bluuebunny/crossref_metadata_2025 huggingface dataset:
Spinal Reflexes of the Dogfish, Scyllium Canicula
Authors: Gray J. , Sand A.
Published: April 2021

In a previous paper (Gray and Sand, 1936) the persistent swimming rhythm of the spinal dogfish was described, and an account was given of experiments which demonstrate that the locomotory rhythm is determined by the intrinsic activity of the spinal cord without the participation of proprioceptor arcs. In the course of this work it became evident that the rhythmic activity of the spinal dogfish can be modified in various ways by external mechanical stimulation. These responses present a relatively simple pattern of reflex behaviour, their number is strictly limited, and they are uniformly reproducible. For these reasons, although our experiments raise a number of physiological questions which our data cannot answer, we have thought it worth while to record these phenomena in the present communication.
The Growth and Morphology of Fibro-BlastsIn Vitroin Relation to Certain Properties of the Plasma Coagulum1
Authors: Jacoby Fritz
Published: April 2021

By placing blood plasma coagula containing growing cultures (fibroblasts from chick embryo) in a vertical position (vertical cultures) certain physical and quantitative chemical alterations of the medium occur under the influence of gravity; the effects of these upon the growth, morphology and products of differentiation (fibre formation) of the cultures are described. In vertical cultures the normal circular shape of the cell colony remains undisturbed, indicating that neither gravity nor a gradient of metabolites seems to play a role controlling the direction of movement of fibroblastic cells. Vertical cover-slip cultures show a greater radial extension (outgrowth) than the horizontal controls, apparently due to increased cell migration rather than to augmented cell division. Vertical cultures of fibroblasts, both on cover-slips and in flasks, do not show the usual appearance of visible fat droplets. If fat appears at all in vertical cultures a fat-free sector can sometimes be observed in the lower half of the culture. Flattening of the coagulum retards but does not prevent the appearance of visible fat in normal cultures. Under certain conditions the appearance of fat is an indicator of reduced activity since activity of fibroblastic cells (growth by migration) can be increased by preventing the accumulation of fat droplets in them. The latent period of offspring of a 10-day-old fat-free vertical culture is shortened as compared with that of offspring of the very fatty horizontal control of the same age. The greater activity observed in the vertical cover-slip cultures is apparently due to the non-appearance of fat. Vertical cover-slip cultures after three days’ cultivation show a slightly stronger formation of argyrophil fibres in the outer growth zone than the controls, but culture pairs fixed at a later time show no appreciable difference in fibre formation.
Exercise-Related Changes in Protein Turnover in Mammalian Striated Muscle
Authors: Goldspink David F.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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.
Effects of Fin Size on Swimming Performance, Swimming Behaviour and Routine Activity of Zebrafish Danio Rerio
Authors: Plaut Itai
Published: April 2021

The zebrafish Danio rerio exhibits substantial morphological variability in the sizes and shapes of the body and the caudal fin. The present study describes swimming performance, swimming behaviour and routine locomotor activity patterns in three of the major morphotypes: wild-type, long-finned and no-tail. Wild-type and long-finned differ in total length (TL), fork length (FL), caudal fin length (CFL) and caudal fin height (CFH). No-tail has no caudal fin and is significantly smaller in standard length (SL) than the other types. Critical swimming speeds (Ucrit) were measured at 28 °C in a modified Brett-type water tunnel. Ucrit of wild-type fish was 56.0±4.8 cm s−1 or 15.5 SL s−1 (mean ± S.D., N=21), significantly faster than the Ucrit of long-finned fish (43.7±6.8 cm s−1 or 12.5 SL s−1, N=17); both were significantly faster than the Ucrit of no-tail fish (19.8±4.7 cm s−1 or 6.9 SL s−1, N=15). When forced to swim in the water tunnel, zebrafish tended to turn and swim downstream for short periods at slow water velocities. Turning frequencies (turns per minute, fT) at the slowest velocity (4 cm s−1) were 10.1±6.5 min−1 (N=63) and 8.6±4.7 min−1 (N=51) for wild-type and long-finned, respectively, significantly different from that of the no-tail fish, 4.7±2.8 min−1 (N=45). These frequencies decreased below 1 min−1 at 56 %, 64 % and 61 % of Ucrit in wild-type, long-finned and no-tail fish, respectively. Activity levels of wild-type fish were generally significantly higher than those of long-finned fish, and the levels of both were significantly higher than those of no-tail fish. The pattern of differences in relative activity levels between types was similar to that for Ucrit. The results show that the wild-type fish, on a size-scaled basis, is one of the fastest-swimming fishes ever measured, reaching the maximum predicted theoretical sustained swimming speed. Ucrit of long-finned fish was 22 % lower than that of wild-type fish, and Ucrit of no-tail fish was 65 % lower. Similar differences were found in turning frequencies and routine activity level.
Mammalian Oxygen Sensing, Signalling and Gene Regulation
Authors: Wenger Roland H.
Published: April 2021

