bluuebunny/crossref_metadata_2025 huggingface dataset:
Alteration of the Respiratory System at the Onset of Locust Flight: I. Abdominal Pumping
Authors: Ramirez J. M. , Pearson K. G.
Published: April 2021

The respiratory behaviour of Locusta migratoria is altered at the onset of flight. The neuronal processes and some of the mechanisms underlying these alterations were studied by using intracellular recording and staining techniques.

It has previously been reported that abdominal pumping ceases for the first seconds of flight. Our data indicate that this phenomenon is not due to inhibition of the respiratory system, since most interneurones and some motoneurones maintain a respiratory rhythm during the onset of flight activity. Likely explanations for the cessation of the abdominal pumping are: (1) increased stiffness of the abdomen due to maintained activation of abdominal muscles and (2) decreased rhythmic modulation in abdominal motor units due to tonic excitatory input.

Two major changes occur in the respiratory system at the onset of flight: (1) the rhythm is reset by an activation of inspiratory and inactivation of expiratory neurones, and (2) the respiratory rate is increased. The increase in the respiratory rate at the onset of flight is in part due to an activation of inspiratory interneurones which are capable of accelerating the respiratory rhythm.

The changes in the respiratory system coinciding with the initiation of flight suggest a feedforward mechanism linking both behaviours. Tonic interneurones, involved in the initiation of flight and influencing respiration, might be involved in linking respiration and flight. At flight onset, one group of these simultaneously disinhibited respiration and flight and thus contributed both to an increase in the respiratory rate and to an activation of the flight system. Another group evoked flight and had variable effects on respiration. One tonic interneurone had a depressing effect on the respiratory rate.

We conclude that respiration is centrally linked to flight in part by the same interneurones controlling the initiation of flight. The existence of such a feedforward mechanism in the locust resembles the situation found in vertebrates, where locomotory and respiratory behaviour can be driven from the same brainstem region.
Photoinactivation of A Portion of A Neurone For Long-Term Studies of Its Role In Behaviour
Authors: Libersat Frederic , Selverston Allen , Camhi Jeffrey M. , Goldstein Ronald S.
Published: April 2021

An important method in the study of the neural basis of behaviour is the removal from a nerve circuit of a single cell in vivo and the subsequent search for changes in behaviour (Atkins et al. 1984; Comer, 1985). In such studies it can also be useful to remove only a part of a cell, such as a segment of its dendritic tree or axon. This can be done by filling the cell with the fluorescent dye Lucifer Yellow (LY) and irradiating the particular segment to be removed (Jacobs & Miller, 1985). However, for behavioural testing, it is often necessary to wait 1 day for the animal to recover from surgery. It is not yet clear in any system whether a small part of cell inactivated in this way repairs itself or remains inactive after 1 day. In this paper we examine this question of the permanence of LY photoinactivation (Miller & Selverston, 1979), and carry out behavioural tests showing the usefulness of this method.
A Critical Analysis of the Use of High-Speed Film to Determine Maximum Accelerations of Fish
Authors: Harper David G. , Blake Robert W.
Published: April 2021

High-speed cinematography is often employed in studies on fish swimming, particularly where performance is estimated (e.g. Wardle, 1975; Eaton et al. 1977; Webb, 1978b; Dorn et al. 1979; Videler, 1981). One commonly reported aspect of performance is the acceleration of fish during fast-starts (bursts of swimming from a standing start; e.g. Weihs, 1973; Webb, 1975, 1976, 1977, 1978a,b, 1982, 1983, 1986; Rand & Lauder, 1981). The present study is a critical examination of the use of cinematography to estimate the maximum acceleration of fish during fast-starts.
Inertial and Aerodynamic Torques on the Wings of Diptera in Flight
Authors: Ennos A. Roland
Published: April 2021

The magnitude and distribution of the torques caused by inertial and aerodynamic forces on the wings of Diptera in flight are calculated. The bending torque at stroke reversal due to the inertia of the virtual mass of air bound to the wing is only slightly less than the torque due to the inertia of the wing mass itself. The maximum inertial torque due to both wing mass and virtual mass is usually slightly greater than the maximum aerodynamic torque encountered by the wings. Bending torques decrease rapidly away from the wing base. Pitching torques are much smaller than bending torques at the wing base, but do not decrease much until near the tip. The pattern of loading affects the wing design. Wings are thicker nearer the base to resist bending, but thin and light near the tip to minimize inertial energy expenditure. Their open, corrugated structure resists bending, while allowing them to be twisted as a result of the weak pitching moments.
Primary Culture of Identified Neurones From a Cnidarians
Authors: Przysiezniak Jan , Spencer Andrew N.
Published: April 2021

Several types of neurones were dissociated from the nerve-rings of the hydrozoan jellyfish Polyorchis penicillatus, using collagenase digestion preceded, and if necessary followed, by removal of external divalent cations. The neurones were cultured for up to 2 weeks in artificial sea water, on a mesogloeal substratum.

