Muscles control body posture and movement by extrafusal and intrafusal (muscle spindle) fibres. The purpose of this thesis was to provide insight into the muscular basis for human jaw function at young age. Extrafusal and intrafusal fibres in the young masseter, and for comparison young biceps, were examined for composition of fibre types and myosin heavy chain (MyHC) isoforms by means of morphological, enzyme-histochemical, biochemical and immuno-histochemical techniques. For evaluation of plasticity during life span the data for young muscles were compared with previous reported data for adult and elderly muscles. The results showed significant differences in extrafusal fibre types and MyHC expression between young masseter and young biceps and between young masseter and masseter in adults and elderly. Compared with young biceps, young masseter was more intricate in composition of extrafusal MyHC expression. Muscle spindles were larger and more frequent in the masseter than in the biceps. Masseter and biceps muscle spindles showed fundamental similarities but also marked differences in MyHC expression. The results suggest that the young masseter is specialized in fibre types already at young age and shows a unique fibre type growth pattern. Whereas masseter extrafusal fibres display marked plasticity in fibre types and MyHC isoforms during life span muscle spindles/intrafusal fibres are morphologically mature already at young age and precede extrafusal fibres in growth and maturation. Results showed similarities in intrafusal MyHC expression between young masseter and biceps, but also differences implying muscle specific proprioceptive control. Differences in fibre types and MyHC expression between young masseter and young biceps extrafusal fibres are proposed to reflect diverse evolutionary and developmental origins and accord with the masseter and biceps being separate allotypes of muscle.

The microtubule cytoskeleton, which consists of dynamic polymers of alpha/beta tubulin heterodimers, organizes the cytoplasm and is essential for chromosome segregation during mitosis. My thesis addresses the significance and potential interplay between four distinct microtubule-regulatory proteins. The experimental approach included the development of a replicating vector system directing either constitutive expression of short hairpin RNAs or inducible ectopic expression, which allows stable depletion and/or conditional exchange of gene-products. Based on the originally observed activities in frog egg extracts, MCAK and TOGp have been viewed as major antagonistic proteins that regulate microtubule-dynamics throughout the cell cycle. Surprisingly, while my thesis work confirmed an essential role of these proteins to ensure mitotic fidelity, tubulin subunits partitioning is not controlled by the endogenous levels of MCAK and TOGp in human somatic cells. Our major discovery in these studies is that the activities of both CaMKII and TOGp are essential for spindle bipolarity through a mechanism involving protection of spindle microtubules against MCAK activity at the centrosome. In our search for the major antagonistic activities that regulates microtubule-dynamics in interphase cells, we found that the microtubule-destabilizing activity of Op18 is counteracted by MAP4. These studies also established Op18 and MAP4 as the predominant regulators of tubulin subunit partitioning in all three human cell model systems studied. Moreover, consistent with phosphorylation-inactivation of these two proteins during mitosis, we found that the microtubule-regulatory activities of both MAP4 and Op18 were only evident in interphase cells. Importantly, by employing a system for inducible gene product replacement, we found that site-specific phosphorylation-inactivation of Op18 is the direct cause of the demonstrated hyper-polymerization in response to T-cell antigen receptor triggering. This provides the first formally proven example of a signal transduction pathway for regulation of interphase microtubules. Op18 is frequently upregulated in various types of human malignancies. In addition, a somatic mutation of Op18 has recently been identified in an adenocarcinoma. This thesis work revealed that the mutant Op18 protein exerts increased microtubule-destabilizing activity. The mutant Op18 protein was also shown to be partially resistant to phosphorylation-inactivation during mitosis, which was associated with increased chromosome segregation aberrancies. Interestingly, we also observed the same phenotype by overexpressing the wild type Op18 protein. Thus, either excessive levels of wild type Op18 or normal levels of mutated hyper-active Op18 seems likely to contribute to tumor progression by exacerbating chromosomal instability.

