bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular Changes in the Prothoracic Glands of Diapausing Pupae of Manduca Sexta
Authors: Smith Wendy A. , Bowen M. F. , Bollenbacher Walter E. , Gilbert Lawrence I.
Published: April 2021

Prothoracic glands from diapausing pupae of the tobacco hornworm, Manduca sexta, synthesize markedly less ecdysone in vitro in response to prothoracicotropic hormone (PTTH) than do glands from non-diapausing pupae. Impaired steroidogenesis is also observed in glands from diapausing animals exposed to agents that enhance ecdysone synthesis in non-diapausing pupal glands by increasing intracellular levels of cAMP (l-methyl-3-isobutylxanthine, dibutyryl cAMP, and the calcium ionophore A23187). In contrast, prothoracic glands from diapausing pupae synthesize significantly more cAMP in response to PTTH and A23187 than do those from non-diapausing pupae. These observations indicate that the PTTH-refractoriness characteristic of prothoracic glands during diapause results from a lesion in the steroidogenic pathway occurring beyond the level of the PTTH receptor-adenylate cyclase system. The diapause condition of the prothoracic glands (reduced ecdysone synthesis accompanied by enhanced cAMP formation) can be mimicked by extirpation of the brain of a non-diapausing pupa. Thus, cellular changes in the prothoracic glands associated with diapause may arise as a result of the absence of some factor produced by the pupal brain (e.g. PTTH).
Spontaneous Miniature Potentials in Denervated Coxal Muscle Fibres of the American Cockroach
Authors: Washio Hiroshi
Published: April 2021

Functional changes following denervation have been studied by intracellular recording at the neuromuscular junction of the cockroach coxal muscle. Spontaneous subthreshold activity disappeared together with nerve-muscle transmission in about 2 days after nerve section at 26°C. The onset of the failure was mainly dependent on the temperature and also on the length of the transected distal stump. After complete cessation of the miniature excitatory postsynaptic potentials (MEPSPs) for about 3 weeks at 26 °C, the miniature potentials resumed at a slower rate. Regeneration occurred faster when axotomy was performed by crushing the nerve rather than by sectioning. Resumption of the MEPSPs was accompanied by response to nerve stimulation. However, hypertonic and hypotonic saline, and excess potassium, failed to increase the frequency of the resumed MEPSPs recorded between 15 and 45 days following denervation. It is suggested that the resumed spontaneous release of transmitter may be derived from regenerating nerve terminals.
Correlation of Iridescence with Changes in Iridophore Platelet Ultrastructure in the Squid Lolliguncula Brevis
Authors: Cooper Kay M. , Hanlon Roger T.
Published: April 2021

Cephalopods are renowned for their unique colour change system in which neurally controlled chromatophore organs in the dermis work in combination with subjacent iridescent cells (iridophores) to produce colours and patterns of a wide range (Messenger, 1979; Hanlon, 1982). Some iridophores in squids are physiologically active and reversibly change from non-iridescent to iridescent (Hanlon,1982) We discovered examples of these active iridophores in the dorsal mantle of the squidLolliguncula brevis. The state of iridescence in these dorsal mantle iridophores can be controlled in vitro in isolated dermal layers with the putative neuromodulator acetylcholine (ACh), as well as by means of other factors (Hanlon & Cooper, 1985). We compared the ultrastructure of non-iridescent and iridescent iridophores in these isolated dermal layers to determine the cytological basis for the change in optical properties. In this paper we report the correlation of structural changes within the iridophore platelets with the appearance of iridescence.
Aerobic and Anaerobic Correlates of Mechanical Work by Gastrocnemius Muscles of the Aquatic Amphibian Xenopus Laevis
Authors: Boutilier R. G. , Emilio M. G. , Shelton G.
Published: April 2021

Isolated, saline-perfused gastrocnemius muscles of Xenopus laevis were used to assess the relationships between aerobic and anaerobic metabolism during conditions of rest, isotonic contraction and recovery. The major part (85 %) of the energy used during 25 min of isotonic contractions in the saline-perfused muscles was from anaerobic rather than aerobic sources. However, the small contribution made by oxidative metabolism during activity can be attributed, in part at least, to limitations imposed by the rate of perfusion and the low O2 capacity of the perfusate. The respiratory exchange ratio of saline-perfused gastrocnemius muscles of Xenopus was 0·82 at rest, increasing to values well above 1·0 during activity. The elevated R value is consistent with liberation of CO2 by metabolic acid titration of the bicarbonate buffer system of the saline perfusate. Recovery from exercise was characterized as a period of net CO2 retention (R values of 0·4) presumably reflecting a replenishment of depleted CO2 stores. Depending on the acid-base status of the venous outflow from the isotonically contracting muscles, hydrogen ions were found to be released at either a greater rate (alkalosis) or slower rate (acidosis) than that of lactate.
The Diabetogenic Hormone of the Pituitary Gland
Authors: Slome David
Published: April 2021

Numerous clinical observations have provided indirect evidence that the pituitary gland exercises a significant effect on carbohydrate metabolism. Glycosuria is frequently a part of the acromegalic syndrome (Borchardt, 1908; Goetsch, Cushing and Jacobson, 1911). Houssay (1931) and Eidelsberg (1932) have emphasised that cases of acromegaly often manifest the symptoms and signs of diabetes.
The Biological Basis of Sexual Behaviour in Amphibia
Authors: Shapiro H. A.
Published: April 2021

