Biomedical subjects

Richard M Single

Publications and source records attributed to Richard M Single.

4 recordsLinked to original sources

PubMed2003

Surface EMG electrodes do not accurately record from lumbar multifidus muscles.

OBJECTIVE: This study investigated whether electromyographic signals recorded from the skin surface overlying the multifidus muscles could be used to quantify their activity. DESIGN: Comparison of electromyography signals recorded from electrodes on the back surface and from wire electrodes within four different slips of multifidus muscles of three human subjects performing isometric tasks that loaded the trunk from three different directions. BACKGROUND: It has been suggested that suitably placed surface electrodes can be used to record activity in the deep multifidus muscles. METHODS: We tested whether there was a stronger correlation and more consistent regression relationship between signals from electrodes overlying multifidus and longissimus muscles respectively than between signals from within multifidus and from the skin surface electrodes over multifidus. RESULTS: The findings provided consistent evidence that the surface electrodes placed over multifidus muscles were more sensitive to the adjacent longissimus muscles than to the underlying multifidus muscles. The R(2) for surface versus intra-muscular comparisons was 0.64, while the average R(2) for surface-multifidus versus surface-longissimus comparisons was 0.80. Also, the magnitude of the regression coefficients was less variable between different tasks for the longissimus versus surface multifidus comparisons. CONCLUSIONS: Accurate measurement of multifidus muscle activity requires intra-muscular electrodes. RELEVANCE: Electromyography is the accepted technique to document the level of muscular activation, but its specificity to particular muscles depends on correct electrode placement. For multifidus, intra-muscular electrodes are required.

Action Potentials↗

PubMed2003

Breast cancer survival according to number of nodes removed.

BACKGROUND: Results from randomized trials indicate a 5.4% survival advantage associated with axillary dissection. To gain insight on survival outcomes when less than an axillary dissection is performed, we performed a retrospective analysis to determine survival outcome for node-negative and node-positive breast cancer patients when a variable number of nodes were excised. METHODS: The data analyzed in this paper are from the Surveillance, Epidemiology, and End Results (SEER) database, from which 72,102 patients were selected whose breast cancer had been diagnosed in 1988 or later and who were aged 40-79 years at diagnosis, had a single primary lesion, and had 0 to 3 positive lymph nodes. Cases were separated into age groups (40 to 49 and 50 to 79 years), and node-negative cases were separated from those with one to three positive nodes. RESULTS: This analysis indicates that even when all regional lymph nodes are pathologically negative, the number of nodes removed is associated with survival. In the group of breast cancer patients who had one to three pathologically positive nodes, as with the node-negative group, the higher the number of nodes removed, the greater the survival. The hazard rate for death in the node-negative group was roughly 5% less for each additional five nodes removed. For the node-positive group, the hazard rate for death was between 8% and 9% less for each additional five nodes removed. CONCLUSIONS: This retrospective study supports the notion that removal of regional nodes, even when such nodes are interpreted as pathologically negative, is important for the long-term survival of breast cancer patients.

Adult↗

PubMed2003

PyPop: a software framework for population genomics: analyzing large-scale multi-locus genotype data.

Software to analyze multi-locus genotype data for entire populations is useful for estimating haplotype frequencies, deviation from Hardy-Weinberg equilibrium and patterns of linkage disequilibrium. These statistical results are important to both those interested in human genome variation and disease predisposition as well as evolutionary genetics. As part of the 13th International Histocompatibility and Immunogenetics Working Group (IHWG), we have developed a software framework (PyPop). The primary novelty of this package is that it allows integration of statistics across large numbers of data-sets by heavily utilizing the XML file format and the R statistical package to view graphical output, while retaining the ability to inter-operate with existing software. Largely developed to address human population data, it can, however, be used for population based data for any organism. We tested our software on the data from the 13th IHWG which involved data sets from at least 50 laboratories each of up to 1000 individuals with 9 MHC loci (both class I and class II) and found that it scales to large numbers of data sets well.

Computational Biology↗

PubMed2002

Haplotype frequency estimation in patient populations: the effect of departures from Hardy-Weinberg proportions and collapsing over a locus in the HLA region.

Haplotype analyses are an important area in the study of the genetic components of human disease. Associations between markers and disease loci that are not evident with a single marker locus may be identified in multi-locus marker analyses using estimated haplotype frequencies (HFs). Procedures that make use of the expectation-maximization (EM) algorithm to estimate HFs from unphased genotype data are in common use in genetic studies. The EM algorithm uses these unphased genotype frequencies along with the assumption of Hardy-Weinberg proportions (HWP) to converge on HF estimates. In this paper, we assess the accuracy of EM estimates of HFs in patients with type I diabetes for whom the true haplotypes are known, but the data are analyzed ignoring family information to allow comparison between estimated and true frequencies. The data consist of six HLA loci with high levels of polymorphism and a range of departures from HWP and linkage equilibrium. While the overall accuracy of the EM estimates is good, there can be large over- and underestimates of particular HFs, even for common haplotypes, especially when the loci involved deviate significantly from HWP. Estimating HFs for three or more loci and then collapsing over loci so as to generate two locus haplotypes can improve the accuracy of the estimation. The collapsing procedure is most beneficial when one of the loci in the two-locus haplotype of interest deviates significantly from HWP and the locus collapsed over is in linkage disequilibrium with the other loci.

Algorithms↗