bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Fin Size on Swimming Performance, Swimming Behaviour and Routine Activity of Zebrafish Danio Rerio
Authors: Plaut Itai 
Published: April 2021

ABSTRACT
The zebrafish Danio rerio exhibits substantial morphological variability in the sizes and shapes of the body and the caudal fin. The present study describes swimming performance, swimming behaviour and routine locomotor activity patterns in three of the major morphotypes: wild-type, long-finned and no-tail. Wild-type and long-finned differ in total length (TL), fork length (FL), caudal fin length (CFL) and caudal fin height (CFH). No-tail has no caudal fin and is significantly smaller in standard length (SL) than the other types. Critical swimming speeds (Ucrit) were measured at 28 °C in a modified Brett-type water tunnel. Ucrit of wild-type fish was 56.0±4.8 cm s−1 or 15.5 SL s−1 (mean ± S.D., N=21), significantly faster than the Ucrit of long-finned fish (43.7±6.8 cm s−1 or 12.5 SL s−1, N=17); both were significantly faster than the Ucrit of no-tail fish (19.8±4.7 cm s−1 or 6.9 SL s−1, N=15). When forced to swim in the water tunnel, zebrafish tended to turn and swim downstream for short periods at slow water velocities. Turning frequencies (turns per minute, fT) at the slowest velocity (4 cm s−1) were 10.1±6.5 min−1 (N=63) and 8.6±4.7 min−1 (N=51) for wild-type and long-finned, respectively, significantly different from that of the no-tail fish, 4.7±2.8 min−1 (N=45). These frequencies decreased below 1 min−1 at 56 %, 64 % and 61 % of Ucrit in wild-type, long-finned and no-tail fish, respectively. Activity levels of wild-type fish were generally significantly higher than those of long-finned fish, and the levels of both were significantly higher than those of no-tail fish. The pattern of differences in relative activity levels between types was similar to that for Ucrit. The results show that the wild-type fish, on a size-scaled basis, is one of the fastest-swimming fishes ever measured, reaching the maximum predicted theoretical sustained swimming speed. Ucrit of long-finned fish was 22 % lower than that of wild-type fish, and Ucrit of no-tail fish was 65 % lower. Similar differences were found in turning frequencies and routine activity level.
Mammalian Oxygen Sensing, Signalling and Gene Regulation
Authors: Wenger Roland H. 
Published: April 2021

ABSTRACT
Oxygen is essential to the life of all aerobic organisms. Virtually every cell type is able to sense a limited oxygen supply (hypoxia) and specifically to induce a set of oxygen-regulated genes. This review summarizes current concepts of mammalian oxygen-sensing and signal-transduction pathways. Since the discovery of the hypoxia-inducible factors (HIFs), a great deal of progress has been made in our comprehension of how hypoxia induces the expression of oxygen-regulated genes. The α subunit of the heterodimeric transcription factors HIF-1, 2 and 3 is unstable under normoxia but is rapidly stabilized upon exposure to hypoxic conditions. Following heterodimerization with the constitutively expressed β subunit, HIFs activate the transcription of an increasing number of genes involved in maintaining oxygen homeostasis at the cellular, local and systemic levels.
The Effects of Acute Hypoxia on Chemically or Neuronally Induced Catecholamine Secretion in Rainbow Trout (Oncorhynchus Mykiss) in Situ and In Vivo
Authors: Perry Steve F. , Montpetit Colin J. , Borowska Maja 
Published: April 2021

