Search PubMed⌕ Search

Biomedical subjects

L Chan

Publications and source records attributed to L Chan.

At least 73 records · Page 4Linked to original sources
PubMed2000

Manual wheelchair pushrim biomechanics and axle position.

OBJECTIVE: The biomechanics of wheelchair propulsion have been linked to upper extremity injury. Specifically, prior studies have correlated increased median nerve dysfunction with increasing propulsion frequency and a higher rate of rise of the resultant, or total, pushrim force. Despite this link, there is little research on the effect of wheelchair setup on propulsion biomechanics. The objective of this study was to determine the effect of rear axle position relative to the shoulder on pushrim biomechanics. DESIGN: Case series. SETTING: Biomechanics laboratory. PARTICIPANTS: Forty individuals with paraplegia who use manual wheelchairs for mobility. INTERVENTION: Subjects propelled their own wheelchairs on a dynamometer at two different steady-state speeds and going from a dead stop to maximum speed. Bilateral biomechanical data were obtained using a force- and moment-sensing pushrim and a motion analysis system. MAIN OUTCOME MEASURES: Position of the axle relative to the shoulder at rest both horizontal (XPOS) and vertical (YPOS), and pushrim biomechanical variables including frequency of propulsion, peak and rate of rise of the resultant force, planar moment, and push angle. Partial correlation coefficients between relative axle position and propulsion biomechanics variables were calculated. RESULTS: After controlling for subject characteristics, XPOS was significantly correlated with the frequency of propulsion (p < .01) and the rate of rise of the resultant force (p < .05). In addition, both XPOS and YPOS were significantly correlated with the push angle at multiple speeds (p < .05). CONCLUSION: Specific biomechanical parameters known to correlate with median nerve injuries were found to be related to axle position relative to the shoulder. Providing wheelchair users with adjustable axle position and then fitting the user to the wheelchair can improve propulsion biomechanics and likely reduce the risk of injury.

Adult↗
PubMed2000

Medicare's payment system: its effect on discharges to skilled nursing facilities from rehabilitation hospitals.

OBJECTIVE: To determine if Medicare's payment system for rehabilitation hospitals encourages discharges to skilled nursing facilities (SNFs). Medicare payments to hospitals are based on limits derived from a hospital's average allowable patient charge during a base year. Thereafter, payments are capped, but hospitals receive additional incentive payments if succeeding costs are reduced. It was a hypothesis of this study that discharges to SNFs would increase after the base year. In this way, rehabilitation hospitals would limit high-cost patients when under reimbursement limitation. METHODS: Medicare claims data for 162,239 discharges from 69 rehabilitation hospitals between 1987 and 1994 were analyzed. After controlling for patient and provider characteristics, we compared the odds of being discharged to a SNF before, during, and after the base year. RESULTS: Before and during the base year, 4.7% and 6.6% of patients were discharged to a SNF. After the base year, 9% of patients were sent to a SNF. After controlling for temporal and seasonal trends, as well as for patient and provider characteristics, those discharged after the base year were significantly more likely to be sent to a SNF than those discharged during the base year. These odds increased with increasing length of stay in the rehabilitation hospital. For those with a length of stay of 29 days (75th percentile) the odds increased by 11% (odds ratio, 1.11; 95% confidence interval, 1.04-1.18). CONCLUSIONS: The incentives of Medicare's reimbursement system may encourage an increase in the percentage of patients discharged to SNFs after the base year. These findings have significant implications regarding the structure of Medicare's prospective payment system currently planned for this class of hospital.

Female↗
PubMed2000

The db/db mouse, a model for diabetic dyslipidemia: molecular characterization and effects of Western diet feeding.

