bluuebunny/crossref_metadata_2025_split huggingface dataset:
Myofibrillar Protein Composition Correlates with Histochemistry in Fibres of the Abdominal Flexor Muscles of the Norway Lobster Nephrops Norvegicus
Authors: Neil Douglas M. , Fowler William S. , Tobasnick Graham 
Published: April 2021

ABSTRACT
The myofibrillar proteins in fibres from the abdominal flexor muscles of the Norway lobster, Nephrops norvegicus, have been identified using SDS–PAGE gel electrophoresis. Several contractile and regulatory proteins are expressed as multiple isoforms in single fibres and, according to these, one fast fibre phenotype (F) can be identified in the deep flexor muscles and two slow fibre phenotypes (S1 and S2) can be distinguished in the superficial flexor muscles. The two slow fibre phenotypes are distributed non-uniformly across the superficial flexor muscle, and in the lateral bundle there is a heterogeneous mixture of both S1 and S2 fibres. Using histochemical procedures applied to intact or freeze-dried fibres in conjunction with measurements of fibre sarcomere length and gel electrophoresis, an exact correspondence can be demonstrated between the morphological properties, enzymatic content and myofibrillar protein composition of individual fibres from the deep and superficial flexor muscles. In the superficial flexor muscle, fibres of the S1 phenotype have a mean sarcomere length of &lt;8 μm, a low oxidative capacity and an acid-labile isoform of myosin ATPase, while fibres of the S2 phenotypes have a longer sarcomere length (mean &gt;9 μm), a higher oxidative capacity and an acid-stable isoform of myosin ATPase. These results are discussed in terms of the relationships between the different muscle fibre properties and the usefulness of procedures applied to single fibres for determining them.
Fundamental Analysis of Three-Dimensional ‘Near Fling’
Authors: Sunada Shigeru , Kawachi Keiji , Watanabe Isao , Azuma Akira 
Published: April 2021

ABSTRACT
A series of experiments on three-dimensional ‘near fling’ was carried out. Two pairs of plates, rectangular and triangular, were selected, and the distance between the rotation axes of the two plates of each pair was varied. The motion of the plates as well as the forces and the moment were measured, and the interference between the two plates of a pair was studied. In addition, a method of numerical calculation was developed to aid in the understanding of the experimental results.
The interference between the two plates of a pair, which acted to increase both the added mass of each plate and the hydrodynamic force due to dynamic pressure, was noted only when the opening angle between the plates was small. The hydrodynamic forces were strongly influenced by separated vortices that occurred during the rotation. A method of numerical calculation, which took into account the effect both of interference between the plates and of separated vortices, was developed to give adequate accuracy in analyzing beating wings in ‘near fling’.
Mechanisms of Intracellular Calcium Release During Hormone and Neurotransmitter Action Investigated with Flash Photolysis
Authors: Ogden D. C. , Khodakhah K. , Carter T. D. , Gray P. T. A. , Capiod T. 
Published: April 2021

ABSTRACTTo understand the complex time course of cytosolic Ca2+ signalling evoked by hormones and neurotransmitters, it is necessary to know the kinetics of steps in the second-messenger cascade, particularly cooperative and inhibitory interactions between components that might give rise to periodic fluctuations. In the case of inositol trisphosphate (InsP3)-evoked Ca2+ release, fast perfusion studies with subcellular fractions or permeabilised cells can be made if sufficient homogeneous tissue is available. Single-cell studies can be made by combining whole-cell patch-clamp techniques and microspectrofluorimetry with flash photolytic release of InsP3 to give quantitative, time-resolved data of Ca2+ release from stores. A technical description is given here of flash photolysis of caged InsP3, and the results of fast perfusion and flash photolytic experiments are reviewed. Studies of kinetics of Ca2+ release have shown that the InsP3 receptor/channel is regulated first by positive and then by negative feedback by free cytosolic Ca2+ concentration, producing a pulse of Ca2+ release having properties that may be important in the spatial propagation of Ca2+ signals within and between cells. The properties of InsP3-evoked Ca2+ release in single cells differ between peripheral tissues, such as the liver, and Purkinje neurones of the cerebellum. Purkinje neurones need 20–50 times higher InsP3 concentrations and release Ca2+ to change the free cytosolic concentration 30 times faster and to higher peak concentrations than in liver. The Ins P3 receptors in the two cell types appear to differ in apparent affinity, and the greater Ca2+ efflux from stores in Purkinje cells is probably due to a high receptor density.
Calcium Transport in Fish Gills and Intestine
Authors: Flik G. , Verbost P. M. 
Published: April 2021

