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Biomedical subjects

D Tan

Publications and source records attributed to D Tan.

At least 37 records · Page 2Linked to original sources
PubMed2001

Optimized analytical method for cyclosporin A by high-performance liquid chromatography-electrospray ionization mass spectrometry.

The Micromass Platform LCZ mass detector parameters were optimized for simultaneous recording of the protonated (CsA-H+), sodium adduct (CsA-Na+) and potassium adduct (CsA-K+) of cyclosporin A eluted from a Symmetry Shield RP8 column. The optimized procedure allows a precise analysis of CsA in whole blood or serum without removal of salts prior to analysis. The ratio of the three forms of CsA varied depending on the assay condition and the types of specimens being analyzed. The summation of three ionic forms of CsA detected by LC-ESI-MS is a reliable and simple method to assess CsA concentration in the blood.

Cations, Monovalent↗
PubMed2001

Genetic disruption of host nitric oxide synthase II gene impairs melanoma-induced angiogenesis and suppresses pleural effusion.

Our previous study showed that genetic disruption of nitric oxide (NO) synthase II (NOS II) expression inhibits the metastatic ability of non-immunogenic B16 melanoma cells in syngeneic mice. In the present study, the mechanisms for this metastasis suppression were determined. B16-BL6 and B16-F10 murine melanoma cells were injected i.v. into syngeneic wild-type (NOS II(+/+)) and NOS II-null (NOS II(-/-)) C57BL/6 mice. Both melanoma cells produced less and smaller experimental pulmonary metastases in NOS II(-/-) mice than in NOS II(+/+) mice. Moreover, less metastatic pleural effusion was observed in NOS II(-/-) mice than in NOS II(+/+) mice. Immunohistochemical analyses indicated that absence of NOS II expression was correlated with decreased vascular endothelial growth factor expression and tumor-associated vascular formation. After activation with lipopolysaccharide and IFN-gamma, neither melanoma cell line produced detectable levels of NO. Our data demonstrate that tumor-induced expression of host NOS II enhances melanoma metastasis and pleural effusion, at least in part, through regulation of vascular formation and vascular permeability.

Animals↗
PubMed2001

Microsporidial keratoconjunctivitis in a healthy contact lens wearer without human immunodeficiency virus infection.

PURPOSE: To present a rare case of microsporidial keratoconjunctivitis in an otherwise healthy contact lens wearer without human immunodeficiency virus infection who responded to treatment with systemic albendazole and topical fumagillin. DESIGN: Interventional case report. METHOD: A cornea epithelial scraping from a man with unilateral keratoconjunctivitis previously treated with topical steroids was evaluated by modified trichome staining. MAIN OUTCOME MEASURES: The patient was evaluated for his symptoms, visual acuity, clinical observations, and pathologic examination of corneal scrapes. RESULTS: Modified trichome staining of an epithelial corneal scraping revealed pinkish to red organisms characteristic of microsporidia. Results of a human immunodeficiency virus (HIV) enzyme-linked immunosorbent assay test were negative. The symptoms of ocular discomfort and clinical signs of keratoconjunctivitis resolved after 2 months of treatment with albendazole and topical fumagillin. CONCLUSIONS: Ocular infection with microsporidia, although classically occurring in patients with HIV infection, may occur rarely in healthy individuals, especially if previously treated with systemic immune suppression or topical steroids. Microsporidial keratoconjunctivitis should be considered in the differential diagnosis of a contact lens wearer with atypical multifocal diffuse epithelial keratitis.

Adult↗
PubMed2001

The tripeptide feG reduces endotoxin-provoked perturbation of intestinal motility and inflammation.

