bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitochondrial Oxyconformity and Cold Adaptation in the Polychaete Nereis Pelagica and the Bivalve Arctica Islandica From The Baltic And White Seas
Authors: Tschischka Katja , Abele Doris , Pörtner Hans O. 
Published: April 2021

ABSTRACT
The rates of oxygen uptake of the marine polychaete Nereis pelagica and the bivalve Arctica islandica depend on the availability of ambient oxygen. This is manifest both at the tissue level and in isolated mitochondria studied between oxygen tensions of 6.3 and 47.6 kPa (47–357 mmHg). Oxyconformity was found in both Baltic Sea (Kiel Bight) and cold-adapted White Sea populations of the two species. However, mitochondria isolated from White Sea specimens of N. pelagica and A. islandica showed a two-to threefold higher aerobic capacity than mitochondria prepared from Baltic Sea specimens. We tested whether mitochondrial oxyconformity can be explained by an additional electron pathway that is directly controlled by . Mitochondrial respiration of both invertebrate species was inhibited by cyanide (KCN) and by salicylhydroxamic acid (SHAM). The overall rate of mitochondrial oxygen consumption increased at high . Phosphorylation efficiency (ADP/O ratio) decreased at elevated (27.5–47.6 kPa, 206–357 mmHg), regardless of whether malate or succinate was used as a substrate. In contrast to the invertebrate mitochondria studied, mitochondria isolated from bovine heart, as an oxyregulating control species, did not show an elevated rate of oxygen uptake at high in any respiratory state, with the exception of state 2 malate respiration. In addition, rates of ATP formation, respiratory control ratios (RCR) and ADP/O ratios remained virtually unchanged or even tended to decreased. In conclusion, the comparison between mitochondria from oxyregulating and oxyconforming organisms supports the existence of an alternative oxidase in addition to the classical cytochrome c oxidase. In accordance with models discussed previously, oxidative phosphorylation does not explain the rate of mitochondrial oxygen consumption during progressive activation of the alternative electron transport system. We discuss the alternative system, thought to be adaptive in confined, usually hypoxic environments, where excess oxygen can be eliminated and oxygen levels can be kept low by an increase in the rate of oxygen consumption, thereby minimizing the risk of oxidative stress.
Cloning and Characterization of Sarco/Endoplasmic Reticulum Ca2+ -ATPase (Serca) From Crayfish Axial Muscle
Authors: Zhang Zhiping , Chen Dongdong , Wheatly Michele G. 
Published: April 2021

ABSTRACT
The discontinuous pattern of muscle growth during the moulting cycle of a freshwater crustacean (the crayfish Procambarus clarkii) was used as a model system to examine the regulation of the expression of Sarco/Endoplasmic Reticulum Ca2+ -ATPase (SERCA). We describe the cloning, sequencing and characterization of a novel SERCA cDNA (3856 bp) obtained from crayfish axial abdominal muscle by reverse transcription/polymerase chain reaction (RT-PCR) followed by rapid amplification of cDNA ends (RACE). This complete sequence contains a 145 base pair (bp) noncoding region at the 5′ end, a 3006 bp open reading frame coding for 1002 amino acid residues with a molecular mass of 110 kDa and 705 bp of untranslated region at the 3′ end. This enzyme contains all the conserved domains found in ‘P’-type ATPases, and the hydropathy profile suggests a transmembrane organization typical of other SERCAs. It exhibits 80 % amino acid identity with Drosophila melanogaster SERCA, 79 % identity with Artemia franciscana SERCA, 72 % identity with rabbit fast-twitch muscle neonatal isoform SERCA1b, 71 % identity with slow-twitch muscle isoform SERCA2 and 67 % identity with SERCA3. Sequence alignment revealed that regions anchoring the cytoplasmic domain in the membrane were highly conserved and that most differences were in the NH2 terminus, the central loop region and the COOH terminus. Northern analysis of total RNA from crayfish tissues probed with the 460 bp fragment initially isolated showed four bands (7.6, 7.0, 5.8 and 4.5 kilobases) displaying tissue-specific expression. SERCA was most abundant in muscle (axial abdominal, cardiac and stomach), where it is involved in Ca2+ resequestration during relaxation, and in eggs, where it may be implicated in early embryogenesis. The level of SERCA mRNA expression in axial abdominal muscle varied during the moulting cycle as determined by slot–blot analysis. SERCA expression was greatest during intermoult and decreased to approximately 50 % of this level during pre- and postmoult. Patterns of gene expression for SERCA and other sarcomeric proteins during the crustacean moulting cycle may be regulated by ecdysteroids and/or mechanical stimulation.
Sources and Mechanisms of Inorganic Carbon Transport for Coral Calcification and Photosynthesis
Authors: Furla Paola , Galgani Isabelle , Durand Isabelle , Allemand Denis 
Published: April 2021

