bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature and the Responsive Mechanism of Cardiac Muscle
Authors: Brown Dugald E. S. 
Published: April 2021

ABSTRACT
The rhythmical stimulation of heart muscle, according to the myogenic theory, is of the nature of an auto-stimulation, dependent upon certain processes in the muscle cells themselves. These processes are associated with a system in the cell which undergoes a rapid alteration when a certain critical condition is reached, with a stimulation of the cell resulting. The system then gradually reconstructs itself, undergoing a similar breakdown when the “critical condition” is reached a second time. The time required for the system to pass from the condition existing at stimulation till the critical condition is again attained determines the rate of beat of the heart muscle cell. This unstable system is closely associated with the entire responsive mechanism in the cell and, therefore, is susceptible to modification by the same conditions which are known to modify other phases of the response of the cardiac muscle, such as the duration and magnitude of contraction. The analysis of the exact nature of the relation existing between the rhythmic process and other processes inherent in the system, under conditions known to modify all cellular processes, is essential to any elucidation of the mechanism. The present paper presents the results of an investigation of the action of temperature upon the automatic rate of the sinus and the duration of the simple sinus twitch.
Chorio-Allantoic Grafts of Entire and Fragmented Blastoderms of the Chick
Authors: Murray P. D. F. , Selby Doris 
Published: April 2021

ABSTRACTThe most important work which has yet been done in the experimental embryology of early stages of the chick is that of Hoadley, whose principal contributions are contained in four papers (1926 a, b, c, d). Three of these describe chorio-allantoic grafts of transverse one-fifths of blastoderms at various stages of incubation, while the fourth (1926 d) deals with experiments in which the blastoderm was cut into two pieces while remaining in situ on the yolk, the operation again being performed at several different stages.
Transport of Thallium Ions Across the Isolated Midgut of Hyalophora Cecropia
Authors: Zerahn Karl , Koefoed Bodil 
Published: April 2021

ABSTRACT
T1+ permeates the Hyalophora cecropia midgut equally in both directions, but the flux of Tl+ per mm is up to 50 times higher than the passive flux for potassium, rubidium and caesium. This is explained by assuming that the T1+ flux is a carrier-mediated facilitated diffusion or a passage through channels similar to gramicidin channels in black membranes. We have found this special way for Tl+ to pass through membranes in the Hyalophora cecropia midgut; some other membranes, such as red blood cells, seem to show the same properties, but others, such as frog muscle and skin, do not.
Structure and Function of the Lateral Giant Neurone of the Primitive Crustacean Anaspides Tasmaniae
Authors: Silvey Gerald E. , Wilson Ian S. 
Published: April 2021

ABSTRACT
The syncarid crustacean Anaspides tasmaniae rapidly flexes its free thoracic and abdominal segments in response to tactile stimulation of its body. This response decrements but recovers in slightly more than one hour.
The fast flexion is evoked by single action potentials in the lateral of two large diameter fibres (40 μm) which lie on either side of the cord. The lateral giant fibre is made up of fused axons of 11 neurones, one in each of the last 5 thoracic and 6 abdominal ganglia. The soma of each neurone lies contralateral to the axon. Its neurite crosses that of its counterpart in the commissure and gives out dendrites into the neuropile of each hemi-ganglion.
The lateral giant neurone receives input from the whole body but fires in response only to input from the fourth thoracic segment posteriorly. Both fibres respond with tactile stimulation of only one side. Since neither current nor action potentials spread from one fibre to the other, afferents must synapse with both giant neurones.
The close morphological and physiological similarities of the lateral giant neurone in Anaspides to that in the crayfish (Eucarida) suggest that the lateral giant system arose in the ancestor common to syncarids and eucarids, prior to the Carboniferous.
Thermal Acclimation of A Central Neurone of Helix Aspersa
Authors: Langley C. K. 
Published: April 2021

