bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Flow Patterns During Prey Capture By Teleost Fishes
Authors: Lauder George V. , Clark Brian D.
Published: April 2021

Water flow into the mouth cavity during suction feeding in centrarchid sunfishes was studied by mapping the trajectories of small particles in the water during prey capture. In Lepomis, a circulation develops as the mouth opens, and water is drawn into the mouth from above, below and in front of the head. Water displaced by movement of the body as the prey is approached during the strike is entrained into the circulation towards the mouth. The parcel of water sucked into the mouth has a diameter approximately one-tenth that of the predator’s length.
The Interrelationship Between Pulmonary Mechanics and The Spontaneous Breathing Pattern in the Tokay Lizard, Gekko Gecko
Authors: Milsom William K.
Published: April 2021

The normal breathing pattern of the Tokay gecko (Gekko gecko) consists of single breaths or bursts of a few breaths separated by periods of breath holding. Increases in pulmonary ventilation that accompany rises in body temperature are caused by increases in respiratory frequency due to shortening of the periods of breath holding. Tidal volume and breath duration remain relatively constant. Measurements of the mechanical work associated with spontaneous breathing yielded values that were similar to those calculated for breaths of the same size and duration based on work curves generated during pump ventilation of anaesthetized animals. In this species, the pattern of periodic breathing and the ventilatory responses to changes in respiratory drive correspond with predictions of optimal breathing patterns based on calculations of the mechanical cost of ventilation. Bilateral vagotomy drastically alters the breathing pattern producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of the breath duration. These alterations greatly increase the mechanical cost of ventilation. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal afferent control and which serves to minimize the cost of breathing.
Calcium-Dependent Action Potentials in Leech Giant Salivary Cells
Authors: Marshall Cameron G. , Lent Charles M.
Published: April 2021

Two pairs of discrete salivary glands are located at the base of the muscular proboscis of the sanguivorous Glossiphoniid leechesHaementeria ghilianii and Haementeria officinalis. Each anterior gland is 0·8 cm to 2cm in length, and comprises over 200 giant salivary cell bodies ranging from 150 μm to over 1000 μm in diameter, depending on the size of the animal. The salivary cells are neither electrically nor dye coupled, and there is no acinar structure or common duct, but instead each cell extends an individual ductule.

The cells fire action potentials of 100–200 ms duration and 70–100 mV amplitude in response to depolarizing pulses, or at the cessation of a hyperpolarizing pulse. The impulse is abolished by procedures known to antagonize calcium currents, and persists in sodium-free solution, or when calcium is replaced with strontium or barium. Our results support the hypothesis of a purely calcium-dependent impulse.
Mechanical Synchronization of Ciliary Beating Within Comb Plates of Ctenophores
Authors: Tamm Sidney L.
Published: April 2021

The mechanism which synchronizes the beating of the hundreds of thousands of long cilia making up a ctenophore comb plate was investigated by microsurgical experiments on single comb plates of Mnemiopsis and Pleurobrachia. Comb plates of lobate ctenophores (e.g. Mnemiopsis) are triggered to beat by ciliated grooves which run between the centres of adjacent plates. By creating gaps or introducing mechanical barriers between two parts of a plate, or by severing the cells at the base of a plate, it was shown that physical proximity of cilia, not tissue continuity, is required for synchronization of beating. In Pleurobrachia only the first comb plate of each row is activated by a ciliated groove, and similar experiments to those done on Mnemiopsis gave identical results. Although adjacent comb plates in Pleurobrachia are triggered mechanically by movements of the preceding plates without the need for an intraplate synchronizing mechanism, unilateral amputation of a plate showed that cilia within these plates may also be synchronized by mechanical coupling. Therefore, in cases where the beating of a comb plate is triggered by a ciliated groove — either at the head of a comb row (in all ctenophores) or along the row (lobates only) - the cilia within the plate are synchronized by hydrodynamic coupling forces between them, not by electrical coupling between their cells as assumed previously.
Antidiuretic Action of a Corpus Cardiacum Factor (Ctsh) on Long-Term Fluid Absorption Across Locust Recta in vitro
Authors: Proux B. , Proux J. , Phillips J. E.
Published: April 2021

Long-term fluid absorption (Jv) by everted rectal sacs from locusts is stimulated by both corpus cardiacum (CC) extracts and cAMP in a dosedependent manner. This hormonal antidiuretic activity (ADH) is present in both nervous and glandular lobes of CC. This distribution is similar to that of chloride transport stimulating hormone (CTSH) but not to that of other factors previously reported from this gland. As expected if ADH were due to CTSH acting on electrogenic Cl- transport, CC extracts also increased the electropotential across rectal sacs, and the stimulation of fluid absorption ceased in Cl-free salines. CC extracts also caused recta to absorb fluid against larger osmotic gradients, suggesting that the antidiuretic factor acts on the ion-dependent active transport of fluid rather than on the osmotic permeability of the rectal wall.
Functional Roles and Circuitry in an Inhibitory Pathway to Feeding Command Neurones in Pleurobranchaea
Authors: London J. A. , Gillette R.
Published: April 2021

