The Experts below are selected from a list of 870 Experts worldwide ranked by ideXlab platform

Mario R Capecchi - One of the best experts on this subject based on the ideXlab platform.

  • targeted disruptions of the murine hoxa 4 and hoxa 6 genes result in homeotic transformations of components of the Vertebral column
    Mechanisms of Development, 1994
    Co-Authors: Dusan Kostic, Mario R Capecchi
    Abstract:

    Abstract It is becoming clear that Hox genes, which encode transcription factors of the Antennapedia homeodomain family, are key players in establishing the body plan of mammalian embryos. They have already been implicated in the formation of the central nervous system, tissues derived from neural crest, the Vertebral column and the limbs. In order to examine the roles of hoxa-4 and hoxa-6 during development, mice with targeted disruptions in these genes were generated. Each shows homeotic transformation of Cervical Vertebrate, at positions that approximate the anterior borders of expression of these genes in the preVertebrae. Defects were not observed in other tissues that normally express these genes. Hoxa-4 − /hoxa-4 − mice show, with 100% penetrance, anterior transformations of the dorsal aspects of the third Cervical Vertebra by acquiring features normally associated with the Second Cervical Vertebra. Mice homozygous for the hoxa-6 mutation show, with incomplete penetrance, even on opposite sides of the same animal, posterior transformations of the seventh Cervical Vertebra to the first thoracic Vertebra. In addition, both hoxa-4 − /hoxa-4 − and hoxa-6 − /hoxa-6 − mice show variability in expressivity. These data indicate that alternative genetic pathways can partially, and at times completely, substitute for the function of these two genes. Other members of these two paralogous Hox families are good candidates for providing the substitutions. As paralogous genes lie on different chromosomes, it is possible to examine the degree of redundancy among these genes by intercrossing mice with the approriate individual disruptions. The analysis of double, triple and even quadruple mutants should determine the ways in which these Hox genes interact in order to specify the multitude of tissues in a restricted region of the developing mouse embryo.

  • mice homozygous for a targeted disruption of hoxd 3 hox 4 1 exhibit anterior transformations of the first and Second Cervical Vertebrae the atlas and the axis
    Development, 1993
    Co-Authors: Brian G Condie, Mario R Capecchi
    Abstract:

    Gene targeting in embryo-derived stem (ES) cells was used to generate mice with a disruption in the homeobox-containing gene Hoxd-3 (Hox-4.1). Mice homozygous for this mutation show a radically remodeled cranioCervical joint. The anterior arch of the atlas is transformed to an extension of the basioccipital bone of the skull. The lateral masses of the atlas also assume a morphology more closely resembling the exoccipitals and, to a variable extent, fuse with the exoccipitals. Formation of the Second Cervical Vertebra, the axis, is also affected. The dens and the superior facets are deleted, and the axis shows ‘atlas-like’ characteristics. An unexpected observation is that different parts of the same Vertebra are differentially affected by the loss of Hoxd-3 function. Some parts are deleted, others are homeotically transformed to more anterior structures. These observations suggest that one role of Hox genes may be to differentially control the proliferation rates of the mesenchymal condensations that give rise to the Vertebral cartilages. Within the mouse Hox complex, paralogous genes not only encode very similar proteins but also often exhibit very similar expression patterns. Therefore, it has been postulated that paralogous Hox genes would perform similar roles. Surprisingly, however, no tissues or structures are affected in common by mutations in the two paralogous genes, Hoxa-3 and Hoxd-3.

G Wilson - One of the best experts on this subject based on the ideXlab platform.

Bernd Turowski - One of the best experts on this subject based on the ideXlab platform.

  • open microsurgical tumor excavation and vertebroplasty for metastatic destruction of the Second Cervical Vertebra outcome in seven cases
    The Spine Journal, 2014
    Co-Authors: Frank W Floeth, Jorg Herdmann, Sascha Rhee, Bernd Turowski, Kara Krajewski, Hansjakob Steiger, Sven O Eicker
    Abstract:

