Clinical, Imaging, and Lab Correlates of Severe COVID-19 Leukoencephalopathy.

BACKGROUND AND PURPOSE: Patients infected with the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) can develop a spectrum of neurological disorders, including a leukoencephalopathy of variable severity. Our aim was to characterize imaging, lab, and clinical correlates of severe coronavirus disease 2019 (COVID-19) leukoencephalopathy, which may provide insight into the SARS-CoV-2 pathophysiology. MATERIALS AND METHODS: Twenty-seven consecutive patients positive for SARS-CoV-2 who had brain MR imaging following intensive care unit admission were included. Seven (7/27, 26%) developed an unusual pattern of "leukoencephalopathy with reduced diffusivity" on diffusion-weighted MR imaging. The remaining patients did not exhibit this pattern. Clinical and laboratory indices, as well as neuroimaging findings, were compared between groups. RESULTS: The reduced-diffusivity group had a significantly higher body mass index (36 versus 28 kg/m2, P < .01). Patients with reduced diffusivity trended toward more frequent acute renal failure (7/7, 100% versus 9/20, 45%; P = .06) and lower estimated glomerular filtration rate values (49 versus 85 mL/min; P = .06) at the time of MRI. Patients with reduced diffusivity also showed lesser mean values of the lowest hemoglobin levels (8.1 versus 10.2 g/dL, P < .05) and higher serum sodium levels (147 versus 139 mmol/L, P = .04) within 24 hours before MR imaging. The reduced-diffusivity group showed a striking and highly reproducible distribution of confluent, predominantly symmetric, supratentorial, and middle cerebellar peduncular white matter lesions (P < .001). CONCLUSIONS: Our findings highlight notable correlations between severe COVID-19 leukoencephalopathy with reduced diffusivity and obesity, acute renal failure, mild hypernatremia, anemia, and an unusual brain MR imaging white matter lesion distribution pattern. Together, these observations may shed light on possible SARS-CoV-2 pathophysiologic mechanisms associated with leukoencephalopathy, including borderzone ischemic changes, electrolyte transport disturbances, and silent hypoxia in the setting of the known cytokine storm syndrome that accompanies severe COVID-19.

An evaluation of high energy bremsstrahlung background in point-projection x-ray radiography experiments.

Backlit pinhole x-ray radiography has provided high-resolution images in many recent high-energy-density laser experiments. Its aim is to image the object of interest with a roughly monochromatic Kα source. However, despite the high intrinsic brightness achieved by the technique, data on x-ray film have shown a signal to background ratio near one, with data on image plates producing a higher background. This has been attributed, without direct evidence, to the interaction of suprathermal electrons with the (high Z) pinhole substrate. We present here the first direct measurement of the hard x-rays produced by such a backlighter target and a test of an approach to reducing the background. Specifically, a thick, low-Z layer was added on the side of the substrate toward the detector, intended to stop the energetic electrons and produce smaller emissions. Results from the Omega-60 laser experiment showed that the oft-seen background signal is in the range of 60-80 keV, a plausible energy range for energetic electrons produced in the laser-irradiated plasma. It also showed a comparable level of background signal in both types of targets. The work presented here includes target design and motivating theory, as well as the unexpected findings about x-ray background production.

Dynamics of relativistic laser-plasma interaction on solid targets.

A novel time-resolved diagnostic is used to record the critical surface motion during picosecond-scale relativistic laser interaction with a solid target. Single-shot measurements of the specular light show a redshift decreasing with time during the interaction, corresponding to a slowing-down of the hole boring process into overdense plasma. On-shot full characterization of the laser pulse enables simulations of the experiment without any free parameters. Two-dimensional particle-in-cell simulations yield redshifts that agree with the data, and support a simple explanation of the slowing-down of the critical surface based on momentum conservation between ions and reflected laser light.

Operon prediction without a training set.

