Browsing by Subject "Skeleton"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Dmp1 Regulates Osteocyte Function Via Wnt/?-Catenin Signaling Pathway
    (2014-05-06) Lin, Shuxian
    DMP1, dentin matrix protein 1, was cloned from a rat dentin cDNA library 20 years ago. Initially, this non-collagenous matrix protein was thought to be dentin specific and gained little interest in other scientific communities except the dental research area. Research that identified DMP1 mutations in humans and deletion in mice lead to the discovery of a novel disease: autosomal recessive hypophosphatemic rickets (ARHR). Functional studies reveal that DMP1 is essential for the maturation and functions of osteoblast and osteocyte via two possible mechanisms: 1) as a transcriptional factor that directly regulates osteo-/odonto-specific genes; and 2) as an extracellular matrix (ECM) protein, which controls bone and dentin mineralization. However, both theories appear controversy. Besides, the mechanism by which ARHR patients or Dmp1- null mice develop osteomalacia is largely unknown. In this study, we initially targeted DMP1 either in the nucleus only by replacing the endogenous signal peptide with the NLS signal peptide (named ^(NLS)DMP1), or targeted it in the ECM by using its own signal secretive peptide with the same recombinant DMP1 protein (named ^(SP)DMP1). The ^(NLS)DMP1 transgene, when expressed in the Dmp1-null osteoblast and osteocyte in vivo, failed to rescue the Dmp1-null phenotype, whereas the ^(SP)DMP1 transgene fully rescued the skeletal abnormalities of Dmp1-null mice, indicating that DMP1 functions as an ECM protein in vivo. In a separate research, we revealed an elevated ?-catenin expression level in Dmp1-KO osteocytes, besides, the targeted expression of ?-catenin in the osteocyte recaptured the osteomalacia phenotype, similar to that in Dmp1-KO mice. Furthermore, the targeted expression of DKK1 (a potent inhibitor of Wnt/?-catenin) in Dmp1-KO osteoblasts by crossing Dmp1-KO and 2.3 Col 1-Dkk1 mice, resulting in consequent blockade of Wnt/?-catenin signaling, significantly improved the rachitic/osteomalacic phenotype. The results of this study will expand our understanding of how the osteocytes regulate bone development and mineralization during the early postnatal period. In addition, this study has clinical relevance, as a high Pi diet alone fails to fully restore the osteomalacic status in patients, and normalizing the Wnt/?-catenin signaling may benefit these patients.
  • No Thumbnail Available
    Item
    i3DTI: Interactive 3D Tele-Immersion
    (2017-05) Raghuraman, Suraj
    3D Tele-Immersion (3DTI) approaches offer collaborative augmented virtuality, by immersing multiple geographically distributed users in a single virtual world. Multiple cameras are used to capture remote users and reconstruct their 3D models, to be rendered in the virtual world. Large volumes of noisy data, captured by the cameras, are cleaned, processed, transmitted, and rendered every frame. The complexities in processing and large transmission payloads result in high latency, low frame rate rendering, leading to very limited interactions between the users of the system. Interactive 3D Tele-Immersion (i3DTI) systems allow geographically distributed users to be immersed in highly engaging and interactive virtual worlds. This dissertation presents a set of novel approaches, that improve the quality and performance of all of the stages of an i3DTI application. An image based meshing approach reduces the time taken for the 3D reconstruction of the captured data, to less than a millisecond. To ensure low latency even over the internet, a skeleton based prediction strategy is presented, that reduces the quantity of data transmitted per frame to just a few hundred bytes, while still maintaining good quality rendering. Naturalistic full body interactions, based on the skeleton that is estimated using multiple RGB-D cameras, keeps the users engaged while using the system. Current 3DTI systems use internal clocks to measure the latency experienced by the users, while ignoring the time for capture, rendering, screen refreshing, etc. Two novel, millisecond accurate approaches, for measuring the latency felt by the user, are presented. One of the approaches measures the latency across the internet while the system is not actively in use, and the other measures the local latency while the system is in use. All of the approaches are implemented as a framework in a highly scalable, performance optimized, easy to use, and extendable architecture. Multiple applications, catering to domains from Tele-Medicine to education, were created using the framework. The patient trials of a remote patient diagnosis system, that was implemented between two geographically distributed locations using the i3DTI framework, was highly appreciated by the users; and the remote patient diagnosis was highly correlated to the in-person diagnosis.
  • No Thumbnail Available
    Item
    Ontogeny and evolutionary morphology of the skeleton in frogs
    (2001-08) Yeh, Jennifer Jean; Dudley, Robert, 1961-; Cannatella, David C.
    Ontogenetic studies, or studies of development, have repeatedly proven insightful in exploring questions of morphological evolution. Here, two projects illuminate the relationship between ontogeny and the evolution of skeletal morphology in frogs. In the first part of this dissertation, I examine the evolution of skull development in pipoid frogs, a group that is exceptional in both morphology and life history. Two methods are used. First, skull bone ossification sequences are examined within a phylogenetic context. Second, studies are made of ontogenetic shape change in the skull using thin-plate spline morphometrics. Important differences between pipoid skull development and that of other frogs are uncovered. These include the convergent evolution of primitive ossification patterns still retained in extant salamanders, and the elaboration of novel trajectories of ontogenetic shape change which create the unusual pipoid morphology. The second part of this dissertation examines the phenomenon of miniaturization in frogs. Because miniaturization has evolved numerous times in frogs and has reached impressive extremes, frogs make an ideal group in which to study the effects of miniaturization on morphological evolution. I use qualitative presence/absence characters in the skull and limbs, as well as shape variables from thin-plate spline morphometrics to identify patterns of morphological change which are statistically associated with the evolution of miniaturization. These statistically significant patterns are discussed in the context of functional constraints and paedomorphosis.
  • No Thumbnail Available
    Item
    Segmentation of cervical and lumbar vertebrae in x-ray images using active appearance models and extensions
    (Texas Tech University, 2003-12) Howe, Benjamin M
    This thesis presents a hierarchical segmentation algorithm tailored to the segmentation of cervical and lumbar vertebrae in digitized X-ray images. The algorithm employs the Generalized Hough Transform (GHT) to obtain a suitable initialization for two segmentation stages that utilize Active Appearance Models (AAMs) that were proposed by Cootes et al. The advantage of using AAMs in medical image segmentation applications is that rather than creating models that are purely data driven, AAMs gain a priori knowledge through a thorough observation of the shape and texture variation across a training set. This thesis presents a detailed summary of the theory behind AAM along with proposed extensions and customizations of AAM. The proposed extensions (1) address the shortcomings of using the basic texture alignment procedures when using Neighborhood AAMs, (2) automate the selection of training parameters, and (3) modify the AAM search criterion to encourage the location of the edges of the vertebrae. In addition, AAM is utilized to rank the quality of multiple initializations provided by GHT. The proposed segmentation algorithm was tested on 273 cervical X-ray images and 262 lumbar images. If a successful segmentation is defined as a case in which the point-to-corresponding-point error is less than ten pixels for cervical images and twenty-five pixels for lumbar images, results from the proposed segmentation algorithm indicate a 65% success rate for segmentation of cervical vertebrae and a 68% success rate for lumbar vertebrae.