bluuebunny/crossref_metadata_2025 huggingface dataset:
From sarcomeres to whole muscles
Authors: Morgan D. L.
Published: April 2021

The series connection of sarcomeres in a muscle raises the possibility of instabilities due to some sarcomeres being capable of greater isometric tension than others, due to non-uniform activation, cross-sectional area or sarcomere length. Such instabilities are heavily damped by the force-velocity curve and stabilized by passive tension. The variation of active tension with sarcomere length may act to stabilize or destabilize the situation. Such instabilities can affect tension in a complex manner, causing both increases and decreases in different situations. Some examples of situations where sarcomere non-uniformities have been observed or inferred are given, and their mode of action explained.
Excitation-contraction coupling: the link between the surface and the interior of a muscle cell
Authors: Peachey L. D.
Published: April 2021

The full contractile tension of a skeletal muscle fibre typically is developed a few tens to a few hundreds of milliseconds after the upstroke of the surface action potential. This generally is an insufficient time for an activator, such as calcium ion, to diffuse from the surface to the centre of the fibre (Hill, 1948, 1949). Yet we know that the centre of the fibre is activated, even in a single twitch (Gonzalez-Serratos, 1971). Measurements of the quantity of calcium entry through the surface membrane per contraction (Bianchi & Shanes, 1959) give values that are at least an order of magnitude smaller than the amount of calcium thought to be needed for full activation of contraction. Additionally, more recent evidence indicates that this calcium entry through the surface occurs too late to be directly involved in contraction activation (Sanchez & Stefani, 1978). All these results argue against a mechanism for coupling electrical activity at the surface of the fibre to contraction of the interior (E-C coupling) that depends on entry and diffusion of calcium ions from the surface to the contractile fibrils.
Ventilation, Circulation and Their Interactions in the Land Crab, Cardisoma Guanhumi
Authors: Burggren Warren , Pinder Alan , Mcmahon Brian , Wheatly Michele , Doyle Michael
Published: April 2021

Physiological variables for ventilation (scaphognathite frequency, branchial chamber pressure and branchial air flow) and for circulation (heart rate, intracardiac and pericardial haemolymph pressure) were measured in the land crab Cardisoma guanhumi (Latreille). Crabs were studied both in air alone and in air with access to a shallow layer of fresh, brackish or sea water.

During complete air exposure, forward scaphognathite beating predominated and reversed scaphognathite beating was very infrequent. Periods of apnoea were rare. When crabs were able to immerse the Milne-Edwards openings to the branchial chambers in water, scaphognathite reversal occurred much more frequently, and most air flow through the branchial chambers was generated by this mode of ventilation. Changes in water salinity had no effect on respiratory patterns. The cyclic variation between forward and reversed scaphognathite beating appears to serve not only to ventilate the branchial chambers with air, but also to flush water through the branchial chambers for non-respiratory purposes such as ion, water and acid-base regulation.

Haemolymph pressures were comparatively low (14 mmHg systolic, 6mmHg diastolic). During diastole a pressure gradient of approximately 0·6 mmHg existed between the pericardial space and the heart lumen. Pauses in heart beat were never observed. Circulatory events were closely coordinated with adjustments in ventilation. Reversed scaphognathite beating produced a transient increase in systolic and diastolic haemolymph pressure due to the rise in branchial air pressure acting directly upon the large, haemolymph-filled spaces lining the branchial chambers. A transient bradycardia accompanied this brief rise in central haemolymph pressures. Possible mechanisms for the regulation of haemolymph pressure are discussed.
A Passive Two Layer Permeability-Water Content Model for Periplaneta Cuticle
Authors: Machin J. , Lampert G. J.
Published: April 2021

Two layers in Periplaneta pronotum, endocuticle and combined epicuticle and exocuticle were functionally distinguished by their permeabilities and water affinities. A passive model combining the permeabilities of these layers and the water content of the endocuticle was designed to predict pronotal water contents in a variety of ambient activities at 20 °C.

The model predicted cuticle water contents with acceptable accuracy above ambient activities of 0·56 but overestimated them in drier conditions. Despite universally high water activities in the endocuticle, differences in water content related to ambient activity were predicted. Cuticle water contents below haemolymph equilibrated values, represented in the literature as evidence of active water regulation, were largely attributed to passive activity gradients combined with evaporation errors.
The Mechanism of Tubocurarine Action on Mechanoreceptor Channels in the Protozoan Stentor Coeruleus
Authors: Wood David C.
Published: April 2021

(+)-Tubocurarine (TC) decreases the probability that the protozoan, Stentor coeruleus Ehrenberg, will contract in response to mechanical stimulation, because it selectively depresses mechanoreceptor currents. Resting membrane properties and action potentials are not significantly altered by the drug.

Stentor incubated in media containing radioactively labelled TC (TC*) retain TC* after extensive washing despite a rather high apparent KD (19·7μmol 1-1). The incubation curve for TC* binding exhibits an initial exponential rise followed by a linear increase. Wash-out of bound TC* and elimination of the exponential component of the incubation curve is observed if the TC* incubation is followed by a 5-s exposure to 8% urea; therefore, the exponential component represents a reversible binding process. TC* binding in the exponential component is highly correlated (r < — 0·96) with the depression in receptor current and response probability when incubation time, drug concentration and drug (gallamine, TC, decamothonium and succinylcholine) are varied. These correlations suggest that the exponential binding is to functional mechanoreceptors.

