bluuebunny/crossref_metadata_2025_split huggingface dataset:
Whole Body Calcium Flux Rates in Freshwater Teleosts as A Function of Ambient Calcium and Ph Levels: A Comparison Between the Euryhaline Trout, Salmo Gairdneri and Stenohaline Bullhead, Ictalurus Nebulosus
Authors: Hōbe Helve , Laurent Pierre , Mcmahon Brian R. 
Published: April 2021

ABSTRACT
The exchange of calcium between the blood and external medium following intravascular injection of 45Ca was investigated in adult fresh water rainbowtrout (Salmogairdneri) acclimated to ambient [Ca2+] of 0.18, 0.65 and 5.0 mequivl−1, and in bull heads (Ictalurus nebulosus) at external [Ca2+] of 0.17 mequivl−1, each at near-neutral ambient pH, 11–12°C and constant Na+ and Cl− levels of 0.06 and 0.03 mequivl−1, respectively.
The dispersal volume of isotope exhibited a slow exponential increase with 8–9 h required for 95% of the radiospace to be filled, irrespective ofthe acclimation medium or fish species. Equilibrium radiospaces in trout (range 1600–2000 ml kg−1) were independent of ambient [Ca2+] but 1.4 -fold higher than in bullheads. In all cases, whole body exchangeable calciumcontent was low, representing ≃3 % of total body calcium content. The whole body calcium exchange rates (mean ranges; influx or efflux) in trout of 7–22μequiv kg−1 h−1 were largely independent of ambient Ca2+ levels; lower values of 2–10μequiv kg−1 h were found in bullheads.
Acute exposure (24 h) to low ambient pH 4.0-4.2 at external [Ca2+] ≃ 0.18 mequivl−1 resulted in whole body ion loss in both species. Net Ca2+ losses in trout were due to a reduction in influx whereas both increased efflux and depressed influx accounted for the response in bullheads. These changes were transitory (12 h) and minor in comparison with concomitantnet Na+ and Cl− losses which unlike Ca2+, exhibited no recovery within 24 h of acid exposure.
Possible mechanisms of Ca2+ regulation in fresh water fish are discussed.
Octopamine Release From an Identified Neurone in the Locust
Authors: Morton David B. , Evans Peter D. 
Published: April 2021

ABSTRACT
The release of octopamine from the extensor-tibiae muscle preparation of the locust in response to high K+ saline and DUMETi stimulation has been demonstrated. This release has been measured using a radioenzyme assay for octopamine. Both forms of stimulated release have been shown to be calcium sensitive. Three potential problems of studying the release of transmitters from neuromuscular preparations using radiolabelled compounds have been identified, (a) The cellular location of the labelled compounds is unknown, (b) The site of the high K induced release is unknown, (c) The contraction of the muscle could cause nonspecific release of radioactivity from the muscle.
Ionic Dependence of Secretory and Electrical Activity Evoked by Elevated K+ in a Peptidergic Neurosecretory System
Authors: Cooke Ian M. , Haylett Beverley A. 
Published: April 2021

ABSTRACT
Secretion of the octapeptide erythrophore-(red pigment-) concentrating hormone (ECH, RPCH) and extracellularly monitored electrical activity were followed simultaneously from individual, isolated sinus glands (neurohaemal organs), of the crab Cardisoma carnifex. Following introduction of saline having elevated [K], 100–196 mmol I−1 (5–11× normal), secretion (bioassayed from 1-min fractions during continuous perfusion) increases from barely detectable (&lt;1 fmol min−1) to a peak, average 31fmolmin−1, within 5 min, and immediately subsides. Additional responses are obtainable following a period, &gt;30 min, of normal saline perfusion. Secretory responses to K are Ca-dependent. If Ca is restored (in high K) following perfusion in 0-Ca, high K, only a small secretory response is observed. Addition of Mn (10mmol I−1, normal Ca) reduces secretion to one-tenth. Increased net uptake of 45Ca of 2·5- to 6-fold is observed in individual sinus glands exposed to 10× K compared to paired, unstimulated organs. The pattern and Ca-dependence of secretory responses to K are unaffected, but the amount of secretion is augmented in Na-deficient or TTX-containing salines. Intracellular recording confirms that brief (10–40 s) bouts of intense firing recorded extracellularly upon commencing a high K perfusion include repetitive firing by terminals, superimposed on rapid depolarization. Firing ceases as the membrane potential reaches a depolarized value (–18 to –15 mV for [K] 100–176 mmol I−1), which is then maintained until restoration of normal saline, when slow repolarization ensues. In 0-Ca, spontaneous impulse firing is increased, resting potential depolarized by 5 to 15 mV, but the bout of impulse firing and the maintained depolarization in response to K are similar. Thus, mechanisms of secretion of a crustacean peptide neurohormone appear closely similar to those of other systems characterized: responsiveness to elevated K, dependence on Ca, depolarization-, but not secretion-dependent inactivation, and lack of dependence on Na inward current. Intracellular recording here permits direct observation of electrical responses of terminals.
Vascular And Renal Actions Of Salmon Calcitonin In Freshwater- and Seawater-Adapted European Eels (Anguilla Anguilla)
Authors: Wales N. A. M. 
Published: April 2021

