bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinematic scaling of locomotion by hydrostatic animals: ontogeny of peristaltic crawling by the earthworm Lumbricus terrestris
Authors: Quillin Kim J.
Published: April 2021

This study examined the relationship between ontogenetic increase in body size and the kinematics of peristaltic locomotion by the earthworm Lumbricus terrestris, a soft-bodied organism supported by a hydrostatic skeleton. Whereas the motions of most vertebrates and arthropods are based primarily on the changes in the joint angles between rigid body segments, the motions of soft-bodied organisms with hydrostatic skeletons are based primarily on the changes in dimensions of the deformable body segments themselves. The overall kinematics of peristaltic crawling and the dynamic shape changes of individual earthworm segments were measured for individuals ranging in body mass (mb) by almost three orders of magnitude (0.012–8.5 g). Preferred crawling speed varied both within and among individuals: earthworms crawled faster primarily by taking longer strides, but also by taking more strides per unit time and by decreasing duty factor. On average, larger worms crawled at a greater absolute speed than smaller worms (U∝mb0.33) and did so by taking slightly longer strides (l∝mb0.41, where l is stride length) than expected by geometric similarity, using slightly lower stride frequencies (f∝mb−0.07) and the same duty factor (df∝mb−0.03). Circumferential and longitudinal body wall strains were generally independent of body mass, while strain rates changed little as a function of body mass. Given the extent of kinematic variation within and among earthworms, the crawling of earthworms of different sizes can be considered to show kinematic similarity when the kinematic variables are normalized by body length. Since the motions of peristaltic organisms are based primarily on changes in the dimensions of the deformable body wall, the scaling of the material properties of the body wall is probably an especially important determinant of the scaling of the kinematics of locomotion.
The linkage between Na+ uptake and ammonia excretion in rainbow trout: kinetic analysis, the effects of (NH4)2SO4 and NH4HCO3 infusion and the influence of gill boundary layer pH
Authors: Salama Annika , Morgan Ian J. , Wood Chris M.
Published: April 2021

The nature of the linkage between between branchial ammonia excretion (JAmm) and unidirectional Na+ influx was studied in the freshwater rainbow trout (Oncorhynchus mykiss). Arterial plasma total [ammonia], PNH and JAmm were all elevated approximately threefold by intravascular infusion for 24 h with either 70 mmol l−1 (NH4)2SO4 or 140 mmol l−1 NH4HCO3 at a rate of approximately 400 μmol kg−1 h−1. Both treatments markedly stimulated . NH4HCO3 induced metabolic alkalosis in the blood plasma, whereas (NH4)2SO4 caused a slight metabolic acidosis. Experiments with Hepes-buffered water (5 mmol l−1) under control conditions demonstrated that increases in gill boundary layer pH were associated with decreases in both and JAmm. Thus, the stimulation of caused by ammonium loading was not simply a consequence of a Na+-coupled H+ extrusion mechanism activated by internal acidosis or by alkalosis in the gill boundary layer. Indeed, there was no stimulation of net acidic equivalent excretion accompanying NH4HCO3 infusion. Michaelis–Menten kinetic analysis by acute variation of water [Na+ ] demonstrated that both infusions caused an almost twofold increase in but no significant change in Km, indicative of an increase in transporter number or internal counterion availability without an alteration in transporter affinity for external Na + . The increase in was larger with (NH4)2SO4 than with NH4HCO3 infusion and in both cases lower than the increase in JAmm. Additional evidence of quantitative uncoupling was seen in the kinetics experiments, in which acute changes in of up to threefold had negligible effects on JAmm under either control or ammonium-loaded conditions. In vitro measurements of branchial Na + /K +-ATPase activity demonstrated no effect of NH4+ concentration over the concentration range observed in vivo in infused fish. Overall, these results are consistent with a dominant role for NH3 diffusion as the normal mechanism of ammonia excretion, but indicate that ammonium loading directly stimulates , perhaps by activation of a non-obligatory Na+/NH4+ exchange rather than by an indirect effect (e.g. Na +-coupled H+ excretion) mediated by altered internal or external acid–base status.
Tegula function during free locust flight in relation to motor pattern, flight speed and aerodynamic output
Authors: Fischer Hanno , Ebert Eckhard
Published: April 2021

Tegulae are complex proprioceptors at the wing base of locusts. Deafferentation of the tegulae causes a lack of specific phasic information related to the wing downstroke and the timing of the upstroke. Employing telemetry during free flight of the locust Schistocerca gregaria, we investigated the consequences of tegula ablation on free flight parameters including motor patterns (wingbeat frequency and the relationship between the activation of flight muscle antagonists), free flight speed and aerodynamic output. We investigated the role of the tegula pairs of both wings on the motor pattern generated in free-flying locusts. We show that the tegula organs are not essential for generating the motor patterns necessary for free flight. However, they are required for increasing the motor output to give additional effective lifting power during adaptive behaviour. We also investigated long-term changes in the free flight parameters after tegula ablation. The recovery of the adult flight system revealed in the present study suggests that there is adaptation to the loss of proprioceptive information; this argues for a full functional and behavioural recovery of the flight system of the locust under closed-loop conditions.
Transformation of leech microglial cell morphology and properties following co-culture with injured central nervous system tissue
Authors: Bernhardi Rommy Von , Nicholls John G.
Published: April 2021

