bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Adrenergic Responses of Carp (Cyprinus Carpio) Red Cells: Effects of and pH
Authors: Salama Annika , Nikinmaa Mikko 
Published: April 2021

ABSTRACT
Carp (Cyprinus carpio) red cells do not show β-adrenergic responses when incubated with 10−5moll−1 adrenaline at atmospheric oxygen tension and a pH value close to the in vivo resting pH (approx. 8·1). However, when either the pH or the oxygen tension of the incubation medium is decreased, the adrenergic responses appear, showing that oxygen or an oxygen-linked phenomenon has a direct influence on the response. Once present, the adrenergic red cell response is similar to that of trout: cellular water content, sodium content and intracellular pH all increase. Quantitatively the effect appears to be much smaller in carp than in trout. Adrenaline induces an increase in red cell oxygen content when the oxygen content is plotted as a function of extracellular pH. This effect coincides with the onset of the Root effect and is caused by the adrenaline-induced increase in intracellular pH, since it disappears when the oxygen content is plotted as a function of intracellular pH. The red cell ATP content decreases metabolically during adrenaline incubations. In contrast, cellular GTP content is not metabolically reduced in adrenaline-treated cells, showing that the rapid and selective decrease in red cell GTP concentration, observed in hypoxic cyprinids, is not adrenergically induced.
Quantitative Analysis of Resting Membrane Electrogenesis in Insect (Diptera) Skeletal Muscle I. Intracellular K+, Na+ and Cl- Activities, Measured Using Liquid Ion-Exchanger and Neutral Ion-Carrier Microelectrodes
Authors: Dawson Jill , Djamgoz M. B. A. 
Published: April 2021

ABSTRACT
Electrophysiological properties of skeletal body-wall muscles of prepupal Calliphora erythrocephala were investigated using double-barrelled intracellular ion-sensitive microelectrodes. The most realistic estimate of the intracellular K+ activity, obtained using K+-sensitive microelectrodes based on a neutral carrier, was 115mmoll-1. The K+ equilibrium potential was consistently more negative than the prevailing resting potential, the average difference being —15 mV. The intracellular Na+ activity and the Na+ equilibrium potential were 7 mmol 1-1 and +46 mV on average, respectively. The mean value of the intracellular Cl- activity was 40 mmol 1-1, and this was apparently higher than that required for passive distribution of Cl-. However, when reversibly exposed to a Ringer containing no Cl-, cells could rapidly exchange most of their intracellular Cl-, although the resting membrane potentials were only transiently affected. It is concluded that an anionic interferent exists inside muscles, that this artefactually elevates the measured intracellular Cl- activities, and that Cl- makes no contribution to resting membrane electrogenesis.
Acid-Base and Ionic Exchanges at Gills and Kidney After Exhaustive Exercise in the Rainbow Trout
Authors: Wood Chris M. 
Published: April 2021

ABSTRACTUnidirectional Na+ and Cl− fluxes, net fluxes of Na+, Cl−, other ions, titratable acid (TA), ammonia and acidic equivalents (net H+) across the gills, together with the comparable renal fluxes, were monitored throughout a 24-h period after exhaustive exercise (simple chasing) in the rainbow trout. The gills were the major site of flux. The renal excretion of [TA—HCO3−], ammonia, lactate and most electrolytes increased after exercise, coincident with diuresis. Relative to the gills, the kidney accounted for only 8 % of net H+ flux, 0–15 %of net electrolyte losses and 50% of lactate loss, though the latter was negligibly small.Approximately 1000 μequiv kg−1 of net H+ were transported across the gills to the water during the first 4h, and then fully recovered over the subsequent 8h, coincident with periods of extracellular acidosis and alkalosis recorded in previous studies. Ammonia efflux increased during the first 4h; changes in titratable acid flux and extracellular and NH4+ levels suggest that this elevation occurred partially as NH3 diffusion in the first hour, and thereafter mainly as NH4+ exchange. Small net Na+ losses (≈300 μequivkg−1), moderate net K+ losses (=600juequivkg−1) and large net Cl− losses (≈1200 μequiv kg−1) correlated well with previously reported plasma changes; only the Na+ deficit was fully corrected by 24 h. Na+ influx was stimulated and Cl− influx inhibited during the 0–4 h period of net H+ excretion, whereas Na+ influx returned to control levels and Cl− influx increased during the 4-12 h period of net H+ uptake. These data indicate dynamic modulation of Na+/NH4+,H+ and C1−/HCO3−,OH− exchanges; however, an excess of Cl− over Na+ efflux also contributed to net H+ excretion. Acidic equivalent flux correlated well with [Na+-Cl−] net flux, in accord with strong lon difference theory.
A Light, Portable Apparatus for The Assessment of Invertebrate Heartbeat Rate
Authors: Buchan Peter , Peck Lloyd , Tublitz Nathan 
Published: April 2021

