bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiac Output and Regional Blood Flow in Gills And Muscles After Exhaustive Exercise in Rainbow Trout (Salmo Gairdneri)
Authors: Neumann Peter , Holeton George F. , Heisler Norbert
Published: April 2021

Rainbow trout (Salmo gairdneri) were electrically stimulated to exhausting activity and the changes in cardiac output and blood flow distribution to gills and systemic tissues resulting from the developing severe lactacidosis were repeatedly measured by the microsphere method (15 μm). Determination of cardiac output by application of the Fick principle resulted in values not significantly different from cardiac output measured by the indicator dilution technique, suggesting that cutaneous respiration, oxygen consumption, and arterio-venous shunting were insignificant under these conditions.

Following muscular activity, cardiac output was elevated by up to 60%. In the gills, the blood flow distribution in the gill arches showed a consistent pattern, even during lactacidosis, with a higher perfusion in gill arches II and III, and in the middle sections of individual gills. Blood flow to white and red muscle was increased much more than cardiac output (+230 and +490%, respectively) such that blood flow to other tissues was actually reduced.

We conclude that the elimination of lactate from muscle cells during the recovery period from strenuous exercise is delayed, not as a result of an impaired post-exercise muscle blood flow, but probably as a result of a high diffusion resistance in the cell membrane.
Motor Output of the Denervated Thoracic Ventral Nerve Cord in the Stick Insect Carausius Morosus
Authors: Bässler Ulrich , Wegner Uta
Published: April 2021

The denervated thoracic ventral nerve cord produces a motor output which is similar to that observed in the intact animal during irregular leg movements (seeking movements) or rocking, but not walking.

When the nerves to some legs are left intact, and the animal walks on a wheel, the motor output in the protractor and retractor motor neurones of the denervated legs is modulated by the stepping frequency of the walking legs. The modulation is similar to that observed in the motor output to a not actually stepping leg of an intact walking animal.

When only the crural nerve of one leg is left intact, stimulation of the trochanteral campaniform sensilli induces protractor and retractor motor output to that leg and the leg behind it. In this case the motor output to the ipsilateral leg is in phase. Stimulation of the femoral chordotonal organ influences activity in motor neurones of the extensor tibiae (FETi and SETi) but not those of the protractor and retractor coxae muscles.

In a restrained leg of an intact animal stretching of the femoral chordotonal organ excites FETi and SETi as long as the other legs walk (as in a walking leg) and inhibits FETi and SETi (as in a seeking leg) when the other legs are unable to walk.
Respiration During Chronic Hypoxia Andhyperoxia in Larval and Adult Bullfrogs (Rana Catesbeiana) I. Morphological Responses of Lungs, Skin and Gills
Authors: Burggren Warren , Mwalukoma Anganile
Published: April 2021

Larval and adult bullfrogs, Rana catesbeiana (Shaw), were exposed to 28 days of normoxia ( 150 mmHg), hypoxia ( 70–80 mmHg) or hyperoxia ( > 275 mmHg) at 20–23 °C, after which the following mor phological measurements were made: (1) mass, thickness, capillary mesh density and blood-water barrier of the skin; (2) mass, volume, cava density and blood-gas barrier of lungs; and, for the larvae, (3) arch length, filament density and size, and blood-water barrier of the gills.

Chronic hypoxia induced profound morphological changes in the gas exchange organs of larvae, but not of adults. In tadpoles, the skin became thinner, with a doubling of capillary mesh density and a halving of the blood-water barrier. The gas diffusion barrier of the lungs remained un changed, but the lung volume and density of the lung wall cava both in creased significantly. The internal gills showed a marked enlargement upon hypoxic exposure, both in numbers of gill filaments and size of each fila ment. The blood-water barrier remained unchanged. Chronic hyperoxia, unlike chronic hypoxia, caused no significant changes in the morphology of the gas exchange organs of larvae.

Chronic exposure to hypoxia or hyperoxia failed to produce any sig nificant morphological changes in adult bullfrogs.

These data indicate that the great morphological plasticity of larvae, culminating in metamorphosis, also extends to profound adjustments in the gas exchange organs when oxygen transfer becomes limited, a response lacking in adults.
Respiration During Chronic Hypoxia and Hyperoxia in Larval and Adult Bullfrogs (Rana Catesbeiana) II. Changes in Respiratory Properties of Whole Blood
Authors: Pinder Alan , Burggren Warren
Published: April 2021

Rana catesbeiana Shaw tadpoles and adults were maintained at 20–23 °C under aerial and aquatic normoxia ( 150 mmHg), hyperoxia ( 275 mmHg) and hypoxia ( 75 mmHg) for 4 weeks, after which the following blood measurements were made: haematocrit, red blood cell count, haemoglobin concentration, mean corpuscular haemoglobin concentration, O2 capacity, O2 equilibrium curve, Bohr shift, Hill’s coefficient and intraerythrocytic concentration of nucleotide triphosphates (ATP+GTP) and 2,3-DPG.

Normoxic tadpoles had much higher blood O2 affinity (P50 9–10 mmHg) than adults (P50 35 mmHg) but a lower haemoglobin concentration, haematocrit and O2 capacity. The concentration of intraerythrocytic phosphates was higher in normoxic tadpoles than in adults, indicating that the higher O2 affinity of normoxic tadpole blood was due to the haemoglobins themselves, rather than affinity modulators.

