Reconstitution of bone-like matrix in osteogenically differentiated mesenchymal stem cells-collagen constructs: a three-dimensional in vitro model to study hematopoietic stem cell niche

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The Pattern of R2 Retrotransposon Activity in Natural Populations of Drosophila simulans Reflects the Dynamic Nature of the rDNA Locus

The pattern and frequency of insertions that enable transposable elements to remain active in a population are poorly understood. The retrotransposable element R2 exclusively inserts into the 28S rRNA genes where it establishes long-term, stable relationships with its animal hosts. Previous studies with laboratory stocks of Drosophila simulans have suggested that control over R2 retrotransposition resides within the rDNA loci. In this report, we sampled 180 rDNA loci of animals collected from two natural populations of D. simulans. The two populations were found to have similar patterns of R2 activity. About half of the rDNA loci supported no or very low levels of R2 transcripts with no evidence of R2 retrotransposition. The remaining half of the rDNA loci had levels of R2 transcripts that varied in a continuous manner over almost a 100-fold range and did support new retrotransposition events. Structural analysis of the rDNA loci in 18 lines that spanned the range of R2 transcript levels in these populations revealed that R2 number and rDNA locus size varied 2-fold; however, R2 activity was not readily correlated with either of these parameters. Instead R2 activity was best correlated with the distribution of elements within the rDNA locus. Loci with no activity had larger contiguous blocks of rDNA units free of R2-insertions. These data suggest a model in which frequent recombination within the rDNA locus continually redistributes R2-inserted units resulting in changing levels of R2 activity within individual loci and persistent R2 activity within the population

Right hip adduction deficit and adolescent idiopathic scoliosis.

PURPOSE: To determine whether right hip adduction deficit is associated with adolescent idiopathic scoliosis. METHODS: 102 adolescents (mean age, 14 years) with idiopathic scoliosis were prospectively studied. Their spinal curve pattern (according to Lenke's classification), curve severity (by Cobb's angle), and hip adduction ranges of both sides were recorded. Additional factors that may affect hip adduction range including the preferred leg during standing, the presence of hip flexor tightness, and the side of the dominant leg were also assessed. RESULTS: The mean Cobb's angle was 27 degrees. The difference in hip adduction range between the right and left hips was 5 degrees (p10 degrees of right hip adduction deficit were associated with a higher proportion of left leg dominance than those with less than or equal to 10 degrees of right hip adduction deficit (18% vs 4%). CONCLUSION: Left leg dominance may play a role in right hip adduction deficit and scoliosis.link_to_subscribed_fulltex

A 3D in vitro model to study interactions between HSCs and their niche cells

Oral Presentation - Concurrent Session