ABSTRACT
The sources and mechanisms of inorganic carbon transport for scleractinian coral calcification and photosynthesis were studied using a double labelling technique with H14 CO3 and 45 Ca. Clones of Stylophora pistillata that had developed into microcolonies were examined. Compartmental and pharmacological analyses of the distribution of 45 Ca and H14 CO3 in the coelenteron, tissues and skeleton were performed in dark or light conditions or in the presence of various seawater HCO3− concentrations.
For calcification, irrespective of the lighting conditions, the major source of dissolved inorganic carbon (DIC) is metabolic CO2 (70–75 % of total CaCO3 deposition), while only 25–30 % originates from the external medium (seawater carbon pool). These results are in agreement with the observation that metabolic CO2 production in the light is at least six times greater than is required for calcification. This source is dependent on carbonic anhydrase activity because it is sensitive to ethoxyzolamide. Seawater DIC is transferred from the external medium to the coral skeleton by two different pathways: from sea water to the coelenteron, the passive paracellular pathway is largely sufficient, while a DIDS-sensitive transcellular pathway appears to mediate the flux across calicoblastic cells. Irrespective of the source, an anion exchanger performs the secretion of DIC at the site of calcification. Furthermore, a fourfold light-enhanced calcification of Stylophora pistillata microcolonies was measured. This stimulation was only effective after a lag of 10 min. These results are discussed in the context of light-enhanced calcification.
Characterisation of the DIC supply for symbiotic dinoflagellate photosynthesis demonstrated the presence of a DIC pool within the tissues. The size of this pool was dependent on the lighting conditions, since it increased 39-fold after 3 h of illumination. Passive DIC equilibration through oral tissues between sea water and the coelenteric cavity is insufficient to supply this DIC pool, suggesting that there is an active transepithelial absorption of inorganic carbon sensitive to DIDS, ethoxyzolamide and iodide. These results confirm the presence of CO2-concentrating mechanisms in coral cells. The tissue pool is not, however, used as a source for calcification since no significant lag phase in the incorporation of external seawater DIC was measured.
Evolution of Air-Breathing and Central CO2/H+ Respiratory Chemosensitivity: New Insights From an Old Fish?
Authors: Wilson R. J. A. , Harris M. B. , Remmers J. E. , Perry S. F. 
Published: April 2021

ABSTRACT
While little is known of the origin of air-breathing in vertebrates, primitive air breathers can be found among extant lobe-finned (Sarcopterygii) and ray-finned (Actinopterygii) fish. The descendents of Sarcopterygii, the tetrapods, generate lung ventilation using a central pattern generator, the activity of which is modulated by central and peripheral CO2/H+ chemoreception. Air-breathing in Actinopterygii, in contrast, has been considered a ‘reflexive’ behaviour with little evidence for central CO2/H+ respiratory chemoreceptors. Here, we describe experiments using an in vitro brainstem preparation of a primitive air-breathing actinopterygian, the longnose gar Lepisosteus osseus. Our data suggest (i) that gill and air-breathing motor patterns can be produced autonomously by the isolated brainstem, and (ii) that the frequency of the air-breathing motor pattern is increased by hypercarbia. These results are the first evidence consistent with the presence of an air-breathing central pattern generator with central CO2/H+ respiratory chemosensitivity in any primitive actinopterygian fish. We speculate that the origin of the central neuronal controller for air-breathing preceded the divergence of the sarcopterygian and actinopterygian lineages and dates back to a common air-breathing ancestor.
Catalytic Activity and Heat Production by the Ca2+-ATPase from Sea Cucumber (Ludwigothurea Grisea) LONGITUDINAL SMOOTH MUSCLE: MODULATION BY MONOVALENT CATIONS
Authors: Landeira-Fernandez Ana Maria , Galina Antonio , De Meis Leopoldo 
Published: April 2021