ABSTRACT
When freshwater eels were given either 5 or 15 i.u. calcitonin kg−1 body weight, there was an increase in dorsal aortic blood pressure as well as a rise in urine volume, glomerular filtration rate and electrolyte excretion rate, 1 h after injection. None of these changes was shown by seawater-adapted eels. When freshwater-adapted eels received 15 i.u. calcitonin kg−1 body weight there were significant changes in plasma electrolyte levels, again a response not shown by seawater-adapted fish. These changes occurred in 1 h after the injection of hormone, during which time plasma levels of sodium, chloride and calcium fell whilst plasma potassium levels increased.
At no time within the first hour were there changes in the relative handling of electrolytes. However, seawater-adapted eels showed hypercalcaemia and a reduced relative calcium clearance 3 h after receiving 15 i.u. calcitonin kg−1 body weight.
Synapses Between an Identified Giant Interneurone and A Filiform Hair Sensory Neurone in the Terminal Ganglion of First Instar Cockroaches (Periplaneta Americana L.)
Authors: Blagburn J. M. , Beadle D. J. , Sattelle D. B. 
Published: April 2021

ABSTRACT
The ultrastructure of input and output synapses of various identified insect neurones has recently been studied (for example Titmus & Hoyle, 1977; Altman, Shaw & Tyrer, 1980; Phillips, 1980; Watson & Burrows, 1981, 1982, 1983; Tolbert & Hildebrand, 1981) and connections between anatomically and physiologically defined axons have been described (King & Wyman, 1980). To date though, synapses have not been visualized in an insect central pathway in which aspects of the anatomy, physiology, pharmacology and associated behaviour have been investigated. The cereal afferent, giant interneurone synapses in the sixth abdominal (A6) ganglion of the cockroach Periplaneta americana are well suited for such studies. Using cobalt staining (Pitman, Tweedle & Cohen, 1972) of single neurones, seven giant interneurones (GIs 1–7) can be identified on the basis of their morphology (Harrow, Hue, Pelhate & Sattelle, 1980; Daley, Vardi, Appignani & Camhi, 1981). In adult cockroaches these interneurones receive sensory input from numerous cereal mechanoreceptor afferents (Callec, Guillet, Pichon & Boistel, 1971 ; Daley et al. 1981). There is considerable evidence for cholinergic monosynaptic transmission at these synapses (Callec, 1974; Sattelle, 1980) and postsynaptic acetylcholine receptors sensitive to the nicotinic cholinergic antagonist a-bungarotoxin are present on GI2 and GI 3 (Harrow, Hue, Pelhate & Sattelle, 1979; Sattelle, David, Harrow & Hue, 1980; Harrow & Sattelle, 1983 ; Sattelle et al. 1983). It has been shown that the cereal afferent, giant interneurone pathways play a part in mediating the escape response of the cockroach following stimulation of the cereal mechanoreceptors (Ritzmann & Camhi, 1978; Camhi, Tom & Volman, 1978).
Ion Transport in the Midgut of the Cockroaches Leucophaea Maderae And Blabera Gigantea
Authors: Giordana B. , Sacchi V. F. , Zerahn K. 
Published: April 2021

