bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non-Spiking Stretch-Receptors in the Crayfish Swimmeret System
Authors: Heitler W. J. 
Published: April 2021

ABSTRACT
Two neurones have been encountered with the properties of non-spiking stretch-receptors on both sides of each swimmeret-bearing segment of the crayfish Pacifastacus leniusculus. Each neurone depolarizes by up to 35 mV (measured intracellularly in the ganglionic neuropil) in response to experimentally imposed retraction of the appropriate swimmeret, but does not generate spikes. Depolarizing and hyperpolarizing current injected into these neurones can excite or inhibit the spike activity of several swimmeret motorneurones. Intracellular injection of dye shows that both non-spiking stretch-receptors have large diameter axons in the anterior branch of the first root and central cell bodies. One has a cell body in the anterior ipsilateral quadrant of the ganglion (NSSR-A), while the other has a cell body in the posterior ipsilateral quadrant (NSSR-P). Both neurones innervate a peripheral elastic strand which spans the base of the swimmeret, with its posterior attachment on the sternal rib at the posterior rim of the swimmeret socket, and its anterior attachment on the swimmeret basipodite. This strand (S1) is stretched by retraction of the swimmeret. A second strand (S2) stretches from the anterior rim of the swimmeret socket to the mid point of Si, and is innervated by several small diameter axons which also do not appear to have cell bodies in the periphery.
Drosophila Flight Motor Pattern: The Evidence from Interspike Intervals
Authors: Wyman Robert J. , Tanouye Mark A. 
Published: April 2021

ABSTRACT
In a variety of Diptera there are five motomeurones which innervate the wing depressor muscle (DLM) (Ikeda, Koenig & Tsuruhara, 1980; King & Wyman, 1980). During flight these motorneurones fire in a repeating cycle. Each motorneurone fires once per cycle. The firing times of the different motorneurones are separated so that no neurone fires immediately before or after any other (Wyman, 1965, 1969a, b). Wyman and co-workers have proposed that this spacing is due to mutual inhibition between the motorneurones (Wyman, 1969a, b;Harcombe & Wyman, 1977; Tanouye & Wyman, 1981). Koenig & Ikeda (1980) have now challenged this theory. They have presented data on the interspike intervals during flight that they believe do not fit the mutual inhibition hypothesis: they suggest that an ‘excitatory effect’ causes the spacing. The present communication argues that the two sets of data are consistent with each other and with the mutual inhibition theory.
A Comparison of Two Methods for Measurement of O2 Content of Small (20 μl) Samples of Fish Blood
Authors: Hughes G. M. , Belaud A. , Peyraud C. , Adcock P. J. 
Published: April 2021

ABSTRACT
Measurements of the oxygen content of blood have been carried out for many years using a variety of methods many of which may be described as volumetric methods, e.g. Van Slyke and Natelson. In recent years methods applicable to small samples (10–20 μl blood) have been developed especially in relation to studies of comparative physiology. Volumetric methods depend upon the release of oxygen chemically bound with haemoglobin, which is frequently achieved by treatment with ferricyanide. With the release of oxygen the resulting increase in can be measured. If the volume is known then the quantity of oxygen released can be estimated. Methods using this principle have been developed by a number of authors including Fabel & Liibbers (1964) and a method using a small cuvette has been described by Tucker (1967).
Scanning Eye Movements in A Heteropod Mollusc
Authors: Land M. F. 
Published: April 2021

ABSTRACT
The eyes of the heteropod molluscs are unusually large and complex, compared with those of other gastropods (Hesse, 1900). They have a basic design not unlike fish eyes, with a large spherical lens of short focal length that forms an image on a retina of highly ciliated photoreceptors (Dilly, 1969). Perhaps the strangest feature of the eyes is the shape of the retina. It is not a hemispherical cup as in fish, cephalopods and alciopid worms, but a long narrow ribbon only a few receptors wide (6 in Pterotrachea coronata, only 3 in Oxygyrus). The ribbon is several hundred receptors long and in some species it is straight whilst in others it is curved into a horseshoe configuration. In either case this means that the field of view of the eye is a narrow strip of space a few degrees high and 80–180° long. Most of the surroundings are therefore not seen by the animal at any given time. In this paper I show that the problem of the narrow field of view is solved in one heteropod species at least by systematic scanning movements of the eyes, in which each retina ‘sweeps’ through a 90° arc.
A Simple Method for Studying the Innervation of A Complex Muscle
Authors: Theophilidis G. 
Published: April 2021

