bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Strain on the Equine Hoof Wall in vivo: Implications for the Material Design and Functional Morphology of the Wall
Authors: Thomason J. J. , Biewener A. A. , Bertram J. E. A. 
Published: April 2021

ABSTRACT
Surface strains were recorded from four rosette gauges at different sites on the right forehooves of three ponies running on a treadmill at seven constant speeds and using three gaits. Principal strains determined from the rosette signals indicate that the hoof material is loaded predominantly in compression and that the wall is distorted in a regular, repeatable manner at all speeds and gaits. Peak principal strains reach –5000 μϵ, compared with –2800 μϵ reported for the equine radius under similar locomotory conditions. Orientations of peak compressive strains do not correlate strongly with microstructural axes in the material. Comparison of our in vivo strain records with previous in vitro studies of the material properties of the wall shows that hoof keratin behaves as a multidirectional composite, capable of tolerating its usual operating strains in any direction. This mechanical behaviour also allows the material to withstand many unpredictable loading situations when the hoof contacts irregular substrata. An important property of the hoof wall is its ability to resist or redirect cracks. We found that the anterior aspect of the wall is loaded in biaxial compression, which assists in preventing the formation or propagation of cracks and reduces peak strain magnitudes. The strain patterns correlate well with current models of hoof distortion during weight bearing. In these models, transmission of force between the ground and the skeleton is seen as the primary cause of compression in the material. The third phalanx, which transmits the weight, is effectively suspended from the inner surface of the hoof wall. Spreading of the posterior borders (heels) of the hoof also occurs. The combination of weight-bearing, suspension of the third phalanx and heel spreading is probably responsible for the uncommon loading condition of biaxial compression on the anterior wall.
Adaptation of Feeding Sequences in Aplysia Oculifera to Changes in the Load and Width of Food
Authors: Hurwitz Itay , Susswein Abraham J. 
Published: April 2021

ABSTRACT
In Aplysia oculifera, we examined how feedback from foods of differing physical characteristics produces feeding sequences that are appropriate to the food. Animals were fed strips of food systematically modified by attaching weights to the end of the strip or by changing the width of the strip. Both changes led to an increase in inter-swallow interval and a decrease in the amount of food that entered the mouth per swallow. These data indicate that the oscillator setting swallowing frequency is affected by feedback, but that the amplitude of swallowing movements may not be regulated by feedback. Some swallows led to partial or complete cutting of the food. In some cases, cutting led to loss of contact and release of the food. When cutting releases food, its function is apparently to prevent food that has already been swallowed from being pulled out of the mouth. Cutting food may also serve additional functions.
Fura-2 Measurement of Cytosolic Free Ca2+ Concentration in Corpus Allatum Cells of Larval Manduca Sexta
Authors: Allen C. U. , Herman B. , Granger N. A. 
Published: April 2021

ABSTRACT
Cytosolic free Ca2+ has been implicated in the regulation of the larval corpus allatum (CA) of the tobacco hornworm Manduca sexta since agents presumed to cause changes in intracellular Ca2+ concentrations affect both basal and neuropeptide-modulated synthesis/release of the juvenile hormones. To determine whether differences in cytosolic free [Ca2+] in CA cells were associated with different levels of gland activity, methods were developed for dissociating CA cells with the retention of biosynthetic activity and for uptake by the dissociated cells of the fluorescent Ca2+ indicator Fura-2. Digitized fluorescence microscopy of the Fura-2-loaded cells enabled measurement of intracellular Ca2+ levels in individual cells. Intracellular free Ca2+ levels were measured in CA cells from selected days during the fifth larval stadium and were found to be highest when the CA were biosynthetically active. Treatment of CA cells from day 6 with the Ca2+ ionophore ionomycin elevated the intracellular Ca2+ level, corroborating the involvement of elevated intracellular [Ca2+] in ionophore effects on juvenile hormone (JH) and JH acid synthesis. The results of the study are considered in relation to our knowledge of the role of Ca2+ in the function of endocrine gland cells.
Direct Measurement of Swimming Speeds and Depth of Blue Marlin
Authors: Block Barbara A. , Booth David , Carey Francis G. 
Published: April 2021