ABSTRACT
The presence of a cation pump on the apical membrane of epithelial cells in insects, responsible for the extrusion of K or Na, has been proposed for Malpighian tubules (Maddrell, 1977) and salivary glands (Berridge, Lindley & Prince, 1976). An essential role of the midgut in K homeostasis has been established only for the phytophagous larvae of Lepidoptera (Harvey & Nedergaard, 1964). The main features of the rheogenic, luminally-directed potassium pump of this tissue have been extensively studied (Zerahn, 1978; Harvey, Cioffi, Dow & Wolfersberger, 1983). Since the midgut of these animals is also peculiar in that it does not actively absorb Na, the presence of the K pump could be the sole example in insect gut physiology. Na absorption in the midgut has been demonstrated in several species of insects (O’Riordan, 1969; Sauer, Schlenz True & Mills, 1969; Farmer, Maddrell & Spring, 1981 ; Dow, 1981a; Koefoed & Zerahn, 1982) while K secretion has been suggested for Periplaneta americana (Sauer & Mills, 1969), Leucophaea maderae (Sacchi & Giordana, 1979) and Schistocerca gregaria (Dow, 1981b).
Do the Motoneurones Constitute A Part of the Spinal Network Generating the Swimming Rhythm in the Lamprey?
Authors: Wallén P. , Lansner A. 
Published: April 2021

ABSTRACT
In the study of the neural control of rhythmic motor acts, the operation of the central neuronal networks that produce the motor pattern is an area of considerable interest (cf. Delcomyn, 1980; Grillner, 1981). The motor pattern underlying swimming in the lamprey, a primitive vertebrate, can be produced in the isolated spinal cord in vitro (Cohen & Wallén, 1980; Wallén & Williams, 1984). The capacity to generate the rhythmic pattern is distributed throughout the spinal cord, and short pieces of just a few segments may produce a coordinated pattern (Cohen & Wallén, 1980; Grillner & Sigvardt, in Grillner et al. 1982).
Analysis of the Scaphognathiteventilatory Pump in the Shore Crab Carcinus Maenas I. Work and Power
Authors: Mercier A. Joffre , Wilkens Jerrel L. 
Published: April 2021

ABSTRACT
Measurements of branchial pressure and ventilation volumes were used to calculate the work and power of gill ventilation in Carcinus maenas, during spontaneous as well as forced unilateral ventilation. With increasing ventilation rate (fR), the stroke work increases as a result of an elevated gradient of branchial pressure, while power output increases as a result of enhancement of both the pressure gradient and the flow rate. To a first approximation, the stroke work is proportional to fR1·5, and the power output is proportional to fR2·5. The available evidence suggests that flow is mainly laminar through the branchial chamber but turbulent through the pumping chamber. Evidence is presented which suggests that the crab is able to vary the resistance to the flow of branchial water.
The increased branchial pressure at elevated ventilation rates constitutes an increased load on the ventilatory muscles. Measurements of isometric tension confirm that the muscles compensate for this increased load by generating greater force. Electromyograms support the notion that the change in force results from appropriate changes in the output from the central pattern generator.
Structural Variability of an Identified Interneurone in Locusts From a Wild Population
Authors: Satterlie Richard A. 
Published: April 2021

ABSTRACT
One property of invertebrate nervous systems used to great experimental advantage is the ‘identifiability’ of individual neurones. A principal tenet of the ‘identified neurone’ concept is that a certain degree of structural regularity can be expected when investigating an identified cell in individual members of a single species. Yet in organisms that reproduce sexually some degree of structural variability should be expected over and above that attributed to developmental noise. Genotypic lineage appears to be a strong determinant of neurone structure. Recent studies using controlled lineages through selective and parthenogenetic breeding have indicated a fairly strong genetic influence on neurone number, structure and interconnections (Macagno, Lopresti & Levinthal, 1973; Goodman, 1977, 1978; Steeves & Pearson, 1983). In wild populations, however, some genetic variability may be selectively eliminated through environmental factors as well as intra-and interspecific biological interactions.
Differences in metabolic potential of skeletal muscle fibres and their significance for metabolic control
Authors: Gollnick P. D. , Riedy M. , Quintinskie J. J. , Bertocci L. A. 
Published: April 2021

ABSTRACT
When exposed to chronic overloads skeletal muscle is remodelled, thereby equipping it to better meet the stresses it is encountering. Examples abound in nature of the adaptive response of muscle exposed to different tasks (i.e. Armstrong, lanuzzo & Kutz, 1977; Newsholme & Start, 1973). The principles that are outlined in this paper for the relationship between metabolic potential and control of metabolism apply to all situations where differences in metabolic potential exist. The basic model discussed is that of physical training, particularly endurance training, on skeletal muscle and metabolic control. Training was selected as the model as it is a convenient method for inducing changes in skeletal muscle and for illustrating the consequences of these adaptations on the local and total body metabolism. Thus, heavy resistance exercise taxes the tension development capacity but not prolonged energy production so the fibres enlarge without a significant modification in the metabolic systems (Gollnick et al. 1972). In contrast, endurance training stresses energy production, particularly aerobic energy production, but not the tension developing capacity, with the end result being augmentation of the aerobic energy-producing systems. Corollaries of these exist throughout the animal kingdom.
Metabolic and circulatory limitations to at the whole animal level
Authors: di Prampero P. E. 
Published: April 2021

