Radial Head Stability in Anterior Monteggia Injuries: An In Vitro Biomechanical Study

Anterior Monteggia fracture-dislocations are frequently complicated by persistent radial head instability leading to suboptimal outcomes. In this biomechanical investigation using a cadaveric elbow motion simulator, we examined the effects of ulnar extension angulation, soft tissue disruption, biceps loading and elbow motion on radial head translation. Our results showed significant anterior radial head translation with progressive ulnar extension angulation, with greater soft tissue injuries and increased biceps loading (P=.000). There was no significant difference in radial head translation between simulated active and passive elbow flexion (P=.251). These findings support the importance of an anatomic reduction of the ulnar fracture. However, in cases with significant soft tissue disruption, even an anatomic reduction of the ulna may not be sufficient to restore radial head alignment. Moreover, postoperative immobilization with the elbow in a flexed position to avoid elbow motion and to relax the biceps should be considered in patients with unstable Monteggia injuries

Selecting and representing information structures for battlefield decision systems

Issued as Progress reports no. [1-2], and Final report, Project no. G-36-62

Role of Retrotransposons as a Major Source of Intra- and Inter-Individual Epigenetic Variations in the Mammalian Genome

Transcription of retrotransposons is usually repressed by DNA methylation, but a few elements partially escape this repression mechanism. I used two approaches as my dissertation study to identify unmethylated intracisternal A-particles (IAPs) and also to understand why some of IAPs escape DNA methylation-mediated repression. Firstly, I sought to catalog the retrotransposons (LTRs and LINEs only) in the mouse genome known as ‘epialleles’ which escape the repression variably even in individuals with an identical genome sequence. Using bioinformatic approaches, 143 candidate epialleles were first identified based on their promoter activity and association with active histone modification marks. Detailed methylation analyses suggested that a subset of these elements showed variable levels of DNA methylation inter-individually, revealing their stochastic nature (metastability) of DNA methylation. The analyses also identified two opposite patterns of DNA methylation, progressive gaining versus losing, during development. qRT-PCR analyses demonstrated that the expression levels of these elements are indeed variable among the individual mice, suggesting functional consequences on their associated endogenous genes. Next, for a large scale individual element or loci-based methylation analyses of the candidate epiallele IAPLTRs and other repeat elements, we proposed and validated a novel high-throughput targeted repeat element bisulfite sequencing (HT-TREBS) technique. We obtained CpG methylation data of 5135 loci of five IAPLTR subtypes in three different tissues of four 1-week-old mouse littermates. An average of 52,000 CpG positions per sample with average sequencing depth of 117x was reported. More than 80% of the targeted subtype loci and less than 15% of the non-targeted subtype loci of IAPLTRs have been covered by this technique. Data analyses revealed that 2% of the IAPLTR loci have less than 80% average CpG methylation with no genomic position preference and the majority of these loci are of the IAPLTR2 and IAPLTR2a subtypes. Further analyses also revealed extensive tissue-specific, individual-specific (epialleles), stochastic (random), and even sex-specific CpG methylation variations in the IAPLTR loci. Overall, our data confirmed the presence of many new retrotransposon-derived epialleles and other epigenetic variations. Our efficient and robust technique HT-TREBS also provided a lot of novel insight in to the epigenome of the IAPLTR repeat elements

A workshop on the gathering of information for problem formulation

Issued as Quarterly progress reports no. [1-5], Proceedings and Final contract report, Project no. G-36-651Papers presented at the Workshop/Symposium on Human Computer Interaction, March 26 and 27, 1981, Atlanta, G