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Biomedical subjects

M C Lee

Publications and source records attributed to M C Lee.

At least 91 records · Page 5Linked to original sources
PubMed2000

The human myoepithelial cell displays a multifaceted anti-angiogenic phenotype.

Human myoepithelial cells which surround ducts and acini of certain organs such as the breast form a natural border separating epithelial cells from stromal angiogenesis. Myoepithelial cell lines (HMS-1-6), derived from diverse benign myoepithelial tumors, all constitutively express high levels of active angiogenic inhibitors which include TIMP-1, thrombospondin-1 and soluble bFGF receptors but very low levels of angiogenic factors. These myoepithelial cell lines inhibit endothelial cell chemotaxis and proliferation. These myoepithelial cell lines sense hypoxia, respond to low O2 tension by increased HIF-1 alpha but with only a minimal increase in VEGF and iNOS steady state mRNA levels. Their corresponding xenografts (HMS-X-6X) grow very slowly compared to their non-myoepithelial carcinomatous counterparts and accumulate an abundant extracellular matrix devoid of angiogenesis but containing bound angiogenic inhibitors. These myoepithelial xenografts exhibit only minimal hypoxia but extensive necrosis in comparison to their non-myoepithelial xenograft counterparts. These former xenografts inhibit local and systemic tumor-induced angiogenesis and metastasis presumably from their matrix-bound and released circulating angiogenic inhibitors. These observations collectively support the hypothesis that the human myoepithelial cell (even when transformed) is a natural suppressor of angiogenesis. Oncogene (2000) 19, 3449 - 3459

Animals↗
PubMed2000

Fusion of coregistered cross-modality images using a temporally alternating display method.

As an aid to the interpretation of functional images, cross-modality coregistration of functional and anatomical images has grown rapidly. Various ways of easily interpreting and visualising coregistered images have previously been investigated; for their display, an intensity-weighted temporally alternating method is used. For brain images, geometric registration involves the automatic alignment method, using the head scalp boundary extracted from the sinogram of a PET emission scan and a surface-matching algorithm; images of the chest or abdomen are registered semi-automatically using a paired point matching algorithm. For the simultaneous display of geometrically registered images, rapid image switching is applied; both images are written with independent colour scales. The rapidly alternating display of two images, synchronised with monitor scanning, induces the fusion of images in the human visual perception system. The accuracy of registration of PET and MRI images is within 2 mm for two point sets. A resulting image is intensified by weighting the display time and/or controlling the intensity map of each image with the degree of interest. This method may be useful for the interpretation and visualisation of coregistered images.

Algorithms↗
PubMed2000

Finite element analysis of brain contusion: an indirect impact study.

The mechanism of brain contusion has been investigated using a series of three-dimensional (3D) finite element analyses. A head injury model was used to simulate forward and backward rotation around the upper cervical vertebra. Intracranial pressure and shear stress responses were calculated and compared. The results obtained with this model support the predictions of cavitation theory that a pressure gradient develops in the brain during indirect impact. Contrecoup pressure-time histories in the parasagittal plane demonstrated that an indirect impact induced a smaller intracranial pressure (-53.7 kPa for backward rotation, and -65.5 kPa for forward rotation) than that caused by a direct impact. In addition, negative pressures induced by indirect impact to the head were not high enough to form cavitation bubbles, which can damage the brain tissue. Simulations predicted that a decrease in skull deformation had a large effect in reducing the intracranial pressure. However, the areas of high shear stress concentration were consistent with those of clinical observations. The findings of this study suggest that shear strain theory appears to better account for the clinical findings in head injury when the head is subjected to an indirect impact.

Brain Injuries↗
PubMed2000

Dosimetry of rhenium-188 diethylene triamine penta-acetic acid for endovascular intra-balloon brachytherapy after coronary angioplasty.

