bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Sectioning Cranial Nerves IX and X on Cardiovascular and Ventilatory Reflex Responses to Hypoxia and Nacn In Channel Catfish
Authors: Burleson Mark L. , Smatresk Neal J.
Published: April 2021

The afferent pathways mediating cardiovascular and ventilatory hypoxic reflexes were identified in anaesthetized, spontaneously breathing (ASB) channel catfish, Ictalurus punctatus (Rafinesque), by bilateral section of cranial nerve IX and branchial branches of cranial nerve X to the four gill arches (Xb1–Xb4). Cardiovascular and ventilatory responses to hypoxia and NaCN were attenuated by partial denervation of the gills. There were no significant cardiovascular or ventilatory reflex responses to either hypoxia or NaCN after total branchial denervation. This suggests that hypoxic reflexes in channel catfish are mediated by O2-sensitive chemoreceptors located peripherally in the gills and innervated by cranial nerves IX and X.
The Effect of Sampling Rate on the Analysis of Digital Electromyograms from Vertebrate Muscle
Authors: Jayne Bruce C. , Lauder George V. , Reilly Stephen M. , Wainwright Peter C.
Published: April 2021

Quantitative electromyography is a widely used, powerful method for determining in vivo patterns of muscle activity in diverse animal behaviours. Recent increased capabilities of microcomputers have simplified quantification of the variation in the intensity of recruitment during muscle activity, whereas the times of onset and offset of muscle activity have commonly been determined without computers (reviewed in Basmajian and De Luca, 1985; Loeb and Gans, 1986). Such computer-assisted analyses of the intensity of electromyograms (EMGs) have facilitated correlating movements with muscle activity (Gorniak and Gans, 1980; Weijs and Dantuma, 1981; De Gueldre and De Vree, 1988), determining the stereotypy of motor patterns within and among taxa (Lauder and Shaffer, 1985; Reilly and Lauder, 1989; Wainwright, 1989; Wainwright et al. 1989) and clarifying the pattern of recruitment within individual muscles (Carrier, 1989; Hutchinson et al. 1989; Jayne et al. 1990).
Initiation of Swimming Activity in the Medicinal Leech by Glutamate, Quisqualate and Kainate
Authors: Brodfuehrer Peter D. , Cohen Avis H.
Published: April 2021

The excitatory amino acid, glutamate, and several of its agonists are known to produce locomotory activity in the lamprey (Brodin et al. 1985), rat (Kudo and Yamada, 1987) and the embryos and larvae of amphibians (Dale and Roberts, 1984; McClellan and Farel, 1985). It is hypothesized that glutamate acts as a neurotransmitter in the neuronal pathway that generates locomotion in these systems. In both the central and peripheral nervous systems of invertebrates, glutamate also acts as a neurotransmitter. For example, at many crayfish neuromuscular junctions, exogenously applied glutamate mimics the effects of the endogenous excitatory transmitter (Takeuchi and Takeuchi, 1964; Kawagoe et al. 1981). In other invertebrates, application of glutamate to central neurons produces a variety of responses depending on the neuron stimulated and the preparation (Walker et al. 1980; Shinozaki, 1988). However, in no invertebrates has glutamate been implicated in eliciting any centrally generated motor patterns.
Urate Does not Accumulate in the Haemolymph of Exercised Blue Crabs, Calunectes Sapidus
Authors: Lallier François H. , Walsh Patrick J.
Published: April 2021

L-Lactate, the only known anaerobic end-product in decapod crustaceans (Gade, 1983), increases haemocyanin oxygen-affinity (Truchot, 1980; Mangum, 1983; Bridges and Morris, 1986). In exercised blue crabs, Callinectes sapidus, the decrease in haemocyanin oxygen-affinity induced by metabolic acidosis via the Bohr shift was substantially balanced by the opposing effect of L-lactate (Booth et al. 1982). Since this study, Morris et al. (1985) have discovered that urate also enhances haemocyanin oxygen-affinity in the crayfish Austropotamobius pallipes. The importance of urate in regulating oxygen transport during environmental hypoxia has recently been stressed in the crab Carcinus maenas and the prawn Penaeus japonicus (Lallier and Truchot, 1989a,b). Since Callinectes sapidus haemocyanin exhibits a urate effect (De Fur et al. 1990), urate may also play a role during functional anaerobiosis.
Control of Catecholamine ReleaseIn VivoandIn Situin the Atlantic Cod(Gadus Morhua) During Hypoxia
Authors: Perry Steve F. , Fritsche Regina , Kinkead Richard , Nilsson Stefan
Published: April 2021

We have characterized the elevation of circulating catecholamines in the intact Atlantic cod (Gadus morhua) during graded acute (30 min) hypoxia. The potential mechanisms contributing to the mobilization of catecholamines during hypoxia were then assessed in vivo using nerve sectioning and pharmacological techniques and in situ using a perfused head kidney preparation.

