COVID-19 Stroke Apical Lung Examination Study: A Diagnostic and Prognostic Imaging Biomarker in Suspected Acute Stroke.

BACKGROUND AND PURPOSE: Diagnosis of coronavirus disease 2019 (COVID-19) relies on clinical features and reverse-transcriptase polymerase chain reaction testing, but the sensitivity is limited. Carotid CTA is a routine acute stroke investigation and includes the lung apices. We evaluated CTA as a potential COVID-19 diagnostic imaging biomarker. MATERIALS AND METHODS: This was a multicenter, retrospective study (n = 225) including CTAs of patients with suspected acute stroke from 3 hyperacute stroke units (March-April 2020). We evaluated the reliability and accuracy of candidate diagnostic imaging biomarkers. Demographics, clinical features, and risk factors for COVID-19 and stroke were analyzed using univariate and multivariate statistics. RESULTS: Apical ground-glass opacification was present in 22.2% (50/225) of patients. Ground-glass opacification had high interrater reliability (Fleiss κ = 0.81; 95% CI, 0.68-0.95) and, compared with reverse-transcriptase polymerase chain reaction, had good diagnostic performance (sensitivity, 75% [95% CI, 56-87]; specificity, 81% [95% CI, 71-88]; OR = 11.65 [95% CI, 4.14-32.78]; P < .001) on multivariate analysis. In contrast, all other contemporaneous demographic, clinical, and imaging features available at CTA were not diagnostic for COVID-19. The presence of apical ground-glass opacification was an independent predictor of increased 30-day mortality (18.0% versus 5.7%, P = .017; hazard ratio = 3.51; 95% CI, 1.42-8.66; P = .006). CONCLUSIONS: We identified a simple, reliable, and accurate COVID-19 diagnostic and prognostic imaging biomarker obtained from CTA lung apices: the presence or absence of ground-glass opacification. Our findings have important implications in the management of patients presenting with suspected stroke through early identification of COVID-19 and the subsequent limitation of disease transmission.

Dielectric properties of isolated adrenal chromaffin cells determined by microfluidic impedance spectroscopy.

Knowledge of the dielectric properties of biological cells plays an important role in numerical models aimed at understanding how high intensity ultrashort nanosecond electric pulses affect the plasma membrane and the membranes of intracellular organelles. To this end, using electrical impedance spectroscopy, the dielectric properties of isolated, neuroendocrine adrenal chromaffin cells were obtained. Measured impedance data of the cell suspension, acquired between 1kHz and 20MHz, were fit into a combination of constant phase element and Cole-Cole models from which the effect of electrode polarization was extracted. The dielectric spectrum of each cell suspension was fit into a Maxwell-Wagner mixture model and the Clausius-Mossotti factor was obtained. Lastly, to extract the cellular dielectric parameters, the cell dielectric data were fit into a granular cell model representative of a chromaffin cell, which was based on the inclusion of secretory granules in the cytoplasm. Chromaffin cell parameters determined from this study were the cell and secretory granule membrane specific capacitance (1.22 and 7.10µF/cm2, respectively), the cytoplasmic conductivity, which excludes and includes the effect of intracellular membranous structures (1.14 and 0.49S/m, respectively), and the secretory granule milieu conductivity (0.35S/m). These measurements will be crucial for incorporating into numerical models aimed at understanding the differential poration effect of nanosecond electric pulses on chromaffin cell membranes.

Extracellular Tau Oligomers Produce An Immediate Impairment of LTP and Memory.

Non-fibrillar soluble oligomeric forms of amyloid-ß peptide (oAß) and tau proteins are likely to play a major role in Alzheimer's disease (AD). The prevailing hypothesis on the disease etiopathogenesis is that oAß initiates tau pathology that slowly spreads throughout the medial temporal cortex and neocortices independently of Aß, eventually leading to memory loss. Here we show that a brief exposure to extracellular recombinant human tau oligomers (oTau), but not monomers, produces an impairment of long-term potentiation (LTP) and memory, independent of the presence of high oAß levels. The impairment is immediate as it raises as soon as 20 min after exposure to the oligomers. These effects are reproduced either by oTau extracted from AD human specimens, or naturally produced in mice overexpressing human tau. Finally, we found that oTau could also act in combination with oAß to produce these effects, as sub-toxic doses of the two peptides combined lead to LTP and memory impairment. These findings provide a novel view of the effects of tau and Aß on memory loss, offering new therapeutic opportunities in the therapy of AD and other neurodegenerative diseases associated with Aß and tau pathology.