When the leech central nervous system (CNS) is injured, microglial cells migrate to the site of the lesion. It is possible that the injured CNS releases diffusible substances that alter the properties of microglial cells; to investigate this, microglial cells were cultured in the presence of injured or uninjured CNS tissue. Grown on Concanavalin A (Con-A), 75 % of microglial cells are rounded in shape and are avoided by growing neurites. However, when chains of leech ganglia with damaged connectives were cultured on Con-A next to microglial cells, many of the microglial cells changed their morphology. The number of rounded cells present decreased to 48 %, 4 % became spindle-shaped and 48 % had an intermediate form. In addition, the presence of crushed ganglionic chains allowed more growth of neurites across microglial cells than occurred under control conditions, although round-shaped microglia were still avoided by growing neurites. Similar changes in microglial cells were produced in cells plated on Con-A in the presence of conditioned medium from crushed ganglionic chains. Hence, a diffusible substance from injured CNS tissue caused the morphology of the microglial cells plated on Con-A to become more like that of microglia plated on laminin, on which only 22 % of the cells are rounded while the remainder are spindle-shaped and are readily crossed by neurites. Changes in morphology were not observed when microglial cells were cultured with frozen and crushed ganglionic chains or with uncrushed chains. These experiments demonstrate that substances released from damaged leech CNS cause microglial cells plated on Con-A to change their morphology and the way in which they interact with growing neurites.
Dopamine stimulates salivary duct cells in the cockroach Periplaneta americana
Authors: Lang Ingo , Walz Bernd
Published: April 2021

This study examines whether the salivary duct cells of the cockroach Periplaneta americana can be stimulated by the neurotransmitters dopamine and serotonin. We have carried out digital Ca2+-imaging experiments using the Ca2+-sensitive dye fura-2 and conventional intracellular recordings from isolated salivary glands. Dopamine evokes a slow, almost tonic, and reversible dose-dependent elevation in [Ca2+]i in the duct cells. Upon stimulation with 10−6 mol l−1 dopamine, [Ca2+]i rises from 48±4 nmol l−1 to 311±43 nmol l−1 (mean ± S.E.M., N=18) within 200–300 s. The dopamine-induced elevation in [Ca2+]i is absent in Ca2+-free saline and is blocked by 10−4 mol l−1 La3+, indicating that dopamine induces an influx of Ca2+ across the basolateral membrane of the duct cells. Stimulation with 10−6 mol l−1 dopamine causes the basolateral membrane to depolarize from −67±1 to −41±2 mV (N=10). This depolarization is also blocked by La3+ and is abolished when Na+ in the bath solution is reduced to 10 mmol l−1. Serotonin affects neither [Ca2+]i nor the basolateral membrane potential of the duct cells. These data indicate that the neurotransmitter dopamine, which has previously been shown to stimulate fluid secretion from the glands, also stimulates the salivary duct cells, suggesting that dopamine controls their most probable function, the modification of primary saliva.
Post-ingestive feedbacks and associative learning regulate the intake of unsuitable sterols in a generalist grasshopper
Authors: Behmer Spencer T. , Elias Damian O. , Bernays Elizabeth A.
Published: April 2021

Behavioural studies of the grasshopper Schistocerca americana were undertaken to identify the mechanisms that regulate the intake of dietary sterols. In the first experiment, grasshoppers were allowed to feed on spinach, a plant containing only unsuitable sterols; immediately after this first meal, a suitable or unsuitable sterol was injected into the haemolymph. Grasshoppers injected with unsuitable sterols had second meals on spinach that were significantly shorter than those of grasshoppers injected with suitable sterols, indicating that unsuitable dietary sterols are detected post-ingestively. In the second experiment, grasshoppers were fed food containing only unsuitable sterols and were then presented with glass-fibre discs containing different concentrations of a suitable sterol or sucrose only (the control). The results suggest that grasshoppers do not use a direct feedback operating on mouthpart chemoreceptors to regulate their intake of suitable sterols. In the third experiment, grasshoppers were presented with artificial diets containing different sterols and flavours, and feeding was observed over a sequence of meals. The results from both the first and last experiments suggest a role for associative learning in regulating the intake of unsuitable sterols.
Does Gill Boundary Layer Carbonic Anhydrase Contribute to Carbon Dioxide Excretion: a Comparison Between Dogfish (Squalus Acanthias) and Rainbow Trout (Oncorhynchus Mykiss)
Authors: Perry S. F. , Gilmour K. M. , Bernier N. J. , Wood C. M.
Published: April 2021

