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Biomedical subjects

H W Tan

Publications and source records attributed to H W Tan.

14 recordsLinked to original sources
PubMed2006

Preoperative and intraoperative diagnosis of low-grade adenosquamous carcinoma of the breast: potential diagnostic pitfalls.

AIMS: Low-grade adenosquamous carcinoma (LGAC), a rare variant of metaplastic breast cancer, may mimic benign or other low-grade malignant lesions histologically. Diagnostic difficulty may be encountered when evaluating breast cytology, core needle biopsy or intraoperative frozen section specimens. METHODS AND RESULTS: Pathology reports, cytology aspirates and histological slides of LGAC diagnosed at the Department of Pathology, Singapore General Hospital, were reviewed. Four cases of LGAC were analysed. Cytology from the first case showed atypical cells and the subsequent surgical excision specimen showed a complex sclerosing lesion with LGAC. The second and third cases were investigated by core needle biopsies: the preoperative histological features were suggestive of but not diagnostic of LGAC, until further excision biopsies were performed. The fourth case entailed a frozen section specimen, for which definitive diagnosis was deferred to paraffins. The patients remained well with no evidence of recurrent disease to date. CONCLUSIONS: When limited material, in the form of needle aspirates, core biopsy specimens or frozen sections, is submitted for histology, making a diagnosis of LGAC is not only challenging, but may be impossible. In difficult cases, careful pathological assessment, clinicopathological correlation and follow-up or complete excision biopsy may prove invaluable in establishing a definitive diagnosis.

Biomarkers, Tumor↗
PubMed2006

An unusual cause of granulomatous inflammation: eosinophilic abscess in Langerhans cell histiocytosis.

Eosinophilic abscess inciting a granulomatous response has rarely been reported and appears not to have been described in the setting of a neoplasm. In this report, a case is described where a granulomatous response occurred around eosinophilic abscesses in a patient with Langerhans cell histiocytosis, an association which has not previously been documented. On histology, the excised lymph node showed the presence of eosinophilic abscess and necrosis surrounded by granulomas, which in turn were surrounded by Langerhans cells, a feature confirmed on immunohistochemistry. Although rare, this case highlights the importance of careful examination of eosinophilic abscess with granulomatous inflammation in order to exclude an underlying neoplasm.

Abscess↗
PubMed2005

Sclerosing haemangioma mimicking hepatocellular carcinoma.

Sclerosing haemangioma is a rare variant of hepatic haemangioma. The radiological features on computed tomography and magnetic resonance imaging may not be typical for haemangioma and can be confused with hepatocellular carcinoma. We report sclerosing haemangioma occurring in a 65-year-old woman where the radiological features raise the possibility of hepatocellular carcinoma.

Aged↗
PubMed2004

Pineal yolk sac tumour with a solid pattern: a case report in a Chinese adult man with Down's syndrome.

Intracranial germ cell tumours are rare. The incidence of primary intracranial yolk sac tumour is even more uncommon, with only two reported cases being associated with Down's syndrome in the English literature. This report details the findings of yolk sac tumour in the pineal region affecting a 22 year old Chinese man with Down's syndrome. Histology revealed yolk sac tumour with only a solid pattern, potentially mimicking the more common germinoma in the pineal region. No other germ cell components were identified. This is the third report of intracranial yolk sac tumour manifesting in a patient with trisomy 21. The pathology of this tumour and its differential diagnoses are discussed.

Adult↗
PubMed2000

Synthesis of tritium-labeled hydroxytyrosol, a phenolic compound found in olive Oil.

