bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Examination Of Central Chemosensitivity In An Air-Breathing Fish (Amia Calva)
Authors: Hedrick M. S. , Burleson M. L. , Jones D. R. , Milsom W. K. 
Published: April 2021

ABSTRACT
The role of central chemosensitivity in the control of ventilation in fishes was investigated directly by perfusing a mock extradural fluid (EDF) through the cranial space in the medullary region of conscious air-breathing fish, Amia calva. Perfusions with Sudan Black dye showed that the mock EDF communicated with the cerebrospinal fluid (CSF) and entered the cerebral ventricles. Altering the , and/or pH of the mock EDF had no effect on gill- or air-breathing rates, heart rate or blood pressure during exposure to normoxic water. Aquatic hypoxia, however, stimulated gill ventilation and elevated blood pressure, but did not affect heart rate; altering the gas tensions and/or pH of mock EDF still had no effect on recorded variables. Sodium cyanide (NaCN) added to the mock EDF caused struggling at concentrations above 500μ gml − 1, but did not uniformly stimulate ventilation. These results suggest that central chemoreceptors, which mediate cardiovascular or ventilatory reflexes, are absent in Amia.
Prey Capture and the Fast-Start Performance of Northern Pike Esox Lucius
Authors: Harper David G. , Blake Robert W. 
Published: April 2021

ABSTRACT
Fast-start performance of northern pike Esox lucius (mean length, 0.38m) during prey capture was measured with subcutaneously implanted accelerometers. Acceleration-time plots and simultaneous high-speed ciné films reveal four behaviours with characteristic kinematics and mechanics. The fast-start types are identified by the number of large peaks that appear in the acceleration-time and velocity-time data.
Comparisons of mean performance were made between each type of feeding fast-start. Type I fast-starts were of significantly shorter duration (0.084 s) and displacement (0.132 m) than type III (0.148 s and 0.235 m) and type IV (0.189 s and 0.306m) behaviours, and higher mean and maximum acceleration (38.6 and 130.3ms− 2, respectively) than type II (26.6 and 95.8ms− 2), type III (22.0 and 91.2ms− 2) and type IV (18.0 and 66.6ms− 2) behaviours. The type II behaviours were of shorter duration (0.115 s) and displacement (0.173 m) and of higher mean acceleration than type IV fast-starts, and were also of significantly shorter duration than type III behaviours.
Prey-capture performance was compared to escapes by the same individuals. When data are combined, regardless of mechanical type, mean acceleration (37.6 vs 25.5 ms− 2), maximum acceleration (120.2 vs 95.9 ms− 2), mean velocity (1.90 vs 1.57 m s− 1) and maximum velocity (3.97 vs 3.09 ms− 1) were found to be larger and duration shorter (0.108 vs 0.133s) during escapes than during prey capture. No differences were found through independent comparisons of the performance of feeding and escape types II and III, but type I escapes had significantly higher mean velocity (2.27 vs 1.58ms− 1), maximum velocity (4.70 vs 3.12ms− 1) and mean acceleration (54.7 vs 38.6 ms− 2) than type II feeding behaviours.
Prey-capture performance was also related to prey size, apparent prey size (defined as the angular size of the prey on the pike’s retina) and strike distance (the distance from the pike to the prey at the onset of the fast-start). Mean and maximum acceleration increased with apparent size and decreased with strike distance, while the duration of the event increased with strike distance and decreased with apparent size. No relationship was found between the actual prey size and any performance parameter.
Strike distance ranged from 0.087 to 0.439 m and decreased as the apparent size increased from 2.6 to 9.9° (r2=0.75). The type I behaviour was usually employed when the strike distance was small and the prey appeared large. As strike distance increased and apparent size decreased, there was a progressive selection of type II, then III and then IV behaviours.
Potassium and Calcium Currents in Dissociated Muscle Fibres of the Mollusc Philine Aperta
Authors: Dorsett D. A. , Evans C. G. 
Published: April 2021

