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Biomedical subjects

B Tan

Publications and source records attributed to B Tan.

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

Sodium hyaluronate enhances colorectal tumour cell metastatic potential in vitro and in vivo.

BACKGROUND: Sodium hyaluronate has been used intraperitoneally to prevent postoperative adhesions. However, the effect of sodium hyaluronate on tumour growth and metastasis in vitro and in vivo is still unknown. METHODS: Human colorectal tumour cell lines SW480, SW620 and SW707 were treated with sodium hyaluronate (10-500 microg/ml) and carboxymethylcellulose (0.125-1 per cent), and tumour cell proliferation and motility were determined in vitro. For the in vivo experiments male BD IX rats were randomized to a sodium hyaluronate group (n = 11; intraperitoneal administration of 0.5 x 10(6) DHD/K12 tumour cells and 5 ml 0.4 per cent sodium hyaluronate) or a phosphate-buffered saline group (n = 11; 0.5 x 10(6) DHD/K12 tumour cells and 5 ml phosphate-buffered saline intraperitoneally). Four weeks later the intraperitoneal tumour load was visualized directly. RESULTS: In vitro sodium hyaluronate increased tumour cell proliferation and motility significantly. Sodium hyaluronate-induced tumour cell motility appeared to be CD44 receptor dependent, whereas sodium hyaluronate-induced tumour cell proliferation was CD44 receptor independent. In vivo there was a significantly higher total tumour nodule count in the peritoneal cavity of the sodium hyaluronate-treated group compared with the control (P = 0.016). CONCLUSION: Sodium hyaluronate enhances tumour metastatic potential in vitro and in vivo, which suggests that use of sodium hyaluronate to prevent adhesions in colorectal cancer surgery may also potentiate intraperitoneal tumour growth. Presented to the Patey Prize Session of the Surgical Research Society and the annual scientific meeting of the Association of Surgeons of Great Britain and Ireland, Brighton, UK, 4-7 May 1999

Animals↗
PubMed2001

Grip strength measurement in competitive ten-pin bowlers.

BACKGROUND: In an attempt to find a more specific grip strength test for bowlers, the conventional grip strength test was modified such that only the fingers used in holding the ball are tested. The objective of this study was to assess the test-retest reliability of this modified bowling grip strength test, to assess the agreement between the bowling and the conventional grip strength tests, and to examine the correlation between the modified test and bowling performance in competitive bowlers. METHODS. EXPERIMENTAL DESIGN: This research was conducted in two parts, each with a different study sample. Study I was a cross-sectional study to assess the correlation between the bowling grip strength and the bowling score. Study II was a comparative study to obtain the test-retest reliability for both the bowling and conventional grip strength tests, and to assess the agreement between the two tests. SETTING AND SUBJECTS: for study I, the subjects were 39 members (26 males and 13 females) of the Singapore National Ten-Pin Bowling Training Squad. Bowling grip strength was measured within one month prior to the selection trials for the national squad, the results of which were used as a measure of bowling performance. For study II, the subjects were 21 members (12 males and 9 females) of the Singapore National Ten-Pin Bowling Squad that was formed after the selection trials. INTERVENTIONS: none. MEASURES: Bowling grip strength, conventional grip strength, and bowling score. RESULTS: The test-retest reliability of the bowling grip strength measurement (r = 0.91, p < 0.01) was comparable to that of the conventional five-finger grip (r = 0.93, p < 0.01). The single measure intraclass correlation coefficient between the bowling and conventional grip strength tests was 0.77; the 95% confidence interval was 0.51 and 0.90. However, the correlation coefficient between the bowling grip strength test and bowling score (r = 0.27) was not significant. CONCLUSIONS: The bowling grip strength test has a high test-retest reliability, and a moderate agreement with the conventional grip strength test. However, despite using only the bowling fingers, the test was unable to predict bowling performance in elite bowlers.

Adolescent↗
PubMed2001

Role of calcitonin gene-related peptide in nitric oxide-mediated myocardial delayed preconditioning induced by head stress.

