bluuebunny/crossref_metadata_2025 huggingface dataset:
Gene-Product Designations for Amino Acid Transporters
Authors: Christensen Halvor N. , Albritton Lorraine M. , Kakuda Donald K. , Macleod Carol L.
Published: April 2021

The molecular cloning of genes that encode amino acid transporters presents the scientific community with the opportunity to name their gene products using a scheme that could usefully recall the well-defined transport system most similar in properties to the newly identified cloned gene product. To avoid the problem of rising confusion, we propose to take advantage of established designation methods that indicate the types of amino acids transported and the co-substrate ion requirement of their transport. The economy obligated by the necessity to keep the number of symbols in a gene name to a minimum will rarely permit a listing of the full range of substrates, since amino acid transport systems have broad substrate specificities with co-substrate requirements that can differ in a substrate-specific manner. Hence, the use of established systems to codify groups of amino acid transport systems, which allow identification of the substrate range by using 1–3 letters, e.g. A, L or even ASC, could be integrated with a system used to indicate the ion-dependence of transport. The discoverers of transporters are mainly proceeding with commendable reserve and are inviting discussion, a desire which this essay urges be facilitated by more formal arrangements for further planning. These discoverers have also shown, along with an expressed desire for guidance, well-advised spontaneity in making reference to the substrate range, two trends that together suggest that a good set of designations can evolve that will be highly descriptive. We propose that this can be accomplished without a struggle to accommodate awkwardly to the requirements of the huge human genome data base cataloging system, nor to any single comprehensive systematic scheme. Instead, a combined scheme that takes into account the biological and biochemical characteristics, as well as the historical designations, of amino acid transport systems, is offered here for evaluation.
Is Walking Costly For Anurans? the Energetic Cost of Walking in the Northern Toad Bufo Boreas Halophilus
Authors: Walton B. Michael , Peterson Charles C. , Bennett Albert F.
Published: April 2021

Locomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. Species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. We tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of Bufo boreas halophilus, a toad that walks, but does not hop. Rates of oxygen consumption during locomotion were measured in an enclosed variable-speed treadmill. The steady-state rate of oxygen consumption increased linearly within a range of sustainable speeds [ (ml O2 g−1 h−1) = 0.93 X speed (km h−1) + 0.28]. The minimum cost of transport, Cmin (the slope of this relationship), varied significantly among individual toads. When expressed in units of oxygen consumed per distance travelled (ml O2 km−1), Cmin scaled isometrically with body mass: Cmin = 0.69mass1.07. Consequently, mass-specific Cmin (ml O2 g−1 km−1) was uncorrelated with body mass. Variation in Cmin was also unrelated to experimental temperature. Mass-specific Cmin estimates were similar to previous allometric predictions for terrestrial animals of similar size, which contrasts with previous findings for another toad species. Maximum rates of oxygen consumption measured in closed, rotating respirometers were significantly higher than the maximum rates achieved on the treadmill, but lower than those measured previously in other Bufo species. Our results indicate that walking is not necessarily a costly gait for toads and that high maximum rates of oxygen consumption are not associated with reliance on walking within the genus Bufo.
Graviresponses in Paramecium Caudatum and Didinium Nasutum Examined Under Varied Hypergravity Conditions
Authors: Bräucker Richard , Machemer-Röhnisch Sigrun , Machemer Hans
Published: April 2021

The swimming behaviours of two species of ciliates characterized by different mechanosensory and ciliary motor properties were investigated under hypergravity up to 5.4 g. The experiments were designed to examine large numbers of cells using video recording, digital data processing and statistics for the documentation of the rates and orientations of swimming. The gravikinetic responses (change in active swimming rates) were calculated from (1) the velocities of vertical swimming in the gravity field, (2) sedimentation of Ni2+ -immobilized cells and (3) the intrinsic rate of propulsion, independent of gravity. Propulsion was determined from the intersection of regression lines of the gravity-dependent upward and downward swimming velocities. The rates of swimming and sedimentation, and consequently the gravikineses, were linear functions of gravitational acceleration. Comparisons of cell populations from different cultures suggest that there is an age-dependent change in gravikinesis. In starved Paramecium caudatum (7-day cultures), the kinetic responses antagonizing sedimentation (negative gravikinesis) increased with acceleration. In Didinium nasutum, negative gravikinesis was documented at 1 g in downward-swimming specimens only, which agrees with the mechanosensory organization of this cell. Hypergravity induced the gravikinesis of Didinium to change sign. In both species, and at all accelerations tested, a neutral gravitaxis was documented. Such behaviour incorporates distinct acceleration-dependent orientational and velocity responses, keeping populations of cells stationary in the gravity field (taxis coefficients close to zero).
Heterothermy, Torpor, Respiratory Gas Exchange, Water Balance and the Effect of Feeding in Gould’s Long-Eared Bat Nyctophilus Gouldi
Authors: Morris Steve , Curtin Alison L. , Thompson Michael B.
Published: April 2021