The paracerebral neurones (PCNs) of the brain of Pleurobranchaea californica serve a command role in the initiation of feeding behaviour (Gillette, Kovac & Davis, 1978). The PCNs are synaptically excited by food stimuli applied to the oral veil of hungry, naive animals. In food avoidance-conditioned animals, the PCNs are inhibited by a barrage of inhibitory postsynaptic potentials concomitant with the suppression of feeding (Davis & Gillette, 1978). In this paper, an interneuronal pathway is described which causes inhibition of the PCNs and potentially mediates the effects of learning. The inhibitory pathway consists of three serially connected interneurones. One population, designated the Interneurone Is (Int-ls), mono-synaptically inhibits the PCNs. A second population, the Interneurone 2s (Int-2s), excites the Int-1 population. They also excite other neurones of the brain including the metacerebral giant neurones. A third population, the Interneurone 3s (Int-3s), monosynaptically excites the Interneurone 2 population. Dual intracellular recordings and current injection show that ipsilateral members of the Int-2 population are electrically coupled via a nonrectifying connection. Contralateral members of the Int-2 population are excitatorily coupled via a polysynaptic pathway. The Int-1 population is phasically active during the rhythmic motor activity that underlies feeding. In the isolated nervous system Int-1 activity is phase-locked with rhythmic PCN activity; Int-1 activity occurs maximally at the end of a PCN burst, during the retraction phase of the cycle. Int-2 activity also occurs during the retraction phase. During actual feeding in the whole animal preparation, the Int-2s are also phasically active; maximal excitation occurs during buccal mass retraction and maximal inhibition during protraction and the bite. Stimulated activity in a single Int-2 can entirely suppress the rhythmic motor activity of the feeding network evoked by electrical stimulation of the stomatogastric nerve. The suppressant effects of Int-2 activity must be mediated widely within the feeding network because the rhythmic motor output so driven is not dependent on PCN spiking. Application of an appetitive chemosensory stimulus to whole and semiintact animal preparations initiated feeding and elicited excitation of the Int-1 and Int-2 populations. Noxious chemosensory stimuli, such as a dilute soap solution or ethanol, elicited oral veil withdrawal and inhibition of the Int-2s by multiple inhibitory postsynaptic potentials. When divalent ion concentration was raised in the saline surrounding the brain, to suppress polysynaptic activity, the Int-2s but not the PCNs were excited by appetitive chemosensory stimuli. This suggests that the Int-2s receive monosynaptic sensory input from the oral veil while the PCNs do not.
The Haemolymph as A Storage Site for Cuticular Ions During Premoult in the Freshwater/Land Crab Holthuisana Transversa
Authors: Sparkes Stephen , Greenaway Peter
Published: April 2021

Holthuisana transversa (von Martens) utilizes the haemolymph as a storage site for ions reabsorbed from the cuticle in premoult. 66 % of the total body calcium, magnesium and phosphate from the preceding intermoult stage was stored in the haemolymph in premoult. Almost all of the calcium and phosphate and 73 % of the magnesium in the haemolymph was located in microspherules of average diameter 0·25μm. The concentration of total calcium in the haemolymph in premoult was 150 times the normal intermoult value (13·2 mmol 1-1) but the activity of calcium in the haemolymph decreased from an intermoult value of 4*52 mmol 1-1 to 3·37 mmol 1-1 in premoult. Postmoult crabs absorbed calcium from the water at a high rate and showed a high affinity for calcium ions; Km = 0·105 ±0·013 mmol 1-1 Ca.
Identification of Neurones in the Leech Through Local Ionic Manipulations
Authors: Friesen W. Otto , Brodfuehrer Peter D.
Published: April 2021

The identification of neurones which generate and control specific animal movements can typically be made with conventional intracellular recording techniques during the expression of the movement pattern. Neurones whose membrane potentials are highly correlated to the patterns under investigation are potentially part of the pattern-controlling system. Further searches may then be made to find the pre-synaptic and postsynaptic cells. Such neuronal circuits are now known for several invertebrates (Friesen & Stent, 1978; Delcomyn, 1980; Kristan, 1980). However, a serious drawback to these search procedures is that many time-consuming trial and error experiments are required, in which hundreds, or even thousands of candidate cells must be impaled with microelectrodes.
Patterns in mammalian muscle energetics
Authors: Kushmerick M. J.
Published: April 2021

A description of cellular energetics of muscular contraction is given in terms of the rates and extents of high-energy phosphate splitting during contractile activity, in terms of high-energy phosphate resynthesis by respiration and net anaerobic glycolysis, and in terms of the associated uptake and/or release of H+. These chemical changes have been studied quantitatively by rapid freeze-clamping methods and by 31P-NMR methods. The pattern of chemical changes in a fast-twitch glycolytic muscle is rapid depletion of phosphocreatine and later ATP levels, cellular acidification, and a much slower rate of resynthesis of high-energy phosphate compounds during the recovery period afterwards than occurs in the slow-twitch oxidative muscles. In steady-state contractile activity below the maximal, graded levels of high-energy phosphates and of cellular respiration are achieved in both fast-twitch and slow-twitch muscles. Within the metabolic range up to the maximal aerobic capacity, which differs several-fold for different fibre types, this gradation is mediated by the creatine kinase reaction and phosphocreatine stores. Thus while the amount of enzyme present and the content of phosphocreatine differs among muscles of different types, the same general energetic function is seen to occur in all muscle cells. The creatine kinase reaction is both an energy reservoir and a buffer preventing large swings in the ATP/ADP ratios.
Development and adaptability of microvasculature in skeletal muscle
Authors: Hudlická O.
Published: April 2021

In skeletal muscle, the size of the capillary bed is adapted to the type of muscle metabolism and can be altered by adaptation to different environments or increased activity. Muscle fibres with high aerobic metabolism have more capillaries, and an increase in aerobic metabolism is usually followed by capillary growth. It is assumed that local hypoxia -created by increased demand for oxygen during growth, cold exposure or increased activity -can stimulate proliferation of capillaries. Capillary density is reduced in parallel with enhanced glycolytic metabolism.