To examine the possibility of using rhenium-188 diethylene triamine penta-acetic acid (DTPA) for endovascular intra-balloon brachytherapy after angioplasty, dose distribution around the balloon was calculated and validated by film dosimetry. Medical internal radiation dosimetry (MIRD) was calculated assuming that the balloon had ruptured and that the contents had been released into the systemic circulation. 188Re-perrhenate eluate from the 188W/188Re generator was concentrated using an ion column and used to label DTPA. The dose distribution around the angioplasty balloon (20 mm length, 3 mm diameter cylinder) was estimated by Monte Carlo simulation using the EGS4 code. The time required for 17.6 Gy to be absorbed at 1 mm from the balloon's surface following application of 3700 MBq/ml of 188Re was found to be 278 s. Fifty percent of the energy was deposited in the first millimetre of the vessel wall from the balloon's surface. The calculated radiation absorbed dose agreed with that measured by film dosimetry, which was performed using a water phantom, with errors ranging from 9.4% to 17%. Upon balloon rupture the total amount of 188Re-DTPA was presumed to enter the systemic circulation. The resulting radiation absorbed dose was calculated using the MIRDOSE3 program and residence times obtained from dogs and amounted to 0.0056 mGy/MBq to the whole body and 4.56 mGy/MBq to the urinary bladder. The absorbed dose of 188Re-DTPA to the whole body was one-tenth of that of 188Re-perrhenate. A window-based program was developed to calculate the exposure time and the radiation dose absorbed as a function of the 188Re concentration and the arbitrary distance from the balloon to the surrounding tissues. We conclude that 188Re-DTPA is easy to prepare, safe to use and suitable for intra-balloon brachytherapy after coronary angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed2000

Comparative study of single-injection, single-acquisition 99mTc-MIBI gated SPET and stress-rest perfusion SPET for the evaluation of myocardial viability after bypass surgery in coronary artery disease.

In patients without previous myocardial infarction, the single-injection stress perfusion/rest function (SISPRF) approach using stress technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (SPET) can substitute for conventional stress-rest myocardial perfusion imaging for the assessment of myocardial viability. This study compared pre-operative single-injection, single-acquisition 99mTc-MIBI gated SPET and conventional stress-rest imaging for the prediction of myocardial viability in patients who underwent coronary artery bypass surgery (CABG). Rest thallium-201 SPET followed by stress 99mTc-MIBI gated SPET was performed in 20 patients [nine with previous myocardial infarction (MI) and 11 without previous MI). The study was performed before and 3 months after CABG, and viability assessment was validated by wall motion improvement after CABG. A four-point scoring system (0-3 for normal to absent tracer uptake) for 17 segments of the left ventricular myocardium was used for the assessment of stress and rest uptake. Wall motion, wall thickening and perfusion status were analysed by semi-quantitative visual assessment. On gated SPET, perfusion defect reversibility was considered present when a definite perfusion defect was observed and wall motion or thickening was normal or showed only a mild decrease. In patients with a previous MI, the left ventricular ejection fraction improved significantly after CABG (46% +/- 7% vs 42% +/- 11% before CABG, P < 0.05). In patients without previous MI, the ejection fraction improved significantly after CABG (50 +/- 12% vs 44% +/- 16% before CABG, P<0.05). In patients with previous MI, positive predictive values using the stress-rest reversibility and SISPRF approaches were 91% and 90%, respectively, and corresponding negative predictive values were 25% and 18%. In patients without previous MI, positive predictive values using the stress-rest and SISPRF approaches were 70% and 61%, respectively, and corresponding negative predictive values were 63% and 14%. It is concluded that SISPRF SPET study is of similar value to conventional stress-rest perfusion study in predicting wall motion improvement in patients with a previous MI, but that it is of limited value in predicting the myocardial viability of patients without previous MI, owing to a lower predictive value.

Aged↗
PubMed2000

Limited performance of quantitative assessment of myocardial function by thallium-201 gated myocardial single-photon emission tomography.

