bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of sonomicrometry demonstrates the link between prey capture kinematics and suction pressure in largemouth bass
Authors: Sanford Christopher P. J. , Wainwright Peter C. 
Published: April 2021

SUMMARYSuction feeding in fishes is the result of a highly coordinated explosive expansion of the buccal cavity that results in a rapid drop in pressure. Prey are drawn into the mouth by a flow of water that is generated by this expansion. At a gross level it is clear that the expansion of the buccal cavity is responsible for the drop in pressure. However, attempts using high-speed video recordings to demonstrate a tight link between prey capture kinematics and suction pressure have met with limited success. In a study with largemouth bass Micropterus salmoides, we adopted a new technique for studying kinematics, sonomicrometry, to transduce the movement of skeletal elements of the head during feeding, and synchronized pressure recordings at a sampling rate of 500 Hz. From the positional relationships of six piezoelectric crystals we monitored the internal movements of the buccal cavity and mouth in both mid-sagittal and transverse planes. We found that peak subambient pressure was reached very early in the kinematic expansion of the buccal cavity, occurring at the time when the rate of percentage change in buccal volume was at its peak. Using multiple regression analyses we were consistently able to account for over 90%, and in the best model 99%, of the variation in buccal pressure among strikes using kinematic variables. Sonomicrometry shows great promise as a method for documenting movements of biological structures that are not clearly visible in the external view provided by film and video recordings.
Adaptive responses of vertebrate neurons to hypoxia
Authors: Bickler Philip E. , Donohoe Paul H. 
Published: April 2021

SUMMARYThe damage caused to mammalian neurons during ischaemic events in the brain(e.g. following a stroke), is an area of major interest to neuroscientists. The neurons of hypoxia-tolerant vertebrates offer unique models for identifying new strategies to enhance the survival of hypoxia-vulnerable neurons. In this review, we describe recent advances in our understanding of how hypoxia-tolerant neurons detect decreases in oxygen and create signals that have immediate and long-term effects on cell function and survival. Sensing and adapting to low oxygen tension involves numerous modalities with different times of activation and effect. Sensors include membrane proteins such as ionotropic ion channels, membrane or cytosolic heme proteins,mitochondrial proteins and/or oxygen sensitive transcription factors such as HIF-1α and NFκB. Signaling molecules involved in O2sensing include mitogen-activated protein kinases, ions such as Ca2+ and metabolites such as adenosine. These signals act rapidly to reduce the conductance of ion channels (ion flux arrest) and production of energy (metabolic arrest), and slowly to activate specific genes. The ability to construct an energy budget, illustrating which physiological processes are depressed during both long-term and acute metabolic suppression in hypoxia-tolerant neurons, would be of significant value in devising new strategies for neuroprotection. Additionally it is not known how metabolism is regulated at `pilot-light' levels at which energy-producing and energy-consuming processes are balanced. The regulation of organelle and cell fate during long-term hypoxia is almost completely unexplored, and whether programmed cell death and regeneration of lost neurons occur following protracted dormancy is also of considerable interest.
GABA-like immunoreactivity in nonspiking interneurons of the locust metathoracic ganglion
Authors: Wildman M. , Ott S. R. , Burrows M. 
Published: April 2021

SUMMARYNonspiking interneurons are important components of the premotor circuitry in the thoracic ganglia of insects. Their action on postsynaptic neurons appears to be predominantly inhibitory, but it is not known which transmitter(s) they use. Here, we demonstrate that many but not all nonspiking local interneurons in the locust metathoracic ganglion are immunopositive for GABA (γ-aminobutyric acid). Interneurons were impaled with intracellular microelectrodes and were shown physiologically to be nonspiking. They were further characterized by defining their effects on known leg motor neurons when their membrane potential was manipulated by current injection. Lucifer Yellow was then injected into these interneurons to reveal their cell bodies and the morphology of their branches. Some could be recognised as individuals by comparison with previous detailed descriptions. Ganglia were then processed for GABA immunohistochemistry. Fifteen of the 17 nonspiking interneurons studied were immunopositive for GABA, but two were not. The results suggest that the majority of these interneurons might exert their well-characterized effects on other neurons through the release of GABA but that some appear to use a transmitter other than GABA. These nonspiking interneurons are therefore not an homogeneous population with regard to their putative transmitter.
Physiological changes of sturgeon Acipenser naccarii caused by increasing environmental salinity
Authors: Martínez-Álvarez R. M. , Hidalgo M. C. , Domezain A. , Morales A. E. , García-Gallego M. , Sanz A. 
Published: April 2021