Mechanoreceptor currents are decreased by hyperpolarization and increased by depolarization, indicating that the mechanoreceptor channel is voltage-dependent. At hyperpolarized potentials the channels are in a form (the U form) which cannot be opened by mechanical stimulation; at depolarized potentials they are in a form (the R form) which can be opened. TC appears to bind to the U form with higher affinity than to the R form, since depolarization reduces the amount of bound TC* and relieves the depression of mechanoreceptor current produced by TC.
Myocardial Oxygen Consumption in the Sea Raven, Hemitripterus Americanus : The Effects of Volume Loading, Pressure Loading and Progressive Hypoxia
Authors: Farrell A. P. , Wood S. , Hart T. , Driedzic W. R.
Published: April 2021

Myocardial oxygen consumption was measured using an in situ, perfused heart preparation at 10°C increased in a linear fashion with power output when cardiac output was elevated (volume loading). The increased was possible through improved O2 delivery , but was reduced. The mechanical efficiency of the heart was improved. also increased in a linear fashion with power output when output pressure was increased with constant (pressure loading). The increased was supported by increased O2 removal from the perfusate since oxygen delivery was constant. Once more, improved mechanical efficiency was observed. decreased as O2 delivery was reduced with progressive hypoxia. Even so, power output was maintained at a perfusate input of 81 Torr. Five of 11 hearts survived a 30-Torr exposure, but with a 29 % decrease in power output and a 5-fold reduction in . The increase in the apparent aerobic efficiency which enabled this is discussed.
The Neural Basis of Escape Swimming Behaviour in the Squat Lobster Galathea Strigosa
Authors: Sillar Keith T. , Heitler William J.
Published: April 2021

A motor programme underlying backward swimming in the squat lobster Galathea strigosa is described. Swimming is accomplished by repeated flexions and extensions of the abdomen. This investigation indicates that the behaviour is generated centrally, possibly in the suboesophageal or thoracic nervous system, and is probably homologous with non-giant escape behaviour in crayfish. The effects of sensory feedback on the swimming rhythm have been investigated in free-swimming and restrained preparations. Proprioceptive feedback, probably originating in the abdominal muscle receptor organs, is involved in the maintenance of high frequency swimming. During swimming, the walking legs and unmodified male swimmerets are rhythmically active in phase with abdominal flexion. Swimmeret ‘flicking’ in the male is effected by high frequency spiking in a single phasic swimmeret motor neurone. The results suggest that, when active, the central pattern generator for swimming dominates other neural oscillators for rhythmic limb movements.
The Neural Basis Of Escape Swimming Behaviour In The Squat Lobster Galathea Strigosa III. Mechanisms For Burst Production
Authors: Sillar Keith T. , Heitler William J.
Published: April 2021

Intracellular recordings have been made from a variety of phasic motor neurones during expression of the motor programme for backward swimming in Galathea strigosa. Fast flexor motor neurones (FFs) are driven by a large depolarization mediated by chemical synapses and are inhibited in the interburst interval. Fast extensor motor neurones (FEs) are driven by a barrage of unitary EPSPs during the extension phase and may receive unitary synaptic in-hibition while the flexors are active. FFs all have similar spike thresholds and fire bursts of spikes super-imposed upon the depolarized peak of the input. FEs show a gradation in spike threshold which is correlated with soma size. The largest FEs (type 2) have higher thresholds than smaller FEs (type 1), and fire fewer spikes. The phasic inhibitor motor neurone to flexor muscles (FI) is driven by complex central pathways and fires a single spike shortly following flexion. The extensor inhibitor (El) appears to receive the same depolarization as do the FFs, but has a low spike threshold and thus fires on the rising phase of the depolarization. Spiking in El is terminated by unitary IPSPs which occur in phase with FF activity and which may have the same origin as the interburst inhibition seen in the FEs.
The Bone Compartment in A Teleost Fish, Ictalurus Punctatus : Size, Composition and Acid-Base Response to Hypercapnia
Authors: Cameron James N.
Published: April 2021

An estimate of the total mass of bone in the Channel catfish Ictalurus punctatus Rafinesque, was obtained by dissection. The wet weight of bone constituted 16·3 ±1·9% (± s.d.) of the total (live) wet weight, and 25·0 ± 2·1 % of the dry weight. Of the dry skeletal material, 66·3 ± 11·1 % was soluble in strong acid. The acid-soluble material was about half mineral salts, consisting of 19·5 ±2·21% Ca2+ and 27·6 + 3·22% PO43-, with minor fractions of Mg2+ (0·33 %) and CO32- (1·67 %). The pH values of fluid compartments associated with skull and vertebral bone tissues were 7·420 ± 0·026 and 7·444 ± 0·017 (± S.E.), respectively, at a normocapnie plasma pH of 7·868 ±0·020. In response to external hypercapnia (7·5 Torr), the blood response consisted of an immediate decrease in pH, and a subsequent compensatory rise in both pH and [HCO3-]. This compensatory phase was accompanied by a net apparent H+ excretion to the water. The participation of the mineral salts of the bone compartment in compensation appeared to be negligible, since there was no significant change in either blood [Ca2+] or [PO43 — ], nor any significant increase in calcium efflux to the water. The intracellular pH values of the bone compartments were only slightly higher than other tissues, and the changes in pHi during hypercapnia were similar in bone and white muscle. Thus, the bone compartment in the fish appears to be well regulated, relatively refractory to acute acid-base disturbance, and does not serve as an ion source during acid-base compensation.
Renal Excretion of Magnesium in a Freshwater Teleost, Salmo Gairdneri
Authors: Oikari A. O. J. , Rankin J. C.
Published: April 2021

