bluuebunny/crossref_metadata_2025 huggingface dataset:
Glucose transport in fish erythrocytes: variable cytochalasin-B-sensitive hexose transport activity in the common eel (Anguilla japonica) and transport deficiency in the paddyfield eel (Monopterus albus) and rainbow trout (Salmo gairdneri)
Authors: Tse C. M. , Young J. D.
Published: April 2021

Erythrocytes from individual common eels (Anguilla japonica Temminck and Schlegel) exhibited widely variable initial rates of cytochalasin-B-sensitive 3-O-methyl-D-glucose (3-OMG) zero-trans influx, in the range 0–19·5 mmol 1-cells−h−1 (5mmoll−1 extracellular concentration at 20°C, 50 animals tested). Storage of cells at 4°C in a glucose-containing medium for up to 72 h had no effect on 3-OMG uptake, and there was no correlation between the sugar permeabilities of erythrocytes from different fish and intracellular ATP levels. Adrenaline and noradrenaline increased cytochalasin-B-sensitive 3-OMG transport activity; half-maximal stimulation occurred at catecholamine concentrations in the region of 1 μmol 1−1. This catecholamine-induced stimulation of sugar transport appeared to be independent of the basal cytochalasin-B-sensitive 3-OMG permeability of the cells. Kinetically, catecholamines increased the Vm of transport without changing the apparent Km (approx. 1·4 mmol 1−1). Saturable 3-OMG influx was inhibited by phloretin, D-glucose, D-deoxyglucose and D-galactose, but not by D-fructose and L-glucose. Transporter stereoselectivity was confirmed by direct measurements of D-and L-glucose uptake. Erythrocytes from two other fish species, Monopterus albus Richardson (paddyfield eel) and Salmo gairdneri Richardson (rainbow trout), unlike those from the common eel, were uniformly deficient with respect to cytochalasin-B-sensitive 3-OMG and D-glucose transport activity. Catecholamines had no effect on sugar uptake in these species.
Spinal Neuronal activity During the Pectoral Fin Reflex of the Dogfish: Pathways For Reflex Generation and Cerebellar Control
Authors: Paul D. H. , Roberts B. L.
Published: April 2021

Single units were recorded from the spinal cord of decerebrate dogfish (Scyliorhinus canicula) during pectoral fin reflexes (PFR) evoked by electrical pulse trains to the fin. The units were classified as primary afferent neurones, motoneurones or interneurones. Motoneurones discharged for limited (and various) periods during the reflex at latencies of 20 ms or more. There was no evidence for monosynaptic activation by primary afferents. Short-latency (S) units received monosynaptic input from fast-conducting afferents at latencies (<20 ms) appropriate for pre-motor interneurones. However, excitation of individual S-units by intracellular current injection never evoked motoneurone discharges, suggesting that convergence is necessary for motoneurone activation. Intracellular recordings from S-units which discharged for periods longer than the duration of the afferent volley generated by the fin stimulus showed that they receive other inputs in addition to those from primary afferent fibres. Intermediate-latency (I) units had similar properties to S-units except for a longer latency (>30ms), which ruled out monosynaptic excitation by fast-conducting afferents. Antidromic activation of S-and I-units by high spinal stimulation was rarely seen and orthodromic driving was also uncommon. A significant number of interneurones with latencies greater than 60 ms (L-units) were antidromically activated by high spinal stimulation. Their discharges were often long-lasting (>1 s) and we suggest that they may provide input to the cerebellum during the PFR.
The effect of varying water Ph on the acidification of expired water in rainbow trout
Authors: Lin Hong , Randall D. J.
Published: April 2021

Acidification of expired water was studied in rainbow trout exposed to water of pH9.91, 6.80 (control) and 3.88. For the high-pH and the control exposures, the water flowing over the gills was acidified because of the dominant effect of CO2 hydration. During the low-pH treatment, the water was alkalized because of ammonium ion formation and perhaps bicarbonate dehydration. Carbon dioxide excretion was not significantly affected by the high-pH and low-pH treatments but ammonia accumulated in the plasma in both cases.
Modulation of tension production by octopamine in the metathoracic dorsal longitudinal muscle of the cricket Teleogryllus Oceanicus
Authors: O’Gara Bruce A. , Drewes Charles D.
Published: April 2021

Application of octopamine to the metathoracic dorsal longitudinal muscle (DLM) of the cricket Teleogryllus oceanicus produced dose-dependent increases of twitch amplitude, contraction rate and relaxation rate. The threshold for octopamine effects was between 10−8 and 10−7mol l−1, while maximal effects were seen at approximately 10−5 mol l−1. The octopamine receptors were classified as octopamine2 receptors on the basis of the differential responsiveness of the muscle to the octopamine agonists naphazoline, tolazoline, clonidine and the octopamine antagonists metoclopramide and chlorpromazine. It was not possible to distinguish between octopamine2A or octopamine2B receptors in this preparation. Octopamine had both presynaptic and postsynaptic effects, since it increased both miniature end-plate potential (mEPP) frequency and muscle relaxation rate. Ata calcium concentration of 11 mmol l−1, octopamine did not affect muscle membrane potential, input resistance or EJP amplitude, but the EJP duration at half amplitude (T1/2) was slightly increased. In low-calcium saline (1.8 mmol l−1), octopamine did not affect membrane potential or T1/2, but EJP amplitude was increased. Stimulation of the octopaminergic dorsal unpaired median neuron (DUMDL), which innervates the metathoracic DLM, increased twitch amplitude in about 25% of the preparations. Failure in the other preparations was apparently due to spike conduction failure within the metathoracic ganglion. These results show that octopamine can be an important modulator of metathoracic DLM tension production.
Ultrasound-induced yaw movements in the flying Australian field cricket (Teleogryllus oceanicus)
Authors: May M. L. , Hoy R. R.
Published: April 2021

