bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Osmolality-Sensitive Taurine Channel in Flounder Erythrocytes is Strongly Stimulated by Noradrenaline Under Hypo-Osmotic Conditions
Authors: Thoroed Steinar M. , Soergaard Margrethe , Cragoe Edward J. , Fugelli Kjell 
Published: April 2021

ABSTRACT
Stimulation of flounder erythrocytes by noradrenaline under isosmotic conditions (330 mosmol kg-1) and physiological Na+concentration (113 mmol l-1) caused swelling of the cells. The EC50 of this cell swelling was 0.65 μmol l-1 noradrenaline. The effect of the noradrenaline-induced cell swelling on the taurine channel under isosmotic conditions was negligible. However, when the cells were stimulated by noradrenaline (1.0 μmol l-1) before, simultaneously with or after reduction of osmolality (255 mosmol kg-1), the volume regulatory efflux of taurine mediated by the taurine channel was transiently accelerated. The rate coefficient for taurine efflux was more than four times higher than in osmolality-stimulated cells not exposed to noradrenaline. The present paper deals with the accelerating effect of noradrenaline on the taurine channel under hypo-osmotic conditions and the lack of effect of noradrenaline-induced cell swelling on the channel under iso-osmotic conditions.
Noradrenaline initiated the cell swelling by interacting with β-receptors which appeared to be more related to the mammalian β1-receptors than to the β2-receptors. The receptor interaction activated the adenylate cyclase system and, in the presence of 1.0 μmol l-1 noradrenaline, the cellular cyclic AMP concentration increased about 23 times. Noradrenaline also stimulated the Na+/H+and Cl-/HCO3-antiporters and this affected the extracellular pH as well as the cell volume. Depending on the extracellular Na+concentration, the incubation medium was acidified (113 mmol l-1 Na+) or alkalized (2.7 mmol l-1 Na+). Under these two conditions, the accelerating effects of noradrenaline on the taurine efflux were of similar magnitude. Similar effects on the cell volume, the extracellular pH and the volume regulatory taurine efflux were obtained in the presence of the cyclic AMP analogue 8-bromo-cyclic AMP. Under hypo-osmotic conditions in the absence of noradrenaline, the cellular level of cyclic AMP was not elevated. There was no significant positive correlation between the water content of the cells (cell volume) under different conditions in the presence or absence of noradrenaline and the state of activation of the osmolality-sensitive taurine channel.
We conclude that the mechanism(s) which activate(s) the osmolality-sensitive taurine channel in flounder erythrocytes is transiently and strongly accelerated by noradrenaline, but not triggered by the noradrenaline-induced events. The acceleration does not appear to be due to increased activity of the antiporters, but to increased cellular levels of cyclic AMP.
No Evidence for Polarization Sensitivity in the Pigeon Electroretinogram
Authors: Hzn J. J. Vos , Coemans M. A. J. M. , Nuboer J. F. W. 
Published: April 2021

ABSTRACT
The electroretinographical response to flashes of linearly polarized light directed at the pigeon’s yellow field was compared with that to flashes of unpolarized light. This was carried out for white light and for monochromatic light of various wavelengths, including ultraviolet. In addition, responses to slow rotation of the E-vector of polarized light were measured. Neither the presence or absence of polarization, nor the orientation of the E-vector, influenced any of the electrophysiological variables that were monitored in these experiments.
A Comparison of the Gill Physiology of two Euryhaline Crab Species, Callinectes Sapidus and Callinectes Similis: Energy Production, Transport-Related Enzymes and Osmoregulation as a Function of Acclimation Salinity
Authors: Piller Sabine C. , Henry Raymond P. , Doeller Jeannette E. , Kraus David W. 
Published: April 2021

ABSTRACT
Callinectes sapidus and C. similis co-occur in estuarine waters above 15 ‰ salinity. Callinectes sapidus also inhabits more dilute waters, but C. similis is rarely found below 15 ‰. Previous work suggests that C. sapidus may be a better hyperosmoregulator than C. similis. In this study, energy metabolism and the levels of transport-related enzymes in excised gills were used as indicators of adaptation to low salinity. Oxygen consumption rates and mitochondrial cytochrome content of excised gills increased in both species as acclimation salinity decreased, but to a significantly greater extent in C. similis gills. In addition, C. similis gills showed the same levels of carbonic anhydrase and Na+/K+-ATPase activities and the same degree of enzyme induction during low-salinity adaptation as has been reported for C. sapidus gills. However, hemolymph osmolality and ion concentrations were consistently lower in C. similis at low salinity than in C. sapidus. Therefore, although gills from low-salinity-acclimated C. similis have a higher oxygen consumption rate and more mitochondrial cytochromes than C. sapidus gills and the same level of transport-related enzymes, C. similis cannot homeostatically regulate their hemolymph to the same extent as C. sapidus.
The Homing Behaviour of Cory’S Shearwaters (Calonectris Diomedea) Studied by Means of a Direction Recorder
Authors: Dall’Antonia Luigi , Dall’Antonia Paolo , Benvenuti Silvano , Ioalè Paolo , Massa Bruno , Bonadonna Francesco 
Published: April 2021