ABSTRACT
The innervation of an insect muscle can be studied by correlating the evoked spikes in neuronal cell bodies with extracellular or intracellularly recorded events in various parts of the muscle (Burrows & Hoyle, 1973; Hoyle & Burrows, 1973 ; Phillips, 1980). However, when a muscle is innervated by a large number of neurones, difficulties may occur: first, in the reliable identification of the neurones (especially when their cell bodies are closely clustered) and secondly, in maintaining stable records from the cell bodies for a sufficient period of time to permit reliable investigation of the muscle.
On the Indentation Hardness of Insect Cuticle
Authors: Hillerton J. E. , Reynolds S. E. , Vincent J. F. V. 
Published: April 2021

ABSTRACT
The indentation hardness of locust cuticle was measured using a Vickers diamond applied to the surface of the cuticle. A number of areas of cuticle showed similar hardness values, approximately 24 kg mm−2, for the dehydrated cuticle but the mandibles (29·8 kg mm−2) and the dorsal mesothorax (33·3 kg mm−2) were harder. The mandibles have localized areas of hardness which are related to their function. It is suggested that the hardness of the dorsal thorax may be related to its function as an energy storing structure in flight. The measured hardness of cuticle depends on the hydration of the material but relative differences between cuticles from different parts of the locust persist whether tested fresh or after dehydration. Hardness is correlated with the dihydroxyphenol content of cuticle (unlike stiffness), conversely it is not correlated with the hydrophobicity of the matrix proteins (unlike stiffness). It is emphasized that hardness and stiffness are very different mechanical properties.
Inhibitors of protein synthesis on 80S ribosomes phase shift theGonyaulaxclock
Authors: Taylor Walter R. , Dunlap Jay C. , Hastings J. W. 
Published: April 2021

ABSTRACTOne-hour pulses of anisomycin (0· 3 μM), streptimidone (30 μM) and cycloheximide (5 μM) caused strong phase-shifts (either advances or delays, of up to 12 h) in the circadian rhythm of the bioluminescence glow in the marine photosynthetic dinoflagellate, Gonyaulax polyedra. Similar pulses of emetine (0·1–100 μM) caused small ( &lt; 4 h) phase shifts. Drug pulses have quantitatively different effects when applied at different phases of the circadian cycle, thus giving rise to ‘phase response curves’ (PRC’s). The results lend additional support to the generalization, based on results from several different organisms, that 80s ribosome protein synthesizing system is of key importance in the mechanism responsible for circadian rhythms.
Hypoxic Vasoconstriction and the Effects of Adrenaline on Gas Exchange Efficiency In Fish Gills
Authors: Pettersson Knut , Johansen Kjell 
Published: April 2021

ABSTRACTA gill perfusion technique allowing control of flow and in the ventral aorta and in the irrigating water is described. The procedure includes measurements of flow and in the dorsal aorta and the inferior jugular vein. Pressure recordings were made in the ventral and dorsal aortas.Lowering the perfusion fluid and/or the irrigating water increased the branchial vascular resistance, without altering flow distribution. This response is probably released by vasoconstriction proximal to the arteriovenous anastomoses in the gill filaments.Adrenaline acted on receptors both proximal and distal to the arteriovenous anastomoses: branchial vascular resistance decreased, dorsal aortic flow increased and oxygenation of the perfusion fluid increased.It is suggested that a combination of a direct myogenic response to hypoxia and release of adrenaline serve to increase O2 uptake efficiency when fish are exposed to hypoxic stress.
The Respiration ofCancer PagurusUnder Normoxic and Hypoxic Conditions
Authors: Bradford S. M. , Taylor A. C. 
Published: April 2021

