ENaC and ROMK channels in the connecting tubule regulate renal K+ secretion

We measured the activities of epithelial Na channels (ENaC) and ROMK channels in the distal nephron of the mouse kidney and assessed their role in the process of K⁺ secretion under different physiological conditions. Under basal dietary conditions (0.5% K), ENaC activity, measured as amiloride-sensitive currents, was high in cells at the distal end of the distal convoluted tubule (DCT) and proximal end of the connecting tubule (CNT), a region we call the early CNT (CNTe). In more distal parts of the CNT (aldosterone-sensitive portion [CNTas]), these currents were minimal. This functional difference correlated with alterations in the intracellular location of ENaC, which was at or near the apical membrane in CNTe and more cytoplasmic in the CNTas. ROMK activity, measured as TPNQ-sensitive currents, was substantial in both segments. A mathematical model of the rat nephron suggested that K⁺ secretion by the CNTe predicted from these currents provides much of the urinary K⁺ required for K balance on this diet. In animals fed a K-deficient diet (0.1% K), both ENaC and ROMK currents in the CNTe decreased by ∼50%, predicting a 50% decline in K⁺ secretion. Enhanced reabsorption by a separate mechanism is required to avoid excessive urinary K⁺ losses. In animals fed a diet supplemented with 3% K, ENaC currents increased modestly in the CNTe but strongly in the CNTas, while ROMK currents tripled in both segments. The enhanced secretion of K⁺ by the CNTe and the recruitment of secretion by the CNTas account for the additional transport required for K balance. Therefore, adaptation to increased K⁺ intake involves the extension of robust K⁺ secretion to more distal parts of the nephron.     

Scymnodon plunketi (Waite, 1910): a junior synonym of Scymnodon macracanthus (Regan, 1906) (Somniosidae: Elasmobranchii)

The taxonomic status and validity of Scymnodon macracanthus (Regan, 1906) and Scymnodon plunketi (Waite, 1910) are revised in light of new material from the Southern Pacific and Indian Oceans. Despite being historically accepted as distinct taxa, recent studies suggested the possibility that these species could represent a single taxon. Morphometrics, meristics and morphology of dermal denticles show that S. plunketi is indeed a junior synonym of S. macracanthus. Previous distinctive characters proved to be the result of intraspecific variation. S. macracanthus is therefore redescribed including an updated comparative diagnosis for the genus Scymnodon in the family Somniosidae.     

Sex differences in the immune response to acute COVID-19 respiratory tract infection

Determine if sex differences exist in clinical characteristics and outcomes of adults hospitalized for coronavirus disease 2019 (COVID-19) in a US healthcare system. Case series study. Sequentially hospitalized adults admitted for COVID-19 at two tertiary care academic hospitals in New Orleans, LA, between 27 February and 15 July 2020. Measures included demographics, comorbidities, presenting symptoms, and laboratory results. Outcomes included intensive care unit admission (ICU), invasive mechanical ventilation (IMV), and in-hospital death. We included 776 patients (median age 60.5 years; 61.4% women, 75% non-Hispanic Black). Rates of ICU, IMV, and death were similar in both sexes. In women versus men, obesity (63.8 vs 41.6%, P < 0.0001), hypertension (77.6 vs 70.1%, P = 0.02), diabetes (38.2 vs 31.8%, P = 0.06), chronic obstructive pulmonary disease (COPD, 22.1 vs 15.1%, P = 0.015), and asthma (14.3 vs 6.9%, P = 0.001) were more prevalent. More women exhibited dyspnea (61.2 vs 53.7%, P = 0.04), fatigue (35.7 vs 28.5%, P = 0.03), and digestive symptoms (39.3 vs 32.8%, P = 0.06) than men. Obesity was associated with IMV at a lower BMI (> 35) in women, but the magnitude of the effect of morbid obesity (BMI ≥ 40) was similar in both sexes. COPD was associated with ICU (adjusted OR (aOR), 2.6; 95%CI, 1.5–4.3) and IMV (aOR, 1.8; 95%CI, 1.2–3.1) in women only. Diabetes (aOR, 2.6; 95%CI, 1.2–2.9), chronic kidney disease (aOR, 2.2; 95%CI, 1.3–5.2), elevated neutrophil-to-lymphocyte ratio (aOR, 2.5; 95%CI, 1.4–4.3), and elevated ferritin (aOR, 3.6; 95%CI, 1.7–7.3) were independent predictors of death in women only. In contrast, elevated D-dimer was an independent predictor of ICU (aOR, 7.3; 95%CI, 2.7–19.5), IMV (aOR, 6.5; 95%CI, 2.1–20.4), and death (aOR, 4.5; 95%CI, 1.2–16.4) in men only. This study highlights sex disparities in clinical determinants of severe outcomes in COVID-19 patients that may inform management and prevention strategies to ensure gender equity.     

