bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of exposure to ammonia on ammonia and taurine pools of the symbiotic clam Solemya reidi
Authors: Lee Raymond W. , Childress James J. , Desaulniers Nicole T. 
Published: April 2021

ABSTRACT
The nutrition of the gutless clam Solemya reidi is supported by the activity of intracellular chemoautotrophic bacteria housed in its gill filaments. Ammonia (the sum of NH3 and NH4+) is utilized as a nitrogen source by the association and is abundant in the clam’s environment. In the present study, clams were exposed to 0.01–1.3 mmol l−1 ammonia for 22–23 h in the presence of thiosulfate as a sulfur substrate. Ammonia exposure increased the ammonia concentration in the tissue pools of the gill, foot and visceral mass from 0.5 to 2 μmol g−1 wet mass, without added ammonia, to as much as 12 μmol g−1 wet mass in the presence of 0.7 and 1.3 mmol l−1 external ammonia. Gill tissue ammonia concentrations were consistently higher than those in the foot and visceral mass. The elevation of tissue ammonia concentration compared with the medium may be due in part to an ammonia trapping mechanism resulting from a lower intracellular pH compared with sea water and greater permeability to NH3 compared with NH4+. Rates of ammonia incorporation into organic matter (assimilation) were determined using 15N as a tracer. 15N-labeled ammonia assimilation was higher in gill than in foot and increased as a function of 15N-labeled ammonia concentration in the medium. The size of the free amino acid (FAA) pool in the gill also increased as a function of ammonia concentration in the medium. This entire increase was accounted for by a single amino acid, taurine, which was the predominant FAA in both gill and foot tissue. Aspartate, glutamate, arginine and alanine were also abundant but their levels were not influenced by external ammonia concentration. Ammonia assimilation appeared to occur at rates sufficient to account for the observed increase in taurine level. These findings suggest that taurine is a major product of ammonia assimilation.
The Three-Dimensional Hydrodynamics of Tadpole Locomotion
Authors: Liu Hao , Wassersug Richard , Kawachi Keiji 
Published: April 2021

ABSTRACT
Tadpoles are unusual among vertebrates in having a globose body with a laterally compressed tail abruptly appended to it. Compared with most teleost fishes, tadpoles swim awkwardly, with waves of relatively high amplitude at both the snout and tail tip. In the present study, we analyze tadpole propulsion using a three-dimensional (3D) computational fluid dynamic (CFD) model of undulatory locomotion that simulates viscous and unsteady flow around an oscillating body of arbitrary 3D geometry. We first confirm results from a previous two-dimensional (2D) study, which suggested that the characteristic shape of tadpoles was closely matched to their unusual kinematics. Specifically, our 3D results reveal that the shape and kinematics of tadpoles collectively produce a small ‘dead water’ zone between the head-body and tail during swimming precisely where tadpoles can and do grow hind limbs – without those limbs obstructing flow. We next use our CFD model to show that 3D hydrodynamic effects (cross flows) are largely constrained to a small region along the edge of the tail fin.
Although this 3D study confirms most of the results of the 2D study, it shows that propulsive (Froude) efficiency for tadpoles is overall lower than predicted from a 2D analysis. This low efficiency is not, however, a result of the high-amplitude undulations of the tadpole. This was demonstrated by forcing our ‘virtual’ tadpole to swim with fish-like kinematics, i.e. with lower-amplitude propulsive waves. That particular simulation yielded a much lower Froude efficiency, confirming that the large-amplitude lateral oscillations of the tadpole do, indeed, provide positive thrust.
This, we believe, is the first time that the unsteady flow generated by an undulating vertebrate has been realistically modelled in three dimensions. Our study demonstrates the feasibility of using 3D CFD methods to model the locomotion of other undulatory organisms.
Acute Regulation of Glucose Uptake in Cardiac Muscle of the American Eel Anguilla Rostrata
Authors: Rodnick Kenneth J. , Bailey John R. , West Jenny L. , Rideout Alison , Driedzic William R. 
Published: April 2021