Pre-branchial plasma adrenaline concentrations were significantly elevated at all levels of aquatic hypoxia utilised [water PO2 (PwO2) = 10 kPa (75 mmHg), 7.3kPa (55 mmHg) or 5.3 kPa (40mmHg)], whereas noradrenaline levels did not increase significantly in these particular experiments in which PwO2 was lowered gradually over a 30 min period. All subsequent experiments were performed using a more rapid induction of hypoxia to reach a final PwO2 of 5.3 kPa within the first 5-10 min of exposure. Blood withdrawn from pre-branchial (ventral aortic) and post-branchial (dorsal aortic) cannulae after 30 min revealed pronounced reductions in PO2 and O2 content (CO2) as well as elevated pH. These data support the notion that blood acidosis is not a prerequisite for catecholamine mobilization during hypoxia. Bilateral sectioning of spinal nerves 1–4 innervating the head kidney prevented the elevation of noradrenaline during rapidly induced hypoxia, but had no effect on the rise in plasma adrenaline concentration. After each experiment, fish were exposed to air for 3 min to induce severe stress. Plasma catecholamine levels were significantly reduced during stress, suggesting that the sectioning of the spinal nerves to the head kidney was indeed effective. These results indicated that mechanisms other than neural stimulation of head kidney chromaffin tissue were contributing to the rise in plasma adrenaline level during hypoxia. Neuronal overflow into the circulation, however, was an unlikely possibility since the increase of adrenaline could not be prevented by treating denervated fish with bretylium (an inhibitor of catecholamine release from adrenergic nerve terminals). These data suggested a local direct stimulatory effect of blood hypoxaemia on adrenaline release from chromaffin tissue. This hypothesis was confirmed using a blood-perfused head kidney preparation in which hypoxaemia markedly stimulated adrenaline overflow into the effluent blood. Further experiments using a Ringer-perfused head kidney preparation were designed to test the hypothesis that blood catecholamine levels in vivo are, in part, controlled by the concentration of catecholamines in the blood entering the head kidney. The results show conclusively that overflow of a particular catecholamine during cholinergic stimulation of the head kidney is controlled independently by the inflowing concentration of that catecholamine. We suggest that this mechanism of ‘auto-inhibition’ of catecholamine overflow is a functional negative feedback mechanism involved in the control of plasma catecholamine levels in the cod.
Entrainment of the Breathing Rhythm of the Carp by Imposed Oscillation of the Gill Arches
Authors: De Graaf P. J. F. , Roberts B. L.
Published: April 2021

Artificial oscillation imposed onto the gill arches could modify the respiratory rhythm in the carp Cyprinus carpio. The degree of modification depended upon the frequency and amplitude of the applied movement. Oscillation at frequencies close to the spontaneous respiratory rhythm and at amplitudes in the range of 2–3 mm resulted in a cyclic pattern of lengthening and shortening of the breathing cycles. When the gill arches were maximally abducted artificially at the end of inspiration or early in expiration, the breathing cycle was shortened. A slight lengthening occurred when maximal gill arch abduction fell during the second half of expiration or during the first half of inspiration. An increase in oscillation amplitude led to entrainment of ventilation at a one-to-one ratio with the imposed movement. After oscillation stopped an aftereffect was seen. It is argued that gill arch proprioceptors contribute to the observed responses.
EFFECTS OF THREE ANTHOZOAN NEUROPEPTIDES, ANTHO-RWamide I, ANTHO-RWamide II and ANTHO-RFamide, ON SLOW MUSCLES FROM SEA ANEMONES
Authors: McFARLANE Ian D. , Anderson Peter A. V. , Grimmelikhuijzen Cornelis J. P.
Published: April 2021

Antho-RWamide I (<Glu-Ser-Leu-Arg-Trp-NH2) and Antho-RWamide II (<Glu-Gly-Leu-Arg-Trp-NH2), the second and third anthozoan neuropeptides to be identified, both induced slow contractions of several endodermal muscles in four species of sea anemone. In a fifth species, Protanthea simplex, Antho-RWamide II, but not Antho-RWamide I, evoked contractions of body wall muscles. Isolated, trimmed sphincter muscle preparations of Calliactis parasitica contracted at a threshold concentration of 10−9moll−1 Antho-RWamide II. Antho-RWamide II was more potent than Antho-RWamide I. Unlike the responses to Antho-RFamide (the first anthozoan neuropeptide described), these were simple contractions with no change in spontaneous activity. The Antho-RWamides did not excite electrical activity in any of the three known conducting systems (the through-conducting nerve net and the slow systems 1 and 2), indicating that they may be acting directly on endodermal muscles. Application of peptides to smooth muscle cells, isolated from the sphincter of C. parasitica, confirmed that Antho-RWamide I and II act directly on the muscle. We conclude that the Antho-RWamides may be neurotransmitters at some neuromuscular synapses in sea anemones.
Initiation and Modulation of Action Potentials in Salivary Gland Cells of Haementeria Ghilianii by Putative Transmitters and Cyclic Nucleotides
Authors: Wuttke Werner A. , Berry Michael S.
Published: April 2021

