The perception of isometric forces was examined under normal conditions, during sustained constant force contractions, and during vibration of the muscle tendon. In these experiments a contralateral limb matching procedure was employed, and force and the brachial biceps and triceps electromyogram (EMG) were recorded from each arm. Under normal conditions it was found that smaller forces were consistently overestimated in magnitude. During sustained constant force contractions the matching forces exerted by the unfatigued arm increased linearly as did the EMG of the fatiguing muscle. These results are consistent with force judgements being made with respect to the excitatory input to the reference muscle. It was further determined that during fatigue subjects were unable to dissociate the force of exertion from the motor command generating the contraction. Muscle tendon vibration increased the variability of force judgements and resulted in the overestimation of forces. This appeared to be due to co-contraction of the antagonist triceps muscle during vibration of the contracting biceps. The increase in the perceived magnitude of force during vibration is again consistent with the centrally-mediated theory of force perception.

The purposes for which the fractionation of proteins are carried out are quite varied and manyfold. However, one of the more important reasons is that of determining the nature and the extent of autolysis or proteolysis on the bovine muscle proteins during post mortem aging. Hence, the development of a procedure for the adequate fractionation of muscle proteins would greatly stimulate the interest and research progress in this difficult field of study. The research reported herein pertains to a study of the fractionation of fresh bovine muscle proteins by ion exchange chromatography. A KCl-phosphate buffer, pH 7.5 and an ionic strength of 0.55, was used to extract the proteins from the muscle. This extract was then diluted to specific ionic strengths in order to separate the gross fractions (actomyosin, myosin, sarcoplasmic + actin) from the total KCl-phosphate soluble proteins. The major protein fractions were then separated by diethylaminoethyl-cellulose (DEAE-cellulose) ion exchange chromatographic procedure. A non-linear gradient elution schedule was used throughout the chromatographic procedure. The disc electrophoresis technique was used to determine the homogeneity of the various protein fractions and sub-fractions. The total KCl-phosphate soluble proteins were fractionated into 9-12 fractions by DEAE-cellulose ion exchange chromatography. The number of fractions differed from one sample to another. The disc electrophoresis results paralleled those of the chromatographic procedure. Some of the fractions appeared to be homogeneous while others were not. The KCl-phosphate soluble proteins minus actomyosin were fractionated by column chromatography into 9-10 different protein components. The disc electrophoresis results also indicated that this fraction contained 9-10 components. The sarcoplasmic + actin proteins were fractionated into six fractions by the chromatographic procedure. These fractions appeared to be electrophoretically homogeneous. Although some success was attained in the separation of the actomyosin proteins, the myosin fraction was quite resistant to chromatographic separation. In spite of the ineffectiveness of the DEAE-cellulose column chromatographic technique to fractionate the myosin and actomyosin proteins, the procedure appears to have some value for studying the other protein fractions during autolysis. Moreover, further work on the adoption of this procedure might provide the necessary information to perfect the technique for muscle protein fractionation. / Graduation date: 1963

During C. elegans embryogenesis, myoblasts initially form two rows along the left and right lateral midlines and at ~290 min of development migrate dorsally and ventrally to form the four muscle quadrants present upon hatching (Sulston et al, 1983). As the myoblasts migrate they are still dividing, as are many other cells in their immediate environment. This means the cell-cell contact of cells during migration is dynamic and can vary from animal to animal (Schnabel et al, 1997). This situation creates an environment where the extracellular matrix (ECM) and cell surface contacts are in constant flux, which begs the questions as to how these cells navigate unerringly to their final destination. In an attempt to identify genes mediating these migrations, I performed an RNAi based screen targeting 776 genes predicted to be members of the extracellular matrix (ECM), or one of its receptors. Using both feeding and injection based RNAi, I was able to identify three genes of interest. Knockdowns of F56B3.2 resulted in paralyzed animals with detached muscle, making it a good candidate for a new component of the muscle attachment complex. F33G12.4 knockdowns resulted in an embryonic arrest phenotype with an abnormal muscle lineage, possibly stemming from polarity defects. The only knockdown that resulted in muscle migration defects was that for lam-2, which encodes for the laminin gamma subunit. Analysis of the lam-2 knockdown, as well as knockdowns for the other laminin subunits, revealed dorsal/ventral migration defects as well as a posterior displacement of the anterior-most ventral muscle cells. Investigation of this posterior displacement has led to the identification of a previously un-described anterior muscle migration event and its dependency upon the extension of muscle processes from the leading cells.