ABSTRACT
We investigated the effects of anoxia and contractile activity on glucose uptake and the intracellular location of hexokinase in cardiac muscle of the American eel Anguilla rostrata. Uptake of 2-deoxyglucose (2-DG) by ventricle strips at 15 °C was increased by 45 % by anoxia and by 85 % by contractile activity over basal conditions. The anoxia- and contraction-induced increase in basal 2-DG uptake was inhibited completely by 25 μmol l−1 cytochalasin B, suggesting that facilitated glucose transporters are involved. Maximal activity of hexokinase in whole homogenates (approximately 10 μmol min−1 g−1 tissue) was 200 times higher than the maximal rate of 2-DG uptake measured in vitro (46 nmol min−1 g−1 tissue). Only 20–25 % of hexokinase activity was localized to the mitochondrial fraction, and this was not altered by perfusion of the hearts with anoxic media. It is therefore unlikely that anoxia-induced stimulation of 2-DG uptake is mediated by intracellular translocation of hexokinase. As in the case of mammalian muscle, glucose 6-phosphate is a potent inhibitor of hexokinase in eel cardiac muscle (IC50=0.44 mmol l−1). In summary, anoxia and contractile activity significantly increase 2-DG uptake in cardiac muscle of American eels, and glucose transport may be rate-limiting for glucose utilization. Increased utilization of glucose during anoxia or contractile activity may involve the recruitment of facilitative glucose transport proteins to the cell surface of myocytes or an increase in the intrinsic activity of glucose transporters already residing at the cell surface.
METABOLIC IMPORTANCE OF Na+/K+-ATPase ACTIVITY DURING SEA URCHIN DEVELOPMENT
Authors: Leong P. K. K. , Manahan D. T. 
Published: April 2021

ABSTRACT
Early stages of animal development have high mass-specific rates of metabolism. The biochemical processes that establish metabolic rate and how these processes change during development are not understood. In this study, changes in Na+/K+-ATPase activity (the sodium pump) and rate of oxygen consumption were measured during embryonic and early larval development for two species of sea urchin, Strongylocentrotus purpuratus and Lytechinus pictus. Total (in vitro) Na+/K+-ATPase activity increased during development and could potentially account for up to 77 % of larval oxygen consumption in Strongylocentrotus purpuratus (pluteus stage) and 80 % in Lytechinus pictus (prism stage). The critical issue was addressed of what percentage of total enzyme activity is physiologically active in living embryos and larvae and thus what percentage of metabolism is established by the activity of the sodium pump during development. Early developmental stages of sea urchins are ideal for understanding the in vivo metabolic importance of Na+/K+-ATPase because of their small size and high permeability to radioactive tracers (86Rb+) added to sea water. A comparison of total and in vivo Na+/K+-ATPase activities revealed that approximately half of the total activity was utilized in vivo. The remainder represented a functionally active reserve that was subject to regulation, as verified by stimulation of in vivo Na+/K+-ATPase activity in the presence of the ionophore monensin. In the presence of monensin, in vivo Na+/K+-ATPase activities in embryos of S. purpuratus increased to 94 % of the maximum enzyme activity measured in vitro. Stimulation of in vivo Na+/K+-ATPase activity was also observed in the presence of dissolved alanine, presumably due to the requirement to remove the additional intracellular Na+ that was cotransported with alanine from sea water. The metabolic cost of maintaining the ionic balance was found to be high, with this process alone accounting for 40 % of the metabolic rate of sea urchin larvae (based on the measured fraction of total Na+/K+-ATPase that is physiologically active in larvae of S. purpuratus). Ontogenetic changes in pump activity and environmentally induced regulation of reserve Na+/K+-ATPase activity are important factors that determine a major proportion of the metabolic costs of sea urchin development.
Fish Foot Prints: Morphology and Energetics of the Wake Behind a Continuously Swimming Mullet (Chelon Labrosus Risso)
Authors: Müller U. K. , Van Den Heuvel B. L. E. , Stamhuis E. J. , Videler J. J. 
Published: April 2021

