bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cardiovascular Effects of Arginine Vasotocin in the Rainbow Trout Oncorhynchus Mykiss
Authors: Conklin Daniel J. , Chavas Angelica , Duff Douglas W. , Weaver Leroy , Zhang Yutong , Olson Kenneth R. 
Published: April 2021

ABSTRACT
The physiological functions of the neurohypophyseal hormone arginine vasotocin (AVT) in teleosts are not clear. In the present studies, the sites and mechanisms of action of AVT on the rainbow trout Oncorhynchus mykiss cardiovascular system were examined in unanesthetized instrumented fish, perfused organs and isolated vessels. Injection of AVT (1, 10 or 100 pmol kg−1 body mass) into trout with dorsal aortic cannulas produced a modest, but dose-dependent, increase in dorsal aortic pressure (PDA). Bolus injection of AVT (100 pmol kg−1 body mass), or continuous infusion (6.7 pmol kg−1 min−1), into trout instrumented with dorsal aortic, ventral aortic and central venous cannulas and a ventral aortic flow probe significantly increased PDA as well as ventral aortic (PVA) and central venous (PVEN) blood pressure. Bradycardia accompanied the rapid rise in PVA while gill resistance (RG) increased. Maximum response to the AVT bolus was reached within 13–21 min and the response decayed slowly over the ensuing 90 min. AVT infusion (6.7 pmol kg−1 min−1) significantly increased PVEN and mean circulatory filling pressure and decreased unstressed blood volume, whereas venous compliance was unaffected. These in vivo studies indicate that AVT increases venous tone, thereby mobilizing blood from the unstressed compartment into the stressed compartment. This increases PVEN, which increases venous return and helps maintain, or slightly elevate, cardiac output. This, combined with an elevated RG and slightly elevated systemic resistance (RS), increases both PVA and PDA; however, the rise in PDA is mitigated by a disproportionate increase in RG relative to RS. In vitro, the effects of AVT are consistent with in vivo responses. AVT increased vascular resistance in the perfused gill and perfused trunk and contracted isolated vascular rings from both rainbow and steelhead trout. The general order of sensitivity of isolated vessels to AVT was (in decreasing order): anterior cardinal vein, celiacomesenteric artery, ductus Cuvier, efferent branchial artery, ventral aorta and coronary artery. Extracellular Ca2+ accounted for over 70 % of the tension in the AVT-contracted efferent branchial artery, but only 57 % of the tension in the anterior cardinal vein. Vascular AVT receptor sensitivity (EC50) in vitro ranged from 0.3 to 6 nmol l−1 and was similar to the estimated ED50 for the dose-dependent increase in PDAin vivo (approximately 1 nmol l−1). AVT was not inotropic in paced ventricular rings nor did it exhibit vasorelaxant activity in perfused organs or vascular rings. These results show that AVT is a potent vasoconstrictor in trout and that its two primary cardiovascular targets are the systemic veins and the branchial vasculature.
The Steroid Pheromone 4-Pregnen-17α,20β-Diol-3-One Increases Fertility and Paternity in Goldfish
Authors: Zheng Wenbin , Strobeck Curtis , Stacey Norm 
Published: April 2021

ABSTRACT
Previous studies in goldfish (Carassius auratus) showed that the oocyte maturation-inducing steroid 4-pregnen-17α,20β-diol-3-one (17,20βP) functions after release as a pheromone that increases male serum gonadotropin II (GtH II) concentration, milt (sperm and seminal fluid) volume and sexual activity, effects hypothesized to increase male reproductive success in the sperm competition of multi-male spawnings. The present study tested this hypothesis by determining whether overnight exposure to 17,20βP increases fertility. In pair spawnings, 17,20βP-exposed males fertilized a greater percentage of eggs than did control males, apparently because 17,20βP-exposed males had more releasable sperm at the onset of spawning. Microsatellite DNA paternity analysis showed that 17,20βP-exposed males also fertilized more eggs in competitive spawnings involving one control male and one 17,20βP-exposed male. This effect of 17,20βP on competitive fertility could be due to demonstrated increases in spawning activity, milt volume, duration of sperm motility and proportion of motile sperm. However, it appears that a change in sperm quality is a major component of the pheromonal effect because, in competitive in vitro fertilizations, sperm from 17,20βP-exposed males fertilized more eggs than did sperm from control males. The results indicate that the response to pheromonal 17,20βP is a major determinant of reproductive success in male goldfish.
Fatigue of Mouse Soleus Muscle, Using the Work Loop Technique
Authors: Askew Graham N. , Young Iain S. , Altringham John D. 
Published: April 2021