In vivo experiments were conducted on spiny dogfish (Squalus acanthias) and rainbow trout (Oncorhynchus mykiss) in sea water to determine the potential role of externally oriented or gill boundary layer carbonic anhydrase in carbon dioxide excretion. This was accomplished by assessing pH changes in expired water using a stopped-flow apparatus. In dogfish, expired water was in acid–base disequilibrium as indicated by a pronounced acidification (ΔpH=−0.11±0.01; N=22; mean ± S.E.M.) during the period of stopped flow; inspired water, however, was in acid–base equilibrium (ΔpH=−0.002±0.01; N=22). The acid–base disequilibrium in expired water was abolished (ΔpH=−0.005±0.01; N=6) by the addition of bovine carbonic anhydrase (5 mg l−1) to the external medium. Addition of the carbonic anhydrase inhibitor acetazolamide (1 mmol l−1) to the water significantly reduced the magnitude of the pH disequilibrium (from −0.133±0.03 to −0.063±0.02; N=4). However, after correcting for the increased buffering capacity of the water caused by acetazolamide, the acid–base disequilibrium during stopped flow was unaffected by this treatment (control Δ[H+]=99.8±22.8 μmol l−1; acetazolamide Δ[H+]=81.3±21.5 μmol l−1). In rainbow trout, expired water displayed an acid–base disequilibrium (ΔpH=0.09±0.01; N=6) that also was abolished by the application of external carbonic anhydrase (ΔpH=0.02±0.01).

The origin of the expired water acid–base disequilibrium was investigated further in dogfish. Intravascular injection of acetazolamide (40 mg kg−1) to inhibit internal carbonic anhydrase activity non-specifically and thus CO2 excretion significantly diminished the extent of the expired water disequilibrium pH after 30 min (from −0.123±0.01 to −0.065±0.01; N=6). Selective inhibition of extracellular carbonic anhydrase activity using a low intravascular dose (1.3 mg kg−1) of the inhibitor benzolamide caused a significant reduction in the acid–base disequilibrium after 5 min (from −0.11±0.01 to −0.07±0.01; N=14). These results demonstrate that the expired water acid–base disequilibrium originates, at least in part, from excretory CO2 and that extracellular carbonic anhydrase in dogfish may have a significant role in carbon dioxide excretion. However, externally oriented carbonic anhydrase (if present in dogfish) plays no role in catalysing the hydration of the excretory CO2 in water flowing over the gills and thus is unlikely to facilitate CO2 excretion.
Morphology and mechanics of tongue movement in the african pig-nosed frog Hemisus marmoratum: a muscular hydrostatic model
Authors: Nishikawa Kiisa C. , Kier William M. , Smith Kathleen K.
Published: April 2021

The goal of this study was to investigate morphological adaptations associated with hydrostatic elongation of the tongue during feeding in the African pig-nosed frog Hemisus marmoratum. Whereas previous studies had suggested that the tongue of H. marmoratum elongates hydraulically, the anatomical observations reported here favour a muscular hydrostatic mechanism of tongue elongation. H. marmoratum possesses a previously undescribed compartment of the m. genioglossus (m. genioglossus dorsoventralis), which is intrinsic to the tongue and whose muscle fibres are oriented perpendicular to the long axis of the tongue. On the basis of the arrangement and orientation of muscle fibres in the m. genioglossus and m. hyoglossus, we propose a muscular hydrostatic model of tongue movement in which contraction of the m. genioglossus dorsoventralis, together with unfolding of the intrinsic musculature of the tongue, results in a doubling in tongue length. Electron micrographs of sarcomeres from resting and elongated tongues show that no special adaptations of the sarcomeres are necessary to accommodate the observed doubling in tongue length during feeding. Rather, the sarcomeres of the m. genioglossus longitudinalis are strikingly similar to those of anuran limb muscles. The ability to elongate the tongue hydrostatically, conferred by the presence of the m. genioglossus dorsoventralis, is associated with the appearance of several novel aspects of feeding behaviour in H. marmoratum. These include the ability to protract the tongue slowly, thereby increasing capture success, and the ability to aim the tongue in azimuth and elevation relative to the head. Compared with other frogs, the muscular hydrostatic system of H. marmoratum allows more precise, localized and diverse tongue movements. This may explain why the m. genioglossus of H. marmoratum is composed of a larger number of motor units than that of other frogs.
Respecified larval proleg and body wall muscles circulate hemolymph in developing wings of Manduca sexta pupae
Authors: Lubischer Jane L. , Verhegge Laura D. , Weeks Janis C.
Published: April 2021

Most larval external muscles in Manduca sexta degenerate at pupation, with the exception of the accessory planta retractor muscles (APRMs) in proleg-bearing abdominal segment 3 and their homologs in non-proleg-bearing abdominal segment 2. In pupae, these APRMs exhibit a rhythmic ‘pupal motor pattern’ in which all four muscles contract synchronously at approximately 4 s intervals for long bouts, without externally visible movements. On the basis of indirect evidence, it was proposed previously that APRM contractions during the pupal motor pattern circulate hemolymph in the developing wings and legs. This hypothesis was tested in the present study by making simultaneous electromyographic recordings of APRM activity and contact thermographic recordings of hemolymph flow in pupal wings. APRM contractions and hemolymph flow were strictly correlated during the pupal motor pattern. The proposed circulatory mechanism was further supported by the findings that unilateral ablation of APRMs or mechanical uncoupling of the wings from the abdomen essentially abolished wing hemolymph flow on the manipulated side of the body. Rhythmic contractions of intersegmental muscles, which sometimes accompany the pupal motor pattern, had a negligible effect on hemolymph flow. The conversion of larval proleg and body wall muscles to a circulatory function in pupae represents a particularly dramatic example of functional respecification during metamorphosis.
Purification and cloning of the salivary peroxidase/catechol oxidase of the mosquito Anopheles albimanus
Authors: Ribeiro José M. C. , Valenzuela Jesus G.
Published: April 2021

