Asymptomatic versus symptomatic patients: [18F]FDG-PET/CT patterns and evolutionary track of COVID-19 associated vasculitis

Several patients experience unexplained persistent symptoms after recovering from severe acute respiratory syndrome-related coronavirus disease 2 (SARS-CoV-2) [the so-called long coronavirus disease (COVID)], with a negative impact on their quality of life. We report the evolutionary track of fluorine-18-fluorodeoxyglucose positron emission tomography-computed tomography ([18F]FDG-PET/CT) in two patients incidentally diagnosed with SARS-CoV-2 infection. In both cases, baseline PET/CT showed bilateral pneumonia associated with [18F]FDG vascular uptake. Vascular uptake was more evident in the baseline scan of the asymptomatic patient. Vice versa, it was more marked in the follow-up examinations of the patient who developed long COVID. These findings suggested that vascular inflammation and its duration are responsible for the clinical course of the disease and the development of long COVID.

High angular resolution study of the super star cluster population in IRAS 17138−1017

Aims. Currently, the global characteristics and evolution of super star clusters (SSCs) are not well understood, due to the large distances to their host galaxies. We aim to study the population of SSCs in IRAS 17138-1017, a luminous infrared galaxy (LIRG), in terms of age, extinction, mass, and luminosity distribution. Methods. We analyzed imaging data in the near-infrared from the GeMS/GSAOI instrument on the Gemini telescope and generated simulations with the radiative transfer code MontAGN. The extraction of SSCs from the images and their photometry in J, H, and Ks allowed us to derive color-color and color-magnitude diagrams. Comparison with a theoretical stellar evolutionary track gives a first hint into the extinction towards each SSC, as well as their ages, despite some degeneracy between those two quantities. Spectra given by our radiative transfer code MontAGN, which includes dust emission, also provide insightful predictions and comparisons. Results. We detect with a fair degree of confidence 54 SSCs of mKs between 16 mag and 21 mag with a median instrumental uncertainty of 0.05 mag. When plotted on a color–color diagram and a color–magnitude diagram, it appears that most of the sources are very much extinct with respect to an intrinsic theoretical evolutionary track. Once de-reddened, the colors point unambiguously to two distinct and very recent starburst episodes at 2.8 and 4.5 Myr. While the SSCs in the 4.5 Myr starburst are distributed along the spiral arms, the 2.8 Myr SSCs are concentrated in the central region. The luminosity and mass functions present a classical power-law behavior, although with shallower slopes than generally observed in LIRGs. Comparison with radiative transfer simulations shows that, the dust thermal emission and scattered light are negligible and could not explain the few very red SSCs that could not be de-reddened safely.

Following the Evolutionary Track of a Highly Specific L-Arginine Oxidase by Reconstruction and Biochemical Analysis of Ancestral and Native Enzymes

ABSTRACT Following the evolutionary track of enzymes can help elucidate how enzymes attain their characteristic functions, such as thermal adaptation and substrate selectivity, during the evolutionary process. Ancestral sequence reconstruction (ASR) is effective for following evolutionary processes if sufficient sequence data are available. Selecting sequences from the data to generate a curated sequence library is necessary for the successful design of artificial proteins by ASR. In this study, we tried to follow the evolutionary track of l-arginine oxidase (AROD), a flavin adenine dinucleotide (FAD)-dependent amino acid oxidase (LAAO) that exhibits high specificity for l-arginine. The library was generated by selecting sequences in which the 15th, 50th, 332nd, and 580th residues are Gly, Ser, Trp, and Thr, respectively. We excluded sequences that are either extremely short or long and those with a low degree of sequence identity. Three ancestral ARODs (AncARODn0, AncARODn1, and AncARODn2) were designed using the library. Subsequently, we expressed the ancestral ARODs as well as native Oceanobacter kriegii AROD (OkAROD) in bacteria. AncARODn0 is phylogenetically most remote from OkAROD, whereas AncARODn2 is most similar to OkAROD. Thermal stability was gradually increased by extending AROD sequences back to the progenitor, while the temperature at which the residual activity is half of the maximum measured activity (T1/2) of AncARODn0 was >20°C higher than that of OkAROD. Remarkably, only AncARODn0 exhibited broad substrate selectivity similar to that of conventional promiscuous LAAO. Taken together, our findings led us to infer that AROD may have evolved from a highly thermostable and promiscuous LAAO. IMPORTANCE In this study, we attempted to infer the molecular evolution of a recently isolated FAD-dependent l-arginine oxidase (AROD) that oxidizes l-arginine to 2-ketoarginine. Utilizing 10 candidate AROD sequences, we obtained a total of three ancestral ARODs. In addition, one native AROD was obtained by cloning one of the candidate ARODs. The candidate sequences were selected utilizing a curation method defined in this study. All the ARODs were successfully expressed in Escherichia coli for analysis of their biochemical functions. The catalytic activity of our bacterially expressed ancestral ARODs suggests that our ASR was successful. The ancestral AROD that is phylogenetically most remote from a native AROD has the highest thermal stability and substrate promiscuity. Our findings led us to infer that AROD evolved from a highly thermostable and promiscuous LAAO. As an application, we can design artificial ARODs with improved functions compared with those of native ones.

What's the Matter with “China”? A Critique of Teleological History

This article argues that the study of China's history has long been caught in a teleological trap that presumes that history could have had only one evolutionary track. The author explains how he came to recognize the problems inherent in the teleological trap and to reconceptualize his approach. The article contrasts the history of the North China Plain, culturally rooted in dry-land grain agriculture and from time immemorial deeply intertwined with that of the adjacent grasslands, with that of the south, a culturally and linguistically diverse land of river valleys and riziculture. It concludes that the holistic empire we know today was not an inevitable outcome of these contrasting trajectories and that alternative paths are plausible, and asserts that scholars must recognize that until history is accomplished it does not follow a teleological trajectory.

Links Between Z Sources and Atoll Sources

It is known that the Z and atoll sources are two typical types of neutron-star sources in low mass X-ray binaries (LMXBs), which present very different Q-ν relations of lower kHz QPOs. We propose that the Z and atoll sources are two different phases in the evolutionary track of neutron star in LMXBs, instead of two types of distinct sources.