bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fibre Heterogeneity in the Closer and Opener Muscles of Crayfish Walking Legs
Authors: Günzel Dorothee , Galler Stefan , Rathmayer Werner 
Published: April 2021

ABSTRACT
The closer and opener muscles in the third walking legs of the three crayfish Pacifastacus leniusculus, Procambarus clarkii and Astacus leptodactylus are composed of fibres which differ in histochemistry, electrophysiology and morphology. Three major groups of fibres (A, B and C) were distinguished. Group A fibres react weakly to histochemical stains for myofibrillar ATPase (mATPase) activity characteristic of fibres with slow shortening speeds. In the opener muscle, they are innervated by the opener excitor (OE) and the specific opener inhibitor (OI). In the closer muscle, group A fibres are innervated by the common inhibitory neurone (CI) in addition to single (slow closer excitor, SCE) or double excitatory (SCE and fast closer excitor, FCE) innervation. Group A fibres have the largest excitatory junction potentials (EJPs), the longest membrane time constants (τ) and the longest sarcomeres. They are located at the very distal and proximal ends of both muscles. Group B fibres show higher mATPase activity than group A fibres. In the opener muscle, they are innervated by OE and OI; in the closer muscle, they receive double excitatory (SCE and FCE) and CI innervation. Single SCE and OE EJPs are small; those caused by FCE are larger. τ is shorter than in the other two fibre groups. Sarcomere lengths lie between those of group A and C fibres. Group B fibres are found along the entire lengths of both muscles. Group C fibres exhibit the highest mATPase activity (characteristic of fibres with fast shortening velocity) which, in contrast to the ATPase of group B fibres, is not resistant to alkaline preincubation at pH10.05. In the closer, these fibres lack innervation by CI, otherwise the innervation pattern is identical to that of group B fibres. EJP size is similar to that of group B fibres; τ ranges between values for group A and B fibres. Sarcomere lengths are the shortest of all the fibre types. Group C fibres constitute the majority of the fibres in the two muscles and mainly occupy the central regions.
The Effects of Body Size on the Acid–Base and Metabolite Status in the White Muscle of Rainbow Trout Before and After Exhaustive Exercise
Authors: Ferguson Ralph A. , Kieffer James D. , Tufts Bruce L. 
Published: April 2021

ABSTRACT
The effect of body size on the white muscle acid–base and metabolite status was examined in rainbow trout (Oncorhynchus mykiss) ranging in length from 8 to 54cm. Following 5min of exhaustive exercise, white muscle lactate concentration was approximately doubled (approximately 32 μmol g−1) in larger fish than in smaller fish (approximately 16 μmol g−1). Associated with this post-exercise increase in lactate was a nearly parallel increase in the number of metabolic protons produced by larger fish. Larger fish did not possess a greater non-bicarbonate buffering capacity or soluble protein concentration, so their mean muscle intracellular pH (pHi) decreased by approximately 0.70 units compared with a change in mean pHi of about 0.40 units in the smallest fish. The relationship between resting pHi and length was independent of size (mean pHi7.31). Concentrations of muscle energy metabolites were also determined in trout white muscle before and after exercise. Under resting conditions, larger fish possessed a twofold greater concentration of ATP (approximately 7 μmol g−1) than did smaller fish (approximately 3μmol g−1). Similarly, resting values of muscle glycogen range from about 6 μmol g−1 in the smallest fish to as high as 15 μmol g−1 in the largest fish. However, the smaller fish had higher levels (approximately 35 μmol g−1) of phosphocreatine (PCr) than the larger fish (approximately 25 μmol g−1). Following exercise, however, both ATP and glycogen concentrations remained size-dependent and increased with increases in fish length. Levels of PCr were size-independent following exercise. These results demonstrate that body size has an important influence on the acid–base and metabolic status of fish before and after exercise.
Discontinuous Ventilation in a Non-Insect, The Tick Amblyomma Marmoreum (Acari, Ixodidae): Characterization and Metabolic Modulation
Authors: Lighton John R. B. , Fielden Laura J. , Rechav Yigal 
Published: April 2021

