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Biomedical subjects

L M Lin

Publications and source records attributed to L M Lin.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1995

Betel quid chewing, cigarette smoking and alcohol consumption related to oral cancer in Taiwan.

A hospital-based case-control study of matched pairs was conducted to explore (a) the relationship between the use of betel quid chewing, cigarette smoking, alcohol drinking and oral cancer and (b) synergism between these factors. The case group consisted of 104 male and 3 female oral cancer patients and these were compared with 194 male and 6 female matched controls. We found by univariate analysis that alcohol consumption, smoking, betel quid chewing, educational level and occupation were associated with oral cancer. The adjusted odds ratios were to be found elevated in patients who were smoking and betel quid chewing. After adjusting for education and occupation covariates, the incidence of oral cancer was computed to be 123-fold higher in patients who smoked, drank alcohol and chewed betel quid than in abstainers. The synergistic effects of alcohol, tobacco smoke and betel quid in oral cancer were clearly demonstrated, but there was a statistically significant association between oral cancer and betel quid chewing alone. Swallowing betel quid juice (saliva extract of betel quid produced by chewing) or including unripened betel fruit in the quid both seemed to enhance the risks of contracting oral cancer.

Adolescent↗
PubMed1995

Immunohistochemical demonstration of epithelial glutathione S-transferase isoenzymes in normal, benign, premalignant and malignant human oral mucosa.

The expression and localization of glutathione S-transferase (GST) isoenzymes in the epithelium of normal oral mucosa (n = 9), overlying reactive fibrous hyperplasia (n = 9), and of potentially malignant [leukoplakia (n = 25), submucous fibrosis (n = 12), verrucous hyperplasia (n = 16)] and malignant [squamous cell carcinoma (n = 36), verrucous carcinoma (n = 13)] oral lesions were examined immunohistochemically using polyclonal antibodies raised against GST isoenzymes (alpha, mu and pi) with the standard avidin-biotin-peroxidase complex (ABC) method. GST alpha, mu and pi were almost completely absent in the epithelium of normal oral mucosa and overlying benign fibrous tissues. GST alpha staining was cytoplasmic and focally positive, while GST mu staining was similar to but weaker than that seen for GST alpha. GST pi showed both cytoplasmic and nuclear staining and was expressed in 60% of leukoplakias with mild dysplasia (n = 15), 80% of leukoplakias with moderate to severe dysplasia (n = 10). 75% of submucous fibrosis samples (n = 12), 75% of verrucous hyperplasias (n = 16), 77% of verrucous carcinomas (n = 13), 81% of well-differentiated squamous cell carcinomas (n = 26) and 70% of moderate- to poorly-differentiated squamous cell carcinomas (n = 10). In addition, GST pi expression was independent of the state of differentiation of oral cancers. Since GST pi was significantly over-expressed in the oral premalignant and malignant lesions, the kinetics of GST pi-positive cells and the value of GST pi as a tumor marker in oral carcinogenesis need further investigation.

Biomarkers, Tumor↗
PubMed1995

Clinical evaluation of different treatment methods for oral submucous fibrosis. A 10-year experience with 150 cases.

Over a 10-year period (1982-1991); a total of 150 patients divided into two groups with varying degrees of oral submucous fibrosis (OSF) were treated by either medical or surgical therapies. Medical treatment involved (a) conservative oral administration of vitamin B-complex, buflomedial hydrochloride and topical triamcinolone acetonide 0.1%, or (b) conventional submucosal injections of a combination of dexamethasone and hyaluronidase, or (c) a combination of both (a) and (b). The surgical group was treated by the excision of fibrotic tissues and covering the defect with split-thickness skin, fresh human amnion, or buccal fat pad (BFP) grafts. Treatment was chosen according to the stage of clinical progression to gain maximal interincisal distance (ID). The cases were followed up by monthly examinations for at least two years, or when possible even longer. A combination of (a) and (b) medical treatment was satisfactory in cases of mild impairment (ID > 20 mm) but in the long term it led to symptomatic relief only. Surgical therapy, on the other hand, when accepted by the patients, led to a significant improvement of trismus in cases of severe limitation (ID < 20 mm). Following this strategy, an additional ID increase was observed in all patients. BFP grafting was particularly successful in diminishing scarring after two years as compared with the other two grafts. Together with a cessation of the betel quid chewing habit before and after therapy, these treatment regimens combined with daily mouth opening exercises were found to be necessary to manage OSF cases in early and advanced stages of progression.

