Biomedical subjects

Michael Olson

Publications and source records attributed to Michael Olson.

5 recordsLinked to original sources

PubMed2022

Genomic Study on Blood Culture Isolates From Patients With Staphylococcus Infection-associated Glomerulonephritis.

INTRODUCTION: Staphylococcus infection-associated glomerulonephritis (SAGN), is an autoimmune sequela of infection affecting a subset of infected patients without specific predictive factors, frequently presenting with acute nephritic syndrome and propensity for chronic kidney disease. We performed a comparative genotypic and phenotypic analysis of S. aureus isolates from patients that did and those that did not develop SAGN. METHODS: We had 22 culture-proven cases of SAGN from Ohio State University Wexner Medical Center (OSUWMC) from 2004 to 2016, 9 of 22 being blood cultures, with archived isolates. These, along with blood culture isolates from 12 patients with no clinical evidence of SAGN (between ages 40 to 80 years) over the same period were used for genotyping. For host demographic comparison, we used all available SAGN cases (n = 85, including those with positive cultures other than blood; and patients with kidney biopsies received from referring hospitals) and all OSUWMC patients with positive Staphylococcus cultures without glomerulonephritis (GN) (n = 23,496). RESULTS: Multiple sequence types (STs) suggesting strain diversity was seen in the GN isolates with mainly clonal complexes (CC) 5 and 59. Mutations in the agr operon were identified in significantly higher number of the GN isolates (83%) than non-GN isolates (16%). Significant differences in β-hemolysis and biofilm formation was also observed between the groups. CONCLUSION: The functionality of these agr mutants remains to be seen, but the presently known effects of reduced agr function, namely increased surface adhesins, biofilm formation, and persistent bacteremia could be important microbial factors predisposing to SAGN and testing for them early during infection could help to predict its development.

MRSA↗

PubMed2005

Flexion-relaxation response to gravity.

The objective of this report was to study the influence of the orientation of gravitational loading on the behavior of anterior and posterior trunk muscles during anterior trunk flexion-extension. Participants (N=13) performed five (5) cycles of trunk flexion-extension while standing with gravity parallel to the body axis and five (5) cycles while in the supine condition (e.g. sit-ups) with gravity perpendicular to the body axis. Surface electromyographic (EMG) patterns from lumbar paraspinal, rectus abdominis, external oblique, rectus femoris, semimembranosis, and biceps femoris muscles were analyzed during each condition. EMG signals were synchronized with lumbar flexion and trunk inclination angles. Flexion-extension from the standing position resulted in a myoelectric silent period of the lumbar posterior muscles (e.g. flexion-relaxation phenomena (FRP)) as well as the hamstring muscles through deep angles during which activity was observed in abdominal muscles. Flexion-extension during sit-ups, however, resulted in a myoelectric silent period of the abdominal muscles and the quadriceps through deep angles during which the lumbar posterior muscles were active. In this condition, the FRP was not observed in posterior muscles. The new findings demonstrate the profound impact of the orientation of the gravity vector on the FRP, the abdominal muscles reaction to gravitational loads during sit-ups and its relationships with lumbar antagonists and thigh musculature. The new findings suggest that gravitational moments requirements dominate the FRP through the prevailing kinematics, load sharing and reflex activation-inhibition of muscles in various conditions. Lumbar kinematics or fixed sensory motor programs by themselves, however, are not the major contributor to the FRP. The new findings improve our insights into spinal biomechanics as well as understanding and evaluating low back disorders.

Adolescent↗

PubMed2005

The assessment of chronic health conditions on work performance, absence, and total economic impact for employers.