ABSTRACT
Acoustic telemetry was used to monitor the swimming speed, depth and water temperature of three blue marlin (60 kg, 70 kg, 125 kg) and 165 h of continuous swimming speed data containing both sustained and burst swimming events were collected. Measurements of swimming speed show that, while blue marlin are capable of high speeds, they spend most of their time swimming slowly. The fastest sustained swimming speeds (80–120 cm s−1) occurred during a 4–6h recovery period immediately after tagging when marlin consistently swim at depths greater than 50 m. Short bursts of speeds up to 225 cm s−1 were usually associated with changes in depth. Slower swimming (15–25 cms−1) occurred when fish were within 10 m of the surface. These velocities are similar to direct measurements of swimming speeds of free-swimming sharks, seals and sea lions, indicating that many large aquatic vertebrates swim slowly to minimize energetic costs of transport.
Calcium Transport By Isolated Skin Of Rainbow Trout
Authors: Marshall William S. , Bryson Sharon E. , Wood Chris M. 
Published: April 2021

ABSTRACT
The skin overlying the cleithrum bone of freshwater-acclimated rainbow trout contains numerous mitochondria-rich (MR) cells, as detected by DASPEI fluorescence. This tissue was mounted in vitro in an Ussing-style chamber with fresh water on the mucosal surface and saline supplemented with bovine serum albumin on the serosal surface. The preparation developed a high transepithelial resistance and a small transepithelial potential (Vt), positive on the serosal side. Radioisotopic flux measurements indicated that the preparation actively transported Ca2+ from the mucosal to the serosal surface, as assessed by the Ussing flux ratio criterion. Ca2+ transport was positively correlated with MR cell density. Cortisol pretreatment in vivo reduced MR cell density and increased Vt but did not significantly alter Ca2+ fluxes. Ca2+ transport was unaffected by adrenergic agonists (10−5moll−1 adrenaline, clonidine, isoprenaline) or cyclic AMP stimulants (10−3molll dibutyryl cyclic adenosine monophosphate, db-cAMP, plus 10−4moll−1 isobutylmethylxanthine, IBMX) applied to the serosal surface. The Ca2+ ionophore ionomycin (1×10−6–3.2× 10−6moll−1 on the mucosal surface) increased both unidirectional Ca2+ fluxes and caused Ca2+ to accumulate within the epithelium. Lanthanum (10−4 mol I−1) did not inhibit unidirectional Ca2+ fluxes, but apparently displaced Ca2+ from binding sites on the mucosal surface. Unlike Ca2+, movements of Na+ and Cl− across the epithelium were passive, as assessed by the flux ratio criterion, and neither adrenaline nor db-cAMP plus IBMX had any effect on Na+ or Cl− fluxes or electrical properties. These results indicate that ion transport across the skin mediated by MR cells (‘chloride cells’) contributes to Ca2+ but not to NaCl balance in freshwater trout.
Transbranchial Ammonia Gradients and Acid-Base Responses to High External Ammonia Concentration in Rainbow Trout (Oncorhynchus Mykiss) Acclimated to Different Salinities
Authors: Wilson R. W. , Taylor E. W. 
Published: April 2021

ABSTRACT
Transbranchial ammonia gradients and blood acid-base status have been examined in rainbow trout acclimated to fresh water (FW), 33% sea water (33 %SW) and sea water (SW) and exposed to 1.0 mmol I−1 total ammonia (TAmm) at pH7.9 for 24 h. At all three salinities trout maintained large negative (inwardly directed) NH3 and NH4+ gradients throughout the exposure, presumably by active excretion of NH4+ to counteract the passive inward diffusion of ammonia. Analysis of blood non-respiratory acid-base status revealed an acid load in FW trout and a base load in SW trout following 24 h of exposure. This indicates that active NH4+/H+ exchange predominates in FW whereas NH4+/Na+ is the principal exchange utilised in SW under these experimental conditions.
The plasma TAmm load incurred during ammonia exposure increased with salinity. Compared to FW trout, plasma TAmm values were 34 and 73 % higher in the 33 %SW and SW trout, respectively, after 24 h. This cannot be explained by differences in the prevailing transbranchial gradient because ambient was substantially lower at the higher salinities (due to higher pK’ and solubility values). We interpret the difference between FW and SW trout as an increased permeability to NH4+ in fish acclimated to the higher-salinity environments. Transbranchial diffusion of NH4+ is, therefore, probably more important as a route for ammonia excretion in SW than in FW trout, especially considering the favourable transepithelial potentials normally found in SW teleosts. In addition, increased NH4+ permeability implies that the toxicity of ammonia will be greater in seawater than in freshwater teleosts and should not simply be measured as a function of the unionised ammonia concentration when considering seawater-adapted species.
A Nerve-Muscle Preparation From the Snail
Authors: Ramsay J. A. 
Published: April 2021

