 66.7%). Other parameters tested were not significantly different for patients receiving placebo compared to those given flumazenil. Sedation scores returned to baseline earlier than other psychomotor and cognitive tests in both groups. Flumazenil reduced the mean observation time from 23.5 minutes to 8.3 minutes (p < 0.0005), a difference of 15.2 minutes (64.7%) based on sedation score. CONCLUSIONS: Flumazenil significantly reduces postsedation observation time. Actual cost savings will vary depending on staff and facility capacity, patient volume, flumazenil cost, and unit cost of observation time.

Adult↗
PubMed1999

Primary oral squamous cell carcinoma: an analysis of 703 cases in southern Taiwan.

We retrospectively analyzed the records of 703 cases of oral squamous cell carcinoma (SCC) collected from 1 January 1985 to 31 December 1996 at a teaching hospital in southern Taiwan, to identify the characteristics of patients and factors associated with survival. There was an overwhelming male predominance (male:female = 15:1). The mean age of the patients was 52. The peak age of oral SCC patients declined from 50 to 59 years in the first six years (1985-1990) and 40-49 years in the last six years (1991-1996). The most common site of oral SCC was the buccal mucosa with 263 patients (37.4%). Most patients (346/703 patients; 49.2%) had stage III cancer. The most common site of occurrence of SCC was the buccal mucosa (263/703 patients; 37.4%), both overall and in patients who chewed betel quid alone or in combination with cigarette smoking and/or alcohol consumption; the tongue was the most common site among patients without any oral habits (18/48 patients; 37.5%). Furthermore, the age of occurrence was on average 6-12 years younger among patients who chewed betel quid than in those who did not. Of the 703 patients, 496 received treatment with surgery, chemotherapy, and/or radiation therapy. Of these, 209 (42.1%) died. The cancer stage significantly influenced mortality: the 5-year survival rate in patients treated from 1985 to 1991 was 72% in those with stage I, 38.9% in those with stage II, 26.7% in those with stage III, and 11.8% in those with stage IV cancer. Six variables were found to significantly affect survival: tumor size, lymph node involvement, surgery, betel quid chewing, staging, and histological differentiation (all p < 0.05, Kaplan-Meier analysis with log rank test). Of these, surgery and cancer stage independently affected survival in a proportional hazards model (both p < 0.0001). Therefore, the early surgical intervention, and the withdrawal from oral habits, especially betel quid chewing, will be advantageous to patients' survival.

Adolescent↗
PubMed1999

High-level disinfection of gastrointestinal endoscopes: are current guidelines adequate?

OBJECTIVE: For a germicide to obtain a high level disinfection (HLD) claim, FDA requires demonstration of a 6-log reduction of mycobacterial inoculum under worst case conditions. The purpose of this study was to assess the adequacy of current guidelines for high level disinfection of GI endoscopes using alkaline glutaraldehyde in simulated-use testing. METHODS: Various gastrointestinal endoscopes were contaminated with Mycobacterium chelonae in 46 experiments. Quantitative cultures were obtained from each endoscope channel separately after each step: inoculation, standardized manual cleaning, immersion in 2% glutaraldehyde (Cidex) for 10, 20, or 45 min at room temperature, 70% isopropanol rinse, and drying. RESULTS: Manual cleaning alone achieved a 4-log reduction. After 10 min of glutaraldehyde exposure, but before alcohol rinse, two of 10 experiments failed to achieve a 6-log reduction. However, after alcohol rinse, all 10 experiments achieved HLD. After 20 min of glutaraldehyde exposure, but before alcohol rinse, one of 18 experiments failed to achieve a 6-log reduction. After alcohol rinse, all 18 experiments achieved HLD. After 45 min of glutaraldehyde exposure, but before alcohol rinse, one of 18 experiments failed to achieve a 6-log reduction. After alcohol rinse, all 18 experiments achieved HLD. Thus, if the entire reprocessing protocol including manual cleaning, glutaraldehyde exposure, alcohol rinse, and drying was taken into account, the required 6-log reduction of mycobacteria was achieved with a minimum of 10 min of glutaraldehyde exposure at room temperature. CONCLUSIONS: Current guidelines for high level disinfection using glutaraldehyde are appropriate. Alcohol rinse is a valuable adjunctive step for drying and for its bactericidal effects.

