bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanics of Escape Responses in Crayfish (Orconectes Virilis)
Authors: Webb P. W.
Published: April 2021

Measurements of acceleration performance of crayfish (mean mass 0·018 kg) were made during lateral giant mediated tail flips (LG tail flips) and truncated tail flips at 15°C. The LG tail flip power stroke was composed of a lift-off phase, when crayfish accelerated vertically from the substrate, and a free swimming phase. The total duration of the power stroke was 44 ms, followed by a recovery stroke lasting 173 ms. Truncated tail flips were used in acceleration and swimming by crayfish free of the substrate. Power strokes had a mean duration of 36 ms, and recovery strokes 92 ms. Net velocities, acceleration rates, and distances travelled by the centre of mass were similar for both types of tail flips. Thrust was generated almost entirely by the uropods and telson. Velocities and angles of orientation to the horizontal of abdominal segments were similar for both types of tail flip. Angles of attack were large, varying from 30° to 90°. Pressure (drag) forces were considered negligible compared to inertial forces associated with the acceleration of added water mass. Thrust forces, energy and power were determined for exemplary tail flips. Thrust was 0·92 and 0·42 N for LG tail flip lift-off and swimming phases respectively, and 0·29 N for the swimming truncated tail flip. Rates of working were 0·39, 0·19, and 0·18 W respectively. The efficiency of converting muscle power to backward motion was estimated to be 0·5 for power strokes and o-68 for complete swimming cycles. Comparisons with fish performance suggested fish would be less efficient (0·1–0·2). The low efficiency is attributed to energy lost in lateral recoil movements.
Changes in Heart Rate and Respiratory Frequency During Natural Behaviour of Ducks, With Particular Reference to Diving
Authors: Butler P. J. , Woakes A. J.
Published: April 2021

Heart rate and respiratory frequency were recorded from free-range pochards and tufted ducks by using an implantable radio-transmitter. Particular attention was paid to the changes associated with natural diving behaviour which occurred on an outside pond (4 × 8 × 0·65 m depth). Spontaneous dives, which occurred in the absence of any obvious external stimuli, often occurred in a series and there could be in excess of 40 dives in fairly quick succession. The first dive in a series was heralded by tachycardia and tachypnoea. Upon submersion there was transient bradycardia, but heart rate then increased over a period of 6– 8 s until it was close to the value recorded when the bird was swimming on the pond before the dive. This rate was maintained throughout the dive. Upon surfacing, heart rate increased when lung ventilation commenced, and then decreased steadily until a few seconds before the next dive when it increased. The average duration of all spontaneous dives of a series was 8·4 ± 0·2 (137) s for pochards and 9·9 ± 0·8 (95) s for tufted ducks. The birds also dived in response to food being thrown onto the water (feeding dives). Changes in heart rate associated with these dives were similar to those described for the spontaneous dives. Heart rate did, however, tend to be higher during all stages of the feeding dives, and it often increased at the end of a dive before the bird started to ventilate its lungs. When being chased with a net, the birds had extremely high values of heart rate and respiratory frequency. Immediately they dived to escape, heart rate fell to a rate which was similar to the rate recorded when the unstressed birds were swimming. This rate was maintained throughout the dive. Anticipatory increases in heart rate preceded lung ventilation at the end of the dives. The birds showed a progressive reduction in heart rate when their heads were submerged under water in the laboratory. After 10 s submersion, heart rate was lower than the lowest heart rate recorded during any of the free-range dives.
The functional morphology and motor innervation of the buccal mass of Tritonia Hombergi
Authors: Bulloch A. G. M. , Dorsett D. A.
Published: April 2021

The anatomy of the buccal mass and the function of nine principal muscle groups involved in the feeding movements, are described for the mollusc Tritonia hombergi. Anatomical and physiological studies on some 40 neurones along the posterior border of the buccal ganglia indicates that many are primary motoneurones to the muscles of the buccal mass. The feeding cycle may be divided into three phases of muscle activity termed Protraction, Retraction and Flattening, which are correlated with the patterned bursting observed in P, R and F motoneurone groups within the motoneurone population. A fourth group of motoneurones are thought to innervate muscles to the outer lips which are active during protraction. The patterned output of impulses in the buccal nerves during feeding cycles confirms that the motor control of the muscle groups may be explained in terms of the sequential activation of the P, R and F cells.
Regional differentiation of neuromuscular synapses in a lobster receptor muscle
Authors: Meiss Dennis E. , Govind C. K.
Published: April 2021

Properties of the synapses and muscle fibres of the distal accessory flexor muscle (DAFM) were examined in the first and second walking legs of the lobster, Homarus americanus. Stimulation of the single excitor axon produces large amplitude, poorly facilitating excitatory postsynaptic potentials (EPSPs) in the distally located fibres and small amplitude, highly facilitating EPSPs in the proximally located fibres. The input resistances (Rin) of the muscle fibres were correlated with EPSP properties such that small ampli­tude, highly facilitating EPSPs occurred in fibres with low Rin and large amplitude, poorly facilitating EPSPs occurred in fibres with higher All muscle fibres were similar for other membrane electrical properties. Re­gression analyses however show a minor contribution of Rin to the size of intracellularly recorded synaptic potentials and to their facilitation properties. Thus, differences in muscle membrane properties cannot explain the observed diversity in EPSPs. Instead EPSP diversity is based on differences in transmitter output at single synaptic foci: highly facilitating synapses with low quantal release occur only on proximally located muscle fibres and poorly facilitating synapses with high release occur only on distally located ones. Thus, the EPSP diversity from the single excitor axon to the lobster DAFM is largely presynaptic in origin.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Needham Joseph , Smith Michael
Published: April 2021

