Biomedical subjects

G Li

Publications and source records attributed to G Li.

At least 415 records · Page 23Linked to original sources

PubMed1999

Seated work postures for manual, visual and combined tasks.

An awkward and static work posture has been recognized as a risk factor for work-related musculoskeletal problems. The objective of this study was to investigate some of the factors that can influence the posture adopted during work and in particular aspects of the task and how their influence is affected by work height. Three types of task were studied: a peg-hole assembly task, which was largely manual with very little visual component; a visual character identification task; and a combination of the two. Two levels of difficulty were included in each of the manual and visual elements. Postures of the head/neck, trunk and arm were recorded during performance of these tasks. The results showed that type and difficulty of task do influence the posture adopted, and that some of the postural responses (although complex) are predictable so that poor postures could be improved by adjusting task design in addition to workplace layout.

Adult↗

PubMed1999

Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods.

Physical exposure to risks for potential work-related musculoskeletal injuries has been assessed using a variety of methods, including pen and paper based observation methods, videotaping and computer-aided analysis, direct or instrumental techniques, and various approaches to self-report assessment. These methods are critically reviewed in this paper. The applications of these techniques in ergonomic and epidemiologic studies are considered, and their advantages and shortcomings are highlighted. Finally, a strategy that considers both the ergonomics experts' view and the practitioners' needs for developing a practical exposure assessment tool is then discussed.

Electronic Data Processing↗

PubMed1999

Cardiopulmonary resuscitation in pediatric trauma patients: survival and functional outcome.

BACKGROUND: Although injury is the leading cause of cardiac arrests in children older than 1 year, few studies have examined the survival and functional outcome of cardiopulmonary resuscitation (CPR) in pediatric trauma patients. METHODS: A historical cohort of 957 trauma patients younger than 15 years who received CPR at the scene of injury or at the admitting hospital was constructed on the basis of the National Pediatric Trauma Registry. The rate of survival to discharge and factors related to survival were examined. Functional impairments were documented for surviving patients. RESULTS: The overall survival rate was 23.5%. With adjustment for the Injury Severity Score, the risk of fatality after CPR increased for children with systolic blood pressure below 60 mm Hg at admission (odds ratio [OR] 24.5, 95% confidence interval [CI] 8.6-69.3), for those who were comatose at admission (OR, 4.7; 95% CI, 1.9-11.6), for those with penetrating injury (OR, 4.4; 95% CI, 1.5-13.3), and for those with CPR initiated at the hospital (OR, 2.4; 95% CI, 1.5-3.9). Surviving patients stayed in hospitals for an average of 24.3 days; at discharge, 64% had at least one impairment in the functional activities of daily living. CONCLUSIONS: Survival outcome of CPR in pediatric trauma patients appears to be comparable to that reported in adults of mixed arrest causes. Future research needs to identify factors underlying the excess mortality associated with penetrating trauma.

Activities of Daily Living↗

PubMed1999

Expression of cell cycle regulators in human cutaneous malignant melanoma.

We postulate that genes involved in the control of cell proliferation are important determinants of melanoma growth and/or transformation. Using Western blot analysis, we compared the expression of nine key cell cycle regulators in metastatic melanomas with that in benign acquired naevi. Among the cyclin-dependent kinases (CDKs) examined, CDK2 was consistently and significantly overexpressed (three- to eight-fold) in metastatic melanomas compared with naevi. CDK1 and CDK4 exhibited no significant difference in expression between benign naevi and metastatic melanomas. CDK6 expression was variable, with four out of 10 metastatic melanomas showing higher expression than naevi. All the cyclins examined, especially cyclins A and D, were expressed more in metastatic melanomas than in naevi. Cyclin E was not detected in benign naevi, but was easily detectable in most of the metastatic melanomas. In addition, there was significantly greater expression of CDC25A, a tyrosine phosphatase that activates CDK kinases, in the metastatic melanomas. Over-expression of CDK2, CDK6, CDC25A and cyclin A was confirmed in melanoma cell lines. These cell cycle regulators may play an important role in melanoma growth and/or transformation.

