bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exercise-Related Changes in Protein Turnover in Mammalian Striated Muscle
Authors: Goldspink David F. 
Published: April 2021

ABSTRACT
Contractile activity is an important determinant of the size, rate of protein turnover and phenotypic properties of muscle. Animal models that decrease muscle activity invariably accelerate the rate of protein degradation, usually complementing decreases in the rate of protein synthesis. The net effect is muscle atrophy. By contrast, increased activity and/or passive stretch enhance the synthesis of new proteins, whilst protein catabolism may be either decreased or increased. Muscle hypertrophy results.
Endurance activities in man and animals usually induce cardiac hypertrophy, and increased fatigue resistance in skeletal muscle. During exercise the whole body and its skeletal musculature exhibit a negative nitrogen balance, and there is general agreement that rates of protein synthesis are decreased. Changes in protein degradation are, however, much less clearly defined.
Resistance exercises induce the opposite changes, with the size of the heart remaining unchanged whilst the bulk and strength of skeletal muscle increase. No real consensus currently exists about the nature of the changes in protein turnover with this type of exercise. More carefully designed and executed experiments are required.
Stepping Patterns In Ants:II. Influence Of Body Morphology
Authors: Zollikofer Christoph P. E. 
Published: April 2021

ABSTRACT
The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals during walking on smoked-glass plates. Subsequent multivariate analyses of walking kinematics and footfall positions showed marked species-specific as well as size-dependent differences in the locomotory behaviour. The geometric properties of the footfall patterns resulting from the alternating tripod gait scale to leg dimensions in a geometric manner. At high speed, footprint distances between succeeding tripods exceed maximum leg extension, indicating that ants are ‘trotting’ from one tripod to the next one with intermittent aerial phases. In at least one species (Cataglyphis bombycina), there is evidence for quadrupedal locomotion at the highest speed. The functional relationship between stride length (s, the distance between successive footprints of the same foot) and speed (v) was best described by a curvilinear model, s=avb. Exponent b ranges from 0.3 to 0.6 and reveals differences between species. Within species, exponent b is constant, whereas factor a scales to leg length. Females and males show metachronal interleg coordination patterns rather than the alternating tripod coordination pattern seen in workers of the same species.
Head Waving in Aplysia Californica: III. Interganglionic Pathways Underlying the Coordination and Control of Searching Movements
Authors: Kuenzi Frederick M. , Carew Thomas J. 
Published: April 2021

ABSTRACT
The central nervous system of the sea hare Aplysia californica is divided into four pairs of ganglia and a fused abdominal ganglion. Work in several laboratories has established that the neural circuitry for producing locomotor rhythms is contained within the pair of pedal ganglia. The cerebropedal connective carries command-like information from the cerebral ganglia, and neurones projecting in the pedal commissure act to synchronize the retrograde pedal wave during locomotion. During head waving, the longitudinal muscles on the two sides of the body work in antiphase, in contrast to the bilateral synchrony of the locomotor rhythm, so we have investigated the roles of these two interganglionic pathways in the production and coordination of head-waving movements. Unilateral transection of the cerebropedal connective prevents animals from making normal horizontal bends towards the side of the lesion: specifically, animals could no longer keep the transverse axis of the head parallel to the substratum. We hypothesize that the increase in twisting about the long axis of the animal is due to decreased activation of longitudinal muscles on the lesioned side, whilst the control of the circular and helical muscles is maintained by the pedal commissure. Transection of the pedal commissure had no effect on individual head-waving movements, but the erect posture of the animal during head waving was disrupted, possibly because of an overall decrease in circular muscle activity. Double lesions (transection of one cerebropedal connective and the pedal commissure) caused a significant reduction in the animal’s ability to extend its body during a bout of head waving, particularly on the side of the lesion. This suggests that, in addition to the activation of specific excitatory circuits for posture and movement, the interganglionic pathways are necessary for tonic inhibition of the motor circuits in the pedal ganglia.
A New Family of Proteins (rBAT and 4F2hc) Involved in Cationic and Zwitterionic Amino Acid Transport: a Tale of Two Proteins in Search of a Transport Function
Authors: Palacín Manuel 
Published: April 2021

