Age- and gender-specific normative data on computerized dynamic posturography in a cohort of Danish adults.

PURPOSE: Balance performance can be measured with a computerized dynamic posturography (CDP). Frequently used CDP protocols include the sensory organization test (SOT), motor control test (MCT) and adaptation test (ADT). The primary aim of this study was to produce normative data using the Bertec® Balance Advantage CDP on a cohort of healthy adults aged 20-79 years for the SOT, MCT and ADT. The secondary aim was to determine age- and gender-related differences. METHODS: The study population of 120 participants were divided into age groups of 20-29, 30-39 years, etc., with an equal number of men and women in each group. Using the Bertec® CDP, the SOT, MCT and ADT protocols were performed. RESULTS: SOT found that the 70-79 age group and men scored lower equilibrium scores (ES) on SOT4, and SOT6. Women had higher ES on SOT1. For the MCT, backward translation. latencies were higher for the 60 s and 70 s age groups. The 60 s age group had higher forward translation latencies. Women had lower latencies on all MCTs. For the ADT toes up test, the 70-79 age group scored higher sway energy. On the toes down test, higher sway energy was registered for the 50-79 age groups. Women had lower sway energy for both ADT's. CONCLUSION: We have produced normative data for healthy adults aged 20-79 years for the SOT, MCT and ADT protocols using the Bertec® Balance Advantage CDP. Balance performance differences might be due to decline in visual acuity, presbyvestibulopathy and differences in body composition.

Expected gene-order distances and model selection in bacteria.

MOTIVATION: The evolutionary distance inferred from gene-order comparisons of related bacteria is dependent on the model. Therefore, it is highly important to establish reliable assumptions before inferring its magnitude. RESULTS: We investigate the patterns of dotplots between species of bacteria with the purpose of model selection in gene-order problems. We find several categories of data which can be explained by carefully weighing the contributions of reversals, transpositions, symmetrical reversals, single gene transpositions and single gene reversals. We also derive method of moments distance estimates for some previously uncomputed cases, such as symmetrical reversals, single gene reversals and their combinations, as well as the single gene transpositions edit distance.

Measuring genome divergence in bacteria: a case study using chlamydian data.

We have studied the relative contribution of inversions, transpositions, deletions, and nucleotide substitutions to the evolution of Chlamydia trachomatis and Chlamydia pneumoniae. The minimal number of rearrangement events required for converting the gene order structure of one genome into that of the other was estimated to 59 +/- 6 events, including 13% inversions, 38% short inversions, and 49% transpositions. In contrast to previous findings, no examples of horizontal gene transfer subsequent to species divergence were identified, nor any evidence for an excessive number of tandem gene duplications. A statistical model was used to compare nucleotide frequencies for a set of genes uniquely present in one species to a set of orthologous genes present in both species. The two data sets were not significantly different, which is indicative of a low frequency of horizontal gene transfer events. This is based on the assumption that a foreign gene of different nucleotide content will not have become completely ameliorated, as verified by simulations of the amelioration rate at twofold and fourfold degenerate codon sites. The frequencies of nucleotide substitutions at twofold and fourfold degenerate sites, deletions, inversions, and translocations were estimated to 1.42, 0.62, 0.18, 0.01, and 0.01 per site, respectively.