Hypoxic cardiorespiratory reflexes in the facultative air-breathing fish jeju (Hoplerythrinus unitaeniatus): role of branchial O2 chemoreceptors

In one series of experiments, heart frequency (f _H), blood pressure (P _a), gill ventilation frequency (f _R ), ventilation amplitude (V _AMP) and total gill ventilation (V _TOT) were measured in intact jeju (Hoplerythrinus unitaeniatus) and jeju with progressive denervation of the branchial branches of cranial nerves IX (glossopharyngeal) and X (vagus) without access to air. When these fish were submitted to graded hypoxia (water PO₂ ~140, normoxia to 17 mmHg, severe hypoxia), they increased f _R , V _AMP, V _TOT and P _a and decreased f _H. In a second series of experiments, air-breathing frequency (f _RA), measured in fish with access to the surface, increased with graded hypoxia. In both series, bilateral denervation of all gill arches eliminated the responses to graded hypoxia. Based on the effects of internal (caudal vein, 150 μg NaCN in 0.2 mL saline) and external (buccal) injections of NaCN (500 μg NaCN in 1.0 mL water) on f _R , V _AMP, V _TOT, P _a and f _H we conclude that the O₂ receptors involved in eliciting changes in gill ventilation and associated cardiovascular responses are present on all gill arches and monitor the O₂ levels of both inspired water and blood perfusing the gills. We also conclude that air breathing arises solely from stimulation of branchial chemoreceptors and support the hypothesis that internal hypoxaemia is the primary drive to air breathing.     

Recent Advances in GFP Folding Reporter and Split-GFP Solubility Reporter Technologies. Application to Improving the Folding and Solubility of Recalcitrant Proteins from Mycobacterium tuberculosis

We have improved our green fluorescent protein (GFP) folding reporter technology [Waldo et al., (1999) Nat. Biotechnol. 17, 691–695] to evolve recalcitrant proteins from Mycobacterium tuberculosis. The target protein is inserted into the scaffolding of the GFP, eliminating false-positive artifacts caused by expression of truncated protein variants from internal cryptic ribosome binding sites in the target RNA. In parallel, we have developed a new quantitative fluorescent protein tagging and detection system based on micro-domains of GFP. This split-GFP system, which works both in vivo and in vitro, is amenable to high-throughput assays of protein expression and solubility [Cabantous et al., (2005) Nat. Biotechnol. 23, 102–107]. Together, the GFP folding reporter and split-GFP technologies offer a comprehensive system for manipulating and improving protein folding and solubility.     

Autonomic control of heart rate is virtually independent of temperature but seems related to the neuroanatomy of the efferent vagal supply to the heart in the bullfrog, Lithobathes catesbeianus

Bullfrogs, Lithobathes catesbeianus, bearing a femoral artery cannula were held at 3 temperatures (10, 20 and 30 °C) for 24 h. Changes in heart rate were recorded before and after injection of cholinergic and adrenergic antagonists. Normal heart rate doubled for each temperature increment. Adrenergic tone on the heart varied around 20% at all 3 temperatures but cholinergic tone increased from −5% to 10% between 10 and 30 °C. In contrast, cholinergic tone increased from 75% at 5 °C to 329% at 25 °C in Xenopus laevis. Injection of the neural tracer True Blue into the cervical vagus of the bullfrog revealed a single location for vagal preganglionic neurons (VPN) in the dorsal vagal motor nucleus (DVN), while Xenopus had 30% of its VPN in a ventro-lateral group outside the DVN. Broader comparative studies have suggested that differences in the extent of vagal tone may relate to the location of VPN in the brainstem and this may be the case in these amphibians.     

Private specificities can dominate the humoral response to self-antigens in patients with cryptogenic fibrosing alveolitis

Background  

The pathogenetic mechanisms that underlie the interstitial lung disease cryptogenic fibrosing alveolitis (CFA) may involve an immunological reaction to unidentified antigens in the lung, resulting in tissue damage.     

Invasive termites in a changing climate: A global perspective

Termites are ubiquitous insects in tropical, subtropical, and warm temperate regions and play an important role in ecosystems. Several termite species are also significant economic pests, mainly in urban areas where they attack human‐made structures, but also in natural forest habitats. Worldwide, approximately 28 termite species are considered invasive and have spread beyond their native ranges, often with significant economic consequences. We used predictive climate modeling to provide the first global risk assessment for 13 of the world's most invasive termites. We modeled the future distribution of 13 of the most serious invasive termite species, using two different Representative Concentration Pathways (RCPs), RCP 4.5 and RCP 8.5, and two projection years (2050 and 2070). Our results show that all but one termite species are expected to significantly increase in their global distribution, irrespective of the climatic scenario and year. The range shifts by species (shift vectors) revealed a complex pattern of distributional changes across latitudes rather than simple poleward expansion. Mapping of potential invasion hotspots in 2050 under the RCP 4.5 scenario revealed that the most suitable areas are located in the tropics. Substantial parts of all continents had suitable environmental conditions for more than four species simultaneously. Mapping of changes in the number of species revealed that areas that lose many species (e.g., parts of South America) are those that were previously very species‐rich, contrary to regions such as Europe that were overall not among the most important invasion hotspots, but that showed a great increase in the number of potential invaders. The substantial economic and ecological damage caused by invasive termites is likely to increase in response to climate change, increased urbanization, and accelerating economic globalization, acting singly or interactively.     

High levels of genetic differentiation and selfing in the Brazilian cerrado fruit tree Dipteryx alata Vog. (Fabaceae)

Dipteryx alata is a native fruit tree species of the cerrado (Brazilian savanna) that has great economic potential because of its multiple uses. Knowledge of how the genetic variability of this species is organized within and among populations would be useful for genetic conservation and breeding programs. We used nine simple sequence repeat (SSR) primers developed for Dipteryx odorata to evaluate the genetic structure of three populations of D. alata located in central Brazil based on a leaf sample analysis from 101 adults. The outcrossing rate was evaluated using 300 open-pollinated offspring from 25 seed-trees. Pollen dispersal was measured by parentage analysis. We used spatial genetic structure (SGS) to test the minimal distance for harvesting seeds in conservation and breeding programs. Our data indicate that the populations studied had a high degree of genetic diversity and population structure, as suggested by the high level of divergence among populations . The estimated outcrossing rate suggested a mixed mating system, and the intrapopulation fixation index was influenced by SGS. We conclude that seed harvesting for genetic conservation and breeding programs requires a minimum distance between trees of 196 m to avoid collecting seeds from related seed-trees.     

Cellular senescence mediated by p16INK4A-coupled miRNA pathways

p16 is a key regulator of cellular senescence, yet the drivers of this stable state of proliferative arrest are not well understood. Here, we identify 22 senescence-associated microRNAs (SA-miRNAs) in normal human mammary epithelial cells. We show that SA-miRNAs-26b, 181a, 210 and 424 function in concert to directly repress expression of Polycomb group (PcG) proteins CBX7, embryonic ectoderm development (EED), enhancer of zeste homologue 2 (EZH2) and suppressor of zeste 12 homologue (Suz12), thereby activating p16. We demonstrate the existence of a tight positive feedback loop in which SA-miRNAs activate and re-enforce the expression of other SA-miRNA members. In contrast, PcG members restrain senescence by epigenetically repressing the expression of these SA-miRNAs. Importantly, loss of p16 leads to repression of SA-miRNA expression, intimately coupling this effector of senescence to the SA-miRNA/PcG self-regulatory loop. Taken together, our findings illuminate an important regulatory axis that underpins the transition from proliferation to cellular senescence.