ABSTRACT
We examined and quantified the discontinuous ventilation cycle (DVC) characteristics of unfed nymphs and adults, as well as engorged nymphal and engorged diapausing and non-diapausing female adult life-stages, of the African tortoise tick Amblyomma marmoreum (Koch). All engorged stages ventilated continuously, with little evidence of active spiracular control. Unfed nymphs and adults ventilated discontinuously; at low activity and standard metabolic rate (SMR) levels, mean DVC duration was approximately 0.4h in nymphs (mean mass 0.7mg) and 2.8h in female adults (mean mass 70mg). SMR, measured as rate of CO2 production (; 0.064 μl mg−1 h−1 and 0.019 μl mg−1 h−1, respectively), was almost tenfold lower than that estimated for spiders of equivalent mass. In adults, the DVC was modulated to accommodate changing chiefly by changes in DVC frequency. Modulation of other DVC characteristics was bimodal; at low (below the ‘SMR threshold’), burst volumes were large and not correlated with but the rate of CO2 emission during the burst was modulated by Above the SMR threshold, burst volumes were small and tightly correlated with . No fluttering-spiracle phase could be detected, but CO2 bursts were triggered at low volumes above the SMR threshold, suggesting that hypoxia in addition to hypercapnia may initiate the termination of DVCs in the burst phase, rather than initiating the flutter phase as in insects. To explain this bimodal modulation of the DVC by (and hence ) above and below the SMR threshold, we hypothesize that, below the SMR threshold, unfed ixodid ticks – with their very low SMR and large surface area/volume ratio – may obtain significant amounts of O2 by transcuticular or other putative non-spiracular avenues of O2 uptake (larval ticks obtain all their O2 in this way).
Paddlefish buccal flow velocity during ram suspension feeding and ram ventilation
Authors: Sanderson S. Laurie , Cech Joseph J. , Cheer A. Y. 
Published: April 2021

ABSTRACT
A micro-thermistor probe was inserted into the buccal cavity of freely swimming paddlefish to measure flow velocity during ram ventilation, ram suspension feeding and prey processing. Swimming speed was measured from videotapes recorded simultaneously with the buccal flow velocity measurements. Both swimming velocity and buccal flow velocity were significantly higher during suspension feeding than during ram ventilation. As the paddlefish shifted from ventilation to feeding, buccal flow velocity increased to approximately 60 % of the swimming velocity. During prey processing, buccal flow velocity was significantly higher than the swimming velocity, indicating that prey processing involves the generation of suction. The Reynolds number (Re) for flow at the level of the paddlefish gill rakers during feeding is about 30, an order of magnitude lower than the Re calculated previously for pump suspension-feeding blackfish. These data, combined with data available from the literature, indicate that the gill rakers of ram suspension-feeding teleost fishes may operate at a substantially lower Re than the rakers of pump suspension feeders.
Help, there are ‘omics’ in my comparative physiology!
Authors: Torson Alex S. , Dong Yun-wei , Sinclair Brent J. 
Published: April 2021

Abstract
‘Omics’ methods, such as transcriptomics, proteomics, lipidomics or metabolomics, yield simultaneous measurements of many related molecules in a sample. These approaches have opened new opportunities to generate and test hypotheses about the mechanisms underlying biochemical and physiological phenotypes. In this Commentary, we discuss general approaches and considerations for successfully integrating omics into comparative physiology. The choice of omics approach will be guided by the availability of existing resources and the time scale of the process being studied. We discuss the use of whole-organism extracts (common in omics experiments on small invertebrates) because such an approach may mask underlying physiological mechanisms, and we consider the advantages and disadvantages of pooling samples within biological replicates. These methods can bring analytical challenges, so we describe the most easily analyzed omics experimental designs. We address the propensity of omics studies to digress into ‘fishing expeditions’ and show how omics can be used within the hypothetico-deductive framework. With this Commentary, we hope to provide a roadmap that will help newcomers approach omics in comparative physiology while avoiding some of the potential pitfalls, which include ambiguous experiments, long lists of candidate molecules and vague conclusions.
The Use of Heart Rate to Estimate Oxygen Consumption of Free-Ranging Black-Browed Albatrosses Diomedea Melanophrys
Authors: Bevan R. M. , Woakes A. J. , Butler P. J. , Boyd I. L. 
Published: April 2021