Predictors and outcome associated with an Enterococcus positive isolate during intensive care unit admission.

This study reports the incidence, risk factors and mortality associated with a positive Enterococcus spp. isolate during admission to two tertiary intensive care units participating in an antibiotic cycling study. Incidence was low, with only 4.2% of admissions (36/852) at Royal Brisbane and Women's Hospital and 2.8% (31/1104) at Westmead Hospital developing a positive Enterococcus spp. isolate (P=0.087). A positive enterococcal isolate, while not an independent predictor of mortality (odds ratio [OR]=1.6, 95% confidence interval [CI] 0.80 to 3.2, P=0.18), may be a marker of the underlying severity of illness with higher unadjusted in-hospital mortality (26% or 17/66 vs 14% or 250/1855, P=0.007). Independent risk factors for a positive isolate were use of meropenem/imipenem (OR=5.7, 95% CI 2.4 to 14, P <0.001) and cefepime (OR=2.5, 95% CI 1.2 to 5.3, P=0.017) within 48 hours of intensive care unit admission, the presence of a nasogastric tube (OR=4.1, 95% CI 1.3 to 14, P=0.018), renal replacement therapy (OR=2.2, 95% CI 1.0 to 4.7, P=0.046), operative intervention (OR=1.8, 95% CI 1.0 to 3.2, P=0.035) and age (OR=1.2, 95% CI 1.1 to 1.5, P=0.009). None of these factors, except for the need for renal replacement therapy (OR=6.2, 95% CI 1.4 to 27, P=0.015), was associated with increased mortality. Enterococci-directed empiric therapy in the treatment of sepsis remains of unproven value, although this negative finding must be evaluated against other higher powered studies.

Cytochrome P450-mediated oxidative damage of nuclear membrane proteins and its prevention by vitamin C.

In this report, we present data to indicate that NADPH-cytochrome P450 reductase/cytochrome P450 system is present in the nuclear membrane. The reactive oxygen species generated in this free metal ion-independent P450 system oxidatively modifies and degrades the membrane proteins. The oxidative modification is evidenced by the formation of carbonyl, bityrosine and tryptophan loss. The degradation of membrane proteins is manifested using fluorescamine reactivity and SDS-PAGE. Ascorbic acid exclusively prevents the oxidative modification and degradation of the membrane proteins. Other antioxidants, such as superoxide dismutase, catalase, glutathione, alpha-tocopherol, probucol, beta-carotene, mannitol, histidine and thiourea are found to be ineffective. The observation assumes significance, particularly in subclinical ascorbic acid deficiency, where oxidative damage of the nuclear membrane would occur. This, in turn, would affect the traffic of cytoplasmic enzymes and proteins required for DNA replication and repair, transcription and RNA processing, ultimately leading to disruption of gene regulation of the cell.

Numerical computation of distortions in magnetic fields and induced currents in physiological solutions produced by microscope objectives.

Identifying distortions produced by commonly employed microscope objectives and their components in uniform DC and 60 Hz AC magnetic fields is important in imaging studies involving exposure of cells to spatially uniform or nonuniform magnetic fields. In this study, DC and 60 Hz AC magnetic flux densities were numerically computed in the presence of finite element models of various components of commonly utilized microscope objectives, as well as a model of a complete objective. Also computed were the distortions in the current density induced by an applied time-varying magnetic field in a physiological buffer contained within a Petri dish. We show that the magnetic flux density could be increased up to 65% in the presence of the nickel-chrome plating of an objective housing and that the presence of ferromagnetic components like a screw or spring could produce peaks that are 7% higher than the undistorted value of magnetic flux density. In addition, a slight tilt of 1% in the objective with respect to the magnetic field could cause a 93% deviation in magnetic flux density from the unperturbed value. These results correlate well with previously published experimental measurements that showed the presence of significant and sometimes asymmetric distortions in both DC and 60 Hz magnetic fields. Moreover, this study further reports that induced current density changed up to 37% compared to values in the absence of the objective. The existence of distortions in applied magnetic fields and induced currents could affect the interpretation of results of cell function studies if it is assumed that the cells are exposed to uniform magnetic flux densities in the presence of a microscope objective. Such assumptions of uniform magnetic flux density could also account for the lack of reproducibility in several studies that examined changes in intracellular calcium by imaging techniques.

