bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Circadian Rhythms on Rat Muscle Glycogen Metabolism During and After Exercise
Authors: Garetto L. P. , Armstrong R. B.
Published: April 2021

Marked circadian fluctuations in skeletal muscle glycogen concentrations have previously been reported. The purpose of the present study was to estimate the influence of these rhythms on muscle glycogen metabolism during and after high-intensity treadmill exercise. Male Sprague-Dawley rats ran five 1-min sprints at 75 m min− 1 interspersed by 1–3 min rest intervals either at 08.00 h (morning) or at 20.00 h (night). All muscles sampled lost significant amounts of glycogen during exercise at both time periods. There were no differences in rates of loss between morning and night, even though glycogen levels in several muscles (high-oxidative muscles) were significantly higher before exercise in the morning. Following exercise, glycogen restoration in muscle samples primarily composed of fast-twitch fibres was more rapid in the morning than at night. There was no difference in glycogen restoration rates between the two time periods in the muscle primarily composed of slow-twitch fibres. Although liver glycogen was lower after exercise at night than in the morning, there were no differences in post-exercise blood glucose levels between the two time periods. In conclusion, circadian rhythms do not appear to influence rates of glycogen loss during high-speed running. However, since glycogen loss is the same at all times of day, one would predict that circadian changes in pre-exercise muscle glycogen concentrations would affect muscular endurance. Muscle glycogen restoration after exercise does appear to be affected by circadian rhythms, although interpretation of these data is complicated by possible changes in patterns of muscle fibre contraction at different times of the day. These circadian influences should be considered in the design of exercise studies using laboratory rodents.
The Organization of Flight Motoneurones in the Moth, Manduca Sexta
Authors: Rind F. Claire
Published: April 2021

The morphology and the innervation of the main wing depressor muscles have been studied. The motoneurones to these muscles have dendrites ipsilateral to the muscle they innervate and located in the dorsal neuropile. With the exception of one motoneurone, to the dorsal longitudinal muscle, all motoneurone cell bodies are ipsilateral to the muscle they innervate. The morphologies of individual cobalt stained motoneurones are described. Flight motoneurones to wing depressor muscles are not electrically or chemically coupled to one another.
The Generation of Rhythmic Activity in A Distributed Motor System
Authors: Cohan Christopher S. , Mpitsos George J.
Published: April 2021

Rhythmic activity that is distributed to the brain and buccal ganglia and which underlies several types of behaviour, can be evoked from isolated nervous systems of Pleurobranchaea californica by tonic nerve stimulation. The experiments presented here were designed to test whether this rhythmic activity is produced by independent neuronal oscillators located in each ganglion or whether the rhythmic activity arises from a single oscillatory locus in the buccal ganglion and is transmitted passively to the brain. By interrupting the conduction of activity in the cerebrobuccal connectives (CBC) between brain and buccal ganglia we show that motor output from the brain depends on sustained, cycle to cycle input from the buccal ganglion and cannot be reset with respect to the buccal activity. The production of rhythmic activity in the brain depends on the generation of rhythmic activity in the buccal ganglia whether the rhythms are activated by stimulation of buccal roots or paracerebral command cells in the brain. Simultaneous intracellular recordings from brain motoneurones and buccal interneurones which project to the brain indicate that these interneurones provide both the drive and the pattern for rhythmic motor output in the brain. Tonic stimulation of the CBC can produce rhythmic activity in isolated brains in which all nerve roots and connectives have been cut. This can be explained by the fact that tonic stimulation of the connectives is transformed into phasic activity by the axons within the connective. We conclude therefore, that rhythmic, coordinated activity in the brain and buccal ganglia of Pleurobranchaea arises from oscillatory circuits that are located only in the buccal ganglia.
Electrophysiology of Mosquito Anal Papillae
Authors: Edwards H. A.
Published: April 2021

The anal papillae of mosquito larvae are classic transporting epithelia that can absorb inorganic ions from extremely dilute external media. Since the original investigations of Wigglesworth (1933a,b,c) and Koch (1938) studies have been made of the ultrastructure of the papillae (Copeland, 1964; Sohal & Copeland, 1965; Meredith & Phillips, 1973a,b), of radio-cation fluxes (Treherne, 1954; Stobbart, 1959, 1960, 1965, 1967, 1971), of their water permeability (Nicolson & Leader, 1974) and their role in osmoregulation (Edwards, 1979). Quantitative understanding of epithelial salt transporting mechanisms, however, requires knowledge of the appropriate electrochemical gradients. Only one attempt has so far been made to provide this information for mosquito larvae (Stobbart, 1974). These measurements were made by recording the potentials between the larval haemolymph and a drop of fluid surrounding the papillae. However, the potentials measured in this way were found to be very unstable and of variable polarity. This communication describes an attempt to measure the electrical properties of the papilla epithelium using isolated anal papillae of Aedes aegypti.
Reversible Changes in the Intracellular Potassium Ion Activities and Membrane Potentials of Aplysia L2–L6 Neurones in Response to Normoxia and Hypoxia
Authors: Coyer Philip E. , Halsey James H. , Strong Edward R.
Published: April 2021