SUMMARY
The possible repercussions of osmoregulatory processes on some indicators of classical and oxidative stress were examined during gradual acclimation of sturgeons (Acipenser naccarii) to full seawater (35% salinity) and after a period of 20∼days at this salinity. Erythrocyte constants and levels of cortisol, protein and glucose in the plasma were determined. In addition, plasma osmolality and muscle-hydration values, as well as liver and heart protein, were determined. Catalase, glutathione peroxidase and superoxide dismutase activities and lipidperoxidation levels were measured in blood (plasma and red blood cells) and tissue (liver and heart). A number of physiological responses, such as disturbance in body fluid, activation of osmoregulatory mechanisms, augmented antioxidant defences in blood and alteration of energy metabolites, were detected with increasing environmental salinity. After 20 days at 35% salinity, plasma osmolality, erythrocyte constants and muscle water content all returned to values usual for low environmental salinity, indicating that osmoregulatory processes have achieved their objective. However, cortisol values, antioxidant enzyme activities in the blood (plasma and red blood cells), lipid peroxidation in plasma, and hepatic proteins did not return to initial values, showing that osmoregulatory processes cause major physiological changes in the fish.
Changes in locomotor activity parameters with variations in cycle time in larval lamprey
Authors: Boyd Malinda R. , McClellan Andrew D. 
Published: April 2021

SUMMARYIn larval lamprey, locomotor activity recorded from whole animals and in vitro brain/spinal cord preparations was analyzed to determine how two parameters of locomotor activity, burst proportion (BP; relative duration of motor burst activity) and intersegmental phase lag (ϕ; normalized delay of burst activity along one side of the body), vary with changes in cycle time(T). In individual animals, the slopes of BP and ϕ versus T were compared using linear regression analysis, followed by statistical analysis of the slopes to determine whether the parameters changed significantly with variations in cycle time.For locomotor muscle activity in whole animals, the BP values increased significantly with decreases in T (i.e. negative slopes), while the slopes for ϕ values versus T were not significantly different from zero. For locomotor activity in preparations in vitro, the mean slopes for BP values versus T, although negative, were not significantly different from zero, and phase lags were also relatively constant with changes in cycle time.Increases in BP with decreases in cycle time and increases in swimming speed can be expected to generate proportionately more force per cycle,presumably to compensate for the increase in viscous resistance of moving the body more rapidly through water. By contrast, constant intersegmental phase lags will ensure that the relative timing of locomotor burst activity is constant and that an approximately single S-wave along the body is retained during different swimming speeds.
Epithelial interactions inHydra: apoptosis in interspecies grafts is induced by detachment from the extracellular matrix
Authors: Kuznetsov Sergey G. , Anton-Erxleben Friederike , Bosch Thomas C. G. 
Published: April 2021

SUMMARYApoptosis plays an important role in immunity and is widely used to eliminate foreign or infected cells. Cnidaria are the most basal eumetazoans and have no specialised immune cells, but some colonial cnidarians possess a genetic system to discriminate between self and non-self. By grafting epithelia of different species we have previously shown that the freshwater polyp Hydra eliminates non-self cells by phagocytosis. Here we have investigated whether apoptosis is involved in the histocompatibility reactions. We studied epithelial interactions between Hydra vulgaris and Hydra oligactis and show that a large number of apoptotic cells accumulate in the contact region of interspecies grafts. Histological analysis of the graft site revealed that displacement of the endodermal layer of Hydra vulgaris by endoderm from Hydra oligactis coincided with impaired cell—cell and cell—matrix contacts. We therefore suggest that in interspecies grafts, apoptosis is induced by the detachment of epithelial cells from the extracellular matrix(anoikis) and not by a discriminative allorecognition system.
Two sniffing strategies in palinurid lobsters
Authors: Goldman J. A. , Patek S. N. 
Published: April 2021