Infusion of magnesium salts into the body cavity of freshwater-adapted rainbow trout led to elevated plasma magnesium concentrations and to stimulation of renal tubular secretion of magnesium. The majority of the infused load was excreted renally, no net branchial excretion being detected. Magnesium sulphate infusion led to increased tubular secretion of sulphate. Magnesium chloride infusion led to reduced tubular reabsorption of chloride. Magnesium could either be reabsorbed or secreted in control freshwater-adapted trout, apparently as a function of nutritional status. Fish could switch from reabsorption to secretion in response to magnesium loading. It is suggested that freshwater fish eliminate excess dietary magnesium renally.
Nervous Control of the Blood Pressure in the Atlantic Cod, Gadus Morhua
Authors: Smith David G. , Nilsson Stefan , Wahlqvist Inger , Eriksson Britt-Marie
Published: April 2021

Dorsal (PDA) and ventral aortic blood pressure (PVA) and heart rate (HR) were measured in conscious resting cod, Gadus morhua L., which has been allowed 24 h recovery from surgery. Plasma adrenalin and nonadrenalin concentrations in these fish were 3·4 and 2·2 nmol 1−1 respectively, and thus lower than previously reported values from partially recovered cod. Twenty-four hours after treatment with the adrenergic neurone blocking agent bretylium, PDA was significantly reduced by 17 % compared to sham-injected controls, although PVA and heart rate were unaltered. Subsequent a-adrenoceptor blockade by phentolamine produced no further fall in PDA and no changes in PVA or HR, provided a 5-h period was allowed to over-come the acute toxic side effects of phentolamine. The effectiveness of the bretylium or phentolamine blockade was confirmed by noting the absence of any vasoconstrictor response during sympathetic nerve stimulation in perfused tails from fish used in the in vivo experiments.

Bretylium had no significant effect on the sensitivity of the isolated coeliac artery to adrenalin, but effectively blocked the adrenergic innervation of this artery or the vasculature of the tail. Evidence for a non-selective blockade of non-adrenergic nerves to the heart was also obtained.

It is concluded that the adrenergic tonus affecting the dorsal aortic blood pressure in resting cod that have recovered for 24 h following surgery is due solely to an adrenergic nervous tone.
Innervation Patterns of Inhibitory Motor Neurones in the Thorax of the Locust
Authors: Hale J. P. , Burrows M.
Published: April 2021

The innervation pattern of inhibitory motor neurones of the locust has been revealed by intracellular recording from their cell bodies in the meso-and metathoracic ganglion and simultaneous recording from muscle fibres in a middle, or in a hind leg.

Three neurones in each ganglion, the common inhibitor (CI = CI1), the anterior inhibitor (AI = Cl2), and the posterior inhibitor (PI = CI3) inner-vate several muscles in one leg and are thus common inhibitory neurones. Metathoracic CI innervates 13 muscles in one hind leg and mesothoracic CI innervates 12 muscles in one middle leg. The muscles are all in the proximal parts of the legs and move the coxa, the trochanter and the tibia. Metathoracic Al and PI innervate four muscles in the more distal parts of one hind leg that move the tibia, the tarsus and the unguis. None of these muscles is innervated by CI. Each inhibitor innervates muscles that have different and often antagonistic actions during movements of a leg.

Al and PI receive many synaptic inputs in common and show similar patterns of spikes during imposed movements of a tibia. Tests fail, however, to reveal evidence for any electrical or synaptic coupling between them. A revised scheme of nomenclature for these inhibitory neurones is proposed.
Acetylcholine Depolarizes Barnacle Photoreceptors
Authors: Timpe Leslie C. , Stuart Ann E.
Published: April 2021

A variety of vertebrate and invertebrate sensory cells are known to be sensitive to acetylcholine (ACh), although the purpose of ACh receptors on these cells is not understood. Acetylcholine elicits action potentials from the sensory cell of the crayfish stretch receptor organ, which receives inhibitory but not excitatory synaptic input (Wiersma, Furshpan & Florey, 1953). Among the vertebrates ACh causes spiking in several visceral and somatic sensory cells, including chemoreceptors and baroreceptors of the carotid body (von Euler, Liljestrand & Zotterman, 1941 ; Diamond, 1955), mechanoreceptors in the skin (Brown & Gray, 1948) and pain receptors (Skouby, 1951). The experiments to be described here demonstrate that ACh depolarizes the median photoreceptor of the giant barnacle, and test the possibility that the photoreceptor receives cholinergic synaptic input.
The Mechanical Properties of the Autotomy Tissues of the Holothurian Eupentacta Quinquesemita and the Effects of Certain Physico-Chemical Agents
Authors: Byrne Maria
Published: April 2021