We investigated the reproducibility between thallium-201 and technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (SPET) for the assessment of indices of myocardial function such as end-diastolic and end-systolic volume (EDV, ESV), ejection fraction (EF) and wall motion. Rest 201Tl (111 MBq) gated SPET was sequentially performed twice in 20 patients. Rest 201Tl gated SPET and rest 99mTc-MIBI (370 MBq) gated SPET were performed 24 h apart in 40 patients. Wall motion was graded using the surface display of the Cedars quantitative gated SPET (QGS) software. EDV, ESV and EF were also measured using the QGS software. The reproducibility of functional assessment on rest 201Tl gated SPET was compared with that on 99mTc-MIBI gated SPET, and also with that between 201Tl gated SPET and 99mTc-MIBI gated SPET performed on the next day. The two standard deviation (2 SD) values for EDV, ESV and EF on the Bland-Altman plot were 29 ml, 19 ml and 12%, respectively, on repeated 201Tl gated SPET, compared with 14 ml, 11 ml and 5.3% on repeated 99mTc-MIBI gated SPET. The correlations were good (r=0.96, 0.97 and 0.87) between the two measurements of EDV, ESV and EF on repeated rest studies with 201Tl and 99mTc-MIBI gated SPET. However, Bland-Altman analysis revealed that the 2 SD values between the two measurements were 31 ml, 23 ml and 12%. We were able to score the wall motion in all cases using the 3D surface display of the QGS on 201Tl gated SPET. The kappa value of the wall motion grade on the repeated 201Tl study was 0.35, while that of the wall motion grade on the repeated 99mTc-MIBI study was 0.76. The kappa value was 0.49 for grading of wall motion on repeated rest studies with 201Tl and 99mTc-MIBI. In conclusion, QGS helped determine EDV, ESV, EF and wall motion on 201Tl gated SPET. Because the EDV, ESV and EF were less reproducible on repeated 201Tl gated SPET or on 201Tl gated SPET and 99mTc-MIBI gated SPET on the next day than on repeated 99mTc-MIBI gated SPET, functional measurement on 201Tl gated SPET did not seem to be interchangeable with that on 99mTc-MIBI gated SPET.

Coronary Disease↗
PubMed2000

Intravascular papillary endothelial hyperplasia in the kidney of a child.

Intravascular papillary endothelial hyperplasia (IPEH) is a benign vascular lesion which is thought to represent an unusual form of organizing thrombus. A case of IPEH in the kidney of a 7-year-old girl is described. She suffered from intermittent flank pain and gross hematuria for 6 months. On radiological examinations, well-defined hypoechoic lesions were identified in the medullary portion of the left kidney. A well-demarcated, sponge-like mass was noted on gross examination. It was an intravascular mass lined by a fibrous capsule of various thicknesses. It was characterized by papillary fronds lined with benign endothelial cells. This is the first description of a renal IPEH in a child.

Child↗
PubMed2000

Regional mortality from motor vehicle traffic injury: relationships among place-of-occurrence, place-of-death, and place-of-residence.

Regional mortality data, which are compiled according to place-of-residence of the decedent, are an important reference for regional health planning and resource allocation. However, it would be inappropriate to apply these data to studies of environmental risk factors if a large proportion of fatal motor vehicle traffic injuries (MVTI) in fact occur outside the resident county. The aim of this study was to determine the proportion and characteristics of residents of a rural area of Taiwan who died from MVTIs that occurred outside the county of residence. We also explored the relationships among the place-of-occurrence, place-of-death, and place-of-residence of these decedents. The families or neighbors of residents of Huatung Area (eastern Taiwan) who died from MVTIs in 1994 or 1995 were interviewed to identify the place-of-occurrence of the MVTI. Of the 882 Huatung Area residents who died as a result of an MVTI during the study period and for whom relevant data were available, the MVTI occurred outside the resident county in 207 (23%) cases. Residents whose MVTI occurred outside the county of residence were more likely to be youths (aged 15-24) or young adults (aged 25-44) and driving automobiles or trucks. Of the 866 cases in which the exact place was known, the place-of-occurrence and the place-of-death (recorded on the death certificate) were in the same county in 849 (98%). Because a high proportion of fatal MVTIs occurred outside the resident county, the mortality rate calculated according to place-of-residence does not accurately reflect the environmental risk factors in this area. The finding that the characteristics of those whose MVTI occurred outside the county differed from those decedents whose MVTI occurred within the county indicates that there are two target groups for prevention programs. In addition, at least in Huatung Area, the place-of-death recorded on the death certificate could serve as a surrogate for the place-of-occurrence in epidemiologic studies.