Salivary homogenates of the adult female mosquito Anopheles albimanus have been shown previously to contain a vasodilatory activity associated with a catechol oxidase/peroxidase activity. We have now purified the salivary peroxidase using high-performance liquid chromatography. The pure enzyme is able to relax rabbit aortic rings pre-constricted with norepinephrine. The peroxidase has a relative molecular mass of 66 907 as estimated by mass spectrometry. Amino-terminal sequencing allowed us to design oligonucleotide probes for isolation of cDNA clones derived from the salivary gland mRNA from female mosquitoes. The full sequence of the cDNA demonstrated homology between A. albimanus salivary peroxidase and several members of the myeloperoxidase gene family. A close comparison of A. albimanus salivary peroxidase with canine myeloperoxidase, for which the crystal structure is known, showed that all six disulfide bridges were conserved and demonstrated identity for all five residues associated with a Ca2+-binding site. In addition, 16 of 26 residues shown to be in close proximity to the heme moiety in the canine myeloperoxidase were identical. We conclude that the salivary peroxidase of A. albimanus belongs to the myeloperoxidase gene family. Other possible functions for this molecule in blood feeding are discussed.
Changes in motor network expression related to moulting behaviour in lobster: role of moult-induced deep hypoxia
Authors: Clemens Stefan , Massabuau Jean-Charles , Meyrand Pierre , Simmers John
Published: April 2021

The well known rhythmically active pyloric neural network in intact and freely behaving lobsters Homarus gammarus was monitored prior to and following ecdysis. Despite long-lasting hormonal and metabolic alterations associated with this process, spontaneous pyloric network activity remained largely unaltered until the last 12–48 h before exuviation. At this time, the most notable change was a progressive lengthening of pyloric cycle period, which eventually attained 500–600 % of control values. It was only in the very last minutes before ecdysis that burst patterning became irregular and the otherwise strictly alternating motor sequence broke down. After the moult, coordinated rhythmicity was re-established within 10 min. Concomitant with these final changes in motor network expression at ecdysis was a drastic reduction in blood oxygen levels which led to a temporary near-anoxia. By imposing similarly deep hypoxic conditions both on intermoult animals and on the pyloric network in vitro, we mimicked to a large extent the moult-induced changes in pyloric network performance. Our data suggest that, despite major surrounding physiological perturbations, the pyloric network in vivo retains stable pattern-generating properties throughout much of the moulting process. Moreover, some of the most significant modifications in motor expression just prior to ecdysis can be related to a substantial reduction in oxygen levels in the blood.
Urine release in freely moving catheterised lobsters (Homarus americanus) with reference to feeding and social activities
Authors: Breithaupt Thomas , Lindstrom Daniel P. , Atema Jelle
Published: April 2021

Previous studies suggest that urine-borne pheromones play an important role in lobster agonistic and sexual behaviour. This paper investigates the pattern of urine release in catheterised, but otherwise freely moving, adult lobsters with respect to feeding, social and non-social activities. Lobsters on average released 4.1 ml (1 % of body mass) of urine over a 12 h period; this more than doubled to 10.6 ml over the 12 h period after feeding. Hourly monitoring revealed that most urine was released in the first hour after feeding (2.84 ml). With the exception of the first hours after feeding, urine release was intermittent, with pauses lasting up to 17 h. The probability of urine release per hour in unfed lobsters was 0.34 (median); this value increased during agonistic interactions elicited by the introduction of a conspecific (median 0.63) and during activity initiated by non-social disturbance (median 0.56). Mean urine volume during output hours in unfed lobsters amounted to 1.09 ml h−1. This volume was significantly increased by the presence of a conspecific (1.88 ml h−1) and decreased during activity initiated by non-social disturbances (0.56 ml h−1). No sex-specific differences in urine release were found. The data demonstrate that lobsters control their urine release in a manner dependent on behavioural context. This supports recent findings suggesting the use of urine for chemical signalling in agonistic interactions.
The case for light-dependent magnetic orientation in animals
Authors: Deutschlander Mark E. , Phillips John B. , Borland S. Chris
Published: April 2021

Light-dependent models of magnetoreception have been proposed which involve an interaction between the magnetic field and either magnetite particles located within a photoreceptor or excited states of photopigment molecules. Consistent with a photoreceptor-based magnetic compass mechanism, magnetic orientation responses in salamanders, flies and birds have been shown to be affected by the wavelength of light. In birds and flies, it is unclear whether the effects of light on magnetic orientation are due to a direct effect on a magnetoreception system or to a nonspecific (e.g. motivational) effect of light on orientation behavior. Evidence from shoreward-orienting salamanders, however, demonstrates that salamanders perceive a 90° counterclockwise shift in the direction of the magnetic field under long-wavelength (⩾500 nm) light. A simple physiological model based on the antagonistic interaction between two magnetically sensitive spectral mechanisms suggests one possible way in which the wavelength-dependent effects of light on the salamander’s magnetic compass response might arise. Assuming that the wavelength-dependent characteristics of the avian magnetic response can be attributed to an underlying magnetoreception system, we discuss several hypotheses attempting to resolve the differences observed in the wavelength-dependent effects of light on magnetic orientation in birds and salamanders. By considering the evidence in the context of photoreceptor- and non-photoreceptor-based mechanisms for magnetoreception, we hope to encourage future studies designed to distinguish between alternative hypotheses concerning the influence of light on magnetoreception.
Hearing with the mouthparts: behavioural responses and the structural basis of ultrasound perception in acherontiine hawkmoths
Authors: Göpfert Martin C. , Wasserthal Lutz T.
Published: April 2021