Nothing can be more characteristic of the physical basis of life than the separation by membranes of phases differing greatly in their constitution and concentration both of organic and inorganic compounds. The prominent part played by membrane phenomena in general physiology is therefore not surprising.
Mn2+ Ions Pass Through Ca2+ Channels in Myoepithelial Cells
Authors: Anderson M.
Published: April 2021

Intracellular recordings were made from the myoepithelial cells of the proventriculus of the marine polychaete worm Syllis spongiphila. Over-shooting responses were elicited either by carbamylcholine added to the bathing medium or by directly applied intracellular current pulses. In control artificial sea water (ASW) directly applied current pulses elicited regenerative responses of 68-119 mV in amplitude and 70-1800 ms in duration; these responses were associated with contractions of the myoepithelial cells. Both pharmacologically and electrically elicited responses were reversibly abolished in Ca-free ASW and were unaffected by TTX or low- sodium solutions. Regenerative responses were elicited by direct intracellular stimulation in calcium-free ASW containing ImmM-Ba2+ or 10 mM-Sr2+. Directly elicited responses were blocked reversibly in ASW containing calcium and 15-20 mM-Co2+ or 2·5-10 mM-Ni2+; they were blocked irre- versibly in ASW containing calcium and 10 mM-Las+ or 100/μM-Zn2+. Regenerative responses were elicited in Ca-free solutions containing 10-50 mM-Mn24; these responses were not associated with contractions, were consistently of longer duration than responses elicited in control ASW, and were blocked by 20 mM-Co2+ or 10 mM-La3+. The overshoots of Mn2+ responses elicited in both Na-free and Na-containing, Ca-free solutions increased as the external concentration of Mn2+ was increased, with a slope of about 27 mV per 10-fold change in concentration of Mn2+. In Ca- containing solutions the slope was reduced to about 15 mV per 10-fold change. The results indicate that the myoepithelial cells generate Ca-spikes and that Mn2+ ions, in addition to Sr24+ and Ba2+ ions, pass through the Ca2+ channels of the myoepithelial cell membranes. Although Mn24+ can replace Ca2+ in generating spikes, it apparently cannot replace Ca2+ in initiating contraction, and it many compete with Ca2+ in activating repolarization of the cell.
Acid-Base Relationships in the Blood of the Toad, Bufo Marinus
Authors: Boutilier R. G. , Randall D. J. , Shelton G. , Toews D. P.
Published: April 2021

When Bufo marinus burrows, the skin becomes intimately surrounded by substrate but the nares always remain exposed to the surface air. Upon entering into a state of dormancy the animal hypoventilates and this together with the loss of the skin as a respiratory site results in a rise in arterial blood despite a probable decline in metabolism. Even though lung ventilation falls, the toad regulates blood pH and the respiratory acidosis is progressively compensated for by a progressive increase in plasma [HCO3−] along the course of an elevated isopleth. At steady state, the acidosis is fully compensated for by a new equilibrium ratio of HCO3−to at the same pH as the non-burrowed animal. Arousal from the dormant state at this time results in a marked lung hyperventilation and a sharp decline in body CO2 stores;
The Development of Interlimb Co-Ordination During Swimming in Postnatal Rats
Authors: Bekoff Anne , Trainer William
Published: April 2021

The postnatal ontogeny of interlimb co-ordination was studied in rats from day 1 after birth to day 22. Swimming rather than walking was studied in order to minimize any effect of weak limb muscles in very young rats. Videotape records of swimming were analysed on a frame-by-frame basis to determine stroke cycle duration for individual limbs and interlimb latency and phase relationships.

Interlimb co-ordination typical of swimming (or trotting) in adult quadrupedal vertebrates was already present on postnatal day 1, and so apparently the neural pattern generating circuitry for this behaviour is already established by this stage. In young rats it was possible to see 1 limb, or almost any combination of 2, 3 or 4 limbs, moving during swimming, and usually with proper phase relationships. This suggests that each limb has its own separate neural pattern generator and that there are effective interlimb co-ordinating mechanisms controlling moving limbs during swimming, even at very early stages.

There was a gradual decrease in stroke cycle duration (increase in frequency) during the first two postnatal weeks. This may be due to maturing sensory input.
The Ventilation, Extraction and Uptake of Oxygen in Undisturbed Flounders, Platichthys Flesus: Responses to Hypoxia Acclimation
Authors: Kerstens A. , Lomholt J. P. , Johansen K.
Published: April 2021