Chronic hypoxia in tadpoles produced little change in whole blood P50, and no significant change in any other blood variable. In adult bullfrogs, on the other hand, O2 capacity doubled through polycythaemia, and the P50 decreased by 11 mmHg (35%), though apparently not from any significant change in concentration of intraerythrocytic phosphates. Hyperoxia produced no haematological changes in either larvae or adults.

In adult bullfrogs exposed to chronic hypoxia, the morphology of the gas exchange organs does not change (Burggren & Mwalukomo, 1983), but instead profound adjustments occur in the blood, favouring O2 transport under these conditions. The blood of the tadpole shows little or no response to chronic hypoxia, with morphological adjustments in skin, gills and lungs constituting the major response.
Motor Control of Movements of the Antennal Flagellum in the Australian Crayfish, Euastacus Armatus
Authors: Sandeman David C. , Wilkens Lon A.
Published: April 2021

Voluntary and reflexive antennal movements of an Australian freshwater crayfish are described. An anatomical and physiological study showed that the flagellar flexor muscle is innervated by three motor neurones (a common inhibitor and two exciters) and the flagellar extensor muscle receives four motor neurones (a common inhibitor and three exciters). The discharges of three of the motor neurones to the flexor and extensor muscles (tonic flexor, tonic extensor, common inhibitor) were recorded simultaneously with the movements of the flagellum in intact but restrained animals. Phase relationships between flexors and extensors are not simply antagonistic for all voluntary movements. The common inhibitor is more often in phase with, or leads, tonic extensor activity, than tonic flexor activity.
Haemodynamic Effects of Adrenaline on the Isolated, Perfused Head of the Dogfish ‘Pup’ (Squalus Acanthias)
Authors: Evans David H. , Claiborne J. B.
Published: April 2021

The isolated, perfused head of the dogfish ‘pup’ (Squalus acanthias) maintained pressure: flow relationships near to those described for the in vivo adult for at least 3 h when perfused at a constant rate. The addition of 3% polyvinylpyrrolidone reversibly increased branchial resistance, and the postbranchial outflow (arterial + venous) equalled the inflow. 10−5M adrenaline reversibly reduced gill resistance (in some cases after a transient increase in resistance) and stimulated perfusate outflow from the dorsal aorta, at the expense of flow from the cephalic and branchial venous system. Phentolamine did not alter the effect of adrenaline on pressure and flow pattern; addition of propranolol inhibited both adrenaline effects and resulted in a slight increase in afferent pressure, indicating that a-adrenergic receptors are present, but that the dominant haemodynamic effects are mediated via β-adrenergic receptors. The isolated, perfused ‘pup’ head may provide a vehicle for investigation of transport phenomena in the elasmobranch branchial epithelium.
The Innervation of the Mesothoracic Flexor Tibiae Muscle of the Locust
Authors: Theophilidis G. , Burns M. D.
Published: April 2021

The anatomy and innervation of the mesothoracic flexor tibiae muscle indicated a subdivision into proximal, middle and distal flexors.

The muscle is innervated by 12 excitors, two inhibitors and two dorsal unpaired median (DUM) neurones. The motor axons were identified by (a) the height of the action potentials recorded extracellularly from the flexor nerve branches of an intact locust, (b) the EPSPs or IPSPs and the tension which they produced in the muscle when they were stimulated and (c) the distribution on the muscle. There was some independent innervation of proximal, middle and distal flexors.
Conditioning Factors(s) Produced By Several Molluscan Species Promote Neurite Outgrowth in Cell Culture
Authors: Wong Richard G. , Martel Elaine C. , Kater S. B.
Published: April 2021

The ability to correlate the behaviour of neurones in intact ganglia with events in isolation as has been shown in the leech (Ready & Nicholls, 1979; Fuchs, Nicholls & Ready, 1981), may provide insight into the intrinsic properties of individual neurones.
Antagonizing Effect of Ultraviolet and Visible Light on the Erg From the Ocellus of Spirocodon Saltatrix (Coelenterata: Hydrozoa)
Authors: Ohtsu Kohzoh
Published: April 2021

Many anthomedusan jellyfish swim when ambient illumination is interrupted (Passano, Mackie & De Ceccatty, 1967; Ohtsu & Yoshida, 1973; Anderson & Mackie, 1977). This shadow response has been attributed to the ocelli, which are located at the margin of the bell. However, in some anthomedusae, it has been demonstrated that the motor neurones that innervate the swimming musculature are, themselves, directly photosensitive (Anderson & Mackie, 1977; Ohtsu, 1983). One species which possesses both classes of photoreceptor is Spirocodon (Ohtsu, 1983). In this animal, near ultraviolet light (u.v.) hyperpolarizes the swimming neurones and inhibits swimming. This effect is tonic, lasting long after the cessation of u.v. irradiation. However, this after-inhibition can be disinhibited by irradiation with visible light (u.v.-vis antagonism). To investigate the role of these two photoreceptor types in the behaviour of Spirocodon, the electroretinogram (ERG) of the ocelli was measured. The results described here are basically similar to those obtained from Sarsia ocelli (Weber, 1982), the only coelenterate photoreceptors investigated to date, but there are some differences.
Synchronous Vocal Response Mediated by the Amphibian Papilla in a Neotropicaltreefrog: Behavioural Evidence
Authors: Narins Peter M.
Published: April 2021