Adipose Tissue↗
PubMed1994

Endodontic treatment of mandibular molars with concrescence.

Endodontic treatment of a permanent mandibular first molar and a second molar presumably joined by cementum is presented. This case illustrates the difficulty in interpreting the vitality testing in such a situation. It also suggests possible irreversible pulp injury of a vital healthy tooth caused by extension of the inflammatory periapical pathosis of the adjacent tooth.

Adolescent↗
PubMed1994

Influence of a base on coronal microleakage of post-prepared teeth.

This study compared the coronal microleakage of post-prepared teeth with and without the placement of a zinc oxide-eugenol cement seal coronal to the gutta-percha. Forty single-rooted extracted teeth were prepared and obturated with sealer and gutta-percha. These teeth were divided into two groups of teeth 20 each. A post space was prepared for each tooth so that 5 to 6 mm of gutta-percha remained in one group and 3 to 4 mm in the other group. To the latter group, 2 to 3 mm of zinc oxide-eugenol cement base was placed directly coronal to the gutta-percha. The sealer was allowed to set for 48 h and the outer root surfaces of the teeth were covered with finger nail varnish and sticky wax, except for the access openings. The teeth were immersed in dye for 1 wk to allow coronal microleakage. The specimens were sectioned and measurements were made on the extent of dye penetration into the root filling. The teeth without a zinc oxide-eugenol base showed significantly greater microleakage than those protected with a zinc oxide-eugenol base.

Dental Cavity Lining↗
PubMed1993

Electric pulp tester and apex locator barrier technique.

Use of the electric pulp tester and the apex locator during assessments of pulp vitality and root length determination involves bacterial cross-contamination of the metal surfaces of the probe tip and lip clip inserts which contact the oral hard and soft tissues. Reuse of these endodontic aids necessitates the sterilization or disinfection of the metal insert or the acquisition of extra attachments. A barrier technique that protects the electric pulp tester probe tip and the apex locator lip clip from bacterial contamination and employs the principle of electric conductive bridging is presented.

Dental Pulp Test↗
PubMed1992

Detection of blood group surface antigens of urinary bladder tumours using monoclonal antibodies with the avidin-biotin complex technique.

We examined 8 normal bladder transitional epithelia and 65 transitional cell carcinomas of the urinary bladder of various stages and grades for the presence of ABO(H) blood group surface isoantigens using the immunoperoxidase staining via the Avidin-Biotin Complex (ABC) methods. It was found that 27% of patients with grade I tumours, 50% with grade II tumours and 82% with grade III tumours had loss of cell surface isoantigens. When correlated with the clinical stage the tumours showed no surface isoantigens in stage D, while 65% of patients with stage A tumours were positive for surface antigens. From among 37 patients (57%), 28 (43%) survived for more than five years. Our results suggest that surface antigens of transitional cell carcinoma of the urinary bladder tended to disappear as the histologic changes of the tumour progressed. It also was noted that a loss of ABH(O) surface isoantigens was a bad prognostic sign.

ABO Blood-Group System↗
PubMed1992

Factors associated with endodontic treatment failures.

Two hundred and thirty-six cases of endodontic treatment failures, none of which had advanced periodontal disease, postperforations, or root or crown fractures were analyzed clinically, radiographically, and histobacteriologically to determine the major factor(s) for treatment failures. It was found that there was a correlation between bacterial infection in the canal system and the presence of periradicular rarefaction in endodontic failures. This report provides evidence indicating that the major factors associated with endodontic failures are the persistence of bacterial infection in the canal space and/or the periradicular area and the presence of preoperative periradicular rarefaction. The apical extent of root canal fillings, i.e. underfilled, flush-filled, or overfilled, seems to have no correlation to treatment failures.

Bacterial Infections↗
PubMed1992

Effect of intracoronal bleaching on external cervical root resorption.