Gill ventilation , extraction of O2 from the ventilatory current and O2-uptake were measured in three groups of undisturbed flounders naturally buried in sand. Two groups were acclimated to normoxic water . One was studied in normoxic water, the other during acute exposure to hypoxic water (P1, O2 = 30 mmHg). A third group was acclimated to and studied in hypoxic water. Gill ventilation was measured directly using an electromagnetic flowmeter. The flowprobe, fitted to a plastic funnel, was placed over the fish’s mouth without making physical contact with the fish. Exhaled water for calculation of O2-extraction was siphoned from another plastic funnel placed over the upper operculum of the flounder. Acute hypoxia exposure of normoxic fish caused nearly a doubling in ventilation volume. In flounders acclimated to chronic hypoxia and studied in hypoxic water the ventilation volume reached a value approximately 3-5 times that of normoxic fish. O2-extraction averaged 76% in normoxic flounders. During acute hypoxia the value declined to 52%, the same O2-extraction was obtained in the chronically hypoxic fish. for the normoxia acclimated fish in normoxic water was 0 · 45 ml O2 · kg −1 .min − 1 declining to 0-12ml O2.kg − 1.min − 1 during acute exposure to hypoxia. of hypoxia acclimated fish in hypoxic water was 0 · 24 ml O2. kg − 1. min − 1. When compared in hypoxic water, the hypoxia acclimated fish show an unchanged O2-extraction of 52% in spite of a nearly two-fold increase in ventilation relative to that of the normoxia acclimated fish. Possible causes for this may be a left shift of the O2-Hb dissociation curves and an increase in the transfer factor for O2 over the gills in the hypoxia acclimated fish.
Salt and Water Balance in Rainbow Trout (Salmo Gairdneri) Rapidly Transferred from Fresh Water to Sea Water
Authors: Bath R. N. , Eddy F. B.
Published: April 2021

Physiological responses of rainbow trout (mean weight 13·3 g) to sudden changes in salinity were investigated. An initial period lasting about 8 h was characterized by increased drinking and an increase in plasma and body ions. Fish failed to survive more than 2 days in full strength sea water but in two-thirds sea water there were few mortalities and adaptation was complete in 7–10 days. During this period there were gradual physiological changes resulting in normal plasma ion concentrations but significantly increased body ionic content. The intracellular concentrations of muscle chloride showed the greatest increase.
The Variable Effects of Ambient and Artificial Light:Dark Cycles On Embryonic Diapause in A Laboratory Population of the Annual Fish Nothobranchius Guentheri
Authors: Markofsky Jules , Matias J. R. , Inglima K. , Vogelman J. H. , Orentreich N.
Published: April 2021

The effects of light:dark cycles (L;D) on embryonic development in a laboratory population of the East African annual fish Nothobranchius guentheri were studied. Under ambient light conditions (40° N) there was a low frequency of embryos entering diapause between June and October. Beginning in November there was an increasing frequency of diapausing embryos with a peak in December, and a lower frequency by February. Under artificial light conditions there was an increasing frequency of diapausing embryos as the L:D changed from 16:8 to 9:15. When individual fish or groups of fish were followed it was found that, even under the same light conditions, variable frequencies of diapausing and non-diapausing embryos were produced and that the frequencies often changed with time. The L: D cycle under which the embryos were incubated had no effect on diapause. As in some species of insects the ‘diapause factor’ was of maternal origin. The ability of the fish to produce both diapausing and non-diapausing embryos under the same and variable L : D is most likely an adaptive trait related to the survival of the fish in the harsh environments of alternating rainy and dry seasons.
Timing of the Action of Photoperiod and Temperature On Events Leading to Diapause and Development in Pupae of Heliothis Punctigera (Lepidoptera: Noctuidae)
Authors: Browning T. O.
Published: April 2021

Diapause in H. punctigera occurs in the pupa at some stage between pupation and the pupal-adult apolysis. Its occurrence is induced by 12 L: 12 D photoperiod, which is specifically effective during the last half of larval life, and by low temperature (19 °C). Irrespective of the conditions during larval life, the insects do not diapause if subjected to high temperature (28 °C) after feeding ceases and before the pupal ecdysis. The insects are most sensitive to high temperature during the short perioid between the larval-pupal apolysis and pupal ecdysis. At both 28° and 19 °C the brain and thoracic glands secrete almost simultaneously to trigger the larval-pupal apolysis, which occurs almost immediately after the release of the hormones. High temperature during the prepupal period results in an increased rate of development from pupal ecdysis to emergence of the adult.
Pharmacological Properties of Axonal Sodium Channels in the Cockroach Periplaneta Americana L.
Authors: Pelhate M. , Hue B. , Sattelle D. B.
Published: April 2021

Condylactis toxin induces a prolonged falling phase in action potentials recorded from giant axons of the cockroach Periplaneta americana L. A distinct plateau potential can be recorded in the presence of Condylactis toxin at concentrations of 0·5 mg/ml and above. In cockroach axons, voltageclamp experiments show that Condylactis toxin acts primarily by slowing the sodium current turn-off without affecting either the time-course of the sodium conductance increase or the peak amplitude of the transient sodium current.
The Role of Vortices and Unsteady Effects During the Hovering Flight of Dragonflies
Authors: Savage Stuart B. , Newman Barry G. , Wong Denis T.-M.
Published: April 2021

Weis-Fogh and Norberg concluded that steady-state aerodynamics is incapable of explaining how the dragonfly supports its weight during hovering. Norberg also concluded that the wing kinematics of Aeschna juncea L., as determined photographically, are incompatible with those proposed by Weis-Fogh for his Flip mechanism. The present paper has proposed an alternative lift-generating mechanism, various aspects of which are novel from the standpoint of animal flight. Flow visualization tests performed in water established the flow field during a complete cycle of the idealized wing motion. Using this information and unsteady inviscid flow theory the forces were analysed. A plausible balance of horizontal forces and more than sufficient lift were obtained. A physical explanation of the theory is provided for those who do not wish to study the mathematical details.
Electrical Properties of Insect Neurones with Spiking and Non-Spiking Somata: Normal, Axotomized, and Colchicine-Treated Neurones
Authors: Goodman Corey S. , Heitler W. J.
Published: April 2021