Blotting, Western↗

PubMed1999

Depolarized light scattering spectroscopy of Ca0.4K0.6(NO3)(1.4): a reexamination of the "knee".

The "knee" found in the depolarized light scattering spectra of Ca0.4K0.6(NO3)(1.4) at low temperatures by G. Li, W.M. Du, X.K. Chen, H.Z. Cummins, and N.J. Tao [Phys. Rev. A 45, 3867 (1992)] appears to have been an experimental artifact. The origin of this feature is analyzed, and its implications for the mode coupling theory of the liquid-glass transition are considered.

Journal Article↗

PubMed1999

Crystallization and preliminary X-ray studies of metallothionein II from rabbit liver.

Metallothionein II (Mw = 6.8 kDa), induced by cadmium and purified from rabbit liver, has been crystallized in space group P6222 or P6422. The unit-cell parameters were a = b = 113.4, c = 219.1 A, alpha = beta = 90.0, gamma = 120.0 degrees when crystallized from sodium citrate buffer and a = b = 113.4, c = 219.6 A, alpha = beta = 90.0, gamma = 120.0 degrees when crystallized from Tris-HCl buffer. There are 12 molecules per asymmetric unit and the solvent content is about 57%.

Animals↗

PubMed1999

Assessing distributions of estimated drug shelf lives in stability analysis.

A stability study is usually conducted to ensure that a drug product can meet the approved specifications prior to its expiration dating period (shelf life). Several approaches for determination of drug shelf life assuming random batches have been proposed. In this paper, we examine sampling distributions of the estimated shelf lives proposed by Shao and Chow (1994, Biometrics 50, 753-763). An application to some stability data from the pharmaceutical industry is presented.

Biometry↗

PubMed1999

Prediction of antagonistic muscle forces using inverse dynamic optimization during flexion/extension of the knee.

This paper examined the feasibility of using different optimization criteria in inverse dynamic optimization to predict antagonistic muscle forces and joint reaction forces during isokinetic flexion/extension and isometric extension exercises of the knee. Both quadriceps and hamstrings muscle groups were included in this study. The knee joint motion included flexion/extension, varus/valgus, and internal/external rotations. Four linear, nonlinear, and physiological optimization criteria were utilized in the optimization procedure. All optimization criteria adopted in this paper were shown to be able to predict antagonistic muscle contraction during flexion and extension of the knee. The predicted muscle forces were compared in temporal patterns with EMG activities (averaged data measured from five subjects). Joint reaction forces were predicted to be similar using all optimization criteria. In comparison with previous studies, these results suggested that the kinematic information involved in the inverse dynamic optimization plays an important role in prediction of the recruitment of antagonistic muscles rather than the selection of a particular optimization criterion. Therefore, it might be concluded that a properly formulated inverse dynamic optimization procedure should describe the knee joint rotation in three orthogonal planes.

Algorithms↗

PubMed1999

A validated three-dimensional computational model of a human knee joint.

This paper presents a three-dimensional finite element tibio-femoral joint model of a human knee that was validated using experimental data. The geometry of the joint model was obtained from magnetic resonance (MR) images of a cadaveric knee specimen. The same specimen was biomechanically tested using a robotic/universal force-moment sensor (UFS) system and knee kinematic data under anterior-posterior tibial loads (up to 100 N) were obtained. In the finite element model (FEM), cartilage was modeled as an elastic material, ligaments were represented as nonlinear elastic springs, and menisci were simulated by equivalent-resistance springs. Reference lengths (zero-load lengths) of the ligaments and stiffness of the meniscus springs were estimated using an optimization procedure that involved the minimization of the differences between the kinematics predicted by the model and those obtained experimentally. The joint kinematics and in-situ forces in the ligaments in response to axial tibial moments of up to 10 Nm were calculated using the model and were compared with published experimental data on knee specimens. It was also demonstrated that the equivalent-resistance springs representing the menisci are important for accurate calculation of knee kinematics. Thus, the methodology developed in this study can be a valuable tool for further analysis of knee joint function and could serve as a step toward the development of more advanced computational knee models.

