bluuebunny/crossref_metadata_2025_split huggingface dataset:
The control of walking in orthoptera
Authors: Burns M. D. , Usherwood P. N. R. 
Published: April 2021

ABSTRACT
A brief description is given of the anatomy, innervation and mechanical properties of the extensor tibiae muscles of the locust. Each is innervated by a ‘fast’ (FETi) and ‘slow’ (SETi) excitatory axon, one branch of a common inhibitor (Cl) and a fourth small axon (DUMETi). The prothoracic and mesothoracic extensors contract more rapidly than the metathoracic muscle but exhibit a stronger ‘catch’, which can be relaxed by Cl or FETi activity.
Records were made of electrical activity in the extensor motor nerves in all the legs of locusts and lubber grasshoppers. During standing only the SETi axons were active. During straight line walking in the locust all three motor axons were active, except in the metathoracic leg. A detailed descrip­tion of the activity pattern of each axon is given. The activity in the grass­hopper was similar, but rather more variable. Measurements were made of the mechanical responses of the extensor muscles to these patterns of activity. As walking speeds increased the response to SETi activity approached a constant tension or muscle length which could be strongly modulated by the phasic contractions due to FETi activity. It is suggested that the timing of SETi activity is only important at low walking speeds, and that at high speeds it simply provides a return force for the flexor muscle. The Cl produces a slow effect and fires at the wrong time in the step to phasically relax the prothoracic or mesothoracic extensors, so it is suggested that its main role is in the relaxation of coxal muscles. The sources of motor neurone activity are discussed.
Studies on the Nutrition of Blow-Fly Larvae
Authors: Hobson R. P. 
Published: April 2021

ABSTRACT
The mid-gut in Lucilia larvae can be divided into three distinct regions (termed anterior, middle and posterior segments). Histologically the anterior and posterior segments are similar. In a feeding larva the cells are highly vacuolated and contain fat ; in a starved larva the cells are deeply staining and non-vacuolated. In the middle segment the cells are always deeply staining and free from vacuoles and fat, whatever the state of nutrition. The hydrogen-ion concentration varies along the gut and with the nature of the food. With liquefied meat as food, the pH is 7·5−8·0 in the crop, 7·5 in the anterior segment, 3·0−3·5 in the middle segment, 7·5−8·3 in the posterior segment, and 8·0−8·5 in the hind-gut. With fresh gelatine (pH 7·0) as food, the values are the same except in the crop and anterior segment, for which the figures are respectively pH 7·0 and 6·5. It has been suggested that the acidity in the middle segment may be due to an acid secretion, the most likely component being phosphoric acid. The alkaline reaction in other parts of the gut is probably caused by ammonia, which is present in the gut-contents and excreta. Tryptase, peptidase and lipase are present in the mid-gut, the enzymes being concentrated in the anterior and posterior segments. The proteolytic enzymes persist in the excreta and some extra-intestinal digestion, therefore, can occur without the aid of micro-organisms. Carbohydrate-splitting enzymes are absent except for a feeble secretion of amylase in the salivary gland. By combining the evidence from various sources, I have attempted to obtain a complete picture of the process of digestion, which I suggest is as follows:
The food is stored unchanged in the crop and, passing into the mid-gut, is rapidly forced into the middle segment. Some absorption of water and simple products of bacterial action occurs along the anterior segment, the concentration of the food being completed in the middle segment where the acidity prevents digestion. The food, by now of a pasty constituency, passes into the posterior segment, dissolves in the alkaline fluid and is digested and absorbed. The digestive enzymes are secreted in the anterior and posterior segments, but digestion does not progress far in the anterior segment owing to the rapid passage of the food.
Potential Differences Across Natural Membranes Separating Unlike Salt Solutions
Authors: Brooks S. C. , Giese A. C. , Giese R. I. 
Published: April 2021

