bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fat Body Cells and Calcium Phosphate Spherules Induce Ice Nucleation in the Freeze-Tolerant Larvae of the Gall Fly Eurosta Solidaginis (Diptera, Tephritidae)
Authors: Mugnano John A. , Lee Richard E. , Taylor Richard T. 
Published: April 2021

ABSTRACT
During the autumn, the third-instar larvae of the gall fly Eurosta solidaginis acquire freeze tolerance and their crystallization temperatures increase into the −8 to −10 °C range. Despite conflicting reports, efficient endogenous ice nucleators have not been identified in this freeze-tolerant insect. We found large crystalloid spheres within the Malpighian tubules of overwintering larvae. Energy-dispersive X-ray microanalysis and infrared spectroscopy indicated that the spherules were a hydrate of tribasic calcium phosphate. To test for ice-nucleating activity, we placed the calcium phosphate spherules in 10 μl of Schneider’s insect medium and cooled them in a refrigerated bath. The addition of spherules increased the crystallization temperature of Schneider’s medium by approximately 8 °C, from -18.4±0.8 °C to −10.1±0.9 °C (mean ± S.E.M., N=20). Ice-nucleating activity (−10.9±0.9 °C) was also demonstrated in fat body cells suspended in 10 μl of Schneider’s medium. Both calcium phosphate spherules and fat body cells have ice-nucleating activity sufficiently high to explain whole-body crystallization temperatures. Furthermore, other crystalloid deposits, commonly found in diapausing or overwintering insects, also exhibited significant ice-nucleating activity. These endogenous crystalloid deposits represent a new class of heterogeneous ice nucleators that potentially regulate supercooling and promote freeze tolerance in E. solidaginis and possibly in other overwintering insects.
Adenosine Receptor Blockade and Hypoxia-Tolerance in Rainbow Trout and Pacific Hagfish II. Effects on Plasma Catecholamines and Erythrocytes
Authors: Bernier Nicholas J. , Fuentes Juan , Randall David J. 
Published: April 2021

ABSTRACT
The purpose of this study was to examine the role of adenosine receptors (ARs) in (1) the regulation of catecholamine secretion and (2) the modulation of blood oxygen capacitance by catecholamines. To this end, we assessed the response of rainbow trout and Pacific hagfish treated with either an AR blocker, theophylline, or saline under hypoxic and normoxic conditions. Compared with the control hypoxic rainbow trout, AR blockade resulted in a smaller increase in haematocrit and haemoglobin (Hb) concentration of the blood, smaller red blood cell transmembrane pH differences and mean cellular [Hb] (MCHC), as well as a 16-fold higher plasma adrenaline concentration after only 10 min of acute hypoxic exposure.
In hypoxic hagfish, AR blockade had no effect on the [Hb] of the blood, and there was no regulation of red blood cell pH or changes in MCHC. However, whereas plasma [adrenaline] did not change following exposure to a of 1.33 kPa in the hypoxic sham group, the concentration increased 3.8-fold within 10 min in the theophylline-injected group. These results suggest that adenosine modulates the circulating level of catecholamines in both hypoxic rainbow trout and hypoxic Pacific hagfish.
Sensory Control Mechanisms of the Uropod Equilibrium Reflex During Walking in the Crayfish Procambarus Clarkii
Authors: Murayama Maki , Takahata Masakazu 
Published: April 2021

ABSTRACT
The temporal characteristics of statocyst and leg proprioceptive inputs to the uropod motor system were investigated in crayfish using behavioural and electromyographic analyses to elucidate their functional roles in the control of the uropod steering response under natural conditions. When the animal, which was suspended in the air without a footboard, was actively extending its abdomen, prolonged stimulation of the statocysts by body rolling elicited a maintained asymmetrical configuration of the bilateral uropods. Prolonged stimulation of the walking legs by footboard tilting with the animal body held in the upright position elicited a transient uropod response. When the treadmill was tilted while the animal was walking on it in the upright position, the uropods showed the same transient response. However, when the animal body was rolled, together with the treadmill, while the animal was walking on it, the uropods showed a transient response which was reversed in direction compared with that observed during body rolling without a footboard. This transient response was abolished by the removal of the statoliths. The results show that the statocysts and leg proprioceptors exert sustained and transient control effects, respectively, on the uropod motor system during walking. It is also suggested that the uropod response to body rolling during walking is controlled primarily by leg proprioceptor signals which result from statocyst-induced changes in the leg position.
Efficiency of Uphill Locomotion in Nocturnal and Diurnal Lizards
Authors: Farley C. T. , Emshwiller M. 
Published: April 2021