Acoustic playback experiments with treefrogs (Eleutherodactylus coqui Thomas) in their natural habitat reveal that males readily synchronize their vocalizations with synthetic calls containing frequencies equal to or lower than their own. Low-level artificial stimuli were used in order preferentially to stimulate auditory fibres originating in the amphibian papilla while avoiding excitation of basilar papillar or saccular fibres. Moreover, the synchronous vocal response persists unabated, even when the synthetic calls were simultaneously ‘masked’ with narrow-and wide-band noise, which strongly excited a large fraction of the basilar papillar fibres. These behavioural findings support the hypothesis that the amphibian papilla alone mediates this critical vocal behaviour.
Co-And Counter-Transport Mechanisms Inbrush Border Membranes and Basal-Lateralmembranes of Intestine and Kidney
Authors: Murer H. , Ahearn G. , Biber J. , Cassano G. , Gmaj P. , Stieger B.
Published: April 2021

One way to obtain a deeper understanding of the complex function of the small intestinal and renal proximal tubular epithelium is to dissect it into single components and then, having defined the components under well-controlled conditions, try to describe the behaviour of the whole system on the basis of the properties of the single components.

Brush border and basal-lateral membranes can be isolated by different methods, including free flow electrophoresis, differential and gradient centrifugation. Transport can be analysed in vesiculated membrane fractions by tracer techniques and spectrophotometric techniques.

Different sodium-solute co-transport mechanisms were identified in the brush border membrane. Until now, studies with vesicles failed to document a sodium-chloride co-transport mechanism satisfactorily. On the other hand, a sodium/proton and a chloride/hydroxyl exchange mechanism were documented. These two exchange mechanisms could represent partial reactions of the postulated electroneutral sodium-chloride co-transport. In addition to different sodium-independent transport systems, the basallateral membrane contains an ATP-driven transport system for calcium as well as a sodium/calcium exchange mechanism.

Studies with membrane vesicles isolated from animals which have been exposed to different dietary conditions or in which the parathyroid hormone or 1·25(OH)2Vit D3 level has been altered show altered transport of calcium and inorganic phosphate. Thereby, it might be possible to identify the biochemical mechanisms involved in transport regulation.
Chloride Cells and the Hormonal Control of Teleost Fish Osmoregulation
Authors: Kevin Foskett J. , Bern Howard A. , Machen Terry E. , Conner Marilyn
Published: April 2021

Teleost fish osmoregulation is largely the result of integrated transport activities of the gill, gut and renal system. The basic ‘epithelial fabric’ in each of these tissues is adapted to provide the appropriate transport mechanisms depending upon whether the fish is in fresh water or sea water. Net NaCl transport by the branchial epithelium reverses direction when euryhaline species migrate between the two media, providing a useful focus in experiments designed to elucidate mechanisms of differentiation and integration of transport function. Isolated opercular membranes and skins from certain seawater-adapted species are good models to study branchial salt extrusion mechanisms. These heterogeneous tissues generate short-circuit currents equal to net chloride secretion. The vibrating probe technique has allowed localization of all current and almost all conductance to the apical crypt of chloride cells. Area-specific surface current and conductance of chloride cells are 18mAcm−2 and 580mScm−2 (1·7Ωcm2), ranking them as one of the most actively transporting and conductive cells known. There is no net sodium transport under short-circuit conditions but the chloride secretion process is sodium-dependent and ouabain and ‘loop’-diuretic sensitive. Sodium fluxes through chloride cells are large (PNa = 5·2 × Ω 10−4cms−1) and appear passive and rate-limited by a single barrier. A link may exist between the active transport and leak pathways since sodium fluxes always account for 50% of chloride cell conductance. The sodium pathway is probably the chloride cell-accessory cell tight junction, although this is still unresolved. Chloride secretion can be rapidly modulated by several hormones, including catecholamines, somatostatin, glucagon, vasoactive intestinal polypeptide and urotensins I and II. Regulation by these hormones may be by rapid alterations of cellular cAMP levels. Differentiation of chloride cells and chloride secretion may be controlled by cortisol and prolactin. Cortisol stimulates chloride cell proliferation and differentiation and appears to interact with NaCl to initiate salt secretion. Prolactin appears to cause chloride cell dedifferentiation by reducing both the active-transport and leak pathways proportionately. Prolactin and cortisol also affect epithelial cell proliferation and differentiation in the other osmoregulatory tissues in fish, suggesting that these hormones are primary agents in the integration of transport activities to achieve whole animal osmoregulation.
Evolution of Control of Epithelial Transport in Vertebrates
Authors: Pang Peter K. T.
Published: April 2021

In this review, the control of osmoregulation in the whole animal is discussed. Two main areas are considered: (i) the interaction between neural and hormonal control of osmoregulation and (ii) the relationship between vascular and osmoregulatory responses to these controlling factors. In the first area, the importance of neural influence on bullfrog kidney is described. The data suggest that a-adrenergic mechanisms are involved in glomerular as well as tubular functions. Innervation of tubular cells is seen in electron microscopic studies. Effects of neurotransmitters on fish gills and amphibian urinary bladder and skin transport are discussed. It is suggested that neural control in fish and amphibian epithelial transport might play an important role in osmoregulation. In the second area, a hypothesis is advanced for the evolution of renal function of arginine vasotocin (AVT). AVT probably first appeared as a vascular hormone. Its diuretic effect on fishes could be due to its systemic pressor action. During evolution, redistribution of vascular receptors, which became more numerous or more sensitive in the preglomerular circulation, resulted in glomerular anti-diuresis as seen in the mudpuppy and bullfrog. Tubular receptors to AVT, present in the bullfrog, enhanced the antidiuretic property of this peptide. Effects of neurotransmitters on gill transport could be due in part to their vascular action on the branchial vasculature. The intimate relationship between vascular and osmoregulatory responses to controlling factors could be important in our understanding of the evolution of the control of osmoregulation.
Na/K/Cl Co-Transport and its Regulation
Authors: Palfrey H. C. , Rao M. C.
Published: April 2021