The size of the capillary bed can also increase without any apparent change in the oxidative metabolism (e.g. in the early stages of chronic electrical muscle stimulation or as a result of long-term administration of vasodilating drugs), and it is argued that the growth of capillaries in these cases may be due to various mechanical factors connected with increased blood flow.
Force development during sustained locomotion: a determinant of gait, speed and metabolic power
Authors: Taylor C. R.
Published: April 2021

This paper develops three simple ideas about force development during sustained locomotion which provide some insights into the mechanisms that determine why animals change gait, how fast they can run, and how much metabolic energy they consume. The first idea is that the alternate stretch-shorten pattern of activity of the muscles involved in locomotion allows muscle-tendon units to function as springs, affecting the amount of force a given cross-sectional area of muscle develops, and the metabolic requirements of the muscles for force development. Animals select speeds and stride frequencies which optimize the performance of these springs. The second idea is that muscle stress (force/cross-sectional area) determines when animals change gait, how fast they run and their peak accelerations and decelerations. It is proposed that terrestrial birds and mammals develop similar muscle stresses under equivalent conditions (i.e. preferred speed within a gait) and that animals change gaits in order to reduce peak stresses as they increase speed. Finally, evidence is presented to support the idea that it is the time course of force development during locomotion, rather than the mechanical work that the muscles perform, that determines the metabolic cost of locomotion.
Efficiency of vertebrate locomotory muscles
Authors: Heglund N. C. , Cavagna G. A.
Published: April 2021

We have examined the efficiency of vertebrate striated muscle at two different organizational levels: whole animals and isolated muscles. Terrestrial locomotion is used as a model of ‘normal’ muscular contraction; animal size and running speed are used as independent variables in order to change either the metabolic requirements of the muscles or the mechanical power production by the muscles over a wide range of values. The weight-specific metabolic power input to an animal increases nearly linearly with speed and increases with decreasing body size, while the weight-specific mechanical power output increases curvilinearly with speed and is independent of size. Consequently, the efficiency of the muscles in producing positive work increases with speed and the peak efficiency increases with increasing body size, attaining values of over 70 % in large animals, but only 7 % in small ones. The isolated muscle experiments were performed on frog muscle, and rat ‘fast’ and ‘slow’ muscles. We measured the work done, the oxygen consumed during recovery from the stimulation, and calculated the efficiency and the ‘economy’ (the cost of maintaining tension). The muscles were made to: (i) emulate the contractions seen during locomotion, i.e. shorten after a pre-stretch; or (ii) shorten at the same velocity and from the same muscle length as in (i), but without the pre-stretch. It was found that in mammalian muscles the peak efficiency with a pre-stretch attained high values, approaching the peak efficiencies in large animals. The maximum efficiency (attained at 1 length s−1 in fast muscle and at 0 · 5 lengths s−1 in slow muscle) did not differ much in the two muscles, whereas economy was greater in the slow muscle than in the fast muscle.
Design and performance of muscular systems: an overview
Authors: Weibel ER
Published: April 2021

For a general physiologist, A.V. Hill’s definition that ‘muscle is a machine that converts chemical to mechanical energy at constant temperature’ is still a valid concept. But it is clearly not sufficient to tell us how muscles are used to perform a variety of different functions, such as locomotion, pumping blood through the circulation or air into the lung, or even catching prey and ingesting food. Muscles must be organized in a proper way, they must be operated in a well controlled fashion, and they need fuel which must be supplied according to needs. The ‘muscular system’ (Fig. 1) can thus be defined as the concerted action of molecular events permitting the generation of mechanical force, with the biochemical and physiological functions of energy supply under the control of the nervous system. Because of the dependence of all parts of the system on all others, any part can in principle limit the performance of the entire system. One important question is therefore to see how the various parts react when the demands on the system are altered, in other words, to see how malleable the system is.
Storage and release of mechanical energy by active muscle: a non-elastic mechanism?
Authors: Cavagna G. A. , Mazzanti M. , Heglund N. C. , Citterio G.
Published: April 2021

In frog muscle fibres, tetanically stimulated at a sarcomere length of about 2 pm, stretched at a velocity of 1 length s-1 and released against a force equal to the maximum isometric, P0, a phase of rapid isotonic shortening takes place after release. As the amplitude of the stretch is increased from 1 · 5 to 9 % of the initial length: (1) the amount of rapid isotonic shortening increases up to 9–10 nm per half sarcomere and (2) the stiffness of the fibre (an indication of the number of bridges attached) decreases to a value about equal to that measured during an isometric contraction. If a 5-10 ms delay is left between the end of stretch and release, the amount of rapid isotonic shortening increases to about 12nmhs-1. A 300-500 ms delay, however, results in a decrease in rapid isotonic shortening to about 5nmhs-1 and also results in velocity transients against P0 that are similar to those described during release from a state of isometric contraction. It is concluded that the force attained after large, fast stretches is due to a greater force developed by each bridge and not to a greater number of bridges. After the elastic recoil (when the force is suddenly reduced to P0), these strained bridges are able to shorten by about 12nmhs-1, suggesting that, during and immediately after stretching, they are charged to levels of potential energy greater than those attained in an isometric contraction.
The influence of inactivity on membrane resting conductances of rat skeletal muscle fibres undergoing reinnervation
Authors: Conte-Camerino Diana , Bryant S. H. , Lograno M. D. , Mambrini M.
Published: April 2021