ABSTRACT
A direction recorder, which can be carried by a flying bird on its back, has been used for the first time on a wild species. The device can detect and record the direction in which a bird is heading during flight. Cory’s shearwaters (Calonectris diomedea) were moved from their nesting colony to five different sites and fitted with direction recorders, and four homing flight paths were obtained. Our data show that the displaced birds were able to assume and maintain a homeward course soon after release over large areas of open sea, completely devoid of guiding features; topographical elements are, therefore, not necessary for correct orientation.
The Relationship between Plasma Urea Levels and Some Muscle Trimethylamine Levels in Xenopus Laevis: A 31P and 14N Nuclear Magnetic Resonance Study
Authors: Wray Susan , Wilkie D. R. 
Published: April 2021

ABSTRACT
Urea is known to be disruptive to proteins, yet high levels occur in a variety of tissues. It has been suggested that trimethylamines counteract the effects of urea on protein. We have, therefore, directly investigated whether elevating tissue urea levels produces an increase in trimethylamine concentrations by using 31P and 14N nuclear magnetic resonance (NMR) spectroscopy to detect two trimethylamines (glycine betaine and glyceryl-phosphorylcholine) in intact, living gastrocnemius muscle from Xenopus laevis. Xenopus laevis naturally elevates its tissue urea levels under dry conditions. This ability was used to obtain plasma urea levels ranging from 1 to 110 mmol l−1. This procedure did not alter pH or levels of ATP or phosphocreatine in the muscles, but did raise trimethylamine levels. We find that there is a significant relationship between plasma urea concentrations and the trimethylamine levels studied. This relationship was, however, limited to the lower range of urea levels. We propose that other trimethylamines or mechanisms come into play at urea concentrations above 20 mmol l−1.
Effects of Extreme pH on the Physiology of the Australian ‘Yabby’ Cherax Destructor: Acute and Chronic Changes in Haemolymph Oxygen Levels, Oxygen Consumption and Metabolite Levels
Authors: Ellis Bronwyn A. , Morris Stephen 
Published: April 2021

ABSTRACT
Respiration and metabolism of the freshwater crayfish Cherax destructor were investigated with respect to the acidification and alkalization of its environment. Crayfish were exposed for up to 504 h (21 days) to pH 4.5, pH 7.1 (control) or pH 8.0 water and oxygen consumption rate, haemolymph oxygen transport and haemolymph glucose and lactate concentrations were determined. The effect of reducing environmental [Ca2+] in acid water from 500 to 50 μmol l−1 was also examined.
In acid water (500 μmol l−1 Ca2+), oxygen uptake by Cherax was reduced by 79 % after 504 h (21 days) compared with ‘control’ animals (pH 7.1, 500 μmol l−1 Ca2+). Haemolymph lactate concentration (mean 0.6 mmol l−1) remained constant, indicating that anaerobiosis was not important, while glucose concentrations were regulated within the range of control values (0.32±0.01 mmol l−1). The arterial-venous CO2 difference of Cherax haemolymph decreased after 288 h and increased from 11.1±0.5 mmHg to 42.4±1.0 mmHg between 96 h and 288 h. Decreased oxygen uptake and delivery without compensatory increases in anaerobiosis or glucose levels describe a hypometabolic response to low pH.
The hypometabolic response of Cherax was greater in alkaline water as shown by a 53 % reduction in O2 uptake rate compared with a 44 % reduction in acid-exposed (500 μmol l−1 Ca2+) animals after 96 h. This decrease in of alkaline-exposed animals was correlated with decreased haemolymph glucose levels (from 0.32±0.01 at 0 h to 0.06±0.01 mmol l−1 at 96 h).
Lowering the [Ca2+] of the water both increased the magnitude of the effects of acid exposure and elicited further changes in haemolymph oxygen transport. The maintenance of high haemolymph during pH stress appears to reduce the involvement of haemocyanin, since this promotes decreased a–v . Hypometabolism probably permits Cherax to conserve resources that might otherwise be used, however, for growth and reproduction. The implications for the fitness of the animal are discussed.
Rhythmic Patterns in the Thoracic Nerve Cord of the Stick Insect Induced by Pilocarpine
Authors: Büschges Ansgar , Schmitz Josef , Bässler Ulrich 
Published: April 2021