ABSTRACT
Loeb and Beutner (1911) showed that when the cutinised epidermis of the apple separates two unlike solutions of electrolytes, a potential difference develops, which they interpret as being due to exchange of ions, mainly cations, across the epidermis. They suppose that the faster-moving ions tend to penetrate more rapidly through the epidermis, and hence build up a potential difference.
Michaelis (1925) gives a mathematical development of essentially this theory to explain his own experiments with “dried” celloidin membranes which are permeable to cations but not to anions, and which, like the apple epidermis, develop a potential difference which is constant for a considerable period of time.
Recently, Mond and Hoffmann (1928) described a membrane made of celloidin and Rhodamin B, which is selectively anion permeable. This was followed by Höber and Hoffmann’s (1928) study of a mosaic membrane made up of alternating areas of cation permeable celloidin and anion permeable celloidin-Rhodamin B. In this case the potential difference obtained was considerably lower than that for either the celloidin or celloidin-Rhodamin B membranes separately, the potential differences of the two areas being in opposite directions and tending to annul one another.
The cutinised epidermis from the inner surface of bulb scales of the onion resembles these membranes in that there is no diffusion of ions through the epidermis from solutions of electrolytes into distilled water (Brooks, 1917).
It, therefore, seemed desirable to study the nature of the potential differences developed by the onion epidermis when it separates two solutions containing ions, with a view to further analysis of the electromotive mechanisms at work.
Studies in the Localisation of Respiratory Exchange in Invertebrates
Authors: Zoond Alexander , Charles Enid 
Published: April 2021

ABSTRACT
The respiratory exchange of the fresh-water crab Potamonautes is almost entirely localised in the gills. This crab can respire and survive in water and in air. In water the ventilation of the gills by the activity of the scaphognathite is indispensable to the maintenance of respiratory exchange. In air the scaphognathite is unimportant; simple diffusion suffices to renew the supply of oxygen at the gills.
The Effect of Increased Metabolic Rate On Renal Function in the Rainbow Trout, Salmo Gairdneri
Authors: Hofmann E. L. , Butler D. G. 
Published: April 2021

ABSTRACT
A highly significant linear correlation was found between glomerular filtration rate and urine flow rate in both freshwater and seawater trout. The percentage tubular reabsorption of water was approximately 33% greater in seawater trout than in freshwater trout. As oxygen consumption increased, the urine flow rate increased in freshwater and seawater rainbow trout. The proportional increase in urine flow with incremental changes in oxygen consumption was approximately the same in fresh water and sea water. A significant positive linear relationship between oxygen consumption and glomerular filtration rate was found in both salinities. The proportional increase in GFR with incremental changes in the oxygen consumption rate was higher in the seawater trout than in the freshwater trout. As oxygen consumption increased, the percentage tubular reabsorption of water decreased in the freshwater trout. No significant relationship between these two factors was found in the seawater trout.
Aerial CO2 Excretion in the Obligate Air Breathing Fish Trichogaster Trichopterus: A Role For Carbonic Anhydrase
Authors: Burggren Warren , Haswell Steve 
Published: April 2021

ABSTRACT
Total oxygen uptake and carbon dioxide excretion and their partitioning between gills and aerial exchange organs have been measured in an obligate air breathing fish, the blue gourami (Trichogaster trichopterus). Measurements were made during normal bimodal breathing and in air-exposed fish. increased during air exposure, but the aerial exchange organs or ‘laby-rinth’ of Trichogaster could assume a highly effective CO2 excretion in the absence of branchial gas exchange. Hence, aerial was greatly increased during air exposure, and the labyrinth gas exchange ratio increased to 0·8 from the value of 0·1 evident during bimodal gas exchange.
The large aerial CO2 excretion in Trichogaster, unobtainable in many air breathing fish, was unaffected by the injection of carbonic anhydrase, but was seriously disrupted in the presence of this enzyme’s potent inhibitor, acetazolamide. In vitro assay for carbonic anhydrase demonstrated the labyrinth epithelium of the gourami to be rich in this enzyme. It is concluded that highly effective CO2 excretion from the labyrinth organs during air exposure in Trichogaster results from dehydration of plasma bicarbonate to molecular CO2 at the catalysed rate; carbonic anhydrase for this purpose being present in the labyrinth epithelium. The distribution of carbonic anyhdrase in the tissues of other air breathing fishes is determined, and its implications to aerial CO2 excretion discussed.
The Mechanics of Labriform Locomotion
Authors: Blake R. W. 
Published: April 2021

