The role of mitochondria in protection of the heart by preconditioning

A prolonged period of ischaemia followed by reperfusion irreversibly damages the heart. Such reperfusion injury (RI) involves opening of the mitochondrial permeability transition pore (MPTP) under the conditions of calcium overload and oxidative stress that accompany reperfusion. Protection from MPTP opening and hence RI can be mediated by ischaemic preconditioning (IP) where the prolonged ischaemic period is preceded by one or more brief (2-5 min) cycles of ischaemia and reperfusion. Following a brief overview of the molecular characterisation and regulation of the MPTP, the proposed mechanisms by which IP reduces pore opening are reviewed including the potential roles for reactive oxygen species (ROS), protein kinase cascades, and mitochondrial potassium channels. It is proposed that IP-mediated inhibition of MPTP opening at reperfusion does not involve direct phosphorylation of mitochondrial proteins, but rather reflects diminished oxidative stress during prolonged ischaemia and reperfusion. This causes less oxidation of critical thiol groups on the MPTP that are known to sensitise pore opening to calcium. The mechanisms by which ROS levels are decreased in the IP hearts during prolonged ischaemia and reperfusion are not known, but appear to require activation of protein kinase Cε, either by receptor-mediated events or through transient increases in ROS during the IP protocol. Other signalling pathways may show cross-talk with this primary mechanism, but we suggest that a role for mitochondrial potassium channels is unlikely. The evidence for their activity in isolated mitochondria and cardiac myocytes is reviewed and the lack of specificity of the pharmacological agents used to implicate them in IP is noted. Some K⁺ channel openers uncouple mitochondria and others inhibit respiratory chain complexes, and their ability to produce ROS and precondition hearts is mimicked by bona fide uncouplers and respiratory chain inhibitors. IP may also provide continuing protection during reperfusion by preventing a cascade of MPTP-induced ROS production followed by further MPTP opening. This phase of protection may involve survival kinase pathways such as Akt and glycogen synthase kinase 3 (GSK3) either increasing ROS removal or reducing mitochondrial ROS production.     

Phylogenetic systematics and biogeography of hummingbirds: Bayesian and maximum likelihood analyses of partitioned data and selection of an appropriate partitioning strategy

Hummingbirds are an important model system in avian biology, but to date the group has been the subject of remarkably few phylogenetic investigations. Here we present partitioned Bayesian and maximum likelihood phylogenetic analyses for 151 of approximately 330 species of hummingbirds and 12 outgroup taxa based on two protein-coding mitochondrial genes (ND2 and ND4), flanking tRNAs, and two nuclear introns (AK1 and BFib). We analyzed these data under several partitioning strategies ranging between unpartitioned and a maximum of nine partitions. In order to select a statistically justified partitioning strategy following partitioned Bayesian analysis, we considered four alternative criteria including Bayes factors, modified versions of the Akaike information criterion for small sample sizes (AIC(c)), Bayesian information criterion (BIC), and a decision-theoretic methodology (DT). Following partitioned maximum likelihood analyses, we selected a best-fitting strategy using hierarchical likelihood ratio tests (hLRTS), the conventional AICc, BIC, and DT, concluding that the most stringent criterion, the performance-based DT, was the most appropriate methodology for selecting amongst partitioning strategies. In the context of our well-resolved and well-supported phylogenetic estimate, we consider the historical biogeography of hummingbirds using ancestral state reconstructions of (1) primary geographic region of occurrence (i.e., South America, Central America, North America, Greater Antilles, Lesser Antilles), (2) Andean or non-Andean geographic distribution, and (3) minimum elevational occurrence. These analyses indicate that the basal hummingbird assemblages originated in the lowlands of South America, that most of the principle clades of hummingbirds (all but Mountain Gems and possibly Bees) originated on this continent, and that there have been many (at least 30) independent invasions of other primary landmasses, especially Central America.     

