bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sexual Dimorphism in Forelimb Muscles of the Bullfrog,Rana Catesbeiana: A Functional Analysis of Isometric Contractile Properties
Authors: Peters Susan E. , Aulner Dwane A. 
Published: April 2021

ABSTRACTIn many species of frog, the forelimb muscles important in amplexus are known to be much larger in males than in females. We studied this dimorphism in three forelimb muscles in the bullfrog [abductor indicus longus (AIL), flexor carpi radialis (FCR) and extensor carpi radialis (ECR)] by testing their isometric contractile properties. One muscle that is not dimorphic, the extensor carpi ulnaris (ECU), was also studied as a control. In addition to being greater in wet mass and in cross-sectional area in the males, our data show that the dimorphic muscles also produce significantly larger isometric forces in males than in females. The tetanic force per cm2 of muscle cross-sectional area did not differ between the sexes, so that force within a muscle varies directly with muscle size. However, a number of the contractile variables we measured show that male muscles differ functionally from those of females. The male twitch contraction times were significantly longer in the AIL, and the male half-relaxation times were longer in both the AIL and FCR. These two dimorphic muscles were also significantly less fatiguable in males than were the corresponding female muscles. Their higher endurance resulted from the maintenance of high levels of unrelaxed force sustained between trains of stimuli during the fatigue test. This sustained force is much less pronounced in the female muscles, suggesting that high levels of sustained force may be a key functional feature that enables males to maintain amplexus economically for prolonged periods.
Relative Metabolic Utilization ofin situRabbit Soleus Muscle: Thermistor-Based Measurements And Model
Authors: Gustafson Kenneth J. , Egrie Glenn D. , Reichenbach Steven H. 
Published: April 2021

ABSTRACTElectrically conditioned skeletal muscle can provide the continuous power source for cardiac assistance devices. Optimization of the available sustained power from in vivo skeletal muscle requires knowledge of its metabolic utilization and constraints. A thermistor-based technique has been developed to measure temperature changes and to provide a relative estimate for metabolic utilization of in situ rabbit soleus muscle. The relative thermistor response, active tension and muscle displacement were measured during cyclic isometric and isotonic contractions across a range of muscle tensions and contraction durations. The thermistor response demonstrated linear relationships versus both contraction duration at a fixed muscle length and active tension at a fixed contraction duration (r2=0.90±0.14 and 0.70±0.21, respectively; means ± S.D.). A multiple linear regression model was developed to predict normalized thermistor response, ΔT, across a range of conditions. Significant model variables were identified using a backward stepwise regression procedure. The relationships for the in situ muscles were qualitatively similar to those reported for mammalian in vitro muscle fiber preparations. The model had the form ΔT=C+atcF+bW, where the constant C, and coefficients for the contraction duration tc (ms), normalized active tension F and normalized net work W were C=−1.00 (P&lt;0.001), a=5.97 (P&lt;0.001) and b=2.12 (P&lt;0.001).
Local Movements Evoked by Chemical Stimulation of the Hind leg in the Locust Schistocerca Gregaria
Authors: Rogers Stephen M. , Newland Philip L. 
Published: April 2021

ABSTRACT
The behavioural responses of desert locusts, Schistocerca gregaria, to solutions of four behaviourally relevant chemicals (sodium chloride, sucrose, nicotine hydrogen tartrate and lysine glutamate) applied as droplets to the hind tarsus were analysed. All responses following within 1 s of chemical stimulation were local leg avoidance reflexes, and the probability of eliciting such a response increased in a dose-dependent manner with increasing concentration for all the chemicals tested. Chemical identity, however, critically determined the concentration threshold at which the different chemicals became an effective stimulus. For example, a 2.5 mmol l−1 concentration of the secondary plant metabolite nicotine hydrogen tartrate (NHT), a potent feeding deterrent to locusts, was sufficient to evoke avoidance responses in 50 % of cases, whilst for the nutrients, sucrose and lysine glutamate, 250–500 mmol l−1 of the chemical was needed to induce avoidance behaviour in 50 % of the locusts. NaCl was of intermediate effectiveness, with a 50 % response rate occurring at a concentration of approximately 50 mmol l−1. The latency to the start of the response following stimulation was negatively correlated with the concentration of NaCl, but for the other chemicals concentration had no effect on latency. The duration of the avoidance behaviour decreased with increasing concentration for NaCl and more weakly for NHT, but not for the other chemicals. Adding a subthreshold concentration of sucrose to 50 mmol l−1 NaCl decreased the incidence of response compared with 50 mmol l−1 NaCl on its own. Experiments with other mixtures combining NaCl, sucrose and NHT indicate that the frequency and dynamics of the responses to chemical mixtures cannot be simply predicted from the responses to their individual constituents.
Effects of Temperature on Escape Jetting in the Squid Loligo Opalescens
Authors: Neumeister H. , Ripley B. , Preuss T. , Gilly W. F. 
Published: April 2021