ABSTRACT
A blade-element approach is used to analyse the mechanics of the dragbased pectoral fin power stroke in an Angelfish in steady forward, rectilinear progression. Flow reversal occurs at the base of the fin at the beginning and at the end of the power stroke. Values for the rate of increase and decrease in the relative velocity of the blade-elements increase distally, as do such values for hydrodynamical angle of attack. At the beginning and end of the power stroke, negative angles occur at the base of the fin. The outermost 40% of the fin produces over 80% of the total thrust produced during the power stroke, and does over 80 % of the total work. Small amounts of reversed thrust are produced at the base of the fin during the early and late parts of the stroke. The total amount of energy required during a cycle to drag the body and inactive fins through the water is calculated to be approximately 2·8 ×10−6 J and the total energy produced by the fins over the cycle (ignoring the recovery stroke) which is associated with producing the hydrodynamic thrust force, is about 1·0×10−5 J ; which gives a propulsive efficiency of about 0·26. The energy required to move the mass of a pectoral fin during the power stroke is calculated to be approximately 2·6 ×10−7 J. Taking this into account reduces the value of the propulsive efficiency by about 4% to about 0·25. The total energy needed to accelerate and decelerate the added mass associated with the fin is calculated and added to the energy required to produce the hydrodynamic thrust force and the energy required to move the mass of the fins; giving a final propulsive efficiency of 0·18.
An Optical Tachometer for Measurement of the Wing-Beat Frequency of Free-Flying Insects
Authors: Unwin D. M. , Ellington C. P. 
Published: April 2021

ABSTRACT
The wing-beat frequency of flying insects has generally been measured by acoustic methods, but even with modern condenser microphones and frequency-selective amplification the signal available from smaller insects may be inadequate. A microphone had to be placed within 1 cm of the midge Smittia aterrima (Mg.) to produce a satisfactory signal and no signals could be obtained from Thrips sp. (Thysanoptera). Acoustic recordings of flying insects in the laboratory may also be degraded by the excited resonant frequencies of the cage material. The optical tachometer uses the minute changes in the intensity of ambient light reflected from an insect’s beating wings to produce an amplified electrical output at the wing-beat frequency, producing an adequate signal from a very much greater range than would be obtained by acoustic methods. With this device Smittia aterrima could be measured at a distance of 1 m, Drosophila melanogaster Mg, at 1·2 m, and larger insects from a much greater range: Calliphora vicina (R-D.) 7 m, and Bombus sp. 10 m. No difficulty is found when making measurements through the sides of transparent flight cages. The sensitivity of the device seems sufficient for recording Thrips, although this has not yet been tested.
Gas Exchange and Transport During Intermittent Breathing in Chelonian Reptiles
Authors: Burggren Warren W. , Shelton Graham 
Published: April 2021

ABSTRACT
The oxygen and carbon dioxide gas tensions in lung gas and blood from the central and peripheral arteries and veins have been measured in unrestrained, undisturbed turtles (Pseudemys scripta) and tortoises (Testudo graced). Lung and blood gas composition fluctuates widely with intermittent and irregular lung ventilation. The pulmonary gas exchange ratio, which progressively falls during apnoea to as low as 0·2–0·3 in Pseudemys, rises dramatically to over 1·5 during lung ventilation in both species. It is postulated that CO2, which has been passively stored by entering the tissues along gas tension gradients during apnoea, Becomes rapidly eliminated into the lungs during ventilation. In diving Pseudemys the lung has only a limited function as a CO2 sink compared to the tissues, but the lung acts as a large oxygen store, which can be drawn upon during apnoea through periodic increases in lung perfusion. Blood gas tensions in the various systemic arches reflect the proximity of the arch’s origin to the systemic or pulmonary venous blood streams in the ventricle. Thus, the brachiocephalic artery and right aorta have identical blood gas compositions while the composition of the left aorta is intermediate between these and that in the pulmonary. These relationships are unaffected by normal intermittent breathing. However, this does affect both the origin and composition of systemic and pulmonary arterial blood, such that the greatest proportion of oxygenated blood perfuses the systemic vascular bed during lung ventilation, while the greatest proportion of deoxygenated blood perfuses the lungs during apnoea. These data are discussed in the light of the marked cardiovascular adjustments to intermittent breathing, which occur in chelonian reptiles.
Effect of Diet Viscosity on the Operation of the Pharyngeal Pump in the Blood-Feeding Bug Rhodnius Prolixus
Authors: Smith J. J. B. 
Published: April 2021

