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Biomedical subjects

A L Tan

Publications and source records attributed to A L Tan.

36 records · Page 2Linked to original sources
PubMed1999

Disseminated Penicillium marneffei infection: a report of five cases in Singapore.

Penicillium marneffei has emerged as an important opportunistic pathogen in HIV-infected patients in Southeast Asia. We report the first 5 cases of P. marneffei diagnosed in Singapore. All the patients were HIV-infected and were either Thai nationals or had frequently travelled to Thailand. Fever, weight loss, anaemia and papular skin lesions were common clinical manifestations in our patients, all of whom had the organism isolated from blood. Skin biopsy specimens showed histological evidence of P. marneffei in 2 patients. In 1 patient each, the organism grew in cultures of specimens from bone marrow and respiratory secretions. Amphotericin B therapy followed by itraconazole were used in 3 of our 5 patients and was associated with good clinical response and outcome.

AIDS-Related Opportunistic Infections↗
PubMed1998

Complexes of salicylaldehyde acylhydrazones: cytotoxicity, QSAR and crystal structure of the sterically hindered t-butyl dimer.

A series of acylhydrazones of salicylaldehyde and their transition metal complexes, predominantly copper(II), have been prepared and characterized. The crystal structure of the Cu(II) complex of the sterically hindered t-butyl derivative contains a phenolato bridged dimer with the ligand coordinated as a tridentate moiety. QSAR analyses of the cytotoxicity of the chelators and their Cu(II) complexes reveals that solubility is the dominant factor for activity. Compounds display a maximum with respect to lipophilicity, allowing optimization of the bioactivity for both the ligands and their complexes. Copper complexes are significantly more cytotoxic than the metal-free ligands and complexes of other metals: Cu > Ni > Zn = Mn > Fe = Cr > Cr > Co.

Aldehydes↗
PubMed1998

Structure-activity relationships of some indolo[3,2-c]quinolines with antimalarial activity.

The synthesis, physicochemical characterization and in vitro antimalarial activity of a series of indolo[3,2-c]quinolines (9a-f) are described. There is only a poor correlation between the activity and hydrophobicity. In contrast, 33% of the observed variation in antimalarial activity can be attributed to the size of the side chain attached to position 9 of the indoloquinoline ring. An increase in the size of this dibasic side chain generally results in a reduction in activity, suggesting that it is accommodated in a site/cavity of limited size on the receptor. More significantly, the charge on the distal nitrogen (N3) on the side chain, located 10-11 A from the quinoline N, could account for 75% of the observed variation. Since a large charge on N3 is associated with improved antimalarial activity, it is suggested that N3 is protonated and functions as a H bond donor in the drug-receptor interaction.

Animals↗
PubMed1998

Normal human corneal cell populations evaluated by in vivo scanning slit confocal microscopy.

PURPOSE: To analyze cellular populations in healthy human corneas. METHODS: The study group consisted of 58 eyes of 45 patients with normal corneas. The age distribution was 45 +/- 17 years (mean +/- SD; range, 20-84). Scanning slit confocal microscopy of the central corneas was performed. The images were analyzed visually for cell morphology, and the densities and areas of cells were measured. RESULTS: No statistically significant differences were measured in cell densities or cell areas of any corneal layer between female and male patients (p = 0.22-0.50) nor between right and left eyes (p = 0.16-0.45). The area of superficial epithelial cells was 913 +/- 326 microm2 (mean +/- SD; range, 518-2,112), and the superficial epithelial cell density was 1,213 +/- 370 cells/mm2 (mean +/- SD; range, 473-1,929). The area of basal epithelial cells was 177 +/- 19 microm2 (mean +/- SD; range, 138-242), and the basal epithelial cell density was 5,699 +/- 604 cells/mm2 (mean +/- SD; range, 4,135-7,267). The average apparent keratocyte density was 1,058 +/- 217 cells/mm2 (mean +/- SD; range, 604-1,599) in the anterior stroma, and 771 +/- 135 cells/mm2 (mean +/- SD; range, 493-1,145) in the posterior stroma. The difference in apparent keratocyte densities between the anterior and posterior stroma was statistically significant (p < 0.001). The average endothelial cell area was 334 +/- 51 microm2 (range, 273-553), and the cell density was 3,055 +/- 386 cells/mm2 (mean +/- SD; range, 1,809-3,668). The endothelial cell density had a negative, statistically significant correlation with age (r = -0.68, p < 0.001). The densities of the other corneal cell layers did not have a statistically significant correlation with age. CONCLUSION: In vivo scanning slit confocal microscopy is a useful tool for studying corneal cell populations. Central corneal cell densities were found to decrease significantly with age only in the endothelium. For the first time in human corneas using in vivo confocal microscopy, this study statistically confirms a higher apparent number of keratocytes in the anterior stroma than in the posterior stroma.