ABSTRACT
Dissociated unstriated muscle fibres from the buccal mass retractor muscles of the mollusc Philine aperta were studied using a two-electrode voltage-clamp. The mean resting potential of the fibres was –76.3±0.44mV (N=30), and the membrane resistance was 42.2±3MΩ. The space constant of the fibres was 2.03±0.33mm (N=5).
Three outward potassium currents were resolved in response to a depolarising step to zero from resting potential. (1) An early transient current, voltage-activated and blocked by 2 mmol I−1 4-aminopyridine (4-AP). This resembled the A-current described in molluscan neurones and some arthropod muscle fibres. (2) A calcium-dependent late transient current, with slower kinetics, which was suppressed by 50 mmol 1−1 tetraethylammonium chloride (TEA–CI), zero-calcium saline, 1 mmol E1 Cd2+ and 1 μmol I−1 verapamil. (3) A delayed voltage-activated current, blocked by 50 mmol I−1 TEA-CI and with kinetics associated with the delayed rectifier current IK.
An inwardly directed current, blocked by zero-calcium salines, Cd2+ and verapamil, was considered to be a calcium current whose activation closely matched that of the Ca2+-dependent potassium current.
A blockade of either the A-current, or exposure to low-calcium artificial sea water, or a combination of both, promoted the development of oscillations and regenerative spikes in the muscle fibre following depolarization.
The Relation Between Growth and Food Consumption in the Brown Trout (Salmo Trutta)
Authors: Pentelow F. T. K. 
Published: April 2021

ABSTRACT
The relation between the amount of food consumed and the growth made is one of considerable ecological importance, though the study of it has hitherto been confined almost entirely to domesticated animals living on artificial foods. In the case of fishes there is a good deal of information available in American and German literature on the food requirements of fish in fish farms and hatcheries but practically none on the relation between the amount of natural food eaten and the growth rate. Dawes (1930–1) studied this relation for the plaice, using chopped mussel (Mytilas edulis) as food, and recently Surber (1935) has described an experiment, similar to those on which this paper is based, on feeding brook trout (Salvelinus fontinalis) and rainbow trout (Salmo gairdneri) with Gammarus fasciatus.
Comparative Measurements of Water and Electrolyte Exchange in A Stenohaline and in A Euryhaline Polychaete
Authors: Ellis W. G. 
Published: April 2021

ABSTRACT
Nereis diversicolor (Müller) is a euryhaline polychaete. In brackish water it is able to “regulate” the water exchange between body fluid and environment. The related stenohaline species Perinereis (Nereis) cultrifera (Grube) has no such powers of regulating its water exchange, which differs from that of Nereis diversicolor in two respects: (1) in. brackish water of a given osmotic pressure the initial water intake is much larger than that of N. diversicolor, relative to the body weight; (2) there is no subsequent water loss (Beadle, 1931).
The Activity of the Spermatozoa of Salmo Salar in Relation to Osmotic Pressure
Authors: Ellis W. G. , Jones J. W. 
Published: April 2021

ABSTRACT
Artificial insemination of trout eggs gives a higher proportion of fertilized eggs than natural fertilization. This paradoxical fact is explained by the very brief time of activity of the sperm in river water (Gray, 1920). Huxley (1930) showed that the activity of trout sperm is increased in various salt solutions, and concluded that the trout “though somatically fully adapted to fresh-water life, is very imperfectly adapted in its reproduction, its sperms being many times more efficient in a medium intermediate between its present and its ancestral environment”.
Exercise In Birds
Authors: Butler P. J. 
Published: April 2021

ABSTRACT
Birds have two independent locomotor systems: the forelimbs (wings) are used predominantly for aerial flight, but may be used for underwater propulsion, e.g. in penguins; the hindlimbs (legs) are used for running, surface swimming and diving. In birds of similar mass, energy consumption during flight is approximately 2.5 times greater than that when running or swimming at maximum speed. This difference is the result not only of the larger mass of the flight muscles compared with that of the leg muscles, but also of their greater oxidative capacity. Interestingly, the relationship of energy consumption to body mass in cursorial birds when running is similar to that of volant birds when flying. Energy consumption during diving may be as high in some birds (e.g. tufted duck) as when they are swimming at maximum sustainable speed, and this is not influenced by water temperature.
The composition of the flight and leg muscles is different. The muscles of the leg consist of deeply situated slow oxidative (SO) fibres, which are active during quiet standing and walking, fast oxidative glycolytic (FOG) fibres, which are recruited during walking and sustained running or swimming, and peripherally located fast glycolytic (FG) fibres, which are recruited at the highest running or swimming speeds. In most volant birds, the pectoralis muscle consists predominantly of FOG fibres with a smaller percentage of FG fibres. There is some controversy over the occurrence of SO fibres in some species, although they are most probably present in those that glide. The FOG fibres are highly oxidative, with a high capillary density.
The respiratory and cardiovascular adjustments that occur during flying, running and diving are described, and the ability of some species of birds to fly at extremely high altitudes, where the partial pressure is one-third of the sea level value, is discussed.
Acid-Base and ion Balance, Metabolism, and Their Interactions, After Exhaustive Exercise in Fish
Authors: Wood Chris M. 
Published: April 2021

