A dusty veil shading Betelgeuse during its Great Dimming.

Red supergiants are the most common final evolutionary stage of stars that have initial masses between 8 and 35 times that of the Sun1. During this stage, which lasts roughly 100,000 years1, red supergiants experience substantial mass loss. However, the mechanism for this mass loss is unknown2. Mass loss may affect the evolutionary path, collapse and future supernova light curve3 of a red supergiant, and its ultimate fate as either a neutron star or a black hole4. From November 2019 to March 2020, Betelgeuse-the second-closest red supergiant to Earth (roughly 220 parsecs, or 724 light years, away)5,6-experienced a historic dimming of its visible brightness. Usually having an apparent magnitude between 0.1 and 1.0, its visual brightness decreased to 1.614 ± 0.008 magnitudes around 7-13 February 20207-an event referred to as Betelgeuse's Great Dimming. Here we report high-angular-resolution observations showing that the southern hemisphere of Betelgeuse was ten times darker than usual in the visible spectrum during its Great Dimming. Observations and modelling support a scenario in which a dust clump formed recently in the vicinity of the star, owing to a local temperature decrease in a cool patch that appeared on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. Our findings suggest that a component of mass loss from red supergiants8 is inhomogeneous, linked to a very contrasted and rapidly changing photosphere.

Structure-activity relationship of the aminomethylcyclines and the discovery of omadacycline.

A series of novel tetracycline derivatives were synthesized with the goal of creating new antibiotics that would be unaffected by the known tetracycline resistance mechanisms. New C-9-position derivatives of minocycline (the aminomethylcyclines [AMCs]) were tested for in vitro activity against Gram-positive strains containing known tetracycline resistance mechanisms of ribosomal protection (Tet M in Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae) and efflux (Tet K in S. aureus and Tet L in E. faecalis). A number of aminomethylcyclines with potent in vitro activity (MIC range of ≤0.06 to 2.0 µg/ml) were identified. These novel tetracyclines were more active against one or more of the resistant strains than the reference antibiotics tested (MIC range, 16 to 64 µg/ml). The AMC derivatives were active against bacteria resistant to tetracycline by both efflux and ribosomal protection mechanisms. This study identified the AMCs as a novel class of antibiotics evolved from tetracycline that exhibit potent activity in vitro against tetracycline-resistant Gram-positive bacteria, including pathogenic strains of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE). One derivative, 9-neopentylaminomethylminocycline (generic name omadacycline), was identified and is currently in human trials for acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP).

Cricoid pressure training using simulation: a systematic review and meta-analysis.

Cricoid pressure (CP) is commonly applied during rapid sequence intubation and may be protective during induction of anaesthesia; however, CP application by untrained practitioners may not be performed optimally. The objective of this systematic review was to synthesize the evidence regarding effectiveness of technology-enhanced simulation training to improve efficacy of CP application. Electronic databases from inception through May 11, 2011 were searched. Eligible studies evaluated CP simulation training. Independent reviewers working in duplicate extracted study characteristics, validity, and outcomes data. Pooled effect size (ES) with 95% confidence intervals (CIs) were estimated from each study that compared technology-enhanced simulation with no intervention or with other methods of CP training using random-effects model. Twelve studies (772 trainees) evaluated CP training as an outcome. Nine studies reported information on baseline skill, with 23% of providers being able to achieve the target CP before training. In a meta-analysis of 10 studies (570 trainees), CP training resulted in a large favourable impact on skills among trainees compared with no intervention (pooled ES 1.18; 95% CI 0.85-1.51; P<0.0001). Four studies found evidence of skills retention for CP application after training, but for a limited time (<4 weeks). Comparative effectiveness research shows beneficial effects to force feedback training over training without feedback. Simulation training significantly improves the efficacy of CP application. Future studies might evaluate the clinical impact of training on CP application during rapid sequence intubation, and the comparative effectiveness of different training approaches.

(Sub)stellar companions shape the winds of evolved stars.