An ultrasonic stimulus induced negative phonotactic steering in the yaw axis of tethered, flying Australian field crickets. The forewings, hindwings and twisting of the thorax generated the forces which induced the yaw turn. However, abdominal ruddering did not contribute to yaw turns. Each aspect of the yaw steering response depended upon the stimulus intensity. At higher ultrasonic intensities, the magnitude and average angular velocity increased while the latency of the yaw turn decreased. Each of these factors varied in a graded manner, revealing that this behavior is more complex than a simple reflex.
Octopaminergic modulation of the forewing stretch receptor in the locust Locusta Migratoria
Authors: Ramirez Jan-Marino , Orchard Ian
Published: April 2021

Modulatory actions of various biogenic amines and peptides on the locust forewing stretch receptor (SR) were examined. The response of the SR to sinusoidal wing movements was unaffected by physiological concentrations (5×10−8mol l−1) of the peptides AKHI, AKHII, proctolin and FMRFamide. The biogenic amine octopamine, however, enhanced the SR response in a dosedependent manner when injected into the haemolymph of an almost intact animal or perfused over an isolated thorax preparation in which head, abdomen, gut and the entire central nervous system were removed (threshold at 5×10−8mol l−1, maximal effect at 5×10−4mol l−1 DL-octopamine). The SR was as sensitive to D-octopamine, the naturally occurring isomer of octopamine, as it was to DL-octopamine. Serotonin was equal to octopamine in effectiveness, followed in order of potency by synephrine, metanephrine and tyramine. Dopamine was ineffective. Phentolamine, but not DL-propranolol, antagonized the action of octopamine. The threshold of the modulatory effect of octopamine on the SR suggests that the increased haemolymph octopamine level which occurs during flight is sufficient to increase the SR activity. Two observations suggest that dorsal unpaired median (DUM) cells are involved in the octopaminergic modulation of the SR during flight: (1) selective stimulation of these cells modulated the SR response and this effect was blocked by phentolamine; and (2) a number of DUM cells were activated during flight. These results suggest that the SR activity is enhanced by octopamine following the onset of flight. Since the SR is involved in the control of wing beat frequency, the modulation of the SR might influence the generation of the motor pattern in flying locusts.
Sodium ion uptake by perfused gills of the blue crab Callinectes Sapidus; effects of ouabain and amiloride
Authors: Burnett Louis E. , Towle David W.
Published: April 2021

Sodium ion uptake in the isolated perfused posterior gill of the blue crab, Callinectes sapidus Rathbun, acclimated to 5‰ salinity and 20°C was measured using 22Na as a tracer. Unidirectional influxes across individual gills occurred against large sodium concentration differences (internal perfusate=273 mmol l−1; external perfusate=l–80 mmol l−1) and depended strongly on the concentration of sodium ions present in the external perfusate. The maximum rate of influx was 3.24 μmol g−1 min−1 and the Km for this process was 23.0 mmol l−1. Ouabain added to the internal perfusate reduced the influx to an average of 51.3 % of the control values and had its maximal effect at 1 mmol l−1. Ouabain (1 mmol l−1) added to the external perfusate had no significant effect on sodium influx. Amiloride (0.1 mmol l−1) added to the external perfusate reduced the influx to an average of 38.9 % of the control values. During all treatments, perfusion pressures showed no treatment-dependent effects, indicating that the observed changes in fluxes were due to specific effects of the treatment on the epithelium and not due to some indirect effect on perfusion pattern within the gill. Treatment of the gill with the metabolic poisons cyanide and iodoacetate resulted in a rapid decline of sodium influx to 20–30% of the control values. This was correlated with a large reduction in gill ATP content to 13% of the control. The overall results of this study are consistent with the general picture of epithelial sodium uptake across gills, supporting the existence of a ouabain-sensitive Na+ pump on the basolateral membrane and an amiloride-sensitive Na+/H+ exchanger on the apical membrane.
Calcium utilization in contractures induced by acetylcholine or high-potassium saline in molluscan proboscis muscles
Authors: Brooks D. D. , Huddart H. , Lennard R. , Hill R. B.
Published: April 2021

The mechanisms by which high-K+ saline and acetylcholine (ACh) mobilize cellular calcium in molluscan muscle was studied in three proboscis muscles of Busycon canaliculatum. BAY K 8644, a calcium agonist, enhanced tonic force induced by exposure to 25 mmol l−1 K+ in the odontophore and radular retractor muscles but inhibited this response in the radular sac muscle. Its effect on the radular protractor muscle was concentration-dependent, excitatory at 10−7 mol l−1 and inhibitory at higher concentrations. The tonic response to 80 mmol l−1 K+ was enhanced by BAY K 8644 in the odontophore retractor and radular retractor muscles but inhibited in the radular sac muscle. In all muscles, BAY K 8644 eliminated the fast twitches induced by 80 mmol l−1 K+, and inhibited the tonic ACh responses. Sucrose-gap studies with the radular protractor muscle showed that the effects of BAY K 8644 on the depolarizations induced by K+ and ACh were similar. The effect on the ACh-induced depolarization suggested that this agent had inhibited sodium influx through the ACh receptor.

