Multiple Sources of Introduction of North American Arabidopsis thaliana from across Eurasia

Large-scale movement of organisms across their habitable range, or migration, is an important evolutionary process that can shape genetic diversity and influence the adaptive spread of alleles. Although human migrations have been studied in great detail with modern and ancient genomes, recent anthropogenic influence on reducing the biogeographical constraints on the migration of nonnative species has presented opportunities in several study systems to ask the questions about how repeated introductions shape genetic diversity in the introduced range. We present an extensive overview of population structure of North American Arabidopsis thaliana by studying a set of 500 whole-genome sequenced and over 2,800 RAD-seq genotyped individuals in the context of global diversity represented by Afro-Eurasian genomes. We use methods based on haplotype and rare-allele sharing as well as phylogenetic modeling to identify likely sources of introductions of extant N. American A. thaliana from the native range in Africa and Eurasia. We find evidence of admixture among the introduced lineages having increased haplotype diversity and reduced mutational load. We also detect signals of selection in immune-system-related genes that may impart qualitative disease resistance to pathogens of bacterial and oomycete origin. We conclude that multiple introductions to a nonnative range can rapidly enhance the adaptive potential of a colonizing species by increasing haplotypic diversity through admixture. Our results lay the foundation for further investigations into the functional significance of admixture.     

Irradiation causes senescence,ATP release,and P2X7 receptor isoform switch in glioblastoma

Glioblastoma (GBM) is the most lethal brain tumor in adults. Radiation, together with temozolomide is the standard treatment, but nevertheless, relapse occurs in nearly all cases. Understanding the mechanisms underlying radiation resistance may help to find more effective therapies. After radiation treatment, ATP is released into the tumor microenvironment where it binds and activates purinergic P2 receptors, mainly of the P2X7 subtype. Two main P2X7 splice variants, P2X7A and P2X7B, are expressed in most cell types, where they associate with distinct biochemical and functional responses. GBM cells widely differ for the level of P2X7 isoform expression and accordingly for sensitivity to stimulation with extracellular ATP (eATP). Irradiation causes a dramatic shift in P2X7 isoform expression, with the P2X7A isoform being down- and the P2X7B isoform up-modulated, as well as extensive cell death and overexpression of stemness and senescence markers. Treatment with P2X7 blockers during the post-irradiation recovery potentiated irradiation-dependent cytotoxicity, suggesting that P2X7B activation by eATP generated a trophic/growth-promoting stimulus. Altogether, these data show that P2X7A and B receptor isoform levels are inversely modulated during the post-irradiation recovery phase in GBM cells.Subject terms: Senescence, CNS cancer     

Contrasting performance of barley and wheat in a wide range of conditions in Mediterranean Catalonia (Spain)

Despite that the idea of better yield adaptation to low‐yielding conditions of barley than wheat is widespread, there have been few efforts in directly comparing their performance in Mediterranean conditions. We compared wheat and barley regional yields in 41 counties of Catalonia for the period 1992–2004. No differences were clear, particularly at low‐yielding conditions, with a trend for a better wheat performance in relatively high‐yielding environments. We then conducted field experiments during two consecutive seasons, sowing wheat and barley with six levels of nitrogen fertilisation under rainfed conditions (2003–04, experiment I) and two levels of nitrogen fertilisation and two water regimes (rainfed and irrigated) in 2004–05 (experiment II). In experiment I, wheat outyielded barley in treatments that received no N fertiliser (4.58 and 3.60 Mg ha^?1, respectively) indicating that the higher yield potential of wheat was associated with better performance in a condition of relatively low yield. In experiment II, wheat and barley yields were found not to be significantly different across all treatments (2.86 and 2.62 Mg ha^?1, respectively) or in the lowest yielding treatments (1.40 and 1.07 Mg ha^?1, respectively). Therefore, it seems that it may not be universally accepted that under Mediterranean conditions barley would unequivocally behave better than wheat.     

Kinetic changes of ethanolamine base exchange activity and increase of viscosity in sarcolemmal membranes of hamster heart during development of cardiomyopathy

The activity of the phospholipid base exchange enzyme specific for ethanolamine has been measured in cardiac sarcolemmal membrane preparations from Syrian golden and UM-X7.1 cardiomyopathic hamsters. In Syrian golden hamsters, the Km of the enzyme for ethanolamine does not change with age, whereas it almost doubles in membranes from cardiomyopathic animals, from the 30th to the 150th day of age. During the same period, the membrane cholesterol content increases by 68% in cardiomyopathic hamsters, whereas it does not change significantly in the Syrian golden hamster strain. As a consequence, in the adult animal, the cholesterol to phospholipid ratio and the viscosity of sarcolemmal membranes are higher in UM-X7.1 strain than in Syrian golden hamsters. A cause consequence relationship between the enzymatic changes and the compositional modifications in the sarcolemma occurring in UM-X7.1 hamsters during the development of cardiomyopahhy is proposed. (Mol Cell Biochem 116: 89–93,1992)     

Effect of sodium and osmolarity on renin secretion.