The paired motorneurones in the metathoracic ganglion of the locust have non-spiking somata whereas the dorsal unpaired media (DUM) neurones have spiking somata. We have studied the electrical properties of two identified neurones in the metathoracic ganglion that have spiking axons innervating the same muscle: the fast extensor tibiae (FETi) motomeurone has a non-spiking soma and the dorsal unpaired median extensor tibiae (DUMETi) neurone has a spiking soma. The inward current of the peripheral axon spikes of both DUMETi and FETi is carried predominantly by Na+, since the spikes are blocked only by removal of Na+ or addition of tetrodotoxin (TTX). The inward current of the soma spike of DUMETi is carried by Na+ and Ca2+, since it is blocked by either removal of Na+, addition of TTX, or addition of Co2+. The non-spiking soma of FETi shows delayed rectification. When some of the outward K+ current is blocked by TEA or 3-AP, the soma is capable of generating overshooting action potentials. The inward current of the TEA-induced soma spike of FETi is carried by Na+ and Ca2+, since it is blocked by either removal of Na+, addition of TTX or addition of Co2+. Axotomy or treatment with colchicine converts the non-spiking soma of FETi into a spiking soma within 4 days. The inward current of the soma spike is carried predominantly by Na+, since it is blocked only by removal of Na+. Five days after axotomy of one of the peripheral axons of DUMETi, Na+ is sufficient for the generation of the soma spike. Increased excitability is also observed in the neuropil of DUMETi after axotomy. When some of the outward K+ current is blocked by Ba2+, the normal and axotomized somata of FETi and DUMETi are all capable of generating long duration Ba2+ action potentials that are blocked by addition of Co2+. The overshooting Ba2+ action potentials in all cases are similar in amplitude and duration. It is concluded that the soma membrane of DUMETi and FETi normally contains both Na+ and Ca2+ inward current channels. The normal difference in excitability between these two somata may result in part or entirely from differences in the outward K+ current. It is suggested that axotomy or colchicine treatment cause an increase in the number of active Na+ channels in the soma membrane, which overcomes any differences in the outward K+ current and results in both cells being able to produce soma spikes.
Comparison of Slow Larval and Fast Adult Muscle Innervated by the Same Motor Neurone
Authors: Rheuben M. B. , Kammer A. E.
Published: April 2021

Muscles innervated by an identified set of motor neurones were compared between larval and adult stages. The structure of the larval muscle is typically tonic: long sarcomeres, irregular Z-bands, and 10–12 thin filaments around each thick filament. The structure of the adult muscle is phasic : 3–4 μm sarcomeres, regular Z-bands, 6–8 thin filaments around each thick filament, and large mitochondrial volume. The tensions produced by these muscles were correspondingly different. The larval twitch was about 7 times slower and the tetanus/twitch ratio 10 times greater than those of the adult. No structural or physiological differences were observed in the neuromuscular junctions of the two stages. The relatively unchanging functional relationship of a single motor neurone with two different muscle fibre types during two developmental stages is compared with the converse situation in which it has been reported that implantation of a different type of motor nerve into a muscle modifies contractile properties.
Ionic and Osmotic Influences on Prostaglandin Release from the Gill Tissue of A Marine Bivalve, Modiolus Demissus
Authors: Freas William , Grollman Sigmund
Published: April 2021

Prostaglandin E2 (PGE2) was identified in Modiolus demissus gill tissue on the basis of solvent extraction, thin layer and column chromatography, bioassay, and radioimmunoassay. The presence of PGE2 was detected in both tissue and sea water incubate surrounding the tissue. Both hyposmotic stress and magnesium-free sea water significantly increased release of prostaglandins into sea water. Hyposmotic stress also significantly increased prostaglandin synthesis. Examination of tissues revealed that homogenates of the mantle and lower visceral mass contained significantly fewer nanograms immunoreactive prostaglandins per gram wet weight than homogenates of the gill, posterior adductor muscle, upper visceral mass, or siphon tissue. Prostaglandin release could be increased by addition of arachidonic acid, and inhibited by addition of acetylsalicylic acid or indomethacin.
The Response of the Kidney of the Freshwater Rainbow Trout to True Metabolic Acidosis
Authors: Kobayashi Kenneth A. , Wood Chris M.
Published: April 2021

Infusion of lactic acid into the bloodstream of trout produced a short-lived depression of blood pH and a long-lasting elevation of blood lactate. The lactate injected was distributed in a volume of 198 ml/kg. Renal excretion of lactate anion and total acid increased by approximately equal amounts during the period of high blood lactate levels, but total renal loss over 72 h accounted for only 2% of the lactate load and 6% of the proton load. Comparable differences in the time courses of blood lactate and pH changes occurred when lactacidosis was induced endogenously by normocapnic hypoxia. The immediate response of the kidney was similar to that with lactic acid infusion, but there was a long-lasting (12–72+ h) elevation of urinary acid efflux that was not associated with lactate excretion. Following hypoxia, renal excretion over 72 h accounted for 1 % of the estimated lactate load and 12-25% °f proton load. A renal lactate threshold of 4–10 μequiv/ml prevents significant urinary lactate excretion. The response of the trout kidney to true metabolic acidosis is similar to that of the mammalian kidney.
Patterns of Activity And Axonal Projections of the Cerebral Giant Cells of the Snail, Lymnaea Stagnalis
Authors: McCrohan C. R. , Benjamin P. R.
Published: April 2021