Binary interactions dominate the evolution of massive stars, but their role is less clear for low- and intermediate-mass stars. The evolution of a spherical wind from an asymptotic giant branch (AGB) star into a nonspherical planetary nebula (PN) could be due to binary interactions. We observed a sample of AGB stars with the Atacama Large Millimeter/submillimeter Array (ALMA) and found that their winds exhibit distinct nonspherical geometries with morphological similarities to planetary nebulae (PNe). We infer that the same physics shapes both AGB winds and PNe; additionally, the morphology and AGB mass-loss rate are correlated. These characteristics can be explained by binary interaction. We propose an evolutionary scenario for AGB morphologies that is consistent with observed phenomena in AGB stars and PNe.

Raised vascular calcium in an animal model: effects on aortic function.

STUDY OBJECTIVE - The aim of the study was to develop an animal model to study the relationships between raised tissue calcium and vascular function. DESIGN - Ectopic calcification was developed in the animal model using chronic vitamin D2 intoxication, after which functional studies were performed in isolated superfused aortic rings. Results were compared with control preparations. EXPERIMENTAL ANIMALS - 160 female Sprague-Dawley rats weighing 200-225 g were randomly divided into experimental (vitamin D2 1 mg.d-1) and control (vehicle only) groups. MEASUREMENTS and RESULTS - Aortas from vitamin D treated animals had a higher calcium content than control aortas, without concomitant increases in cardiac calcium. Aortas with high calcium content were found to develop greater tension than control aortas when exposed to noradrenaline in the absence of extracellular calcium, but the tension maxima achieved in response to noradrenaline in calcium containing media or to high potassium depolarising solution were the same. The rate of development of contraction in response to noradrenaline was greater in aortas from the vitamin D treated animals than in controls. Isoprenaline and sodium nitroprusside produced less relaxation in the animal model aortas than in the controls. CONCLUSIONS - The results suggest that increased aortic calcium affects the response of the tissue to vasoactive agents. It appears that the additional vascular calcium may be stored in an agonist releasable pool, probably within the sarcoplasmic reticulum. The enlarged or newly developed pools appear to be refillable from the extracellular medium but not by intracellular reuptake of calcium, suggesting a bicompartmental model of intracellular calcium release and reuptake.

A new initiative with multiple sponsors to help prepare medical students to be safe and effective prescribers.

Most medical schools in the US, and in other countries as well, continue to struggle to teach their medical students to be safe and effective prescribers before they graduate and set off for their residency programs. We describe a new initiative supported by several national organizations to help medical schools address this need by producing and making available online learning modules that can be used by medical students at any US medical school.

Hypercalcemia of immobilization in an adult patient with peripheral neuropathy.

A 48-year-old man developed a marked and persistent hypercalcemia 3 months after admission for paraplegia resulting from severe peripheral neuropathy most likely of alcoholic etiology. Serum ionized calcium was elevated, and parathyroid hormone levels were low normal by the two separate radioimmunoassays. Urinary calcium excretion was markedly elevated, and serum 1,25-dihydroxyvitamin D level was decreased. An extensive clinical evaluation for possible occult malignancy, myeloma, and sarcoidosis as a cause of hypercalcemia produced no positive findings. Treatment with calcitonin caused prompt normalization of serum calcium, and its discontinuation resulted in recurrence of hypercalcemia. With improvement of neuropathy, the patient started active physical therapy. We gradually discontinued calcitonin, and the patient's serum calcium remained normal during the following 11 months. We discuss difficulties in both clinical and laboratory diagnosis of hypercalcemia of immobilization in the adult patient because no specific laboratory test is available.

Antagonism of the lethal effects of cyanide with resealed erythrocytes containing rhodanese and thiosulfate.

A new concept has been presented for the antagonism of cyanide and possibly other chemical toxicants. Until now, only a half dozen truly specific "antidotes" were known. There are many other "antidotes" which merely prevent the absorption or enhance the elimination of a toxic compound rather than specifically destroying the substance to prevent its toxic effect. This new approach has considerable conceptual significance in toxicology, as it suggests the encapsulating other enzymes to degrade various other chemical toxicants. There are many chemical toxicants for which there are no specific antidotes, and the conceptual approach of employing erythrocyte-encapsulated enzyme provides an innovative, specific approach to antagonize the toxic and lethal effects of these chemicals.

Contribution of early glycemic status in the development of severe retinopathy of prematurity in a cohort of ELBW infants.