Oxygen is essential to the life of all aerobic organisms. Virtually every cell type is able to sense a limited oxygen supply (hypoxia) and specifically to induce a set of oxygen-regulated genes. This review summarizes current concepts of mammalian oxygen-sensing and signal-transduction pathways. Since the discovery of the hypoxia-inducible factors (HIFs), a great deal of progress has been made in our comprehension of how hypoxia induces the expression of oxygen-regulated genes. The α subunit of the heterodimeric transcription factors HIF-1, 2 and 3 is unstable under normoxia but is rapidly stabilized upon exposure to hypoxic conditions. Following heterodimerization with the constitutively expressed β subunit, HIFs activate the transcription of an increasing number of genes involved in maintaining oxygen homeostasis at the cellular, local and systemic levels.
The Effects of Acute Hypoxia on Chemically or Neuronally Induced Catecholamine Secretion in Rainbow Trout (Oncorhynchus Mykiss) in Situ and In Vivo
Authors: Perry Steve F. , Montpetit Colin J. , Borowska Maja
Published: April 2021

The potential direct and modulating effects of acute hypoxia on catecholamine secretion in rainbow trout (Oncorhynchus mykiss) were assessed in situ, using a perfused cardinal vein preparation, and in vivo, using chronically cannulated fish. Acute (10 min) perfusion with hypoxic saline or homologous hypoxic blood did not have a statistically significant effect on basal (non-stimulated) catecholamine secretion. A field stimulation technique was used to excite the sympathetic nerves innervating the chromaffin cells electrically in situ under conditions of high- (saline or low- (saline perfusion at constant (2.3 mmHg). The results demonstrated that neuronally evoked catecholamine secretion was significantly lowered by 50 % during perfusion with hypoxic saline. To assess whether the inhibitory effect of hypoxia during neuronal stimulation in situ resulted from modulation of nicotinic and/or muscarinic receptor-linked pathways, perfused posterior cardinal vein preparations were injected with selective nicotinic (10−7 or 10−6 mol kg−1 nicotine) or muscarinic (10−3 mol kg−1 methacholine) receptor agonists. For both doses of nicotine, catecholamine secretion was significantly lowered during hypoxia by 55 %. During muscarinic receptor stimulation, perfusion with hypoxic saline caused a 42 % reduction in the rate of catecholamine secretion. In contrast, catecholamine secretion elicited by depolarising levels of KCl (60 mmol l−1) was unaffected by the oxygen status of the perfusate. In vivo, intra-arterial injections of nicotine (300–600 nmol kg−1) into normoxic or moderately hypoxic fish caused a dose-dependent elevation of circulating catecholamine levels. However, despite the inhibitory influence of localised hypoxia on chromaffin cell responsiveness previously demonstrated in situ, the increase in plasma catecholamine levels after intra-arterial injection of nicotine was significantly enhanced in the hypoxic fish. The differences between the results from the in vivo and in situ experiments may reflect the contribution of higher control centres and modulating factors in vivo that are absent in situ.
Nitric Oxide Modulates Cardiac Performance in the Heart of Anguilla Anguilla
Authors: Imbrogno Sandra , Iuri Lucia De , Mazza Rosa , Tota Bruno
Published: April 2021

