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Biomedical subjects

David Chen

Publications and source records attributed to David Chen.

27 records · Page 2Linked to original sources
PubMed2003

Amiodarone optic neuropathy--review.

The antiarrhythmic agent, amiodarone (Cordone), Pacerone), has been reported to cause optic neuropathy. However, the clinical manifestations are similar to non-arteritic anterior ischemic optic neuropathy (AION), which makes diagnosing amiodarone optic neuropathy difficult. There is controversy whether or not amiodarone optic neuropathy actually exists as a distinct entity. The clinical manifestations and the proposed pathophysiology of amiodarone optic neuropathy are discussed.

Amiodarone↗
PubMed2003

Spinal Cord Injury Risk Assessment for Thromboembolism (SPIRATE Study).

OBJECTIVE: To identify risk factors for venous thromboembolism (VTE) during the rehabilitation phase of spinal cord injury. DESIGN: A comprehensive review of the charts of all patients admitted between 1992 and 1995 for rehabilitation after spinal cord injury. Only records including evidence for objective testing for thromboembolism were included. The analysis variables included type and location of spinal cord injury, American Spinal Injury Association classification, concomitant injuries, surgical procedures, complications, preexisting illnesses, and use of antithrombotic prophylaxis. Hierarchically optimal classification tree analysis was employed to develop a nonlinear model for predicting deep vein thrombosis. RESULTS: The analysis sample consisted of these 243 persons with acute spinal cord injury, 51 of whom had venous thromboembolism, and eight of whom died. A three-variable model emerged that identified patient groups differing in relative likelihood of experiencing deep vein thrombosis. The highest likelihood group were patients with cancer over the age of 35 yrs. Women between the ages of 36 and 58 yrs without cancer were also at increased risk, as were cancer-free men with flaccid paralysis. CONCLUSIONS: Venous thromboembolism is more likely to develop in spinal cord injury patients who are older, obese, and have flaccid paralysis or cancer. These patients should receive vigorous prophylaxis against venous thromboembolism.

Adult↗
PubMed2003

Using the observer to analyze learning in virtual worlds.

In this study, we describe and analyze the ways in which high school students explored a virtual solar system (VSS). VSS is a nonimmersive virtual environment that affords visual manipulations of space by altering its frame of reference. The Observer software was used to code and analyze the participants' real-time free-exploration task. Two basic behaviors were identified across participants: establishing several home bases, and shifting between a still mode and a dynamic mode. Moreover, three overall exploration patterns emerged: the butterfly pattern represents a superficial mode of learning; the bee pattern represents an in-depth mode of studying the various celestial objects; and the eagle pattern represents a global approach of studying the complex system. This virtual reality environment promises to provide a setting in which to further study consistent patterns and individual differences in exploration strategies.

Adolescent↗
PubMed2002

Memory lateralization in medial temporal lobe epilepsy assessed by functional MRI.

PURPOSE: To determine the utility of functional magnetic resonance imaging (fMRI) in preoperative lateralization of memory function in patients with medial temporal lobe epilepsy (MTLE). METHODS: Nine patients with MTLE underwent standard preoperative assessment including video-EEG and intracarotid amytal testing (IAT). fMRI was performed while subjects encoded four types of stimuli (patterns, faces, scenes, and words). Activation maps were created for each subject representing areas more active for novel than for repeated stimuli. Regions of interest were drawn around the MTL in individual subjects, suprathreshold voxels were counted, and an asymmetry index was calculated. RESULTS: In eight of nine subjects, lateralization of memory encoding by fMRI was concordant with that obtained from the IAT. Group-level analysis demonstrated greater activation in the MTL contralateral to the seizure focus such that in the left MTLE group, verbal encoding engaged the right MTL, whereas in the right MTLE group, nonverbal encoding engaged the left MTL. CONCLUSIONS: fMRI is a valid tool for assessing of memory lateralization in patients with MTLE and may therefore allow noninvasive preoperative evaluation of memory lateralization. FMRI revealed that memory encoding may be reorganized to the contralateral MTL in patients with MTLE.

Adult↗
PubMed2002

Patient colonization and environmental contamination by vancomycin-resistant enterococci in a rehabilitation facility.