ABSTRACT
The function of many muscles requires that they perform work. Fatigue of mouse soleus muscle was studied in vitro by subjecting it to repeated work loop cycles. Fatigue resulted in a reduction in force, a slowing of relaxation and in changes in the force–velocity properties of the muscle (indicated by changes in work loop shape). These effects interacted to reduce the positive work and to increase the negative work performed by the muscle, producing a decline in net work. Power output was sustained for longer and more cumulative work was performed with decreasing cycle frequency. However, absolute power output was highest at 5 Hz (the cycle frequency for maximum power output) until power fell below 20 % of peak power. As cycle frequency increased, slowing of relaxation had greater effects in reducing the positive work and increasing the negative work performed by the muscle, compared with lower cycle frequencies.
Pharmacology of Skeletal Muscle Gaba-Gated Chloride Channels in the Cockroach Periplaneta Americana
Authors: Schnee Michael E. , Rauh James J. , Buckingham Steven D. , Sattelle David B. 
Published: April 2021

ABSTRACT
The pharmacology of γ-aminobutyric acid (GABA)-gated chloride channels of the coxal levator (182c,d) muscle of the cockroach Periplaneta americana has been investigated and the data compared with similar findings for the cell body of the cockroach fast coxal depressor motor neurone (Df). Muscle GABA receptors resembled those of the motor neurone cell body in their sensitivity to picrotoxinin and insensitivity to bicuculline. However, muscle GABA receptors were insensitive to the neuronal GABA receptor agonists isoguvacine (10−4 mol l−1) and 3-aminopropane sulphonic acid (10−3 mol l−1). The benzodiazepine flunitrazepam, which at 10−6 mol l−1 greatly enhances the amplitude of the motor neurone GABA-induced responses, failed to affect muscle responses to GABA when tested at the same and at a higher (10−4 mol l−1) concentration. The convulsant t-butylbicyclophosphorothionate was a weak antagonist of cockroach muscle GABA receptors, whereas several cyclodienes were much more effective antagonists. Thus, studies using a benzodiazepine and several convulsant antagonists reveal differences in the pharmacology of muscle and neuronal GABA receptors of the cockroach Periplaneta americana.
Vestibular Compensation in Lampreys: Role of Vision at Different Stages of Recovery of Equilibrium Control
Authors: Deliagina T. G. 
Published: April 2021

ABSTRACT
The main motor disorder evoked by unilateral labyrinthectomy (UL) in the lamprey (Lampetra fluviatilis) is a complete loss of equilibrium and rolling (rotation about the longitudinal axis) during swimming. A previous study has shown that the recovery of equilibrium control in the lamprey takes, on average, 33 days. However, lampreys were able to maintain equilibrium if UL was combined with removal of the ipsilateral eye (‘surgical compensation’ of the vestibular deficit). It was suggested that tonic excitatory inflow, rather than specific information about the orientation of the animal in space delivered by the remaining eye, is important for the recovery of equilibrium control.
In the present study, a number of experiments were designed to test this hypothesis. It was found that illumination of the eye contralateral to the UL or continuous electrical stimulation (10 Hz) of the corresponding optic nerve resulted in immediate restoration of equilibrium control. The same result was obtained when the vestibular nerve on the UL side was stimulated. Thus, the roll control system in the lamprey, driven by only one labyrinth, is able to maintain equilibrium provided that the lack of tonic inflow from the missing labyrinth is compensated for by tonic vestibular or visual input.
The present study has also shown that the importance of visual input for maintaining equilibrium after UL decreases with time. In animals that achieved a high degree of compensation, removal of the eyes on day 23 after UL evoked decompensation, whereas removal on day 70 did not. A reduction of the significance of visual input was also observed in surgically compensated UL lampreys. In these animals, removal of the remaining eye on days 1–3 after the first surgery resulted in a complete loss of equilibrium, removal on day 7 resulted in a partial loss, whereas removal on days 48–55 did not affect the postural stability.
Three lines of evidence suggest that asymmetrical visual input evokes plastic changes in the roll control system. (i) In one group of animals, initially one eye was removed, and then 50 days later the labyrinth ipsilateral to the missing eye and remaining eye were removed. These animals exhibited a mild impairment of equilibrium control, in contrast to the animals in which both surgeries were performed simultaneously. (ii) In another group of animals, initially one eye was removed, and then 50 days later the remaining eye and both labyrinths were removed. These animals exhibited rolling towards the eye that remained intact for longer. (iii) A short-term electrical stimulation (5–10 min daily for 3 days) of the optic nerve (contralateral to UL) in blinded animals considerably improved the equilibrium control compared with that of non-stimulated animals; the improvement was observed for 60 days after stimulation.
A Novel Udp-Sugar, Udp-3-Ketoglucosamine or Udp-4-Ketoglucosamine, From Bovine Heart Muscle Reduces Metmyoglobin With Nad(P)H
Authors: Kariya Mieko , Sado Katsuyuki , Namiki Hideo 
Published: April 2021