ABSTRACTThe respiration of Cancer pagurus under normoxic conditions and its respiratory responses to hypoxia are described. Respiration of quiescent crabs is characterized by a rhythmic pattern of ventilation and cardiac activity in which periods of apnoea and bradycardia of approximately 5 min duration alternate with longer periods of active ventilation and cardiac activity. The significance of this rhythmic ventilatory behaviour is discussed and evidence is presented to account for this behaviour in terms of allowing energy savings to be made during periods of inactivity. During a ventilatory pause the of the post-branchial blood falls from its normal level of 94 + 5 torr to only 24 ± 3 torr. The blood of Cancer provides a store of oxygen which is used during pausing to maintain aerobic metabolism. Anaerobic metabolism does not appear to contribute significantly to energy production during these periods since no increase in the blood lactate concentration was recorded.Cancer haemocyanin has a high oxygen affinity (P50 = 5–10 torr) and exhibits a large, positive Bohr shift (Δ log P50/pH = – 1·18). However, under normal conditions the pigment has only a minor role in supplying oxygen to the tissues, since over 91 % is carried in solution.Cancer pagurus exhibits quite a high degree of respiratory independence and is able to maintain its rate of oxygen consumption approximately constant over a wide range of ambient oxygen tension, down to a of 60–80 torr, below which it declines. Similarly there was little change in heart rate during hypoxia until a of 20–40 torr was reached below which it also declined sharply. Oxygen consumption during hypoxia was maintained primarily as a result of an increase in ventilation volume and oxygen extraction. During hypoxia the of both the pre- and post-branchial blood declined and resulted in a reduction in the gradient across the respiratory surface . Oxygen uptake during hypoxia was facilitated, however, by an increase in the transfer factor .
The respiratory responses of the fowl to hot climates
Authors: Kassim H. , Sykes A. H. 
Published: April 2021

ABSTRACTRespiratory rate (f) and tidal volume (VT) have been measured at normal and at warm ambient temperatures (Ta) in adult domestic fowl by means of a whole body plethysmograph. Resting values of f = 23 ± 9 min−1 and of VT = 25·6 ± 0·9 ml min−1 were found. At Ta 30, 35 or 40 °C f increased in direct relation to the severity of the heat stress reaching a maximum value of 273 ±12 min−1; VT fell uniformly in all three climates to a minimum of 9·0 ± 0·5 ml. Total ventilation showed a linear relation with f during first-phase panting. Second-phase panting occurred only at Ta 40 °C ; K increased at first but subsequently fell as the decline in f became more pronounced.
The effect of changes in blood oxygen-carrying capacity on ventilation volume in the rainbow trout (Salmo gairdneri)
Authors: Smith Frank M. , Jones David R. 
Published: April 2021

ABSTRACT
Changes in ventilation volume of rainbow trout caused by hypercapnia, hypoxia and anaemia were measured directly by collection of expired water. Exposure to hypercapnic water ( range 0·5–2 kPa) increased (by up to four times) by augmenting ventilatory stroke volume; breathing frequency remained constant. O2 added to the inspired water in maintained hypercapnia reduced at all but the highest level of . increased when blood oxygen content was decreased by exposure to normoxic hypercapnia, but addition of O2 to the water increased blood oxygen content and decreased. When blood oxygen-carrying capacity was depressed by hypoxia or anaemia, increased as it did during normoxic hypercapnia. We suggest that ventilatory responses to low levels of hypercapnia, to hyperoxic hypercapnia, to hypoxia, and to anaemia in trout are related to changes in levels of blood oxygen content under these conditions.
Relationship between muscle force and muscle area showing glycogen loss during locomotion
Authors: Armstrong R. B. , Taylor C. R. 
Published: April 2021

ABSTRACTThis experiment was designed to study the relationship between the crosssectional area of rat skeletal muscle showing glycogen loss and the muscle forces exerted during exercise. Muscular force exerted by the extensors of the elbows and ankle was increased by 24 % by loading rats with 24 % of their body mass while running them on a treadmill at 30 m. min−1. increased by 24 % and stride frequency was unchanged when the rats ran with loads. Cross-sectional areas of the elbow and ankle extensor muscles showing glycogen loss were compared from rats running with and without the load. We found a nearly direct proportionality between the changes in force and the changes in muscle area showing glycogen loss, i.e. when the force of the extensors was increased by 24%, the cross-sectional area of the elbow extensors showing glycogen loss increased by 28%, and that of the ankle extensor group increased by 24%. The more peripheral muscles in each group accounted for a greater proportion of the increase in cross-sectional area of the group showing glycogen loss (i.e. lateral and long heads of triceps brachii muscle accounted for 91 % of the increase in the elbow extensor group, and gastrocnemius muscle accounted for 84 % of the increase in the ankle extensor group). Most of the increases in muscle area showing glycogen loss occurred in fast-twitch-glycolytic fibres (84% in the elbow and 88 % in the ankle). The data suggest that increasing muscle force requirements by 24 % by loading resulted in proportional increases in cross-sectional area of muscles recruited to produce the force, i.e. that spatial recruitment primarily accounted for the elevation in force. The relatively greater increases in cross sectional area showing glycogen loss of peripheral muscles within a group indicate the importance of studying whole groups of muscles when considering muscular recruitment patterns during exercise.
Morphology of identified cercal afferents and giant interneurones in the hatchling cockroachPeriplaneta americana
Authors: Blagburn J. M. , Beadle D. J. 
Published: April 2021