ABSTRACT
A major problem for invertebrate physiologists is that most measurements of physiological parameters are made in the laboratory, rather than in the field, often because of restrictions imposed by equipment size and sensitivity. It is questionable as to how representative such results are of animals in their natural environment. One technique that has been employed in the laboratory involves the measurement of electrical impedance, for example to monitor heartbeat (Hoggarth & Trueman, 1967; Ansell, 1973; Tublitz & Truman, 1985). To allow such measurements to be made in the field as well as the laboratory, a small, light and portable apparatus has been designed.
Ontogenesis of Contractile Properties of Skeletal Muscle and Sprint Performance in the Lizard Dipsosaurus Dorsalis
Authors: Marsh Richard L. 
Published: April 2021

ABSTRACT
Ontogenetic allometries of running performance in 3-to 4-m burst runs (sprints) and of the contractile properties of the fast-twitch, glycolytic region of the iliofibularis muscle (FG-IF) were measured in Dipsosaurus dorsalis. This iguanid lizard hatches at a body mass of about 4 g and reaches adult masses of 40–70 g. Running velocity was little influenced by changes in body mass during development. Stride frequency (f) declines ontogenetically and was proportional to body mass (Mb) to approximately the −0·2 power (determined by regression analysis). Stride length (Ls) appeared to be related to the allometry of hindlimb length (LHL); both Ls and LHL were proportional to about Mb0·28. Intrinsic shortening velocity of the FG-IF decreased only slightly with increasing body mass, and was consequently not proportional to f as has been assumed by various models of running dynamics. In contrast, twitch time lengthened markedly with increasing body mass, and the ratio of twitch time to stride time remained approximately constant. These results suggest that the intrinsic velocity of the muscles does not directly or solely determine maximal f, but instead limb kinematics are determined in part by other biomechanical constraints related to body dimensions. Further, the allometry of twitch kinetics supports the idea that the properties of the muscles are adjusted to allow ample time for full activation and deactivation within the biomechanically determined stride time.
Regulation of Binding of Phosphofructokinase to Myofibrils in the Red and White Muscle of the Barred Sand Bass, Paralabrax Nebulifer (Serranidae)
Authors: Roberts Susan J. , Lowery Mary Sue , Somero George N. 
Published: April 2021

ABSTRACT
The binding of phosphofructokinase (PFK) to myofibrils from the white muscle of the fish Paralabrax nebulifer (Girard, 1854) is sensitive to factors known to be allosteric regulators of PFK activity. PFK in Triton-X-100-extracted muscle remains bound to myofibrils at pH 7·0 and is fully solubilized by increasing the pH to 8-0. The curve describing the pH-dependence of PFK binding to myofibrils is similar in its steepness to pH versus activity curves of PFK at low temperature. Nucleotides are also potent modulators, preventing the association of PFK with myofibrils at concentrations between 20 and 60 μmol l−1 of ATP, ADP, MgATP or GTP, listed in order of effectiveness. PFKs in the red and white muscle extracts differ in their pH-dependence of binding to myofibrils, and their kinetic and regulatory properties (response to citrate, pH and fructose-2,6-bisphosphate). Reversible binding of PFK to myofibrils may be important in the control of glycolysis, especially in the highly glycolytic white muscle fibres.
Kinematics and Estimated Thrust Production of Swimming Harp and Ringed Seals
Authors: Fish Frank E. , Innes S. , Ronald K. 
Published: April 2021

