Expression of transport proteins in the rete mirabile of european silver and yellow eel

Background In physoclist fishes filling of the swimbladder requires acid secretion of gas gland cells to switch on the Root effect and subsequent countercurrent concentration of the initial gas partial pressure increase by back-diffusion of gas molecules in the rete mirabile. It is generally assumed that the rete mirabile functions as a passive exchanger, but a detailed analysis of lactate and water movements in the rete mirabile of the eel revealed that lactate is diffusing back in the rete. In the present study we therefore test the hypothesis that expression of transport proteins in rete capillaries allows for back-diffusion of ions and metabolites, which would support the countercurrent concentrating capacity of the rete mirabile. It is also assumed that in silver eels, the migratory stage of the eel, the expression of transport proteins would be enhanced. Results Analysis of the transcriptome and of the proteome of rete mirabile tissue of the European eel revealed the expression of a large number of membrane ion and metabolite transport proteins, including monocarboxylate and glucose transport proteins. In addition, ion channel proteins, Ca2+-ATPase, Na+/K+-ATPase and also F1F0-ATP synthase were detected. In contrast to our expectation in silver eels the expression of these transport proteins was not elevated as compared to yellow eels. A remarkable number of enzymes degrading reactive oxygen species (ROS) was detected in rete capillaries. Conclusions Our results reveal the expression of a large number of transport proteins in rete capillaries, so that the back diffusion of ions and metabolites, in particular lactate, may significantly enhance the countercurrent concentrating ability of the rete. Metabolic pathways allowing for aerobic generation of ATP supporting secondary active transport mechanisms are established. Rete tissue appears to be equipped with a high ROS defense capacity, preventing damage of the tissue due to the high oxygen partial pressures generated in the countercurrent system.

Adrenergically induced translocation of red blood cell β-adrenergic sodium-proton exchangers has ecological relevance for hypoxic and hypercapnic white seabass

White seabass (Atractoscion nobilis) increasingly experience periods of low oxygen (O2; hypoxia) and high carbon dioxide (CO2, hypercapnia) due to climate change and eutrophication of the coastal waters of California. Hemoglobin (Hb) is the principal O2 carrier in the blood and in many teleost fishes Hb-O2 binding is compromised at low pH; however, the red blood cells (RBC) of some species regulate intracellular pH with adrenergically-stimulated sodium-proton-exchangers (β-NHE). We hypothesized that RBC β-NHEs in white seabass are an important mechanism that can protect the blood O2-carrying capacity during hypoxia and hypercapnia. We determined the O2-binding characteristics of white seabass blood, the cellular and sub-cellular response of RBCs to adrenergic stimulation, and quantified the protective effect of β-NHE activity on Hb-O2 saturation. White seabass had typical teleost Hb characteristics, with a moderate O2 affinity (PO2 at half-saturation; P50 2.9 kPa) that was highly pH-sensitive (Bohr coefficient -0.92; Root effect 52%). Novel findings from super-resolution microscopy revealed β-NHE protein in vesicle-like structures and its translocation into the membrane after adrenergic stimulation. Microscopy data were corroborated by molecular and phylogenetic results, and a functional characterization of β-NHE activity. The activation of RBC β-NHEs increased Hb-O2 saturation by ~8% in normoxic hypercapnia, and by up to ~20% in hypoxic normocapnia. Our results provide novel insight into the cellular mechanism of adrenergic RBC stimulation within an ecologically relevant context. β-NHE activity in white seabass has great potential to protect arterial O2 transport during hypoxia and hypercapnia but is less effective during combinations of these stressors.

Red blood cell carbonic anhydrase mediates oxygen delivery via the Root effect in red drum

ABSTRACTOxygen (O2) and carbon dioxide (CO2) transport are tightly coupled in many fishes as a result of the presence of Root effect hemoglobins (Hb), whereby reduced pH reduces O2 binding even at high O2 tensions. Red blood cell carbonic anhydrase (RBC CA) activity limits the rate of intracellular acidification, yet its role in O2 delivery has been downplayed. We developed an in vitro assay to manipulate RBC CA activity while measuring Hb-O2 offloading following a physiologically relevant CO2-induced acidification. RBC CA activity in red drum (Sciaenops ocellatus) was inhibited with ethoxzolamide by 53.7±0.5%, which prompted a significant reduction in O2 offloading rate by 54.3±5.4% (P=0.0206, two-tailed paired t-test; n=7). Conversely, a 2.03-fold increase in RBC CA activity prompted a 2.14-fold increase in O2 offloading rate (P<0.001, two-tailed paired t-test; n=8). This approximately 1:1 relationship between RBC CA activity and Hb-O2 offloading rate coincided with a similar allometric scaling exponent for RBC CA activity and maximum metabolic rate. Together, our data suggest that RBC CA is rate limiting for O2 delivery in red drum.