    Abstract Background context Metastatic osteolytic involvement of the Second Cervical Vertebra (C2) is rare, but usually very painful. Percutaneous vertebroplasty has shown to be effective regarding pain control, but carries the risk of cement leakage. Purpose To describe an alternative microsurgical procedure suitable for patients suffering from C2 osteolysis who are considered to be high risk with respect to cement leakage. Study design A technical report. Patient sample It included seven patients. Outcome measures They include the assessment of clinical safety regarding approach- and procedure-related morbidity and radiologic safety regarding extraVertebral cement leakage and the assessment of clinical efficacy by monitoring the pain activity using the visual analog scale (VAS). Materials and methods Seven patients (five men, two women; mean age 70 years) presented with an acute onset of excruciating neck pain (VAS>6) due to osteolytic destruction of the axis Vertebra. There was no neurologic deficit and no compression of the spinal cord preoperatively requiring surgical decompression or stabilization in any of the cases. An open treatment strategy via an anterolateral microsurgical approach was performed. Under biplanar fluoroscopic control, the soft tumor tissue was resected out of the Vertebral body through a drilled entry in the anterior wall. After the excavation procedure, the resection cavity was filled with minimal pressure with polymethylmethacrylate bone cement. Results All patients suffered from severe spontaneous neck pain (mean VAS 8.1, range 6–9), with head motion-dependent pain exacerbation despite high dose of opiates and fixation of the head with a brace.Mean duration of the operative procedure was 51 minutes. Histologic analysis revealed a diagnosis of cancer metastasis in all cases. On average, 1.9 mL cement was placed within the Vertebral body, and no cement leakage was observed in postoperative computed tomography and X-ray controls. All patients experienced immediate pain relief at Day 1 after the procedure (mean VAS 4.0, range 2–6), and a further decrease of pain levels was observed at Week 6 after the completion of radiation therapy (mean VAS 2.0, range 0–5). Conclusions In cases of metastatic C2 destruction, tumor excavation via an anterolateral approach and subsequent filling of the resection cavity with bone cement offers a safe and effective alternative to percutaneous approaches.

  • fatal ethibloc embolization of vertebrobasilar system following percutaneous injection into aneurysmal bone cyst of the Second Cervical Vertebra
    American Journal of Neuroradiology, 2005
    Co-Authors: Bernd Turowski, Jorg Herdmann, Frank Schellhammer, Frank Rommel
    Abstract:

    Peraud et al ([1][1]) reported a fatal injection of Ethibloc into an aneurysmatic bone cyst of C2 due to inadvertent embolization in the vertebrobasilar system. The embolization material was found in a small branch artery of the Vertebral artery at the C2 level. The authors suspect that the

Frank Rommel - One of the best experts on this subject based on the ideXlab platform.

Sang Hyuk Song - One of the best experts on this subject based on the ideXlab platform.

  • 36 Copyright © 2012. The Korean Society for Radiation Oncology Radial displacement of clinical target volume in node negative head and neck cancer
    2016
    Co-Authors: Wan Jeon, Sang Hyuk Song, Jung-in Kim
    Abstract:

    Purpose: To evaluate the radial displacement of clinical target volume in the patients with node negative head and neck (H&N) cancer and to quantify the relative positional changes compared to that of normal healthy volunteers. Materials and Methods: Three node-negative H&N cancer patients and fi ve healthy volunteers were enrolled in this study. For setup accuracy, neck thermoplastic masks and laser alignment were used in each of the acquired computed tomography (CT) images. Both groups had total three sequential CT images in every two weeks. The lymph node (LN) level of the neck was delineated based on the Radiation Therapy Oncology Group (RTOG) consensus guideline by one physician. We use the Second Cervical Vertebra body as a reference point to match each CT image set. Each of the sequential CT images and delineated neck LN levels were fused with the primary image, then maximal radial displacement was measured at 1.5 cm intervals from skull base (SB) to caudal margin of LN level V, and the volume differences at each node level were quantifi ed. Results: The mean radial displacements were 2.26 (±1.03) mm in the control group and 3.05 (±1.97) in the H&N cancer patients. There was a statistically signifi cant difference between the groups in terms of the mean radial displacement (p = 0.03). In addition, the mean radial displacement increased with the distance from SB. As for the mean volume differences, there was no statistical signifi cance between the two groups. Conclusion: This study suggests that a more generous radial margin should be applied to the lower part of the neck LN for bette

  • radial displacement of clinical target volume in node negative head and neck cancer
    Radiation oncology journal, 2012
    Co-Authors: Wan Jeon, Honggyun Wu, Sang Hyuk Song
    Abstract:

    Purpose: To evaluate the radial displacement of clinical target volume in the patients with node negative head and neck (H&N) cancer and to quantify the relative positional changes compared to that of normal healthy volunteers. Materials and Methods: Three node-negative H&N cancer patients and fi ve healthy volunteers were enrolled in this study. For setup accuracy, neck thermoplastic masks and laser alignment were used in each of the acquired computed tomography (CT) images. Both groups had total three sequential CT images in every two weeks. The lymph node (LN) level of the neck was delineated based on the Radiation Therapy Oncology Group (RTOG) consensus guideline by one physician. We use the Second Cervical Vertebra body as a reference point to match each CT image set. Each of the sequential CT images and delineated neck LN levels were fused with the primary image, then maximal radial displacement was measured at 1.5 cm intervals from skull base (SB) to caudal margin of LN level V, and the volume differences at each node level were quantifi ed. Results: The mean radial displacements were 2.26 (±1.03) mm in the control group and 3.05 (±1.97) in the H&N cancer patients. There was a statistically signifi cant difference between the groups in terms of the mean radial displacement (p = 0.03). In addition, the mean radial displacement increased with the distance from SB. As for the mean volume differences, there was no statistical signifi cance between the two groups. Conclusion: This study suggests that a more generous radial margin should be applied to the lower part of the neck LN for better clinical target coverage and dose delivery.