ABSTRACT
The currently identified cDNA clones of mammalian amino acid transporters can be grouped into five different families. One family is composed of the proteins rBAT and the heavy chain (hc) of the cell surface antigen 4F2. RNAs encoding these two proteins induce a system bo,+-like (rBAT) and a system y+L-like (4F2hc) activity in Xenopus oocytes. Surprisingly, rBAT and 4F2hc do not seem to be pore-forming proteins. This finding supports the hypothesis that rBAT and 4F2hc are subunits or modulators of the corresponding amino acid transport systems. Expression of rBAT in oocytes induces high-affinity transport of cystine, which is shared with transport of cationic and zwitterionic amino acids. The rBAT gene is expressed mainly in kidney and small intestine. The rBAT protein is localized to the microvilli of proximal straight tubules of the kidney and mucosa from the small intestine. This finding is consistent with the involvement of rBAT in a high-affinity resorption system for cystine in the proximal straight tubule of the nephron. All of these characteristics suggest that rBAT is a good candidate for a cystinuria gene. Cystinuria is an inheritable defect in high-affinity transport of cystine, shared with cationic amino acids, through epithelial cells of the renal tubule and intestinal tract. Very recently, point missense mutations have been found in the rBAT gene of cystinuria patients. The most frequent rBAT mutation, M467T (threonine substitution of methionine at residue 467) nearly abolished the amino acid transport activity elicited by rBAT in oocytes. This result offers convincing evidence that rBAT is a cystinuria gene. Biochemical, cytological and genetic approaches are now needed to delineate the mechanism of action of rBAT and 4F2hc in the transport of amino acids.
Regulatory Volume Decrease in Carp Red Blood Cells: Mechanisms and Oxygenation-Dependency of Volume-Activated Potassium and Amino Acid Transport
Authors: Jensen Frank B. 
Published: April 2021

ABSTRACT
Hypo-osmotic swelling of carp red blood cells (RBCs) induced a regulatory volume decrease (RVD), which restored the original cell volume within 140 min in oxygenated RBCs, whereas volume recovery was incomplete in deoxygenated RBCs. The complete RVD in oxygenated RBCs resulted from a sustained volume-activated release of K+, Cl− and amino acids (AAs). In the absence of ouabain, the cells also lost Na+ as released K+ was partially regained via the Na+/K+ pump. Inorganic osmolytes contributed approximately 70%, and organic osmolytes approximately 30 %, to the RVD of oxygenated RBCs. Oxygenation in isotonic medium per se activated a K+ efflux from the RBCs. Hypo-osmotic cell swelling stimulated an additional K+ release. The oxygenation-activated and the volume-activated K+ efflux were both inhibited by DIDS and by the replacement of Cl− with NO3−, showing that both types of K+ efflux were Cl−-dependent and probably occurred via the same K+/Cl− cotransport mechanism. Once activated by oxygenation, the K+/Cl− cotransport was further stimulated by cell swelling. Deoxygenation inactivated the oxygenation-induced Cl−-dependent K+ release and cell swelling was not a sufficient stimulus to reactivate it significantly. In deoxygenated RBCs, the volume-induced K+ release was transient and primarily Cl−-independent and, in the absence of ouabain, the cell K+ content recovered towards control values via the Na+/K+ pump. The Cl−-independent K+ efflux seemed to involve K+/H+ exchange, but other transport routes also participated. Swelling-activated AA release differed in kinetics between oxygenated and deoxygenated RBCs but was important for RVD at both oxygenation degrees. Approximately 70 % of the AA release was inhibited by DIDS and substitution of NO3− for Cl− produced a 50 % inhibition, suggesting that the AA permeation was partly Cl−-dependent. In oxygenated RBCs, a reduction in pH lowered the volume-activated Cl−-dependent K+ efflux but not the AA efflux. In deoxygenated RBCs, the acute volume-stimulated K+ and AA release were both increased by acidification. The data are discussed in relation to possible transducer mechanisms and physiological implications.
Functionally significant allelic variation in myosin light chain composition in a tropical cichlid
Authors: Crockford Tony , Johnston Ian A. , McAndrew Brendan J. 
Published: April 2021