ABSTRACT
In muscle cells, excitation–contraction coupling involves the translocation of Ca2+ between intracellular compartments and the cytosol. Heat derived from the hydrolysis of ATP by the sarcoplasmic reticulum Ca2+-ATPase of skeletal muscle plays an important role in the thermoregulation and energy balance of the cell. Although several Ca2+-ATPase isoforms have been described in vertebrates, little is known about Ca2+ transport in invertebrates. In this report, a Ca2+-ATPase is identified in the microsomal fraction obtained from sea cucumber (Ludwigothurea grisea) smooth muscle. The activity of this enzyme is enhanced three-to fivefold by K+ and Na+. During Ca2+ transport, the ATPase can synthesise ATP from ADP and inorganic phosphate (Pi) using the energy derived from the Ca2+ gradient formed across the microsomal membrane (ATP↔Pi exchange). The apparent affinity of the enzyme for Pi is increased by more than one order of magnitude by K+. In the presence of K+, the fraction of ATP synthesised during the exchange reaction by sea cucumber microsomes was found to be larger than that measured in microsomes derived from either rabbit or trout muscle. Like the isoforms found in skeletal muscle, the sea cucumber Ca2+-ATPase can convert osmotic energy into heat. The amount of heat produced after the hydrolysis of each ATP molecule increases two-to threefold when a Ca2+ gradient is formed across the microsomal membrane.
The cardiovascular responses of the red-eared slider (Trachemys scripta) acclimated to either 22 or 5 °C: I. Effects of anoxic exposure on in vivo cardiac performance
Authors: Hicks J. M. T. , Farrell A. P. 
Published: April 2021

ABSTRACT
The extreme anoxia-tolerance of freshwater turtles under cold conditions is well documented, but little is known about their cardiac performance in such situations. Using chronic catheterization techniques, we measured systemic cardiac power output (POsys), systemic cardiac output (Q̇sys), heart rate (fH), systemic stroke volume (Vs,sys), systemic resistance (Rsys) and mean arterial pressure (Psys) in red-eared sliders (Trachemys scripta). The effects of cold acclimation and anoxic exposure were studied. Turtles were acclimated to either 22 °C or 5 °C, and the anoxic exposure was either acute (6 h) at 22 °C or chronic (3 weeks) at 5 °C. Cold acclimation alone decreased POsys by 15-fold, representing a Q10 of 8.8. In addition, fH and Vs,sys decreased significantly, while Rsys increased and moderated the arterial hypotension. Acute and chronic anoxic exposures significantly decreased POsys, Vs,sys, fH and Psys and increased Rsys. But the changes were qualitatively much larger with chronic anoxia. For example, acute anoxia in 22 °C-acclimated turtles decreased POsys by 6.6-fold, whereas chronic anoxia in 5 °C-acclimated turtles decreased POsys by 20-fold. The remarkable cardiovascular down-regulation that accompanies long periods of cold anoxia in these turtles was characterized by comparing cardiovascular status during chronic anoxia at 5 °C with that during normoxia at 22 °C. Car.diac POsys was reduced 330-fold, through decreases in Qsys (120-fold), fH (24.2-fold), Vs,sys (5.7-fold) and Psys (2.2-fold), while Rsys was increased 64.6-fold. We also compared cardiac glycolytic rates by assuming that POsys was proportional to ATP supply and that glycolysis yielded 18 times less ATP per mole of glucose than oxidative metabolism. At 22 °C, the 6.6-fold decrease in POsys with anoxia suggests that a Pasteur effect was needed in cardiac tissues during acute anoxia. However, this would not be so with chronic anoxia at 5 °C because of the 22-fold decrease in POsys. We propose that the suppression of the Pasteur effect and the large Q10 values for cold acclimation would conserve glucose stores and enable turtles to withstand anoxia much longer under cold than under warm conditions.
Connections Between Thoraco-Coxal Proprioceptive Afferents and Motor Neurons in the Locust
Authors: Wildman Mark 
Published: April 2021

ABSTRACT
The position of the coxal segment of the locust hind leg relative to the thorax is monitored by a variety of proprioceptors, including three chordotonal organs and a myochordotonal organ. The sensory neurons of two of these proprioceptors, the posterior joint chordotonal organ (pjCO) and the myochordotonal organ (MCO), have axons in the purely sensory metathoracic nerve 2C (N2C). The connections made by these afferents with metathoracic motor neurons innervating thoraco-coxal and wing muscles were investigated by electrical stimulation of N2C and by matching postsynaptic potentials in motor neurons with afferent spikes in N2C. Stretch applied to the anterior rotator muscle of the coxa (M121), with which the MCO is associated, evoked sensory spikes in N2C. Some of the MCO afferent neurons make direct excitatory chemical synaptic connections with motor neurons innervating the thoraco-coxal muscles M121, M126 and M125. Parallel polysynaptic pathways via unidentified interneurons also exist between MCO afferents and these motor neurons. Connections with the common inhibitor 1 neuron and motor neurons innervating the thoraco-coxal muscles M123/4 and wing muscles M113 and M127 are polysynaptic. Afferents of the pjCO also make polysynaptic connections with motor neurons innervating thoraco-coxal and wing muscles, but no evidence for monosynaptic pathways was found.
Identification of a Ubiquitous Family of Membrane Proteins and Their Expression in Mouse Brain
Authors: Grossman Tamar R. , Luque Juan M. , Nelson Nathan 
Published: April 2021