Aged↗

PubMed1999

Murine transgenic cells lacking DNA topoisomerase IIbeta are resistant to acridines and mitoxantrone: analysis of cytotoxicity and cleavable complex formation.

Murine transgenic cell lines lacking DNA topoisomerase II (topo II)beta have been used to assess the importance of topo IIbeta as a drug target. Western blot analysis confirmed that the topo IIbeta -/- cell lines did not contain topo IIbeta protein. In addition, both the topo IIbeta +/+ and topo IIbeta -/- cell lines contained similar levels of topo IIalpha protein. The trapped in agarose DNA immunostaining assay (TARDIS) was used to detect topo IIalpha and beta cleavable complexes in topo IIbeta -/- and topo IIbeta +/+ cells. These results show that both topo IIalpha and beta are in vivo targets for etoposide, mitoxantrone, and amsacrine (mAMSA) in topo IIbeta +/+ cells. As expected, only the alpha-isoform was targeted in topo IIbeta -/- cells. Clonogenic assays comparing the survival of topo IIbeta -/- and topo IIbeta +/+ cells were carried out to establish whether the absence of topo IIbeta caused drug resistance. Increased survival of topo IIbeta -/- cells compared with topo IIbeta +/+ cells was observed after treatment with amsacrine (mAMSA), methyl N-(4'-[9-acridinylamino]-2-methoxyphenyl) carbamate hydrochloride (AMCA), methyl N-(4'-[9-acridinylamino]-2-methoxyphenyl)carbamate hydrochloride (mAMCA), mitoxantrone, and etoposide. These studies showed that topo IIbeta -/- cells were significantly more resistant to mAMSA, AMCA, mAMCA, and mitoxantrone, than topo IIbeta +/+ cells, indicating that topo IIbeta is an important target for the cytotoxic effects of these compounds.

Acridines↗

PubMed1999

Quantitative analysis of T-cell receptor beta variable-gene usage in cutaneous late-phase reactions: implications for T-lymphocyte recruitment in cutaneous inflammation.

To determine if functionally distinct T-lymphocyte (T cell) subsets accumulate in late-phase immunoglobulin E-mediated reactions (LPR), we quantitatively analyzed the immunophenotype and the T-cell receptor beta variable-gene (Vbeta) repertoire of T cells in cutaneous LPR. Peripheral blood and skin biopsies were obtained 6 or 24 h after sensitive subjects were challenged with intradermal injections of grass pollen allergen (Ag) and control (C) solution. The frequency of cells expressing CD3, CD4, CD8, CD45RO, and CD25/mm2 was determined by immunohistochemistry in nine subjects. Vbeta usage was assessed by reverse transcription-PCR in five of nine subjects. A significantly greater frequency of CD3(+) and CD45RO+ (memory) T cells was detected in Ag sites than in C sites at 24 h after challenge but not at 6 h. The frequency of activated (CD25(+)) and helper (CD4(+)) T cells appeared to be increased in Ag sites as well, though not significantly. Vbeta6 was the most commonly expressed Vbeta detected in Ag sites, but it was also detected in accompanying C sites. Vbeta2 was the most commonly expressed Vbeta detected in C sites. Sequence analysis in one case revealed Vbeta expression in a 6-h Ag site to be essentially polyclonal. Our findings suggest that memory T cells with Vbeta expression similar to that in normal skin accumulate in developing cutaneous LPR. The limited usage of Vbeta suggests a preferential recruitment or retention of reactive T cells from an endogenous subset of skin-homing T cells with its own skewed Vbeta repertoire.

Adult↗

PubMed1999

Alcohol and other psychoactive drugs in trauma patients aged 10-14 years.