In contrast to previous assumptions, mouthparts form hearing organs not only in choerocampine hawkmoths but also in some distantly related acherontiine hawkmoth species. Four of the six acherontiine species studied revealed responses to ultrasonic sounds when stimulated during tethered flight. The responses included changes in flight speed and non-directional turns. Individuals from two species also responded by emitting sound. The minimum thresholds of the flight pattern changes were approximately 70 dB in all species studied, with species-specific best frequencies between 30 and 70 kHz. Some acherontiine species also move their tongue in a stereotyped way when stimulated acoustically. The activity of the muscles involved in this tongue reflex was characterized in the present study and used in combination with ablation experiments to localize the hearing organ. These experiments revealed auditory functions of the labial palps and the labral pilifers similar to those found in Choerocampina. The palp contributes a 20–25 dB rise in sensitivity, whereas the pilifer appears to contain the sensory organ. Structural differences suggest a convergent evolution of hearing in hawkmoths: in the place of the swollen palps of Choerocampina, acherontiine species capable of hearing possess a scale-plate of the palps that interacts with an articulating pilifer, while this modification is absent in closely related non-hearing species.
Lack of glomerular intermittency in the river lamprey Lampetra fluviatilis acclimated to sea water and following acute transfer to iso-osmotic brackish water
Authors: Brown J. Anne , Rankin J. Clifford
Published: April 2021

Previous studies have suggested that in the lamprey Lampetra fluviatilis, in contrast to teleost fish, all glomeruli are actively filtering. In the present study, we have applied the ferrocyanide technique to obtain more definitive values for the population of filtering nephrons in the lamprey under conditions of high (in fresh water) and low (in sea water) glomerular filtration rate (GFR) and when the branchial osmotic gradient was eliminated by acute transfer of freshwater lampreys to iso-osmotic brackish water. These studies demonstrated that the renal antidiuresis in lampreys acclimated to full-strength sea water does not involve any reduction in the filtering population of glomeruli. Transfer to brackish water significantly reduced GFR and thereby urine flow rate (287±23 ml kg−1 24 h−1 in fresh water; 6.9±2.5 ml kg−1 24 h−1 in brackish water). In four of the eight fish examined, 100 % of glomeruli remained filtering; in the other four fish, non-filtering glomeruli occurred in patches along the kidney, always associated with an absence of vascular perfusion, which implies possible endocrine/neural control of vascular tone. The numbers of non-filtering glomeruli were always small, and these glomeruli do not appear to make a major contribution to the overall decline in urine output. The results provide firm evidence that although lampreys, like teleosts, show considerable variations in urine output, the renal mechanisms by which lampreys and the teleosts achieve this differ fundamentally, with glomerular intermittency playing little or no part in the lamprey.
Venom of a parasitoid wasp induces prolonged grooming in the cockroach
Authors: Weisel-Eichler Aviva , Haspel Gal , Libersat Frederic
Published: April 2021

The parasitoid wasp Ampulex compressa hunts cockroaches Periplaneta americana, stinging them first in the thorax and then in the head, the sting penetrating towards the subesophageal ganglion. After being stung the cockroach grooms almost continuously for approximately 30 min, performing all the normal components of grooming behavior. This excessive grooming is only seen after the head sting and cannot be attributed to stress, to contamination of the body surface or to systemic or peripheral effects. This suggests that the venom is activating a neural network for grooming.

We suggest that the venom induces prolonged grooming by stimulating dopamine receptors in the cockroach, for the following reasons. (1) Reserpine, which causes massive release of monoamines, induces excessive grooming. (2) Dopamine injected into the hemocoel also induces excessive grooming and is significantly more effective than octopamine or serotonin. In addition, the dopamine agonist SKF 82958 induces excessive grooming when injected directly into the subesophageal ganglion. (3) Injection of the dopamine antagonist flupenthixol greatly reduces venom-induced grooming. (4) Dopamine, or a dopamine-like substance, is present in the venom.
Ionic mechanisms of phototransduction in photoreceptor cells from the epistellar body of the octopus Eledone cirrhosa
Authors: Cobb Christopher S. , Williamson Roddy
Published: April 2021

