bluuebunny/crossref_metadata_2025 huggingface dataset:
Delayed Effects of Anoxia Upon the Electrical Properties of an Identified Cockroach Motoneurone
Authors: Pitman Robert M.
Published: April 2021

In nerve preparations isolated from cockroaches that had survived exposure to carbon dioxide or nitrogen for 1–3 h, the cell body of the metathoracic ‘fast’ coxal depressor motoneurone (Df) gained the ability to support all-or-none action potentials. Such responses were observed between 10 h and 5 days after the anoxic period. Recordings from isolated cell bodies indicated that the action potentials were generated in the cell body itself rather than in adjacent regions of the neurone. Action potentials were abolished in a sodium-free medium or in the presence of tetrodotoxin, but persisted in saline containing manganese ions, indicating that sodium ions are the major ions involved in the rising phase of these action potentials. Elevation of the intracellular H+ concentration by acid injection or by bathing the preparation in saline containing 40 mmol 1−1 ammonium chloride caused a marked depolarization of the membrane potential and action potentials could not be elicited. This indicates that a fall in intracellular pH during anoxia could not itself directly produce the enhancement in excitability reported here. Histological examination of the neurone, after periods of anoxia sufficient to enable the cell body to generate the action potentials reported here, showed no detectable change in the perinuclear distribution of RNA and hence did not indicate any alteration in protein synthesis.
Fluid Mechanical Valving of Air Flow in Bird Lungs
Authors: Kuethe Dean O.
Published: April 2021

The unidirectional flow through the gas-exchanging bronchi of bird lungs is known to be effected by (1) the structure of the major bronchi and (2) a pressure difference between the cranial and caudal air sacs.

To study the effects of bronchial structure, simple physical models of bird lungs were constructed. They suggested that, to achieve unidirectional flow, air in the caudal portion of the primary bronchus must be directed towards the orifices of the mediodorsal bronchi.

To study the effect of air sac pressures, a controllable pressure difference was produced between the air sac orifices of fixed duck lungs. The cranial orifices had a higher pressure than the caudal ones during inhalation and vice versa during exhalation. There was a set of pressure differences for which the paleopulmo received the same flow rate during inhalation as during exhalation. High pressure differences caused more flow in the paleopulmo during exhalation than during inhalation; low pressure differences had the converse effect.
The Distribution of Ammonia and H+ Between Tissue Compartments in Lemon Sole (Parophrys Vetulus) at Rest, During Hypercapnia and Following Exercise
Authors: Wright P. A. , Randall D. J. , Wood C. M.
Published: April 2021

The distribution of ammonia and [146C]DMO was compared in white muscle, heart, brain, red cells and plasma of lemon sole (Parophrys vetulus Girard) at rest, during hypercapnia and following strenuous exercise. In red cells at rest, measured intracellular ammonia levels were equal to those predicted by the plasma to red cell pH gradient. Red cells are unusual in that hydrogen ions are passively distributed according to membrane potential (EM), whereas in other tissues this is not the case. In white muscle, heart and brain under all experimental conditions, intracellular ammonia levels far exceed those predicted by transmembrane pH gradients. Calculated values in these tissues are very close to published resting values of EM. We conclude that, in lemon sole, NH4+ permeates cell membranes and that intracellular ammonia stores are not determined by transmembrane pH gradients.
Distribution of Amino Acids to Internal Tissues After Epidermal Uptake in the Annelid Glycera Dibranchiata
Authors: Qafaiti Michael , Stephens Grover C.
Published: April 2021

Net uptake rates by Glycera dibranchiata Ehlers of 18 amino acids, each present in artificial sea water at an initial concentration of 1 μmol 1-1, were estimated using high-performance liquid chromatography (HPLC). Uptake rates for 14C-labelled alanine, arginine, aspartate, glutamate, glycine and serine, presented singly at an initial concentration of l μmoll−1, were estimated by observing disappearance of radioactivity from the ambient solution. Net entry of alanine, arginine, aspartate and serine was estimated by HPLC in parallel samples of the medium. There was no significant difference in the rate of influx of labelled substrate and net entry estimated by HPLC for these amino acids. Ligature of the anterior and posterior ends of the worms did not perceptibly modify rates of uptake. Distribution of radioactivity to the internal and external body wall, coelomocytes, gut and coelomic fluid was observed after lh of incubation in lμmol11 serine. Rates of exchange of labelled carbon were estimated for all combinations of these internal tissues by taking advantage of morphological features of Glycera. Amino acid pools in each of the tissues of the worms are described, based on HPLC analyses. Internal distribution of radioactivity derived from [14C]serine is com-pared with total pools based on estimates of tissue volume and the normal serine content of free amino acid pools for each tissue. The distribution of the non-metabolized analogue cycloleucine is also described at the end of lh of incubation.
The Cooling Power Of Pigeon Legs
Authors: Martineau Lucie , Larochelle Jacques
Published: April 2021

