bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Antagonists On Putative Histamine Receptors in the First Visual Neuropile of the Housefly (Musca Domestica)
Authors: Hardie Roger C. 
Published: April 2021

ABSTRACTIntracellular recordings were made from the large monopolar cells (LMCs), which are the cells postsynaptic to photoreceptors, in the housefly Musca domestica. A multi-barrelled ionophoretic pipette glued to the recording electrode was used to apply a variety of cholinergic and histaminergic antagonists onto the recorded neurones. All substances which blocked the physiological response to light also antagonized the response to ionophoretically applied histamine, supporting the hypothesis that histamine is the neurotransmitter released by insect photoreceptors. In order of potency, the following drugs were found to block or reduce the LMC’s responses to light: benzoquinonium ⩾ gallamine &gt; ranitidine ⩾ atropine ≈ cimetidine &gt; metiamide≈SK&F93479 ⩾ mepyramine. Mecamylamine, scopolamine, dexetimide, nicotine, mequitazine, chlorpheniramine and clemastine were ineffective.Two other cholinergic ligands, hexamethonium and decamethonium, were much more potent than even benzoquinonium, but had the effect of facilitating and greatly slowing down the responses to light. Responses evoked by acetylcholine showed a different pharmacology, being blocked by mecamylamine but unaffected by hexamethonium. Despite testing a number of known cholinergic and histaminergic agents, no effective agonist for histamine was found. The results indicate the existence of a novel class of histamine-sensitive receptor with nicotinic features. In addition the unusual effects of a traditional Hl agonist, 2-thiazolylethylamine, suggested the presence of a second, distinct class of histamine receptor.
Speed, Stride Frequency and Energy Cost Per Stride: How Do They Change With Body Size and Gait?
Authors: Heglund Norman C. , Taylor C. Richard 
Published: April 2021

ABSTRACTIn this study we investigate how speed and stride frequency change with body size. We use this information to define ‘equivalent speeds’ for animals of different size and to explore the factors underlying the six-fold difference in mass-specific energy cost of locomotion between mouse-and horse-sized animals at these speeds. Speeds and stride frequencies within a trot and a gallop were measured on a treadmill in 16 species of wild and domestic quadrupeds, ranging in body size from 30 g mice to 200 kg horses. We found that the minimum, preferred and maximum sustained speeds within a trot and a gallop all change in the same rather dramatic manner with body size, differing by nine-fold between mice and horses (i.e. all three speeds scale with about the 0·2 power of body mass). Although the absolute speeds differ greatly, the maximum sustainable speed was about 2·6-fold greater than the minimum within a trot, and 2·1-fold greater within a gallop. The frequencies used to sustain the equivalent speeds (with the exception of the minimum trotting speed) scale with about the same factor, the -0·15 power of body mass. Combining this speed and frequency data with previously published data on the energetic cost of locomotion, we find that the mass-specific energetic cost of locomotion is almost directly proportional to the stride frequency used to sustain a constant speed at all the equivalent speeds within a trot and a gallop, except for the minimum trotting speed (where it changes by a factor of two over the size range of animals studied). Thus the energy cost per kilogram per stride at five of the six equivalent speeds is about the same for all animals, independent of body size, but increases with speed: 5·0 J kg−1 stride−1 at the preferred trotting speed; 5·3 J kg−1 stride−1 at the trot-gallop transition speed; 7·5 J kg−1 stride−1 at the preferred galloping speed; and 9·4J kg−1 stride−1 at the maximum sustained galloping speed. The cost of locomotion is determined primarily by the cost of activating muscles and of generating a unit of force for a unit of time. Our data show that both these costs increase directly with the stride frequency used at equivalent speeds by different-sized animals. The increase in cost per stride with increasing speed may be related to differences in mechanical advantage of the limb muscles (necessitating higher muscle forces for the same ground reaction force) as stride length increases both in the trot and in the gallop.
Ion Replacement as a Buoyancy Mechanism in a Pelagic Deep-Sea Crustacean
Authors: Sanders N. K. , Childress J. J. 
Published: April 2021