Mytelase enhanced ACh-induced tonic force, but at 10−4mol l−1 it inhibited the response to doses of ACh above 10−5mol l−1. Mytolon reduced the maximum ACh-induced tonic force and increased the response threshold to ACh. ACh and high-K+ depolarization pathways were not synergistic for force development.

The existence of two separate cellular calcium pools, independently released by high-K+ saline and ACh, seems improbable. We suggest that K+ and ACh act via separate mechanisms to release calcium from a single cellular calcium pool.
Intermittent gliding flight in the pipistrelle bat (Pipistrellus Pipistrellus) (Chiroptera: Vespertilionidae)
Authors: Thomas Adrian L. R. , Jones Gareth , Rayner Jeremy M. V. , Hughes Patricia M.
Published: April 2021

The pipistrelle bat Pipistrellus pipistrellus intersperses wingbeats in flapping flights with brief (0.1–0.3 s) glides. This undulating intermittent flight mode probably saves energy in flight. In large flight cages, captive pipistrelles glided for approximately 13.4 % of flight time, but glides were steep, and the bat accelerated during the glides. The bats sometimes glided during turns. During the glides the bat may have been unable to emit echolocation pulses and, if so, this would explain occasional wide interpulse intervals in wild pipistrelles. The steepness of the glides may be a means of improving undulating flight performance, and may also be unavoidable owing to the very small size and relatively small wings of pipistrelles.
Body drag, feather drag and interference drag of the mounting strut in a peregrine falcon, Falco Peregrinus
Authors: Tucker Vance A.
Published: April 2021

The mean, minimum drag coefficients (CD,B) of a frozen, wingless peregrine falcon body and a smooth-surfaced model of the body were 0.24 and 0.14, respectively, at air speeds between 10.0 and 14.5 ms−1. These values were measured with a drag balance in a wind tunnel, and use the maximum crosssectional area of the body as a reference area. The difference between the values indicates the effect of the feathers on body drag. Both values for CD,B are lower than those predicted from most other studies of avian body drag, which yield estimates of CD,B up to 0.41. Several factors must be controlled to measure minimum drag on a frozen body. These include the condition of the feathers, the angle of the head and tail relative to the direction of air flow, and the interference drag generated by the drag balance and the strut on which the body is mounted. This study describes techniques for measuring the interference drag generated by (a) the drag balance and mounting strut together and (b) the mounting strut alone. Corrections for interference drag may reduce the apparent body drag by more than 20 %. A gliding Harris’ hawk (Parabuteo unicinctus), which has a body similar to that of the falcon in size and proportions, has an estimated body drag coefficient of 0.18. This value can be used to compute the profile drag coefficients of Harris’ hawk wings when combined with data for this species in the adjoining paper (Tucker and Heine, 1990).
Effects of operating frequency and temperature on mechanical power output from moth flight muscle
Authors: Stevenson R. D. , Josephson Robert K.
Published: April 2021

Mechanical work output was determined for an indirect flight muscle, the first dorsoventral, of the tobacco hawkmoth Manduca sexta. Work output per cycle was calculated from the area of force-position loops obtained during phasic electrical stimulation (1 stimulus cycle−1) and imposed sinusoidal length change. There was an optimal stimulus phase and an optimal length change (strain) that maximized work output (loop area) at constant cycle frequency and temperature. When cycle frequency was increased at constant temperature, work output first increased and then decreased. It was always possible to find a frequency that maximized work output. There also always existed a higher frequency (termed the ‘optimal’ frequency in this paper) that maximized the mechanical power output, which is the product of the cycle frequency (s−1) and the work per cycle (J). As temperature increased from 20 to 40 °C, the mean maximum power output increased from about 20 to about 90 W kg−1 of muscle (Q10=2.09). There was a corresponding increase in optimal frequency from 12.7 to 28.3 Hz, in the work per cycle at optimal frequency from 1.6 to 3.2 J kg−1 muscle and in mean optimal strain from 5.9 to 7.9 %. Two electrical stimuli per cycle cannot increase power output at flight frequencies, but if frequency is reduced then power output can be increased with multiple stimulation. Comparison of mechanical power output from muscle and published values of energy expenditure during free hovering flight of Manduca suggests that mechanical efficiency is about 10 %. In the tobacco hawkmoth there is a good correspondence between, on the one hand, the conditions of temperature (35–40°C) and cycle frequency (28–32 Hz) that produce maximal mechanical power output in the muscle preparation and, on the other hand, the thoracic temperature (35–42°C) and wing beat frequency (24–32 Hz) observed during hovering flight.
Unitary K+ currents in growth cones and perikaryon of identified Helix Neurones in Culture
Authors: Green K. A. , Powell B. , Cottrell G. A.
Published: April 2021