NaCl and Na/K/Cl co-transport systems in many cell types show a number of similarities, among which are sensitivity to ‘loop’ diuretic inhibition and extremely high anion selectivity. Avian erythrocytes possess a Na + K + 2C1 co-transporter that is stimulated by agents raising intracellular cAMP. The system is also inhibited following ATP-depletion of the cells, in agreement with results in other tissues; this nucleotide may exert a regulatory role on the operation of the co-transporter. A Na/K/Cl co-transport system is also present in flounder intestine, where it plays a central role in salt absorption at the luminal border of the tissue. In contrast to the avian erythrocyte this system is inhibited by raising intracellular cyclic nucleotide content, cGMP being more effective than cAMP. From these results it is concluded that second messenger regulation of Na/K/Cl cotransport processes is heterogeneous and may exhibit some tissue specificity.
Cellular Mechanisms and Control of KCL Absorption in Insect Hindgut
Authors: Hanrahan J. W. , PHILLIPS J. E.
Published: April 2021

The hindgut of the desert locust possesses an unusual chloride transport system. The isolated locust rectum absorbs chloride from the mucosal (lumen) to the serosal (haemolymph) side at a rate which is equal to the short-circuit current (Isc). Net chloride transport persists in nominally Na-free or HCO3(CO2)-free saline, is insensitive to normal inhibitors of NaCl co-transport and anion exchange, and is independent of the net electrochemical gradient for sodium across the apical membrane. However, active chloride transport is strongly dependent on mucosal potassium (K2 = 5·3mm-K). Chloride entry across the apical membrane is active, whereas the net electrochemical gradient across the basal membrane favours passive Cl exit from the cell. Although mucosal potassium directly stimulates ‘uphill’ chloride entry, there is no evidence for coupled KCL co-transport, nor would co-entry with potassium be advantageous energetically.

Net chloride absorption and IK are stimulated by a peptide hormone from the central nervous system which acts via cyclic-AMP. Cyclic-AMP increases Isc and approximately 1000% and transepithelial conductance (Gt) ˜100%. Approximately half of the ΔGt during stimulation results from increased Cl conductance at the basal cell border. This increase is also reflected in a shift of the basal membrane e.m.f. towards the Nemst potential for chloride. The remainder of the cAMP-induced ΔGt is due to an elevation of apical membrane K conductance, which causes a 400% increase in transepithelial potassium permeability as estimated by radiotracer diffusion. Because of this stimulation of K conductance, potassium serves as the principal counterion for active chloride transport under open-circuit conditions. Very high luminal levels of K oppose the stimulatory actions of cAMP on active Cl transport and K conductance. These and other results have been incorporated into a cellular model for KCL absorption across this insect epithelium.
Control of Na+ and Water Absorption Across Vertebrate ‘Tight’ Epithelia By ADH and Aldosterone
Authors: Lewis Simon A.
Published: April 2021

Salt and water balance in vertebrates is controlled by the release of two blood borne hormones: aldosterone and antidiuretic hormone (ADH). It is the purpose of this chapter to review the mechanisms (at the plasma membrane level) by which these hormones cause an increase in salt (sodium) and water movement in the target tissues. The primary effect of aldosterone is to increase the Na+ permeability of the lumen-facing (apical) membrane by activation of pre-existing quiescent channels at short times, and by the incorporation of newly synthesized channels after prolonged exposure. Other effects might involve an increase in energy supply and synthesis of Na+-K+ ATPase which is responsible for Na+ extrusion from cell cytoplasm to blood. Similarly, ADH stimulates pre-existing quiescent apical membrane Na+ channels. The second effect of ADH is to increase epithelial water permeability. Evidence strongly suggests that water channels exist in cytoplasmic vesicles which, upon ADH challenge, fuse into the apical membrane causing a rapid increase in apical membrane hydraulic conductivity. The movements of vesicles are dependent on an intact cytoskeleton. Regulation of electrolyte and non-electrolyte transport will be discussed in the light of the above two mechanisms.
Blood Pressure in the Leech Hirudo Medicinalis
Authors: Krahl Bodo , Zerbst-Boroffka Irene
Published: April 2021

Intravascular pressure recordings in the lateral vessels of the leech, Hirudo medicinalis, show two distinct pressure patterns: high pressure phases (diastolic pressure: 5 ± 3 mmHg, systolic pressure: 48 ± 14mmHg) alternate with low pressure phases (diastolic pressure: 4 ± 2·5 mmHg, systolic pressure: 26 ± 11 mmHg). The lateral vessel of one side produces high pressure pulses during peristaltic action while the other vessel generates low pressure pulses during non-peristaltic action. After 20–60 pulses a transition occurs, which sometimes appears more gradually.
Quantitative Analysis of Walking in A Decapod Crustacean, the Rock Lobster Jasus Lalandii I. Comparative Study of Free and Driven Walking
Authors: Clarac F. , Chasserat C.
Published: April 2021

The study compares the relative validity of the data obtained from two experimental situations, i.e. free walking and driven walking, in relation to leg coordination in Jasus lalandii (Milne-Edwards).

