bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of Buccal Pressure During Prey Capture in Hexagrammos Decagrammus (Teleostei: Hexagrammidae)
Authors: Nemeth Donna Henriques
Published: April 2021

Changes in intraoral pressure during prey capture were recorded for a trophic generalist, Hexagrammos decagrammus, feeding on different prey species. Prey were grouped into elusive (shrimps), grasping (isopods and crabs) and non-elusive (pieces of shrimp) categories. Elusive and grasping prey elicited strikes with a larger and faster reduction in buccal pressure than did non-elusive prey. The suction force generated by the predator differed for strikes among the shrimp genera in the elusive prey category. The most sedentary shrimps (Crangon alaskensis and C. nigricauda) elicited the fastest and greatest reduction in pressure relative to the most evasive shrimps (Pandalus danae and Heptacarpus stylus). A preparatory phase, during which the buccal cavity is compressed prior to the strike, occurred significantly more frequently in strikes at grasping prey than in strikes at elusive and non-elusive prey, and more frequently for elusive than for non-elusive prey. Prey size did not influence the suction force generated by the predator. No differences in buccal pressure patterns were detected between strikes that resulted in a capture or a miss, suggesting that misses were due to the escape behavior of the prey and were not the result of an inappropriate suction force. These data support the current view that fish can modify their feeding mode in response to prey behavior, and they emphasize that the behavioral responses of the individual prey must be considered when defining the appropriate strategy for prey capture. The use of a flexible, modifiable feeding behavior is associated with a broad diet in H. decagrammus and may increase capture success on diverse prey relative to that of other species showing stereotypical feeding responses.
Developmental Changes in Chemoreceptive Control of Gill Ventilation in Larval Bullfrogs (Rana Catesbeiana) II. Sites Of O2-Sensitive Chemoreceptors
Authors: Jia Xi Xi , Burggren Warren W.
Published: April 2021

The time course of reflex changes in gill ventilation variables caused by a step-wise change in of inspired water and by the introduction of NaCN into inspired water was measured in two populations of unanesthetized larval bullfrogs (Rana catesbeiana) – one with intact gill arches and a second with bilateral ablation of the first gill arch. Developmental stages TK V–VII, IX–XI and XVII–XIX were examined. Inspiring hypoxic water or a pulse of NaCN significantly increased gill ventilation within 7 s in control larvae. Ablation of the first gill arches in larval R. catesbeiana eliminated the initial, quick response of gill ventilation to changes in the of inspired water and to the presence of NaCN in all three developmental groups. These data suggest that O2-sensitive chemoreceptors are located on the first gill arch and are responsible for the initial rapid ventilatory response. However, a slow response (>15 s) to changes in of inspired water persisted even after removal of the first gill arch. This response is far slower than the minimum blood circulation time (approximately 5–8 s as measured in all three groups), indicating that a second population of receptors is not directly monitoring arterial or venous blood. Instead, this second population of receptors is likely to be located ‘behind’ a significant diffusion barrier, possibly monitoring cerebrospinal fluid.
Actin-Based Vesicular Transport in the First 20 Min after Dusk is Crucial for Daily Rhabdom Synthesis in the Compound Eye of the Grapsid Crab Hemigrapsus Sanguineus
Authors: Matsushita Atsuko , Arikawa Kentaro
Published: April 2021

In the crab Hemigrapsus sanguineus, maintained under a 12 h:12 h light:dark cycle, the amount of vesicular smooth endoplasmic reticulum (vesicular sER) in the photoreceptor cell body increases after the light is turned off. This paper demonstrates that actin filaments in the photoreceptor cell body are involved in the transport of vesicular sER towards the rhabdom. To specify the time of actin contribution to rhabdom synthesis, we disrupted the organization of actin filaments in the cell body with cytochalasin D at various time around dusk. We then measured the rhabdom size and also examined the ultrastructure of the photoreceptor cell body 3 h after extinguishing the light. When cytochalasin D was applied from either 1 h before or immediately after extinguishing the light, the rhabdom size did not increase, whereas vesicular sER accumulated in the cell body. In contrast, cytochalasin D applied to the eyes from 20 min after turning the light off did not inhibit rhabdom synthesis. These results indicate that the first 20 min after the light is turned off is particularly important for the transport of vesicular sER towards the rhabdom by the cell body actin filaments.
The Effects of Artificial Lung Inflation on Pulmonary Blood Flow And Heart Rate In The Turtle Trachemys Scripta
Authors: Herman Jay , Wang Tobias , Smits Allan W. , Hicks James W.
Published: April 2021