ABSTRACT
In Loligo opalescens, a sudden visual stimulus (flash) elicits a stereotyped, short-latency escape response that is controlled primarily by the giant axon system at 15 °C. We used this startle response as an assay to examine the effects of acute temperature changes down to 6 °C on behavioral and physiological aspects of escape jetting. In free-swimming squid, latency, distance traveled and peak velocity for single escape jets all increased as temperature decreased. In restrained squid, intra-mantle pressure transients during escape jets increased in latency, duration and amplitude at low temperature. Recordings of stellar nerve activity revealed repetitive firing of the giant motor axon accompanied by increased activity in the non-giant motor axons that run in parallel. Selective stimulation of giant and non-giant motor axons in isolated nerve–muscle preparations failed to show the effects seen in vivo, i.e. increased peak force and increased neural activity at low temperature. Taken together, these results suggest that L. opalescens is able to compensate escape jetting performance for the effects of acute temperature reduction. A major portion of this compensation appears to occur in the central nervous system and involves alterations in the recruitment pattern of both the giant and non-giant axon systems.
Comparison of a Ca2+-Gated Conductance and a Second-Messenger-Gated Conductance in Rat Olfactory Neurons
Authors: Okada Yukio , Fujiyama Rie , Miyamoto Takenori , Sato Toshihide 
Published: April 2021

ABSTRACT
The effect of a rise in intracellular Ca2+ concentration was analyzed in isolated rat olfactory neurons using a whole-cell patch-clamp technique. Intracellular dialysis of 1 mmol l−1 Ca−1 in a standard-K+, low-Cl− internal solution (ECl=−69 mV) from the patch pipette into the olfactory neurons induced a sustained outward current of 49±5 pA (N=13) at −50 mV in all the cells examined. The outward currents were inhibited by external application of 100 μmol l−1 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB). External application of a Ca2+ ionophore, 3 μmol l−1 ionomycin, induced an inward current in three of eight cells whose voltages were clamped using the gramicidin-perforated technique, but ionomycin elicited an outward current in the other five cells, suggesting that natural intracellular Cl− concentration in the olfactory neurons was heterogeneous. While intracellular dialysis of 50 μmol l−1 inositol 1,4,5-trisphosphate (1,4,5-InsP3) in the standard-K+, low-Cl− internal solution induced the NPPB-sensitive outward current in 31 % of cells, and 500 μmol l−1 cAMP induced it in 21 % of cells, a large proportion of the cells displayed an inward current in response to 1,4,5-InsP3 and cAMP. The results suggest that 1,4,5-InsP3 and cAMP can elicit Ca2+-dependent Cl− conductance and Ca2+-independent cation conductance in rat olfactory neurons.
Pacap and Nitric Oxide Inhibit Contractions in the Proximal Intestine of the Atlantic Cod, Gadus Morhua
Authors: Olsson Catharina , Holmgren Susanne 
Published: April 2021