ABSTRACT
The structure of the wake behind a continuously swimming mullet was analysed qualitatively and quantitatively by applying two-dimensional particle image velocimetry. A detailed analysis of the flow pattern and of the swimming movements of the fish allowed us to derive a kinematic explanation of the flow pattern as well as an estimate of the relative contributions of the body and the tail to thrust production. During active propulsion, the undulatory swimming fish shed a wake consisting in the medio-frontal plane of a rearward, zigzagging jet flow between alternating vortices. The fish shed one vortex per half tailbeat when the tail reached its most lateral position. Part of the circulation shed in the vortices had been generated previously on the body by the transverse body wave travelling down the body. This undulatory pump mechanism accounted for less than half of the energy shed in the wake. The remainder was generated by the tail. The vortex spacing matched the tailbeat amplitude and the stride length.
Allatostatin Decreases Stomatogastric Neuromuscular Transmission in the Crab Cancer Borealis
Authors: Jorge-Rivera Juan Carlos , Marder Eve 
Published: April 2021

ABSTRACT
The effects of insect allatostatins (ASTs) 1–4 were studied on the stomach musculature of the crab Cancer borealis. Of these, Diploptera-allatostatin 3 (D-AST-3) was the most effective. D-AST-3 (10−6 mol l−1) reduced the amplitude of nerve-evoked contractions, excitatory junctional potentials and excitatory junctional currents at both cholinergic and glutamatergic neuromuscular junctions. Muscle fiber responses to ionophoretic applications of both acetylcholine and glutamate were reduced by the peptide, but D-AST-3 produced no apparent change in the input resistance of the muscle fiber. D-AST-3 reduced the amplitude of muscle contractures evoked by both acetylcholine and glutamate, but had no effect on contractures induced by a high [K+]. These data suggest that D-AST-3 decreases the postsynaptic actions of both neurally released acetylcholine and glutamate. Because an AST-like peptide is found in peripheral sensory neurons that innervate stomatogastric muscles and in the pericardial organs, we suggest that an AST-like peptide may play a role in controlling the gain of the excitatory neuromuscular junctions in the stomach.
Modulation of Electrical Activity by 5-Hydroxytryptamine in Crayfish Neurosecretory Cells
Authors: Sáenz Francisco , García Ubaldo , Aréchiga Hugo 
Published: April 2021

ABSTRACT
The effect of 5-hydroxyptryptamine (5-HT) was tested in a population of X organ neurosecretory cells in the eyestalk of the crayfish Procambarus clarkii. Tests were conducted both in situ and on isolated neurones kept in culture.
The application of 5-HT induced action potentials in silent cells. In spontaneously active neurones, 5-HT increased the firing rate and either induced firing or enhanced bursting activity. The effect of 5-HT was dose-dependent within the range 1–100 μmol l−1 in cells of the intact organ. The effect persisted for 20–30 min after 5-HT had been removed from the bathing solution. Successive applications of 5-HT onto the same neurone reduced responsiveness, suggesting that desensitization had occurred. The effects of 5-HT were blocked by prior incubation with the 5-HT antagonist methysergide.
In X organ cells whose axons and branches in the neuropile had been severed, 5-HT induced a depolarisation associated with a slow inward current. In X organ neurones isolated from the eyestalk and kept in culture, 5-HT was capable of evoking bursts of action potentials and elicited a slow inward current. This effect was also blocked by methysergide (10−4 mol l–1).
These results suggest a direct modulatory effect of 5-HT on the pattern of electrical activity in the X organ cells.
In Vivo Performance of Trunk Muscles in Tree Frogs During Calling
Authors: Girgenrath M. , Marsh R. L. 
Published: April 2021

ABSTRACT
We used high-speed video and electromyography (EMG) to measure in vivo performance of the trunk muscles (external obliques) in two related species of North American gray tree frogs, Hyla versicolor and Hyla chrysoscelis. Both species produce trilled calls with high sound intensity, but the sound pulse frequency within calls in H. chrysoscelis is twice that in H. versicolor. In both species, sound pulse frequency is directly correlated with the active contractions of the trunk muscles. The length trajectory during contraction and relaxation displays a saw-tooth pattern with a longer shortening phase compared with the lengthening phase. The longer time spent shortening may enhance power production, because the shortening phase is the active part of the cycle during which the muscle produces positive work. A similar total strain (approximately 21 % and approximately 19 % in H. versicolor and H. chrysoscelis respectively) is achieved in the first few pulses, and during subsequent pulses the muscle cycles with a reduced pulse strain (approximately 12 % and approximately 7.3 % in H. versicolor and H. chrysoscelis respectively). The higher pulse frequencies of H. chrysoscelis are thus associated with lower pulse strains. The EMG pattern is different in the two species. A single EMG stimulus occurs for each cycle in H. chrysoscelis, but two stimuli per cycle are found in H. versicolor. Indirect evidence suggests that the initial phase of shortening during a pulse is partly due to elastic recoil of the trunk.
Effects of Vagal Stimulation on Swimbladder Blood Flow in the European Eel Anguilla Anguilla
Authors: Schwerte Thorsten , Axelsson Michael , Nilsson Stefan , Pelster Bernd 
Published: April 2021

