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Biomedical subjects

M Lim

Publications and source records attributed to M Lim.

At least 37 records · Page 2Linked to original sources
PubMed2004

Particle and carbon dioxide emissions from passenger vehicles operating on unleaded petrol and LPG fuel.

A comprehensive study of the particle and carbon dioxide emissions from a fleet of six dedicated liquefied petroleum gas (LPG) powered and five unleaded petrol (ULP) powered new Ford Falcon Forte passenger vehicles was carried out on a chassis dynamometer at four different vehicle speeds--0 (idle), 40, 60, 80 and 100 km h(-1). Emission factors and their relative values between the two fuel types together with a statistical significance for any difference were estimated for each parameter. In general, LPG was found to be a 'cleaner' fuel, although in most cases, the differences were not statistically significant owing to the large variations between emissions from different vehicles. The particle number emission factors ranged from 10(11) to 10(13) km(-1) and was over 70% less with LPG compared to ULP. Corresponding differences in particle mass emission factor between the two fuels were small and ranged from the order of 10 microg km(-1) at 40 to about 1000 microg km(-1) at 100 km h(-1). The count median particle diameter (CMD) ranged from 20 to 35 nm and was larger with LPG than with ULP in all modes except the idle mode. Carbon dioxide emission factors ranged from about 300 to 400 g km(-1) at 40 km h(-1), falling with increasing speed to about 200 g km(-1) at 100 km h(-1). At all speeds, the values were 10% to 18% greater with ULP than with LPG.

Air Pollutants↗
PubMed2004

A comparison of the nature and abundance of microsatellites in 14 fungal genomes.

An overview of the character of microsatellites in 14 fungal genomes was obtained by analyzing databases containing complete or nearly complete genome sequences. Low GC content, rather than genome size, was the best predictor of high microsatellite density, although very long iterations of tandem repeats were less common in small genomes. Motif type correlated with %GC in that low-GC genomes were more likely to be dominated by A/T-rich motifs, and vice versa, although some exceptions were noted. The experimentally useful dinucleotide and trinucleotide arrays were analyzed in greater detail. Although these varied in sequence and length among fungal species, some that are likely to be universally useful were identified. This information will be useful for researchers wanting to identify the most useful microsatellites to analyze for the fungi included in this survey and provides a platform for choosing microsatellites to target in fungi that are not yet sequenced.

Base Sequence↗
PubMed2004

Collateral vessel physiology and functional impact-in vivo assessment of collateral channels.

The existence and recruitment of collateral vessels within the coronary circulation may account for the tremendous variability in presentation, symptoms and outcome in patients with coronary atherosclerosis. Multiple episodes of ischemia have been found to produce the stimuli necessary for the growth of new vessels which result in collateral blood flow. Furthermore, there is also a subset of patients with readily recruitable collateral vessels that function to limit myocardial necrosis during an acute ischemic event. Promising early studies have utilized angiogenic growth factors as a means to stimulate collateral growth, bringing a renewal interest in their assessment and significance. We review, in brief, the significance and understanding of the development of coronary collaterals as well as the available means to assess them.

Collateral Circulation↗
PubMed2002

Evaluation on the use of a portable unit versus the laboratory for the monitoring of International Normalized Ratio (INR) in orally anticoagulated patients.