ABSTRACT
The propulsive motions of swimming harp seals (Phoca groenlandica Erxleben) and ringed seals (Phoca hispida Schreber) were studied by filming individuals in a flume. The seals swam at velocities ranging from 0·6 to 1·42 ms−1. Locomotion was accomplished with alternate lateral sweeps of the hind flippers generated by lateral flexions of the axial body in conjuction with flexion of the flippers. The frequency of the propulsive cycle increased linearly with the swimming velocity, and the maximum angle of attack of the flipper decreased, but the amplitude remained constant. The kinematics and morphology of this hind flipper motion indicated that phocid seals do not swim in the carangiform mode as categorized by Lighthill (1969), but in a distinct mode that mimics swimming by thunniform propulsors. The hind flippers acted as hydrofoils, and the efficiency, thrust power and coefficient of thrust were calculated from unsteady wing theory. The propulsive efficiency was high at approximately 0·85. The thrust power increased curvilinearly with velocity. The drag coefficient ranged from 0·012 to 0·028 and was found to be 2·8–7·0 times higher than the theoretical minimum. The drag coefficient was high compared with that of phocid seals examined during gliding or towing experiments, indicating an increased drag encumbered by actively swimming seals. It was determined that phocid seals are capable of generating sufficient power for swimming with turbulent boundary layer conditions.
Preferred Speeds in Terrestrial Vertebrates: Are They Equivalent?
Authors: Perry Andrew K. , Blickhan Reinhard , Biewener Andrew A. , Heglund Norman C. , Taylor C. Richard 
Published: April 2021

ABSTRACT
Terrestrial animals have ‘preferred speeds’ within each gait, that are used much more frequently than others for moving along the ground. Energy costs reach minimal values at these speeds within each gait. In this study we asked whether these speeds are mechanically equivalent among different animals (i.e. speeds where the same levels of peak muscle stress occur). If so, this would help in establishing a link between the energetics and the mechanics of the active muscles at these speeds, providing a first step in understanding why energy costs are minimal. We also asked whether peak muscle stress reaches a similar fraction of the maximal isometric stress at these speeds. If so, this would suggest that muscles are structured so that a similar reserve capacity remains, with a similar safety factor for avoidance of injury in response to prolonged repetitive loading. We compared two species that use quite different locomotory methods at their preferred speeds: white rats that gallop and kangaroo rats that hop. We measured peak stress in the ankle extensor muscles of these two species, as they moved at their preferred speeds, using a force platform/ciné analysis technique. We also measured the maximum isometric force that this muscle group could develop in situ in the same individuals. We found the ankle extensors of white rats and kangaroo rats developed virtually identical levels of peak stress at their preferred speeds (70 ± 6 kPa and 69 ± 6 kPa, respectively, mean ± S.E.), despite a fourfold difference in peak ground reaction force per unit body mass exerted on each limb. The values of peak isometric stress in situ were also virtually identical (206 ±17 kPa and 200 ±9 kPa, respectively). Our finding that the peak muscle stress is about one-third of maximum isometric stress at the preferred speeds is consistent with the idea that these are mechanically equivalent speeds, where the same fraction of available muscle fibres is recruited. Finding nearly identical values in two species that move in such different ways (galloping vs hopping), and have such large differences in ground reaction force exerted by each limb, suggests this may be true more generally for terrestrial vertebrates.
Measured Behavioural Latency in Response to Sex-Pheromone Loss in the Large Silk Moth Antheraea Polyphemus
Authors: Baker T. C. , Vogt R. G. 
Published: April 2021