ABSTRACT
The influence of the vagus nerve on swimbladder blood flow in the European eel (Anguilla anguilla) was characterized by recording the changes in blood flow rate and blood pressure following stimulation of the vagus nerve. After electrical stimulation, blood flow in the swimbladder artery increased from 0.9 ml min−1 to 2.1 ml min−1. Video recordings of small vessels on the caudal side of the rete mirabile revealed an increase in erythrocyte velocity combined with a small vasodilation. This effect could not be blocked by injection of the α-adrenergic antagonist phentolamine, the β-adrenergic antagonist propranolol or the muscarinic cholinoceptor antagonist atropine. In all preparations with a high initial flow rate (&gt;1.9 ml min−1), vagotomy resulted in a marked decrease in blood flow (by approximately 80 %). This effect was not observed in preparations with a low initial swimbladder blood flow. Stimulation of the vagus nerve produced a decrease, and vagotomy produced an increase, in perfusion pressure in blood-perfused swimbladder preparations. Histological studies revealed the presence of a ganglion in the vagus nerve located on the anterior part of the resorbing section of the swimbladder close to the origin of the ductus pneumaticus, which is probably associated with swimbladder function. These results suggest that swimbladder blood flow, at least to some extent, is under vagal tonic control. The effects do not, however, appear to involve the classical α- and β-adrenergic or muscarinic cholinoceptor functions.
Renal Function and Plasma Levels of Arginine Vasotocin During Free Flight in Pigeons
Authors: Giladi Itamar , Goldstein David L. , Pinshow Berry , Gerstberger Rüdiger 
Published: April 2021

ABSTRACT
We examined urinary water loss and plasma levels of arginine vasotocin (AVT) in free-flying, tippler pigeons trained to fly continuously for up to 5 h. First, we used [3H]polyethyleneglycol ([3H]PEG) as a glomerular filtration marker by implanting an osmotic minipump into each bird. In two flights (10 birds in winter at an ambient temperature of 13–15 °C and seven in summer at 23 °C), we measured pre-flight (hydrated, resting control birds) and post-flight [3H]PEG activity and osmolality in blood and ureteral urine. For comparison, we measured these variables in 10 birds in winter before and after controlled dehydration (24 h at 25 or 30 °C). Second, we measured plasma levels of AVT in 6–8 birds before and immediately after each of three different summer flights. Urine osmolality increased significantly by up to three times the control level in both post-flight and dehydrated pigeons; urine:plasma osmolality ratios did not exceed 2. Compared with controls, glomerular filtration rate (GFR) was significantly lower after flight in summer, but did not change in either post-flight or dehydrated winter pigeons. In winter, mean post-flight urine flow rate (UFR) decreased significantly to less than half the control level, while in summer, post-flight UFR did not differ from control levels. In general, mean filtered water reabsorption increased from 95 % in controls to 98 % in post-flight and dehydrated birds. Plasma levels of AVT increased after flight to between three and eight times the preflight levels. The data from this first study of kidney function during flight are consistent with previous studies of dehydration in birds and exercise in mammals in which both increased and decreased GFR contribute to renal conservation of water.
Migration and Bidirectional Phototaxis in Dictyostelium Discoideum Slugs Lacking the Actin Cross-Linking 120 kDa Gelation Factor
Authors: Wallraff Eva , Wallraff Hans G. 
Published: April 2021