Accidents, Traffic↗
PubMed2000

Preparation of rhenium-188-tin colloid as a radiation synovectomy agent and comparison with rhenium-188-sulfur colloid.

As a generator-produced beta-emitting radionuclide, the importance of 188Re for radionuclide therapy is increasing rapidly. We prepared 188Re-tin colloid and compared its properties with 188Re-sulfur colloid. Labeling efficiencies reached >98% for tin colloid at 2 h and 89-94% for sulfur colloid at 3 h. All the preparations were stable for 72 h in water, serum, and synovial fluid. If labeled at higher temperature, the particle size of tin colloid increased. The residual radioactivity of 188Re-sulfur colloid in disposable polypropylene syringes after injecting mice was high (62.0+/-7.0%) due to its hydrophobic nature, while that of 188Re-tin colloid was low (2.9+/-1.6%). Although both 188Re-tin colloid and 188Re-sulfur colloid might be useful for radionuclide therapy, we conclude that 188Re tin colloid is more advantageous over 188Re sulfur colloid, due to higher labeling efficiency, control of the particle size, and lower residual activity in the injection syringes.

Animals↗
PubMed2000

Older, hypertensive, and hypercholesterolemic fairgoers visit more booths and differ in their health concerns at a community health fair.

The purpose of this study was to determine whether persons attending a community health fair had different health concerns and booth visitation patterns based on their risk factor profiles. All fairgoers were encouraged to complete an anonymous survey of demographic information, top 4 health concerns, and selected cardiac risk factors. Over the five-hour duration of the fair, 329 surveys were collected from about 450 fairgoers. There were no exclusion criteria for the survey. The fair was sponsored by the Maryland Chapter of the American College of Physicians, organized by medical students from the University of Maryland and Johns Hopkins University, and included 23 booths on a variety of health topics. Older fairgoers and fairgoers with a self-reported history of high blood pressure or elevated cholesterol showed an increased interest in hypertension and heart disease (p < 0.05). Older fairgoers also showed an increased interest in health topics related to aging, such as estrogen replacement therapy and geriatric medicine. Older, hypertensive and hypercholesterolemic fairgoers visited an increased mean number of total booths when compared to other respondents (p < 0.05). Most booths reported a higher percentage of older, hypertensive, and hypercholesterolemic visitors than the overall percentage of fairgoers who reported these risk factors. These results suggest that booth visitation patterns of health fair participants may be viewed as a deliberate attempt by at risk populations to access health information particular to their needs.

Adolescent↗
PubMed2000

Identification of a novel four-domain member of the proteinase inhibitor II family from the stigmas of Nicotiana alata.

Proteinase inhibitors (PIs) of the potato type II family have been identified in a number of solanaceous species. Most family members have two PI domains which are specific for either chymotrypsin or trypsin. More recently family members have been described with three or six repeated PI domains. Here we describe a novel four-domain family member produced in the stigmas and leaves of the ornamental tobacco, Nicotiana alata, which has high sequence identity with a six-domain member from the same species. Both proteins are produced as precursors that enter the secretory pathway and are subsequently processed into a series of 6 kDa Pis. The four- and six-domain precursor proteins were isolated from immature stigmas and characterised by mass spectrometry which revealed that both proteins had been trimmed at the N-terminus, at a position corresponding to the predicted signal peptide cleavage site. Furthermore, no post-translational modifications were apparent.

