bluuebunny/crossref_metadata_2025_split huggingface dataset:
Motor Programme Switching in the Crayfish Swimmeret System
Authors: Heitler W. J. 
Published: April 2021

ABSTRACT
Intracellular and extracellular recordings have been made from neurones of the swimmeret system in the semi-isolated abdominal ganglion of the crayfish during rhythmic activity. Extracellular recordings commonly reveal a motor programme (MP1) consisting of low-amplitude symmetrical power and return stroke activity with phase-constant posterior-to-anterior intersegmental coordination. Occasionally a different motor programme (MP2) is expressed. MP2 has higher amplitude episodic activity, with return stroke duration greater than power stroke, and with latency-constant anterior-to-posterior or near synchronous intersegmental coordination. Preparations may switch spontaneously between the two motor programmes. Intracellular recordings show that interneurones whose membrane potentials oscillate during MP1 and which can reset its rhythm usually cease to oscillate during MP2. During production of MP1, current injected into any one of a small number of interneurones can induce MP2. The polarity of current required is usually such as to drive the membrane potential towards the level normally associated with return stroke during MP1. During MP1 many motor neurones receive synaptic input with approximately sinusoidal waveform. During MP2 they may receive an episodic input with approximately sawtooth waveform, and/or input consisting of large, unitary EPSPs. The unitary EPSPs drive a ‘bursty’ mode of MP2 activity that is sometimes seen. The bursts of unitary EPSPs in MP2 appear to derive from a different source to that of the sinusoidal input in MP1. These sources are probably caudally-conducting through-interneurones and non-spiking local interneurones respectively. Thus experimental perturbation of a single neurone can induce a motor programme switch such as to change the activity of some hundreds of neurones in at least three ganglia. Neurones with this property would be convenient targets for controlling influences in the intact animal.
Contractile and Metabolic Characteristics of Muscle Fibres From Antarctic Fish
Authors: Johnston Ian A. , Harrison Paul 
Published: April 2021

ABSTRACT
Contractile properties were determined for muscles from three species of Antarctic fish with broadly similar activity patterns: Trematomus hansoni, Notothenia rossii and Chaenocephalus aceratus. C. aceratus differs from the other species in that the genes for the respiratory pigments are not expressed.
Red and white fibres were isolated from the pectoral fin adductor and trunk muscles, respectively. Fibre segments were chemically skinned with the nonionic detergent Brij-58. All experiments were carried out at 0°C. Maximum isometric tensions (P0) were 6·6–7·1 Ncm−2 for red, and 21·4–25·1 N cm−2 for white muscle fibres. The force-velocity (P-V) characteristics of muscle fibres were determined by step isotonic releases. Unloaded contraction velocities (muscle lengthss−1, L0S−1) were 0·7 for red, and 0·9–1·1 for white fibres. Maximum mechanical power outputs (Wkg−1 muscle for white muscle), calculated using Hill’s equation for muscle shortening, were 26·7 (T. hansoni), 15·7 (A. rossii) and 22·7 (C. aceratus). Corresponding values for red pectoral muscle fibres were around 4·2Wkg−1 for all three species.
Maximum activities of enzymes of carbohydrate utilization (hexokinase, phosphofructokinase, lactate dehydrogenase), fatty acid metabolism (carnitine palmitoyl transferase, 3-OH acyl CoA dehydrogenase) and aerobic mitochondrial metabolism (cytochrome oxidase) were measured in muscle homogenates from C. aceratus and N. rossii at 0°C. Red pectoral muscle fibres from C. aceratus and N. rossii had similar activities of cytochrome oxidase, carnitine palmitoyltransferase and glycolytic enzymes. Hexokinase activities were two times higher in the red fibres of C. aceratus than N. rossii, suggesting a greater capacity for aerobic glucose utilization in the former species.
In spite of the lack of respiratory pigments, the metabolic and mechanical characteristics of the swimming muscles in C. aceratus apppear to be similar to those of other Notothenioids. Power outputs and enzyme activities of Antarctic fish muscle measured at 0 °C are comparable to those for temperate species measured at 15 or 25 °C, indicating a high degree of cold-adaptation of both energy-producing and energy-utilizing pathways.
The Ventilation Cycle in Octopus
Authors: Wells M. J. , Smith P. J. S. 
Published: April 2021

ABSTRACT
Pressure measurements made at various points inside the mantle show that the ventilatory stream of the resting animal is driven by very small (often less than 0·5 cmH2O) pressure differences. Inspiration occupies less than one-third of the total cycle time, while flow across the gills is evidently continuous, since there is always a pressure differential between the prebranchial and postbranchial parts of the mantle cavity. The fact that branchial heartbeats do not correlate with ventilatory movements is further evidence that water flow through to the gills is both steady and continuous.
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTIn 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

ABSTRACTThe 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

ABSTRACT
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

ABSTRACTNeuronal 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

ABSTRACTOptical 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

ABSTRACT
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.