Evisceration in the holothurian Eupentacta quinquesemita (Selenka) results from a rapid softening of autotomy structures comprised of connective tissue. The mechanical properties of two autotomy tissues, the introvert and the retractor muscle tendon, were tested to investigate their function in the non-evisceration state and their behaviour during autotomy. The results show that these structures do not have a pre-existing mechanical weakness to account for their rapid failure during evisceration. The autotomy response was mimicked in vitro by increasing K+ concentration. The introvert exhibited viscous behaviour and the absence of Ca2+ and Mg2+ decreased introvert viscosity, whereas excess Ca2+, and low and high pH, increased viscosity. These agents may influence the mechanical properties of the autotomy structures by directly affecting connective tissue ionic interactions and may induce proteoglycan conformational changes. K+ may also exert an indirect effect through responses of cells controlling connective tissue tensility. The most likely mechanism of autotomy is through an alteration of connective tissue ionic interactions.
Free And Total Calcium Concentrations in the Blood of Rainbow Trout, Salmo Gairdneri, During ‘Stress’ Conditions
Authors: Andreasen Peter
Published: April 2021

Measurements were made of the free and total calcium concentrations ([Ca2−] and Cat), acid-base status, haemoglobin concentration, haematocrit and plasma protein concentration in the blood of the rainbow trout, Salmo gairdneri. In isolated blood, [Ca2+] was proportional to Cat while log[Ca2+] was inversely proportional to pH. Similar findings have been reported from human blood. During intense activity, [Ca2+] increased by 16% without any significant change in Cat. Neither sustained exercise, hypercapnic acidosis nor hypoxia affected [Ca2+] or Cat. These data indicate that during common natural stress conditions [Ca2+] is maintained within a narrow range.
Developmental and Metabolic Constraints of the Scope for Activity in Young Rainbow Trout (Salmo Gairdneri)
Authors: Wieser Wolfgang
Published: April 2021

The relationship between routine or ‘steady’ rate and maximum rate of metabolism after forced bursts of activity was studied in the fry and young (weight range 0·08–7 g) of Salmo gairdneri at 4 and 12 °C. The relationship between metabolic rate (y) and body weight (x) can be described by the function y = axb. The mass exponent b equals 0·96 and 0·93 for the routine rate, and 1·11 and 1·14 for the maximum rate of metabolism at 4 and 12 °C respectively, the two sets of b-values differing significantly from each other. The difference between the routine and the active rate of metabolism is called the relative scope for activity. Expressed as a percentage of the routine rate it increases from 85–166 % in the sac fry, to approximately 400% in fish weighing 10 g. Within each of four size classes there is a linear relationship between and , the slope of the relationship always being greater than one and increasing with the weight of the fish from 1·1 in the sac fry to 5·3 in the 3–7 g size class. That is, in the larger size class each increase in the steady rate of oxygen consumption by one unit adds 5·3 units to the aerobic scope for activity. It is speculated that routine and active rate of metabolism are related by a constant factor of expansion so that, up to a limiting value, an increase of the former will lead to an increase of the amount of oxygen available to each fish for additional locomotor activity.
Blood Gas Tensions and Acid-Base Regulation in the Salt-Water Crocodile, Crocodylus Porosus, at Rest and After Exhaustive Exercise
Authors: Seymour R. S. , Bennett A. F. , Bradford D. F.
Published: April 2021

Salt-water crocodiles, Crocodylus porosus Schneider, were catheterized and , pH and lactate concentration ([lactate]) were measured in arterial blood during rest and after forced exhaustive activity at 30° C. Gas exchange ratio (R), calculated from blood and , decreased from about 1·0 to 0·3 during resting voluntary breath-holding and indicated CO2 sequestration in the body fluids. The mean value for R in undisturbed animals was 0·6, which substantiates the hypothesis that some CO2 excretion is extrapulmonary. In vitro buffer value of true plasma was – 23·5 +1·9mmol HCO2−I−1 pH−1. In vivo buffer value, determined by short-term self titration with metabolic CO2, was – 12·2 + 4·7mmolHCOs− I−1 pH−1. Exhaustive activity for 5 min in laboratory animals resulted in pronounced metabolic lactacidosis: pH decreased approximately from 7·43 to 7·11 while lactate concentration increased from 1·2 to 20–30 mmol I−1. The acidosis was reduced by respiratory compensation during the first hour of recovery and by metabolic adjustments that were practically complete after the third hour. Greater acidosis (pH down to 6·4) in larger field-captured animals was resolved over a longer period. During recovery, lactate and proton fluxes between the blood and other tissue were uncoupled. The virtual absence of the fixed-acid Bohr effect in C. porosus blood is adaptive in large individuals because it facilitates continued O2 uptake from the lung into blood which may be acidified by as much as 1 pH unit as a result of physical activity.
The Seasonal Intrinsic Cardiac Performance of a Marine Teleost
Authors: Graham Mark , Farrell Anthony
Published: April 2021

An in situ heart preparation was used to evaluate cardiac performance in the sea raven, Hemitripterus americanus, under physiological inflow and outflow pressure conditions. Winter and summer fish were subjected to an acute 10 °C temperature change from the seasonal ambient value. The maximum cardiac output under each temperature condition was determined by altering inflow pressure to the heart. Acute temperature increase produced positive chronotropic and inotropic effects in winter fish. Acute temperature decrease produced a negative chronotropic and inotropic effect in summer fish. The inotropic and chronotropic states of the heart were different in winter and summer fish. Intrinsic heart rate was higher in summer fish at all experimental temperatures. The sensitivity of the summer fish hearts to input pressure was also greater, especially during the warm experimen-tal temperatures. It was evident from heartbeat rate measurements and power output calculations that the advent of summer and winter seasons did not promote any compensatory ability in intrinsic heart function.
Three-Dimensional Reconstruction of Animal Flight Paths and the Turning Flight of Microchiropteran Bats
Authors: Rayner J. M. V. , Aldridge H. D. J. N.
Published: April 2021

