Biomedical subjects

A L Perlman

Publications and source records attributed to A L Perlman.

22 records · Page 2Linked to original sources

PubMed1989

Electrical activity from the superior pharyngeal constrictor during reflexive and nonreflexive tasks.

The purpose of this investigation was to determine, in a quantitative manner, which, if any, nonswallowing tasks produce significant levels of activation in the superior pharyngeal constrictor muscle of normal human subjects. Bipolar hooked wire electrodes were inserted in the superior pharyngeal constrictor muscle of 15 healthy subjects. Electrode placement was controlled. Each subject performed two reflexive tasks, six voluntary tasks requiring phonation, and four nonspeech voluntary tasks. The electromyogram (EMG) was rectified and integrated. The resulting number was then transformed by taking its natural logarithm. An ANOVA was performed and a linear model was estimated. The magnitude of the EMG activity was related to the location of the electrodes. The largest values were recorded in the lateral-superior placement, followed by the lateral-inferior, medial-inferior and medial-superior. The superior pharyngeal contrictor was found to be a muscle activated primarily during reflexive activity. There was a general trend in the amplitude of EMG activity in relationship to task. Swallowing produced the greatest amount of activity and a gag produced about 60% of the activity produced by the swallow. Two tasks, production of the work /hok/ in which the phoneme /k/ was stressed, and a "modified Valsalva," which was actually a hard /k/ held for several seconds, produced the next greatest level of EMG.

Adult↗

PubMed1988

Development of an in vitro technique for measuring elastic properties of vocal fold tissue.

The purpose of this investigation was to develop an in vitro technique for measurement of elastic properties of isolated vocal fold tissue. Larynges were excised from anesthetized dogs, immediately submerged in a Krebs-Ringer solution, and aerated with 95% oxygen and 5% carbon dioxide. The tissue was maintained in the aerated electrolyte solution throughout the experiment. The vocalis muscle was carefully dissected, with attachments to the arytenoid and thyroid cartilages maintained. The preparation was then subjected to isometric (constant length) force-elongation measures, which were converted to stress-strain values. Stage I of the investigation identified the dog model with the least intrastudy variability relative to the age, sex, and breed of the research animal, as well as to the effects of curare. Stage II investigated the effects of different instrumentation, definitions of reference length, methods of elongation, and effects of electrical stimulation. Once the procedure had been refined, the effects of age and sex were retested. There was a significant interaction between sex and strain and between age and strain. The least variability was obtained with curarized tissue from one sex of young, mixed-breed dogs, where an arbitrary 1 gram of initial force was the criterion for establishing "zero" strain. Problems associated with determination of reference length and various approaches to this problem are discussed.

Aging↗

PubMed1984

Elasticity of canine vocal fold tissue.

Stress-strain curves were obtained from vocalis muscle tissue that was kept viable in an aerated Krebs-Ringer solution after excision of the larynx from live dogs. Results are compared to similar curves obtained from dead tissue and suggest that vocal fold elasticity depends on the level of strain, the elapsed time after elongation, the condition of the tissue, and the choice of rest length for strain computation. Tables of Young's moduli for various conditions are given.

Animals↗

PubMedDate not supplied

Comparative study of the physiological properties of the vocalis and cricothyroid muscles.

Viable tissue samples of the vocalis muscle and pars recta portion of the cricothyroid muscle were dissected from the excised larynges of middle-aged, male, mixed breed dogs. The samples were maintained in an aerated Krebs-Ringer solution and curarized. Temperature and pH were controlled. Field stimulation was performed with parallel-plate platinum electrodes. Using a dual mode ergometer, in vitro measurements were made at increased levels of strain. Least-squares regression analyses were performed on contraction times and 50% relaxation times as a function of strain. Results of this investigation indicated important differences in the active and passive properties of the pars recta portion of the cricothyroid and the vocalis muscle. The mean contraction time of the vocalis muscle was 24 ms and that of the cricothyroid muscle, 33.5 ms. The mean half relaxation time was 20 ms for the vocalis muscle and 30 ms for the cricothyroid. The twitch contraction and half relaxation times of the vocalis remained independent of strain, whereas those of the cricothyroid showed strong positive dependence on strain level. Differences in the passive properties of the two muscles were also evidenced; the vocalis muscle was found to be stiffer at all levels of strain.

Animals↗