ABSTRACT
Heart rates (fH) and rates of oxygen consumption were measured in eight black-browed albatrosses (Diomedea melanophrys) when walking on a treadmill, with the aim of using fH to predict in free-ranging albatrosses. The resulting relationship between the variables was: (ml min−1) = [0.0157fH (beats min−1)]1.60, r2=0.80, P&lt;0.001. In addition to the calibration procedure, six of the albatrosses were injected with doubly labelled water (DLW), and fH and were monitored continuously over a 3 day period while the birds were held in a respirometer. During the 3 day period, the birds were walked for up to 3–4 h day−1 in bouts lasting approximately 0.5 h. The heart rate data were used to estimate the metabolic rates of these birds using the above regression. Estimates of metabolic rate derived from fH, DLW and respirometry did not differ (ANOVA; P=0.94), primarily because of the variance between individual birds. There was also no significant difference between the different estimates obtained from the different equations used to calculate energy expenditure from the DLW technique (ANOVA; P=0.95). Mean estimates of from fH under active and inactive conditions differed from measured values of by -5.9% and -1.7% respectively. In addition, the estimates of from fH at different walking speeds did not differ significantly from the measured values. It appears that, in the black-browed albatross, fH is as good a predictor of the mean metabolic rate of free-ranging birds as DLW or time–energy budgets combined with either respirometry or DLW. However, the method should be applied to as many individuals and as many instances of a particular behaviour as possible. The heart rate technique offers potential for much more detailed analyses of the daily energy budgets of these birds, and over much longer periods, than has previously been possible.
Sexually Dimorphic Spatial Learning in Meadow Voles Microtus Pennsylvanicus and Deer Mice Peromyscus Maniculatus
Authors: Galea Liisa A. M. , Kavaliers Martin , Ossenkopp Klaus-Peter 
Published: April 2021

ABSTRACT
A number of studies examining developmental, neural and hormonal aspects of sexually dimorphic spatial learning (Morris water-maze) in meadow voles (Microtus pennsylvanicus) and deer mice (Peromyscus maniculatus) are described. We found that, in adult deer mice, female spatial performance decreased during the breeding season relative to the non-breeding season, whereas the reverse pattern was observed in male performance. There was a sex difference favouring males in spatial learning during the breeding season, but not during the non-breeding season. In adult meadow voles, females with low levels of oestradiol and males performed better in the water-maze than females with high levels of oestradiol. Postweaning voles (20 and 25 days after birth) acquired the water-maze task more quickly than preweaning voles (day 10). No sex difference in water-maze performance was evident at any of these juvenile ages. When these same voles were tested again as adults to investigate retention and re-acquisition of the water-maze, both males and females from male-biased litters re-acquired the task better than males and females from female-biased litters. Together, the results of these studies indicate that sexually dimorphic spatial ability is dependent on the organizational (in utero) and activational effects of gonadal hormones. These studies provide the first demonstration of the influence of natural changes in reproductive status on spatial learning of deer mice and meadow voles. The results also demonstrate that spatial performance of males and females is differentially affected by changes in reproductive status and that group differences in the laboratory are associated with group differences in space utilization in the wild. These findings help to clarify previous apparently contradictory findings about sex differences in spatial ability.
The Mechanics Of Swallowing And The Muscular Control Of Diverse Behaviours in Gopher Snakes
Authors: Moon Brad R. 
Published: April 2021