Exposure of 7 L2–L6 neurones to hypoxia for 65 min resulted in hyperpolarization of the membrane potential (EM) from a mean of –49 ·1 ±2 ·1 to –54 ·l ±3 ·6mV (S.E.). Intracellular potassium ion activities increased significantly from 137 ·7 ±4 ·0 to 155 ·6 ±3 ·4 mM –K+. This is equivalent to a change in EK from –74 ·2 mV commensurate with the observed hyperpolarization of 5 mV. The reversibility of these responses was noted by reoxygenating the solution surrounding the ganglion for a period of 55 min. In another group (n = 7) of L2–L6 neurones, the responses in , EM, and EK were slower, although following hypoxia for 90 –110 min, similar changes in the levels of these membrane phenomena were recorded. PNa/PK ratios were computed for both L2–L6 groups of neurones using a modified version of the Goldman equation. There were only slight decreases in this ratio with hypoxia, which were not significantly different from the control (normoxia). Therefore, we conclude that this period of hypoxia is capable of stimulating the sodium pump of these cells since the membrane potentials seem to hyperpolarize according to the increase in . However, tonic release of neurotransmitter, which could hyperpolarize these neurones and attract intracellular potassium, cannot be ruled out as an effect of hypoxia.
Transport of Uric Acid by the Malpighian Tubules of Rhodnius Prolixus and Other Insects
Authors: O’Donnell M. J. , Maddrell S. H. P. , Gardiner B. O. C.
Published: April 2021

Urate is transported against an electrochemical gradient into the lumen of the lower Malpighian tubule of Rhodnius. In vivo, higher urate transport rates are induced by the increase in haemolymph urate concentration that follows feeding. The induced rate of transport is sufficient to account for the amount of urate eliminated. In vitro experiments with the tsetse fly Glossina suggest a possible induction of transport as a direct response of the tubule cells to an increase in urate concentration in the surrounding fluid.

Urate transport has been shown for Malpighian tubules of insects from several different orders, suggesting that the mechanism is widespread. Insect urate transport differs from that of vertebrates; it is ouabain-insensitive and results in the precipitation of free uric acid instead of urate salts.
Energetic Cost of Active Branchial Ventilation in the Sharksucker, Echeneis Naucrates
Authors: Steffensen John Fleng , Lomholt Jens Peter
Published: April 2021

Sharksuckers use active branchial ventilation when swimming or at rest in stationary water. When attached to a moving object or when placed in a water current, they shift to ram gill ventilation as water velocity exceeds a certain threshold. Water velocities required for the transition from active to ram gill ventilation were from 10–50 cm s −1, depending on the size of the fish. Oxygen consumption increased between 3·7 and 5·7 % when the fish shifted from ram gill ventilation to active branchial pumping. When water velocity was increased beyond the threshold for ram gill ventilation, no further increase in oxygen consumption was observed. It is concluded that the energetic cost of active ventilation in shark suckers is lower than has previously been reported for fish in general.
Haemodynamic Effects of Secretory Agents On the Isolated Elasmobranch Rectal Gland
Authors: Shuttleworth T. J.
Published: April 2021

Perfusion flow rate in the isolated elasmobranch rectal gland, perfused at in vivo pressures, was measured in Scyliorhinus canicula L. and Squalus acanthias L. Flow through the secretory parenchyma of the gland was reduced in the presence of concentrations of catecholamines in the physiological range, an effect mediated via α-adrenergic receptors within the gland vasculature. Flow through the non-secretory vascular shunts of the rectal gland was unaffected. The vasoconstriction induced by noradrenaline was blocked by the addition of cyclic AMP + theophylline or adenosine at concentrations known to stimulate secretion by the gland. In Squalus, a similar effect was seen with the secretagogue vasoactive intestinal peptide, but this agent had no effect in the glands of Scyliorhinus. Experiments indicate that the blockage of the noradrenaline effect by the secretory agents does not involve any stimulation of vasodilatory β-adrenergic receptors and, furthermore, that the vasomotor effects of these agents appear to be entirely independent of their actions on the secretory cells. Evidence is presented indicating that the vasomotor action of adenosine may be mediated via receptors specific for the ribose moiety of the nucleoside (R2 receptors) activating adenylate cyclase, and that this may, in turn, explain the observed effects of the addition of exogenous cyclic AMP. The significance of the observed vascular effects in the overall control of secretion rate by the gland in vivo is discussed.
Aerial Gas Exchange In Australian Freshwater/Land Crabs of the Genus Holthuisana
Authors: Greenaway Peter , Taylor H.H. , Bonaventura J.
Published: April 2021

Holthuisana valentula Riek and H. agassizi (Rathbun) both ventilate their lungs by lateral oscillations of the thoracic walls within the branchial chambers. Air enters and leaves the lungs via the prebranchial apertures and the Milne-Edwards apertures. At rest, active ventilation in H. transversa was low (0·95 mlg−1 h−1) and a high diffusional component was evident. After disturbance, rose to 45·4mlg−1h−1 and % extraction was low (1·1%). Yentilation increased during moderate hypercapnia and marked hypoxia. was high after disturbance (2·95 μmolg−1 h−1) but declined to very low levels at rest (0·45 μmolg−1 h−1). The haemocyanin had a relatively low affinity for oxygen during air-breathing (P50 = 13 Torr) but it was saturated with oxygen at normal (56·1 Torr). CCO2 in the haemolymph (13 mmol l−1) was characteristic of air-breathing crabs. The respiratory performances of H. transversa in air and water are compared.
Reversal of an Intersegmental Reflex Elicited by A Muscle Receptor Organ
Authors: Dicaprio R. A. , Clarac F.
Published: April 2021