Amino Acid Sequence↗
PubMed2000

Identification of four novel mutations in five unrelated Korean families with Fabry disease.

Fabry disease is a X-linked recessively inherited metabolic disorder, which results from the deficient activity of the lysosomal hydrolase alpha-galactosidase A leading to the systemic deposition of glycosphingolipids with terminal alpha-galactosyl moieties. Single-strand conformation polymorphism (SSCP) analysis was performed, followed by DNA sequencing of PCR amplified exons of the human alpha-galactosidase A gene in 5 unrelated Korean patients with classic Fabry disease. Five different mutations were identified; two nonsense mutations (Y86X and R342X), one missense mutation (D266N), and two small deletions (296del2 and 802del4). Except for R342X mutation, four were novel mutations (Y86X, D266N, 296del2, 802del4). A T to G transversion at nucleotide position 5157 in exon 2 caused a tyrosine-to-stop substitution at codon 86. A G to A transition at position 10287 in exon 5 substituted an asparagine for an aspartate at codon 266. Mutation 296del2 in exon 2 resulted in a frame shift with a stop signal at the 22th codon downstream from the mutation, whereas mutation 802del4 resulted in a stop codon at the site of 4 bp deletion. In addition, the 802del4 was found to be a de novo mutation. This is the first report on mutation analysis of the human alpha-galactosidase A gene in Korean patients with Fabry disease.

Adolescent↗
PubMed2000

Ischemic stroke in Korean young adults.

OBJECTIVES: To evaluate the characteristics of ischemic stroke in Korean young adults. MATERIAL AND METHODS: We prospectively studied 149 consecutive patients with acute ischemic stroke aged between 15 to 44 years who were admitted to Asan Medical Center. All patients underwent brain CT/MRI and the majority of them underwent cerebral anglogram, echocardiography and laboratory studies for coagulopathy and vasculitis. Stroke subtypes were classified according to TOAST criteria. RESULTS: In our study, men (75.2%) significantly outnumbered women. Stroke subtypes were: large artery atherosclerosis 20.8%), small artery occlusive disease 17.4%), cardioembolism 18.1%, undetermined causes 16.8%, and other determined etiologies 26.8%. The prevalence of hypertension, cigarette smoking and habitual alcohol consumption was significantly higher in men than in women. CONCLUSIONS: Compared to the western studies, the deviation of sex ratio and the relative proportion of large artery atherosclerosis/small artery occlusion was higher. Heavy exposure to risk factors such as hypertension and cigarette smoking in Korean young men may explain these differences.

Adolescent↗
PubMed2000

Supradiaphragmatic ectopic adrenocorticotropic hormone-secreting adenoma.

A 22-year-old woman with Cushing's syndrome, caused by an extremely rare suprasellar ectopic pituitary adenoma, is presented. Magnetic resonance imaging and computed tomography revealed a well-circumscribed mass in the right suprasellar region. Endocrinological tests showed elevated s-adrenocorticotropic hormone level and hypercortisolemia. The tumor was totally removed by right subfrontal approach. At the time of the operation, the tumor was in continuity with the distal pituitary stalk but not with the pituitary gland. The diaphragma sellae was intact. Histologic diagnosis of the tumor specimen was confirmed as a pituitary adenoma. After surgical removal of the tumor, continued improvement in the patient's laboratory results and disappearance of her endocrine symptoms strongly indicated the absence of adenoma cells in the pituitary gland or stalk. Six years post-surgery, there was no evidence of recurrence in the patient's clinical and laboratory examination. This tumor probably originated from aberrant anterior pituitary cells of the pituitary stalk.

Adenoma↗
PubMed2000

Monte Carlo characterization of clinical electron beams in transverse magnetic fields.