Nothing is known about the effects of nitric oxide (NO) on cardiac performance in fish. Using an in vitro working heart preparation that generates physiological values of output pressure, cardiac output and ventricular work and power, we assessed the effects of NO on the cardiac performance of the eel Anguilla anguilla. We examined basal cardiac performance (at constant preload, afterload and heart rate), the effects of cholinergic stimulation and the Frank–Starling response (preload-induced increases in cardiac output at constant afterload and heart rate). The NO synthase (NOS) inhibitors NG -monomethyl-L-arginine (L-NMMA) and L-N5 (1-iminoethyl)ornithine (L-NIO), the guanylate cyclase inhibitor 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ) and Triton X-100, a detergent that damages the endocardial endothelium, all increased stroke volume (VS) and stroke work (WS). In contrast, the endogenous NOS substrate L-arginine, tested before and after treatment with haemoglobin, the NO donor 3-morpholinosydnonimine, tested with and without the superoxide scavenger superoxide dismutase, and the stable cGMP analogue 8-bromoguanosine 3’, 5’ -cyclic monophosphate (8-Br-cGMP) decreased VS and WS. Acetylcholine chloride produced a biphasic effect. At nanomolar concentrations, in 34 % of the preparations, it induced a NO–cGMP-dependent positive inotropism that required the integrity of the endocardial endothelium. Pretreatment with Triton X-100 or with NO–cGMP pathway inhibitors (L-NMMA, L-NIO, NG -nitro-L-arginine methyl ester, Methylene Blue and ODQ) abolished the positive effect of acetylcholine. In contrast, at micromolar concentrations, acetylcholine produced a negative effect that involved neither the endocardial endothelium nor the NO–cGMP pathway. Pre-treatment with L-arginine (10− 6 mol l− 1) was without effect, whereas L-NIO (10− 5 mol l− 1) significantly reduced the Frank–Starling response. Taken together, these three experimental approaches provide evidence that NO modulates cardiac performance in the eel heart.
Plasticity of Chemotaxis Revealed by Paired Presentation of A Chemoattractant and Starvation in the Nematode Caenorhabditis Elegans
Authors: Saeki Satoshi , Yamamoto Masayuki , Iino Yuichi
Published: April 2021

While the basic functioning of the nervous system of Caenorhabditis elegans has been extensively studied, its behavioural plasticities have not been fully explored because of the limited availability of assay systems. We report here a simple form of chemotaxis plasticity in this organism: when worms are starved on plates that contain NaCl, their chemotaxis towards NaCl falls dramatically. This conditioning requires both the presence of NaCl and the absence of a bacterial food source, indicating that it is not merely adaptation or habituation, but that it is likely to be a form of associative learning. While chemotaxis towards volatile chemoattractants does not change significantly after conditioning with NaCl, chemotaxis towards other water-soluble attractants does decrease. This suggests that an altered response of a cell or a group of cells specifically involved in chemotaxis towards water-soluble chemoattractants is responsible for the behavioural alteration. The decrease in chemotaxis occurred slowly over 3–4 h of conditioning and returned quickly to the original level when either of the conditioning stimuli, NaCl or starvation, was removed. The application of serotonin partially blocked this reduction in chemotaxis, consistent with the proposed function of this neurotransmitter in food signalling. Using this assay, we have isolated three mutants with reduced plasticity. This assay system expands the opportunities for studying the molecular and cellular mechanisms of behavioural plasticity in C. elegans.
The Application of Ground Force Explains The Energetic Cost of Running Backward and Forward
Authors: Wright Seth , Weyand Peter G.
Published: April 2021

We compared backward with forward running to test the idea that the application of ground force to support the weight of the body determines the energetic cost of running. We hypothesized that higher metabolic rates during backward versus forward running would be directly related to greater rates of ground force application and the volume of muscle activated to apply support forces to the ground. Four trained males ran backward and forward under steady-state conditions at eight treadmill speeds from 1.75 to 3.50 m s−1. Rates of oxygen uptake were measured to determine metabolic rates, and inverse periods of foot–ground contact (1/tc) were measured to estimate rates of ground force application. As expected, at all eight speeds, both metabolic rates and estimated rates of ground force application were greater for backward than for forward running. At the five slowest speeds, the differences in rates of ground force application were directly proportional to the differences in metabolic rates between modes (paired t-test, P<0.05), but at the three highest speeds, small but significant differences in proportionality were present in this relationship. At one of these three higher speeds (3.0 m s−1), additional measurements to estimate muscle volumes were made using a non-invasive force plate/video technique. These measurements indicated that the volume of muscle active per unit of force applied to the ground was 10±3 % greater when running backward than forward at this speed. The product of rates of ground force application and estimated muscle volumes predicted a difference in metabolic rate that was indistinguishable from the difference we measured (34±6 % versus 35±6 %; means ± S.E.M., N=4). We conclude that metabolic rates during running are determined by rates of ground force application and the volume of muscle activated to apply support forces to the ground.
Red and white muscle development in the trout (Oncorhynchus mykiss) as shown byin situhybridisation of fast and slow myosin heavy chain transcripts
Authors: Rescan Pierre-Yves , Collet Bertrand , Ralliere Cecile , Cauty Chantal , Delalande Jean-Marie , Goldspink Geoffrey , Fauconneau Benoit
Published: April 2021

