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Biomedical subjects

S Tan

Publications and source records attributed to S Tan.

At least 19 recordsLinked to original sources
PubMed2007

The effects of oxygen concentration on in vitro output of prostaglandin E2 and interleukin-6 from human fetal membranes.

Labour at all gestational ages has clear biochemical parallels with an inflammatory response, typified by the increased output of prostaglandins (PGs) and cytokines within the pregnant uterus. The main sources are the fetal membranes, including the amnion, chorion and decidua, and it is well established that stimuli [bacteria, bacterial endotoxins, interleukin (IL)-1beta, corticotrophin releasing hormone and platelet activating factor], as well as negative regulators (progesterone and IL-10), control the net output of PGs and cytokines in vitro. In this study, we have investigated the effect of oxygen tension on fetal membrane biology, as a reconsideration of the literature suggests that fetal membranes are normally exposed to approximately 3% O(2) (approximately 20 mmHg) in vivo, rather than the 20% O(2) (150 mmHg) used for in vitro culture. The output of prostaglandin E(2) from non-activated fetal membranes in response to IL-1beta was decreased by approximately 80% at 16 and 24 h of culture, whereas the inhibition of IL-6 production was time-dependent, reaching 90% after 16 h and 50% after 24 h. Tissues obtained after labour (or after the activation of inflammatory processes leading to labour) were not inhibited by the low levels of oxygen, indicating that only before the onset of labour does oxygen regulate fetal membrane biology. The data identify oxygen as a regulator of fetal membrane inflammatory functions during human pregnancy, and its mechanism of action requires further study.

Dinoprostone↗
PubMed2007

Risk factors for hepatitis C fibrosis: a prospective study of United States veterans compared with nonveterans.

Chronic hepatitis C virus (HCV) infection causes cirrhosis in many infected patients; however, a better understanding of the risk factors for fibrosis progression in high HCV prevalence groups such as US veterans is needed. We wished to compare the demographic, clinical characteristics, and independent variables that influence fibrosis in US veterans vs nonveterans with chronic HCV. HCV-seropositive US veterans (n = 459) and nonveterans (n = 395) prospectively completed a detailed medical, social and occupational questionnaire. Clinical factors for progressive liver disease were compared between veterans and nonveterans and fibrosis stage assessed on liver biopsies (168 veterans and 208 nonveterans). Using polychotomous logistic regression, fibrosis was analysed as both a progressive and categorical outcome to determine independent risk factors for both patient groups. Although veterans were significantly older and had higher lifetime alcohol consumption than nonveterans, their median fibrosis scores did not differ from nonveterans. By univariate analysis, alanine aminotransferase, necroinflammatory activity (NIA), and cryoglobulin positivity were associated with fibrosis in veterans and nonveterans (P < 0.05, all comparisons), whereas steatosis was associated with fibrosis only in nonveterans (P < 0.0001). By multivariate analysis, NIA was an independent risk factor for fibrosis in both groups (P < 0.01). However, fibrosis in nonveterans was also independently associated with steatosis, significant alcohol consumption and age (P < 0.04, all comparisons). Independent risk factors for fibrosis vary among high HCV prevalence groups such as veterans when compared with nonveterans. Understanding specific patient cohort effects is important for determining independent risk factors for disease progression in chronic HCV infection.

Adult↗
PubMed2006

Mortality within 30 days of chemotherapy: a clinical governance benchmarking issue for oncology patients.

No national benchmark figures exist for early mortality due to chemotherapy unlike for surgical interventions. Deaths within 30 days of chemotherapy during a 6-month period were identified from the Royal Marsden Hospital electronic patient records. Treatment intention--curative or palliative, cause of death and number of previous treatments--were documented. Between April 2005 and September 2005, 1976 patients received chemotherapy with 161 deaths within 30 days of chemotherapy (8.1%). Of these, 124 deaths (77.0%) were due to disease progression. Of the other 37 deaths, 12 (7.5%) were related to chemotherapy, six each for solid tumours and haematological malignancies, of which seven (4.3%) were due to neutropenic sepsis. For the remaining 25 deaths (15.5%) there was insufficient information. There were more deaths after third and subsequent lines of therapy than with first and secondlines of therapy. Only 12 of the 161 deaths occurred in patients who were receiving potentially curative chemotherapy to give a mortality rate in breast and gastrointestinal malignancy of 0.5 and 1.5%, respectively. It is possible to audit mortality within 30 days of chemotherapy and this should become a benchmark for standard practice nationally. Most deaths were due to disease progression in the palliative setting. We practice this form of audit each quarter and feed back to the treating teams so that deaths are discussed and practice monitored.