Diabetic dyslipidemia is a major factor contributing to the accelerated atherosclerosis in type 2 diabetes mellitus. Although several mouse models are available, the plasma lipoproteins in response to diet have not been fully characterized in these animals. In this study, we have characterized the plasma lipoproteins and related apolipoproteins, as well as the vascular lipases, in diabetes (db/db) mice and their nondiabetic controls (+/?) in the C57BL/KsJ strain. Within 6 weeks of age, db/db mice developed significant obesity, fasting hyperglycemia, and hyperinsulinemia. By FPLC analysis, db/db mice showed a prominent peak in the low-density lipoprotein (LDL) range that was absent in +/? mice, although high-density lipoprotein (HDL) was the predominant species in both groups of animals. Postheparin lipoprotein lipase (LPL) activity in db/db mice was 28% of the level in +/? mice. Upon feeding a human-like 0.15% (wt/wt) cholesterol and 21% (wt/wt) fat "Western" diet, db/db mice developed elevated plasma cholesterol, accompanied by an exaggerated apolipoprotein E (apoE) response compared with +/? mice. FPLC analysis showed that the marked hypercholesterolemic response in db/db mice was the result of a massive increase in the LDL region, which overshadowed a moderate increase in HDL. We next isolated lipoproteins by ultracentrifugation and characterized them by nondenaturing gradient gel electrophoresis. With regular chow, db/db mice had almost exclusively small dense LDL with a peak size at 21.4 nm, as compared with 26.6 nm in nondiabetic controls. On the Western diet, the small dense LDLs persisted but larger particles also appeared in db/db mice, whereas the size distribution in +/? mice was unchanged by the diet. Our results suggest that db/db mice fed a Western diet have a plasma lipoprotein phenotype that shows some similarities to that in patients with type 2 diabetes mellitus, and that db/db mice are a useful model to study the pathogenesis and treatment of diabetic dyslipidemia.

Age Factors↗
PubMed2000

Absence of perilipin results in leanness and reverses obesity in Lepr(db/db) mice.

Obesity is a disorder of energy balance. Hormone-sensitive lipase (HSL) mediates the hydrolysis of triacylglycerol, the major form of stored energy in the body. Perilipin (encoded by the gene Plin), an adipocyte protein, has been postulated to modulate HSL activity. We show here that targeted disruption of Plin results in healthy mice that have constitutively activated fat-cell HSL. Plin -/- mice consume more food than control mice, but have normal body weight. They are much leaner and more muscular than controls, have 62% smaller white adipocytes, show elevated basal lipolysis that is resistant to beta-adrenergic agonist stimulation, and are cold-sensitive except when fed. They are also resistant to diet-induced obesity. Breeding the Plin -/- alleles into Leprdb/db mice reverses the obesity by ncreasing the metabolic rate of the mice. Our results demonstrate a role for perilipin in reining in basal HSL activity and regulating lipolysis and energy balance; thus, agents that inactivate perilipin may prove useful as anti-obesity medications.

Adipose Tissue↗
PubMed2000

Relationship between fetal monitoring and resuscitative needs: fetal distress versus routine cesarean deliveries.

BACKGROUND: There is debate as to whether pediatricians should be present at all cesarean deliveries. Little published data exist regarding the differences in resuscitative needs of infants delivered by cesarean section for "fetal distress" versus those without this diagnosis. OBJECTIVE: To describe the differences in resuscitative and immediate postnatal intervention needs for neonates with fetal distress delivered by cesarean section and those without fetal distress delivered in the same manner. Also, to devise an evaluation tool to assess and compare levels of neonatal resuscitation between infants and groups of infants. METHODS: The delivery records of 1411 term infants delivered by cesarean section after uncomplicated pregnancies at Los Angeles County/University of Southern California Medical Center from March 3, 1995 through March 8, 1997 were examined retrospectively. Apgar scores and resuscitative needs were assigned to a newly devised, weighted scoring system. Resuscitation subscores and total resuscitation scores were compared using non-parametric methods. RESULTS: The fetal distress group (n = 80) had a significantly greater resuscitative needs mean score (p < 0.001) and subscores (p < 0.001 to p = 0.004) than did the non-fetal distress group (n = 419). Of the non-fetal distress group, 48.7% still received some active form of intervention. CONCLUSION: In our study group, infants with fetal distress had significantly greater intervention needs than infants without fetal distress.

