Biomedical subjects

S M Tan

Publications and source records attributed to S M Tan.

At least 19 recordsLinked to original sources

PubMed2006

How relevant is breast cancer screening in the Asia/Pacific region?

Nationwide breast cancer screening with mammography is well-established in many western countries. Many studies have shown its benefit in mortality reduction. However, breast cancer screening in Asia has been slow to implement, as it was perceived that the breast cancer incidence was low and the parenchyma of Asian women was difficult to assess mammographically. With changing disease patterns, breast cancer is now one of the most common cancers amongst women in Asia. Breast cancer screening has become an important and relevant health problem. However, apart from biological differences between western and Asian women, cultural and economic considerations need to be addressed. This paper looks at the various issues pertaining to the feasibility and relevance of population-based screening in the Asia/Pacific region.

Asia↗

PubMed2005

The ProSeal laryngeal mask airway size selection in male and female patients in an Asian population.

The aim of this study was to investigate if size 5 compared with size 4 ProSeal laryngeal mask airway (PLMA) in Asian men and size 4 compared with size 3 ProSeal laryngeal mask airway (PLMA) in Asian women, would give a better glottic seal. We conducted a randomized crossover study involving 30 male and 30 female patients of Asian origin. Size 4 and size 5 PLMA were studied in men and size 3 and size 4 PLMA were studied in women. The patients were anaesthetized and paralysed and the PLMA was inserted with the introducer. The oropharyngeal leak pressure (OLP), ease of insertion, anatomical position, mucosal injury, visibility of cuff in the mouth and volume of air required to achieve an intracuff pressure of 60 cmH2O were studied. In male patients, oropharyngeal leak pressure was higher when size 5 PLMA was used (P < 0.001) and there was a higher incidence of mucosal injury (P = 0.025). For female patients, oropharyngeal leak pressure was higher with size 4 PLMA (P = 0.036) while the number of insertion attempts, anatomical position and mucosal injury were similar. The cuff was not visible in the oral cavity in any cases. The mean volume of air required to achieve an intracuff pressure of 60 cmH2O was less than the maximum recommended by the manufacturers. The size 5 PLMA in Asian men and size 4 PLMA in Asian women resulted in a more effective glottic seal. The use of size 5 PLMA in Asian men led to increased mucosal injury.

Adult↗

PubMed2004

Raised levels of anti-glucose-6-phosphate isomerase IgG in serum and synovial fluid from patients with inflammatory arthritis.

BACKGROUND: In K/BxN mice, anti-glucose-6-phosphate isomerase (GPI) antibodies (Abs) are arthritogenic, and their transfer into naive mice induces arthritis. Anti-GPI Abs develop in many human patients with RA and are associated with more severe forms of the disease. OBJECTIVE: To elucidate the serum and synovial fluid (SF) anti-GPI IgG profiles among different patient groups with a variety of arthritides. METHODS: Blood and SF obtained concomitantly from 91 patients with clinically well defined arthritis were tested for concentrations of total anti-GPI IgG, anti-GPI IgG subclasses, B lymphocyte stimulator (BLyS), and APRIL by ELISA. RESULTS: Anti-GPI IgG was detected in sera and SF of patients with many arthritic diseases, but was preferentially associated with inflammatory arthritis, in general, and RA, in particular. The anti-GPI IgG subclass usage was skewed and varied among the different arthritic disease groups. Inverse correlations between serum levels of BLyS and anti-GPI IgG and positive correlations between serum levels of APRIL and anti-GPI IgG were seen among immune based arthritic patients and patients with RA but not among non-immune based patients. No correlations were found in SF from any group of arthritic patients. CONCLUSION: Raised circulating anti-GPI Abs are not unique to patients with RA but are present in many patients with inflammatory arthritis. The difference in anti-GPI IgG subclass usage among disease groups may influence effector function and disease outcome. The inverse correlation between serum BLyS and anti-GPI IgG levels suggests that anti-GPI B cells may be regulated differently from other autoantibody producing B cells. Anti-GPI Abs may serve a pathogenic function in humans by promoting the maintenance of existing disease.

Adult↗

PubMed2002

Diffusion resonances in action space for an atom optics kicked rotor with decoherence.