OBJECTIVE: The objective of this study is to investigate the relationship between glycemic status and severe retinopathy of prematurity (ROP). STUDY DESIGN: This is a retrospective cohort study of 114 infants <1000 g admitted to a level IV neonatal intensive care unit within 48 h of life. A cumulative, time-weighted glucose level (TWGL) derived from plotting glucose values over time was included in logistic regression analysis to identify predictors for severe ROP. RESULT: Infants had 26.6 ± 2 weeks gestational age and had a birth weight of 782 ± 136 g. TWGL during first 10 and 30 days of life were greater in the severe ROP group (P<0.01). Unlike single events of glucose levels ≥ 150 mg dl(-1), 10 days TWGL ≥ 100 mg dl(-1) (odds ratio (OR) 5.2, P<0.02) and 30 days TWGL ≥ 118 mg dl(-1) (OR 5.7, P<0.02) were predictors for severe ROP (univariate). Multivariate regression confirmed 30 days TWGL ≥ 118 mg dl(-1) (OR 9.4 to 10) and gram-positive sepsis (OR 4.1 to 5) as predictors for severe ROP (P<0.05). CONCLUSION: High overall glycemic status is associated with the development of severe ROP.

Limited uptake of the cyanobacterial toxin cylindrospermopsin by Vero cells.

Cylindrospermopsin (CYN) is a cyanobacterial toxin increasingly found in drinking water sources worldwide. Toxicity studies have shown CYN can induce effects in a range of different cell types with primary hepatocytes consistently shown to be the most sensitive cellular model. How CYN enters the intracellular environment is not clear, although the size and hydrophilic nature of the toxin suggest it would not readily cross a lipid bilayer. In this study, a Vero cell line expressing green fluorescent protein (GFP) was used to monitor for CYN uptake based on the toxin's potent effects on protein synthesis. Effects on the GFP signal were compared with inhibitors cycloheximide (CHEX) and emetine. While CYN potency was demonstrated in a cell-free system (CYN>CHEX>emetine) it was considerably reduced in the Vero-GFP cell model (CHEX, emetine>>CYN). In contrast to other inhibitors, CYN effects on GFP signal increased 6 fold over 4-24 h incubation indicating slow, progressive uptake of the toxin. Confirming that the uptake process is not energy dependent CYN entry also occurred at 4 degrees C, while competition experiments excluded the uracil nucleobase transporter system as potential mechanism for CYN uptake. Dilution of media enhanced CYN uptake by Vero-GFP cells although mechanism by which this occurred is unknown.

Preschoolers' magnitude comparisons are mediated by a preverbal analog mechanism.

We report a study of 3- to 5-year-olds who performed a magnitude-comparison task. Stimuli were a series of pairs of arrays that sometimes differed in numerosity, and the children were asked to point to the more numerous array in each pair. The proportion of accurate responses was above chance for all age groups. However, error patterns were consistent with analog models of magnitude representation. Errors varied systematically with the ratio of stimulus pairs. Items with a 2:3 ratio were harder than items with a 1:2 ratio. Performance on posttests of verbal counting ability was variable, but did not predict performance on the numerical discrimination task. We argue that neither verbal counting nor nonnumerical perceptual strategies can explain these results. This study supports the hypothesis that adults and children share preverbal, analog representations of magnitude.

Encapsulation of rhodanese and organic thiosulfonates by mouse erythrocytes.