ABSTRACT
Unlike most pelagic crustaceans, the deep-sea shrimp Notostomus gibbosus (A. Milne-Edwards) (Oplophoridae) is positively buoyant, possessing a dorsally enlarged carapace which contains a low-density fluid. This fluid comprises 43% of the animal’s wet mass, has a low pH, and gives a lift of 17·7mgml−1; when this fluid is drained, the animal sinks. Low density is achieved by the replacement of less buoyant ions with ions which reduce density via two mechanisms: a change in total solute mass by the use of ions of lesser mass, and an ion-specific disruption of the structure of water molecules (resulting in an increase in fluid volume) caused by ions having large, positive partial molal volumes. The presence of large amounts of trimethylamine (Me3NH+), a relatively large, heavy ion which, together with NH4+, replaces nearly 90% of the Na+ in the carapace fluid, results in little change in the total solute mass of the carapace fluid of N. gibbosus (33·2 ‰) relative to sea water (approximately 34·1 ‰). Reduced fluid density is primarily a result of the large, positive partial molal volumes of Me3NH+ and NH4+, rather than a function of reduced solute masses.
Postural Changes Occurring During One Month of Vestibular Compensation in Goldfish
Authors: Ott Janet F. , Platt Christopher 
Published: April 2021

ABSTRACT
Postural behavioural changes during vestibular compensation were studied in goldfish. The tilting posture induced by directional light in the dorsal light reflex (DLR) was monitored by an automated camera system. Responses were measured over a 1-month period following a partial unilateral labyrinthectomy. After the fish had recovered from the ataxic stage, the first observable DLR had shifted strongly towards the operated side. This early bias decreased rapidly, then more gradually. Mean values for the DLR reached a steady state within 2 weeks. Recovery rates were slowest for DLR tilts elicited by light presented from the operated side. The DLR did not recover to preoperative control values for light from either the intact or operated side. Shortly after the operation, light from the operated side produced DLR values nearly double the normal; light from the intact side had an effect very little different from normal. At steady state, the light effect from the operated side had decreased from the high immediately postataxic levels to a level roughly 1·5 times normal, but the light effect from the intact side had increased, also reaching a level roughly 1·5 times normal. Thus the final values again show symmetry. Variability appears to be an important feature of the response.
Biomechanics of Frog Swimming I. Estimation of the Propulsive Force Generated byHymenochirus Boettgeri
Authors: Gal Julianna M. , Blake R. W. 
Published: April 2021

ABSTRACTCiné films were used to study swimming in the frog, Hymenochirus boettgeri (Tornier) during near-vertical breathing excursions. The animals generally decelerated during hindlimb flexion (recovery phase) and accelerated throughout hindlimb extension (power phase). Body velocity patterns of frogs are distinct from those of other drag-based paddlers, such as angelfish and water boatman, where the body is accelerated and decelerated within the power stroke phase. The propulsive force, estimated for a single sequence from quasi-steady drag and inertial considerations, was positive throughout extension. The upper and lower bounds of this estimate were calculated by considering additional components of the force balance, including the net effect of gravity and buoyancy, and the longitudinal added mass forces associated with the body. Consideration of the force balance implies that simple drag-based propulsion may not be sufficient to explain the swimming patterns observed in frogs.
Biomechanics of Frog Swimming: II. Mechanics of the Limb-Beat Cycle in Hymenochirus Boettgeri
Authors: Gal Julianna M. , Blake R. W. 
Published: April 2021

ABSTRACT
The hindlimb kinematics of Hymenochirus boettgeri (Tornier) were investigated using high-speed ciné films. The movement pattern was stereotypic, flexion and extension of the metatarsal-phalangeals and feet always lagging behind flexion and extension of the femora and tibiofibulae. The right hindlimb was modelled as a series of linked circular cylinders and a flat plate. A blade-element approach was used to calculate the quasi-steady drag-based and accelerative force components parallel to the direction of motion, based on the hindlimb kinematics of sequence 1 (see preceding paper). Positive thrust is generated primarily during the initial stages of extension (power stroke) because of unsteady (added mass) effects. Negative thrust occurs over the latter half of extension, despite the continued acceleration of the animal. Hindlimb interaction is thought to provide propulsive thrust for the latter half of the extension phase. It is suggested that a jet and/or reflective effect may be involved.
Mechanisms of Coupling Between the Ipsilateral Legs of a Walking Insect (Carausius Morosus)
Authors: Cruse H. , Schwarze W. 
Published: April 2021