MOTIVATION: Annotation of operons in a bacterial genome is an important step in determining an organism's transcriptional regulatory program. While extensive studies of operon structure have been carried out in a few species such as Escherichia coli, fewer resources exist to inform operon prediction in newly sequenced genomes. In particular, many extant operon finders require a large body of training examples to learn the properties of operons in the target organism. For newly sequenced genomes, such examples are generally not available; moreover, a model of operons trained on one species may not reflect the properties of other, distantly related organisms. We encountered these issues in the course of predicting operons in the genome of Bacteroides thetaiotaomicron (B.theta), a common anaerobe that is a prominent component of the normal adult human intestinal microbial community. RESULTS: We describe an operon predictor designed to work without extensive training data. We rely on a small set of a priori assumptions about the properties of the genome being annotated that permit estimation of the probability that two adjacent genes lie in a common operon. Predictions integrate several sources of information, including intergenic distance, common functional annotation and a novel formulation of conserved gene order. We validate our predictor both on the known operons of E.coli and on the genome of B.theta, using expression data to evaluate our predictions in the latter.

Detecting protein sequence conservation via metric embeddings.

MOTIVATION: Comparing two protein databases is a fundamental task in biosequence annotation. Given two databases, one must find all pairs of proteins that align with high score under a biologically meaningful substitution score matrix, such as a BLOSUM matrix (Henikoff and Henikoff, 1992). Distance-based approaches to this problem map each peptide in the database to a point in a metric space, such that peptides aligning with higher scores are mapped to closer points. Many techniques exist to discover close pairs of points in a metric space efficiently, but the challenge in applying this work to proteomic comparison is to find a distance mapping that accurately encodes all the distinctions among residue pairs made by a proteomic score matrix. Buhler (2002) proposed one such mapping but found that it led to a relatively inefficient algorithm for protein-protein comparison. RESULTS: This work proposes a new distance mapping for peptides under the BLOSUM matrices that permits more efficient similarity search. We first propose a new distance function on peptides derived from a given score matrix. We then show how to map peptides to bit vectors such that the distance between any two peptides is closely approximated by the Hamming distance (i.e. number of mismatches) between their corresponding bit vectors. We combine these two results with the LSH-ALL-PAIRS-SIM algorithm of Buhler (2002) to produce an improved distance-based algorithm for proteomic comparison. An initial implementation of the improved algorithm exhibits sensitivity within 5% of that of the original LSH-ALL-PAIRS-SIM, while running up to eight times faster.

Health professionals and breastfeeding counseling: client and provider views.

Health care providers are the most influential and trusted source of information about breastfeeding, yet many are neither prepared nor able to provide good breastfeeding counseling to their clients. This paper reports findings on low-income mothers' and on providers' perceptions of professional breastfeeding counseling. Data collection included focus group discussions with mothers recruited from public health department clinics in the Southeast USA and who were stratified by age, parity, rural/urban residence and feeding method, and focus groups and individual interviews were conducted with health care providers from the same geographic area. The results of the study indicate a gap between the promotion and support processes for breastfeeding, and point to areas where breastfeeding counseling can be strengthened.

"America Responds to AIDS": its content, development process, and outcome.

During the 1987-90 period, five phases of new AIDS information materials were released to the general public in the ARTA campaign, including a national mailer. The five were "General Awareness: Humanizing AIDS" in October 1987, "Understanding AIDS," the national mailout, April 1988, "Women at Risk/Multiple Partner, Sexually Active Adults," October 1988, "Parents and Youth," May 1989, and "Preventing HIV Infection and AIDS: Taking The Next Steps," July 1990. From planning to implementation to evaluation, ARTA is based on well-established theory and practice. Initially, the campaign was a response to an immediate crisis. It has evolved into the deliberate and systematic development of objectives to combat a chronic problem. ARTA represents one of the most comprehensive formative research processes in the history of public service campaigns. The dynamic process of carefully developing each new phase to include such important entities as State and local health agencies and community-based organizations is at least as important as the quality of the end materials. The objectives of each new phase are based on the needs of the public and of specific audiences. Maximum input from all relevant constituencies is obtained to ensure that they support the campaign's objectives and implementation strategy.