Acute and chronic temperature dependence of Na+/H+ exchange activity of Pimephales promelas gills.

Na+/H+ exchangers (NHE) mediate at least part of Na+ entry into gill epithelia via Na+/NH4+ exchange. For homeostasis, Na+ entry into and exit via Na+/K+ ATPase from gill epithelia must balance. Na+/K+ ATPase activity is reduced in cold- compared to warm-acclimated freshwater temperate fish. We hypothesized gill NHE activity is greater in warm- than cold-acclimated fish when measured at acclimation temperatures, and NHE activity displays a temperature dependence similar to Na+/K+ ATPase. Since NHE mRNA expression does not differ, we measured the Na+-dependence of pH-induced Na+ fluxes in gill vesicles from warm- and cold-acclimated fathead minnows at 20o and 7 °C, and calculated maximum transport rates (Vmax) and Na+ K1/2s. We also measured NH4+-induced Na+ fluxes and Na+-induced H+ fluxes. In vesicles from warm-acclimated fish, NHE Vmaxs were 278 ± 33 and 149 ± 23 arbitrary unit/s (au/s) and Na+ K1/2s were 12 ± 4 and 6 ± 4 mmol/l when assayed at 20o and 7 °C (p < 0.004), respectively. In vesicles from cold-acclimated fish, Vmaxs were 288 ± 35 and 141 ± 13 au/s and Na+ K1/2s 17 ± 5 and 7 ± 2 mmol/l when assayed at 20o and 7 °C (p < 0.002), respectively. Na+-induced H+ fluxes were 98 ± 8 and 104 ± 26 au/s in warm- and cold-acclimated fish assayed at 20 °C, respectively. Na+/NH4+ exchange was 120 ± 11 and 158 ± 13 au/s in warm- and cold-acclimated fish, respectively. Conclusions: Gill NHE activity was greater in warm- than cold-acclimated fish assayed at acclimation temperatures. The temperature dependence of NHE activity was similar in both groups, but differed from that reported for Na+/K+ ATPase suggesting complex mechanisms to maintain Na+ homeostasis.

Comparison of thrombotic and clinical outcomes in SARS-CoV-2-pneumonia versus other viral pneumonia in an urban academic medical center.

BACKGROUND: Infection with viral pneumonia (PNA) is known to offset the coagulation cascade. Recent studies assessing novel SARS-CoV-2 infection observed a high frequency of systemic thrombotic events resulting in ambiguity if severity of infection or specific viral strain drive thrombosis and worsen clinical outcomes. Furthermore, limited data exists addressing SARS-CoV-2 in underrepresented patient populations. OBJECTIVES: Assess clinical outcomes events and death in patients diagnosed with SARS-CoV-2 pneumonia compared to patients with other types of viral pneumonia. METHODS: Retrospective cohort study evaluated electronic medical records in adult patients admitted to University of Illinois Hospital and Health Sciences System (UIHHSS) with primary diagnosis of SARS-CoV-2 PNA or other viral (H1N1 or H3N2) PNA between 10/01/2017 and 09/01/2020. Primary composite outcome was the following event incidence rates: death, ICU admission, infection, thrombotic complications, mechanical ventilation, renal replacement therapy, and major bleeding. RESULTS: Of 257 patient records, 199 and 58 patients had SARS-CoV-2 PNA and other viral PNA, respectively. There was no difference in primary composite outcome. Thrombotic events (n = 6, 3%) occurred solely in SARS-CoV-2 PNA patients in the ICU. A significantly higher incidence of renal replacement therapy (8.5% vs 0%, p=0.016) and mortality (15.6% vs 3.4%, p=0.048) occurred in the SARS-CoV-2 PNA group. Multivariable logistic regression analysis revealed age, presence of SARS-CoV-2, and ICU admission, aOR 1.07, 11.37, and 41.95 respectively, was significantly associated with mortality risk during hospitalization; race and ethnicity were not. CONCLUSION: Low overall incidence of thrombotic events occurred only in the SARS-CoV-2 PNA group. SARS-CoV-2 PNA may lead to higher incidence of clinical events than those observed in H3N2/H1N1 viral pneumonia, and that race/ethnicity does not drive mortality outcomes.

Transcriptomic landscape of the blastema niche in regenerating adult axolotl limbs at single-cell resolution.

Regeneration of complex multi-tissue structures, such as limbs, requires the coordinated effort of multiple cell types. In axolotl limb regeneration, the wound epidermis and blastema have been extensively studied via histology, grafting, and bulk-tissue RNA-sequencing. However, defining the contributions of these tissues is hindered due to limited information regarding the molecular identity of the cell types in regenerating limbs. Here we report unbiased single-cell RNA-sequencing on over 25,000 cells from axolotl limbs and identify a plethora of cellular diversity within epidermal, mesenchymal, and hematopoietic lineages in homeostatic and regenerating limbs. We identify regeneration-induced genes, develop putative trajectories for blastema cell differentiation, and propose the molecular identity of fibroblast-like blastema progenitor cells. This work will enable application of molecular techniques to assess the contribution of these populations to limb regeneration. Overall, these data allow for establishment of a putative framework for adult axolotl limb regeneration.

A Tissue-Mapped Axolotl De Novo Transcriptome Enables Identification of Limb Regeneration Factors.

Mammals have extremely limited regenerative capabilities; however, axolotls are profoundly regenerative and can replace entire limbs. The mechanisms underlying limb regeneration remain poorly understood, partly because the enormous and incompletely sequenced genomes of axolotls have hindered the study of genes facilitating regeneration. We assembled and annotated a de novo transcriptome using RNA-sequencing profiles for a broad spectrum of tissues that is estimated to have near-complete sequence information for 88% of axolotl genes. We devised expression analyses that identified the axolotl orthologs of cirbp and kazald1 as highly expressed and enriched in blastemas. Using morpholino anti-sense oligonucleotides, we find evidence that cirbp plays a cytoprotective role during limb regeneration whereas manipulation of kazald1 expression disrupts regeneration. Our transcriptome and annotation resources greatly complement previous transcriptomic studies and will be a valuable resource for future research in regenerative biology.