One subset of large neurones, the swimming motor neurones (SMNs; soma approx. 20×50 μm), exhibited distinct morphological features in vitro, such as large size, wide processes, clear cytoplasm and membranous inclusions around the nucleus. These neurones retained their characteristic action potential shape in culture, with spikes measuring 50 ±11 mV (N=18) in peak amplitude and 37 ± 11 ms in duration. SMNs could be labelled in vivo with carboxyfluorescein or Lucifer Yellow, subsequently dissociated, and identified in vitro.

Two subsets of small neurones were also identifiable. One exhibited electrophysiological similarities with B system neurones, known to be presynaptic to the SMNs in vivo, showing a burstlike pattern of spikes of short duration (5·4 ± 1·4 ms; N=6) and small amplitude (25 ±7mV). Another subset of small neurones could be labelled with antiserum against the carboxy-terminal peptide moiety, Arg-Phe-amide.

Biophysical and neurotransmitter studies at the level of the single identified hydrozoan neurone will be easier in isolated cell culture. This approach will avoid problems encountered in studying the semidissected nerve-ring preparation.
Microelectrode Evidence for the Electrical Isolation of Goblet Cell Cavities in Manduca Sexta Middle Midgut
Authors: Dow Julian A. T. , Peacock Jillian M.
Published: April 2021

The middle midgut of Manduca sexta is known to transport K+ actively from the basal to the apical side, and is thought to be involved in the generation of an extremely high pH in the midgut lumen.

An experimental configuration is described which allows visually guided microelectrode impalements to be made of any compartment in the midgut tissue, with simultaneous verification by fluorescent dye ionophoresis in the live tissue. In this way, many impalements can be performed and verified on a single gut.

The potential differences between impalement sites and the apical compartment were plotted against transepithelial potential difference (TEP) for three sites: goblet cell cytoplasm, columnar cell cytoplasm and goblet cell cavities. In all three cases, the potentials recorded varied significantly and linearly with gross TEP.

Goblet and columnar cell cytoplasm impalements resembled each other both in size and direction of potential, being always negative relative to the lumen. This implied electrical coupling was confirmed by the observation that the two cell types were linked by gap junctions.

Goblet cavity impalements were characterized by a positive potential relative to the lumen. The goblet cavities were isolated from the lumen by a high resistance, and no leakage of Lucifer Yellow or 6-carboxyfluorescein markers through the apical valve was detected.

Using sensible estimates for midgut intracellular pH and in vivo TEP, it was shown that the potential difference across the goblet cavity apical membrane in vivo would agree closely with the Nernst potential for protons across the membrane, in agreement with a model for generation of high pH.
Metabolic–Membrane Coupling in Red Blood Cells of Trout: The Effects of Anoxia and Adrenergic Stimulation
Authors: Ferguson R. A. , Boutilier R. G.
Published: April 2021

Under oxygenated conditions, in vitro, the highly aerobic red cells of the rainbow trout (Salmo gairdneri) exhibit tight coupling between energy (i.e. nucleotide triphosphate, NTP)-consuming and NTP-producing metabolic activity, as shown by strict maintenance of red cell NTP: haemoglobin ratios. This coupling is maintained following adrenergic stimulation of oxygenated red cells when the increased NTP demands of ion transporting systems are met by enhanced energy production via aerobic metabolism. In unstimulated anoxic red cells, membrane–metabolic coupling is preserved via the arrest of NTP-consuming processes. Adrenergic stimulation of anoxic red cells, however, leads to a functional uncoupling of membrane metabolism with the result that NTP levels decline rapidly. At this time, cellular [NTP] is negatively correlated with [Na+]i and [Cl−]i and positively correlated with [K+]i. This, in addition to the fact that the pH of the intracellular compartment is also highly dependent on cellular NTP levels, provides evidence for the integration of energy and membrane metabolisms.
Electromyography of the Fin Musculature of the Cuttlefish Sepia Officinalis
Authors: Kier William M. , Smith Kathleen K. , Miyan Jaleel A.
Published: April 2021

The musculature of the fins of the cuttlefish Sepia officinalis (Mollusca, Cephalopoda) was studied with electromyography to test predictions of the functional role of the various muscle masses. Previous research had shown the fins to consist of a tightly packed, three-dimensional array of muscle with distinct zones of anaerobic glycolytic and oxidative muscle fibres. In addition, a network of crossed oblique connective tissue fibres was observed within the musculature. In a previous paper a model of the function of the muscle and connective tissue was presented. In the present paper, we present recordings of electrical activity from the various muscle bundles in the fin, in conjunction with the output from an electronic movement-monitoring device, and correlate muscle activity with both the phase and the intensity of the fin-beat cycle. The results obtained here support the hypothesis that the oxidative muscle fibres produce gentle fin movements and are consistent with the hypothesis that the network of crossed oblique connective tissue fibres provides skeletal support. The results also support predictions that the anaerobic glycolytic muscle fibres both produce vigorous fin movements and provide support for that movement. This study provides a critical test of models of the role of the tightly packed, three-dimensional array of muscle found in muscular hydrostats such as the arms and tentacles of cephalopods and tongues of mammals and lizards.
Endothermy and Temperature Regulation in Bees: A Critique of ‘Grab and Stab’ Measurement of Body Temperature
Authors: Stone G. N. , Willmer P. G.
Published: April 2021

