The value of decreasing the duration of the infectious period of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection

Finding medications or vaccines that may decrease the infectious period of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could potentially reduce transmission in the broader population. We developed a computational model of the U.S. simulating the spread of SARS-CoV-2 and the potential clinical and economic impact of reducing the infectious period duration. Simulation experiments found that reducing the average infectious period duration could avert a median of 442,852 [treating 25% of symptomatic cases, reducing by 0.5 days, reproductive number (R₀) 3.5, and starting treatment when 15% of the population has been exposed] to 44.4 million SARS-CoV-2 cases (treating 75% of all infected cases, reducing by 3.5 days, R₀ 2.0). With R₀ 2.5, reducing the average infectious period duration by 0.5 days for 25% of symptomatic cases averted 1.4 million cases and 99,398 hospitalizations; increasing to 75% of symptomatic cases averted 2.8 million cases. At $500/person, treating 25% of symptomatic cases saved $209.5 billion (societal perspective). Further reducing the average infectious period duration by 3.5 days averted 7.4 million cases (treating 25% of symptomatic cases). Expanding treatment to 75% of all infected cases, including asymptomatic infections (R₀ 2.5), averted 35.9 million cases and 4 million hospitalizations, saving $48.8 billion (societal perspective and starting treatment after 5% of the population has been exposed). Our study quantifies the potential effects of reducing the SARS-CoV-2 infectious period duration.     

Regulation of Fas ligand-induced apoptosis by TNF.

Fas ligand (FasL, CD95L) expression helps control inflammatory reactions in immune privileged sites such as the eye. Cellular activation is normally required to render lymphoid cells sensitive to FasL-induced death; however, both activated and freshly isolated Fas(+) lymphoid cells are efficiently killed in the eye. Thus, we examined factors that might regulate cell death in the eye. TNF levels rapidly increased in the eye after the injection of lymphoid cells, and these cells underwent apoptosis within 24 h. Coinjection of anti-TNF Ab with the lymphoid cells blocked this cell death. Furthermore, TNFR2(-/-) T cells did not undergo apoptosis in the eyes of normal mice, while normal and TNFR1(-/-) T cells were killed by apoptosis. In vitro, TNF enhanced the Fas-mediated apoptosis of unactivated T cells through decreased intracellular levels of FLIP and increased production of the pro-apoptotic molecule Bax. This effect was mediated through the TNFR2 receptor. In vivo, intracameral injection of normal or TNFR1(-/-) 2,4,6-trinitrophenyl-coupled T cells into normal mice induced immune deviation, but TNFR2(-/-) 2,4,6-trinitrophenyl-coupled T cells were ineffective. Collectively, our results provide evidence of a role for the p75 TNFR in cell death in that TNF signaling through TNFR2 sensitizes lymphoid cells for Fas-mediated apoptosis. We conclude that there is complicity between apoptosis and elements of the inflammatory response in controlling lymphocyte function in immune privileged sites.     

Nitrogen Oxyanion-dependent Dissociation of a Two-component Complex That Regulates Bacterial Nitrate Assimilation

Nitrogen is an essential nutrient for growth and is readily available to microbes in many environments in the form of ammonium and nitrate. Both ions are of environmental significance due to sustained use of inorganic fertilizers on agricultural soils. Diverse species of bacteria that have an assimilatory nitrate/nitrite reductase system (NAS) can use nitrate or nitrite as the sole nitrogen source for growth when ammonium is limited. In Paracoccus denitrificans, the pathway-specific two-component regulator for NAS expression is encoded by the nasT and nasS genes. Here, we show that the putative RNA-binding protein NasT is a positive regulator essential for expression of the nas gene cluster (i.e. nasABGHC). By contrast, a nitrogen oxyanion-binding sensor (NasS) is required for nitrate/nitrite-responsive control of nas gene expression. The NasS and NasT proteins co-purify as a stable heterotetrameric regulatory complex, NasS-NasT. This protein-protein interaction is sensitive to nitrate and nitrite, which cause dissociation of the NasS-NasT complex into monomeric NasS and an oligomeric form of NasT. NasT has been shown to bind the leader RNA for nasA. Thus, upon liberation from the complex, the positive regulator NasT is free to up-regulate nas gene expression.     

Specificity of GlcNAc-PI de-N-acetylase of GPI biosynthesis and synthesis of parasite-specific suicide substrate inhibitors.