ABSTRACT
Bath application of the muscarinic agonist pilocarpine onto the deafferented stick insect thoracic nerve cord induced long-lasting rhythmic activity in leg motoneurones. Rhythmicity was induced at concentrations as low as 1X10−4 mol l−1 pilocarpine. The most stable rhythms were reliably elicited at concentrations from 2X10−3 mol l−1 to 5×10−3 mol l−1. Rhythmicity could be completely abolished by application of atropine. The rhythm in antagonistic motoneurone pools of the three proximal leg joints, the subcoxal, the coxo-trochanteral (CT) and the femoro-tibial (FT), was strictly alternating. In the subcoxal motoneurones, the rhythm was characterised by the retractor burst duration being correlated with cycle period, whereas the protractor burst duration was almost independent of it. The cycle periods of the rhythms in the subcoxal and CT motoneurone pools were in a similar range for a given preparation. In contrast, the rhythm exhibited by motoneurones supplying the FT joint often had about half the duration. The pilocarpine-induced rhythm was generated independently in each hemiganglion. There was no strict intersegmental coupling, although the protractor motoneurone pools of the three thoracic ganglia tended to be active in phase.
There was no stereotyped cycle-to-cycle coupling in the activities of the motoneurone pools of the subcoxal joint, the CT joint and the FT joint in an isolated mesothoracic ganglion. However, three distinct ‘spontaneous, recurrent patterns’ (SRPs) of motoneuronal activity were reliably generated. Within each pattern, there was strong coupling of the activity of the motoneurone pools. The SRPs resembled the motor output during step-phase transitions in walking: for example, the most often generated SRP (SRP1) was exclusively exhibited coincident with a burst of the fast depressor trochanteris motoneurone. During this burst, there was a switch from subcoxal protractor to retractor activity after a constant latency. The activity of the FT joint extensor motoneurones was strongly decreased during SRP1. SRP1 thus qualitatively resembled the motoneuronal activity during the transition from swing to stance of the middle legs in forward walking. Hence, we refer to SRPs as ‘fictive step-phase transitions’.
In intact, restrained animals, application of pilocarpine also induced alternating activity in antagonistic motoneurone pools supplying the proximal leg joints. However, there were marked differences from the deafferented preparation. For example, SRP1 was not generated in the latter situation. However, if the ipsilateral main leg nerve was cut, SRP1s reliably occurred. Our results on the rhythmicity in leg motoneurone pools of deafferented preparations demonstrate central coupling in the activity of the leg motoneurones that might be incorporated into the generation of locomotion in vivo.
Basolateral Transport of Taurine in Epithelial Cells of Isolated, Perfused Mytilus Californianus Gills
Authors: Neufeld Douglas S. , Wright Stephen H. 
Published: April 2021