Lipopolysaccharide (LPS)-induced intestinal endotoxaemia perturbs motility and causes activation and influx of inflammatory cells into the muscle tissue. Because rat submandibular gland peptide T (SGP-T; Thr-Asp-Ile-Phe-Glu-Gly-Gly), its carboxyl-terminal fragment tripeptide, FEG (Phe-Glu-Gly) and its D-isomeric analogue, feG, modulate intestinal anaphylactic reactions, we examined whether these peptides also modulate LPS-induced intestinal endotoxaemia in conscious rats. The disruption of the fasting pattern of intestinal MMCs (migrating motor complexes), induced by intravenous LPS (20 microg kg-1) injection, was prevented by all three peptides. The extravasation of leucocytes into the peritoneal cavity and increased expression of the activation marker CD18 on mesenteric tissue leucocytes (18 h after intraperitoneal injection of LPS) were reduced by orally administered feG, which also significantly decreased the number of intestinal tissue leucocytes expressing the integrin CD18. We conclude that feG attenuates both the immediate (intestinal motility) and late ( approximately 18 h) inflammatory reactions provoked by endotoxaemia.

Animals↗
PubMed2001

Ethnic comparisons of disease severity in children hospitalized with pneumonia in New Zealand.

OBJECTIVE: To determine if there are ethnic differences in disease severity in children hospitalized with pneumonia in New Zealand. METHODOLOGY: A population based audit of children hospitalized in Auckland with pneumonia over 12 months from 1 November 1994 to 31 October 1995. The study population was children aged from 0 to 14 years with a discharge diagnosis of pneumonia. The sample was stratified by ethnicity and included 151 Pacific, 85 Mäori and 151 European children. Measurements were made of demographics and prehospital care; vital signs and therapy received in the emergency department and inpatient wards and laboratory investigations performed. Comparisons between the three ethnic groups were adjusted for age, weight, gender, socio-economic status and relationship with primary care. RESULTS: A larger proportion of Pacific (15%) and Mäori (22%) children than European children (8%) had a respiratory rate elevated for > or = 2 days, odds ratio (OR) (95% CI): Pacific versus European 2.7 (1.1, 6.8), Mäori versus European 4.3 (1.7, 11.6). A larger proportion of Pacific (15%) and Mäori (15%) children than European children (< 1%) had a heart rate elevated for > or = 2 days, OR Pacific versus European 17.2 (3.2, 320), Mäori versus European 26.1 (4.4, 508). Compared with European children, a larger proportion of Pacific and Mäori children received intravenous fluids and antibiotics. A larger proportion of Pacific (29%) and Mäori (27%) children than European children (11%) received oxygen for > = 2 days, OR Pacific versus European 3.2 (1.6, 6.6), Mäori versus Europeans 2.6 (1.2, 6.2). CONCLUSIONS: Based on the comparisons of vital signs and intensity of therapy, Pacific and Mäori children hospitalized with pneumonia have more severe pneumonia than European children.

Adolescent↗
PubMed2001

Myopia and night lighting in children in Singapore.

AIM: To examine the role of night time lighting and myopia in children in Singapore METHODS: A cross sectional study was conducted on 1001 children in two Singapore schools. Cycloplegic refraction and A-scan biometry measurements were made in both eyes. A detailed questionnaire was completed by the parents to obtain information on night time lighting, near work activity, educational and demographic factors. RESULTS: There was no difference in myopia prevalence rates in children exposed to night time light (33.1%) compared with children who slept in the dark (31.4%) before age 2. In addition, vitreous chamber depth was not related to night light (p = 0.58) before age 2. These results remained even after controlling for near work. CONCLUSION: Myopia is not associated with night light in Asian populations.

Anterior Chamber↗
PubMed2001

Microbiological profile of a shipboard environment and the flora on contact lenses of seamen.