Intracellular recordings were made from extraocular photoreceptor cells within isolated epistellar bodies of the lesser or northern octopus Eledone cirrhosa. The cells had resting potentials around −41±5 mV (mean ± S.D., N=60) and showed light-flash-induced membrane depolarisation. The evoked response to a brief light flash consisted of a transient peak depolarisation, followed by a plateau component. The magnitude of the light-induced peak depolarisation response was decreased by bathing the epistellar body in artificial sea water (ASW) low in Na+, where choline+ replaced Na+, or by passing steady depolarising current. Replacement of external Na+ by Li+ had no effect on the light-stimulated response. The external application of the Na+ channel blocker tetrodotoxin (3 μmol l−1) increased the light-evoked response, but this was accompanied by a loss of action potential activity. The amplitude and duration of the response to a light flash was increased by bathing the epistellar body in ASW low in Ca2+, or in ASW containing 10 mmol l−1 Co2+, and after intracellular microinjection of the Ca2+ buffer EGTA. Intracellular microinjection of Ca2+ or inositol 1,4,5-trisphosphate, or external application of the phospholipase C inhibitor U-73122, had no apparent effect on the light-evoked response. These results are consistent with the interpretation that (1) the majority of the light-induced inward current is carried by Na+, probably via a non-selective cation channel, and (2) an increase in the intracellular free Ca2+ concentration, mediated by the phototransduction process, is involved in regulating the light-induced inward photocurrent and thus, in effect, determines the amplitude, time course and sensitivity of the receptor potential.
Responsiveness of gill Na+/K+-ATPase to cortisol is related to gill corticosteroid receptor concentration in juvenile rainbow trout
Authors: Shrimpton J. Mark , McCormick Stephen D.
Published: April 2021

A positive relationship between receptor concentration and tissue responsiveness is an often-assumed and rarely tested principle in endocrinology. In salmonids, seasonal changes in levels of plasma cortisol and gill corticosteroid receptors (CRs) during the spring indicate a potential role for this hormone in the parr–smolt transformation. It is not known whether these seasonal changes result in alterations in gill responsiveness to cortisol. The relationship between CR concentration and tissue responsiveness was, therefore, examined in the gills of juvenile rainbow trout (Oncorhynchus mykiss). Gill CR concentration (Bmax) and affinity (Kd) were assessed using a radioligand binding assay with the synthetic glucocorticoid triamcinolone acetonide. Gill responsiveness to cortisol was quantified by measuring in vitro Na+/K+-ATPase activity. Gill CR concentration was manipulated by stress or hormonal treatments. Repeated handling stresses resulted in a significant reduction in CR numbers. The decrease in CR Bmax corresponded to a reduction in gill responsiveness to cortisol. Triiodothyronine, but not growth hormone, treatment was found to increase CR Bmax significantly. The increase in CR numbers was correlated with a marked increase in gill responsiveness to cortisol. A significant positive linear relationship exists between the in vitro gill Na+/K+-ATPase activity response to cortisol and CR Bmax (r2=0.614, P<0.001). We have demonstrated that binding sites for cortisol in the gills of rainbow trout have high affinity, high specificity and saturable binding and that the number of binding sites is correlated with the tissue response to cortisol.
Inhibitory and excitatory responses of olfactory receptor neurons of Xenopus laevis tadpoles to stimulation with amino acids
Authors: Vogler Christina , Schild Detlev
Published: April 2021

Recordings were made from olfactory receptor neurons of Xenopus laevis tadpoles using the patch-clamp technique to investigate the responses of these cells to odorants. Four amino acids (glutamate, methionine, arginine and alanine) both individually and as a mixture were used as stimuli. Of the 156 olfactory neurons tested, 43 showed a response to at least one of the stimuli. Of the cells tested, 19 % responded to glutamate, 16 % to methionine, 12 % to arginine and 10 % to alanine. Each amino acid was able to induce both excitatory and inhibitory responses, although these occurred in different cells. Each amino acid produced approximately equal numbers of inhibitory and excitatory responses. Inhibitory responses could best be observed in the perforated-patch configuration using gramicidin as an ionophore and a recording configuration that is a current-clamp for fast signals and a voltage-clamp for slow signals. The diversity of the odorant responses, in particular the existence of excitatory and inhibitory responses, is not consistent with a single transduction pathway in olfactory neurons of Xenopus laevis tadpoles.
Behaviour of migrating birds exposed to X-band radar and a bright light beam
Authors: Bruderer Bruno , Peter Dieter , Steuri Thomas
Published: April 2021

Radar studies on bird migration assume that the transmitted electromagnetic pulses do not alter the behaviour of the birds, in spite of some worrying reports of observed disturbance. This paper shows that, in the case of the X-band radar ‘Superfledermaus’, no relevant changes in flight behaviour occurred, while a strong light beam provoked important changes.

Large sets of routine recordings of nocturnal bird migrants obtained using an X-band tracking radar provided no indication of differing flight behaviour between birds flying at low levels towards the radar, away from it or passing it sideways. Switching the radar transmission on and off, while continuing to track selected bird targets using a passive infrared camera during the switch-off phases of the radar, showed no difference in the birds’ behaviour with and without incident radar waves.