ABSTRACT
Maximal O2 consumption increases with increasing O2 partial pressure in inspired air (Bannister & Cunningham, 1954; Fagraeus, Karlsson, Linnarsson & Saltin, 1973; Kaijser, 1970; Margaria, Camporesi, Aghemo & Sassi, 1972; Margaria, Cerretelli, Marchi & Rossi, 1961 ; Nielsen & Hansen, 1937 ; Welch & Pedersen, 1981) and following the transfusion of red blood cells (Buick et al. 1980 ; Ekblom, Goldbarg & Gullbring, 1972; Ekblom, Wilson & Åstrand, 1976); it decreases in hypoxia (both acute and chronic) (see Cerretelli, 1981 for review), following CO inhalation (Ekblom & Huot, 1972; Ekblom, Huot, Stein & Sthorstenson, 1975; Pirnay, Dujardin, Deroanne & Petit, 1971; Raven et al. 1974; Vogel & Gleser, 1972) and after acute anaemia (Woodson, Wills & Lenfant, 1978).
Temperature and muscle
Authors: Bennett A. F. 
Published: April 2021

ABSTRACT
Rates of force development, contraction and relaxation of vertebrate skeletal muscle are temperature dependent with Q10 values of approximately 2. Maximal forces developed have a low or negative thermal dependence. The functional basis of these patterns is poorly understood. Muscle performance generally does not acclimate. There appears to have been some evolutionary adaptation among species and classes to different thermal regimes, such that muscles from cold-adapted species maintain better mechanical performance at low temperatures than do those from warm-adapted animals. However, rate processes remain strongly thermally dependent even in animals with low or variable body temperatures. This thermal dependence of muscle in vitro is reflected in behavioural performance: maximal force generation in vivo is temperature independent and time-dependent activities are more rapid at higher muscle temperatures.
Malleability of the system in overcoming limitations: functional elements
Authors: Saltin B. 
Published: April 2021

ABSTRACT
Three different views can be found in the literature concerning the classical question in exercise physiology: what limits maximal oxygen uptake in man? Some authors believe that the limitation is the maximal rate of oxygen delivery by the cardiovascular system. Others argue that oxygen uptake is limited by the capillary bed or metabolic capacity of skeletal muscle, and the third line of thought is that no single factor can be found to be directly limiting as all links in the oxygen transport are so closely matched. The stand taken in this paper is that the skeletal muscle of man can be excluded as a limiting factor for maximal oxygen uptake in whole body exercise. It can be shown, by direct measurements, that in sedentary and in trained man maximal perfusion and oxygen utilization of skeletal muscle is so high that if all muscles in the body were engaged in intense exercise, the cardiac pump function would have to be 2-3 fold larger than it is. What happens in whole body exercise is that each muscle group receives only a fraction of the blood it can accommodate. The primary role for a larger capillary network observed in trained muscles is to keep or extend mean transit time. Elevated mitochondrial enzyme activities affect the metabolic response (i.e. lipid oxidation is elevated in trained muscles). However, these adaptations are not necessary for increasing the maximal oxygen uptake of man, as the capacity of the heart is limiting. Improved training techniques (which induce even larger improvements in cardiac pump function) may reveal that pulmonary diffusion capacity is the limiting factor.
Malleability of the motor system: training for maximizing power output
Authors: Howald H. 
Published: April 2021

ABSTRACT
Power output is very high in international athletes and their performances are still improving in most sports. Such improvement is possible because of the remarkable malleability of the human motor system in response to highly specific training methods. Skeletal muscle of man can adapt to the needs for either short maximum effort (e.g. weightlifting, sprinting, etc.) or prolonged exercise (e.g. long-distance running, cycling, cross-country skiing, etc.). In many sports, however, performance capacity depends on both strength and endurance of the muscles involved (e.g. in rowing, middle-distance running, swimming and ball games), whereas in others the success of an athlete is mainly a question of optimized neuromuscular control (e.g. in gymnastics and figure skating). At the level of the muscle cell, training-induced adaptations occur in structure as well as in metabolic function and the changes are highly specific to the particular training stimulus. Some of the cellular adaptations are accompanied by adaptive processes in the cardiovascular and respiratory system, since skeletal muscle must be provided with both energy-supplying substrates and oxygen during exercise of more than one or two minutes.
Developmental Changes in the Interference Reflectors and Colorations of Tiger Beetles (Cicindela)
Authors: Schultz T. D. , Rankin M. A. 
Published: April 2021