A series of organic thiosulfonates were synthesized and studied as sulfur donor substrates for rhodanese encapsulated within murine carrier erythrocytes. Previous studies have indicated that resealed erythrocytes containing rhodanese (CRBC) and sodium thiosulfate can rapidly metabolize cyanide to the less toxic thiocyanate. This thiosulfate-rhodanese system was very efficacious as a new conceptual approach to antagonize cyanide intoxication both in vitro and in vivo. However, its potential is restricted because of the limited availability of thiosulfate due to its poor permeability through RBC membrane. Present studies suggest that there are advantages in using alternative sulfur donors, i.e., organic thiosulfonates in this rhodanese-containing resealed erythrocyte system, since these compounds have higher lipid solubility than inorganic thiosulfates and can readily penetrate the red blood cell membrane. Therefore, this system could provide a virtually unlimited amount of sulfur donor to the encapsulated rhodanese even if the substrates are in solution outside the cells. Moreover, the rhodanese reaction rate of any of these organic thiosulfonates is much faster than the rate observed with the classic cyanide antidote, sodium thiosulfate. This CRBC system will continue to detoxify cyanide even when these encapsulated sulfur donors are depleted, as the lipid soluble organic thiosulfonate outside the cells will diffuse past the membrane into the cell to replenish the sulfur donor. The encapsulation efficiency for rhodanese is about 30%, and the velocity of the rhodanese reaction increases linearly with the volume of enzyme-laden erythrocytes. Similarly, reaction velocity increases linearly with substrate concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Rhodanese and sodium thiosulfate encapsulated in mouse carrier erythrocytes. II. In vivo survivability and alterations in physiologic and morphologic characteristics.

Biodegradable drug carrier mechanisms were employed in drug antagonism studies. Prior studies indicated that erythrocytes containing encapsulated rhodanese and sodium thiosulfate metabolized cyanide to thiocyanate in vitro. Studies were conducted to investigate the properties of these sulfurtransferase-loaded red blood cells in vivo by administering the carrier red blood cells intravenously. Approximately 40 to 50% of the cells were eliminated within the first few hours while the remaining loaded erythrocytes persisted in the circulation. The present studies were initiated to investigate the characteristics of the disposition of the loaded erythrocytes and to examine differences in the properties between carrier and noncarrier erythrocytes. Also, the disposition and viability of the erythrocytes in vivo were studied with relation to various biochemical, physiological, and morphological properties. These studies indicated that the carrier erythrocytes had a smaller cell volume and were more susceptible to hemolysis than normal erythrocytes. Morphologic studies by electron microscopy indicated that extensive morphologic changes occurred during the procedures after hypotonic dialysis, isotonicity adjustment, and resealing were completed. Differences were noted between those cells that were only resealed and those cells that were also subjected to annealing. The morphologic characteristics of most of the cells were restored to the "normal" morphologic appearance only after annealing. Annealed erythrocytes' in vivo survivability was correlated with the physical properties of these cells.

In vivo studies on rhodanese encapsulation in mouse carrier erythrocytes.

Resealed erythrocytes containing sodium thiosulfate and rhodanese (CRBC) are being employed as a new approach in the antagonism of cyanide intoxication. In earlier in vitro studies, the behavior of red blood cells containing rhodanese and sodium thiosulfate was investigated with regard to their properties and their capability of metabolizing cyanide to thiocyanate. The present studies are concerned with the properties of these rhodanese-containing carrier erythrocytes in the intact animal. These carrier erythrocytes were administered intravenously and the survival of the encapsulated enzyme was compared with the administration (iv) of free exogenous enzyme. Also, the amount of leakage of the encapsulated rhodanese from the red blood cell was determined. The survival of the carrier red blood cell. prepared by hypotonic dialysis, was found to be characterized by a biphasic curve. There was an initial rapid loss of approximately 40 to 50% of the carrier cells with a t1/2 = 2.5 hr. Subsequently the remaining resealed annealed carrier erythrocytes persisted in the vascular system with a t1/2 = 8.5 days. When free exogenous rhodanese was administered directly into the vascular system, it was rapidly eliminated with a t1/2 = 53 min. Red blood cells containing sodium thiosulfate and rhodanese apparently are effective in vivo in the biotransformation of cyanide. In animals pretreated with encapsulated rhodanese and sodium thiosulfate, blood cyanide concentrations are appreciably decreased with a concomitant increase in thiocyanate ion, a metabolite of cyanide. When erythrocytes, which contained no rhodanese or sodium thiosulfate, were subjected to hypotonic dialysis, cyanide was not metabolized to any appreciable extent. Furthermore, carrier erythrocytes containing rhodanese and sodium thiosulfate were found to increase the protection against the lethal effects of cyanide by approximately twofold. The ability of these carrier erythrocytes alone to metabolize cyanide and to antagonize the lethal effects of cyanide reflects the potential of this new antidotal approach in the antagonism of chemical toxicants.