‘Grab and stab’ methods have become standard in the measurement of insect body temperatures. The gradient of the best-fit regression of body temperature on ambient temperature is often used as a measure of the thermoregulatory ability of a species. The temperatures recorded are commonly accepted as slight underestimates of actual values prior to capture due to passive cooling between capture and insertion of the thermocouple. Here we present laboratory experiments involving tethered flight which show that bees often warm up on cessation of flight, and that errors due to warm-up over the time interval typically associated with ‘grab and stab’ sampling may be significant. More importantly, the errors due to warm-up in two species are shown to change with ambient temperature, thus affecting the form of the relationship between ambient and body temperatures. We compare laboratory and field data to illustrate the way in which warm-up errors may exaggerate apparent thermoregulatory ability, and we urge greater caution in the interpretation of ‘grab and stab’ data.
Parachlorophenylalanine Retards Tail Regeneration in the Gekkonid Lizard Hemidactylus Flaviviridis Exposed to Continuous Light
Authors: Ramachandran A. V. , Ndukuba Patrick I.
Published: April 2021

Parachlorophenylalanine (p-CPA) was used for chemical pinealectomy in a study of tail regeneration in the gekkonid lizard, Hemidactylus flaviviridis. Two doses of p-CPA (200 or 400 μg kg−1body mass) were injected into two groups of lizards (5 days prior to and 30 days after caudal autotomy) exposed to continuous light of 2500lx intensity during the summer season (March-May). Our observations show that the initiation of regeneration, the daily growth rate, the total length of new growth (regenerate) produced, and the total percentage replacement of the lost (autotomized) tails 30 days after autotomy were all significantly less with 400 μg kg−1 and insignificantly less with 200 μg kg−1 of p-CPA than in the control group of animals. The results may indicate that the effect of the drug p-CPA, an agent employed for chemical pinealectomy, on tail regeneration in H. flaviviridis is dose-dependent and that p-CPA at the high dose of 400 μg kg−1 has a similar retardation effect to that of complete pineal ablation. The role of the pineal in photoperiodic photoreception, and the effect of p-CPA on serotonin melatonin biosynthesis and the consequent effects on tail regeneration, are discussed.
Size Limits in Escape Locomotion of Carridean Shrimp
Authors: Daniel Thomas L. , Meyhöfer Edgar
Published: April 2021

Escape locomotion of the common dock shrimp, Pandalus danae Stimpson, is the result of a rapid flexion of the abdomen that lasts approximately 30 ms. The hydrodynamic forces that result from this motion lead to body accelerations in excess of 100 ms−2 and body rotations of about 75°. We examined the mechanics and kinematics of this mode of locomotion with both experimental and theoretical approaches. Using a system of differential equations that rely on conservation of both linear and angular momenta, we develop predictions for body movements, thrust forces and muscle stresses associated with escape locomotion. The predicted movements of the body agree to within 10 % with data from high-speed ciné-photography for body translations and rotations. The thrust from rapid tail flexion is dominated by accelerational forces and by the force required to squeeze fluid out of the gap created by the cephalothorax and the abdomen at the end of tail flexion. This squeeze force overwhelms any propulsive drag forces that arise from the tail-flip.

Using the theoretical analysis, we identify two additional features about unsteady, rotational aquatic locomotion. First, as either the relative length of the propulsive appendage increases or the absolute body size increases, rotational motions become disproportionately greater than translational motions, and escape performance decays. Second, if muscle stresses developed during escape cannot exceed the maximum isometric stress, there is a unique body length (6 cm) that maximizes the distance travelled during the escape event.
Functional Wing Morphology and Aerodynamics of Panorpa Germanica (Insecta: Mecoptera)
Authors: Ennos A. Roland , Wootton Robin J.
Published: April 2021

The functional wing morphology of the wings of the scorpion fly Panorpa germanica L. was investigated using a combination of light microscopy, high-speed cinematography, wing manipulation and mechanical testing.

In rising forward flight the wings are flapped 40° out of phase along a shallow stroke plane, the forewings leading. Aerodynamic analysis suggests that unsteady effects are important in flight.

During the downstroke, both wings are straight and cambered, the chord being parallel to the body axis, which is angled 45° upwards from horizontal. Both wings are supinated at lower stroke reversal, the hindwing to a much greater extent, and flex ventrally halfway along their length for the first half of the upstroke. Flexion is parallel to the chord in the hindwing, but is oblique in the forewing, so distal forewing areas are supinated relative to proximal areas.

The behaviour of the wings is related to their structure. Spars at the leading and trailing edges of both wings support the wing during the downstroke, and flexion during the upstroke is facilitated by buckling of the weak ventral thyridium region. The oblique flexion seen in the forewing is due to its relatively longer leading edge spar.