One of the most common reflexes observed in invertebrates is the resistance reflex, in which a proprioceptor at a given joint excites the motor neurones innervating the muscles controlling the joint so as to resist imposed movement (Bush, 1962, 1963, 1965; Barnes, Spirito & Evoy, 1972). As well as these intrasegmental reflexes, proprioceptive reflexes in which sensory information is used to control muscles at joints other than the one spanned by a given proprioceptor have been reported (Ayers & Davis, 1977; Clarac, Vedel & Bush, 1978). These intersegmental reflexes may also control the state of excitation of other receptors (Moody, 1970; Clarac et al. 1978). Resistance reflexes and intersegmental reflexes are presumed to have a role in postural maintenance and load compensation (op. cit.; for review see Mill, 1976). However, resistance reflexes can be suppressed during locomotion (Barnes et al. 1972) and intersegmental reflexes may be modified during walking (Ayers & Davis, 1977). In addition, we have recently shown that a resistance reflex elicited by the thoracic-coxal muscle receptor organ (TCMRO) in the crab can be reversed to become a positive feedback assistance reflex (DiCaprio & Clarac, 1981). In this report we demonstrate that an intersegmental reflex activation of the basipodite levator and depressor motor neurones mediated by the TCMRO can also be reversed with respect to movement of the thoracic-coxal (TC) joint.
Proctolin and an Endogenous Proctolin-Like Peptide Enhance the Contractility of the Limulus Heart
Authors: Watson W. H. , Augustine G. J. , Benson J. A. , Sullivan R. E.
Published: April 2021

Synthetic proctolin increases the force but not the rate of heart contractions of Limulus in a time- and dose-dependent manner. The threshold of this effect is 3 X 10−10M and the EDS0 is approximately 10−10M. At concentrations up to 10−7 M, proctolin has no effect on the rhythmic electrical activity of the isolated cardiac ganglion, and it does not change the simple and compound postsynaptic potentials recorded at the cardiac neuromuscular junction. Proctolin acts directly on the cardiac muscle fibres. Electrically stimulated myocardia show a proctolin-induced increase in contraction amplitude with the same concentration dependence as the intact heart. A compound with an apparent molecular weight of 700–800 occurs in the Limulus nervous system, particularly in the cardiac ganglion. This compound resembles proctolin in being heat-stable, resistant to trypsin and chymotrypsin cleavage, and losing activity in a time-dependent manner in response to treatment with leucine aminopeptidase or pronase. This peptide induces spontaneous contractions and a contracture of the cockroach hindgut in a manner similar to proctolin. Moreover, the Limulus inotropic peptide, like proctolin, increases the force of contraction of the Limulus heart without affecting beat frequency. It is concluded that an endogenous, proctolin-like peptide is an inotropic modulator of the Limulus heart, acting directly on the muscle fibres and not affecting cardiac ganglion activity.
Luminescence of Isolated Photocytes from Porichthys Photophores: Adrenergic Stimulation
Authors: Christophe B. , Baguet F.
Published: April 2021

A fast transient peak of light, followed by a slow luminescence, was produced by isolated photophores of Porichthys notatus when exposed to 1 mm-epinephrine, norepinephrine or phenylephrine, an α-adrenergic agonist. Only a slow luminescence was induced by 1 mm-isoproterenol, the β-adrenergic agonist. After removal of the reflector and surrounding tissues, the isolated photogenic cells, i.e. the photocytes, responded to norepinephrine and phenylephrine by producing a fast transient peak of light, and to isoproterenol by a slow luminescence. Epinephrine evoked both types of luminescence. The emission latency time, the amplitude and the total duration of the light responses were significantly less than those of the photophore. The results suggest that both epinephrine and norepinephrine combine with sympathetic α or β receptors upon the photocytes to trigger light production.
Nerve Net Pacemakers And Phases of Behaviour in the Sea Anemone Calliactis Parasitica
Authors: Mcfarlane Ian D.
Published: April 2021

Bursts of through-conducting nerve net (TCNN) pulses, 20–45 min apart, were recorded from Calliactis attached to shells. Within 15–25 min of the anemones being detached the TCNN bursts suddenly became more frequent (only 4–11 min apart). Such bursts continued for several hours if re-attachment was prevented. In an attached anemone simultaneous electrical stimulation of the TCNN and ectodermal slow system (SSI) with 20–30 shocks at one every 5 s also led to more frequent TCNN bursts, whether or not detachment took place. If, however, the anemone remained attached, the intervals between bursts returned to the normal resting duration after about 90 min. In all cases the decay of the 4–11 min interval TCNN bursts involved a reduction in pulse number, not an increase in burst interval. Partial activation of the TCNN pacemakers followed stimulation of the SS1 alone. It is suggested that in sea anemones the change from one behavioural phase to another is associated with a change in the patterned output of nerve net pacemakers.
Potassium Metabolism in Seawater Teleosts: II. Evidence for Active Potassium Extrusion Across the Gill
Authors: Sanders Martin J. , Kirschner Leonard B.
Published: April 2021

Unidirectional K-fluxes were estimated in unanaesthetized trout and sculpin and in anaesthetized sculpin from observed 86Rb movement (JK = 1·3 JRb). In all three groups efflux exceeded influx; Jo/Jin was 2–3. The values predicted by the flux ratio equation were 0·5 for trout and 1·0 for sculpin, so active K-extrusion is indicated. The results also show that more than one half of the total influx must be ingested with food rather than passing across the gills. Flux data show that the gills are more permeable to K+ than to Na+, PK/PNa was 5·4 in trout and 2·6 in sculpin.