AIM: To study the role of calcitonin gene-related peptide (CGRP) in nitric oxide (NO)-mediated myocardial delayed preconditioning induced by heat stress. METHODS: The isolated rat heart was perfused in a Langendorff model. Hearts for all groups were subjected to 4 h hypothermia (4 degrees C) and 40 min reperfusion (37 degrees C). In the hyperthermia-treated group, rats were subjected to whole-body hyperthermia (rectal 42 degrees C, 15 min) 24 h before the experiment. Heart rate, coronary flow, left ventricular pressure, and its derivative (+/- dp/dtmax) were recorded, and calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in plasma and the activity of creatine kinase (CK) in the coronary effluent were measured. RESULTS: Pretreatment with hyperthermia significantly improved the recovery of cardiac protection, reduced the release of CK, and increased plasma concentrations of CGRP. Pretreatment with L-NAME, an inhibitor of NOS, or capsaicin, which selectively depleted sensory neurotransmitter content, abolished the protective effects and the increased level of CGRP elicited by hyperthermia. CONCLUSION: Endogenous NO is involved in the cardioprotection afforded by heat stress, and the beneficial effects of NO are mediated by CGRP in the rat.

Animals↗
PubMed2000

The important role of residue F268 in ligand binding by LXRbeta.

Liver X receptors (LXRs) are nuclear receptors that regulate the metabolism of cholesterol and bile acids. Despite information on the specificity of their natural ligands, oxysterols, relatively little is known about the ligand binding site in LXRs. The helix 3 region in the ligand binding domain (LBD) of peroxisome proliferator-activated receptors (PPARs) has been implicated in ligand entry. Sequence alignment of LXRs, farnesoid X receptor (FXR), and PPARs identified the corresponding helix 3 region in the LXRbeta LBD. Residues F268 and T272, which are conserved in all the aligned sequences and only in LXRs and FXR, respectively, were replaced with alanine. The effects of these mutations on ligand binding and receptor activation were examined using an in vitro ligand binding assay and a cell based reporter assay, respectively. The LXRbeta mutant F268A did not bind ligand. In contrast, conversion of T272 to alanine has no effect on ligand binding. By transiently expressing a chimeric receptor containing Escherichia coli tetracycline repressor (TetR) and LXRbeta LBD and a reporter with a TetR binding site, we show that mutant F268A lost the ability to activate transcription of the reporter, whereas mutant T272A still has an activity similar to that of the wild-type LXRbeta. These data, consistent with the findings in the in vitro ligand binding assay and our 3D modeling, are the first study that identifies a residue critical for ligand binding in LXRbeta.

Amino Acid Sequence↗
PubMed2000

Quantitative analysis of thymosin alpha1 in human serum by LC-MS/MS.

A high performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was developed to measure the thymosin alpha 1 (Talpha1) concentration in human serum. Tá1 in human serum was determined by solid phase extraction and reverse phase LC-MS/MS. The high-performance liquid chromatography (HPLC) system interfaced with the MS/MS system with a Turbo Ion spray interface. Positive ion detection and multiple reaction monitoring (MRM) mode were used for this human serum quantitation. Eight different concentration standards were used to establish the detection range. Six quality control (QC) and 2 matrix blanks were checked by calibration curves performed on the same day. The lower quantitation limit was 0.5 ng/mL Talpha1 in human serum. Calibration curves were established between 0.5 to 100 ng/mL by weighted linear regression. The correlation coefficients for different days were 0.9955 or greater. Quantitation of Talpha1 by the LC-MS/MS method is fast, accurate, and precise.

Calibration↗
PubMed2000

Correlations between physiological parameters and performance in elite ten-pin bowlers.

The increasing acceptance of ten-pin bowling as a sport, as well as the keen competition amongst bowlers, necessitates the identification of performance indicators to aid training. The aim of this cross-sectional study was to determine if age, height, weight, aerobic power index, bowling grip strength, 10-RM leg press performance, and the sit-and-reach distance correlated with bowling performance in 42 elite bowlers (26 males and 16 females). At the same time, the physiological profiles of bowlers classified as heavy ball strokers, heavy ball crankers, and light ball spinners were compared. The results showed that for the male bowlers, none of the parameters correlated with performance, while for the female bowlers, the only parameter that correlated with performance was the aerobic power index. Bowlers using the three different releases had similar anthropometric and physiological profiles. The implications from this study are that bowlers of diverse age and build can be equally competitive in the sport; that aerobic capacity (as reflected by the aerobic power index) may, to a certain extent, contribute to bowling performance; and that strength and flexibility measures do not seem to be useful performance indicators amongst elite bowlers.

Adult↗
PubMed2000

Prevention of postsplenectomy sepsis: how much do patients know?