Tracking single nocturnal migrants while switching on and off a strong searchlight mounted parallel to the radar antenna, however, induced pronounced reactions by the birds: (1) a wide variation of directional shifts averaging 8 ° in the first and 15 ° in the third 10 s interval after switch-on; (2) a mean reduction in flight speed of 2–3 m s−1 (15–30 % of normal air speed); and (3) a slight increase in climbing rate. A calculated index of change declined with distance from the source, suggesting zero reaction beyond approximately 1 km. These results revive existing ideas of using light beams on aircraft to prevent bird strikes and provide arguments against the increasing use of light beams for advertising purposes.
Comparative three-dimensional kinematics of the hindlimb for high-speed bipedal and quadrupedal locomotion of lizards
Authors: Irschick Duncan J. , Jayne Bruce C.
Published: April 2021

Although lizards have been model organisms for testing locomotor performance and in ecomorphological studies, the limb movements of lizards during high-speed locomotion are poorly understood. Thus, we quantified the three-dimensional kinematics of the hindlimb, body and tail for five morphologically distinct species of lizard during steady-speed locomotion near maximum sprinting speed (2–5 m s−1 ). The kinematics of different species had little multivariate overlap. More than half of the strides of all species had digitigrade foot posture, but the frequency of using digitigrade foot posture varied among species. The combination of digitigrade foot posture and large foot size of the lizards contributed substantially to the high values of hip height. For each species, different suites of kinematic variables distinguished bipedal from quadrupedal strides. Interspecific morphological variation did not correspond globally to variation in kinematics, although lizard species with elongated hindlimbs took longer strides than species with shorter hindlimbs. The Froude numbers and relative stride lengths of all lizards running near maximal speeds were large compared with those reported previously for other vertebrates.
Monoamines and the isolated auricle of Sepia officinalis: are there β-like receptors in the heart of a cephalopod?
Authors: Versen B. , Gokorsch S. , Fiedler A. , Schipp R.
Published: April 2021

Pharmacological examinations of isolated auricles from Sepia officinalis were carried out to analyze the putative role of the monoaminergic transmitter/receptor system in the control of auricle function. In conjunction with histofluorescence studies and HPLC analyses, evidence of a double excitatory serotonergic and noradrenergic innervation of the auricles was obtained. Serotonin-induced positive chronotropic and inotropic effects were blocked by mianserin (5-HT1 and 5-HT2) but not by cyproheptadine (5-HT2). It is assumed that the auricular serotonin (5-HT) receptor represents a 5-HT1-like subtype and is not identical to the ventricular 5-HT receptor. Noradrenaline, adrenaline and dopamine evoked mainly positive chronotropic reactions and less prominent positive inotropic reactions. The potency range (pD2 frequency: noradrenaline 6.65 ⪢ adrenaline 5.69 > dopamine 5.34; pD2 amplitude: noradrenaline 6.09 ⩾ adrenaline 5.91 > dopamine 5.33) indicates out that noradrenaline might be the effective neurotransmitter in vivo. The α-mimetics clonidine (α2) and phenylephrine (α1) induced positive chronotropic and inotropic effects, while the β-mimetics albuterol (β2>β1) and dobutamine (β1) revealed only positive inotropic reactions. The β-agonist isoprenaline mimicked the positive chronotropic effects of noradrenaline and induced the strongest positive inotropic effects of all the agonists tested. Urapidil (α1) or phentolamine (α1 and α2) blocked only the positive chronotropic effects of noradrenaline and isoprenaline. The positive inotropic effects of isoprenaline could be blocked by the adenylate cyclase inhibitors MDL-12,330A or SQ-22,536, which had no effect on the chronotropic effects of isoprenaline. These results suggest that two catecholaminergic receptors are present in the auricles of Sepia officinalis: an α-like adrenoreceptor mediating mainly chronotropic effects, and a β-like receptor which appears to mediate inotropic effects by activating the cyclic AMP pathway. These results suggest that the auricles exert a regulatory effect on ventricular performance.
Identification and expression analysis of two developmentally regulated myosin heavy chain gene transcripts in carp (Cyprinus carpio)
Authors: Ennion Steven , Wilkes David , Gauvry Laurent , Alami-Durante Hélene , Goldspink Geoffrey
Published: April 2021

Whilst developmentally regulated genes for the myosin heavy chain (MyoHC) have been characterised in mammalian, avian and amphibian species, no developmental MyoHC gene has previously been characterised in a species of fish. In this study, we identify two developmentally regulated MyoHC gene transcripts (named Eggs22 and Eggs24) in carp (Cyprinus carpio) and characterise their expression patterns during embryonic and larval development. The transcripts showed an identical temporal pattern of expression commencing 22 h post-fertilisation (18 °C incubation temperature), coincident with the switch from exclusive expression of genes for β-actin to expression of genes for both β- and α-actin, and continuing for 2 weeks post-hatching. No expression of these myosin transcripts was detected in juvenile or adult carp. Wholemount in situ hybridisation showed that both transcripts are expressed initially in the rostral region of the developing trunk and progress caudally. Both are expressed in the developing pectoral fin and protractor hyoideus muscles. However, the muscles of the lower jaw express only the Eggs22 transcript. No expression of either transcript was detected in cardiac or smooth muscle. A distinct chevron pattern of expression was observed in the myotomal muscle. This was shown to be caused by localisation of the mRNAs to the myoseptal regions of the fibres, the sites of new sarcomere addition during muscle growth, suggesting transport of MyoHC mRNA transcripts. The 3′ untranslated region of the Eggs24 transcript contains a 10 base pair motif (AAAATGTGAA) which is shown to be also present in the 3′ untranslated regions of MyoHC genes from a wide range of species. Possible reasons for the need for developmental isoforms of myosin heavy chain isoforms are discussed.
Convective oxygen transport and tissue oxygen consumption in Weddell seals during aerobic dives
Authors: Davis Randall W. , Kanatous Shane B.
Published: April 2021