As for most ectothermic vertebrates, the breathing pattern of turtles is episodic, and pulmonary blood flow (Q̇;pul) and heart rate (fH) normally increase several-fold during spontaneous ventilation. While some previous studies suggest that these cardiovascular changes are caused by stimulation of pulmonary stretch receptors (PSRs) during ventilation, it has been noted in other studies that blood flows often change prior to the initiation of breathing. Given the uncertainty regarding the role of PSRs in the regulation of central vascular blood flows, we examined the effect of manipulating lung volume (and therefore PSR stimulation) on blood flows and heart rate in the freshwater turtle Trachemys scripta.

Turtles were instrumented with blood flow probes on the left aortic arch and the left pulmonary artery for measurements of blood flow, and catheters were inserted into both lungs for manipulation of lung volume. In both anaesthetized and fully recovered animals, reductions or increases in lung volume by withdrawal of lung gas or injection of air, N2, O2 or 10 % CO2 (in room air) had no effect on blood flows. Furthermore, simulations of normal breathing bouts by withdrawal and injection of lung gas did not alter Q̇pul or fH. We conclude that stimulation of PSRs is not sufficient to elicit cardiovascular changes and that the large increase in Q̇pul and fHnormally observed during spontaneous ventilation are probably caused by a simultaneous feedforward control of central origin.
Hypoxia and Ischaemia in Buffer-Perfused Toad Hearts
Authors: Mckean Tom , Scherzer Anna , Park Han
Published: April 2021

Previous studies on the effects of ischaemia or hypoxia in ectothermic vertebrate hearts have generally used preparations that were not performing at physiological levels of pressure and flow. The conclusions that ischaemia or hypoxia are not stressful to these organisms were examined in another species, Bufo marinus, in which a buffer-perfused heart was performing physiological levels of work. The in situ preparation demonstrated the Frank–Starling relationship and mechanical characteristics similar to the hearts of intact animals. The hearts recovered from 60 min of ischaemia and reperfusion with no reduction in pressure, flow or heart rate parameters. Hearts exposed to 30 min of hypoxia at physiological filling and diastolic afterload pressures ceased generating a continuous cardiac output during the hypoxia. In most cases, there was a gradual reduction of cardiac output to zero, but in 27 % of the hearts studied, intermittent beating was observed. During reoxygenation, the hearts recovered 50–90 % of their prehypoxic function and were damaged. Hearts exposed to hypoxia with reduced filling and diastolic afterload continued to develop a cardiac output throughout the hypoxia and demonstrated an overshoot phenomena with the onset of reoxygenation. If demand is in the normal range at the onset of hypoxia, the hearts intrinsically reduce demand either by reducing pressure development or by conversion to intermittent beating. Toad hearts appear not to be damaged by ischaemia, a condition in which demand is low.
Role of V-ATPase-rich cells in acidification of the male reproductive tract
Authors: Brown Dennis , Smith Peter J. S. , Breton Sylvie
Published: April 2021

Specialized proton-secreting cells play important physiological roles in a variety of tissues. On the basis of the immunocytochemical detection of carbonic anhydrase and V-ATPase in distinct epithelial cells of the epididymis and vas deferens, we predicted that the vacuolar V-ATPase that is located on the apical membrane of these cells should be a major contributor to luminal acidification in parts of the male reproductive tract. Physiological studies using the proton-selective vibrating probe in the vas deferens confirmed this hypothesis. As discussed recently, maintenance of the pH of the reproductive tract is probably under tight physiological control, by analogy with the situation in the kidney. Manipulation of luminal pH might, therefore, provide a point of intervention for the regulation of male fertility. In addition, it is possible that some cases of unexplained male infertility might result from defective acidification, resulting either from pathological states or potentially from environmental factors that may inhibit proton secretory pathways.
Role of the Ca2+-Sensing Receptor in Divalent Mineral Ion Homeostasis
Authors: Hebert Steven C. , Brown Edward M. , Harris H. William
Published: April 2021