ABSTRACT
The possible inhibitory roles of pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP) and nitric oxide in the control of intestinal motility were investigated in the Atlantic cod, Gadus morhua. Circular and longitudinal smooth muscle preparations developed spontaneous contractions that were inhibited by atropine (10−5 mol l−1). PACAP 27 and PACAP 38 (10−7 mol l−1) reduced the amplitude of the contractions but did not usually affect the resting tension. In the circular preparations, the mean active force developed (above resting level; ± S.E.M.) was reduced from 0.62±0.18 mN to 0.03±0.03 mN (N=10) by PACAP 27 and from 0.53±0.20 mN to 0.31±0.13 mN (N=7) by PACAP 38, while neither cod nor mammalian VIP (10−10–10−6 mol l−1) had any effect. In the longitudinal preparations, PACAP 27 reduced the force developed from 1.58±0.22 mN to 0.44±0.25 mN (N=8) and PACAP 38 reduced it from 1.61±0.47 mN to 0.75±0.28 mN (N=5). The nitric oxide donor sodium nitroprusside (NaNP) almost abolished the contractions in the circular preparations, reducing the mean force developed from 0.47±0.05 mN to 0.02±0.06 mN (10−6 mol l−1; N=9) and 0±0.07 mN (10−5 mol l−1; N=8). In the longitudinal preparations, NaNP reduced the force developed from 2.03±0.36 mN to 0.33±0.22 mN (10−6 mol l−1; N=8) and 0.19±0.30 mN (10−5 mol l−1; N=8). The L-arginine analogue NG-nitro-L-arginine methyl ester (L-NAME; 3×10−4 mol l−1) enhanced the contractions in both circular and longitudinal preparations, increasing the mean force developed from 0.51±0.12 mN to 0.94±0.21 mN (N=8) and from 1.49±0.36 mN to 3.34±0.67 mN (N=7), respectively. However, preincubation with L-NAME before a second addition of PACAP 27 (10−7 mol l−1) did not affect the response to PACAP, neither did preincubation with the guanylate cyclase inhibitor 6-anilinoquinoline-5,8-quinone (LY83583; 10−5 mol l−1), while the inhibitory response to NaNP (3×10−7 mol l−1) was abolished by LY83583. The PACAP analogue PACAP 6-27 (3×10−7 mol l−1) had no effect on the response to either NaNP (3×10−7 mol l−1) or PACAP 27 (10−8 mol l−1) in the circular preparations. These findings indicate the presence of both a cholinergic and a nitrergic tonus in the smooth muscle preparations of the cod. Although PACAP and NaNP both inhibit contractions, there is no evidence of any interactions between the two substances. In addition, NaNP, but not PACAP, probably acts via stimulating the production of cyclic GMP. In conclusion, both PACAP and nitric oxide may act as inhibitory transmitters, using distinct signalling pathways, in the control of intestinal motility in the Atlantic cod.
Song Recognition in Female Bushcrickets Phaneroptera Nana
Authors: Tauber E. , Pener M. P. 
Published: April 2021

ABSTRACT
Unlike most acoustic systems evolved for pair formation, in which only males signal, in many species of phaneropterine bushcrickets both sexes sing, producing a duet. We used the duetting species Phaneroptera nana as a model to explore the cues in the male’s song that elicit the female’s phonoresponse. Different synthetic male songs (chirps containing 2–6 pulses) were presented to Ph. nana females, and their acoustic responses were recorded. The threshold of the female response is lowest at 16 kHz (best frequency), coinciding with the dominant frequency of the male song. The specific amplitude pattern of consecutive pulses in the song of the male is not a critical factor in his signal. That is, songs with both a normal and a reversed order of pulses equally elicit a female response. By systematically deleting pulses from the synthetic male chirp, we found that at least two pulses are needed to elicit a female reply. Under no-choice conditions, increasing the number of pulses did not result in a higher probability of response and did not change the latency of the response; i.e. two pulses are necessary and sufficient to elicit a female response. The range of pulse duration that elicits a female response is 0.2–25 ms, and the inter-pulse silent interval ranges from 5 to 30 ms.
Antidiuretic Effects of a Factor in Brain/Corpora Cardiaca/Corpora Allata Extract on Fluid Reabsorption Across the Cryptonephric Complex of Manduca Sexta
Authors: Liao Sha , Audsley Neil , Schooley David A. 
Published: April 2021

ABSTRACT
Extracts of the brain/corpora cardiaca/corpora allata (Br/CC/CA) complex of Manduca sexta larvae elicit an antidiuretic effect, measured by an increase in fluid reabsorption across the cryptonephric complex of larval M. sexta. Separation of the extract by reversed-phase liquid chromatography gave two fractions with antidiuretic effects. The more potent of these two factors was further characterized for its effects on the cryptonephric complex. Its antidiuretic effect is not inhibited by bumetanide, a drug that inhibits M. sexta diuretic hormone (Mas-DH)-stimulated fluid reabsorption. These data indicate that the mechanism of the antidiuretic effect of the factor is different from that of Mas-DH on the cryptonephric complex. The basal reabsorption of the cryptonephric complex is blocked when treated on the lumen side with bafilomycin A1, an inhibitor of the H+-ATPase, or with amiloride, an inhibitor of the H+/K+ antiporter. However, the antidiuretic-factor-stimulated fluid reabsorption is not affected by either bafilomycin A1 or amiloride. The increase in reabsorption triggered by the semi-purified factor can be inhibited by Cl− channel blockers or by removing Cl− from the lumen side of the cryptonephric complex. It appears that this factor activates a Cl− pump associated with the cryptonephric complex. Forskolin mimics the effect of this factor on fluid reabsorption, and the effect of forskolin is not inhibited by bumetanide. A selective and potent inhibitor of protein kinase A, H-89, also inhibits antidiuretic-factor-stimulated fluid reabsorption. Addition of the factor to cryptonephric complexes maintained in vitro caused a significant increase in cyclic AMP levels extracted from these tissues compared with values for controls. These data suggest that the antidiuretic effect of the factor in Br/CC/CA extract is mediated by cyclic AMP.
Molecular Systematics of the African Electric Fishes (Mormyroidea: Teleostei) and A Model for the Evolution of Their Electric Organs
Authors: Sullivan John P. , Lavoué Sébastien , Hopkins Carl D. 
Published: April 2021