INTRODUCTION: Measuring the International Normalized Ratio (INR) through a laboratory requires venipuncture and takes about 1 hour for results to be available. A portable monitor (CoaguChek Plus System), which measures the INR using fingerstick samples, is evaluated in this study to determine its clinical significance in anticoagulated and non-anticoagulated individuals. The hospital's outpatient and inpatient laboratories were also compared in the study. MATERIALS AND METHODS: Paired venous and capillary blood INRs were performed on anticoagulated patients using the monitor and the Singapore General Hospital (SGH) outpatient and inpatient laboratories (OPS and IPS labs). Paired INRs of control samples were also performed using the monitor and the IPS lab. RESULTS: We plotted the difference in INR by the 2 methods (monitor and OPS lab, n = 91) against their mean, and calculated the limits of agreement (95% of the difference would lie between -0.90 to 0.70). After a logarithmic transformation on the data, we found that for 95% of the cases, the OPS lab would differ from the monitor by 13% below to 14% above. There was also a marginal difference (95% limits of agreement of -0.14 to 0.10) when we compared the INR obtained from OPS and IPS laboratories (n = 43). Our control sample (n = 19) showed that the 95% confidence interval for the bias was -0.04 to 0.10. CONCLUSION: The monitor should be used with caution in patients with INR > 3. We suggest use of the monitor in situations where the non-anticoagulated state of a patient needs to be measured. There is a difference in INR measured by laboratories within the same institution.

Anticoagulants↗
PubMed2001

Skp2 is oncogenic and overexpressed in human cancers.

Skp2 is a member of the F-box family of substrate-recognition subunits of SCF ubiquitin-protein ligase complexes that has been implicated in the ubiquitin-mediated degradation of several key regulators of mammalian G(1) progression, including the cyclin-dependent kinase inhibitor p27, a dosage-dependent tumor suppressor protein. In this study, we examined Skp2 and p27 protein expression by immunohistochemistry in normal oral epithelium and in different stages of malignant oral cancer progression, including dysplasia and oral squamous cell carcinoma. We found that increased levels of Skp2 protein are associated with reduced p27 in a subset of oral epithelial dysplasias and carcinomas compared with normal epithelial controls. Tumors with high Skp2 (>20% positive cells) expression invariably showed reduced or absent p27 and tumors with high p27 (>20% positive cells) expression rarely showed Skp2 positivity. Increased Skp2 protein levels were not always correlated with increased cell proliferation (assayed by Ki-67 staining), suggesting that alterations of Skp2 may contribute to the malignant phenotype without affecting proliferation. Skp2 protein overexpression may lead to accelerated p27 proteolysis and contribute to malignant progression from dysplasia to oral epithelial carcinoma. Moreover, we also demonstrate that Skp2 has oncogenic potential by showing that Skp2 cooperates with H-Ras(G12V) to malignantly transform primary rodent fibroblasts as scored by colony formation in soft agar and tumor formation in nude mice. The observations that Skp2 can mediate transformation and is up-regulated during oral epithelial carcinogenesis support a role for Skp2 as a protooncogene in human tumors.

Agar↗
PubMed2001

Changes in the biomechanical properties of neutrophils and endothelial cells during adhesion.

This study examined changes in the biomechanical properties of cultured pulmonary microvascular endothelial cells (ECs) and neutrophils induced by adhesion of neutrophils to these ECs. The biomechanical properties of cells were evaluated using magnetic twisting cytometry, which measures the angular rotation of ferromagnetic beads bound to cells through antibody ligation on application of a specified magnetic torque. Adhesion of neutrophils to 24-hour tumor necrosis factor-alpha (TNF-alpha)-treated ECs, but not to untreated ECs, induced an increase in EC stiffness within 2 minutes, which was accompanied by an increase and a reorganization of F-actin in ECs. A cell-permeant, phosphoinositide-binding peptide attenuated the EC stiffening response, suggesting that intracellular phosphoinositides are required. The stiffening response was not inhibited by ML-7, a myosin light-chain kinase inhibitor, or BAPTA, an intracellular Ca2+ chelator. Moreover, the phosphorylation pattern of the regulatory myosin light chains was unaltered within 15 minutes of neutrophil adherence. These data suggested that the EC stiffening response appeared not to be mediated by myosin light-chain-dependent mechanisms. Concomitantly, neutrophil adhesion to 24-hour TNF-alpha-treated ECs also induced changes in the biomechanical properties of neutrophils compared to neutrophils bound to untreated ECs. Taken together, these results demonstrated that neutrophil adhesion to TNF-alpha-treated ECs induces changes in the biomechanical properties of both cell types through actin cytoskeletal remodeling. These changes may modulate neutrophil transmigration across the endothelium during inflammation.