ABSTRACT
In calcium-transporting epithelia, calcium can move transcellularly (when it passes inwards, from mucosa to serosa) and paracellularly (when it moves in both an inward and outward direction). An epithelium is considered to be ‘tight’ when the transcellular route dominates and leaky when there is additional significant paracellular transport. The branchial epithelium of the gills of freshwater fish is a good model for tight epithelia, whereas the gills of seawater fish and the intestine present a model for leaky epithelia. Generally, the regulation of transcellular inward calcium transport determines whether net absorption occurs and the regulation of paracellular calcium transport is pivotal to secretion in calcium-transporting epithelia. In its simplest form, transcellular transport requires movement of Ca2+ across the apical membrane, through the cytosol and across the basolateral membrane. At the same time, cellular calcium homeostasis must be maintained and, to this end, calcium is buffered in the cytosol by calcium-binding proteins and sequestered in the endoplasmic reticulum and mitochondria. Movement of calcium from the exterior of the cell to the cytosol is passive, down an electrochemical gradient, and appears to be regulated through channel or carrier proteins. The apical membrane contains a hormone-regulated carrier mechanism for Ca2+ entry. Movement from the cytosol to the exterior requires energy-consuming extrusion mechanisms, involving Ca2+-ATPase and/or Na+/Ca2+ exchange. The roles of such mechanisms in calcium transport phenomena in fish gills and intestine will be addressed.
Role of Prolactin and Somatolactin in Calcium Regulation in Fish
Authors: Kaneko Toyoji , Hirano Tetsuya 
Published: April 2021

ABSTRACT
The endocrine control of calcium metabolism in fish is performed by hyper-and hypocalcaemic hormones as in terrestrial vertebrates. However, the hormones involved in calcium regulation in fish, which lack parathyroid glands, differ from those in terrestrial vertebrates. The pituitary is important in hypercalcaemic regulation in fish; prolactin exerts a hypercalcaemic action in addition to its well-established hypernatraemic effect. However, alternation of plasma calcium concentration may not be the primary factor influencing prolactin secretion; changes in osmolality or sodium levels seem to be more critical for the regulation of prolactin release. Somatolactin, a putative pituitary hormone related structurally to both growth hormone and prolactin, is another possible factor responsible for hypercalcaemic regulation in fish. Exposure of rainbow trout to high-calcium environments reduces the activity of somatolactin-producing cells located in the hypophysial pars intermedia. Conversely, an increased activity of somatolactin cells is observed in low-calcium environments. Somatolactin has also been implicated in fat metabolism from comparisons of normal rainbow trout with a blue-coloured variant, which lacks most of the somatolactin cells normally present in the pituitary. Diverse functions for somatolactin, in maturation, in the stress response, in acid–base regulation and in background adaptation, have also been proposed. More detailed studies are needed to define the function of somatolactin.
Amphibian Calcium Metabolism
Authors: Stiffler Daniel F. 
Published: April 2021

