bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differing mechanisms of cold-induced changes in capillary supply in m. tibialis anterior of rats and hamsters
Authors: Deveci Durmus , Egginton Stuart 
Published: April 2021

SUMMARY
The physiological, metabolic and anatomical adaptations of skeletal muscle to chronic cold exposure were investigated in Wistar rats (Rattus norvegicus), a species that defends core temperature, and Syrian hamsters (Mesocricetus auratus), which may adopt a lower set point under unfavourable conditions. Animals were exposed to a simulated onset of winter in an environmental chamber, progressively shortening photoperiod and reducing temperature from 12 h:12 h L:D and 22°C to 1 h:23 h L:D and 5°C over 4 weeks. The animals were left at 4°C for a further 4 weeks to complete the process of cold-acclimation. M. tibialis anterior from control (euthermic) and cold-acclimated animals of similar mass showed a significant hyperactivity-induced hypertrophy in the rat, but a small disuse atrophy in the hamster. Little evidence was found for interconversion among fibre types in skeletal muscle on cold-acclimation, and only modest differences were seen in activity of oxidative or glycolytic enzymes in either species. However, adjustments in Type II fibre size paralleled the muscle hypertrophy in rat and atrophy in hamster. Cold-induced angiogenesis was present in the rat, averaging a 28 % increase in capillary-to-fibre ratio (C:F) but, as this was balanced by fibre hypertrophy across the whole muscle, there was no change in capillary density (CD). In contrast, the C:F was similar in both groups of hamsters, whereas CD rose by 33 % in line with fibre atrophy. Within distinct regions of the m. tibialis anterior, there was a correlation between angiogenesis and fibre size in rats, in which oxygen diffusion distance increased, but not in hamsters, in which there was a reduced oxygen diffusion distance. Consequently, the change in C:F was greatest (39 %) in the glycolytic cortex region of the m. tibialis anterior in rats. We conclude that non-hibernator and hibernator rodents improve peripheral oxygen transport following cold-acclimation by different mechanisms. In rats, an increase in fibre girth was accompanied by a true angiogenesis, while the improved apparent capillary supply in hamsters was due to smaller fibre diameters. These responses are consistent with the strategies of resisting and accommodating, respectively, an annual fall in environmental temperature.
Effects of metamorphosis on the aquatic escape response of the two-lined salamander (Eurycea bislineata)
Authors: Azizi Emanuel , Landberg Tobias 
Published: April 2021

SUMMARYAlthough numerous studies have described the escape kinematics of fishes, little is known about the aquatic escape responses of salamanders. We compare the escape kinematics of larval and adult Eurycea bislineata, the two-lined salamander, to examine the effects of metamorphosis on aquatic escape performance. We hypothesize that shape changes associated with resorption of the larval tail fin at metamorphosis will affect aquatic locomotor performance. Escape responses were recorded using high-speed video, and the effects of life stage and total length on escape kinematics were analyzed statistically using analysis of covariance. Our results show that both larval and adult E. bislineata use a two-stage escape response (similar to the C-starts of fishes) that consists of a preparatory (stage 1) and a propulsive (stage 2) stroke. The duration of both kinematic stages and the distance traveled during stage 2 increased with total length. Both larval and adult E. bislineata had final escape trajectories that were directed away from the stimulus. The main kinematic difference between larvae and adults is that adults exhibit significantly greater maximum curvature during stage 1. Total escape duration and the distance traveled during stage 2 did not differ significantly between larvae and adults. Despite the significantly lower tail aspect ratio of adults, we found no significant decrease in the overall escape performance of adult E. bislineata. Our results suggest that adults may compensate for the decrease in tail aspect ratio by increasing their maximum curvature. These findings do not support the hypothesis that larvae exhibit better locomotor performance than adults as a result of stronger selective pressures on early life stages.Movie available on-line: http://www.biologists.com/JEB/movies/jeb3978.html.
Kinematics of the buccal mass during swallowing based on magnetic resonance imaging in intact, behaving Aplysia californica
Authors: Neustadter David M. , Drushel Richard F. , Chiel Hillel J. 
Published: April 2021