The rate of heat loss from legs and feet (ḢLEG) was studied in resting pigeons preheated to a body temperature (43·1 °C) close to those recorded during flight. The experimental system was designed to allow the calculation of ḢLEG from whole-body cooling rates following exposure of the legs and feet to various combinations of wind speed (0–75 km h−1) and air temperature (5–25°C). The pigeons remained hyperthermic when their hindlimbs were kept insulated, but their bodies cooled markedly as a result of exposure of the legs and feet. With a 12·5kmh−1 wind at 25°C, ḢLEG corresponded to 240% of the resting heat production. HLEG was increased by higher wind speed and lower air temperature, but it became essentially independent of wind speed above 37·5 km h−1. The maximum values of ḢLEG were 4–6 times as large as the resting heat production and could account for 50–65 % of the total heat produced during flight. It is concluded that in a non-aquatic bird the legs and feet can play a major role in whole-body thermoregulation, both at rest and during flight.
Physiological Correlates of Interspecific Variation in Acid Tolerance in Fish
Authors: Freda J. , Mcdonald D. G.
Published: April 2021

This study investigated ion regulation in relation to water pH in three species of fish of differing tolerance to low pH (common shiners, Notropis cornutus, most sensitive; rainbow trout, Salmo gairdneri, intermediate; yellow perch, Perea flavescens, least sensitive). Increasing sensitivity to exposure to low pH was characterized by shorter survival times, greater losses of whole-body ions, more complete inhibition of Na+ uptake, and greater stimulation of Na+ efflux, the latter being the most important factor in determining survival. Interspecific variations in acid tolerance were also correlated with Na+ transport characteristics at circumneutral pH; Km was directly correlated Vmax and inversely correlated with acid tolerance. In addition, there were large qualitative differences among the species in the Ca2+-dependence of Na+ efflux. Sodium efflux induced by low pH was markedly Ca2+-dependent in both trout and shiners in a manner consistent with a simple competition between Ca2+ and H+ for gill binding sites. The increased sensitivity of shiners relative to trout was related to lowered Cam binding activity. In contrast, Na+ efflux in perch was virtually unaffected by water [Ca2+], Similarly, La3+ (a Ca2+ antagonist) stimulated higher Na+ losses from shiners than from trout, but had little effect upon perch. Ionic losses produced by saturating La3+ concentrations were generally lower than those produced by H+, suggesting that Ca2+ displacement is not the only mechanism for increased gill permeability at low pH. Nonetheless, the results obtained are consistent with the notion that acid tolerance may be related to Ca2+-binding activity in some species (e.g. trout and shiners) although not in others (e.g. perch).
Unpaired Median Neurones in a Lepidopteran Larva (Antheraea Pernyi): I. Anatomy And Physiology
Authors: Brookes S. J. H. , Weevers R. DE G.
Published: April 2021

The anatomy and physiology of two unpaired median neurones (MCI and MC2) with bilaterally symmetrical axons in abdominal ganglia 3, 4, 5 and 6 of Antheraea pernyi larvae were studied. Intracellular dye filling of MCI and MC2 revealed that they were distinguishable from all other neurones in the ganglia and that they both had axons projecting out of the ganglia in right and left nerves 1. The two cells were identical in their central anatomy and physiology, but could be distinguished from one another by their peripheral branching patterns. The significance of these patterns was investigated by detailed study of the neural and muscular anatomy of the proleg-bearing segments 3, 4, 5 and 6. The peripheral axons of MCI and MC2 were exclusively associated with nerve trunks that could be traced to blocks of muscle.

Intracellular recordings of the two median cells characteristically showed overshooting soma action potentials that were followed by a long afterhyperpolarization lasting many seconds. Simultaneous recordings from median cells in the same ganglion revealed that MCI and MC2 shared an excitatory synaptic drive that largely determined their patterns of firing. Recordings from median cells in different ganglia showed that the common synaptic drive was also shared by median cells in different segments. Selective lesions of the ventral nerve cord indicated that the synaptic drive to MCI and MC2 originated in the suboeso-phageal ganglion. These cells were similar in anatomy and physiology to the median cells in several other insects.
Muscle Forces During Locomotion in Kangaroo Rats: Force Platform and Tendon Buckle Measurements Compared
Authors: Biewener Andrew A. , Blickhan Reinhard , Perry Andrew K. , Heglund Norman C. , Taylor C. Richard
Published: April 2021

The muscle forces and stresses occurring during normal locomotor activity in kangaroo rats are compared with the peak isometric force developed by the same muscles in situ. Two methods were used simultaneously to determine the stresses (force/cross-sectional area) acting in the ankle extensors during steady-speed hopping and during jumps when animals were startled: a direct measurement using a force buckle surgically implanted around a tendon; and an indirect measurement using a force platform/ciné analysis technique. We obtained essentially the same values with the two techniques. We found that at slow speeds (0·7ms−1) the ankle extensor muscles of kangaroo rats exerted 20% of the maximum isometric force developed when the muscles were stimulated via the tibial nerve. This increased to 53% at higher speeds (l·9 ms−1). At the animal’s preferred hopping speed (1·5 ms−1), peak force was approximately 40% of maximum isometric force. In jumps when animals were startled, peak forces as high as 175% of the maximal elicited isometric force were recorded. These high forces always occurred when the muscles were being stretched. It appears that kangaroo rats utilize nearly the entire range of muscle force possible during normal locomotor events (i.e. up to 175% of maximum isometric force when muscles are stretched).
Stimulation Of Sodium Transport and Fluid Secretion by Ouabain in an Insect Malpighian Tubule
Authors: Maddrell S. H. P. , Overton J. A.
Published: April 2021