ABSTRACT
Calcium is present in amphibian blood at a concentration similar to that in other vertebrates, about 1–2mmol l−1. The fraction of free calcium in amphibians is lower than that in other tetrapod vertebrates because about 50% of the plasma Ca2+ is bound to plasma proteins and perhaps other molecules. Plasma [Ca2+] varies seasonally, increasing in spring and summer and decreasing in winter. Changes in plasma [Ca2+] also occur during larval development, as the concentration of this ion increases in larval forms as they approach metamorphosis. Calcium is exchanged at a variety of sites in animals. There is evidence for Ca2+ uptake across the skin and gills of larval anurans. It is also transported into the blood from the small intestine (especially the duodenum) and reabsorbed in renal tubules from the glomerular filtrate. The possibility of Ca2+ absorption from urine stored in the urinary bladder has not been confirmed, however. Calcium is stored in bone and in specialized endolymphatic sacs. This Ca2+ can be mobilized when the need arises. There are a number of endocrine and other humoral factors that appear to be involved in amphibian calcium metabolism. These include parathyroid hormone, calcitonin, vitamin D and prolactin.
Homologous Recombinant Growth Hormone and Calcium Metabolism in the Tilapia, Oreochromis Mossambicus, Adapted to Fresh Water
Authors: Flik G. , Atsma W. , Fenwick J. C. , Rentier-Delrue F. , Smal J. , Bonga S. E. Wendelaar 
Published: April 2021

ABSTRACT
Homologous recombinant tilapia growth hormone (rtGH) was tested for its effects on calcium metabolism in freshwater tilapia Oreochromis mossambicus. Fish were fed an optimal ration of 5% of their body mass per day. A positive correlation was found between the amount of food given and the branchial calcium influx. In male tilapia, the mean calcium influxes were 5.80 and 11.71 μmol h−1 100 g−1 when they were fed 2 % and 5% food, respectively. In female fish fed 5% food, the calcium influx was 6.20 μmol h−1 100 g−1. Calcium influx via the gills was not affected by rtGH. However, in rtGH-treated fish, the net efflux of calcium was lower than in the controls. Apparently, the calcium taken up from the water was more efficiently stored in the body. GH increased the hepatosomatic index and had mild growth-promoting effects (mass and length increases); it increased the total body calcium pool without affecting bone or scale calcium density. The chloride cell density in the opercular epithelium almost doubled after GH treatment. GH did not influence plasma ion composition. Plasma cortisol levels were lower in rtGH-treated fish. A comparison of the roles of GH and prolactin (the products of the prolactin gene family) in calcium regulation of the tilapia led us to conclude that GH has specific calcitropic effects on freshwater tilapia that differ from those of prolactin.
Glucose Metabolism of the Swimbladder Tissue of the European Eel Anguilla Anguilla
Authors: Pelster Bernd , Scheid Peter 
Published: April 2021

ABSTRACT
Glucose uptake from, and lactate release into, the blood have been analysed in the active gas-depositing swimbladder of the immobilized European eel Anguilla anguilla. Under normoxic conditions, 0.72 μmolmin−1 glucose was removed from the blood supply, while lactate was released into it at a rate of 1.16 μmolmin−1. The rate of gas deposition into the swimbladder was significantly correlated with the rate of lactate production. Under hypoxic conditions, glucose consumption by, and lactate production of, the swimbladder tissue were reduced, as was the rate of gas deposition. Compared with normoxic conditions, lactate concentration in the swimbladder tissue was elevated after 1h of hypoxia, indicating a decrease in lactate release. No difference in the osmolality of arterial and venous blood could be detected in these experiments.
Combining the data for glucose uptake and lactate release measured under normoxic conditions with the values for O2 uptake and CO2 production of the swimbladder tissue measured under similar conditions in a previous study, a quantitative evaluation of glucose catabolism was performed. According to the O2 uptake of the tissue, only about 1 % of the glucose was oxidized, while about 80% was fermented to lactic acid. The remaining 0.14 μmolmin−1 glucose was presumably catabolized through the pentose phosphate shunt, as indicated by the CO2 production of 0.16 μmolmin−1 that cannot be explained by aerobic metabolism.
Dynamic Mechanical Properties of Passive Single Cardiac Fibers From the Crab Cancer Magister
Authors: Meyhöfer Edgar 
Published: April 2021