Disinfectants↗
PubMed1999

Adenomatoid hyperplasia in the mandibular retromolar area. Case report.

This paper reports a case of adenomatoid hyperplasia of minor salivary glands in the retromolar area, with a unique symptom of painful swelling. This appears to be the first reported case in the Chinese population. It would be useful for clinical dentists to be aware of this tumour.

Diagnosis, Differential↗
PubMed1999

Rate and extent of digestion of the ethanol-soluble and neutral detergent-insoluble fractions of corn grain.

The objectives of this study were to partition corn grain into three digestible fractions and to measure the rate of disappearance of these fractions in vitro. Seventeen corn grain samples with varied fiber concentrations were extracted with either 80% ethanol or neutral detergent to obtain estimates of the pool size and digestion kinetics of the A, B1, B2, and C fractions. The carbohydrate soluble in 80% ethanol averaged only 2.6+/-.3% of the DM, although 80% ethanol extracted 7.1+/-1.2% of DM of corn grain. The ethanol-soluble fraction of corn grain contained protein, ether-extractable compounds, and a small amount of ash in addition to carbohydrate. Because of this chemical heterogeneity and because of the small size of the ethanol-soluble fraction, it was not possible to determine the digestion rate of this fraction by measuring gas production. The NDF content of the corn grain was 10.6+/-.7% of DM and was highly digestible (94.6+/-1.4%). The digestible NDF contributed 9.5% of the total gas production from corn grain. Because the size, digestibility, and digestion rate of the digestible NDF fraction varied little among corn grain samples, it is not necessary to routinely analyze the digestion kinetics of the digestible NDF fraction of dried corn grain. An average gas production curve of this fraction can be used as a base to subtract from the total gas production curve to generate the gas production curve of the neutral detergent-soluble fraction for dried, ground corn grain samples.

Detergents↗
PubMed1998

Placental glutathione S-transferase isoenzyme expression in polycyclic aromatic hydrocarbon-induced hamster buccal pouch mucosa.

Placental glutathione S-transferase (GST-P) immunohistochemical activity in polycyclic aromatic hydrocarbon (PAH)-induced hamster buccal pouch mucosa (HBPM) was investigated. Equimolar concentrations of 3,4-benzo[a]pyrene (BP), benz[a]anthracene (BA) and 20-methylcholanthrene (MC) in mineral oil solution were applied three times per week for up to 20 weeks to bilateral pouches of the hamsters. Control pouches were treated with 7,12-dimethylbenz[a]anthracene (DMBA), turpentine and mineral oil, respectively. A significant increase in the number of GST-P foci in the dysplastic pouches was found when compared with the hyperkeratotic and hyperplastic pouches after 5 weeks' DMBA treatment. The average numbers of GST-P positive stainings were significantly higher in DMBA-treated groups than in BP-, BA- and MC-treated groups killed at 5, 20, 30 and 40 weeks. No GST-P positivity was found in any pouches treated with turpentine and mineral oil observed at various periods. These results highlight the carcinogen-specificity of GST-P chemically induced in HBPM and indicate that induction of GST-P in pouch mucosa is linked with the carcinogenic potency of PAHs. The present study underpins the hypothesis that GST-P chemically induced in HBPM is an early marker of ongoing squamous cell carcinogenesis.

Animals↗
PubMed1998

Comparison of two rapid urease tests for detection of Helicobacter pylori infection.