Cesarean Section↗
PubMed2000

Compound heterozygosity of Leu252Val and Leu252Arg causing lipoprotein lipase deficiency in a chinese patient with hypertriglyceridemia.

BACKGROUND: We investigated lipoprotein lipase (LPL) gene mutations in a Chinese male with severe hypertriglyceridemia and recurrent pancreatitis. METHODS: We screened for LPL sequence mutation in the LPL gene in this patient, his relatives and 160 unrelated hypertriglyceridaemic subjects. We determined the postheparin plasma LPL activity of subjects carrying a LPL mutation and studied the in vitro expression of mutant LPL in COS-1 cells. RESULTS: The proband was found to be a compound heterozygote for a novel Leu252Val and a reported Leu252Arg mutation in the LPL gene. He had low plasma levels of postheparin LPL activity and mass. The two mutations segregated independently in his family. In vitro expression analysis showed that Leu252Arg abolished both the catalytic function and secretion of LPL, while Leu252Val abolished the catalytic function but only reduced secretion by about half. We have also detected heterozygous Leu252Val and Leu252Arg mutations each in one hypertriglyceridaemic individual. CONCLUSION: These results indicated that the leucine 252 is critical for the catalytic activity and secretion of LPL. Why the substitution by valine instead of arginine resulted only in a partial suppression of LPL secretion, remains to be investigated. Leu252Val and Leu252Arg are the likely cause of hypertriglyceridemia in these subjects because of their deleterious effects on LPL activity or secretion. Leu252Val/Leu252Arg is the first compound heterozygous mutation known to occur in the same codon of the LPL gene. So far they are found only in Chinese.

Adolescent↗
PubMed2000

The comparative accuracy of radiolucent foreign body detection using ultrasonography.

The purpose of this prospective study was to determine the accuracy of ultrasonography in detecting radiolucent foreign bodies and to compare the performance of three newly trained emergency physicians with two experienced ultrasound technologists and one radiologist. One hundred-four chicken thighs were penetrated with a needle-driver, half of them embedded with a 1.5 cm toothpick. An 8.0 MHZ linear array ultrasound probe was used to detect the presence or absence of the foreign body. The overall accuracy (95% confidence interval [CI]) was 82% (79, 85); sensitivity 79% (74, 83), specificity 86% (82, 90), positive predicative value (PPV) 85% (81, 89), and negative predicative value (NPV) 80% (76, 84). The accuracy (95% CI) of the radiologist was 83% (75, 90); of the ultrasound technologists was 85% (80, 90); and of the emergency physicians was 0% (76, 85). The difference in accuracy among the three types of personnel was not statistically significant. Ultrasonography is an accurate modality in detecting radiolucent foreign bodies. Emergency physicians can be trained to provide a degree of accuracy comparable with more experienced ultrasonographers.

Allied Health Personnel↗
PubMed2000

The association between meconium and the production and reabsorption of lung liquid and lactate loss by in vitro lungs from fetal guinea pigs.

