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101 result(s) for "Steward, Christopher"
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Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study
Lyme borreliosis is the most common tick-borne disease in the northern hemisphere. It is a multisystem disease caused by Borrelia burgdorferi sensu lato genospecies and characterised by tissue localisation and low spirochaetaemia. In this study we aimed to describe a novel Borrelia species causing Lyme borreliosis in the USA. At the Mayo clinic, from 2003 to 2014, we tested routine clinical diagnostic specimens from patients in the USA with PCR targeting the oppA1 gene of B burgdorferi sensu lato. We identified positive specimens with an atypical PCR result (melting temperature outside of the expected range) by sequencing, microscopy, or culture. We collected Ixodes scapularis ticks from regions of suspected patient tick exposure and tested them by oppA1 PCR. 100 545 specimens were submitted by physicians for routine PCR from Jan 1, 2003 to Sept 30, 2014. From these samples, six clinical specimens (five blood, one synovial fluid) yielded an atypical oppA1 PCR product, but no atypical results were detected before 2012. Five of the six patients with atypical PCR results had presented with fever, four had diffuse or focal rash, three had symptoms suggestive of neurological inclusion, and two were admitted to hospital. The sixth patient presented with knee pain and swelling. Motile spirochaetes were seen in blood samples from one patient and cultured from blood samples from two patients. Among the five blood specimens, the median oppA1 copy number was 180 times higher than that in 13 specimens that tested positive for B burgdorferi sensu stricto during the same time period. Multigene sequencing identified the spirochaete as a novel B burgdorferi sensu lato genospecies. This same genospecies was detected in ticks collected at a probable patient exposure site. We describe a new pathogenic Borrelia burgdorferi sensu lato genospecies (candidatus Borrelia mayonii) in the upper midwestern USA, which causes Lyme borreliosis with unusually high spirochaetaemia. Clinicians should be aware of this new B burgdorferi sensu lato genospecies, its distinct clinical features, and the usefulness of oppA1 PCR for diagnosis. US Centers for Disease Control and Prevention Epidemiology and Laboratory Capacity for Infectious Diseases (ELC) Cooperative Agreement and Mayo Clinic Small Grant programme.
Spontaneous traveling waves naturally emerge from horizontal fiber time delays and travel through locally asynchronous-irregular states
Studies of sensory-evoked neuronal responses often focus on mean spike rates, with fluctuations treated as internally-generated noise. However, fluctuations of spontaneous activity, often organized as traveling waves, shape stimulus-evoked responses and perceptual sensitivity. The mechanisms underlying these waves are unknown. Further, it is unclear whether waves are consistent with the low rate and weakly correlated “asynchronous-irregular” dynamics observed in cortical recordings. Here, we describe a large-scale computational model with topographically-organized connectivity and conduction delays relevant to biological scales. We find that spontaneous traveling waves are a general property of these networks. The traveling waves that occur in the model are sparse, with only a small fraction of neurons participating in any individual wave. Consequently, they do not induce measurable spike correlations and remain consistent with locally asynchronous irregular states. Further, by modulating local network state, they can shape responses to incoming inputs as observed in vivo. Spontaneous traveling cortical waves shape neural responses. Using a large-scale computational model, the authors show that transmission delays shape locally asynchronous spiking dynamics into traveling waves without inducing correlations and boost responses to external input, as observed in vivo.
Emergence of a New Pathogenic Ehrlichia Species, Wisconsin and Minnesota, 2009
A newly discovered ehrlichia species closely related to E. muris was identified as a cause of illness in three people in Wisconsin and one in Minnesota. The syndrome is described, and the likely vector identified. Ehrlichiosis and anaplasmosis are tickborne zoonoses caused by obligate intracellular gram-negative bacteria in the family Anaplasmataceae. 1 Symptoms typically include fever, myalgia, and headache, with rash in rare instances. Severe disease may be associated with gastrointestinal, renal, respiratory, and central nervous system involvement and, in rare cases, death. In the United States, ehrlichiosis in humans is caused primarily by infection with Ehrlichia chaffeensis, which infects monocytes, and less commonly by E. ewingii, which infects granulocytes. Anaplasma phagocytophilum is closely related to the ehrlichiae and causes human granulocytic anaplasmosis. 1 , 2 E. ewingii and E. chaffeensis are transmitted to humans by the bite . . .
