Quiescence is the most common and, arguably, most poorly understood cell cycle state. This is in part because pure populations of quiescent cells are typically difficult to isolate. We report the isolation and characterization of quiescent and nonquiescent cells from stationary-phase (SP) yeast cultures by density-gradient centrifugation. Quiescent cells are dense, unbudded daughter cells formed after glucose exhaustion. They synchronously reenter the mitotic cell cycle, suggesting that they are in a G0 state. Nonquiescent cells are less dense, heterogeneous, and composed of replicatively older, asynchronous cells that rapidly lose the ability to reproduce. Microscopic and flow cytometric analysis revealed that nonquiescent cells accumulate more reactive oxygen species than quiescent cells, and over 21 d, about half exhibit signs of apoptosis and necrosis. The ability to isolate both quiescent and nonquiescent yeast cells from SP cultures provides a novel, tractable experimental system for studies of quiescence, chronological and replicative aging, apoptosis, and the cell cycle.

Background. Sensitive and specific SARS-CoV-2 serologic assays are needed to inform diagnostic, therapeutic, and public health decision-making. We evaluated three commercial serologic assays as stand-alone tests and as components of two-test algorithms. Methods. Two nucleocapsid (Abbott IgG and Roche total antibody) and one spike-protein (DiaSorin IgG) antibody tests were included. We assessed sensitivity using 128 serum samples from symptomatic PCR-confirmed COVID-19-infected patients, and specificity using 1204 samples submitted for routine serologies prior to COVID-19's emergence, plus 64 pandemic-era samples from SARS-CoV-2 PCR-negative patients with respiratory symptoms. Assays were evaluated as stand-alone tests and as components of a two-test algorithm in which positive results obtained using one assay were verified using a second assay. Results. The two nucleocapsid antibody tests were more sensitive than the spike-protein antibody test overall (70% and 70% versus 57%; P≤0.003), with pronounced differences observed using samples collected 7-14 days after symptom onset. All three assays were comparably sensitive (≥89%, P≥0.13) using samples collected >14 days after symptom onset. Specificity was higher using the nucleocapsid antibody tests (99.3% and 99.7%) compared with the spike protein antibody test (97.8%, P≤0.002). When any two assays were paired in a two-test algorithm, specificity was 99.9% (P<0.0001 to 0.25 compared with the individual assays), and positive predictive value (PPV) improved substantially with minimal effect on negative predictive value (NPV). Conclusions. Two nucleocapsid antibody tests outperformed a spike protein antibody test. Pairing two different serologic tests in a two-test algorithm improves PPV compared with the individual assays alone, while maintaining NPV.

The tissue micromilieu in disorders (inflammation, ischemia, tumor) often shows pronounced metabolic acidosis that may alter signaling and transcriptional activity in resident cells which can be of special importance for omnipresent fibroblasts. In the present study we investigated the impact of metabolic acidosis on rat fibroblasts with special emphasis on their role in inflammation by regulation of TNF-α, MCP-1, COX-2 and iNOS expression and the signaling pathways involved. Extracellular acidosis led to an enhanced expression of TNF-α, COX-2 and iNOS in parallel to an activation of p38 and ERK1/2 kinases that was not observed by sole intracellular acidosis. Accordingly, the protein amounts of TNF-α and COX-2 as well as the production of nitrate and nitrite were elevated. Acidosis-induced expression of COX-2 and iNOS depended on p38 kinase, but not on ERK1/2. In contrast acidosis-induced TNF-α expression was independent of both kinases. Although GPR4, GPR68 and GPR132 are expressed in fibroblasts, the involvement of these potential candidate pH sensors could be ruled out since no acidosis-induced elevation in intracellular cAMP or free calcium content was observed. Furthermore our data show that MAPK activation by an acidic micromilieu depends on Ser/Thr phosphatase activity, but not on the production of reactive oxygen species and is sensitive to cAMP antagonism by Rp-cAMPS. In conclusion, our results show that an acidic microenvironment induces a differential transcriptional program of pathological relevant genes in fibroblasts via the cAMP-phosphatase-MAPK pathway and thereby generates a parainflammatory situation that can result in tissue remodeling.

Background Global electrical heterogeneity (GEH) is associated with sudden cardiac death (SCD) in adults of 45 years and above. However, GEH has not been previously measured in young athletes. The goal of this study was to establish a reference for vectorcardiograpic (VCG) metrics in male and female athletes. Methods Skiers (n = 140; mean age 19.2 ± 3.5 years; 66% male, 94% white; 53% professional athletes) were enrolled in a prospective cohort. Resting 12‐lead ECGs were interpreted per the International ECG criteria. Associations of age, sex, and athletic performance with GEH were studied. Results In age and training level‐adjusted analyses, male sex was associated with a larger T vector [T peak magnitude +186 (95% CI 106–266) µV] and a wider spatial QRS‐T angle [+28.2 (17.3–39.2)°] as compared to women. Spatial QRS‐T angle in the ECG left ventricular hypertrophy (LVH) voltage group (n = 21; 15%) and normal ECG group did not differ (67.7 ± 25.0 vs. 66.8 ± 28.2; p = 0.914), suggesting that ECG LVH voltage in athletes reflects physiological remodeling. In contrast, skiers with right ventricular hypertrophy (RVH) voltage (n = 26, 18.6%) had wider QRS‐T angle (92.7 ± 29.6 vs. 66.8 ± 28.2°; p = 0.001), larger SAI QRST (194.9 ± 30.2 vs. 157.8 ± 42.6 mV × ms; p < 0.0001), but similar peak SVG vector magnitude (1976 ± 548 vs. 1939 ± 395 µV; p = 0.775) as compared to the normal ECG group. Better athletic performance was associated with the narrower QRS‐T angle. Each 10% worsening in an athlete's Federation Internationale de’ Ski downhill ranking percentile was associated with an increase in spatial QRS‐T angle by 2.1 (95% CI 0.3–3.9) degrees (p = 0.013). Conclusion Vectorcardiograpic adds nuances to ECG phenomena in athletes.