The effects of temperature and nutritional status on the metabolic rate of Nyctophilus gouldi were examined. Bats fed marked meals first defecated approximately 1.34 h after feeding and were calculated to have a mean retention time of 5.38±0.57 h but to be truly post-absorptive after 9 h. Over the temperature range 1–35°C, the metabolic rate and body temperature (Tb) of fasted bats were extremely labile. Below 30°C, the bats all entered torpor and between 10 and 15°C showed a mean 84% reduction over the maximal . Body temperature was also minimal over this range (Tb=12.5°C, Ta=10–15°C). Both total and dry thermal conductance increased in a curvilinear manner with temperature, total conductance from 3.38±0.65 J g−1 h−1°C−1 at 1°C to 24.25±1.99 J g−1 h−1°C−1 at 35°C (mean ± S.E.M.), while the rate of evaporative water loss increased with Ta by a maximum of 10-fold from 0.21 mg g−1 h−1 at 5°C to 2.69 mg g−1 h−1 at 35°C. Between 10 and 25°C, intermittent respiration characterised by episodic bouts of breathing/gas exchange and periods of apnoea with no measurable occurred. Although the duration of apnoea decreased when temperature was increased, the volume of oxygen taken up in each episode did not change. Mean respiratory exchange ratio (RER) was low (0.64–0.77) in post-absorptive bats, typical of fat utilisation, but during torpor ranged from near 0 to near 2, indicating discontinuous and disproportional gas exchange. Feeding produced a condition of relatively sustained homeothermy and high RER in the bats which persisted for 9 h, after which the N. gouldi became torpid. Immediately after feeding, the of the bats increased fivefold above the post-absorptive level, while the increased by more than eightfold. Similarly, body temperature also increased, declining to torpid values after 9 h. The RER in immediately post-feeding bats was near 1.0 but subsequently declined to near 0.7, indicating a switch from carbohydrate to fat utilisation. Therefore, the N. gouldi were heterothermic, exhibited a highly labile metabolic rate, and rates of heat and water loss, and a Tb which were influenced both by ambient temperature and by nutritional status.
Modulating a Modulator: Biogenic Amines at Subthreshold Levels Potentiate Peptide-Mediated Cardioexcitation of the Heart of the Tobacco Hawkmoth Manduca Sexta
Authors: Prier K. R. , Beckman O. H. , Tublitz N. J.
Published: April 2021

The central nervous system of the moth Manduca sexta contains a group of myoregulatory neuropeptides, the CAPs (Cardioacceleratory Peptides), which cause a physiologically important, dose-dependent increase in heart rate during wing inflation and flight in adult moths. We report here that the response of the adult heart to a subset of the CAPs, the CAP2s, is potentiated nearly twofold in the chronic presence of subthreshold levels of the biogenic amine octopamine or near-threshold levels of the biogenic amine serotonin. Subthreshold levels of the CAP2s fail to alter the response of the heart to octopamine.

We have begun to investigate the molecular mechanisms underlying this potentiation. Previous work on the adult heart has shown that the CAP2s act through an inositol-1,4,5-trisphosphate second-messenger system. Here, we demonstrate that the cardioexcitatory effects of the two amines, in contrast to those of the CAP2s, are both mediated by cyclic AMP. Application to the heart of either 10−5 mol l−1 octopamine or 10−6 mol l−1 serotonin elicits a threefold increase in intracellular cyclic AMP levels. The CAP2s have no effect on cyclic AMP levels in the heart. These results illustrate a mechanism by which the effectiveness of a neurohormone can be increased with minimal cost to the animal. In Manduca sexta, subthreshold levels of octopamine are found in the haemolymph during wing inflation and flight. Thus, it is possible that octopamine up-regulates the effects of CAP2 via a cyclic-AMP-dependent mechanism during these activities.
The Dorsal Giant Interneurons Mediate Evasive Behavior in Flying Cockroaches
Authors: Libersat Frederic
Published: April 2021