The paired cerebral giant cells (CGCs) of Lymnaea were studied using electrophysiological and anatomical techniques. A strong electrotonic junction coupling the CGCs is located in the buccal ganglia, several millimetres distal to the cell bodies. This leads to i : i spike activity in the two cells. The CGCs receive phasic and tonic inputs which appear to be common to the two cells. Two types of phasic input are synchronous with synaptic input to feeding motoneurones in the buccal ganglia. Morphological studies, using three separate dye injection techniques, confirm the axonal projections shown by electrophysiological methods. The CGCs project ipsilaterally into one lip nerve, the cerebrobuccal connective, and all buccal nerves. Symmetry of anatomy and of firing activity cause the CGCs to function as a single neural unit.
Control of Sound Production in the Syrinx of the Fowl Gallus Gallus
Authors: Brackenbury John
Published: April 2021

Changes in the configuration of the fowl syrinx during experimental stimulation of the extrinsic syringeal muscles were assessed by monitoring simultaneous changes in the airway resistance at a constant airflow rate. Stimulation of the caudal part of the tracheolateralis muscle produced a change away from the sound-producing configuration. The tympanum was drawn craniad, the external tympaniform membranes were stretched and airway resistance fell as the syringeal lumen enlarged. Stimulation of the sternotrachealis muscles produced a change towards the sound-producing configuration. The tympanum was drawn caudad, the membranes relaxed and airway resistance rose due to the constriction of the syringeal lumen. Tetanic stimulation of the cranial parts of both tracheolateralis and tracheohyoideus produced a marked retraction of the larynx and rostral part of the trachea. The threshold levels of air-sac pressure and airflow rate necessary to produce sound by passive ventilation of the respiratory system were monitored. Passive sound could be abolished either by stimulating the tracheolateralis muscle or by marginally increasing the tracheal resistance, simulating glottal constriction. Results are discussed in relation to current opinions on the importance of active and passive factors during vocalization in birds. It is concluded that the involvement of the extrinsic muscles may be necessary when producing low volume sounds by relatively weak physical effort. Passive factors appear to be more important during vigorous calling, such as crowing. In the latter case the main function of the extrinsic muscles may be to ensure the retraction of the larynx and changes in shape of the anterior respiratory tract.
The Forces Exerted on the Substrate By Walking and Stationary Crickets
Authors: Harris Jack , Ghiradella Helen
Published: April 2021

The gait and the protraction/retraction ratios (P/R ratios) for the cricket are described. They are essentially the same as for the cockroach and the grasshopper. The vertical forces exerted on the substrate by all six legs of walking and stationary crickets are measured. On the basis of the ‘forceprints’ obtained and differences in P/R ratios among the legs of different thoracic segments, it is pointed out that all segments are not functionally identical. Specifically, the greater irregularity of the forceprints of the prothoracic legs, and the lower magnitude of peak force exerted on the substrate by the prothoracic legs suggest that the prothoracic legs are more involved in balancing or searching than in propulsion. The metathoracic legs exert an increased vertical force on the substrate just before the initiation of protraction. This increase correlates with an extension of the leg apparently through extension of the femoral-tibial joint. A slight decrease in the force exerted on the substrate by the meso-thoracic legs occurs when the leg is at right angles to the body. Placing or lifting one mesothoracic leg does not affect the force exerted by the contralateral mesothoracic leg in a regular way. This argues against mechanical interactions between the legs and in favour of theories invoking central generation of pattern. At a stepping frequency of below 2 steps s−1 the shapes of the forceprints of all legs are no longer repetitive. Also, below 2 steps s−1 there is an increase in the variability of the peak force exerted on the substrate. It is possible that the animal switches to a more sensory sensitive mode below a step frequency of 2 s−1. During stationary periods the forces exerted on the substrate continue to show oscillations which may be metachronal. This suggests a mechanism whereby a central oscillatory mechanism can account for the behaviour of an animal starting to walk following such a stationary period.
The Role of Physico-Chemical Buffering and of Bicarbonate Transfer Processes in Intracellular pH Regulation in Response to Changes of Temperature in the Larger Spotted Dogfish (Scyliorhinus Stellaris)
Authors: Heisler N. , Neumann P.
Published: April 2021

In order to evaluate the contributions of physico-chemical buffering to the adjustment of intracellular pH in response to changes of temperature in tissues of dogfish (Scyliorhinus stellaris), the CO2 equilibration method for the determination of intracellular buffer values was modified to yield data for the mathematical simulation of the intracellular compartments as closed buffer systems, and for the calculation of transmembrane bicarbonate transfer in vivo.