OBJECTIVE: We sought to use an in vitro approach to determine relationships between meconium and fetal lung liquid production and to relate meconium to possible problems in lung liquid removal at birth. STUDY DESIGN: Near-term fetal guinea pigs were divided according to the level of spontaneously occurring meconium (no meconium, light meconium, or heavy meconium). Their lungs were maintained in vitro in Krebs-Henseleit saline solution for 3 hours. Lung liquid production or reabsorption was measured by a dye-dilution method, and loss of lactate to the lung liquid and outer Krebs-Henseleit solution was monitored. Reabsorptions were investigated by activating powerful responses with dinitrophenol during the middle hour. RESULTS: During the first hour, lungs from meconium-free fetuses produced liquid at 1.25 +/- 0.12 mL/kg(-1) body weight. h(-1); rates from light or heavy meconium groups were not significantly different (n = 18). Similarly, total lactate loss was not significantly different between the meconium-free and light-meconium groups but was twice as high in heavy-meconium preparations (73.68 +/- 10.60 micromol/L. g(-1) dry lung tissue. h(-1); P <.025, analysis of variance). The meconium-free and heavy-meconium groups continued to produce fluid, with no significant change throughout the 3 hours of incubation; lactate losses fell slightly. Therefore there were no problems with fluid production with meconium present, but the high-lactate losses with heavy meconium suggested long-term intrauterine hypoxia. Dinitrophenol produced powerful reabsorptions in lungs from meconium-free fetuses (-0.85 +/- 0.35 mL. kg(-1) body weight. h(-1); P <.005, analysis of variance; P <.0005, regression analysis) but failed to do so in heavy-meconium fetuses (n = 36). Lactate losses rose 2-fold in both groups (P <.005 to P < 0.0005, analysis of variance and regression analysis), despite already elevated losses with heavy meconium (n = 12). Therefore, in heavy-meconium fetuses, dinitrophenol affected metabolic pathways but did not activate fluid reabsorption, suggesting damage to reabsorptive mechanisms. CONCLUSION: Unless major airways are blocked, meconium is not associated with reduced fetal lung liquid production, which can cause poor lung development, but there may well be poor fluid removal after birth because of compromised reabsorptive mechanisms, which are unlikely to be helped by possible hormonal intervention.

Absorption↗
PubMed2000

Perceived risk and help-seeking behavior for breast cancer. A Chinese-American perspective.

Delay in the diagnosis and treatment of breast cancer diminishes a woman's chance of survival. How do women decide whether and when to seek an evaluation of breast symptoms that may signal breast cancer? Prior studies of African-American, white, and Latino women have described a number of critical factors associated with making the judgment to delay, but at this writing, there have been no studies factors influencing Chinese-American women. By means of focus group methods in English, Mandarin, and Cantonese, a sample of 45, predominantly first-generation Chinese-American women explained their understanding of breast cancer risk and their likelihood of delaying versus seeking evaluation of self-discovered breast symptoms. There was much congruence with the ideas of other American women despite the differing cultural heritage. Unique to these Chinese Americans was a sense of invulnerability to breast cancer, a linking of cancer to tragic luck, and the predominant likelihood of delay. To preserve modesty and to conserve wealth and time, many study participants favored using Chinese medicine and delaying Western therapies. This study suggests ways by which health care providers must approach guidelines for breast cancer early detection in this population.

Adult↗
PubMed2000

Effect of prehospital advanced life support on outcomes of major trauma patients.

OBJECTIVE: Determine whether prehospital advanced life support (ALS) improves the survival of major trauma patients and whether it is associated with longer on-scene times. METHODS: A 36-month retrospective study of all major trauma patients who received either prehospital bag-valve-mask (BVM) or endotracheal intubation (ETI) and were transported by paramedics to our Level I trauma center. Logistic regression analysis determined the association of prehospital ALS with patient survival. RESULTS: Of 9,451 major trauma patients, 496 (5.3%) had either BVM or ETI. Eighty-one percent received BVM, with a mean Injury Severity Score of 29 and a mortality rate of 67%; 93 patients (19%) underwent successful ETI, with a mean Injury Severity Score of 35 and a mortality rate of 93%. Adjusted survival for patients who had BVM was 5.3 times more likely than for patients who had ETI (95% confidence interval, 2.3-14.2, p = 0.00). Survival among patients who received intravenous fluids was 3.9 times more likely than those who did not (p = not significant). Average on-scene times for patients who had ETI or intravenous fluids were not significantly longer than those who had BVM or no intravenous fluids. CONCLUSION: ALS procedures can be performed by paramedics on major trauma patients without prolonging on-scene time, but they do not seem to improve survival.