SUMMARYMost studies of lobster chemoreception have focused on the model systems of Panulirus argus (Palinuridae) and Homarus americanus(Nephropidae). We compare antennule morphology across lobsters and conduct the first kinematic study of antennule flicking in a palinurid species other than P. argus. High-speed video analysis shows that Palinurus elephas flicks at a rate more than an order of magnitude higher than in P. argus. However, both species flick their antennular flagella at a Reynolds number (Re) of approximately one, such that an asymmetry in the speed of the flick phases causes both species to have a leaky closing flick phase and a non-leaky opening phase. The antennular flagella of P. argus are nearly seven times longer than those of P. elephas,and, when compared across palinurid genera, Panulirus species sample far greater areas of water over greater spatial and time scales than do any other palinurid genera. Palinurid lobsters appear to have two sniffing strategies: low flick rates over a large area of water (e.g. P. argus) or high flick rates over a small area of water (e.g. P. elephas). P. argus is a highly informative model system in which to study aquatic chemoreception; however, its antennule anatomy and kinematics suggest a separate strategy, unique to Panulirus species, for sensing chemical plumes in fluid environments.
`Fixed-axis' magnetic orientation by an amphibian: non-shoreward-directed compass orientation, misdirected homing or positioning a magnetite-based map detector in a consistent alignment relative to the magnetic field?
Authors: Phillips John B. , Borland S. Chris , Freake Michael J. , Brassart Jacques , Kirschvink Joseph L. 
Published: April 2021

SUMMARYExperiments were carried out to investigate the earlier prediction that prolonged exposure to long-wavelength (&gt;500 nm) light would eliminate homing orientation by male Eastern red-spotted newts Notophthalmus viridescens. As in previous experiments, controls held in outdoor tanks under natural lighting conditions and tested in a visually uniform indoor arena under full-spectrum light were homeward oriented. As predicted, however,newts held under long-wavelength light and tested under either full-spectrum or long-wavelength light (&gt;500 nm) failed to show consistent homeward orientation. The newts also did not orient with respect to the shore directions in the outdoor tanks in which they were held prior to testing. Unexpectedly, however, the newts exhibited bimodal orientation along a more-or-less `fixed' north-northeast—south-southwest magnetic axis. The orientation exhibited by newts tested under full-spectrum light was indistinguishable from that of newts tested under long-wavelength light,although these two wavelength conditions have previously been shown to differentially affect both shoreward compass orientation and homing orientation. To investigate the possibility that the `fixed-axis' response of the newts was mediated by a magnetoreception mechanism involving single-domain particles of magnetite, natural remanent magnetism (NRM) was measured from a subset of the newts. The distribution of NRM alignments with respect to the head—body axis of the newts was indistinguishable from random. Furthermore, there was no consistent relationship between the NRM of individual newts and their directional response in the overall sample. However, under full-spectrum, but not long-wavelength, light, the alignment of the NRM when the newts reached the 20 cm radius criterion circle in the indoor testing arena (estimated by adding the NRM alignment measured from each newt to its magnetic bearing) was non-randomly distributed. These findings are consistent with the earlier suggestion that homing newts use the light-dependent magnetic compass to align a magnetite-based `map detector'when obtaining the precise measurements necessary to derive map information from the magnetic field. However, aligning the putative map detector does not explain the fixed-axis response of newts tested under long-wavelength light. Preliminary evidence suggests that, in the absence of reliable directional information from the magnetic compass (caused by the 90° rotation of the response of the magnetic compass under long-wavelength light), newts may resort to a systematic sampling strategy to identify alignment(s) of the map detector that yields reliable magnetic field measurements.
Hyperpnea training attenuates peripheral chemosensitivity and improves cycling endurance
Authors: McMahon Michael E. , Boutellier Urs , Smith Richard M. , Spengler Christina M. 
Published: April 2021

