Search PubMed⌕ Search

Biomedical subjects

Y Lin

Publications and source records attributed to Y Lin.

At least 469 records · Page 26Linked to original sources
PubMed1996

Tumour suppressor p53 and Rb genes in human hepatocellular carcinoma.

Aberrations of the p53 and Rb tumour suppressor genes were examined in 12 human hepatocellular carcinoma (HCC)-derived cell lines from different geographic areas and 9 local HCCs by restriction fragment length polymorphisms (RFLP), polymerase chain reaction-single-strand conformation polymorphisms (PCR-SSCP) and DNA sequencing. The relationships between genetic changes and hepatitis B virus (HBV) DNA integration in samples were compared. None of the cell lines and tumours showed structural changes in the Rb gene, while 6 cell lines and 2 tumours had mutation or deletion in exons 5 to 8 of p53. Mutations include an AGG --> AGT (Arg --> Ser) transversion at codon 249 in PLC/PRF/5 and Mahlavu, an AAT --> AAA (Asn --> Cys) transversion at codon 200 in TONG/HCC, an AAG --> GAG (Lys --> Glu) transition at codon 139 in HCC-T, a CAT --> CGT (His --> Arg) transition at codon 214 in SC4, and a CCC --> CTC (Pro --> Leu) transition at codon 250 in SC8. In Huh4, an 18-bp deletion from codon 264 to 270 resulted in loss of Leu-Gly-Arg-Asn-Ser-Phe from the amino acid sequences 265 to 270, whereas Hep3B had a 7-kb deletion after exon 7 of p53. Our data indicate that whereas Rb may not have pleiotropic effects on HCC, p53 aberrations are frequently involved in hepatocarcinogenesis. Further, HBV infection appears to be unrelated to the micro-genetic changes of p53. The G to T codon-249-mutation is consistent with HCCs arising from areas at high risk for both aflatoxin B1 (AFB1) exposure and HBV infection.

Animals↗
PubMed1996

Immunochemical and genetic analysis of the p53 gene in liver preneoplastic nodules from aflatoxin-induced rats in one year.

Mutations of the p53 tumour-suppressor gene in human hepatocellular carcinomas from certain geographic areas appear to be associated with high dietary exposure to aflatoxin B1 (AFB1). In this study, the effects of AFB1 on p53 locus at the preneoplastic stage of rat liver oncogenesis were assessed. Male Wistar rats were treated with a single dose of 1.5 mg AFB1/kg body weight by a gastric tube. Liver biopsies over a period of one year were examined for aberrations of the p53 gene together with the expression of placental glutathione-S transferase (GST-P), a marker for preneoplasia. Immunohistochemistry, Western blot, polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and DNA sequencing techniques were used. AFB1 induction resulted in GST-P overexpression, forming GST-P-positive multi-foci and nodules of hepatocytes, but no aberrations in the p53 expression and the microstructure of exons 5-8 of the p53 gene. These results suggested that p53 mutation(s) might not occur at this early stage of AFB1-induced hepatocarcinogenesis.

Aflatoxins↗
PubMed1996

Biomarkers: a molecular approach to cancer epidemiology.

The rapidly evolving field of molecular epidemiology represents a paradigm shift in medical research, illustrating the convergence of basic, clinical and epidemiologic research, as well as the application of laboratory methods to population studies. As a complement and improvement to traditional epidemiologic approaches, the use of biomarkers offers more accurate exposure assessment at an individual level, better understanding of the biological mechanism of carcinogenesis by tracking a continuum of events between exposure and disease, as well as the ability to discern host or genetic factors that may account for variations in cancer susceptibility among individuals or ethnic populations. Further, biomarkers have also proved useful in cancer diagnosis and prognosis. This article attempts to review the latest progress in molecular cancer epidemiology and to summarise the current state of research in Singapore.

Biomarkers, Tumor↗
PubMed1996

Quantification of bovine neutrophil migration across mammary epithelium in vitro.

A microassay system was developed to quantify bovine neutrophil transepithelial migration in vitro. The bovine mammary epithelial cell line (MAC-T) formed a confluent monolayer that served as a biologically meaningful barrier for neutrophil migration. Neutrophils added into the upper compartment of an inverted monolayer were driven to migrate across the epithelium from a basal-to-apical direction by the addition of zymosan activated serum (ZAS) into the lower compartment. The numbers of migrated neutrophils were determined by assaying the neutrophil azurophilic granule marker, myeloperoxidase. Results showed that ZAS stimulated neutrophil migration across the epithelium in a time-and dose-dependent manner. In the presence of 5% ZAS and 2 x 10(6) neutrophils, approximately 2.4 x 10(5) neutrophils migrated across the epithelium in 120 min. The procedures we have developed in this study provide a simple precisely controlled system to investigate the normal dynamics of bovine neutrophil transepithelial migration and a means to detect and study impaired neutrophil migration.

Animals↗
PubMed1996

[Surgical management for severe complications following radial keratotomy].

OBJECTIVE: To investigate the surgical treatment for severe complications after radial keratotomy (RK). METHODS: A protocol of surgical treatment for 3 severe complications after RK, i.e., early corneal perforation and infection, corneal rupture following contusion and corneal leucoma, is proposed based on modern microsurgical techniques and computer assisted corneal topography. RESULTS: All eyes with such severe complications were salvaged and their visual outcomes were also satisfactory. CONCLUSIONS: Severe complications after RK threaten the eye. Special management should be applied for these situations. With the help of corneal topography, the refractive results of corneal surgeries can be improved.