Adolescent↗
PubMed2006

A safe and efficient strategy for endoscopic resection of large, gastrointestinal lipoma.

BACKGROUND: Gastrointestinal (GI) lipomas are benign, slowly growing, submucosal tumors, which may cause gastrointestinal bleeding, anemia, intussusception, and bowel obstruction. The aim of this study is to explore the safe and effective strategy for endoscopic removal of large GI lipomas. METHODS: During last 10 years, fifteen large and symptomatic GI lipomas were resected under endoscopy in our hospital. In them, two large lipomas with small stalk (< 2 m in diameter) were resected by polypectomy; ten large lipomas with base size greater than 2 cm in diameter were removed using a "subtotal resection." Three other large lipomas with small stalk (< 2 m in diameter) were resected by multistep resection. Endoscopic ultrasonography (EUS) and miniprobe endoscopic ultrasound were performed in six cases from January 2000 to July 2004 to confirm that those lesions were lipomas that were superficial to the muscularis propria. RESULTS: All 15 lesions were successfully removed and were histopathologically confirmed to be lipomas. No severe complications, such as perforation or hemorrhage, developed after endoscopic removal. No recurrence was observed after 1-8 years follow-up endoscopic examination. CONCLUSIONS: Various, large GI lipomas can be removed safely by electrosurgical snare resection under endoscopy following the guidance of the present therapeutic strategy.

Adult↗
PubMed2006

Herbicidal inhibitors of amino acid biosynthesis and herbicide-tolerant crops.

Acetohydroxyacid synthase (AHAS) inhibitors interfere with branched-chain amino acid biosynthesis by inhibiting AHAS. Glyphosate affects aromatic amino acid biosynthesis by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Glufosinate inhibits glutamine synthetase and blocks biosynthesis of glutamine. AHAS gene variants that confer tolerance to AHAS inhibitors have been discovered in plants through selection or mutagenesis. Imidazolinone-tolerant crops have been commercialized based on these AHAS gene variants. A modified maize EPSPS gene and CP4-EPSPS gene from Agrobacterium sp. have been used to transform plants for target-based tolerance to glyphosate. A gox gene isolated from Ochrobactrum anthropi has also been employed to encode glyphosate oxidoreductase to detoxify glyphosate in plants. Glyphosate-tolerant crops with EPSPS transgene alone or both EPSPS and gox transgenes have been commercialized. Similarly, bar and pat genes isolated from Streptomyces hygroscopicus and S. viridochromogenes, respectively, have been inserted into plants to encode phosphinothricin N-acetyltransferase to detoxify glufosinate. Glufosinate-tolerant crops have been commercialized using one of these two transgenes.

Adaptation, Physiological↗
PubMed2006

The combination of increased ovarian volume and follicle number is associated with more severe hyperandrogenism in German women with polycystic ovary syndrome.