Unitary potassium (K+) currents of several different conductances have been recorded from the growth cones of isolated Cl neurones from Helix aspersa. The isolated neurones were maintained in culture for up to 1 week. Similar unitary currents were recorded in the growth cones of other isolated Helix neurones. The activity of one type of unitary K+ current recorded from the growth cones of the Cl neurone and other neurones was very similar to that described for the S-charmel of the perikarya of Aplysia sensory neurones. Another type of unitary K+ current showed fast flickering and reduced amplitude when the membrane was held at large positive potentials, which is suggestive of channel block by some agent. The conductances of the K+ channels in the growth cones of isolated Cl neurones were generally smaller than those recorded in this and in previous studies from the perikarya of Cl neurones in situ. However, unitary K+ currents recorded from the perikaryon of the Cl neurone, and from other identified neurones, in culture also had lower conductances than those recorded in situ. The mean resting potential of the isolated neurones was smaller than those from neurones in situ. This and other results suggested that reduced intracellular K+ concentration in the isolated neurones might be an important factor in deciding the conductance of the recorded channels.
The Clasping Reflex In Frogs And Toads And The Seasonal Variation In The Development Of The Brachial Musculature
Authors: Smith C. L.
Published: April 2021

By the methods described in this paper it has been shown that:

A clasping action can be produced in male frogs at all times of the year. This reaction is peculiar to the male. The course of the decline and onset of the hypertrophy of the brachial musculature up to a maximum at the breeding period can be followed. This hypertrophy appears to follow fairly closely the changes occurring in the interstitial tissue of the testis.
Proprioception In Insects
Authors: Pringle J. W. S.
Published: April 2021

A group of campaniform sensilla occurs on each of the joints of the maxillary palp of Periplaneta americana. Each group is supplied from a single large sensory nerve fibre. Impulses in the nerves from the sensilla can be recorded at the base of the maxilla. Adaptation is slow and incomplete. The sensilla respond to passive straight or sideways bending of the joint, and also strongly to pressure on the cuticle. They are excited only to a lesser extent when the segment is moved actively by its own muscle. It is shown that the observations are consistent with the view that the campaniform sensilla are “stress receptors” responding to strains in the cuticular skeleton. Their action as proprioceptors is compared with that of the vertebrate tension receptor.
A Comparative Study Of The Double Motor Innervation In Marine Crustaceans
Authors: Wiersma C. A. G. , Harreveld A. Van
Published: April 2021

A double motor innervation has been shown for several muscles of marine crustaceans. The adductors of the claws of Randallia and Blepharipoda and the adductor of the dactylopodite of the walking leg of Cancer were studied physiologically.

The two motor axons which innervate these muscles have a different diameter (ratio 1·4 : 1). Stimulation of the thick fibre causes a response, which, though it is not always faster than the response of the thin fibre, must be considered as a “fast” contraction. In Randallia and in Blepharipoda the slow contraction is higher than the fast with frequencies of less than ±50 per sec., in Cancer with frequencies less than 100 per sec.

The action currents of the two kinds of contraction are different. Both show facilitation, but under the same conditions of stimulation the fast-action currents are higher. The first stimulus of the thick fibre causes an action current top which is clearly distinguishable, the action currents of the slow contraction show up only after a number of stimuli. Even when the mechanical reaction on stimulation of the thick fibre is smaller than on similar stimulation of the thin fibre, the action currents are higher in the first case.

A single impulse in the thick fibre does not cause a contraction, but sets up a muscle-action current. The chronaxie of this action current in Blepharipoda and Randallia is 0·8σ and is about the same as that found for the action current of the nerve. Two impulses in the thick fibre may cause a mechanical response, as is shown by summation experiments. The pseudo-chronaxie of this contraction was measured as 3·5 σ. The second action current shows facilitation, when it follows the first within 1 sec.; a mechanical reaction results with summation intervals of two stimuli of less than 10 σ. The facilitation of the action current increases with decrease of the time interval between the two impulses ; with the shortest intervals that give summation the resulting action current is a smooth high spike.
The Role Of The Fins In The Equilibrium Of The Swimming Fish
Authors: Harris J. E.
Published: April 2021

The paired fins of fishes are largely concerned with the production of vertical forces, and thus principally affect the pitching (rising and diving) equilibrium. In the sharks the pelvic fins increase to a small extent the static stability for pitching movements. Nevertheless, the relatively large area and forward position of the pectoral fins preponderates over the influence of the pelvics on the pitching stability, so that the contribution of the latter is very small. This is borne out by amputation experiments. In the bony fishes, the development of the actinopterygian fin leads to a much greater mobility of the fins. In consequence, the pelvic fins of the bony fishes exhibit a considerable adaptive radiation. In the percoid fishes the use of the pectoral fins as brakes produces a lift as well as a drag force. It is shown that the neutralization of this lift force by a downward force produced by the pelvic fins necessitates the forward migration of the latter. If this migration did not take place, the fish would either tilt upwards or rise bodily during the stop. The dynamical basis for this migration of the paired fins is considered in an approximate mathematical treatment of the equilibrium during the stop. This hypothesis is confirmed by amputation experiments, and also by the occurrence of a convergent fin migration in the Coelacanthidae. The absence of the forward pelvic fin migration in flying fishes also affords indirect support. There is no evidence to suggest that the pelvic fins can function as bilge keels, though they may be used actively to produce a rolling moment.
The Colour Changes In Lizards, Particularly In Phrynosoma
Authors: Parker G. H.
Published: April 2021

The activities of the melanophore system of Phrynosoma in comparison with that of Chamaeleo may be stated categorically in the following way.