The role of activity in the maintenance of the normal component resting conductances of skeletal muscle fibres has been evaluated in vitro in rat extensor digitorum longus muscle during reinnervation from 2 to 40 days (a) after crushing of the peroneus nerve and (b) after local application of tetrodotoxin (TTX) to the crushed nerve. Whereas membrane conductances were regained after crushing alone, they were not completely restored when impulse propagation was blocked faith TTX. It is concluded that nerve trophic factors are of primary importance in the control of muscular membrane conductances, and that transmission at the endplate and the muscle usage triggered by it have a minor but significant effect.
Gill and Body Surface Areas of the Carp in Relation to Body Mass, With Special Reference to the Metabolism-Size Relationship
Authors: Oikawa Shin , Itazawa Yasuo
Published: April 2021

The relationships of resting metabolism per unit mass of body to gill and body surface areas were examined by measuring gill, body surface and fin areas of carp ranging from 0·0016 to 2250g. There was a triphasic allometry for the relationship between gill area and body mass : during the prelarval (0·0016-0·003g) and postlarval (0·003-0·2g) stages there was a positive allometry (slopes of 7·066 and 1·222, respectively), during the juvenile and later stages (0·2-2250 g) there was a negative allometry with a slope of 0·794. There was a diphasic negative allometry for the relationship between surface area of the body or the fins and body mass, with a slope of 0·596 or 0·523 during the larval stage and 0·664 or 0·724 during the juvenile and later stages, respectively. Except for the 3rd phase (juvenile to adult) of gill area, these slopes were significantly different (P<0·01) from the slope for the relationship between resting metabolism and body mass of intact carp (0·84; value from Winberg, 1956). It is considered, therefore, that gill, body surface and fin areas do not directly regulate the resting metabolism of the fish, in the larval stage at least.
Sensory Control of Respiratory Pumping in Aplysia Californica
Authors: Croll Roger P.
Published: April 2021

The frequency of respiratory pumping in Aplysia increases when CO2 is bubbled through the bathing sea water. Air, O2 and N2 do not have this effect. The sensitivity to CO2 may be mediated by receptors which are sensitive to pH changes within the range encountered during hypercapnia. In addition to the frequency change during hypercapnia, increases in the rate of pumping occur after titration to low pH with hydrochloric, acetic, nitric and sulphuric acids, thus indicating sensitivity to changes in the concentration of hydrogen ions and not to any specific anions. High pH and large deviations from normal in the tonicity of the sea water are ineffective in influencing the rate of pumping. The locus of pH sensitivity resides primarily within the mantle cavity. Lesions of the osphradium indicate that this chemosensory organ mediates a large degree of sensory control over respiratory pumping.
Oculomotor Function at Low Temperature: Antarctic Versus Temperate Fish
Authors: Montgomery J. C. , Macdonald J.A.
Published: April 2021

The peripheral oculomotor system can be modelled as a first order linear system (Montgomery, 1983), and hence specified by its characteristic frequency and ‘d. c.’ gain. These parameters can be determined by recording eye movements produced by stimulation of the abducens nerve with sinusoidally modulated pulse trains, and compare well with those independently derived from the relationship between motoneurone firing and spontaneous eye movement. Characteristic frequency and gain of the peripheral oculomotor system were determined for two species of antarctic teleost and one temperate species, to examine temperature compensation within a complete motor output pathway. Compared with low temperature function in temperate fish, the characteristic frequency is clearly temperature compensated in antarctic fish, which explains in part the observed temperature compensation of their rapid eye movement. The ‘d.c.’ gain of the peripheral oculomotor system is inversely related to temperature, providing an automatic compensation for possible reductions in central nervous system output and sensory gain at low temperature.
Comparison of Running Energetics in Male and Female Domestic Fowl
Authors: Brackenbury J. H. , El-Sayed M. S.
Published: April 2021

Carbon dioxide production and end-exercise venous lactate concentration were compared in intensively-trained, mature male and female domestic fowl running on a treadmill for 10-min periods at maximal and sub-maximal work loads. The relationship between and running speed was linear and had the same slope in male and female birds. However the maximum sustainable running speed of the males was. approximately twice that in the females and the maximum weight-specific was 60 % higher in males. End-exercise venous lactate concentration rose significantly above resting at work loads above 75 % maximum in females, but only at work loads above 95 % maximum in fully-trained males. The results indicate a greater work capability in male than in female birds in the conditions of the experiments.
Mass-Dependence of Anaerobic Metabolism and Acid-Base Disturbance During Activity in the Salt-Water Crocodile,Crocodylus Porosus
Authors: Bennett A. F. , Seymour R. S. , Bradford D. F. , Webb G. J. W.
Published: April 2021