The relationship between ipsilateral and contralateral legs during the forward as well as the backward walking sequences has been analysed in the two situations. They operate roughly in opposition. Although little dif ference in the mean phase values has been observed in the two experimental situations, the strength of coupling is greater in the driven walking animals.

The power stroke (PS) duration correlates well with the period, but the return stroke (RS) is more variable and varies according to the leg considered. The phase does not appear to be correlated with the step period during free walking, but is correlated in the treadmill situation.

Initially, several of the properties of the single motor unit discharges correlated with movement have identical mean values in both free and driven walking. However, several significant differences have been observed in the intra-burst organization. These differences indicate that the constraint of the treadmill decreases the variability of all parameters and produces a stable and more stereotyped walking pattern.
The Mechanics of the Predatory Strike of the Praying Mantid Heirodula Membranacea
Authors: Gray P. T. A. , Mill P. J.
Published: April 2021

The mechanics of the predatory strike of Heirodula membranacea (Burm.) have been studied using high speed ciné, electrophysiological and anatomical techniques. Calculations of the muscle output required to produce the strike suggest that muscle performance generally lies within the range observed elsewhere and that no specializations for prior energy storage, as are found in some other rapid insect movements, are necessary. This view is supported by simultaneous EMG and ciné studies showing no significant delay between the onset of EMG activity and the onset of stress development required by the direct action model. The apodemes of a number of forelimb muscles are found to have complex two-point suspensions; these have a significant role in determining the moment-arm/joint-angle relationships of the muscles. The parallel-fibred part of the tibial flexor muscle has a high strain rate, 17·5 s−1, at 27–30°C. This is the fastest recorded strain rate for an insect muscle, and approaches the fastest strain rates of mammalian muscles operating at 37 °C.
Nervous Control of the Salivary Glands of the Carnivorous Mollusc Philineaperta
Authors: Barber Andrew
Published: April 2021

Evidence is presented to show that the electrical activity of the salivary glands of Philine aperta is controlled by two largely independent systems which elicit different responses from salivary acinar cells. The excitatory junction potentials (EJPs) recorded from salivary cells result from the activity of a pair of identified buccal ganglion neurones. Each of these salivary effector neurones innervates only the ipsilateral gland. The effector neurones are driven to fire by synaptic input which is timed to occur during the retraction phase of the feeding cycle. Gland cell excitatory post-synaptic potentials (EPSPs) and action potentials appear to be mediated by a small group of peripheral neurones located at the base of each salivary gland. These cells give rise to a tract of fibres which cross to the contralateral gland and which may be responsible for communicating EPSP/action potential activity between the glands. The possible functions of the EJP and EPSP/ spiking activities are discussed.
Graded Potentials and Spiking in Single Units of The Oval Organ, A Mechanoreceptor in the Lobster Ventilatory System: I. Characteristics of Dual Afferent Signalling
Authors: Pasztor V. M. , Bush B. M. H.
Published: April 2021

The lobster oval organ sends three afferent fibres to the sub-oesophageal ganglion: X (mean diameter 41 μm), Y (32 μm) and Z (22 μm). The distance between the oval organ and the ganglion is 10–15 mm in animals of approximately 10 cm carapace length. The cell bodies of the sensory units lie centrally amidst the ventilatory motoneurones, and their central branches permeate the same lateral neuropile. Intracellular recordings from each fibre show that the afferent response to stretch has two components: overshooting, regenerative, TTX-sensitive impulses, and an underlying graded depolarization. The analogue signal has the characteristics of a receptor potential: a dynamic response with rapidly depolarizing initial component, some adaptive fall leading to a maintained static plateau, and a post-release hyperpolarizing undershoot. The two signals are not equally represented in the response of the three afferents. Fibre X has the largest graded potentials (up to 30 mV in recordings 6mm proximal to the confluence of the sensory dendrites). Fibre Z attains the highest firing frequencies (usually around 100 s−1). Fibre Y has intermediate properties. Both the amplitude of the graded potential and the number of spikes per response (in fibres Y and Z) relate linearly to pull amplitude. Estimates of length constant (approximately 10 mm) and specific membrane resistance (l00 kΩcm2) are consistent with the hypothesis that the graded potentials spread into the presynaptic terminals with sufficient magnitude to bring about postsynaptic events.
Labial Extension in the Dragonfly Larva Anax Imperator
Authors: Parry D. A.
Published: April 2021

