No evidence for distinct types in the evolution of SARS-CoV-2

A recent study by Tang et al. claimed that two major types of severe acute respiratory syndrome-coronavirus-2 (CoV-2) had evolved in the ongoing CoV disease-2019 pandemic and that one of these types was more ‘aggressive’ than the other. Given the repercussions of these claims and the intense media coverage of these types of articles, we have examined in detail the data presented by Tang et al., and show that the major conclusions of that paper cannot be substantiated. Using examples from other viral outbreaks, we discuss the difficulty in demonstrating the existence or nature of a functional effect of a viral mutation, and we advise against overinterpretation of genomic data during the pandemic

Using Total Fluorescence Increase (Signal Mass) to Determine the Ca2+ Current Underlying Localized Ca2+ Events

The feasibility of determining localized Ca2+ influx using only wide-field fluorescence images was explored by imaging (using fluo-3) single channel Ca2+ fluorescence transients (SCCaFTs), due to Ca2+ entry through single openings of Ca2+-permeable ion channels, while recording unitary channel currents. Since the image obtained with wide-field optics is an integration of both in-focus and out-of-focus light, the total fluorescence increase (ΔFtotal or “signal mass”) associated with a SCCaFT can be measured directly from the image by adding together the fluorescence increase due to Ca2+ influx in all of the pixels. The assumptions necessary for obtaining the signal mass from confocal linescan images are not required. Two- and three-dimensional imaging was used to show that ΔFtotal is essentially independent of the position of the channel with respect to the focal plane of the microscope. The relationship between Ca2+ influx and ΔFtotal was obtained using SCCaFTs from plasma membrane caffeine-activated cation channels when Ca2+ was the only charge carrier of the inward current. This relationship was found to be linear, with the value of the slope (or converting factor) affected by the particular imaging system set-up, the experimental conditions, and the properties of the fluorescent indicator, including its binding capacity with respect to other cellular buffers. The converting factor was used to estimate the Ca2+ current passing through caffeine-activated channels in near physiological saline and to estimate the endogenous buffer binding capacity. In addition, it allowed a more accurate estimate of the Ca2+ current underlying Ca2+ sparks resulting from Ca2+ release from intracellular stores via ryanodine receptors in the same preparation

The Gcs1 and Age2 ArfGAP proteins provide overlapping essential function for transport from the yeast trans-Golgi network

Many intracellular vesicle transport pathways involve GTP hydrolysis by the ADP-ribosylation factor (ARF) type of monomeric G proteins, under the control of ArfGAP proteins. Here we show that the structurally related yeast proteins Gcs1 and Age2 form an essential ArfGAP pair that provides overlapping function for TGN transport. Mutant cells lacking the Age2 and Gcs1 proteins cease proliferation, accumulate membranous structures resembling Berkeley bodies, and are unable to properly process and localize the vacuolar hydrolase carboxypeptidase (CPY) and the vacuolar membrane protein alkaline phosphatase (ALP), which are transported from the TGN to the vacuole by distinct transport routes. Immunofluorescence studies localizing the proteins ALP, Kex2 (a TGN resident protein), and Vps10 (the CPY receptor for transport from the TGN to the vacuole) suggest that inadequate function of this ArfGAP pair leads to a fragmentation of TGN, with effects on secretion and endosomal transport. Our results demonstrate that the Gcs1 + Age2 ArfGAP pair provides overlapping function for transport from the TGN, and also indicate that multiple activities at the TGN can be maintained with the aid of a single ArfGAP

Imaging Ca2+ Entering the Cytoplasm through a Single Opening of a Plasma Membrane Cation Channel

Discrete localized fluorescence transients due to openings of a single plasma membrane Ca2+ permeable cation channel were recorded using wide-field digital imaging microscopy with fluo-3 as the Ca2+ indicator. These transients were obtained while simultaneously recording the unitary channel currents using the whole-cell current-recording configuration of the patch-clamp technique. This cation channel in smooth muscle cells is opened by caffeine (Guerrero, A., F.S. Fay, and J.J. Singer. 1994. J. Gen. Physiol. 104:375–394). The localized fluorescence transients appeared to occur at random locations on the cell membrane, with the duration of the rising phase matching the duration of the channel opening. Moreover, these transients were only observed in the presence of sufficient extracellular Ca2+, suggesting that they are due to Ca2+ influx from the bathing solution. The fluorescence transient is characterized by an initial fast rising phase when the channel opens, followed by a slower rising phase during prolonged openings. When the channel closes there is an immediate fast falling phase followed by a slower falling phase. Computer simulations of the underlying events were used to interpret the time course of the transients. The rapid phases are mainly due to the establishment or removal of Ca2+ and Ca2+-bound fluo-3 gradients near the channel when the channel opens or closes, while the slow phases are due to the diffusion of Ca2+ and Ca2+-bound fluo-3 into the cytoplasm. Transients due to short channel openings have a “Ca2+ spark-like” appearance, suggesting that the rising and early falling components of sparks (due to openings of ryanodine receptors) reflect the fast phases of the fluorescence change. The results presented here suggest methods to determine the relationship between the fluorescence transient and the underlying Ca2+ current, to study intracellular localized Ca2+ handling as might occur from single Ca2+ channel openings, and to localize Ca2+ permeable ion channels on the plasma membrane

Nonequivalent effects of PKC activation by PMA on murine CD4 and CD8 cell‐surface expression

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154260/1/fsb2002012010.pd

Individual freedom versus collective responsibility: an ethicist's perspective

Philosophical theories of collective action have produced a number of alternative accounts of the rationality and morality of self-interest and altruism. These have obvious applications to communicable disease control, the avoidance of antibiotic resistance, the responsibility of healthcare professionals to patients with serious communicable diseases, and the sharing of personal data in epidemiological research

Second bound state of the positronium molecule and biexcitons

A new, hitherto unknown bound state of the positronium molecule, with orbital angular momentum L=1 and negative parity is reported. This state is stable against autodissociation even if the masses of the positive and negative charges are not equal. The existence of a similar state in two-dimension has also been investigated. The fact that the biexcitons have a second bound state may help the better understanding of their binding mechanism.Comment: Latex, 8 pages, 2 Postscript figure