ABSTRACT
The potential direct and modulating effects of acute hypoxia on catecholamine secretion in rainbow trout (Oncorhynchus mykiss) were assessed in situ, using a perfused cardinal vein preparation, and in vivo, using chronically cannulated fish. Acute (10 min) perfusion with hypoxic saline or homologous hypoxic blood did not have a statistically significant effect on basal (non-stimulated) catecholamine secretion. A field stimulation technique was used to excite the sympathetic nerves innervating the chromaffin cells electrically in situ under conditions of high- (saline or low- (saline perfusion at constant (2.3 mmHg). The results demonstrated that neuronally evoked catecholamine secretion was significantly lowered by 50 % during perfusion with hypoxic saline. To assess whether the inhibitory effect of hypoxia during neuronal stimulation in situ resulted from modulation of nicotinic and/or muscarinic receptor-linked pathways, perfused posterior cardinal vein preparations were injected with selective nicotinic (10−7 or 10−6 mol kg−1 nicotine) or muscarinic (10−3 mol kg−1 methacholine) receptor agonists. For both doses of nicotine, catecholamine secretion was significantly lowered during hypoxia by 55 %. During muscarinic receptor stimulation, perfusion with hypoxic saline caused a 42 % reduction in the rate of catecholamine secretion. In contrast, catecholamine secretion elicited by depolarising levels of KCl (60 mmol l−1) was unaffected by the oxygen status of the perfusate. In vivo, intra-arterial injections of nicotine (300–600 nmol kg−1) into normoxic or moderately hypoxic fish caused a dose-dependent elevation of circulating catecholamine levels. However, despite the inhibitory influence of localised hypoxia on chromaffin cell responsiveness previously demonstrated in situ, the increase in plasma catecholamine levels after intra-arterial injection of nicotine was significantly enhanced in the hypoxic fish. The differences between the results from the in vivo and in situ experiments may reflect the contribution of higher control centres and modulating factors in vivo that are absent in situ.
Nitric Oxide Modulates Cardiac Performance in the Heart of Anguilla Anguilla
Authors: Imbrogno Sandra , Iuri Lucia De , Mazza Rosa , Tota Bruno 
Published: April 2021

ABSTRACT
Nothing is known about the effects of nitric oxide (NO) on cardiac performance in fish. Using an in vitro working heart preparation that generates physiological values of output pressure, cardiac output and ventricular work and power, we assessed the effects of NO on the cardiac performance of the eel Anguilla anguilla. We examined basal cardiac performance (at constant preload, afterload and heart rate), the effects of cholinergic stimulation and the Frank–Starling response (preload-induced increases in cardiac output at constant afterload and heart rate). The NO synthase (NOS) inhibitors NG -monomethyl-L-arginine (L-NMMA) and L-N5 (1-iminoethyl)ornithine (L-NIO), the guanylate cyclase inhibitor 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ) and Triton X-100, a detergent that damages the endocardial endothelium, all increased stroke volume (VS) and stroke work (WS). In contrast, the endogenous NOS substrate L-arginine, tested before and after treatment with haemoglobin, the NO donor 3-morpholinosydnonimine, tested with and without the superoxide scavenger superoxide dismutase, and the stable cGMP analogue 8-bromoguanosine 3’, 5’ -cyclic monophosphate (8-Br-cGMP) decreased VS and WS. Acetylcholine chloride produced a biphasic effect. At nanomolar concentrations, in 34 % of the preparations, it induced a NO–cGMP-dependent positive inotropism that required the integrity of the endocardial endothelium. Pretreatment with Triton X-100 or with NO–cGMP pathway inhibitors (L-NMMA, L-NIO, NG -nitro-L-arginine methyl ester, Methylene Blue and ODQ) abolished the positive effect of acetylcholine. In contrast, at micromolar concentrations, acetylcholine produced a negative effect that involved neither the endocardial endothelium nor the NO–cGMP pathway. Pre-treatment with L-arginine (10− 6 mol l− 1) was without effect, whereas L-NIO (10− 5 mol l− 1) significantly reduced the Frank–Starling response. Taken together, these three experimental approaches provide evidence that NO modulates cardiac performance in the eel heart.
Plasticity of Chemotaxis Revealed by Paired Presentation of A Chemoattractant and Starvation in the Nematode Caenorhabditis Elegans
Authors: Saeki Satoshi , Yamamoto Masayuki , Iino Yuichi 
Published: April 2021