A method is presented by which a microcomputer is used to reconstruct the structure of a three-dimensional object from images obtained with a pair of non-metric cameras when the images contain the vertices of a cube as test pattern and the camera—object configuration satisfies straightforward geometrical conditions. With a still camera and stroboscopic or repeating flash illumination, or with a ciné camera, this method provides a simple and economic means of recording the flight-path and wing movements of a flying animal accurately and reliably. Numerical methods for the further analysis of three-dimensional position data to determine velocity, acceleration, energy and curvature, and to interpolate and to correct for distortion due to inaccurate data records are described. The method is illustrated by analysis of a slow, powered turn of the bat Plecotus auritus (L.). Accurate reconstruction of the flight path permits mechanical forces and accelerations acting on the bat during the turn to be estimated: turning speed and radius in a narrow space are restricted by the bat’s ability to generate sufficient lift to support the weight in nonlinear level flight.
The Development of the Locust Jumping Mechanism : I. Allometric Growth and its Effect on Jumping Performance
Authors: Gabriel Julie M.
Published: April 2021

The jump range of locusts of all instars varies throughout an instar, reaching a peak at apolysis in hoppers, and about 3 weeks after the final moult in adults. Mature adult locusts have an escape jump range three times that of young hoppers. During a period of repeated jumping, mature adults have an average jump range three times that of the hoppers. Allometric growth of the metathoracic leg occurs during development, and accounts for 25 % of the increase in range between the fourth instar and adult, the remaining increment being due to absolute size increase. The allometric changes do not, however, affect the mechanics of the femoro-tibial joint. The extensor apodeme to tarsus lever ratio remains at 27:1 in the fourth, fifth and adult stages. The extension of the joint would be expected to follow a similar pattern in the fourth instar and adult stages. The change in form of the metathoracic leg of the locust also means that the adult femur accommodates more muscle, i.e. 6·3 % of the total body weight in the adult male, as opposed to 4·3 % in the fourth instar male. Therefore relatively more force and energy may be available for use in a jump. The lengthening of the semilunar processes may be expected to have an effect on the energy storage capacity of the leg. In an escape jump, all instars use the same specific power output, which is more than the published figures for maximum specific power output (250Wkg-1, Weis-Fogh & Alexander, 1977, and 860Wkg-1, Pennycuick & Parker, 1966). This suggest that energy storage is necessary in locust hoppers.
Effects of Adrenalin on the Oxygen Consumption and Luminescence of the Photophores of the Mesopelagic Fish Argyropelecus Hemigymnus
Authors: Mallefet J. , Baguet F.
Published: April 2021

Photophores isolated from the mesopelagic fish Argyropelecus hemigymnus consume oxygen at a rate of 1·22± 0·17 nmol min-1 in saline at 20°C. In the presence of 5 x 10−4moll-1 adrenalin the preparations that responded by a long-lasting luminescence showed a significant decrease of their resting respiration rate. After the adrenalin had been washed out, oxygen consumption increased immediately to the previous resting level and was inhibited by 5 x 10−4moll-1 KCN. It is suggested that the mechanism of light production by isolated photophores of the epipelagic fish Porichthys and the mesopelagic fish Argyropelecus are different.
Further Studies of Crayfish Escape Behaviour : I. The Role of the Appendages and the Stereotyped Nature of Non-Giant Escape Swimming
Authors: Cooke Ian R. C. , Macmillan David L.
Published: April 2021

High-speed cinematography of the escape behaviour of freelymoving crayfish showed that the thoracic and abdominal appendages exhibit stereotyped movements in giant axon-mediated tail flips and in non-giant flips. Three distinct classes of non-giant tail flips were recognized in this study: linear, pitching and twisting flips. In medial giant flips and linear non-giant flips the chelipeds and pereiopods were promoted and extended in a manner which minimized the hydrodynamic resistance of the animal. The exopodites of the uropods were promoted. In lateral giant flips and pitching non-giant flips the thoracic appendages moved only passively. The uropod protopodites were promoted but the exopodites remained remoted. When giant axon-mediated tailflips were elicited with natural stimuli they were followed by sequences of non-giant flips which appeared quite stereotyped.
Viscoelastic Behaviour and Wet Supercontraction of Major Ampullate Silk Fibres of Certain Orb-Web-Building Spiders (Araneae)
Authors: Work Robert W.
Published: April 2021

The axial retractive stresses that cause the supercontraction of wetted major ampullate silk fibres and the stresses developed upon reextension from the supercontracted condition are quantified and illustrated. The viscoelastic behaviour of major ampullate silk fibres, subjected to the amounts of elongation that would be produced by a spider on its dragline, is described and illustrated. When major ampullate silk fibres are either wet elongated from supercontraction or when dry from initial lengths, viscoelastic stress relaxations are found to be functions of the logarithms of time. Regression curves illustrate these relationships and normalized results are subjected to statistical analyses. Viscoelastic memory of major ampullate silk fibres is illustrated. The characteristics of viscoelastic stress relaxation and viscoelastic memory of major ampullate silk fibres appear not to be associable with taxonomy. Examples are suggested in which supercontraction and stress relaxation act in the formation and placement of major apipullate silk fibres as structural elements of the orb web.
Frequency Selectivity in the Ampullary System of an Elasmobranch Fish (Scyliorhinus Canicula)
Authors: Peters R. C. , Evers H. P.
Published: April 2021