ABSTRACT
Single fast muscle fibres in the tropical fish Oreochromis andersonii were found to contain two myosin light chains (LC1s; LC1f1* or LC1f2*). Breeding experiments confirmed that the different LC1s were of allelic origin and their inheritance patterns conformed to Mendelian expectations (1:2:1). The LC1s differed in apparent relative molecular mass by 800–900. No other differences in myosin subunits were found between the LC1 genotypes. The molar ratios of LC3:LC1(total) in the fast muscle of O. andersonii homozygous for LC1f1* or LC1f2* and heterozygous for both alleles were 2.0:1, 2.1:1 and 2.2:1, respectively, as determined by capillary electrophoresis. The maximum contraction velocity (Vmax) of single skinned muscle fibres was determined at 20 °C by the slack-test method. Vmax values (fibre lengths s-1) for fast muscle fibres from O. andersonii which were homozygous for either LC1f2* or LC1f1* were 5.3 and 3.3, respectively, compared with 3.8 when both alleles were present. Crosses between Oreochromis niloticus and O. andersonii produced F1 hybrids which were heterozygous for either LC1n/LC1f1* or LC1n/LC1f2*, where LC1n is the myosin light chain for O. niloticus. The distribution of myosin light chain genotypes in hybrid offspring was not significantly different from the expected Mendelian 1:1 ratio (47 %: 53 %). The Vmax (fibre lengths s-1) of muscle fibres containing LC1f2* from hybrid Oreochromis was 4.3 compared with 3.1 for the LC1f1* genotype. The results are consistent with a functionally significant allelic variation in myosin LC1 in fast muscle fibres from O. andersonii which is also expressed in hybrid genotypes.
The Feeding Stimulus in Rhodnius Prolixus is Transmitted to the Brain by a Humoral Factor
Authors: Mulye H. , Davey K. G. 
Published: April 2021

ABSTRACT
Neurosecretory cells in the brain of Rhodnius prolixus are known to be the source of an ovulation hormone released at feeding. They were selected to test the hypothesis that feeding brings about the release of another hormone in the abdomen which is transported forward to activate the neuroendocrine axis in the brain, and that severing the aorta interferes with this transport. These cells have previously been shown to exhibit an increase in action potential frequency at the time of release of their hormone. In normal females, the spike frequency of the cells increased after feeding and remained high over at least the next 24 h. In females with the dorsal vessel severed, the spike frequency remained low, at levels near those of unfed females, except for a transitory increase 4 h after feeding.
The spike frequency of the neurosecretory cells in females with the dorsal vessel severed increased when hemolymph from fed normal females or from those with their dorsal vessel severed was placed directly on the brains of the test females. Hemolymph taken from unfed females did not produce this response. The activity in the hemolymph was heat-stable and disappeared after pronase or trypsin digestion. Similar activity was present in the fused thoracico-abdominal ganglionic mass, but absent from fore-, mid-and hindgut and from the abdominal neurosecretory organs.
Functional Morphology of the Vanes of the Flight Feathers of the Pigeon Columba Livia
Authors: Ennos A. Roland , Hickson John R. E. , Roberts Anna 
Published: April 2021

ABSTRACT
The functional morphology of feather vanes was examined by combining morphological examination with mechanical tests. A geometrical model was derived which related the in-plane behaviour of the vane to the orientation of the barbs and barbules. This predicted that the small branching angles of both barbs and proximal barbules should result in a vane which is easier to move distally than proximally. These predictions were verified by mechanical tests on primary and secondary feathers of the pigeon Columba livia. A further prediction, that the inclination of the barbs’ cross section should make the vanes more resistant to forces from below than those from above, was also confirmed by mechanical tests.
Differences in the mechanical behaviour of feathers are related to differences in their morphology and function. The vanes of outer primaries are more resistant to out-of-plane forces than those of the inner primaries and secondaries, particularly towards their tip, a property which will help them withstand the larger aerodynamic forces to which they may be subjected in flight. The outermost primary vane also showed the least asymmetry to out-of-plane forces as a result of the more vertical orientation of its barbs. This may help it to act as a reversible aerofoil during take-off.
Adenosine and Anoxia Reduce N-Methyl-D-Aspartate Receptor Open Probability in Turtle Cerebrocortex
Authors: Buck Leslie T. , Bickler Philip E. 
Published: April 2021