I. The blanching of Phrynosoma blainvillii is due

(1) to the action of its concentrating nerve-fibres on its melanophores, (2) to the action of a hydrohumour, probably adrenalin, on the same cells, (3) to the direct response of these cells to darkness, and (4) to high temperatures.

II. The blanching of Chamaeleo is due to the first, third, and fourth of these factors. Whether the second factor is effective in this lizard is not yet determined.

III. The darkening of Phrynosoma is due

(5) to the action of a pituitary neurohumour on its melanophores, (6) to the direct response of these cells to strong light, and (7) usually, to low temperatures.

There are no dispersing nerve-fibres known in Phrynosoma.

IV. The darkening of Chamaeleo is due to the sixth and probably to the seventh of these factors. This lizard presents strong indications of possessing dispersing nerve-fibres. Whether it darkens from a pituitary neurohumour or not is unknown.
A Manometric Respirometer for Snails
Authors: Wells G. P.
Published: April 2021

In the course of an investigation into the physiology of the edible snail (Helix pomatia L.), it became necessary to measure the respiration individually of large numbers of animals. A system in which CO2-free air was passed over the animals and then through baryta was tried but rejected because the snails apparently dislike currents of air, tending to withdraw into their shells. Analysis of gas samples from containers in which the animals respire was not employed, partly because the accumulation of CO2 involved may conceivably affect the respiratory exchanges, and partly because the accuracy of the method is insufficient except in very experienced hands. It was therefore decided to adopt a manometric method.
The Absorption of Fluid from the Tracheal System of Mosquito Larvae At Hatching and Moulting
Authors: Wigglesworth V. B.
Published: April 2021

During development the tracheal system of insects is at first filled with fluid. About the time of hatching from the egg and at each subsequent moult this fluid is absorbed into the tissues. The mechanism of absorption was studied in a number of insects, and earlier work on the subject reviewed, by Sikes & Wigglesworth (1931), who concluded that although secretory activity might be responsible for the presence in the tracheal system of a fluid which could be absorbed by osmosis, the final absorption was probably brought about by the osmotic pressure of the blood. At the suggestion of Prof. A. Krogh, who has taken an active interest throughout this work, the problem has been reinvestigated with a view to differentiating the part played by secretion.
The Humidity Gradient at the Surface of a Transpiring Leaf
Authors: Ramsay J. A. , Butler C. G. , Sang J. H.
Published: April 2021

An hygrometer and an evaporimeter, capable of investigating atmospheric conditions over small areas close to the surface of a leaf, are described. In the case of rapidly transpiring leaves in a slow air stream a humidity gradient has been detected up to a height of 1.2 cm.
Host-Finding by Insect Parasites
Authors: Laing J.
Published: April 2021

Experiments are described in which Trichogramma females were provided with Sitotroga eggs arranged at various distances from 0·05 to 0·40 in. The frequency with which the parasite found the neighbouring egg varied inversely with the distance between the eggs. The relation between frequency of contact and distance between the hosts depends chiefly, but not entirely, on chance. The rate of finding the eggs varied inversely with the distance between them. By consideration of the conditions of the experiments, this relation between the rate of finding and the distance between the eggs is seen to indicate that the Trichogramma does not seek at random over the whole area available for movement but restricts its search to the neighbourhood of hosts. From experiments with eggs of four sizes it is shown that frequency of neighbouring contact is correlated positively with the size of the eggs. The influence of size is largely mechanical ; but not entirely, for small eggs of Sitotroga are found less efficiently in proportion to their size than are larger eggs. When provided simultaneously with hosts of two different sizes, a Trichogramma finds more of the larger than of the smaller hosts. If the hosts are arranged alternately, the amount of selection that occurs by finding depends entirely upon the relative sizes of the eggs. If they are arranged in separate groups, however, relatively more of the larger eggs are found.
Tracheal Pulsation in the Flea
Authors: Herford G. M.
Published: April 2021

The phenomenon of tracheal pulsation has been demonstrated in three different species of fleas. It is shown to be independent of the other body rhythms, such as those of the heart and gut. Experiments are described showing the effect of oxygen, carbon dioxide, evacuation and of sectioning the central nervous system. Three theories are put forward to explain the phenomenon, and their relative merits are discussed.
The Spherical form of the Mammalian Erythrocyte
Authors: Ponder Eric , Neurath Hans
Published: April 2021

The most suggestive observation which we have regarding the remarkable disk-sphere transformation which occurs when mammalian red cells in saline are enclosed between slide and coverslip is that the velocity and extent of the shape change depends on the distance between the surfaces, and upon whether or not both surfaces are wetted by the suspension medium (Ponder, 1929). Thus the transformation occurs rapidly and completely between two glass surfaces 50μ. apart, but slowly and incompletely between two glass surfaces 1 mm. apart, and paraffining of both surfaces, or the substitution of surfaces unwetted by saline, prevents the shape change completely. That the transformation is due to electrostatic charges on the surfaces, pressure,2 or diffusion of alkali from the glass, has been disproved experimentally (Ponder, 1929, 1936), and the only suggestion which still remains is that the surfaces have an orienting effect, of an obscure nature, on a “liquidcrystal” structure in the red-cell envelope.
Regulation of Amphibian Gastrulae with Added Ectoderm1
Authors: Waddington C. H.
Published: April 2021