Ouabain, at all concentrations higher than 2×l0−7mol l−1, stimulates the rate at which the Malpighian tubules of the insect, Rhodnius, transport sodium ions and fluid into the lumen. An effect on paracellular movement of sodium ions is unlikely because ouabain makes the electrical potential of the lumen more positive, which would slow diffusion of sodium into the lumen. Radioactive ouabain binds to the haemolymph-facing sides of the tubule cells but not to the luminal face. This binding is reduced in the presence of elevated levels of potassium or of non-radioactive ouabain. Bound ouabain is only slowly released on washing in ouabain-free saline. The evidence suggests that there is a Na+/K+-ATPase on the outer (serosal) membranes of the tubules. Such a pump would transport sodium in a direction opposed to the flow of ions and water involved in fluid transport; poisoning it with ouabain would remove this brake, and fluid flow and sodium transport would increase, as observed.
Effects of Hyposmotic Shock on Ion Fluxes in Isolated Trout Hepatocytes
Authors: Bianchini L. , Fossat B. , Porthé-Nibelle J. , Ellory J. C. , Lahlou B.
Published: April 2021

Isolated trout hepatocytes exposed to hypotonic Hank’s medium (isotonicity × 0·70) swelled to 1·17 times the control volume after 3 min; by 15 min the cell volume had returned to normal.

The ouabain-insensitive K+ uptake increased, indicating an immediate rise in K+ membrane permeability. As indicated by analysis of cellular contents, the regulatory volume decrease (RVD) was ensured by a release of intracellular K+. Na+ was not implicated in this mechanism. This potassium permeability induced by hypotonic shock was transient (maximum at 6min), insensitive to blocking agents of voltage-and Ca2+-dependent K+ channels, and chloride-dependent.

This result, together with a time-course of Cl− uptake similar to that of K+, suggests a K+/C1− cotransport mechanism. This cotransport is inhibited by high furosemide concentrations (10−3mol l−1) but not by bumetanide (10−4mol l−1) or piretanide (10−4mol l−1).
Induction of Bioluminescence Capability in the Marine Fish, Porichthys Notatus, by Vargula (Crustacean) [14C]Luciferin and Unlabelled Analogues
Authors: Thompson Eric M. , Toya Yoshiaki , Nafpaktitis Basil G. , Goto Toshio , Tsuji Frederick I.
Published: April 2021

Along the Pacific coast of North America, the marine fish, Porichthys notatus, is distributed as a northern nonluminescent population and a southern luminescent one. Bioluminescence capability is inducible in nonluminescent P. notatus by a single oral or intraperitoneal administration of a small amount of luciferin, a compound used by the marine ostracod crustacean, Vargula, as substrate for light emission. Once induced, the fish is capable of luminescing for more than 2 years. The results of the present study show that: (1) P. notatus photophores incorporate 14C-labelled Vargula luciferin: (2) the specific activity of the incorporated label is undiluted when recovered from the photophores 7 weeks later; (3) two chemical analogues of Vargula luciferin do not induce bioluminescence capability in the fish; (4) luciferinol, another close analogue of Vargula luciferin, induces a very weak bioluminescent capability in the fish; and (5) two key intermediates in the degradation of Vargula luciferin, oxyluciferin and etioluciferin, are ineffective in inducing bioluminescence capability. The conclusions to be drawn from this study are that P. notatus recycles luciferin and that, in the uninduced fish, the recycling does not involve the resynthesis of luciferin from oxyluciferin or etioluciferin.
Photoreceptor Potential Causing Phototaxis of Paramecium Bursaria
Authors: Matsuoka Kohji , Nakaoka Yasuo
Published: April 2021

Paramecium bursaria shows phototaxis by accumulating in a lighted region. Intracellular recordings from both chlorella-containing and chlorella-free cells showed that a step-increase in the light intensity induced a steady depolarization of membrane potential, and a step-down caused recovery to the original level. The action spectrum of the depolarization corresponded to that for phototaxis, and showed two peaks at 420 and 560 nm. The amplitude of the depolarization became larger as light intensity was increased. Cells which accumulated in a lighted spot decreased their swimming velocity or stayed in the same place. As the light intensity was increased from dark, swimming velocity decreased and became zero at the intensity at which the cell showed the most noticeable photoaccumulation. Further increase in light intensity produced an increase in swimming velocity. The degree of photoaccumulation was inversely proportional to the swimming velocity. These results suggest that a step-increase in light intensity induces the steady depolarization and causes the decrease in swimming velocity, resulting in accumulation of cells in the lighted region.
Effect of Temperature Upon Carbon Dioxide Stores in the Snake Coluber Constrictor and the Turtle Chrysemys Scripta
Authors: Stinner Jerry N. , Wardle Robert L.
Published: April 2021