Reconstructed Phase Space of Tropical Cyclone Activity in the North Atlantic Basin for Determining the Predictability of the System
Tropical cyclone prediction is often described as chaotic and unpredictable on time scales that cross into stochastic regimes. Predictions are bounded by the depth of understanding and the limitations of the physical dynamics that govern them. Slight changes in global atmospheric and oceanic conditions may significantly alter tropical cyclone genesis regions and intensity. The purpose of this paper is to characterize the predictability of seasonal storm characteristics in the North Atlantic basin by utilizing the Largest Lyapunov Exponent and Takens’ Theorem, which is rarely used in weather or climatological analysis. This is conducted for a post-weather satellite era (1960–2022). Based on the accumulated cyclone energy (ACE) time series in the North Atlantic basin, cyclone activity can be described as predictable at certain timescales. Insight and understanding into this coupled non-linear system through an analysis of time delay, embedded dimension, and Lyapunov exponent-reconstructed phase space have provided critical information for the system’s predictability.
Baseline White Matter Is Associated With Physical Fitness Change in Preclinical Alzheimer’s Disease
White matter (WM) microstructure is a sensitive marker to distinguish individuals at risk of Alzheimer's disease. The association of objective physical fitness (PF) measures and WM microstructure has not been explored and mixed results reported with physical activity (PA). Longitudinal studies of WM with PA and PF measures have had limited investigation. This study explored the relationship between objective PF measures over 24-months with \"normal-appearing\" WM microstructure. Data acquired on magnetic resonance imaging was used to measure \"normal-appearing\" WM microstructure at baseline and 24-months. Clinical variables such as cognitive and blood-based measures were collected longitudinally. Also, as part of the randomized controlled trial of a PA, extensive measures of PA and fitness were obtained over the 24 months. Bilateral corticospinal tracts (CST) and the corpus callosum showed a significant association between PF performance over 24-months and baseline WM microstructural measures. There was no significant longitudinal effect of the intervention or PF performance over 24-months. Baseline WM microstructural measures were significantly associated with PF performance over 24-months in this cohort of participants with vascular risk factors and at risk of Alzheimer's disease with distinctive patterns for each PF test.
Development and Implementation of a Corriedale Ovine Brain Atlas for Use in Atlas-Based Segmentation
Segmentation is the process of partitioning an image into subdivisions and can be applied to medical images to isolate anatomical or pathological areas for further analysis. This process can be done manually or automated by the use of image processing computer packages. Atlas-based segmentation automates this process by the use of a pre-labelled template and a registration algorithm. We developed an ovine brain atlas that can be used as a model for neurological conditions such as Parkinson's disease and focal epilepsy. 17 female Corriedale ovine brains were imaged in-vivo in a 1.5T (low-resolution) MRI scanner. 13 of the low-resolution images were combined using a template construction algorithm to form a low-resolution template. The template was labelled to form an atlas and tested by comparing manual with atlas-based segmentations against the remaining four low-resolution images. The comparisons were in the form of similarity metrics used in previous segmentation research. Dice Similarity Coefficients were utilised to determine the degree of overlap between eight independent, manual and atlas-based segmentations, with values ranging from 0 (no overlap) to 1 (complete overlap). For 7 of these 8 segmented areas, we achieved a Dice Similarity Coefficient of 0.5-0.8. The amygdala was difficult to segment due to its variable location and similar intensity to surrounding tissues resulting in Dice Coefficients of 0.0-0.2. We developed a low resolution ovine brain atlas with eight clinically relevant areas labelled. This brain atlas performed comparably to prior human atlases described in the literature and to intra-observer error providing an atlas that can be used to guide further research using ovine brains as a model and is hosted online for public access.