The differences between the wings are, in turn, related to their pitch control mechanisms. The forewing has a well-developed clavus, like that of the forewing of a locust, and pitch is altered by relative movement of this and the leading edge, but only within a narrow range. Oblique flexion is necessary to invert the aerofoil. The weaker and less well-developed clavus of the hindwing, more similar to that of the Diptera, allows a greater degree of supination, effected largely by wing inertia. No oblique flexion is necessary.
Post-Moult Calcification in the Blue Crab, Callinectes Sapidus: Timing and Mechanism
Authors: Cameron James N.
Published: April 2021

A series of experiments was conducted to elucidate the events immediately preceding and following moulting (ecdysis) in the blue crab, Callinectes sapidus Rathbun. The crabs gain weight (mostly water) to a level more than twice the premoult value excluding the shed carapace. The gain begins about 4 h before ecdysis, accelerates rapidly to a maximum rate at about the time of ecdysis, and is essentially complete by 2h after ecdysis. Both calcification and net H+ excretion remain at control (intermoult) levels until 1–2 h post-moult, whereupon a very rapid increase in both begins, with the same time course for both processes. The ratio of internal to external calcium concentration drops from 1·4:1 during intermoult to 0·85:1 by 2 days after the moult, reversing the electrochemical gradient during the post-moult period. Calcification is strongly inhibited by the protein synthesis inhibitors actinomycin D and cycloheximide. Isolated whole gills and gill slices do not show significant changes in rates of calcium uptake related to moult stage, indicating that the uptake of calcium across the gills may be largely passive. A low-affinity Ca2+-activated ATPase is present in both gills and epithelium, but only the epithelial activity shows a substantial (fivefold) increase in the hours after ecdysis. The control mechanisms for stimulation of the transport processes remain elusive. Eyestalkless crabs progress normally through moult and post-moult calcification. Peptide profiles from blood and from suspected neurohormone-producing tissues differ markedly with moult stage, but several different approaches to developing a bioassay using peptides from crab tissues and vertebrate sources have been unsuccessful. The physiological events in the hours surrounding ecdysis suggest a complex and precisely timed series of control signals.
Maintenance of Oxygen Consumption in Resting Silurus Glanis at Different Levels of Ambient Oxygenation
Authors: Forgue Jean , Burtin Bernard , Massabuau Jean-Charles
Published: April 2021

The mechanisms of adaptation that allow the teleost Silurus glanis to maintain its resting oxygen consumption constant when the O2 partial pressure in the inspired water varied between 40 and 3 kPa were studied at 13 °C. Steady state values of oxygen consumption, ventilatory and circulatory flow rates, in the inspired and expired water, and O2 concentration in the arterial and venous blood, haematocrit and acid-base status in the arterial blood were determined after 1-day exposures at selected values. Whole-blood O2-binding characteristics were also determined.

The key adaptation after 1 day of acclimation was maintenance of oxygen consumption by ventilatory adjustment with no change in blood flow rate or pH (no Bohr effect). At each value (i) the ventilatory adjustment was minimal as the O2 extraction coefficient from water always remained around 80 –90 % and (ii) stayed constant at about 2 kPa. Data are compared with previous results in crayfish and other teleosts. It is concluded that the principle of a constant O2 status in the milieu intérieur - independent of large changes in for a given state of activity - should be valid in many crustaceans and teleosts.
Involvement of A Circadian Rhythm in the Photoperiodic Ovarian Response of the Yellow-Throated Sparrow, Gymnorhis Xanthocollis
Authors: Dixit Anand S. , Tewary P. D.
Published: April 2021

Groups of the photosensitive female yellow-throated sparrow were placed under various light-dark cycles, in which a fixed ultrashort photophase of 3 h was combined with dark phases of varying duration, resulting in cycles of 18–30 h. Simultaneously, two groups of birds, one in short days (8L/16D) and the other in long days (15L/9D), were kept as controls. Significant ovarian growth, observed at 30 and 60 days, was induced by 3h ultrashort photophase only if it was introduced in the cycles of 18h (3L/15D), 20h (3L/17D), 26h (3L/23D), 28h (3L/25D) and 30 h (3L/27D) as well as under long days (15L/9D), whereas there was no response to the ultrashort photophase in cycles of 22 h (3L/19D) and 24 h (3L/21D) and in short days (8L/16D). It seems that there is an ovarian response to the ultrashort day cycles when a phase advance or delay of photosensitivity of the response system repeatedly produces coincidence of the external photophase (3h) with the photosensitive phase of an endogenous circadian rhythm. The results are thus consistent with the Bünning hypothesis, which suggests the involvement of an endogenous circadian rhythm in photoperiodic time measurement.
Ventilatory Action of the Hypaxial Muscles of the Lizard Iguana Iguana: A FuncTion Of Slow Muscle
Authors: Carrier David R.
Published: April 2021

Patterns of muscle activity during lung ventilation, patterns of innervation and some contractile properties were measured in the hypaxial muscles of green iguanas. Electromyography shows that only four hypaxial muscles are involved in breathing. Expiration is produced by two deep hypaxial muscles, the transversalis and the retrahentes costarum. Inspiration is produced by the external and internal intercostal muscles. Although the two intercostal muscles are the main agonists of inspiration, neither is involved in expiration. This conflicts with the widely held notion that the different fibre orientations of the two intercostal muscles determine their ventilatory action.