We numerically investigate momentum diffusion rates for the pulse kicked rotor across the quantum to classical transition as the dynamics are made more macroscopic by increasing the total system action. For initial and late time rates we observe an enhanced diffusion peak which shifts and scales with changing kick strength, and we also observe distinctive peaks around quantum resonances. Our investigations take place in the context of a system of ultracold atoms which is coupled to its environment via spontaneous emission decoherence, and the effects should be realizable in ongoing experiments.

Journal Article↗

PubMed2002

A retrospective study comparing the individual modalities of triple assessment in the pre-operative diagnosis of invasive lobular breast carcinoma.

AIMS: Early invasive lobular breast carcinoma (ILC) is associated with few symptoms and signs. The individual sensitivity of clinical examination, mammography, ultrasonography, cytology and core biopsy have each been reported to be of limited value. The aim of this study was to evaluate the accuracy of triple assessment in the pre-operative detection of patients identified to have ILC from their surgical pathology. METHODS: Pure ILC was defined as tumours containing at least 90% lobular features. The triple assessment of 273 patients diagnosed primarily at our institution were reviewed. RESULTS: 87.5% of women were symptomatic and 12.5% were screen detected. The mean patient age was 59 (range 30-81) years and the median tumour size was 26 (range 5-110) mm. The main mammographic abnormalities were a spiculated lesion (33.3%), an ill-defined mass (33.3%) or architectural distortion (23.5%). The sensitivities for detecting ILC of each modality were: clinical examination (76.6%), mammography (79.8%), ultrasound examination (93.9%), fine-needle aspiration cytology (FNAC) (60.5%) and core biopsy (90.8%). Combining the three modalities of clinical examination, imaging and cyto/pathology increased the pre-operative detection rate of ILC. CONCLUSION: Triple assessment is useful in the diagnosis of ILC. As the features of ILC may be subtle, a high index of suspicion is required to facilitate early diagnosis.

Adult↗

PubMed2002

The auditory steady-state response is not a suitable monitor of anesthesia.

UNLABELLED: Previous studies show that the human 40-Hz auditory steady-state response (ASSR) disappears on induction of general anesthesia, suggesting that it may be a good candidate for a monitor of anesthesia. In this study, we aimed to learn whether all normal alert adults display ASSRs with adequate signal-to-noise ratio. Clicks were presented at a series of frequencies between 35 and 70 Hz and electroencephalographic records taken at the vertex were Fourier transformed. ASSRs were observable as sharp peaks in the electroencephalograph spectrum at the frequency of the clicks. Initial results showed that a discernible ASSR could not be obtained from about half the subjects studied at any click frequency used. Further investigation revealed that in subjects whose ASSR was undetectable in the alert state, induction of a drowsy mental state resulted in appearance of an observable ASSR. This was attributable to an increase in signal in the drowsy state, not to a decrease in noise. We conclude that, because a significant proportion of subjects do not display easily recordable ASSRs when alert, it is not practical to use disappearance of the ASSR as a routine test for adequacy of anesthesia. IMPLICATIONS: Auditory steady-state responses (ASSRs) are brain waves evoked by auditory stimuli. Because they reportedly disappear under general anesthesia, they have been suggested as potential indicators of anesthetic depth. However, in this study, we show that about half our normal adult subjects did not produce measurable ASSRs when awake. This suggests that ASSRs are not good candidates for use in monitoring anesthetic depth during surgery.

Acoustic Stimulation↗

PubMed2002

An undiagnosed phaeochromocytoma of the urinary bladder.

Phaeochromocytoma of the urinary bladder is rare. We report a case of a patient with undiagnosed bladder phaeochromocytoma who developed haemodynamic disturbances during routine diagnostic cystoscopy. The diagnosis was only confirmed postoperatively.

Aged↗

PubMed2002

Appropriate size of laryngeal mask airway for children.

