This dissertation contributed three main areas to flexibility testing and biomechanical characterization of human spinal segments. The first was a literature review of existing testing methodology, the second examined common spine fixation procedures, and the third developed an improved fixation method. Spine biomechanical characterization is the primary technique for assessing the healthy, diseased, and surgically treated response of spinal tissues. However, despite decades of use, no standard testing protocol or reporting methodology for flexibility testing conditions has been established. As part of the present work, a comprehensive, systematic literature review was performed, and the methods sections of 242 relevant journal articles provided key information regarding preparation processes, fixation methods, testing temperatures, loading rates, loading magnitudes, and pre-conditioning procedures. The collated information was utilized to recommend best practices for testing and reporting flexibility testing methodology. Exothermic cementing processes were the dominant spinal fixation method from the reviewed articles. In these cases, fixation occurred when the most superior and inferior vertebrae of a functional spinal unit (FSU) were embedded into a cementing material that bound tightly to the cortical surface of the vertebrae, yielding a strong and geometrically favorable attachment point. The four most common fixation materials are highly exothermic and were tested to quantify the temperature rise in the adjacent intervertebral disc (IVD), as well as any associated thermal iatrogenic damage. Three thermocouples, inserted into three distinct locations of the IVD, measured temperatures throughout the cementing process. Polymethyl methacrylate (PMMA), the most frequently used cementing material, resulted in the greatest temperature increases, with a mean temperature rise up to 57°C above room temperature. Visible macro- and microscopic changes occurred in each of the cemented FSU IVDs. Changes included morphological changes, tissue desiccation, cracks, a breakdown in striations in the annulus fibrosus (AF), and denaturation and cell migration in the nucleus pulposus (NP). Based on these results, alternative vertebral attachment methods were considered and investigated. A structured design process was followed, and a mechanical ex vivo spinal fixation device which comprised a compliant vertebral clamp was designed. The geometry of the vertebral clamp was optimized based on pseudo-rigid body and finite element analyses. The final design was fabricated in titanium alloy (Ti6Al4V) using a 3D laser sintering process. Three clamps were manufactured and functionally validated. The opening/deployment and physiological loads of ± 7.5 N•m were cyclically tested on each clamp. The clamps showed no signs of failure and remained securely attached to the vertebrae. The resultant device/vertebrae interface stiffnesses were 4 to 10x greater than their corresponding FSU stiffnesses. The clamp design eliminated thermal iatrogenic damage, had minimal structural iatrogenic damage, was reusable, adjustable, and resulted in less than 10% of the previous preparation time.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13537号 / 論医博第2277号 / 新制||医||1065(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 篠原 隆司, 教授 近藤 玄, 教授 齋藤 潤 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

It is usually assumed that the reduction of nitrite by nitrite reductase results in the formation of ammonia. The purpose of this investigation was to enquire whether more than one nitrite reductase activity is responsible for in vivo nitrite reduction. An assay system which measures the production of ammonia, as a result of nitrite reductase is described. The. reduction of nitrite by nitrite reductase did not result in the formation of stoichiometric amounts of ammonia. Nitrite non-utilizing mutants showed that nitrite reduction could occur in vitro with no subsequent formation of ammonia or could result in the formation of essentially stoichiometric amounts of ammonia. Sedimentation velocity gradient centrifugation resulted in the separation of at least two peaks of nitrite reductase activity. A model is described which accounts for the results in terms of two nitrite reductase activities, necessary for in vivo nitrite reduction. / Thesis / Master of Science (MSc)

<p> In vivo and in vitro studies on the biosynthesis of vasopressin in the supraoptic nuclei of the dog and guinea pig1 using 35s-cysteine and 3H-tyrosine have suggested that vasopressin could be synthesized by wa;y of a precursor, which is modified to release active hormone. In vivo injection of 3H-tyrosine into the cerebrospinal fluid of rats2 had resulted in incorporation of the label into both oxytocin and vasopressin. In this work, an attempt was made to develop an in vitro system for the biosynthesis of oxytocin. Incubations of either 3H-isoleucine or 14c-leucine with rat hypothalamic neuronal perikaya, ribosomes and cell sap, cell sap, fractions of cell sap and homogenate, and incubations of 3H-isoleucine and l4C-leucine with rat hypothalamic tissue fragments were analyzed for the incorporation of label into purified hormone. Gel filtration, partition chromatography, high voltage electrophoresis, and thin layer chromatography were applied, followed by measurement of radio-activity and biological activity. It is concluded that in no reproducible case was either radioactive isotope incorporated into material with the chromatographic and biological properties of oxytocin. Other radioactive products of incubation were detected in hypothalamic cell sap, ribosomes and cell sap, and homogenate. In hypothalamic homogenate incubations, considerable degradation of both oxytocin and other material absorbing at 280 nm was observed. It is suggested that future investigations should attempt to first develop isolation procedures for the labelled hormone produced in vivo, and then reduce the complexity of the system in small stages, through the cultured hypothalamic-neurohypophyseal system of Sachs3 to simpler in vitro systems. </P> / Thesis / Master of Science (MSc)

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