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Biomedical subjects

Y K Chen

Publications and source records attributed to Y K Chen.

At least 55 records · Page 3Linked to original sources
PubMed1998

Osseous choristoma of oral cavity--report of two cases and review of the literature.

Osseous choristoma of the oral cavity is an extremely rare lesion. Two cases of osseous choristomas of oral cavity, representing two different natures of such lesions are reported. One was situated on the dorsal surface of posterior tongue just anterior to the circumvallate papillae and the other on the right buccal mucosa just below the orifice of the Stensen's duct. To date, about 73 cases of oral osseous choristoma have been reported in the literature including the two present cases, of which, 61 and 8 cases occurred in the tongue and buccal mucosa, respectively. The clinical and microscopic characteristics, and their common sites of these peculiar lesions are presented. The origin and pathogenesis of the lesion are discussed and the literature on the subject is reviewed.

Adult↗
PubMed1997

High-performance liquid chromatographic determination of clindamycin in human plasma or serum: application to the bioequivalency study of clindamycin phosphate injections.

This paper presents an assay of clindamycin phosphate injection in human plasma or serum. A 0.5-ml volume of plasma was used with the internal standard, propranolol. The sample was loaded onto a silica extraction column. The column was washed with deionized water and then eluted with methanol. The eluates were evaporated under nitrogen gas. The residue was reconstituted with the mobile phase and injected onto the high-performance liquid chromatographic system: a 5-micron, 25 cm X 4.6 mm I.D. ODS2 column was used with acetonitrile, tetrahydrofuran and 0.05 M phosphate buffer as the mobile phase and with ultraviolet detection at 204 nm. A limit of quantitation of 0.05 microgram/ml was found, with a coefficient of variation of 11.6% (n = 6). The linear range is between 0.05 and 20.00 micrograms/ml and gives a coefficient of determination (r2) or 0.9992. The method has been successfully applied to the bioavailability study of two commercial preparations of clindamycin phosphate injection (300 mg each) in twelve healthy adult male volunteers.

Adult↗
PubMed1997

Evaluation of glutathione S-transferase activity in human buccal epithelial dysplasias and squamous cell carcinomas.

Glutathione S-transferase (GST) activity and amount of GST alpha, mu and pi isoforms were measured in 40 patients with histopathologically confirmed oral epithelial dysplasia (OED) and squamous cell carcinoma of buccal mucosa. The results were compared with those of normal mucosa in an equal number of age- and sex-matched healthy controls. Mean total GST activities were significantly elevated from normal buccal mucosa for mild OED, moderate OED, severe OED and squamous cell carcinoma. GST activity of value approximating 100 nmol/min/mg distinguished between normal and dysplasia, and of value about 400 nmol/min/mg delineated between dysplasia and squamous cell carcinoma were observed. GST pi was the predominant class in both the diseased and normal buccal mucosa examined. This class pi GST was present at an intracellular concentration, which was significantly higher in diseased buccal mucosa than in normal buccal mucosa. These results indicated that pi class GST was the major form of this enzyme in the cytosolic fraction of oral mucosa. The severity of OED related to squamous cell carcinoma development seemed to increase concomitantly with an increase in the level of this enzyme. Further studies will validate the role of GST pi estimation in predicting the potential malignancy of OED.

Adult↗
PubMed1997

Diurnal variation of gamma-glutamyl transpeptidase activity during DMBA-induced hamster buccal pouch carcinogenesis.

OBJECTIVE: The aim of the present study is to assess the diurnal variation of gamma-glutamyl transpeptidase (GGT) during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis. MATERIALS AND METHODS: The right buccal pouches of 108 Syrian golden hamsters, divided into three experimental groups, were treated three times weekly with 0.5% DMBA in mineral oil over an 11-week treatment regimen. The left buccal pouches were untreated and served as the controls. Within each group, six animals were killed at 4-h intervals (04.00, 08.00, 12.00, 16.00, 20.00 and 24.00) for 24 h. GGT histochemical stain, according to the method of Ruthenberg and coworkers, was applied. The number of GGT-positive foci in the pouch mucosa was recorded at 3, 7 and 11 experimental weeks. RESULT: Diurnal variation of GGT histochemical activity during DMBA-induced hamster buccal pouch carcinogenesis was substantiated in the present study. CONCLUSION: This investigation highlights the importance of the diurnal variation in experimental oral carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1997

Cancer-promoting effect of Taiwan betel quid in hamster buccal pouch carcinogenesis.