ABSTRACT
3-Ketoglucose and similar ketosugars have been identified in microorganisms only and little is known about their functions. UDP-sugars are widely found as an intermediate in sugar metabolism in living organisms. Yet what role UDP-sugars play, or whether they play a direct role in metabolism, is still unknown. UDP-sugars were isolated and purified from bovine heart muscle, and a UDP-sugar fraction capable of NAD(P)H-dependent catalytic reduction of metmyoglobin was detected. Subsequent identification revealed that the active UDP-sugar was UDP-3-or UDP-4-ketoglucosamine. These compounds were purified from bovine cardiac muscle by ultrafiltration, anion-exchange column chromatography and reverse-phase chromatography. They were further characterized by determination of their chemical reducing activity, by comparison with synthetic UDP-3-or UDP-4-ketoglucosamine standards using high-performance liquid chromatography, by estimation of molecular mass using fast atom bombardment mass spectrometry, and by Fourier transform infrared microspectroscopy and electron probe microanalysis. The results suggest that UDP-3-or UDP-4-ketoglucosamine reduces metmyoglobin in bovine cardiac muscle. It is important that the reducing activity displayed by this ketosugar is not the effect of UDP-3-or UDP-4-ketoglucosamine alone but depends on NAD(P)H. In other words, this action of UDP-3-or UDP-4-ketoglucosamine is catalytic.
The Dynamics of Flight-Initiating Jumps in the Common Vampire Bat Desmodus Rotundus
Authors: Schutt William A. , Altenbach J. Scott , Chang Young Hui , Cullinane Dennis M. , Hermanson John W. , Muradali Farouk , Bertram John E. A. 
Published: April 2021

ABSTRACT
Desmodus rotundus, the common vampire bat (Phyllostomidae: Desmodontinae), exhibits complex and variable terrestrial movements that include flight-initiating vertical jumps. This ability is unique among bats and is related to their unusual feeding behavior. As a consequence of this behavior, the wing is expected to have design features that allow both powered flight and the generation of violent jumps. In this study, high-speed cine images were synchronized with ground reaction force recordings to evaluate the dynamics of jumping behavior in D. rotundus and to explore the functional characteristics of a wing operating under competing mechanical constraints.
The pectoral limbs are responsible for generating upward thrust during the jump. The hindlimbs stabilize and orient the body over the pectoral limbs. The thumbs (pollices) stabilize the pectoral limb and contribute to extending the time over which vertical force is exerted. Peak vertical force can reach 9.5 times body weight in approximately 30 ms. Mean impulse is 0.0580±0.007 N s (mean ± S.D., N=12), which accelerates the animal to a mean take-off velocity of 2.38±0.24 m s−1. A model of the muscular activity during jumping is described that accounts for the characteristic force output shown by these animals during flight-initiating jumps.
A Dynamic Force and Moment Analysis System for Brachiation
Authors: Chang Y. H. , Bertram John E. A. , Ruina Andy 
Published: April 2021

ABSTRACT
We describe a transducer system and analysis strategy that allows the determination of dynamic forces and moments applied by an arm-swinging animal during locomotion. We have employed readily available technology and analysis procedures to produce a low-cost but effective system. The solutions to several problems in the design of the system are provided, and the functional characteristics of the system are demonstrated using both an inert pendulum and an actively brachiating gibbon (Hylobates lar).
Spatial Variation in Epaxial Muscle Activity During Prey Strike in Largemouth Bass (Micropterus Salmoides)
Authors: Thys Tierney 
Published: April 2021