Changes in K-concentration in the external medium did not appear to affect efflux; there was no exchange component in the total fluxes. When both Na+ and K+ were omitted from the bathing solution, efflux decreased to about 15 % of the normal seawater value. This is more than would be expected if the flux were purely diffusive and supports the conclusion that extrusion contains an active component. Repletion of the ion-deficient medium with K+ (alone) increased K-efflux. However, it also repolarized the gill and increased plasma [K+], and the flux change could be accounted for by the augmented driving force; i.e. it was diffusive.

The additional plasma K came from the intracellular compartment, rather than an augmented influx from the medium.
The Role of Urinary Precipitates in the Excretion of Electrolytes and Urate in the Domestic Fowl
Authors: Long S. , Skadhauge E.
Published: April 2021

In order to quantify losses of Na and K associated with precipitate fractions in semi-solid avian urines, Na, K, uric acid and urates (UA + U) and inulin were measured in plasma, in whole ureteral urine, and in urinary precipitates of hens. Ten animals were used, five fed a control commercial poultry meal (Diet A) and five maintained on a high protein, low-Na feed (Diet B). In ureteral urines from hens on Diet A, dried precipitate accounted for 5·6% of the total whole urine weight, on the average. UA + U constituted about two-thirds of the precipitates’ weight and 80 % of the total excreted UA + U load of 97-4 mm. The average molar fractions, [Na]/[UA + U] and [K]/[UA + U], in precipitates were in the range 0·1–0·2; and the Na and K lost in these fractions were 12·8 mequiv and 9·6 mequiv, respectively, per 1 whole urine. These losses represent 9 % and 23 % of total Na and K excretion. Diet B was used to accentuate potential cation loss in precipitates if obligatory binding of K and especially Na were to occur in precipitates. Urinary [UA + U] in whole urine rose to 146 mm of which 95 % was found in precipitates. The average molar fraction [Na]/[UA+ U], however, fell to 0·06 and that of [K]/[UA + U] to 0-08. Renal loss of Na was 8·5 mequiv and of K was 11·5 mequiv per 1 whole urine. These experiments reveal that significant but minor fractions of excreted Na and K are associated with precipitates of avian urine, although the loss is insignificant compared to that reported in starlings (Braun, 1978). They further indicate that the Na/inulin clearance ratio, based on measurements in whole urine and plasma, adequately reflects fractional excretion which, on Diet A, was 1·8% of the filtered load and, on the Na-poor Diet B, less than 0·1 %.

These values place the Na-reabsorbing abilities of these birds easily within the range reported for ureotelic vertebrates and suggest that uricotelism does not impose a major renal salt loss in birds.
Renal Acid Excretion In The Domestic Fowl
Authors: Long S. , Skadhauge E.
Published: April 2021

In order to assess the role of uricotelism in net renal acid excretion, blood and ureteral urine samples were collected from five hens fed a commercial poultry feed (Diet A) and five hens fed a protein-rich, Na-poor feed (Diet B). All samples were analysed for pH, , ammonium, phosphate, uric acid and urates (UA + U) and inulin. On Diet A, average pH in venous blood was 7·42, while urinary pH (pHu) ranged from 4·74 to 7·25. At average pHu (6·10), uric acid accounted for 52 % of total acid excreted, H2PO4 for 20 % and NH4 for 28 %. Net acid excretion in ureteral urine was 345 μequiv h−1 kg body weight−1, or 5–10 times that observed in ureotelic vertebrates (amphibians and mammals). The relative contributions of these urinary buffers to net renal acid excretion changed with pHu. Significant negative correlations exist between pHu and both total phosphate and ammonium excretion rates (P< 0·001). Excretion rates of (UA + U) showed a positive correlation (P< 0·05) with pHu. Feeding on Diet B revealed the homeostatic power of the avian kidney. Blood pH and were not changed relative to values in hens fed the control diet while striking increases in excretion rates of all urinary buffers (except HCO3) were observed. Average pHu fell to 5·12, and the average net renal acid excretion rate doubled.
Utilization of the Ethanol Pathway in Carp Following Exposure to Anoxia
Authors: Johnston Ian A. , Bernard Lynne M.
Published: April 2021

Crucian carp (Carassius carassius L.) and Common carp (Cyprinus carpió L.) were subjected to 2h progressive hypoxia followed by up to 6 h anoxia in closed respirometers at 15 °C. The concentrations of glycogen, glucose, phosphoryl creatine, alanine, succinate, lactate, ethanol and ammonia were determined in whole Crucian carp following exposure to both hypoxia and anoxia. Ethanol and lactate were the main anaerobic end products. Glycogen utilization during anoxia amounted to 2 mmol glucose equivalents-kg wet weight−1 h−1. Around 85% of the ethanol produced (2·8 mmol kg−1 h−1) was excreted. Lactate accumulation (0·7 mmol kg−1 h−1) was only sufficient to account for 18-5 % of the glycogen stores utilized. Ammonia production (0·2 mmol-kg body wt−1 h−1) was independent of the environmental oxygen availability. Ethanol concentrations (μmol-gwet wt−1) were 7 in red myotomal muscle, 4 in white myotomal muscle, and 2 in liver after 6h anoxia. In contrast to Crucian carp, Common carp (Cyprinus carpio L.) did not produce ethanol at 15 °C even after near lethal exposure to anoxia (5–6 h).
Responses to Acute Aquatic Hypoxia In Larvae of the Frog Rana Berlandieri
Authors: Feder Martin E.
Published: April 2021