Lentivirus vector-mediated gene transfer to the developing bronchiolar airway epithelium in the fetal lamb

BACKGROUND: Development of effective and durable gene therapy for treatment of the respiratory manifestations of cystic fibrosis remains a formidable challenge. Obstacles include difficulty in achieving efficient gene transfer to mature airway epithelium and the need to stably transduce self-renewing epithelial progenitor cells in order to avoid loss of transgene expression through epithelial turnover. Targeting the developing airway epithelium during fetal life offers the prospect of circumventing these challenges. METHODS: In the current study we investigated vesicular stomatitis virus glycoprotein (VSVg)-pseudotyped HIV-1-derived lentivirus vector-mediated gene transfer to the airway epithelium of mid-gestation fetal lambs, both in vitro and in vivo. In the in vitro studies epithelial sheet explants and lung organ culture were used to examine transduction of the proximal and more distal airway epithelium, respectively. For the in vivo studies, vector was delivered directly into the proximal airway. RESULTS: We found that even during the early pseudoglandular and canalicular phases of lung development, occurring through mid-gestation, the proximal bronchial airway epithelium was relatively mature and highly resistant to lentivirus-mediated transduction. In contrast, the more distal bronchiolar airway epithelium was relatively permissive for transduction although the absolute levels achieved remained low. CONCLUSION: This result is promising as the bronchiolar airway epithelium is a major site of pathology in the cystic fibrosis airway, and much higher levels of transduction are likely to be achieved by developing strategies that increase the amount of vector reaching the more distal airway after intratracheal delivery.     

Alterations of endophytic microbial community function in Spartina alterniflora as a result of crude oil exposure

Biodegradation - The 2010 Deepwater Horizon disaster remains one of the largest oil spills in history. This event caused significant damage to coastal ecosystems, the full extent of which has yet...     

The relevance of pedigrees in the conservation genomics era

Over the past 50 years conservation genetics has developed a substantive toolbox to inform species management. One of the most long-standing tools available to manage genetics—the pedigree—has been widely used to characterize diversity and maximize evolutionary potential in threatened populations. Now, with the ability to use high throughput sequencing to estimate relatedness, inbreeding, and genome-wide functional diversity, some have asked whether it is warranted for conservation biologists to continue collecting and collating pedigrees for species management. In this perspective, we argue that pedigrees remain a relevant tool, and when combined with genomic data, create an invaluable resource for conservation genomic management. Genomic data can address pedigree pitfalls (e.g., founder relatedness, missing data, uncertainty), and in return robust pedigrees allow for more nuanced research design, including well-informed sampling strategies and quantitative analyses (e.g., heritability, linkage) to better inform genomic inquiry. We further contend that building and maintaining pedigrees provides an opportunity to strengthen trusted relationships among conservation researchers, practitioners, Indigenous Peoples, and Local Communities.     

Management of upland calcareous grasslands for target vascular plant community impacts upon abundance but not diversity of non-target bryophytes

Biodiversity and Conservation - Calcareous grasslands, valued for their high species richness and diversity, are a European nature conservation priority. Their plagioclimax nature means that...     

Effects of SmartWater,a fluorescent mark,on the dispersal,behavior, and biocontrol efficacy of Phytoseiulus persimilis

New marking methods for studying small biocontrol agents (especially predatory mites) are needed because many current techniques are expensive, ineffective or not applicable to small organisms. The objective of this study was to determine whether SmartWater, a liquid and permanent fluorescent dye, can be used to mark Phytoseiulus persimilis for experimentation without any deleterious effects on its dispersal, behavior, reproduction, and biocontrol efficacy. Our results show that there were no significant differences in movement, inter-plant dispersal, feeding behavior, survivability, and reproduction between marked P. persimilis and control individuals sprayed with water. We also found that the SmartWater mark lasted for the duration of the mites’ life, indicating strong durability over time. Marking efficacy may be reduced, due to a trade-off between batch marking efficacy and the possibility of drowning study organisms. However, we feel future research could improve liquid marking techniques that would reduce this risk. Overall, this study concludes that SmartWater could be a useful marking tool for predatory mites in both laboratory and field studies.

     

Methodological inconsistencies define thermal bottlenecks in fish life cycle: a comment on Dahlke et al. 2020

Evolutionary Ecology - Comparative analyses require researchers to not only ensure data quality, but to also make prudent and justifiable assumptions about data comparability. A failure to do so...     

The influence of wastewater pretreatment,attachment material,and inoculation strategy on the growth of target algal species in cultivated biofilms

Journal of Applied Phycology - Microalgal biofilms are promising sources of sustainable biofuels and bioproducts because of their minimal growth requirements, ability to sequester CO2, and high...