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Biomedical subjects

Y Y Tan

Publications and source records attributed to Y Y Tan.

28 records · Page 2Linked to original sources
PubMed1995

Gall bladder tumour, choledochal cyst and an anomalous pancreatico-biliary junction.

This report highlights the association of a tumour in an acalculous gall bladder with an anomalous pancreatico-biliary junction (PBJ) and a type IVa choledochal cyst. Cholecystectomy and Rouxen-Y hepatico-jejunostomy (RHJ) was performed after division of the common bile duct (CBD) and excision of the dilated segment. The details of the case are presented and the role of an abnormal PBJ in gall bladder carcinogenesis is discussed.

Adenoma, Villous↗
PubMed1993

Comparative antibody response to Salmonella antigens in genetically resistant and susceptible mice.

The ELISA was used to titrate the antibody response in mice inoculated with salmonella antigens. The genetically resistant A/J and susceptible C57BL/6J mice were either infected with the virulent or the avirulent Salmonella typhimurium. Alternatively, they were inoculated either once or twice with the heat-killed salmonella vaccine. No appreciable difference could be detected in the relative ability of these two strains of mice to produce antibodies against the lipopolysaccharide antigens of this pathogen under these four conditions.

Animals↗
PubMed1992

Risk factors and a risk scoring system for the prediction of malignancy in ovarian cysts.

A retrospective study was carried out on 396 patients who presented with ovarian masses. Sixty five (16%) patients were found to have ovarian malignancy while the rest either had benign ovarian tumours (n = 159), endometriotic cysts (n = 130), physiological cysts (n = 20) or inflammatory masses (n = 7). The relative risk for ovarian malignancy among these patients increased significantly (p < 0.001) after the age of 40 years. The presence of ascites, abdominal distension, urinary complaints and loss of appetite and weight were significant individual risk factors for malignancy. Ultrasound image of a complex cyst is also associated with increased risk of malignancy in an ovarian mass. None of the individual risk factors was discriminatory between a benign and malignant cyst. However, these factors can be combined to form a 20-point risk scoring system. The risk of malignancy in an ovarian cyst increased with increasing scores. In this study, the median scores were 3 for benign cyst, 7 for borderline malignancy and 12 for malignant cysts. Using a total score of 7 as a cut off point, one can detect 75% of malignant cysts with a specificity of 84.1%, a positive predictive value of 47.5% and a negative predictive value of 94.6%. It is concluded that the majority of malignant ovarian cysts can be identified preoperatively to allow arrangement and planning of an optimal surgery.

Adult↗
PubMed1992

Outcome prediction in early management of severe head injury: an experience in Malaysia.

The outcome of 109 patients with severe head injury was studied in relation to clinical and computed tomographic (CT) criteria on admission, after resuscitation. Age, Glasgow Coma Score (GCS) and state of pupils strongly correlated with outcome. The presence of hypothalamic disturbances, hypoxia and hypotension were associated with an adverse outcome. The CT indicators associated with poor outcome were perimesencephalic cistern (PMC) obliteration, subarachnoid haemorrhage, diffuse axonal injury and acute subdural haematoma. The prognostic value of midline shift and mass effect were influenced by concomitant presence of diffuse brain injury. For the subset of patients aged < 20 years, with GCS 6-8 and patent PMC (n = 21), 71.4% correct predictions were made for a good outcome. For the subset of patients aged > 20 years, with GCS 3-5 and partial or complete obliteration of PMC (n = 28), 89.3% correct predictions were made for a poor outcome.

Adolescent↗
PubMed1989

In vitro evaluation of 6-thioguanine and alpha-interferon as a therapeutic combination in HL-60 and natural killer cells.

The effect of 6-thioguanine (6-TG) and alpha-interferon (IFN-alpha) was evaluated in vitro to determine their effectiveness in combination on the therapeutically relevant events of: HL-60 cell cytotoxicity, HL-60 cell differentiation, and natural killer (NK)-cell mediated cytotoxicity. 6-TG was toxic to HL-60 cells (ID50 = 0.6 microM; 24-h exposure) while IFN-alpha (up to 1000 IU/ml) had minimal cytotoxic activity. Sequence-dependent activity was observed, inasmuch as the IFN-alpha pretreatment sequence was antagonistic, while the other schedules were additive or, possibly, synergistic. The combination of 0.5 microM 6-TG and 100 IU/ml IFN-alpha produced the same level of HL-60 cell differentiation as each agent alone, suggesting no benefit from the combination on this process. The effect of 6-TG and IFN-alpha on NK cell-mediated cytotoxicity was found to be sequence dependent. NK cell activity was markedly stimulated by IFN-alpha, whereas 6-TG alone seemed to have no direct effect. However, when the NK cells were pretreated with 100 IU/ml IFN-alpha followed by 10 microM 6-TG, the IFN-alpha-enhanced activity of NK cells was ablated. These results suggest that the immunosuppressive activity of 6-TG may be related to the acute inhibition of cytokine activation. Our results suggest that 6-TG and IFN-alpha have considerable interactions, which are sequence dependent. The optimal sequence for potential therapeutic application of these anticancer agents appears to be 6-TG pretreatment followed by IFN-alpha.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

Correlation between ribosomal RNA production and RNA-directed fluoropyrimidine cytotoxicity.