ABSTRACT
Nocturnal geckos can walk on level ground more economically than diurnal lizards. One hypothesis for why nocturnal geckos have a low cost of locomotion is that they can perform mechanical work during locomotion more efficiently than other lizards. To test this hypothesis, we compared the efficiency of the nocturnal gecko Coleonyx variegatus (average body mass 4.2 g) and the diurnal skink Eumeces skiltonianus (average body mass 4.8 g) when they performed vertical work during uphill locomotion. We measured the rate of oxygen consumption when each species walked on the level and up a 50 ˚ slope over a range of speeds. For Coleonyx variegatus, the energetic cost of traveling a unit distance (the minimum cost of transport, Cmin) increased from 1.5 to 2.7 ml O2 kg−1 m−1 between level and uphill locomotion. For Eumeces skiltonianus, Cmin increased from 2.5 to 4.7 ml O2 kg−1 m−1 between level and uphill locomotion. By taking the difference between Cmin for level and uphill locomotion, we found that the efficiency of performing vertical work during locomotion was 37 % for Coleonyx variegatus and 19 % for Eumeces skiltonianus. The similarity between the 1.9-fold difference in vertical efficiency and the 1.7-fold difference in the cost of transport on level ground is consistent with the hypothesis that nocturnal geckos have a lower cost of locomotion than other lizards because they can perform mechanical work during locomotion more efficiently.
Peripheral Control of the Gain of a Central Synaptic Connection Between Antagonistic Motor Neurones in the Locust
Authors: Jellema T. , Heitler W. J. 
Published: April 2021

ABSTRACT
The metathoracic fast extensor tibiae (FETi) motor neurone of locusts is unusual amongst insect motor neurones because it makes output connections within the central nervous system as well as in the periphery. It makes excitatory chemical synaptic connections to most if not all of the antagonist flexor tibiae motor neurones. The gain of the FETi–flexor connection is dependent on the peripheral conditions at the time of the FETi spike. This dependency has two aspects. First, sensory input resulting from the extensor muscle contraction can sum with the central excitatory postsynaptic potential (EPSP) to augment its falling phase if the tibia is restrained in the flexed position (initiating a tension-dependent reflex) or is free to extend (initiating a movement-dependent resistance reflex). This effect is thus due to simple postsynaptic summation of the central EPSP with peripheral sensory input. Second, the static tibial position at the time of the FETi spike can change the amplitude of the central EPSP, in the absence of any extensor muscle contraction. The EPSP can be up to 30 % greater in amplitude if FETi spikes with the tibia held flexed rather than extended. The primary sense organ mediating this effect is the femoral chordotonal organ. Evidence is presented suggesting that the mechanism underlying this change in gain may be specifically localised to the FETi–flexor connection, rather than being due to general position-dependent sensory feedback summing with the EPSP. The change in the amplitude of the central EPSP is probably not caused by general postsynaptic summation with tonic sensory input, since a diminution in the amplitude of the central EPSP caused by tibial extension is often accompanied by overall tonic excitation of the flexor motor neurone. Small but significant changes in the peak amplitude of the FETi spike have a positive correlation with changes in the EPSP amplitude, suggesting a likely presynaptic component to the mechanism of gain control. The change in amplitude of the EPSP can alter its effectiveness in producing flexor motor output and, thus, has functional significance. The change serves to augment the effectiveness of the FETi–flexor connection when the tibia is fully flexed, and thus to increase its adaptive advantage during the co-contraction preceding a jump or kick, and to reduce the effectiveness of the connection when the tibia is partially or fully extended, and thus to reduce its potentially maladaptive consequences during voluntary extension movements such as thrusting.
Characterization of a Basolateral Electroneutral Na+/H+ Antiporter in Atlantic Lobster (Homarus Americanus) Hepatopancreatic Epithelial Vesicles
Authors: Duerr Jeffrey M. , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
Purified basolateral membrane vesicles (BLMVs) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using a Percoll density gradient technique. Enrichments of the Na+/K+-ATPase and alkaline phosphatase activities of these vesicles were 15.4-and 1.2-fold, respectively. The presence of amiloride-sensitive Na+/H+ exchange was demonstrated. Contrary to electrogenic 2Na+/1H+ exchange on apical membranes from the same tissue, kinetic studies of Na+ transport by these basolateral membranes indicate an electroneutral antiport with a Km of 28±1.7 mmol l−1 and a Jmax of 1.74±0.13 μmol mg−1 min−1. Amiloride interacted at a single binding site (Ki=39 μmol l−1) and external Li+ was shown to be an effective competitive inhibitor of the exchange process (Ki=493 μmol l−1). The presence of a membrane-potential-sensitive, Na+-accepting ion channel was also demonstrated. The basolateral Na+/H+ exchanger physiologically resembles members of the NHE family of Na+/H+ antiporters described in vertebrates and departs from the apical electrogenic system previously described in lobster. Whether or not the basolateral Na+/H+ antiporter is an NHE isoform remains to be determined.
Interneurones Involved in Stridulatory Pattern Generation in the Grasshopper Chorthippus Mollis (CHARP.)
Authors: Ocker W.-G. , Hedwig B. 
Published: April 2021