In the previous paper in this series (Shapiro, this Journal) a technique was described for inducing the mating reflex in Xenopus laevis (the South African clawed toad) by means of extracts of pregnancy urine or of anterior pituitary tissue. In this way the mating reflexes of the animals, and ovulation on the part of the females, can be controlled adequately and observed conveniently.
The Biological Basis of Sexual Behaviour in Amphibia
Authors: Berk L. , Cheetham R. W. S. , Shapiro H. A.
Published: April 2021

The elaborate pattern of motor behaviour involved in the accurate establishment of the lumbar embrace during coupling in Xenopus laevis suggested that the distance receptors might play an important part in the correct orientation of the partners. It was therefore decided to investigate the problem experimentally.
On the Excitation of Crustacean Muscle
Authors: Pantin C. F. A.
Published: April 2021

In the second paper of this series (Pantin, 1936) the responses of the muscles of various limbs to stimuli of different frequency and intensity in Carcinus maenas were described. Particular attention was paid to the flexor of the dactylopodite of the walking legs. If, while the frequency is kept constant, the intensity of the stimulus is gradually raised, the response of the muscle at first remains unaltered. But when a certain critical intensity is reached, the strength of the contraction diminishes. This is true of all the muscles investigated. Even in the crusher-claw adductor a sufficient increase in intensity results in a failure of the response. This failure is due to the excitation of the inhibitory nerve, the threshold of which, in normal preparations, is invariably higher than that of the motor nerve. The existence of inhibitory nerve fibres in crustacean limbs rests upon excellent evidence. The most convincing proofs are those in which the inhibitory nerve supply to the muscle has been stimulated separately from the motor supply to the muscle. These have been given in experiments reviewed and confirmed by Hoffmann (1914) and Knowlton and Campbell (1929).
The Rhythmical Movements of the Gills of Nymphal Leptophlebia Marginata (Ephemeroptera) and the Currents Produced by Them in Water
Authors: Eastham L. E. S.
Published: April 2021

Reference has been made to the general problem of gill movements of ephemerid nymphs (Eastham, 1932), and the special features presented by Caenis horaria have already been described (Eastham, 1934). The following is an account of gill movement in Leptophlebia marginata.
The Control of Respiratory Movements in Crustacea by Oxygen and Carbon Dioxide. II
Authors: Johnson M. L.
Published: April 2021

The investigations made by Fox and Johnson (1934) into the respiratory control of certain Crustacea showed that there was considerable variation in the response to carbon dioxide and oxygen. Thus the rate of limb movements of Balanus and Chirocephalus was not affected by the gas content of the water, whereas the respiratory rhythm of Astacus and Asellus was quickened by oxygen lack, and that of Gammarus by both oxygen lack and carbon dioxide excess. Even within one genus some degree of variation was found, for whereas the effect of changes of the gas content of the medium on the rate of pleopod beat in G. pulex was permanent, in G. locusta it was transitory. It was hoped that by extending these investigations to more species of Crustacea, some phylogenetic or ecological significance might be discovered in this variation of response to the respiratory gases.
Variance: A Possible Coding Mechanism for Gustatory Sensilla on the Labellum of the FleshflySarcophaga Bullata
Authors: Mitchell B. K. , Smith J. J. B. , Albert P. J. , Whitehead A. T.
Published: April 2021

In behavioural tests, 2-day-old female Sarcophaga bullata consumed more liver or fish powder in solution than 100 mmol 1−1 sucrose. We investigated the chemosensory basis of this discrimination by recording electrophysiological responses of 177 medium-length labellar taste sensilla from 10 different flies to two applications of each of these three solutions. Responses from three chemosensory cells were evident in most records. Cell 1 produced a mean response of 37.6 impulses s−1, and similar responses to all three stimuli. It was the most active of the three cells. Cell 2 produced a significantly greater response to fish than to liver or sucrose in one of the two stimulus applications. Cell 3, the least active, responded with twice the firing rate to fish than to liver or sucrose. However, the mean firing rates did not provide information that could account for the observed behavioural discrimination. The only difference in the electrophysiological responses to the three stimuli which correlated with the behavioural discrimination was the variance of the response of cell 1, which was much higher to sucrose than to either fish or liver. We propose that variance itself could provide the necessary information to allow the fly’s nervous system to distinguish between a ‘simple’ stimulus such as sucrose and a ‘complex’ stimulus such as fish or liver.
An Analysis of the Effects of pH on Oxygen Binding by Squid (Illex Illecebrosus, Loligo Pealei) Haemocyanin
Authors: Pörtner Hans-Otto
Published: April 2021

The in vitro oxygen-binding characteristics of haemocyanin were investigated in whole blood of two species of pelagic squid, Illex illecebrosus and Loligo pealei. pH-independent Haldane coefficients (ΔHCO3−/ΔHcyO2) (where HcyO2 is haemocyanin-bound oxygen) slightly smaller than −1 were found in both species. Oxygen-linked CO2 binding was not present. Buffer values ranged between 5 and 5.8mmol l−1 pHuniC1. For further analyses a pH/saturation diagram was selected to show the effect of pH on oxygen binding at constant in a continuous plot. The slopes of the resulting oxygen isobars (ΔHcyO2/ΔpH or ΔS/ΔpH) (where S is oxygen saturation) depend on pH. The diagram allows evaluation of both the Bohr coefficients (ΔlogP50/ΔpH) and the Hill coefficients (riso) at specific pH values. It provides an integrated illustration of the importance of the Bohr effect and cooperativity for oxygen binding.

