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Biomedical subjects

J R Chen

Publications and source records attributed to J R Chen.

88 records · Page 5Linked to original sources
PubMed1986

T.I.A. revisited: new wine--old bottle.

TIA has been accepted as a concept of transient cerebral ischemia. There is an ever enlarging body of literature sparking controversies considering its natural history, prognosis, outcomes of clinical trials and usefulness of the concept. Much of the controversy is related to the diverse pathophysiology of TIAs, the selection of patients for clinical trials and the associated risk factor in the studied population. The advantages of the concept are a warning of the possibility of future irreversible pathology an opportunity to treat and/or remove risk factors an opportunity to establish a basis for monitoring the patient and making interim decisions concerning intervention. The risks of the concept are: administering a specific therapy to all patients, failure to fully evaluate the patient once the diagnosis is made, tendency to rely on "experts" for guidance. TIA is a useful concept if one recognizes: the pathophysiology is polymorphous and multiplex, the concept is a signal for diligent search for the underlying cause or causes, it is more important to treat the risk factors than to give a specific therapy.

Anticoagulants↗
PubMed1983

High-performance liquid chromatographic determination of vincristine sulfate in preformulation studies.

A fast and simple procedure was developed for the quantitative determination of vincristine sulfate for use in preformulation studies. The procedure involves the use of high-performance liquid chromatography with a reverse-phase column and a mobile phase containing the sodium salt of 1-pentanesulfonic acid for ion-pairing. The procedure has been shown to be specific for vincristine sulfate in the presence of forced degradation products of this substance, vinblastine (a structurally similar Vinca alkaloid), and several possible formula excipients. The procedure is linear from 10-200% of the normal injection concentration, and has an assay precision (relative 2 sigma) of +/- 1.6%. Recovery of known samples averaged 99.7%.

Chromatography, High Pressure Liquid↗
PubMed1983

The underlying problems resulting in controversies in the clinical management of transient ischemic attacks: an overview.

Of all the controversial topics in the management of cerebrovascular diseases the subject of transient ischemic attacks is perhaps the most controversial. A preponderance of literature related to the subject, reflecting a remarkable degree of interest in the topic, is a result of this controversy. Each conclusion serves to stimulate more interest, more evaluation, and more controversy. We will attempt to give an overview of the controversies in the management of transient ischemic attacks.

Anticoagulants↗
PubMed1979

Legionnaires' disease: concentrations of selenium and other elements.

Selenium concentrations in the serums of 17 acutely ill Legionnaires' disease patients were significantly lower than in their matching convalescent-phase serums. This trend was not observed in ten similarly paired samples of serum from control patients with pneumonia. There were no significant differences in the concentrations of nickel, copper, bromine, rubidium, lead, barium, or titanium in the serums of Legionnaires' disease and control patients.

Humans↗
PubMed1979

Neurologic disturbances in Paget disease of bone: response to calcitonin.

The neurologic manifestations of Paget disease and the therapeutic effect of calcitonin were studied in 49 patients. Twenty-four patients (49%) had neurologic disorders involving cranial nerves other than the auditory system, brainstem, spinal cord, or spinal roots and nerves. Eighteen of the 24 patients (75%) showed significant subjective or objective improvement after calcitonin treatment. The effect of calcitonin treatment on spinal cord compression was dramatic in three of six patients. The observations made of these patients support previous data suggesting that the neurologic signs and symptoms of Paget disease have their pathogenesis in both mechanical impingement and vascular distortion. The importance of early detection of neurologic signs and symptoms is emphasized, since prompt treatment with calcitonin may prevent severe complications.

Aged↗
PubMed1977

Legionnaires' disease: nickel levels.

Nickel concentrations in lung tissues of nine deceased Legionnaire victims average nine times that of controls. There is a significant correlation between the nickel levels in the lungs of the Legionnaire victims and the weights of the lung specimens. No similar correlation is evident in the study of the victims' kidney tissues or tissues from the controls.

Humans↗
PubMedDate not supplied

Performance of elbow tracking under constant torque disturbance in normotonic stroke patients and normal subjects.

OBJECTIVE: In this study, the influences of externally imposed constant torque on the voluntary elbow movements of stroke and normal subjects were investigated quantitatively. BACKGROUND: Muscle weakness, spasticity and incoordination are the major factors that interfere with stroke patient's limb functions. Imposing external torque disturbance may worsen the motor performance. This experiment was designed to investigate the effects of small constant external torque on the performance of voluntary elbow movements. METHODS: Tracking of a ramp-and-hold angle trajectory in the direction of extension was used as the main task for performance assessment. Each subject repeated the same tracking movement six times in each of three loading conditions: no, assistive or resistive loading. Five normal and six stroke subjects were recruited for this study. We used parameters extracted from movement trajectory and processed electromyograms as the performance indicators. RESULTS: For normal subjects, there was no difference in the tracking performance in the three loading conditions. For stroke patients, the affected side had inferior performance to the healthy side in the free loading condition and the difference diminished in assistive and resistive loading conditions as the performance of the affected side improved. Integrated electromyograms of biceps or triceps did not show significant changes in different loading conditions. CONCLUSIONS: Small externally imposed constant torque, either resistive or assistive, may improve motor performance of affected elbows in stroke patients. RELEVANCE: Most of the currently available prostheses are passive devices, aiming at providing better support and improving stability. The results of the current study imply that an active prosthetic device that applies a small constant torque to the hemiparetic elbow can improve its motor performance in stroke patients. The direction of external torque is to assist the weaker side of the antagonistic muscle pair.

Elbow↗
PubMedDate not supplied

Assessment of coke oven emissions exposure among coking workers.

Coking workers are regularly exposed to coke oven emissions, which consist primarily of polycyclic aromatic hydrocarbons and volatile organic compounds. This study measured the workers' exposure to the benzene soluble fraction of total particulates (BSF). The study population consisted of 88 coking workers as an exposure group and 59 referents. Personal breathing-zone samples of BSF and total particulates were taken from all study subjects for 3 consecutive days. The highest BSF concentrations were found among the topside oven workers (geometric mean; range) (microgram/m3): lidman (515; 72-18, 181), tar chaser (432; 51-4334), and larry car operator (185; 55-649). The lowest was 7 micrograms/m3 in the referents. Among the samples at the topside oven 84% exceeded the Occupational Safety and Health Administration standard (150 micrograms/m3 BSF). The percentage of BSF in total particulates varied across job classifications, ranging from 0.3% in wharfmen to 24% in tar chasers. Area sampling indicated that the BSF concentration at the topside area was sixtyfold higher than that at the administrative area, which was approximately 2 km from the coke oven plant.

Air Pollutants, Occupational↗