The respective buffer values of imidazole-like and phosphate-like buffer substances were estimated to be about 39 and 11 in white muscle, 21 and 18 in red muscle and 27 and 10 mequiv/(pH.l cell water) in heart muscle. In white muscle, the observed changes of intracellular pH can be explained by physico-chemical buffering and changes of . In red muscle and heart muscle considerable amounts of bicarbonate have additionally to be transferred across the cell membrane to achieve the temperature-dependent variations of pH observed in vivo.
Localization of Baroreceptors and Gain of the Baroreceptor-Heart Rate Reflex in the Lizard Trachydosaurus Rugosus
Authors: Berger P. J. , Evans B. K. , Smith D. G.
Published: April 2021

The location of arterial baroreceptors was studied in unanaesthetized Trachydosaurus rugosus by inflation of strategically placed perivascular cuffs. There was no evidence for baroreceptors at the site homologous with the carotid sinus of mammals or at the site homologous with the aortic arch baroreceptors of mammals and birds. The baroreceptors of T. rugosus probably lie in the truncus arteriosus. When the sensitivity or gain of the cardiac response to changes in systemic arterial pressure was expressed as change in heart period per unit change in mean aortic blood pressure, the value for 6 animals was 1370 ms/ kPa (100 ms/mmHg). This is very much greater than reported values for rabbits. If, instead, gain was calculated as the percentage increase in heart rate per unit fall in mean aortic pressure, a mean gain of 98%/kPa (7·2%/ mmHg) was obtained. It is suggested that the latter method provides the better comparative value. Adrenergic neurone blockade with bretylium and muscarinic blockade with atropine or hyoscine indicated that sympathetic fibres probably play the dominant role in generating the gain of the cardiac baroreflex.
Microtubules and the Propagation of Bending Waves by the Archigregarine, Selenidium Fallax
Authors: Mellor J. S. , Stebbings H.
Published: April 2021

The trophozoites of Selenidium fallax propagate bending waves at rates of up to 35 μm s−1, of a similar character to those manifested by eukaryotic cilia and flagella. A beat frequency of 0·12–0·15 Hz appears average, though rates outside this range have been recorded. Translatory locomotion at up to 6 μm s−1 has been observed. The protozoan demonstrates the presence of an active bending mechanism, probably along its entire length, and a means of coordinating adjacent bends. The Reynolds number for the motion is 10−5-10−4, suggesting that the hydrodynamic aspects of the trophozoite movement are amenable to analysis by similar means to those already employed for cilia and flagella. It is possible that the protozoans exhibit a sliding microtubule mechanism, which could be very usefully compared with that occurring in the ciliary axoneme.
The Function of Hair Sensilla on the Locust’s Leg: the Role Of tibial hairs
Authors: Pflüger Hans-Joachim
Published: April 2021

In Schistocerca americana gregaria hairs of the simple trichoid sensillum type on the hind tibia near the tibia-tarsus joint can mediate an avoidance response during which the hind leg is lifted by flexion of several joints. The responsiveness of this reflex can be improved by partially isolating the metathoracic ganglion. In these operated animals, the response can even be elicited after stimulation of one hair.

Myograms from various muscles in the tibia, femur, coxa and thorax revealed which muscles were active during the avoidance response. The delay times between the stimulus (bending several hairs with an eyelash) and the first muscle activity are variable (median values 150–200 msec). It is concluded that the pathway is polysynaptic and situated within the metathoracic ganglion.
Repriming of Delayed Potassium Conductance in Frog Skeletal Musclex
Authors: Ballou E. W.
Published: April 2021

A dissection of the semitendinosus muscle from Rana pipiens was developed for three-microelectrode voltage-clamp studies of the delayed potassium-selective conductance system. The delayed conductance inactivates in muscles bathed in high concentrations of potassium or rubidium, but can be reprimed by hyperpolarizing voltage pulses to membrane potentials beyond –80 mV. The repriming time-course was studied by measuring the delayed conductance that could be activated following hyperpolarizing pulses of varying duration. Responses following 20–100 s pulses to potentials between –90 and – 140 mV could not be reconciled with an exponential approach to the conductance present in normally polarized fibres. The sigmoid appearance of the early ( < 25 s) time course was exaggerated by cooling from 20 to 10 °C. This effect was described by a sequential model invoking two inactivated states with different temperature dependences. An explanation is suggested for differences in the kinetics and voltage dependence of repriming between briefly and chronically depolarized muscle cells.
Ventilatory CO2 Drive in the Tortoise Testudo Horsfieldi
Authors: Benchetrit G. , Dejours P.
Published: April 2021

Ventilation was recorded by pneumotachography, before and after bilateral vagotomy, in conscious tortoises (Testudo horsfieldi) (breathing o, 2, 3 or 4% CO2 in air or oxygen). Each breath consists of expiratory and inspiratory phases and an apneic plateau (absence of air flow). Inhalation of hypercapnic mixtures led to increased ventilatory flow, augmentation of tidal volume, and an increase in respiratory frequency through the shortening of the apneic plateau. Intact tortoises breathing hypercapnic-hyperoxic mixtures hyperventilated less than with hypercapnic-normoxic mixtures. In bivagotomized animals, the respiratory frequency decreased, the expiratory and inspiratory durations lengthened, and the apneic plateau was prolonged. The tidal volume was increased, but ventilation, nevertheless, decreased slightly. Bivagotomized animals breathing hypercapnic-normoxic or hypercapnic-hyperoxic mixtures hyperventilated, but less than intact animals under the same conditions. It is concluded that in tortoises there are : ( 1 ) peripheral chemoreceptors which are innervated by branches of the vagus nerves, and are sensitive to CO2; and (2) an extrathoracic, probably central, ventilatory CO2 drive.
Automatic Continuous Variation of Solute Concentration in a Perfusate
Authors: Buchan P. B.
Published: April 2021