ABSTRACT
The mechanisms by which the legs of a stick insect influence one another during walking were investigated by running the animals on a horizontal plane covered with a thin film of silicone oil to prevent mechanical coupling between the legs. Coupling between ipsilateral legs was investigated by interrupting the retraction (power stroke) of a leg for a short time and observing how the legs return to normal coordination following this disturbance.
The results show that three ipsilateral coupling mechanisms exist: (a) a forward-directed influence that inhibits the start of a protraction of the leg as long as the posterior leg is performing a protraction; (b) a forward-directed influence that excites the start of a protraction of the leg when the posterior leg starts a retraction movement; (c) a backward-directed influence that excites the start of a protrac-tion, the influence being stronger the further the anterior leg has moved backwards during its retraction. The latter influence depends on the position but not the phase of the anterior leg.
Amino Acid Metabolism and Water Transport Across the Seawater Eel Intestine
Authors: Ando Masaaki 
Published: April 2021

ABSTRACTTo elucidate how intracellular L-alanine enhances water transport across the seawater eel intestine, effects of various metabolic inhibitors were examined. The L-alanine-induced water flux was inhibited by amino-oxyacetate, an inhibitor of aminotransferase. After blocking the synthesis of pyruvate from L-alanine with this drug, water transport was stimulated with pyruvate, whose effects were inhibited by oxythiamine, an inhibitor of pyruvate dehydrogenase. 2,4-Dinitro-phenol (DNP) also inhibited the effects of L-alanine. Furthermore, L-alanine enhanced ouabain-sensitive O2 consumption in this tissue, and the enhancement in O2 consumption preceded that in the transepithelial potential difference (PD) and the net water flux. These results indicate that L-alanine is metabolized through the citric acid cycle to produce ATP, and that a metabolic product stimulates ion and water transport. L-Glutamine also seems to be metabolized just like L-alanine because: L-glutamine acted from inside the enterocyte; DNP inhibited the effects of L-glutamine; neither of the effects of L-glutamine and L-alanine were additive but they were mutually complementary; L-glutamine also enhanced ouabain-sensitive O2 consumption; and the increment in O2 consumption preceded that in the PD and the net water flux. The effects of L-glutamine on the PD and the net water flux depended on glutamine concentration and the concentration-response curve was of the Michaelis-Menten type, indicating that the rate of L-glutamine uptake into the enterocyte limits the overall rate of L-glutamine metabolism. A regulatory role of amino acids for ion and water transport is discussed.
Depression Of Whole-Body Calcium Uptake During Acute Hypercalcaemia In American Eel, Anguilla Rostrata, is Mediated Exclusively by Corpuscles of Stannius
Authors: Perry S. F. , Seguin D. , Lafeber F. P. J. G. , Bonga S. E. Wendelaar , Fenwick J. C. 
Published: April 2021

ABSTRACT
The role of the corpuscles of Stannius (CS) in acute modulation of wholebody calcium influx in American eel, Anguilla rostrata, was investigated by (i) assessing the effects of stanniectomy on and plasma total calcium concentration ([Catot]), (ii) comparing the abilities of sham-operated and stanniectomized eels to reduce during artificially induced hypercalcaemia, and (iii) monitoring the effects of homologous hypocalcin (a 54×103Mr glycoprotein) injection on . Stanniectomy (STX) caused a pronounced elevation of and hypercalcaemia measured 7 days after surgery. When hypercalcaemia was induced by intra-arterial infusion of CaCl2, a treatment known to cause degranulation of the CS and the specific release of hypocalcin, was reduced significantly within 1 h in intact fish. NaCl infusion did not affect plasma [Catot] or in any group tested. Stanniectomy prevented the reduction of associated with the hypercalcaemia induced by CaCl2 infusion. Intra-arterial infusion of MgCl2 caused a significant elevation of plasma total magnesium concentration [Mgtot] but did not alter . Intra-arterial infusion of hypocalcin (18.5 nmol kg−1 body mass) into intact eels decreased to an extent similar to that seen following artificially induced hypercalcaemia. We conclude that the rapid reduction of during experimental hypercalcaemia is mediated by hypocalcin released from the corpuscles of Stannius and suggest that calcitonin, another putative hypocalcaemic hormone, is not involved. The results are discussed with respect to the relative importance of hypocalcin and calcitonin as hypocalcaemic hormones in fish.
Photosensitive and Photostable Pigments in the Retinae of Old World Monkeys
Authors: Bowmaker J. K. , Astell Susan , Hunt D. M. , Mollon J. D. 
Published: April 2021