The effect of temperature upon respiratory exchange ratio (R) was measured in snakes (Coluber constrictor) and turtles (Chrysemys scripta). Increasing body temperature produced a transient elevation of R, and lowering body temperature transiently depressed R. These thermal effects resulted from an ‘excess’ and a ‘deficit’ CO2 elimination, respectively. Steady-state blood CO2 content in C. constrictor decreased linearly with rising temperature. Plasma bicarbonate concentration, calculated from in vivo arterial and pH, followed the same pattern. Also, time courses of blood were consistent with the metabolic studies. Less than half of the change in blood could be explained by shifts of the in vitro CO2 dissociation curve; the remainder was contributed by other tissues. Blood lactate levels changed little with temperature. Based upon the blood studies, the predicted quantity of CO2 eliminated from the extracellular space when temperature increases is about 29% of the excess CO2 eliminated from the snakes. Thus, in other tissues also decreases with rising temperature. It is concluded that reptiles function as open systems with respect to , which does not agree with alphastat control. Systemic arterial and increased with rising body temperature in C. constrictor. The mechanisms producing these increases are discussed.
Freezing Avoidance and the Distribution of Antifreeze Glycopeptides in Body fluids and Tissues of Antarctic Fish
Authors: Ahlgren Jeffrey A. , Cheng Chi-Hing C. , Schrag Joseph D. , Devries Arthur L.
Published: April 2021

The distribution of antifreeze glycopeptides (AFGPs) in the body fluids and tissues of antarctic notothenioid fish was determined. In Dissostichus mawsoni (Norman), the peritoneal, pericardial and extradural fluid, like the blood, contained all eight AFGPs and in concentrations sufficient to depress freezing points below that of sea water (−1·9°C). Secreted fluids including urine, endolymph and aqueous and vitreous humour either lack all AFGPs or have very low concentrations of only the low molecular weight forms and have freezing points of about −1·0°C, and are therefore undercooled with respect to environmental temperature.

Fluids with high concentrations of AFGPs also contain high levels of proteins similar to plasma proteins. Systemic administration of tritiated AFGPs in the closely related species Trematomus bernacchii (Boulenger) yielded a distribution pattern similar to that of the native AFGPs in D. mawsoni. This suggests passive distribution of AFGPs into the various fluid compartments following secretion from the liver; a pattern typical of secreted blood proteins.

Tissue distribution of AFGPs was determined by comparison with that of the extracellular space marker [14C]polyethylene glycol. AFGPs were found in the interstitial fluid of all body tissues examined except brain tissue. No tissue showed any intracellular accumulation of tritiated AFGPs from the blood.
The Role of Phosphoinositide Metabolism in Signal Transduction in Secretory Cells
Authors: Putney James W.
Published: April 2021

Activation of a variety of cell surface receptors results in a biphasic increase in the cytoplasmic Ca2+ concentration, due to the release, or mobilization, of intracellular Ca2+ stores and to the entry of Ca2+ from the extracellular space. Stimulation of these same receptors also results in the phospholipase-C-catalysed hydrolysis of the minor plasma membrane phospholipid, phosphatidylinositol 4,5-bisphosphate, with the concomitant formation of inositol 1,4,5-trisphosphate [Ins(l,4,5)P3] and diacylglycerol. Analogous to the adenylyl cyclase signalling system, receptor-mediated stimulation of phospholipase C also appears to occur through one or more intermediary guanine nucleotide-dependent regulatory proteins. It is well established that phosphatidylinositol 4,5-bisphosphate hydrolysis is responsible for the changes in Ca2+ homeostasis. There is strong evidence that Ins(l,4,5)P3 stimulates Ca2+ release from intracellular stores. The Camreleasing actions of Ins(l,4,5)P3 are terminated by its metabolism through two distinct pathways. Ins(l,4,5)P3 is dephosphorylated by a 5-phosphatase to Ins(l,4)P2; alternatively, Ins(l,4,5)P3 can also be phosphorylated to Ins(l,3,4,5)P4 by a 3-kinase. Whereas the mechanism of Ca2+ mobilization is understood, the precise mechanisms involved in Ca2+ entry are not known; a recent proposal that Ins(l,4,5)P3, by emptying an intracellular Ca2+ pool, secondarily elicits Ca2+ entry will be considered. This review summarizes our current understanding of the mechanisms by which inositol phosphates regulate cytoplasmic Ca2+ concentrations.
Optimizing Release From Peptide Hormone Secretory Nerve Terminals
Authors: Bicknell R. J.
Published: April 2021

Secretion of the peptide neurohormones oxytocin and vasopressin from terminals of magnocellular neurones in the mammalian neurohypophysis is elicited by conduction of depolarizing action potentials into terminal membranes, inducing opening of voltage-sensitive Ca2+ channels, entry of Ca2+ from the extracellular space and a rise in cytoplasmic Ca2+ concentration. The amount of peptide released per action potential is not immutable. In particular, the patterns in which action potentials are generated at the cell somata of the two types of neurone each appear exquisitely suited to optimize the release process at the terminal by utilizing a frequency-facilitation mechanism and by minimizing a mechanism of fatigue in the release process. The different properties of oxytocin and vasopressin neurones are of important physiological significance. The secretory terminals are also a site of receptor-mediated influences of neuromodulators which can greatly alter release efficiency. The mechanisms underlying facilitation and fatigue are not clearly understood. The evidence suggests that processes both prior to depolarization of the terminals (propagation and form of the action potentials) and directly at the terminals (frequency/pattern-dependent Ca2+ entry and channel openings) are involved. Transient activity-related increases in extracellular K+ concentration may be involved at both sites. Two types of neuromodulation have been partly characterized. K-Opioid receptors in secretory terminal membranes directly modulate depolarization-evoked peptide release probably via interactions with Ca2+ channels. β-Adrenergic receptors localized on neurohypophyseal astroglial cells mediate more subtle effects of noradrenaline. In the more chronic situation the neurohypophyseal astroglia alter their morphological relationships with neurosecretory elements and the basal lamina at release sites, changes which may also serve to optimize the secretory process.
The Humidity Reactions of the Wood-Louse,Porcellio Scaber(Latreille)
Authors: Gunn D. L.
Published: April 2021