The divalent mineral cations Ca2+ and Mg2+ play many and diverse roles both in the function of cells and in extracellular processes. The metabolism of these cations is a complex process involving the coordinated function of several organ systems and endocrine glands. A recently cloned G-protein-coupled receptor responds to extracellular calcium concentration (Ca2+o-sensing receptor, CaSR) and mediates several of the known effects of Ca2+o on parathyroid and renal function. The CaSR, which is also expressed in a number of other tissues including thyroidal C-cells, brain and gastrointestinal tract, may function as a Ca2+o sensor in these tissues as well. Thus, Ca2+o is a first messenger (or hormone) which, via CaSR-mediated activation of second messenger systems (e.g. phospholipases C and A2, cyclic AMP) leads to altered function of these cells. Several mutations in the human CaSR gene have been identified and shown to cause three inherited diseases of calcium homeostasis, clearly implicating the CaSR as an important component of the homeostatic mechanism for divalent mineral ions.

Ca2+ and Mg2+ losses from the body are regulated by altering the urinary excretion of these divalent cations. The localization of the CaSR transcripts and protein in the kidney not only provides a basis for a direct Ca2+o (or Mg2+o) -mediated regulation of Ca2+ (and Mg2+) excretion but also suggests a functional link between divalent mineral and water metabolism. In the kidney, the thick ascending limb of Henle (TAL) plays crucial roles in regulating both divalent mineral reabsorption and urine concentration. Recent studies have suggested models whereby extracellular Ca2+, via the CaSR expressed in the TAL as well as in the collecting duct system, modulates both Ca2+o and Mg2+o as well as water reabsorbtion. When taken together, these studies suggest that the CaSR not only provides the primary mechanism for Ca2+o-mediated regulation of parathyroid hormone secretion from parathyroid glands but also for direct modulation of renal divalent mineral excretion and urinary concentrating ability. These latter functions may furnish a mechanism for integrating and balancing water and divalent cation losses that minimizes the risk of urinary tract stone formation. This mechanism can explain hypercalcemia-mediated polyuria (diabetes insipidus).
Intracellular Ca2+ Signalling in Secretory Cells
Authors: Shuttleworth Trevor J.
Published: April 2021

The secretion of ions and fluid plays a critical role in a variety of physiological activities that are vital to homeostatic mechanisms in animals. Control of such secretory activity is achieved by a range of neurotransmitters and hormones many of which act intracellularly by generating the second messenger inositol 1,4,5-trisphosphate (InsP3) and increasing cytosolic free calcium ion concentrations ([Ca2+]i). These increases are achieved by a combination of the InsP3-induced release of Ca2+ from specific intracellular stores and the activation of Ca2+ entry from the extracellular environment. The [Ca2+]i signal represents a balance between the adequate activation of components of the secretory mechanism and the avoidance of [Ca2+]i levels that are toxic to the cell. Resting [Ca2+]i is maintained low by the action of Ca2+ pumps on the intracellular stores and plasma membrane, with the result that gradients for Ca2+ movement into the cytosol from either of these two sources are very large and there is considerable potential for achieving rapid increases in [Ca2+]i. Consequently, for successful Ca2+ signalling, it is imperative that these two mechanisms of raising [Ca2+]i (i.e. Ca2+ release and Ca2+ entry) are closely integrated. Current models emphasize the activation of Ca2+ entry as a downstream result of the emptying of the intracellular stores (‘capacitative’ model). Whilst this may be true for situations of maximal stimulation, recent experiments on the oscillatory [Ca2+]i responses typical of more physiological levels of stimulation indicate a previously unsuspected, independent activation of Ca2+ entry involving arachidonic acid.

This arachidonic-acid-activated entry plays a key role, along with InsP3, in inducing the repetitive release of Ca2+ from the stores to produce the [Ca2+]i oscillations. In this way, the two components responsible for the elevation of [Ca2+]i are intimately related and their dual effects closely coordinated, resulting in the finely tuned control of agonist-induced changes in [Ca2+]i.
Association of the Band 3 Protein with a Volume-Activated, Anion and Amino Acid Channel: A Molecular Approach
Authors: Motais René , Fiévet Bruno , Borgese Franck , Garcia-Romeu Federico
Published: April 2021