Many physiological experiments involve switching between two or more solutions. For example, when drugs are applied to tissues the concentration of the drug is usually changed as a step function, by switching from a control saline to a saline containing the drug. There are many instances where it would be advantageous to change the concentration according to some other function such as a ramp. This paper describes how this has been achieved by a mixing valve under electronic control.
Spectral Sensitivity and Retinal Pigment Movement in the Crab Leptograpsus Variegatus (Fabricius)
Authors: Stowe Sally
Published: April 2021

The retina of Leptograpsus contains five types of movable screening pigment. The positions of these were found under various conditions of illumination in the day and at night. Intracellular recordings were made of the spectral responses of retinula cells R1–7 under the same conditions, with the eye in situ. The spectral absorptions of the individual screening pigments were measured by ultramicrospectrophotometry. Calculations based on a simple model of screening pigment action suggest that the observed variation in spectral sensitivity with light and dark adaptation may be largely explicable in terms of the effects of these screening pigments on a rhodopsin of peak absorbance at 485 nm. Light-adapted angular sensitivities are comparable to those of insects with high acuity apposition eyes.
The Hydraulic Mechanism of the Predatory Strike in Dragonfly Larvae
Authors: Tanaka Yoshitaka , Hisada Mituhiko
Published: April 2021

Aeschna larvae catch prey with a fast-moving elongated labium. The mechanism of this movement was analysed by high-speed cinematographs and by hydrostatic and electrophysiological measurements. The strike movement consists of an initial, mid and late phase. The angular acceleration of the joints of the labium is 2·6 × 105 and 7·8 × 105 deg. s−2 during the initial and mid phase respectively. The torque necessary for the acceleration was calculated to be 1·3 × 10−5 and 4·0 × 10−5 N.m for the initial and mid-phases respectively. The relation between the pressure applied to the labium and the extension torque at the joints has been established. No torque develops about the postmentum-prementum joint as long as the click of the flexed labium is engaged. The power production of the extensor muscles is less than the power output of the mid phase. The power for the mid phase is derived from the internal body pressure developed by the contraction of the abdominal dorso-ventral muscles. The required pressure for the mid phase is about 60 cm H2O if the resistance is neglected and 80 cm H2O when the resistance is considered. Abdominal dorso-ventral muscles contract 110–500 ms before the onset of the strike and the body pressure of the animal increases to a peak of 40–120 cm H2O at the onset of the strike. The geometry of the labial joints gives the primary flexor muscles of the labium a large mechanical advantage over the extensor muscles in the fully flexed labium, and allows the extensor muscles to contract almost isometrically. The extensor muscles and the primary flexor muscles co-contract for 75–100 ms before the strike. The strike movement begins when the flexor muscles relax. The stored energy in the extensor system is released suddenly and disengages the click producing the initial phase. Once the click is disengaged the internal pressure produces the large torque to move the labium with great acceleration during the mid phase.
Flight Energetics and Heat Exchange of Gypsy Moths in Relation to Air Temperature
Authors: Casey Timothy M.
Published: April 2021

Gypsy moths elevate thoracic temperature (Tth) during flight by endogenous heat production but do not regulate it. Thoracic temperature of moths in free, near-hovering flights exceeded air temperature by approximately 6–7 °C at all Ta’s between 17 and 32 °C. Mean rates of mass specific oxygen consumption varied between 40 and 47 ml O2 (g·h) −1 and were not correlated with air temperature. Wing-beat frequency increased from 27 to 33 (s) −1 between air temperatures of 18 and 35 °C. Thoracic heating and cooling constants are similar in live and dead moths, and removal of thoracic scales increases heating constants by about 12%. Preflight warm-up occurs at low Ta’s but the moths are capable of immediate, controlled flight at Ta’s above 22 °C. Relatively low levels of heat production by the flight muscles are a consequence of low power requirements associated with the flight morphology of gypsy moths. Calculated rates of thoracic and respiratory heat loss of free-flying moths are slightly lower than values of heat production.
Electrogenesis in the Euryhaline Osmoconformer Cordylophora Lacustris (Hydrozoa)
Authors: Chain Benjamin M.
Published: April 2021

The electrical signals propagated through the ectodermal epithelium of Cordylophora lacustris (the Josephson pulses) were recorded as trans-epithelial action potential-like events. Experiments on the ionic basis of electrogenesis of these action potentials suggested that they result from an outward flow of chloride ions from the ectodermal cells into the enteron. Further evidence for this hypothesis came from measurements of the ionic concentrations in the tissues of Cordylophora, which showed that these cells have unusually high levels of chloride. Chloride dependent electrogenesis allows this excitable system to function in media of low and variable ionic strength, which are a typical feature of this organism ‘s natural environment.
Physiology of Pupal Ecdysis in the Tobacco Hornworm, Manduca Sexta
Authors: Truman James W. , Taghert Paul H. , Reynolds Stuart E.
Published: April 2021

The time of pupal ecdysis in Manduca sexta can be accurately predicted by the appearance of external markers late in pupal development. Eclosion hormone injections resulted in premature ecdysis of staged pharate pupae. The latency between injection and initiation of ecdysis movements was inversely correlated with dosage and served as the basis for a sensitive, rapid, and quantitative bioassay for the hormone.