The purpose of this study was to examine histologically and radiographically the effect of a bleaching agent, a mixture of sodium perborate and superoxol (30% hydrogen peroxide), without a heat source on the cervical root surface and periodontal tissue of endodontically treated teeth of dogs. Endodontic treatment was performed on anterior teeth of dogs. The endodontically treated teeth were then divided into two groups. One group received walking bleach procedures, while the other group did not. The animals were killed at intervals of 1 and 3 months after bleaching for histological and radiographic examination. External cervical root resorption was only observed in bleached teeth at 3-month but not at 1-month observation.

Animals↗
PubMed1991

Clinical, radiographic, and histologic study of endodontic treatment failures.

One hundred fifty cases of endodontic treatment failures were studied clinically, radiographically, and histologically. Fifty-seven percent of the teeth were asymptomatic. Pain alone and/or associated with swelling was present in 21% of the teeth. There was no correlation between the size of periradicular rarefaction and the occurrence or severity of clinical signs and/or symptoms. Stainable bacteria were demonstrated in 69% of the teeth and were present mostly in the canal. The severity of periradicular inflammation was related to presence of stainable bacteria in the canal. Swelling and pain or a draining sinus tract was often associated with stainable bacteria inside the canal. The development of a radicular cyst associated with an endodontically treated tooth that has failed is not necessarily the cause of endodontic treatment failure.

Dental Pulp Cavity↗
PubMed1991

Histological study of furcation perforations treated with tricalcium phosphate, hydroxylapatite, amalgam, and Life.

One-hundred twenty experimental furcation perforations were created in the mandibular and maxillary premolars and molars of six rhesus monkeys. Tricalcium phosphate, hydroxylapatite, amalgam, and Life were used to repair the furcation perforations. The animals were sacrificed at the intervals of 2, 4, and 6 months after the experiment. Histological evaluation revealed lack of complete healing of furcation perforations repaired with any materials. Epithelium was present in the furcation perforations in both experimental and positive control groups. No hard tissue formation was observed in this study. Inflammation in the furcation area may be due to inadequate sealing ability of the repair materials.

Animals↗
PubMed1991

Simultaneous determination of toxic metabolites by linear combination derivative spectrophotometry.

A linear combination derivative spectrophotometric method is described. The method overcomes the problem of overlapping in derivative spectrophotometry and allows the maximum use of quantitative information. In addition, the method can be used to increase the selectivity, sensitivity and accuracy of the simultaneous analysis of multicomponent mixtures. The application of the method to the simultaneous determination of bongkrekic acid and toxoflavin, the toxic metabolites produced by Pseudomonas farinofermentans, is described.

Bongkrekic Acid↗
PubMed1991

Creatine kinase isoenzymes activity in serum and buccal pouch tissue of hamsters during DMBA-induced squamous cell carcinogenesis.

The sequential changes of creatine kinase (CK) isoenzyme activity in serum and hamster buccal pouch tissue (HBPT) of normal, premalignant, and malignant stages during 13 wk of DMBA induced hamster buccal pouch squamous cell carcinogenesis, were studied. We found that the total CK activity in both serum and HBPT of the DMBA painted groups increased during the premalignant period (3-7 wk), with the peak being at 7 wk, while declining in the malignant period (9-13 wk). No significant difference in the serum and HBPT CK-MM, CK-MB and CK-BB activity, in DMBA-induced carcinogenesis, could be established. However, the macro CK type 2 (MCK-2), a cathodically migrating atypical creatine kinase isoenzyme, initially appeared in the sera and tissues of the 3rd wk DMBA-treated group. Its activity gradually increased during the premalignant and malignant stages, paralleling the increasing number of DMBA applications. There was a correlation between the degree of differentiation, and the size and number of the induced tumors with MCK-2. No MCK-2 could be detected in any of the sera or tissues of the control, nor in the 1st wk DMBA-treated group. We propose that MCK-2 is a potential tumor marker in oral malignancy and its presence may provide valuable information for early diagnosis of a possibly premalignant transforming oral lesion.

9,10-Dimethyl-1,2-benzanthracene↗