SUMMARY
Well-trained endurance athletes frequently have a lower peripheral chemoreceptor (pRc) sensitivity and a lower minute ventilation(V̇E) during exercise compared to untrained individuals. We speculated that the decreased pRcresponse may be specifically associated with repeated exposure to the high rates of ventilation occurring during exercise training. We therefore examined the effect of respiratory muscle training (RMT; 20× 30 min sessions of voluntary normocapnic hyperpnea) on the pRc sensitivity during exercise and on cycling performance. RMT was chosen to achieve a high V̇E, similar to that of heavy exercise,while avoiding the other accompanying effects of whole body exercise. 20 trained male cyclists were randomized into RMT (N=10) or control(N=10) groups. Subjects' pRc response was assessed by a modified Dejours O2 test (10-12 breaths of 100% O2,repeated 4-6 times) during cycling exercise at 40% of the maximal work capacity (Ẇmax). Cycling performance was measured during a cycling test to exhaustion (85%Ẇmax). The RMT group exhibited a significantly reduced pRc sensitivity (mean ±S.D.) compared to the control group (-5.8±6.0% versus0.1±4.6%, P&lt;0.5). Cycling endurance improved significantly after RMT in comparison to the control group (+3.26±4.98 versus -1.46±3.67 min, P&lt;0.05). However, these changes in pRc response were not significantly correlated with exercise ventilation or cycling endurance time. We conclude that the high levels of ventilation achieved during exercise, as simulated by RMT in this study, appear to be accompanied by a reduction in pRc sensitivity;however, the role of the pRc in the control of ventilation during exercise seems to be minor.
Maternal and direct effects of the intestinal nematode Heligmosomoides polygyrus on offspring growth and susceptibility to infection
Authors: Kristan Deborah M. 
Published: April 2021

SUMMARY
The laboratory mouse (Mus musculus) has a naturally occurring intestinal nematode (Heligmosomoides polygyrus) that induces an immune response, causes phenotypic plasticity in metabolism and in organ structure and function, and results in changes in host reproductive output. The objectives of the present study were to determine (1) whether pups infected with parasites at weaning grew differently and had a different body composition at adulthood compared with uninfected pups, (2) whether offspring from parasitized mothers grew differently and had a different body composition at adulthood compared with offspring from unparasitized mothers, (3) whether parasite effects on body composition of pups varied under different infection intensities and (4) whether maternal parasite infection affected susceptibility, duration and intensity of offspring parasite infection. H. polygyrus had direct and maternal effects on offspring growth, but final adult mass was not affected by parasites. Parasite infection in offspring had no effect on overall fat mass, but mass changes for some organs were greater for mice that had a high infection intensity compared with mice that had a low infection intensity. Only offspring from parasitized mothers cleared their parasite infection; however, if the infection was not cleared, the final infection intensity was greater for offspring born to parasitized mothers than to unparasitized mothers. This study shows that chronic, sublethal parasite infection with H. polygyrus has both maternal and direct effects that induce physiological changes in growing mice sufficient to alter host growth trajectories, morphology and susceptibility to parasite infection.
Electrospray ionisation mass spectrometric analysis of lipid restructuring in the carp (Cyprinus carpio L.) during cold acclimation
Authors: Brooks S. , Clark G. T. , Wright S. M. , Trueman R. J. , Postle A. D. , Cossins A. R. , Maclean N. M. 
Published: April 2021