ABSTRACTMicrospectrophotometric measurements of retinal receptors are reported for eight species of Old World monkey. Although the animals vary greatly in size, colourings and habitat, they all appear to be trichromats and the peak sensitivities of their cones invariably lie near 430, 535 and 565 nm. This consistent pattern contrasts with the results reported earlier for New World monkeys and with the results reported here for Tupaia glis. The trichromacy of frugivorous catarrhine monkeys may have co-evolved with a particular class of coloured fruit.Short-wave cones were rare in all species. The ratio of the numbers of middle-wave and long-wave cones varied between individual animals, but had an overall value close to unity.In the case of all the species examined here, we have recorded a photostable pigment in the inner segments of rods and cones. The latter pigment has a peak sensitivity close to 420 nm and an absorbance spectrum that is narrower than that of a photosensitive visual pigment.
The Kinematics and Performance of the Escape Response in the Angelfish(Pterophyllum Eimekei)
Authors: Domenici Paolo , Blake Robert W. 
Published: April 2021

ABSTRACTThe kinematics of turning manoeuvres and the distance-time performance in escape responses of startled angelfish (Pterophyllum eimekei) are investigated employing high-speed cinematography (400Hz). All escape responses observed are C-type fast-starts, in which the fish assumes a C shape at the end of the initial body contraction (stage 1). Kinematic analysis of the subsequent stage (stage 2) allows the response to be classified into two types: single bend (SB), in which the tail does not recoil completely after the formation of the C, and double bend (DB), in which it does.The two types of response have different total escape angles (measured from the subsequent positions of the centre of mass, SB 120·0°; DB 73·3°, P&lt;0·005), different stage 2 turning angles (in the same direction as stage 1 for SB, 11·0°; in the direction opposite to stage 1 for DB, –21·9°: P&lt;0·0005) and different maximum angular velocities in the direction opposite to the initial one (SB –8·08 rads−1; DB –56.62rads−1: P&lt;0·001). There are no significant differences in stage 1 kinematics for the two types of escape. Stage 1 turning angle is linearly correlated to stage 2 turning angle for DB only (P&lt;0·0l; r2=0·60) and to total escape angle for both types of response (P&lt;0·000l; r2=0·80). Stage 1 duration is linearly correlated to stage 1 turning angle (P&lt;0.0001; r2=0.83) and to total escape angle (P&lt;0·0001; =0·72) for both types of escape.Distance-time performance is also different in the two response types, mainly because of differences in stage 2 (maximum velocity for SB 0&lt;99ms−1; maximum velocity for DB 1·53ms−1: maximum acceleration for SB 34&lt;1ms−2; maximum acceleration for DB 74&lt;7 ms−2: P&lt;0·000l in both cases). As a result, there are significant differences in the performance throughout the whole response (maximum velocity 1&lt;02 ms−1 and 1&lt;53 ms−1 for SB and DB fast-starts, respectively; maximum acceleration 63&lt;2 ms−2 and 91&lt;9 ms−2 for SB and DB fast-starts, respectively) as well as within a fixed time (0&lt;03 s). Overall, higher distance-time performances associated with smaller angles of turn are found in DB than in SB responses. Comparison with previous studies reveals that angelfish have a good fast-start performance despite specializations for low-speed swimming. In addition, the angelfish turning radius (0·065 ±0·0063L, where L is body length; mean±2s.E.) is lower than that previously reported for any fish.
Proton-Equivalent Ion Transfer inSipunculus Nudusas a Function of Ambient Oxygen Tension: Relationships With Energy Metabolism
Authors: Pörtner H. O. , Andersen N. A. , Heisler N. 
Published: April 2021