INTRODUCTION: Asplenia causes a deficiency in immunity with a long-term risk of fulminant infection, associated with significant mortality. Patient compliance requires an understanding of risks of infection and its prevention. The impact of patient education has been little studied. MATERIALS AND METHODS: To ascertain the degree of knowledge held by patients who have undergone splenectomy, a comprehensive survey was designed. This also aimed to determine which group of health professionals was most successful in conveying information to patients. Patients who had undergone total splenectomy were interviewed by telephone, using a standardised list of questions to assess their understanding of the post-operation risks. RESULTS: Of 40 consecutive patients, 32.5% had a good knowledge of the risks of asplenia and their prevention, 52.5% had a fair knowledge and 15% a poor knowledge. Haematologists were most successful in initially conveying information to patients, and general practitioners also played a critical role in patient education. In this survey, it appears that surgeons were not effective at educating patients. CONCLUSION: Patient education postsplenectomy is poor. Measures to prevent infection in the asplenic patient are not being adequately implemented.

Adolescent↗
PubMed2000

Multidrug resistance transporters and modulation.

Multidrug resistance (MDR), whereby tumor cells simultaneously possess intrinsic or acquired cross-resistance to diverse chemotherapeutic agents, hampers the effective treatment of cancer. Molecular investigations in MDR resulted in the isolation and characterization of genes coding for several proteins associated with MDR, including P-glycoprotein (P-gp), the multidrug resistance associated protein (MRP1), the lung resistance protein (LRP), and, more recently, the breast cancer resistance protein (BCRP). These transmembrane proteins cause MDR either by decreasing the total intracellular retention of drugs or redistributing intracellular accumulation of drugs away from target organelles. These proteins are expressed at varying degrees in different neoplasms, including the AIDS-associated non-Hodgkin lymphoma and Kaposi sarcoma and are generally associated with poor prognosis. Several MDR-reversing agents are in various stages of clinical development. First-generation modulators such as verapamil, quinidine, and cyclosporin required high doses of drugs to reverse MDR and were associated with unacceptable toxicities. Second- and third-generation MDR inhibitors include PSC 833, GF120918, VX-710, and LY335979, among others. Limitations to the use of these modulators include multiple and redundant cellular mechanisms of resistance, alterations in pharmacokinetics of cytotoxic agents, and clinical toxicities. Studies to validate the role of MDR reversal in the treatment of various malignancies are underway. A potential use of these agents may be to enhance intestinal drug absorption and increase drug penetration to biologically important protective barriers, such as the blood-brain, blood-cerebrospinal fluid, and the maternal-fetal barriers. The use of MDR modulators with drugs such as the antiviral protease inhibitors and cytotoxics may enhance drug accumulation in sanctuary sites that are traditionally impenetrable to these agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Arginine vasopressin gene expression in supraoptic nucleus and paraventricular nucleus of hypothalamous following cerebral ischemia and reperfusion.

BACKGROUND: Our previous studies indicated that the increased arginine vasopressin (AVP) in ischemic brain regions of gerbils could exacerbate the ischemic brain edema. This experiments is further clarify the relation between AVP and cerebral ischemia at the molecular level. METHODS: The contents of AVP, AVP mRNA, AVP immunoreactive (ir) neurons in supraoptic nucleus(SON) and paraventricular nucleus (PVN) after cerebral ischemia and reperfusion were respectively determined by radioimmunoassay (RIA), immunocytochemistry (II C), situ hybridization and computed image pattern analysis. RESULTS: The contents of AVP in SON, PVN were increased, and the AVP ir positive neurons in SON and PVN were also significantly increased as compared with the controls after ischemia and reperfusion. And there were very light staining of AVP ir positive neurons in the other brain areas such as suprachiasmatic nucleus (SC) and periventricular hypothalamic nucleus (PE), but these have no significant changes as compared with the controls. During different periods of cerebral ischemia (30 approximately 120 min) and reperfusion (30 min), AVP mRNA expression in SON and PVN were more markedly increased than the controls. CONCLUSIONS: The transcription of AVP gene elevated, then promoting synthesis and release of AVP in SON, PVN. Under the specific condition of cerebral ischemia and reperfusion, the activity and contents of central AVP increased abnormally is one of the important factors which causes ischemia brain damage.

Animals↗
PubMed2000

[Solution of inverse problem of therman equation in quantitative X-ray fluorescence analysis. Theoretical effect coefficient method and fundamental parameter method].