The giant salivary cells of Haementeria ghilianii are known to produce Cam-dependent action potentials and to release their secretory products in response to stimulation of the stomatogastric nerve. In this study, the electrophysiological effects of some putative transmitters were examined by perfusion of the gland and two promising candidates were selected for detailed analysis. Acetylcholine (ACh) was the only substance tested which excited the gland cells. It produced a large, Na+-dependent depolarization that elicited 1-3 action potentials and desensitized to about 24% of its maximal value within 2 min. Carbachol, tetramethylammonium and nicotine elicited similar responses to ACh, whereas choline and pilocarpine had negligible effects. The ACh response was completely blocked by d-tubocurarine and strych-nine, and was reduced by tetraethylammonium, hexamethonium and atropine. The receptors, therefore, cannot be clearly distinguished as nicotinic or muscarinic. ACh did not elicit secretion, but this does not necessarily preclude it from acting as a neuroglandular transmitter. 5-Hydroxytryptamine (5-HT) was the only transmitter candidate that elicited secretion, though it did not excite the gland cells. 5-HT produced a subthreshold depolarization and an increase in input resistance. Action potentials, elicited by depolarizing pulses, were increased in amplitude and duration, and showed greatly reduced adaptation. 5-HT potentiated the net inward current, evoked by subthreshold depolarizing pulses, by reducing outward K+ current. The inward current, carried by Ca2+, was not directly affected. In addition, 5-HT increased an inwardly rectifying current, carried by Na+ and K+. All the effects of 5-HT tended to increase cell excitability. Salivary cell responses to 5-HT were reversibly antagonised by methysergide. 10. Responses to ACh or 5-HT were not mimicked by 3’,5’-cyclic guanosine monophosphate, which greatly reduced spike amplitude and excitability. The effects were specific to the 3’,5’ form; 2’,3’-cyclic GMP had no effect. Cyclic GMP dramatically reduced the duration of action potentials that had been artificially prolonged by TEA+ or removal of external Ca2+. Cyclic 3’,5’-adenosine monophosphate and its dibutyryl derivative had little effect on membrane properties. 8-Bromo-cyclic AMP, however, mimicked all the effects of 5-HT. It is thought that 5-HT may exert its actions via cyclic AMP. 12. The possible role of 5-HT in salivary secretion is discussed.
Metabolic Rates at Different Oxygen Levels Determined by Direct and Indirect Calorimetry in the Oxyconformer Sipunculus Nudus
Authors: Hardewig I. , Addink A. D. F. , Grieshaber M. K. , Pörtner H. O. , Van Den Thillart G.
Published: April 2021

Oxygen uptake and the mode of energy production in Sipunculus nudus L. were determined at different oxygen levels by means of direct and indirect calorimetry. Oxygen consumption declined linearly with decreasing ambient . A similar decrease in heat production was observed down to a of 8.66 kPa. At lower oxygen tensions, a discrepancy between aerobic and total heat production indicated the onset of anaerobic metabolism. The occurrence of the critical between 8.66 and 2.66 kPa was confirmed by estimation of anaerobic end products in the body wall musculature. The contributions of aerobic and anaerobic metabolism to total ATP production were determined at a of 2.66 kPa and were found to be 48 and 52 %, respectively. Measured heat dissipation under extreme hypoxia ( nominally zero) (21.5±3.5mJh-1g-1) agreed with the enthalpy changes calculated from the rates of formation of anaerobic end products (17.9±4.7mJh-1g-1). For the sake of redox balance maintenance, saturation of fatty acids was assumed; this would be accompanied by an additional heat production of 3.3mJh-1g-1, so that the total calculated enthalpy change amounted to 21.2mJh-1g-1.
The Shaker and shaking-B genes specify elements in the processing of gustatory information in Drosophila melanogaster
Authors: Balakrishnan Rohini , Rodrigues Veronica
Published: April 2021

Mutations that affect the physiological properties of neurones or the development of neuronal circuits are likely to have profound effects on sensory and motor pathways. We have examined the effects of mutations in two loci -the Shaker complex and shaking-B -on the taste pathway of Drosophila melanogaster Meigen at the behavioural and electrophysiological levels. The Shaker locus encodes a variety of A-type potassium channels that are likely to be tissue-and stage-specific. Flies containing the different Shaker alleles examined exhibit a variety of defects in their gustatory responses to sucrose, NaCl and KCl. The firing patterns of the labellar chemosensory neurones in response to these stimuli are normal. This suggests that the channels encoded by the Shaker locus are probably not involved in taste transduction, but affect central gustatory circuits. The shaking-B locus affects neuronal connectivity, though its molecular nature is unknown. Mutants at this locus show increased thresholds for detection of sucrose and fructose and lack the attraction response to 0.1 mol 1-1 sodium chloride that is exhibited by the wild-type fly.
Negative Pressure Generated by Octopus Suckers: A Study of the Tensile Strength of Water in Nature
Authors: Smith Andrew M.
Published: April 2021

The decrease in hydrostatic pressure generated by octopus suckers adhering to wettable and non-wettable surfaces was measured using a flush-mounted miniature pressure transducer. The cavitation thresholds, or lowest sustainable pressures, of sea water on the same surfaces were also measured and were compared with the pressures generated by octopuses. It is shown that suckers can generate hydrostatic pressures below 0MPa on moderately wettable surfaces. This disproves the commonly repeated assumption that suckers cannot produce pressures below a vacuum and suggests that the importance of suction in attachment mechanisms may have been overlooked. On epoxy, the lowest recorded pressure was —0.168MPa (0.268MPa or 2.66atm below ambient), and the octopus generated negative pressure in 35 % of the pulls that were considered maximal efforts. The suckers never generated negative pressures on non-wettable surfaces. These results are in agreement with the range of pressures that sea water can sustain on the same surfaces. It is suggested, therefore, that cavitation, the failure of water in tension, limits the attachment force of suckers. The difference between the cavitation threshold of water in nature and the cavitation threshold of pure water is discussed.
Water Balance in Flesh Fly Pupae and Water Vapor Absorption Associated with Diapause
Authors: Yoder Jay A. , Denlinger David L.
Published: April 2021