The extension mechanism of the larval dragonfly’s labium has been under discussion since Snodgrass (1954) drew attention to the absence of muscles at the head/postmentum joint (p–h, Fig. 1A) and proposed that it was extended by blood pressure, due to the abdominal muscles which also cause jet propulsion. This proposition is supported by evidence that the anus closes (Pritchard, 1965), and the abdominal muscles contract (Caillère, 1972; Olesen, 1972) during labial extension; and by reports of an increase in abdominal pressure of 5000 Pa (Olesen, 1979) and 4000—12000Pa (Tanaka & Hisada, 1980). From high-speed film of Aeschna nigroflava, Tanaka & Hisada (1980) calculate a maximum torque of 40 αN.m (neglecting water resistance) and state that this would require a joint pressure of 6000 Pa. They also claim that the labium extends normally when a pressure of 8000 Pa is applied to a dead animal under water, thus indicating the relatively small effect of water resistance. However, these conclusions raise a number of questions. In deriving the pressure of 6000 Pa, they appear to have used the torque/pressure characteristic of the postmentum/prementum joint (p–p, Fig. 1A). Had they used the p-h joint characteristic (their Fig. 6) a required pressure of 24 000 Pa would have been obtained. And the statement that 8000 Pa, applied to a head preparation under water, produces normal extension, is not borne out by a comparison of their Figs 5 and 8. which again only relates to the p–p joint. Confusion between the p–h and p–p joint may be due to the erroneous view that the torques at the two joints must, for mechanical reasons, be equal. Their data on labial movement is subject to large standard error and no estimate is made of the error caused by the use of a simplified model, which assumes that the mass of the prementum is concentrated at the end of the postmentum.
Intersegmental to Intrasegmental Conversion by Ganglionic Fusion in Lateral Giant Interneurones of Crayfish
Authors: Kondoh Yasuhiro , Hisada Mituhiko
Published: April 2021

The central nervous system (CNS) of arthropods in general consists of a chain of ganglia in the form of a ladder. Each ganglion has a basically homologous neuronal organization and is contained in one body segment (Bullock & Horridge, 1965). This basic pattern is often modified by ganglionic fusion. What changes are caused by ganglionic fusion, particularly with regard to segmentally homologous neurones?
Photoperiodic Effects On Thermoregulation in A ‘Blind’ Subterranean Mammal
Authors: Haim A. , Heth G. , Pratt H. , Nevo E.
Published: April 2021

Thermoregulatory responses to changes in photoperiod were studied in the ‘blind’ mole rat Spalax ehrenbergi (Nehring). Acclimation of coldsensitive individuals to short photoperiod (8L: 16D) at an ambient temperature (Ta) of 22 °C increased their thermoregulatory capacity in cold conditions, when compared to individuals which were acclimated to a photoperiod of 12L: 12D at the same Ta. Acclimation of cold-resistant individuals to Ta= 17 °C but with a photoperiod of 16L:8D caused a decrease in thermoregulatory capacity.

Evaluation of the visual pathway through the visual-evoked potentials showed that the mole rat does not respond to flash stimuli and can thus be considered to be effectively blind.
Comparison Between Active Transport of Tl+, K+ and Rb+ Across the Isolated Short-Circuited Frog Skin
Authors: Zerahn Karl
Published: April 2021

Active transport of Tl+ by frog skin was compared with transport of K+ and Rb+. Tl+ was transported actively (using a Na,K-ATPase) by the epithelium and the adrenalin-stimulated glands.

In the epithelium, K+, Tl+ and Rb+ competed for transport in the ratio 1:1 ·7: 0· 9; in the glands the ratio was 1:1:1.
Nerve Nets and Conducting Systems in Sea Anemones: Two Pathways Excite Tentacle Contractions in calliactis Parasitica
Authors: Mcfarlane Ian D.
Published: April 2021

Single shocks to the column sometimes evoke tentacle contractions, ranging from slight movement of a few scattered tentacles to rapid bending or shortening of all the tentacles. Some individuals are more responsive than others. Complex bursts of electrical activity follow single shocks, but only in tentacles that contract. These single shocks excite pulses in two conducting systems - the through-conducting nerve net (TCNN) and the ectodermal slow conduction system (SS1). When a single shock evokes contractions and bursts of electrical activity, these usually follow the SSI pulse, rarely the TCNN pulse. Stimulation of the SS1 alone causes tentacle contraction in responsive anemones. Fast tentacle contractions always follow the second of two closely-spaced TCNN pulses: the TCNN shows facilitation (Pantin, 1935a). An SSI pulse, however, does not facilitate subsequent pulses in either the SSI or TCNN. There are two pathways for activation of tentacle contractions. The TCNN pathway is mechano-sensitive and normally requires facilitation. The SS1 pathway is mechano- and chemosensitive, only requires a single SSI pulse to evoke contraction, but is very labile. It is proposed that the TCNN and the SS1 do not excite the ectodermal muscles directly, but via a multipolar nerve net.
Reversal of the Direction of Mucus-Flow on the Ciliated Pharynx of a Sea Anemone
Authors: Holley M. C. , Shelton G. A. B.
Published: April 2021

The ciliated pharynx of the sea anemone Calliactisparasitica (Couch) acts as an independent selective barrier for the admission of material to the coelenteron. Direct observation shows that reversal of the direction of the mucus flow is effected by a reversal of the direction of the ciliary power-stroke. Reversal of the power-stroke can only be stimulated by food juices applied directly to the pharynx and it is not propagated to unstimulated areas. Reversal of the power-stroke occurs in the absence of all recordable electrical activity. This is one of the few examples among the Metazoa where it has been shown that a modification of the ciliary beating pattern is unlikely to be controlled by an electrical conduction system.
Foetal-Maternal Blood Respiratory Properties of an Ovoviviparous Snake the Cottonmouth, Agkistrodon piscivorus
Authors: Birchard Geoffrey F. , Black Craig P. , Schuett Gordon W. , Black Virginia
Published: April 2021

