The 2021 SIIM-FISABIO-RSNA Machine Learning COVID-19 Challenge: Annotation and Standard Exam Classification of COVID-19 Chest Radiographs.

We describe the curation, annotation methodology, and characteristics of the dataset used in an artificial intelligence challenge for detection and localization of COVID-19 on chest radiographs. The chest radiographs were annotated by an international group of radiologists into four mutually exclusive categories, including "typical," "indeterminate," and "atypical appearance" for COVID-19, or "negative for pneumonia," adapted from previously published guidelines, and bounding boxes were placed on airspace opacities. This dataset and respective annotations are available to researchers for academic and noncommercial use.

Cesarean delivery in a parturient with a left ventricular assist device.

Left ventricular assist devices are implanted pumps designed to treat patients with heart failure, and in some cases, to be a bridge to transplantation for patients who qualify. The preconception presence of a left ventricular assist device is a relative contraindication to pregnancy. Few cases have been published regarding the anesthetic management of parturients with left ventricular assist devices. We present the care of a 24-year-old gravida seven, para two woman who presented for induction of labor at gestational age 34 and 6/7 weeks. Her medical history was significant for the presence of a left ventricular assist device, inserted due to heart failure associated with polysubstance abuse. To our knowledge, this is the first description of successful cesarean delivery under neuraxial anesthesia of a parturient with a left ventricular assist device.

Postprandial oesophageal integrated acidity is a reliable predictor of gastro-oesophageal reflux disease.

BACKGROUND: Measurement of oesophageal acid exposure parameters postprandially has been shown to distinguish gastro-oesophageal reflux disease patients from normal individuals. AIMS: To calculate the accuracy of postprandial oesophageal integrated acidity in diagnosing gastro-oesophageal reflux disease. METHODS: Ambulatory 24-h pH studies of 626 patients were analysed retrospectively. Gastro-oesophageal reflux disease, defined as pH < 4 for > 4.2% of time, was identified in 305 subjects. Postprandial oesophageal integrated acidity was measured for 2 and 3 h after the largest meal peak as determined from gastric pH. Postprandial symptom-associated probability was calculated. RESULTS: Gastro-oesophageal reflux disease subjects had a greater postprandial oesophageal integrated acidity than non-gastro-oesophageal reflux disease subjects [median (IQR): 0.57 (0.08-2.66) vs. 0.03 (0.01-0.15) mmol*h/L]. Median postprandial oesophageal integrated acidity did not differ with gender or age in gastro-oesophageal reflux disease and non-gastro-oesophageal reflux disease subjects (P > 0.05 for all). A 3-h postprandial oesophageal integrated acidity value of 0.121 mmol*h/L had a 71.1% sensitivity and 71.7% specificity in diagnosing gastro-oesophageal reflux disease. Gastro-oesophageal reflux disease subjects with symptoms had a higher postprandial oesophageal integrated acidity than those without (P = 0.043), whereas non-gastro-oesophageal reflux disease subjects with and without symptoms did not differ (P = 0.74). The correlation between symptom-associated probability and postprandial oesophageal integrated acidity was poor (gastro-oesophageal reflux disease: r = 0.15; non-gastro-oesophageal reflux disease: r = 0.25). CONCLUSION: Postprandial oesophageal integrated acidity provides a robust estimation of oesophageal acid exposure and may predict symptoms in gastro-oesophageal reflux disease patients.

Interferon-alpha induces dendritic cell differentiation of CML mononuclear cells in vitro and in vivo.

The ability of interferon-alpha (IFN-alpha) to induce dendritic cell (DC) differentiation in chronic myeloid leukemia (CML) was evaluated. Peripheral blood mononuclear cells from CML patients cultured with IFN-alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF) developed a dendritic morphology. Fluorescence in situ hybridization demonstrated that the DCs harbored the bcr/abl translocation. The DCs prepared with IFN-alpha/GM-CSF expressed significantly higher levels of class I and II HLA than those grown in interleukin-4 (IL-4) and GM-CSF. The DCs prepared from newly diagnosed CML patients using IFN-alpha/GM-CSF expressed immunoregulatory proteins at levels comparable to normal DCs. In contrast, DCs cultured from CML patients who did not achieve a cytogenetic response to IFN-alpha expressed significantly lower levels of class I HLA, CD40, CD54, CD80 and CD86 than normal DCs. The expression of CD86 by CML DCs was enhanced when they were cultured with IFN-alpha/IL-4/GM-CSF, or when IFN-alpha/GM-CSF-treated cells were induced to mature by CD40 ligand. The DCs from IFN-alpha failures were less stimulatory than normal DCs in the allogeneic mixed leukocyte reaction. CML patients who had a cytogenetic response to IFN-alpha initially had low numbers of bone marrow DCs that increased significantly with treatment, while nonresponders had more prevalent DCs at baseline that showed no consistent change with treatment. Therefore, IFN-alpha can induce DC differentiation from CML progenitor cells both in vitro and in vivo. The therapeutic activity of IFN-alpha in CML may be due to its ability to stimulate the generation of DCs that can present CML-specific antigens. Resistance to IFN-alpha may result when DC differentiation becomes impaired.