In accordance with Wyman’s finkage equation, Bohr and Haldane coefficients are found to be identical. Both are pH-independent between pH7 and 8. The changing slopes of the oxygen isobars are likely to reflect changes in cooperativity with pH. Maximum values of n50 coincide with maximum steepness of the oxygen isobars in the physiological range of pH and . Assuming that the haemocyanin acts as a buffer for venous , this maximum in pH sensitivity and its decrease in the higher and lower pH ranges are discussed in the light of the maintenance of pigment function in vivo.
Plateau-Generating Nerve Cells in Helix: Morphological and Electrophysiological Characteristics
Authors: Pin T. , Crest M. , Ehile E. , Jacquet G. , Gola M.
Published: April 2021

We describe the anatomical and electrophysiological characteristics of a group of Helix nerve cells, styled P cells, that generate long-lasting depolarizations in response to repeated stimulations at low frequencies. Four neurones were identified in the perioesophageal ganglia of the snail Helix pomatia. Their structure was determined by intracellular injection of Lucifer Yellow, cobaltlysine or horseradish peroxidase. The soma was found to contain neurosecretory granules. These cells innervated the whole foot muscle and the mantle, but were not involved in muscle movement or locomotion. They may participate in mucus secretion. Upon depolarization they fired Ca2+-dependent spikes; at a critical firing rate (5–6Hz), the spikes were converted into depolarized plateaus (+10 to +20mV) lasting for several seconds. The plateau was Ca2+-dependent and persisted in Na+-free saline. It was sustained by a slowly inactivating Ca2+ current that produced a large intracellular Ca2+ accumulation (monitored with the Ca2+-sensitive dye Arsenazo III). The plateau was restricted to the soma and the proximal axon and may act as a driver potential inducing axon firing and prolonging the release of neurosecretory materials.
Inhibitory Connections Underlying the Directional Sensitivity of the Equilibrium System in the CrayfishProcambarus Clarkii
Authors: Nakagawa H. , Hisada M.
Published: April 2021

Neuronal mechanisms underlying the directional sensitivity of the crayfish equilibrium system were studied in the brain by intracellular recording combined with mechanical statocyst hair deflection. Five primary afferents were successfully characterized. Three of them showed a decrease in response to inward hair deflection. The remaining two showed the opposite directional response. Directional sensitivity was found in six interneurones. Two of them were excited during inward hair deflection while the other four were excited during outward deflection. Both groups exhibited active inhibition during hair deflections in the opposite direction. This ‘null-phase inhibition’ appeared to arise from the convergence of the two classes of afferents onto an interneurone with the opposite sign. Three identified descending statocyst interneurones, S3, S6 and S7, were found to receive excitatory input from one statocyst and inhibitory input from the other. The results thus indicated that the directional sensitivity of the crayfish equilibrium system was achieved by selective excitatory connections between the interneurone and the directionally arranged receptor and sharpened by inhibitory mechanisms.
Contractions of the squid stellate ganglion
Authors: Sanchez Maria Elena , Nuño Claudia M. , Buchanan Joann , Augustine George J.
Published: April 2021

Optical recording methods were used to characterize the intrinsic movements of squid stellate ganglia. Ganglionic contractions were rhythmic and occurred at a mean frequency of 8 min−1. Contractions were eliminated when Na+ in the external saline were replaced by Tris, but were only slowed when Na+ was replaced by sucrose. This suggests that Na+ plays some role in generating the contractions, but the complete abolition produced by Tris-containing saline may be due to a secondary pharmacological action of this ion. The Na+ channel blocker, tetrodotoxin, had no effect on contractions. Contractions were eliminated by removal of external Ca2+, by treatment with the inorganic Ca2+ channel blockers Mn2+ and Cd2+, or by treatment with the organic dihydropyridine Ca2+ channel blockers nitrendipine and nimodipine. Thus, extracellular Ca2+ plays an important role in generating the contractions. Because dihydropyridines eliminate contractions, but not synaptic transmission, they offer a means of studying transmission at the giant synapse of the stellate ganglion without having to contend with ganglionic movement. Electron microscopy of stellate ganglia revealed the presence of two types of cell that contained the organized arrays of cytoskeletal elements usually associated with contractile cells. One type was a pericyte that surrounded blood vessels within the stellate ganglion. The second type was distributed throughout the ganglion and resembled a smooth muscle cell. Either of these cell types might generate ganglionic contractions.
Na+ and Cl− Uptake Kinetics, Diffusive Effluxes and Acidic Equivalent Fluxes Across the Gills Of Rainbow Trout: I. Responses To Environmental Hyperoxia
Authors: Goss Greg G. , Wood Chris M.
Published: April 2021