ABSTRACT
In fish, exhaustive exercise stress differs from steady-state aerobic exercise in causing (1) a depletion of glycogen, creatine phosphate (CP) and ATP reserves and an accumulation of lactate and metabolic acid in white muscle; (2) blood respiratory and metabolic acidoses ( and elevations, respectively); (3) marked ionic and fluid volume disturbances; and (4) a surge in plasma catecholamines. During recovery, the smaller fast component (20%) of excess postexercise oxygen consumption (EPOC) is explained by CP and ATP resynthesis and aerobic demands, but the larger slow component (80%) is considerably greater than the cost of lactate clearance and glycogen resynthesis. Ionic and H2O shifts may contribute significantly to EPOC; net fluxes are greatest between extracellular (ECF) and intracellular fluid (ICF) compartments, with smaller disturbances at the kidney (increased filtration, reabsorption and excretion) and gills (passive ion losses and H2O uptake). Modulation of branchial Na+ and Cl− exchange is important in the temporary storage of in the environment during recovery. Movements of lactate and , from ICF to ECF are dissociated processes; the major portions of both are retained in the white muscle and are probably cleared by oxidation and/or glycogen resynthesis in situ. Elevated catecholamine levels are implicated in many of these responses and serve to protect metabolic processes against acid-base disturbances, but do not appear to contribute to EPOC directly. Catecholamines also cause an elevation in blood by a mechanism linked to the β-adrenergic activation of red blood cell Na+/H+ exchange that protects O2 transport. The compound blood acidosis stimulates ventilation to meet the demands of EPOC.
Intrinsic Mechanisms Controlling Cardiac Stomach Volume of the Rainbow Trout (Oncorhynchus Mykiss) Following Gastric Distension
Authors: Grove David J. , Holmgren Susanne 
Published: April 2021

ABSTRACT
Inflation of the cardiac stomach of the rainbow trout induced reflex muscular contractions. The stomach then slowly relaxed asymptotically towards its maximum volume. Continued distension caused the stomach to become compliant and this was irreversible within the time course of each experiment (8h). Repeated periods of rest and distension revealed a short-term inhibition of reflex contractions which recovered as resting periods were extended. Sectioning the vagosympathetic trunk did not influence the response to distension. Similar responses occurred in isolated, perfused stomachs. Both tetrodotoxin and atropine plus methysergide induced immediate compliance, suggesting that it was caused by the blockade of enteric excitatory neurones. Atropine alone primarily reduced reflex contractions whilst methysergide completed this suppression and induced profound gastric relaxation. Somatostatin reversibly suppressed reflex contractions whilst vasoactive intestinal polypeptide (VIP) induced gastric relaxation. A model is proposed in which distension initially causes reflex activity via cholinergic and serotonergic nerves, whilst gastric tone remains high. Somatostatin then suppresses rhythmic contractions, whilst VIP suppresses the tryptamin-ergic mechanisms that maintain gastric tone. The rainbow trout stomach possesses intrinsic mechanisms that mimic the extrinsic, nerve-controlled ‘receptive relaxation’ or ‘accommodation’ that follows feeding in higher vertebrates.
Opposite Actions of the Anthozoan Neuropeptide Antho-Rnamide on Antagonistic Muscle Groups in Sea Anemones
Authors: McFarlane Ian D. , Reinscheid Rainer K. , Grimmelikhuijzen Cornelis J. P. 
Published: April 2021