ABSTRACT
Snakes are excellent subjects for studying functional versatility and potential constraints because their movements are constrained to vertebral bending and twisting. In many snakes, swallowing is a kind of inside-out locomotion. During swallowing, vertebral bends push food from the jaws along a substantial length of the body to the stomach. In gopher snakes (Pituophis melanoleucus) and king snakes (Lampropeltis getula), swallowing often begins with lateral bending of the head and neck as the jaws advance unilaterally over the prey. Axial movement then shifts to accordion-like, concertina bending as the prey enters the oesophagus. Once the prey is completely engulfed, concertina bending shifts to undulatory bending that pushes the prey to the stomach. The shift from concertina to undulatory bending reflects a shift from pulling the prey into the throat (or advancing the mouth over the prey) to pushing it along the oesophagus towards the stomach. Undulatory kinematics and muscular activity patterns are similar in swallowing and undulatory locomotion. However, the distinct mechanical demands of internal versus external force exertion result in different duty factors of muscle activity. Feeding and locomotor movements are thus integral functions of the snake axial system.
Brainstem lateral line responses to sinusoidal wave stimuli in still and running water
Authors: Kröther Sophia , Mogdans Joachim , Bleckmann Horst 
Published: April 2021

SUMMARYThe fish lateral line consists of superficial and canal neuromasts. In still water, afferent fibers from both types of neuromast respond equally well to a sinusoidally vibrating sphere. In running water, responses to a vibrating sphere of fibers innervating superficial neuromasts are masked. In contrast,responses of fibers innervating canal neuromasts are barely altered. It is not known whether this functional subdivision of the peripheral lateral line is maintained in the brain. We studied the effect of running water on the responses to a 50 Hz vibrating sphere of single units in the medial octavolateralis nucleus (MON) in goldfish Carassius auratus. The MON is the first site of central processing of lateral line information. Three types of units were distinguished. Type I units (N=27) were flow-sensitive; their ongoing discharge rates either increased or decreased in running water, and as a consequence, responses of these units to the vibrating sphere were masked in running water. Type II units (N=7) were not flow-sensitive; their ongoing discharge rates were comparable in still and running water, so their responses to the vibrating sphere were not masked in running water. Type III units (N=7) were also not flow-sensitive, but their responses to the vibrating sphere were nevertheless masked in running water. Although interactions between the superficial and canal neuromast system cannot be ruled out, our data indicate that the functional subdivision of the lateral line periphery is maintained to a large degree at the level of the medial octavolateralis nucleus.
Squeaking with a sliding joint: mechanics and motor control of sound production in palinurid lobsters
Authors: Patek Sheila N. 
Published: April 2021

SUMMARYThe origin of arthropod sound-producing morphology typically involves modification of two translating body surfaces, such as the legs and thorax. In an unusual structural rearrangement, I show that one lineage of palinurid lobsters lost an antennal joint articulation, which transformed this joint from moving with one degree of freedom into a sliding joint with multiple degrees of freedom. With this sliding joint, `stick-and-slip' sounds are produced by rubbing the base of each antenna against the antennular plate. To understand the musculo-skeletal changes that occurred during the origin and evolutionary variation of this sound-producing mechanism, I examined joint morphology and antennal muscle anatomy across sound-producing and non-sound-producing palinurids. Plectrum movement and antennal muscle activity were measured in a sound-producing species, Panulirus argus. The promotor muscle pulls the plectrum over the file during sound-producing and non-sound-producing movements; a higher intensity of muscle activity is associated with sound production. The promotor muscle is larger and attaches more medially in sound-producing palinurids than in non-sound producers. In Panulirus argus, each shingle on the file has an additional ridge; in Palinurus elephas, the shingle surfaces are smooth. These differences in shingle surface features suggest variation in the stick-and-slip properties of the system. Translational motion permitted by the sliding joint is necessary for sound production; hence, the construction of a sliding joint is a key modification in the origin of this sound-producing mechanism.
A kinematic model of swallowing inAplysia californicabased on radula/odontophore kinematics andin vivomagnetic resonance images
Authors: Neustadter David M. , Drushel Richard F. , Crago Patrick E. , Adams Benjamin W. , Chiel Hillel J. 
Published: April 2021