The substrate specificities of Trypanosoma brucei and human (HeLa) GlcNAc-PI de-N-acetylases were determined using 24 substrate analogues. The results show the following. (i) The de-N-acetylases show little specificity for the lipid moiety of GlcNAc-PI. (ii) The 3'-OH group of the GlcNAc residue is essential for substrate recognition whereas the 6'-OH group is dispensable and the 4'-OH, while not required for recognition, cannot be epimerized or substituted. (iii) The parasite enzyme can act on analogues containing betaGlcNAc or aromatic N-acyl groups, whereas the human enzyme cannot. (iv) Three GlcNR-PI analogues are de-N-acetylase inhibitors, one of which is a suicide inhibitor. (v) The suicide inhibitor most likely forms a carbamate or thiocarbamate ester to an active site hydroxy-amino acid or Cys or residue such that inhibition is reversed by certain nucleophiles. These and previous results were used to design two potent (IC50 = 8 nM) parasite-specific suicide substrate inhibitors. These are potential lead compounds for the development of anti-protozoan parasite drugs.     

Effect of high temperature on calcium uptake by suspension-cultured pear fruit cells

Uptake of Ca²⁺ by suspension-cultured pear (Pyrus communis L. cv Passe Crassane) cells and protoplasts was significantly enhanced by exposure to 38°C compared to 25°C. The increased uptake was specific for Ca²⁺ and was not due to cell wall binding. Tissues pretreated at 38°C showed increased uptake even upon return to 25°C. Treatment with carbonylcyanide m-chlorophenylhydrazone, salicylhydroxamic acid + KCN, or arsenite also increased Ca²⁺ content of cells. Results are discussed with regard to membrane permeability changes, the cellular control of Ca²⁺, and heat treatments used to inhibit softening of fruit during postharvest storage.     

Aging alterations in the modulation of central dopaminergic cilioinhibition by etorphine in the marine mussel,Mytilus edulis: Decrease in the inhibition of presynaptic dopamine release

1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress.     

The periplasmic nitrate reductase of Rhodobacter capsulatus; purification,characterisation and distinction from a single reductase for trimethylamine-N-oxide,dimethylsulphoxide and chlorate

The periplasmic dissimilatory nitrate reductase from Rhodobacter capsulatus N22DNAR⁺ has been purified. It comprises a single type of polypeptide chain with subunit molecular weight 90,000 and does not contain heme. Chlorate is not an alternative substrate. A molybdenum cofactor, of the pterin type found in both nitrate reductases and molybdoenzymes from various sources, is present in nitrate reductase from R. capsulatus at an approximate stoichiometry of 1 molecule per polypeptide chain. This is the first report of the occurrence of the cofactor in a periplasmic enzyme. Trimethylamine-N-oxide reductase activity was fractionated by ion exchange chromatography of periplasmic proteins. The fractionated material was active towards dimethylsulphoxide, chlorate and methionine sulphoxide, but not nitrate. A catalytic polypeptide of molecular weight 46,000 was identified by staining for trimethylamine-N-oxide reductase activity after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The same polypeptide also stained for dimethylsulphoxide reductase activity which indicates that trimethylamine-N-oxide and dimethylsulphoxide share a common reductase.Abbreviations DMSO dimethylsulphoxide - LDS lithium dodecyl sulphate - MVH reduced methylviologen - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulphate - TMAO trimethylamine-N-oxide     

Relationships between structure, toxicity and genetic effects in Salmonella typhimurium and Saccharomyces cerevisiae for substituted aniline mustards

A series of 4-substituted aniline mustards of widely varying reactivities have been evaluated for their mutagenic effects in Salmonella typhimurium strains of varying uvrB gene and plasmid status, and for their ability to cause mitotic crossing-over in Saccharomyces cerevisiae. The 4-methyl aniline mustard N,N-bis(2-chloroethyl)-4-methylaniline and its corresponding half-mustard N-(2-chloroethyl)-4-methylaniline showed widely different effects in the various bacterial strains, with the half-mustard being much less toxic than the full mustard in the uvrB- strain TA100. However, in the uvrB+ strain TA1978+, possessing an intact excision repair system, both compounds were equally toxic and the full mustard was the more mutagenic. Both compounds were equally effective in promoting mitotic crossing-over in yeast. For a series of 4-substituted full mustards, the toxicity in S. typhimurium strain TA100 correlated with substituent electronic parameters in the same way as does mammalian cell toxicity, supporting the view that the primary mode of toxicity is via DNA cross-linking, even for unreactive analogues. However, there were no obvious correlations between substituent physiochemical properties and mutagenic potential in bacteria, suggesting that mutagenic events are subject to a variety of influences other than the reactivity of the mustard group. In contrast, the most chemically reactive compounds were the most toxic and most recombinogenic in yeast.