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Biomedical subjects

G C Gorniak

Publications and source records attributed to G C Gorniak.

10 recordsLinked to original sources
PubMed1990

Bite-to-bite variation of muscular activity in cats.

Changes in electromyographic (EMG) activity between successive bites in the jaw-closing muscles of cats are described for the reduction of food with different textures. Plots of these data suggest, and statistics confirm, that one cannot predict the magnitude of EMG activity from one bite to the next, but that predicting the direction of change in EMG activity (i.e. increases or decreases) may be possible, given the relative magnitude of a bite. The patterns observed also show that the degree of variability between masticatory cycles differs among the jaw-closing muscles and with food texture. These patterns of muscle activity are related to the neural control of jaw movements.

Animals↗
PubMed1986

Architecture of the masticatory apparatus in eastern raccoons (Procyon lotor lotor).

The structure and function of the masticatory apparatus of raccoons resemble those found in carnivores. In this study, the architecture of the skull, dentition, and masticatory apparatus is described, and a model is proposed that suggests a mechanism used by raccoons to reduce different foods. The model suggests that jaw movements are similar to those of cats, the posterior regions of the superficial and deep parts of the temporalis and the anterior region of the medial pterygoid generate horizontal jaw movements, and the anterior portions of the superficial and deep temporalis as well as portions of the masseteric complex generate vertical closing movement. The distributions of slow, fast fatigable, and fast fatigue-resistant fibers for the temporalis and masseteric complex are related to the possible actions of these muscles during mastication, as are the regional cross-sectional areas of the masticatory muscles.

Animals↗
PubMed1986

Correlation between histochemistry and muscle activity of jaw muscles in cats.

Studies on limb muscles of mammals indicate that the pattern of electromyographic (EMG) activity reflects the histochemical profile of the muscle. This relationship suggests that EMG activity may permit a prediction of certain morphological characteristics of the muscle being studied. In this study numerical descriptors of EMG activity of the masticatory muscles of cats are correlated with the distribution of fiber types, as well as with fiber and fascicle areas, to test the extent to which EMG can be used to predict regional morphology. The results show that the level of EMG activity and its duration have a significant positive correlation with the percentage of slow- and fast-twitch fatigue-resistant fibers and a significant negative correlation with the percentage of fast-twitch fatigable fibers and the ratio of fast-twitch fatigable to fast-twitch fatigue-resistant, plus slow fibers. No correlation was found between activity and fiber cross-sectional area; the descriptors showing significant correlation vary with the hardness of the food. Thus the level of EMG activity and its duration seemingly do provide an indicator of the relative difference in fiber distribution among muscles in a species.

Adenosine Triphosphatases↗
PubMed1982

Functional morphology of lingual protrusion in marine toads (Bufo marinus).

Bufo marinus catches its prey by stiffening the intrinsic muscles of the tongue, rapidly flipping the tongue out of the mouth. High-speed cinematography synchronized with computer-analyzed electromyograms (EMGs)shows that during the flip the tongue is supported by the M. genioglossus medialis and that this muscle stiffens into a rod when stimulated. Coincident stiffening of the transversely arranged M. genioglossus basalis provides a wedge under the anterior tip of this rod. Stiffening of the M. submentalis depresses the mandibular symphysis and brings the dentary tips together. The M. submentalis also acts on the wedge of the basalis to raise and rotate the rigid rod of the medialis over the symphysial attachment. The tip of this lingual rod carries along the pad and soft tissues of the tongue. The lingual pad, positioned the posterodorsal portion of the resting tongue, rotates during eversion so that its dorsal surface impacts onto the prey object. Retraction starts by contraction of the elongate, parallel fibers of the M. hyoglossus; this retracts the medical sulcus of the pad and holds the prey by a suction cup-like effect. The extensibility of the buccal membranes allows the pad to be retracted first; it reaches the posterior portion of the buccal cavity before the still-rigid, backward rotating M. genioglossus has reached the level of the symphysis. Protraction of the hyoid facilitates the extension of the M. hyoglossus. The M. sternohyoideus only retracts the hyoid and stabilizes it when the tongue starts to pull posteriorly; it does not assist tongue protrusion. The Mm. petrohyoideus and omohyoideus show only incidental activity, and the M. depressor mandibulae participate in mouth opening but is not otherwise involved in the flip. Previous hypotheses of the flipping mechanism are reviewed and evaluated.