ABSTRACT
While the basic functioning of the nervous system of Caenorhabditis elegans has been extensively studied, its behavioural plasticities have not been fully explored because of the limited availability of assay systems. We report here a simple form of chemotaxis plasticity in this organism: when worms are starved on plates that contain NaCl, their chemotaxis towards NaCl falls dramatically. This conditioning requires both the presence of NaCl and the absence of a bacterial food source, indicating that it is not merely adaptation or habituation, but that it is likely to be a form of associative learning. While chemotaxis towards volatile chemoattractants does not change significantly after conditioning with NaCl, chemotaxis towards other water-soluble attractants does decrease. This suggests that an altered response of a cell or a group of cells specifically involved in chemotaxis towards water-soluble chemoattractants is responsible for the behavioural alteration. The decrease in chemotaxis occurred slowly over 3–4 h of conditioning and returned quickly to the original level when either of the conditioning stimuli, NaCl or starvation, was removed. The application of serotonin partially blocked this reduction in chemotaxis, consistent with the proposed function of this neurotransmitter in food signalling. Using this assay, we have isolated three mutants with reduced plasticity. This assay system expands the opportunities for studying the molecular and cellular mechanisms of behavioural plasticity in C. elegans.
The Application of Ground Force Explains The Energetic Cost of Running Backward and Forward
Authors: Wright Seth , Weyand Peter G. 
Published: April 2021

ABSTRACT
We compared backward with forward running to test the idea that the application of ground force to support the weight of the body determines the energetic cost of running. We hypothesized that higher metabolic rates during backward versus forward running would be directly related to greater rates of ground force application and the volume of muscle activated to apply support forces to the ground. Four trained males ran backward and forward under steady-state conditions at eight treadmill speeds from 1.75 to 3.50 m s−1. Rates of oxygen uptake were measured to determine metabolic rates, and inverse periods of foot–ground contact (1/tc) were measured to estimate rates of ground force application. As expected, at all eight speeds, both metabolic rates and estimated rates of ground force application were greater for backward than for forward running. At the five slowest speeds, the differences in rates of ground force application were directly proportional to the differences in metabolic rates between modes (paired t-test, P&lt;0.05), but at the three highest speeds, small but significant differences in proportionality were present in this relationship. At one of these three higher speeds (3.0 m s−1), additional measurements to estimate muscle volumes were made using a non-invasive force plate/video technique. These measurements indicated that the volume of muscle active per unit of force applied to the ground was 10±3 % greater when running backward than forward at this speed. The product of rates of ground force application and estimated muscle volumes predicted a difference in metabolic rate that was indistinguishable from the difference we measured (34±6 % versus 35±6 %; means ± S.E.M., N=4). We conclude that metabolic rates during running are determined by rates of ground force application and the volume of muscle activated to apply support forces to the ground.
Red and white muscle development in the trout (Oncorhynchus mykiss) as shown byin situhybridisation of fast and slow myosin heavy chain transcripts
Authors: Rescan Pierre-Yves , Collet Bertrand , Ralliere Cecile , Cauty Chantal , Delalande Jean-Marie , Goldspink Geoffrey , Fauconneau Benoit 
Published: April 2021

SUMMARYThe axial muscle of most teleost species consists of a deep bulk of fast-contracting white fibres and a superficial strip of slow-contracting red fibres. To investigate the embryological development of fast and slow muscle in trout embryos, we carried out single and double in situ hybridisation with fast and slow myosin heavy chain (MyHC)-isoform-specific riboprobes. This showed that the slow-MyHC-positive cells originate in a region of the somite close to the notochord. As the somite matures in a rostrocaudal progression, the slow-MyHC-positive cells appear to migrate radially away from the notochord to the lateral surface of the myotome, where they form the superficial strip of slow muscle. Surprisingly, the expression pattern of the fast MyHC showed that the differentiation of fast muscle commences in the medial domain of the somite before the differentiation and migration of the slow muscle precursors. Later, as the differentiation of fast muscle progressively spreads from the inside to the outside of the myotome, slow-MyHC-expressing cells become visible medially. Our observations that the initial differentiation of fast muscle takes place in proximity to axial structures and occurs before the differentiation and migration of slow muscle progenitors are not in accord with the pattern of muscle formation in teleosts previously described in the zebrafish Danio rerio, which is often used as the model organism in fishes.
Flight-motor-driven respiratory air flow in the hawkmothManduca sexta
Authors: Wasserthal Lutz T. 
Published: April 2021