ABSTRACT
Three mutant strains of Dictyostelium discoideum, lacking different actin-binding proteins, were tested for behavioural deficits in the multicellular pseudoplasmodium (slug) stage. Two strains, defective in the production of either α-actinin (an actin cross-linker) or severin (an actin capping and severing protein), did not show changes in slug behaviour. Slugs of the mutant lacking another actin cross-linker, the 120 kDa gelation factor (ABP-120), however, migrated shorter distances in darkness as well as in horizontally directed light. More remarkably, they migrated at an angle of approximately 45 ° to the left or right of the incident light, whereas wild-type slugs migrated on fairly straight paths towards the light. We discuss the hypothesis that this bidirectional oblique-angle phototaxis is due to changes in the optical properties of the pseudoplasmodia. Normally, in wild-type slugs, a lens effect causes stronger stimulation on the side distal to the incident light. We propose that in the mutant the lens quality is reduced, so that at small angles between the slug axis and the rays of light the proximal side is stimulated more intensely. As a result, the intended symmetrical stimulation is achieved at a certain angle to the left or right of the incident light. We assume that the absence of ABP-120 alters the shape of the lens and/or enhances internal light scattering via degradation of intercellular coherence; however, intracellular attenuation of light remains an additional or alternative possibility.
FMRFamide-Like Peptides in the Crayfish (Procambarus Clarkii) Stomatogastric Nervous System: Distribution and Effects on the Pyloric Motor Pattern
Authors: Tierney Ann Jane , Blanck Jennifer , Mercier A. Joffre 
Published: April 2021

ABSTRACT
Whole-mount immunocytochemistry was used to map the location of FMRFamide-like peptides in the crayfish (Procambarus clarkii) stomatogastric nervous system. This system contains the pyloric and gastric mill central pattern generators, which receive modulatory inputs from projection neurons with somata located primarily in other ganglia of the stomatogastric nervous system. Our studies revealed stained somata in the commissural and esophageal ganglia. A pair of stained somata was located in the inferior ventricular nerve, and another pair of somata was located in the stomatogastric nerve where it is joined by the two superior esophageal nerves. The stomatogastric ganglion contained no stained somata, but the neuropil was brightly stained and 2–4 axons projected laterally in small nerves directly from the ganglion. These results indicate that FMRFamide or related peptides may act as neuromodulators in the crayfish stomatogastric nervous system.
To test this hypothesis, we studied the effects of FMRFamide and four related peptides (DF2, NF1, F1 and LMS) on the pyloric motor pattern. DF2, NF1 and F1 all excited certain pyloric cells, especially the lateral pyloric (LP) and ventricular dilator (VD) neurons, and enhanced pyloric cycling frequency in most actively rhythmic preparations. FMRFamide had no detectable effects on pyloric cells, and LMS had inhibitory effects, causing disruption of the pyloric rhythm in actively cycling preparations and reducing tonic activity in non-rhythmic preparations.
The Two Essential Light Chains of Carp Fast Skeletal Myosin, Lc1 and Lc3, are Encoded by Distinct Genes and Change their Molar Ratio Following Temperature Acclimation
Authors: Hirayama Yasushi , Kanoh Satoshi , Nakaya Misako , Watabe Shugo 
Published: April 2021

ABSTRACT
cDNA libraries were constructed from fast skeletal muscles of carp acclimated to 10 and 30 °C for a minimum of 5 weeks and were screened for myosin alkali light chains, LC1 and LC3, using an anti-skipjack LC1 polyclonal antibody. Two types of LC1 cDNA clone were isolated and termed LC1a and LC1b: their nucleotide sequences showed 92 % homology. The ratio of LC1a to LC1b cDNA clones isolated was approximately 3:1, showing no apparent changes following temperature acclimation. The occurrence of the two isoforms was further confirmed by N-terminal amino acid sequencing of purified LC1. No isoform was, however, detected for LC3, while homology in the overlapping region between LC1a and LC3 cDNAs was only 65 % even after the most probable alignment.
Southern blot analyses probed with cDNA clones specific to LC1a and LC3 showed different hybridization patterns from each other, demonstrating that carp LC1 and LC3 are encoded by different genes. These results are in marked contrast to those from higher vertebrates which express LC1 and LC3 from a single gene by alternative RNA transcription and two modes of splicing. Northern blot analysis showed that the ratios of LC3/LC1 mRNAs were significantly higher (3.93) in 30 °C-acclimated than in 10 °C-acclimated (3.10) carp.