SUMMARYA kinematic model of the buccal mass of Aplysia californica during swallowing has been developed that incorporates the kinematics of the odontophore, the muscular structure that underlies the pincer-like grasping structure, the radula. The model is based on real-time magnetic resonance images (MRIs) of the mid-sagittal cross section of the buccal mass during swallowing. Using kinematic relationships derived from isolated odontophores induced to perform feeding-like movements, the model generates predictions about movement of the buccal mass in the medio-lateral dimension during the feeding cycle that are well-matched to corresponding coronal MRIs of the buccal mass during swallowing. The model successfully reproduces changes in the lengths of the intrinsic (I) buccal muscles I2 and I3 measured experimentally. The model predicts changes in the length of the radular opener muscle I7 throughout the swallowing cycle, generates hypotheses about the muscular basis of radular opening prior to the onset of forward rotation during swallowing and suggests possible context-dependent functions for the I7 muscle, the radular stalk and the I5 (ARC) muscle during radular opening and closing.
A Critical Study of Techniques for Determining the Cytological Position of Alkaline Phosphatase
Authors: Danielli J. F. 
Published: April 2021

ABSTRACT
It has been proved that the technique of Takamatsu and of Gömorri indicates the cytological sites of alkaline phosphatase activity. The critical time limits for the various operations in the technique have been determined. Several alternative techniques are given for demonstrating phosphatase activity on the cytological level. A selection of fixatives is given which do not produce severe destruction of alkaline phosphatase activity. It has been shown that alkaline phosphatase in fixed preparations is found in sites which are those in which it occurs under physiological conditions. It is suggested that the function of the phosphatase found in the brush borders of the proximal tubules of the kidney is to hydrolyse phosphate esters in the glomerular filtrate, and thereby permit the reabsorption of the component molecules by tubular processes.
The Effects of Low Atmospheric Pressure on the Fertility of Male Rabbits
Authors: Walton Arthur , Uruski W. 
Published: April 2021

ABSTRACT
Low atmospheric pressure has a detrimental effect upon the fertility of male rabbits. Changes can be detected in semen samples and by histological examination of the testis. The changes induced in the testis take a chronic course but are completely reversible on returning the animal to normal atmospheric pressures.
The Nature of the Action Potentials of Crustacean Muscles
Authors: Wiersma C. A. G. , Wright Ernest B. 
Published: April 2021

ABSTRACT
An investigation has been made of the action potentials of the muscles of the crayfish, Cambarus clarkii. It was found that the polarity of these potentials was in many instances the reverse of that expected. It is shown that ‘positive’ potentials cannot be explained by injury to the active tissue, by the complex structure of the muscles, or by the direction of the muscle fibres. Using muscles in which all extraneous connexions could be rigorously avoided, the muscle action potentials were invariably found to be negative. Direct evidence is presented for the local non-conducted nature of the crustacean muscle action potentials. An hypothesis is offered to explain the monophasicity and polarity of these action potentials on the basis of multiple unilateral innervation of the muscle fibres.
Spontaneous Rhythmical Impedance Changes in the Egg of the Trout. II
Authors: Rothschild Lord 
Published: April 2021

ABSTRACT
The spontaneous rhythmical impedance changes that occur in fertilized and unfertilized eggs of the rainbow trout after about 7 hr. immersion in tap water have been analysed. They are found to be almost entirely capacitative and correspond to a change of between 5 and 10 % when measured at a frequency of about 1.0 kc. The possibility of any associated resistance change being virtually unobservable is discussed. These changes, which have not so far been recorded in other living material, are compared with the impedance changes that occur in nerve cells and Nitella.