ABSTRACT
I determined the dynamic mechanical properties of single relaxed cardiac fibers from the Dungeness crab Cancer magister. Single fibers were mechanically isolated, chemically skinned and subjected to small-amplitude sinusoidal length perturbations over a wide range of strain rates and sarcomere lengths to characterize their viscoelastic behavior. The observed mechanical properties, together with transcardiac pressure recordings and ultrastructural measurements, were related to the overall function of the heart.
Single fibers, often longer than 1mm, could be mechanically dissected from the heart of Cancer magister. They typically ranged from 20 to 100 μm in diameter and were surrounded by a 100–400nm thick extracellular matrix. In situ, under normal physiological loads, the heart of Cancer magister generated transcardiac pressures of about 1000Pa and beat at 1Hz, while the sarcomere lengths of fibers changed by 10 % from about 4.0 to 4.4 μm during contractions. The total stiffness of all fibers increased from approximately 0.01MPa to 1MPa in the sarcomere length range from 3.8 to 6.0 μm and increased two-to threefold with a rise in strain rate from 0.01 to 5rad s−1. In the physiological range of sarcomere length (4.0–4.4 μm) and strain rate (0.5–1.2rad s−1), single cardiac fibers behaved viscoelastically, with average values for the relative energy dissipation ranging from 0.5 to 0.7. The volume fraction of the extracellular matrix correlated positively with the stiffness of single cardiac fibers.
On the basis of these results, I propose a dual role for the viscoelastic behavior of Cancer magister cardiac fibers: (1) the viscous energy dissipation confers dynamic mechanical stability at the level of the single fiber, and (2) the storage and return of elastic strain energy saves energy at the level of the whole heart.
Recruitment Patterns and Contractile Properties of Fast Muscle Fibres Isolated From Rostral and Caudal Myotomes of the Short-Horned Sculpin
Authors: Johnston Ian A. , Franklin Craig E. , Johnson Timothy P. 
Published: April 2021

ABSTRACT
Muscle action during swimming and the contractile properties of isolated muscle fibres were studied in the short-horned sculpin Myoxocephalus scorpius at 5 ° C. Semi-steady swimming, startle responses and prey-capture events were filmed with a high-speed video at 200frames s−1, using fish 22–26cm in total length (L). Electromyographical (EMG) recordings, synchronised with the video, were made from fast muscle in rostral and caudal myotomes at points 0.40L and 0.80L along the body. Fast muscle fibres were first recruited at tail-beat frequencies of 3.7–4.2Hz, corresponding to a swimming speed of 1.7 L s−1. Electrical activity in the muscles occurred during 16–38% of each tail-beat cycle regardless of frequency. Muscle fibres were activated during the lengthening phase of the cycle. In caudal myotomes, the onset of the muscle activity occurred at a phase of 75–105 ° at 3.7Hz, decreasing to approximately 50 ° at frequencies greater than 4.5Hz (0 ° phase was defined as the point at which muscle fibres passed through their resting lengths in the stretch phase of the cycle; a full cycle is 360 °). Prey capture was a stereotyped behaviour consisting of a preparatory movement, a powerstroke at 7–9Hz and a glide of variable duration. The delay between the activation of muscle fibres in rostral and caudal myotomes during prey capture and startle responses was approximately 10ms.
Fast muscle fibres isolated from rostral and caudal myotomes were found to have similar isometric contractile properties. Maximum tetanic stress was 220kN m−2, and half-times for force development and relaxation were approximately 50ms and 135ms respectively. Power output was measured by the ‘work loop’ technique in muscle fibres subjected to sinusoidal length changes at the range of frequencies found during swimming. Under optimal conditions of strain and stimulation, muscle fibres from rostral and caudal myotomes produced similar levels of work (3.5 J kg−1) and generated their maximum power output of 25–30 W kg−1 at the tail-beat frequencies used in swimming (4–8Hz). Progressively delaying the onset of stimulation relative to the start of the strain cycle resulted in an initial modest increase, followed by a decline, in the work per cycle. Maximum positive work and net negative work were done at stimulus phase values of 20–50° and 120–140° respectively. The EMG and swimming studies suggest that fast muscle fibres in both rostral and caudal myotomes do net positive work under most conditions.
The Activity Pattern of Identified Neurosecretory Cells During Feeding Behaviour in the Locust
Authors: Schachtner Joachim , Bräunig Peter 
Published: April 2021