The respiratory properties of maternal, foetal and juvenile whole blood were studied in the ovoviviparous snake, Agkistrodon piscivorus. Haematocrit, haemoglobin concentration, O2 capacity, Bohr effect and Hill coefficients were not significantly different in foetal and maternal blood and were similar to values previously reported from snakes. A significant difference in foetal-maternal blood P50 (foetal 19·5, maternal 48·8) was found. Nucleoside triphosphate (NTP) levels were lower in foetal than in maternal and juvenile snakes. The foetal-maternal difference in P50 and NTP levels disappeared soon after birth (juvenile P50 45·5). Starch gel electrophoresis revealed no difference in foetal and maternal haemoglobins. We suggest that the foetal-maternal shift in blood oxygen affinity is modulated directly and/or indirectly by NTP levels.
The Transition to Air Breathing in Fishes: III. Effects of Body Size and Aquatic Hypoxia on the Aerial Gas Exchange of the Swamp Eel Synbranchus Marmoratus
Authors: Graham Jeffrey B. , Baird Troy A.
Published: April 2021

Synbranchus marmoratus (Bloch) breathes air during terrestrial excursions and while dwelling in hypoxic water and utilizes its gills and adjacent buccopharyngeal epithelium as an air-breathing organ (ABO). This fish uses gills and skin for aquatic respiration in normoxic (air-saturated) water but when exposed to progressive aquatic hypoxia it becomes a metabolic O2 conformer until facultative air breathing is initiated. The threshold (aquatic O2 tension or partial pressure in mmHg) that elicits air breathing in S. marmoratus is higher in larger fish. However, neither air-breathing threshold nor the blood haemoglobin (Hb) concentration of this species were changed following hypoxia acclimation. In hypoxic water S. marmoratus supplies all of its metabolic O2 requirement through air breathing. ABO volume scales with body weight raised to the power of 0 ·737 and the amount of O2 that is removed from each air breath depends upon the length of time it is held in the ABO. Ambient directly affects the air-breath duration of this fish, but the effect is smaller than in other species. Also, average air-breath duration (15·7 min at mmHg) and the average inter-air-breath interval (15 1 min) of 5. marmoratus are both longer than those of other air-breathing fishes. Although the gills of 5. marmoratus are involved in aerial O2 uptake, expelled air-breath CO2 levels are not high and always closely correspond to ambient , indicating that virtually no respiratory CO2 is released to air by this fish. CO2 extrusion therefore must occur aquatically either continuously across another exchange surface or intermittently across the gills during intervals between air breaths. This study with S. marmoratus from Panama reveals physiological differences between this population and populations in South America. The greater Hb content of South American S. marmoratus may be the result of different environmental selection pressures.
The Effects of Reducing Gill Area on the Capacity to Regulate Oxygen Uptake and on Metabolic Scope in a Cephalopod
Authors: Wells M. J. , Wells J.
Published: April 2021

Octopus vulgaris is able to maintain its oxygen uptake at a steady level down to a of below 80 mmHg. This capacity is scarcely affected by surgical reduction of the gill area to between 30 and 50%, a finding which confirms previous work suggesting that regulation is achieved by increasing the affinity of the haemocyanin rather than by circulatory adjustments. The same reductions in gill area seriously reduce the already very limited metabolic scope of Octopus. Experiments in an exercise wheel show that this is in the region of 115 ml kg-1 h-1 (against an SMR of 42 for a 1-kg animal at 21 C) in the intact Octopus; reduction of the gill area to 30–50% approximately halves this figure. Animals with their gills reduced will run in the wheel until they have accumulated an oxygen debt in the region of 22ml kg-1, and then stop; recovery is slower than in intact animals.
Acclimation of the Euryhaline Toad Bufo Viridis to Hyperosmotic Solution (NaCl, Urea and Mannitol)
Authors: Katz U. , Degani G. , Gabbay S.
Published: April 2021

Bufo viridis were acclimated to hyperosmotic solutions of NaCl, urea or mannitol. The toads could not be acclimated to mannitol solutions of osmotic strength higher than 300 mosmol kg-1 H2O, but could be acclimated easily to NaCl and urea higher than 500 mosmol kg-1 H2O. Water uptake diminished under mannitol acclimation while the apparent osmotic permeability under NaCl and urea acclimation increased. Urea and sodium influx across the isolated skin changed inversely upon hyperosmotic acclimation, but they did not seem to depend on one another. The adaptational advantages of the observed changes are discussed.
A Particle Velocity Microphone for the Song of Small Insects and Other Acoustic Measurements
Authors: Bennet-Clark H. C.
Published: April 2021

Conventional particle velocity microphones (see Olson, 1957) are not readily available, are expensive, fragile and large, so they are not commonly used in biological research, though their use in one situation where the source is highly reactive, the recording of Drosophila song, is now standard practice. Here, the particle velocity produced by the fly is far louder than the sound pressure, so high quality recordings can be made with minimal sound insulation (see Bennet-Clark, 1971; Bennet-Clark, Leroy & Tsacas, 1980). The microphones can also be used to localize sources of echoes and to measure other reactive conditions. The present design was developed as an alternative to the fragile aluminum-ribbon microphones used previously (Bennet-Clark, 1973) and has the advantages of low cost, small size, robustness and a broad frequency response.
Rhythmic and Bilaterally Coordinated Motor Activity in the Isolated Brain of Pleurobranchaea
Authors: London J. A. , Gillette R.
Published: April 2021