Rapid urease tests are widely used at endoscopy to determine the presence of Helicobacter pylori infection. In this prospective study, we compared the accuracy of two rapid urease tests, CLOtest and PyloriTek, using histology as the gold standard. Histologic staining was performed using both H&E and Giemsa, and all slides were reviewed by a single pathologist who was blinded to the results of the rapid urease tests and endoscopic findings. One hundred two patients were enrolled; their mean age was 59 years (range 16 to 95 years), and there were 45 males and 57 females. Histology confirmed the presence of H. pylori infection in 39% of patients. The proportions of false positives for CLOtest (8.0%) and PyloriTek measured at 1 hr (29.0%) were significantly different (Z = 2.90, P = 0.0038). No significant difference was seen between the proportions of false negatives. We conclude that the clinical usefulness of PyloriTek urease test is limited by its lack of specificity.

Adolescent↗
PubMed1998

Randomized prospective trial of early versus delayed feeding after percutaneous endoscopic gastrostomy placement.

OBJECTIVE: By convention, most clinicians delay feeding through the gastrostomy tube until 24 h after placement. However, evidence is lacking to support the rationale for such a delay in PEG use. This randomized, prospective study was designed to assess the safety of early feeding after PEG placement. METHODS: One hundred-twelve patients referred for PEG were randomized to begin tube feedings at 4 h (group A) or at 24 h (group B) after placement. All patients received prophylactic antibiotics. Full-strength Isocal was administered with the following schedule: day 1, 100 ml every 4 h for six feedings; day 2, 200 ml every 4 h for six feedings. Immediately before each scheduled feeding, gastric residual volume was recorded and the next feeding was withheld if the residual volume was > 50 percent (gastric retention). Patients were evaluated on day 1, day 2, day 7, and day 30 for major and minor complications. RESULTS: The two groups were similar with regard to age, gender, baseline nutritional status, and indications for PEG placement. On the first day of feeding, 14 of 57 patients (25%) in group A, but only five of 55 patients (9%) in group B, had evidence of gastric retention, p = 0.029. The proportion of patients with high gastric residual volumes was not significantly different on day two. In group B, one death occurred because of aspiration of gastric contents on day 2. All other complications were minor and did not differ significantly between the two groups. CONCLUSIONS: Early initiation of PEG feedings is safe, well tolerated, and reduces cost by decreasing hospital stay.

Adult↗
PubMed1998

Efficacy of various disinfectants in killing a resistant strain of Pseudomonas aeruginosa by comparing zones of inhibition: implications for endoscopic equipment reprocessing.

OBJECTIVE: Previous studies have shown that high-level disinfection of GI endoscopes may not be reliably achieved using glutaraldehyde at room temperature. In our laboratory, we have isolated a strain of Pseudomonas aeruginosa that is resistant to disinfection with glutaraldehyde. We compared the bactericidal activity of various disinfectants against this organism. METHODS: One hundred microliters of an overnight culture of this organism was spread onto blood agar plates. Twenty microliters of a disinfectant was placed on a sterile 7-mm filter paper, placed on the blood agar plate, and incubated overnight at 37 degrees C to determine the zone of inhibition for each disinfectant tested. Disinfectants included Cidex, Dispatch, Virahol, OMNI II, Lysol, IodoFive, Lysol I.C. Spray, and Chlorox. The zone of inhibition (i.e., clearing) roughly correlates with the bactericidal strength of the disinfectant. RESULTS: Compared with the glutaraldehyde-containing solution Cidex, the alcohol-containing disinfectants Lysol I.C. Spray and Virahol had the largest mean zones of inhibition (11.33 vs 20.60 and 20.55 mm; p = 0.0001). The hypochlorite compounds Chlorox (1:10 dilution) and Dispatch had mean zones of inhibition similar to that of Cidex (11.08 and 11.25 mm vs 11.33 mm; p = not significant). The phenolic compounds OMNI II and Lysol had mean zones of inhibition smaller than that of Cidex (10.50 and 10.35 mm vs 11.33 mm; p < 0.006), and the phosphoric acid and iodine-containing IodoFive had the smallest mean zone of inhibition (9.70 vs 11.33 mm; p = 0.0001). CONCLUSIONS: The alcohol-containing disinfectants had the largest zones of inhibition against resistant P. aeruginosa. These compounds may be more effective than glutaraldehyde for endoscopic equipment reprocessing.

2-Propanol↗