We report the water balance characteristics for diapausing and nondiapausing pupae of the flesh fly Sarcophaga crassipalpis. The challenge of maintaining water balance is particularly acute for pupae that spend 9–10 months in diapause, without access to drinking water. While diapausing pupae can tolerate a loss of up to 24.5% of their total body water content (67.3%), they have also acquired several other physiological attributes that have enhanced their capacity for maintaining water balance. Net transpiration rates for diapausing pupae (0.008 % h-1) are far lower than rates for nondiapausing pupae (0.023 % h-1). In addition, diapausing pupae can counter water loss with their ability to absorb water vapor from lower humidities (approximate water vapor activity, av, 0.58 at 20°C) than can nondiapausing pupae (approximate av0.74 at 20°C). The high critical transition temperature for diapausing pupae (39 °C, compared to 30 °C for nondiapausing pupae) suggests that epicuticular lipids have been modified to restrict water loss during diapause.
Adaptive Modifications in the Flight System of the Locust After the Removal Of Wing Proprioceptors
Authors: Büschges Ansgar , Pearson Keir G.
Published: April 2021

Previous investigations on the flight system of the locust have found that removal of the wing tegulae in mature locusts (Locusta migratoria) results in an immediate change in the flight motor pattern: the wingbeat frequency (WBF) decreases, the interval between the activity of the depressor and the elevator muscles (the D-E interval) increases, and the phase of the elevator activity in the depressor cycle increases. Here we report the results of a detailed quantitative analysis of these changes. We also examined the flight motor pattern for up to 14 days after removal of the tegulae and found that the changes caused by this operation were not permanent. Beginning on the first day after the operation there was a time-dependent recovery of the WBF, the D-E interval and the phase towards their normal values. In about 80% of the experimental animals the flight motor pattern recovered almost completely. Intracellular recordings from elevator motoneurones showed that this recovery was associated with changes in the pattern of excitatory input to these motoneurones. The modification of activity in elevator motoneurones was dependent on afferent input since complete deafferentation of recovered animals resulted in a motor pattern similar to that following deafferentation of normal animals.
African Elephants Respond to Distant Playbacks of Low-Frequency Conspecific Calls
Authors: Langbauer William R. , Payne Katharine B. , Charif Russell A. , Rapaport Lisa , Osborn Ferrel
Published: April 2021

We conducted 58 playback experiments with free-ranging African elephants in Etosha National Park, Namibia, to estimate the distance over which some of their low-frequency calls are audible to other elephants. We broadcast pre-recorded elephant calls to elephants that were 1.2 and 2.0 km from the speaker while making simultaneous video and audio recordings of their behavior. In order to reduce the risk of habituation, we used a variety of call types as stimuli. Elephants responded to playbacks at both 1.2 and 2.0 km, with a full response consisting of the elephant vocalizing, lifting and spreading its ears, remaining motionless in this position (‘freezing’), moving the head from side to side (‘scanning’) and, in the case of males responding to female estrous calls, orienting to and finally walking 1 km or more towards the loudspeaker.

We analyzed our data quantitatively for three of these responses. The occurrence of each behavior increased substantially immediately after playbacks.

Owing to limitations of the loudspeaker, we were only able to broadcast calls at half the sound pressure level (i.e. —6dB) of the strongest calls we have recorded. Since sound at the frequencies of these calls is predicted to suffer from little, if any, attenuation in excess of that caused by spherical spreading, we estimate these calls to be audible to elephants at least 4 km from the source (twice the distance over which we documented responses).

These results are consistent with the hypothesis that the very low-frequency calls of elephants function in communication between individuals and groups of elephants separated by distances of several kilometers.
Compensation of Visually Simulated Wind Drift in the Swarming Flight of the Desert Locust (Schistocerca Gregaria)
Authors: Preiss R. , Gewecke M.
Published: April 2021

The visual control of translatory movements in the desert locust Schistocerca gregaria was investigated under open-loop conditions. When locusts were flown tethered in a wind tunnel, wind drift, visually simulated by ground pattern motion either in line with or transverse to their long body axis, induced a modulation of yaw-torque, thrust and lift correlated with the reversal of the direction of motion. Yaw-torque and thrust responses were independent of each other. Spon-taneous modulation of amplitude and differences in the time course of these responses indicate that a gain control mechanism is involved in the conversion of the visual stimuli to a behavioural response. Two opposing types of response were observed for each flight parameter and they were found equally often. They were elicited by either transverse or longitudinal pattern motion. The polarity of yaw-torque, thrust or lift responses was thus either positively or negatively correlated with the direction of pattern motion and was preserved throughout an experiment or reversed repeatedly. The yaw responses revealed a tendency for locusts to orient either upwind or downwind under the same stimulus situation. Modulations of thrust and lift confirm that locusts compensate for deviations of the retinal image flow from a preferred value by adjusting both air speed and altitude in free flight. They either speed up or slow down and either increase or decrease flight altitude under the same stimulus situation. The visually induced turning tendency often interacts with a variable internal turning tendency. The internal turning tendency might be responsible for the orientation menotactic to wind seen in the field. The threshold of optomotor responses in the visual control of translation is below 0.15°s-1 for both transverse and longitudinal pattern motion, indicating that wind-related orientation can occur at altitudes of several hundred metres. The orientation behaviour of locusts subjected to visually simulated wind drift depended on the transverse and longitudinal components of pattern motion and on internal factors. The observed variability of response is assumed to result from the locust’s ability to modulate independently the gain and sign of the optomotor responses for yaw-torque, thrust and lift.
Gain Control in the Femur–Tibia Feedback System of the Stick Insect
Authors: Kittmann Rolf
Published: April 2021

This paper presents a quantitative description of the variability and the adaptive properties of information processing in the femur-tibia feedback system of the stick insect. The gain of this proprioceptive feedback system is determined by external stimuli changing the behavioural state of the animal and by internal properties that make it dependent on different parameters of the stimulus programme, e.g. stimulus frequency and amplitude, repetition rate and resting pauses.