Muscle spindles are skeletal muscle mechanoreceptors that mediate the stretch reflex and provide axial and limb position information to the central nervous system. They have been proposed to play a major role in the pathophysiology of muscle pain. Knowledge about the normal human muscle spindles is needed in order to understand their role in muscle disease or dysfunction. The aim of this study was to investigate the fiber content and MyHC composition of the muscle spindles in the human biceps brachii (BB) and deep muscles of the neck (DN); to determine whether there are age-related changes in human muscle spindles with respect to structure and MyHC composition; to investigate the distribution of SERCA isoforms and to evaluate whether there is a coordinated expression of SERCA and MyHC isoforms in intrafusal fibers. The myosin heavy chain (MyHC) content correlates to contraction velocity and force and the sarcoplasmic reticulum Ca2+ ATPase (SERCA) is a major determinant of muscle fiber relaxation velocity. Muscle specimens obtained from young and old subjects were serially sectioned and the pattern of distribution of different proteins along the length of the intrafusal fibers was revealed by immunocytochemistry. The MyHC content of single muscle spindles was assessed with SDS-PAGE and immunoblots. There were clear differences between BB and DN with regard to the morphology and MyHC composition of muscle spindles. Virtually each muscle spindle in the BB, but not in the DN, had a unique allotment of numbers of bag1, bag2 and chain fibers. In DN, a number of muscle spindles lacked either bag1 or bag2 fibers. Four major MyHC isoforms (MyHCI, IIa, α-cardiac and intrafusal) were detected by SDS-PAGE. In both BB and DN, immunocytochemistry revealed co-expression of several MyHC isoforms in each intrafusal fiber and regional heterogeneity. Both nuclear bag1 and bag2 fibers contained slow tonic MyHC uniformly and MyHCI, α-cardiac, embryonic and fetal with regional variations. Nuclear chain fibers contained MyHCIIa, embryonic and fetal and in the BB also MyHCIIx. The total number of intrafusal fibers per spindle decreased significantly with aging, due to a significant reduction in the number of nuclear chain fibers. The patterns of MyHC expression were also affected by aging. The bag1 fibers predominantly contained both SERCA isoforms in the encapsulated region. The bag2 fibers were more heterogeneous in their SERCA composition and 16-27% of them lacked both isoforms. Chain fibers contained SERCA1. There was a poor correlation between the MyHC and SERCA isoforms in nuclear bag fibers, whereas a strong correlation existed between MyHCIIa and SERCA1 in the nuclear chain fibers. Human muscle spindles, each being unique, proved to be more complex than anticipated. The clear differences shown between the BB and DN muscle spindles suggest functional specialization in the control of movement among different human muscles. Aging apparently had profound effects on intrafusal fiber content and MyHC composition. The age-related changes in muscle spindle phenotype may reflect deterioration in sensory and motor innervation and are likely to have a detrimental impact on motor control in the elderly.

The focus for this study is the illumination of the function of loom weights and their purpose within the warp-weighted loom. This study deals with Iron Age loom weights excavated at Birka, within the area known as the Garrison. This category of objects was originally classified as being fragments of bellow shields, an interpretation seemingly more corresponding with the site’s traditional interpretation. In order to give a fuller depiction of the textile production as a whole, spindle whorls found within the same defined area have also been included in this study. The main goal for the analyses of these two groups of fragmented finds has been to establish and re-create the functioning variables of these objects, that is, foremost their original shape and weight. Furthermore the objective has been to enhance the understanding of the functional parameters of the textile production in this area. This is partly achieved with the aid of comparing data regarding textile implements found in other areas of Birka. The results can confirm that the area held a capacity to manufacture a variety of different textiles, including very fine threads and weaves.