SUMMARY
A novel magnetic resonance imaging interface has been developed that makes it possible to image movements in intact, freely moving subjects. We have used this interface to image the internal structures of the feeding apparatus (i.e. the buccal mass) of the marine mollusc Aplysia californica. The temporal and spatial resolution of the resulting images is sufficient to describe the kinematics of specific muscles of the buccal mass and the internal movements of the main structures responsible for grasping food, the radula and the odontophore. These observations suggest that a previously undescribed feature on the anterior margin of the odontophore, a fluid-filled structure that we term the prow, may aid in opening the jaw lumen early in protraction. Radular closing during swallowing occurs near the peak of protraction as the radular stalk is pushed rapidly out of the odontophore. Retraction of the odontophore is enhanced by the closure of the lumen of the jaws on the elongated odontophore, causing the odontophore to rotate rapidly towards the esophagus. Radular opening occurs after the peak of retraction and without the active contraction of the protractor muscle 12 and is due, in part, to the movement of the radular stalk into the odontophore. The large variability between responses also suggests that the great flexibility of swallowing responses may be due to variability in neural control and in the biomechanics of the ingested food and to the inherent flexibility of the buccal mass.
Expression ofManduca sextaV-ATPase genesmvB, mvGandmvdis regulated by ecdysteroids
Authors: Reineke Stephan , Wieczorek Helmut , Merzendorfer Hans 
Published: April 2021

SUMMARYV-ATPases are complex proteins consisting of a peripheral, ATP-hydrolysing V1 complex and a membrane-bound H+-translocating Vo complex. The plasma membrane V-ATPase from the tobacco hornworm(Manduca sexta) midgut is made up of eight different V1and four different Vo subunits. During starvation and moulting,V-ATPase activity decreases as a result of the dissociation of the V1 complex from the Vo complex. To determine whether subunit biosynthesis is reduced during periods of enzyme inactivity, we measured the transcript levels and transcriptional activities of V-ATPase genes. Northern blots revealed the downregulation of almost all V-ATPase transcripts during starvation. During moulting, transcript levels of the three V-ATPase genes examined, mvB, mvG and mvd, also decreased,and this decrease was negatively correlated with the titre of 20-hydroxyecdysone (20-HE) and positively correlated with the titre of juvenile hormone (JH). To test the biological significance of these correlations, we injected both hormones into feeding larvae and measured transcript levels several hours later. A short-term increase and a long-term decrease in levels of mRNA were observed after 20-HE injection, whereas JH injection had no significant effect. Immunohistochemical studies of the midgut epithelium revealed that 20-HE injection led to changes in goblet cell morphology and in the subcellular distribution of the V1 complex comparable with the situation during the moult and during starvation. Reporter gene assays in Sf21 cells using mvB, mvG and mvdpromoters to initiate transcription of firefly luciferase led, after incubation of the cells with 20-HE, to results comparable with those obtained in the injection experiments. These findings suggest that putative ecdysone-responsive elements are present in all three promoters. Taken together, our results suggest that the expression of V-ATPase genes is controlled in a coordinated manner by ecdysteroids.
Reflections on colourful ommatidia of butterfly eyes
Authors: Stavenga Doekele G. 
Published: April 2021

SUMMARYThe eye shine of butterflies from a large number of ommatidia was observed with a modified epi-illumination apparatus equipped with an objective lens of large numerical aperture. A few representative cases are presented: the satyrine Bicyclus anynana, the heliconian Heliconius melpomene, the small white Pieris rapae and the small copper Lycaena phlaeas. The colour of the eye shine is determined mainly by the reflectance spectrum of the tapetal mirror and the transmittance spectrum of the photoreceptor screening pigments, if present near the light-guiding rhabdom. Reflectance spectra measured from individual ommatidia show that tapetum and screening pigments are co-expressed in fixed combinations, thus determining different ommatidial classes. The classes are distributed in an irregular pattern that can be rapidly assessed with the novel epi-illumination apparatus. Many butterfly species appear to have red-reflecting ommatidia,which is interpreted to indicate the presence of red-sensitive photoreceptors.
Performance and adaptive value of tarsal morphology in rove beetles of the genusStenus(Coleoptera, Staphylinidae)
Authors: Betz Oliver 
Published: April 2021