The effect of changes in sodium and osmolarity on renin secretion has been studied in the isolated perfused rat kidney. Perfusion with low sodium buffer (110 mM/l) produced a significant increase in renin secretion compared with control experiments (Na+:135 mM/l). Since the presence of tubules seems necessary for such an effect to take place, it suggests that the high renin secretion stimulated by a low sodium buffer centers in the Macula densa. Perfusion with high sodium buffer (170 mM/l; osmolarity 350 mOs/l) induces a stimulation on renin release. However, a greater rise in renin is achieved in control experiments if choline chloride increases the osmolarity from 300 to 350 mOs/l. All this suggests that high sodium buffer, independently of its osmotic effect, has an inhibitory role on renin release.     

Significance of computed tomography in the assessment of invasiveness of malignant tumors of upper respiratory tract

In the work there are summarized the results of the examination of the 112 patients with the malignant neoplasms of larynx (70), pharynx (24), rhinopharynx with spreading to the cells of ethmoidal labyrinth and maxillary sinus (18), aged from 14 till 69. There are described the methods of computed tomography. There are show the possibilities computed tomography in estimation of the localization specification, prevalence, structure, degree of invasion into the neoplasms gathering round the cells, as well as the definition of the bony destruction.     

Synaptic Membrane Freezing Affects Modulatory Sites in Avian Central Nervous System GABAA Receptor

Studies were carried out to determine whether barbiturates and neurosteroids share common recognition sites at the GABA_A receptor complex in avian CNS. To achieve this, differentially prepared fresh and frozen synaptic membranes were used. Both the barbiturate, pentobarbital, and the neurosteroid, 3-hydroxy-5-pregnan-20-one, were able to stimulate GABA binding in both types of membranes. Stimulation differed markedly when both drugs were added jointly to different treated tissue. In frozen membranes drugs acted synergistically and were differentially displaced by picrotoxinin, while in fresh ones, where both compounds were inhibited by the convulsant, this additivity was absent. Post-freezing wash supernatants were collected and used as a source of putative endogenous factors involved in the above mentioned membrane differences. Addition of a high molecular weight fraction from supernatants to frozen synaptic membranes led to an inhibition of barbiturate and neurosteroid potentiation, as well as a loss of their additive effect. Our results indicate that GABA_A receptor modulation by barbiturates and neurosteroids is affected by synaptic membrane treatment, with a common modulatory site in fresh membranes and separate recognition sites after a freeze-thawing procedure. There may also be endogenous factors involved in overlapping of modulatory sites, which would thus regulate GABA_A receptor functionality by direct interaction with the complex.     

The turn sequence directs beta-strand alignment in designed beta-hairpins

A previous NMR investigation of model decapeptides with identical beta-strand sequences and different turn sequences demonstrated that, in these peptide systems, the turn residues played a more predominant role in defining the type of beta-hairpin adopted than cross-strand side-chain interactions. This result needed to be tested in longer beta-hairpin forming peptides, containing more potentially stabilizing cross-strand hydrogen bonds and side-chain interactions that might counterbalance the influence of the turn sequence. In that direction, we report here on the design and 1H NMR conformational study of three beta-hairpin forming pentadecapeptides. The design consists of adding two and three residues at the N- and C-termini, respectively, of the previously studied decapeptides. One of the designed pentadecapeptides includes a potentially stabilizing R-E salt bridge to investigate the influence of this interaction on beta-hairpin stability. We suggest that this peptide self-associates by forming intermolecular salt bridges. The other two pentadecapeptides behave as monomers. A conformational analysis of their 1H NMR spectra reveals that they adopt different types of beta-hairpin structure despite having identical strand sequences. Hence, the beta-turn sequence drives beta-hairpin formation in the investigated pentadecapeptides that adopt beta-hairpins that are longer than the average protein beta-hairpins. These results reinforce our previous suggestion concerning the key role played by the turn sequence in directing the kind of beta-hairpin formed by designed peptides.     

Correcting delayed reporting of COVID-19 using the generalized-Dirichlet-multinomial method

The COVID-19 pandemic has highlighted delayed reporting as a significant impediment to effective disease surveillance and decision-making. In the absence of timely data, statistical models which account for delays can be adopted to nowcast and forecast cases or deaths. We discuss the four key sources of systematic and random variability in available data for COVID-19 and other diseases, and critically evaluate current state-of-the-art methods with respect to appropriately separating and capturing this variability. We propose a general hierarchical approach to correcting delayed reporting of COVID-19 and apply this to daily English hospital deaths, resulting in a flexible prediction tool which could be used to better inform pandemic decision-making. We compare this approach to competing models with respect to theoretical flexibility and quantitative metrics from a 15-month rolling prediction experiment imitating a realistic operational scenario. Based on consistent leads in predictive accuracy, bias, and precision, we argue that this approach is an attractive option for correcting delayed reporting of COVID-19 and future epidemics.