Several observations indicate that ventilation is produced by slow (i.e. non twitch) fibres of these four muscles. First, electromyographic (EMG) activity recorded from these muscles during ventilation has an unusually low range of frequencies (<100Hz). Such low-frequency signals have been suggested to be characteristic of muscle fibres that do not propagate action potentials (i.e. slow fibres). Second, during inspiration, EMG activity is restricted to the medial sides of the two intercostal muscles. Muscle fibres from this region have multiple motor endplates and exhibit tonic contraction when immersed in saline solutions of high potassium content. Like the intercostals, the transversalis and retrahentes costarum muscles also contain fibres with multiple motor endplates. Thus, although breathing is a phasic activity, it is produced by tonic (i.e. slow) muscle fibres. The intercostal muscles are also involved in postural and locomotor movements of the trunk. However, such movements employ twitch as well as slow fibres of the intercostal muscles.
Modulation of Screening-Pigment Position in Crayfish Photoreceptors by Serotonin: Possible Involvement of Na+/K+-Atpase Activity
Authors: Frixione Eugenio , HernÁndez Jorge
Published: April 2021

The possibility that serotonin might play a role in the modulation of screening pigment position in crayfish photoreceptors was explored through experiments with isolated eyes and a membrane fraction from retinal homogenates. In the isolated eye serotonin (⩾10−4moll−1) and some of its agonists exerted a limited dark-adapting influence over the pigment position, irrespective of the presence or absence of light, and this effect was abolished by the simultaneous addition of serotonin antagonists. In the retinal membrane fraction serotonin and quipazine produced a methysergide-sensitive stimulation of the Na+/K+-ATPase activity. These results are interpreted in terms of a serotonin-mediated efferent input on the photoreceptors, which would affect the ionic regulation of the pigment transport mechanisms.
Depression of Excitatory Motoneurones by A Single Neurone in the Leech Central Nervous System
Authors: Wadepuhl Martin
Published: April 2021

Intracellular staining techniques have been used to characterize the morphology of a newly identified neurone, cell 151, in the segmental ganglia of the leech. This neurone ramifies extensively within the neuropile and sends multiple extensions into roots and connectives.

Strong dye coupling and non-rectifying electrical coupling were observed between the contralateral homologues. No action potentials were recorded from the cell body, but postsynaptic potentials and slow potential changes (>1s, >15 mV) were observed. Upon injection of hyperpolarizing currents, the efferent spike activity, recorded extracellularly, was depressed in both the ipsi- and the contralateral roots of the ganglion. The depression was gradual and non-adapting and occurred reliably only within the ganglion where cell 151 is situated. Depolarization of cell 151 was without consequence for the tonic firing of isolated ganglia.

Many identified excitatory motoneurones follow the hyperpolarization of cell 151. Currents can be exchanged between cell 151 and motoneurones via rectifying electrical synapses. Spontaneous hyperpolarizations of cell 151 were correlated with depression of spike frequencies, recorded in whole nerves as well as in identified motoneurones. The membrane potential of cell 151 was drastically altered by bursts from mechanosensory cells.

The ability of cell 151 to distribute inhibition onto a great number of motoneurones and to curtail excessive neuronal activity is discussed.
Respiratory Gases and Acid–Base Balance in Shell-Less Avian Embryos
Authors: Rowlett Karen , Simkiss K.
Published: April 2021

The and levels of oxygenated and deoxygenated embryonic blood were measured in normal and shell-less cultured embryos. Embryos in shell-less culture were both hypoxic and hypocapnic, suggesting that wetting the respiratory membranes and the reduction in their functional area is distorting their normal function. Despite this hypocapnia, there was evidence for an increase in base excess during incubation. This suggests that plasma bicarbonate is derived from renal sources rather than by resorbing the eggshell calcium carbonate, which is, of course, absent from shell-less cultures.
Behavioural Effects of Injection of Small Cardioactive Peptide, SCPB, on the Slug Limax Maximus
Authors: Schagene Kimberly A. , Welsford Ian G. , Prior David J. , Banta Pamela A.
Published: April 2021

The molluscan neuropeptide, small cardioactive peptide B (SCPB; Lloyd, 1978; Morris et al. 1982), has been shown to have excitatory effects on both central neurones and peripheral effectors associated with feeding behaviour in gastropod molluscs (Krajniak et al. 1985; Willows & Lloyd, 1983; Murphy et al. 1985; see Lloyd, 1988; Prior & Welsford, 1988, for reviews).
Locomotion in Lamprey and Trout: the Relative Timing of Activation and Movement
Authors: Williams Thelma L. , Grillner Sten , Smoljaninov Vladimir V. , Wallén Peter , Kashin Sergei , Rossignol Serge
Published: April 2021

Most fish swim by the rhythmic passage of a wave of lateral displacement from head to tail, thereby developing a reactive thrust from the water which pushes the fish forward (Marey, 1894). Breder (1926) classified this type of swimming into different modes according to how much of the body performs undulations. In the anguilliform (eel-like) mode most or all of the body is flexible and participates in the passage of the wave, whereas in the carangiform mode the amplitude of the lateral movement becomes significant only as the wave approaches the tail. Anguilliform swimmers tend to have a fairly constant lateral projection along the length of the body, whereas the carangiform swimmers have the more familiar fish shape, with the body tapering to a minimum in the caudal peduncle and then widening again in the caudal fin. The hydrodynamic models appropriate for the theoretical analysis of these two types of swimming reflect these differences in form and function (Lighthill, 1969).
Swelling Behaviour of the Catch Connective Tissue In Holothurian Body Wall
Authors: Eylers John P. , Greenberg Alan R.
Published: April 2021

