bluuebunny/crossref_metadata_2025 huggingface dataset:
Ocular Freezing Avoidance in Antarctic Fish
Authors: Turner Jeffrey D. , Schrag Joseph D. , Devries Arthur L.
Published: April 2021

A series of experiments was undertaken to determine the underlying mechanism of ocular freezing avoidance in a variety of antarctic fish. The three possible mechanisms that were examined include the depression of the freezing point through (1) colligative or (2) non-colligative means or (3) the supercooling of the ocular fluids. The ocular fluids of antarctic fish, like those of most vertebrates, are slightly hypotonic with respect to plasma and contain very low levels of serum proteins. The chief means of ocular freezing avoidance appears to involve supercooling of the ocular fluids. The presence of suitable barriers to prevent ice propagation into the eye has been demonstrated both in vitro and in vivo.
Multisegmental Integration and Divergence of Afferent Information from Single Tactile Hairs in A Cricket
Authors: Hustert R.
Published: April 2021

The long tactile hairs of crickets contribute to intersegmental receptive fields of interneurones that integrate input from different types of tactile mechano-sensory hairs. Afferent input from the identified long hairs studied converges on a group of multisegmental interneurones of the abdominal and thoracic ganglia. Conversely, the input from each tactile hair receptor diverges to several multisegmental interneurones and also to motoneurones of their own and neighbouring segments. The interneurones have spike initiating zones in each ganglion they reach. Spikes initiated by hair afferents can travel caudally and rostrally in an interneurone. These interneurones spreading tactile information from single sensory cells to several ganglia are not suited for fine discrimination of sources of touch which could elicit specific somatotopically oriented motor behaviour of the cricket. More specific pathways from long tactile hairs to motoneurones exist in abdominal and thoracic segments.
The Development of the Locust Jumping Mechanism : II. Energy Storage and Muscle Mechanics
Authors: Gabriel Julie M.
Published: April 2021

In an escape jump, the adult locust extensor tibiae muscle produces more than twice the specific energy output of the fourth instar muscle. If forced to jump repeatedly, the extensor muscles of hoppers and adults produce the same specific energy output. In escape jumping, specific energy production increases with age within an instar, but this does not seem to be the case in repeated jumping over a 10-min period. Adult locusts have thicker cuticle, including thicker semilunar processes, than hoppers. They also have relatively larger extensor apodemes. The cuticle thickness of all instars increases with age up to apolysis or maturity. The fourth instar extensor muscle has a lower angle of pennation and relatively longer muscle fibres than the adult muscle. The stiffness of the semilunar processes increases with age both within and between instars,’so that the mature adult leg has the highest energy storage capacity. To produce the required amount of energy storage, the adult muscle fibres must shorten slightly more than those of the fourth instar, but they must produce more than twice the force per unit area. The strain on the apodeme is similar in adults and hoppers, and greater at the distal than at the proximal end.
Neurohormonal Modulation of theLimulusHeart: Amine Actions on Neuromuscular Transmission and Cardiac Muscle
Authors: Watson Winsor H. , Hoshi Toshinori , Colburne John , Augustine George J.
Published: April 2021

The responses of Limulus cardiac neuromuscular junctions and cardiac muscle cells to four endogenous amines were determined in order to identify the cellular targets underlying amine modulation of heartbeat amplitude. The amines increased the amplitude of the Limulus heartbeat, with dopamine (DA) being more potent than octopamine, epinephrine or norepinephrine. The effect of DA on heartbeat amplitude was not blocked by phentolamine. DA enhanced the contractility of deganglionated heart muscle, with time course and dose-dependence similar to its effect on the intact heart. The amines also enhanced neuromuscular transmission, with time course and dose-dependence similar to their effects upon the intact heart. The amplitude of unitary excitatory junction potentials (EJPs) and frequency of miniature excitatory junction potentials (mEJPs) were increased by DA, while mEJP amplitude was unchanged. Thus DA, and probably the other amines, had a presynaptic effect. Combined actions upon cardiac muscle and cardiac neuromuscular transmission account for the ability of these amines to increase the amplitude of the Limulus heartbeat.
Light-Dependent Eye Coupling During The Optokinetic Response Of The Crab Carcinus Maenas (L.)
Authors: Nalbach H.-O. , Thier P. , Varjú D.
Published: April 2021

The movements of both distal eye stalks in the horizontal plane, elicited by optokinetic stimuli, have been recorded simultaneously. A panorama was split into two separate halves and was either oscillated around the animal in a sinusoidal fashion or displaced in a stepwise manner. Both eyes could be stimulated independently. The stimuli on both sides differed either (a) in the illumination, or (b) in the total amount of light impinging upon the eyes or (c) in the relative phase of the sinusoidal stimuli to either eye. As the illumination decreases the optokinetic response weakens. If one eye has no or only weak optokinetic input, it will be driven by the other eye. The response mediated by the contralateral optokinetic stimulus diminishes if the amount of light impinging upon the driven eye is increased. There is a logarithmic relationship between the response of the driving eye and that of the driven eye. The possible biological significance of these relationships is seen in the enhanced coupling at low light intensities. The variable strength of coupling and possible roles of movable eyes are discussed.
The Recovery From a Transient Inhibition of the Oxidative Metabolism of the Photoreceptors of the Drone (Apis Mellifera ♂)
Authors: Dimitracos S. A. , Tsacopoulos M.
Published: April 2021