OBJECTIVE: To examine the prevalence of alcohol and/or other psychoactive drugs, such as marijuana and cocaine (AODs), involved in preteen trauma patients. METHODS: Toxicological testing results were analyzed for 1356 trauma patients aged 10-14 years recorded in the National Pediatric Trauma Registry for the years 1990-95. RESULTS: Of the 1356 patients who received toxicological screening at the time of admission, 116 (9%) were positive for AODs. AOD involvement increased with age. Patients with pre-existing mental disorders were nearly three times as likely as other patients to be AOD positive (23% v 8%, p < 0.01). AOD involvement was more prevalent in intentional injuries and in injuries that occurred at home. CONCLUSIONS: AODs in preteen trauma are of valid concern, in particular among patients with mental disorders or intentional injuries. The role of AODs in childhood injuries needs to be further examined using standard screening instruments and representative study samples.

Adolescent↗

PubMed1999

Hodgkin's disease: immunoglobulin heavy and light chain gene rearrangements revealed in single Hodgkin/Reed-Sternberg cells.

AIM: To corroborate and investigate the nature of Hodgkin/Reed-Sternberg cells (H/R-S) of various subtypes of Hodgkin's disease. METHOD: Single H/R-S cells were micro-picked from frozen sections of tissues affected by Hodgkin's disease. The DNA from these cells was amplified by the polymerase chain reaction (PCR) with immunoglobulin heavy chain (IgH) gene FRIIIa/JH primers and light chain gene family specific primers. RESULTS: Fifty two of 135 isolated cells gave specific reaction products (36%). IgH and V kappa 4 gene rearrangements were found repeatedly in many H/R-S cells from one case of lymphocyte predominant Hodgkin's disease. Repeated V kappa 4 and individual IgH/V kappa 4,2 rearrangements were seen in one case, and individual IgH and V lambda 3/V kappa 4 rearrangements were seen in another case of nodular sclerosis-type Hodgkin's disease. Repeated IgH/V lambda 3 and individual V lambda 2,4 rearrangements, repeated V kappa 4 and individual IgH/V kappa 3 rearrangements, and repeated IgH and individual V kappa 3/V kappa 4 rearrangement were detected, respectively, in three cases of mixed cellularity-type Hodgkin's disease. Repeated and individual IgH rearrangements were found in another two cases of mixed cellularity-type Hodgkin's disease. CONCLUSION: The H/R-S cells isolated from lymphocyte predominant Hodgkin's disease had IgH and V kappa 4 gene rearrangements, which supports the conclusion that this disease results from a proliferation of neoplastic B cells. The IgH and kappa and/or lambda gene rearrangements seen in H/R-S cells isolated from classic Hodgkin's disease (mixed cellularity-type and nodular sclerosis-type) support the theory that these cells derive from B lineage cells at various stages of differentiation. To our knowledge, this is first time that lambda gene rearrangements have been detected in H/R-S cells.

Electrophoresis, Polyacrylamide Gel↗

PubMed1999

Metallothionein inhibits ischemia-reperfusion injury in mouse heart.

Oxidative stress is believed to play a major role in ischemia-reperfusion injury to the heart. Metallothionein (MT), a potential free radical scavenger, may function in cardiac protection against ischemia-reperfusion damage. To test this hypothesis, a specific cardiac MT-overexpressing transgenic mouse model was used. The hearts isolated from these animals were subjected to 50 min of warm (37 degrees C) zero-flow ischemia followed by 60- or 90-min reflow. Compared with the nontransgenic controls, the transgenic mouse hearts with MT concentrations approximately 10-fold higher than normal showed significantly improved recovery of contractile force postischemia (69.2 +/- 4.2 vs. 26.0 +/- 6.0% at the end of 60-min reperfusion, P < 0.01). Efflux of creatine kinase from these transgenic hearts was reduced by more than 50% (P < 0.01). In addition, the zone of infarction induced by ischemia-reperfusion at the end of 90-min reperfusion was suppressed by approximately 40% (P < 0.01) in the transgenic hearts. The results strongly indicate that MT provides protection against ischemia-reperfusion-induced heart injury.