Porcellio scaber exhibits hygrokinesis, being very active in dry air and almost motionless in nearly saturated air. With rising humidity a steadily increasing proportion of a batch of specimens is found to be inactive at any one moment. P. scaber also shows hygrophobotactic behaviour. The effect of both reactions is to collect the animals into moist air. In a humidity gradient of given steepness the intensity of the humidity preference varies at different parts of the humidity range. There is no reaction at all if the gradient does not include a region below 65 per cent R.H. There is definite reaction to a difference of 6 per cent R.H. in approximately half-saturated air. The humidity receptors, if they are confined to one area, apparently do not lie on the abdomen or on the head region.
The Determination of the Auditory Placode in the Chick
Authors: Waddington C. H.
Published: April 2021

The presumptive ear ectoderm, removed from its normal site and transplanted to the amnio-cardiac vesicle, does not develop into an otic placode unless it comes from an embryo with more than nine pairs of somites. The ectoderm which grows over the place from which the presumptive ear ectoderm is removed is induced to form an otic placode, the size of the placode being smaller the older the embryo at the time of operation. If the wall of the neural tube, including the neural crest, is removed from the region of the ear in embryos younger than the nine-somite stage, an ear may nevertheless be formed. Since the ear ectoderm at this stage is not capable of differentiating when isolated, this result shows that inducing agencies other than the neural material are active at this stage. In some of the operated embryos, the acoustico-facialis ganglion was completely lacking, so this structure cannot be the sole organizer of the ear, as Szepsenwol suggested. If both the wall of the neural tube and the presumptive ear ectoderm are removed, no ear is formed even in stages younger than the nine-somite stage, so that it appears that the non-neural inducing agents are more effective when working on presumptive ectoderm of this age than when working on non-presumptive ectoderm. This suggests that the ear ectoderm is beginning to be determined some time before it acquires the capacity for independent differentiation. The wall of the neural tube, from the ear region, can induce a small ear when grafted under the ectoderm of the anterior part of the head. The evidence suggests that the induction of the ear in normal development is due to the combined action of several structures, of which the wall of the neural tube, and the tissues derived from it (ganglia), is one but not the only one.
On the Structure and Function of the Wandering Cells in the Wall of the Alimentary Canal of Nudibranchiate Mollusca
Authors: Millott Norman
Published: April 2021

The lining epithelium and subjacent tissues of the gut of nudibranch molluscs contain characteristic wandering cells. Although probably amoeboid when alive, the wandering cells after fixation are seen to possess a very definite rounded form. They have a distinct nucleus. The cytoplasm contains a variety of inclusions, and, characteristically, a well-marked eosinophile area. The reaction of the cells to stains is described. The wandering cells were found to take up iron saccharate, which had been injected into the haemocoele. The wandering cells are regarded as a special type of blood cell. Evidence indicates that the wandering cells of nudibranchs are excretory, taking up effete matter from the haemocoele and discharging it into the lumen of the gut.
On Phosphorus Metabolism in Embryonic Life
Authors: Lehmann Hermann , Needham Joseph
Published: April 2021

The chick embryo possesses the power of synthesizing creatinephosphate from phosphopyruvic acid and creatine with adenylic acid as phosphate transporter. This reaction has been followed back into the early stages of development. At the 43 rd hour (approximately the beginning of cardiac activity) it is present in an unweakened state. At the 23rd hour (during the closure of the neural folds), although phosphopyruvic acid is dephosphorylated by adenylic acid, phosphagen synthesis is exceedingly weak. At no age does the synthesis of argininephosphate occur in the chick embryo. The significance of this and the above facts is discussed in the text.
Muscular Mechanisms of Snake Locomotion: an Electromyographic Study of the Sidewinding and Concertina Modes of Crotalus Cerastes, Nerodia Fasciata and Elaphe Obsoleta
Authors: Jayne Bruce C.
Published: April 2021

Synchronized electromyography and cinematography were used to determine the muscle activity of colubroid snakes during sidewinding and concertina locomotion. The primary muscles studied were the three largest, most superficial epaxial muscles: the Mm. semispinalis-spinalis, longissimus dorsi and iliocostalis. Sidewinding locomotion of Nerodia fasciata and Crotalus cerastes was the result of continuous posterior propagation of contractile blocks consisting of several adjacent muscle segments. During sidewinding, the activity of the M. longissimus dorsi and M. iliocostalis was primarily unilateral, beginning when a body region was convex and ending when it was maximally concave on the side of the active muscle. Unilateral activity of the M. semispinalis-spinalis correlated with lateral flexion in addition to bilateral activity that correlated with dorsiflexion of the vertebral column. During concertina locomotion of N. fasciata and Elaphe obsoleta, muscle activity also involved blocks of several simultaneously active adjacent muscle segments, but all major activity was unilateral and was not propagated posteriorly in a simple continuous fashion. Muscle activity during concertina locomotion correlated either with lateral flexion towards the side of the active muscle or with the maintenance of static contact with the sides of a tunnel. The number of simultaneously active adjacent muscle segments and the maximum duration of continuous muscle activity varied significantly between Nerodia and Elaphe and among the different widths of tunnels. Theoretical considerations combined with observed differences suggest that the more elongate body of Elaphe is advantageous for performing concertina locomotion. There was no consistent evidence that nonhomologous muscles with tendinous interconnections functioned as single units during either of these two locomotor modes. Although individual segments of the studied epaxial muscles span several vertebrae, via long, tendinous connections, consistent kinematic correlations with muscle activity were observed only between the contractile portion of a muscle segment and the vertebrae adjacent to that contractile portion.
Power Output and Force-Velocity Relationship of Live Fibres From White Myotomal Muscle of the Dogfish, Scyliorhinus Canicula
Authors: Curtin N. A. , Woledge R. C.
Published: April 2021