ABSTRACT
A nerve-muscle preparation from the snail and its method of removal from the animal are described. Further description is given of the apparatus used for obtaining records of its activity. The nerve appears to contain fibres which fall into two groups according to their diameters. It is suggested that the thin fibres are derived from the thick ones. No physiological evidence of double innervation has been found. There is clear evidence of neuro-muscular facilitation. The muscle contracts in response to low concentrations of acetylcholine.
Ambulatory Reflexes in Spinal Amphibians
Authors: Gray J. , Lissmann H. W. 
Published: April 2021

ABSTRACT
The profound effect of spinal deafferentation upon the locomotory activity of amphibians (Gray & Lissmann, 1940) suggests that peripheral sense organs play an essential role in the maintenance of normal ambulatory activity. In order to test this conclusion, a preliminary study has been made of those reflex responses which can be elicited from the limbs of spinal newts, frogs and toads, by the application of peripheral stimuli similar in kind and intensity to those which arise automatically during normal progression. Unless otherwise stated, all observations were made on preparations in which the nerve cord had been severed at or about the level of the first vertebra. All operations were performed under ether, and the preparations were allowed to recover from shock. The animals employed were Triton cristatus, Rana temporaria and Bufo bufo.
Catecholamine-Activated Sodium/Proton Exchange in the Red Blood Cells of the Marine Teleost Gadus Morhua
Authors: Berenbrink M. , Bridges C. R. 
Published: April 2021

ABSTRACT
The effects of catecholamines on the pH and the cellular ion and water content were investigated in red blood cells from the Atlantic cod (Gadus morhua). Noradrenaline induced a rapid decrease in the extracellular pH (pHe) of red blood cells suspended in a CO2/bicarbonate or in a CO2/bicarbonate-free buffer system. The noradrenaline-induced changes in pHe were a saturable function of the external sodium ion concentration and were inhibited by amiloride but not by DIDS (4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid, final concentration of both 10×4 mol l−1). The catecholamine-induced extracellular acidification was accompanied by an intracellular alkalization and protons were moved from their electrochemical equilibrium. Proton extrusion was associated with an increase in the red blood cell sodium and chloride concentrations. In the presence of DIDS, the chloride movements were blocked and the net proton efflux under these conditions matched the net sodium influx. The results strongly suggested the activation of a sodium/proton exchanger by catecholamines in the red blood cells of the Atlantic cod. The red blood cell receptor affinity for adrenaline was three times higher than that for noradrenaline. Comparison with data in the literature for in vivo catecholamine concentrations indicated that adrenaline was more effective than noradrenaline in activating the red blood cell sodium/proton exchanger in the Atlantic cod in vivo.
Reconstitution of Metachronal Waves in Ciliated Cortical Sheets of Paramecium: II. Asymmetry of the Ciliary Movements
Authors: Okamoto Ken-Ichi , Nakaoka Yasuo 
Published: April 2021