SUMMARYTo evaluate the adaptive value of the widening of the bilobed tarsi that has paralleled the tremendous radiation of the staphylinid genus Stenus, the performance of slender versus wide tarsi has been evaluated in two different contexts: (i) locomotion on the surface of water, and (ii) climbing on vertical (plant) surfaces. Contact angle measurements at the underside of the tarsi have revealed that, irrespective of tarsus width, all the investigated species are well supported by the surface of water while walking on it. The main selective demands driving the widening of the tarsi in several lineages have instead come from their firm attachment to smooth plant surfaces. This is suggested by measurements of the maximum vertical pulling forces exerted by intact and manipulated individuals on various rough and smooth surfaces. Species with widened tarsi associated with considerably more tenet setae attain significantly higher pulling forces,particularly on smooth surfaces. The tarsal setae are of greater importance on smooth surfaces, but the claws seem to be more important on rough substrata. On substrata that combine the attributes of rough and smooth surfaces, both claws and tenent setae add significantly to the pulling forces exerted,suggesting a functional synergism. The contribution of the present study to our understanding of insect tarsal attachment to surfaces with a variety of textures is discussed.
Analysis of monoamines, adenosine and GABA in tissues of the land snailHelix lucorumand lizardAgama stellio stellioduring hibernation
Authors: Michaelidis Basile , Loumbourdis Nikolaos S. , Kapaki Elizabeth 
Published: April 2021

SUMMARYThe aim of the present study was to determine the levels of monoamines,GABA and adenosine in the brain, heart and haemolymph of the land snail Helix lucorum and in the brain, heart and blood of lizard Agama stellio stellio during long-term hibernation. We measured levels of the monoamines serotonin (5-HT) and its main metabolite 5-hydroxyindole-3-acetic acid (5-HIAA), dopamine (DA) and its metabolites dihydroxyphenylacetic acid(DOPAC) and homovanilic acid (HVA), norepinephrine (NE) and epinephrine (E). The most abundant amines detected in the brain and heart of active H. lucorum were 5-HT and DA. Of the metabolites examined only 5-HIAA was found in the brain. NE was found at very low levels but only in the brain,while E was not detected in the brain and heart. The levels of 5-HT and 5-HIAA increased in the brain and heart of H. lucorum within the first months of hibernation, showing a significant decrease thereafter. The levels of DA did not change during hibernation. The results indicated that 5-HT might be involved in preparing snails for entry into hibernation. GABA was only found in the brain of H. lucorum, and the levels were low; these levels remained during hibernation. Adenosine was present in brain and heart of H. lucorum, and during hibernation, the level of adenosine decreased significantly in the brain but remained steady in the heart. The monoamines 5-HT, DA and NE were present in the brain of active lizards A. stellio stellio, whereas E was found only at very low levels. Moreover,the metabolites 5-HIAA, DOPAC and HVA were detected in the brain of active lizards. The monoamines 5-HT, DA, NE and E were also detected in the heart and blood of active lizards. During hibernation the levels of these four monoamines were decreased significantly in the brain and heart of A. stellio stellio. In contrast, the levels of E increased in the heart and blood of hibernating lizards. Adenosine was detected in both heart and brain of active lizards, but hibernation caused a marked decrease in its levels at both tissues. GABA was found at higher levels than monoamines and adenosine in the brain of active lizards, and hibernation caused a significant increase in its levels, indicating an important role of GABA in inhibition of neuronal activity in hibernating lizards.
Trade-offs between speed and endurance in the frogXenopus laevis
Authors: Wilson Robbie S. , James Rob S. , Van Damme Raoul 
Published: April 2021

