16,400 research outputs found

    Optimizing Filter-Probe Diffusion Weighting in the Rat Spinal Cord for Human Translation

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    Diffusion tensor imaging (DTI) is a promising biomarker of spinal cord injury (SCI). In the acute aftermath, DTI in SCI animal models consistently demonstrates high sensitivity and prognostic performance, yet translation of DTI to acute human SCI has been limited. In addition to technical challenges, interpretation of the resulting metrics is ambiguous, with contributions in the acute setting from both axonal injury and edema. Novel diffusion MRI acquisition strategies such as double diffusion encoding (DDE) have recently enabled detection of features not available with DTI or similar methods. In this work, we perform a systematic optimization of DDE using simulations and an in vivo rat model of SCI and subsequently implement the protocol to the healthy human spinal cord. First, two complementary DDE approaches were evaluated using an orientationally invariant or a filter-probe diffusion encoding approach. While the two methods were similar in their ability to detect acute SCI, the filter-probe DDE approach had greater predictive power for functional outcomes. Next, the filter-probe DDE was compared to an analogous single diffusion encoding (SDE) approach, with the results indicating that in the spinal cord, SDE provides similar contrast with improved signal to noise. In the SCI rat model, the filter-probe SDE scheme was coupled with a reduced field of view (rFOV) excitation, and the results demonstrate high quality maps of the spinal cord without contamination from edema and cerebrospinal fluid, thereby providing high sensitivity to injury severity. The optimized protocol was demonstrated in the healthy human spinal cord using the commercially-available diffusion MRI sequence with modifications only to the diffusion encoding directions. Maps of axial diffusivity devoid of CSF partial volume effects were obtained in a clinically feasible imaging time with a straightforward analysis and variability comparable to axial diffusivity derived from DTI. Overall, the results and optimizations describe a protocol that mitigates several difficulties with DTI of the spinal cord. Detection of acute axonal damage in the injured or diseased spinal cord will benefit the optimized filter-probe diffusion MRI protocol outlined here

    External loading determines specific ECM genes regulation

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    Bio artificial matrices embedded with cells are simulated in bioreactors to facilitate ECM production. As cells attach, they develop forces, which are dependent on cell type and matrix stiffness. External forces (i.e strain), however, are critical for tissue homeostasis and elicit specific cellular responses, such as gene expression and protein production. Collagen Type I is a widely used scaffold in Tissue engineering. The aim of this study was to study the mechanical and molecular responses, of different cell types to increasing collagen substrate stiffness

    Activation of Long Descending Propriospinal Neurons in Cat Spinal Cord

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    Isolated mammalian spinal cord has been shown capable of generating locomotor activity. Propriospinal systems assumed to coordinate fore- and hindlimb activity are poorly understood. This study characterizes the long descending propriospinal (LDP) neurons in terms of the location of the somas and their peripheral inputs by direct neuronal recording. Anatomical studies using axonal retrograde transport of horseradish peroxidase from the lumbar to the cervical spinal cord as a tracer first described these neurons. Two hundred and thirty-one LDP neurons were identified in electrophysiological experiments. Of these, 123 responded to natural stimulation, and about 50% of the others were activated only by electrical stimulation. The majority of cells were located in laminae VII and VIII in agreement with anatomical data. The most effective stimuli were mechanical stimulation of skin, deep pressure to subcutaneous tissues, and paw joint movement. Bot excitatory and inhibitory responses were observed

    Connections of the Mesencephalic Locomotor Region (MLR) in the Cat

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    The cat entopeduncular nucleus (EN), which is the main output of the basal ganglia, is known to project to the mesencephalic tegmentum. We have been able to elicit antidromic responses in single EN neurons from the region of the mesencephalic locomotor region (MLR), then transect (precollicular-postmamillary) the brainstem and elicit rhythmic movements of the limbs by stimulation of the same site in the same animal. Injections of the fluorescent dye 2,4 diamidino phenylindole 2 HCL (DAPI) into this area induces retrograde labeling of cell bodies in EN and motor cortex. Injections of a tritiated amino acid (leucine) into the motor cortex induce terminal labeling in the area of the MLR. These studies describe convergent projections from EN and motor cortex to the MLR. These connections may be involved in the sequencing and ordering of voluntary movements in which locomotion is necessary