Endogenous respiratory acidosis and metabolic alkalosis were induced in bladder-catheterized freshwater rainbow trout by exposure to environmental hyperoxia (72 h) and its subsequent removal. Unidirectional and net fluxes of Na+, Cl− and acidic equivalents across the gills were examined over 0.5 h intervals. Hyperoxia resulted in a positive Na+ balance, negative Cl− balance and net acidic equivalent excretion. Return to normoxia caused a negative Na+ balance, a positive Cl− balance and net basic equivalent excretion (=acidic equivalent uptake). Cl−/basic equivalent exchange was more important than Na+/acidic equivalent exchange in the homeostatic responses, and alkalosis was a more potent stimulus than acidosis for change in branchial ion fluxes. Kinetic analysis demonstrated that alterations in ion fluxes were achieved by complex changes in both the Km (inverse of affinity) and the Jmax (maximal transport rate) of the branchial C1−/HCO3− (OH−) and Na+/H+(NH4+) transporters. (control=165μequivl−1) and 114μequivl−1) were increased during hyperoxic acidosis to 250 and 44μ μequivl−1, respectively. (291μequiv kg−1h−1) and (456 μequiv kg−1 h−1) did not change significantly. During post-hyperoxic alkalosis, was further increased to 559μequivl−1, increased to 445μequivkg−1h−1, while and decreased to 137μequivl−1 and 309μequiv kg−1 h−1, respectively. Diffusive efflux was examined using a novel method. There was no significant differential diffusive efflux of Na+ and Cl− during hyperoxia but diffusive Na+ efflux exceeded Cl− efflux during posthyperoxic alkalosis, thereby serving as an additional mechanism for basic equivalent excretion.
Inhibition of escape tailflip in crayfish during backward walking and the defense posture
Authors: Beall SP , Langley DJ , Edwards DH
Published: April 2021

A major question in neuroethology is how animals coordinate transitions between incompatible behavior patterns. The recent demonstration that the lateral giant (LG) tailflip is inhibited during eating (Krasne and Lee, 1988) suggested to us that inhibition may play a general role in preventing maladaptive transitions between incompatible behavior patterns. We wished to determine whether the LG tailflip is inhibited during other incompatible behavior such as backward walking and the defense posture.
Integration of Colour Signals in the Medulla of the Swallowtail Butterfly Larva
Authors: Ichikawa Toshio
Published: April 2021

Spatial and chromatic properties of 25 types of medulla neurones which integrate input from different optical units (stemmata) of the larval eye in the swallowtail butterfly were examined by illuminating individual stemmata with chromatic stimuli. Eleven neurones received different types of colour (opponent) input from a few stemmata; thus, the receptive fields are spectrally heterogeneous. The stemmata dominating these complex neurones were usually located in the frontal (central) region of the eye. Seven neurones showed a relatively homogeneous spectral profile over the receptive field by receiving similar spectral input from two or three stemmata which were usually located in the dorsolateral (peripheral) region of the eye. Three of these simple units showed tonic or phasic responses. The remaining seven were also spectrally simple neurones but with larger receptive fields covering four to all six stemmata. Some units showed a spatial summation of responses or a spatial antagonism between central and peripheral or dorsal and ventral regions of the eye.
Characterization of Receptors Mediating The Actions of Dopamine on an Identified Inhibitory Motoneurone of the Cockroach
Authors: Davis Julian P. L. , Pitman Robert M.
Published: April 2021

The effects of a number of dopaminergic agonists and antagonists upon the soma of a prothoracic inhibitory motoneurone of the cockroach (Periplaneta americana) have been recorded under voltage-clamp conditions. Dopamine generates inward currents that are extremely voltage-dependent: currents increase rapidly at membrane potentials more negative than about —120 to —150 mV and also show a peak at membrane potentials of approximately —20 mV. As a result of this voltage-dependence, dopamine induces a region of negative resistance in the current-voltage relationship of the neurone. The dopaminergic agonists apomorphine, bromocryptine, ergometrine and A-6,7-DTN mimic the action of dopamine on this neurone, all having a similar voltage-dependence to that of dopamine. The selective D-l receptor agonist SK&F 82526 and the D-2 agonist LY171555, however, were both inactive on the preparation. Responses to dopamine were suppressed by a number of D-l and D-2 receptor antagonists, indicating that the pharmacological profile of the dopaminesensitive receptor in this insect preparation is different from that of vertebrate dopamine receptors.
The Transmission of Bush-Cricket Calls in Natural Environments
Authors: Stephen R. O. , Hartley J. C.
Published: April 2021

This study discusses the structure of the calls of bush crickets Steropleurus nobrei and examines the way the structure of records of a bush-cricket call, comprising pure tone bursts and bursts of white noise, changes as these sounds propagate through different environments. Measurements of the coherence and spectral composition at different distances from the sound source are made in open and thickly vegetated environments. The results show that coherent frequency components in reproductions of the records of the natural call propagate over greater distances than do other components. The results are discussed in relation to the possible sources of information contained in insect calls and how the environment degrades these information sources as the call propagates away from the source. The consequences of the structure of the calls on the properties of the auditory organs of bush crickets is also discussed.
Lactate Utilization By AnIn SituPerfused Trout Heart: Effects Of Workload And Blockers Of Lactate Transport
Authors: Milligan C. Louise , Farrell Anthony P.
Published: April 2021