Swelling tests in a series of isotonic and isoionic solutions of varying calcium-to-sodium ratios were conducted on isolated dermal connective tissue of the holothurian Thyonella gemmata Verrill. The tissue swelled rapidly and attained a maximum volume increase of approximately 40 % when transferred from distilled water to NaCl solution; however, the volume did not change significantly in isotonic CaCl2 solution. At Ca2+/Na+ ratios ⩽0·04 the tissue swelled at its maximum rate. The rate decreased with increasing calcium concentration, until at Ca2+/Na+ ⩾0·40 no detectable swelling occurred. Similar results were obtained for Pentacta pygmaea Goldfuss. When tissues previously swollen in NaCl were placed in CaCl2, the volume decreased significantly. Uniaxial tensile tests indicated that the elastic modulus of the tissue was much greater in Ca2+ solutions than in Na+ solutions. We hypothesize that dermal stiffness in holothurians is regulated by cation-sensitive crosslinks.
Amino Acid Transport Systems in Brush-Border Membrane Vesicles from Lepidopteran Enterocytes
Authors: Hanozet Giorgio M. , Giordana Barbara , Sacchi V. Franca , Parenti Paolo
Published: April 2021

The presence of different potassium-dependent amino acid transport systems in the luminal membrane of the larval midgut of Philosamia cynthia Drury (Saturnidae, Lepidoptera) was investigated by means of countertransport experiments performed with brush-border membrane vesicles. The vesicles were preloaded with 14 different unlabelled amino acids, whose ability to elicit an intravesicular accumulation over the equilibrium value of six labelled amino acids (L-alanine, L-leucine, L-phenylalanine, L-glutamic acid, L-lysine and L-histidine) was tested. For histidine, the results were compared with those obtained from inhibition experiments, in which the same 14 amino acids were used as inhibitors on the cis side of the brush-border membrane. The data demonstrate the presence in the lepidopteran luminal membrane of distinct transport pathways for lysine and glutamic acid. The transport of most neutral amino acids, with the exclusion of glycine and proline, seems to occur through a system that may be similar to the neutral brush-border system (NBB) found in mammalian intestinal membranes. This system is also able to handle histidine.
Presynaptic calcium currents and facilitation of serotonin release at synapses between cultured leech neurones
Authors: Stewart R. R. , Adams W. B. , Nicholls J. G.
Published: April 2021

The role of presynaptic Ca2+ entry in facilitation of transmitter release has been analysed by voltage-clamp measurements at synapses formed in culture by Retzius and P neurones isolated from the central nervous system (CNS) of the leech. The transmitter released by Retzius cells is serotonin. Synaptic transmission persisted in solutions containing raised concentrations of divalent cations, reduced concentrations of Na+, and tetraethylammonium (TEA+) and 4-AP (to block K+ currents). Ca2+ and Sr2+ were more effective in promoting transmitter release than Ba2+, as assessed by the postsynaptic potentials in P cells. The degree and time course of facilitation in Ca2+- and Sr2+-containing solutions were similar to those observed for synapses bathed in normal L-15 medium. Transmitter release depended upon the amplitude and the duration of presynaptic depolarization and inward Ca2+ current. Peak Ca2+ currents and postsynaptic potentials occurred with depolarizing steps to +15 mV. Frequent or prolonged pulses depressed the postsynaptic potentials. Pairs of depolarizing pulses that caused facilitation were accompanied by identical inward Ca2+ currents. These results indicate that the mechanism responsible for facilitated serotonin release must occur following Ca2+ entry and that residual Ca2+ plays a role.
Mechanisms for Neural Signal Enhancement in the Blowfly Compound Eye
Authors: Laughlin Simon B. , Osorio Daniel
Published: April 2021

In the blowfly Calliphora vicina visual signals are enhanced by amplification and antagonism as they pass from the site of phototransduction in the retina to second-order neurones (LMCs) in the first optic neuropile, the lamina. The mechanisms responsible for amplification and antagonism were investigated, using current-clamp techniques, to examine the conductance mechanisms generating LMC responses. LMCs responded Ohmically to injected current. Voltage-sensitive conductances and feedback mechanisms driven by the potential of a single LMC played a minor role in shaping responses. The LMC’s response to an increment in illumination, a transient hyperpolarization, was generated by a large and transient conductance increase with a reversal potential close to the maximum response amplitude (30–40mV below dark resting potential). The depolarization of the LMC in response to a decrement in light intensity was partially generated by a reduction in direct synaptic input from the photoreceptors. Changes in depolarizing conductances with positive reversal potentials played a secondary role, contributing to large-amplitude responses to dimming or light-off, and to the slow decay of the LMC response to steady illumination. Antagonism, including lateral antagonism, operated principally by shutting down the direct photoreceptor input, presumably by presynaptic regulation. The results of dye injection suggested that the identified large monopolar cell L2 is more strongly affected by lateral antagonism than the similar cells LI and L3. We conclude that LMCs are essentially passive integrators of a well-regulated direct input from the photoreceptors. This suggests that the intrinsic properties of photoreceptor-LMC synapses and presynaptic interactions are primarily responsible for amplification and antagonism.
A Comparison of the Effects of FMRFamide-Like Peptides on Locust Heart and Skeletal Muscle
Authors: Cuthbert Brian A. , Evans Peter D.
Published: April 2021