ABSTRACT
Males of the giant silk moth Antheraea polyphemus Cramer (Lepidoptera: Saturniidae) were video-recorded in a sustained-flight wind tunnel in a constant plume of sex pheromone. The plume was experimentally truncated, and the moths, on losing pheromone stimulus, rapidly changed their behaviour from up-tunnel zig-zag flight to lateral casting flight. The latency of this change was in the range 300–500 ms. Video and computer analysis of flight tracks indicates that these moths effect this switch by increasing their course angle to the wind while decreasing their air speed. Combined with previous physiological and biochemical data concerning pheromone processing within this species, this behavioural study supports the argument that the temporal limit for this behavioural response latency is determined at the level of genetically coded kinetic processes located within the peripheral sensory hairs.
Wing Shape and Flight Behaviour in Butterflies (Lepidoptera: Papilionoidea and Hesperioidea): A Preliminary Analysis
Authors: Betts C. R. , Wootton R. J. 
Published: April 2021

ABSTRACTRepresentatives of six butterfly species, flying freely in the field or in simulated field conditions, were filmed with a high-speed ciné camera and subjected to kinematic and morphometric analysis. This is the first detailed investigation on an insect performing the varied patterns of ‘natural’ flight. Kinematic parameters in representative sequences of selected flight modes were calculated and compared, and wing shapes were characterized using aspect ratio and non-dimensional moment parameters.The analyses and field observations of these and other butterflies suggest possible correlations between flight performance and wing shape. The behaviour of individual species conforms reasonably well with crude predictions based on aspect ratio, wing loading and wing inertia.
Quasielastic Laser Light Scattering and Laser Doppler Electrophoresis as Probes of Synaptic and Secretory Terminal Function
Authors: Sattelle David B. 
Published: April 2021

ABSTRACT
The intensity fluctuations of scattered laser light provide a rapid, nondestructive probe of hydrodynamic size and polydispersity of nerve-ending subcellular particles. This method yields information on diffusive and directed motion of secretory granules and synaptic vesicles. It also enables accurate measurements of surface charge properties of isolated granules and plasma membranes. Recently, a fast, total intensity light-scattering change, sensitive to many of the factors that influence secretion, has been detected in neurosecretory terminals. Here a slower, but equally reversible, light-scattering change is detected using an intact invertebrate neurosecretory organ. Scattering at rest is dominated by particles of diameter similar to that of secretory vesicles detected in electron micrographs of the same tissue. Simultaneous release and light-scattering observations demonstrate an increase in the proportion of total scatter derived from mobile as opposed to fixed components, with no change in mean particle diameter. Since the major changes in intensity fluctuations are detected during the declining phase of the release of secretory product, they may represent longer term reorganization of terminals following intense secretory activity.
As a prelude to dissecting the origin of the fast light-scattering changes, the hydrodynamic properties of secretosomes and purified secretory granules from mouse neurohypophysis have been characterized. In this way, size, dispersity and aggregation can be followed, and subpopulations can be characterized. Application of an electric field to various subcellular fractions enables measurement of electrophoretic mobility, and hence calculation of surface-charge properties of granules and plasma membranes. The effects of divalent cations on granule surface charge in vitro indicate that surface-charge neutralization is not a calciumspecific event in exocytosis. The possibility that some of the light-scattering signal reflects dynamic changes in cytoskeletal components of the secretory terminal is examined.
The Cytoskeleton as a Barrier to Exocytosis in Secretory Cells
Authors: Aunis Dominique , Bader Marie-France 
Published: April 2021