The oxygen consumption of larvae of the trog Rana berlandieri Baird was reduced during exposure to aquatic hypoxia at 25 °C, and under severe hypoxia the larvae lost oxygen to the water. The larvae responded to aquatic hypoxia by increasing aerial oxygen consumption and lung ventilatory frequency, and also by altering their heart rate and gill ventilation frequency. Under severe or prolonged aquatic hypoxia without access to air, Rana larvae accumulated lactate. When prevented from breathing air, the larvae were unable to compensate fully by increasing their aquatic oxygen consumption. Body size or the interaction of body size and oxygen partial pressure significantly affected the aerial oxygen consumption, the total oxygen consumption and gill ventilation frequency, but did not affect other aspects of larval gas exchange. Anuran larvae resemble air-breathing fishes in some responses to aquatic hypoxia (e.g. increased dependence upon aerial oxygen uptake and changes in ventilatory frequencies), but are unusual in some ways (e.g. oxygen loss to the water). The interactions of body size and hypoxia are not sufficient to explain why so many anuran larvae without lungs are small.
Patterns of Circular And Radial Mantle Muscle Activity in Respiration and Jetting of the Squid Loligo Opalescens
Authors: Gosline John M. , Steeves John D. , Harman Anthony D. , Demont M. Edwin
Published: April 2021

By simultaneously recording the electromyographic (EMG) activity of squid mantle muscles, changes in mantle cavity pressure and changes in mantle diameter, we have been able to distinguish the pattern of radial muscle activity from circular muscle activity, and in so doing were able to determine the functional role of these muscle groups in motor behaviours. Three distinguishable phases of activity appear during escape jets : (i), hyper-inflation brought about by the contraction of the radial muscles; (ii), the jet powered by the contraction of circular muscles; and (iii), refilling powered largely by the elastic recoil of the mantle wall, but with a small contribution from the radial muscles. Two distinctly different patterns of muscular activity were seen in respiratory movements. One pattern (pattern I) is powered by the radial muscles alone, while the other (pattern II) is powered by the circular muscles alone. In both modes of respiration, the muscles are apparently antagonized by tissue elasticity. Thus, the storage of elastic energy in the connective tissue fibre-lattice of the mantle wall plays a very important role in both modes of squid movement.
The Effects of Aquatic Oxygen Concentration, Body Size and Respiratory Behaviour on the stamina of Obligate Aquatic (bufo americanus) and facultative air-breathing (Xenopus Laevis and Rana Berlandieri) Anuran Larvae
Authors: Wassersug Richard J. , Feder Martin E.
Published: April 2021

Larvae of the anurans Rana berlandieri and Xenopus laevis have lungs and can breathe air as well as irrigate buccal and pharyngeal surfaces for aquatic respiration. Larvae of Bufo americanus lack lungs until just before metamorphosis and are obligately aquatic. We examined the relationship between the locomotor stamina (time to fatigue), aquatic oxygen concentration, body size, and respiratory behaviour of swimming larvae of these species, with the following results:

Stamina is size-dependent in all three species. Aquatic hypoxia reduces stamina in larvae of all three species, but most conspicuously in Bufo. Breathing air increases stamina in Rana larvae, especially in large animals and under aquatic hypoxia. In contrast to Rana larvae, Xenopus larvae swimming in normoxic water undergo a reduction in stamina when allowed to breathe air. In hypoxic water, aerial respiration moderates the reduction in stamina seen in Xenopus larvae. Branchial irrigation is associated with increased stamina in Xenopus, and is increased under hypoxia and at high swimming velocities. Respiratory demand, buoyancy and the drag associated with branchial irrigation all affect respiratory behaviour in Xenopus larvae.

The great amount of interspecific variation in the relationship between respiratory behaviour and stamina reveals the importance of measuring performance directly when attempting to interpret the functional significance of respiratory structures and behaviour.
Anatomy of Motor Axons to Direct Flight Muscles in Drosophila
Authors: King David G. , Tanouye Mark A.
Published: April 2021

The direct flight muscles of Drosophila melanogaster are innervated by the anterior dorsal mesothoracic (ADM) nerve and the mesothoracic accessory (MAC) nerve. Each of the four conspicuously large axons in the ADM nerve serves one of the muscles designated pal, pa3, pa4 and pa5. Muscle pa4 is additionally innervated by a very small neurosecretory axon. Muscle pa6, also innervated by the ADM nerve, receives at least one small nerve fibre but no large axon. Musclepa2 is innervated by a large axon from the MAC nerve. Large motor axons, identified by serial section tracing from their respective muscles, are consistent among different individuals in both relative positions and relative diameters within the ADM nerve.
Temperature Sensitivity in the Prothoracic Ganglion of the Cockroach, Periplaneta Americana, and its Relationship to Thermoregulation
Authors: Murphy Bernard F. , Heath James E.
Published: April 2021

Activity of neurones in the prothoracic ganglion of the cockroach, Periplaneta americana, recorded extracellularly, showed a wide range of temperature sensitivity. These responses were categorized by linear regression. The regression lines with the greatest slopes are proposed to characterize central temperature receptors; warm units with lower slopes may be the result of nonspecific Q10 responses of ordinary neurones. An overlap of regression lines from cells with high slopes occurs near the acclimation temperature of the animals; the regression lines of most of the warm-sensitive units reach zero firing rate near the mean chill-coma temperature (10·5 °C) for this species. The temperature selection by the whole animal in a temperature gradient shuttlebox was found to require central temperature receptors as well as the peripheral temperature receptors on either the antennae or tarsi. Both neural and behavioural data indicate a greater sensitivity to heat than cold in cockroach thermoregulatory behaviour.
Acetylcholine Receptors on the Cell Body Membrane of Giant Interneurone 2 in the Cockroach, Periplaneta Americana
Authors: Harrow I. D. , Sattelle D. B.
Published: April 2021