Monte Carlo simulations were employed to study the characteristics of the electron beams of a clinical linear accelerator in the presence of 1.5 and 3.0 T transverse magnetic fields and to assess the possibility of using magnetic fields in conjunction with modulated electron radiation therapy (MERT). The starting depth of the magnetic field was varied over several centimetres. It was found that peak doses of as much as 2.7 times the surface dose could be achieved with a 1.5 T magnetic field. The magnetic field was shown to reduce the 80% and 20% dose drop-off distance by 50% to 80%. The distance between the 80% dose levels of the pseudo-Bragg peak induced by the magnetic field was found to be extremely narrow, generally less than 1 cm. However, by modulating the energy and intensity of the electron fields while simultaneously moving the magnetic field, a homogeneous dose distribution with low surface dose and a sharp dose fall-off was generated. Heterogeneities are shown to change the effective range of the electron beams, but not eliminate the advantages of a sharp depth dose drop-off or high peak-to-surface dose ratio. This suggests the applicability of MERT with magnetic fields in heterogeneous media. The results of this study demonstrate the ability to use magnetic fields in MERT to produce highly desirable dose distributions.

Algorithms↗
PubMed2000

Energy- and intensity-modulated electron beams for radiotherapy.

This work investigates the feasibility of optimizing energy- and intensity-modulated electron beams for radiation therapy. A multileaf collimator (MLC) specially designed for modulated electron radiotherapy (MERT) was investigated both experimentally and by Monte Carlo simulations. An inverse-planning system based on Monte Carlo dose calculations was developed to optimize electron beam energy and intensity to achieve dose conformity for target volumes near the surface. The results showed that an MLC with 5 mm leaf widths could produce complex field shapes for MERT. Electron intra- and inter-leaf leakage had negligible effects on the dose distributions delivered with the MLC, even at shallow depths. Focused leaf ends reduced the electron scattering contributions to the dose compared with straight leaf ends. As anticipated, moving the MLC position toward the patient surface reduced the penumbra significantly. There were significant differences in the beamlet distributions calculated by an analytic 3-D pencil beam algorithm and the Monte Carlo method. The Monte Carlo calculated beamlet distributions were essential to the accuracy of the MERT dose distribution in cases involving large air gaps, oblique incidence and heterogeneous treatment targets (at the tissue-bone and bone-lung interfaces). To demonstrate the potential of MERT for target dose coverage and normal tissue sparing for treatment of superficial targets, treatment plans for a hypothetical treatment were compared using photon beams and MERT.

Algorithms↗
PubMed2000

Accuracy of cause-of-death coding in Taiwan: types of miscoding and effects on mortality statistics.

BACKGROUND: The objectives of this study were to assess the accuracy of cause-of-death coding, determine the extent to which coders follow the selection rules of coding set out in the International Classification of Diseases, 9th Revision (ICD-9), and the effects of miscoding on mortality statistics in Taiwan. METHOD: A systematic sample of 5621 death certificates was reviewed. The underlying cause of death (UCD) selected by the reviewer for each death certificate was compared with that selected by the original coder. The UCD was selected according to ACME (Automated Classification of Medical Entities) Decision Tables. RESULTS: The overall agreement rates between the reviewer and coders according to the three-digit and two-digit categories of ICD-9 were 80.9% and 83.9%, respectively. Good agreement was found for malignant neoplasms (kappa = 0.94) and injuries and poisoning (kappa = 0.97), but there was poor agreement for nephrotic diseases (kappa = 0.74), hypertension-related diseases (kappa = 0.74), and cerebral infarction (kappa = 0.77). Reasons for disagreements included disagreement in nomenclature (42.8%), inappropriate judgement of causal relationships (41.5%), and incorrect interpretation of Selection Rule 3 and Modification Rules (15.7%). CONCLUSION: This study showed various levels of agreement for different diseases between the reviewer and the original coders in selection of the UCD. Owing to the 'compensatory effect of errors', the national mortality statistics were not affected significantly. The national administration should undertake routine internal studies to control the quality of UCD coding practices.

Age Distribution↗