Cigarette smoke-induced protein oxidation and proteolysis is exclusively caused by its tar phase: prevention by vitamin C.

We have reported before that whole phase cigarette smoke (CS) contains stable oxidants that cause oxidative damage and increased proteolysis of proteins [Free Radic. Biol. Med. 27 (1999) 1064]. Here, we demonstrate that these oxidants are exclusively present in the tar phase of the CS and not its gas phase and can almost wholly account for the observed whole phase CS-induced oxidation of human plasma proteins as well as extensive oxidative proteolysis of guinea pig lung and heart microsomal proteins in vitro. The mechanism of the tar phase CS-induced proteolysis of microsomal proteins involves two-steps: (i) initial oxidation of the proteins by oxidants present in the tar extract followed by (ii) rapid proteolytic degradation of the oxidized proteins by proteases present in the microsomes. Like the whole phase CS, the oxidative damage of proteins caused by the tar phase CS, as evidenced by the formation of protein carbonyl and bityrosine as well as loss of tryptophan residues and thiol groups, is also almost completely prevented by ascorbic acid and only partially by glutathione. Other antioxidants, including superoxide dismutase, catalase, vitamin E, beta-carotene and mannitol are ineffective. This again leads us to suggest that adequate intake of vitamin C may help smokers to evade the CS-induced degenerative diseases associated with oxidative damage. The revelation of the acute toxicity of the tar phase with respect to CS-induced oxidative damage also urges the necessity of trapping it more effectively by suitable cigarette filters to reduce the health damage caused to smokers.

Structural basis for nucleotide exchange and competition with tRNA in the yeast elongation factor complex eEF1A:eEF1Balpha.

The crystal structure of a complex between the protein biosynthesis elongation factor eEF1A (formerly EF-1alpha) and the catalytic C terminus of its exchange factor, eEF1Balpha (formerly EF-1beta), was determined to 1.67 A resolution. One end of the nucleotide exchange factor is buried between the switch 1 and 2 regions of eEF1A and destroys the binding site for the Mg(2+) ion associated with the nucleotide. The second end of eEF1Balpha interacts with domain 2 of eEF1A in the region hypothesized to be involved in the binding of the CCA-aminoacyl end of the tRNA. The competition between eEF1Balpha and aminoacylated tRNA may be a central element in channeling the reactants in eukaryotic protein synthesis. The recognition of eEF1A by eEF1Balpha is very different from that observed in the prokaryotic EF-Tu:EF-Ts complex. Recognition of the switch 2 region in nucleotide exchange is, however, common to the elongation factor complexes and those of Ras:Sos and Arf1:Sec7.

Vitamin C prevents cigarette smoke-induced oxidative damage in vivo.