The binding site for UCH-L3 on ubiquitin: mutagenesis and NMR studies on the complex between ubiquitin and UCH-L3.

The ubiquitin fold is a versatile and widely used targeting signal that is added post-translationally to a variety of proteins. Covalent attachment of one or more ubiquitin domains results in localization of the target protein to the proteasome, the nucleus, the cytoskeleton or the endocytotic machinery. Recognition of the ubiquitin domain by a variety of enzymes and receptors is vital to the targeting function of ubiquitin. Several parallel pathways exist and these must be able to distinguish among ubiquitin, several different types of polymeric ubiquitin, and the various ubiquitin-like domains. Here we report the first molecular description of the binding site on ubiquitin for ubiquitin C-terminal hydrolase L3 (UCH-L3). The site on ubiquitin was experimentally determined using solution NMR, and site-directed mutagenesis. The site on UCH-L3 was modeled based on X-ray crystallography, multiple sequence alignments, and computer-aided docking. Basic residues located on ubiquitin (K6, K11, R72, and R74) are postulated to contact acidic residues on UCH-L3 (E10, E14, D33, E219). These putative interactions are testable and fully explain the selectivity of ubiquitin domain binding to this enzyme.

Multiple lysophosphatidic acid acyltransferases in Neisseria meningitidis.

Lysophosphatidic acid (LPA) and phosphatidic acid (PA) are critical phospholipid intermediates in the biosynthesis of cell membranes. In Escherichia coli, LPA acyltransferase (1-acyl-sn-glycerol-3-phosphate acyltransferase; EC 2.3.1.51) catalyses the transfer of an acyl chain from either acyl-coenzyme A or acyl-acyl carrier protein onto LPA to produce PA. While E. coli possesses one essential LPA acyltransferase (PlsC), Neisseria meningitidis possesses at least two LPA acyltransferases. This study describes the identification and characterization of nlaB (neisserial LPA acyltransferase B), the second LPA acyltransferase identified in N. meningitidis. The gene was located downstream of the Tn916 insertion in N. meningitidis mutant 469 and differed in nucleotide and predicted amino acid sequence from the previously characterized neisserial LPA acyltransferase homologue nlaA. NlaB has specific LPA acyltransferase activity, as demonstrated by complementation of an E. coli plsC(Ts) mutant in trans, by decreased levels of LPA acyltransferase activity in nlaB mutants and by lack of complementation of E. coli plsB26,X50, a mutant defective in the first acyltransferase step in phospholipid biosynthesis. Meningococcal nlaA mutants accumulated LPA and demonstrated alterations in membrane phospholipid composition, yet retained LPA acyltransferase activity. In contrast, meningococcal nlaB mutants exhibited decreased LPA acyltransferase activity, but did not accumulate LPA or display any other observable membrane changes. We propose that N. meningitidis possesses at least two LPA acyltransferases to provide for the production of a greater diversity of membrane phospholipids.

T-cell co-stimulation through B7RP-1 and ICOS.

T-cell activation requires co-stimulation through receptors such as CD28 and antigen-specific signalling through the T-cell antigen receptor. Here we describe a new murine costimulatory receptor-ligand pair. The receptor, which is related to CD28 and is the homologue of the human protein ICOS, is expressed on activated T cells and resting memory T cells. The ligand, which has homology to B7 molecules and is called B7-related protein-1 (B7RP-1), is expressed on B cells and macrophages. ICOS and B7RP-I do not interact with proteins in the CD28-B7 pathway, and B7RP-1 co-stimulates T cells in vitro independently of CD28. Transgenic mice expressing a B7RP-1-Fc fusion protein show lymphoid hyperplasia in the spleen, lymph nodes and Peyer's patches. Presensitized mice treated with B7RP-1-Fc during antigen challenge show enhanced hypersensitivity. Therefore, B7RP-1 exhibits co-stimulatory activities in vitro and in vivo. ICOS and B7RP-1 define a new and distinct receptor-ligand pair that is structurally related to CD28-B7 and is involved in the adaptive immune response.