The gain of the feedback loop in the inactive animal was investigated under open-loop conditions by applying mechanical sine-wave stimuli to the femoral chordotonal organ (fCO). The resistance movement of the tibia caused by these stimuli was measured with a new optoelectronic device.

A large increase or decrease in gain (up to a factor of 50) can be induced by stimulation, but also occurs spontaneously. The system shows habituation and sensitization. The initial gain can be decreased by repetitive sine-wave stimulation of the fCO. Disturbance of the animal (e.g. by tactile stimuli) increases the gain. The gain of the system decreases with increasing stimulus amplitude.

The described nonlinearities form a system which adjusts gain to a value that permits effective feedback and prevents instability. This was verified by closed-loop experiments.
Oxygen Consumption, Carbon Dioxide Production and Enzyme Activities of Isolated Working Octopus Heart
Authors: Agnisola C. , Driedzic W. R. , Foster A. R. , Houlihan D. F. , Stewart J. M.
Published: April 2021

The heart of Octopus vulgaris (Lam.) presents an ideal tissue for in vitro studies. Its performance, when perfused with haemocyanin solutions or blood, closely matches that in vivo in terms of power output (Agnisola and Houlihan, 1991) and the heart tissue is self-perfused so that with each contraction a proportion of the fluid in the lumen passes through the heart wall in a system of blood vessels to produce coronary flow (Houlihan et al. 1987). Comparison of in vitro activity levels of key enzymes from energy-generating pathways (Driedzic et al. 1990) with rates of oxygen consumption of perfused hearts, working at subphysiological levels (Houlihan et al. 1987) suggested that the tissue is fuelled primarily by a glucose-based metabolism. In this experiment, the analysis is refined with the simultaneous measurement of oxygen consumption, carbon dioxide production and enzyme activity levels on the same tissues. Hexokinase activity was determined since it is a good indicator of maximal aerobic glucose use in a variety of muscles (Crabtree and Newsholme, 1972), citrate synthase and cytochrome oxidase activities were measured as markers of aerobic capacity, and 3-hydroxyacyl CoA dehydrogenase activity was assayed as a qualitative index of the capacity to oxidize fatty-acid-derived fuels.
A Motion-Sensitive Visual Descending Neurone in Apis Mellifera Monitoring Translatory Flow-Fields in the Horizontal Plane
Authors: Ibbotson M. R.
Published: April 2021

Behavioural studies in insects have shown that simulated rotations of the visual panorama in the yaw, roll and pitch planes lead to optokinetic responses which, under natural conditions, counteract involuntary rotations of the body and thus maintain a stable visual orientation. Electrophysiological investigations have found neurones that respond selectively to rotatory motion in these planes. This evidence, in conjunction with lesioning and electrical stimulation studies, has led to the hypothesis that these rotation-sensitive neurones control optokinetic responses (for a review, see Hausen and Egelhaaf, 1989). Two other types of visually induced behaviour, landing responses and the control of forward flight speed, rely on the detection of translatory rather than rotatory visual flow-fields. For example, it has been shown that flight speed is controlled in insects by adjusting the power output of the wings such that there is a constant preferred angular velocity of image flow from front to back (progressive motion) over both eyes (Apis mellifera:Esch et al. 1975; Drosophila melanogaster:David, 1982). Similarly, landing responses can be induced in flies by moving visual images progressively over both eyes (Eckert, 1984). In spite of these behavioural data there is little evidence, except for a few preliminary reports (Baader, 1988; Rowell, 1989), of neurones that monitor translatory flow-fields, i.e. cells that are maximally sensitive to motion in the same direction over both eyes and not sensitive (or less sensitive) to rotatory motion.
N-Methyl-D-Aspartate (NMDA) and Non-Nmda Type Glutamate Receptors are Present on Squid Giant Axon Schwann Cells
Authors: Evans Peter D. , Reale Vincenzina , Merzon Rosa Maria , Villegas Jorge
Published: April 2021

The role of the amino acid glutamate in neuronal-glial signalling is becoming increasingly recognised in both vertebrate and invertebrate nervous systems (Barres, 1989). Although the ability of glutamate to depolarize cultured astrocytes has been known for some time (Bowman and Kimelberg, 1984; Kettenmann and Schachner, 1985), there has been a debate over whether this was due to a direct activation of glutamate receptors or resulted from an electrogenic glutamate uptake mechanism (Brew and Attwell, 1987; Cull-Candy et al. 1988). However, recent evidence using patch-clamping techniques suggests the presence of ionic currents activated by glutamate receptors in cultured astrocytes (Sontheimer et al. 1988; Usowicz et al. 1989). Responses to glutamate have also been obtained from glial cells in a number of intact preparations, including the adaxonal glia of the squid giant axon (Villegas, 1978) and the glia of the optic nerve of Necturus maculosa (Tang and Orkand, 1986). The responses of the former preparation (Lieberman et al. 1989) and of the neuropile glia of the leech segmental ganglion (Ballanyi et al. 1989) have been demonstrated to be due to glutamate receptor activation. In all the above studies the glutamate receptors present on glial cells have been demonstrated pharmacologically to belong to the non-NMDA subtype. Here we present evidence, for the first time in any glial preparation, that NMDA type glutamate receptors are present in the adaxonal glial or Schwann cells of the giant axon of the tropical squid Sepioteuthis sepioidea and that they mediate a slow depolarization of these cells. In addition, these Schwann cells also possess a second distinct population of glutamate receptors that mediate rapid signalling responses and are pharmacologically similar to the non-NMDA glutamate receptors described in other glial preparations (Ballanyi et al. 1989; Lieberman et al. 1989; Sontheimer et al. 1988; Usowicz et al. 1989).
Renin, Atrial Natriuretic Peptide and Blood Plasma Ions in Parr and Smolts of Atlantic Salmon Salmo Salar L. and Rainbow Trout Oncorhynchus Mykiss (Walbaum) in Fresh Water and after Short-Term Exposure to Sea Water
Authors: Smith N. F. , Eddy F. B. , Struthers A. D. , Talbot C.
Published: April 2021