The responses of the semi-isolated heart preparation of the locust to the peptide FMRFamide and a range of its analogues is described. The nature of the response observed depended on the structure of the analogue and its concentration. In some cases the responses were cardio-excitatory, in some they were cardioinhibitory, and in others they were biphasic. The cardioexcitatory responses consisted of increases in both the amplitude and the frequency of spontaneous heart contractions. The nature of the latter effect depended on the form of the basal contractile activity pattern exhibited before the application of the peptide. The pharmacological profile of the cardioexcitatory responses observed in the locust heart preparation was very similar to that observed for the potentiation of neurally evoked tension in the extensor tibiae muscle preparation of the locust. In addition, both the profiles show similarities with the responses of various molluscan hearts and non-cardiac muscle preparations to the same peptides. The results are discussed in terms of possible physiological roles for FMRFamide-like peptides in the regulation of contractile activity of the locust heart.
The effects of dietary phosphorus and parathyroid hormone (PTH) infusion rates on the avian phosphaturic response to PTH
Authors: Stanton T. S. , Glahn R. P. , Wideman R. F.
Published: April 2021

Experiments were performed to evaluate the effects of dietary available phosphorus (aP) and PTH infusion rates on avian urinary inorganic phosphate (Pi) excretion. In experiment I, female domestic fowl were fed diets containing low (0-45%) or high (0·83%) aP for 2–4 weeks prior to renal function studies. Pi excretion was significantly higher for birds fed the high-aP diet than for birds fed the low-aP diet. PTH was infused (60–240 units kg body mass−1 h−1) unilaterally into the renal portal system. Para-aminohippuric acid (PAH), included in the unilateral infusate as a marker for effective renal portal perfusion, indicated that PTH must have been delivered to the peritubular surfaces of the infused kidney. However, bilateral but not unilateral phosphaturia occurred, and there were no significant differences in the phosphaturic responses to PTH when low-and high-aP diet treatment groups were compared. In experiment II, PTH was infused at rates of l–5 units h−1. Infusing PTH at 5 units h−1 caused a unilateral increase in urine flow but the phosphaturic response was still bilateral. It appears unlikely that unilateral renal portal PTH infusions can be used to trigger unilateral phosphaturia in domestic fowl.
The Absence of Rapid Chloride/Bicarbonate Exchange in Lamprey Erythrocytes: Implications for CO2 Transport and Ion Distributions Between Plasma and Erythrocytes in the Blood of Petromyzon Marinus
Authors: Tufts B. L. , Boutilier R. G.
Published: April 2021

Carbon dioxide transport and ion distributions were examined in the blood of the lamprey, Petromyzon marinus. Over the range studied, the erythrocytes had the highest total CO2 content, followed by whole blood and true plasma. The nonbicarbonate buffer values were —37·0mequivl-1pHunit-1 for erythrocytes, —3·3mequivl-1pH unit-1 for whole blood and —0·1mequivl-1 pH unit-1 for true plasma. These results are in sharp contrast to the models of carbon dioxide transport in the blood of other vertebrates and are consistent with the view that chloride/bicarbonate exchange is virtually absent in agnathan erythrocytes. Protons are passively distributed in Petromyzon blood. However, the distribution ratio for chloride between plasma and erythrocytes was strikingly different from the distribution ratio for protons. In the absence of rapid chloride/bicarbonate exchange, the erythrocyte volume is relatively constant over the physiological pH range. A model is presented to explain carbon dioxide transport in lamprey blood which does not involve a rapid chloride/bicarbonate exchange mechanism on the erythrocyte membrane.
Leg Coordination in the Stick Insect Carausius Morosus: Effects of Cutting Thoracic Connectives
Authors: Dean Jeffrey
Published: April 2021

Behavioral studies of stick insects have identified six mechanisms which coordinate leg stepping. All six are active between ipsilateral leg pairs. As a first step towards locating the neurons mediating these interactions, the present study describes the effects of cutting one of the paired thoracic connectives. After the operation the following changes in step coordination occurred. The ipsilateral leg immediately caudal to the severed connective generally showed weak stepping. In free-walking animals it often remained near its posterior extreme position and dragged along the substratum. During supported walking, rhythmic stepping was common, but the swing phase of this leg was longer and both temporal and spatial coordination were disturbed. When the leg made a pause it usually stopped in the air near the end of its swing movement. During steady walking, the operation interrupted information from the adjacent forward leg normally used to guide the end-point of the swing or to signal errors in leg placement and elicit a corrective treading-on-tarsus reflex. It also interrupted position information affecting the start of the swing. For the leg rostral to the cut, the inhibition during the swing of the posterior leg and the excitation when the latter started its retraction were both interrupted. These results indicate that all six ipsilateral coordination mechanisms are primarily mediated by the ipsilateral connective. In addition, the data show that contralateral coordination within the segmental ganglion is strongest for the front legs, weaker for the rear legs, and not discernible for the middle legs.
Histamine-induced modulation of olfactory receptor neurones in two species of lobster, Panulirus argus and Homarus americanus
Authors: Bayer T. A. , McClintock T. S. , Grünert U. , Ache B. W.
Published: April 2021