The prevalence and relevance of polycystic ovaries (PCO) in German women with polycystic ovary syndrome has not been evaluated. This retrospective study included 212 PCOS patients (mean age 28 years) diagnosed by the NIH-criteria and consecutively recruited since 2003. Clinical features including anthropometric variables and the degree of hirsutism, family history, menstrual cyclicity as well as endocrine biochemical parameters were recorded. In addition, 3-h oral glucose tolerance testing for indices of insulin resistance and glucose metabolism was performed in each patient. Transvaginal ultrasound was used to detect polcystic ovaries, defined as the presence of at least one ovary > 10 ml or with at least 12 follicles of 2-9 mm diameter. In this German PCOS cohort, PCO were identified in 166 women (78%). Women with PCO (PXO+) had significantly higher LH/FSH ratios (median 2.1 vs. 1.7) and IGF-1 levels (median 182.5 vs. 160.5 ng/ml) compared to patients without PCO (PCO-). In addition, a significantly higher prevalence of acne (50% vs. 33%) and higher hirsutism scores (median 9 vs. 7) were found in PCO+ patients. Testosterone levels and the free androgen index (FAI) correlated significantly with ovarian volume and the number of ovarian follicles. Also, a subgroup of PCO+ women with a combination of increased ovarian volume and follicle number had higher testosterone levels (median 3.1 vs. 2.1 nmol/l) and FAI (median 7.6 vs. 4.5) compared to women with increased follicle count but normal volume. No differences were found in metabolic parameters or insulin resistance indices. PCO are common finding in German PCOS women. PCO appear to be associated with a more pronounced hyperandrogenemia, especially when both ovarian volume and follicle number are increased.

Adult↗
PubMed2006

Low serum 25-hydroxyvitamin D concentrations are associated with insulin resistance and obesity in women with polycystic ovary syndrome.

Insulin resistance (IR) and central obesity are common features of the polycystic ovary syndrome (PCOS). Vitamin D is thought to play a role in the pathogenesis of type 2 diabetes by affecting insulin metabolism. The aim of our study was to investigate the effect of 25-hydroxyvitamin D (25-OH-VD) on metabolic parameters and IR in PCOS. In 120 untreated PCOS patients (median age 28 years) levels of 25-OH-VD (radioimmunoassay method provided by DiaSorin), calcium and anorganic phosphate were measured. In addition, endocrine and metabolic variables were evaluated and a glucose tolerance test was performed to assess indices of IR. In the entire PCOS cohort, 25-OH-VD concentrations were negatively correlated with body mass index (r=-0.2765), body fat (r=-0.2490), HOMA-IR (r=-0.1947), hyperinsulinemia (r=-0.1892) and leptin levels (r=-0.2834), and positively correlated with HDL cholesterol (r=0.2630) (all p<0.05). Subgroup analysis of lean, overweight and obese women revealed significant higher 25-OH-VD levels in lean women. Differences remained significant when women were divided according to their 25-OH-VD levels. Women with hypovitaminosis D (<9 ng/ml) had higher mean BMI, indices of IR and leptin levels compared to women with normal serum levels (all p<0.05). Analysis of vitamin D and biochemical endocrine PCOS features revealed a significant correlation only between 25-OH-VD and sex hormone-binding globulin as well as the free androgen index. In conclusion, in PCOS women, low 25-OH-VD levels are associated with obesity and insulin resistance but not with PCOS per se.

Adolescent↗
PubMed2006

Stiff skin syndrome.

Stiff skin syndrome is a rare disorder characterized by pronounced skin induration, mild hypertrichosis and limited joint mobility, predominantly on the buttocks and thighs. Many heterogeneous cases have been reported under the name of stiff skin syndrome. We present a case of stiff skin syndrome from China, the diagnosis based on the patient's typical clinical and histopathological features.

Child, Preschool↗
PubMed2005

Universal DNA primers amplify bacterial DNA from human fetal membranes and link Fusobacterium nucleatum with prolonged preterm membrane rupture.