Unlike their terrestrial counterparts, marine mammals stop breathing and reduce their convective oxygen transport while performing activities (e.g. foraging, courtship, aggressive interactions, predator avoidance and migration) that require sustained power output during submergence. Since most voluntary dives are believed to remain aerobic, the goal of this study was to examine the potential importance of the dive response in optimizing the use of blood and muscle oxygen stores during dives involving different levels of muscular exertion. To accomplish this, we designed a numerical model based. on Fick’s principle that integrated cardiac output , regional blood flow, convective oxygen transport , muscle oxymyoglobin d. esaturation and regional rates of oxygen consumption . The model quantified how the optimal matching or mismatching of to affected the aerobic dive limit (ADL). We chose an adult Weddell seal Leptonycotes weddellii on which to base our model because of available data on the diving physiology and metabolism of this species. The results show that the use of blood and muscle oxygen stores must be completed at the same time to maximize the ADL for each level of . This is achieved by adjusting (range 19–94 % of resting levels) and muscle according to the rate of muscle oxygen consumption . At higher values of and muscle perfusion must increase to maintain an appropriate ratio so that available blood and muscle oxygen stores are depleted at the same time. Although the dive response does not sequester blood oxygen exclusively for brain and heart metabolism during aerobic dives, as it does during forced submersion, a reduction in and muscle perfusion below resting levels is necessary to maximize the ADL over the range of diving (approximately 2–9 ml O2 min−1 kg−1). Despite the reduction in , convective oxygen transport is adequate to maintain aerobic metabolism and normal function in the splanchnic organs, kidneys and other peripheral tissues. As a result, physiological homeostasis is maintained throughout the dive. The model shows that the cardiovascular adjustments known as the dive response enable the diving seal to balance the conflicting metabolic demands of (1) optimizing the distribution and use of blood and muscle oxygen stores to maximize the ADL over the normal range of diving and (2) ensuring that active muscle receives adequate oxygen as increases.
Rotation of F1-ATPase and the hinge residues of the β subunit
Authors: Masaike Tomoko , Mitome Noriyo , Noji Hiroyuki , Muneyuki Eiro , Yasuda Ryohei , Kinosita Kazuhiko , Yoshida Masasuke
Published: April 2021

Rotation of a motor protein, F1 -ATPase, was demonstrated using a unique single-molecule observation system. This paper reviews what has been clarified by this system and then focuses on the role of residues at the hinge region of the β subunit. We have visualised rotation of a single molecule of F1 -ATPase by attaching a fluorescent actin filament to the top of the γ subunit in the immobilised F1 -ATPase, thus settling a major controversy regarding the rotary catalysis. The rotation of the γ subunit was exclusively in one direction, as could be predicted by the crystal structure of bovine heart F1 -ATPase. Rotation at low ATP concentrations revealed that one revolution consists of three 120 ° steps, each fuelled by the binding of an ATP to the β subunit. The mean work done by a 120 ° step was approximately 80 pN nm, a value close to the free energy liberated by hydrolysis of one ATP molecule, implying nearly 100 % efficiency of energy conversion. The torque is probably generated by the β subunit, which undergoes large opening–closing domain motion upon binding of AT(D)P. We identified three hinge residues, βHis179, βGly180 and βGly181, whose peptide bond dihedral angles are drastically changed during domain motion. Simultaneous substitution of these residues with alanine resulted in nearly complete loss (99 %) of ATPase activity. Single or double substitution of the two Gly residues did not abolish the ATPase activity. However, reflecting the shift of the equilibrium between the open and closed forms of the β subunit, single substitution caused changes in the propensity to generate the kinetically trapped Mg-ADP inhibited form: Gly180Ala enhanced the propensity and Gly181Ala abolished the propensity. In spite of these changes, the mean rotational torque was not changed significantly for any of the mutants.
Synaptic-Like Microvesicles, Synaptic Vesicle Counterparts in Endocrine Cells, are Involved in a Novel Regulatory Mechanism for the Synthesis and Secretion of Hormones
Authors: Moriyama Yoshinori , Hayashi Mitsuko , Yamada Hiroshi , Yatsushiro Shouki , Ishio Shougo , Yamamoto Akitsugu
Published: April 2021

Microvesicles in endocrine cells are the morphological and functional equivalent of neuronal synaptic vesicles. Microvesicles accumulate various neurotransmitters through a transmitter-specific vesicular transporter energized by vacuolar H+ -ATPase. We found that mammalian pinealocytes, endocrine cells that synthesize and secrete melatonin, accumulate L-glutamate in their microvesicles and secrete it through exocytosis. Pinealocytes use L-glutamate as either a paracrine- or autocrine-like chemical transmitter in a receptor-mediated manner, resulting in inhibition of melatonin synthesis. In this article, we briefly describe the overall features of the microvesicle-mediated signal-transduction mechanism in the pineal gland and discuss the important role of acidic organelles in a novel regulatory mechanism for hormonal synthesis and secretion.