Pax3 protein is initially expressed in the dermomyotome of embryonic somites, which gives rise to skeletal muscle. Following myogenesis, Pax3 expression is mostly down-regulated and becomes restricted to a few satellite cells (SCs) of select mature muscles. SCs are activated to form new myonuclei during muscle hypertrophy, regeneration and repair. Intrafusal fibers of muscle spindles are thought to persist in a comparatively immature state as, unlike extrafusal fibers, they maintain small diameters, developmental myosins, Myf5 expression and high SC concentrations. This thesis tests the hypotheses that Pax3 expression is preferentially maintained in SCs of adult skeletal muscle spindles and can be augmented under conditions of SC activation. To study Pax3 through development, immunohistochemical techniques were used to identify SCs by their Pax7 expression, and analyze the proportion of SCs and myonuclei (MN) expressing Pax3 in chicken anterior latissimus dorsi (ALD) muscle excised at 9, 30, 62, and 145 days post-hatch. To induce SC activation, tenotomy was performed on the right ALD muscle of 138-day post-hatch chicks to induce compensatory hypertrophy of the ipsilateral synergistic posterior latissimus dorsi (PLD) muscle. The PLD was analyzed seven days after ALD tenotomy using similar immunohistochemical techniques. This is the first study to show Pax3 expressing SCs within intrafusal fibers of muscle spindles. This thesis demonstrates that throughout development there is a higher percentage of Pax3 expressing SCs within intrafusal fibers of muscle spindles than the surrounding extrafusal fibers that compose the bulk of the muscle. It is also revealed that the proportion of the SC population expressing Pax3 declines with age in both intrafusal and extrafusal fibers. Compensatory hypertrophy of the PLD resulted in a greater percentage of Pax3 expressing SCs in intrafusal and extrafusal fibers than under control conditions. The percentage of SCs expressing Pax3 after PLD overload was similar to that seen in young control muscle. The percentage of Pax3 expressing MN also increased after muscle overload to levels seen in young muscle. A disproportionate decrease in the proportion of SCs expressing Pax3 during development, and a disproportionate increase in the percentage of Pax3 positive SCs as a result of experimentally induced muscle hypertrophy, suggests that Pax3 expression in maturing muscle may be more than just a developmental vestige. Pax3 may be a factor in the activation and differentiation of SCs in maturing muscle.

Pax3 protein is initially expressed in the dermomyotome of embryonic somites, which gives rise to skeletal muscle. Following myogenesis, Pax3 expression is mostly down-regulated and becomes restricted to a few satellite cells (SCs) of select mature muscles. SCs are activated to form new myonuclei during muscle hypertrophy, regeneration and repair. Intrafusal fibers of muscle spindles are thought to persist in a comparatively immature state as, unlike extrafusal fibers, they maintain small diameters, developmental myosins, Myf5 expression and high SC concentrations. This thesis tests the hypotheses that Pax3 expression is preferentially maintained in SCs of adult skeletal muscle spindles and can be augmented under conditions of SC activation. To study Pax3 through development, immunohistochemical techniques were used to identify SCs by their Pax7 expression, and analyze the proportion of SCs and myonuclei (MN) expressing Pax3 in chicken anterior latissimus dorsi (ALD) muscle excised at 9, 30, 62, and 145 days post-hatch. To induce SC activation, tenotomy was performed on the right ALD muscle of 138-day post-hatch chicks to induce compensatory hypertrophy of the ipsilateral synergistic posterior latissimus dorsi (PLD) muscle. The PLD was analyzed seven days after ALD tenotomy using similar immunohistochemical techniques. This is the first study to show Pax3 expressing SCs within intrafusal fibers of muscle spindles. This thesis demonstrates that throughout development there is a higher percentage of Pax3 expressing SCs within intrafusal fibers of muscle spindles than the surrounding extrafusal fibers that compose the bulk of the muscle. It is also revealed that the proportion of the SC population expressing Pax3 declines with age in both intrafusal and extrafusal fibers. Compensatory hypertrophy of the PLD resulted in a greater percentage of Pax3 expressing SCs in intrafusal and extrafusal fibers than under control conditions. The percentage of SCs expressing Pax3 after PLD overload was similar to that seen in young control muscle. The percentage of Pax3 expressing MN also increased after muscle overload to levels seen in young muscle. A disproportionate decrease in the proportion of SCs expressing Pax3 during development, and a disproportionate increase in the percentage of Pax3 positive SCs as a result of experimentally induced muscle hypertrophy, suggests that Pax3 expression in maturing muscle may be more than just a developmental vestige. Pax3 may be a factor in the activation and differentiation of SCs in maturing muscle.