Frequency characteristics of the electroreceptive system in Scylior-hinus canicula were determined both by electrophysiological recording of the primary afferent responses and by optical recording of respiratory reflexes after electrical stimulation. The frequency response of the primary afferents shows a maximum gain at about 5 Hz, with slopes of +2·3 and — 3·4dBoctave−1 at the low and high frequency side respectively. The phase changes from +60° at 0·03 Hz to -120° at 15 Hz. The sensitivity curve determined by recording the respiratory reflex has a plateau from 0·1 to 1 Hz, with slopes of + 2·8 and — 11·4dBoc-tave−1. The highest sensitivity for sinusoidal electrical stimuli was 40 nV cm−1 peak-to-peak, in the frequency range 0·1 to 1 Hz. We suggest that the difference between the two curves reflects the convergence of primary afferents on to secondary neurones. We conclude that the low pass filter properties are not imposed by the time constant of the ampulla wall. The low frequency slope found in the behavioural curve presumably represents the slope of the receptor-cell-synapse complex. The Lorenzinian ampullae apparently act as peripheral filters with different tuning curves; these must play a part in frequency discrimination.
Attack Behaviour and Distance Perception in the Australian Bulldog Ant Myrmecia Nigriceps
Authors: Eriksson E. Sture
Published: April 2021

The behaviour of the Australian bulldog ant Myrmecia nigriceps (Fr. Smith) has been studied by using moving targets characterized by sizedistance equivalence in relation to a stationary zero-point. The attack behaviour of freely moving animals demonstrated that the ants can discriminate between different targets, in the range of 5–80 cm, using movement parallax to extract information about the targets. By studying the antenna response it was possible to demonstrate that the stationary bulldog ant can utilize binocular disparity information and that this mechanism has an effective range of about 90 mm.
Electrical Responses of the Carnivorous Ciliate Didinium Nasutum in Relation to Discharge of the Extrusive Organelles
Authors: Hara Ritsuo , Asai Hiroshi , Naitoh Yutaka
Published: April 2021

The carnivorous ciliate Didinium nasutum discharged its extrusive organelles when a strong inward current was injected into the cell in the presence of external Ca2+ ions. In the absence of external Ca2+ ions, the strong inward current produced fusion of the apex membrane of the proboscis. External application of Ca2+ ions after the fusion of the apex membrane produced discharge of the organelles. An increase in Ca2+ concentration around the organelles seems to cause discharge of the organelles. Ca2+ concentration threshold for the discharge of the pexicysts seems to be lower than that for the toxicysts. External Ca2+ ions were not necessary for discharge of the organelles upon contact with Paramecium. Chemical interaction of the apex membrane with Paramecium membrane may cause intracellular release of Ca2+ ions from hypothetical Ca2+ storage sites around the organelles. A small hyperpolarizing response seen before the discharge upon contact with Paramecium seems to correlate with the chemical interaction, The depolarizing spike response associated with discharge of the organelles is caused by the depolarizing mechanoreceptor potential evoked by mechanical stimulation of the proboscis membrane by the discharging organelles.
Force-Velocity Characteristics and Metabolism of Carp Muscle Fibres Following Temperature Acclimation
Authors: Johnston Ian A. , Sidell Bruce D. , Driedzic William R.
Published: April 2021

Common carp (Cyprinus carpio L.), 1 kg body weight, were acclimated for 1–2 months to water temperatures of either 7–8°C (cold-acclimated group) or 23–24°C (warm-acclimated group). Single fast fibres and small bundles of slow fibres were isolated from the myotomal muscles and chemically skinned. Force-velocity (P-V) characteristics were determined at 7°C and 23°C.

The contractile properties of carp muscle fibres are dependent on acclimation temperature. In the warm-acclimated group maximum isometric tensions (P0, kN m−2) are 47 ± 6 and 64 ± 5 for slow muscle fibres and 76 ± 10 and 209 ±21 for fast muscle fibres at 7°C and 23°C, respectively. Maximum contraction velocities (Vmm, muscle lengths−1), are 0·4 ± 0·05 and 1·5 ± 0·1 at 7°C (slow fibres) and 0·6 ± 0·04 and 1·9 ± 0·4 at 23°C (fast fibres). All values represent mean ± S.E.

P0 and Vmax at 7°C are around 1·5–2·0 times higher for slow and fast muscle fibres isolated from the cold-acclimated group. Fibres from 7°C-acclimated carp fail to relax completely following maximal activations at 23°C. The resulting Ca-insensitive force component (50–70% Po) is associated with the development of abnormal crossbridge linkages and very slow contraction velocities.