OBJECTIVE: To investigate the cancer-promoting effect of Taiwan betel quid in hamster buccal pouch carcinogenesis. MATERIALS AND METHODS: Two hundred and fifty-two non-inbred male adult Syrian golden hamsters were randomly divided into six groups, each containing forty-two animals. A treatment regimen over a 14-week experimental period was employed with six animals per group being killed at seven different periods (every 2 weeks). The right buccal pouch of each animal was painted three times a week with various combinations of 7,12-dimethylbenz[a]anthracene (DMBA), Taiwan betel quid extract, dimethyl sulfoxide (DMSO) and mineral oil. RESULT: Both the number and size of tumors in animals concurrently treated with DMBA and betel quid were significantly higher than those in animals treated with DMBA alone in each killing period of 8, 10, 12 and 14 weeks. No visible tumors but hyperkeratosis and acanthosis were observed in pouches treated with betel quid alone for all killing periods. CONCLUSION: Our results indicate Taiwan betel quid may be a co-carcinogen in human oral carcinogenesis, if extrapolation can be made from the current animal study.

Animals↗
PubMed1997

Dyspepsia in primary care: perceived causes, reasons for improvement, and satisfaction with care.

BACKGROUND: While dyspepsia is a common problem in primary care populations, very little is known about patient perceptions of medical care for this disease. The present study of patients with dyspepsia treated by primary care physicians looks at causes, procedures, and reasons for improvement from the patient's viewpoint and relates these factors to patient satisfaction with family physicians' medical care. METHODS: Medical chart and billing data were collected for 545 adult patients who visited five family health centers for digestive complaints during a 6-month period in 1993. A questionnaire was completed by 288 patients 6 to 8 weeks after patient's index visit. Baseline findings are reported. RESULTS: The two most common causes of gastrointestinal problems were attributed to stress or anxiety (58%) and diet (46%). Between the time of the index visit and the baseline survey, 48% reported that they had recovered or improved. Of those who recovered or improved, most (75%) credited "taking GI medicine" followed by change in diet (44%). Patients who reported recovery or improvement of their gastrointestinal complaints (P < .001) and older patients (P = .032) were the most satisfied with overall medical care. Satisfaction with medical care was not associated with insurance coverage, procedures done, race, antiulcer medication treatment, diagnosis, general health status, or sex. CONCLUSIONS: Specific health status, ie, improvement of gastrointestinal (GI) problems, predicted patient satisfaction for 70% of cases in this study. Most patients who improved credited GI medicines for their improvement, and those who improved were more satisfied with their medical care.

Adult↗
PubMed1996

Superscan in patients with nasopharyngeal carcinoma.

Bone scintigraphy plays an important role in the early detection of bone metastases in patients with nasopharyngeal carcinoma and serial scans may aid the clinician to assess the therapeutic response. A superscan is a pattern described as abnormal bone scan, indicating extensive bony metastases associated with various neoplastic diseases. Bone scans from 407 patients with nasopharyngeal carcinoma were reviewed retrospectively. Only six superscans (1.5%) were found. The appearance of a superscan is frequently accompanied by an abnormal titer of serological markers IgG-VCA and IgA-VCA, liver metastases, and poor survival. Although a superscan rarely occurs in nasopharyngeal carcinoma, its appearance may represent a poor prognosis in these patients.

Adult↗
PubMed1996

Minimal arecaidine concentrations showing a promotion effect during DMBA-induced hamster cheek pouch carcinogenesis.

The purpose of the present study was to determine the minimal arecaidine concentrations showing a synergistic effect on DMBA-induced hamster cheek pouch carcinogenesis. One hundred and twelve male adult Syrian golden hamsters were divided into 16 groups, each containing seven animals. After eight weeks of DMBA initiation and then four weeks of arecaidine promotion, 100% tumor incidence was found with arecaidine concentrations of 400 micrograms/ml and 500 micrograms/ml; average tumor numbers were 1.86 +/- 0.63 and 1.86 +/- 0.93 respectively (P < 0.05). After four weeks of DMBA and a subsequent eight weeks of arecaidine painting, all hamsters developed visible tumors with arecaidine concentrations of 900 micrograms/ml and 1000 micrograms/ml; average tumor numbers were 1.86 +/- 0.82 and 2.14 +/- 1.09 respectively (P < 0.05). The tumor dimensions varied little and differences were not statistically significant. Without DMBA pretreatment, regardless of the high arecaidine concentrations (1000 micrograms/ml, 2000 micrograms/ml and 3000 micrograms/ml) applied, no visible tumor growth was observed; only hyperkeratosis and inflammation could be discerned histologically. Thus, the minimal concentrations of arecaidine displaying a synergistic effect in the DMBA-induced hamster cheek pouch of carcinogenesis were found to be 400 micrograms/ ml applied for four weeks after eight weeks of DMBA application, and 900 micrograms/ml applied for eight weeks after four weeks of DMBA painting. These findings may be useful for other studies concerning the tumorgenicity of arecaidine.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Sequential expression of placental glutathione S-transferase (GST-P) during DMBA-induced hamster buccal pouch squamous cell carcinogenesis.