Adult↗
PubMed1998

In vivo confocal microscopy of Fuchs' endothelial dystrophy.

PURPOSE: The purpose of this study is to analyze in vivo confocal microscopic findings of corneas with Fuchs' endothelial dystrophy. METHODS: Central corneas of 17 eyes of 11 patients aged 41-86 years were examined using in vivo scanning slit confocal microscopy after being diagnosed with Fuchs' endothelial dystrophy. The cellular structure of the corneas was analyzed morphologically and quantitatively and compared to control results from 22 healthy corneas. RESULTS: Bullae were detected in the basal epithelial layer of one eye. Eight of 17 eyes (47%) exhibited an abnormal Bowman's layer: diffuse bright reflection and absence of nerves. Eleven eyes (65%) exhibited abnormal anterior stroma: lacunae and diffuse increased light reflection due to edema. In 12 eyes (71%), lacunae or dark bands 5-20 microm wide against increased background reflection were noted in the posterior stroma. Descemet's membrane was thickened in all eyes. Dark bands were detected in six eyes (35%). Guttae (137-1,231/mm2) 20-40 microm in diameter were found in every endothelial cell layer. The mean endothelial cell count was 1,202 +/- 850 (cells/mm2 +/- SD; range, 0-2,735). There was a positive correlation between endothelial cell counts obtained by specular microscopy and those obtained by confocal microscopy (r = 0.95). CONCLUSION: In vivo confocal microscopic findings of Fuchs' endothelial dystrophy are described for the first time in a series of cases. Pathological changes in Fuchs' dystrophy were detected in all corneal layers, more frequently in the posterior layers. Endothelial cell counts obtained with confocal microscopy were statistically similar to those obtained with standard specular microscopy.

Adult↗
PubMed1995

Comparison of Pseudomonas pseudomallei from humans, animals, soil and water by restriction endonuclease analysis.

Pseudomonas pseudomallei isolates from 62 human, 17 animal, 3 soil and 3 water samples were examined by genomic DNA digestion with PstI. Five major (RE I, II, III, IV, V) reproducible restriction patterns were observed, with most (56/62) of the human isolates displaying RE I (30/62), II (5/62), III (15/62), IV (4/62), V (2/62), and the animal (16/17), soil (2/3), water (3/3) isolates showing predominantly RE II profiles. Six human and one soil isolates showed patterns different from those of RE I to V. Restriction endonuclease analysis may be applied in epidemiological studies of melioidosis.

Animals↗
PubMed1994

Bacteroides fragilis meningitis.

Bacteroides fragilis is an obligate anaerobic bacillus residing in the normal intestinal flora of the colon. Anaerobic bacterial meningitis due to this pathogen is rarely diagnosed and if present, a predisposing source of infection should be actively sought for. Anaerobic cultures of cerebrospinal fluids should be done for patients with meningitis, especially those with concomitant pathologies that predispose to anaerobic infections. Two cases of anaerobic meningitis due to Bacteroides fragilis, one associated with cholesteotoma and the other with nasopharyngeal carcinoma, are reported. Both were successfully treated with metronidazole.

Adult↗
PubMed1992

Renal tubular function of cadmium exposed workers.

The kidney is considered the critical organ following long term occupational or environmental exposure to cadmium. Tubular dysfunction in the form of low molecular weight proteinuria is the earliest manifestation of cadmium nephrotoxicity. The current acceptable critical concentration of cadmium in the urine is 10 ug Cd/g creatinine. The aim of this paper is to identify the presence of tubular dysfunction among workers with less than 10 ug Cd/g creatinine. The exposed group of 92 workers were from a nickel-cadmium battery factory. The control group of 122 workers were factory and sedentary office workers with no known history of exposure to nephrotoxic agents. The urinary excretion of N-acetyl-D-glucosaminidase (NAG), beta-2-microglobulin (beta 2m) and alpha-1-microglobulins (alpha 1m) were measured from morning spot urine samples. The age, sex and race adjusted NAG and alpha 1m showed increasing trend with rising urinary cadmium levels. Levels were significantly raised when the urinary cadmium was above 5 ug Cd/g creatinine. A similar trend was seen with increasing length of exposure. Renal tubular dysfunction is present among cadmium exposed workers with levels below the current critical concentration.