ABSTRACT
During normoxia, glutamate and the glutamate family of ion channels play a key role in mediating rapid excitatory synaptic transmission in the central nervous system. However, during hypoxia, intracellular [Ca2+ ] increases to neurotoxic levels, mediated largely by the N-methyl-D-aspartate (NMDA) subfamily of glutamate receptors. Adenosine has been shown to decrease the magnitude of the hypoxia-induced increase in [Ca2+ ]i in mammalian brain slices, delaying tissue injury. Turtle brain is remarkably tolerant of anoxia, maintaining a pre-anoxic [Ca2+ ]i while cerebral adenosine levels increase 12-fold. Employing cell-attached single-channel patch-clamp techniques, we studied the effect of adenosine (200 µmol l−1 ) and anoxia on NMDA receptor open probability (Popen ) and current amplitude. After 60 min of anoxic perfusion, channel Popen decreased by 65% (from 6.8±1.6 to 2.4±0.8%) an effect that could also be achieved with a normoxic perfusion of 200 µmol l−1 adenosine (Popen decreased from 5.8±1.1 to 2.3±1.2%). The inclusion of 10 µmol l−1 8-phenyltheophylline, an A1 receptor blocker, prevented the adenosine- and anoxia-induced decrease in Popen . Mean single-channel current amplitude remained at approximately 2.7±0.23 pA under all experimental conditions. To determine whether a change in the membrane potential could be part of the mechanism by which Popen decreases, membrane and threshold potential were measured following each experiment. Membrane potential did not change significantly under any condition, ranging from −76.8 to −80.6 mV. Therefore, during anoxia, NMDA receptors cannot be regulated by Mg2+ in a manner dependent on membrane potential. Threshold potentials did decrease significantly following 60 min of anoxic or adenosine perfusion (control −33.3±1.9 mV, anoxia −28.4±1.5 mV, adenosine −23.4±2.8 mV). We conclude that anoxia modulates NMDA receptor activity and that adenosine plays a key role in mediating this change. This is the first direct measurement of ion channel activity in anoxic turtle brain and demonstrates that ion channel regulation is part of the naturally evolved anoxic defence mechanism of this species.
A Computational Fluid Dynamic Study of Hawkmoth Hovering
Authors: Liu Hao , Ellington Charles P. , Kawachi Keiji , Van Den Berg Coen , Willmott Alexander P. 
Published: April 2021

ABSTRACT
A computational fluid dynamic (CFD) modelling approach is used to study the unsteady aerodynamics of the flapping wing of a hovering hawkmoth. We use the geometry of a Manduca sexta-based robotic wing to define the shape of a three-dimensional ‘virtual’ wing model and ‘hover’ this wing, mimicking accurately the three-dimensional movements of the wing of a hovering hawkmoth. Our CFD analysis has established an overall understanding of the viscous and unsteady flow around the flapping wing and of the time course of instantaneous force production, which reveals that hovering flight is dominated by the unsteady aerodynamics of both the instantaneous dynamics and also the past history of the wing.
A coherent leading-edge vortex with axial flow was detected during translational motions of both the up- and downstrokes. The attached leading-edge vortex causes a negative pressure region and, hence, is responsible for enhancing lift production. The axial flow, which is derived from the spanwise pressure gradient, stabilises the vortex and gives it a characteristic spiral conical shape.
The leading-edge vortex created during previous translational motion remains attached during the rotational motions of pronation and supination. This vortex, however, is substantially deformed due to coupling between the translational and rotational motions, develops into a complex structure, and is eventually shed before the subsequent translational motion.
Estimation of the forces during one complete flapping cycle shows that lift is produced mainly during the downstroke and the latter half of the upstroke, with little force generated during pronation and supination. The stroke plane angle that satisfies the horizontal force balance of hovering is 23.6°, which shows excellent agreement with observed angles of approximately 20–25°. The time-averaged vertical force is 40% greater than that needed to support the weight of the hawkmoth.
Extreme Resistance to Desiccation in Overwintering Larvae of the Gall Fly Eurosta Solidaginis (Diptera, Tephritidae)
Authors: Ramløv Hans , Lee Richard E. 
Published: April 2021