ABSTRACT
In tethered grasshoppers, Chorthippus mollis, stridulatory leg movements were elicited by d.c. brain stimulation. Stridulatory chirps comprise both slow up-and-down movements and rapid oscillations of the hindlegs. Intracellular recording, stimulation and staining of interneurones within the metathoracic ganglion complex were performed simultaneously with recordings of leg movement.
Five interneurones were identified in the metathoracic ganglion complex. The branching patterns of these interneurones were typical of stridulatory interneurones. Three of these neurones had a structure very similar to stridulatory interneurones already characterized in the species Omocestus viridulus.
During stridulation, the spike activity of all interneurones was phasically coupled to the chirp rhythm; two interneurones additionally exhibited coupling to the rapid leg oscillations. Intracellular stimulation of interneurones A1-AC-2 and A1-AI-1 prolonged the duration of the rapid leg oscillations and influenced the generation of the chirp rhythm. Interneurones T3-LI-2 and T3-LC-4 decreased the amplitude of the slow up-and-down movement.
The data indicate that at least part of the metathoracic stridulatory network of C. mollis is organized in a structurally and functionally similar way to that of O. viridulus.
Maximum Cardiac Performance of Rainbow Trout (Oncorhynchus Mykiss) at Temperatures Approaching Their Upper Lethal Limit
Authors: Farrell A. P. , Gamperl A. K. , Hicks J. M. T. , Shiels H. A. , Jain K. E. 
Published: April 2021

ABSTRACT
Numerous studies have examined the effect of temperature on in vivo and in situ cardiovascular function in trout. However, little information exists on cardiac function at temperatures near the trout’s upper lethal limit. This study measured routine and maximum in situ cardiac performance in rainbow trout (Oncorhynchus mykiss) following acclimation to 15, 18 and 22 °C, under conditions of tonic (30 nmol l-1), intermediate (60 nmol l-1) and maximal (200 nmol l-1) adrenergic stimulation. Heart rate increased significantly with both temperature and adrenaline concentration. The Q10 values for heart rate ranged from 1.28 at 30 nmol l-1 adrenaline to 1.36 at 200 nmol l-1 adrenaline. In contrast to heart rate, maximum stroke volume declined by approximately 20 % (from 1.0 to 0.8 ml kg-1) as temperature increased from 15 to 22 °C. This decrease was not alleviated by maximally stimulating the heart with 200 nmol l-1 adrenaline. Because of the equal and opposite effects of increasing temperature on heart rate and stroke volume, maximum cardiac output did not increase between 15 and 22 °C. Maximum power output decreased (by approximately 10–15 %) at all adrenaline concentrations as temperature increased. This reduction reflected a poorer pressure-generating ability at temperatures above 15 °C. These results, in combination with earlier work, suggest (1) that peak cardiac performance occurs around the trout’s preferred temperature and well below its upper lethal limit; (2) that the diminished cardiac function concomitant with acclimation to high temperatures was associated with inotropic failure; (3) that Q10 values for cardiac rate functions, other than heart rate per se, have a limited predictive value at temperatures above the trout’s preferred temperature; and (4) that heart rate is a poor indicator of cardiac function at temperatures above 15 °C.
The Uptake and Release of Serotonin and Dopamine Associated With Locust (Locusta Migratoria) Salivary Glands
Authors: Ali Declan W. , Orchard Ian 
Published: April 2021