SUMMARY
Cold acclimation of carp from 30°C to 10°C causes a restructuring of liver microsomal phospholipids characterised by increased proportions of monounsaturated fatty acid in phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Here, we have used electrospray ionisation mass spectrometry (ESI-MS) to determine the patterns of alteration to individual molecular species compositions of PC, PE and phosphatidylinositol (PI) in response to gradually decreasing temperature. The results demonstrate that cold induces precise changes to a limited number of phospholipid species, and that these changes are distinct and different for each phospholipid class. The major change for PC was increased 16:1/22:6, but for PE the species that increased was 18:1/22:6. By contrast, the PI species that increased during cold acclimation were characterised by an sn-1 monounsaturated fatty acid in combination with arachidonoyl or eicosapentaenoyl fatty acid at the sn-2 position. Analysis of acyl distribution indicates that cold only caused the accumulation of monounsaturated fatty acids at the sn-1 and not at the sn-2 position of phospholipids. These results highlight the tight and restricted range of modifications that membranes make to their phospholipid composition in response to thermal stress.
Evidence for increased myofibrillar mobility in desmin-null mouse skeletal muscle
Authors: Shah Sameer B. , Su Fong-Chin , Jordan Kimberly , Milner Derek J. , Fridén Jan , Capetanaki Yassemi , Lieber Richard L. 
Published: April 2021

SUMMARY
Quantitative electron microscopy was used to characterize the longitudinal mobility of myofibrils during muscle extension to investigate the functional roles of skeletal muscle intermediate filaments. Extensor digitorum longus fifth toe muscles from wild-type (+/+) and desmin-null (des –/–) animals were passively stretched to varying lengths, and the horizontal displacement of adjacent Z-disks in neighboring myofibrils (Δxmyo) and average sarcomere length (SL) were calculated. At short SL (&lt;2.20 μm), wild-type and desmin-null Δxmyo were not significantly different, although there was a trend towards greater Z-disk misalignment in muscles from knockout animals (Δxmyo 0.34±0.04 μm versus 0.22±0.09 μm; P&gt;0.2; means ± s.e.m.). However, at higher SL (&gt;2.90 μm), muscles from knockout animals displayed a dramatically increased Δxmyo relative to wild-type muscles (0.49±0.10 μm versus 0.25±0.07 μm; P&lt;0.05). The results, which establish a maximum extension of the desmin network surrounding the Z-disk, provide what we believe to be the first quantitative estimation of the functional limits of the desmin intermediate filament system in the presence of an intact myofibrillar lattice. The existence of a limit on the extension of desmin suggests a mechanism for the recruitment of desmin into a network of force transmission, whether as a longitudinal load bearer or as a component in a radial force-transmission system.
Determining patterns of motor recruitment during locomotion
Authors: Wakeling James M. , Kaya Motoshi , Temple Genevieve K. , Johnston Ian A. , Herzog Walter 
Published: April 2021

SUMMARY
Motor units are the functional units of muscle contraction in vertebrates. Each motor unit comprises muscle fibres of a particular fibre type and can be considered as fast or slow depending on its fibre-type composition. Motor units are typically recruited in a set order, from slow to fast, in response to the force requirements from the muscle. The anatomical separation of fast and slow muscle in fish permits direct recordings from these two fibre types. The frequency spectra from different slow and fast myotomal muscles were measured in the rainbow trout Oncorhynchus mykiss. These two muscle fibre types generated distinct low and high myoelectric frequency bands. The cat paw-shake is an activity that recruits mainly fast muscle. This study showed that the myoelectric signal from the medial gastrocnemius of the cat was concentrated in a high frequency band during paw-shake behaviour. During slow walking, the slow motor units of the medial gastrocnemius are also recruited, and this appeared as increased muscle activity within a low frequency band. Therefore, high and low frequency bands could be distinguished in the myoelectric signals from the cat medial gastrocnemius and probably corresponded, respectively, to fast and slow motor unit recruitment. Myoelectric signals are resolved into time/frequency space using wavelets to demonstrate how patterns of motor unit recruitment can be determined for a range of locomotor activities.