ABSTRACT
A family of genes encoding membrane proteins with a unique structure has been identified in DNA and cDNA clones of various eukaryotes ranging from yeast to human. The nucleotide sequences of three novel cDNAs from Drosophila melanogaster and mouse were determined. The amino acid sequences of the two mouse proteins have human homologs. The gene (TMS1) encoding the yeast member of this family was disrupted, and the resulting mutant showed no significant phenotype under several stress conditions. The expression of the mouse genes TMS-1 and TMS-2 was examined by in situ hybridization of sections from brain, liver, kidney, heart and testis of an adult mouse as well as in a 1-day-old whole mouse. While the expression of TMS-2 was found to be restricted to the central nervous system, TMS-1 was also expressed in kidney and testis. The expression of TMS-1 and TMS-2 in the brain overlapped and was localized to areas associated with glutamatergic excitatory neurons, such as the hippocampus and cerebral cortex. High-magnification analysis indicated that both mRNAs are expressed in neurons. Semiquantitative analysis of mRNA expression was performed in various parts of the brain. The conservation, unique structure and localization in the mammalian brain of this novel protein family suggest an important biological role.
Cloning and Molecular Characterisation of the Trout (Oncorhynchus Mykiss) Vacuolar H+-Atpase B Subunit
Authors: Perry Steve F. , Beyers Matthew L. , Johnson Douglas A. 
Published: April 2021

ABSTRACT
The current model of transepithelial ion movements in the gill of freshwater fish incorporates an apically oriented vacuolar H+-ATPase (H+V-ATPase; proton pump) that is believed to facilitate both acid excretion and Na+ uptake. To substantiate this model, we have cloned and sequenced a cDNA encoding the B subunit of the rainbow trout (Oncorhynchus mykiss) H+V-ATPase. The cloning of the B subunit enabled an examination by northern analysis of its tissue distribution and expression during external hypercapnia.
Degenerate oligonucleotide primers to the B subunit of the H+V-ATPase were designed and used in a semi-nested polymerase chain reaction (PCR) to amplify an 810 base pair (bp) product from a trout gill/kidney cDNA library. This PCR product was cloned and sequenced and then used to screen the same cDNA library. The assembled 2262 bp cDNA included an open reading frame coding for a deduced protein of 502 amino acid residues. A BLAST search of the GenBank nucleotide database revealed numerous matches to other vertebrate and invertebrate H+V-ATPase B subunits. Protein alignment demonstrated that the trout H+V-ATPase B subunit is more than 85 % identical and more than 90 % similar to those in other vertebrate species.
An initial analysis of H+V-ATPase mRNA tissue distribution revealed significant expression in blood. Although a comparison of perfused tissues (blood removed) with non-perfused tissues demonstrated no obvious contribution of the blood to total tissue H+-ATPase mRNA levels, all subsequent experiments were performed using perfused tissues. Levels of H+V-ATPase mRNA expression were high in the gill, kidney (anterior or posterior), intestine, heart and spleen, but lower in liver and white muscle. Exposure of the fish to 12 h of external hypercapnia (water ; 1 kPa) was associated with a transient increase (at 2 h) in the levels of H+V-ATPase B subunit mRNA in gill and kidney; liver mRNA levels were unaffected.
These results are consistent with the hypothesis of an apically localised plasma membrane H+V-ATPase in the freshwater trout gill and that the expression of this proton pump is increased during periods of acidosis, at least in part because of an increased steady-state level of H+V-ATPase mRNA.
Patterns of White Muscle Activity During Terrestrial Locomotion in the American Eel (Anguilla Rostrata)
Authors: Gillis Gary B. 
Published: April 2021