ABSTRACT
The rate of pumping and total number of pump strokes was recorded whilst Rhodnius prolixus fed on measured amounts of artificial diets. Increasing the viscosity of the diet caused a decline in both the frequency with which the pharyngeal pump operates and the average stroke volume of the pump. In 5th-instar Rhodnius, the stroke volume tends toward a maximum value of about 60 nl at viscosities lower than about 3 cP. Feeding rates (volume per unit time) agree with Poiseuille’s law at high viscosities, but are less than predicted at low viscosities. The maximum power output of the pump occurs at a viscosity between i and 3 cP, which is probably the range of the effective viscosity of blood in tubes with the dimensions of Rhodnius stylets. These results are inconsistent with a hypothesis of a central nervous system ‘oscillator’ controlling the pump muscle, independent of feedback, but are consistent with a model involving peripheral feedback from stretch receptors, with an appropriate delay.
Cinematographic and Electromyographic Analysis of Vertical Standing Jump in the Dog
Authors: Tokuriki Mikihiko 
Published: April 2021

ABSTRACT
The electromyograms of 37 skeletal muscles were obtained using the bipolar wire electrode method in the vertical standing jump of a dog. Their electromyographic patterns were analyzed in conjunction with cinematographic films. Co-contraction of muscles of the extremities was observed during take-off and landing. Electromyograms also revealed that the forelimbs were accelerated against the body just after take-off and that the fore quarters transferred the centre of gravity of the body in a much more complicated movement than the hind quarters. In the floating phase, the muscles of the lower extremities had no activity, apart from some proximal ones. That the muscles of the four extremities exhibited their activity just before landing indicates that the activity may have been controlled by a central programme. In the vertical standing jump, the dog brings the centre of gravity of the body near to the kicking or landing paws by skillful movement of the axial skeleton. Cinematography revealed that, in the leaping gallop gait, the dog makes a similar movement of its axial skeleton.
A Non-Linear Mechanical Model of A Non-Spiking Muscle Receptor
Authors: Berger C. S. , Bush B. M. H. 
Published: April 2021

ABSTRACT
The sensory response of a mechanoreceptor is generally assumed to be a compound function of its mechanical and electrochemical properties. In a muscle receptor such as the mammalian muscle spindle or crayfish stretch receptor, the former depend upon the visco-elastic elements of the receptor muscle and its linkages with the sensory endings, while the latter properties reside within the sensory neurone itself. Analysis of these systems is complicated, however, by the difficulty in defining the precise stimulus obtaining at the site of transduction, and by the possible modifying influence of the impulse encoding process.
Vertical Banding Evoked by Electrical Stimulation of the Brain in Anaesthetized Green Sunfish, Lepomis Cyanellus, And Bluegills, Lepomis Macrochirus
Authors: Bauer Diana H. , Demski Leo S. 
Published: April 2021

ABSTRACT
A pattern of dark vertical bands is a characteristic agonistic display in the green sunfish, Lepomis cyanellus and the bluegill, L. macrochirus. The rapidity with which the display can appear and disappear indicates that it is neurally controlled. Electrical stimulation of the brain was carried out in anaesthetized green sunfish and bluegills to map those regions from which this colour change can be elicited. Banding was evoked by stimulation of sites near the midline in the preoptic area, ventral thalamic-dorsal hypothalmic transition zone, the midbrain tegmentum (just dorsal to the nucleus prerotundus pars medialis), in and near the torus semicircularis, in the basal midbrain (region of the crossing tectobulbar tracts), and in the rostral basomedial medulla. A ‘transition’ zone was located basally in the middle medulla, caudal to which only paling was evoked. Areas found to be negative for evoked banding included the telencephalic lobe, the inferior lobe of the hypothalamus, the optic tract, the optic tectum, the body and valvula of the cerebellum and the caudal medulla. It is postulated that the vertical banding pattern is made up of a separate, selectively controlled system of dermal melanophores. The possible neural mechanisms controlling banding are discussed.
Relation Between Non-Bicarbonate Buffer Value and Tolerance to Cellular Acidosis: A Comparative Study of Myocardial Tissue
Authors: Hansen Henry Damm , Gesser Hans 
Published: April 2021