In response to swelling, cells recover their initial volume by releasing intracellular solutes via volume-sensitive pathways. There is increasing evidence that structurally dissimilar organic osmolytes (amino acids, polyols, methyl amines), which are lost from cells in response to swelling, share a single pathway having the characteristics of an anion channel. However, the molecular identity of this pathway remains to be established. It has been suggested that the erythrocyte anion exchanger (AE1) or some AE1-related proteins could be involved. A direct evaluation of this possibility has been made by comparing the functional properties of two AE1s when expressed in Xenopus laevis oocytes: tAE1 is from a fish erythrocyte which releases taurine when swollen, and mAE1 is from a mammalian erythrocyte which does not regulate its volume when swollen. While mAE1 performs exclusively Cl−/Cl− exchange, tAE1 behaves as a bifunctional protein with both anion exchange and Cl−/taurine channel functions. Construction of diverse tAE1/mAE1 chimaeras allows the identification of protein domains associated with this channel activity. Thus, some AE1 isoforms could act as a swelling-activated osmolyte channel, a result having a potentially important implication in malaria. This review also discusses the possibility that several different proteins might function as swelling-activated osmolyte channels.
The mechanics of flight in the hawkmoth Manduca sexta I. Kinematics of hovering and forward flight
Authors: Willmott Alexander P. , Ellington Charles P.
Published: April 2021

High-speed videography was used to record sequences of individual hawkmoths in free flight over a range of speeds from hovering to 5 m s−1. At each speed, three successive wingbeats were subjected to a detailed analysis of the body and wingtip kinematics and of the associated time course of wing rotation. Results are presented for one male and two female moths. The clearest kinematic trends accompanying increases in forward speed were an increase in stroke plane angle and a decrease in body angle. The latter may have resulted from a slight dorsal shift in the area swept by the wings as the supination position became less ventral with increasing speed. These trends were most pronounced between hovering and 3m s−1, and the changes were gradual; there was no distinct gait change of the kind observed in some vertebrate fliers.

The wing rotated as two functional sections: the hindwing and the portion of the forewing with which it is in contact, and the distal half of the forewing. The latter displayed greater fluctuation in the angle of rotation, especially at the lower speeds. As forward speed increased, the discrepancy between the rotation angles of the two halfstrokes, and of the two wing sections, became smaller. The downstroke wing torsion was set early in the halfstroke and then held constant during the translational phase.
Aerial performance of Drosophila melanogaster from populations selected for upwind flight ability
Authors: Marden James H. , Wolf Melisande R. , Weber Kenneth E.
Published: April 2021

A computerized system for three-dimensional tracking of large numbers of individual free-flying insects was used to assess the performance of Drosophila melanogaster from populations that had undergone 160 generations of selection for upwind flight ability. Compared with control lines, the selected lines showed significant increases in mean flight velocity, decreases in angular trajectory and a significant change in the interaction between velocity and angular trajectory. Maximal flight velocity was apparent as a sharply defined upper boundary of the distribution of horizontal and vertical velocity as a function of angular trajectory; this upper bound (0.85 m s−1) differed little between the selected and control lines, although individuals from the selected lines attained maximal performance levels much more frequently. Maximum induced power output was calculated directly from the product of maximum vertical velocity and body weight. This measure (28W kg−1 muscle) was closely predicted by a scaling relationship derived from the load-lifting limits of larger insects and vertebrates, as well as tethered D. melanogaster stimulated via their optomotor reflex to produce maximal lift. These results indicate that selection for flight performance can readily alter the relative effort and/or the frequency of phenotypes capable of attaining population-wise maximal performance levels, but shows little ability to increase population-wise maximal performance.
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

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

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

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

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

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

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

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

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

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

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

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

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

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.
MeV-Ion Microprobe Analyses of Whole Drosophila Suggest That Zinc and Copper Accumulation is Regulated Storage not Deposit Excretion
Authors: Schofield Robert M. S. , Postlethwait John H. , Lefevre Harlan W.
Published: April 2021