A large number of bacterial species have been identified in fetal membranes after preterm labour (PTL) associated with intrauterine infection by microbiological culture. In this study, we have investigated a molecular and bioinformatic approach to organism identification which surmounts the need for specific and diverse microbiological culture conditions required by conventional methods. Samples of fetal membranes were taken from 37 preterm infants, and 6 normal term controls delivered by caesarean section, in which bacteria had been detected by in situ hybridization of 16S ribosomal RNA using a generic probe. Degenerate primers were designed to amplify bacterial 16S ribosomal DNA by PCR and used to amplify bacterial DNA from human fetal membranes. Amplicons were cloned, sequenced and bacteria were identified bioinformatically by comparison of sequences with known bacterial DNA genomes. In situ hybridization using an organism specific probe was then used to confirm the presence of the commonest identified organism in tissue samples. Bacterial DNA amplified from 15/43 samples, all from preterm deliveries, and the bioinformatic approach identified organisms in all cases. Multiple bacteria were identified including Mycoplasma hominis, Pasturella multocida, Pseudomonas PH1, Escherichia coli and Prevotella bivia. The commonest organism Fusobacterium nucleatum was found in 9/15 (60%) of samples. Ten of the 12 samples obtained after prolonged membrane rupture were positive for bacterial DNA, and 7 of these (70%) contained DNA from F. nucleatum. Bacteria from fetal membranes may be identified by molecular and bioinformatic methods. Further work is warranted to investigate the apparent linkage between F. nucleatum, fetal membrane rupture and preterm delivery.

Bacterial Typing Techniques↗
PubMed2005

Clinical and biochemical characterization of women with polycystic ovary syndrome in North Rhine-Westphalia.

Polycystic ovary syndrome (PCOS), defined as the combination of oligoanovulation and hyperandrogenism, affects more than 5% of women of reproductive age. Insulin resistance and hyperinsulinemia appear to play an important role in its pathogenesis. Here, we will present a characterization of a PCOS cohort from North Rhine-Westphalia in Germany. Clinical features, family history as well as endocrine and metabolic parameters were prospectively recorded from 200 successive patients. All patients were evaluated for insulin resistance and beta-cell-function by oral glucose tolerance test. Patient data were compared with those of 98 age-matched control women. PCOS patients showed significantly higher BMI, body fat mass and androgen levels as well as impaired glucose and insulin metabolism. A positive family history of PCOS and diabetes was more frequent in PCOS patients. Insulin resistance (71%) was the most common metabolic abnormality in PCOS patients followed by obesity (52%) and dyslipidemia (46.3%), with an incidence of 31.5% for the metabolic syndrome. C-reactive protein and other cardiovascular risk factors were frequently elevated even in young PCOS patients. While the clinical characteristics and endocrine parameters of this German PCOS cohort were heterogeneous, they were comparable to those from other Caucasian populations.

Adult↗
PubMed2005

Traditional Chinese medicine based subgrouping of irritable bowel syndrome patients.

Partly from lack of effective conventional therapeutics, patients with irritable bowel syndrome (IBS) turn to complementary and alternative approaches, including Traditional Chinese Medicine (TCM). Key to TCM's approach to IBS is individualized therapies targeted at subgroups. Subgroups represent distinct patterns of dysregulation (e.g. "excess" or "deficiency") identified by both intestinal and extra-intestinal symptoms. Our objective was to identify operational criteria supporting the existence of TCM-based subgroups in IBS and to assess reliability and validity of these criteria. Using TCM principles, items were selected on face validity from conventional questionnaires. TCM practitioners evaluated items for content and face validity. Symptom items and a set of patient cases with item responses were validated by examining patient's pattern of response to items and assessing the consistency with which practitioners diagnosed patients on the spectrum of an "excess" or "deficiency" syndrome. Standard correlation analysis revealed 33 intestinal and extra-intestinal symptom items. There was high degree of practitioner agreement in assessing individual items to particular patterns. External validation by practitioners of cases showed high internal consistency among practitioners (Cronbach's alpha coefficients of 0.91 and 0.87 for excess and deficiency, respectively) and high correlation of average practitioner rating to original questionnaire generated scores (Pearson correlation coefficients of 0.94 and 0.92 for excess and deficiency, respectively). This pilot study provides preliminary support for a methodology to identify novel subgroups of IBS patients related to the TCM classification, which may differ in underlying pathophysiology and treatment responses.

Case-Control Studies↗
PubMed2005

Insulin resistance syndrome and polycystic ovary syndrome: implications for diagnosis and treatment.