ABSTRACT
During winter, larvae of the goldenrod gall fly Eurosta solidaginis are exposed for extended periods to severe low ambient temperatures and low humidities within plant galls. The resistance of these larvae to desiccation at various temperatures and humidities, the transition (critical) temperature, and the effects of treatment with organic solvents on the larval rates of water loss and on changes in osmolality during desiccation were examined. The water loss rates of the flesh fly Sarcophaga crassipalpis under desiccating conditions were also measured.
The water permeability of the cuticle of E. solidaginis larvae was very low (0.038 μg h−1 cm−2 Pa−1 at 20 °C and 4 % relative humidity) compared with that of larvae of other species. The value for E. solidaginis is equivalent to that of the very drought-resistant larvae of the tenebrionid beetle Tenebrio molitor (0.038 μg h−1 cm−2 Pa−1 at 30 °C). In contrast, the permeability of larvae of the flesh fly Sarcophaga crassipalpis at 20 °C and 4 % relative humidity was 0.331 μg h−1 cm−2 Pa−1.
The thermal dependence of the cuticular permeability increased with temperature by approximately 0.0010 μg h−1 cm−2 Pa−1 °C−1 in the interval between 4 and 40 °C. At the transition temperature of 40 °C, the thermal dependence of the permeability increased abruptly to 0.0400 μg h−1 cm−2 Pa−1 °C−1. Larvae treated with hexane and acetone remained remarkably resistant to water loss. However, treatment with chloroform:methanol increased the water loss rate approximately 25-fold.
During desiccation at 4 °C and 4 % relative humidity for 21 days, E. solidaginis larvae showed a mass loss of 18.5±4.4 % (mean ± S.E.M., N=6). Animals dried under the same conditions over the same period showed a haemolymph osmolality of 851±75 mosmol kg−1 (N=4). Larvae freshly removed from the galls showed a haemolymph osmolality of 918±67 mosmol kg−1 (N=3). A higher osmolality in the dried compared with the fresh larvae would have been expected. The present observation suggests that important ions in the haemolymph may have been excreted or rendered osmotically inactive during desiccation.
Prey Transport Kinematics In Tupinambis Teguixin And Varanus Exanthematicus: Conservation Of Feeding Behavior In ‘Chemosensory-Tongued’ Lizards
Authors: Elias Jason A. , Mcbrayer Lance D. , Reilly Stephen M. 
Published: April 2021

ABSTRACT
Although lizards have been predicted to show extensive intraoral prey-processing behaviors, quantitative analyses of the types of prey-processing behavior they demonstrate and of their kinematics have been limited. The more basal lizard lineages (Iguanians) have undergone some study, but the prey-processing repertoires of crown taxa have not been thoroughly examined and quantitative comparisons of behaviors within or among species have not been made. In this study, the prey transport behavior of the savannah monitor (Varanus exanthematicus) and gold tegu (Tupinambis teguixin) are described. Although these two lineages have independently evolved tongues that are highly specialized for chemoreception, we found that they share the same three distinct types of transport behavior. These behavior patterns are (i) a purely inertial transport, (ii) an inertial transport with use of the tongue, and (iii) a non-inertial lingual transport. The tongue is used extensively in both the inertial and the purely lingual transport behaviors. More than 75 % of all transport behaviors involved tongue movements. These species appear to exhibit a conservation of feeding kinematics compared with patterns known for basal lizards. A hypothesis for the evolution of inertial feeding is proposed.