Animals↗
PubMed1980

Electromyograms are repeatable: precautions and limitations.

Electromyograms recorded by bipolar, fine wire electrodes placed into anatomically equivalent sites in skeletal muscles of vertebrates are repeatable when the animals use the muscles in a similar way. Repeatability applies to the number of spikes recorded from a given site and to their average amplitude as well as to the root-mean-square value, though the values obtained for these descriptors differ among muscles, and perhaps fascicles, of particular animals even when the animals are performing equivalent actions. Tests suggest that these results are not affected by the nature of most kinds of recording equipment. Also, substantial differences in electrode tip configuration and wire diameter induce relatively minor, less than 8 percent, differences in electrode resistance and impedance. Doubling the length of the fine wire leads produces less than an 8 percent (15 percent when the length is tripled) effect; however, the effect of electrode material may be as much as 85 percent in resistance and 20 percent in impedance. Reports of nonreproducibility or variability of electromyograms apparently result mainly from anatomically inexact placement into physiologically and histochemically different fascicles of compound muscles, from recordings of muscles that are active at very low levels, and perhaps from comparison among recordings of muscles that really differ in their activity level.

Action Potentials↗
PubMed1980

Quantitative assay of electromyograms during mastication in domestic cats (Felis catus).

Mastication has been studied by cinematography with synchronized electromyography (computer quantified and analyzed), while unanesthetized, freely feeding cats (Felis catus) were reducing equivalent-sized chunks of raw and cookded beef and cooked chicken. Cats reduce food on one side at a time, and their chewing cycles show horizontal and anteroposterior deflections. Food objects are shifted from side to side by lateral jerks of the head and movements of the tongue. During the opening phase, the lower jaw is rotated relatively straight downward, and the digastric muscles are active in bilateral symmetry. Near the end of opening, the head jerks upward, both zygomaticomandibulares start to fire, and opening acceleration of the mandible decreases. Closing starts with horizontal displacement of the mandibular canines toward the working side, accompanied by asymmetrical activities from the working side deep temporalis and the balancing side medial pterygoid, as well as a downward jerk of the head. As closing proceeds the mandibular canines remain near the working side and the working side zygomaticomandibularis and deep masseter are very active. Near the end of closing, the mandibular canine on the working side moves toward the midline, and adductors, digastrics, and lateral pterygoids of both sides are active. The adductors of the working side are generally more active than those of the balancing side. During a reduction sequence, the number and shape of the masticatory cycles, as well as movements of the head, during a reduction sequence are affected significantly by food type. As reduction proceeds, the duration of bite and the muscular activity (as characterized by number and amplitude of spikes) change significantly among muscles of the working and balancing sides. The adductors of the working side are generally most active when cats chew raw beef, less for cooked beef, and least for cooked chicken. In general, the adductor activity reflect food consistency, whereas that of the digastrics and lateral pterygoids reflects more the vertical and lateral displacements of the mandible. Statistical analysis documents that the methods of electrode insertion and test give repeatable results for particular sites in different animals. Thus, it should be possible to compare these results with those produced while other mammals are masticating.

Animals↗
PubMed1979

Muscle fiber regeneration after transplantation: prediction of structure and physiology from electromyograms.

Digitized electromyographic activity of transplanted extensor digitorum longus (EDL) muscles in cats differs from that of control EDL and anterior tibialis muscles lying adjacent to transplanted EDL muscles. In autotransplanted muscles, the cross-sectional area of the fibers shows a negative correlation with mean spike frequency and a positive correlation with mean amplitude. The mean frequency-amplitude products correlate with isometric tetanic tensions.

Action Potentials↗