bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural Control of Heart Beat in the African Giant Snail, Achatina Fulica Férussac: II. Interconnections Among the Heart Regulatory Neurones
Authors: Furukawa Yasuo , Kobayashi Makoto
Published: April 2021

The synaptic connections between identified heart regulatory neurones were examined in the central nervous system of the African giant snail, Achatina fulica Férussac. Two cerebral ganglion cells, the dorsal right and left cerebral distinct neurones (d-RCDN and d-LCDN), were found to have excitatory connections with several neurones in the suboesophageal ganglia (the periodically oscillating neurone, PON, the tonically autoactive neurones, TAN, TAN-2 and TAN-3, and the visceral intermittent firing neurone, VIN) and the connections are probably monosynaptic. VIN had a weak electrical coupling with PON. VIN inhibited TAN, TAN-2 and TAN-3, and the connections were considered to be monosynaptic. At the same time, TAN, TAN-2, TAN-3 and the visceral ganglion neurone (VG1) inhibited PON and VIN although the connections are unlikely to be monosynaptic. Another neurone in the pedal ganglia, the dorsal left pedal large neurone (d-LPeLN), was found to excite PON, VIN, TAN, TAN-2 and TAN-3. These connections were not monosynaptic. These results are interpreted in relation to heart regulation in Achatina.
Thermal dependence of maximum Ca2+-activated force in skinned muscle fibres of the toad Bufo marinus acclimated at different temperatures
Authors: Rees B. B. , Stephenson D. G.
Published: April 2021

Mechanically skinned muscle fibres from the twitch region of the iliofibularis muscle of cool-(16 ± 1°C) and warm- (32 ± 1°C) acclimated cane toads (Bufo marinus) were activated maximally by Ca2+ in solutions of different pH and at different temperatures (approx. 1–35°C). Acclimation of up to 12 weeks at 16°C and up to 8 weeks at 32°C did not modify the marked thermal dependence of isometric force in the skeletal muscle fibres of the cane toad. The prominent decline of maximum Ca2+-activated force at lower temperatures, a property which is not characteristic of muscles from other anurans, was associated with an obvious decline in fibre stiffness at temperatures below about 20°C, regardless of the temperatures at which the toads were kept prior to experimentation. The results suggest that the decline of isometric force at lower temperatures is due both to a reduction in the number of cross-bridges and to a decrease in the force output per cross-bridge. The maximum Ca2+-activated force response increased when fibres were activated in solutions of increasing pH at all temperatures investigated. This trend is expected to have a compensatory effect on the thermal dependence of the maximum Ca2+-activated force under physiological conditions, because of the elevation of intracellular pH as temperature declines. 4.The isometric force did not depend on the concentration of the zwitterionic species of the pH buffer in solutions. 5.The skinned fibre preparation developed a Ca2+-insensitive residual force following maximal activation. The increment in residual force followed a linear relationship with the duration of activation at a given temperature and a power relationship of activation temperature for a given duration of activation. Fibres from warm-acclimated animals developed less residual force following activations at 15 °C than did fibres from cool-acclimated animals, suggesting that thermal acclimation may substantially reduce the magnitude of this phenomenon at temperatures below 20°C.
A local interneurone which receives differential input from the medial and lateral giant axons
Authors: Takahata M , Wine JJ
Published: April 2021

The crayfish ventral nerve cord contains two pairs of giant axons which are termed command axons for escape because impulses in either pair of cells trigger a complex series of neural events that culminates in a rapid flexion and extension of the abdomen, i.e. a ‘tailflip’ (Wine & Krasne, 1982). Each pair of axons triggers a specific trajectory of escape by virtue of differences in its intersegmental pattern of synapses with flexor motor neurones (Larimer, Eggleston, Masukawa & Kennedy, 1971 ; Wine & Krasne, 1972; Mittenthal & Wine, 1973; Miller, Hagiwara & Wine, 1985; Dumont & Wine, 1987b). However, while some of the flexor motor pathways are differentiated in a way that is consistent with the observed behaviour, a persistent puzzle has been the extraordinary degree of overlap in the output connections of the two kinds of giant axons to other portions of the flexor motor pathway. These overlapping connections should blur the distinction between the escape trajectories, and thus are inconsistent with the observed behaviour.
Roles of individual honeybee workers and drones in colonial thermogenesis
Authors: Harrison J. M.
Published: April 2021