lonophoresis of acetylcholine (ACh) onto the cell body membrane of an identified giant interneurone (GI2) in the central nervous system of the cockroach Periplaneta americana induced a depolarizing response at resting potential which was attributed to a population of extrasynaptic ACh receptors. The sensitivity of the cell body membrane of GI 2 to ionophoresis of ACh was determined. Perfusion of 1·0 × 10−6M neostigmine, an inhibitor of acetylcholine esterase, potentiated the ACh sensitivity of the cell body membrane of GI 2. This indicated that a high acetylcholinesterase activity was present in the periphery of the sixth abdominal ganglion (A6). The nicotinic antagonist, a-bungarotoxin (at a concentration of 1·0 × 10−7M) was found to block the ACh response of the cell body membrane of GI 2. By contrast, the muscarinic antagonist, quinuclidinyl benzilate, (at concentrations up to 1·0 × 10−5 M) had no detectable effect on the ACh response. It is suggested that an extrasynaptic nicotinic type of ACh receptor is present on the cell body membrane of GI 2.
Renal Function in Unanaesthetized River Lampreys (Lampetra Fluviatilis L.): Effects of Anaesthesia, Temperature and Environmental Salinity
Authors: Mcvicar A. J. , Rankin J. C.
Published: April 2021

Improved estimates of urine flow rates of lampreys in various salinities were obtained by the collection of urine for periods of up to 48 h from minimally-stressed, unanaesthetized fish, following catheterization of the urinogenital papilla. The mean urine flow rate of freshwater lampreys was 200·7 ± 14·3 ml kg−1 day−1. Urine flow in freshwater lampreys was correlated with spontaneous changes in gill ventilation rate. MS222 anaesthesia reduced both ventilation and urine flow rates, but pronounced effects were only observed at concentrations greater than those needed to induce light anaesthesia (50–55 mgl−T). Urine flow rate in unanaesthetized fish was extremely sensitive to rapid (6°Ch−1) changes in temperature and Q10 (6–16°C) was approximately 5. Urine flow rate decreased rapidly as the osmotic difference between the body fluids and environment approached zero, and the rate of flow in 30% seawater lampreys was only 7·6% that of freshwater fish. There was no evidence for an effect of environmental calcium concentration on branchial osmotic permeability. Extensive tubular reabsorption of ions occurred in freshwater lampreys. The total daily excretion rate of sodium ions generally decreased in salinities hyperosmotic to the plasma, indicating enhanced reabsorption, but secretion of magnesium and sulphate ions was greatly increased. Urine osmolarity was significantly increased in lampreys in hyperosmotic salinities. Present data compare favourably with data obtained previously from anaesthetized animals, indicating that renal function in lampreys is not significantly impaired by light MS222 anaesthesia.
The Kinetics of Active K Transport by the Midgut of Lepidopteran Larvae: Effects of Divalent Ions
Authors: Moffett David F. , Koch Alan R.
Published: April 2021

The isolated midgut of lepidopteran larvae actively transports K from haemolymph to lumen, providing a model for K transport in insect secretory and excretory tissues (reviewed by Harvey, 1980). The dependence of this transport on extracellular K has been studied by several investigators. Recently, Zerahn (1982) estimated a value of 10 mM for Km in Hyalophora cecropia from his data and also from previous observations (Harvey & Zerahn, 1972), and obtained a value of 40 mM from data for Manduca sexta (Moffett, 1979). In the studies upon H. cecropia, the only cation present in the bathing solution was K; in the study upon M. sexta, 5 mM-Ca and 5 mM-Mg were also present as well as sufficient NaCl to maintain constant osmolarity. Although there may be slight innate differences in the transport kinetics of the two species, we show here that the reported differences can be accounted for by the presence or absence of divalent cations.
The pCa-Tension Characteristics of Single Skinned Fibres Isolated from the Anterior and Posterior Latissimus Dorsi Muscles of the Chicken
Authors: Moore G. , Johnston I. A. , Goldspink G.
Published: April 2021

The anterior latissimus dorsi (ALD) muscles of the chicken are mostly composed of multiply innervated slow fibres, and the posterior latissimus dorsi (PLD) muscles consist mostly of focally innervated fast fibres (Ginsborg, 1960). The rate of development of isometric tension is 8–10 times higher in the PLD than in the ALD, and the unloaded speed of shortening is 4–5 times higher (Canfield, 1971). On tetanic stimulation ALD fibres are able to maintain a steady isometric tension for more than 2 min, whereas the PLD begins to fatigue after only 1 s (Canfield, 1971). The fatigue resistance and economy (Goldspink, Larson & Davies, 1970) of the ALD when contracting isometrically are probably related to its postural role in holding the wings against the body. The rate of relaxation of PLD fibres following short tetani is eight times faster than for the ALD (Canfield, 1971). This difference is attributable in part to the less highly developed sarcoplasmic reticulum in the ALD (Page, 1969). The present study investigates the pCa-tension relationship of these fibres.
Control of A Central Pattern Generator by an Identified Modulatory Interneurone in Crustacea: II. Induction and Modification of Plateau Properties in Pyloric Neurones
Authors: Dickinson P. S. , Nagy F.
Published: April 2021

In the isolated stomatogastric nervous system of the lobster Jasus lalandii, the strong modifications of the pyloric motor pattern induced by firing of the single anterior pyloric modulator neurone (APM) are due primarily to modulation by APM activity of the regenerative membrane properties which are responsible for the ‘burstiness’ of all the pyloric neurones and particularly of the non-pacemaker neurones (constrictor motoneurones).