ABSTRACT
Coelenterates are generally assumed to be primitive animals with simple nervous systems. We believe, however, that in at least one group, the sea anemones, the nervous system is in reality rather complex, a view supported by the growing number of neuropeptides recently extracted from these animals (Grim-melikhuijzen et al. 1990a,b). Three of these peptides (Antho-RFamide and the Antho-RWamides I and II) have demonstrable physiological actions on sea-anemone muscle preparations (McFarlane et al. 1987, 1990; McFarlane and Grimmelikhuijzen, 1991) and, in the case of the Antho-RWamides, on isolated muscle cells (McFarlane et al. 1991). Here we consider a fourth neuropeptide from sea anemones, Antho-RNamide (L-3-phenyllactyl-Leu-Arg-Asn-NH2) (Grim-melikhuijzen et al. 1990), and show that it has opposite actions on adjacent antagonistic muscles in sea anemones.
Membrane Potential Responses to Thermal Stimulation and the Control of Thermoaccumulation in Paramecium Caudatum
Authors: Tominaga Takashi , Naitoh Yutaka 
Published: April 2021

ABSTRACT
The overall membrane potential response of the ciliate Paramecium caudatum to a rise in the temperature of its environment was depolarizing when the ambient temperature before stimulation (Te) was equal to or higher than the culture temperature (Tc), but hyperpolarizing when Te was lower than Tc. The anterior region of the cell responded to a rise in temperature with a localized membrane depolarization. The posterior region was depolarized when Te was equal to or higher than Tc, but hyperpolarized when Te was lower than Tc. The Te-dependent polarity reversal of the posterior response was responsible for the comparable reversal of the overall response. The temperature at which the polarity reversal of the posterior response took place shifted according to Tc. This shift caused a comparable shift in the temperature at which polarity reversal occurred for the overall response. The Tc -dependent polarity reversal of the posterior response and its Tc-dependence are major causes of thermoaccumulation mediated by ciliary activity of Paramecium in regions with temperatures close to Te.
The Potentiating Effect of Prestretch on the Contractile Performance of Rat Gastrocnemius Medialis Muscle During Subsequent Shortening and Isometric Contractions
Authors: Ettema G. J. C. , Huijing P. A. , De Haan A. 
Published: April 2021

ABSTRACT
The aim of the present study was to investigate the effect of an active stretch during the onset of a muscle contraction on subsequent active behaviour of the contractile machinery within an intact mammalian muscle-tendon complex. Muscle length and shortening velocity were studied because they may be important variables affecting this so-called prestretch effect. Seven gastrocnemius medialis (GM) muscles of the rat were examined. Tetanic, isovelocity shortening contractions from 3 mm above muscle optimum length (l0) to l0—2 mm, at velocities of 10–50mm s-1 (dynamic experiments), were preceded by either an isometric contraction (PI) or an active stretch (PS). By imposing quick length decreases between the prephase and the concentric phase, all excess force generated in the prephase was instantaneously eliminated. This procedure only allowed small force changes during subsequent shortening (caused by the intrinsic properties of the contractile machinery). In this way, the influence of series elastic structures on subsequent muscle performance was minimized. Experiments were also performed at lengths ranging from l0+2.5mm to l0–1.5 mm, keeping the length constant after the initial quick length changes (isometric experiments). For the dynamic experiments, enhancement of the performance of the contractile machinery (potentiation) was calculated as the ratio of the average force level over each millimetre of shortening during PS to that during PI conditions (PS/PI). For the isometric experiments, the PS/PI force ratio after 300 ms of stimulation was used.
The main result of the present study confirmed results reported in the literature and experiments on isolated muscle fibres. For all conditions, a potentiation effect was found, ranging from about 2 to 16 %. Muscle length appeared to have a large positive effect on the degree of potentiation. At the greatest lengths potentiation was largest, but at lengths below optimum a small effect was also found. A negative influence of shortening velocity was mainly present at increased muscle lengths (l0+2.5 mm and l0+1.5 mm). For the dynamic experiments, no interaction was found between the effects of muscle length and shortening velocity on potentiation. However, there was a clear difference between the isometric and dynamic responses: the dependence of potentiation on muscle length was significantly greater for the isometric contractions than for the dynamic ones. These isometric-dynamic differences indicate that the processes underlying prestretch effects operate differently under isometric and dynamic conditions. The conditions under which the experiments were performed allow us to suggest that the potentiation effects described here might play an important role in ballistic movements containing active stretch periods (e.g. countermovement jumping).
Insect Cardioactive Peptides: Regulation of Hindgut Activity by Cardioacceleratory Peptide 2 (Cap2) During Wandering Behaviour In Manduca Sexta Larvae
Authors: Tublitz N. J. , Allen A. T. , Cheung C. C. , Edwards K. K. , Kimble D. P. , Loi P. K. , Sylwester A. W. 
Published: April 2021