Our recent in vitro results [4] indicate that cigarette smoke induces oxidation of human plasma proteins and extensive oxidative degradation of the guinea pig lung, heart, and liver microsomal proteins, which is almost completely prevented by ascorbic acid. In this paper, we substantiate the in vitro results with in vivo observations. We demonstrate that exposure of subclinical or marginal vitamin C-deficient guinea pigs to cigarette smoke causes oxidation of plasma proteins as well as extensive oxidative degradation of the lung microsomal proteins. Cigarette smoke exposure also results in some discernible damage of the heart microsomal proteins. The oxidative damage has been manifested by SDS-PAGE, accumulation of carbonyl and bityrosine, as well as loss of tryptophan and protein thiols. Cigarette smoke exposure also induces peroxidation of microsomal lipids as evidenced by the formation of conjugated dienes, malondialdehyde, and fluorescent pigment. Cigarette smoke-induced oxidative damage of proteins and peroxidation of lipids are accompanied by marked drop in the tissue ascorbate levels. Protein damage and lipid peroxidation are also observed in cigarette smoke-exposed pair-fed guinea pigs receiving 5 mg vitamin C/animal/day. However, complete protection against protein damage and lipid peroxidation occurs when the guinea pigs are fed 15 mg vitamin C/animal/day. Also, the cigarette smoke-induced oxidative damage of proteins and lipid is reversed after discontinuation of cigarette smoke exposure accompanied by ascorbate therapy. The results, if extrapolated to humans, indicate that comparatively large doses of vitamin C may protect the smokers from cigarette smoke-induced oxidative damage and associated degenerative diseases.

Vitamin C prevents cigarette smoke induced oxidative damage of proteins and increased proteolysis.

Aqueous extract of cigarette smoke (CS) contains some stable oxidants, which oxidize human plasma proteins, bovine serum albumin, amino acid homopolymers, and also cause extensive oxidative degradation of microsomal proteins. Similar observations are made when the aqueous extract of cigarette smoke is replaced by whole phase CS solution or whole phase cigarette smoke. CS-induced microsomal protein degradation is a two step process: (i) oxidation of proteins by the oxidants present in the CS and (ii) rapid proteolytic degradation of the oxidized proteins by proteases present in the microsomes. Using aqueous extract of CS equivalent to that produced from one-twentieth of a cigarette, the observed initial and postcigarette smoke treated values of different parameters of oxidative damage per milligram of microsomal proteins are respectively: 0.24 and 1.74 nmoles for carbonyl formation, 125.4 and 62.8 fluorescence units for tryptophan loss, 10.2 and 33.4 fluorescence units for bityrosine formation, and 58.3 and 12.2 nmoles for loss of protein thiols. When compared with sodium dodecyl sulphate polyacrylamide gel electrophoresis profiles of untreated microsomal proteins, the extent of microsomal protein degradation after treatment with whole phase CS solution or aqueous extract of CS is above 90%. Ascorbate (100 microM) almost completely prevents cigarette smoke-induced protein oxidation and thereby protects the microsomes from subsequent proteolytic degradation. Glutathione is partially effective, but other antioxidants including superoxide dismutase, catalase, vitamin E, probucol, beta-carotene, mannitol, thiourea, and histidine are ineffective. The gas phase cigarette smoke contains unstable reactive oxygen species such as superoxide (O2*-) and hydrogen peroxide (H2O2) that can cause substantial oxidation of pure protein like albumin but is unable to produce significant oxidative damage of microsomal proteins. Gas phase cigarette smoke-induced albumin oxidation is not only inhibited by ascorbate and glutathione but also by superoxide dismutase, catalase and mannitol. The stable oxidants in the cigarette smoke are not present in the tobacco and are apparently produced by the interaction of O2*-/H2O2/OH* of the gas phase with some components of the tar phase during/following the burning of tobacco.

Effects of microscope objectives on magnetic field exposures.

Distortions in magnetic field intensity generated by commonly used microscope objectives (1x to 100x) were characterized within a Helmholtz coil-based exposure system. Objectives from a variety of manufacturers distorted applied field intensities by up to 23% in the image plane. Components that contribute to distortions include (1) nickel-chrome plating of objective housings, (2) the presence of steel springs in objectives with compression collars, and (3) steel screws or studs used to hold together separately manufactured parts. Steel springs and screws produce radially asymmetric profiles, whereas distortions generated by nickel-chrome plating are typically radially symmetric. All components can produce spatial gradients in field intensity if objectives are not perfectly aligned with exposure systems or if placed in the earth's magnetic field. Alterations in the magnitude of magnetic field intensities as well as the production of spatial gradients might have an effect on biological responses. By maintaining optical glass components and replacing metallic components, functional objectives can be reconstructed that produce no measurable effects on magnetic flux densities.