Supranutritional Sodium Selenate Supplementation Delivers Selenium to the Central Nervous System: Results from a Randomized Controlled Pilot Trial in Alzheimer's Disease
Insufficient supply of selenium to antioxidant enzymes in the brain may contribute to Alzheimer's disease (AD) pathophysiology; therefore, oral supplementation may potentially slow neurodegeneration. We examined selenium and selenoproteins in serum and cerebrospinal fluid (CSF) from a dual-dose 24-week randomized controlled trial of sodium selenate in AD patients, to assess tolerability, and efficacy of selenate in modulating selenium concentration in the central nervous system (CNS). A pilot study of 40 AD cases was randomized to placebo, nutritional (0.32 mg sodium selenate, 3 times daily), or supranutritional (10 mg, 3 times daily) groups. We measured total selenium, selenoproteins, and inorganic selenium levels, in serum and CSF, and compared against cognitive outcomes. Supranutritional selenium supplementation was well tolerated and yielded a significant (p < 0.001) but variable (95% CI = 13.4–24.8 μg/L) increase in CSF selenium, distributed across selenoproteins and inorganic species. Reclassifying subjects as either responsive or non-responsive based on elevation in CSF selenium concentrations revealed that responsive group did not deteriorate in Mini-Mental Status Examination (MMSE) as non-responsive group (p = 0.03). Pooled analysis of all samples revealed that CSF selenium could predict change in MMSE performance (Spearman's rho = 0.403; p = 0.023). High-dose sodium selenate supplementation is well tolerated and can modulate CNS selenium concentration, although individual variation in selenium metabolism must be considered to optimize potential benefits in AD. The Vel002 study is listed on the Australian and New Zealand Clinical Trials Registry (http://www.anzctr.org.au/), ID: ACTRN12611001200976.
Iron changes within infarct tissue in ischemic stroke patients after successful reperfusion quantified using QSM
Purpose For nearly half of patients who undergo Endovascular Thrombectomy following ischemic stroke, successful recanalisation does not guarantee a good outcome. Understanding the underlying tissue changes in the infarct tissue with the help of biomarkers specific to ischemic stroke could offer valuable insights for better treatment and patient management decisions. Using quantitative susceptibility mapping (QSM) MRI to measure cerebral iron concentration, this study aims to track the progression of iron within the infarct lesion after successful reperfusion. Methods In a prospective study of 87 ischemic stroke patients, successfully reperfused patients underwent MRI scans at 24-to-72 h and 3 months after reperfusion. QSM maps were generated from gradient-echo MRI images. QSM values, measured in parts per billion (ppb), were extracted from ROIs defining the infarct and mirror homolog in the contralateral hemisphere and were compared cross-sectionally and longitudinally. Results QSM values in the infarct ROIs matched those of the contralateral ROIs at 24-to-72 h, expressed as median (interquartile range) ppb [0.71(-7.67-10.09) vs. 2.20(-10.50-14.05) ppb, p  = 0.55], but were higher at 3 months [10.68(-2.30-21.10) vs. -1.27(-12.98-9.82) ppb, p  < 0.001]. The infarct QSM values at 3 months were significantly higher than those at 24-to-72 h [10.41(-2.50-18.27) ppb vs. 1.68(-10.36-12.25) ppb, p  < 0.001]. Infarct QSM at 24-to-72 h and patient outcome measured at three months did not demonstrate a significant association. Conclusion Following successful endovascular reperfusion, iron concentration in infarct tissue, as measured by QSM increases over time compared to that in healthy tissue. However, its significance warrants further investigation.
Bridging the Gap: Comparative Analysis of a Gap Filling X-Band Radar QPE Algorithms and Their Implications for Nowcasting and Hydrological Modeling
Accurate Quantitative Precipitation Estimations (QPE) are foundational for hydrological modeling and proactive watershed management. This research examines how a single X-Band radar bridges the gap in QPE estimation and its implications for hydrological modeling and nowcasting. Initially, a comparison between X-band and S-band radars with Integrated Multi-satellitE Retrievals for GPM (IMERG) showed comparable performances within 80 km, with both radars surpassing IMERG estimations. However, the X-band's efficacy decreased with range. To address this, the \"dynamic distance algorithm\" was introduced for X-band radar QPE. This method dynamically adjusts power function coefficients based on distance and significantly reduced the error compared to other advanced methodologies. When applied to the SWAT hydrological model in the Hinkson Creek Catchment, this algorithm outperformed both Multi-Radar Multi-Sensor (MRMS) QPE and rain gauge inputs for days of extreme discharge rates. Lastly, the effectiveness of six nowcasting models were explored with the MZZU radar. The LINDA nowcast system was identified as the most proficient but computationally intensive. Notably, SPROG and STEPS surpassed the extrapolation model in longer simulations. The research highlights the potential of the dynamic distance algorithm in enhancing hydrological modeling and underscores the pivotal role of select nowcasting models in weather forecasting.