ABSTRACT
In conditions in which ciliated cortical sheets prepared from detergent-extracted Paramecium multimicronucleatum cells adhered to glass coverslips on a microscope stage, perfusion of a reactivation medium containing ATP plus cyclic AMP or cyclic GMP generated metachronal waves. An analysis of the ciliary movements that generate these metachronal waves yielded the following results. During the generation of metachronal waves, there were phase differences in the ciliary orientation of adjacent cilia in the direction of wave propagation. Addition of cyclic AMP or cyclic GMP increased the rotational angular velocities during the effective stroke of ciliary beating, but did not increase the rotational angular velocity of the recovery stroke. When the ATP concentration in the cyclic GMP reactivation medium was increased, the rotational angular velocity during the effective stroke rose steeply and saturated at 0.8 mmol l-1 ATP, whereas that during the recovery stroke rose gradually. Addition of cyclic nucleotides caused a single cilium isolated from neighbouring cilia on the cortical sheet to incline almost parallel to the cortical surface during the recovery stroke. Addition of cyclic GMP increased the amplitude of bending of cilia detached from the cortical sheet. From these results, it was concluded that increases in the asymmetrical movement of individual cilia, caused by the addition of cyclic nucleotides, create the ciliary interaction that generates the metachronal waves.
Transduction Diversity in Olfaction
Authors: Dionne Vincent E. , Dubin Adrienne E. 
Published: April 2021

ABSTRACT
Odors are powerful stimuli that can focus the attention, elicit behaviors (or misbehaviors) and even resurrect forgotten memories. These actions are directed by the central nervous system, but they depend upon the initial transduction of chemical signals by olfactory receptor neurons. Electrophysiological recordings suggest that the responses of olfactory receptor neurons to odors are more diverse than was initially believed, being mediated by effects on several different conductances. Both excitatory and inhibitory responses are produced by these effects and some, if not all, odors can affect more than one component of the membrane conductance. The extent of this diversity is reviewed here, and its impact on our understanding of odor discrimination is discussed.
Intracellular ion Concentrations in Branchial Epithelial Cells of Brown Trout (Salmo Trutta L.) Determined by X-Ray Microanalysis
Authors: Morgan I. J. , Potts W. T. W. , Oates K. 
Published: April 2021

ABSTRACT
The intracellular concentrations of sodium, chloride, phosphorus and potassium under normal conditions in pavement epithelial (PE) cells of brown trout (Salmo trutta) gill were 66, 51, 87 and 88 mmol l−1 respectively. The concentrations of these elements under identical conditions in mitochondria-rich (MR) cells were not significantly different, except for that of chlorine, which was lower in MR cells (40 mmol l−1). The concentration of sodium in the PE cells decreased slightly after exposure of the fish to low external [Na+] (25 μmol l−1) for 7 days but increased greatly within 5 min of subsequent exposure to 1 mmol l−1 external Na+. These changes in external [Na+] had no significant effect on MR cells. Exposure of fish to low [Cl−] (25 μmol l−1) had no effect on PE or MR cells, but on exposure to 1 mmol l−1 Cl− the concentrations of chlorine, phosphorus and potassium in both types of cells increased, whilst the intracellular sodium concentration decreased only in MR cells. The PE cells were little affected by exposure of the fish to the carbonic anhydrase inhibitor acetazolamide. In contrast, 0.5 mmol l−1 external acetazolamide caused a significant decrease in intracellular phosphorus, chlorine and potassium concentrations in MR cells. This suggests that the PE cells are the sites of sodium uptake in the gills of the brown trout and that chloride uptake occurs via the MR cells. These results are discussed with respect to the sites and possible mechanisms of ionic exchange in freshwater vertebrates.
Allatostatin Peptides in the Crab Stomatogastric Nervous System: Inhibition of the Pyloric Motor Pattern and Distribution of Allatostatin-Like Immunoreactivity
Authors: Skiebe Petra , Schneider Henning 
Published: April 2021

ABSTRACT
The effects of four Diploptera punctata allatostatin peptides on the stomatogastric nervous system of the crab Cancer borealis were studied. All of the peptides had similar actions on the activity of neurons involved in rhythmic movements of the pyloric region of the stomach, decreasing the frequency of the pyloric rhythm in a dose-dependent manner. Diploptera allatostatin 3 (D-AST-3) was slightly more effective than the others. The absolute change in the frequency of the pyloric rhythm depended on the starting frequency, demonstrating that the effect of D-AST-3 depends on the preceding physiological state of the preparation. The largest decreases were observed when the starting frequency was slower than 0.8 Hz.
Whole-mount immunocytochemistry with anti-Diploptera allatostatin 1 antibodies demonstrated the presence of allatostatin-like peptides in the paired commissural ganglia, the unpaired oesophageal ganglion and the stomatogastric ganglion, and in their connecting and motor nerves. Dense processes were labeled in the stomatogastric ganglion, 12–19 cell bodies and neuropil staining were found in each commissural ganglion, two cell bodies were stained in the oesophageal ganglion and two pairs of cell bodies, the gastropyloric receptor neurons, were stained in peripheral nerves.
Jamming Bat Echolocation: the Dogbane Tiger Moth Cycnia Tenera Times Its Clicks to the Terminal Attack Calls of the Big Brown Bat Eptesicus Fuscus
Authors: Fullard James H. , Simmons James A. , Saillant Prestor A. 
Published: April 2021