ABSTRACT
Epaxial muscle activity during prey strike was measured in two discrete myomeric regions of the largemouth bass Micropterus salmoides to test whether (1) the extreme dorsal region of the epaxial muscle (the epaxial arm region) plays a larger role in prey strike than the region bordering the main horizontal septum (the epaxial cone region), (2) whether the epaxial arm region is more active anteriorly than posteriorly during prey strike and (3) whether the epaxial arm region activity is correlated with the epaxial cone region activity. Electromyographic recordings (EMGs) of four bass were taken from eight different longitudinal, epaxial muscle sites: five sites in the arm region and three sites in the cone region. Selection of electrode sites was based on epaxial muscle dissections in which a set of previously undefined tendons, neurocranial-epineural-epaxial connector tendons, were described. Every strike had some activity in the arm region, while 48 % of the total number of prey strikes had zero cone activity. Muscle activity was recorded consistently from the first four anterior electrodes in the arm region of each fish, while the posteriormost arm electrodes showed varying degrees of activity. Muscle intensity recorded from the anterior three epaxial arm electrodes was consistently higher than from the two posterior epaxial arm electrodes, while the onset times and durations of EMGs were variable. Most notably, the arm region of the epaxial muscle is capable of being active without the adjoining cone region, thus demonstrating that activity in the epaxial muscle mass can be spatially regionalized in a manner dependent on behavior.
Amiloride Analog Stimulation of Short-Circuit Current in Larval Frog Skin Epithelium
Authors: Cox Thomas 
Published: April 2021

ABSTRACT
The skin of the bullfrog Rana catesbeiana tadpole contains an apical non-selective cation channel that is activated by amiloride. This is in contrast to the adult skin, which has a highly Na+-selective channel that is blocked by amiloride. The purpose of the present study was to characterize further the nature of the tadpole channel using amiloride and its analogs benzamil, dimethyl amiloride (DMA), 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) and methyl isobutyl amiloride (MIBA). Tadpole skins were mounted in modified Ussing chambers with Ca2+-free KCl or NaCl Ringer on the apical side and standard NaCl Ringer (containing 2 mmol l−1 Ca2+) on the basolateral side. Drugs were added to the apical solution at concentrations between 0.1 and 1000 μmol l−1. Amiloride caused the short-circuit current (Isc) to increase rapidly from near zero to a peak of approximately 30–50 μA and then to decline back towards zero over several seconds. The peak response was largest at 100 μmol l−1. The rate of decline was noticeably faster at the higher concentrations. Benzamil and DMA had similar time courses to amiloride, but with smaller effects on Isc. The largest peak responses occurred at 5–50 μmol l−1. EIPA and MIBA gave small responses at 1–10 μmol l−1 and, at higher concentrations (50–500 μmol l−1), the responses consisted of rapid, small increases in Isc followed by rapid decreases. The largest peak response occurred at 10 μmol l−1 for both drugs. After apical membrane resistance had been reduced by nystatin, addition of analogs to the apical solution caused no change in Isc or transepithelial resistance. This suggests that the decline in Isc after amiloride analog treatment was not due to increases in the resistance of the basolateral membrane. N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7) blocked stimulation by all of the analogs. These data are consistent with amiloride analogs acting as both activators and inhibitors of short-circuit current in tadpole skin and extend the list of ligands that activate these channels.
Localization and Release of 5-Hydroxytryptamine in the Crayfish Eyestalk
Authors: Rodríguez-Sosa Leonardo , Picones Arturo , Calderón Rosete Gabina , Islas Socorro , Aréchiga Hugo 
Published: April 2021