ABSTRACTProton-equivalent ion transfer processes between animals and ambient water were determined under normoxic control conditions during anaerobiosis and the subsequent recovery period in the marine worm Sipunculus nudus L. During anaerobiosis and recovery, transepithelial H+-equivalent ion transfer was generally correlated with changes in extracellular pH, with some disparities in ‘spring’ animals. The typical initial alkalosis induced by phosphagen cleavage during early anaerobiosis was reflected by a loss of basic equivalents. The acidosis, which developed later, reflecting production of acidic metabolic intermediates, resulted in a relatively small net extrusion of protons into the water. The coelomic acidosis during recovery was greatly exaggerated by the release of protons during phosphagen repletion and by the considerable elevation of after normoxia had been reattained. The acidosis stimulated the net release of H+ to the water at a rate several times higher than that during anaerobiosis. The efficient transfer of protons from the body fluids to the environmental water during recovery facilitated normalization of coelomic pH, long before protons dissociated from the large amounts of organic acids produced as anaerobic intermediates could be removed from the body fluids by metabolism.Although the transfer of net H+ equivalents to the water coincided with coelomic acidosis, the rates of transfer during different periods of the experiment were primarily correlated with overall metabolic rate. Low net proton transfer rates associated with anaerobiosis were not sufficient to maintain acid-base parameters typical for normoxia, whereas re-establishment of aerobic conditions facilitated a greatly increased transepithelial H+ transfer rate. These data suggest that the transfer capacity of the energy-consuming translocation mechanism may primarily be determined by the rate of metabolic turnover and, accordingly, by the amount of available energy.
Receptive Fields and Properties of A New Cluster Of Mechanoreceptor Neurons Innervating the Mantle Region and the Branchial Cavity of the Marine MolluskAplysia California
Authors: Dubuc Bruno , Castellucci Vincent F. 
Published: April 2021

ABSTRACTThe rostral LE cluster (rLE) is a new set of mechanoreceptor neurons of the abdominal ganglion innervating the mantle area, the branchial cavity, the gill and the siphon of the marine mollusk Aplysia californica Cooper. We have compared the organization of rLE cell receptive fields with that of three other clusters of sensory neurons in the abdominal ganglion (LE, RE and RF) that we have reanalysed. There is extensive overlap of receptive fields from the four populations of sensory cells, and the most exposed areas of the mantle are the most densely innervated. The sensory threshold is similar for all groups. The action potentials of the LE, rLE and RE neurons are broadened by serotonin and the peptide SCPB and narrowed by dopamine and FMRFamide. The RF group does not show the same kind of sensitivity to these neuromodulators. The synaptic outputs of the LE and rLE neurons undergo similar synaptic depression and homosynaptic and heterosynaptic facilitation. We estimate that 100 mechanoreceptor neurons innervate the entire mantle and siphon skin, gill and branchial cavity of Aplysia. The degree of their convergence onto various interneurons and motor neurons mediating the gill- and siphon-withdrawal reflex and other reflexes is under investigation.
Defense Mechanisms in Notaspid Snails: Acid Humor and Evasiveness
Authors: Gillette Rhanor , Saeki Mayuko , Huang Rong-Chi 
Published: April 2021

ABSTRACTNotaspid snails are known for their defensive skin secretion of sulfuric acid (pH 1–2) in response to noxious stimuli. We observed acid secretion and behavior in five notaspid species, and studied them in detail in Pleurobranchaea californica. All species secreted acid in response to skin abrasion or compression. Moreover, all species showed stereotypic avoidance behavior to acidified sea water less acidic (pH2–3) then their own secretions. In Pleurobranchaea, secretion could also be stimulated by dilute solutions of taurine, 10−5–10−2moll−1. Secretion began at the stimulated region and spread slowly for about a minute following stimulation. Local contraction and transient edema of the skin were associated with acid secretion. In de-ganglionated preparations secretion could be caused by orthodromic stimulation of body wall nerves, by mechanical stimulation or by taurine.These data suggest that acid secretion is a positive feedback process modulated by inhibitory paths and coordinated by both central and peripheral nervous systems. A picture emerges of a defensive secretory response that provides an additional noxious stimulus initiating or potentiating avoidance behavior. The data also suggest a potential role for taurine release from injured tissue and the existence of specific nociceptive neural pathways regulating complex behavior. In addition to deterring extraspecific predation, acid secretion could regulate interactions between animals of the same species.