The aim of this crossover study was to determine the optimal size of laryngeal mask airway in children weighing 10 to 20 kg. In each of 67 apnoeic anaesthetized children, the size 2 and size 2 1/2 laryngeal mask airways were inserted consecutively by a skilled user and the cuff inflated to 60 cmH2O. Each LMA was assessed for the ease of insertion (by the number of attempts), oropharyngeal leak pressure, anatomical position (assessed fibreoptically) and the volume of air required to achieve intracuff pressure of 60 cmH2O. During the measurement of oropharyngeal leak pressure, the airway pressure was not allowed to exceed 30 cmH2O. There was no failed attempt at insertion with any size. The oropharyngeal leak pressure was significantly less for the size 2 LMA compared to the size 2 1/2 LMA (P < 0.001). The oesophagus was visible on three occasions, all with the size 2 LMA. Gastric insufflation occurred in three patients, all with the size 2 LMA. The incidence of low oropharyngeal leak pressure (< 10 cmH2O) was low (9.0%) and all occurred with the size 2 LMA. The fibreoptic bronchoscope scores were not significantly different between the two sizes of LMAs. The volume of air to achieve intracuff pressure of 60 cmH2O was much lower than the maximum recommended volume (5.1 ml for size 2 and 6.2 ml for size 2 1/2). We conclude that the size 2 1/2 LMA provides a better fit than size 2 in children 10 to 20 kg.

Anesthesia↗

PubMed2001

Respiratory effects of relocating to areas of differing air pollution levels.

We studied 110 children (59 boys and 51 girls, who were 10 yr of age at enrollment and 15 yr of age at follow-up) who had moved from communities participating in a 10-yr prospective study of respiratory health (The Children's Health Study [CHS]) to determine whether changes in air quality caused by relocation were associated with changes in annual lung function growth rates. The subjects were given health questionnaires and underwent spirometry in their homes across six western states, according to a protocol identical to evaluations performed annually on the CHS cohort in school. Changes in annual average exposure to particulate matter with a mean diameter of 10 microm (PM(10)) were associated with differences in annual lung function growth rates for FEV(1), maximal midexpiratory flow, and peak expiratory flow rate. As a group, subjects who had moved to areas of lower PM(10) showed increased growth in lung function and subjects who moved to communities with a higher PM(10) showed decreased growth in lung function. A stronger trend was found for subjects who had migrated at least 3 yr before the follow-up visit than for those who had moved in the previous 1 to 2 yr. We conclude that changes in air pollution exposure during adolescent growth years have a measurable and potentially important effect on lung function growth and performance.

Adolescent↗

PubMed2001

Defining the repeating elements in the cysteine-rich region (CRR) of the CD18 integrin beta 2 subunit.

The cysteine-rich region (CRR) of the integrin beta subunits is organised into four repeating elements. By expression of a panel of truncated beta 2 subunits, and CRR segments fused to the C-terminal end of a CD4 soluble fragment, the segment required for the expression of two monoclonal antibody conformational epitopes was determined. This segment, E482-Q574, contains 16 cysteines representing two repeating units. We have thus defined the CRR unit motif of 'xC---C---C---CxCxxCxC---Cx', where 'x' represents a single residue, and '---' represents a stretch of four to 14 residues.

Amino Acid Sequence↗

PubMed2001

The N-terminal region and the mid-region complex of the integrin beta 2 subunit.

In the primary sequence of the integrin beta subunit, the N-terminal region (NTR) and mid-region are separated by the I-like domain. To determine the spatial relationship and functional properties of the integrin beta(2) NTR and mid-region, we constructed beta(2)/beta(7) chimeras in which the NTR, I-like domain, and the mid-region of the beta(2) subunit were replaced by those of beta(7). Changing either the beta(2) NTR or mid-region, but not the I-like domain to that of beta(7) did not affect LFA-1 (alpha(L)beta(2)) formation and surface expression. Thus, the specificity of alpha(L)beta(2) pairing is conferred by the I-like domain but not the NTR or mid-region. Using these chimeras, the epitopes of six anti-beta(2) mAbs (H52, 7E4, AZN-L18, AZN-L27, KIM202, and MEM-148) were mapped. All except H52 require both the NTR and mid-region for epitope expression. Since these mAbs have distinct properties in terms of epitope expression and effect on LFA-1 binding to ICAM-1, we conclude that the beta(2) NTR and mid-region interact extensively. Although the I-like domain is located between the NTR and mid-region, its removal does not affect the folding of the beta(2) NTR/mid-region complex because this complex alone can be expressed as a soluble protein and precipitated by the appropriate mAbs. Finally, the mAbs H52 and 7E4, abrogated KIM185- but not Mg/EGTAinduced LFA-1/ICAM-1 binding and the epitope of MEM-148 is expressed on Mg/EGTA-activated but not resting LFA-1. These results suggest that the NTR/mid-region complex is involved in the regulation of LFA-1 function.