Thesis (PhD) -- University of South Australia, 1998

Thesis (MAppSc in Physiotherapy) -- University of South Australia, 1998

Thesis (MAppSc) -- University of South Australia, 1998

Master of Dental Surgery / A study of the masticatory apparatus can be divided into the following sections:- Bony structure Teeth and supporting structures Temporomandibular articulation (and ligaments) Muscles of mastication (elevation and depression) Muscles of facial expression and deglutition Neurology Vascular and lymphatic supply This work is concerned with the muscles of mastication and the positions and movements of the mandible for which they are responsible. It is of course impossible to divorce this particular aspect from the others, as they are all completely interdependent, and, in particular, a study of the neurology is essential for an understanding of the function of the muscles of mastication. When all parts of the apparatus are in the correct functional relationship they operate with the greatest efficiency and the least effort. The jaws and neuromuscular system should be in correct relationship to avoid neuromuscular tension and damage to the component parts of the masticatory system.

Master of Science / A mechanical stimulus producing stretch in human or animal muscle may evoke a reflex response in the muscle that tends to oppose the length change. In decerebrate preparations, limb flexion generates a tonic stretch reflex that manifests as a sustained increase in resistance (Liddell and Sherrington, 1924; Widmalm, 1976b). This tonic response is not readily apparent in the conscious human subject, however, the phasic response may be observed as a burst of action potentials produced by the synchronous firing of several motor units, and as such represents the classic tendon reflex. The analogous compound action potential in the jaw musculature may be demonstrated following a sudden downward mechanical impulse to the mandible in the human or animal subject (Goodwill, 1968; Matthews, 1976) and has been termed the jaw-closing reflex or the jaw jerk reflex, the latter so named in view of its similarity to the knee-jerk and other tendon reflexes induced by sudden stretch (Goodwill, 1968; Munro and Griffin, 1971; Tardieu, Tabary and Tardieu, 1973). The use of the term “jaw jerk” to describe this reflex may be inappropriate as it has been used to describe a sudden opening movement (Riblet and Mitchell, 1971). It would appear preferable therefore to avoid the term “jaw jerk” in in favour of less ambiguous terminology such as “jaw-closing” reflex or monosynaptic myotatic reflex potential (MSP; Widlam, 1976a and b). The jaw-closing reflex is considered a fundamental phenomenon of the facial and oropharyngeal areas (Dubner, Sessle and Stoery, 1978) as it utilises afferent and efferent components involved in the generation, learning and modulation of programmed jaw movement sequences. Thus the reflex would appear to form the basis of more complex functions such as mastication and swallowing (Sessle, 1981), although the response itself probably appears only infrequently in normal function. A downwards tap delivered to the chin in a relaxed human subject causes muscle stretch and this produces an afferent projection along group Ia and group II pathways (Figure:1) which in turn exert monsynaptic and polysynaptic influences on motoneurones in the trigeminal motor nucleus. Inter-segmental and suprasegmental projections onto alpha and fusimotoneurones located in this motor nucleus (Greenwood and Sessle, 1976; Sessle, 1977a and b) modulate ongoing motoneurone excitability thus influencing the mainifestation of evoked monosynaptic reflexes.

Thesis (Ph. D.)--University of Washington. / Bibliography: l. [106]-132.

Thesis (M.S.)--Michigan State University. Dept. of Kinesiology, 2007. / Includes bibliographical references (leaves 64-66).