ABSTRACT
There is a large variation in the tolerance of myocardial tissue to cellular acidosis. Assuming the cytoplasmic acid-base status to be mainly a result of intracellular processes, this variation could be produced by variations in the tissue non-bicarbonate buffer value. In the myocardial tissue from nine vertebrate species, the non-bicarbonate buffer value did not correlate either with ability to develop tension under hypercapnic acidosis or with the indirectly estimated capacity for anaerobic glycolysis. Therefore, differences in myocardial tolerance to acidosis must be explained either by an active pH regulation or by other compensatory mechanisms.
Structure and Electrical Properties of Eye Muscles in Cave- and Surface-Dwelling Crayfishes
Authors: Mellon Deforest , Lnenicka Gregory 
Published: April 2021

ABSTRACT
The morphologies and passive electrical parameters of fibres in two eye muscles of a surface- and a cave-dwelling crayfish were compared. In the cave-dwelling form the muscles contained fewer fibres, of less diameter, and hence had a smaller cross-sectional area. Current-voltage relationships were similar in both species. Input resistance was higher in the cave-dweller, but the difference was not as great as would be expected on the basis of geometry alone. Accordingly, the specific membrane resistance of muscle fibres in the cave-dweller is 50–60 % smaller than that in the surface-dweller. This may account partially for the observation that identified excitatory junctional potentials in muscles of cave- and surface-dwellers have similar amplitudes. We conclude that a functional oculomotor system is maintained in cave-dwelling crayfish, and that this system confers some positive selective advantage.
Nervous Control of the Heartbeat in Octopus
Authors: Wells M. J. 
Published: April 2021

ABSTRACT
The circulatory system of cephalopods is based on a trio of hearts, with two pairs of associated ganglia linked to the CNS by a pair of visceral nerves. The beat of the hearts was recorded from free-moving octopuses before and after surgical removal or disconnexion of elements of the nervous system. Severing the visceral nerves does not stop the hearts, which continue to beat in a powerful well co-ordinated manner in isolation from the CNS. The nerves seem to be concerned in raising the cardiac output in exercise, and with stopping the hearts when mantle movements cease, but they are not necessary for the initiation of maintenance of the normal rhythm. Removal of the fusiform ganglia severs all nervous connexions between the two gill hearts, and deprives the systemic heart of its nerve supply. The trio of hearts continues to beat as strongly as before. Removal or disconnexion of a cardiac ganglion disrupts the beat of the corresponding gill heart which now tends to contract in an ill-coordinated and rather feeble manner, though at much the same frequency as before ; with both cardiacs gone the systemic heart, which contracts only when it is filled, tends to drop in frequency and the mean aortic pressure falls. The system remains rhythmic, however, and the beat may recover, to the point where aortic pressures and frequencies approach those found in intact animals at rest ; even octopuses with both fusiform and both cardiac ganglia removed can survive for many hours. From the performance of the isolated branchial heart, the existence of a pulsating vesicle in each cardiac ganglion, the effects of cardiac ganglion removal and the remarkable steadiness of heartbeat frequency shown by intact animals under a variety of conditions, it is argued that the heartbeat rhythm is normally controlled by pacemakers in the branchial heart/ cardiac ganglion complexes, and perhaps, in intact animals, from within the cardiac ganglia themselves.
The picture of the control of the heartbeat that emerges from the study of free moving essentially intact animals is quite different from that arising from in vitro and acute preparation studies. It suggests that the conventional wisdom about the control of the heartbeat in cephalopods (and perhaps by implication, in other molluscs) may need to be considerably revised.