(3,4-Dihydroxyphenyl)ethanol, commonly known as hydroxytyrosol (1), is the major phenolic antioxidant compound in olive oil, and it contributes to the beneficial properties of olive oil. Bioavailability and metabolism studies of this compound are extremely limited, in part, related to unavailability of radiolabeled compound. Studies with radiolabeled compounds enable use of sensitive radiometric analytical methods as well as aiding elucidation of metabolic and elimination pathways. In the present study a route for the formation of hydroxytyrosol (1), by reduction of the corresponding acid 2 with tetrabutylammonium boronate, was found. Methods for the incorporation of a tritium label in 1 were investigated and successfully accomplished. Tritiated hydroxytyrosol (1t) was synthesized with a specific activity of 66 Ci/mol. The stability of unlabeled and labeled hydroxytyrosol was also investigated.

Biological Availability↗
PubMed1998

Flow-injection determination of total ammonia and total carbon dioxide in blood based on gas-diffusion separation and with a bulk acoustic wave impedance sensor.

A novel flow-injection (FIA) system, for the rapid and direct determination of both total ammonia (T[NH3]) and total carbon dioxide (T[CO2]) in clinical blood samples, has been developed. Samples were injected into a carrier stream of H2O, then emerged with a reagent stream, where the analyte was converted into a gaseous species and diffused across a PTFE gas-permeable membrane into an acceptor stream. The trapped NH3/CO2 in the acceptor was determined on line by a bulk acoustic wave (BAW) impedance sensor. At a through-put of 20 and 65 h(-1), the proposed system exhibited a linear frequency response up to 200 micromol l(-1) ammonium and 20 mmol l(-1) bicarbonate with a detection limit of 1.0 and 10 micromol l(-1), respectively. Results obtained for T(NH3) in serum and T(CO2) in plasma were in agreement with those obtained by the conventional glutamate dehydrogenase (GDH) method and gas-sensing electrode method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rate and potential interferents on the FIA signals were also discussed.

Acoustics↗
PubMed1992

Once daily felodipine monotherapy in mild to moderate hypertension.

In a single-blind study conducted at our centres, 78 hypertensive patients were enrolled with 58 completing the study according to the protocol. Mean supine and standing blood pressures were significantly reduced after treatment with felodipine, reductions being 27/21 mmHg (p < 0.0001) and 25/19 mmHg (p < 0.0001) respectively. Of 46 patients given felodipine 5 mg, 44 (95.7%) achieved target blood pressure defined as a diastolic blood pressure of < 90 mmHg, while all 12 patients on felodipine 10 mg did so. The 2 patients who did not achieve target pressure at the final visit did so on previous visits. There were no differences in pre and post-treatment laboratory variables. Treatment was discontinued in 6 patients because of headaches. No adverse events of clinical significance were reported in the 58 patients who completed the study. In conclusion, we found felodipine given once daily to be effective in the treatment of mild to moderate hypertension.

Adult↗
PubMed1992

Oral pefloxacin in the treatment of CAPD peritonitis.

Continuous ambulatory peritoneal dialysis (CAPD), a widely used replacement therapy for end stage renal failure, is frequently complicated by bacterial peritonitis. The infecting organisms are mainly staphylococci and gram negative aerobes. Pefloxacin is a fluorinated quinolone with good in-vitro activity against these pathogens. The objective of this open non comparative study is to determine the effectiveness and safety of oral pefloxacin mesylate as a single first line antimicrobial treatment of CAPD peritonitis. 28 episodes of CAPD peritonitis were treated with a stat dose of pefloxacin 800 mg. followed by 400 mg. 12 hourly for about 15-18 days. A pefloxacin sensitive organism was isolated in 17 episodes. 11 episodes were culture negative. Treatment results showed a cure in seventeen (60.7%), no treatment response in seven (25%), and relapses in four (14.2%). Side effects encountered were not serious except for one incident of a generalized seizure. We conclude that oral pefloxacin is convenient, safe and effective enough as a single first line antimicrobial treatment for CAPD peritonitis.

Administration, Oral↗
PubMed1991

Drug interaction between cyclosporine A and quinine in a renal transplant patient with malaria.