Failed instrumental delivery: how safe is the use of a second instrument?

An audit of failed instrumental deliveries was undertaken to assess the incidence of complications and the adequacy of documentation. When one instrument has failed to effect delivery, the use of a second instrument could in most cases be used to complete the delivery without harm to the mother or baby. However in a small but significant number of cases there are severe maternal or perinatal complications, and these could be the subject of litigation. This could be avoided by adequate pre-application assessment, standard conduct of instrumental delivery and full documentation. Inadequate documentation could be overcome by the use of a pro forma. Selective use of plastic and metal cups could reduce the incidence of failed attempts.

DNA repair in higher plants.

Numerous studies have demonstrated a requirement in plants for repair of DNA damage arising from either intrinsic or extrinsic sources. Investigations also have revealed a capacity for repair of certain types of DNA damage, and conversely, identified mutants apparently defective in such repair. This article provides a concise overview of nuclear DNA repair mechanisms in higher plants, particularly those processes concerned with the repair of UV-induced lesions, and includes surveys of UV-sensitive mutants and genes implicated in DNA repair.

Hydroxylated naphthoquinones as substrates for Escherichia coli anaerobic reductases.

We have used two hydroxylated naphthoquinol menaquinol analogues, reduced plumbagin (PBH2, 5-hydroxy-2-methyl-1,4-naphthoquinol) and reduced lapachol [LPCH2, 2-hydroxy-3-(3-methyl-2-butenyl)-1, 4-naphthoquinol], as substrates for Escherichia coli anaerobic reductases. These compounds have optical, solubility and redox properties that make them suitable for use in studies of the enzymology of menaquinol oxidation. Oxidized plumbagin and oxidized lapachol have well resolved absorbances at 419 nm (epsilon=3.95 mM-1. cm-1) and 481 nm (epsilon=2.66 mM-1.cm-1) respectively (in Mops/KOH buffer, pH 7.0). PBH2 is a good substrate for nitrate reductase A (Km=282+/-28 microM, kcat=120+/-6 s-1) and fumarate reductase (Km=155+/-24 microM, kcat=30+/-2 s-1), but not for DMSO reductase. LPCH2 is a good substrate for nitrate reductase A (Km=57+/-35 microM, kcat=68+/-13 s-1), fumarate reductase (Km=85+/-27 microM, kcat=74+/-6 s-1) and DMSO reductase (Km=238+/-30 microM, kcat=191+/-21 s-1). The sensitivity of enzymic LPCH2 and PBH2 oxidation to 2-n-heptyl-4-hydroxyquinoline N-oxide inhibition is consistent with their oxidation occurring at sites of physiological quinol binding.

NADPH-initiated cytochrome P450-dependent free iron-independent microsomal lipid peroxidation: specific prevention by ascorbic acid.

In this paper we demonstrate that ascorbic acid specifically prevents NADPH-initiated cytochrome P450 (P450)-mediated microsomal lipid peroxidation in the absence of free iron. Lipid peroxidation has been evidenced by the formations of conjugated dienes, lipid hydroperoxide and malondialdehyde. Other scavengers of reactive oxygen species including superoxide dismutase, catalase, glutathione, alpha-tocopherol, uric acid, thiourea, mannitol, histidine, beta-carotene and probucol are ineffective to prevent the NADPH-initiated P450-mediated free iron-independent microsomal lipid peroxidation. Using a reconstituted system comprised of purified NADPH-P450 reductase, P450 and isolated microsomal lipid or pure L-alpha-phosphatidylcholine diarachidoyl, a mechanism has been proposed for the iron-independent microsomal lipid peroxidation and its prevention by ascorbic acid. It is proposed that the perferryl moiety P450 Fe3+.O2.- initiates lipid peroxidation by abstracting methylene hydrogen from polyunsaturated lipid to form lipid radical, which then combines with oxygen to produce the chain propagating peroxyl radical for subsequent formation of lipid peroxides. Apparently, ascorbic acid prevents initiation of lipid peroxidation by interacting with P450 Fe3+.O2.-.