In this paper, firstly the algorithmic relation between the weight fraction Ci, X-ray fluorescence relative intensity Ri and matrix effect factor Fi is created for the multi-element specimen on theoretical basis. Secondly, according to this algorithm relation, the typical method to solve inverse problem of Therman equation can be developed that is the theoretical influence coefficience method and the fundamental parameter method. Six standards are analysed by these two methods respectively, and results are good agree with the certified values.

English Abstract↗
PubMed1999

The effects of EMLA and a topical formulation of 4% amethocaine (Ametop) on pain associated with retrobulbar injection.

Retrobulbar block is commonly performed to provide anaesthesia for cataract extraction. This technique can cause significant discomfort. A prospective, randomised, placebo-controlled trial was carried out to investigate the efficacy of a eutectic mixture of local anaesthetics (EMLA) and a 4% amethocaine topical formulation (Ametop) in reducing the pain of retrobulbar injection. Ametop and EMLA proved to be of similar efficacy, both being superior to a placebo in alleviating the discomfort of retrobulbar block. No significant side-effects were observed with the use of either formulation.

Aged↗
PubMed1999

Distinct human immunodeficiency virus strains in the bone marrow are associated with the development of thrombocytopenia.

We analyzed bone marrow and blood from human immunodeficiency virus type 1 (HIV-1)-infected individuals and described the HIV-1 quasispecies in these cellular compartments. HIV-1 isolates from the bone marrow of thrombocytopenic patients contained distinct amino acids in the V3 loop and infected T-cell lines, implicating this virus in the development of thrombocytopenia.

Amino Acid Sequence↗
PubMed1999

[Study of calcitonin gene methylation in chronic myeloid leukemia by using Hpa II-PCR].

To investigate the role of calcitonin(CT) gene hypermethylation in the transformation from the initial chronic phase to blast crisis of chronic myeloid leukemia, 31 CML patients were studied by using Hpa II-PCR. The results showed that the 10.52%(2/19) chronic phase, 71.4%(5/7) accelerated phase and 80.0%(4/5) blast crisis of patients had CT gene hypermethylation and that the increased methylation of the CT gene were related with the disease progression. The reports indicated that the hypermethylation of CT gene might be a useful marker for predicting the evolution of CML and selecting chronic phase patients for BMT.

Adolescent↗
PubMed1998

[Studies on biological monitoring of adrenocortical function in workers exposed to carbon disulfide].

OBJECTIVE: To study the effects of carbon disulfide on adrenocortical function and analyze and compare the various biological materials used in biological monitoring by observing the changes of adrenocortical hormones and their metabolites in blood, saliva and urine of a viscose rayon mill exposed to carbon disulfide for long-term. METHODS: Cortisol in blood and saliva was determined by 125I-radioimmunoassay (RIA), cortisol and cortisone in urine by high performance liquid chromatogaphy (HPLC), and their metabolite 17-ketosteroid by chemical method. Data collected were analyzed by SPSS software in microcomputer to compare their difference between two groups, relationship between them and concentrations of carbon disulfide, and consistence between nontraumatic indices in saliva and urine and blood hormone. RESULTS: Levels of adrenocortical hormones and their metabolites in blood, urine and saliva decreased in the workers exposed to concentrations of carbon disulfide exceeding the national allowable standard, and correlated closely with them. There was a good correlationship between indices in blood and in urine. CONCLUSION: Blood cortisol, urine free cortisol, cortisone and its metabolite 17-ketosteroid all are good indices for biological effects reflecting adrenocortical function, and detection for urine cortisol and its metabolite is more practicable because of its non-traumatic features.

17-Ketosteroids↗
PubMed1998

[Detection of interleukin-2 receptor in patients with idiopathic thrombocytopenic purpura].

Using ELISA and indirect fluorescent antibody techniques(IFAT), the serum soluble inter-leukin-2 receptor(sIL-2R) and membrane IL-2R (mIL-2R) on lymphocyte cells induced by phyto-hemagglutinin (PHA) were studied in patients with idiopathic thrombocytopenic purpura (ITP). The results showed that the level of sIL-2R increased significantly before treatment and decreased after treatment; the percentages of mIL-2R induced by PHA decreased. There was no correlation between the level of serum sIL-2R and that of mIL-2R. Our observations suggest that increased level of serum sIL-2R in ITP patients may be one of causes evoking cellular immunological abnormalities.

Adolescent↗