SUMMARYOne of the most interesting trade-offs within the vertebrate locomotor system is that between speed and endurance capacity. However, few studies have demonstrated a conflict between whole-animal speed and endurance within a vertebrate species. We investigated the existence of trade-offs between speed and endurance capacity at both the whole-muscle and whole-animal levels in post-metamorphs of the frog Xenopus laevis. The burst-swimming performance of 55 frogs was assessed using a high-speed digital camera, and their endurance capacity was measured in a constant-velocity swimming flume.The work-loop technique was used to assess maximum power production of whole peroneus muscles at a cycle frequency of 6 Hz, while fatigue-resistance was determined by recording the decrease in force and net power production during a set of continuous cycles at 2 Hz. We found no significant correlations between measures of burst swimming performance and endurance capacity, suggesting that there is no trade-off between these two measures of whole-animal performance. In contrast, there was a significant negative correlation between peak instantaneous power output of the muscles at 6 Hz and the fatigue-resistance of force production at 2 Hz (other correlations between power and fatigue were negative but non-significant). Thus, our data support the suggestion that a physiological conflict between maximum power output and fatigue resistance exists at the level of vertebrate muscles. The apparent incongruence between whole-muscle and whole-animal performance warrants further detailed investigation and may be related to factors influencing both whole-muscle and whole-animal performance measures.
Copper uptake across rainbow trout gills
Authors: Grosell Martin , Wood Chris M. 
Published: April 2021

SUMMARYSeveral components of branchial copper uptake were identified in juvenile freshwater rainbow trout (Oncorhynchus mykiss) using 64Cu. On the basis of competitive interactions between sodium and copper uptake,inhibition of copper uptake by a proton pump inhibitor (bafilomycin A1, 2μmol l-1) and a Na+ channel blocker (phenamil, 100μmol l-1), it appears that a proportion of the branchial copper uptake occurs via an apical Na+ channel. This sodium-sensitive copper uptake demonstrates saturation kinetics, with a Km of 7.1 nmol l-1 and a Jmax of 21.2 pmol g-1 h-1, and is characterized by an IC50 of 104 μmol l-1 sodium. On the basis of residual copper uptake in the presence of high sodium concentrations (20 mmol l-1) and differential inhibition of sodium and copper uptake by phenamil (100 μmol l-1), a sodium-insensitive component of copper uptake is also present in trout gills. It demonstrates saturation kinetics with a comparably low Km (9.6 nmol l-1) but a lower maximum transport capacity (Jmax=3.5 pmol g-1 h-1)than the sodium-insensitive system. Sodium uptake exhibits saturation kinetics with a Km of 69 μmol l-1. Copper reduced branchial sodium transport affinity but increased the maximal sodium transport capacity.
Buoyancy and maximal diving depth in penguins
Authors: Sato Katsufumi , Naito Y. , Kato A. , Niizuma Y. , Watanuki Y. , Charrassin J. B. , Bost C.-A. , Handrich Y. , Le Maho Y. 
Published: April 2021

SUMMARYUsing a newly developed data logger to measure acceleration, we demonstrate that free-ranging king and Adélie penguins only beat their flippers substantially during the first part of descent or when they were presumed to be chasing prey at the bottom of dives. Flipper beating stopped during the latter part of ascent: at 29±9 % (mean ± S.D.) of dive depth(mean dive depth=136.8±145.1 m, N=425 dives) in king penguins,and at 52±20 % of dive depth (mean dive depth=72.9±70.5 m, N=664 dives) in Adélie penguins. Propulsive swim speeds of both species were approximately 2 m s-1 during dives; however, a marked increase in speed, up to approximately 2.9 m s-1, sometimes occurred in king penguins during the passive ascending periods. During the prolonged ascending, oblique ascent angle and slowdown near the surface may represent one way to avoid the potential risk of decompression sickness. Biomechanical calculations for data from free-ranging king and Adélie penguins indicate that the air volume of the birds (respiratory system and plumage) can provide enough buoyancy for the passive ascent. When comparing the passive ascents for shallow and deep dives, there is a positive correlation between air volume and the depth of the dive. This suggests that penguins regulate their air volume to optimize the costs and benefits of buoyancy.
Drosophilaas a new model organism for the neurobiology of aggression?
Authors: Baier Andrea , Wittek Britta , Brembs Björn 
Published: April 2021

SUMMARYWe report here the effects of several neurobiological determinants on aggressive behaviour in the fruitfly Drosophila melanogaster. This study combines behavioural, transgenic, genetic and pharmacological techniques that are well established in the fruitfly, in the novel context of the neurobiology of aggression. We find that octopamine, dopamine and a region in the Drosophila brain called the mushroom bodies, all profoundly influence the expression of aggressive behaviour. Serotonin had no effect. We conclude that Drosophila, with its advanced set of molecular tools and its behavioural richness, has the potential to develop into a new model organism for the study of the neurobiology of aggression.
Independent and conjugate eye movements during optokinesis in teleost fish
Authors: Fritsches Kerstin A. , Marshall N. Justin 
Published: April 2021