The axial muscle of most teleost species consists of a deep bulk of fast-contracting white fibres and a superficial strip of slow-contracting red fibres. To investigate the embryological development of fast and slow muscle in trout embryos, we carried out single and double in situ hybridisation with fast and slow myosin heavy chain (MyHC)-isoform-specific riboprobes. This showed that the slow-MyHC-positive cells originate in a region of the somite close to the notochord. As the somite matures in a rostrocaudal progression, the slow-MyHC-positive cells appear to migrate radially away from the notochord to the lateral surface of the myotome, where they form the superficial strip of slow muscle. Surprisingly, the expression pattern of the fast MyHC showed that the differentiation of fast muscle commences in the medial domain of the somite before the differentiation and migration of the slow muscle precursors. Later, as the differentiation of fast muscle progressively spreads from the inside to the outside of the myotome, slow-MyHC-expressing cells become visible medially. Our observations that the initial differentiation of fast muscle takes place in proximity to axial structures and occurs before the differentiation and migration of slow muscle progenitors are not in accord with the pattern of muscle formation in teleosts previously described in the zebrafish Danio rerio, which is often used as the model organism in fishes.
Flight-motor-driven respiratory air flow in the hawkmothManduca sexta
Authors: Wasserthal Lutz T.
Published: April 2021

Intratracheal pressure during tethered flight was analyzed at the anterior spiracles and mesoscutellar air sacs in the hawkmoth Manduca sexta using electronic pressure sensors. CO2 emission from the anterior spiracles and the posterior thoracic and abdominal spiracles was measured using a URAS gas analyzer with a split-specimen chamber. Experiments were accompanied by photocell recordings of the wingbeat. The structural differences between the mesothoracic and metathoracic spiracles are described. Deformations of the lateral thorax and their effect upon the spiracles were observed under stroboscopic light.

During shivering, ventilation pulses are generated by the flight muscles reminiscent of an autoventilation mechanism with tidal air flow. During steady flight, however, a unidirectional airstream arises with a mean negative (subatmospheric) pressure at the first (mesothoracic) spiracles and a mean positive pressure in the mesoscutellar air sacs. As a result of this pressure difference during flight, CO2 is emitted only at the posterior spiracles.

The suction force for the inspiration flow at the anterior spiracles is generated by the flight apparatus as a result of prevention of inspiration through the posterior thoracic spiracles. During the downstroke, the volume of the thoracic air sacs increases, while the posterior thoracic spiracles are automatically enclosed in the subalar cleft below the wing hinge and are probably closed. During the upstroke, the air sac volume decreases and the moth expires through the open posterior spiracles.
Spatial integration in polarization-sensitive interneurones of crickets: a survey of evidence, mechanisms and benefits
Authors: Labhart Thomas , Petzold Jürgen , Helbling Hansruedi
Published: April 2021

Many insects exploit the polarization pattern of the sky for compass orientation in navigation or cruising-course control. Polarization-sensitive neurones (POL1-neurones) in the polarization vision pathway of the cricket visual system have wide visual fields of approximately 60° diameter, i.e. these neurones integrate information over a large area of the sky. This results from two different mechanisms. (i) Optical integration; polarization vision is mediated by a group of specialized ommatidia at the dorsal rim of the eye. These ommatidia lack screening pigment, contain a wide rhabdom and have poor lens optics. As a result, the angular sensitivity of the polarization-sensitive photoreceptors is very wide (median approximately 20°). (ii) Neural integration; each POL1-neurone receives input from a large number of dorsal rim photoreceptors with diverging optical axes. Spatial integration in POL1-neurones acts as a spatial low-pass filter. It improves the quality of the celestial polarization signal by filtering out cloud-induced local disturbances in the polarization pattern and increases sensitivity.
Immunochemical analysis of the vacuolar proton-ATPase B-subunit in the gills of a euryhaline stingray (Dasyatis sabina): effects of salinity and relation to Na+/K+-ATPase
Authors: Piermarini Peter M. , Evans David H.
Published: April 2021