Cockroaches escape from terrestrial predators by making an evasive turn and running away (Camhi, 1984). The air displacement produced by the predator’s strike is sensed by wind-sensitive receptors on the cerci, two posterior antenna-like organs. These receptors excite two distinct populations of giant interneurons, the ventral giant interneurons (vGIs) and the dorsal giant interneurons (dGIs), in the last abdominal ganglion of the nerve cord (Camhi, 1984). The vGIs are known to control the direction of the escape turn when the animal is on the ground (Camhi, 1988; Ritzmann, 1993; Comer and Dowd, 1993; Liebenthal et al. 1994), while the dGIs are known to initiate and maintain flight (Ritzmann et al. 1982; Libersat et al. 1989; Libersat, 1992). Since cockroaches are not equipped with an ultrasonic hearing sense (Yager and Scaffidi, 1993) and consequently do not respond to ultrasound with escape maneuvers, as many other insects do (Hoy et al. 1989; Libersat and Hoy, 1991), it is reasonable to envisage that, while flying, cockroaches may recruit their wind escape circuit to evade aerial predators such as bats. Indeed, recently Ganihar et al. (1994) have shown that flying cockroaches produce various flight maneuvers that should cause an evasive turn away from a wind stimulus. Such flight maneuvers are not produced after cercal ablation. The most likely candidates to mediate these evasive flying maneuvers are the dGIs, because the wind sensitivity of the vGIs is greatly reduced during flight (Libersat et al. 1989; Libersat, 1992). In contrast, the dGIs retain their wind sensitivity during flight (Libersat, 1992) and also they respond in a directionally sensitive manner to a wind puff delivered from the side (Ganihar et al. 1994). In this study, the possibility that the dGIs mediate evasive flying maneuvers was investigated by stimulating individual identified dGIs during flight and measuring the asymmetrical responses in a pair of left and right flight depressor muscles, the subalars of the metathoracic wings.
Spiking Induced By Cooling In The Myocardium Of The Lobster Panulirus Japonicus
Authors: Kuramoto T.
Published: April 2021

The heart rate of crustaceans changes with variations in ambient temperature within the normal environmental range (Maynard, 1960). The temperature coefficient (Q10) of the heart rate of crabs over the range 4–19°C is about 2 (Florey and Kriebel, 1974). There are few studies of the heart response to a rapid change in temperature, although aquatic crustaceans often meet with warm or cold water masses (Spaargaren and Achituv, 1977). Electromechanical coupling of muscle fibres becomes less effective with decreasing temperature (Dudel and Ruedel, 1968), but a mechanism has been described that compensates for the tonus effect during leg muscle activity (Fischer and Florey, 1981). Compensatory mechanisms may also exist for heart muscle, and I have recently found that myocardial cells of a marine lobster begin to produce large action potentials in response to cooling. Lobster myocardial fibres develop tension in response to excitatory junction potentials (EJPs) generated by impulse activity of motor neurones in the cardiac ganglion (Van der Kloot, 1970; Anderson and Cooke, 1971; Kuramoto and Kuwasawa, 1980; Kuramoto and Ebara, 1984a). The heart tension produced is fed back to the cardiac ganglion because the cardiac neurones are sensitive to filling pressure (Maynard, 1960; Kuramoto and Ebara, 1984a, 1985, 1988, 1991). Thus, the responses of the isolated heart to cooling will result from the combined activities of the cardiac ganglion and the muscle cells. This report focuses on the development of a spiking response by the myocardial cells when the heart is cooled. The spikes produced correspond to enhanced contractions of the myocardium, suggesting that the myocardial cells may use this as a mechanism to compensate for the reduced efficacy of excitation–contraction coupling that occurs with falling temperature.
The MalpighianC Tubules Of Drosophila Melanogaster: A Novel Phenotype For Studies Of Fluid Secretion And Its Control
Authors: Dow Julian A. T. , Maddrell Simon H. P. , Görtz Andreas , Skaer Nick J. V. , Brogan Scott , Kaiser Kim
Published: April 2021