We examined Drosophila spp. using a penetrative ion microprobe technique that allows us to quantify element contents in whole organs and organisms. Comparatively non-penetrative techniques, such as electron microscopy, could not have been used to make many of these measurements because material is lost during sectioning. We found that zinc was accumulated predominantly within a single organ: in the main segments of both the anterior and posterior Malpighian tubules. In contrast to zinc, iron and copper were more generally distributed throughout the body. Zinc concentrations as high as 2.8 % of dry mass were measured in cell-sized volumes of the Malpighian tubules. The large quantities of zinc (approximately 2×10−8 g in 8-day-old male adults) were sequestered by an unidentified mechanism. We found less than 1 % of the estimated amount of consumed zinc and copper in the abdomen of flies fed food containing several hundred parts per million dry mass of these metals. Our results are inconsistent with the detoxification hypothesis that predicts that a large proportion of the heavy metals passing through the gut are absorbed and stored permanently. We found for both zinc and copper that the quantity in the abdomen was not proportional to the concentration of these metals in the consumed food but was, instead, relatively invariant. For these reasons, we suggest that regulated biological availability, not detoxification, may be the primary benefit of zinc and copper storage.
Regulation of Ecdysis-Triggering Hormone Release by Eclosion Hormone
Authors: Kingan Timothy G. , Gray William , žitňan Duŝan , Adams Michael E.
Published: April 2021

Ecdysis behavior in the tobacco hornworm Manduca sexta (Lepidoptera: Sphingidae) is triggered through reciprocal peptide signaling between the central nervous system and the epitracheal endocrine system. Recent evidence indicates that eclosion hormone may initiate endocrine events leading to ecdysis through its action on epitracheal glands to cause the release of ecdysis-triggering hormone (ETH). Here, we report that direct exposure of epitracheal glands to eclosion hormone in vitro leads to secretion of ETH. The threshold concentration of eclosion hormone needed to evoke release of ETH is approximately 3 pmol l−1. Eclosion hormone also induces elevation of cyclic GMP, but not cAMP, concentration in epitracheal glands at concentrations similar to those causing release of ETH. Both cGMP and 8-Br-cGMP mimic the secretory action of eclosion hormone. The sensitivity of the secretory response to eclosion hormone occurs during a narrow window of development, beginning approximately 8 h prior to pupal ecdysis. However, eclosion hormone can cause elevation of cGMP levels in epitracheal glands long before they acquire competence to release ETH, showing that the initial portion of the signal transduction cascade is in place early in development, but that the absence of a downstream step in the cascade prevents secretion. Measurements of cGMP levels in epitracheal glands during the ecdysis sequence show a sudden elevation some 30 min after the onset of pre-ecdysis, well after ETH secretion has been initiated. ETH secretion can therefore be viewed as a two-step process, beginning at pre-ecdysis when cGMP levels are relatively low, followed by a massive release resulting from a logarithmic elevation of cGMP levels.
Heart Rates and Abdominal Temperatures of Free-Ranging South Georgian Shags, Phalacrocorax Georgianus
Authors: Bevan R. M. , Boyd I. L. , Butler P. J. , Reid K. , Woakes A. J. , Croxall J. P.
Published: April 2021

The South Georgian shag (Phalacrocorax georgianus) shows a remarkable diving ability comparable to that of penguins, yet nothing is known of the physiology of these birds. In this study, heart rates and abdominal temperatures were recorded continuously in four free-ranging South Georgian shags using an implanted data-logger. A time–depth recorder was also attached to the back of the implanted birds to record their diving behaviour.

The diving behaviour of the birds was essentially similar to that reported in other studies, with maximum dive durations for individual birds ranging between 140 and 287 s, and maximum depths between 35 and 101 m. The birds, while at the nest, had a heart rate of 104.0±13.1 beats min−1 (mean ± S.E.M.) and an abdominal temperature of 39.1±0.2 °C. During flights of 221±29 s, heart rate and abdominal temperature rose to 309.5±18.0 beats min−1 and 40.1±0.3 °C, respectively. The mean heart rate during diving, at 103.7±13.7 beats min−1, was not significantly different from the resting values, but the minimum heart rate during a dive was significantly lower at 64.8±5.8 beats min−1. The minimum heart rate during a dive was negatively correlated with both dive duration and dive depth. Abdominal temperature fell progressively during a diving bout, with a mean temperature at the end of a bout of 35.1±1.7 °C.

The minimum heart rate during diving is at a sub-resting level, which suggests that the South Georgian shag responds to submersion with the ‘classic’ dive response of bradycardia and the associated peripheral vasoconstriction and utilisation of anaerobic metabolism. However, the reduction in abdominal temperature may reflect a reduction in the overall metabolic rate of the animal such that the bird can remain aerobic while submerged.s