Acetylglucosaminidase↗
PubMed1992

Clotest (rapid urease test) in the diagnosis of Helicobacter pylori infection.

Over a period of 3 months, 85 patients who underwent gastroscopy had antral biopsy taken for Clotest, histology and/or culture for Helicobacter pylori (HP). The sensitivity and specificity of Clotest were found to be 77% and 96% respectively with negative predictive value of 63% and positive predictive value of 98%. Ninety-two percent of the positive Clotests were positive within 20 minutes, thus giving rapid result. Therefore, Clotest is a rapid, sensitive and highly specific test for HP infection. A high correlation between HP infection and chronic gastritis was noted and the prevalence of HP infection in patients with duodenal ulcer (90%) was higher than that of gastric ulcer (64%) or non-ulcer group (65%).

Adolescent↗
PubMed1991

Serodiagnosis of melioidosis in Singapore by the indirect haemagglutination test.

Melioidosis is endemic in Singapore, with diagnosis dependent upon both bacteriological culture and serodiagnosis. Using the polysaccharide (melioidin)-sensitized turkey red cells in the indirect haemagglutination test (IHAT), 20 (100%) of the Pseudomonas pseudomallei culture-positive cases were detectable by the IHAT with titles ranging from 1:16 to 1:32, 768. Eight of these patients who died within a few days after the IHAT was performed had titres ranging from 1:16 to 1:1028. Five culture-negative patients, with clinical symptoms suggestive of melioidosis infection and who responded to treatment with ceftazidime, showed IHA titres between 1:64 and 1:8,192. One hundred and twenty one sera from patients with pneumonia, abscesses, or diabetes mellitus were IHAT negative. The IHAT showed good specificity since negative titres were seen in tests using sera from 2 patients with culture-positive Pseudomonas aeruginosa and 4 patients positive for Legionella. IHAT negative results were obtained from tests of 50 normal blood donors and 50 sewerage workers. Of 683 national servicemen tested, 5 (0.73%) had IHAT titres ranging from 1:16 to 1:128. Unlike hyperendemic areas such as Thailand where interpretation of IHAT is seriously hampered by IHA titres found in one-third to half of the population, serodiagnosis of melioidosis by the sensitive IHAT may be employed in Singapore as a routine procedure since background IHA titres are low.

Hemagglutination Tests↗
PubMed1990

Melioidosis: epidemiology and antibiogram of cases in Singapore.

There has been an increased incidence of melioidosis in Singapore. The disease affects mainly males, older patients and a disproportionately higher number of Indians and Malays. Possible predisposing illness include diabetes mellitus. Most patients are bacteraemic. Mortality rate is 72% for bacteraemic patients, as compared to 32% for non-bacteraemic patients. Local strains of Pseudomonas pseudomallei have been consistently sensitive to ceftazidime, chloramphenicol and piperacillin, and nearly always sensitive to tetracycline.

Adolescent↗
PubMed1977

A short measure of Eriksonian ego identity.

Developed a new measure of Erikson's (1950, 1959) concept of ego identity which would meet the following criteria: (a) that it be short, with an acceptable level of reliability; (b) that it be objective and easily scored; and (c) that it be free of response set contamination. A 12-item scale (Ego Identity Scale) with a forced choice format was constructed. Two further studies were conducted to test the validity of the scale. These studies showed that the Ego Identity Scale correlated as predicted with measures Of locus of control, intimacy, dogmatism, Tomkins' Left, occupational commitment, and political commitment. It also correlated in the predicted direction with measures of interpersonal trust and moral commitment though these correlations did not reach statistical significance.

Journal Article↗
PubMedDate not supplied

Epithelioid trophoblastic tumor: a case report.

Epithelioid trophoblastic tumor is a rare and distinctive pathologic entity within the complex family of gestational trophoblastic disease. We describe a case of epithelioid trophoblastic tumor occurring in a 34-year-old woman, who presented with a large uterine tumor 3 years following an uncomplicated pregnancy. The clinicopathologic findings in this case are typical of this unusual entity and consistent with current literature, with the exception of negative beta-human chorionic gonadotrophin levels. The distinguishing features from other intermediate trophoblastic tumors and tumor-like lesions are discussed.

Adult↗