ABSTRACT
We present a new molecular phylogeny for 41 species of African mormyroid electric fishes derived from the 12S, 16S and cytochrome b genes and the nuclear RAG2 gene. From this, we reconstruct the evolution of the complex electric organs of these fishes. Phylogenetic results are generally concordant with earlier preliminary molecular studies of a smaller group of species and with the osteology-based classification of Taverne, which divides the group into the Gymnarchidae and the Mormyridae, with the latter including the subfamilies Petrocephalinae (Petrocephalus) and Mormyrinae (all remaining taxa). However, we find that several genera previously recognized by Taverne are non-monophyletic. Within the Mormyrinae, the genus Myomyrus is the sister group to all the remaining taxa. Other well-supported clades within this group are recovered. A reconstruction of electrocyte evolution on the basis of our best-supported topology suggests that electrocytes with penetrating stalks evolved once early in the history of the mormyrids followed by multiple paedomorphic reversals to electrocytes with non-penetrating stalks.
Serotonin Activates A Ca2+-Dependent K+ Current in Identified Peptidergic Neurons from the Crayfish
Authors: Alvarado-Álvarez Ramón , Aréchiga Hugo , García Ubaldo 
Published: April 2021

ABSTRACT
The effects of 5-hydroxytryptamine (5-HT) were investigated in red pigment concentrating hormone (RPCH)-containing neurons isolated from the X-organ of the crayfish (Procambarus clarkii). Under current-clamp conditions and using the gramicidin-perforated-patch configuration, 5-HT elicited a prolonged hyperpolarization that suppressed neuronal firing concomitant with an increase in membrane conductance. Under voltage-clamp conditions, 5-HT evoked an outward current at a holding potential of −50 mV. This current reversed at an EK of −90 mV, which shifted by 30 mV when the extracellular K+ concentration was increased from 5.4 to 19 mmol l−1. The effect of 5-HT was dose-dependent within the range 1–100 μmol l−1 and followed simple
Michaelis–Menten kinetics, with a half-maximal response being elicited at 10 μmol l−1. Preincubation with charybdotoxin (100 nmol l−1), tetraethylammonium (500 μmol l−1) or methysergide (100 μmol l−1) was effective in blocking the response to 5-HT. These results suggest that 5-HT is an inhibitory mediator of the release of red pigment concentrating hormone by acting on a Ca2+-dependent K+ current.
Effect of Wind and Solar Radiation on Metabolic Heat Production in a Small Desert Rodent, Spermophilus Tereticaudus
Authors: Wooden K. Mark , Walsberg Glenn E. 
Published: April 2021

ABSTRACT
To understand better how complex interactions between environmental variables affect the energy balance of small diurnal animals, we studied the effects of the absence and presence of 950 W m−2 simulated solar radiation combined with wind speeds ranging from 0.25 to 1.00 m s−1 on the metabolic rate and body temperature of the round-tailed ground squirrel Spermophilus tereticaudus. As wind speed increased from 0.25 to 1.00 m s−1, metabolic heat production increased by 0.94 W in the absence of solar radiation and by 0.98 W in the presence of 950 W m−2 simulated solar radiation. Exposure to simulated solar radiation reduced metabolic heat production by 0.68 W at a wind speed of 0.25 m s−1, by 0.64 W at 0.50 m s−1 and by 0.64 W at 1.00 m s−1. Body temperature was significantly affected by environmental conditions, ranging from 32.5 °C at a wind speed of 1.0 m s−1 and no irradiance to 35.6 °C at a wind speed of 0.50 m s−1 with 950 W m−2 short-wave irradiance.
In addition, several unusual findings resulted from this study. The coat of S. tereticaudus is very sparse, and the observed heat transfer of 5.68±0.37 W m−2 °C−1 (mean ± S.E.M., N=11) is much higher than expected from either allometric equations or comparative studies with other rodents of similar mass. Solar heat gain was remarkably low, equalling only 10 % of intercepted radiation and suggesting a remarkably high regional thermal resistance at the tissue level. Animals remained normally active and alert at body temperatures as low as 32.5 °C. These findings suggest a unique combination of adaptations that allow S. tereticaudus to exploit a harsh desert environment.
Sun-Compass Orientation in Homing Pigeons: Compensation for Different Rates of Change in Azimuth?
Authors: Wiltschko Roswitha , Walker Michael , Wiltschko Wolfgang 
Published: April 2021