Adolescent↗
PubMed2000

Recent advances in liver-directed gene therapy: implications for the treatment of dyslipidemia.

Somatic gene therapy for the treatment of dyslipidemia is an area of active investigation. A substantial body of data indicates that the transfer of various lipid-lowering genes to the liver is an effective method of restoring normal plasma lipids in animal models of dyslipidemia. Most studies have used adenoviral vectors because of their excellent gene-transfer efficiency. However, the first and second-generation adenoviral vectors used in these experiments are highly toxic and are associated with substantial morbidity and mortality. This article reviews current data on the properties of two novel vectors, the adeno-associated virus and the helper-dependent adenovirus that is devoid of all protein-encoding genes. Each type of vector has its advantages and drawbacks. They appear to be the most promising vectors to date for liver-directed gene transfer in the treatment of dyslipidemia.

Adenoviridae↗
PubMed2000

Ultrasound training for emergency physicians--a prospective study.

OBJECTIVES: Bedside ultrasound examination by emergency physicians (EPs) is being integrated into clinical emergency practice, yet minimum training requirements have not been well defined or evaluated. This study evaluated the accuracy of EP ultrasonography following a 16-hour introductory ultrasound course. METHODS: In phase I of the study, a condensed 16-hour emergency ultrasound curriculum based on Society for Academic Emergency Medicine guidelines was administered to emergency medicine houseofficers, attending staff, medical students, and physician assistants over two days. Lectures with syllabus material were used to cover the following ultrasound topics in eight hours: basic physics, pelvis, right upper quadrant, renal, aorta, trauma, and echo-cardiography. In addition, each student received eight hours of hands-on ultrasound instruction over the two-day period. All participants in this curriculum received a standardized pretest and posttest that included 24 emergency ultrasound images for interpretation. These images included positive, negative, and nondiagnostic scans in each of the above clinical categories. In phase II of the study, ultrasound examinations performed by postgraduate-year-2 (PGY2) houseofficers over a ten-month period were examined and the standardized test was readministered. RESULTS: In phase I, a total of 80 health professionals underwent standardized training and testing. The mean +/- SD pretest score was 15.6 +/- 4.2, 95% CI = 14. 7 to 16.5 (65% of a maximum score of 24), and the mean +/- SD posttest score was 20.2 +/- 1.6, 95% CI = 19.8 to 20.6 (84%) (p < 0. 05). In phase II, a total of 1,138 examinations were performed by 18 PGY2 houseofficers. Sensitivity was 92.4% (95% CI = 89% to 95%), specificity was 96.1% (95% CI = 94% to 98%), and overall accuracy was 94.6% (95% CI = 93% to 96%). The follow-up ultrasound written test showed continued good performance (20.7 +/- 1.2, 95% CI = 20.0 to 21.4). CONCLUSIONS: Emergency physicians can be taught focused ultrasonography with a high degree of accuracy, and a 16-hour course serves as a good introductory foundation.

Clinical Competence↗
PubMed2000

Antiviral properties of a series of 1,6-naphthyridine and 7, 8-dihydroisoquinoline derivatives exhibiting potent activity against human cytomegalovirus.

