Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Biomedical Engineering." Includes bibliographical references.

No description available.

Osteotomies made between premolar 3 and premolar 4 in the body of the mandible in canine cadaver hemimandibles (n = 48) were stabilized with five interdental fixation apparatuses in a preliminary biomechanical study. Testing in bending determined ultimate strength, stiffness, and yield strength of the interdental fixation apparatuses. Erich arch bar supplemented with acrylic had significantly (P < 0.05) greater ultimate strength, stiffness, and yield strength than Stout loop supplemented with acrylic, Acrylic, Stout loop, and Erich arch bar alone. Due to the combined superior biomechanical strength of Erich arch bar supplemented with acrylic, it was utilized as the interdental fixation apparatus for the <i>in vivo</i> study. Bilateral osteotomies made between premolar 3 and premolar 4 in the body of the mandible were stabilized with monocortical bone plate (n = 6), interdental (n = 6), and external skeletal fixation (n = 6). None of the dogs showed clinical evidence of pain or discomfort associated with the fixation devices or the development of neuromas. Radiographic signs of bone healing were observed at all osteotomy sites by 16 weeks. Histologic evaluation of bone healing of the mandible with monocortical bone plate, interdental fixation, and external skeletal fixator was not significantly different (P > 0.05) at 8 and 16 weeks postoperatively. The inferior alveolar nerves were evaluated electrophysiologically pre-operatively and at 4, 8, and 16 weeks postoperatively. Nerves were histologically evaluated at 4, 8, and 16 weeks after injury. Nerve function disappeared immediately postoperatively and returned in 64% (24 of 36) by 4 weeks, in 78% (28 of36) by 8 weeks, and 83% (30 of 36) by 16 weeks. Neuromas developed in 100% (36 of 36) of the nerves. Using a transverse osteotomy model, results indicate that the type of bone and nerve healing does not significantly differ between fixation groups tested. Therefore, a simpler and more economical fixation device, Erich arch bar-acrylic, should be suitable to repair selected mandibular fractures in the dog. / Master of Science

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Ling Eva. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 175-202). / Abstracts in English and Chinese. / Abstract --- p.i / 論文摘要 --- p.iv / Acknowledgement --- p.vi / Abbreviations Frequently Used --- p.vii / Table of Contents --- p.viii / Chapter Chapter One --- Introduction --- p.1 / Chapter Chapter Two --- Materials and Methods --- p.35 / Chapter Chapter Three --- Results --- p.64 / Chapter Chapter Four --- Discussion --- p.148 / References --- p.175 / Tables --- p.203

Spontaneous intracerebral haemorrhage (ICH) is one of the most lethal forms of stroke and has a relatively higher morbidity in Asian people. The high disability rate of 50% in all survivors and lack of clinically effective regeneration medicine make ICH a major unanswered problem worldwide. Considerable preclinical evidence suggests that neuroprotective interventions are urgently needed to lessen the effects of this disease. To date, less preclinical researches with proven positive results have successfully translated to the clinical setting, mainly due to poor modelling, a lack of behavioural testing, inadequate experimental design and failure to consider white matter damage. According to the few previous studies, white matter is a key predictor of ICH outcomes and a potential target of recovery. The long-term axonal degeneration in rodent ICH has been ignored for decades, and almost every preclinical study has focused on mechanisms in the acute phase. Clinically ICH patients may suffer a permanent loss of brain function or long-term deficits that take years to recover from. If the preclinical researches target