Freshwater Atlantic salmon (Salmo salar L.) smolts were abruptly transferred to sea water in May and over 3 days blood plasma ion concentrations were determined together with atrial natriuretic peptide (ANP) and plasma renin activity (PRA) using antibodies raised against human ANP and angiotensin I. Blood plasma Na+ and Cl− levels in smolts increased and, between 24 and 72 h, PRA increased significantly to 0.9ngml−1 h−1, while there was a gradual rise in ANP levels to 10pmoll−1 at 72 h. Similar measurements were made on parr transferred to sea water in September; in these fish Na+ and Cl− levels increased as in smolts, PRA remained unchanged at about 0.6ngml−1h−1 and ANP levels increased significantly to about 20pmoll−1 at 24 and 72 h. After 2h in sea water parr showed wide variability in ANP levels, in keeping with circulatory stress, hypoxia and increased atrial stretching. Parr transferred to sea water in December showed 10w drinking rates of 1.95 ml kg−1 h−1, even after 20 days, compared to a high drinking rate of about 7 ml kg−1 h−1 reported for smolts transferred in May.

Rainbow trout acclimated to sea water for 3 weeks showed elevated levels of both ANP and PRA, similar to values reported for marine species. Freshwater rainbow trout fed a high-salt diet (12 % NaCl) showed significantly elevated levels of ANP compared to fish fed a normal diet (1.5 % NaCl), while PRA levels were depressed, though not significantly.

It is concluded that, in fish acclimating to sea water, ANP is involved in excretion of salt 10ads, while the response to dehydration is activation of the renin-angiotensin system, which is required to initiate drinking. It is suggested that, in freshwater salmonids, as is the case in mammals, ANP and the renin-angiotensin system are antagonistic, but successful acclimation to sea water requires the systems, in alternation with the renin-angiotensin system, to ‘break through’ ANP suppression.
Effect of Environmental Water Salinity on Acid–Base Regulation During Environmental Hypercapnia in the Rainbow Trout (Oncorhynchus Mykiss)
Authors: Iwama George K. , Heisler Norbert
Published: April 2021

Acid-base regulation in rainbow trout acclimated to about 3, 100 and 300mmoll−1 Na+ and Cl−, at constant water [HCO3−], was assessed during 24h of exposure to 1% CO2 and during recovery. The respiratory acidosis induced by a rise in plasma to about 1.15kPa (8.5mmHg, 3mmoll−1), 1.33kPa (10 mmHg, 100 mmol I−1) or 1.5 kPa (11.2 mmHg, 300 mmol I−1) was partially compensated for by accumulation of plasma HCO3−. The degree of pH compensation depended on the salinity of the environmental water, being about 61,82 and 88% at 3, 100 and 300mmoll−1 Na+ and Cl−, respectively. [HCO3−] in animals acclimated to 100 and 300 mmol I−1 rose to higher values than that in fish at 3 mmol I−1.

Plasma [Cl−] decreased during hypercapnia as compared to control concentrations in all groups of fish. Plasma [Na+] rose during the first 8h of hypercapnia in fish acclimated to all three salinities, but recovered towards control values during the remainder of hypercapnia. The rise in plasma [HCO3−] was significantly related to the fall in plasma [Cl−], whereas the changes in plasma [Na+] were unaffected by simultaneous changes in plasma [HCO3−]. Time courses of changes in plasma [Na+] and total ammonia concentration, [Tamm], were similar but in opposite directions.

The transepithelial potential (TEP) of blood relative to water was negative, close to zero and positive, averaging —21, —5.8 and +6.2 mV for fish acclimated to 3, 100 and 300 mmol I−1 Na+, respectively. After initiation of hypercapnia, which caused a quite heterogeneous response among groups, a clear trend towards depolarization was observed during the remainder of hypercapnia.