OBJECTIVE: The objective of this study was to determine the prevalence and estimate total costs for chronic health conditions in the U.S. workforce for the Dow Chemical Company (Dow). METHODS: Using the Stanford Presenteeism Scale, information was collected from workers at five locations on work impairment and absenteeism based on self-reported "primary" chronic health conditions. Survey data were merged with employee demographics, medical and pharmaceutical claims, smoking status, biometric health risk factors, payroll records, and job type. RESULTS: Almost 65% of respondents reported having one or more of the surveyed chronic conditions. The most common were allergies, arthritis/joint pain or stiffness, and back or neck disorders. The associated absenteeism by chronic condition ranged from 0.9 to 5.9 hours in a 4-week period, and on-the-job work impairment ranged from a 17.8% to 36.4% decrement in ability to function at work. The presence of a chronic condition was the most important determinant of the reported levels of work impairment and absence after adjusting for other factors (P < 0.000). The total cost of chronic conditions was estimated to be 10.7% of the total labor costs for Dow in the United States; 6.8% was attributable to work impairment alone. CONCLUSION: For all chronic conditions studied, the cost associated with performance based work loss or "presenteeism" greatly exceeded the combined costs of absenteeism and medical treatment combined.

Absenteeism↗

PubMed2003

Genome diversification in phylogenetic lineages I and II of Listeria monocytogenes: identification of segments unique to lineage II populations.

Thirteen different serotypes of Listeria monocytogenes can be distinguished on the basis of variation in somatic and flagellar antigens. Although the known virulence genes are present in all serotypes, greater than 90% of human cases of listeriosis are caused by serotypes 1/2a, 1/2b, and 4b and nearly all outbreaks of food-borne listeriosis have been caused by serotype 4b strains. Phylogenetic analysis of these three common clinical serotypes places them into two different lineages, with serotypes 1/2b and 4b belonging to lineage I and 1/2a belonging to lineage II. To begin examining evolution of the genome in these serotypes, DNA microarray analysis was used to identify lineage-specific and serotype-specific differences in genome content. A set of 44 strains representing serotypes 1/2a, 1/2b, and 4b was probed with a shotgun DNA microarray constructed from the serotype 1/2a strain 10403s. Clones spanning 47 different genes in 16 different contiguous segments relative to the lineage II 1/2a genome were found to be absent in all lineage I strains tested (serotype 4b and 1/2b) and an additional nine were altered exclusively in 4b strains. Southern hybridization confirmed that conserved alterations were, in all but two loci, due to absence of the segments from the genome. Genes within these contiguous segments comprise five functional categories, including genes involved in synthesis of cell surface molecules and regulation of virulence gene expression. Phylogenetic reconstruction and examination of compositional bias in the regions of difference are consistent with a model in which the ancestor of the two lineages had the 1/2 somatic serotype and the regions absent in the lineage I genome arose by loss of ancestral sequences.

Biological Transport↗

PubMed2002

Post-cytochrome C protection from apoptosis conferred by a MAPK pathway in Xenopus egg extracts.

In response to many different apoptotic stimuli, cytochrome c is released from the intermembrane space of the mitochondria into the cytoplasm, where it serves as a cofactor in the activation of procaspase 9. Inhibition of this process can occur either by preventing cytochrome c release or by blocking caspase activation or activity. Experiments involving in vitro reconstitution of apoptosis in cell-free extracts of Xenopus laevis eggs have suggested that extracts arrested in interphase are susceptible to an endogenous apoptotic program leading to caspase activation, whereas extracts arrested in meiotic metaphase are not. We report here that Mos/MEK/MAPK pathways active in M phase-arrested eggs are responsible for rendering them refractory to apoptosis. Interestingly, M phase-arrested extracts are competent to release cytochrome c, yet still do not activate caspases. Concomitantly, we have also demonstrated that recombinant Mos, MEK, and ERK are sufficient to block cytochrome c-dependent caspase activation in purified Xenopus cytosol, which lacks both transcription and translation. These data indicate that the MAP kinase pathway can target and inhibit post-cytochrome c release apoptotic events in the absence of new mRNA/protein synthesis and that this biochemical pathway is responsible for the apoptotic inhibition observed in meiotic X. laevis egg extracts.

Animals↗