The relationship between cytotoxicity and fluoropyrimidine effects on the production of mature cytoplasmic 28S and 18S ribosomal RNA was studied in S-180 cells for the fluoropyrimidines: 5-fluorouracil (FUra), 5-fluorouridine (FUrd), 5-fluorodeoxyuridine (FdUrd), and 5'-deoxy-5-fluorouridine (5'-dFUrd). After a 6-hr drug exposure, the total cytotoxicity in the absence of added thymidine (dThd) was determined by soft-agar cloning and resulted in LC90 (lethal concentration to 90% of cells) values of 0.6 microM FdUrd, 0.7 microM FUrd, 5.3 microM FUra and 93 microM 5'-dFUrd. The RNA-directed (dThd-nonreversible) cytotoxicity was assessed by cloning the cells in the presence of 10 microM dThd. This resulted in an altered order of potency and increased LC90 values to 5.5 microM FUrd, 20 microM FUra, 265 microM FdUrd and 870 microM 5'-dFUrd. The production of mature cytoplasmic rRNA was determined by measuring the amount of [3H]cytidine incorporated into the 28S and 18S rANA species following their separation by agarose gel electrophoresis, compared with the level of [3H]cytidine incorporated into the nuclear rRNA. When all four fluoropyrimidines were compared together, the degree of inhibition of cytoplasmic rRNA production was poorly predictive of the total cytotoxicity in the absence of dThd (correlation coefficient, r = 0.77). FdUrd, in particular, had a very minor effect on rRNA production even at very toxic drug concentrations. When toxicity was assessed in the presence of dThd, however, there was a strong and significant correlation between rRNA production and RNA-directed cytotoxicity (r = 0.95, P less than 0.001), for all the fluoropyrimidines tested, including FdUrd. Thus, when the inhibition of thymidylate formation was eliminated as a site of drug action and only RNA-directed cytotoxicity was assessed, the impaired production of cytoplasmic rRNA was strongly associated with cytotoxicity. These results demonstrate that the inhibition of mature cytoplasmic rRNA production may be an important common mechanism of RNA-directed cytotoxicity for all the fluoropyrimidines, and not limited to FUrd or FUra.

Animals↗
PubMedDate not supplied

Management delays for early gastric cancer in a country without mass screening.

BACKGROUND/AIMS: To examine the symptoms of early gastric cancer and the time scale of management delays in a country without a mass screening program. METHODOLOGY: Retrospective review of 44 patients with early gastric cancer. RESULTS: Epigastric pain (63.3%) and gastrointestinal hemorrhage (27.3%) were the main symptoms found. Total delay was made up of patient delay (48.6%), doctor delay (25.5%) and treatment delay (25.9%). Median patient delay (from symptom onset to medical consult) was 30 days (inter-quartile range 2 to 365). Patient delay of more than 6 months was associated with patients aged 50 and younger (P = 0.04) and those presenting with pain (P = 0.05). Median doctor delay (consult to diagnosis) was 21 days (1 to 35) and median treatment delay (diagnosis to surgery) was 8 days (2 to 21). Doctor delay of more than 6 months was associated with a negative gastroscopy or barium meal in the previous 12 months (P = 0.03). CONCLUSIONS: The detection of early gastric cancer at the symptomatic-detectable stage is possible and this potential window for diagnosis can be more than 1 year for up to one third of cases. Efforts to reduce management delays should be aimed at public education and improving the quality and accessibility of endoscopic evaluation.

Adult↗
PubMedDate not supplied

Solid phase synthesis and biological activity of rat relaxin.

The peptide hormone relaxin was isolated in good yield from the ovaries of the pregnant rodent Rattus rattus using a simplified purification schedule. It was subjected to comprehensive chemical characterization to confirm both its purity and predicted composition. The peptide was also chemically synthesized by the solid phase procedure. The two chains comprising the hormone were each assembled by the Boc-polystyrene method and, following conventional purification, combined in solution to form the single intramolecular and two intermolecular disulfide bonds. Following purification, the synthetic rat relaxin was fully chemically characterized and shown to be indistinguishable from the native peptide including by secondary structure analysis using circular dichroism spectroscopy. The native and synthetic rat relaxins were shown to be equally biologically active in the in vitro rat uterine relaxation assay and had pEC50 values that were comparable to synthetic human H2 relaxin.

Amino Acid Sequence↗