Behavioural responsiveness to the hormone arose about 8 h before normal ecdysis at 23 °C. When insects were injected at these early times the larval cuticle was not sufficiently digested to allow its rupture and these animals remained permanently trapped inside the larval cuticle.

Measurement of eclosion hormone in the blood of pharate pupae showed the appearance of biological activity in the blood about 30 min before the onset of ecdysis.

It is concluded that pupal ecdysis is under endocrine control and that the hormone involved is likely to be the eclosion hormone.
Physiology of Pupal Ecdysis in the Tobacco Hornworm, Manduca Sexta
Authors: Taghert Paul H. , Truman James W. , Reynolds Stuart E.
Published: April 2021

Eclosion hormone activity was found in the brain and ventral ganglia of pharate pupae of Manduca sexta. No activity was detected in the corpora cardiaca-corpora allata complex. At the time of ecdysis the store of activity dropped by 50−75 % in the ventral cord whereas the hormone level in the brain remained unchanged. Also, larvae whose brains were removed at the wandering stage subsequently showed pupal ecdysis behaviour and also had essentially normal levels of hormonal activity in their blood at the start of the behaviour. It was concluded that at pupal ecdysis the hormone responsible for the initiation of the behaviour is released from the ventral nerve cord rather than from the brain.

The chemical characteristics of the pharate pupal eclosion hormone were determined. The factors from the brain and ventral nerve cord were both active in a number of adult and pupal eclosion hormone bioassays. Both showed an apparent molecular weight of 8500 daltons and an isoelectric point of about 5−0, values essentially the same as that seen for the adult form of the hormone. We concluded that pupal ecdysis and adult eclosion are triggered by the same hormone but for the former it is released from the ventral nerve cord and, for the latter, from the brain. The choice of release site may depend on whether or not the release is under circadian control.
The Detection of Waterborne Vibration by Sensory Hairs on the Chelae of the Crayfish
Authors: Tautz J. , Sandeman D. C.
Published: April 2021

Sensory hairs on the chelae of the Australian freshwater crayfish Cherax destructor are grouped together into pits. Electrophysiological recordings from the sensory axons of isolated chelipeds show that the hairs are maximally sensitive to water vibration frequencies between 150−300 Hz. The amplitude threshold is about 0·2 µm water molecule oscillation.
The Suction Feeding Mechanism in Sunfishes (Lepomis): An Experimental Analysis
Authors: Lauder George V.
Published: April 2021

The process of prey capture by inertial suction was studied in three species of sunfishes (Lepomis auritus, L. macrochirus, and L. gibbosus) by the simultaneous recording of buccal and opercular cavity pressures in order to test current hydrodynamic models of feeding in fishes. Synchronous high-speed films permitted the correlation of kinematic patterns of jaw bone movement with specific pressure waveforms. Opercular cavity pressures averaged one-fifth buccal pressures and pressure magnitude was correlated with prey type. Peak buccal and opercular pressures were — 650 cm H2O and — 150 cm H2O respectively; peak rate of pressure change was — 100 cm H2O/ms. Buccal pressure magnitude varied inversely with degree of predator satiation.

Opercular pressure waveforms have an initial positive phase followed by a prolonged negative phase and then a final positive phase. The initial positive pressure may be absent during slow strikes at worms. Buccal pressure waveforms show considerable variability. The modal waveform consists of a sharp negative pressure pulse followed by a positive phase and finally by another pressure reduction. Delayed opercular abduction relative to mouth cavity compression correlates with the presence of a positive buccal phase. The second buccal negative pressure is the result of rapid mouth closing causing a pressure reduction (water hammer effect) as water flow continues posteriorly. These data indicate that (1) the buccal and opercular cavities are functionally separated by a gill curtain of high resistance, (2) that inertial effects of water are important in the description of the suction feeding process, (3) that a reverse flow of water (opercular to buccal cavity) may occur during the early phase of mouth opening prior to establishment of a buccal to opercular flow regime, and (4) current models of respiratory pressure and flow pattern cannot be applied to feeding. Current hydrodynamic models of suction feeding in fishes are re-evaluated in the light of this analysis.
Protein Phosphorylation and The Regulation of Cation Cotransport
Authors: Palfrey H. Clive , Alper Seth L. , Greengard Paul
Published: April 2021

The turkey erythrocyte is a useful system in which to investigate the relationship between protein phosphorylation and membrane transport. This cell possesses a catecholamine-and cyclic AMP-stimulated Na+-K+ ‘cotransport’ system in its plasma membrane, and the physiological properties of this system have been partially elucidated. It is distinct from the Na+-K+ ‘pump’ and is insensitive to ouabain, but can be blocked by certain diuretic agents such as furosemide and bumetanide.

A plasma membrane protein of MW 230000, called goblin, has been identified as the major protein whose state of phosphorylation increases upon incubation of turkey erythrocytes with catecholamines or cyclic AMP. The kinetics of phosphorylation of goblin at its cyclic AMP-sensitive sites correlate well with the kinetics of Na+-K+ cotransport activation under various conditions. This protein may play a role in the regulation of the Na+-K+ cotransport system by catecholamines and cyclic AMP