Lactate concentration ([lactate−]), pH, and bicarbonate concentration ([HCO3−]) were measured in the blood of salt-water crocodiles (Crocodylus porosus Schneider) exhausted during field capture. Body temperature after capture averaged 31·1 °C. All animals underwent high levels of anaerobic metabolism and metabolic acidosis. The largest animals attained the highest blood [lactate−] and lowest pH ever observed in any animal as a result of activity. Peak levels of [lactate−] increased with increasing body mass (slope = 9·72 mmol 1−1 logM−1; mass M in kg), indicating a greater anaerobic capacity in larger animals. Several large crocodiles had [lactate−] in excess of 50mmol 1−1. Blood pH decreased with mass (slope = 0·163 pH unitslogM−1) and reached 6·6 in the largest animals. One animal remained acidotic for several hours and had a minimal pH of 6·42. Blood increased significantly and [HCO3−] decreased significantly with increasing body mass. Struggling time before exhaustion was greater in larger animals, ranging from about 5min in small (<1 kg) crocodiles to over 30min in animals over 100 kg. During recovery, mean blood [lactate−] decrement after 2h was 6·0 mmol 1−1 and was not significantly related to mass. Proton elimination from the blood, however, was more rapid in larger animals (slope = 0·0443 μmol 1 −1 log M −1 ). The positive mass-dependence of acid-base disturbance could be related to the greater susceptibility of large crocodiles (>700 kg) to post-capture mortality.
Adrenalin-Induced Na+/H+ Exchange In Trout Erythrocytes and its Effects Upon Oxygen-Carrying Capacity
Authors: Cossins A. R. , Richardson P. A.
Published: April 2021

Addition of adrenalin (10−4moll−1) to trout erythrocytes in an unbuffered saline resulted in a rapid acidification of the extracellular medium. This process was inhibited by amiloride (K1/2∼10−4moll−1) and by the removal of extracellular Na +. The rate of acidification was a saturable function of extracellular Na+ concentration.

When extracellular pH was maintained constant by continual titration with KOH, adrenalin induced a transient burst of H+ efflux. During this period the loss of cellular H+ equivalents was approximately equal to the net gain of Na+, providing evidence for a Na+/H+ exchange with a stoichiometry of 1. The steady state following stimulation with adrenalin could be disturbed by changes in extracellular pH. After the addition of adrenalin, intracellular pH (pHi) was increased by 0·2–0·3 units but did not exceed extracellular pH, as required if the Na+ and H+ concentration ratios came into equilibrium. The increase in pHi in stimulated compared with control cells was maintained approximately constant over a wide range of pH0, suggesting that pH equilibration by the Jacob-Stewart cycle was operating normally and that the activation of Na+ / H+ exchange provides an offset to the normal relationship between pHi and pHo. The steady state results from a balance of an increase Na+/H+ and CD/HCO3− exchange with an increased rate of Na+ pumping and next KC1 efflux.

In a buffered saline, adrenalin caused a 22–46 % increase in the oxygen-carrying capacity of trout erythrocytes. It is suggested that this was due to a Root effect of trout haemoglobin caused by cellular alkalinization when the Na+/H+ exchange mechanism was activiated. This observation suggests that many published values for oxygencarrying capacity of fish blood require re-evaluation.
Muscle Protein Synthesis Rates During Temperature Acclimation in a Eurythermal (Cyprinus Carpio) and a Stenothermal (Salmo Gairdneri) Species of Teleost
Authors: Loughna P. T. , Goldspink G.
Published: April 2021

Rates of protein synthesis were measured in the white myotomal muscle of carp (Cyprinus carpio) and rainbow trout (Salmo gairdneri) at a number of environmental temperatures before and after they had spent an acclimatory period at these temperatures. For carp previously kept at a mid-range temperature of 15 °C the rates of muscle protein synthesis showed a Q10 of 3·07 over the range of 10–25 °C. Acclimation to low temperatures resulted in the rate of protein synthesis being elevated whilst acclimation to high temperatures resulted in the depression of protein synthesis rate. Rainbow trout also initially maintained at 15 °C showed an initial Q10 of 3·57 between 5 and 20 °C. In this species, however, there was no significant difference in protein synthesis rates after being kept for 1 month at any given temperature within this temperature range. In the carp where acclimatory changes were recorded, it was found that these changes occurred at a faster rate at 25 °C than at 10°C. The ability of the carp to modify its protein metabolism in this way is discussed as a strategy for reducing temperature effects upon growth and muscle function.
Ventilation and Oxygen Uptake byNautilus
Authors: Wells M. J. , Wells J.
Published: April 2021