These results confirm the role of active HCO3−/C1− exchange processes for the compensation of extracellular pH during respiratory acidoses in fish.
Characterization of β-Adrenoreceptors of Rainbow Trout (Oncorhynchus Mykiss) Erythrocytes
Authors: Reid Scott D. , Moon T. W. , Perry Steve F.
Published: April 2021

Although many studies have characterized these receptors according to pharmacological criteria, this work represents only the second direct characterization of the rainbow trout β-adrenergic receptors. Radioligand binding assays using (±)-4-(3-t-butylamino-2-hydroxy-propoxy)-[5,7-3H]benzimidazol-2-one ([3H]CGP 12177) and l-[4,6-propyl 3H]dihydroalprenolol ([3H]DHA) were conducted to determine equilibrium binding times, ligand-receptor dissociation constants (KD) and binding capacities (Bmax). Furthermore, we assessed the influence of erythrocyte handling, suspension medium and endogenous catechol amines on Bmax and KD. Maximal binding was obtained when erythrocytes were handled minimally and maintained suspended in plasma rather than physiological saline. Washing and resuspending the erythrocytes, as well as the transfer of the erythrocytes into saline, significantly impaired apparent radioligand affinity and receptor density. Endogenous catecholamines, at levels considered normal for non-stressed animals, did not interfere with the radioligand binding assays, and thus eliminated the need to wash and resuspend erythrocytes. Based on the binding characteristics after intentional lysis of erythrocytes, it is shown that the total receptor population of trout erythrocytes can be estimated by propranolol-displaceable DHA binding, the density of high-affinity surface receptors can best be determined by isoproterenol-displaceable CGP binding, and the number of receptors located within the erythrocytes can be calculated from the difference between the total receptor density and the number of isoproterenol-displaceable DHA binding sites. Each of these components must be considered when performing radioreceptor assays using these radioligands and this has significant implications for the interpretation of erythrocyte β-adrenoreceptor localization and mobilization.
Circulatory Mechanics in the Toad Bufo Marinus I. Structure and Mechanical Design of the Aorta
Authors: Gibbons Carol A. , Shadwick Robert E.
Published: April 2021

This study describes several important mechanical design features of the aorta of a typical poikilothermic vertebrate. A strong functional similarity to the aorta of mammals is apparent, but some structural and mechanical differences are seen that reflect the lower pressure and simpler haemodynamics of the poikilothermic circulation.

The aorta is highly distensible, resilient and non-linearly elastic, giving it the requisite properties to act as an effective storage element in the arterial circulation. An abrupt transition from high compliance (low elastic modulus) to relatively low compliance (high elastic modulus) takes place at pressures above the resting physiological range of 2-4 kPa. This behaviour reflects the composite nature of the artery wall in which rubbery elastin fibres and relatively rigid collagen fibres are the predominant elements. The longitudinal tethering of the aorta when inflated is due primarily to anisotropy in elastic properties, rather than to links to the axial skeleton by branch vessels or connective tissue. No significant changes in elastic properties or connective tissue content occur along the length of the toad arterial tree, in contrast to the situation in mammals.
The Auditory System of an Atympanate Bushcricket Phasmodes Ranatriformes (Westwood) (Tettigoniidae: Orthoptera)
Authors: Lakes-Harlan Reinhard , Bailey Winston J. , Schikorski Thomas
Published: April 2021

The auditory system of the atympanate tettigoniid Phasmodes ranatriformes has been investigated using anatomical and physiological methods. The prothoracic tracheae show no specialization in terms of an acoustic spiracle, acoustic bullae or an enlargement of the trachea in the proximal tibia. Instead of a true tympanum, a depression with small cuticular protuberances is found on the proximal tibia of the foreleg. The complex tibial organ is formed from the three sensory organs usually found in tettigoniids. The crista acustica consists of about 16–18 receptor cells. Extracellular recordings from the leg nerve reveal sensitive responses to vibrational stimuli (at a threshold comparable to that found in other tettigoniids) only, and not to airborne sounds. The two possibilities either that this animal shows a secondary reduction of the auditory system or that it represents a primitive form are discussed. Developmental data from other tettigoniids seem to confirm the latter hypothesis.
Leg Design In Hexapedal Runners
Authors: Full R. J. , Blickhan R. , Ting L. H.
Published: April 2021

Many-legged animals, such as crabs and cockroaches, utilize whole-body mechanics similar to that observed for running bipeds and trotting quadrupedal mammals. Despite the diversity in morphology, two legs in a quadrupedal mammal, three legs in an insect and four legs in a crab can function in the same way as one leg of a biped during ground contact. To explain how diverse leg designs can result in common whole-body dynamics, we used a miniature force platform to measure the ground reaction forces produced by individual legs of the cockroach Blaberus discoidalis. Hexapedal runners were not like quadrupeds with an additional set of legs. In trotting quadrupedal mammals each leg develops a similar ground reaction force pattern that sums to produce the whole-body pattern. At a constant average velocity, each leg pair of the cockroach was characterized by a unique ground reaction force pattern. The first leg decelerated the center of mass in the horizontal direction, whereas the third leg was used to accelerate the body. The second leg did both, much like legs in bipedal runners and quadrupedal trotters. Vertical force peaks for each leg were equal in magnitude. In general, peak ground reaction force vectors minimized joint moments and muscle forces by being oriented towards the coxal joints, which articulate with the body. Locomotion with a sprawled posture does not necessarily result in large moments around joints. Calculations on B. discoidalis showed that deviations from the minimum moments may be explained by considering the minimization of the summed muscle forces in more than one leg. Production of horizontal forces that account for most of the mechanical energy generated during locomotion can actually reduce total muscle force by directing the ground reaction forces through the leg joints. Whole-body dynamics common to two-, four-, six- and eight-legged runners is produced in six-legged runners by three pairs of legs that differ in orientation with respect to the body, generate unique ground reaction force patterns, but combine to function in the same way as one leg of a biped.
Auditory Interneurones in the Metathoracic Ganglion of the Grasshopper Chorthippus Biguttulus: I. Morphological and Physiological Characterization
Authors: Stumpner Andreas , Ronacher Bernhard
Published: April 2021