If a young Urodele gastrula is cut or constricted into two along the frontal plane, so that the dorsal and ventral halves are separated, the dorsal part contains the whole organization centre but an abnormally small amount of presumptive ectoderm; nevertheless, as Spemann (1903) and Ruud & Spemann (1922) showed, it regulates to form a complete embryo of normal proportions but of small absolute size. Schmidt (1933) demonstrated the same thing for Anuran gastrulae. Thus an absence of ectoderm causes modification of the normal development of the organization centre. We have much less information of the effect of increase in the proportion of presumptive ectoderm. Bruns (1931) added fairly small pieces of ectoderm to entire gastrulae, and obtained embryos apparently indistinguishable from normal ; but the amounts added were so small that one could not expect easily visible effects. In the experiments to be reported here, very much larger quantities of ectoderm were added to normal gastrulae, and, as will be shown, it was found that the presence of this added material caused an increase in size of the invaginated roof of the gut, so that an embryo of normal proportions but increased size was developed.
The Relative Toxicity of Salts of Lead, Zinc and Copper to the Stickleback (Gasterosteus Aculeatus L.) and The Effect of Calcium on the Toxicity of Lead and Zinc Salts
Authors: Jones J. R. Erichsen
Published: April 2021

Lethal limits of concentration are determined for lead, zinc and copper for the three-spined stickleback (Gasterosteus aculeatus L.). The addition of calcium salts to solutions of lead nitrate or zinc sulphate reduces the toxicity of these salts to Gasterosteus. 50 mg. per 1. of calcium (as nitrate or chloride) is sufficient to annul the toxicity of a 1 × 10−6 g. per c.c. solution of lead or a 2 × 10−6 g. per c.c. solution of zinc. The reactions of the fish in the solutions with and without calcium are compared, and the respiratory symptoms are described with the aid of graphs illustrating the variation in respiration rate during the survival time. It is shown that a running supply of “hard” tap water containing approximately 50 mg. per 1. of calcium as calcium bicarbonate is harmless to the minnow, Phoxinusphoxinus (L.) and to the stickleback, when there is added to it the maximum amount of lead that it can hold in solution (7 ×10−7g. per c.c.). This concentration of lead in soft water is fatal to Gasterosteus in 3812 hr. The same amount of calcium renders a 10 × 10−6 g. per c.c. solution of lead harmless to the goldfish, Carassius auratus (L.). It is concluded that, in the presence of sufficient calcium, the interaction between the lead, or zinc, and the mucus secreted by the fish does not take place. This conclusion was endorsed by experiments in vitro on the slime secreted by the eel, Anguilla anguilla (L.). The application of these results to the pollution of natural waters by effluents from lead and zinc workings is briefly discussed.
The Mechanism of Locomotion in the Leech (Hirudo Medicinalis Ray)
Authors: Gray J. , Lissmann H. W. , Pumphrey R. J.
Published: April 2021

Considerable uncertainty still exists concerning the nature of the mechanism which maintains the normal locomotory rhythm of terrestrial animals. Two types of theory have been advanced: (i) That the rhythm is determined by the existence of a closed chain of peripheral reflexes, each phase of a complete locomotory cycle setting up automatically the particular pattern of peripheral stimulation requisite for the elicitation of the succeeding phase in the cycle, (ii) That the rhythm is, fundamentally, a property of the central nervous system which is, however, susceptible to modification or extinction by peripheral stimulation.
The Rates of Conduction of Nerve Fibres of Various Diameters in Cephalopods
Authors: Pumphrey R. J. , Young J. Z.
Published: April 2021

The rates of conduction of nerve fibres of Sepia and Loligo varying from 30 to 718μ in diameter have been estimated from records of their action potentials. The limits of conduction velocity were found to be 2.2-22.8 m./sec. at 20° C. Although the fibres examined have different functions, and come from animals which differ considerably in structure and mode of life, yet the conduction rates of all of them can be approximately expressed as a single function of the diameter. These fibres, therefore, do not differ greatly from each other in any respect but size. Calculation of the regression coefficient of the log. of the conduction rate on the log. of the diameter of the fibres shows that the rate increases with the power 0.614+0.027 of the diameter. On account of various sources of error however the exact relation does not necessarily lie within these limits, but it is not likely to be very far from the square root. The possession of giant fibres produces a significant saving of time for the animal, it being calculated that the reaction time of a squid is about half that of a similar animal without giant fibres. The presence of rapidly conducting fibres is probably also an advantage in that it decreases the discrepancies between the times of contraction of parts of the mantle at varying distances from the central nervous system. In Loligo there is a graded series of fibres with the larger in the longer nerves, and this is apparently a further device for ensuring more nearly simultaneous contraction. The relative thickness of the myelin-like sheath increases from about 1% of the diameter of the axon in cephalopods to 5% in Crustacea and annelids and 25% in vertebrates: the conduction velocity of fibres of a given size also increases in the same series. This parallelism provides strong support for the view that the layer of oriented lipoids increases the velocity of propagation of the nerve impulse in proportion to its thickness.
Proprioception in Insects
Authors: Pringle J. W. S.
Published: April 2021