We report a previously undocumented drug interaction between cyclosporine A and quinine. A 39 year old Asian with a recent renal transplant was diagnosed to have a mild cerebral falciparum malaria. He was treated with seven days of oral quinine (600 mg, 8 hourly), followed by a stat dose of pyrimethamine (75 mg)--sulfadoxime (1200mg) because of a strong suspicion of chloroquine resistant falciparum malaria. Using a polyclonal radioimmunoassay method, we measured morning trough cyclosporine A level before, during and after the quinine treatment. Results showed a gradual decrease in the cyclosporine A level from a baseline value of 328 ng/ml to 107 ng/ml after seven days of oral quinine with a subsequent rise to pre-treatment level after discontinuation of quinine. There was no significant change in the dose of cyclosporine A administered during the period of quinine treatment (4.05 to 3.83 mg/kg body weight). Biochemical liver function tests, serum creatinine and hematological parameters were also essentially unchanged during this period. In vitro study showed no significant methodological interference in the cyclosporine assay by quinine dihydrochloride. These findings suggest an in vivo drug interaction between cyclosporine A and quinine. The mechanism of this interaction is not clear. Further studies are required to confirm the significance of this observation. Quinine and its stereoisomer, quinidine should be used with caution until further information is available.

Adult↗
PubMed1990

The histopathological pattern of primary IgA nephropathy in a Malaysian patient population.

In the 10-year period from October 1977 to July 1987, 149 cases of primary IgA nephropathy were histologically confirmed through renal biopsies in the Department of Pathology, University Hospital, Kuala Lumpur. The ages of these patients ranged from 5 to 72 years, with the majority in the 20-30 year age group. There was no sex preponderance. The ethnic distribution showed a significant predominance of Chinese with 107 (71.8%) Chinese, 24 (16.1%) Malays, 15 (10.1%) Indians and 3 others. A wide range of renal glomerular pathology was seen, the commonest being diffuse mesangioproliferative glomerulonephritis (59.1%). Focal proliferative glomerulonephritis (14.1%) followed by minimal change glomerulonephritis (10.7%) were next in order of frequency. Immunofluorescence studies consistently demonstrated heavy and predominant IgA deposition in the mesangium. Weak deposition of C3, IgG and IgM were also observed in various combinations.

Adolescent↗
PubMed1988

Gastric mucosal blood flow response to stimulation and inhibition of gastric acid secretion.

The effect of stimulation (with graded doses of intravenous pentagastrin) and inhibition (with an H2-blocker or a proton pump inhibitor) of acid secretion on corpus mucosal blood flow was investigated. Hydrogen gas clearance was used to measure blood flow in the basal portion of the mucosa of anesthetized rats. A dose-related increase in acid output increments above resting level was observed with the doses of pentagastrin from 0 (saline infusion) to 40 micrograms/kg.h. With the doses of pentagastrin from 0 to 80 micrograms/kg.h there was a dose-related increase in mucosal blood flow increments above resting levels. A linear correlation (r = 0.7) was observed between increments in acid output and increments in mucosal blood flow with increasing doses of pentagastrin from 0 to that producing maximal acid secretion (40 micrograms/kg.h). Inhibition of pentagastrin-stimulated acid secretion by cimetidine or omeprazole returned stimulated gastric mucosal blood flow to baseline levels.

Animals↗
PubMedDate not supplied

Automatic integrated circuit die positioning in the scanning electron microscope.

In scanning electron microscope (SEM)-based integrated circuit (IC) failure analysis, there is often a need for manual location of a prespecified failure site in several ICs. Such a procedure is both tedious and time consuming. This paper presents a new vision-based die positioning system that can automatically locate a specified failure site without the need for a high-accuracy specimen stage. Depending on the appearance of the desired failure site, the system applies either image registration or feature tracking to locate the site. Experiments performed on a variety of IC samples show that the system is able to locate the failure site accurately, even in the presence of unfavorable conditions such as IC sample rotation and repetitive IC patterns.

Journal Article↗