the long-term axon degeneration/regeneration in the chronic stage, it might help to develop successful clinical interventions for functional reconstruction and rehabilitation. / Thus, to obtain the evidence of axonal degeneration and regeneration in the chronic stage of experimental ICH, this study at first systematically assessed the histological and functional outcomes of axonal regeneration in experimental ICH from day 3 to day 56 and secondly find the effective markers and methods for investigation axons in experimental ICH models in vivo. The long-term gait disturbance of a computer-generated CatWalk system, the electrophysiological changes, axonal loss by PKC gamma (PKCγ) immunohistochemistry and axonal degeneration by Bielschowsky silver staining were examined in unilateral striatum lesioned ICH (ST-ICH) rats. As the ST-ICH model demonstrated a spontaneous functional recovery within one or two month, we further developed a modified internal capsule lesioned ICH (IC-ICH) rat model which mimic clinical conditions, and investigated whether an internal capsule lesion leads to long-term axonal damage and long lasting functional deficits. / The finding demonstrated that haematoma in striatum led to severe axonal degeneration/loss in ipsilateral medullary corticospinal tract (CST) and functional deficits in a long-term duration (1-2 months after ICH). PKCγ level was an effective marker to quantify the axonal loss in experimental ICH and it indicated a significant axonal loss on day 56 after ICH in ipsilateral CST. Bielschowsky silver staining was a useful method to illustrate the morphological changes of axonal degeneration and regeneration in longitudinal sections of CST and it clearly showed the process of axon swelling, disrupted and regenerated in 2 months’ duration after ICH. / Somatosensory evoked potentials (SSEPs) and gait analysis were valuable functional assessments to characterize the long-term behavioral deficits resulting from axonal degeneration/regeneration in experimental ICH. The decrease in electrophysiological parameter SSEP amplitudes was observed in experimental ICH. Multiple gait parameters changed after ICH and some of that such as paw print area, paw pressure, stand index, duty cycle can be used as long-term evaluating markers in chronic stage of experimental ICH. / Compared to ST-ICH, the modified IC-ICH model exhibited a relatively smaller lesion volume with consistent axonal loss/degeneration and long-lasting neurological dysfunction at 2 months after ICH. Functionally, the impairment of the mNSS, ratio of contralateral forelimb usage, four limb stand index, contralateral duty cycle and ipsilateral SSEPs amplitude remained significant in the IC-ICH model at 56 days compared with the sham group, and asymmetries in the hind paw print area of the IC-ICH model exhibited significant differences from the ST-ICH model at 56 days. Structurally, the significant loss of PKCγ in ipsilateral CST of IC-ICH and the consistent axonal degeneration with several axonal retraction bulbs and enlarged tubular space was observed at 56 days after ICH. / In summary, the data from this study systematically characterize the histological and functional outcomes (especially gait parameter and SSEPs changes) in the experimental ICH model. A modified internal capsule lesioned ICH model was developed for rats, and proved to have long lasting neurological deficits. A comprehensive understanding of the dynamic progression after experimental ICH should aid further successful clinic translation in animal ICH studies, and provide new insights into the potential biomarkers and therapeutic targets of ICH. / 原發性腦出血（ICH）是一種致死性較高的卒中類型。在亞洲人群眾發病率相對較高。高致殘率和臨床上缺乏有效的治療手段，使得腦出血成為世界範圍內的健康問題。因此需要大量的臨床前研究尋找有效的治療方法。然而，迄今為止，臨床前研究獲得的陽性結果中，只有少數被成功的轉化到臨床應用。臨床轉化存在的部分失敗，歸結於幾個主要的因素包括動物模型的不足，動物行為學實驗的不恰當使用，實驗設計的缺陷以及對白質損傷機制的忽略。有研究認為，腦白質是卒中後功能恢復的關鍵指標和潛在治療靶點。