Activities of enzymes associated with energy metabolism were determined at a common temperature of 15°C. Marker enzymes of the electron transport system (cytochrome oxidase), citric acid cycle (citrate synthase), fatty acid metabolism (carnitine palmitoyl transferase, β-hydroxyacyl CoA dehydrogenase) and aerobic glucose utilization (hexokinase) have 30–60% higher activities in slow muscle from cold-acclimated than from warm-acclimated fish. Activities of cytochrome oxidase and citrate synthase in fast muscle are also elevated following acclimation to low temperature. It is concluded that thermal compensation of mechanical power output by carp skeletal muscle is matched by a concomitant increase in the potential to supply aerobically-generated ATP at low temperatures.
Mosaic Collodion Membranes as Analogues of the Plasma Membrane
Authors: Brooks S. C.
Published: April 2021

This paper deals with an attempt to demonstrate selective accumulation of ions by the use of a cell bounded by two dense collodion membranes, one of which was impermeable to anions and the other impermeable to cations. Such a cell would, if successful, constitute a system analogous to many living cells (Brooks, 1929).
The Role of Iron and Silica in the Structure of the Radular Teeth of Certain Marine Molluscs
Authors: Jones E. I. , McCANCE R. A. , Shackleton L. R. B.
Published: April 2021

Although the morphology of the radulae of molluscs have been extensively studied, but little is known of their composition ; it is generally stated to be of a chitinous nature. There are two exceptions to this statement: Troschel (1856) and Sollas (1907). The former reported that calcium, phosphorus and iron were present in the enamel which covered the teeth and that the organ contained both organic and inorganic constituents. Sollas found that the radulae of the Docoglossa contained up to 27 per cent, of ash of which silica was the chief constituent: from microdeterminations of specific gravity she suggested that the silica was in the form of a hydrate or opal ; the marginal teeth were found to contain no silica. She recognised the presence of iron and stated that “the ash contained (in addition to silica) a noticeable quantity of calcium, iron, magnesium and phosphoric acid.” No other groups of molluscs were found to have siliceous teeth in their radulae, but to have chitinous teeth hardened by deposits of iron, calcium and phosphorus. The Chitonidae were somewhat exceptional, for the most important constituent of their teeth was ferric oxide.
A Method for Determining the Amount of Oxygen Dissolved in I C.C. of Water
Authors: Van Dam L.
Published: April 2021

A description is given of a simple micromethod for determining the amount of oxygen dissolved in water. The method is based on the Winkler procedure and requires only 1 c.c. of water for each analysis. It has the further advantage of avoiding all contact between water and air ; consequently, even water of a very low oxygen content may be analysed accurately.
Iodine Compounds and Fertilisation
Authors: Carter G. S.
Published: April 2021

In the earlier papers of this series (1931–2) the action of iodine compounds on the fertilisation reactions of the two common British species of sea-urchin, Echinus esculentus and E. miliaris, has been discussed, and a theory of the changes which occur at fertilisation in this genus has been founded on the results of the discussion. Before this theory can be accepted as true of fertilisation in general, it is clear that gametes of other types must be investigated. Up to the present the only experiments discussed in these papers which have been concerned with animals other than the sea-urchins have been those on the sperm of the rabbit which formed the subject of the preceding paper (1932e).
Metabolic Rates of Ephemerid Nymphs From Swiftly Flowing and From Still Waters
Authors: Fox H. Munro , Simmonds B. G. , Washbourn R.
Published: April 2021

The oxygen consumptions of the small ephemerid nymphs Ephemerella ignita and Coenis sp. are (anaesthetised at 10° C.) 950 and 290 c.mm./gm./hour. Their habitats are respectively a stream and a pond. The oxygen consumptions of the large ephemerid nymphs Ecdyonurus venosus, Ephemera danica and E. vulgata are (anaesthetised at io° C.) 604, 370 and 278 c.mm./gm./hour. They live, respectively, under stones in a swift stream, burrowing in sand in a stream, and burrowing in mud in a pond. Ecdyonurus venosus is less resistant to oxygen deficiency than Ephemera danica and E. vulgate; and Baetis rhodani (swift stream) is less resistant than Chloeon dipterum (pond).
Impulses in the Segmental Nerves of the Earthworm
Authors: Prosser C. Ladd
Published: April 2021

The literature dealing with the peripheral components of the nervous system of the earthworm has been reviewed recently by Stephenson (1930) and Prosser (19346). Hence it is necessary only to mention the principal elements. The sensory endorgans are said to consist of (1) a variety of epidermal cells (“sensory cells”) which have peripheral terminations, are of different shapes, and may be grouped as “sense organs” or may be isolated, (2) free nerve endings, some of which are closely associated with the glandular cells, and (3) intermuscular cells. Certain of the epidermal sensory cells have been shown to be photosensitive; the function of the others is uncertain. Most of them are connected to a subepidermal plexus which appears to be a true network of anastomosing fibres and to contain nerve cells. In each segment three pairs of nerves lead from the central ganglion to nerve rings from which fibres are distributed either by nerve branches or by the peripheral network to the muscles and sensory cells. There is some evidence for and some against conduction of locomotor impulses by the peripheral plexus across segments lacking the nerve cord. Prosser (19346) concluded that the contrary evidence is slightly stronger.
The Respiratory Rate of Gammarus Chevreuxi in Relation to Differences in Salinity
Authors: Löwenstein Otto
Published: April 2021

The rate of oxygen uptake was studied in the brackish water amphipod Gammarus chevreuxi in water of different salinities (25 per cent, sea water and sea water). The respiratory rate was found to be approximately 20 per cent, lower in sea water than in 25 per cent, sea water which is a concentration occurring in the natural habitat. Anaesthetised animals showed the same percentage decrease as unanaesthetised animals. The change in oxygen consumption takes place immediately after the transfer and remains constant thereafter. It is completely reversible. A comparison with the unanaesthetised respiratory rates of the related freshwater species G. pulex and marine G. marinus shows that the rate of oxygen consumption of the brackish water form G. chevreuxi in 25 per cent, sea water lies between the two others.
Serum Relationships Within the Family Cercopithecidae
Authors: Zuckerman S. , Sudermann Ann E.
Published: April 2021