    The Gendering of Cancer Survivorship

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    This article examines the relationship between gender and cancer survivorship. I argue that gender is as critical as a category of analysis for understanding cancer survivorship as it is missing from survivorship studies, particularly as concerns the identificatory basis of survivor culture and clinical studies regarding survivors’ quality of life (QOL). This under-studied question of the gendering of survivorship is critical because the consequences of the social production of disease is far-reaching, from the nature of medical research to social awareness, to funding to the well-being of cancer survivors themselves

    Development of Ground-testable Phase Fresnel Lenses in Silicon

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    Diffractive/refractive optics, such as Phase Fresnel Lenses (PFL's), offer the potential to achieve excellent imaging performance in the x-ray and gamma-ray photon regimes. In principle, the angular resolution obtained with these devices can be diffraction limited. Furthermore, improvements in signal sensitivity can be achieved as virtually the entire flux incident on a lens can be concentrated onto a small detector area. In order to verify experimentally the imaging performance, we have fabricated PFL's in silicon using gray-scale lithography to produce the required Fresnel profile. These devices are to be evaluated in the recently constructed 600-meter x-ray interferometry testbed at NASA/GSFC. Profile measurements of the Fresnel structures in fabricated PFL's have been performed and have been used to obtain initial characterization of the expected PFL imaging efficiencies.Comment: Presented at GammaWave05: "Focusing Telescopes in Nuclear Astrophysics", Bonifacio, Corsica, September 2005, to be published in Experimental Astronomy, 8 pages, 3 figure

    Perceptions of Positive Relationship Traits in Gay and Lesbian Couples

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    The following study examined perceptions of positive traits in homosexual relationships. Students (n = 216) and professional counselors (n = 96) read one of three variations of a transcript of a couple’s counseling session that were identical in all aspects except for the names of the couple members and associated pronouns, implying sexual orientation (either John and Amy, Amy and Jennifer, or John and David). Participants then rated the couple’s level of commitment, satisfaction, investment, and closeness. Surprisingly, the student group perceived no differences between the couples, but the counselor group perceived the gay and lesbian couples as having higher levels of the positive relationship traits. Implications regarding counselor bias are discussed

    Master of Science

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    thesisCadaver dissection has been a fundamental part of the education of medical students for hundreds of years. Since the 16th century, dissection has been touted as the premier method for educating doctors in training on human anatomy. Research in the field of medical pedagogy has explored the multifaceted learning experience of dissection. The literature has focused on the emotional impact, utility, and academic merits of dissection. Yet conceptual literature in the field suggests that cadaver dissection offers an even greater learning experience than what is represented in the existing research. The purpose of the current study was to expand on the preexisting research with a more focused and in-depth examination of medical students' experiences in the anatomy lab. The questions guiding this research were: What is the impact of cadaver dissection on medical students, and what do medical students really learn during cadaver dissection? The research was qualitative in nature and based on an interpretivist paradigm. Data were collected from three distinct sources: field observation of a gross anatomy course, in-depth individual interviews with 15 first-year medical students who participated in the gross anatomy course, and a focus group of three students from the same course. The data were analyzed using grounded theory methodology. From the analysis five distinct themes emerged, with one core concept, Balancing Respect as the central theme supported by the remaining four themes: Discovery, The Shock of Medicine, Utility as Motivation/Coping, and Humanity. The results of the research led to the development of a theoretical model of the process in which cadaver dissection aids medical students in developing a balanced sense of respect for the human body. The act of dissecting evoked two contrasting reactions; a sense of discovery and a sense of shock, and students use the notions of utility and humanity to filter these reactions into a congruent sense of respect. The results of this study have implications for research in the field of medical pedagogy as well as clinical implications for those instructing students through the use of cadaver dissection
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