ABSTRACT
We found that the basolateral surface of the gill epithelium of the marine mussel Mytilus californianus possesses a carrier-mediated process capable of concentrating taurine within epithelial cells. We used retrograde perfusion of gill sections to demonstrate the kinetics, specificity and ion-dependence of taurine transport. [3H]taurine was concentrated relative to a space marker ([14C]mannitol); this accumulation was blocked by the inclusion of 10 mmol l−1 unlabeled taurine in the perfusate. The drop in [3H]taurine uptake at increasing concentrations of unlabeled taurine was fitted to Michaelis–Menten kinetics and indicated a basolateral process with a taurine concentration at which transport is half-maximal (Kt) of 35.3 μmol l−1 and a maximal flux (Jmax) of 0.35 μmol g−1 wet mass h−1. Taurine accumulation on the apical surface had a higher affinity (Kt=9.5 μmol l−1) and a higher maximum rate of transport (Jmax=1.23 μmol g−1 h−1). Basolateral transport was inhibited by inclusion in the perfusate of 1 mmol l−1 of another β-amino acid (β-alanine), but not by inclusion of βalanine, glutamic acid or betaine. The dependence of basolateral taurine transport on Na+ (when replaced with N-methyl-D-glucamine) was sigmoidal with an apparent Hill coefficient of 2.3, indicating that more than one Na+ is necessary for the transport of each taurine molecule. Complete substitution of Cl− in bathing media reduced taurine accumulation by 90 % and 70 % on the apical and basolateral surfaces, respectively. Taurine accumulation on both surfaces was reduced by only 20 % when Cl− was reduced from 496 to 73 mmol l−1, suggesting that taurine uptake is not significantly influenced by the changes in Cl− concentration accompanying the salinity fluctuations normally encountered by mussels. We estimate that the various Na+ and Cl− gradients naturally encountered by epithelial cells are capable of providing ample energy to maintain a high intracellular concentration of taurine. We suggest that the ability of epithelial cells to accumulate taurine across the basolateral surface from the hemolymph plays a significant role in the intracellular regulation of this important osmolyte and may effect osmolality-dependent changes in the intracellular concentration of taurine.
Echolocation Call Structure and Intensity in Five Species of Insectivorous Bats
Authors: Waters Dean A. , Jones Gareth 
Published: April 2021

ABSTRACT
Echolocation call intensity was measured in the laboratory for five species of British insectivorous bats in free flight and in the hand. All species showed similar call intensities of between 80 and 90 dB peSPL (peak equivalent SPL) at 1 m during flight except Plecotus auritus, whose call intensity was between 68 and 77 dB peSPL at 1 m. Calls from stationary bats were about 13 dB less intense than calls during flight. A method is proposed to measure the root mean square (rms) amplitude of echolocation calls and, hence, to calculate the energy flux density of the call.
The constant−frequency calls of Rhinolophus hipposideros have energy flux densities approximately ten times higher than those of bats using frequency−modulated calls as a result of their longer durations and lower crest factors. It is argued that the low−intensity calls of P. auritus allow it to approach tympanate moths more closely before triggering their escape response.
Glucose Transport in Carp Erythrocytes: Individual Variation and Effects of Osmotic Swelling, Extracellular pH and Catecholamines
Authors: Tiihonen Kirsti , Nikinmaa Mikko , Lappivaara Jarmo 
Published: April 2021

ABSTRACT
The characteristics of the uptake of 3-O-methyl-D-glucose (3-OMG) by carp (Cyprinus carpio) erythrocytes were studied in vitro with tracer methods. There is large individual variation in the permeability of the carp erythrocyte membrane to 3-OMG. Although transport is inhibited by cytochalasin B and phloretin, the lack of saturation kinetics for transport in a physiologically relevant concentration range suggests either that a glucose transporter does not exist or that its affinity for glucose is extremely low. The marked increase in transport after osmotic swelling and the inhibition of swelling-induced glucose transport by cytochalasin B suggest that the glucose transport pathway in carp erythrocytes (both in isotonic and hypotonic conditions) may be similar to the volume-activated channel described for flounder erythrocytes. 3-OMG transport across the carp erythrocyte membrane is increased by catecholamines by a mechanism independent of the catecholamine-induced cell swelling.
Neuromodulation by 5-Hydroxytryptamine in the Antennal Lobe of the Sphinx Moth Manduca Sexta
Authors: Kloppenburg Peter , Hildebrand John G. 
Published: April 2021

ABSTRACT
Using intracellular recording techniques, we have begun to examine the effects of 5-hydroxytryptamine (5-HT) on antennal-lobe (AL) neurones in the brain of the adult moth Manduca sexta. 5-HT modulated the responses of local interneurones and projection neurones, which were recognized on the basis of well-established electrophysiological criteria, to primary synaptic input elicited by electrical stimulation of the ipsilateral antennal nerve. 5-HT applied at low concentration (10−8 mol l-1) reduced the excitatory responses evoked by electrical stimulation of the antennal nerve, whereas at high concentration (10−4 mol l-1), 5-HT enhanced the responses. At 10−4 mol l-1, 5-HT increased cell input resistance, led to broadening of action potentials and caused increased cell excitability in many AL neurones.
Modulatory Effects of 5-Hydroxytryptamine on Voltage-Activated Currents in Cultured Antennal Lobe Neurones of the Sphinx Moth Manduca Sexta
Authors: Mercer Alison R. , Hayashi Jon H. , Hildebrand John G. 
Published: April 2021