SUMMARYIn response to movements involving a large part of the visual field, the eyes of vertebrates typically show an optokinetic nystagmus, a response in which both eyes are tightly yoked. Using a comparative approach, this study sets out to establish whether fish with independent spontaneous eye movements show independent optokinetic nystagmus in each eye. Two fish with independent spontaneous eye movements, the pipefish Corythoichthyes intestinalisand the sandlance Limnichthyes fasciatus were compared with the butterflyfish Chaetodon rainfordi, which exhibits tightly yoked eye movements. In the butterflyfish a single whole-field stimulus elicits conjugate optokinesis, whereas the sandlance and pipefish show asynchronous optokinetic movements. In a split drum experiment, when both eyes were stimulated in opposite directions with different speeds, both the sandlance and the pipefish compensated independently with each eye. The optokinetic response in the butterflyfish showed some disconjugacy but was generally confused. When one eye was occluded, the seeing eye was capable of driving the occluded eye in both the butterflyfish and the pipefish but not in the sandlance. Monocular occlusion therefore unmasks a link between the two eyes in the pipefish, which is overridden when both eyes receive visual input. The sandlance never showed any correlation between the eyes during optokinesis in all stimulus conditions. This suggests that there are different levels of linkage between the two eyes in the oculomotor system of teleosts, depending on the visual input.
Song discrimination by male cicadas Cicada barbara lusitanica(Homoptera, Cicadidae)
Authors: Fonseca P. J. , Revez M. A. 
Published: April 2021

SUMMARY
Cicada barbara lusitanica males presented a stereotyped singing response behaviour when exposed to a playback of the conspecific song. Males preferred (as measured by the time taken to sing) the conspecific signal to heterospecific songs that differed markedly in temporal pattern. Manipulation of the gross temporal pattern of C. barbara calling song significantly reduced stimulus attractiveness. Indeed, C. barbaramales stopped responding to stimuli in which the temporal pattern approached the characteristic C. orni song, a sympatric and closely related species. If present in females, the preference for stimuli with pauses not exceeding 30 ms could reflect the evolution of a behavioural pre-copulatory isolating mechanism based on song analysis. Males discriminated frequencies within 3-15 kHz, clearly preferring 6 and 9 kHz; both these frequencies matched the main spectral peaks of the song. The preference for specific frequencies was not associated with maximum neuronal excitation as estimated by auditory nerve recordings, which suggests that this frequency-dependent behaviour is not based on the strength of the auditory system's response to different frequencies. Rather, it is likely to reflect fine frequency resolution in the central nervous system.
Serotonin sets the day state in the neurons that control coupling between the optic lobe circadian pacemakers in the cricketGryllus bimaculatus
Authors: Saifullah A. S. M. , Tomioka Kenji 
Published: April 2021

SUMMARYThe bilaterally paired optic lobe circadian pacemakers of the cricket Gryllus bimaculatus mutually exchange photic and circadian information to keep their activity synchronized. The information is mediated by a neural pathway, consisting of the so-called medulla bilateral neurons,connecting the medulla areas of the two optic lobes. We investigated the effects of serotonin on the neural activity in this coupling pathway. Spontaneous and light-induced electrical activity of the neurons in the coupling pathway showed daily variations, being more intense during the night than the day. Microinjection of serotonin or a serotonin-receptor agonist,quipazine, into the optic lobe caused a dose- and time-dependent inhibition of spontaneous and light-induced responses, mimicking the day state. The amount of suppression was greater and the recovery from the suppression occurred faster during the night. Application of metergoline, a non-selective serotonin-receptor antagonist, increased spontaneous activity and light-evoked responses during both the day and the night, with higher effect during the day. In addition, metergoline effectively attenuated the effects of serotonin. These facts suggest that in the cricket's optic lobe, serotonin is released during the daytime and sets the day state in the neurons regulating coupling between the bilaterally paired optic lobe circadian pacemakers.