PURPOSE: The purpose of this study was to culture and identify the spectrum of organisms (and their sensitivities) that contaminate the extended wear contact lenses of seamen in their working environment. A secondary aim was to identify the most appropriate first-line antibiotic regimen to be used on seamen who sustain contact lens-related corneal keratitis on board ship. METHODS: Twenty pairs of contact lenses of 20 seamen in one group and 24 pairs in another group wearing contact lenses were collected at the end of 1 week of extended wear. Groups one and two differed only in the way lenses were stored prior to culturing. All contact lenses were then brought to the microbiological lab within 24 hours for culture and sensitivity testing. RESULTS: The most common contaminants on the contact lenses in this study were Staphylococcus epidermidis and Staphylococcus aureus, organisms resident on the normal eyelids. Enterobacterand Pseudomonas species, present in a shipboard environment, were also identified as contaminants on the contact lenses. The organisms cultured from the contact lenses correlated well with those of normal lid flora as well as from the ship environment and are probably derived from these sources. Storage in saline-containing preservatives yielded significantly less positive bacterial cultures from the contact lenses in our study. All bacterial isolates were sensitive to ciprofloxacin whereas several bacteria resistant to cefazolin and gentamicin were identified. CONCLUSION: The most common contaminants on the contact lenses in this study were Staphylococcus epidermidis and Staphylococcus aureus, organisms resident on the normal eyelids. Enterobacter and Pseudomonas species, which are normally present in a shipboard environment, were also identified as contaminants on the contact lenses. Ciprofloxacin is effective against all organisms identified as contaminants on the contact lenses in this study. Of all the antibiotics tested, it is probably the most suitable agent against contact lensrelated keratitis under such shipboard circumstances and is thus recommended in these situations.

Anti-Infective Agents↗
PubMed2001

A prospective evaluation of surgeon performed sonography as a screening test in blunt abdominal trauma.

INTRODUCTION: Sonography has found a role in the evaluation of patients with abdominal injury. However, the accuracy of sonography as performed by non-radiologists remains controversial. This study aims to determine the accuracy of focused abdominal sonography for trauma when performed by surgeons. MATERIALS AND METHOD: Over a 1-year period, 48 patients with abdominal injury were initially evaluated for free intraperitoneal fluid by sonography. These tests were performed by 2 surgeons who had received instructions and performed a minimum of 30 examinations. Sonographic findings were then compared with other diagnostic modalities including computed tomography (CT) scan, diagnostic peritoneal lavage and exploratory laparotomy. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for sonography were found to be 0.86, 0.92, 0.89, 0.90 and 0.89, respectively. Although not specifically sought for, 2 cases of solid organ injury and 1 haemothorax, which were missed in initial examinations and X-rays, were detected on sonography. CONCLUSION: In conclusion, our initial experience suggests that local surgeons can perform a focused sonographic examination for trauma with acceptable accuracy. Although sonography lacks the sensitivity of diagnostic peritoneal lavage and the accuracy of CT scan, the diagnostic algorithm for abdominal trauma should include sonography as a screening test.

Abdominal Injuries↗
PubMed2001

Myopia in Singapore kindergarten children.

PURPOSE: The purpose of this study was to examine whether close-up work was related to myopia in Singapore kindergarten children. METHODS: One hundred twenty-eight children, ages 3 to 7 years, from a kindergarten in Singapore were examined by cycloplegic autorefraction. The parents also completed a questionnaire on the different types of close-up work activities each child was engaged in, socioeconomic status, and parental history of myopia. RESULTS: Myopic children spent 3.0 hours per day (median) on close-up work activity, while nonmyopic children spent 2.0 hours per day (median) on close-up work activity. The prevalence of myopia in the sample was 8.6%. CONCLUSION: Close-up work activity was not related to myopia in pre-school children.

Child↗
PubMed2000

The carboxamide feG(NH2) inhibits endotoxin perturbation of intestinal motility.

The submandibular gland rat-1 (SMR1) salivary gland prohormone contains several peptides, submandibular gland peptide-T (SGP-T) and the tripeptide, FEG, which possess anti-inflammatory activities. The D-isomeric form of FEG, feG, also is a potent anti-inflammatory peptide. In this study, we compared the inhibitory activity of feG and its carboxamide derivative, feG(NH2), on the perturbations of intestinal motility induced by intravenous lipopolysaccharide. feG(NH2) was 20-30 times more potent than feG in reducing the motility disturbances induced by lipopolysaccharide. feG may undergo square-amidation to yield a hormone that strongly down-regulates intestinal responsiveness to endotoxin.