Lactate utilization was studied in an in situ perfused trout heart preparation that was capable of performing at levels similar to in vivo maximum cardiac performance. Hearts were perfused with modified Cortland saline containing 0.5 mmol l-1 iodoacetic acid (to block endogenous glycolysis) and varying amounts of lactate (1 or 10 mmol l-1). We confirmed previous observations that lactate utilization is limited by substrate availability. However, contrary to previous observations, exogenous fuel availability did not limit cardiac performance, even at the high workload. Furthermore, when plentiful (i.e. 10mmoll-1), exogenous lactate was preferred over endogenous fuel and was able to supply the heart’s energy requirements at both the low and high workloads. Pyruvate at 10fold greater concentration, had no apparent effect on lactate utilization at the high workload. α-Cyano-4-hydroxycinnamate (α-CIN) (2.5 mmol l-1) proved to be an unsuitable probe of lactate transport in the trout heart as it caused a reduction in both lactate utilization and cardiac performance. However, addition of 20 μmol l-1 isobutyl carbonyl lactyl anhydride or 100μmoll-1 4-acetamido-4 ′-isothiocyano-stilbene-2,2 ′-disulphonic acid (putative lactate transport blockers) to the perfusate virtually abolished lactate oxidation at the high workload without affecting cardiac performance. These observations suggest that lactate uptake by the in situ perfused trout heart is carrier-mediated.
Acid–Base Transport and Control in Locust Hindgut: Artefacts Caused by Short-Circuit Current
Authors: Thomson R. Brent , Audsley N. , Phillips John E.
Published: April 2021

The commonly used method of passing short-circuit current (Isc) across insect epithelia through Ag-AgCl electrodes, without the use of salt bridges, leads to significant OH− production at the cathode (lumen side) when high currents are applied. The alkalization of the lumen previously reported when cyclic AMP was added to short-circuited locust hindgut is a result of this phenomenon rather than cyclic-AMP-mediated stimulation of acid-base transport in the hindgut. When salt bridges are used to pass short-circuit current across locust hindgut, acid secretion (JH) into the lumen equals alkaline movement (JOH) to the haemocoel side, and JH is similar under both open- and short-circuit conditions. JH is similar (1.5μequiv cm_2h_1) in recta and ilea. Addition of cyclic AMP inhibits JH across the rectum by 42–66 %, but has no effect on the ileum when salt bridges are used. Electrical parameters (Isc, Vt, Rt) reflecting hindgut Cl− transport (JC1) before and after stimulation with cyclic AMP are the same whether or not salt bridges are used. We found no evidence of any coupling between JcI and JH / JOH.
Distinct Receptors, Second Messengers and Conductances Underlying the Dual Responses to Serotonin in an Identified Leech Neurone
Authors: Sanchez-Armass Sergio , Merz David C. , Drapeau Pierre
Published: April 2021

Pressure-sensitive mechanosensory (P) neurones of the leech Hirudo medicinalis produce two responses to serotonin (5-HT): activation of a Cl−conductance and of a non-selective monovalent cation conductance. The effects of channel blockers, the receptor pharmacology and the second-messenger dependence of these responses were studied in voltage-clamped P cells in culture. Antagonists were applied by superfusion and agonists by pressure ejection. Zn2+ (100μmoll−1) and H+ (pH 6.5 and lower) reversibly reduced the Cl−conductance activated by 5-HT. The cation conductance was impermeant to calcium ions and was reduced by micromolar concentrations of the Na+ channel inhibitors amiloride and 3,4-dichlorobenzamil. High concentrations of antagonists or agonists of 5-HT1 receptors and an antagonist of 5-HT3 receptors had no effect on either response of P cells to 5-HT. Micromolar concentrations of ketanserin or cyproheptadine, which selectively antagonize 5-HT2 receptors, reduced the cation but not the Cl− conductance. From these results, the receptor underlying the cation conductance appears to be of the 5-HT2 subtype, whereas the receptor activating the Cl− conductance does not fit within the mammalian classification scheme. Brief (<500 ms) application of membrane-permeant agonists of the second messenger cyclic AMP elicited a Cl− conductance, whereas antagonists of cyclic-AMP-dependent protein kinase A reversibly suppressed the Cl− conductance elicited by 5-HT and by cyclic AMP agonists. Compounds affecting other second messenger pathways were without effect on the Cl− conductance. It therefore appears that the Cl− conductance is activated by cyclic-AMP-dependent protein kinase A. Cyclic nucleotide agonists and antagonists were without effect on the cation conductance. However, brief application of phorbol esters, which activate protein kinase C, elicited an amiloride-sensitive cation current. An inhibitor of protein kinase C reduced the cation conductance activated by 5-HT and by phorbol esters. Therefore, the cation conductance appears to depend on activation of protein kinase C. We conclude that 5-HT activates two types of receptor coupled to separate ionic channels via different second messenger pathways in P cells. A receptor that is distinct from the mammalian subtypes activates Cl− channels via cyclic-AMP-dependent protein kinase A. 5-HT2 receptors appear to activate cation channels by means of protein kinase C.
Forces Generated by the Jaws of Clypeasteroids (Echinodermata: Echinoidea)
Authors: Ellers Olaf , Telford Malcolm
Published: April 2021