Amino Acid Sequence↗

PubMed2001

Locally advanced primary breast cancer: medium-term results of a randomised trial of multimodal therapy versus initial hormone therapy.

We report the medium-term (median follow-up=52 months) results of a prospective randomised trial of multimodal therapy (neoadjuvant chemotherapy, Patey mastectomy, postoperative radiotherapy and adjuvant hormone therapy) (n=56) versus initial hormone therapy (n=52) for locally advanced primary breast cancer. Compared with multimodal therapy, initial hormone therapy was associated with reduced number of therapies for disease control (mean=3.6 versus 4.9) and mastectomy rate (31%). Multimodal therapy conferred better initial locoregional control and a longer disease-free interval. Nevertheless, there was no statistically significant differences in the rates of survival, metastasis and uncontrolled locoregional disease, as well as in the time to metastasis between the two therapy groups. Regardless of the therapy groups, oestrogen receptor positivity conferred a lower metastasis rate, better survival and locoregional control. Thus, initial hormone therapy may be a reasonable option for managing locally advanced primary breast cancer, especially for oestrogen receptor-positive tumours.

Adult↗

PubMed2001

Characterization of four CD18 mutants in leucocyte adhesion deficient (LAD) patients with differential capacities to support expression and function of the CD11/CD18 integrins LFA-1, Mac-1 and p150,95.

Leucocyte adhesion deficiency (LAD) is a hereditary disorder caused by mutations in the CD18 (beta2 integrin) gene. Four missense mutations have been identified in three patients. CD18(A270V) supports, at a diminished level, CD11b/CD18 (Mac-1, alphaMbeta2 integrin) and CD11c/CD18 (p150,95, alphaXbeta2 integrin) expression and function but not CD11a/CD18 (LFA-1, alphaLbeta2 integrin) expression. Conversely, CD18(A341P) supports a limited level of expression and function of CD11a/CD18, but not of the other two CD11/CD18 antigens. CD18(C590R) and CD18(R593C) show a decreasing capacity to associate with the CD11a, CD11c and CD11b subunits. Transfectants expressing the CD11a/CD18 with the C590R and R593C mutations are more adhesive than transfectants expressing wild-type LFA-1, and express the reporter epitope of the monoclonal antibody 24 constitutively. Thus, the four mutations affect CD18 differently in its capacities to support CD11/CD18 expression and adhesion. These results not only provide a biochemical account for the clinical diversity of patients with leucocyte adhesion deficiency, but also offer novel insights into the structural basis of interaction between the alpha and beta subunits, which is an integral component in our understanding of integrin-mediated adhesion and its regulation.

Alleles↗

PubMed2001

CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leucoencephalopathy): an Australian perspective.

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leucoencephalopathy (CADASIL) is a recently described cause of stroke or stroke-like episodes. It is caused by mutations in the Notch3 gene on chromosome 19p. We sought to demonstrate mutations of the Notch3 gene in Australian patients suspected of having CADASIL. Patients from several families were referred to the study. A diagnosis was determined clinically and by neuroimaging. Those suspected of having CADASIL had sequencing of exons 3 and 4 of the Notch3 gene. Eight patients, two of whom were siblings, were suspected of having CADASIL. Five patients (including the siblings) had mutations. Because of strong clustering of Notch3 mutations in CADASIL, this has potential as a reliable test for the disease in Australian patients.

Aged↗

PubMed2001

Chimeras of the integrin beta subunit mid-region reveal regions required for heterodimer formation and for activation.