The insect renal (Malpighian) tubule has long been a model system for the study of fluid secretion and its neurohormonal control (Maddrell, 1981; Maddrell and O’Donnell, 1992). Classical physiology suggests a model for tubular secretion of iso-osmotic fluid in most insects, in which ions are thought to enter basally either through a series of ion channels (Na+, K+ and Cl−) or through a bumetanide-sensitive Na+/K+/2Cl− cotransport. Apical fluxes are energised by a plasma-membrane H+-pumping V-ATPase, driving secretion of Na+ or K+ through one or more exchangers, at least one of which is amiloride-sensitive and appears to be closely similar to the Na+/H+ exchanger of vertebrates (Maddrell and O’Donnell, 1992). Cl− follows passively, perhaps through apical Cl− channels. Water follows the major ions, and haemolymph solutes diffuse across the tubule wall passively via a paracellular route. There are also transcellular active transport processes for certain metabolites or toxins, such as acylamides (Maddrell et al. 1974) and plant alkaloids (Maddrell, 1976; O’Donnell et al. 1983).
Periodic Air-Breathing Behaviour In A Primitive Fish Revealed By Spectral Analysis
Authors: Hedrick Michael S. , Katz Stephen L. , Jones David R.
Published: April 2021

The ventilatory patterns of air-breathing fish are commonly described as ‘arrhythmic’ or ‘irregular’ because the variable periods of breath-holding are punctuated by seemingly unpredictable air-breathing events (see Shelton et al. 1986). This apparent arrhythmicity contrasts with the perceived periodism or regularity in the gill ventilation patterns of some fish and with lung ventilation in birds and mammals. In this sense, periodism refers to behaviour that occurs with a definite, recurring interval (Bendat and Piersol, 1986). The characterisation of aerial ventilation patterns in fish as ‘aperiodic’ has been generally accepted on the basis of qualitative examination and it remains to be validated with rigorous testing.
The Effects of Branchial Chloride Cell Proliferation on Respiratory Function in the Rainbow Trout Oncorhynchus Mykiss
Authors: Bindon Shawn D. , Gilmour Kathleen M. , Fenwick James C. , Perry Steve F.
Published: April 2021

The objectives of this study were to induce chloride cell (CC) proliferation on the gill lamellae of rainbow trout Oncorhynchus mykiss and to evaluate the consequences for respiratory function. Chronic elevation of hormone levels was used to induce CC proliferation; fish were injected with a combination of cortisol (8 mg kg−1 intramuscularly every day for 10 days) and ovine growth hormone (2 mg kg−1 intraperitoneally every second day for 10 days). The extent of CC proliferation was quantified using scanning electron microscopy and a two-dimensional analysis. An extracorporeal preparation in combination with environmental hypoxia was used to assess the effects of CC proliferation on respiratory function. Arterial blood was routed from the coeliac artery through an external circuit in which pH (pHa), partial pressure of oxygen and partial pressure of carbon dioxide were monitored continuously. Environmental hypoxia was imposed by gassing a water equilibration column supplying the experimental chamber with N2.

The hormone treatment increased the average CC surface area by 2.7-fold and CC density by 2.2-fold; the combined effect was a fivefold increase in CC fractional area. While the values of hormone-treated and control fish were similar at >12.0 kPa, the arterial O2 tensions of treated fish were significantly lower than those of the control group for ⩽12.0 kPa. In comparison with control fish at all environmental O2 tensions, the hormone-treated fish exhibited elevated values and a significant acidosis. The effects of CC proliferation on blood gas variables in hormone-treated fish were accompanied by a significantly elevated ventilation amplitude and a lowered ventilation frequency.

The results of this study demonstrated (i) that impairment of respiratory gas transfer coincides with CC proliferation, (ii) that O2 and CO2 transfer are influenced differently and (iii) that partial compensation is achieved through physiological adjustments.
The Neural Control of Egg-Laying Behaviour in the Pond Snail Lymnaea Stagnalis: Motor Control of Shell Turning
Authors: Hermann P. M. , Maat A. Ter , Jansen R. F.
Published: April 2021

Behavioural and neurophysiological techniques were used to study the neuronal control of shell turning during egg-laying in the pond snail Lymnaea stagnalis. Egg-laying consists of three phases: resting, turning and oviposition, and is triggered by an electrical discharge in a group of neuroendocrine cells, the caudodorsal cells. During the discharge, several peptides encoded on two CDCH genes are known to be released. Behavioural experiments in which different combinations of nerves were lesioned indicated that the inferior cervical nerves are necessary for turning behaviour to occur. The right inferior cervical nerve innervates the right dorsal longitudinal muscle and contains axons of neurones that are active just prior to, and during, shell movements in freely behaving animals. These axons are probably the axons of motor neurones. The motor neurones of the dorsal longitudinal muscle were identified in the cerebral A and pedal N clusters. We have demonstrated that there is a correlation between the state of excitability of the caudodorsal cells and the electrical activity of the pedal N motor neurones. Our results indicate that the pedal N motor neurones are involved in executing the turning phase during egg-laying.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Modulation of the Buccal Muscle Contraction by Identified Serotonergic and Peptidergic Neurons in the Snail Achatina Fulica
Authors: Yoshida Masayuki , Kobayashi Makoto
Published: April 2021