Aristotle’s lantern acts like a five-toothed ‘vice grip.’ Contraction of the interpyramidal muscles creates tangential stresses that are converted to radial forces along the teeth. Two mechanical models are proposed to explain this conversion. In the first, the lantern is regarded as a thick-walled cylinder resisting internal pressure; in the second, it is treated as a cluster of wedges. The two models differ primarily in the allowance of radial forces within the muscle in the cylinder and their exclusion in the wedge model. Maximum muscle stress required for a given force along the teeth depends on the ratio of external to internal lantern radii (ro/ri). Maximal force requires that ro/ri should be greater than 2, which is the case in Clypeaster rosaceus (L.). The models allow calculation of a dimensionless number,. ℱ, which scales the force exerted by the teeth for changes in lantern size and the number of pyramids. Biting force was measured in C. rosaceus and used to calculate the muscle stress required by the mechanical models. For the thick-walled cylinder, maximum interpyramidal muscle stress was calculated to be 2.8×106Nm−2. For the wedge model it was 1.9×105Nm−2. The models were supported by comparison of predicted with observed biting forces in another clypeasteroid, Encope michelini L. Agassiz.
The Inorganic Composition of the Body Fluids of Three Marine Invertebrates
Authors: Robertson James D.
Published: April 2021

Analyses have been made of the body fluids of Echinus esculentus, and two decapod Crustacea, Homarus vulgaris and Cancer pagurus, before and after dialysis with sea water in which they were living. The composition of the perivisceral fluid of Echinus is identical with that of seawater, complete physico-chemical equilibrium existing between the two fluids. The blood plasmas of Homarus and Cancer are maintained in dynamic equilibrium with sea water. They contain more Na, K and Ca and less Cl, Mg and SO4 than sea water. The antennary gland fluid of Cancer contains less Na, K, Ca and Cl and more Mg and SO4 than the blood plasma. The importance of the antennary glands and the surface membranes in regulating the inorganic composition of the blood is discussed.
Invertebrate Athletes: Trade-Offs Between Transport Efficiency and Power Density in Cephalopod Evolution
Authors: O’dor R. K. , Webber D. M.
Published: April 2021

Jet propulsion concentrates muscle power on a small volume of high-velocity fluid to give high thrust with low Froude efficiency. Proponents are typically escape artists with high maintenance costs. Nonetheless, oceanic squids depend primarily on jets to forage over large volumes of relatively unproductive ocean (low power density, Wm−3). A survey of locomotor performance among phyla and along an ‘evolutionary continuum’ of cephalopods (Nautilus, Sepia, Loligo and Illex) suggests that increasing speed and animal power density are required if animals are to compete effectively in environments of decreasing power density. Neutral buoyancy and blood oxygen reserves require unproductive volume, keeping drag high. Undulatory fins increase efficiency, but dependence on muscular hydrostats without rigid skeletal elements limits speed. Migratory oceanic squids show a remarkable range of anatomical, physiological and biochemical adaptations to sustain high speeds by maximizing power density. Muscle mitochondrial density increases 10-fold, but metabolic regulation is realigned to optimize both aerobic and anaerobic capacity. The origins of these adaptations are examined (as far as possible, and perhaps further) along the continuum leading to the most powerful invertebrates.
The Influence of Temperature on Muscle Function in the Fast Swimming Scup : I. Shortening Velocity and Muscle Recruitment During Swimming
Authors: Rome Lawrence C. , Choi In-Ho , Lutz Gordon , Sosnicki Andrzej
Published: April 2021

In this study, electromyography showed that scup can swim to a maximum speed of 80 cm s−1 with their red muscle whereas previous results showed that carp can swim to only 45cms−1. Our aim was to evaluate the adaptations that enable scup to swim nearly twice as fast as carp. Although we anticipated that, at their respective maximum speeds, the red muscle of scup would be shortening at twice the velocity (V) of carp muscle, we found that the values of V were the same (2.04 muscle lengths s−1). At any given swimming speed, V was higher in carp than in scup because carp had a larger sarcomere length excursion and higher tail-beat frequency. The smaller sarcomere excursion in scup is primarily associated with using a less undulatory style of swimming (i.e. with a smaller backbone curvature). This less undulatory style of swimming may be an important adaptation that not only reduces V but may also reduce drag. At their respective maximum speeds, however, the 28 % lower sarcomere length excursion in scup is balanced by a 26 % higher tail-beat frequency, giving an equal V to that of carp. Although the scup in this study were somewhat longer than the carp in the previous one (19.7 vs 13.4cm), we believe that many of the observed differences are species-related rather than size-related.

We also found that scup swam in a kinematically similar fashion at 10°C and 20°C. However, at 10°C, the scup could swim to only 54cm s−1 before recruiting their white muscle whereas, at 20°C, they could swim to 80cms−1. The difference in speed of initial white muscle recruitment, as well as information on muscle mechanics (see the following paper), suggests that the scup compress their recruitment order into a narrow speed range at low temperatures, thereby recruiting more muscle fibres. Quantitative analysis of red muscle electromyograms in this paper supports this hypothesis.
5′-p-Fluorosulfonylbenzoyladenosine Binds to the 28Kda Subunit of Larval Manduca Sexta Midgut Vacuolar-Type ATPase
Authors: Zheng X. Y. , Spaeth D. D. , Harvey W. R. , Wolfersberger M. G.
Published: April 2021