Rhythmic ingestive behaviour in the predatory marine snail Pleurobranchaea is characterized by cycles of protraction and retraction of the buccal mass, during which food material is taken into the buccal cavity and swallowed (Davis & Mpitsos, 1971). Fictive feeding is demonstrable in the isolated nervous system; the rhythmic motor programme appropriate to feeding behaviour can occur spontaneously or can be elicited by stimulation of different populations of ‘command’ neurones (Davis et al. 1975; Gillette & Davis, 1977; Croll & Davis, 1981; Gillette & Gillette, 1983). Oscillatory motor output is most striking in the isolated buccal ganglion; however, cyclic activity has been recorded in the brain (the cerebropleural ganglion) when it was isolated from the buccal ganglion by cutting the cerebrobuccal connectives (CBCs) (Davis, Siegler & Mpitsos, 1973). Such cyclic activity was recorded in the nerves of the brain while the CBC was stimulated by repetitive electrical shocks. These and other results were interpreted as indicating that oscillators existed both in the brain and the buccal ganglion. Interneurones were identified in both the brain and buccal ganglion which appeared to coordinate the oscillators via axons in the CBCs (Davis et al. 1973; Gillette & Davis, 1977; Gillette, Kovac & Davis, 1978, 1982).
Excitatory Effects of Dopamine on the Cardiac Ganglia of the Crabs Portunus Sanguinolentus and Podophthalmus Vigil
Authors: Miller Mark W. , Benson Jack A. , Berlind Allan
Published: April 2021

Dopamine, a cardioexcitor in decapod crustaceans, increased the frequency and/or duration of bursts of action potentials in the semi-isolated cardiac ganglia of two species of crabs. The number of motoneurone action potentials in each burst was increased, which in the intact heart would increase the force and amplitude of heart contraction. The effects were concentration-dependent, with a threshold concentration of 10−8M or lower when dopamine was applied by continuous perfusion. At 5 × 10−6M, dopamine increased burst frequency by 200%. The main site of dopamine action was the group of four posterior small interneurones which normally function as the pacemaker for the cardiac ganglion system. Effects on the five large motoneurones occurred at higher concentrations. This regional difference in sensitivity was demonstrated by selective applications of dopamine to different parts of the cardiac ganglion and by the use of preparations in which the two ends of the ganglion had been functionally separated by a ligature around the ganglionic trunk. In the small neurones, dopamine was found to stimulate the slow tetrodotoxin-resistant regenerative depolarizations known as driver potentials. The effects on driver potential frequency and train duration were concentration dependent. In one of the two species of crabs, in which electrotonic connections between small and large neurones are strong, large neurone driver potentials were indirectly induced by dopamine. In the tetrodotoxin-treated large motoneurones, dopamine, at a concentration about ten-fold higher than needed to activate the small neurones, decreased the threshold for current-induced driver potentials, and slightly reduced membrane resistance. We suggest that the excitatory action of dopamine on the untreated cardiac ganglion can in large part be accounted for by its action on driver potential production in the small neurones.
Effects of Perfusion Pressure on the Isolated Heart of the Lobster, Panulirus Japonicus
Authors: Kuramoto Taketeru , Ebara Arinobu
Published: April 2021

Systolic contractions of the isolated heart were usually composed of a first and second systolic contraction (FSC and SSC) which corresponded to the first and second large potentials (FLP and SLP), respectively, recorded in the cardiac muscle cells and represented excitatory junction potentials produced by impulse bursts of the large cells of the cardiac ganglion. Under constant pressure, the magnitudes of the FSC and the SSC appeared to change according to the amplitudes and durations of the FLP and the SLP. Further, the total amplitude of systole was often affected by the time of occurrence of the SSC (or the SLP). Internal perfusion pressure and heart tonus were linearly related over a considerable range. With an increase in heart tonus (0-30mg), the magnitude of the FSC was enhanced markedly in the absence of equivalent increases in the amplitude and duration of the FLP. The elevation of heart tonus was also related to an increase in beat frequency. The SSC decreased in magnitude and disappeared when the beat frequency exceeded approx. 1 Hz under high perfusion pressure. Further, the abolition of the SSC resulted in a steeper slope in the curve relating beat frequency to tonus. The SSC was absent during the decline of beating caused by rapid reduction of the pressure. The SSC was abolished by transverse cuts of the ganglionic trunk between the 4th and 5th large cells or between the 5th large and the 6th small cells, but the SSC often remained after the trunk was severed at the region between the 6th and 7th small cells. After severing the trunk, the heart still had the ability to respond to pressure as detected by a change of the beat frequency. Spontaneous slow contractions of the cardioarterial valves were often observed.
Reduced aerobic capacity and locomotory endurance in thyroid-deficient lizards
Authors: John-Alder H. B.
Published: April 2021

This study was undertaken to examine the effects of thyroid hormonal deficiency on (1) standard (SMR) and maximal (max) rates of O2 consumption, (2) tissue glycolytic and oxidative capacities and (3) submaximal locomotory endurance in a lizard (Dipsosaurus dorsalis). Surgical thyroidectomy induced hypothyroidism in all animals as determined by levels of plasma thyroxine. Hypothyroid lizards had lower levels of SMR (−48 %), max (−16 %) and citrate synthase activity in liver, heart and skeletal muscle compared to controls. There was a correlated decrease in locomotory endurance in thyroid-deficient animals. Pyruvate kinase activity (an index of glycolytic capacity) in all tissues, and myofibrillar ATPase activity (an index of contractile velocity) in white iliofibularis muscle, showed no significant changes in thyroid-deficient animals. Thyroid hormones appear to be important in ultimately establishing an animal’s capacity for locomotory endurance. These findings suggest a new selective context for understanding the evolution of thyroid function.