Quantitative tests show that an antiserum for an individual of one species of the Old World monkey family Cercopithecidae may react no more strongly with the blood of another individual of the same species than it does with the blood of monkeys belonging to other species or genera of the same family. They also show that in this family of Primates interspecific precipitin responses may be no stronger than intergeneric ones. Furthermore, the specific and generic serum interrelationships of these monkeys may be no closer than their interfamilial serum relationships to the chimpanzee. The latter relationship appears, however, to be closer than the monkeys’ interfamilial serum relationship to man. Human serum nevertheless does give a group reaction to anti-Old World monkey serum, whereas such a response is not given either by the brown capuchin, a New World monkey, or by the lemur, Perodicticus potto.

These findings support the view, developed both by Erhardt (1929) and Manwaring (1934), that the serum-precipitin test is of limited value in tracing phylogenetic relationships.
Termination of Pregnancy in the Rabbit by Intravenous Injection of Anterior Lobe Pituitary Extract
Authors: Bellerby C. W.
Published: April 2021

Ovulation can be induced in the pregnant rabbit at different stages of gestation by a single intravenous injection of extract prepared from the anterior lobe of the pituitary. It is almost invariably associated with either resorption or abortion of the embryos. In most cases, atrophy of all the existing corpora lutea of pregnancy is produced, but in the early stages both atrophic and non-atrophic structures can be found together. Ovulation does not occur exclusively; haemorrhagic follicles being also produced as a result of the action of the extract. The proportions in which ruptured and haemorrhagic follicles are formed varies according to the stage of pregnancy at which injection is made.
Methods of Measuring the Evaporation of Water from Animals
Authors: Ramsay J. A.
Published: April 2021

The physical theory of evaporation in still air and in moving air is outlined. An apparatus is described in which controlled conditions of temperature, humidity and wind velocity are obtained. The effects of these three factors upon the rate of evaporation from simple physical systems have been investigated. Sources of error attaching to experiments carried out in still air are enumerated. The law of saturation deficiency is shown to be theoretically untrue.
The Evaporation of Water from the Cockroach
Authors: Ramsay J. A.
Published: April 2021

The effects of temperature, humidity and wind velocity upon the rate of evaporation of water from the cockroach Periplaneta americana have been studied. The effects of these factors upon the rate of evaporation from the tracheal system are shown to be similar to their effects upon purely physical systems. The effects of these factors upon the rate of evaporation from the body surface are shown to be complicated by the presence of a film of fatty substance which undergoes a change of state at about 30° C.
The Fused Thoracic-Abdominal Ganglion of the Hermit Crab (Pagurus Pollicaris): Neuromuscular Relationships in the Thoracic and Abdominal Flexor Muscles
Authors: Stephens Philip J.
Published: April 2021

The physiological and morphological properties of the thoracic flexor neuromuscular systems are described for the hermit crab Pagurus pollicaris. There are two pairs of flexor muscles in thoracic segments 3 to 5 : the dorsal flexors and the ventral flexors. The dorsal flexors are composed of fast fibres and are asymmetrical. On the left side the muscle branches laterally so that it has two points of insertion on the thoracic-abdominal sternite, compared with only one for the right side. The ventral flexors are composed of slow fibres. The dorsal flexors are supplied by two excitatory motor axons that run in the thin nerve of the first abdominal root. The ventral flexors are innervated by at least seven excitors: two from the thin nerve of the first abdominal root, three from the thick nerve of the first abdominal root, and two from the thin nerve of the fifth thoracic root. Cobalt backfilling of the first abdominal root revealed that most cells are located on the dorsal and ventral surfaces in the centre of the thoracic-abdominal (TA) ganglion. Although most of the efferent cell bodies from the thin nerve of the fifth thoracic root are located rostrally in the midline of the TA ganglion, two or three somata can be found in the same region as cell bodies from the first abdominal root. Stimulation of the giant interneurone elicits a spike in the giant flexor motor neurone and a contraction of the dorsal flexor muscles, and a spike in one of the axons in the thin nerve of the fifth thoracic root and a contraction of the ventral flexors. Axons in the third abdominal root innervate the flexor muscles in the first abdominal segment. Motor axons in this root, which includes a giant flexor motor neurone, have cell bodies in the TA ganglion - not in the first abdominal ganglion. Most of the motor axons in the fourth and fifth thoracic roots have cell bodies located in the fused TA ganglion. This suggests that the TA ganglion consists of a fusion of the first abdominal ganglion and the fourth and fifth thoracic ganglia.
Metabolic Responses of Trout (Salmo Gairdneri) To Acute Environmental Hypoxia
Authors: Dunn J. F. , Hochachka P. W.
Published: April 2021

Rainbow trout were subjected to 1 and 3h of environmental hypoxia (20 Torr, 4°C), after which samples of blood, heart, brain, liver, and red and white muscle were removed for metabolite determination. The heart, brain and white muscle all showed signs of glycolytic activation. High-energy phosphate stores in the liver were greatly depleted, although there was no measurable decline in liver glycogen content. Glycolytic activation in the white muscle is argued to have a major impact on the hypoxia tolerance of trout, as this tissue produces the bulk of the lactate. These responses of the trout are contrasted with those of the African lungfish, a fish which is relatively tolerant of hypoxia.