The shell of Nautilus prevents the mantle from playing any part in creating the ventilatory stream. This is generated instead by movements of the collar and funnel folds which fuse to form flaps (the ‘wings’), overlapping below and joined to the head above. The gills lie horizontally, dividing the space enclosed by the wings into three cavities, two lateral and prebranchial, on either side of the head, and a common ventral postbran-chial space. Water is drawn in above, behind the eyes, and expelled forward through the siphon of the funnel, which is used both for ventilation and jet propulsion. The pressures driving the ventilatory stream are small (of the order of 0·1 kPa), but the complex movement of the wings, described below, is such that there is (very nearly) always a pressure differential and a water flow across the gills, despite a pulsed intake and outward jet. Oxygen extraction is low by the standards of other cephalopods, only 5-10%, falling during jet propulsion and rising (exceptionally to 40 %) at rest after exercise. Ventilation frequency, 35 min−1 at 16°C, rises with temperature. Ventilation stroke volumes ranged from 5 to 22 ml for an animal of 395 g. At 17 °C Nautilus can regulate its oxygen uptake down to a of about 75 mmHg. Uptake at rest ranged from 0·22 to 0·46 ml kg−1 min−1 (exceptionally 0·75 ml kg−1 min−1 after feeding) for animals of 351-395 g. In terms of flesh weight, this yields an average of 0·50 ml kg−1 min−1, half to one-third of the uptake one would expect from coleoids of similar weights and at similar temperatures.
Nereistoxin: Actions on a Cns Acetylcholine Receptor/ion Channel in the CockroachPeriplaneta Americana
Authors: Sattelle D. B. , Harrow I. D. , David J. A. , Pelhate M. , Callec J. J. , Gepner J. I. , Hall L. M.
Published: April 2021

Nereistoxin hydrogen oxalate (NTX), at low concentrations (in the range 2·0 × 10−8—1·0 × 10−6 mol 1−1), induced a dose-dependent partial block of transmission at cereal afferent, giant interneurone synapses in the terminal abdominal ganglion (A6) of the cockroach Periplaneta americana which was not accompanied by changes in either membrane potential or input resistance of the postsynaptic membrane. At a concentration of 1·0xl0−7moH−1, NTX suppressed, in a voltage-dependent manner, acetylcholine-induced currents recorded from voltage-clamped cell bodies of both giant interneurone 2 (GI 2) in A6, and the fast coxal depressor motoneurone of the metathoracic ganglion (T3). At higher concentrations (in the range 1·0 × 10−5—1·0 × 10−3moll−1) depolarization of the postsynaptic membrane was observed. Axonal depolarization was noted at concentrations above 1·0 × 10−4moll−1. Voltage-clamp experiments showed that the axonal actions of NTX included suppression of sodium and potassium currents and an increase in the membrane leak current. The concentrations of NTX (in the range 1·0 × 10−5-1·0 × 10−3 moll−1) which show the postsynaptic depolarizing effect are in the same range as the NTX concentrations (1·7 × 10−4 and 6·6 × 10−5moll−1) required for 50% inhibition of the binding of 125I-α-bungarotoxin to Periplaneta abdominal nerve cord extracts and Drosophila head extracts, respectively. Thus a potent, voltage-dependent, blocking action of NTX is detected at the CNS acetylcholine receptor/ion channel complex of the cockroach. This, possibly together with the synaptic and axonal depolarizing effects noted at much higher concentrations, may contribute to the mechanism of action of this natural invertebrate neurotoxin which is also the active form of the synthetic insecticide Cartap.
Body Hydration and Haemolymph Osmolality Affect Feeding and its Neural Correlate in the Terrestrial Gastropod,Limax Maximus
Authors: Phifer Curtis B. , Prior David J.
Published: April 2021

When terrestrial slugs (Limax maximus) are dehydrated to 65–70 % of their initial body weight (IBW) their feeding responsiveness is greatly decreased. There is a 90 % decrease in feeding responsiveness when slugs are injected with hyperosmotic mannitol solution that raises the haemolymph osmolality to that of slugs dehydrated to 65–70 % IBW (i.e. 200 mosmolkg−1 H2O). The duration of the Feeding Motor Programme (FMP) that can be recorded from an isolated CNS-lip preparation is reduced by increasing the osmolality of the saline bathing the preparation. The osmolality of the saline that can modify the FMP corresponds to that of the haemolymph of a slug dehydrated to 65–70 % IBW. The pattern of the motor programme is not affected. A gradual increase in saline osmolality which temporally mimics the progressive increase in haemolymph osmolality of a dehydrating slug also causes a decrease in the duration of the FMP. The neural network underlying the FMP appears to adapt to hyperosmotic saline since the duration of FMP bouts gradually returns to normal levels after long-term exposure (6–8 h).
Efferent Influences on the Afferent Activity From the Octopus Angular Acceleration Receptor System
Authors: Williamson R.
Published: April 2021

Electrophysiological recordings were made from afferent units of the octopus angular acceleration receptor system during the electrical stimulation of efferent axons to this system. Of the afferent units examined, 93% changed their activity in response to stimulation of the efferent axons.

During efferent stimulation 77% of the afferent units decreased their activity. The magnitude of the inhibition and the time to maximum response were frequency dependent, with most units showing an increase in inhibition with increase in efferent stimulation frequency. The poststimulus recovery from inhibition was of two types: either a gradual increase in activity to the pre-stimulus resting level of activity (Fig. 3) or a rapid increase in activity to a level above the pre-stimulus level, i.e. a post-inhibitory rebound or facilitation, and then a gradual decline to the resting level of activity (Fig. 4). During long periods of efferent stimulation (> 40 s) the inhibition was not maintained.

During stimulation of the efferent axons 16% of the afferent units increased their activity. The post-stimulus response consisted of either a gradual decrease in activity to the pre-stimulus level of resting activity or a rapid increase in activity followed by a gradual decrease to the resting level of activity (Fig. 6). During long periods of efferent stimulation the excitation increased to a plateau level which was maintained for the duration of the stimulus period (Fig. 7).