ABSTRACT
The content and regional distribution of 5-hydroxytryptamine (5-HT) in the crayfish eyestalk was determined by high-performance liquid chromatography. Levels of the 5-HT precursors L-tryptophan (L-TRP) and 5-hydroxytryptophan (5-OH-TRP), and of three metabolites, 5-hydroxytryptophol (5-HTPH), N-acetylserotonin (NA-5-HT) and 5-hydroxy-indole-3-acetic acid (5-HIAA), were also determined. The total content of 5-HT in the eyestalk was 95.4±49.3 pg mg−1 wet mass (mean ± S.D., N=55) while the specific content was 9.6±4.9 fmol μg−1 protein (mean ± S.D. N=5). 5-HT was present in all four ganglia of the eyestalk. The highest proportion was found in the medulla terminalis (40.2 %) and the lowest in the retina lamina ganglionaris (9.9 %), which also had the lowest specific content. Conversely, the highest specific content of L-TRP was in the retina lamina ganglionaris.
5-HT biosynthesis and metabolism were explored in isolated eyestalks. The monoamine oxidase blocker pargyline, at concentrations between 0.8 and 10 mmol l−1, elicited a dose-dependent increase in 5-HT content. The biosynthesis of 5-HT in the crayfish eyestalk is suggested by the presence of its immediate precursor (5-OH-TRP) and by the suppression of 5-HT synthesis induced by m-hydroxybenzyl-hydrazine (m-HBH), a blocker of 5-OH-TRP decarboxylase.
The presence of immunopositive cell bodies and axons was demonstrated using an anti-5-HT antiserum. 5-HT-like immunopositivity was detected in various regions of the eyestalk. Efferent immunopositive axons were also identified in the optic nerve, and these may have originated in the protocerebral lobe of the supraoesophageal ganglion. The branchings of these axons were profusely distributed in the neuropile of the medulla terminalis.
A basal level release of 5-HT was detected in isolated eyestalks. The amount recovered was increased two-to threefold after blocking 5-HT uptake with fluoxetine (1 μmol l−1). Incubation of eyestalks in solutions containing a high K+ concentration (80 mmol l−1) released 5-HT. Electrical stimulation of the optic nerve released 5-HT as a function of the intensity of stimulation. Both the basal and evoked release were suppressed by lowering the Ca2+ concentration in the medium.
These observations support a role for 5-HT as a neurotransmitter or neuromodulator in the crayfish eyestalk.
Flow and Flexibility I. Effects of Size, Shape and Stiffness in Determining Wave Forces on the Stipitate Kelps Eisenia Arborea and Pterygophora Californica
Authors: Gaylord Brian , Denny Mark W. 
Published: April 2021

ABSTRACT
Wave action on exposed rocky coasts can be severe, generating large hydrodynamic forces that have been proposed to constrain the size of intertidal animals and plants. In contrast, flows subtidally are more benign, and organisms, particularly seaweeds, may grow quite large. The large dimensions of these flexible macroalgae allow them to move during much or most of a passing wave cycle, reducing relative water velocities and modifying the forces the plants must endure. The consequences of such wave-induced motion are explored for the stipitate understory kelps Eisenia arborea and Pterygophora californica using a numerical model that approximates these seaweeds as vertically oriented cantilever beams subjected to lateral hydrodynamic forces acting at their stipe tips. Bending moments and peak stresses induced in the stipes of these species during the passage of waves are calculated as functions of plant size and shape and of water depth and sea state. Model predictions for a subset of conditions are validated against real-time measurements of bending moments acting on a Pterygophora individual in the field. The results suggest that the allometric patterns of growth exhibited by Eisenia and Pterygophora can greatly reduce the stresses generated in the stipes of these plants relative to isometric growth. Low stipe stiffness acts as a general, particularly effective, stress-lowering mechanism. The dynamic swaying associated with this low stiffness can also modulate the magnitudes of peak stresses induced in the stipes of these kelps. In particular, in shallow water under large waves, dynamic loading can substantially increase induced stress, suggesting that plant motion is an important factor affecting the loading regime encountered by these organisms.
Flow and Flexibility II. The Roles of Size and Shape in Determining Wave Forces on the Bull Kelp Nereocystis Luetkeana
Authors: Denny Mark W. , Gaylord Brian P. , Cowen Edwin A. 
Published: April 2021

ABSTRACT
Giant kelps (which may reach lengths of 45 m) are a prominent exception to the general rule that wave-swept organisms are small. The ability of these kelps to maintain their large size in the presence of ocean waves has been attributed to their extreme flexibility and the concomitant tendency to ‘go with the flow’, a tendency that reduces the hydrodynamic forces imposed on the plant. However, the flexibility of giant kelps carries with it the potential for the organism to apply an inertial load to its own structure if the blade mass reaches the end of its tether. Here, we examine the complex trade-off between flexibility and inertial loading using a simple computational model of the bull kelp Nereocystis luetkeana. In field and laboratory tests, the model accurately predicts the forces and motions imposed on flexible structures in wave-induced flows. Subsequent predictions from the model suggest that mature N. luetkeana can indeed benefit from moving with the flow, but that the forces imposed on juveniles are actually increased by the plant’s flexibility. Furthermore, the benefit accrued from going with the flow is sensitive to the shape of the plant. If the bull kelp were to grow while maintaining a juvenile shape, the stress placed on its stipe would be drastically increased by dynamic loading, and these inappropriately shaped plants would be subjected to a high risk of breakage. For certain combinations of wave height, wave period and stipe length, the increased stress in hypothetical ‘small’-shaped plants may be associated with chaotic motion of the blade mass.