Adult↗
PubMed1996

Tandem repeating of the expression cartridge--a novel strategy to enhance the expression efficiency of cloned gene in Escherichia coli.

A novel strategy to enhance the expression efficiency of cloned target gene in Escherichia coli was developed. The whole expression cartridge, consisting of promoter, SD sequence, target gene and transcription terminator, was tandem repeatedly engineered into a expression plasmid. Consequently, the copy number of specific gene was increased substantially, leading to the improvement of expression efficiency. Using this approach, a recombinant plasmid, designed as pLYD, was constructed and transformated into the Escherichia coli strain DH5 alpha. Upon induction, the desired protein was synthesized in a considerable level and accumulated up to 63% of the total cell proteins. The present study revealed that tandem repeating of expression cartridge provided a convenient means to improve expression level efficiently.

DNA, Recombinant↗
PubMed1996

[Use of condyle positioning plate in sagittal split ramus osteotomy of mandible].

17 patients underwent an orthognathic operation. The condyle positioning plate was used in each sagittal split ramus osteotomy of mandible in order to maintain the condyle position. The results of postoperative X-ray examination showed that no obvious displacement of condyle in posterioranterior, and vertical dimension was detected in all joints and obvious horizontal condyle displacement were only found in two joints. Based on this work the author believe that condyle positioning plate is useful to position condyle during operation.

Bone Plates↗
PubMed1996

[RAAS changes due to dysfunction of pulmonary ventilation].

OBJECTIVE: RAAS was determined to investigate the relationship between their changes and the dysfunction of pulmonary ventilation for evaluating the pathogenesis of early pulmonary hypertension in chronic bronchitis with or without emphysema. METHODS: Angiotensin II (AT II), plasma renin activity (PRA) and aldosterone (Ald) were determined at 8:00 AM in sitting position for 30 minutes in 12 heathy nonsmokers, 50-60 years old, with normal functions of small airway, normal FEV1 and lung volumes, and in 23 patients with chronic bronchitis with or without emphysema. RESULTS: All patients with chronic bronchitis showed dysfunction of small airway with or without abnormalities of FEV1 and lung volumes. In healthy control group, the plasma PRA, AT II and Ald levels were 0.22 +/- 0.12 microgram.L-1.h-1 (x +/- sx), 52 +/- 7 ng/L and 315 +/- 26 pmol/L respectively comparing with those levels of 0.43 +/- 0.11 microgram.L-1.h-1, 197 +/- 32 ng/L and 388 +/- 59 pmol/L in aged patients with chronic bronchitis. It was found that dysfunction of small airway alone could cause remarkable elevation of PRA and AT II levels. In patients with mild pulmonary emphysema, the levels of PRA and AT II were significantly increased. The moderate pulmonary emphysema induced greatly increase of PRA, AT II and Ald levels. In patients with severe pulmonary emphysema, however, the plasma levels of PRA and AT II were significantly attenuated from the levels in moderate pulmonary emphysema while Ald level was still getting higher. There were no evidence to indicate the relationship between the changes of RAAS and hypoxemia. CONCLUSION: The elevation of AT II and PRA might partly be the pathogenesis of early pulmonary hypertension in COPD.

Aldosterone↗
PubMed1996

[Detection of MG7 antigen expression in predicting high-risk in gastric cancer by automatic image analysis].

To study the predictive value of gastric cancer monoclonal antigen (MG7-Ag) in detecting atypical hyperplasia of gastric mucosa, its expression in 72 cases of the illness with follow-up was determined quantitatively by computer-aided image analysis system with immunohistochemical stain for MG7 antibody. Critical value of MG7-Ag expression for high-risk in gastric cancer was explored preliminarily by Youden index and receiver operator characteristic curve. Results of immunohistochemical stain showed there were 24 with positive expression (70.6%) in 34 cancerous cases, and only seven in 38 non-cancerous cases (18.4%), with a significant difference. Image analysis showed an average MG7-Ag density equal to or greater than 0.19 was regarded as the critical value for high-risk in gastric cancer, which could be used to discriminate atypical hyperplasia from canceration, with a sensitivity of 82.4%, a specificity of 78.9%, and an accuracy of 80.6%. Thus, it could be concluded that MG7-Ag expression correlated closely with canceration of gastric atypical hyperplasia, positive MG7-Ag expression in gastric mucosa of patients with atypical hyperplasia, especially in cases with a density of equal to or greater than 0.19, was an indicator for high risk in canceration. If they are put under strict follow-up, early detection of gastric cancer will be improved.

Antibodies, Monoclonal↗
PubMed1996

[Effects of pentoxifylline on leukocyte adhering to endothelial cell].

Using flow chamber, we quantitatively studied the effects of pentoxifylline on normal leukocytes adhering to cultured human umbilical vein endothelial cells. The results showed that pentoxifylline reduced the adhesive number of leukocytes to endothelial cells by acting mainly on leukocytes. The mechanism may be that pentoxifylline inhibits the adherence caused by oxygen free radicals from the leukocytes.

Cell Adhesion↗