Animals↗

PubMed1999

Attitudes toward the mentally ill in a sample of professionals working in a psychiatric hospital in Beijing (China).

The attitudes of psychiatric doctors and nurses toward the mentally ill in a large urban psychiatric hospital in China were compared using the Community Attitudes toward the Mentally Ill (CAMI). Data indicated that the attitude of professionals differed on 11 of the 40 questions of this instrument. Those questions are divided along 4 dimensions: authoritarianism, benevolence, social restrictiveness and rehabilitation in the community. Results showed that psychiatric doctors have a more liberal and positive attitude toward the mentally ill than psychiatric nurses, especially about their rehabilitation in the community. Factor analysis also indicated that nurses were more likely than doctors to attribute negative characteristics to the mentally ill. Some explanations are proposed to explain these differences.

Adult↗

PubMed1999

Ultraviolet radiation-induced p53 responses in the epidermis are differentiation-dependent.

BACKGROUND: The tumour suppressor, p53, is recognized as a crucial molecule in regulating cellular responses to various DNA-damaging agents. Very early on in the development of nonmelanoma cancers p53 is mutated or lost, suggesting that p53 is crucial in protecting normal keratinocytes from the harmful effects of ultraviolet (UV) radiation. OBJECTIVE: Using two mouse models, one with multiple copies of mutant p53 and the other a p53 "knockout," our laboratory has examined a role for p53 in UV-induced DNA damage and determined if these effects are differentiation dependent. CONCLUSION: We outline in this review a proposed model reflecting differentiation-dependent p53 regulation of UV-induced responses in keratinocytes. After exposure to UV, basal keratinocytes repair damaged DNA, whereas differentiating keratinocytes undergo cell death, both processes are regulated by p53.

Animals↗

PubMed1999

The biology of fracture healing: optimising outcome.

Optimising the results of fracture treatment requires a holistic view of both patients and treatment. The nature of the patient determines the priority targets for outcome, which differ widely between the elderly and the young, and between the victims of high and low energy trauma. The efficacy of treatment depends on the overall process of care and rehabilitation as well as the strategy adopted to achieve bone healing. The rational basis for fracture treatment is the interaction between three elements: (i) the cell biology of bone regeneration; (ii) the revascularisation of devitalized bone and soft tissue adjacent to the fracture; and (iii) the mechanical environment of the fracture. The development of systems for early fracture stabilisation has been an advance. However, narrow thinking centred only on the restoration of mechanical integrity leads to poor strategy--the aim is to optimise the environment for bone healing. Future advances may come from the adjuvant use of molecular stimuli to bone regeneration.

Combined Modality Therapy↗

PubMed1999

Back injury in municipal workers: a case-control study.

OBJECTIVES: The purpose of this study was to identify factors associated with acute low back injury among municipal employees of a large city. METHODS: For each of 200 injured case patients, 2 coworker controls were randomly selected, the first matched on gender, job, and department and the second matched on gender and job classification. In-person interviews were conducted to collect data on demographics, work history, work characteristics, work injuries, back pain, psychosocial and work organization, health behaviors, and anthropometric and ergonomic factors related to the job. Psychosocial work organization variables were examined with factor analysis techniques; an aggregate value for job strain was entered into the final model. Risk factors were examined via multivariate logistic regression techniques. RESULTS: High job strain was the most important factor affecting back injury (odds ratio [OR] = 2.12, 95% confidence interval [CI] = 1.28, 3.52), and it showed a significant dose-response effect. Body mass index (OR = 1.54, 95% CI = 1.08, 2.18) and a work movement index (twisting, extended reaching, and stooping) (OR = 1.42, 95% CI = 0.97, 2.08) were also significant factors. CONCLUSIONS: Results suggest that increasing workers' control over their jobs reduces levels of job strain. Ergonomic strategies and worksite health promotion may help reduce other risk factors.

Accidents, Occupational↗