Both insulin resistance syndrome (IRS) and polycystic ovary syndrome (PCOS) are common endocrinopathies. IRS, usually associated with ages of 50+, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD), is highly prevalent in young PCOS patients, exceeding the expected rate from their prevailing obesity. While it is clear that women with PCOS cluster risk factors, prospective studies to prove a higher morbidity and mortality from T2DM and CVD are not available. Nevertheless, apart from cosmetic concerns and gynecological problems, therapeutic intervention should also be designed to reduce the metabolic risk of PCOS, which may well be the main determinant of long-term health in affected women.

Animals↗
PubMed2004

Habitat heterogeneity and niche structure of trees in two tropical rain forests.

Dispersal-assembly theories of species coexistence posit that environmental factors play no role in explaining community diversity and structure. Dispersal-assembly theories shed light on some aspects of community structure such as species-area and species-abundance relationships. However, species' environmental associations also affect these measures of community structure. Measurements of species' niche breadth and overlap address this influence. Using a new continuous measure of niche and a dispersal-assembly null model that maintains species' niche breadth and aggregation, we tested two hypotheses assessing the effects of habitat heterogeneity on the ability of dispersal-assembly theories to explain community niche structure. We found that in both homogenous and heterogeneous environments dispersal-assembly theories cannot fully explain observed niche structure. The performance of the dispersal-assembly null models was particularly poor in heterogeneous environments. These results indicate that non-dispersal based mechanisms are in part responsible for observed community structure and measures of community structure which include species' environmental associations should be used to test theories of species diversity.

Altitude↗
PubMed2003

Examination stress in Singapore primary schoolchildren: how compliance by subjects can impact on study results.

OBJECTIVE: Examinations are anecdotally viewed as extremely stressful to Singapore schoolchildren. We test this postulate by obtaining parental ratings of children's emotional stress levels longitudinally in a large representative sample of sixth (P6) and fifth (P5) class primary schoolchildren, respectively, exposed and unexposed to a streaming examination. METHOD: Children's stress levels were rated monthly by a parent for 10 months. RESULTS: Analyses failed to find evidence of any differential stress impact across P6 and P5 comparison groups, apart from a subset of P6 children whose parents complied with every monthly survey. CONCLUSION: The streaming examination in the final year of primary school did not emerge as a general stressor to children, but achieved salience within a defined subset of children whose parents were highly study compliant. Study compliance may be a proxy variable of some import, and have wider relevance to other cohort studies and to intervention trials.

Child↗
PubMed2002

Diclofenac or paracetamol for analgesia in paediatric myringotomy outpatients.

This prospective, randomized, double-blind study compared the analgesic efficacy of oral diclofenac resinate 0.5 mg.kg(-1) with paracetamol 15 mg/kg(-1) for control of postoperative pain in paediatric patients for outpatient bilateral myringotomy and tube insertion. Paracetamol, the most commonly used oral analgesic for paediatric patients, was compared with a new palatable syrup formulation of diclofenac. Sixty-three ASA 1 orA SA 2 children aged one year and above were randomly assigned to receive diclofenac (Group A) or paracetamol (Group B). The study drug was given 30 to 60 minutes before induction of anaesthesia. Anaesthesia was induced with either inhalational sevoflurane or intravenous thiopentone. All subjects received intravenous fentanyl 1 microg/kg(-1) intraoperatively. Postoperative pain was assessed by a blinded observer using the CHEOPS score on eye-opening, and then at 10, 30 and 60 minutes. Children with a CHEOPS score > 7 received further fentanyl 1 microg x kg(-1). The number of cases requiring this "rescue" analgesia was recorded. Both groups were comparable in demographics, induction technique, duration of anaesthesia and time between premedication and induction of anaesthesia. Overall, CHEOPS scores were low for both groups at all times and did not differ between the groups at any time. Twenty per cent of the diclofenac group and 27% of the paracetamol group required rescue analgesia (not statistically significant). The efficacy of diclofenac 0.5 mg x kg(-1) and paracetamol 15 mg x kg(-1) as oral analgesic premedication for BMT was comparable in children receiving an anaesthetic which included intraoperative administration of fentanyl 1 microg x kg(-1).

Acetaminophen↗