The aim of the present study was to investigate the sequential expression of placental glutathione S-transferase (GST-P) during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch squamous cell carcinogenesis. Both immunohistochemical and immunoblot analyses were employed to detect the epithelial GST-P in hamster buccal pouch mucosa over a 15-week treatment regimen. No GST-P positivity was demonstrated in the pouches of the control group. GST-P positive cells were first noted as early as 1 week after DMBA applications. A gradual increase in both the mean number and size of GST-P-positive foci was noted in the first 12 experimental weeks, but a plateau level was approached thereafter. The early GST-P-positive-area were located in the basal layer, or occasionally in the middle layer, of DMBA-treated hamster buccal pouch mucosa. Later, the stained sites became enlarged and were scattered randomly in different layers or in the whole thickness of the dysplastic and non-dysplastic epithelium. The keratin layer was only occasionally involved during the first 12 weeks of DMBA treatment but positive staining was more noticeable in the final stage of the experiment. Both exophytic (8-12 weeks) and invasive (13-15 weeks) squamous cell carcinomas showed GST-P positivity, in both cytoplasmic and nuclear components. Immunoblot analysis revealed no band in the crude tissue extracts of the control pouches whereas GST-P polypeptide of molecular weight approximately 26 kD was demonstrated in DMBA-treated pouches over the whole 15-week treatment regimen. Results of the present work indicate that GST-P is a stable and persistent label for almost all of the carcinogen-altered cells during DMBA-induced hamster buccal pouch carcinogenesis. Immunohistochemically detectable GST-P may be a potential marker throughout oral chemical carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Endoscopic cecal perforation: mechanisms of injury.

OBJECTIVE: Most endoscopic perforations of the colon occur in the rectosigmoid area and are thought to be secondary to direct injury from the endoscopic instrument. The aim of this study was to describe the mechanisms of injury and clinical outcome of endoscopic perforation involving the cecum. METHODS: Retrospective review of 6684 consecutive colonoscopic procedures performed at a university hospital over a 7-yr period. RESULTS: Colonoscopy was complicated by perforation in 0.22%. Five of the 15 perforations occurred in the cecum. The mean age of these five patients was 79.6 +/- 17.7 yr (mean +/- SD). Indications for the procedure were bleeding (n = 4) and suspected obstructing cecal mass (n = 1). Abnormal endoscopic findings included diverticulosis, vascular malformations, cecal ulcer/inflammation, mass, and polyps. Perforation was directly attributable to an ancillary procedure (three routine biopsies, one electrocautery) in the cecal area in four patients, and cecal pathology (inflammation, ulceration) was a contributing risk factor in three patients. Mortality was 80%. In contrast, a noncecal perforation usually occurred at the sigmoid region and was associated with technical difficulties, e.g., inability to traverse a stricture or reach the cecum. CONCLUSIONS: Routine forceps biopsy (without electrocautery) is an under-recognized cause of cecal perforation. Ancillary endoscopic interventions in the cecal region should be minimized in elderly patients with evidence of cecal inflammation. Pneumatic injury may be an additional risk factor for cecal perforation in patients with a colonic stricture or a tortuous colon.

Aged↗
PubMed1995

The antioxidant and prooxidant activity of some B vitamins and vitamin-like compounds.