ABSTRACT
The uptake and release characteristics of dopamine and serotonin in the salivary glands of the locust Locusta migratoria were examined. Cyclic AMP levels were determined in salivary glands in which the salivary nerve was stimulated under different experimental paradigms. Stimulation of the salivary nerve leads to time-and frequency-dependent elevations of cyclic AMP levels in the glands. The potent and specific D1 receptor antagonist SCH-23390 is capable of partially inhibiting the electrophysiologically induced elevations of cyclic AMP levels. The salivary glands appear to possess uptake transporters for serotonin and dopamine. [3H]serotonin uptake is Na+-dependent and is composed of high-and low-affinity components. [3H]dopamine uptake is Na+-independent and can be partially reduced by a challenge with high-K+ saline and by a challenge with ice-cold saline. Uptake inhibitors are capable of blocking the uptake of radiolabelled serotonin and dopamine. There is a Ca2+-dependent efflux of [3H]serotonin and [3H]dopamine from previously loaded salivary glands in response to stimulation of the salivary nerve and to treatment with a high-K+ saline.
Mechanical Design of Mussel Byssus: Material Yield Enhances Attachment Strength
Authors: Bell Emily C. , Gosline John M. 
Published: April 2021

ABSTRACT
The competitive dominance of mussels in the wave-swept rocky intertidal zone is in part due to their ability to maintain a secure attachment. Mussels are tethered to the substratum by a byssus composed of numerous extracellular, collagenous threads secreted by the foot. Each byssal thread has three serially arranged parts: a corrugated proximal region, a smooth distal region and an adhesive plaque. This study examines the material and structural properties of the byssal threads of three mussel species: Mytilus californianus, M. trossulus, and M. galloprovincialis. Tensile tests in general reveal similar material properties among species: the proximal region has a lower initial modulus, a lower ultimate stress and a higher ultimate strain than the distal region. The distal region also yields at a stress well below its ultimate value. In whole thread tests, the proximal region and adhesive plaque are common sites of structural failure and are closely matched in strength, while the distal region appears to be excessively strong. We propose that the high strength of the distal region is the byproduct of a material designed to yield and extend before structural failure occurs. Experimental and theoretical evidence is presented suggesting that thread yield and extensibility provide two important mechanisms for increasing the overall attachment strength of the mussel: (1) the reorientation of threads towards the direction of applied load, and (2) the ‘recruitment’ of more threads into tension and the consequent distribution of applied load over a larger cross-sectional area, thereby reducing the stress on each thread. This distal region yield behavior is most striking for M. californianus and may be a key to its success in extreme wave-swept environments.
Dynamics of cyclic GMP levels in identified neurones during ecdysis behaviour in the locust Locusta migratoria
Authors: Truman James W. , Ewer John , Ball Eldon E. 
Published: April 2021