ABSTRACT
The chemical composition of the haemolymph of adult snails was significantly altered during thermal acclimation (from 19° to 4°, 12° and 30°C), The osmotic concentration was highest in cold groups (4° and 12°C) and lowest in warm-acclimated animals. The concentration of sodium in the haemolymph was highest in warm- and cold-acclimated individuals and lowest at intermediate temperatures (12° and 19°C), and showed significant correlation with [Mg], Potassium concentrations were also increased during warm and cold (4°C) acclimation, the increase being largest in warm-acclimated individuals. The concentrations of calcium and magnesium ions showed relatively small changes during thermal acclimation. Calcium activity was found to be highest in warm and lowest in cold-acclimated snails. Feeding increased the levels of potassium and calcium most significantly in the warm-acclimated group. pH remained relatively constant in all groups.
Thermal Acclimation of A Central Neurone of Helix Aspersa
Authors: Langley C. K. 
Published: April 2021

ABSTRACT
The effects of thermal acclimation on the activity of a central autoactive neurone and its temperature dependence were investigated in Helix aspersa. Resting membrane potential was changed by acclimation temperature, but not with a simple relationship: cells from both 30°C-acclimated and 4°C-acclimated groups were more depolarized at 20°C than were control cells (acclimated to 19°C). The input resistance of the neurone decreased as the temperature of acclimation was raised. Rates of change of potential during an action potential decreased with increasing acclimation temperature. Raising the temperature of measurement on the other hand increased dV/dt at a given acclimation temperature. Spike amplitude was little affected. The frequency of spontaneous spike discharge at a given temperature declined with increasing temperature of acclimation but increased with step changes of temperature in a manner suggestive of a compensatory process. All the measured electrical parameters showed a pronounced hysteresis during rewarming after cold block. Upper lethal and cold block temperatures were both significantly raised by acclimation to higher temperatures. Block temperature was much reduced in cold-acclimated individuals, but the upper lethal temperature was less affected. By sampling during the acclimation period of 4 weeks, the above changes were shown to occur progressively. During the initial stages (5–12 days) they could be partially reversed by incubating isolated ganglia at various temperatures for 30–45 min: but after 2 weeks or more the changes could not be reversed by incubations of up to 5 h.
The Heartbeat of Octopus Vulgaris
Authors: Wells M. J. 
Published: April 2021

ABSTRACT
Heartbeat frequencies and blood pressures were monitored in free-moving Octopus vulgaris. Typical resting frequencies (for animals of 500 g ± at 22° C) were 40–50 beats min−1, with resting pressures measured at the dorsal aorta of 40 cm H2O in systole and 15 cm in diastole, rising to 100 cm or more with a pulse of 50 cm in exercise. Beat frequency changes very little and any increased oxygen demand results mainly in an increase in stroke volume. Temperature affects heartbeat frequency with a Q10 of about 3 over the range 7–27°C. Systemic heartbeat rate and pulse amplitude also change with the oxygen content of the water, slowing as this decreases and stopping, reversibly (at least for short periods), at about 2·5 parts O2 per million.
Evidence That K-Dependent Transport Components in Addition to Na-K ATPase Are Involved in Na and Cl Excretion in Marine Teleost Gills
Authors: Pic P. , Ellory J. C. , Lucu C. 
Published: April 2021

ABSTRACT
Although Tl+ ions can substitute for K+ with a ten-fold higher affinity in activating the sodium pump in mullet red cells and mullet gill microsomal ATPase, they cannot mimic the effects of K+ in stimulating Na+ and Cl− efflux across the gill. This is interpreted in the light of an additional Insensitive transport component being involved.
Blood Acid-Base Balance in Brook Trout (Salvelinus Fontinalis)*
Authors: Packer Randall K. , Sunkin Arthur L. 
Published: April 2021