SUMMARYIntratracheal pressure during tethered flight was analyzed at the anterior spiracles and mesoscutellar air sacs in the hawkmoth Manduca sexta using electronic pressure sensors. CO2 emission from the anterior spiracles and the posterior thoracic and abdominal spiracles was measured using a URAS gas analyzer with a split-specimen chamber. Experiments were accompanied by photocell recordings of the wingbeat. The structural differences between the mesothoracic and metathoracic spiracles are described. Deformations of the lateral thorax and their effect upon the spiracles were observed under stroboscopic light.During shivering, ventilation pulses are generated by the flight muscles reminiscent of an autoventilation mechanism with tidal air flow. During steady flight, however, a unidirectional airstream arises with a mean negative (subatmospheric) pressure at the first (mesothoracic) spiracles and a mean positive pressure in the mesoscutellar air sacs. As a result of this pressure difference during flight, CO2 is emitted only at the posterior spiracles.The suction force for the inspiration flow at the anterior spiracles is generated by the flight apparatus as a result of prevention of inspiration through the posterior thoracic spiracles. During the downstroke, the volume of the thoracic air sacs increases, while the posterior thoracic spiracles are automatically enclosed in the subalar cleft below the wing hinge and are probably closed. During the upstroke, the air sac volume decreases and the moth expires through the open posterior spiracles.
Spatial integration in polarization-sensitive interneurones of crickets: a survey of evidence, mechanisms and benefits
Authors: Labhart Thomas , Petzold Jürgen , Helbling Hansruedi 
Published: April 2021

SUMMARYMany insects exploit the polarization pattern of the sky for compass orientation in navigation or cruising-course control. Polarization-sensitive neurones (POL1-neurones) in the polarization vision pathway of the cricket visual system have wide visual fields of approximately 60° diameter, i.e. these neurones integrate information over a large area of the sky. This results from two different mechanisms. (i) Optical integration; polarization vision is mediated by a group of specialized ommatidia at the dorsal rim of the eye. These ommatidia lack screening pigment, contain a wide rhabdom and have poor lens optics. As a result, the angular sensitivity of the polarization-sensitive photoreceptors is very wide (median approximately 20°). (ii) Neural integration; each POL1-neurone receives input from a large number of dorsal rim photoreceptors with diverging optical axes. Spatial integration in POL1-neurones acts as a spatial low-pass filter. It improves the quality of the celestial polarization signal by filtering out cloud-induced local disturbances in the polarization pattern and increases sensitivity.
Immunochemical analysis of the vacuolar proton-ATPase B-subunit in the gills of a euryhaline stingray (Dasyatis sabina): effects of salinity and relation to Na+/K+-ATPase
Authors: Piermarini Peter M. , Evans David H. 
Published: April 2021

SUMMARY
In the gills of freshwater teleost fishes, vacuolar proton-ATPase (V-H+-ATPase) is found on the apical membrane of pavement and chloride (Na+/K+-ATPase-rich) cells, and is an important transporter for energizing Na+ uptake and H+ excretion. In the gills of elasmobranch fishes, the V-H+-ATPase has not been extensively studied and its expression in freshwater individuals has not been examined. The goals of this study were to examine the effects of environmental salinity on the expression of V-H+-ATPase in the gills of an elasmobranch (the Atlantic stingray, Dasyatis sabina) and determine if V-H+-ATPase and Na+/K+-ATPase are expressed in the same cells. We found that gills from freshwater stingrays had the highest relative abundance of V-H+-ATPase and greatest number of V-H+-ATPase-rich cells, using immunoblotting and immunohistochemistry, respectively. When freshwater animals were acclimated to sea water for 1 week, V-H+-ATPase abundance and the number of V-H+-ATPase-rich cells decreased significantly. Atlantic stingrays from seawater environments were characterized by the lowest expression of V-H+-ATPase and least number of V-H+-ATPase-rich cells. In contrast to teleost fishes, localization of V-H+-ATPase in freshwater stingray gills was not found in pavement cells and occurred on the basolateral membrane in cells that are presumably rich in mitochondria. In freshwater stingrays acclimated to sea water and seawater stingrays, V-H+-ATPase localization appeared qualitatively to be stronger in the cytoplasm, which may suggest the transporter was stored in vesicles. Using a double-immunolabeling technique, we found that V-H+-ATPase and Na+/K+-ATPase occurred in distinct cells, which suggests there may be two types of mitochondrion-rich cells in the elasmobranch gill epithelium. Based on these findings, we propose a unique model of NaCl and acid–base regulation where the V-H+-ATPase-rich cells and Na+/K+-ATPase-rich cells are the sites of Cl– uptake/HCO3– excretion and Na+ uptake/H+ excretion, respectively.
Comparative kinematics of the forelimb during swimming in red-eared slider (Trachemys scripta) and spiny softshell (Apalone spinifera) turtles
Authors: Pace Cinnamon M. , Blob Richard W. , Westneat Mark W. 
Published: April 2021