Concentrations of hair sensilla have been noted by a number of authors in the joints of the insect body and limbs. Special groups of such sensilla in the form of “hair plates” are described from three positions on the legs of Periplaneta americana. The hairs of the hair plates are mechanical sense organs with a slow rate of adaptation. In life the hairs are excited by a fold of the intersegmental membrane, the excitation varying with the position of the joint. It is suggested that these and similar structures in other parts of the bodies of insects act as “position” sense organs.
The Posture of the Abdomen during Locust Flight: Regulation by Steering and Ventilatory Interneurones
Authors: Baader Andreas
Published: April 2021

Tethered flying locusts (Locusta migratoria) make correctional steering movements with the abdomen when stimulated with a moving artificial horizon and integrated wind jet, simulating deviation from a straight course. Neurones in the metathoracic and first abdominal neuromeres of the metathoracic ganglion have been characterized morphologically and physiologically. The selective stimulation of these cells causes movements of the abdomen. One group of neurones responds directionally to visually perceived horizon movements and is excited by wind on the head. Some of these neurones are rhythmically activated at the flight frequency while others receive tonic drive from the flight oscillator. Electrical depolarization results in bending of the abdomen; the direction of this movement is always compatible with compensatory steering. Interneurones which are active during the expiration phase of ventilation also contribute to the posture of the abdomen in flight. They are not visually responsive but their selective inhibition at the onset of flight activity helps to bring the abdomen into flight posture. Some of these Interneurones are modulated at the flight frequency. The efficiency of cooperation between different sets of Interneurones in producing behavioural patterns and the signficance of single neurone stimulation are discussed.
Glycolytic Enzyme Binding and Metabolic Control in Estivation and Anoxia in the LandSnail Otala Lactea
Authors: Brooks Stephen P. J. , Storey Kenneth B.
Published: April 2021

The mechanisms controlling glycolytic rate were examined in foot muscle of the terrestrial snail Otala lactea (Müller) (Pulmonata, Helicidae), during short and long periods of estivation and anoxia. Binding associations between glycolytic enzymes and the particulate fraction of the cell were assessed in both states. The percentage of enzyme activity bound to particulate matter decreased significantly over the short term (4 days estivation and 14·5 h anoxia); significant changes were seen for hexokinase (HK), phosphofructokinase (PFK), aldolase and lactate dehydrogenase (LDH) in estivation and, for these enzymes plus triosephosphate isomerase and pyruvate kinase (PK), in anoxia. Over the longer term in estivation (22 days) and anoxia (45 h), enzyme binding returned to control values. Tissue content of fructose-2,6-bisphosphate, a potent phosphofructokinase activator, decreased under all experimental conditions. Total glycogen phosphorylase activity decreased during short-term anoxia (14·5 h) and during long-term estivation (22 days), but the percentage of the active a form decreased significantly during anoxia only. Significant changes in the maximal activities of several enzymes were observed during both estivation and anoxia. Decreases in the maximal activity of HK, PFK, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase (PGK) and LDH were observed during long-term estivation. Increases in PGK and PK maximal activity in short-term anoxia and aldolase and PGK in long-term anoxia were also observed. These results suggest that changes in glycolytic enzyme binding may be part of an immediate mechanism used to cause a rapid decrease in glycolytic flux and initiate glycolytic rate depression, which also includes a reduction of fructose-2,6-bisphosphate content and decreased glycogen phosphorylase activity. In the long term, however, control of snail glycolytic rate is reorganized, so that enzyme binding associations revert to the control values. In the long term, then, control is mediated by lower fructose-2,6-bisphosphate concentrations and, during estivation, also by a decrease in maximal enzyme activities.
Effects of Hypoxia and Drugs on the Cardiovascular Dynamics of the Atlantic HagfishMyxine Glutinosa
Authors: Axelsson Michael , Farrell Anthony P. , Nilsson Stefan
Published: April 2021

Cardiac output, ventral and dorsal aortic blood pressure and heart rate were recorded simultaneously in unanaesthetized hagfish, Myxine glutinosa L. Mean cardiac output was 8.7 ml min−1 kg−1 and mean heart rate 22.3 beats min−1. The absence of beat-to-beat oscillations in heart rate was consistent with the lack of an extrinsic cardiac innervation in hagfish. Mean blood pressures were 1.04 kPa (ventral aorta) and 0.77kPa (dorsal aorta).

Injection of adrenaline into the caudal vein significantly increased cardiac output, stroke volume, heart rate and blood pressures of both aortas. Peak cardiac output was close to 25 ml min−1 kg−1. Injection of the β-adrenoreceptor antagonist sotalol decreased resting heart rate significantly. We conclude that endogenous catecholamines from chromaffin cells of the heart are instrumental in the regulation of cardiac function in Myxine.

Injection of acetylcholine had little direct effect on the recorded cardiac variables, but caused marked branchial vasoconstriction. Heart rate increased as the pressor response subsided. The cholinergic antagonist atropine had no effect on any of the resting parameters.

Injection of adenosine had no direct cardiac effects but reduced the systemic vascular resistance.

Severe hypoxia (kPa for 15–35 min) had very little effect on the cardiovascular variables recorded. The remarkable ability of the hagfish heart to maintain normal cardiac output during severe hypoxia is discussed with respect to the anaerobic pumping capacity of the heart.