The relationship between force and velocity of shortening and between power and velocity were examined for myotomal muscle fibre bundles from the dogfish. The maximum velocity of shortening, mean value 4·8 ± 0·2 μms−1 half sarco-mere−1 (±S.E.M., N = 13), was determined by the ‘slack steP′ method (Edman, 1979) and was found to be independent of fish length. The force-velocity relationship was hyperbolic, except at the high-force end where the observations were below the hyperbola fitted to the rest of the data. The maximum power output was 91 ± 14 W kg−1 wet mass (±S.E.M., N = 7) at a velocity of shortening of 1·3 ± 0·3 jams−1 half sarcomere−1 (±S.E.M., N = 7). This power output is considerably higher than that previously reported for skinned fibres (Bone et al. 1986). Correspondingly the force-velocity relationship is less curved for intact fibres than for skinned fibres. The maximum swimming speed (normalized for fish length) predicted from the observed power output of the muscle fibres decreased with increasing fish size; it ranged from 12·9 to 7·8 fish lengths s−1 for fish 0 155-0·645m in length.
Hypocalcaemic Activity of Trout Hypocalcin and Bovine Parathyroid Hormone in Stanniectomized Eels
Authors: Lafeber Floris P. J. G. , Hanssen R. G. J. M. , Bonga S. E. Wendelaar
Published: April 2021

Hypocalcin isolated from trout corpuscles of Stannius (CS) and bovine parathyroid hormone (bPTH) induce hypocalcaemia when injected intra-arterially in hypercalcaemic, stanniectomized (STX) eels. On a molar basis, both hormones have almost the same potency. Upon injection of hypocalcin we observed a decrease in blood ionic calcium level which fully accounts for the decrease in total calcium. Injections of bPTH also resulted in a decrease of total and ionic calcium concentrations in the blood. The decrease in ionic calcium level upon injection of bPTH, however, did not fully account for the decrease in total calcium concentration of the blood. Nevertheless, hypocalcin and bPTH showed striking similarity in bioactivity in stanniectomized eels. Some similarity in three-dimensional structure of both hormones may underlie this phenomenon.
In Vivo and In Vitro Effects of Adrenergic Stimulation on Chloride/Bicarbonate Exchange in Rainbow Trout Erythrocytes
Authors: Tufts B. L. , Ferguson R. A. , Boutilier R. G.
Published: April 2021

In vitro and in vivo experiments were carried out to determine the effect of catecholamines on erythrocytic chloride/bicarbonate exchange in the rainbow trout. A further modified boat assay is described and was used to measure bicarbonate flux through intact erythrocytes. Catecholamines had no significant effect on the bicarbonate flux in vitro. The erythrocytes were sensitive to adrenergic stimulation, however, since the agonists used caused a decrease in the pH gradient across the erythrocyte membrane. Exhaustive exercise was associated with an increase in bicarbonate flux through the intact erythrocytes. The mechanism for this increase is not clear, but it is evidently not adrenergic in origin.
Activation of Multiply Innervated Fast and Slow Myotomal Muscle Fibres of the Teleost Myoxocephalus Scorpius
Authors: Altringham J. D. , Johnston I. A.
Published: April 2021

A nerve-muscle preparation from the sculpin Myoxocephalus scorpius was used to study the membrane response of fast and slow muscle fibres to stimulation of the spinal nerves. There was no significant difference between resting potential in fast (−81·9mV) and slow fibres (−80·8mV). Fast fibres responded to a supra-threshold stimulus in the spinal nerve with an action potential. Overshoots of up to +32 mV were recorded. Both junction potentials and overshooting action potentials were observed in the slow fibres.

The twitch/tetanus characteristics of myotomal muscle were investigated using isolated bundles of ‘live’ fast and slow fibres. Both fibre types responded to a single stimulus with a mechanical twitch. Fused tetani were obtained at around 50Hz in fast fibres and 20 Hz in slow fibres. In the slow fibres, tetanic tension increased with frequency up to around 50 Hz. At frequencies giving maximum tetanic tension, the twitch/tetanus ratio was 0·70 for fast fibres and 0·29 for slow ones.