Serotonergic and peptidergic modulation of buccal muscle contraction at an identified neuromuscular synapse in the African giant snail Achatina fulica was examined. A pair of excitatory motoneurons of the radula protractor was identified in the buccal ganglia and these were named B10 neurons. Pharmacological experiments revealed the B10s to be cholinergic. The serotonergic cerebral neuron v-CDN enhanced B10-evoked contraction of the radula protractor, and it is suggested that this effect is mediated postsynaptically by serotonin released from the v-CDN terminals.

Immunohistochemical analyses revealed that the B10 motoneurons contained an Achatina cardioexcitatory peptide-1 (ACEP-1)-like substance in their cell body, axon and terminals in the radula protractor. From electron microscopic observation, the ACEP-1-like immunoreactive substance was found to be localized in dense-cored vesicles but not in clear vesicles in the nerve terminals. ACEP-1 applied to the radula protractor markedly enhanced B10-evoked contraction of the muscle by increasing the amplitude of excitatory junction potentials (EJPs). The increase of EJP amplitude in the presence of the peptide was probably due to the increased release of acetylcholine from the terminals of B10. It is suggested that the cholinergic motoneuron B10 uses ACEP-1 as an excitatory cotransmitter.
Behavioural and Endocrinological Responses of Mature Male Goldfish to the Sex Pheromone 17α,20β-Dihydroxy-4-Pregnen-3-One in the Water
Authors: Bjerselius R. , Olsén K. H. , Zheng W.
Published: April 2021

The behavioural response of spermiated male goldfish to the sex pheromone 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) in the ambient water was measured using a computerized video-image analysis system. The position and spontaneous locomotor activity of single spermiated male goldfish were continuously recorded in an artificial stream. 17α,20β-P (final concentration 10−11 mol l-1) was supplied to one half and its ethanol carrier to the other half of the test area. The results showed that the fish spent significantly less time in water scented with 17α,20β-P than in control water. Moreover, both the spontaneous locomotor activity and the gonadotropin II concentration in the plasma increased significantly because of contact with 17α,20β-P in the ambient water. The swimming speed was unchanged, whether the fish resided in the 17α,20β-P section or in the section without 17α,20β-P added. In view of the complex dual hormone–pheromone system in goldfish, the possibility of an additional function of 17α,20β-P is discussed. Because the release of the pheromone 17α,20β-P occurs before ovulation and the level then drops drastically, we suggest that the avoidance reaction observed allows the sexually mature male to avoid misdirected courting of non-ovulated females and thus to continue its search for an ovulated female.
Drag Reduction by Wing Tip Slots in a Gliding Harris’ Hawk, Parabuteo Unicinctus
Authors: Tucker Vance A.
Published: April 2021

The anterior-most primary feathers of many birds that soar over land bend upwards and separate vertically to form slotted wing tips during flight. The slots are thought to reduce aerodynamic drag, although drag reduction has never been demonstrated in living birds. Wing theory explains how the feathers that form the tip slots can reduce induced drag by spreading vorticity horizontally along the wing and by acting as winglets, which are used on aircraft to make wings non-planar and to spread vorticity vertically. This study uses the induced drag factor to measure the induced drag of a wing relative to that of a standard planar wing with the same span, lift and speed. An induced drag factor of less than 1 indicates that the wing is non-planar.

The minimum drag of a Harris’ hawk gliding freely in a wind tunnel was measured before and after removing the slots by clipping the tip feathers. The unclipped hawk had 70–90 % of the drag of the clipped hawk at speeds between 7.3 and 15.0 m s-1.

At a wing span of 0.8 m, the unclipped hawk had a mean induced drag factor of 0.56, compared with the value of 1.10 assumed for the clipped hawk. A Monte Carlo simulation of error propagation and a sensitivity analysis to possible errors in measured and assumed values showed that the true mean value of the induced drag factor for the unclipped hawk was unlikely to be more than 0.93. These results for a living bird support the conclusions from a previous study of a feathered tip on a model wing in a wind tunnel: the feathers that form the slotted tips reduce induced drag by acting as winglets that make the wings non-planar and spread vorticity both horizontally and vertically.