ABSTRACT
A grasshopper hatches from its egg, which is laid in soil, as a vermiform larva. This larva continues the stereotyped hatching behaviour as it digs through the egg pod, which provides a passageway to the soil surface. Once at the surface, shedding, or ecdysis, of the vermiform cuticle is initiated. When this process is complete, the first-instar cuticle is expanded to assume the form of the first-instar hopper. We have demonstrated, using immunocytochemical techniques, that these behaviour patterns are associated with dramatic increases in intracellular levels of cyclic GMP in sets of identified neurones in the ventral central nervous system.
The most prominent cyclic-GMP-expressing cells are 34 neurones that appear to contain crustacean cardioactive peptide (CCAP). These CCAP cells show no detectable cyclic GMP at hatching or while the vermiform larva digs through the soil. Upon reaching the surface and freeing itself, the larva initiates ecdysis and associated air-swallowing and tracheal filling within about 1 min. These changes are immediately preceded by the appearance of cyclic GMP in the CCAP cells. Cyclic GMP levels in these neurones peak by 5 min and then decline back to basal levels by 20–30 min. Conditions that cause ecdysing animals to resume digging prolong the elevation of cyclic GMP levels. Once animals have assumed their ‘hopper’ form, however, external stimuli can no longer affect the time course of the cyclic GMP response. The neurones containing elevated cyclic GMP levels probably influence the air-swallowing, tracheal filling and circulatory changes that are associated with ecdysis behaviour.
Pairs of descending midline neurones in abdominal segments 2–4 also become cyclic-GMP-immunoreactive, but they show peak expression after cyclic GMP levels in the CCAP cells have declined. Also, neurones in the caudolateral region of the abdominal ganglia often become cyclic-GMP-immunoreactive when ecdysing animals are forced to resume digging for an extended period.
Seasonal Temperature Acclimatisation of Rainbow Trout: Cardiovascular and Morphometric Influences on Maximal Sustainable Exercise Level
Authors: Taylor S. E. , Egginton S. , Taylor E. W. 
Published: April 2021

ABSTRACT
Adult rainbow trout (mass 600–1500 g; length 40–44 cm) were held in the laboratory for up to 28 days at seasonally appropriate temperatures. The maximal sustainable aerobic exercise level (involving slow-twitch muscle activity alone) was determined by following muscle recruitment patterns using electromyography. The mean (± S.E.M.) speeds recorded for maximal sustainable aerobic exercise were 0.52±0.02, 0.81±0.06 and 0.39±0.02 BL s−1 (body lengths per second) for animals swimming at their acclimatisation temperatures of 4, 11 and 18 °C, respectively. Thus, fish acclimatised to 11 °C reached the highest maximal sustainable (purely aerobic) levels of exercise. They had similar stride lengths to the 4 °C animals, but generated less thrust per stride, as indicated by increased tail-beat frequency. Acclimatisation to 4 °C led to an increased mass of slow muscle and more effective tail beats (greater stride length at lower frequencies), relative to animals at higher temperatures. Fish acclimatised to 18 °C had the lowest stride length and a reduced aerobic swimming capacity.
Sustainable levels of aerobic exercise were reflected in unchanged values for mean heart rate and arterial blood pressure between rest and imposed, graded exercise. Radiolabelled m.icrospheres were used to determine cardiac output and regional blood flow distribution simultaneously in fish, both at rest and while swimming, for each acclimatisation temperature. Fish acclima.tised to 11 °C had the greatest scope for increasing . This resulted in a significant hyperaemia in slow muscle upon exercise (10-fold increase), without an a.ctive redistribution of flow from other tissues. Maximum at 18 °C did not d.iffer significantly from that at 11 °C but, because resting was higher, the scope was reduced and was similar to that found at 4 °C. Specific blood flow to the active muscle was also reduced and this, together with decreased blood oxygen content and reduced slow muscle mass, may limit aerobic swimming performance at 18 °C.
The Peripheral Auditory Characteristics of Noctuid Moths: Information Encoding and Endogenous Noise
Authors: Waters Dean A. 
Published: April 2021

ABSTRACT
The ability of the noctuid A1 cell acoustic receptor to encode biologically relevant information from bat echolocation calls is examined. Short-duration stimuli (less than approximately 6 ms) reduce the dynamic resolution of the receptor, making intensity, and hence range, estimates of foraging bats unreliable. This low dynamic range is further reduced by inaccurate encoding of stimulus intensity, reducing the real dynamic range of the A1 cell to 1 bit at stimulus durations below 3.1 ms. Interspike interval is also an unreliable measure of stimulus intensity at low stimulus levels and/or for short-duration stimuli. The quantity of information encoded per stimulus is reduced as the presentation rate of stimuli is increased. The spontaneous generation of A1 cell action potentials may reduce the ability of the moth to discriminate bat from non-bat signals. Even with a recognition criterion of three A1 cell spikes per call, the moth would regularly make wrong decisions about a bat being present in the immediate environment. Removing this noise would necessitate a considerable loss of information through filtering at the interneurone level. It is proposed that, for bats using short-duration calls, the moth would only be able to recognise an approaching bat from the repetitious nature of the incoming signal.