Amides↗
PubMed2000

Renal toxicity of the carcinogen delta-aminolevulinic acid: antioxidant effects of melatonin.

An increased incidence of cancer in patients suffering from acute intermittent porphyria (AIP) is thought to be related to delta-aminolevulinic acid (ALA) accumulation. Chronic treatment with ALA augmented 8-oxo-7,8-dihydro-2'-deoxyguanosine levels, decreased microsomal and mitochondrial membrane fluidity and increased lipid peroxidation in blood serum. Co-treatment with melatonin completely counteracted the effects of ALA. Melatonin effectively protects DNA and microsomal and mitochondrial membranes in rat kidney from oxidative damage due to ALA. Because of its low toxicity and anticarcinogenic properties, melatonin could be tested as an agent to reduce oxidative damage in patients with AIP.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2000

Melatonin reduces phenylhydrazine-induced oxidative damage to cellular membranes: evidence for the involvement of iron.

Phenylhydrazine and iron overload result in augmented oxidative damage and an increased likelihood of cancer. Melatonin is a well known antioxidant and free radical scavenger. The aim of this study was to determine whether melatonin would protect against phenylhydrazine-induced oxidative damage to cellular membranes and to evaluate the possible role of iron in this process. Changes in lipid peroxidation and microsomal membrane fluidity were estimated after the treatment of rats with phenylhydrazine (15 mg/kg body weight, daily, 7 days) alone and melatonin or ascorbic acid (15 mg/kg body weight, two times daily, 8 days), or their combination. Additionally, lipid peroxidation was measured in liver homogenates from untreated and melatonin or ascorbic acid-treated rats in vivo and exposed to iron in vitro. Melatonin, but not ascorbic acid, reduced phenylhydrazine-induced lipid peroxidation in vivo in spleen (3.16+/-0.06 vs. 3.83+/-0.12 nmol/mg protein, P<0.05) and plasma (7. 73+/-0.52 vs. 9.96+/-0.71 nmol/ml, P<0.05) and attenuated the decrease in hepatic microsomal membrane fluidity (1/polarization, 3. 068+/-0.007 vs. 3.027+/-0.008, P<0.05). In vitro exposure to iron significantly enhanced the lipid peroxidation in liver homogenates from untreated (3.34+/-0.75 vs. 1.25+/-0.28, P<0.05) or ascorbic acid-treated rats (2.72+/-0.39 vs. 0.88+/-0.06, P<0.05) but not from melatonin-treated rats (1.49+/-0.55 vs. 0.68+/-0.20, NS). It is concluded that free radical mechanisms are involved in the toxicity of phenylhydrazine and that the antioxidant melatonin, but not ascorbic acid, reduces the toxic affects of phenylhydrazine in vivo and of iron in vitro in cell membranes. Therefore, melatonin co-treatment in conditions of iron overload may prove beneficial.

Animals↗
PubMed2000

Risk factors for the development of pterygium in Singapore: a hospital-based case-control study.

PURPOSE: A hospital-based case-control study, designed to evaluate the risk factors for the development of pterygium in Singapore. METHODS: Sixty-one cases and 125 controls were interviewed at the Singapore National Eye Centre. Information on present and past (5 and 10 years ago) exposure to sunlight on weekdays and weekends, sociodemographic data, behavior lifestyle and family history of eye disease was collected. RESULTS: Patients with pterygia were mostly males, smoked and drank alcohol more often, had lower combined family incomes and were more likely to have a family history of eye disease. The adjusted odds ratios for the development of pterygia were 1.27 (95 percent confidence interval 1.06 to 1.54) and 1.31 (95 percent confidence interval 1.09 to 1.57) for participants who had spent more time in the sun five and ten years ago respectively. CONCLUSIONS: Pterygium is an important public health problem in Singapore and its development is related to the amount of sunlight exposure.