The (alpha2-->8)-linked polysialic acid capsule and lipooligosaccharide structure both contribute to the ability of serogroup B Neisseria meningitidis to resist the bactericidal activity of normal human serum.

The molecular basis for the resistance of serogroup B Neisseria meningitidis to the bactericidal activity of normal human sera (NHS) was examined with a NHS-resistant, invasive serogroup B meningococcal isolate and genetically and structurally defined capsule-, lipooligosaccharide (LOS)-, and sialylation-altered mutants of the wild-type strain. Expression of the (alpha2-->8)-linked polysialic acid serogroup B capsule was essential for meningococcal resistance to NHS. The very NHS-sensitive phenotype of acapsular mutants (99.9 to 100% killed in 10, 25, and 50% NHS) was not rescued by complete LOS sialylation or changes in LOS structure. However, expression of the capsule was necessary but not sufficient for a fully NHS-resistant phenotype. In an encapsulated background, loss of LOS sialylation by interrupting the alpha2,3 sialyltransferase gene, lst, increased sensitivity to 50% NHS. In contrast, replacement of the lacto-N-neotetraose alpha-chain (Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc) with glucose extensions (GlcN) in a galE mutant resulted in a strain resistant to killing by 50% NHS at all time points. Encapsulated meningococci expressing a Hep2(GlcNAc)-->KDO2-->lipid A LOS without an alpha-chain demonstrated enhanced sensitivity to 50% NHS (98% killed at 30 min) mediated through the antibody-dependent classical complement pathway. Encapsulated LOS mutants expressing truncated Hep2-->KDO2-->lipid A and KDO2-->lipid A structures were also sensitive to 50% NHS (98 to 100% killed at 30 min) but, unlike the wild-type strain and mutants with larger oligosaccharide structures, they were killed by hypogammaglobulinemic sera. These data indicate that encapsulation is essential but that the LOS structure contributes to the ability of serogroup B N. meningitidis to resist the bactericidal activity of NHS.

Termination of peripheral tolerance to a T cell epitope by heteroclitic antigen analogues.

Treating mice with an immunodominant T cell epitope from moth cytochrome c (MCC(88-103)) can induce T cell unresponsiveness under certain conditions of administration. In this report, we determined whether T cell tolerance to MCC(88-103) in adult animals can be overcome by immunization with cross-reactive analogues of the tolerizing Ag. A panel of analogues of the tolerogen were tested for their capacity to terminate the tolerant state following in vivo immunization. As analyzed by their stimulatory capacity for a representative MCC(88-103)-specific T cell clone, this panel covered a wide range of cross-reactivity, including nonantigenic, antagonistic, weakly, and strongly antigenic peptides. Interestingly, only heteroclitic analogues, as measured in vitro by their enhanced antigenicity for the T cell clone that was specific for MCC(88-103), were capable of breaking tolerance. Thus, an immune response to the cross-reactive, heteroclitic analogues of tolerized self Ags may represent a mechanism by which Ag molecular mimicry operates.

Prophylactic angiotensin II infusion during spinal anesthesia for elective cesarean delivery.

BACKGROUND: Angiotensin II may prove useful in treating regional anesthesia-induced hypotension in obstetric patients, because it causes less uterine vasoconstriction than do other vasoconstrictor drugs (such as phenylephrine). This study compared (1) maternal blood pressure and heart rate and (2) fetal status at delivery in parturients given either prophylactic angiotensin II or ephedrine infusion during spinal anesthesia for elective cesarean delivery. METHODS: Fifty-four women were randomized to receive either angiotensin II or ephedrine infusion intravenously during spinal anesthesia for elective cesarean section delivery. Simultaneous with subarachnoid injection, infusion of angiotensin II (2.5 microg/ml) or ephedrine (5 mg/ml) was initiated at 10 ng x kg(-1) x min(-1) and 50 microg x kg(-1) x min(-1), respectively. The rate of each infusion was adjusted to maintain maternal systolic blood pressure at 90-100% of baseline. RESULTS: Cumulative vasopressor doses (mean+/-SD) through 10, 20, and 30 min were 150+/-100, 310+/-180, and 500+/-320 ng/kg in the angiotensin group and 480+/-210, 660+/-390, and 790+/-640 microg/kg in the ephedrine group. Maternal heart rate was significantly higher (P < 0.001) during vasopressor infusion in the ephedrine group than in the angiotensin group. Umbilical arterial and venous blood pH and base excess were all significantly higher (P < 0.05) in the angiotensin group than in the ephedrine group. CONCLUSIONS: Angiotensin II infusion maintained maternal systolic blood pressure during spinal anesthesia without increasing maternal heart rate or causing fetal acidosis.