In the honey-bee drone retina (Apis mellifera) oxidative metabolism is carried out largely by the photoreceptors. We have studied the effects of a transient inhibition of this metabolism, by recording receptor potential simultaneously with measurements of local and extracellular [K+] ([K+]o), using O2-and K+-sensitive microelectrodes. When the retina was subjected to anoxia or exposed to Na-amobarbital (amytal), the photoreceptors depolarized by about 30 my, in parallel with an increase of [K+]o of up to 30 mmol 1−1, and the receptor potential was abolished in 2–3 min. The reduction of the receptor potential followed the beginning of anoxia with a delay, which we define as a ‘resistance’ of the photoreceptors to anoxia. The resistance to anoxia was greater if the photoreceptors were stimulated with only low intensity light flashes, suggesting that the effects of anoxia are due to the progressive consumption of a substance stored in the photoreceptors. This substance is probably ATP. When O2 was reintroduced, or amytal washed out, oxidative metabolism rapidly resumed. [K+]o quickly decreased and, after a large undershoot, returned to the baseline in less than 5 min. There was in parallel a repolarization of the photoreceptors, followed by recovery of the receptor potential. About 5 min after réintroduction of O2, when the [K+]o, the membrane potential and the amplitude and kinetics of the receptor potential had completely recovered, exposure of the retina to a second anoxia suppressed the receptor potential faster than had the first anoxia. Full recovery of the resistance to anoxia thus takes longer (by about 10 min) than recovery of the electrical properties of the photoreceptor cells. The amplitude of the extra oxygen consumption measured after a flash of light recovered in parallel with the resistance to anoxia.
Analysis of the Phase Difference Between Particle Motion Components of Sound By Teleosts
Authors: Van Den Berg A. V.
Published: April 2021

The hypothesis that fish may remove 180° ambiguities concerning the sound source direction by a timing analysis between particle motion components is addressed. Analysis of the phase difference ψ (w, v) between the horizontal (v) and the vertical (w) components of the particle velocity of sound signals by teleost fish is investigated by cardiac conditioning. Standing wave sound stimuli (90 Hz) are used with ψ (w, v) = + or – 90° and equal amplitudes of v and w. The water particles move along circular trajectories for such stimuli: however, the direction of revolution is reversed in the two stimuli. These stimuli were discriminated by one whiting, one catfish and several cod, indicating that these teleosts are able to discriminate signals on a pure timing cue. If the w/v ratio is lowered, the cod can discriminate the resulting elliptical motions on the direction of revolution down to a w/v ratio of –12 dB. Moreover, down to the same w/v ratio the cod discriminates an elliptical particle motion signal from a pure translatory particle motion signal. At this level, the threshold signal-to-noise ratio for the w component is exceeded by 9 dB. Apparently phase analysis can be limited by ‘cross talk’ between horizontal and vertical particle motion detectors. The results are discussed with respect to models of directional hearing by fish.
Partitioning of Regulatory Sites in Bufo Marinus During Hypercapnia
Authors: Tufts Bruce L. , Toews Daniel P.
Published: April 2021

Ureters were cannulated in specimens of Bufo marinus (L.) in order to partition the regulatory contributions of the kidney and skin. The in vivo roles of the kidney, skin and internal calcareous deposits in the response of these animals to chronic hypercapnia were then evaluated.

There was no compensatory adjustment by the skin and only a minimal regulatory response by the kidney. Major adjustments which have been attributed to combined skin and urinary tract in previous studies must therefore come from the urinary bladder. Removal of the bladder as a regulatory site in these animals completely eliminated the compensatory elevation of HCO3− in the extracellular fluid. Mobilization of internal calcareous deposits as a source of HCO3− was found to contribute 50% of the compensatory response of these animals during hypercapnia.
Cholinergic and Monoaminergic Mechanisms Associated with Control of Bioluminescence in the Ctenophore Mnemiopsis Leidyi
Authors: Anctil Michel
Published: April 2021

The effects of cholinergic and monoaminergic drugs and blocking agents on luminescence responses of the comb-jelly Mnemiopsis leidyi were investigated, using isolated strips of meridional cells. Catecholamines elicited dose-dependent flash activity and adrenalin was the most patent. The adrenalin response was abolished by propranolol (0·1 mmol l−1), but not phentolamine. Reserpine (0·1mmol l−1) suppressed the flash response to electrical stimulation without affecting the adrenalin response. Acetylcholine (ACh) elicited flash activity which was propagated along the meridional canals. Eserine (0·01 mmol l−1) potentiated the flash response to either ACh or electrical stimulation. Tubocurarine reduced or abolished responses to either ACh or electrical stimulation. Atropine elicited intense flash activity and potentiated the response to electrical stimulation, but failed to block the ACh response. Prolonged exposure of meridional canals to serotonin (5-HT) depressed or abolished flash responses to ACh, adrenalin and electrical stimulation. The ACh flash response was abolished by propranolol but the response to adrenalin was not altered by tubocurarine. It is concluded that nicotinic cholinergic and beta-adrenergic mechanisms are interrelated and indirectly involved in excitation of luminescence in Mnemiopsis.
The Effect of Sewage on Brown Trout (Salmo Trutta L.)
Authors: Longwell J. , Pentelow F. T. K.
Published: April 2021

Fresh undiluted sewage contains unstable substances which are directly toxic to fish. Sewage which has been kept for 1 or 2 days and stirred in an open tank at 180 C. is more toxic than fresh sewage, possibly owing to the production of other toxic substances. It has also been shown that the biochemical oxygen demand is directly proportional to the “strength” of the sewage which is closely related to toxicity. Consequently a large biochemical oxygen demand of fresh sewage indicates a certain degree of toxicity.

It appears that when fresh sewage is discharged into a river in concentrations up to 10 per cent, of the river water, it has no directly toxic effect on fish. A river can purify a certain proportion of sewage effluent without becoming seriously deoxygenated. In one river with which we are acquainted a sewage effluent forms about 3·7 per cent, of the river flow at normal summer levels. The dissolved oxygen content of the river during the period it was under observation never fell below 60 per cent, of the saturation value, and such a mixture of sewage and water would have no directly injurious effect on fish. If, however, the proportion of sewage is increased, then the river will become more deoxygenated and eventually at a certain ratio of sewage to river water the toxicity will become more apparent, partly owing to the oxygen depletion. This condition is of course readily produced in a small river. The final stage will be attained when the quantity of sewage is sufficient to remove all the dissolved oxygen of the water. When there is a belt of deoxygenated water, sewage will decompose under anaerobic conditions and sulphide will be formed. As it has been shown that this substance is directly toxic to trout in small concentrations, 0-3 part per 100,000 being rapidly fatal, the fish are exposed to a definite poison as well as the danger of asphyxiation. In a slow-flowing river below a sewage works, mud is deposited on the river bed. Anaerobic conditions can exist in this mud although the supernatant water is fully oxygenated and any sulphate present may be reduced to sulphide which will be washed downstream when the river is in flood.

It may therefore be concluded that in a river where there is a plentiful supply of oxygen, sewage in moderate quantity has no directly harmful effect on fish unless it is in a septic condition and contains sulphide. When sewage is discharged into a slow-flowing river, mud banks will be formed which may have the necessary anaerobic conditions for the production of sulphide. These, during floods, may be harmful to fish before they are oxidised. There remains the possibility that, although the fish are not directly affected, their food and spawning grounds may suffer from the pollution. This possibility has not been overlooked, but the data on these points are not yet complete.
Studies in Reptilian Colour Response
Authors: Zoond A. , Bokenham N. A. H.
Published: April 2021

In a recent paper (Zoond and Eyre, 1934) the responses of blind and normal chameleons on different backgrounds and with strong and weak illumination were described. Starting with animals adapted to darkness (maximum pallor) colour indices, recorded at intervals of 2 min., were plotted. The time curves thus obtained demonstrated the following facts: (a) In strong light on a black background the animals darken rapidly, and attain a maximum intensity after about 4 min.(b) Blind animals under the same conditions behave in a similar way.(c) In strong light, on a white background, intact chameleons darken perceptibly during the first 2 min. and then slowly become paler, but they never attain a pallor as extreme as in total darkness.(d) Blind animals under the same conditions darken in much the same way as they do on a black background.(e) In weak light, on a black background, intact chameleons darken quite as intensely as in strong light, but blind animals under these conditions remain pale.(f) On a white background, in weak light, the intact animals become slowly dark, the blind animals remain relatively pale.
The Inheritance of Acquired Immunity
Authors: Clay Janet
Published: April 2021

In 1927 Metalnikov published L’infection microbienne et l’immunité chez la mite des abeilles Galleria melonella. Amongst his many interesting experiments was a paper on the much discussed problem of the inheritance of acquired immunity.
Studies on Living Protoplasm
Authors: Harris J. E.
Published: April 2021

In recent years many attempts have been made to determine the absolute coefficient of viscosity of “protoplasm.” The values for this constant obtained by different workers differ widely, and while it is probable that the protoplasm from different sources is never the same in its composition, and cannot be expected to be constant in its viscosity, many sources of error in such determinations have not been sufficiently appreciated. One of the most serious of these, the presence of powerful currents in the protoplasm, forms the subject of this communication.
On the Utilisation of Oxygen by My A Arenaria
Authors: Van Dam L.
Published: April 2021

A study of the rather scarce and widely scattered literature concerning the respiratory exchange of Lamellibranchia shows that even under constant external conditions the oxygen intake of a given specimen is extremely variable. This phenomenon was observed by Mitchell (1912) and Galtshoff and Whipple (1930) in Ostrea, by Weinland (1918) in Anodonta, by Collip (1921) in Mya, by Bruce (1926) and Bouxin (1931) in Mytilus.
Pro-Vitamin A in the Food of Whales
Authors: Drummond J. C. , Macwalter R. J.
Published: April 2021

The origin of the large reserves of vitamin A which may be found in certain tissues, particularly the livers, of fish has been the subject of considerable study. In the case of some species (e.g. cod and halibut) an examination of the food has shown that the concentrations of vitamin A and its acknowledged precursor carotene are curiously small (Drummond and Hilditch, 1930; Lovern and Sharp, 1933). This striking fact has even led to the suggestion that some fish possess the power to synthesise vitamin A from unknown precursors. Alternatively, it seems not improbable that although the food may itself contain but slight traces of vitamin A, the retention of the latter by the liver might in time lead to an accumulation sufficient to account for the large reserves which are encountered.
The Nerve-Net of the Actinozoa
Authors: Pantin C. F. A.
Published: April 2021

Polarity exists in Calliactis, particularly in the tentacles. In these, there is a centripetal polarity of anatomical origin, but there is in addition a physiological polarity running centrifugally. More stimuli are required to facilitate a conducting path centrally from a point on the tentacle than in the reverse direction. Polarity may originate by the development of differential facilitation rates. In some individuals, a kind of after-discharge is observed. A series of one or more extra contractions follows the primary response to a stimulus. Though these appear only after a stimulus has been given they are only indirectly caused by it. Their presence or absence cannot be predicted and seems to bear no relation to the strength of the stimulus. They introduce an arbitrary element into the otherwise singularly regular relation between stimulus and response. Several possible sources for the phenomenon are considered, including synaptic junctions between conducting units of the nerve net, but there are difficulties in accepting any of them. The nerve net of Calliactis possesses many of the properties of the nervous systems of more highly organised animals. The danger is pointed out of employing the unique skeletal neuromuscular system of the Vertebrata as the standard by which the nervous arrangement of other phyla are to be compared.
The Toxic Action of Heavy Metal Salts on the Three-Spined Stickleback (Gastrosteus Aculeatus)
Authors: Erichsen Jones J. R.
Published: April 2021

The observations and conclusions of Carpenter (1927, 1930) regarding the toxic effect of heavy metal salts on the minnow (Leuciscus phoxinus) are shown to apply equally well to the three-spined stickleback (Gastrosteus aculeatus). It is shown that in the case of heavy metal salts the toxic effect of hypertonic solutions is due chiefly to the metallic cation, the toxicity of the anion being relatively small, while in the case of hypotonic solutions the toxicity is due entirely or almost entirely to the cation. Nevertheless, in equimolar concentrations, different salts of the same metal do not have equal or approximately equal toxicity. At the same molar concentration the sulphates of heavy metals are much less toxic than the nitrates or chlorides. This is not due to difference of pH. This difference in toxicity is shown to be closely related to difference in relative electrical conductivity; the toxicity of nitrate, chloride and sulphate is determined, not by the normality alone, but by the product of the normality and conductance ratio. It is concluded that the factors responsible for the lower electrical conductivity of the sulphate also lower the chemical activity of the sulphate so that the toxicity falls in proportion to the conductivity.
The Vapour Pressures of the Blood of Arthropods from Swift and Still Fresh Waters
Authors: Fox H. Munro , Baldes E. J.
Published: April 2021

It has been shown that the oxygen consumption of caddis larvae and mayfly nymphs from swift streams is considerably greater than that of comparable species from still waters, and that within one species of isopod Crustacea, Asellus aquaticus, individuals from swift water consume more oxygen than those from slow water (Fox and Simmonds, 1933; Fox, Simmonds and Washbourn, 1935).

It has also been shown that the oxygen consumption of fresh-water Crustacea is greater than that of their marine relatives (Fox and Simmonds, 1933). Now, in marine invertebrates, the osmotic pressure of the blood is close to that of sea water, whereas in fresh-water invertebrates the difference between the osmotic pressures of blood and water is great. In fresh water compared with marine Crustacea, then, a higher oxygen consumption goes together with a considerable inequality between internal and external osmotic pressures.
Effects of Infra-Red Light on Subsequent Cleavage of the Eggs of Urechis Caupo
Authors: Nelson Clarence , Brooks S. C.
Published: April 2021

We have recently reported (Nelson and Brooks, 1933) that infra-red light of wavelengths of approximately 1μ, interfered with successful formation of fertilisation membranes by subsequently inseminated eggs of Urechis caupo and two species of Strongylocentrotus. We now show that this injury is still traceable in the rate of cleavage of the fertilised eggs of Urechis, but that gradual recovery, or some process which simulated it, takes place both before and after insemination.
The Photoreceptors of Lampreys
Authors: Young J. Z.
Published: April 2021

The tail of larval and adult L. planeri and adult L. fluviatilis contains a photoreceptive mechanism involving an initial short sensitization period, and a latent period. The impulses initiated by the photochemical change are carried in the lateral line nerves, as is shown by the facts that section of these nerves abolishes the response, whereas section of the spinal cord does not do so. Motor responses are only occasionally seen after illumination of parts of the body other than the tail. These responses are apparently due to direct stimulation of the spinal cord, and can be regularly elicited if the pigment protecting the latter be removed. Motor responses may follow illumination of the head, either of larvae or adults, but only after illumination periods much longer than are necessary to obtain a response from the tail. The responses play a part in the normal behaviour of the animals by assisting them to bury themselves completely in the mud. The stimulus of illumination of the tail simply initiates swimming movements, and there is no orientation of the animal with reference to the direction of the light. This is confirmed by the observation that, following illumination of the tail from one side, the first movement of the head may be either towards or away from the side stimulated. Further, after section of one lateral line nerve only no forced movements occur on illumination. The reaction may thus be described as a photokinesis, and does not involve any true topotaxis, its effect is to prevent the animal remaining in any illuminated area.
An Oil-Soluble Neurohumour in the Catfish Ameiurus
Authors: Parker G. H.
Published: April 2021

The skin and fins of Ameiurus, irrespective of their original state, take on the dark coloration (dispersion of melanophore pigment) whenever they are triturated. Hence oil extracts can be made from these parts only in the dark condition. Olive oil extracts from the skin and fins of dark Ameiurus when injected under the skin of light-tinted individuals induce the formation of temporary dark splotches in an otherwise light skin. These splotches result from the dispersion of pigment in the melanophores, both epidermal and dermal, in the region of the injection. On the spontaneous disappearance of these splotches, which ordinarily occurs a few days after their formation, the melanophore pigment reassumes its concentrated state. Newly formed dark splotches in Ameiurus may be obliterated by an injection of adrenalin and will return spontaneously after the adrenalin has disappeared. From these several tests it is concluded that the nervous factor in the dispersion of the melanophore pigment of Ameiurus is an oil-soluble neurohumour of local activity. Ether extractions, hot and cold, yielded residues that were only slightly active in darkening the skin of the catfish. No effective oil extracts could be obtained from the dark skins and fins of Fundulus heteroclitus probably because of the inaccessibility of the tissues to the oil.
The Photoreceptors of Lampreys
Authors: Young J. Z.
Published: April 2021

Illumination of the dorsal region of the head of an ammocoete larva is followed by movements of the animal, but only after exposure for longer periods than are necessary to elicit responses from the tail. Since this reaction persists unaffected after removal of the pineal and paired eyes, it is concluded that it is produced by the direct effect of light on some tissue in the brain. Larval and adult L. planeri show very pronounced daily rhythms of colour change, becoming pale at night and dark during the daytime. Continuous artificial illumination of the animals produces maximal darkening and stops the diurnal rhythm. When animals are left in total darkness the diurnal changes usually persist, though diminished in extent; sometimes the melanophores come to rest in the expanded phase. Since section or faradic stimulation of spinal nerves is not followed by local changes in the melanophores, it is concluded that these are not under nervous control. After removal of either the whole pituitary complex or its pars nervosa and intermedia the animals become maximally pale, and remain so indefinitely in spite of changes of illumination. Injection of extracts of mammalian posterior pituitary lobe causes darkening of such hypophysectomised lampreys. Pituitrin was also found to be capable of maintaining the expansion of isolated melanophores. After removal of the pineal complex from ammocoetes the rhythms of colour change were interrupted, the melanophores remaining in the expanded phase under all conditions of illumination. Removal of the pineal of adult L. planeri disturbed the colour rhythm, which was then completely abolished if the paired eyes were also removed. Thus the paling of an ammocoete when it passes from light to darkness is probably due to the inhibition of posterior pituitary secretion by nervous impulses set up by the change of illumination of the pineal complex.
The Effect of Hypophysectomy on the Reproductive Organs of the Male Guinea-Pig
Authors: Allanson M. , Hill R. T. , McPhail M. K.
Published: April 2021

Atrophic changes in the testes and accessory organs following hypophysectomy have now been described in a number of mammals, but not as yet in the guinea-pig. McPhail and Parkes (1933), in describing a method of removing the pituitary in guinea-pigs, noted that regression of the testes occurred but gave no details. Pencharz and Lyons (1934) have described the effects of hypophysectomy on the pregnant female, while Selye, Collip and Thomson (1934) record the operation on a single pregnant female.
The Nerve Net of the Actinozoa
Authors: Pantin C. F. A.
Published: April 2021

The relation of the “staircase “effects in the vertebrate heart, in the bell of Medusae and in the sphincter of Calliactis is discussed. Whereas in the heart the effect is due to an intrinsic increase of contractility of the whole contractile tissue, evidence is brought to show that the staircase in Calliactis and in Medusae depends upon neuromuscular facilitation by which each stimulus in a series reaches more and more individual muscle fibres. The relation of different types of contraction in coelenterate muscle is discussed. It is shown how this depends upon the relation of the stimulation interval necessary for a facilitated response and the duration of a complete contraction and relaxation of the muscle. If these are about equal the step-like contraction of the sphincter of Calliactis results ; if the facilitation interval is long a staircase similar to that of a Medusa bell is produced ; if the duration of the twitch is relatively long a smooth contraction as in the mesenteric muscle of Calliactis is produced.
Photo-Electric Records of the Colour Change in Fundulus Heteroclitus
Authors: Hill A. V. , Parkinson J. L. , Solandt D. Y.
Published: April 2021

The colour change in Fundulus is produced by an alteration in the size of its chromatophores, caused by impulses in special nerve fibres running to them. According to Parker (1934 a, b, and elsewhere) the nerves produce their effects not directly, but by chemical transmitters (“neurohumors”) of some kind. The movements of the chromatophores are very rapid, although they are not, as in the cuttlefish and squid, due to muscle fibres pulling the chromatophores out, or allowing them to relax elastically.
Tissue Intracellular Acid-Base Status and the Fate of Lactate After Exhaustive Exercise in the Rainbow Trout
Authors: Milligan C. Louise , Wood Chris M.
Published: April 2021

Exhaustive ‘burst-type’ exercise in the rainbow trout resulted in a severe acidosis in the white muscle, with pHi dropping from 7·21 to a low of 6·62, as measured by DMO distribution. An accumulation of lactate and pyruvate, depletions of glycogen, ATP and CP stores, and a fluid shift from the extracellular fluid to the intracellular fluid of white muscle were associated with the acidosis. The proton load was in excess of the lactate load by an amount equivalent to the drop in ATP, suggesting that there was an uncoupling of ATP hydrolysis and glycolysis. Initially, lactate was cleared more quickly than protons from the muscle, a difference that was reflected in the blood. It is suggested that during the early period of recovery (0–4 h), the bulk of the lactate was oxidized in situ, restoring pHi to a point compatible with glyconeogenesis. At that time, lactate and H+ were used as substrates for in situ glyconeogenesis, which was complete by 24 h. During this time, lactate and H+ disappearance could account for about 75 % of the glycogen resynthesized. The liver and heart showed an accumulation of lactate, and it is postulated that this occurred as a result of uptake from the blood. Associated with the lactate load in these tissues was a metabolic alkalosis. Except for an apparent acidosis immediately after exercise, the acid-base status of the brain was not appreciably affected. Despite the extracellular acidosis, red cell pHi remained nearly constant.
Electrical and Chemical Synapses Between Giant Interneurones and Giant Flexor Motor Neurones of the Hermit Crab (Pagurus Pollicaris)
Authors: Stephens Philip J.
Published: April 2021

An examination is made of the characteristics of the synapses between the single pair of giant interneurones (GIs) and the giant flexor motor neurones (GFMNs) in the fused thoracic-abdominal (TA) ganglion of the hermit crab Pagurus pollicaris. There is an electrical synapse between each GI and its ipsilateral GFMN. Evidence for this includes (a) dye (Lucifer Yellow CH) coupling between the two neurones, (b) a short synaptic (0·2 ms) delay between spikes in the two axons, (c) the ability to pass hyperpolarizing current between the two neurones and (d) the sensitivity of the connection to bath applications of N-ethylmaleimide. This synaptic connection is rectifying, since a GFMN spike does not provoke an action potential in the GI. There is a connection between the GI and the contralateral GFMN. Data indicating that this synaptic connection is chemical includes (a) a synaptic delay of between 0·6 and 0·8 ms, (b) transmission is easily and irreversibly fatigued, (c) the synapse is insensitive to N-ethylmaleimide and (d) there is no dye coupling between the two neurones. Branches of the GFMN come in close proximity with the GI on both sides of the TA ganglion. However, it is not known whether there is a direct connection or an intervening neurone between the GI and the contralateral GFMN.
The Organization and Role During Locomotion of the Proximal Musculature of the Cricket Foreleg I. Anatomy and Innervation
Authors: Laurent Gilles , Richard Daniel
Published: April 2021

The structure of the proximal segments of the cricket (Gryllus bimaculatus) foreleg, together with the associated musculature and its innervation are described. The morphology of 50 motor neurones involved in the control of this musculature has been revealed using backfilling techniques with cobalt, horseradish peroxidase and Lucifer Yellow.

The ‘ball and socket’ pleurocoxal joint is moved by three sets of anatomical antagonists (promotor-remotor, abductor-adductor, anterior-posterior rotator muscles) inserted on each side of the three axes of rotation.

The axial coxotrochanteral joint is moved by the intrinsic levator and the depressor muscles; these depressors are composed of an intrinsic (coxotrochanteral) and a ‘double’ (pleurotrochanteral) subgroup.

The double depressors, and all the muscles inserting on the trochantin (promotors) or the anterior coxal rim (adductor, abductors, anterior rotators) are supplied by at least eighteen neurones, whose axons run in nerve 3.

The muscles that insert on the posterior coxal rim (remotors, posterior rotators) are innervated by at least twelve similar neurones whose axons run in nerve 4.

The intrinsic coxal muscles are supplied by branches of nerve 5 (ten motor neurones to the levators, two to the depressors).

Three presumably common inhibitors, and one Dorsal Unpaired Median (DUM) neurone have also been found.
Effective and Morphometric Oxygen-Diffusing Capacity of the Gills of the Elasmobranch Scyliorhinus Stellaris
Authors: Piiper Johannes , Scheid Peter , Perry Steven F. , Hughes George M.
Published: April 2021

Calculations of the effective O2 conductance (diffusing capacity or transfer factor, Deff) of fish gills, obtained from experimental data on gill O2 exchange, were compared with the predicted O2-exchange properties of gill models based on morphometric measurements of the elasmobranch, Scyliorhinus stellaris. Deff was calculated from O2 uptake and in gill water and blood, using a modified Bohr integration technique. In the morphometric gill model, O2 conductance was considered for both the water-blood tissue barrier (Dm) and the interlamellar water (Dw). Dm was calculated from the total secondary lamellar surface area, the harmonic mean water-blood barrier thickness, and an assumed Krogh O2-diffusion constant for gill tissue. Dw was estimated from the dimensions of the interlamellar spaces, the mean respiratory water flow velocity, and the diffusion coefficient of O2 in water.

The ratio Dm/Dw was 1·84 in quiescently resting, 1·68 in resting alert, and 1·47 in swimming fish, showing that diffusion across interlamellar water was somewhat more important than that across the water-blood barrier in limiting the diffusive O2 transfer between water and blood. The total morphometric diffusing capacity, Dmorph, estimated by the combined membrane-and-water diffusing capacity, Dm+w, which is defined as l/Dm+w= 1/Dm+1/Dw, was similar to Deff, the ratio Dm+w/ Deff being 1·64 for quiescently resting, 1-02 for resting alert, and 0·92 for swimming fish. The good agreement between the effective and morphometric D estimates validates the approach, and leaves, at least for the alert and swimming fish, little space for functional inhomogeneities, which are expected to reduce Deff as compared to Dm+w.
Primary Cultures of Muscle From Embryonic Locusts (Locusta Migratoria, Schistocerca Gregaria): Developmental, Electrophysiological and Patch-Clamp Studies
Authors: Duce J. A. , Usherwood P. N. R.
Published: April 2021

Primary cultures of muscle tissue from 10-day-old embryos of Locusta migratoria and 11-day-old embryos of Schistocerca gregaria have been grown and maintained in 5+4 insect medium and Grace’s insect medium. Myofibres grown in 5+4 medium reached maximum size after about 5 weeks in culture and could be maintained for 2–3 months. They were often branched and rarely striated in appearance. Those grown in Grace’s medium reached maximum size within 3 weeks and could be maintained for about 4 weeks in toto. They were striated and resembled, at least superficially, locust myofibres in vivo. Patch-clamp recordings from myofibre cultures grown in 5+4 medium, either on the myofibres or from excised membrane patches, indicated the presence of a diffusely-distributed population of receptors for L-glutamate. 10−6moll−1 concanavalin A blocked the desensitization of these receptors. The glutamate receptors gated large conductance channels which had reversal potentials of about 0mV. The amplitude of the channel current was sensitive to the concentration of calcium in the membrane environments.
Myofibrillar ATPase Activity in the Carp Cyprinus Carpio: Interactions Between Starvation and Environmental Temperature
Authors: Heap S. P. , Watt P. W. , Goldspink G.
Published: April 2021

The myofibrillar ATPase activity of the epaxial white muscle was measured in carp Cyprinus carpio L. acclimated to 10°C or 28°C. As previously reported, cold acclimation was associated with an increase in the ATPase specific activity and a decrease in the thermostability. The water content of the white muscle was significantly higher in cold-acclimated fish than in warm-acclimated fish (P< 0·002). Starvation for 10 weeks resulted in a significant increase in the white muscle water content of both warm- and cold-acclimated fish (P< 0·002). When carp were starved, the ability of the myofibrillar ATPase to show thermal compensation disappeared. Previously acclimated fish, when starved, showed steady alterations of the myofibrillar ATPase activity to a level mid-way between the acclimated extremes. Refeeding resulted in a gradual return to the normal acclimated level.
Plasma Catecholamines in the Lesser Spotted Dogfish and Rainbow Trout at Rest and During Different Levels of Exercise
Authors: Butler P. J. , Metcalfe J. D. , Ginley S. A.
Published: April 2021

The hypothesis that there is an increase in plasma catecholamines during exercise in fish and that they play an important role in the cardiovascular adjustments during exercise was investigated in the lesser spotted dogfish and rainbow trout. In resting fish plasma catecholamines were at a concentration of 10−9–10−8 mol I−1. During spontaneous swimming in the dogfish, adrenaline increased by 3·3 times to l·9× 10−8mol I−1 and noradrenaline increased by 2·3 times to 3·2× 10−8mol I−1. In rainbow trout swimming at a steady 1 body lengths−1 (Ls−1) in a water channel, the levels of both amines decreased to approximately 25% of the resting values. When swimming to apparent exhaustion at approximately 2Ls−1, adrenaline was 10 times the resting value at 1·4× 10−8mol I−1, whereas noradrenaline was 2·2 times the resting value at 2·3 × 10−8mol l−1. Only after repeated burst swimming for 2–3 min did the levels of plasma catecholamines increase substantially above the resting values. In the dogfish, both amines were at 10−7moll−1, whereas in the rainbow trout, noradrenaline was at 8·5× 10−8mol I−1 and adrenaline was at 2× 10−7mol l−1.

These levels were compared with the concentrations of catecholamines used by other workers to elicit changes in the branchial vasculature, gas exchange at the gills or gas transport to the tissues. In lesser spotted dogfish, the levels of adrenaline and noradrenaline present in the plasma during spontaneous swimming have 80% and 50% of maximum effect on gill blood vessels, respectively, whereas in rainbow trout the levels present when swimming to apparent exhaustion have approximately 20 % of maximum effect on the branchial vasculature. The levels present in the trout after repeated burst swimming have 40% of maximum effect on blood vessels in the gills. The difference between the dogfish and the trout may be related to the lack of innervation of the gill blood vessels in the former. Enhancement of gas exchange across the gills of rainbow trout can be demonstrated by using adrenaline at the concentration found after repeated burst swimming. It is possible, however, that the concentration of adrenaline found in the plasma of trout after swimming to apparent exhaustion may cause an increase in the concentration of oxygen in arterial blood, thus enhancing oxygen delivery to the tissues.

It therefore appears that, in rainbow trout, only the levels of plasma catecholamines attained during repeated burst swimming are likely to have clear effects on oxygen delivery to the tissues. Burst swimming is powered by the white anaerobic muscle fibres, so oxygen delivery during the exercise will not be of value. An elevated supply of oxygen after such exercise could well be important, although it is not certain to what extent a fish would engage in repeated burst swimming for several minutes in its natural environment.
Intracellular and Extracellular Acid-Base Status and H+ Exchange with the Environment After Exhaustive Exercise in the Rainbow Trout
Authors: Milligan C. Louise , Wood Chris M.
Published: April 2021

Exhaustive exercise induced a severe short-lived (0–1 h) respiratory, and longer-lived (0–4 h) metabolic, acidosis in the extracellular fluid of the rainbow trout. Blood ‘lactate’ load exceeded blood ‘metabolic acid’ load from 1–12 h after exercise. Overcompensation occurred, so that by 8–12 h, metabolic alkalosis prevailed, but by 24 h, resting acid-base status had been restored. Acid-base changes were similar, and lactate levels identical, in arterial and venous blood. However, at rest venous RBC pHi was significantly higher than arterial (7·42 versus 7·31). After exercise, arterial RBC pHi remained constant, whereas venous RBC pHi fell significantly (to 7·18) but was fully restored by 1 h. Resting mean whole-body pHi, measured by DMO distribution, averaged approx. 7·25 at a pHe of approx. 7·82 and fell after exercise to a low of 6·78 at a pHe of approx. 7·30. Whole-body pHi was slower to recover than pHe, requiring up to 12 h, with no subsequent alkalosis. Whole-body ECFV decreased by about 70 ml kg−1 due to a fluid shift into the ICF. Net H+ excretion to the water increased 1 h after exercise accompanied by an elevation in ammonia efflux. At 8–12 h, H+ excretion was reduced to resting levels and at 12–24 h, a net H+ uptake occurred. Lactate excretion amounted to approx. 1 % of the net H+ excretion and only approx. 2% of the whole blood load. Only a small amount of the anaerobically produced H+ in the ICF appeared in the ECF and subsequently in the water. By 24 h, all the H+ excreted had been taken back up, thus correcting the extracellular alkalosis. The bulk of the H+ load remained intracellular, to be cleared by aerobic metabolism.
Hormonally Mediated Reprogramming of Muscles and Motoneurones During the Larval-Pupal Transformation of the Tobacco Hornworm, Manduca Sexta
Authors: Weeks Janis C. , Truman James W.
Published: April 2021

The larval-pupal transformation of Manduca sexta results from an exposure to ecdysteroids in the absence of juvenile hormone (the commitment pulse), followed by a larger exposure to ecdysteroids (the prepupal peak) with a reappearance of juvenile hormone (JH). The prepupal ecdysteroid peak triggers the degeneration of abdominal muscles, and the dendritic regression and death of identified moto-neurones. The present experiments examined the role of the commitment pulse in the larval-pupal reprogramming of these cells. The commitment pulse did not overtly affect the muscles and motoneurones, but it switched their hormonal responsiveness; before the commitment pulse, exposure to ecdysteroids in the presence of JH had no effect on the larval cells, whereas after the commitment pulse the same treatment caused regression and death. Thus, JH lost its ability to prevent pupal development. Furthermore, treatment with ecdysteroids in the absence of JH before the commitment pulse promoted pupal development much less effectively than did the same treatment given after the commitment pulse, indicating that the commitment pulse facilitates the subsequent responsiveness to ecdysteroids. Thus, the commitment pulse covertly causes both qualitative and quantitative changes in the hormonal sensitivity of the larval muscles and motoneurones.
The Effects of Sensory Manipulation Upon Interlimb Coordination During Fast Walking in the Cockroach
Authors: Tang Twen Poh , Macmillan David L.
Published: April 2021

A re-examination of fast stepping in free-walking cockroaches showed that there was considerable variation in the alternating tripod gait. Small load increments applied to the whole animal significantly reduced this variability and concentrated the range and speed of movements used. Animals suspended above oiled glass surfaces moved their legs in normal gait patterns indicating that mechanical coupling via the substrate was not a critical factor for normal high-speed coordination. Increasing the viscosity of the oil produced the same reduction in variability found with load increment so the change cannot be due to increased mechanical coupling. Increasing the viscosity of the oil under one leg alone resulted in concentration over the whole pattern so the result was not considered to be due to viscosity changes. The changes seen in artificial loading situations were mimicked in natural loading situations such as walking up a slight incline. The functional significance of the phenomenon for the stability of the rapidly moving animal is considered and the role of load afference in biasing central pattern generators to produce a continuous range of functional output is discussed.