Genetic characterization of Colombian Brahman cattle using microsatellites markers

Genetic structure and diversity of 3789 animals of the Brahman breed from 23 Colombian regions were assessed. Considering the Brahman Zebu cattle as a single population, the multilocus test based on the HW equilibrium, shows significant differences (P < 0.001). Genetic characterization made on the cattle population allowed to examine the genetic variability, calculating a H _o = 0.6621. Brahman population in Colombia was a small subdivision wthin populations (F _it = 0.045), a geographic subdivision almost non-existent or low differentiation (F _st = 0.003) and the F _is calculated (0.042) indicates no detriment to the variability in the population, despite the narrow mating takes place or there is a force that causes the variability is sustained without inbreeding actually affect the cattle population. The outcomes of multivariate analyses, Bayesian inferences and interindividual genetic distances suggested that there is no genetic sub-structure in the population, because of the high rate of animal migration among regions.     

oiwa,a Female Gametophytic Mutant Impaired in a Mitochondrial Manganese-Superoxide Dismutase,Reveals Crucial Roles for Reactive Oxygen Species during Embryo Sac Development and Fertilization in Arabidopsis

Reactive oxygen species (ROS) can function as signaling molecules, regulating key aspects of plant development, or as toxic compounds leading to oxidative damage. In this article, we show that the regulation of ROS production during megagametogenesis is largely dependent on MSD1, a mitochondrial Mn-superoxide dismutase. Wild-type mature embryo sacs show ROS exclusively in the central cell, which appears to be the main source of ROS before pollination. Accordingly, MSD1 shows a complementary expression pattern. MSD1 expression is elevated in the egg apparatus at maturity but is downregulated in the central cell. The oiwa mutants are characterized by high levels of ROS detectable in both the central cell and the micropylar cells. Remarkably, egg apparatus cells in oiwa show central cell features, indicating that high levels of ROS result in the expression of central cell characteristic genes. Notably, ROS are detected in synergid cells after pollination. This ROS burst depends on stigma pollination but precedes fertilization, suggesting that embryo sacs sense the imminent arrival of pollen tubes and respond by generating an oxidative environment. Altogether, we show that ROS play a crucial role during female gametogenesis and fertilization. MSD1 activity seems critical for maintaining ROS localization and important for embryo sac patterning.     

Effect of habitat disturbance on pollination biology of the columnar cactus Stenocereus quevedonis at landscape‐level in central Mexico

Stenocereus quevedonis (‘pitire’) is a columnar cactus endemic to central Mexico, grown for its edible fruit. Phenology, pollination biology and behaviour of flower visitors of this species were compared in six conserved and disturbed sites, hypothesising that: (i) pitire pollination is self‐incompatible, requiring animal vectors; (ii) higher incidence of radiation on plants in cleared forest may lead to a higher number of flowers per pitire plant and longer blooming season, and disturbing and differential spatial availability of flower resources may determine differential attraction of pollinators to conserved and disturbed areas; (iii) if pitire pollination system is specialised, reproductive success would decrease with pollinator scarcity, or other species may substitute for main pollinators. In all sites, pitire reproduction started in January, flowering peak occurring in April, anthesis duration was 15 h and predominantly nocturnal (9 h), pollen was released at 23:00 h, nectar was produced throughout anthesis, and breeding system was self‐incompatible. Flower production per plant was similar in disturbed and conserved sites, but flower availability was higher (because of higher tree density) and longer in disturbed sites. Pollination is nocturnal, the most frequent legitimate pollinator being the bat Leptonycteris yerbabuenae; diurnal pollination is rare but possible, carried out by bee species. Fruit and seed set in control and nocturnal pollination treatments at disturbed sites were higher than in conserved sites. Frequency of L. yerbabuenae visits was similar among site types, but more visits of complementary nocturnal and diurnal pollinators were recorded in disturbed sites, which could explain differences in reproductive success.     