Differences in caloric utilization in eating disordered adolescents.

Caloric utilization is an important aspect of the clinical management of eating disorders. Caloric intake and body weight of 32 inpatient bulimic and anorectic girls and 30 normal adolescents were measured. Normal weight bulimics ate fewer calories while anorectics ate more calories per kilogram body weight compared with the control group. Anorectics have greater difficulty to eat sufficient calories to maintain their weight. These findings indicate that treatment should be extended beyond the point of time where normal weight is reached.

Differential T cell signaling induced by antagonist peptide-MHC complexes and the associated phenotypic responses.

Certain changes in TCR contact residues have been shown to have profound effects on the capacity of a peptide Ag to stimulate a T cell response. Although some of these changes apparently lead to a complete loss of the ability to interact with the TCR, others result in partial agonist activity (e.g., cytokine production without proliferation) or antagonist activity (i.e., the capacity to inhibit the engagement to the TCR by Ag). We show MHC class II-restricted antagonist activity was associated with a differential pattern of early tyrosine phosphorylation events that was characterized by a preponderance of phosphorylation of low molecular mass TCRzeta and the failure to phosphorylate Zap-70. These early tyrosine phosphorylation patterns are the same as those previously described for partial agonists. Thus, a partial agonist phenotype such as anergy induction cannot be ascribed in a causal manner to this pattern of tyrosine phosphorylation. We further extend the studies of signal transduction elicited by agonist and antagonist peptides by characterizing differential recruitment of Zap-70 associated with TCRzeta isoforms and differential phosphorylation of p120 proto-oncogene c-Cbl. Another early event following TCR engagement by Ag, down-modulation of the TCR, was studied with antagonist peptides. We show that antagonist peptides do not cause TCR down-modulation. This failure may represent a mechanism by which antagonists inhibit antigen-mediated stimulation of T cells.

An E. coli B mutation, rpoB5081, that prevents growth of phage T4 strains defective in host DNA degradation.

An E. coli B Tab strain, EM121, was isolated that restricts T4 denA (DNA endonuclease II) mutants at 37 degrees C and above, but is permissive for wild-type T4 at all temperatures examined. At 42 degrees C, other mutants affected in nucleic acid metabolism (T4 dexA, regA and uvsW strains) are also restricted. Genetic analysis revealed that one mutation (rpoB5081) in the RNA polymerase beta subunit gene is sufficient for restricting all denA mutants. rpoB5081, together with a second linked mutation, is also required for restricting the other T4 mutants, rpoB5081 (P806S), previously shown to increase transcription termination in E. coli K-12, causes delayed synthesis of T4 late proteins and reduced DNA synthesis in denA infections. Thus, T4 DNA synthesis and gene expression are impaired by the rpoB5081 beta subunit when degradation of host DNA is reduced. Because the restricted T4 mutants are not readily distinguished from wild-type phage under typical plating conditions, EM121 is an important host for screening and mapping T4 denA mutations.

Plasminogen and plasminogen activator assembly on the human endothelial cell.

Through assembly of plasminogen and its activators, the endothelial cell surface may provide a favorable environment for constitutive generation of plasmin. This system may be regulated at multiple levels. Abundant expression of a 40-kDa protein with dual ligand-binding capacity may promote cell surface plasmin formation by colocalizing t-PA and plasminogen in a catalytically favorable configuration. Conversion of Glu-PLG to the preactivated form Lys-PLG, in the vicinity of the cell surface, may also precede plasmin formation. Physiologic concentrations of Lp(a), furthermore, may serve to modulate plasminogen activation at the cell surface by competing for binding sites, whereas elevated levels of Lp(a) might suppress this mechanism and lead to a subclinical prothrombotic state. Finally, cell surface binding sites for both plasmin and t-PA appear to protect these molecules from their physiologic antagonists, alpha 2-plasmin inhibitor and plasminogen activator inhibitor, type-1, respectively. Plasmin formation may contribute to the nonthrombogenicity of the blood vessel wall.