Adult↗
PubMed2000

[Lymphocyte subset and its apoptosis in chronic hepatitis C].

OBJECTIVE: To explore the autoimmune pathogenesis induced by hepatitis C virus. METHODS: Serum anti-GOR and peripheral blood lymphocyte subset and its apoptosis rate after activated by Pokeweed mitogen (pwm) in vitro were measured by enzyme-linked immunosorbent assay and flow cytometry, respectively. Eighteen individuals with chronic hepatitis C and 16 healthy controls were observed. RESULTS: The positive rates of serum anti-GOR (66.7%) and ANA (44.4%) were significantly higher in chronic hepatitis C than normal controls (chi(2)=26.86, chi(2)=9.30, P<0.005). The apoptosis percentage of PBMCs and CD3(+)T cell was elevated in individuals with chronic hepatitis C when compared with normal controls (t=2.44, P<0.05). However, the apoptosis percentage of CD4(+)T and CD19(+)B cells in PBMCs was significantly decreased in patients with anti-GOR positive compared to anti-GOR negative (t=3.17, P<0.01; t=2.294, P<0.05). Similarly, the percentage of CD4(+)CD8(+) T cells in anti-GOR positive patients was increased and CD3(+)/CD4(+) was decreased (t=2. 18, P<0.05) compared to anti-GOR negative (t=2.44, P<0.05; t=2.18, P<0.05). CONCLUSION: autoimmune response exists in chronic hepatitis C patients. There is an imbalance of lymphocyte subset and its apoptosis, which may be one of the important reasons for the mechanism of autoimmune pathogenesis of chronic hepatitis C.

Adult↗
PubMed2000

[A prospective study of posttransfusion hepatitis B virus infection].

OBJECTIVE: To understand the status of HBV posttransfusion infection after blood HBsAg screening of the blood donors. METHODS: Serum samples of blood recipients and donors were detected for HBV-M and HBV DNA by ELISA technique and polymerase chain reaction respectively. RESULTS: There were 326 sera positive for HBV-M and 57 for HBV DNA in 583 blood donors' sera. 39 sera were positive for HBV-M and 23 positive for HBV-DNA in 136 sera of blood recipients, the positive seroconversion rates were 28.68% and 16.9% respectively. CONCLUSIONS: There is high incidence of HBV infection in blood donors though they have been screened for HBsAg. The posttransfusion HBV infections are still occurring, therefore, the blood donors should be strictly tested for HBV-M. If conditions are possible, the HBV DNA had better been screened.

Adolescent↗
PubMed2000

[Ecological effect of CdCl2 on plasmid and role of plasmid in Cd-tolerance of its host].

After treating the plasmid of Escherichia coli HB101 by CdCl2 in vitro or in vivo, the effect of Cd on the structure of plasmid pWH58 DNA was studied through argarose gel electrophesis and restriction fragment length polymorphism analysis. By comparing the growth of E. coli with and without plasmid cultured in the medium with Amp LB and non-anti LB under different concentrations of CdCl2, the effect of Cd on plasmid E. coli of in vivo and the role of plasmid in Cd-tolerance of its host were studied. Cd treatments of E. coli in vitro or in vivo didn't cause an obvious change of the structure of plasmid pWH58 DNA. Plasmid pWh58 could replicate for regeneration and gene express under Cd stress. Plasmid pWH58 of E. coli in vivo lowered Cd-tolerance of its host form 75 mg.L-1 to 50 mg.L-1. Cd-tolerance of E. coli ascended markedly after Cd taming, but had a trend of reversing to original level after restoration, indicating that Cd-tolerance of E. coli could be tamed, but the tamed Cd-tolerance still had no genetic basis.

Cadmium Chloride↗