<p>The cell cycle is a series of ordered events that culminates in a single cell dividing into two daughter cells. These events must be properly coordinated to ensure the faithful passage of genetic material. How cell cycle events are carried out accurately remains a fundamental question in cell biology. In this dissertation, I investigate mechanisms orchestrating cell-cycle events in the yeast, <italic>Saccharomyces cerevisiae</italic>. </p><p>Cyclin dependent kinase (CDK) activity is thought to both form the fundamental cell-cycle oscillator and act as an effector of that oscillator, regulating cell-cycle events. By measuring transcript dynamics over time in cells lacking all CDK activity, I show that transcriptional oscillations are not dependent on CDK activity. This data indicates that CDKs do not form the underlying cell-cycle oscillator. I propose a model in which a transcription factor network rather than CDK activity forms the cell-cycle oscillator. In this model, CDKs are activated by the periodic transcription of cyclin genes and feedback on the network increasing the robustness of network oscillations in addition to regulating cell-cycle events. </p><p>I also investigate CDK-dependent and -independent mechanism regulating the duplication of the yeast centrosome, the spindle pole body (SPB). It is critical for the formation of a bipolar spindle in mitosis that the SPB duplicates once and only once per cell cycle. Through a combination of genetic and microscopic techniques I show that three distinct mechanisms regulate SPB duplication, ensuring its restriction to once per cell cycle. </p><p>Together, the data presented in this dissertation support a model in which CDKs, periodic transcription, and a TF-network oscillator are all important cell-cycle regulatory mechanisms that collaborate to regulate the intricate collection of events that constitute the cell cycle.</p> / Dissertation

A friction stir welding equipment with high rotation speed and constant load is successfully developed in this study to weld the multi-laminated silicon steel sheets widely used on regular transformers. This equipment consists of a spinning unit, a loading unit, and a feeding unit. A WC round rod with 3 mm diameter is used as welding tool. Under different operating conditions, such as the normal load(140~480 N), the spindle speed (12000~24000rpm), the feeding rate (0~1.58 mm/s), the welding characteristics and the welding mechanism of multi-laminated silicon steel sheets, and the welding feasibility of the transformer are investigated. Firstly, the contour map of welding depth in terms of spindle speed,normal load, and depth of point welding is established for dwell welding time 15 seconds. Secondly, based on this contour map, two experimental conditions of the long-pass welding tests are selected to investigate the effect of normal load (Fd), the spindle speed (Ns), and the feeding rate (f) on the failure load of weld under the shear. According to the experimental results, the empirical formula is obtained as Ff =40.6(Fd¡DNs)1.123(f)-0.791. In this formula,(Fd¡DNs)1.123(f)-0.791 is proportional to the frictional work per unit moving distance. With the larger frictional work, this represents the heat generation of the workpiece material is higher with more uniform friction stir, so that the bonding strength of the material increases and the failure load of weld is larger. According to the micrograph observations, the thermo-mechanically affected zone is significantly influenced by high heat action generated from the friction between the tool and the weld surface region, so that the plastic flow of the workpiece material occurs to cause the multi-laminated silicon steel sheets bonding together. Finally, the transformer is successfully welded under the experimental conditions of the long-pass welding tests with the smaller welding depth and the better failure load.

The aim of this thesis is to analyze the kinematic and dynamic characteristics of a high-speed bearing system. The examined kinematic characteristics will include the maximal speed, fatigue life and stiffness of a bearing system. The stability and transmission force of a bearing system as well as the vibration of its shaft were the studied dynamic characteristics. These analyses were based on the kinemitics of bearing systems, rotor dynamics and elastohydrodynamic lubrication theory. According to these analyses, the interaction and consequence among these characteristics and the parameters of a bearing system will be explained. After these analyses, preliminary and simple design trends about a high-speed bearing system are going to be proposed.

The aim of this thesis is to develop a Computer-aided Design software for high speed angular contact ball bearing system. First, to analyze the interaction of among the characteristics and parameters of a high-speed spindle system with angular contact ball bearing. These analyses were based on the kinematics of bearing systems and rotor dynamics. According to these analyses, several design charts for bearing system will be established by computer simulations. Secondly, an optimum design for high speed spindle system will also be proposed. After these analyses, an Computer-Aided Design software for high speed bearing system will be established. From the study, preliminary design trends about high speed spindle system will be proposed.