Actins↗
PubMed2001

New selectable marker/auxotrophic host strain combinations for molecular genetic manipulation of Pichia pastoris.

We describe the isolation and characterization of three new biosynthetic genes-ARG4, ADE1, and URA3-from the methylotrophic yeast Pichia pastoris. The predicted products of the genes share significant sequence similarity to their Saccharomyces cerevisiae counterparts, namely argininosuccinate lyase, PR-aminoimidazolesuccinocarboxamide synthase, and orotidine-5'-phosphate decarboxylase, respectively. Along with the previously described HIS4 gene, each gene was incorporated as the yeast selectable marker into a set of shuttle vectors designed to express foreign genes in P. pastoris. In addition, we have constructed a series of host strains containing all possible combinations of ade1, arg4, his4, and ura3 auxotrophies to be used with these new vectors.

Amino Acid Sequence↗
PubMed2001

Therapeutic strategies to correct malfunction of CFTR.

Cystic fibrosis (CF) is a systemic autosomal recessive inherited disorder that results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Although the gene was cloned 11 years ago, there still is no definitive treatment to correct the functional deficit. Current treatment strategies focus on pancreatic enzyme replacement and control of pulmonary inflammation and infection. This review examines novel strategies still in preclinical development or phase 1 clinical trials. Gene therapy is an evolving area of study that offers the potential for a cure for cystic fibrosis. CF lung disease is a significant barrier to effective gene delivery and transfer, but new vectors show promise in overcoming these limitations. There are also new pharmacological therapies aimed at correcting defects in CFTR processing and function. These are tailored to the specific class of mutation but may offer therapeutic benefit to many patients. They include phenylbutyrate, flavonoids, aminoglycosides and xanthines.

Animals↗
PubMed2001

Reversible posterior leukoencephalopathy occurring during resection of a posterior fossa tumor: case report and review of the literature.

OBJECTIVE AND IMPORTANCE: Our goal was to present a clinically and radiographically documented case of reversible posterior leukoencephalopathy (RPL) that occurred during resection of a posterior fossa tumor. Although RPL has been previously described in multiple nonsurgical settings, we hope that this case description makes RPL more clinically and radiographically recognizable to neurosurgeons. CLINICAL PRESENTATION: RPL is the clinical syndrome of headaches, altered mental status, seizures, and visual loss, with radiographic findings of reversible parieto-occipital changes on cerebral computed tomographic and magnetic resonance imaging scans. It has been previously reported in the settings of malignant hypertension, renal disease, eclampsia, and immunosuppression. To our knowledge, the patient presented represents the first clinically and radiographically documented case of RPL occurring during resection of a posterior fossa tumor. The patient intraoperatively exhibited wide fluctuations in blood pressure and awoke with clinical and radiographic findings consistent with RPL. INTERVENTION: Aggressive intraoperative and postoperative management of the patient's blood pressure, supportive intensive care, rehabilitation, and close radiographic follow-up were performed. CONCLUSION: RPL can occur as a result of intraoperative variations in blood pressure, even among young, previously healthy individuals. With the aforementioned interventions, the patient experienced significant clinical and radiographic recovery.

Adult↗
PubMed2001

Interrogation of the tricuspid annulus by Doppler tissue imaging in patients with chronic pulmonary hypertension: implications for the assessment of right-ventricular systolic and diastolic function.