ABSTRACT
The modulatory effects of 5-hydroxytryptamine (5-HT or serotonin) on voltage-gated currents in central olfactory neurones of the moth Manduca sexta have been examined in vitro using whole-cell patch-clamp recording techniques. Central olfactory neurones were dissociated from the antennal lobes of animals at stage 5 of the 18 stages of metamorphic adult development. The modulatory actions of 5-HT on voltage-activated ionic currents were examined in a subset of morphologically identifiable antennal lobe neurones maintained for 2 weeks in primary cell culture. 5-HT caused reversible reduction of both a rapidly activating A-type K+ current and a relatively slowly activating K+ current resembling a delayed rectifier-type conductance. 5-HT also reduced the magnitude of voltage-activated Ca2+ influx in these cells. The functional significance of 5-HT-modulation of central neurones is discussed.
Moving Cheaply: Energetics of Walking in the African Elephant
Authors: Langman V. A. , Roberts T. J. , Black J. , Maloiy G. M. O. , Heglund N. C. , Weber J.-M. , Kram R. , Taylor C. R. 
Published: April 2021

ABSTRACT
Large animals have a much better fuel economy than small ones, both when they rest and when they run. At rest, each gram of tissue of the largest land animal, the African elephant, consumes metabolic energy at 1/20 the rate of a mouse; using existing allometric relationships, we calculate that it should be able to carry 1 g of its tissue (or a load) for 1 km at 1/40 the cost for a mouse. These relationships between energetics and size are so consistent that they have been characterized as biological laws. The elephant has massive legs and lumbers along awkwardly, suggesting that it might expend more energy to move about than other animals. We find, however, that its energetic cost of locomotion is predicted remarkably well by the allometric relationships and is the lowest recorded for any living land animal.
Exotic Collagen Gradients in the Byssus of the Mussel Mytilus Edulis
Authors: Qin Xiaoxia , Waite J. Herbert 
Published: April 2021

ABSTRACT
Byssal threads of the common mussel Mytilus edulis contain collagenous molecules from which two pepsin-resistant fragments have been isolated and characterized. These show a complementary distribution along the length of the thread, such that one predominates distally (Col-D) and the other proximally (Col-P). Both fragments contain three identical a.-like chains with molecular masses of 50 kDa (Col-P) and 60 kDa (Col-D) and have typically collagenous amino acid compositions; for example, 35 % glycine and almost 20 % proline plus 4-trans- hydroxyproline. Hydroxylysine and 3-hydroxyproline were absent. Col-P sequences are also typical of collagen in consisting of tandem repeats of the triplet Gly-X-Y in which X and Y generally represent any amino acid. When proline occurs, it is hydroxylated to 4-trans-hydroxyproline only in the Y position. Seven instances where X is glycine have been detected in Col-P. Specific polyclonal anti-Col antibodies were used to isolate the precursors of Col-P and Col-D from the mussel foot. PreCol-P has a molecular mass of 95 kDa and contains 36 % glycine but a lower imino acid content (13 %). It has a complementary distribution with another precursor (preCol-D, 97 kDa) along the length of the foot. The two precursor compositions suggest resilin-like and silk-fibroin-like structures, respectively, in the noncollagenous domains of preCol-P and preCol-D. Immunogold labelling studies indicate that Col-P is associated with the coiled fibers of the inner core in the proximal portion of the thread, whereas Col-D is localized to the straight fiber bundles of the distal thread as well as to the outer core of the proximal thread.
Bioacoustics of a Miniature Cricket, Cycloptiloides Canariensis (Orthoptera: Gryllidae: Mogoplistinae)
Authors: Dambach Martin , Gras Agnes 
Published: April 2021

ABSTRACT
Male crickets, Cycloptiloides canariensis (body length 5 mm), stridulate with their forewings, which are hidden during rest under the large shield-like pronotum. The wings are opened into the stridulatory position by bending the body between the pro-and mesothorax. The song is a 2 s trill composed on average of 260 pulses (syllables) with a carrier frequency of about 6 kHz. The sound-emitting structures on the wings have been studied by laser vibrometry and particle dusting. A distinct membrane area, which includes a prominent mirror cell, acts as a resonator, amplifying the fundamental carrier frequency produced by interactions between the file and plectrum. The resonating membrane is extremely thin (mirror cell thickness 0.2 µm), which is a physical requirement for maintaining the carrier frequency in the cricket-specific range. Covering the wings after singing is probably an adaptation to protect these delicate structures from damage by mechanical contact during social interactions, especially mating.