bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Vapour Absorption in Terrestrial Isopods
Authors: Wright Jonathan C. , Machin John 
Published: April 2021

ABSTRACT
Continuous and intermittent gravimetric measurements have identified active water vapour absorption (WVA) in three species of terrestrial Isopoda. Water activity thresholds for uptake lie in the range 0.92–0.95. Above the threshold, WVA shows non-saturated kinetics; the rectum apparently serves as a supplementary avenue for fluid resorption during rapid uptake. Standardized uptake fluxes, corrected for vapour pressure deficit, can be varied, allowing animals to balance water losses accurately over long periods.
Blocking experiments have localised the ventral pleon as the uptake site. The pleopods display ventilatory cycling during WVA. Cycle frequency increases with humidity, compensating for changes in activity deficit between uptake fluid and air, and allowing uptake rate to be maximised. Freezing-point depression studies reveal hyperosmotic fluid in the ventral pleon. Osmolalities are compatible with prior uptake rates of the specimens studied.
WVA would allow terrestrial isopods to regulate their water balance in external activities below the haemolymph activity (approximately 0.99) and above the uptake threshold. Liquid water - an alternative source for hydration - is rapidly absorbed across the hydrophilic cuticle, posing severe danger of drowning.
Foreign Connections are Formed In Vitro by Aplysia Californica Interneurone L10 and Its In Vivo Followers and Non-Followers
Authors: Kleinfeld D. , Parsons T. D. , Raccuia-Behling F. , Salzberg B. M. , Obaid A. L. 
Published: April 2021

ABSTRACT
Aplysia californica interneurone L10 forms a set of presynaptic connections with many postsynaptic ‘follower’ cells in the abdominal ganglion. These followers do not connect back to L10. The present study tests whether the direction and sign of these connections are obligatory and are reconstructed when neuronal processes regenerate in vitro. L10 was co-cultured with one of six different followers and two non-followers. In vitro connections that preserve the sign of those formed in vivo were made by L10 onto neurones L11, L12 and L13. The connections consisted of inhibitory postsynaptic potentials (IPSPs) with characteristic fast and slow components.In vitro connections that did not preserve the sign of connections found in vivo were made by L10 onto R15, R16 and L7. Neurones R15 and R16 receive excitatory inputs from L10 in vivo and L7 receives a dual-action input in vivo, with inhibition followed by excitation. A purely inhibitory connection from L10 was formed in vitro onto all these cells.Connections that have never been observed in vivo in terms of both direction and sign were formed in vitro. Followers L7, L11, L12, L13 and R16 and nonfollower L14A formed novel connections onto L10. All these connections were inhibitory and some were strong. For example, IPSPs with a magnitude of 20 mV were observed in L10 following a single action potential in L13.
Our results show that identified Aplysia neurones can form stereotyped specific connections in vitro. The specificity is different from that in the intact ganglion. The ubiquity of novel connections suggests that restrictions imposed on synapto-genesis in the animal are distinct from those regulating synapse formation in culture.
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTWe 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

ABSTRACT
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

ABSTRACT
Antho-RWamide I (&lt;Glu-Ser-Leu-Arg-Trp-NH2) and Antho-RWamide II (&lt;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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.