Auditory interneurones originating in the metathoracic ganglion of females of the grasshopper Chorthippus biguttulus can be classified as local (SN), bisegmental (BSN), T-shaped (TN) and ascending neurones (AN). A comparison of branching patterns and physiological properties indicates that auditory interneurones of C. biguttulus are homologous with those described for the locust. Eighteen types of auditory neurones are morphologically characterized on the basis of Lucifer Yellow staining. All of them branch bilaterally in the metathoracic ganglion. Smooth dendrites, from which postsynaptic potentials (PSPs) can be recorded, predominate on the side ipsilateral to the soma. If ‘beaded’ branches exist, they predominate contralaterally. The ascending axon runs contralaterally to the soma, except in T-fibres. Auditory receptors respond tonically. The dynamic range of their intensityresponse curve covers 20–25 dB. Local, bisegmental and T-shaped neurones are most sensitive to stimulation ipsilateral to the soma. The responses of SN1 and TNI to white-noise stimuli are similar to those of receptors, while phasic-tonic responses are found in SN4, SN5, SN7 and BSN1. The bisegmental neurones receive side-dependent inhibition that corresponds to a 20-30dB attenuation. One local element (SN6) is predominantly inhibited by acoustic stimuli. Ascending neurones are more sensitive to contralateral stimulation (i.e. on their axon side). Only one of them (AN6) responds tonically to white-noise stimuli at all intensities; others exhibit a tonic discharge only at low or at high intensities. One neurone (AN12) responds with a phasic burst over a wide intensity range. The most directional neurones (AN1, AN2) are excited by contralateral stimuli and (predominantly) inhibited by ipsilateral stimuli. Three ascending neurones (AN13–AN15) are spontaneously active and are inhibited by acoustic stimuli. All auditory interneurones, except SN5, are more sensitive to pure tones below 10 kHz than to ultrasound.
The Function of Spider Coxal Organs: Effects of Feeding and Salt-Loading on Porrhothele Antipodiana (Mygalomorpha: Dipluridae)
Authors: Butt A. G. , Taylor H. H.
Published: April 2021

The contributions to ionic regulation of two putative excretory systems, the gut-derived anal system and the coelomoduct-derived coxal organs, were investigated in Porrhothele antipodiana. Coxal fluid was produced continuously during feeding. The fluid was transported anteriorly from the openings of the coxal organs on the coxae of walking legs 1 and 3, via a cuticular groove on the ventral surface of the cephalothorax, to the pre-oral region. The rate of production (70 μlg−1h−1) and normal composition of the fluid (Na+ 125, K+ 36mmoll−1) could account for the observed loss of Na+ into the prey remains during feeding and their final enrichment with Na+ relative to K+. In normally feeding spiders, coxal fluid was hypo-osmotic to the haemolymph. Salt-loading of the prey induced compensatory changes in both systems. Elevation of the Na+ or K+ content of the prey increased anal fluid excretion, the concentration of the corresponding ion in the stercoral fluid and thus the anal output of that ion. Likewise, dietary Na+-loading increased coxal fluid production and the [Na+] of the coxal fluid. K+-loading of the prey did not induce a regulatory response by the coxal organs. Spiders normally released coxal fluid only during feeding. Spiders that had been fed Na+-loaded prey produced coxal fluid intermittently for several days after the meal. Elevation of haemolymph [Na+] by injection of Na+ into the haemocoel also induced coxal excretion in non-feeding spiders, while having little effect on the volume and composition of the anal urine.

Clearance of inulin by the coxal organs was consistent with fluid production by ultrafiltration. It is concluded that in P. antipodiana both systems contribute importantly to ion and water balance and both contribute to the regulatory response to ion loading.

It is postulated that the coxal organs of P. antipodiana have an additional (perhaps primary) role in the mechanics of prey ingestion. Delivery of coxal fluid to the pre-oral region may facilitate the supply of predigested prey to the sucking stomach and prevent a rise in viscosity of the food by evaporative concentration. An auxiliary role for the anal urine is as a vehicle for nitrogenous excretion.
Arginine Kinase and Creatine Kinase Appear to be Present in the Same Cells of an Echinoderm Muscle
Authors: Ellington W. Ross
Published: April 2021

Phosphagens are phosphorylated guanidine compounds which, via the catalytic action of corresponding phosphagen kinases, function as temporal and possibly spatial ATP buffers (Meyer et al. 1985) in cells capable of dramatic metabolic transitions such as muscle, neurons and spermatozoa. At least eight different phosphagen kinases have been identified and these enzymes are widely distributed throughout the animal kingdom (see excellent reviews by Van Thoai, 1968; Watts, 1968).
Reflex Pathways Responsive to Depression of the Locust Coxotrochanteral Joint
Authors: Skorupski Peter , Hustert Reinhold
Published: April 2021

Resistance reflexes in arthropods are negative feedback reflexes broadly analogous to the vertebrate stretch reflex (Bush, 1962). Such reflexes may well be concerned with the maintenance of stable posture as a prerequisite for motor behaviour. Proprioceptors in the arthropod limb monitoring position and movement include muscle receptor organs and the chordotonal organs (see Mill, 1976, for reviews). In insects, an additional class of joint receptor has been described: the strand receptors (Bräunig and Hustert, 1980; Bräunig et al. 1981; Bräunig, 1982). The cell bodies of strand receptor primary afferent neurones are located within the segmental ganglia rather than at the peripheral sense organ.