ABSTRACT
Chromaffin cells of the adrenal medulla synthesize, store and secrete catecholamines. These cells contain numerous electron-dense secretory granules which discharge their contents into the extracellular space by exocytosis. The subplasmalemmal area of the chromaffin cell is characterized by the presence of a highly organized cytoskeletal network. F-Actin seems to be exclusively localized in this area and together with specific actin-binding proteins forms a dense viscoelastic gel; fodrin, vinculin and caldesmon, three actin cross-linking proteins, and gelsolin, an actin-severing protein, are found in this subplasmalemmal region. Since fodrin-, caldesmon- and alpha-actinin-binding sites exist on secretory granule membranes, actin filaments can also link secretory granules. Chromaffin granules can be entrapped in this subplasmalemmal lattice and thus the cytoskeleton acts as a barrier preventing exocytosis. When cells are stimulated, molecular rearrangements of the subplasmalemmal cytoskeleton take place: F-actin depolymerizes and fodrin reorganizes into patches. In addition, introduction of monospecific antifodrin immunoglobulins into digitonin-permeabilized cells blocks exocytosis, demonstrating the crucial role of this actin-binding protein. In bacterial toxin-permeabilized chromaffin cells, experiments using actin-perturbing agents such as cytochalasin D and DNAase I suggest that exocytosis is in part controlled by the cytoskeleton. The intracellular signal governing the cytoskeletal reorganization (associated with exocytosis) is calcium. Calcium inhibits some and activates other actin-binding proteins and consequently causes dissolution of the subplasmalemmal cytoskeleton. This dissolution of cytoskeletal filaments should result in granule detachment and permit granules free access to exocytotic sites on the plasma membrane.
Electrophysiology of Neurosecretory Cells from the Pituitary Intermediate Lobe
Authors: Mcburney Robert N. , Kehl Steven J. 
Published: April 2021

ABSTRACT
One of the goals in studying the electrical properties of neurosecretory cells is to relate their electrical activity to the process of secretion. A central question in these studies concerns the role of transmembrane calcium ion flux in the initiation of the secretory event.
With regard to the secretory process in pituitary cells, several research groups have addressed this question in vitro using mixed primary anterior pituitary cell cultures or clonal cell lines derived from pituitary tumours. Other workers, including ourselves, have used homogeneous cell cultures derived from the pituitary intermediate lobes of rats to examine the characteristics of voltagedependent conductances, the contribution of these conductances to action potentials and their role in stimulus-secretion coupling.
Pars intermedia (Pl) cells often fire spontaneous action potentials whose frequency can be modified by the injection of sustained currents through the recording electrode. In quiescent cells action potentials can also be evoked by the injection of depolarizing current stimuli. At around 20°C these action potentials have a duration of about 5 ms. Although most of the inward current during action potentials is carried by sodium ions, a calcium ion component can be demonstrated under abnormal conditions. Voltage-clamp experiments have revealed that the membrane of these cells contains high-threshold, L-type, Ca2+ channels and low-threshold Ca2+ channels.
Since hormone release from PI cells appears not to be dependent on action potential activity but does depend on external calcium ions, it is not clear what role these Ca2+ channels play in stimulus-secretion coupling in cells of the pituitary pars intermedia. One possibility is that the low-threshold Ca2+ channels are more important to the secretory process than the high-threshold channels.
The Role of Calcium in Stimulus-Secretion Coupling in Excitable and Non-Excitable Cells
Authors: Penner Reinhold , Neher Erwin 
Published: April 2021

ABSTRACT
Secretion of vesicular contents by exocytosis is a common feature of excitable (neurones, chromaffin cells, beta cells) and non-excitable cells (platelets, neutrophils, mast cells). The simplistic view that the universal mechanism controlling secretion is elevation of [Ca2+]i -whatever the source of this second messenger may be -is no longer tenable in view of recent reports demonstrating secretion at basal or even reduced [Ca2+]i. It is nevertheless clear that in excitable cells an increase in [Ca2+]i is the triggering event that induces secretion. In non-excitable cells, secretion is presumably triggered by other second messengers, although [Ca2+]i appears to act as an important modulator of the rate of secretion. Conversely, these second messenger systems may serve a regulatory function in excitable cells.
Given the relative importance of [Ca2+]i in the regulation of cellular functions in excitable and non-excitable cells, it is not surprising that several mechanisms are expressed in these cells to regulate intracellular calcium concentration. The major pathway for Ca2+ in excitable cells is by voltage-activated Ca2+ channels, but release of Ca2+ from intracellular stores, via second messengers, predominates in non-excitable cells, and may also be important in excitable cells. In addition, receptor-operated channels and second messenger-gated conductances may prove to be important. All of these pathways are subject to regulation by a variety of interactive second messenger systems, which provide necessary tuning for an appropriate control of intracellular calcium level.