ABSTRACT
The functional relationship between cardioacceleratory peptide 2 (CAP2) and hindgut activity during wandering behaviour was investigated in fifth-instar larvae of the tobacco hawkmoth Manduca sexta. Inspection of the alimentary canal on the day prior to wandering showed that the gut, in preparation for metamorphosis, was voided of all contents by 18:00 h. Associated with this event, which we refer to as ‘gut emptying’, was an increase in the frequency of hindgut contractions measured in vivo. No change in heart activity was seen during this developmental period. Measurements of the amount of CAP2 in the central nervous system (CNS) of fifth-instar caterpillars revealed that CAP2 storage levels declined sharply on the day of gut emptying. The drop in CNS levels of CAP2 at gut emptying was temporally correlated with the appearance of CAP2 in the haemolymph. CAP2, when applied at physiological concentrations to an in vitro larval hindgut bioassay, caused changes in several parameters, including contraction frequency and amplitude, and basal tension. In vivo administration of CAP2 elicited hindgut responses that were qualitatively and quantitatively similar to those seen in vitro. Developmental studies on changes in CAP2 responsiveness during the last larval instar demonstrated that the hindgut is maximally sensitive to CAP2 on the day of gut emptying. Direct evidence in support of a role for CAP2 in fifth-instar larvae was provided by experiments in which the increase in gut activity in vivo seen at gut emptying was significantly reduced by injections of an anti-CAP antibody. Based on data from cobalt backfills and anti-CAP immunohistochemical staining, we propose that CAP2 exerts its effect on the larval hindgut at wandering via a local release from CAP-containing neurones in the terminal ganglion that project directly to the hindgut.
Dicyclohexylcarbodiimide Reacts Specifically with The 16 kDa Subunit of Larval Manduca Sexta Midgut Vacuolar-Type Atpase
Authors: Zheng X. Y. , Spaeth D. D. , Harvey W. R. , Wolfersberger M. G. 
Published: April 2021

ABSTRACT
Proton-motive vacuolar-class ATPases (V-ATPases) are commonly associated with membrane-bound organelles other than mitochondria and chloroplasts. They are found in the vacuoles of Neurospora crassa and yeasts, in tonoplasts of plants and in endomembranes such as lysosomes, endosomes, clathrin-coated vesicles and secretory granules (Sze, 1985; Rudnick, 1986; Mellman et al. 1986; Rodman et al. 1991). However, they have also been found in plasma membranes of kidney tubules (Brown et al. 1987; Wang and Gluck, 1990). Recently, the pump responsible for the large lumen-directed net flux of potassium across larval Manduca sexta midgut has been shown to consist of a plasma membrane protonmotive V-ATPase functioning in conjunction with an nH+/K+ antiporter (Wieczorek et al. 1991).
Disk-Sphere Transformation in Mammalian Red Cells
Authors: Furchgott Robert F. 
Published: April 2021

ABSTRACT
The purpose of this paper is to try to explain the phenomenon of the transformation of the mammalian erythrocytes from disks to spheres when a small drop of a saline suspension is placed between glass slide and cover-glass. Ponder (1934) several years ago reviewed the work which had been done in connexion with this phenomenon. As was pointed out by Ponder, who was the first to show clearly the necessity of having the glass surfaces in close proximity for the formation of perfect spheres (1928-9), the two explanations which have been put forth to explain the phenomenon are both inadequate. As will be seen later, that of Waller (1930) is somewhat closer to the true explanation than that of Brinkman & van Dam (1920).