ABSTRACT
Eels (Anguilla rostrata) are known to make occasional transitory excursions into the terrestrial environment. While on land, their locomotor kinematics deviate drastically from that observed during swimming. In this study, electromyographic (EMG) recordings were made from white muscle at various longitudinal positions in eels performing undulatory locomotion on land to determine the muscle activity patterns underlying these terrestrial movements. As during swimming, eels propagate a wave of muscle activity from anterior to posterior during terrestrial locomotion. However, the intensity of EMG bursts is much greater on land (on average approximately five times greater than in water). In addition, anteriorly located musculature has higher-intensity EMG bursts than posteriorly located muscle during locomotion on land. EMG duty cycle (burst duration relative to undulatory cycle time) is significantly affected by longitudinal position during terrestrial locomotion, and duty cycles are significantly greater on land (0.4–0.5 cycles) than in water (0.2–0.3 cycles). Finally, as in swimming, a phase shift in the timing of muscle activity exists such that posteriorly located muscle fibers become activated earlier in their strain cycle than do more anteriorly located fibers. However, fibers become activated much later in their muscle strain cycle on land than in water. Therefore, it is clear that, while eels propagate a wave of muscle activity posteriorly to generate backward-traveling waves that generate propulsive thrust both in water and on land, the specific patterns of timing and the intensity of muscle activity are substantially altered depending upon the environment. This suggests that physical differences in an animal’s external environment can play a substantial role in affecting the motor control of locomotion, even when similar structures are used to generate the propulsive forces.
Ecdysis of Decapod Crustaceans is Associated With a Dramatic Release of Crustacean Cardioactive Peptide into the Haemolymph
Authors: Phlippen Markus K. , Webster Simon G. , Chung J. Sook , Dircksen Heinrich 
Published: April 2021

ABSTRACT
On the basis of detailed analyses of morphological characteristics and behavioural events associated with ecdysis in a crab (Carcinus maenas) and a crayfish (Orconectes limosus), a comprehensive substaging system has been introduced for the ecdysis stage of the moult cycle of these decapod crustaceans. In a remarkably similar stereotyped ecdysis sequence in both species, a passive phase of water uptake starting with bulging and rupture of thoracoabdominal exoskeletal junctions is followed by an active phase showing distinct behavioural changes involved in the shedding of the head appendages, abdomen and pereiopods. Together with an enzyme immunoassay for crustacean cardioactive peptide (CCAP), the substaging has been used to demonstrate a large, rapid and reproducible peak in haemolymph CCAP levels (increases of approximately 30-fold in the crab and more than 100-fold in the crayfish compared with intermoult titres) during the later stages of active ecdysis. We suggest that the release of CCAP (accumulated in late premoult) from the crab pericardial organs or the crayfish ventral nerve cord accounts for many of the changes in behaviour and physiology seen during ecdysis and that this neurohormone is likely to be of critical importance in crustaceans and other arthropods.
Agonistic Behaviour and Biogenic Amines in Shore Crabs Carcinus Maenas
Authors: Sneddon Lynne U. , Taylor Alan C. , Huntingford Felicity A. , Watson David G. 
Published: April 2021

ABSTRACT
To investigate the role of certain neurohormones in agonistic behaviour, fights were staged between pairs of size-matched male shore crabs Carcinus maenas, and blood samples were taken immediately after the contests had been resolved. Samples were also taken from these crabs at rest (before and after fighting) and after walking on a treadmill. A control group of crabs also had samples taken on each experimental day. Concentrations of tyramine, dopamine, octopamine, serotonin (5-HT) and norepinephrine were determined in each blood sample using a gas chromatography/mass spectrometry (GC-MS) system. Norepinephrine was not detectable in any of the samples, but the standards were recovered. Tyramine values were not significantly different between the control group and the fought group, so tyramine does not appear to be important in agonistic behaviour. A comparison between the control and fought groups shows that fighting had an effect on the concentrations of octopamine, dopamine and 5-HT, but exercise only had an effect on octopamine levels, which showed a reduction from resting values in both winners and losers. Resting and post-fight concentrations of octopamine, dopamine and 5-HT were higher in winners than in losers. 5-HT concentration increased in the blood of fought crabs from resting values, whereas dopamine concentration decreased. In winners, octopamine concentrations decreased from resting values, but in losers octopamine levels increased from resting concentrations. The escalatory behaviour or intensity of fighting performed by winners and losers was related to dopamine levels but not to those of octopamine or 5-HT. Therefore, there appears to be a link between relative concentrations of these three amines (dopamine, octopamine and 5-HT) and fighting ability; the effects are not simply a result of activity. The better competitors have higher concentrations of these three amines at rest and after fighting.