OBJECTIVES: To determine the frequency of environmental contamination in patient and common-use rooms and patient colonization by vancomycin-resistant enterococci (VRE). DESIGN: Cross-sectional study. SETTING: A 146-bed rehabilitation facility. PARTICIPANTS: Rectal cultures were collected from 74 (80%) of 93 patients. Environmental cultures were obtained from surfaces in 15 patient rooms (5 floors) and common-use areas on 8 floors. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gastrointestinal colonization of patients and environmental contamination of surfaces by VRE. RESULTS: VRE was detected from 13 (18%) of 74 patients and 32 (10%) of 319 surfaces. The frequency of positive environmental cultures varied by location; cultures were more likely to be positive in patient rooms (15%), followed by common areas on patient floors (9%) and common areas separate from patient floors (1.3%). Surfaces were more likely to be positive in rooms with a VRE-colonized patient (24%), compared with rooms in which patient colonization status was unknown (13%, P=.13) or the patient was not colonized (0%, P=.002). Surfaces were more likely to be contaminated in a room that housed an incontinent compared with continent patients (22% vs 7%, P=.01). CONCLUSIONS: Although environmental contamination by VRE was common in patient rooms, contamination of common-use areas separate from patient floors was infrequent. Despite use of common-use areas by colonized patients, isolation practices at this facility appear to have minimized environmental surface contamination in these areas.

Cross-Sectional Studies↗
PubMed2002

Impact of respiratory complications on length of stay and hospital costs in acute cervical spine injury.

CONTEXT: Respiratory complications are frequent in patients with acute cervical spinal injury (CSI); however, the importance of respiratory complications experienced during the initial hospitalization following injury is unknown. OBJECTIVE: To determine if respiratory complications experienced during the initial acute-care hospitalization in patients with acute traumatic cervical spinal injury (CSI) are more important determinants of the length of stay (LOS) and total hospital costs than level of injury. DESIGN: A retrospective analysis of an inception cohort for the 5-year period from 1993 to 1997. SETTING: The Midwest Regional Spinal Cord Injury Care System, a model system for CSI, at Northwestern Memorial Hospital, a tertiary referral academic medical center. PATIENTS: Four hundred thirteen patients admitted with acute CSI and discharged alive. Patients with concurrent thoracic injuries were excluded. MAIN OUTCOME MEASURES: Initial acute-care LOS and hospital costs. RESULTS: Both mean LOS and hospital costs increased monotonically with the number of respiratory complications experienced (p < 0.001, between none and one complication, and between one and two complications; p = 0.24 between two and three or more complications). A hierarchical regression analysis showed that four variables-use of mechanical ventilation, occurrence of pneumonia, need for surgery, and use of tracheostomy-explain nearly 60% of the variance in both LOS and hospital costs. Each of these variables, when considered independently, is a better predictor of hospital costs than level of injury. CONCLUSIONS: The number of respiratory complications experienced during the initial acute-care hospitalization for CSI is a more important determinant of LOS and hospital costs than level of injury.

Acute Disease↗
PubMed2002

Regulation of osteoprotegerin production by androgens and anti-androgens in human osteoblastic lineage cells.

BACKGROUND: Estrogens and androgens have anti-resorptive effects on bone, although recent evidence indicates that, even in men, estrogen is the dominant sex steroid regulating bone resorption. The receptor activator of NF-kappaB ligand is essential for osteoclastic bone resorption, and its effects are blocked by the decoy receptor, osteoprotegerin (OPG). While estrogen has been shown to induce osteoblastic OPG production, the effects of androgens on OPG production have not been defined. METHODS: In this study, we assessed the regulation of OPG by androgens in hFOB/AR-6, an immortalized fetal osteoblastic cell line stably transfected with the human androgen receptor (AR), and MSC cells, primary human pluripotent marrow stromal cells capable of differentiating towards mature osteoblasts. RESULTS AND CONCLUSIONS: 5Alpha-dihydrotestosterone (DHT) dose-dependently decreased OPG mRNA levels and protein concentrations in hFOB/AR-6 cells by up to 50 and 60% respectively (P<0.001). Inhibition of OPG mRNA levels and protein production by 5alpha-DHT was completely abrogated by the AR antagonist, hydroxyflutamide (OHF), indicating that these effects are directly mediated by the AR. Of note, OHF alone increased OPG mRNA levels and protein secretion by 2- to 3-fold. Moreover, 5alpha-DHT and testosterone also decreased OPG protein secretion by 40-46% in the untransformed MSC cells, while OHF stimulated it. In conclusion, we demonstrate that androgens specifically inhibit OPG mRNA levels and protein secretion by osteoblastic cells.

Androgen Antagonists↗
PubMedDate not supplied

Transient multifocal electroretinogram dysfunction in multiple evanescent white dot syndrome.

A 22-year-old female patient with acute monocular scotomata after an upper respiratory infection and the fluorescein angiographic findings consistent with the diagnosis of multiple evanescent white dot syndrome (MEWDS) is described. Unlike full-field ERG, which shows a generalized depressed signal in MEWDS, the authors showed areas of depressions corresponding to the scotomata using multifocal electroretinogram (MFERG). The MFERG abnormalities seen at presentation resolved with the resolution of clinical symptoms after 6 weeks, in contrast to a previous report. The MFERG may be a useful tool to further characterize MEWDS and other blind-spot enlarging syndromes.

Adult↗