Sinusoidal oscillations of the statocyst evoked bursts of afferent activity in time with the movement. The magnitude of these bursts could be decreased or increased by stimulation of the efferent axons (Fig. 8).

It is proposed that two populations of efferents are present in the octopus statocyst, one inhibitory and the other excitatory, and that both types of efferent affect single afferent units.
Differences Between Upstroke and Downstroke in Swimming Dolphins
Authors: Videler John , Kamermans Pauline
Published: April 2021

Steady swimming movements of dolphins were recorded in a search for direct evidence of asymmetry between upstrokes and downstrokes. Kinematic swimming and gliding data from frame-by-frame analysis of ciné pictures taken at constant frame rates with a camera in a fixed position are presented. We estimated the propulsive forces generated by the tail blade with a simple hydrodynamic model.

Dolphins accelerate during the downstroke and decelerate during the upstroke: the net hydrodynamic force in the animal is always positive during the downstroke and negative during the upstroke. Both parts of the stroke cycle are equally long. The propulsive forces of downstrokes are on average larger than the forces of the upstrokes. Occasionally the average forces within an upstroke are greater than within a downstroke of the same sequence. Our data suggest that the drag on the body during the upstroke exceeds the drag in the course of the downstroke. The specific swimming speed or stride length of dolphins swimming at low speeds is about 0·9 body lengths per tail beat.
Experimental Demonstration of Volterra’s Periodic Oscillations in the Numbers of Animals
Authors: Gause G. F.
Published: April 2021

From purely theoretical considerations Lotka (1920) and Volterra (1926) concluded that a biological system consisting of two interdependent species (predator and prey) will exhibit regular periodic fluctuations in respect to the absolute and relative abundance of each species, even when random fluctuations due to external environmental factors have been eliminated. So far as is known this conclusion has not been investigated by direct experimental methods.
The Effect of Bacterial Products on Amoebic Growth
Authors: Cutler D. Ward , Crump Lettice M.
Published: April 2021

The interrelationships that exist between various groups of Protozoa in nature and the bacteria which occur in the same environments are undoubtedly of more than academic interest. This is especially the case perhaps in soil, where both types of organisms are present in very large numbers, and where a marked degree of activity is evidenced by the continual fluctuation to which these numbers are subject. The food relationships of one member of the soil population, the amoeba Hartmanella hyalina, was described in a previous paper (2), where it was shown that certain kinds of bacteria afforded a more efficient food supply than others as judged by the reproductive rate of the amoeba. A priori this might have been due to the fact that the bacteria giving a high reproductive rate to the amoebae were of greater food value than the others ; or that the by-products formed by the less valuable bacterium in the course of growth were deleterious in their effects; but preliminary experiments indicated that for the species of bacteria concerned it was a true food value effect and not one caused by the presence of any by-products.
The Effect of Captivity Upon the Reproductive Cycle of the South African Clawed Toad (Xenopus Laevis)
Authors: Alexander S. S. , Bellerby C. W.
Published: April 2021

The South African clawed toad (Xenopus laevis) can be maintained in captivity in a healthy condition provided that it is adequately fed. No atrophic changes are found to occur in the ovary as reported by Zwarenstein and Shapiro for animals kept in captivity in Cape Town. The developmental condition of the ovary depends directly upon the amount of food available. The normal periods of ovarian growth and retrogression which occur in the toad under natural conditions can be explained on the basis of fluctuation in food supply.
The Effects of Temperature and Humidity on the Cheese Skipper, Piophila Casei (L.)
Authors: Smart John
Published: April 2021

The extraordinary resistance of all the developmental stages of Piophila casei (L.) to adverse conditions and their general tenacity to life has been noticed by several authors. Alessandrini (1909) reports the results of the treatment of the larvae with some seventy reagents; Krausse (1909) reports on a similar series of tests, and Simmons (1927) gives details of some rather more carefully controlled experiments together with a general summary of our knowledge of the fly at the time of the publication of his paper. The resistance of the fly in its various stages to conditions usually lethal for insects, suggested that it might prove of interest to examine some of the reactions of the Cheese Skipper to conditions of controlled temperature and humidity such as Buxton (1931 b) and Mellanby (1932,1934) have applied to various other insects. The present paper is the result of this investigation.
Blood Flow in Acute Hypoxia in A Cephalopod
Authors: Wells M. J. , Wells J.
Published: April 2021

This paper reports a method of measuring blood flow in the dorsal aorta of Octopus vulgaris using fixed magnet flow meters. Blood flow, like blood pressure, falls progressively during acute hypoxia. Flow increases greatly as soon as the ambient rises, with values for a given external exceeding those found during the preceding development of hypoxia. On average, about 70 % of the total systemic blood flow runs down the aorta to the head and arms; the rest goes to the gonad, to the mantle, to the coronary circulation and to the guts. This pattern remains unchanged as the ambient falls.
A Potassium-Selective Channel in Isolated Lymnaea Stagnalis Heart Muscle Cells
Authors: Brezden B. L. , Gardner D. R. , Morris C. E.
Published: April 2021

Lymnaea stagnalis heart ventricle muscle cells, isolated by enzymatic dispersion, are suitable for patch clamp recording. A channel has been identified which is primarily selective for potassium, although it also appears to conduct sodium. This channel is not blocked by 4-aminopyridine or tetraethylammonium but is sensitive to quinidine. The relationship between the membrane potential, the external potassium concentration and the channel currents, when compared with results obtained from whole cell recording, suggests that this channel could mediate a large part of the cell’s resting conductance.