The individual roles of honeybee workers and drones in heat regulation were investigated using single combs of bees and brood (about 1000 individuals) placed in boxes at 1S°C. After 1h and before cluster formation, I measured the elevation of bee thoracic surface temperature (Tths) above local ambient temperature (Ta). Bees were then left overnight at 15 °C. During the preclustering period, the density of bees over the brood slowly increased. In the clusters left overnight, bees in the innermost layer were significantly younger than bees in the outermost layer. One-day-old bees and drones were always located in the innermost cluster layer. 89% of all workers measured had Tths−Ta 3 ⩾ 2°C, indicating that most workers contribute to colonial thermogenesis. Average Tths−Ta was 4·1 °C. Drones measured had the same average Tths−Ta as unmarked workers. Tths−Ta did not differ among bees 2 days of age and older. Location on or off the brood did not affect Tths−Ta. Cooling constants of dead bees placed near the comb in the box averaged 1·036 min−1 and were independent of location on the comb. Calculated average thoracic conductance was 0·829 calg−10C−1 min−1. Average calculated heat production per worker was 0·095 cal min−1, less than 15 % of the maximal oxygen consumption of 4-day-old bees. Calculations indicate that the larger drones contribute more heat per bee than do the workers. Brood warming prior to clustering is due to relatively uniform heat production by individual bees and the attraction of bees to the brood area. This results in a higher heat production per unit volume of air over the brood than away from the brood.
The Function of the Calciferous Glands of Earthworms
Authors: Robertson James D.
Published: April 2021

In the Lumbricidae the secretion of the calciferous glands consists mainly of calcium carbonate, the percentage of carbonate in the calcite concretions being 95−97 per cent. Feeding experiments indicate that the calcium of the secretion can be derived from the common inorganic salts such as the carbonate, sulphate, phosphate, oxalate, chloride, and nitrate, and also from pear leaves. Measurements of the hydrogen-ion concentration of the gut, soil, and castings of specimens of Lumbricus terrestris show that the tendency of the cast to be more neutral than the soil is due to the secretions of the gut as a whole, and not to the secretion of the calciferous glands. The optimum pH’s of two of the main intestinal enzymes have been −measured. Amylase has an optimum at pH 6-8-yo, and lipase at pH 6’4-6-6 and 7-37-7 depending on the substrate. The amount of carbon dioxide bound as carbonate by the glands was measured in a series of experiments with earthworms kept in different calcium salts. The percentage of carbon dioxide excreted as carbonate never exceeded 10 per cent, of the total metabolic carbon dioxide. Absorption of iron saccharate injected into worms took place occasionally, in groups of adjacent cells in the intestine and in isolated cells in the calciferous glands. The true function of the calciferous glands is excretion, calcium carbonate being passed into the gut as crystals of calcite which are chemically inactive in the gut.
The Mechanism of Urine Formation in Invertebrates
Authors: Picken L. E. R.
Published: April 2021

In Carcinus maenas : (a) The blood may be hypertonic, isotonic or hypotonic to the external medium. (b) The urine may be hypertonic, isotonic or hypotonic to the blood, and its concentration may differ in the two antennary glands. (c) The hydrostatic pressure of the body fluid is c. 13 cm. of water. (d) The colloid osmotic pressure of the blood is c. 11 cm. of water. (e) The urine probably contains protein and has a colloid osmotic pressure of c. 3 cm. of water. In Potamobius fluviatilis : (a) The blood is hypertonic to the external medium. (b) The urine is hypotonic to the blood but hypertonic to the external medium and its concentration may differ in the two antennary glands. (c) The hydrostatic pressure of the body fluid is c. 20 cm. of water. (d) The colloid osmotic pressure of the blood is c. 15 cm. of water. (e) The urine may contain protein and has a colloid osmotic pressure (calculated) of c. 2 cm. of water. In Peripatopsis spp. : (a) The blood is hypertonic to the urine. (b) The hydrostatic pressure of the body fluid is c. 10 cm. of water. (c) The colloid osmotic pressure (calculated) of the blood is c. 5 cm. of water. (d) The urine may contain protein and has a colloid osmotic pressure (calculated) of c. 2-5 cm. of water. (e) It is concluded that filtration is possible and that secretion and resorption almost certainly occur in the formation of the urine. (f) A microthermopile is described. (g) Methods are described for measuring the hydrostatic pressure and the colloid osmotic pressures of the body fluids in small animals.
Blood Gases, and Extracellular/Intracellular Acid-Base Status as a Function of Temperature in the Anuran Amphibians Xenopus Laevis and Bufo Marinus
Authors: Boutilier R. G. , Glass M. L. , Heisler N.
Published: April 2021

Blood gases, and parameters of the extracellular and intracellular acid-base status, were measured in the anuran amphibians Bufo marinus and Xenopus laevis acclimated to temperatures of 10, 20 and 30°C for 12 days. Arterial rose with temperature so that approximately constant oxygen saturation of the blood was maintained, a phenomenon explained on the basis of models for O2 transport in animals with central vascular shunts and temperature-dependent shifts in O2 equilibrium characteristics. Arterial plasma pH of both species varied inversely with temperature, the pH/temperature coefficient being not significantly different from that required for constant relative alkalinity or dissociation of imidazole. The change in plasma pH was brought about mainly by changes in , although plasma bicarbonate concentration also changed significantly. Intracellular pH/temperature relationships were found to be non-linear in most of the tissues. There was considerable variability among body tissue compartments and between the two species. These data confirm that the various tissue compartments in ectotherms maintain unique ΔpH/ Δt relationships, and indicate that measurement of extracellular pH as a function of temperature is not a good indicator for alphastat-type, temperature-dependent, acid-base regulation.
Oxygen and Carbon Dioxide Transport Characteristics of the Blood of the Nile Monitor Lizard (Varanus Niloticus)
Authors: Hicks James W. , Ishimatsu Atsushi , Heisler Norbert
Published: April 2021

Oxygen and carbon dioxide dissociation curves were constructed for the blood of the Nile monitor lizard, Varanus niloticus, acclimated for 12h at 25 and 35°C. The oxygen affinity of Varanus blood was low when was in the range of in vivo values (25°C: P50 = 34·3 at 35°C: P50 = 46·2mmHg at 1 mmHg = 133·3 Pa), and the oxygen dissociation curves were highly sigmoidal (Hill’s n = 2·97 at 25°C and 3·40 at 35°C). The position of the O2 curves was relatively insensitive to temperature change with an apparent enthalpy of oxygenation (ΔH) of −9·2kJmol−1. The carbon dioxide dissociation curves were shifted to the right with increasing temperature by decreasing total at fixed , whereas the state of oxygenation had little effect on total blood CO2 content. The in vitro buffer value of true plasma (Δ [HCO3−]pl/−ΔpHp1) rose from 12·0mequivpH−11−1 at 25°C to 17·5 mequivpH−11−1 at 35°C, reflecting a reversible increase of about 30 % in haemoglobin concentration and haematocrit levels during resting conditions in vivo.
Body Accelerations During the Wingbeat in Six Bat Species: The Function of the Upstroke in Thrust Generation
Authors: Aldridge H. D. J. N.
Published: April 2021