These results are discussed with reference to the polyneuronal/multiterminal innervation pattern of the myotomal muscle in teleost fish and its role in locomotion.
Responses of Intermediary Metabolism to Acute Handling Stress and Recovery in Untrained and Trained Leuciscus Cephalus (Cyprinidae, Teleostei)
Authors: Lackner R. , Wieser W. , Huber M. , Via J. Dalla
Published: April 2021

Juvenile Leuciscus cephalus L. were forced to swim against a current of 25cms−1 (3-5 body lengths s−1) intermittently for more than 2 months. Their metabolic responses to acute handling stress and recovery were compared to those of untrained L. cephalus. The concentrations of glycolytic intermediates, malate and phosphocreatine were determined in whole-body homogenates of different fish before and immediately after mechanical stimulation leading to exhaustion, as well as after 5, 15, 30, 60 and 120 min of recovery. The time course of recovery was described by fitting a bi-exponential equation. In untrained fish glycolytic metabolites, except pyruvate, showed maximum concentrations immediately after termination of the stress period, whereas in trained fish these maxima were delayed. In trained L. cephalus the concentrations of all metabolites investigated returned to pre-exercise levels much faster than in untrained fish. Most characteristically, lactate was removed about four times faster from the tissues of trained than from those of untrained L. cephalus. It is argued that anaerobic recovery, a well-known characteristic of exercise physiology in man and other vertebrates, is the driving force of accelerated recovery of trained L. cephalus.
Molecular Basis of the Difference in Oxygen Affinity Between Maternal and Foetal Red Blood Cells in the Viviparous Garter Snake Thamnophis Elegans
Authors: Berner Nancy J. , Ingermann Rolf L.
Published: April 2021

Molecular mechanisms that may explain why oxygen affinity is higher in foetal than in maternal red blood cells were studied in the viviparous garter snake, Thamnophis elegans (Baird and Girard). Foetal and adult haemoglobins were structurally indistinguishable, as demonstrated by native polyacrylamide gel electrophoresis (PAGE), sodium dodecyl sulphate PAGE, low pH/urea PAGE, and gel filtration column chromatography. Oxygen-binding studies of haemoglobin in the absence of organic phosphates showed that adult and foetal haemoglobins had relatively high affinities for oxygen, low Bohr coefficients, and Hill coefficients of about 4·0 at pH 7·0. Adenosine triphosphate (ATP) lowered the oxygen affinity of the haemoglobins from about 3·6 to 9·6 mmHg (1 mmHg = 133·3 Pa) at pH6·8. Maternal red cells contained more nucleoside triphosphate (NTP) (primarily ATP) than did foetal cells by about 0·9molNTP mol−1 haemoglobin tetramer. No 2,3-diphosphoglycerate was detected in the cells. Combined levels of magnesium and calcium were comparable in maternal and foetal red cells. Mean corpuscular haemoglobin concentrations (MCHC) in foetal red cells were about 79% of maternal values. There were no significant differences in maternal and foetal methaemoglobin levels. It appears that a difference in maternal and foetal red cell organic phosphate concentrations, and possibly MCHC values, rather than a difference in haemoglobin structures, explain why oxygen affinity is higher in foetal than in maternal red blood cells in T. elegans.
Role of Midgut Electrogenic K+ Pump Potential Difference in Regulating Lumen K+ and Ph in Larval Lepidoptera
Authors: Dow Julian A. T. , Harvey William R.
Published: April 2021

Larvae of Manduca sexta were fed on tobacco leaves or synthetic diets with differing potassium content. For all diets tested, midgut lumen K+ activity coefficients were low, and midgut lumen K+ activities, K+ concentrations and pH values were as closely regulated as in blood. The transmidgut electrochemical potential difference for potassium based on activities was lower than had previously been estimated from concentrations, but was dominated by the electrical gradient established by the electrogenic K+ ATPase. Midgut K+ activities and pH profiles were similar, as would be suggested by a model in which the generation of high pH was linked to electrogenic K+ transport.
Production of Single-Domain Magnetite Throughout Life by Sockeye Salmon, Oncorhynchus Nerka
Authors: Walker Michael M. , Quinn Thomas P. , Kirschvink Joseph L. , Groot Cornelis
Published: April 2021

Although single-domain particles of biogenic magnetite have been found in different species of pelagic fishes, nothing is known about when it is synthesized, or about whether the time during life when it is produced is correlated with the development of responses to magnetic field stimuli. We have investigated production of biogenic magnetite suitable for use in magnetoreception in different life stages of the sockeye salmon, Oncorhynchus nerka (Walbaum). Sockeye salmon were chosen because responses in orientation arenas to magnetic field stimuli have been demonstrated in both fry and smolt stages of this species.

We found significant quantities of single-domain magnetite in connective tissue from the ethmoid region of the skull of adult (4-year-old) sockeye salmon. The ontogenetic study revealed an orderly increase in the amount of magnetic material in the same region of the skull but not in other tissues of sockeye salmon fry, yearlings and smolts. The physical properties of this material closely matched those of magnetite particles extracted from the ethmoid tissue of the adult fish. We suggest that single-domain magnetite particles suitable for use in magnetoreception are produced throughout life in the ethmoid region of the skull in sockeye salmon. Based on theoretical calculations, we conclude that there are enough particles present in the skulls of the fry to mediate their responses to magnetic field direction. By the smolt stage, the amount of magnetite present in the front of the skull is sufficient to provide the fish with a magnetoreceptor capable of detecting small changes in the intensity of the geomagnetic field.