腦出血慢性期的軸索變性在齧齒類動物模型中的研究被忽視了幾十年，而幾乎所有的臨床前研究都關注於急性期的機制。而臨床上倖存的腦出血病人大多罹患永久性的腦功能損傷，往往需要數年才能恢復或者難以恢復。如果臨床前轉化實驗以腦出血後慢性期的神經軸索損傷/再生作為研究目標，也許可以找到有助於卒中後功能重建和康復的治療手段。 / 為了尋找腦出血慢性期神經軸索損傷的證據，本研究首先從組織學和功能行為學兩個方面對對實驗性腦出血後的軸索再生進行了系統的評價。並建立了有效反應慢性期神經軸索再生的一系列方法和標誌物。本研究將步態分析，電生理評價， Bielschowsky銀染和PKCγ組織學染色結合起來對腦出血後的動物模型的軸索蛻變和再生進行長期觀察。結果顯示傳統的紋狀體損傷模型在1到2個月出現自發的功能恢復。本研究進一步假設內囊出血模型可能會獲得更加持久的功能損傷，也更為接近臨床患者的情況。因此，為了更好地研究腦出血慢性期的白質損傷和類比臨床情況，本研究建立了一種改進的內囊出血大鼠模型，並用組織學和行為學方法對其長期的功能損傷進行評價。 / 研究結果顯示，位於紋狀體的血腫可以引起同側的延髓皮質脊髓束(CST)出現嚴重的慢性期退化和變性，並同時伴有神經功能損傷。PKCγ是評價實驗性腦出血後神經軸索損傷程度的有效標誌物，資料表明同側皮質脊髓束PKCγ的表達水準在ICH損傷56天后仍有顯著降低。對延髓椎體CST的Bielschowsky銀染，可以從結構上有效的反應軸索變形和再生的過程，CST縱行切片染色清楚地顯示了腦出血損傷後2個月的時間內軸索水腫、斷裂和再生的過程。 / 體感誘發電位（SSEPs）和步態分析的方法可以從功能上對腦出血後神經軸索損傷進行較為全面的評價和定量分析。單側紋狀體腦出血可以引起同側皮層SSEP波幅的降低。多個步態分析參數在腦出血後也存在明顯的變化，其中前後掌爪印面積（paw print area），爪印壓力（paw pressure），站立指數（stand index），患側肢體站立百分比（duty cycle）都可作為觀察腦出血後慢性期功能損傷和恢復的評價指標。 / 改進後的內囊腦出血模型顯示病灶體積相比較小但神經軸索的損失和神經功能障礙較為持久。從神經功能方面評判，與假手術組相比，神經功能評分（mNSS），對側前肢使用率（cylinder test），四肢站立指數（stand index），患側肢體站立百分比（duty cycle）和患側體感誘發電位波幅（SSEPs amplitude）在出血後2個月仍然顯著降低。後掌的爪印面積（print area）與紋狀體腦出血的動物比較在出血後第56天后仍有顯著差異。從軸索結構評判，內囊出血模型顯示出更為嚴重的神經軸索退變和損傷，表現為在出血後56天PKCγ蛋白表達量的持續降低，軸索斷裂結節和管狀間隙的形成。 / 綜上所述，本研究系統地分析了實驗腦出血後的組織學和功能特點，建立了一個改進的內囊腦出血大鼠模型，並證明該模型存在更為持久的神經功能障礙和神經軸索損傷。 / Liu, Yao. / Thesis Ph.D. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 168-200). / Abstracts also in Chinese. / Title from PDF title page (viewed on 18, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Severe traumatic injuries and surgical procedures like tumor resection often create peripheral nerve gaps, accounting for over 250,000 injuries in the US annually. The clinical "gold standard" for bridging peripheral nerve gaps is autografts, with which 40-50% of patients regain useful function. However, issues including their limited availability and collateral damage at the donor site limit the effectiveness and use of autografts. Therefore, it is critical to develop alternative bioengineered approaches that match or exceed autograft performance. With the use of guidance channels, the endogenous regeneration process spontaneously occurs when successful bridging of short gaps (< 10mm) occurs, but fails to occur in the bridging of longer gaps (≥15mm). Several bioengineered strategies are currently being explored to bridge these critical size nerve gaps. Other labs and ours have shown how filler materials that provide topographical cues within the nerve guides are able to enhance nerve growth and bridge critical length gaps in rats. However, the mechanism by which intra-luminal fillers enhance nerve regeneration has not been explored. The main goal of this dissertation was to explore the interplay between intra-luminal scaffolds and orchestrated events of provisional fibrin matrix formation, glial cell infiltration, ECM deposition and remodeling, and axonal infiltration - a sequence we term the 'regenerative' sequence. We hypothesized that the mechanism by which thin films with topographical cues enhance regeneration is by serving as physical 'organizing templates' for Schwann cell infiltration, Schwann cell orientation, extra-cellular matrix deposition/organization and axon infiltration. We demonstrate that aligned topographical cues mediate their effects to the neuronal cells through optimizing fibronectin adsorption in vitro. We also demonstrate that aligned electrospun thin films are able to enhance bridging of a critical length nerve gap in vivo by stabilizing the provisional matrix, creating a pro-inflammatory environment and influencing the maturation of the regenerating cable leading to faster functional recovery compared to smooth films and random fibers. This research will advance our understanding of the mechanisms of peripheral nerve regeneration, and help develops technologies that are likely to improve clinical outcomes after peripheral nerve injury.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy