bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the Nutrition of Maggots of Australian Blow-Flies
Authors: Mackerras M. J. , Freney M. R. 
Published: April 2021

ABSTRACT
Larvae of L. cuprina and Ch. rufifacies are capable of liquefying and digesting protein media without the intervention of bacteria. Both species and L. sericata secrete tryptic and peptic enzymes and at least L. cuprina does so from the moment of hatching. Tryptase is more abundant than pep tase. Predatory activity, though a normal habit of Ch. rufifacies, is not necessary for any of these species and did not occur in the masses of Lucilia larvae used for extraction of the enzymes, although they were kept for periods up to 24 hours without food. Partial development of larvae occurred in sheep dung, faeces-stained wool and in the products of keratin hydrolysis. Complete development took place in wool containing a “gummy crust” of dried exudate and in. some samples of faeces-stained wool. Some of the samples of faeces-stained wool and those containing a “crust” have been demonstrated serologically by Dr I. M. Mackerras to have an increased content of soluble sheep protein as compared with normal wool. A marked increase of soluble protein has been demonstrated in struck wool both chemically and serologically. Moisture, warmth, shelter and aeration are essential physical conditions for larval development. In addition, an alkaline reaction is relatively favourable and an acid reaction relatively unfavourable. There are normally two stages in the development of a primary strike, the first stage being from hatching up to the time the larvae attack the skin, the outer layer or epidermis of which is approximately 36µ thick (Whitnall, 1931). During this stage they must feed, if at all, on materials already present. The second stage is from the commencement of an actual skin lesion up to full development of the maggots. During this stage there is a more or less copious serous exudation, which has been shown to be an adequate food for the full development of the maggots. Faeces-staining, presence of exudate due to a prior lesion, and products of wool hydrolysis have been shown to be adequate to carry the larvae through the first stage. Wool hydrolysis on the living sheep is probably not an important factor, judging by an examination of wool samples, but we have isolated organisms which, when growing on a nutrient medium, are capable of disintegrating wool fibre. The role of bacterial activity in strike is complex and appears to be substantially as follows : (a) to produce substances which attract the flies and stimulate them to oviposit ; (b) to provide food for the initial growth of the maggots, either by rendering assimilable the inert proteins, or by causing a skin reaction with a serous exudation. The immediate work for the future is a more exact determination of: (a) the nature of the food of the larvae in the early stage of growth on the living sheep; (b) the factors which influence its production ; and (c) the mechanism by which the larvae invade the skin.
The Effects of Hypophysectomy and Anterior Lobe Administration on the Skin and Thyroid of Triton Cristatus
Authors: Adams A. Elizabeth 
Published: April 2021

ABSTRACT
The skins of many vertebrates react to variations in the amount of hormones of the endocrine glands, especially of the thyroid and pituitary. Moulting in Triturus viridescens is inhibited after both thyroidectomy and hypophysectomy or both operations simultaneously performed. The cornified layers continue to form and the accumulation of these makes the animal appear grimy (Adams and Richards, 1929; Adams, Richards and Kuder, 1930; Adams, Kuder and Richards, 1932). The series of experiments here reported demonstrates that a similar effect occurs after hypophysectomy in immature or mature Triton cristatus (Adams, 1931a). The moult in Triturus viridescens operated in the above ways can be induced by various methods. Supplying thyroid hormone by thyroid grafts or thyroxin injections, or administering iodine to thyroidectomised or hypophysectomised animals or to ones lacking both glands, or stimulating the thyroid glands of hypophysectomised animals either by giving pars anterior grafts or injections or by pinching them in situ, will cause the shedding of the cornified layers (Adams et al. 1930, 1932; Adams, 1931 b, 1932). Similarly in hypophysectomised Triton cristatus, the moult can be induced by administration of pars anterior substance or by injection of certain extracts of mammalian anterior lobe.
The Defence-Arousal System and its Relevance for Circulatory and Respiratory Control
Authors: Hilton S. M. 
Published: April 2021

ABSTRACTIt was proposed some fifty years ago that the visceral and hormonal changes accompanying fear and rage reactions can best be understood as adaptations which prepare an organism to cope with an emergency and specifically to perform the extreme muscular exertion of flight or attack. This is well exemplified by the pattern of cardiovascular response which is characteristic of the alerting stage of these reactions and consists of an increase in cardiac output directed mainly to the skeletal muscles.This group of behavioural responses has been collectively termed the defence reaction. The regions of the hypothalamus and brainstem which organize it have been mapped. They function as a reflex centre for the visceral components of the altering response as well as initiating the behavioural response. So far as the cardiovascular system is concerned, this is a preparatory reflex and not compatible with short-term homeostasis. Indeed, the baroreceptor reflex, which is homeostatic, is strongly inhibited. By contrast, the chemoreceptor reflex is facilitated. The input from peripheral chemoreceptors is itself an alerting stimulus.The visceral alerting response has been studied in most detail in the cat, but there is evidence for the same cardiovascular pattern and an accompanying group of respiratory changes in other mammalian species (rat, rabbit, dog, monkey and man).On the efferent pathway for the cardiovascular response pattern, there is a group of relay neurones near the ventral surface of the caudal medulla, which seem important for the maintenance of arterial blood pressure. The visceral alerting system may therefore be continually engaged to some extent in the awake state, as well as being acutely activated in response to novel, and especially to noxious, stimuli.
Respiratory and Cardiovascular Control During Diving In Birds and Mammals
Authors: Butler P. J. 
Published: April 2021

ABSTRACTRecent studies on freely diving birds and mammals indicate that, contrary to the classical hypothesis, the majority of dives are aerobic with minimal cardiovascular adjustments (i.e. bradycardia and selective vasoconstriction). It is postulated that during these aerobic dives the cardiovascular adjustments result from the opposing influences of exercise and the classical diving response, with the bias towards the exercise response. It is envisaged that the active muscles, as well as the brain and heart, are adequately supplied with blood to enable them to metabolize aerobically. Intense mental activity, particularly in carnivores seeking their prey, may also attenuate the classical response. Aerobic dives are usually terminated well before the oxygen stores are depleted, and another dive follows once they have been replenished. In this way a series of dives is performed.Prolonged dives are endured as a result of a shift towards the classical response of bradycardia, presumably more intense vasoconstriction, and anaerobiosis. This may be a form of alarm response, particularly in small animals such as ducks and coypus, or it may be a means of allowing the marine birds and mammals that dive deeply for their food to engage in unusually long hunting expeditions. For those that dive under ice, it may also allow long periods of underwater exploration as well as being a safety mechanism should the animal become disoriented.
Respiratory and Circulatory Control During Sleep
Authors: Coote J. H. 
Published: April 2021

ABSTRACT
A survey of the literature on a large number of vertebrate animals shows that sleep is associated with profound cardiovascular and respiratory adjustments which are very similar in each species. A hypothesis is advanced that these adjustments are ‘goal directed’ by neural structures in the brainstem, to ensure an adequate O2 and CO2 transport to and from the brain whilst at the same time reducing energy cost. During synchronised sleep there is a vagal bradycardia leading to reduced cardiac output and a fall in blood pressure; despite this cerebral blood flow increases. During desynchronized sleep there is a tonic fall in blood pressure and heart rate resulting from a unique repatterning of sympathetic discharge, that to heart, kidney, splanchnic and pelvic vascular beds decreasing whilst that to skeletal muscle increasing ; cerebral blood flow shows a further increase. This differential pattern is probably initiated by neurones located in the caudal raphe nucleus obscurus. Phasic increases in blood pressure and heart rate also occur during desynchronized sleep mainly as a consequence of increases in sympathetic activity. Ventilation decreases during synchronized sleep accompanied by an increase in partial pressure of arterial CO2, which vasodilates cerebral blood vessels, indicating that the influence of CO2 on the level of ventilation has changed. During desynchronized sleep ventilation increases and becomes very irregular but the partial pressure of O2 and CO2 in arterial blood is little changed from wakefulness. Control of respiration is shifted to a central generator which apparently is different to the automatic/ metabolic one which is normally dominant during wakefulness. Reflex control of the circulation and respiration is mainly governed by peripheral chemoreceptors, the threshold of most other afferent inputs being significantly raised during sleep.
Control and Co-Ordination of Ventilation and Circulation in Crustaceans: Responses to Hypoxia and Exercise
Authors: Taylor E. W. 
Published: April 2021

ABSTRACT
The functional morphology, nervous and hormonal control and coordination of the cardiovascular and ventilatory systems in decapodan crustaceans is reviewed. Pacemaker function reflects the reliance of crustaceans on small numbers of large, multipolar neurones. Respiratory gas exchange and transport may be limited by the potential diffusion barrier presented by chitin on the gills and by the relatively low O2 capacity of the haemolymph, though this is compensated by the relatively high O2 affinity of haemocyanin and the large volume of the haemocoel. Haemolymph buffering capacity is attributable to haemocyanin and to bicarbonate, including an internal source of fixed base, possibly the exoskeleton.
The typical hypoxic response includes a bradycardia and hyperventilation resulting in a respiratory alkalosis and resultant increase in O2 affinity of the haemocyanin. Diffusive conductance may increase. When 02 transport is limiting there is a switch to anaerobiosis with normoxic recovery including repayment of an O2 debt. Some species are facultative air-breathers and compensate for a respiratory and metabolic acidosis when in air by elevation of buffer base. Central and peripheral O2 receptors may be involved in determining respiratory and cardiovascular responses to hypoxia and airbreathers may respond to changes in haemolymph pH. Exercise induces a rapid increase in ventilation, diffusive conductance improves and O2 consumption is elevated. There is also a major anaerobic contribution causing a metabolic acidosis and recovery includes prolonged repayment of an O2 debt.
Pulmonary And Respiratory Tract Receptors
Authors: Widdicombe J. G. 
Published: April 2021

ABSTRACT
Nervous receptors in the lungs and respiratory tract can be grouped into four general categories.
Deep, slowly adapting end-organs, which respond to stretch of the air-way wall and have large-diameter myelinated fibres; those in the lungs are responsible for the Breuer–Hering reflex. Endings in and under the epithelium which respond to a variety of chemical and mechanical stimuli (i.e. are polymodal), usually with a rapidly adapting discharge, and with small-diameter myelinated fibres; they are responsible for defensive reflexes such as cough and sneeze, and for the reflex actions to inhaled irritants and to some respiratory disease processes. Receptors with nonmyelinated nerve fibres which, being polymodal, are stimulated by tissue damage and oedema and by the mediators released in these conditions ; these receptors may be similar in function to * nociceptors’ in other viscera, and set up appropriate reflexes as a reaction to respiratory damage. Specialized receptors such as those for taste and swallowing, and those around joints and in skeletal muscle.
Stimulation of any group of receptors may cause reflex changes in breathing (including defensive reflexes), bronchomotor tone, airway mucus secretion, the cardiovascular system (including the vascular bed of the airways), laryngeal calibre, spinal reflexes and sensation. The total pattern of motor responses is unique for each group of receptors, although it is probably unusual for one type of receptor to be stimulated in isolation. The variety of patterns of motor responses must reflect the complexity of brainstem organization of these systems.
Limb Mechanics as A Function of Speed and Gait: A Study of Functional Strains in the Radius and Tibia of Horse and Dog
Authors: Rubin Clinton T. , Lanyon Lance E. 
Published: April 2021

ABSTRACT
Rosette strain gauges were attached to the midshaft of the radius and tibia of two horses and two dogs, which ran on a treadmill through their entire range of speed and gait. The relative magnitudes of the principal strains on the opposite cortices of each bone remained constant through the stance phase of the stride, and their orientation varied by a maximum of only 14° through the entire speed range. The maximum strain rate increased linearly with speed, but the peak strain magnitude was also dependent upon the gait used, increasing incrementally by up to 59% at the transition from walk to trot, and dropping by 42 % from a trot to a canter. Force transducers attached to the shoes of one horse indicated similar changes in ground load.
The peak strains induced during vigorous activity are remarkably uniform in a wide range of animals. This suggests that the skeleton is scaled to provide constant safety margins between peak functional strains and those at which yield and ultimate failure occur.
Acid-Base Balance in Callinectes Sapidus During Acclimation from High to Low Salinity
Authors: Henry Raymond P. , Cameron James N. 
Published: April 2021

ABSTRACT
When transferred from 865 to 250 m-osmol salinity, the blue crab C. sapidus maintains its blood Na+ and Cl− concentrations significantly above those in the medium. When branchial carbonic anhydrase is inhibited by acetazolamide, ion regulation fails and the animals do not survive the transfer. An alkalosis occurs in the blood at low salinity, indicated by an increase in HCO3− and pH at constant . The alkalosis is closely correlated with an increase in the Na+–Cl− difference, a convenient indicator of the overall strong ion difference. The contribution’ of changes in to acid-base changes was negligible, but the change in the total weak acid (proteins) may be important. It is suggested that the change in blood acidbase status with salinity is related to an increase in the strong ion difference, which changes during the transition from osmoconformity to osmoregulation in the blue crab, and which is related to both carbonic anhydrase and ion-activated ATPases.
Reflex Effects of the Femoral Chordotonal Organ Upon Leg Motor Neurones of the Locust
Authors: Field L. H. , Burrows M. 
Published: April 2021

ABSTRACT
The femoral chordotonal organ (FCO) in a hind leg of a locust monitors the position and movement of the tibia about the femur. It consists of a group of sensory neurones embedded in connective tissue attached distally by two structures: the apodeme, which inserts close to the apodeme of the extensor tibiae muscle, and the flexor strand, which inserts at the base of the apodeme of the flexor tibiae muscle. The action of the apodeme and the flexor strand is reciprocal during movements of the tibia; the apodeme is stretched during flexion of the tibia whilst the flexor strand is relaxed. During extension, the apodeme is relaxed and the flexor strand is stretched. To analyse the reflex effects of this sense organ, all other sense organs of a hind leg were denervated. The apodeme of the FCO was then grasped between forceps, severed from its distal attachment site and its movements controlled by a function generator. The flexor strand remained intact and could be stimulated independently by moving the tibia.
The different reflex effects mediated by the separate stimulation of the two components of the FCO were revealed by making intracellular recordings from the somata of leg motor neurones in the metathoracic ganglion. A movement stimulus to either component in a way that corresponded to tibial extension, excited flexor tibiae and inhibited extensor tibiae motor neurones. There was also an inter-joint effect whereby extension excited the depressor tarsi and inhibited the levator tarsi motor neurones. A flexion movement had the converse effects on these motor neurones.
The effectiveness of the two components was dependent upon the velocity of the stimulus, the set position of the femoro-tibial joint at which the stimulus was applied, the initial direction of movement, and the activity of other neurones in the central nervous system. Slow motor neurones were depolarized more by low velocities of movement, whereas fast ones were depolarized more by high velocities. The two components produced their greatest effects at the set positions where they were most stretched ; thus the apodeme was most effective when the joint was flexed, and the flexor strand when it was extended.
Elicited movements of the hind legs or apparently spontaneous changes of excitability enhanced or masked the typical response of the motor neurones to stimulation of the FCO, indicating that the effects of this sense organ are not to be viewed as rigid, but as modifiable in the context of the behaviour of the animal.
The Control System of the Femur-Tibia Joint in the Standing Leg of A Walking Stick Insect Carausius Morosus
Authors: Cruse H. , Schmitz J. 
Published: April 2021

ABSTRACT
The control system of the femur-tibia joint of the stick insect (Carausius morosus) shows different properties depending on whether the animal is standing or walking. The properties of the system were examined when the animal was walking on a treadwheel and when the examined leg rested on a platform fixed beside the wheel. The results show that the properties of the system in the standing leg of a walking animal are similar to those of a walking animal rather than those of the standing animal. This indicates that the state of the leg (standing or walking) does not seem to be controlled by the neural subsystem of the leg itself but by a more generalized system, which differs in its properties depending upon whether the whole animal is standing or walking. Furthermore the results show how the behaviour of the system changes for the two alternative states.
Modulation of Synaptic Transmission and Excitation-Contraction Coupling in the Opener Muscle of the Crayfish, Astacus Leptodactylus, By 5-Hydroxytryptamine and Octopamine
Authors: Fischer Ludwig , Florey Ernst 
Published: April 2021

ABSTRACT
The modulatory actions of 5-hydroxytryptamine (5-HT) and octopamine (OA) were investigated in the opener nerve-muscle preparation of the crayfish, Astacus leptodactylus. Membrane resistance and resting potential were unaltered by 5-HT and OA at concentrations up to 2·5 × 10−5 M; but EPSP-amplitudes were increased, up to 3-fold by OA and up to 18-fold by 5-HT. The lowest effective concentration was 2·5 × 10−9M; a maximal effect was produced at 2·5 × 10−6M. The effect was reversible only after prolonged washing. The enhancement of EPSPs by 5-HT or OA is due to an increased amplitude of the synaptic current; the current duration is not altered. The facilitation ratio (ratio of amplitudes of a pair of EPSPs) is not significantly affected by 5-HT or OA despite the often enormous increase of the absolute EPSP-amplitudes.
The modulatory action also affects the excitation-contraction (e-c) coupling process: the effectiveness of e-c coupling was increased 7·4-fold by 5-HT (2·5 × 10−6M) and 18-7-fold by OA (5 × 10−6M). The threshold potential of e-c coupling was not affected.
The Effect of Efferent Stimulation on the Phase and Amplitude of Extracellular Receptor Potentials in the Lateral Line System of the Perch (Perca Fluviatius)
Authors: Russell I. J. , Lowe D. A. 
Published: April 2021

ABSTRACT
Microphonic and summating potentials were recorded extracellularly from lateral line organs in the suborbital canal of the perch in response to sinusoidal movements of canal fluid. These potentials were changed in amplitude, shape and phase, relative to the mechanical stimulus, by electrical stimulation of efferent fibres in the lateral line nerve. The receptor potential amplitude/stimulus intensity relationships for the microphonic and summating potentials saturated at high levels of stimulation, and at progressively lower amplitudes with increasing frequencies of mechanical stimulation. Efferent stimulation tended to reduce this rate of saturation. Amplitude versus frequency relationships plotted at different stimulus intensities for the microphonic potential showed that the lateral line organs were most sensitive to frequencies between 35–65 Hz (centre frequency), and at these frequencies efferent stimulation caused the greatest increase in amplitude. Analysis of the second order and third order harmonic components of the microphonic showed that these were reduced by efferent stimulation and that the strongest reduction occurred at the centre frequency. The phase of the receptor potential led that of the mechanical stimulus at very low frequencies by nearly 90 °. This changed to zero phase at the centre frequency and to a phase lag at higher frequencies. Efferent stimulation caused no change in phase of the microphonic relative to the control state at the centre frequency, but caused a progressive phase lead and lag as the frequency was decreased and increased respectively about the centre frequency. In the linear response range, the lateral line organs responded as critically damped low frequency resonators to the velocity of the stimulus. Efferent stimulation appeared to alter the damping of this resonance. The possibility is discussed that efferent stimulation can alter the mechanical properties of the lateral line hair cells.