ABSTRACTCobalt backfills from the thoracic connectives of the hatchling Periplaneta americana allowed identification of giant interneurones in the terminal abdominal ganglion, morphologically comparable to GI 1, 2 and 3 in the adult. The bipolar neurone innervating each cereal filiform wind receptor ‘hair is ultrastructurally similar to the adult cell and possesses an individually identifiable afferent axon, four of which provide the behaviourally functional escape response system with a simplified sensory input. Both pre-and post-synaptic neurones can be identified and may provide a good preparation for the study of cholinergic synapses.
Tail Thrust of BluefishPomatomus SaltatrixAt Different Buoyancies, Speeds, and Swimming Angles
Authors: Ogilvy Christopher S. , DuBois Arthur B. 
Published: April 2021

ABSTRACTThe tail thrust of bluefish Pomatomus saltatrix was measured using a body accelerometer at different water speeds, buoyancies, and angles of water flow to determine the contribution of tail thrust in overcoming parasitic drag, induced drag, and weight directed along the track. The lengths and weights of the fish averaged 0·52 m and 1·50 kg respectively. The tail thrust overcoming parasitic drag in Newtons, as measured during neutral buoyancy, was: 0·51 × speed+ 0·15, with a standard error of estimate of 0·09 N. When buoyancy was altered by the introduction or removal of air from a balloon implanted in the swim bladder, the tail thrust was altered by an amount of the same order as the value calculated for the induced drag of the pectoral fins. The component of weight directed backward along the track was the weight in water multiplied by the sine of the angle of the swimming tunnel relative to horizontal. When this force was added to the calculated induced drag and tail thrust measured at neutral buoyancy, the rearward force equal to the tail thrust, at 45 ml negative buoyancy, 0·5 m s−1, and 15°head up, was 0·12 N due to weight+ 0·05 N due to induced drag+ 0·40 N due to parasitic drag = 0·57 N total rearward force. The conditions required for gliding were not achieved in our bluefish because the drag exceeded the component of the weight in water directed forward along the track at speeds above the stalling speed of the pectoral fins.
Lability of Conduction Velocity During Repetitive Activation of an Excitable Epithelium
Authors: Schwab Walter E. , Josephson Robert K. 
Published: April 2021

ABSTRACT
Conduction velocity lability was studied in the electrically excitable epithelium of Euphysa japonica by means of intracellular recordings. Three classes of response latency change were identified in response to bursts of stimuli: an initial jump, uniform drift and abrupt jumps in latency. In each case an increase in stimulus frequency produced an increase in latency. The initial jump in latency, which occurred between the first and second response of a series, was related to the afterpotential of the first response. The increased latency of the second response appears to result from the drop in membrane resistance during the hyperpolarizing afterpotential. The uniform drift in latency remains unexplained but may be the result of ion accumulation within the tissue, progressive inactivation of the ionic channels involved in producing the action potential, or junctional phenomena. The abrupt jumps in latency, which often preceded failure to respond, were found to be impulse initiation phenomena.
Oxygenation and Deoxygenation Kinetics of Red Cells In Isolated Lamellae of Fish Gills
Authors: Hills B. A. , Hughes G. M. , Koyama T. 
Published: April 2021

ABSTRACT
The kinetics of oxygen transfer across the water-blood barrier in fish gills were studied by measuring oxygenation and deoxygenation of single red blood cells contained within isolated secondary lamellae using a microphotometric technique. Recordings of the overall time courses show that both oxygenation and deoxygenation are more rapid in the carp than in the eel. In both species the half-time for deoxygenation is about five times slower than for oxygenation. It is shown that the resistances to oxygenation and deoxygenation are identical ; the differences in the shapes of the O2v. time curves recorded being attributable to the influence of the HbO2 dissociation curve upon the driving force for diffusion. It is concluded that a diffusional as opposed to a chemical reaction resistance provides the main barrier to oxygen transfer in gill secondary lamellae.
Chemosensitivity of Walking Legs of the LobsterHomarus Americanus:Neurophysiological Response Spectrum and Thresholds
Authors: Derby Charles D. , Atema Jelle 
Published: April 2021