ABSTRACT
Certain tiger moths emit high-frequency clicks to an attacking bat, causing it to break off its pursuit. The sounds may either orient the bat by providing it with information that it uses to make an attack decision (aposematism) or they may disorient the bat by interrupting the normal flow of echo information required to complete a successful capture (startle, jamming). At what point during a bat’s attack does an arctiid emit its clicks? If the sounds are aposematic, the moth should emit them early in the attack echolocation sequence in order to allow the bat time to understand their meaning. If, however, the sounds disrupt the bat’s echo-processing behaviour, one would expect them to be emitted later in the attack to maximize their confusion effects. To test this, we exposed dogbane tiger moths (Cycnia tenera) to a recording of the echolocation sequence emitted by a big brown bat (Eptesicus fuscus) as it attacked a stationary target. Our results demonstrate that, at normal echolocation intensities, C. tenera does not respond to approach calls but waits until the terminal phase of the attack before emitting its clicks. This timing is evident whether the moth is stationary or flying and is largely independent of the intensity of the echolocation calls. These results support the hypothesis of a jamming effect (e.g. ‘phantom echoes’) and suggest that, to determine experimentally the effects of arctiid clicks on bats, it is important that the bats be tested under conditions that simulate the natural context in which this defence operates.
The Metabolic Characteristics of the Locomotory Muscles of Grey Seals (Halichoerus Grypus), Harbour Seals (Phoca Vitulina) and Antarctic Fur Seals (Arctocephalus Gazella)
Authors: Reed J. Z. , Butler P. J. , Fedak M. A. 
Published: April 2021

ABSTRACT
It is not known precisely how marine mammals are able to maintain muscle function during active swimming in breath-hold dives, when ventilation stops and heart rate falls. Examination of muscle biochemistry and histochemistry can provide information on the relative importance of different metabolic pathways, the contractile potential of the muscle fibres, the oxygen storage capacity of the muscle and the capillary distribution in these animals. In this study, samples of locomotory muscle were taken from wild grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and Antarctic fur seals (Arctocephalus gazella); Wistar rat muscle was analysed for comparative purposes.
Activities of citrate synthase and β-hydroxyacyl CoA dehydrogenase were higher in the harbour seal muscle than in the grey seal muscle, suggesting that harbour seals have a greater aerobic capacity. Both phocid muscles had a greater reliance on fatty acid oxidation than the fur seal or rat muscles. The myoglobin data demonstrate that the grey seals have the highest oxygen storage capacity of the three pinniped species, which correlates with their greater diving ability. Myoglobin levels were higher in all three pinniped species than in the Wistar rat. The fibre type compositions suggest that the muscles from the fur seals have higher glycolytic capacities than those of the phocid seals [fur seal pectoralis, 7% slow-twitch oxidative fibres (SO), 25% fast-twitch oxidative glycolytic fibres (FOG), 68% fast-twitch glycolytic fibres (FG); grey seal 57% SO, 5% FOG, 38% FG; area per cents]. However, the pectoralis muscle of the fur seal, although the most glycolytic of the pinniped muscles studied, has the highest capillary density, which indicates a high capacity for fuel distribution.
These results show that, while pinniped muscle has an increased oxygen storage potential compared with the muscle of a typical terrestrial mammal, there are no distinct adaptations for diving in the enzyme pathways or fibre type distributions of the pinniped muscle. However, the muscle characteristics of each species can be related to its diving behaviour and foraging strategy.