Theory-Assessment in the Historiography of Science

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Biomineralisation in the Palaeozoic oceans: evidence for simultaneous crystallisation of high and low magnesium calcite by phacopine trilobites

The chemical composition and microstructure of the calcite cuticles of eleven species of phacopine trilobites have been investigated by electron beam imaging, diffraction, and microanalysis, and results reveal that the lenses of their schizochroal eyes differed significantly in chemical composition from the rest of the cuticle in vivo. Apart from the eye lenses, most cuticles are inferred to have escaped extensive recrystallisation because their constituent crystals are sub-micrometre in size and have a preferred orientation that is consistent between species. Their current compositions of ~1.4 to 2.4 mol% MgCO3 are likely to be close to original values, although as they commonly luminesce and contain detectable manganese and iron, some diagenetic alteration has taken place. The associated lenses have a microstructure that is suitable for focusing light, yet are optically turbid owing to the presence within calcite of micropores and crystals of microdolomite, apatite, celestite and pyrite. The microdolomite indicates that lenses recrystallised from an original high-Mg calcite composition and this is supported by the presence of nanometre-scale modulated microstructures in both the calcite and dolomite. These lenses currently contain ~1 to 6 mol% MgCO3, and by comparison with the proportion of magnesium lost from echinoderm stereom in the same thin sections, may have contained ~7.5 mol% MgCO3 in vivo. In some samples, more extensive diagenetic alteration is evidenced by recrystallisation of the cuticle including lenses to coarse equant calcite or enrichment of the cuticle, but not necessarily the lenses, in magnesium accompanying replacement by a Mg–Fe phyllosilicate. The phacopine trilobites had to modify partition coefficients for magnesium considerably in order to grow lenses with contrasting compositions to the rest of their cuticles, and such a strong vital effect on biomineralisation suggests that incorporation of magnesium was essential for functioning of their calcite optical s

The variable region of the pneumococcal pathogenicity island 1 is responsible for the unusually high virulence of a serotype 1 isolate

Streptococcus pneumoniae is the leading infectious cause of death in children in the world. However, the mechanisms that drive the progression from asymptomatic colonization to disease are poorly understood. Two virulence-associated genomic accessory regions (ARs) were deleted in a highly virulent serotype 1 clinical isolate (strain 4496) and examined for their contribution to pathogenesis. Deletion of a prophage encoding a platelet-binding protein (PblB) resulted in reduced adherence, biofilm formation, reduced initial infection within the lungs, and a reduction in the number of circulating platelets in infected mice. However, the region’s overall contribution to the survival of mice was not significant. In contrast, deletion of the variable region of pneumococcal pathogenicity island 1 (vPPI1) was also responsible for a reduction in adherence and biofilm formation but also reduced survival and invasion of the pleural cavity, blood, and lungs. While the 4496�PPI1 strain induced higher expression of the genes encoding interleukin-10 (IL-10) and CD11b in the lungs of challenged mice than the wild-type strain, very few other genes exhibited altered expression. Moreover, while the level of IL-10 protein was increased in the lungs of 4496�PPI1 mutant-infected mice compared to strain 4496-infected mice, the levels of gamma interferon (IFN-�), CXCL10, CCL2, and CCL4 were not different in the two groups. However, the 4496�PPI1 mutant was found to be more susceptible than the wild type to phagocytic killing by a macrophage-like cell line. Therefore, our data suggest that vPPI1 may be a major contributing factor to the heightened virulence of certain serotype 1 strains, possibly by influencing resistance to phagocytic killing

Apathy Is Associated With Ventral Striatum Volume in Schizophrenia Spectrum Disorder

Apathy is prevalent in schizophrenia, but its etiology has received little investigation. The ventral striatum (VS), a key brain region involved in motivated behavior, has been implicated in studies of apathy. We therefore evaluated whether apathy is associated with volume of the VS on MRI in 23 patients with schizophrenia using voxel-based morphometry. Results indicated that greater self-reported apathy severity was associated with smaller volume of the right VS even when controlling for age, gender, depression, and total gray matter volume. The finding suggests that apathy is related to abnormality of brain circuitry subserving motivated behavior in patients with schizophrenia

