T1rho and T2 mapping of ankle cartilage of female and male ballet dancers.

BACKGROUND: Since ballet dancers begin their training before skeletal maturity, accurate and non-invasive identification of cartilage diseases is clinically important. Angle-dependent analysis of T1rho and T2 sequences can be useful for quantification of the composition of cartilage. PURPOSE: To investigate the angle-dependent T1rho and T2 profiles of ankle cartilage in non-dancers and dancers. MATERIAL AND METHODS: Ten female non-dancers, ten female dancers, and 9 male dancers were evaluated using T1rho and T2 mapping sequences. Manual segmentation of talar and tibial cartilage on these images was performed by two radiologists. Inter- and intra-rater reliabilities were calculated using intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Mean thickness and volume of cartilage were estimated. Angle-dependent relaxation time profiles of talar and tibial cartilage were created. RESULTS: ICCs of the number of segmented pixels were poor to excellent. Bland-Altman plots indicated that differences were associated with segment sizes. Segmented cartilage on T1rho demonstrated larger thickness and volume than those on T2 in all populations. Male dancers showed larger cartilage thickness and volume than female dancers and non-dancers. Each cartilage demonstrated angular-dependent T1rho and T2 profiles. Minimal T1rho and T2 values were observed at approximately 180°-200°; higher values were seen at the angle closer to the magic angle. Minimal T2 value of talar cartilage of dancers was larger than that of non-dancers. CONCLUSION: In this small cohort study, regional and sex variations of ankle cartilage T1rho and T2 values in dancers and non-dancers were demonstrated using an angle-dependent approach.

DNA recognition by a σ(54) transcriptional activator from Aquifex aeolicus.

Transcription initiation by bacterial σ(54)-polymerase requires the action of a transcriptional activator protein. Activators bind sequence-specifically upstream of the transcription initiation site via a DNA-binding domain (DBD). The structurally characterized DBDs from activators all belong to the Fis (factor for inversion stimulation) family of helix-turn-helix DNA-binding proteins. We report here structures of the free and DNA-bound forms of the DBD of NtrC4 (4DBD) from Aquifex aeolicus, a member of the NtrC family of σ(54) activators. Two NtrC4-binding sites were identified upstream (-145 and -85bp) from the start of the lpxC gene, which is responsible for the first committed step in lipid A biosynthesis. This is the first experimental evidence for σ(54) regulation in lpxC expression. 4DBD was crystallized both without DNA and in complex with the -145-binding site. The structures, together with biochemical data, indicate that NtrC4 binds to DNA in a manner that is similar to that of its close homolog, Fis. The greater sequence specificity for the binding of 4DBD relative to Fis seems to arise from a larger number of base-specific contacts contributing to affinity than for Fis.

Rib head protrusion into the central canal in type 1 neurofibromatosis.

BACKGROUND: Intraspinal rib head dislocation is an important but under-recognized consequence of dystrophic scoliosis in patients with neurofibromatosis 1 (NF1). OBJECTIVE: To present clinical and imaging findings of intraspinal rib head dislocation in NF1. MATERIALS AND METHODS: We retrospectively reviewed clinical presentation, imaging, operative reports and post-operative courses in four NF1 patients with intraspinal rib head dislocation and dystrophic scoliosis. We also reviewed 17 cases from the English literature. RESULTS: In each of our four cases of intraspinal rib head dislocation, a single rib head was dislocated on the convex apex of the curve, most often in the mid- to lower thoracic region. Cord compression occurred in half of these patients. Analysis of the literature yielded similar findings. Only three cases in the literature demonstrates the MRI appearance of this entity; most employ CT. All of our cases include both MRI and CT; we review the subtle findings on MRI. CONCLUSION: Although intraspinal rib head dislocation is readily apparent on CT, sometimes MRI is the only cross-sectional imaging performed. It is essential that radiologists become familiar with this entity, as subtle findings have significant implications for surgical management.

Advances in spinal fusion.

Since its initial description about a century ago, spinal fusion has become a common surgical intervention in the treatment of various debilitating spinal disorders. However, given the complexities and demands of the procedure, patient selection remains a key component in the success of the operation. In this article, we will review the various indications for spinal fusion, the current advances in fusion techniques, as well as the potential complications associated with the procedure.