In two species of lobster, application of the biogenic amine, histamine (HA), to the soma of olfactory receptor cells suppressed both spontaneous and odour-evoked activity, as shown by electrophysiological recording from single cells. The action of HA was graded, reversible, specific to HA, and had a threshold between 0·1 and 1 μmol l−1. HA increased the conductance of the membrane, primarily to chloride ions. The vertebrate HA receptor antagonist, cimetidine, and the nicotinic receptor antagonist, d-tubocurarine, but not other known vertebrate HA receptor antagonists, reversibly blocked the action of HA. These results suggest that a histaminergic mechanism modulates stimulus–response coupling in lobster olfactory receptor cells and potentially implicate a novel HA receptor, pharmacologically similar to the one recently described in the visual system of flies.
Integration of ultrasound and flight inputs on descending neurons in the cricket brain
Authors: Brodfuehrer P. D. , Hoy R. R.
Published: April 2021

In response to ultrasonic stimuli, tethered flying crickets perform evasive steering movements that are directed away from the sound source (negative phonotaxis). In this study we have investigated the responsiveness to ultrasound of neurons that descend from the cricket brain, and whether flight activity facilitates the responsiveness of these neurons.

Ultrasonic stimuli evoke descending activity in the cervical connectives both ipsilateral and contralateral to the sound source. Both the amount of descending activity and the latency of this response in the cervical connectives are linearly correlated with ultrasonic stimulus intensity, regardless of the cricket’s behavioral state. Flight activity significantly increases the amount of descending activity evoked by ultrasound at all stimulus intensities, and significantly decreases the latency of the response in the cervical connectives compared with non-flying crickets. Flight activity, however, does not significantly affect the activity in an interneuron (Int-1) carrying ultrasound input to the brain. Thus, the increase in the amount of descending activity produced during flight activity is due to the integration of input from Int-1 and the flight motor system to ultrasound-sensitive neurons in the cricket brain. Descending units recorded in the cervical connectives originate in the cricket brain. A reduction in the amount of descending activity is correlated with a decrease in the magnitude of the negative phonotactic response of the abdomen during flight activity, suggesting that these descending units play a role in eliciting negative phonotaxis.
Water Uptake in a Cephalopod and the Function of the so-called ‘Pancreas’
Authors: Wells M. J. , Wells J.
Published: April 2021

If the gut of Octopus vulgaris is ligated at both ends, the animal loses weight at about 10% per day at 21 °C, dying after about 48 h. Ligation of the ducts to the midgut gland has the same effect. If one or both ducts are cannulated and led to the exterior with a sufficient length of duct remaining, sea water is taken up by peristalsis and there is little or no weight loss. As body weight falls, blood and urine osmolality remain unchanged, but blood conductivity falls and blood copper concentration rises, indicating a loss of salts as well as water. Muscle dry weight, as a percentage of muscle wet weight, increases as body weight falls. Octopus is hyperosmotic compared with sea water and the rate of ultrafiltration through the branchial heart appendages into the kidney sacs is estimated to be sufficient to account for the observed body weight losses.

Each side of the midgut gland, connected to the gut by a digestive duct, includes two distinct structures. One, the digestive gland, produces enzymes and is also concerned with absorption of the fluid and particulate products of digestion. The other, the digestive gland appendage (the so-called ‘pancreas’), is composed of cells with characteristics that strongly indicate bulk fluid transport; it seems likely that this is the principal site of the fluid uptake. This evidently includes salts as well as water, since sea water taken into the gut (notably by rectal pumping) is not concentrated as fluid is withdrawn.
Respiratory Function in Exercising Fowl Following Occlusion of the Thoracic Air Sacs
Authors: Brackenbury John H. , Darby Carl , El-Sayed Mahmoud S.
Published: April 2021

Oxygen consumption, respiratory evaporative water loss, respiratory rate and gas tensions in the clavicular and abdominal air sacs and in arterial blood were monitored after occluding either the cranial thoracic air sac only (CRT group) or the cranial and caudal thoracic air sacs together (CRT-CT group). Respiratory water loss was used to estimate minute ventilation. Both experimental groups were able to maintain control levels of ventilation at rest and during treadmill exercise at approximately three times the resting metabolic rate. The CRT group regulated blood and intrapulmonary and normally, but there was a slight hypoxaemia/hypercapnaemia in the CRT-CT group, apparently as a result of parabronchial hypoventilation. The differential distribution of gas tensions between the cranial and caudal groups of air sacs was the same in control and experimental birds, suggesting that a normal intrapulmonary airflow pattern was preserved in the absence of the thoracic air sacs. The findings are discussed in the light of current models of the control of intrapulmonary airflow in birds.