The antioxidant and prooxidant properties of some B vitamins (BVIT) and vitamin-like compounds (VLC) that are commonly included in multivitamin preparations were investigated. Microsomal lipid peroxidation induced by FeCl3 and ascorbate was dose-dependently inhibited by pyridoxal and pantothenate but was stimulated by thiamin, pyridoxine and carnitine. Among the compounds tested, only pyridoxine and pyridoxal reacted, but rather poorly, with superoxide anions. All test compounds reacted with .OH with second-order rate constants comparable or higher than that for mannitol, as assayed using deoxyribose oxidation by a system containing EDTA-chelated Fe(III), H2O2 and ascorbate. When assayed in the absence of EDTA, pyridoxal showed increased inhibition of deoxyribose oxidation over that in the presence of EDTA, suggesting a potent ability of pyridoxal to bind and deactivate iron. Pantothenate, pyridoxine and myo-inositol appeared to equally inhibit deoxyribose oxidation both in the presence and absence of EDTA. The lack of inhibition on deoxyribose oxidation in the absence of EDTA by thiamin, carnitine and choline may suggest that the .OH-scavenging ability is equalled by the ability of the scavenger-iron complexes to form .OH or other redox active species. However, stimulation of lipid peroxidation by pyridoxine was unexplained and the effect was not attributed to reduction of Fe(III) to Fe(II). This study shows that the radical-scavenging ability of BVIT and VLC did not correlate with their effects on microsomal lipid peroxidation. Moreover, the stimulation of lipid peroxidation by thiamin, pyridoxine and carnitine suggests that supplementation of large amounts of these compounds may not be desirable.

Animals↗
PubMed1995

Prevalence of fatty liver in Japanese children and relationship to obesity. An epidemiological ultrasonographic survey.

The prevalence of fatty liver in children is unknown and its relationship to obesity is poorly defined. The present study of 810 northern Japanese children (4-12 years old) determined the prevalence of fatty liver in the pediatric population and its relationship to obesity. Diagnosis of fatty liver was based on established real-time ultrasonographic criteria. The overall prevalence of fatty liver was 2.6% and was higher for boys (3.4%) than for girls (1.8%), although not statistically significant (P = 0.15). Fatty liver was found in children as young as 6 years of age. There was no significant association between the prevalence of fatty liver and height (physical growth). There was a strong positive correlation between fatty liver prevalence and established obesity indices: Rohrer's Index--chi 2 linear trend = 59.2, P < 0.0001; body mass index--chi 2 linear trend = 91.6, P < 0.0001; and age-gender-adjusted Japanese standard index of weight for height--chi 2 linear trend = 93.2, P < 0.0001. However, direct measurement of abdominal subcutaneous fat thickness by ultrasonography was the best predictor of fatty liver: chi 2 linear trend = 159, P < 0.0001. These results indicate that fatty liver may develop very early in life, and there is a direct relationship between degree of obesity and fatty liver in children.

Body Height↗
PubMed1995

Experience with a catheter-based ultrasound probe in the bile duct and pancreas.

BACKGROUND AND STUDY AIMS: Complete examination of the biliary tree and pancreatic duct may be difficult or unsuccessful using conventional imaging instruments. The purpose of this study was to evaluate the cannulation success rate, clinical utility, and safety of a new catheter-based ultrasound probe (CBUSP) used in the biliary tree and pancreas. PATIENTS AND METHODS: The probes used in this study are manufactured by Microvasive (Watertown, MA, U.S.A.) and were 6.2 Fr in diameter, operated at 12.5 MHz. Thirty-six patients (11 with malignant bile-duct strictures, 12 with benign bile-duct strictures, two with bile duct stones, three with pancreatic duct strictures, one with a pancreatic cyst, one with pancreas divisum, three with sphincter of Oddi dysfunction, and three normal) underwent examination with a CBUSP. RESULTS: Cannulation was successful in all 36 patients. The hepatic artery and portal vein could be visualized with the probe in the proximal bile duct in 81% and 94% of the cases, respectively. The portal vein could not be adequately visualized in any patients when the probe was in the distal bile duct. The mean thickness of the normal bile duct wall was 0.17 cm, and the mean wall thicknesses proximal to a benign and malignant stricture were 0.16 and 0.17 cm, respectively. The mean thicknesses of benign and malignant biliary strictures were 0.32 cm and 0.31 cm, respectively (not significant). Eight of 12 benign biliary strictures (67%) and five of 11 malignant strictures (45%) were symmetrical. However, no obvious differences could be identified between benign and malignant biliary strictures. There were no catheter related complications. CONCLUSIONS: Further catheter modifications are needed, but it appears to be feasible to assess vascular invasion in cholangiocarcinoma and to characterize biliary strictures in a way that may be able to influence therapy options in some patients. The currently available CBUSP cannot distinguish between benign and malignant strictures. However, with technical modifications, this may be possible in the future. The clinical usefulness of CBUSP in the pancreas awaits further investigation, but pancreatic imaging is feasible.

Adult↗