BACKGROUND: Chronic pulmonary hypertension (CPHT) has a great impact on both right-ventricular (RV) systolic and diastolic properties and the assessment of those properties is not always feasible by traditional echocardiographic examination. Doppler tissue imaging (DTI) interrogation of the tricuspid annulus (TA) identifies the pattern of TA motion (TAM) and can help to assess RV function when other methods are not feasible. AIMS: To determine RV systolic and diastolic function in patients with CPHT using DTI parameters of the TA. METHODS: Eighty-seven patients with CPHT and 90 normal controls were studied. DTI parameters were measured including early diastolic, late diastolic and systolic velocities and time velocity integrals (TVI) of the TAM at both its lateral and medial aspect. RESULTS: Early diastolic and systolic velocities, the ratio of early to late diastolic velocities and TVI of TAM at both lateral and medial aspects were significantly decreased in patients with CPHT compared to controls. No significant differences were seen in late diastolic velocities and TVI in both groups. Systolic velocity of the TAM at both its lateral and medial aspects significantly correlated with RV systolic function as measured by fractional RV area change. CONCLUSIONS: DTI of the TAM can be used to assess RV systolic and diastolic properties in patients with CPHT.

Aged↗
PubMed2000

Generation and structural analysis of soluble oligomeric gp140 envelope proteins derived from neutralization-resistant and neutralization-susceptible primary HIV type 1 isolates.

We generated DNA constructs expressing soluble truncated forms of the envelope of SF162, a neutralization-resistant primary human immunodeficiency virus type 1 isolate, and SF162AV2, a neutralization-susceptible virus derived from SF162 after the deletion of 30 amino acids from the V2 loop. The constructs express the entire gp120 subunit and the extracellular region of the gp41 subunit, with either the presence ("cleaved" forms, designated gp140C) or the absence ("fused" forms, designated gp140F) of the gp120-gp41 cleavage site. Both gp140 forms derived from SF162 and SF162deltaV2 are secreted in the cell medium and are recognized by the oligomer-specific anti-gp41 MAb T4. As is the case for the corresponding virion-associated envelope molecules, the CD4-binding region is occluded within both gp140F and gp140C forms. However, structural differences exist between these two forms. The gp140F proteins are less efficiently recognized than the gp140C proteins by antibodies present in the sera of HIV-infected patients with neutralizing activities against SF162 and SF162AV2. Also, the V3 loop is more exposed on gp140F than gp140C. As is the case for intact virions, on CD4 binding both the gp140F and gp140C proteins undergo conformational changes that result in the exposure of the epitope recognized by MAb 17b, which has been implicated in coreceptor binding. In contrast, during these structural changes the exposure of specific V3 loop epitopes is not increased on either gp140C or gp140F. Taken together, our data indicate that although these gp140 forms differ structurally from the native envelope, their similarities, in particular that of gp140C, outweigh their differences.

Animals↗
PubMed2000

Global experience in cervical carotid artery stent placement.

The purpose of this article is to review and update the current status of carotid artery stent placement in the world. Surveys to major interventional centers in Europe, North and South America, and Asia were initially completed in June 1997. Subsequent information from these 24 centers in addition to 12 new centers has been obtained to update the information. The survey asked the various questions regarding the patients enrolled, procedure techniques, and results of carotid stenting, including complications and restenosis. The total number of endovascular carotid stent procedures that have been performed worldwide to date included 5,210 procedures involving 4,757 patients. There was a technical success of 98.4% with 5,129 carotid arteries treated. Complications that occurred during the carotid stent placement or within a 30-day period following placement were recorded. Overall, there were 134 transient ischemic attacks (TIAs) for a rate of 2.82%. Based on the total patient population, there were 129 minor strokes with a rate of occurrence of 2.72%. The total number of major strokes was 71 for a rate of 1.49%. There were 41 deaths within a 30-day postprocedure period resulting in a mortality rate of 0.86%. The combined minor and major strokes and procedure-related death rate was 5.07%. Restenosis rates of carotid stenting have been 1.99% and 3.46% at 6 and 12 months, respectively. The rate of neurologic events after stent placement has been 1.42% at 6-12-month follow-up. Endovascular stent treatment of carotid artery atherosclerotic disease is growing as an alternative for vascular surgery, especially for patients that are high risk for standard carotid endarterectomy. The periprocedure risks for major and minor strokes and death are generally acceptable at this early stage of development and have not changed significantly since the first survey results. Cathet. Cardiovasc. Intervent. 50:160-167, 2000.

Carotid Stenosis↗