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Biomedical subjects

O M Evans

Publications and source records attributed to O M Evans.

7 recordsLinked to original sources
PubMed1992

Steadiness in one-legged stance: development of a reliable force-platform testing procedure.

Postural steadiness in one-legged stance has potential for evaluation of unilateral injuries and disorders, but any test protocol must be demonstrated to be both feasible and reliable. A testing protocol for using a force platform to measure steadiness in one-legged stance with eyes opened and eyes closed was successfully developed, and its within-session retest reliability was investigated in a group of 24 young, healthy subjects. Strategies were used to minimize the loss of data for trials in which the subjects incurred significant loss of balance from the one-legged position. The performance scores examined were the standard deviation of the three orthogonal force components and the two horizontal center of pressure (CP) coordinates averaged over four consecutive five-second trials. The retest coefficients for all test conditions were substantially improved compared with testing protocols reported earlier. Retest reliability was higher for performance scores based on force measures than for performance scores based on CP measures. The difference was statistically significant in two of the stances, with a similar trend in the other two stances. Further, factor analysis showed that force measures were the best predictors of steadiness in one-legged stance. Analysis of variance failed to detect any systematic effect for leg preference or laterality on steadiness in one-legged stance with eyes opened or eyes closed in the healthy subjects with no history of injury (p greater than .05). The test protocol described enables the development of clinical or experimental trials with repeated-measures design using the subject's nonaffected leg as a control.

Adolescent↗
PubMed1991

Clinical evaluation of closed-loop control of blood pressure in seriously ill patients.

OBJECTIVE: To compare the effectiveness of a new method of closed-loop (automatic) control of BP with usual manual control. DESIGN: Within-subject crossover trial. SETTING: General and open heart ICUs in a university teaching hospital. PATIENTS: Convenience sample of 74 seriously ill patients aged 17 to 88 yr. Twenty had hypertension: postoperative (n = 7), neurologic damage (n = 6), miscellaneous (n = 7), and were prescribed nitroprusside (n = 11) or nitroglycerin (n = 9). Fifty-four had hypotension: septic (n = 33), other (n = 21), and were prescribed norepinephrine (n = 30), dopamine (n = 11), epinephrine (n = 8), or dobutamine (n = 5). An additional 21 trials were omitted from analysis because of technical (n = 7), clinical (n = 1), or drug-related problems (n = 13). INTERVENTION: Closed-loop and manual drug administrations 1-hr were studied during periods in each patient. The target and observed mean arterial pressure (MAP) and drug infusion rate were recorded electronically every 30 sec. MAIN OUTCOME MEASUREMENTS: Time taken to achieve initial control (min); fidelity of control (the integral of size and duration of error from target MAP +/- 10% in mm Hg.hr/hr); and average drug dose administered (microgram/min as % maximum possible per drug). RESULTS: Compared with manual control, closed-loop achieved faster initial control (log-rank chi 1 = 5.04, p less than .05) and greater fidelity (mean 1.37 vs. 2.36; F = 7.15, p less than .01). There was no difference in average drug dose administered. There was uniformity in the efficacy advantage of closed-loop drug administration across drugs and patient classifications. CONCLUSION: The new closed-loop system is more effective than the usual manual control in managing acute BP disturbances in the seriously ill patient.

Adolescent↗
PubMed1991

Treadmill gait retraining following fractured neck-of-femur.

The rehabilitation outcome of two methods of gait retraining, was studied in 40 elderly women who had fractured the neck-of-femur. Twenty control subjects received conventional gait retraining, and 20 experimental subjects participated in a treadmill gait retraining program. Rehabilitation outcome was determined by temporal-distance gait parameters and mobility level (house-bound, limited, or unlimited). Muscle strength and range of movement of the lower limb were measured. Previously reported predictors of poor outcome (age, prefracture mobility, admission from sites other than own home, availability of caring person, type of ambulatory aid, presence or absence of senile dementia, and number of concomitant medical diseases) were recorded. Subjects were assessed on admission to the gait retraining program and at discharge from hospital. A 3 x 2 chi-square analysis on discharge mobility level showed the mobility level of the treadmill group to be significantly (p less than .05) higher than the mobility level attained by the control group. Analysis of variance showed no significant differences between the two groups at either assessment time. However, a significant increase in within-group variance from admission to discharge (p less than .01) was noted, and this led to the analysis of a subgroup containing six pairs of subjects matched for number of predictors of poor outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

A new and rapid method for the selection and cloning of antigen-specific hybridomas with magnetic microspheres.

A new and highly selective procedure is described for the rapid selection and cloning of antibody-secreting hybridomas with antigen-coated magnetic beads. Immune splenocytes were fused to Sp2 myeloma cells with a PEG/DMSO mixture. Cells were cultured in HAT and screened for the presence of specific antibody after 7-10 days. Hybridomas from the positive colonies were mixed with antigen-coated magnetic polymer beads and antigen-specific cells separated on a magnet. Cloning was carried out directly by limiting dilution with the magnetic beads still bound on the cells. No obvious toxic effects were observed. The antibodies established by this technique were of a high affinity (greater than 10(9) l/mol) and were generated in 50% of the usual process time. The procedure described here should greatly facilitate the process of obtaining hybridomas and expand the range of monoclonal antibodies available.

Animals↗
PubMed1989

Force platform measures for evaluating postural control: reliability and validity.

The reliability and validity of force platform measures used to evaluate steadiness of stance were investigated in a group of 28 healthy subjects in four basic stance positions: two-legged, step, tandem, and one-legged stance. In each stance position five indices of steadiness were obtained by sampling the three orthogonal force signals and the two horizontal center of pressure (CP) signals for 15 seconds and computing the standard deviation for each signal. Correlations between these five indices derived from the force platform showed that the relationship between force and CP measures was generally weak. In fact, approximately 40% of the correlations were nonsignificant (p greater than .05). There was a strong trend for the retest reliability of force measures to be higher than the retest reliability of CP measures. The difference was statistically significant in three stances (p less than .05). Force measures were more sensitive than CP measures in discriminating the changes in steadiness which resulted from alterations to the base of support in the four stance positions. Factor analysis showed that force measures were the best predictors of steadiness in each stance, but the axis varied according to the particular stance condition. Although it may be appropriate in some cases to justify the choice of measure according to the nature of the clinical condition being studied, these results provide a rationale for choosing force measures in preference to CP measures on the fundamental principles of reliability and validity.

Adult↗
PubMed1987

Long-latency stretch reflexes of the human elbow extensors during voluntary relaxation: differences between agonistic muscles.

Reflex electromyographic (EMG) responses of elbow extensor muscles to unexpected elbow flexion were recorded in the absence of initial tonic activity from subjects instructed not to resist the stretch. The monosynaptic component M1 was present only in the anconeus muscle and only for high accelerations. The acceleration value at which the long-latency components M2 and M3 appeared was lower for anconeus than for triceps brachii. Increases in peak acceleration of stretch resulted in decreases in M2 and M3 latencies and increases in M2 and M3 magnitudes in both muscles. However, M2 and M3 latencies for anconeus were shorter than those of triceps brachii, except at high acceleration values. Furthermore, the magnitude of M2 and M3 components of anconeus activity increased faster for low accelerations than for high accelerations, whereas those of triceps brachii increased in proportion to the acceleration. These differences between anconeus and triceps brachii were similar to those described earlier for voluntary movements. It is suggested that the motoneurons of all elbow extensor muscles may be recruited as a single motoneuron pool following Henneman's size principle, irrespective of whether the activity is voluntary or reflex in origin.

Adult↗