Predominance of soil vs root effect in rhizosphere microbiota reassembly

ABSTRACT Rhizosphere community assembly is simultaneously affected by both plants and bulk soils and is vital for plant health. However, it is still unclear how and to what extent disease-suppressive rhizosphere microbiota can be constructed from bulk soil, and the underlying agents involved in the process that render the rhizosphere suppressive against pathogenic microbes remain elusive. In this study, the evolutionary processes of the rhizosphere microbiome were explored based on transplanting plants previously growing in distinct disease-incidence soils to one disease-suppressive soil. Our results showed that distinct rhizoplane bacterial communities were assembled on account of the original bulk soil communities with different disease incidences. Furthermore, the bacterial communities in the transplanted rhizosphere were noticeably influenced by the second disease-suppressive microbial pool, rather than that of original formed rhizoplane microbiota and homogenous nontransplanted rhizosphere microbiome, contributing to a significant decrease in the pathogen population. In addition, Spearman's correlations between relative abundances of bacterial taxa and the abundance of Ralstonia solanacearum indicated Anoxybacillus, Flavobacterium, Permianibacter and Pseudomonas were predicted to be associated with disease-suppressive function formation. Altogether, our results showed that bulk soil played an important role in the process of assembling and reassembling the rhizosphere microbiome of plants.

The evolution of novel hemoglobin functions and physiological innovation

Chapter 7 explores the evolution of novel hemoglobin functions and physiological innovations. In the epic sweep of life’s history on Earth, globin proteins such as vertebrate hemoglobin were only recently co-opted for a respiratory function in circulatory O2 transport. Even after blood-O2 transport became an entrenched feature of vertebrate physiology, red blood cell hemoglobins evolved additional specializations of function in particular lineages. In some cases, like the Root effect of fish hemoglobins, these new functions represent key physiological innovations that have contributed to adaptive radiation. This chapter explores several case studies of how the evolution of novel allosteric properties have enhanced and expanded the physiological capacities of particular vertebrate groups, with an emphasis on teleost fishes and crocodilians.

Stress response ofChironomus ripariusto changes in water temperature and oxygen concentration in a lowland stream

The increasing impairment of lotic ecosystems has promoted a growing effort into assessing their ecological status by means of biological indicators. While community-based approaches have proven valuable to assess ecosystem integrity, they mostly reflect long-term changes and might not be suitable for tracking and monitoring short-term events. Responses to rapid changes in environmental conditions have been rarely studied under natural conditions. Biomarkers offer the benefit of integrating biological responses at different time scales. Here we used a field experiment to test how the synthesis of heat shock protein 70 (HSP70) and Haemoglobin (Hb) in laboratory-reared larvae ofChironomus riparius(Diptera, Chironomidae) were influenced by short-term changes to water temperature and oxygen concentration in a lowland stream. Our aim was to determine whether HSP70 mRNA expression and Hb content could be used as anin situ“early warning system” for freshwater habitats undergoing environmental change. HSP70 exhibited a clear response to changes in temperature measured over a one-day period, confirming its suitability as an indicator of environmental stress. Hb concentration was related to oxygen concentration, but not to temperature. Our findings support the hypothesis that depletion in oxygen induces Hb synthesis inC. ripariuslarvae. Because tolerance to low oxygen is not only related to total Hb, but also to a more efficient uptake (binding to Hb, e.g. Bohr effect) and release of oxygen to the cell (Root effect), we cannot discern from our data whether increased efficiency played a role. We suggest thatC. ripariusis a suitable model organism for monitoring sub-lethal stress in the field and that the approach could be applied to other species as more genomic data are available for non-model organisms.

Methodology for the engineering calculation of flaps on Wind Turbines using BEM codes

Aeroelastic codes based on Blade Element Momentum theory are the standard used by many wind turbine designers. These codes usually include models and corrections for unsteady aerodynamics, tip and root effect, tower shadow and other effects. In general, this kind of codes does not include models to adequately simulate aerodynamic control devices. This paper presents a method to take into account the unsteady contributions due to the flap motion (based on indicial models) and the spanwise effects (based on circulation theory), in order to simulate flaps on the blades. This method can be included in BEM codes in general and it could also be applied to another kind of control devices. The validation and verification show the accuracy of this method using experimental data for two-dimensional unsteady cases, and CFD for three-dimensional steady and unsteady cases.