Pump-perfused, in situ gill preparations were used to examine branchial vasoactivity. Acetylcholine and adrenaline produced dose-dependent vasoconstriction, whereas isoprenaline, noradrenaline and adenosine dilated the branchial vasculature.
An Analytical Electron Microscopy Study of Iron-Rich Teeth from the Butterflyfish (Chaetodon Ornatissimus)
Authors: Sparks N. H. , Motta P. J. , Shellis R. P. , Wade V. J. , Mann S.
Published: April 2021

Iron is known to be a common constituent of vertebrate teeth, yet little is known about the form it takes or the extent to which it modifies the structural properties of the tooth. Analytical electron microscopy was used to study the iron-rich tooth cap of the butterflyfish Chaetodon ornatissimus Cuvier, 1831. Images of thin sections of the tooth cap showed three distinct layers of hydroxyapatite crystals; a densely packed cuticle, a crystallographically organized superficial enameloid and a randomly oriented inner enameloid. Energy dispersive X-ray analysis (edXa) showed that iron was concentrated in the cuticular layer of the tooth cap, the concentration increasing to a maximum at the tip. Elemental analysis showed the level of calcium to be inversely related to iron concentration. An identical relationship was found for synthetic iron-doped hydroxyapatite. The implications of these results for the functional role of iron in the tooth caps are discussed.
A Quantitative Description of Nodal Membrane Currents in Myelinated Nerve Fibres of theLizard Anous Carolinensis
Authors: Benoit Evelyne
Published: April 2021

Experiments were performed on individual nodes of Ranvier from a lizard at 15–16°C, using the method of Nonner (1969). In addition to a leakage current (mean conductance of 19·7 nS), the membrane ionic currents consisted of a Na+ current, completely inhibited by lμmol l−1 external tetrodotoxin, and a K+ current, sensitive to external tetraethylammonium ions and to internal caesium ions. The inactivation time course of the Na+ current at 0 mV was well fitted by the sum of two exponential phases, one fast and one slow, with mean time constants of 0·68 and 2·92 ms, respectively. In contrast to observations on amphibian and mammalian preparations, the peak Na+ current showed an almost linear potential dependence at large positive membrane potentials. A mean maximum Na+ conductance of 146·8 nS was calculated. Both the time and potential dependence of the K+ current indicated that it was similar to that found in amphibian nodes of Ranvier. The mean maximum K+ conductance was 51·9 nS. Furthermore, as described in amphibians, three different components of the K+ current (s, ft and f2) could be separated. We conclude that, under similar experimental conditions, nodal ionic currents are qualitatively and quantitatively similar in lizard and amphibian myelinated nerve fibres, suggesting that the nodal membrane of these two preparations contains similar types of ionic channels. These results strengthen the view that the near absence of nodal K+ channels is a peculiarity of mammalian nerves.
Dynamic Mechanical Properties of Extensor Muscle Cells of the ShrimpPandalus Danae:Cell Design for Escape Locomotion
Authors: Meyhöfer Edgar , Daniel Thomas
Published: April 2021

We measured the dynamic stiffness of passive single extensor cells from the abdomen of the shrimp Pandalus danae. These stiffness measurements, consisting of both elastic and viscous moduli, were carried out by imposing sinusoidal length changes on single cells and recording, simultaneously, the resultant force. Our measurements were made over a broad range of loading frequencies (1–120 Hz) and sarcomere lengths (1·9–3·2μm), encompassing the physiological range of these parameters.

We found that: (1) there is an exponential increase in both elastic and viscous moduli with increases in sarcomere length; (2) there is a weak increase in these moduli with increasing frequency; (3) the relative energy dissipated by the viscous behavior of cells is largest in the relevant physiological range of loading frequencies and sarcomere lengths, with the magnitude of the viscous modulus nearly equal to the elastic modulus; and (4) the energy dissipated by the viscous behavior of these cells alone constitutes about 10 % of the total energy required to accelerate the animal in its aquatic environment. We propose that such large values for viscous energy dissipation in passive cells may be necessary to prevent unstable responses of muscle to the rapid dynamic loads imposed by the escape event.
The Neuromuscular Junction Revisited: Ca2+ Channels and Transmitter Release in Cholinergic Neurones in Xenopus Nerve and Muscle Cell Culture
Authors: Feng T. P. , Dai Zheng-Shan
Published: April 2021

Although the entry of calcium ions into the presynaptic nerve terminals through voltage-gated Ca2+ channels is now universally recognized as playing an essential role in evoked transmitter release at the neuromuscular junction (NMJ), and indeed in chemical synapses generally, we have as yet very little direct knowledge of the Ca2+ channels of the presynaptic terminals. In this work, making use of cocultured nerve and muscle cells from Xenopus embryos, we studied the NMJ formed between the soma of identified cholinergic neurones and myoball, which allowed the use of patch-clamps on both the pre- and postsynaptic components. Both whole-cell and single-channel recordings of Ca2+ channels in the presynaptic cell were made. We found only one type of voltage-gated Ca2+ channel with high-voltage activation and slow inactivation characteristics, allowing its classification either as the L or the N type. The channels were susceptible to block by met-enkephalin but not to block by nifedipine or to enhancement by Bay K 8644. This combination of pharmacological properties favours their classification as the N type. Preliminary observations on the correlation between calcium currents and transmitter release disclosed a strikingly rapid run-down of the evoked release with unchanged calcium currents and spontaneous release during whole-cell recording, indicating a specific wash-out effect on some link between calcium entry and evoked transmitter release.