Getting a grip on tetrapod grasping: form,function, and evolution

Human beings have been credited with unparalleled capabilities for digital prehension grasping. However, grasping behaviour is widespread among tetrapods. The propensity to grasp, and the anatomical characteristics that underlie it, appear in all of the major groups of tetrapods with the possible exception of terrestrial turtles. Although some features are synapomorphic to the tetrapod clade, such as well‐defined digits and digital musculature, other features, such as opposable digits and tendon configurations, appear to have evolved independently in many lineages. Here we examine the incidence, functional morphology, and evolution of grasping across four major tetrapod clades. Our review suggests that the ability to grasp with the manus and pes is considerably more widespread, and ecologically and evolutionarily important, than previously thought. The morphological bases and ecological factors that govern grasping abilities may differ among tetrapods, yet the selective forces shaping them are likely similar. We suggest that further investigation into grasping form and function within and among these clades may expose a greater role for grasping ability in the evolutionary success of many tetrapod lineages.     

Chromothripsis: Breakage-fusion-bridge over and over again

The acquisition of massive but localized chromosome translocations, a phenomenon termed chromothripsis, has received widespread attention since its discovery over a year ago. Until recently, chromothripsis was believed to originate from a single catastrophic event, but the molecular mechanisms leading to this event are yet to be uncovered. Because a thorough interpretation of the data are missing, the phenomenon itself has wrongly acquired the status of a mechanism used to justify many kinds of complex rearrangements. Although the assumption that all translocations in chromothripsis originate from a single event has met with criticism, satisfactory explanations for the intense but localized nature of this phenomenon are still missing. Here, we show why the data used to describe massive catastrophic rearrangements are incompatible with a model comprising a single event only and propose a molecular mechanism in which a combination of known cellular pathways accounts for chromothripsis. Instead of a single traumatic event, the protection of undamaged chromosomes by telomeres can limit repetitive breakage-fusion-bridge events to a single chromosome arm. Ultimately, common properties of chromosomal instability, such as aneuploidy and centromere fission, might establish the complex genetic pattern observed in this genomic state.     

Shadoo/PrP (Sprn0/0/Prnp0/0) double knockout mice

Shadoo (Sho) is a brain glycoprotein with similarities to the unstructured region of PrP^C. Frameshift alleles of the Sho gene, Sprn, are reported in variant Creutzfeldt-Jakob disease (vCJD) patients while Sprn mRNA knockdown in PrP-null (Prnp^0/0) embryos produces lethality, advancing Sho as the hypothetical PrP-like “pi” protein. Also, Sho levels are reduced as misfolded PrP accumulates during prion infections. To penetrate these issues we created Sprn null alleles (Daude et al., Proc. Natl. Acad. Sci USA 2012; 109(23): 9035–40). Results from the challenge of Sprn null and TgSprn transgenic mice with rodent-adapted prions coalesce to define downregulation of Sho as a “tracer” for the formation of misfolded PrP. However, classical BSE and rodent-adapted BSE isolates may behave differently, as they do for other facets of the pathogenic process, and this intriguing variation warrants closer scrutiny. With regards to physiological function, double knockout mice (Sprn^0/0/Prnp^0/0) mice survived to over 600 d of age. This suggests that Sho is not pi, or, given the accumulating data for many activities for PrP^C, that the pi hypothesis invoking a discrete signaling pathway to maintain neuronal viability is no longer tenable.