ABSTRACT
Samples of cicindelid cuticle were examined at various stages of adult ecdysis. The multilayered potential reflector was secreted in the initial stages of the moult, verifying that it is not tectocuticle and supporting the contention that it is a form of inner epicuticle. At early stages of ecdysis, the electron-dense layers were visible only when the section was post-stained. During post-ecdysial colour development, the dense layer increased in in-herent electron density. Concurrently, the reflector increased in refractive index and the interference coloration increased in intensity and wavelength of maximum reflectance. Black pigment was also deposited simultaneously within the outer portion of the cuticle. It is proposed that electron-dense material was deposited in situ within the inner epicuticle after ecdysis, thereby increasing the wavelength and reflectance of interference colour.
An Investigation of Haemocyanin Oxygen Affinity in the Semi-Terrestrial Crab Ocypode Saratan Forsk
Authors: Morris S. , Bridges C. R. 
Published: April 2021

ABSTRACT
The oxygen affinity of the haemocyanin in the supralittoral crab Ocypode saratan was investigated at temperatures between 20 and 35 °C. The effect of L-lactate on dialysed and undialysed haemolymph oxygen affinity was also examined.
In general, the temperature sensitivity of the haemocyanin was low: ΔH was —3·1 kJ mol-1, between 25 and 30°C. Temperature sensitivity was temperature-dependent, being larger at the extreme temperatures (ΔH = — 26kJmol-1). The Bohr effect (ΔlogP50/ΔpH) was temperature-independent and averaged — 0·67.
No specific effect of CO2 on oxygen affinity was observed but L-lactate increased oxygen affinity in both dialysed and undialysed haemolymph. The maximal effect of lactate on oxygen affinity was similar in dialysed and undialysed haemolymph, but was evident at a lower lactate concentration (4 mmol I-1) in dialysed, compared with undialysed, haemolymph (7 mmol I-1). Dialysed haemolymph showed a higher oxygen affinity than undialysed haemolymph at low lactate concentration (&lt;4mmoll-1). The Bohr effect and buffer value both decreased with increasing lactate concentration in both dialysed and undialysed haemolymph. The physiological implications of these findings are discussed.
Postsynaptic Potentials of Limited Duration in Visual Neurones of a Locust
Authors: Simmons Peter J. 
Published: April 2021

ABSTRACT
Large, second-order neurones of locust ocelli (‘L-neurones’) make both excitatory and inhibitory connections amongst each other. A single L-neurone can be presynaptic at both types of connection. At the excitatory connections, transmission can be maintained for long periods without decrement. In contrast, inhibitory postsynaptic potentials (IPSPs) never last for more than 15–35 ms. This paper examines mechanisms which could limit the duration of these IPSPs.
An IPSP begins 4-5 ms after a presynaptic neurone starts to depolarize from its resting potential, and the time-to-peak is 7 ms. The amplitude of an IPSP depends both upon the amplitude of the peak presynaptic potential and upon the potential at which a presynaptic neurone is held before it is depolarized. The rate at which a postsynaptic neurone hyperpolarizes to produce an IPSP is proportional to the rate at which the presynaptic neurone depolarizes, independent of the potential from which the presynaptic depolarization starts. A maximum rate of postsynaptic hyperpolarization is reached when the presynaptic neurone depolarizes at 10 mV ms−1. Once an IPSP has occurred, both the amplitudes and the rates of hyperpolarization of subsequent IPSPs are depressed. The connection recovers its full ability to transmit over a period of 1-5 s. Larger IPSPs are followed by initially greater depression than smaller IPSPs. A connection can begin to recover from depression while the presynaptic neurone is held depolarized from resting. Transmission fails when a presynaptic neurone is depolarized by pulses shorter than 2 ms. The most likely reason why the duration of the IPSPs is limited is that calcium channels in the presynaptic terminal inactivate within 7 ms of first opening.