This modulation has been studied under experimental conditions where the main extrinsic influences usually received by the pyloric constrictor neurones (intra-network synaptic interactions, activity of pacemaker neurones, and phasic central inputs from two premotor centres) are minimal. Under these conditions a brief discharge of neurone APM induces long plateaus of firing in all of the pyloric neurones.

The non-pacemaker neurones of the pyloric network are not simply passive follower neurones, but can produce regenerative depolarizations (plateau potentials) during which the neurones fire spikes. The ability of the pyloric constrictor neurones to produce plateau potentials (plateau properties) contributes greatly to the generation of the rhythmical pyloric motor pattern. When these neurones spontaneously express their plateau properties, firing of neurone APM amplifies these properties. When most of the central inputs usually received by the pyloric constrictor neurones are experimentally suppressed, these neurones can no longer produce plateau potentials. In such conditions, firing of the single modulatory neurone APM can reinduce plateau properties of the pyloric constrictor neurones.

In addition, firing in APM neurone slows down the active repolarization phase which terminates the plateau potentials of pyloric constrictor neurones. This effect is long-lasting and voltage-dependent.

Modulation by APM of the plateau properties of the pyloric neurones also changes the sensitivity of these neurones to synaptic inputs. This effect can explain the strong modifications that an APM discharge exerts on a current pyloric motor pattern. Moreover, it might render the motoneurones of the pyloric pattern generator more sensitive to inputs from a command oscillator, and contribute to switching on the pyloric motor pattern.
Proton Secretion by the Gastric Parietal Cell
Authors: Rabon E. , Cuppoletti J. , Malinowska D. , Smolka A. , Helander H. F. , Mendlein J. , Sachs G.
Published: April 2021

The parietal cell occupies a unique niche among eukaryotic cells in that it develops a proton gradient of more than 4 million-fold across the membrane of the secretory canaliculus. At rest, the cell is still able to develop a proton gradient across intracellular membranes, such that the acid compartment has a pH of less than 4. Acidification depends on the simultaneous presence of ATP, K+ and Cl− as demonstrated in permeabilized cells. With acidification of the luminal side of the proton pump, there is a corresponding alkalinization of the cytosolic face as revealed by carboxyfluorescein fluorescence enhancement. Disposal of the resultant alkali depends on carbonic anhydrase activity and the functioning of a coupled Na+:H+ and Cl−: OH − antiport across the basal lateral membrane. Accordingly, with secretion there is an increased cellular Cl− level, which is exported across the apical membrane in association with K+. The Na+ pump dependent secretion of KCl across this membrane is one of the major sites of regulation of acid secretion since K+ is required at the luminal face of the gastric ATPase. Membranes isolated from secreting tissue contain a KC1 permeation pathway largely absent from membranes isolated from resting tissue. The pump itself acts as an H+ for K+ exchange ATPase which is most probably composed of at least two peptides of 100000Mr. That catalytic cycle consists of formation and breakdown of a covalent aspartyl phosphate. Formation of the intermediate depends on loss of K+ from cytosolic binding sites, and breakdown of the intermediate depends on K+ binding to the luminal face of the enzyme. During breakdown, an acid labile E P is formed, and, at high ATP concentrations, loss of this form of the enzyme is probably the rate limiting step.
Regulation of Proton Transport in Urinary Epithelia
Authors: Al-Awqati Qais , Gluck Stephen , Reeves Westley , Cannon Christopher
Published: April 2021

In urinary epithelia, like the turtle bladder, protons are transported by a H+-trans locating ATPase located in the luminal membrane. We have recently discovered that the H+ pump is stored in small vesicles that lie underneath the luminal membrane. CO2, a major regulator of H+ transport, causes these vesicles to fuse with the membrane thereby inserting more H+ pumps.

We have now isolated these vesicles from the turtle bladder and from beef kidney medulla. Based on inhibitor sensitivity and substrate specificity this proton translocating ATPase is different from the mitochondrial F0-F1 ATPase, yeast plasma membrane and the gastric H+,K+-ATPase. Solubilization and reconstitution of the enzyme into liposomes shows retention of transport activity and inhibitor sensitivity.
Mechanism and Control of Hyperosmoticnacl-Rich Secretion by the Rectal Gland of Squalus Acanthias
Authors: Epstein Franklin H. , Stoff Jeffrey S. , Silva Patricio
Published: April 2021

Secretion of chloride from blood to lumen is accomplished in the rectal gland of elasmobranchs by a process of secondary active transport involving the co-transport of Cl− with Na+ across the basolateral membranes of rectal gland cells. Energy is provided by ATP via membrane Na-K-ATPase, which establishes an electrochemical gradient favouring Na+ influx into the cell. The involvement of K+ in the co-transport mechanism, so as to provide a ratio of 1 Na+: 1 K+: 2 Cl− entering the cell, would increase the energetic efficiency of the process, and is consistent with the CI/O2 ratio of 27–30 observed in secreting rectal glands. Secretion is stimulated by cyclic AMP (cAMP) and by vasoactive intestinal peptide (VIP) and adenosine, which activate adenylate cyclase. Activation of the gland in vivo probably occurs via VIP-secreting nerves as well as circulating agents; it is inhibited by somatostatin. Cyclic AMP probably stimulates chloride secretion by at least three mechanisms: (1) increasing chloride conductance across the luminal cell membrane, (2) enhancing the co-transport pathway for transmembrane movements of Na+, K+ and Cl− and (3) activating Na-K-ATPase.
Effects of Potassium and Osmolality on Spermatozoan Motility of Salmonid Fishes
Authors: Morisawa M. , Suzuki K. , Morisawa S.
Published: April 2021