The larval lepidopteran midgut contains a mechanism for the active transport of potassium ions from blood to lumen (Harvey and Nedergaard, 1964). This insect K+ pump has been localized to the apical membrane of the midgut goblet cells (Dow et al. 1984). Recently it has been shown to consist of a proton-motive ATPase of the vacuolar class (V-ATPase) functioning in conjunction with a K+/ nH+ antiporter (Wieczorek et al. 1991).
Factors Influencing Facilitation in Actinozoa. The Action of Certain Ions
Authors: Ross D. M. , Pantin C. F. A.
Published: April 2021

In at least some of the muscles in Coelenterates the size of response is controlled by the neuromuscular junction. The sphincter in Calliactis and the longitudinal mesenteric retractor muscles of Metridium senile are served by part of the nerve network which acts as a single excitable system. The response is not graded through a large number of separate motor units. A single stimulus applied to this nerve net is ineffective, or only causes a trivial response ; but it leaves behind it an effect which facilitates the transmission of a second impulse to the muscle. Each impulse in a series facilitates the transmission of excitation to more and more muscle fibres. After each stimulus the facilitating effect gradually dies away (Pantin, 1935 b). In a short discussion, the relation of this “facilitation” process to other cases of junctional transmission was considered (Pantin, 1937). The process by which excitation is only effective if one stimulus follows its predecessor before the period of facilitation has departed, is analogous to the condition of vertebrate skeletal muscle during partial curarization. But at present the nature of the facilitation process is still unknown. A study of the action of ions and other substances throws considerable light upon its nature, and it is the object of this paper to describe and discuss these effects.
Stepping Patterns in Ants: III. Influence of Load
Authors: Zollikofer Christoph P. E.
Published: April 2021

Stepping pattern geometry and walking kinematics of individual foragers of Cataglyphis fortis (Formicidae: Hymenoptera) were recorded during outward and homeward trips to and from a food source. While returning homewards, the animals were supplied with food items of defined mass (load ratio from 1.3 to 6.4) and volume. Under the influence of load, the temporal interleg coordination pattern was maintained (alternating tripod gait), but the spatial tripod pattern was modified. Tripod deformation was found to be proportional to the displacement of the centre of mass induced by the load. Stride length and stride frequency were not altered at any speed when animals carried loads compared with trips without a load. However, in order to maintain stability, mean stride length, mean speed and mean stride frequency were reduced while carrying loads.
Carbonic Anhydrase Injection Provides Evidence for the Role of Blood Acid–Base Status in Stimulating Ventilation after Exhaustive Exercise in Rainbow Trout
Authors: Wood Chris M. , Munger R. S.
Published: April 2021

This study tests the hypothesis that the increase in blood and associated respiratory acidosis after exhaustive exercise play an important role in stimulating ventilation during post-exercise recovery in fish. Injection of bovine carbonic anhydrase (10 mg kg−1) into the bloodstream of rainbow trout caused a persistent 40% increase in the HCO3− dehydration capacity of the blood. The treatment was designed to increase CO2 excretion and therefore to reduce build-up and acidosis after exercise. Aerobic and anaerobic swimming performance were not affected by carbonic anhydrase, and there were only very minor effects on arterial blood acid–base status in resting fish. However, carbonic anhydrase attenuated post-exercise increases in and decreases in pHa by about 50% without altering arterial O2 variables, red cell swelling or the intracellular pH of the brain or muscle tissues. The effects on arterial pH (pHa) resulted largely from alleviation of the increase in . In accordance with the original hypothesis, normal post-exercise hyperventilation was greatly attenuated, through reductions in both ventilatory stroke volume and frequency, and excess post-exercise O2 consumption was reduced. Post-exercise increases in plasma levels of adrenaline and noradrenaline were also reduced by the carbonic anhydrase treatment. Overall, there was a strong correlation between increases in relative ventilation and decreases in pHa after exhaustive exercise. The results provide functional significance for the phenomenon of elevation and associated respiratory acidosis after exercise and are consistent with other recent studies indicating an important secondary drive to ventilation in fish based on arterial acid–base status, in addition to the primary drive based on arterial O2 levels.
Head Waving in Aplysia Californica: II. Functional Anatomy and Muscular Activity During Behaviour
Authors: Kuenzi Frederick M. , Carew Thomas J.
Published: April 2021

Bending and twisting movements of the body during head-waving behaviour of the sea hare Aplysia californica are produced by the concerted action of the muscles of the body wall on the hydrostatic skeleton formed by the haemocoel and internal organs. In this study, we describe the orientations and possible mechanical actions of muscles in the body wall. We also describe the spatial and temporal patterns of longitudinal muscle activity during different head-waving movements in a freely moving animal.

The body-wall muscles are arranged as a network of longitudinal, circular and left-and right-handed helical muscle fascicles. Each fascicle consists of a few to several hundred muscle fibres enclosed in a connective tissue sheath. The sheath also connects muscle fascicles of different orientations at the points where they cross, forming a tightly connected network. In addition, a series of large longitudinal muscle fascicles, including the lateral columellar muscles, lies against the inside wall of the dorsal hemicylinder of the animal.

In animals with hydrostatic skeletons, longitudinal and circular muscles are necessary for producing all basic elongation, shortening and bending movements, and in Aplysia, the extensive distribution of helical muscles provides the animal with the ability to twist its body about the longitudinal axis, as is observed during horizontal head-waving movements.