ABSTRACT
A nomogram is presented which allows the rapid assessment of acid-base status in brook trout (Salvelinus fontinalis Mitchill) at 18°C.
Due to a of 3·5–4·3 mmHg in the respirometer water, the fish from which data were obtained for determination of zero base excess values were suffering from slight respiratory acidosis. Trauma of surgery and anaesthetization as well as confinement in the respirometer might also have generated a slight metabolic acidosis.
Base excess values for trout with a chronically implanted dorsal aortic cannula ranged from −3 to + 3m-equiv/l. Blood buffer values of d[HCO3−]/dpH = 7·50±4·42 slykes and were found. Mean plasma protein concentration was 3·6± 0·8 g/100 ml plasma and the buffering power of plasma was approximately 40% that of whole blood. Plasma proteins are more important blood buffers in fish than in humans.
Acid-Base Balance and Gas Exchange in Brook Trout (Salvelinus Fontinalis) Exposed to Acidic Environments
Authors: Packer Randall K. 
Published: April 2021

ABSTRACT
Brook trout (Salvelinus fontinalis Mitchill) with a chronically implanted dorsal aortic cannula were exposed to acidic environments. During exposure, trout developed severe metabolic acidosis as shown by decreases in standard plasma bicarbonate levels as well as negative base excess values. Reduced oxygen consumption seen in acidotic trout resulted from decreased gill oxygen transfer and reduced available blood oxygen capacity.
Bilateral Effects On Retinal Shielding Pigments During Monocular Photic Stimulation in the Crayfish, Procambarus
Authors: Barrera-Mera Baltazar , Berdeja-García G. Yolanda 
Published: April 2021

ABSTRACT
Bilateral light adaptation of distal retinal shielding pigments was observed a few minutes after 60 min of sustained photic stimulation (2·69 Cd/m2) of a single eyestalk of the dark-adapted crayfish. Pigment migration was observed in intact animals as a diminution of eye glow area and electroretinogram amplitude, and was confirmed in sectioned material. The effect upon the contralateral eye was abolished by surgical bisection of the cerebral ganglion. It is suggested that the mechanism involved in the bilateral effect may be responsible for the mutual entrainment of ERG circadian rhythms of both eyes.
Potentiation of Neuromuscular Transmission by An Octopaminergic Neurone in the Locust
Authors: O’Shea Michael , Evans Peter D. 
Published: April 2021

ABSTRACT
Spikes in the octopaminergic dorsal unpaired median (DUM) neurone which innervates the extensor tibiae muscle of the locust metathoracic leg (DUMETi) produce direct and indirect effects on muscle tension. Direct effects include a slowing of an intrinsic rhythm of contraction and relaxation, a relaxation of muscle tone and a small hyperpolarization of the muscle membrane potential. The latter two effects are weak and variable. All three effects are mimicked by superfusion of octopamine and are mediated by octopamine receptors on the muscle fibres. Indirect effects are found when the DUMETi neurone is stimulated at the same time as the motoneurones innervating the extensor muscle. They include (a) potentiation of tension generated in the extensor muscle by spikes in the slow excitatory motoneurone (SETi), (b) reduction in duration of each twitch contraction generated by SETi due to an increase in the rate at which the muscle relaxes, (c) increase in the amplitude of the synaptic potential generated by SETi. These various effects have a time course of several minutes and far outlast the duration of DUMETi stimulation. They can be mimicked by superfusion of octopamine. The effect of DUMETi on neuromuscular transmission is mediated by receptors with a high affinity for octopamine located both on the muscle and on the terminals of the slow motoneurone. The presence of the presynaptic receptors is revealed by the increase in the frequency of spontaneous miniature end plate potentials recorded in the muscle in the presence of octopamine. DUMETi is a member of a group of similar aminergic neurones and it is suggested that they may share a role in modulating transmission at peripheral neuromuscular synapses, and possibly central synapses.
Mechanics of Escape Responses in Crayfish (Orconectes Virilis)
Authors: Webb P. W. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.
Mn2+ Ions Pass Through Ca2+ Channels in Myoepithelial Cells
Authors: Anderson M. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.