A series of 1,6-naphthyridine (L. Chan, H. Jin, T. Stefanac, J. F. Lavallee, G. Falardeau, W. Wang, J. Bedard, S. May, and L. Yuen, J. Med. Chem. 42:3023-3025, 1999) and isoquinoline (L. Chan, H. Jin, T. Stefanac, W. Wang, J. F. Lavallee, J. Bedard, and S. May, Bioorg. Med. Chem. Lett. 9:2583-2586, 1999) analogues exhibiting a high level of anti-human cytomegalovirus (HCMV) activity were investigated in a series of studies aimed at better understanding the mechanism of action of some representatives of this class of compounds. In vitro antiviral profiling revealed that these compounds were active against a narrow spectrum of viruses, essentially the human herpesviruses and type 2 rhinovirus. In HCMV assays, a 39- to 223-fold lower 50% inhibitory concentration was obtained for compound A1 than for ganciclovir against strains AD 169 and Towne. In addition, ganciclovir, foscarnet, cidofovir, and BDCRB (2-bromo-5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole)-resistant HCMV strains remained susceptible to 1,6-naphthyridines and 7, 8-dihydroisoquinolines tested in this study, supporting the view that a novel mechanism of action could be involved. Drug combination studies showed a small but significant synergistic antiviral effect between compound B2 and ganciclovir. Cytotoxicity profiling of representative compounds under various cell growth conditions indicated a generally similar cytotoxic effect, relative to ganciclovir, in log-phase growing cells. However, in stationary cells, a relatively higher level of toxicity was observed than that for control compound. Effect of time of drug addition showed that the anti-HCMV activity of compound A1, ganciclovir, and cidofovir was lost at approximately the same time (72 h postinfection), indicating that the compound was affecting events at the early and late stage of virus replication. This interpretation is also supported by reduction of de novo synthesis of pp65 tegument protein and lack of any effect of the compound on viral adsorption. A reduction of the HCMV enhancer-promoter-directed luciferase expression was also observed in a stably transfected cell line when compound A1 was present at relatively high concentrations.

Antiviral Agents↗
PubMed2000

Cloning and expression of immunoreactive antigens from Mycobacterium tuberculosis.

Four immunoreactive proteins, B.4, B.6, B.10, and B.M, with molecular weights ranging from 16,000 to 58,000, were observed from immunoblots of Mycobacterium tuberculosis total lysates screened with sera from individuals with active tuberculosis. These proteins were identified from microsequence analyses, and genes of proteins with the highest homology were PCR amplified and cloned into the pQE30 vector for expression studies. In addition, a 37.5-kDa protein, designated C17, was identified from a phage expression library of M. tuberculosis genomic DNA. Preliminary immunoblot assays indicated that these five resultant recombinant proteins could detect antibodies in individuals with active pulmonary and extrapulmonary tuberculosis. The overall ranges of sensitivities, specificities, positive predictive values, and negative predictive values for the recombinant antigens were 20 to 58, 88 to 100, 69 to 100, and 56 to 71%, respectively. The B.6 antigen showed preferential reactivity to antibodies in pulmonary compared to nonpulmonary tuberculosis serum specimens. All of these recombinant antigens demonstrated potential for serodiagnosis of tuberculosis.

Antigens, Bacterial↗
PubMed2000

Detection of Legionella pneumophila using a real-time PCR hybridization assay.

A real-time PCR hybridization assay for Legionella pneumophila is described; the assay uses LightCycler (Idaho Technology) methodology to specifically detect 2.5 CFU/reaction, equivalent to 1,000 CFU/liter of starting water sample. The assay, including DNA extraction and confirmation of product identity, is completed within 90 min of receipt of a sample.

DNA, Bacterial↗
PubMed2000

The effect of the doctor-patient relationship on emergency department use among the elderly.

OBJECTIVES: This study sought to determine the rate of emergency department use among the elderly and examined whether that use is reduced if the patient has a principal-care physician. METHODS: The Health Care Financing Administration's National Claims History File was used to study emergency department use by Medicare patients older than 65 years in Washington State during 1994. RESULTS: A total of 18.1% of patients had 1 or more emergency department visits during the study year; the rate increased with age and illness severity. Patients with principal-care physicians were much less likely to use the emergency department for every category of disease severity. After case mix, Medicaid eligibility, and rural/urban residence were controlled for, the odds ratio for having any emergency department visit was 0.47 for patients with a generalist principal-care physician and 0.58 for patients with a specialist principal-care physician. CONCLUSIONS: The rate of emergency department use among the elderly is substantial, and most visits are for serious medical problems. The presence of a continuous relationship with a physician--regardless of specialty--may reduce emergency department use.

Aged↗