Muscle activity in the lateral muscles is antiphasically coordinated during horizontal bends, and when the animal is bent to one side, movement towards the centre is accompanied by muscle activity on the side of shortening, i.e. there is no passive return to centre. The muscles near the holdfast are the most active during head-waving movements, with relatively little activity in the head region. The activity of dorsal muscles corresponds to both the existing vertical posture of the body and to discrete dorsal bending movements. In most cases, depression of the head is passive, i.e. both dorsal and ventral longitudinal muscles relax, although foot muscles may also be involved. These observations, together with the constancy of the hydrostatic pressure in the haemocoel during all movements in animals attached to the substratum, suggest specific patterns of motor neurone coordination during different movements.
Metamorphosis of Research on Ion-Coupled Metabolite Transport
Authors: Slayman Clifford L.
Published: April 2021

A defining moment in the history of active transport research came in August 1960, in a symposium at the Czeckoslovak Academy of Sciences, which became known among membrane biologists as the Prague Symposium (Kleinzeller and Kotyk, 1961). By that date, the enzymatic nature of sodium transport in animal cells had been demonstrated (Skou, 1957) and a generalized concept of transport-related, vectorial metabolism was being formulated (Mitchell, 1961). Specifically concerning uptake of organic metabolites, a pivotal observation had been made by Riklis and Quastel (1958): that active transport of sugars by intestinal villus membrane is dependent upon sodium ions in the luminal bathing solution. This finding was extended by Crane et al. (1961), who suggested in Prague that sugar and sodium ions might be simultaneously transported, and was further discussed by Mitchell. Subsequently, both Crane and Mitchell elaborated hypotheses of ion-coupled sugar transport: Na+–glucose in mammalian intestine (Crane, 1962) and H+–galactoside in Escherichia coli (Mitchell, 1962), which became incorporated into a comprehensive picture of proton-linked ‘chemiosmotic’ processes in bioenergetics.
Ca2+ Transport in Saccharomyces Cerevisiae
Authors: Cunningham Kyle W. , Fink Gerald R.
Published: April 2021

Cytosolic free Ca2+ is maintained at submicromolar levels in budding yeast by the activity of Ca2+ pumps and antiporters. We have recently identified the structural genes for two Ca2+ pumps, PCM1 and PMR1, which are required for Ca2+ sequestration into the vacuole and secretory organelles, respectively. The function of either Ca2+ pump is sufficient for yeast viability, but deletion of both genes is lethal because of elevation of cytosolic [Ca2+] and activation of calcineurin, a Ca2+-and calmodulin-dependent protein phosphatase. Calcineurin activation decreases Ca2+ sequestration in the vacuole by a putative Ca2+ antiporter and may also increase Ca2+ pump activity. These regulatory processes can affect the ability of yeast strains to tolerate high extracellular [Ca2+]. We propose a model in which the cellular response to changes in the environmental levels of Ca2+ is mediated by calmodulin and calcineurin which, in turn, modulate the various types of Ca2+ transporters.
The Lactose Permease Meets Frankenstein
Authors: Kaback H. Ronald , Frillingos Stathis , Jung Heinrich , Jung Kirsten , Privé Gilbert G. , Ujwal M. L. , Weitzman Cindy , Wu Jianhua , Zen Kevin
Published: April 2021

The lactose permease (lac) of Escherichia coli is a paradigm for membrane transport proteins. Encoded by the lacY gene, the permease has been solubilized, purified to homogeneity, reconstituted into phospholipid vesicles and shown to catalyse the coupled translocation of β-galactosides and H+ with a stoichiometry of unity. Circular dichroism and other spectroscopic approaches demonstrate that the purified permease is about 80% helical. Based on hydropathy analysis of the primary amino-acid sequence, a secondary structure has been proposed in which the protein has 12 hydrophobic domains in α-helical conformation that traverse the membrane in zigzag fashion connected by hydrophilic loops. A variety of other approaches are consistent with the model and demonstrate that both the N and C termini are on the inner surface of the membrane, and studies on an extensive series of lac permease/alkaline phosphatase fusion proteins provide exclusive support for the topological predictions of the 12-helix motif. This presentation concentrates on the use of site-directed fluorescence spectroscopy to study structure–function relationships in the permease.
Measurement of Water and Carbon Dioxide Loss From Insects Using Radioactive Isotopes
Authors: Croghan P. C. , Noble-Nesbitt J. , Appel A. G.
Published: April 2021

A method is described for investigating the rate of loss of water and carbon dioxide from terrestrial insects by absorbing tritiated water and 14CO2 from a gas stream flowing past the insect. The loss of water and carbon dioxide can be studied simultaneously with a time resolution (nominal) down to 2 min.

The theoretical and experimental bases of analysing the data are considered in detail. The determination of the efflux rate constant for water is straightforward and, if an estimate of surface area is available, the efflux rate constant can be converted to a permeability coefficient. In the case of 14CO2 loss, the interpretation is complicated by the presence of other compartments within the body that can be labelled with 14C. A multicompartment model of 14C exchange is developed and a method of obtaining the efflux rate constant of 14CO2 is described. The efflux rate constant for 14CO2 can be used to estimate CO2 output.