Other tissues of the salmon, such as the eye and skin, often contained ferromagnetic material, although the magnetizations of these tissues were usually more variable than in the ethmoid tissue. These deposits of unidentified magnetic material, some of which may be magnetite, appear almost exclusively in adults and so would not be useful in magnetoreception by young fish. We suggest that tissue from within the ethmoid region of the skull in pelagic fishes is the only site yet identified where magnetite suitable for use in magnetoreception is concentrated.
An Acoustic Oxygen Telemetry Transmitter for the Study of Exposure of Fish to Variations in Environmental Dissolved Oxygen
Authors: Priede I. G. , Solbé J. F. DE L. G. , Nott J. E.
Published: April 2021

In natural waters the dissolved oxygen concentration can vary considerably both spatially and temporally in rivers (Solbé, 1988), lakes (Gnaiger, 1983), coral reefs (Griffith et al. 1987) and the thermocline in the open ocean (Dizon et al. 1987). There are uncertainties in extrapolating laboratory studies on effects of hypoxia on fish performance (Jones, 1971) to field situations (Priede et al. 1988). This paper describes a transmitter which enables a continuous readout of fluctuations experienced by fish during normal activity in such conditions to be monitored by a remote receiving station on the shore or in a boat.
Electrophysiology of the Mantle of Anodonta Cygnea
Authors: Coimbra J. , Machado J. , Fernandes P. L. , Ferreira H. G. , Ferreira K. G.
Published: April 2021

When gassed with a CO2-containing mixture, under short-circuit conditions, the isolated outer mantle epithelium (OME) of Anodonta cygnea generated a current which exhibited cyclic variations throughout the year. The intracellular potential, under short-circuit conditions, had an average value of –31 ±0·5 mV (N =65). The potential was sensitive to changes in concentration of potassium and chloride on the haemolymph side of the preparation, but not on the shell side, and was insensitive to changes in sodium concentration on either side. When the preparation was gassed with pure oxygen the current fell by 85 ± 1% (N = 8). A similar fall in current (88 ± 2%, N = 8) was observed when the solution bathing the apical side of the epithelium was prepared without bicarbonate and gassed with 95% O2 + 5% CO2. If this same bathing solution was gassed with 100% oxygen, the current fell by 67 ± 2% (N= 8) at pH7·2 and by 92±4% (N =8) at pH4·5. The short-circuit current was inhibited by DIDS (0·5 mmol 1−1) and SITS (0·5 mmol 1−1) when these drugs were applied on the haemolymph side. The current was also inhibited by DNP (1 mmol 1−1), iodoacetamide (1 mmol 1−1) and diamox (1 mmol 1−1). Amiloride (1 mmol 1−1) blocked the current but only when applied on the haemolymph side. Ouabain (0-1 mmol 1−1) did not affect the current. The net fluxes of rubidium (used as a tracer for potassium), chloride and calcium, measured with 86Rb, 36C1 and 45Ca, respectively, were very small when compared with the short-circuit current. There was a small net flux of sodium (measured with 22Na) towards the haemolymph side. The net flux of bicarbonate (measured with [14C]bicarbonate) was equal to the short-circuit current and was inhibited by DIDS. The permeability of the preparation to calcium was an order of magnitude higher than the permeability to sodium, potassium or chloride. The intracellular concentrations of potassium and chloride measured with ion-sensitive microelectrodes were 26·5 ±1·1 (N =16) and 7·9 ±0·3 (N =30) mmol 1−1, respectively. When these concentrations were measured with chemical methods the values found were 29·4 ±0·4 (N =20) and 12·9 ±0·6 (N =20) mmol 1−1, respectively. The chemically measured intracellular concentration of sodium was 14·0 ± 0·4 (N = 20) mmoll−1. When bicarbonate was removed from the haemolymph side the intracellular concentration of chloride increased. The movements of calcium across the OME are by simple diffusion and the calcification of the shell probably results from the balance between a diffusion of calcium towards the extrapallial compartment when a favourable electrochemical gradient for this ion is created and the equally passive movement of calcium which results from the uphill transport of bicarbonate ions carried out by the epithelium. The balance between these two processes might undergo annual cyclic variations.
Nonspiking Stretch Receptors of the Crayfish Swimmeret Receive an Efference Copy of the Central Motor Pattern for the Swimmeret
Authors: Paul Dorothy H.
Published: April 2021

In crayfish, the movement of each swimmeret is monitored by a pair of nonspiking stretch receptors (NSR) with central somata and dendrites that are embedded in an elastic strand at the base of the appendage. I provide evidence that the neuropile segments of these primary sensory neurones receive synaptic input from the hemiganglionic central pattern generator for the swimmeret.

In nonbursting isolated abdominal nerve cords of Pacifastacus leniusculus Dana, the membrane potentials of the NSRs (recorded in the neuropile) are stable; whenever the central pattern generator is active, they oscillate in phase with the motor output. Every perturbation of the central pattern generator’s activity is precisely reflected in analogous changes (in phase and/or amplitude) of the NSRs’ oscillations. This activity must arise via central, synaptic input to the NSRs, because it occurs when all ganglia except the sixth are deafferented.

Lucifer Yellow dye-fills show that the neurites of the NSRs are confined to the ipsilateral lateral neuropile, which is the region of the hemiganglion where swimmeret functions are integrated.

These results imply that during rhythmic beating of the swimmerets, the NSRs receive an efference copy of the motor output to the limb whose movements they monitor. In vivo, therefore, the incoming sensory signal must be subject to modulation (gating) by the limb’s central pattern generator.