Is a Two-Day Cardiopulmonary Exercise Test a Valid Tool for The Diagnosis of Post-Exertional Malaise in Long COVID?

A two-day cardiopulmonary exercise testing (CPET) protocol (maximal ramp-incremental cycle test repeated 24hr apart) in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients has suggested that day-2 performance is decreased relative to day-1. This difference has been attributed to post-exertional malaise (PEM), suggesting the two-day CPET as a protocol to investigate PEM in Long COVID (LC) patients. PURPOSE: We aimed to investigate any effects of PEM on exercise performance and cardiorespiratory and perceptual responses to a two-day CPET in LC patients to determine whether the day-1 CPET would impair performance, cardiorespiratory responses or perceptions of exercise at day-2. METHODS: Fifteen LC patients with one or more symptoms persisting for more than three months after their initial infection [n=7 females; n=1 hospitalized; mean(SD); age 53(11) yrs; body mass index 32.2(8.5) kg/m2; time between COVID-19 onset and CPET 13(7) months; forced expiratory volume in 1 second 89(15) %pred; forced vital capacity 92(14) %pred; diffusing capacity of the lungs for carbon monoxide 92(15) %pred; total lung capacity 86(12) %pred] were studied. Prior to any exercise testing, PEM was assessed relative to the past six months using the modified DePaul Symptom Questionnaire (mDSQ) (0-4 symptoms frequency and severity scores). Each performed a two-day CPET protocol; ramp was 10-20 W/min, with the same ramp rate used for the day-1 and day-2 CPET. Peak oxygen uptake, peak work rate, and gas exchange threshold were measured using standard techniques. Ratings of perceived dyspnea and leg effort during cycling were recorded at peak exercise using the modified Borg’s Scale (0-10). One-sample t-tests were used to assess significance of test-retest mean difference. RESULTS: The mDSQ indicated the presence of PEM symptoms in 80% of participants. However, no significant differences between day-1 and day-2 CPET were found in any of the variables assessed. CONCLUSION: The absence of any difference in cardiorespiratory and perceptual responses in 2-day CPET testing, despite patient reported presence of PEM symptoms, suggests that the two-day CPET protocol may not be a valid tool for the diagnosis of PEM in LC patients

DNA methylation dynamics during intestinal stem cell differentiation reveals enhancers driving gene expression in the villus

Background: DNA methylation is of pivotal importance during development. Previous genome-wide studies identified numerous differentially methylated regions upon differentiation of stem cells, many of them associated with transcriptional start sites. Results: We present the first genome-wide, single-base-resolution view into DNA methylation dynamics during differentiation of a mammalian epithelial stem cell: the mouse small intestinal Lgr5+ stem cell. Very little change was observed at transcriptional start sites and our data suggest that differentiation-related genes are already primed for expression in the stem cell. Genome-wide, only 50 differentially methylated regions were identified. Almost all of these loci represent enhancers driving gene expression in the differentiated part of the small intestine. Finally, we show that binding of the transcription factor Tcf4 correlates with hypo-methylation and demonstrate that Tcf4 is one of the factors contributing to formation of differentially methylated regions. Conclusions: Our results reveal limited DNA methylation dynamics during small intestine stem cell differentiation and an impact of transcription factor binding on shaping the DNA methylation landscape during differentiation of stem cells in vivo

Crystal structure of [1,1′:3′,1′′-terphenyl]-2′,3,3′′-tricarboxylic acid

The asymmetric unit of the title compound, C21H14O6, comprises two symmetrically independent molecules that form a locally centrosymmetric hydrogen-bonded dimer, with the planes of the corresponding carboxylic acid groups rotated by 15.8 (1) and 17.5 (1)° relative to those of the adjacent benzene rings. The crystal as a whole, however, exhibits a noncentrosymmetric packing, described by the polar space group Pca21. The dimers form layers along the ab plane, being interconnected by hydrogen bonds involving the remaining carboxylic acid groups. The plane of the central carboxylic acid group forms dihedral angles of 62.5 (1) and 63.0 (1)° with those of the adjacent benzene rings and functions as a hydrogen-bond donor and acceptor. As a donor, it interconnects adjacent layers, while as an acceptor it stabilizes the packing within the layers. The `distal' carboxylic acid groups are nearly coplanar with the planes of the adjacent benzene rings, forming dihedral angles of 1.8 (1) and 7.1 (1)°. These groups also form intra- and inter-layer hydrogen bonds, but with `reversed' functionality, as compared with the central carboxylic acid groups

Protonation and Alkylation Induced Multidentate C–H···Anion Binding to Perrhenate

A family of pyridyl-functionalized arylacetylene C–H hydrogen bonding (HB) receptors were synthesized and binding interactions to perrhenate (ReO₄^–) studied in the solid state. The protonation and alkylation state of the pyridine nitrogen dictate the location and denticity of the interactions. X-ray structures of neutral <b>1</b> and singly charged <b>2a</b>⁺·ReO₄^– reveal the formation of favorable self-complementary dimers, owing to the presence of nitrogen HB acceptor sites. Dismissal of these dimers upon elimination of nitrogen HB acceptors on the receptor result in an array of multidentate C–H HB receptor–guest contacts

The Berkeleylactones, Antibiotic Macrolides from Fungal Coculture

A carefully timed coculture fermentation of <i>Penicillium fuscum</i> and <i>P. camembertii/clavigerum</i> yielded eight new 16-membered-ring macrolides, berkeleylactones A–H (<b>1</b>, <b>4</b>, <b>6</b>–<b>9</b>, <b>12</b>, <b>13</b>), as well as the known antibiotic macrolide A26771B (<b>5</b>), patulin, and citrinin. There was no evidence of the production of the berkeleylactones or A26771B (<b>5</b>) by either fungus when grown as axenic cultures. The structures were deduced from analyses of spectral data, and the absolute configurations of compounds <b>1</b> and <b>9</b> were determined by single-crystal X-ray crystallography. Berkeleylactone A (<b>1</b>) exhibited the most potent antimicrobial activity of the macrolide series, with low micromolar activity (MIC = 1–2 μg/mL) against four MRSA strains, as well as <i>Bacillus anthracis</i>, <i>Streptococcus pyogenes</i>, <i>Candida albicans</i>, and <i>Candida glabrata</i>. Mode of action studies have shown that, unlike other macrolide antibiotics, berkeleylactone A (<b>1</b>) does not inhibit protein synthesis nor target the ribosome, which suggests a novel mode of action for its antibiotic activity