ABSTRACT
Birds using their sun compass must compensate for the apparent movement of the sun with the help of their internal clock. The movement of the sun is not uniform, being much faster around noon than near sunrise and sunset. If the sun-compass mechanisms are not adjusted to these variations, considerable errors might arise. To learn whether birds are able to take the different rates of sun azimuth change into account, we subjected homing pigeons to a 4 h fast clock-shift. The experiments were performed near Auckland, New Zealand, at a latitude of 37°S, where the expected deflections for a 4 h shift in summer vary from less than 40 ° to more than 120 °, depending on time of day. One group of birds was released just after sunrise or during the corresponding period in the afternoon when the expected deflections were minimal, the other group during late morning when they were maximal. The different sizes of the observed deflections – between 26 ° and 51 ° in the first group, and between 107 ° and 153 ° in the second group – clearly show that the birds’ compensation mechanisms are closely tuned to the varying rates of change in sun azimuth. The results suggest that pigeons have a rather precise internal representation of the sun curve, which makes the avian sun compass a highly accurate mechanism of direction finding.
Avian Pectoral Muscle Size Rapidly Tracks Body Mass Changes During Flight, Fasting and Fuelling
Authors: Lindström Åke , Kvist Anders , Piersma Theunis , Dekinga Anne , Dietz Maurine W. 
Published: April 2021

ABSTRACT
We used ultrasonic imaging to monitor short-term changes in the pectoral muscle size of captive red knots Calidris canutus. Pectoral muscle thickness changed rapidly and consistently in parallel with body mass changes caused by flight, fasting and fuelling. Four knots flew repeatedly for 10 h periods in a wind tunnel. Over this period, pectoral muscle thickness decreased in parallel with the decrease in body mass. The change in pectoral muscle thickness during flight was indistinguishable from that during periods of natural and experimental fasting and fuelling. The body-mass-related variation in pectoral muscle thickness between and within individuals was not related to the amount of flight, indicating that changes in avian muscle do not require power-training as in mammals. Our study suggests that it is possible for birds to consume and replace their flight muscles on a time scale short enough to allow these muscles to be used as part of the energy supply for migratory flight. The adaptive significance of the changes in pectoral muscle mass cannot be explained by reproductive needs since our knots were in the early winter phase of their annual cycle. Instead, pectoral muscle mass changes may reflect (i) the breakdown of protein during heavy exercise and its subsequent restoration, (ii) the regulation of flight capacity to maintain optimal flight performance when body mass varies, or (iii) the need for a particular protein:fat ratio in winter survival stores.
A Conserved Location For the Central Nervous System Control of Mating Behaviour in Gastropod Molluscs: Evidence From a Terrestrial Snail
Authors: Koene Joris M. , René Jansen F. , Maat Andries Ter , Chase Ronald 
Published: April 2021

ABSTRACT
We have investigated the role of the right mesocerebrum in the expression of mating behaviour in the garden snail Helix aspersa. Using an in vivo stimulation and recording technique, we provide evidence for both sensory and motor functions in the mesocerebral neuronal population. Some neurones were specifically sensitive to tactile stimuli delivered to the skin on the superior tentacles and around the genital pore. Electrical stimulation of the right mesocerebrum evoked genital eversion and, in combination with tactile stimulation, dart-shooting and penial eversion. Genital eversions were also elicited by injections of APGWamide. During courtship, one recorded unit increased its activity only in correlation with penial eversion, while six other units increased their activity only during dart-shooting. Three additional units increased their activity during both types of behaviour. In addition, most of the recorded units showed increased neuronal activity during times of contact with a partner. Comparison of our results with available data from other molluscs leads us to conclude that the right anteromedial region of the cerebral ganglion is an evolutionarily conserved region of the gastropod brain specialised for the control of male mating behaviour. It is striking to find such functional conservation in the central nervous system of phylogenetically distant gastropods given the large differences in behaviour during mating.