ABSTRACTResponses of chemoreceptors in the walking legs of the lobster Homarus americanus to 35 individual compounds and 3 mixtures (prey odours and extracts) were studied using extracellular recording techniques. Compared against a standard mussel (Mytilus edulis) extract, these receptors were most sensitive to the amino acids L-glutamate, hydroxy-L-proline, L-aspartate, L-arginine, glycine, taurine, and L-alanine, as well as such other compounds as ammonium chloride, betaine, and the tripeptide glutathione. Most of these excitants are among those compounds most prevalent in the prey of lobsters. Some proteins and odours from live prey were also effective stimuli. In general, carbohydrates, alcohols, nucleosides, and nucleotides were only slightly excitatory. The lowest thresholds for 10 compounds ranged from 3·5×10−6 to 3·5 × 10−14M; these thresholds are lower than previously reported for crustacean taste receptors.
The Effects of Axotomy Upon the Extrasynaptic Acetylcholine Sensitivity of An Identified Motoneurone in The Cockroach Periplaneta Americana
Authors: David J. A. , Pitman R. M. 
Published: April 2021

ABSTRACT
The effects of axotomy on the sensitivity of the fast coxal depressor motoneurone (Df) of the cockroach (Periplaneta americana) to applied acetylcholine (ACh) and carbamylcholine (CCh) have been investigated.
ACh and CCh applied to the soma membrane either by bath perfusion or by ionophoresis caused depolarization; repeated application of large doses of these agonists resulted in a relatively rapid desensitization and depression of the response.
Axotomy performed 3-10 days before recordings were made caused an approximately threefold increase in the sensitivity to ACh but had no affect upon the sensitivity to CCh. The resting potential, input resistance and membrane time-constant remained within the normal range. In addition there was no change in the rise-times of the responses or of the ACh reversal potential, or in the apparent number of ACh molecules needed to combine with individual cholinoceptors to produce a response.
The anticholinesterases physostigmine and neostigmine potentiated the ACh response at relatively low concentrations (10−7 M-10−8 M). This potentiation was significantly greater in the normal cells than in the axotomized cells. It is therefore concluded that the increase in ACh sensitivity of this motoneurone results at least partly from a fall in the activity of choline esterase in the region of the applied drug.
Unstirred Mucus Layers: Ion Exchange Properties and Effect on Ion Regulation in Lymnaea Stagnalis
Authors: Schlichter L. C. 
Published: April 2021

ABSTRACT
Mucus from the footsole of the freshwater snail Lymnaea stagnate behaves as a weak, negatively charged ion exchanger. Activities and concentrations of Na, K, Ca, and Cl were measured in mucus dialysed to equilibrium against artificial pond water or physiological saline. Observed activity coefficients (activity/concentration) in mucus were compared with those predicted by the Debye-Huckel theory to interpret the effects of electrostatic forces between the polyelectrolyte ions and small ions. The affinity of mucus for small ions decreased in the series, Ca2+, K+, Na+, Cl−.
The extent to which mucus can concentrate cations was measured using three different methods: by titrating the fixed acidic groups with K or Ca and by equilibrium dialysis after which the electrical potential difference was either measured directly or was calculated from the Nernst potential for Na. Ion exchange titration indicated a much smaller exchange capacity than did the other two methods.
Kinetics of cation uptake by the snail from dilute media were re-interpreted by considering the enhanced concentrations of cations in the mucus layer. It was shown that the presence of mucus in the unstirred layer adjacent to a transporting epithelium can result in an underestimate of the Michaelis constant (Km) determined from influx measurements.
Transport of Sodium and Potassium Across the Isolated Midgut of the Larvae of Tenebrio Molitor Related to the Fine Structure of the Epithelium
Authors: Koefoed Bodil M. , Zerahn Karl 
Published: April 2021

ABSTRACT
For meal-worms, which are able to survive under extremely dry living conditions, the normal situation is that the K+ concentration of the haemolymph regulates the process of water conservation via the rectal complex (Grimstone, Mullinger & Ramsay, 1968; Koefoed, 1975). The aim of this paper has been to study the handling of sodium and potassium by the midgut epithelium of the larva of Tenebrio molitor and to discover if the transport of these ions is reflected in the structure of the epithelium.