ABSTRACT
In the locust, Locusta migratoria, the activity of identified efferent neurones of the suboesophageal ganglion was recorded extracellularly for long periods (hours or days). During recording, the animals were free to move in their enclosures. Activity of the cells appears to accompany feeding behaviour: they become active shortly before feeding starts and their activity persists during feeding. The cells have previously been shown to be serotonin-immunoreactive and to have a dense network of neurohaemal terminals on the sheath of the peripheral nerves supplying the mouthparts. The role of serotonin as a neuromediator involved in feeding activities is discussed for insects and other organisms.
The Multisegmental Motor Supply to Transverse Muscles Differs in a Cricket and a Bushcricket
Authors: Consoulas Christos , Hustert Reinhold , Theophilidis George 
Published: April 2021

ABSTRACT
Most abdominal sternites of the cricket Gryllus bimaculatus and the bushcricket Decticus albifrons are bridged by a transverse muscle (TM) which supports expiratory movements. In the cricket, ventilatory contractions are controlled both within each segment, by a bilateral pair of excitatory motoneurones in the abdominal ganglion supplying the left and right halves of the TM independently, and intersegmentally, by peripheral collaterals of homologous motoneurones from adjacent segments. The axons of these motoneurones run in the ipsilateral paramedian nerve. This unique divergence of excitatory motoneurones to different muscles also results in massive convergence of excitatory inputs from different ganglia, especially on the TMs of the middle abdominal segments. TM contraction rates are increased by this intersegmentally divergent and convergent motor supply, especially in the middle abdominal segments.
In bushcrickets, each transverse muscle in segments 3–7 is innervated bilaterally by four pairs of neurones: (i) two pairs of contralateral excitatory motoneurones with axons that diverge, supplying two adacent muscles; (ii) one pair of contralateral excitatory neurones found in the second anterior ganglion and (iii) a pair of median inhibitory neurones in the segmental ganglion. Transverse muscles 2 and 8 receive reduced innervation. The excitatory motoneurones generate slow excitatory postsynaptic potentials (EPSPs), which must sum to cause muscle contractions. During ventilation, contralateral paired transverse motoneurones fire at similar frequencies, thus sychronizing the contractions of the left and right halves of the muscle so that the whole muscle acts as a single unit.
Wireless Transmission of Muscle Potentials During Free Flight of a Locust
Authors: Kutsch W. , Schwarz G. , Fischer H. , Kautz H. 
Published: April 2021

ABSTRACT
Scientists have long been interested in recording data from freely moving animals. For larger animals, several telemetric techniques are available not only for following the movement of unrestrained animals in the wild (White and Garrott, 1990) but also for transmitting measures of heartbeat, body temperature, wingbeat, respiration, etc. (e.g. Lord et al. 1962; Butler and Woakes, 1980; Funk et al. 1993; for an overview, see Amlaner and Macdonald, 1980). Because of the size of such transmission devices, however, data acquisition has been restricted to larger animals. The development of lightweight batteries and microchips has only recently facilitated efforts to transmit data from smaller animals such as insects. Such data should greatly enhance our understanding of the processes involved in the neuronal control of unrestricted behaviour. Eventually it should be possible to monitor the activity of individual units (neurones, muscles) under closed-loop conditions, which closely resemble free movement. It is to be expected that this new approach will surpass previous studies involving intact but surface-bound animals implanted with long flexible electrodes (for crickets, see Kutsch, 1969) or animals tethered in a windstream (for improvement of the flight balance device, compare Weis-Fogh, 1956, with Dombrowsky, 1991). Increased freedom has been achieved in experiments on ‘free flight’ of large insects (Möhl, 1988; Stolley, 1990), although even these animals were restricted to a short or stationary flight handicapped by several implanted flexible electrodes.