SUMMARYSoftshell turtles (Family Trionychidae) possess extensive webbing between the digits of the manus, suggesting that the forelimb may serve as an effective thrust generator during aquatic locomotion. However, the hindlimb has previously been viewed as the dominant propulsive organ in swimming freshwater turtles. To evaluate the potential role of the forelimb in thrust production during swimming in freshwater turtles, we compared the forelimb morphology and three-dimensional forelimb kinematics of a highly aquatic trionychid turtle, the spiny softshell Apalone spinifera, and a morphologically generalized emydid turtle, the red-eared slider Trachemys scripta. Spiny softshells possess nearly twice as much forelimb surface area as sliders for generating drag-based thrust. In addition, although both species use drag-based propulsion, several aspects of forelimb kinematics differ significantly between these species. During the thrust phase of the forelimb cycle, spiny softshells hold the elbow and wrist joints significantly straighter than sliders, thereby further increasing the surface area of the limb that can move water posteriorly and increasing the velocity of the distal portion of the forelimb. These aspects of swimming kinematics in softshells should increase forelimb thrust production and suggest that the forelimbs make more substantial contributions to forward thrust in softshell turtles than in sliders. Spiny softshells also restrict forelimb movements to a much narrower dorsoventral and anteroposterior range than sliders throughout the stroke, thereby helping to minimize limb movements potentially extraneous to forward thrust production. These comparisons demonstrate considerable diversity in the forelimb kinematics of turtles that swim using rowing motions of the limbs and suggest that the evolution of turtle forelimb mechanics produced a variety of contrasting solutions for aquatic specialization.
The Salivary Apyrase of the Blood-Sucking Sand Fly Phlebotomus Papatasi Belongs to the Novel Cimex Family of Apyrases
Authors: Valenzuela Jesus G. , Belkaid Yasmine , Rowton Edgar , Ribeiro José M. C. 
Published: April 2021

ABSTRACT
Apyrases are enzymes that hydrolyze nucleotide di- and triphosphates to orthophosphate and mononucleotides. At least two families of enzymes, belonging to the 5′-nucleotidase and to the actin/heat shock 70/sugar kinase superfamily, have evolved independently to serve the apyrase reaction. Both families require either Ca2+ or Mg2+ for their action. A novel apyrase enzyme sequence, with no homology to any other known protein sequence, was found recently in the salivary glands of the hematophagous bed bug Cimex lectularius. This enzyme functions exclusively with Ca2+. Here, we report the finding of a cDNA similar to that of the C. lectularius salivary apyrase isolated from a salivary gland cDNA library of Phlebotomus papatasi. Transfection of insect cells with the P. papatasi salivary gland apyrase cDNA resulted in the secretion of a Ca2+-dependent apyrase whose activity was indistinguishable from that in salivary homogenates of P. papatasi. Homologous sequences were found in humans, in another sand fly (Lutzomyia longipalpis), in the fruit fly Drosophila melanogaster, in the nematode Caenorhabditis elegans and in the protozoan Cryptosporidium parvum, indicating that this family of enzymes is widespread among animal species.