Respiratory electromyographic estimates of ventilatory functions in piglets.

The best electromyographic (EMG) predictors of respiratory drive (P100), tidal volume (VT) and ventilation (VE) were determined from diaphragmatic (DI) and posterior cricoarytenoid (PCA) EMG measures in 8-48-day-old, anesthetized piglets. Progressive hypercapnia was employed to obtain a wide range of muscle activity. A custom-designed, microcomputer-based system was employed to measure the duration, peak amplitude, rate of rise (initial slope) as well as the summed total and initial (first 100 ms) EMG activity from the DI and the PCA. For each respiratory function, the following combinations of EMG measures were identified as significant predictors using regression analyses: (1) for P100, DI amplitude, PCA initial area and PCA rate of rise; (2) for VT, DI amplitude, PCA duration and DI duration; (3) for VE, DI amplitude, DI initial area, PCA initial area, PCA rate of rise, PCA duration, DI area and DI rate of rise. Thus, whereas the traditionally employed measure of DI amplitude is an important correlate of P100, VT or VE, a complete estimate of these respiratory functions requires the inclusion of initial EMG measures and duration.

Multichannel electromyographic observations in spasmodic dysphonia patients and normal control subjects.

Spasmodic dysphonia is primarily a disorder of vocalization. Increasing evidence, however, suggests that individuals with this disorder comprise a heterogeneous population characterized by abnormal motor control throughout the vocal tract. Multichannel simultaneous electromyography was performed on 11 spasmodic dysphonia patients and 10 normal awake subjects to investigate both the distribution of neuromotor abnormality within the vocal tract (eg, intrinsic and extrinsic laryngeal muscles, tongue, and palate) and the contribution of activation of higher central nervous system centers to observed abnormality. Experimental tasks ranged from vegetative (quiet breathing) to simple linguistic (short sentences). Digitized electromyographic signals were analyzed to compute the amplitude envelope and extract a set of parameters that represent amplitude characteristics. Electrode insertions were cross-validated by quantitative analysis of patterns of activation across selected reference tasks and by traditional qualitative methods. Between-group differences were found for measures of normalized median and peak token amplitudes. These differences are both task- and measure-dependent. Results highlight the complex and interactive effects of muscle, task, and quantitative measures on between-group differences.

Systems architecture for quantification of dynamic myoelectric and kinematic activity of the human vocal tract.

This paper describes a systems architecture useful for scientific investigations that require the acquisition and analysis of multiple, time-synchronous signals in large volume. The architecture has recently been developed by this group to enhance our capability to research and quantify central nervous system function in the production of normal and pathologic speech. The architecture utilizes modern advances in desktop microcomputers and has been designed so that vocal motor control laboratories (or similar settings) with modest funding can more fully participate in comprehensive investigations of speech production. Research experiments organized with this architecture may involve many more subjects and measures than previously possible without significant increases in time and personnel resources. This paper will demonstrate the technique and practicality of this architecture as it is being used to successfully guide research to map hierarchic central nervous system regions of involvement in two speech disorders: spasmodic dysphonia and stuttering. The architecture has broad usefulness to many areas of otolaryngology and health science.

Studies on human heart citrate synthase.

Citrate synthase from human heart was purified by affinity chromatography with Sepharose-ATP. The molecular weight (100,000) and the presence of two presumably identical subunits do not differ from other mammalian citrate synthases. However, the kinetics constants and immunologic characteristics of the enzyme differed from other mammalian citrate synthases. The Km values for acetyl-CoA (0.4 microM) and oxaloacetate (0.25 microM) were about an order of magnitude lower than those previously found for other mammalian (and eucaryotic) citrate synthases. The kinetics constants for the reverse reaction Km for citrate (420 microM) and CoA (70 microM), were of similar magnitude to the values for other mammals. Anti-human heart antiserum developed a single precipitin line in an Ouchterlony plate against a heart extract, no precipitin line with brain, and a precipitin line with spurs against liver and kidney extract. Following myocardial infarction in men, the enzyme appeared in peripheral blood rarely and in low concentration in contrast with earlier experiences with experimental infarction in dogs.