A central region of the beta2 integrin subunit, RN (residues D300 to C459), was replaced by the equivalent sequences from beta1 and beta7 to give the chimeras beta2RN1 and beta2RN7. Whilst the former construct failed to form heterodimer at the cell surface with alphaL, the later of these could be expressed together with the alphaL subunit to form a variant LFA-1. Based on recent modelling work, the RN region consists of two parts, one is the C-terminal end of the putative A-domain (RB, residues D300 to A359), and the other the mid-region (BN, residues Y360 to C459). Chimeras exchanging the two component regions were made. Of the four resultant chimeras, only the beta2RB1 chimera failed to support LFA-1 expression. Thus the beta1 specific residues of this region affect the interaction with the alphaL subunit. Whereas the alphaL/beta2RB7 LFA-1 variant is wildtype like with respect to ICAM-1 adhesion, the alphaLbeta2BN1 and alphaLbeta2BN7, as well as the alphaLbeta2RN7, variants are more adhesive than the wildtype. These results suggest that an authentic beta2 mid-region is, in part, required for maintaining the LFA-1 in a resting state.

Amino Acid Sequence↗

PubMed2001

Intravenous regional anaesthesia using lignocaine and tramadol.

INTRODUCTION: This prospective, randomised, double-blind study was designed to assess if the addition of 50 mg tramadol to 30 mL 0.5% lignocaine would improve the efficacy of intravenous regional anaesthesia. MATERIALS AND METHODS: Fifty-four adult patients undergoing upper limb surgery were randomly allocated to receive either 30 mL 0.5% lignocaine and 1 mL normal saline (group A) or 30 mL 0.5% lignocaine and 50 mg tramadol (group B). They were then assessed for onset of sensory and motor block and the VbAS score for tourniquet pain. RESULTS: Although more patients in group B had a faster onset of sensory and motor block, this was not significantly different. Patients in group B had a significantly lower VbAS score 30 min after tourniquet inflation and after change over to the distal tourniquet (P < 0.05). There were no complaints of postoperative nausea and vomiting. Two patients in group B developed localised skin urticaria of the forearm which resolved with the release of the tourniquet. CONCLUSION: There is a positive trend that tramadol might improve the quality of intravenous regional anaesthesia.

Adult↗

PubMed2001

Effects of soybean fibers on blood sugar, lipid levels and hepatic-nephritic histomorphology in mice with diabetes mellitus.

OBJECTIVE: To study the influence of soybean fibers on blood sugar, blood-lipid metabolism, and histomorphology in mice models with diabetes mellitus (DM). METHOD: After normal mice and mice with Streptozocin (STZ)-induced DM were fed with forage containing a certain amount of soybean fiber (SF) for 5 weeks, blood sugar and blood lipid were determined, and morphological changes of hepatic and nephritic tissues were observed. RESULT: The results of 5-week experiment had shown: 1. In normal mice fed with SF, the blood sugar level was decreased (P < 0.05). There were no obvious changes in serum total cholesterol (TC) and the triglyceride (TG). The high-density-lipoprotein cholesterol (HDL-C) level was increased significantly (P < 0.05); 2. Among DM mice, blood sugar was decreased considerably (P < 0.001), TC and TG also decreased noticeably (P < 0.05), HDL-C increased clearly (P < 0.05); 3. SF has a protective role to the liver and kidney of DM mice. CONCLUSION: It is suggested that SF has the function of decreasing blood sugar, blood-lipid and improving their metabolism, and of protecting liver and kidney of DM mice.

Animals↗

PubMed2000

Effect of integrin beta 2 subunit truncations on LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) assembly, surface expression, and function.

LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) are members of the beta2 integrins involved in leukocyte function during immune and inflammatory responses. We aimed to determine a minimized beta2 subunit that forms functional LFA-1 and Mac-1. Using a series of truncated beta2 variants, we showed that the subregion Q23-D300 of the beta2 subunit is sufficient to combine with the alphaL and alphaM subunits intracellularly. However, only the beta2 variants terminating after Q444 promote cell surface expression of LFA-1 and Mac-1. Thus, the major cysteine-rich region and the three highly conserved cysteine residues at positions 445, 447, and 449 of the beta2 subunit are not required for LFA-1 and Mac-1 surface expression. The surface-expressed LFA-1 variants are constitutively active with respect to ICAM-1 adhesion and these variants express the activation reporter epitope of the mAb 24. In contrast, surface-expressed Mac-1, both the wild type and variants, require 0. 5 mM MnCl2 for adhesion to denatured BSA. These results suggest that the role of the beta2 subunit in LFA-1- and Mac-1-mediated adhesion may be different.

Animals↗