The probability of this channel being open is increased by stretching the patched cell membrane. This has led to speculations about further possible functional roles for this channel.
Hydrostatic Pressures in Glomeruli and Renal Vasculature of the Hagfish, Eptatretus Stouti
Authors: Riegel J. A.
Published: April 2021

Hydrostatic pressures in the renal vasculature of hagfish have been studied. Estimates of the blood colloid osmotic pressure (COP) have been made. In blood vessels supplying the renal corpuscles, the average hydrostatic pressure is about 1 kPa. The average hydrostatic pressure falls to a value of 0·04 kPa within the postcardinal vein efferent to the renal corpuscle. Within the glomerular capillaries the hydrostatic pressure averages 0·21 kPa. Since the blood COP averages about 1–4 kPa, it is clear that glomerular filtration in the hagfish is not underlain by the hydrostatic pressure of the arterial pulse.

In some blood vessels efferent to the renal corpuscles, hydrostatic pressure may be as high as in the afferent supply. Evidence is presented that the glomerular capillaries are shunted by this high pressure vascular pathway.
Blood Oxygen Transport In The Free-Swimming Hagfish, Eptatretus Cirrhatus
Authors: Wells R. M. G. , Forster M. E. , Davison W. , Taylor H. H. , Davie P. S. , Satchell G. H.
Published: April 2021

Arterial and mixed venous blood were sampled through chronically implanted cannulae from rested and swimming hagfish. remained high when hagfish were swum for 15min at a velocity of 20cms-1. fell from 17-2mmHg at rest to 3’5 mmHg after swimming, and the arteriovenous pH difference increased from 0·15 to 0·25 pH units. Whole blood oxygen equilibrium curves were essentially hyperbolic (Hill’s n value = 1·38) and gave a half-saturation (P50) value of 12·3 mmHg at pH 7·8 and 16°C. A CO2-Bohr factor (ϕ = ΔlogP50/ΔpH) of –0·43 and a limited buffering capacity of the blood, amounting to approx. 4slykes, were observed. The role of the blood in transporting oxygen and carbon dioxide both at rest and after swimming is established by in vivo blood gas measurements and in vitro oxygen-binding data. The low internal at rest is close to the P50 measured under similar conditions and the hyperbolic equilibrium curve permits further oxygen unloading when falls during swimming.
The Relationship of Muscle Electrical Activity, Tremor And Heat Production To Shivering Thermogenesis In Japanese Quail
Authors: Hohtola Esa , Stevens E. Don
Published: April 2021

We measured the electrical activity and the tremor of the pectoral muscle and total body heat production in control and cold-acclimated Japanese quail at +26°C, + 12°C and +2°C before and after 3 weeks of acclimation, using electromyography, accelerometer recordings, and indirect calorimetry. Japanese quail shiver in 0·2- to 3-s bursts that occur in groups. An increase in both the frequency and the duration of bursts and burst groups contributes to the increase in heat production by shivering at low temperatures. A compilation of shivering patterns in birds is given and its implications for the neural control and phylogeny of shivering are discussed. A rather non-specific increase in electromyographic (EMG) activity and heat production was observed after cold acclimation at all experimental temperatures, although many of the normal signs of cold acclimation (e.g. decrease in gonad mass, increase in heart mass and serum triiodothyronine) were seen. The increase in muscle electrical activity was greater than the increase in oxygen uptake, which resulted in a lower ratio. The amplitude distribution of muscle electrical activity remained normal, but a shift towards higher frequencies occurred in the EMG spectra of cold-acclimated birds. Despite the increase in muscle electrical activity, power spectra of accelerometer recordings indicated that the amplitude of the muscle tremor was lower in cold-acclimated birds. The increase in the high-frequency components of the EMG indicates that decreased synchronization of motor unit firing may account for the lower tremor amplitude. We suggest that this change is adaptive because it reduces heat loss and/or because more fatigue-resistant motor units are recruited. These results show that temperature acclimation modifies the neural control of shivering in skeletal muscle.
Mechanical Analysis of Spontaneous Breathing in the Semi-Aquatic Turtle, Pseudemys Scripta
Authors: Vitalis Timothy Z. , Milsom William K.
Published: April 2021

The normal breathing pattern of Pseudemys scripta (Schoepff) consists of a continuous burst of breaths separated by a variable period of breath holding. Under normoxic conditions, tidal volume was 6·9 ml kg−1 and the number of breaths was 1·9 min−1. Increases in pulmonary ventilation upon stimulation by hypercapnia (3 % CO2) or hypoxia (4 % O2) are caused primarily by increases in the number of breaths per minute due to a shortening of the breath-hold period. Tidal volume and breath duration remain unchanged. The instantaneous breathing frequency (f′ = 60/Ttot) of 35 ± 2min−1 corresponds to continuous pump frequencies that minimize the rate of the mechanical work of breathing in anaesthetized turtles. This indicates that turtles breathe at a combination of tidal volume and f′ that minimizes the power required to ventilate the lungs. To increase ventilation, the breath hold is shortened and more breaths are taken at this optimal combination. Bilateral vagotomy drastically alters the breathing pattern, producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of breath duration while total ventilation remains unchanged. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal control and which serves to minimize the cost of breathing.