In the gills of freshwater teleost fishes, vacuolar proton-ATPase (V-H+-ATPase) is found on the apical membrane of pavement and chloride (Na+/K+-ATPase-rich) cells, and is an important transporter for energizing Na+ uptake and H+ excretion. In the gills of elasmobranch fishes, the V-H+-ATPase has not been extensively studied and its expression in freshwater individuals has not been examined. The goals of this study were to examine the effects of environmental salinity on the expression of V-H+-ATPase in the gills of an elasmobranch (the Atlantic stingray, Dasyatis sabina) and determine if V-H+-ATPase and Na+/K+-ATPase are expressed in the same cells. We found that gills from freshwater stingrays had the highest relative abundance of V-H+-ATPase and greatest number of V-H+-ATPase-rich cells, using immunoblotting and immunohistochemistry, respectively. When freshwater animals were acclimated to sea water for 1 week, V-H+-ATPase abundance and the number of V-H+-ATPase-rich cells decreased significantly. Atlantic stingrays from seawater environments were characterized by the lowest expression of V-H+-ATPase and least number of V-H+-ATPase-rich cells. In contrast to teleost fishes, localization of V-H+-ATPase in freshwater stingray gills was not found in pavement cells and occurred on the basolateral membrane in cells that are presumably rich in mitochondria. In freshwater stingrays acclimated to sea water and seawater stingrays, V-H+-ATPase localization appeared qualitatively to be stronger in the cytoplasm, which may suggest the transporter was stored in vesicles. Using a double-immunolabeling technique, we found that V-H+-ATPase and Na+/K+-ATPase occurred in distinct cells, which suggests there may be two types of mitochondrion-rich cells in the elasmobranch gill epithelium. Based on these findings, we propose a unique model of NaCl and acid–base regulation where the V-H+-ATPase-rich cells and Na+/K+-ATPase-rich cells are the sites of Cl– uptake/HCO3– excretion and Na+ uptake/H+ excretion, respectively.
Comparative kinematics of the forelimb during swimming in red-eared slider (Trachemys scripta) and spiny softshell (Apalone spinifera) turtles
Authors: Pace Cinnamon M. , Blob Richard W. , Westneat Mark W.
Published: April 2021

Softshell turtles (Family Trionychidae) possess extensive webbing between the digits of the manus, suggesting that the forelimb may serve as an effective thrust generator during aquatic locomotion. However, the hindlimb has previously been viewed as the dominant propulsive organ in swimming freshwater turtles. To evaluate the potential role of the forelimb in thrust production during swimming in freshwater turtles, we compared the forelimb morphology and three-dimensional forelimb kinematics of a highly aquatic trionychid turtle, the spiny softshell Apalone spinifera, and a morphologically generalized emydid turtle, the red-eared slider Trachemys scripta. Spiny softshells possess nearly twice as much forelimb surface area as sliders for generating drag-based thrust. In addition, although both species use drag-based propulsion, several aspects of forelimb kinematics differ significantly between these species. During the thrust phase of the forelimb cycle, spiny softshells hold the elbow and wrist joints significantly straighter than sliders, thereby further increasing the surface area of the limb that can move water posteriorly and increasing the velocity of the distal portion of the forelimb. These aspects of swimming kinematics in softshells should increase forelimb thrust production and suggest that the forelimbs make more substantial contributions to forward thrust in softshell turtles than in sliders. Spiny softshells also restrict forelimb movements to a much narrower dorsoventral and anteroposterior range than sliders throughout the stroke, thereby helping to minimize limb movements potentially extraneous to forward thrust production. These comparisons demonstrate considerable diversity in the forelimb kinematics of turtles that swim using rowing motions of the limbs and suggest that the evolution of turtle forelimb mechanics produced a variety of contrasting solutions for aquatic specialization.
The Salivary Apyrase of the Blood-Sucking Sand Fly Phlebotomus Papatasi Belongs to the Novel Cimex Family of Apyrases
Authors: Valenzuela Jesus G. , Belkaid Yasmine , Rowton Edgar , Ribeiro José M. C.
Published: April 2021

Apyrases are enzymes that hydrolyze nucleotide di- and triphosphates to orthophosphate and mononucleotides. At least two families of enzymes, belonging to the 5′-nucleotidase and to the actin/heat shock 70/sugar kinase superfamily, have evolved independently to serve the apyrase reaction. Both families require either Ca2+ or Mg2+ for their action. A novel apyrase enzyme sequence, with no homology to any other known protein sequence, was found recently in the salivary glands of the hematophagous bed bug Cimex lectularius. This enzyme functions exclusively with Ca2+. Here, we report the finding of a cDNA similar to that of the C. lectularius salivary apyrase isolated from a salivary gland cDNA library of Phlebotomus papatasi. Transfection of insect cells with the P. papatasi salivary gland apyrase cDNA resulted in the secretion of a Ca2+-dependent apyrase whose activity was indistinguishable from that in salivary homogenates of P. papatasi. Homologous sequences were found in humans, in another sand fly (Lutzomyia longipalpis), in the fruit fly Drosophila melanogaster, in the nematode Caenorhabditis elegans and in the protozoan Cryptosporidium parvum, indicating that this family of enzymes is widespread among animal species.