Comparison of Season-Long Diffusivity Measures in a Cohort of Non-Concussed Contact and Non-Contact Athletes

Introduction: Concern surrounding short- and long-term consequences of participation in contact sports has become a significant public health topic. Previous literature utilizing diffusion tensor imaging in sports-related concussion has exhibited notable variety of analysis methods and analyzed regions of interest, and largely focuses on acute effects of concussion. The current study aimed to compare diffusivity metrics across a single season within athlete cohorts with no history of concussion. Methods: A prospective cohort of 75 contact and 79 non-contact division I athletes were compared across diffusion tensor imaging metrics (i.e. TRACULA); examinations were also performed assessing the relationship between neuroimaging metrics, head impact exposure metrics (in-helmet accelerometer), and neurocognitive variables. Assessment occurred at pre-and post-season time points. Results: Seasonal changes in fractional anisotropy and mean diffusivity values did not differ between athlete cohorts, nor did they differ within cohort groups, across pre- and post-season scans. Specific to contact athletes, positive associations were found between uncinate fasciculus mean diffusivity values and season linear acceleration (p =.018), season rotational acceleration (p =.017), and season hit severity (p =.021). Conclusions: Results suggest an influence of impact frequency, type, and severity on white matter integrity in select brain regions in contact athletes. Current findings expand our knowledge of anatomical changes over the course of a single season, and underscore the importance of considering methodology when interpreting findings in this population, as differing image analysis techniques may lead to different conclusions regarding significant effects

Test–retest, retest, and retest: Growth curve models of repeat testing with Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT)

Computerized neuropsychological testing has become an important tool in the identification and management of sports-related concussions; however, the psychometric effect of repeat testing has not been studied extensively beyond test–retest statistics. The current study analyzed data from Division I collegiate athletes who completed Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) baseline assessments at four sequential time points that varied over the course of their athletic careers. Administrations were part of a larger National Institutes of Health (NIH) study. Growth curve modeling showed that the two memory composite scores increased significantly with successive administrations: Change in Verbal Memory was best represented with a quadratic model, while a linear model best fit Visual Memory. Visual Motor Speed and Reaction Time composites showed no significant linear or quadratic growth. The results demonstrate the effect of repeated test administrations for memory composite scores, while speed composites were not significantly impacted by repeat testing. Acceptable test–retest reliability was demonstrated for all four composites as well

Effect of head impacts on diffusivity measures in a cohort of collegiate contact sport athletes

Objective: To determine whether exposure to repetitive head impacts over a single season affects white matter diffusion measures in collegiate contact sport athletes. Methods: A prospective cohort study at a Division I NCAA athletic program of 80 nonconcussed varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration time history of the head following impact, and 79 non–contact sport athletes. Assessment occurred preseason and shortly after the season with diffusion tensor imaging and neurocognitive measures. Results: There was a significant (p 5 0.011) athlete-group difference for mean diffusivity (MD) in the corpus callosum. Postseason fractional anisotropy (FA) differed (p 5 0.001) in the amygdala (0.238 vs 0.233). Measures of head impact exposure correlated with white matter diffusivity measures in several brain regions, including the corpus callosum, amygdala, cerebellar white matter, hippocampus, and thalamus. The magnitude of change in corpus callosum MD postseason was associated with poorer performance on a measure of verbal learning and memory. Conclusion: This study suggests a relationship between head impact exposure, white matter diffusion measures, and cognition over the course of a single season, even in the absence of diagnosed concussion, in a cohort of college athletes. Further work is needed to assess whether such effects are short term or persisten

Platelet‐Derived Growth Factor Stimulates Bone Fill and Rate of Attachment Level Gain: Results of a Large Multicenter Randomized Controlled Trial

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141430/1/jper2205.pd