In salmonid fishes, rainbow trout and masu salmon, and the plecoglossid fish, ayu, seminal plasma had an osmolality around 300 mosmol kg−1, isotonic to the blood plasma, and contained a higher concentration of potassium than the blood plasma. Spermatozoa of salmonid fishes were motile when semen was diluted 1:100 with solutions of sodium chloride or mannitol, over the osmotic range of 0-300 mosmol kg−1. They were immotile in sodium chloride solution containing several mm potassium. This indicates that osmolality is not an essential determinant of sperm motility in the Salmonidae, and that sperm motility in these species is suppressed by the seminal potassium in the sperm duct, and initiated by a decrease in potassium concentration surrounding spawned spermatozoa when they are released into fresh water.
The Identification of Motor Neurones Innervating an Abdominal Ventilatory Muscle in the Locust
Authors: Yang Qin-Zhao , Burrows Malcolm
Published: April 2021

Motor neurones to abdominal ventilatory muscles, with their axons in nerve 6 of the metathoracic ganglion of the locust, have been identified by intracellular recording and staining. Three muscles are innervated by the larger branches of this nerve: nerve 6a contains six motor neurones innervating the ventral diaphragm; nerve 6b contains four motor neurones innervating the median internal ventral muscle, and nerve 6d contains five motor neurones innervating the longitudinal dorsal muscle. All motor neurones innervate muscles on one side of the body only. Both the median internal ventral and the longitudinal dorsal muscles contract during the expiratory phase of ventilation. Three excitatory motor neurones to the median internal ventral muscles spike during expiration whilst the fourth, an inhibitory motor neurone, is active during both expiration and inspiration. Two of the excitatory motor neurones have cell bodies in the half of the ganglion ipsilateral to the muscle they innervate. Their neuropilar branches, however, are in both left and right halves of the ganglion. The third excitatory motor neurone has its cell body close to the midline and has most of its neuropilar branches in the half of the ganglion ipsilateral to its axon. The inhibitory motor neurone has its cell body just to the contralateral side of the midline, and three distinct areas of neuropilar branches, two contralateral and one ipsilateral to its axon.
Partitioning of Energy in Fish: Can Reduction of Swimming Activity Compensate for the Cost of Production?
Authors: Koch Franz , Wieser Wolfgang
Published: April 2021

By using a new video activity monitoring processor (Kaufmann, 1983) in conjunction with a large respirometer, we have measured swimming activity, oxygen consumption and reproductive investment (in the form of gonadal growth) of roach (Rutilus rutilus L.) during a seasonal cycle. If the effect of temperature on metabolism is taken into account it can be shown that swimming activity is drastically reduced during the period of gonadal synthesis (July–December). On the basis of a calibration curve established for the preproductive phase (Januar–June), the reduction in locomotor activity is estimated to represent a saving of 1485 kJ kg−1 of metabolizable energy during a period in which 364 kJ worth of gonadal tissue per kg of fish are being synthesized. Our data provide the first evidence that even in a poikilothermic animal reduction of locomotor activity may compensate for the costs of producing gonadal tissue.
Wing Hair Plates in Crickets: Physiological Characteristics and Connections with Stridulatory Motor Neurones
Authors: Elliott C. J. H.
Published: April 2021

Hairs in the subcostal hair plates of the wings of crickets have a high angular stiffness (5·5 μNmrad−1) when bent about their base. The mean threshold required to elicit action potentials is 15°. Viscous drag from air movements will not deflect the hairs sufficiently to excite them; this will only occur when the hair is bent by the opposite wing. The hair sensillae project to the ventral association area of the mesothoracic ganglion, but the endings of the stridulatory motor neurones are all in dorsal or lateral neuropiles of the thoracic ganglia. Electrical stimulation of the hair plates evokes reliable EPSPs in opener (M99), closer (M90) and wing folding (M85) motor neurones, after latencies of 4–20 ms, depending on the neurone. Properties of the hairs and motor neurones suggest that these EPSPs in the wing folding muscle (M85) and closer (M90) could play an important role in the control of wing position seen in recent behavioural study.
Quantitative Analysis of Walking in A Decapod Crustacean, the Rock Lobster Jasus Lalandii II. Spatial and Temporal Regulation of Stepping in Driven Walking
Authors: Chasserat C. , Clarac F.
Published: April 2021

Spatial and temporal stepping parameters have been studied in a rock-lobster walking on a treadmill moving at a wide range of speeds. The stride and the return stroke (RS) duration remain more or less stable and independent of the belt speed. Nevertheless, these ‘invariant’ parameters can act as spatial and temporal buffers resulting in a very precise adjustment of individual steps.

A careful study of the power stroke (PS) duration demonstrates that the rock-lobster, although constrained to walk at an imposed belt speed, continues to correct its leg speed over a narrow range when the speed is considerably different from its natural one. Ipsilateral phases are always speed dependent, with an interleg ascending delay that is almost constant. The contralateral phase between legs of the same pair is approximately constant.

Some of the parameters described are greatly influenced by gradual or abrupt variations in the belt speed. For a given speed, there is no absolute significance in the step period and ipsilateral phase. At very slow speeds, the interleg relations are significantly changed and have been studied separately. The metachrony observed at other speeds is discussed in relation to data from other arthropods.