The kinematics and aerodynamics of Rhinolophus ferrumequinum, R. hipposideros, Myotis nattereri, M. mystacinus, Plecotus auritus and Eptesicus serotinus in horizontal flight at various flight speeds are described. Three kinematic patterns can be recognized. At low speeds M. nattereri, M. mystacinus and P. auritus use a ‘tip-reversal’ upstroke in which thrust is generated during the backward ‘flick’ of the chiropatagium. R. hipposideros also uses this kinematic pattern, but does not appear to generate thrust during the upstroke. Both R. ferrumequinum flying at 3·12ms−1 and E. serotinus flying at 3·44ms−1 accelerate during the ‘vertical’ upstroke (in which the wings move perpendicularly to the flight path), indicating that their wings are active. When flying at 4·16 m s−1, E. serotinus also uses a’vertical’upstroke, but in this case it decelerates, which suggests that thrust is not being generated. At minimum power speed (4·8ms−1), R.ferrumequinum uses a ‘reduced-span’ upstroke, thrust is not generated during the upstroke and the animal decelerates.
A new microcomputer-based method for measuring walking phonotaxis in field crickets (Gryllidae)
Authors: Doherty JA , Pires A
Published: April 2021

Calling songs of male crickets attract sexually mature, conspecific females for mating (for recent reviews see Elsner & Popov, 1978; Huber & Thorson, 1985; Doherty & Hoy, 1985). This communication system has been the subject of many behavioural studies on the relevant properties of the male’s calling song for recognition by females (e.g. Walker, 1957; Popov & Shuvalov, 1977; Pollack & Hoy, 1979, 1981; Thorson, Weber & Huber, 1982; Stout, DeHaan & McGhee, 1983; Doherty, 1985b; Doolan & Pollack, 1985). The behavioural investigations have required some means of measuring the female’s phonotaxis (her locomotion or turning towards a sound source). These include ‘closed-loop’ methods in which the animal moves freely in acoustic space and ‘open-loop’ methods in which the animal is tethered and is not allowed to experience changes in sound intensities as it runs in the direction of the sound source. Closed-loop methods include free walking in arenas (e.g. Murphey & Zaretsky, 1972; Paul, 1976; Hoy, Hahn & Paul, 1977; Pollack & Hoy, 1979; Stout et al. 1983); open-loop methods include tethered flight (Moiseff, Pollack & Hoy, 1978; Pollack & Hoy, 1979, 1981; Pollack, Huber & Weber, 1984), tethered walking on Y-maze globes (Hoy & Paul, 1973) and free walking on a spherical locomotion compensator (Wendler, Dambach, Schmitz & Scharstein, 1980; Thorson & Huber, 1981; Thorson et al. 1982; Pollack et al. 1984; Doherty, 1985a,b,c; Schmitz, 1985).
Ca2+-Dependent Photoreceptor Potential in Paramecium Bursaria
Authors: Nakaoka Yasuo , Kinugawa Kohsaku , Kurotani Tohru
Published: April 2021

Photostimulation of deciliated specimens of chlorella-free P. bursaria elicited a transient depolarization of the membrane potential. The amplitude of this receptor potential became larger as light intensity was increased and the relationship showed a Michaelis equation. The action spectrum of the receptor potential showed two peaks at around 420 and 560 nm. When constant current was injected to depolarize the membrane gradually, the receptor potential showed a decrease in amplitude. The potential at which the response disappeared depended on the external concentration of Ca2+ (27 mV/log [Ca2+]o), and the amplitude of the receptor potential was also dependent upon external Ca2+ concentration. Therefore, the receptor potential is primarily caused by a transient increase in the membrane conductance to Ca2+.
Gamma-Aminobutyric Acid Receptors on Cultured Cockroach Brain Neurones
Authors: Shimahara T. , Pichon Y. , Lees G. , Beadle C. A. , Beadle D. J.
Published: April 2021

Gamma-aminobutyric acid (GABA) at 10−4 mol l−1 inhibited spontaneous activity and produced conductance changes in 60% of cultured cockroach neurones tested. The reversal potential for the GABA-evoked response was between −65 mV and−75 mV. Under whole-cell voltage-clamp conditions, with 114 mmol l−1 potassium chloride in the electrode, the reversal potential had a similar value to that predicted for a chloride current. The response was blocked by 10−5 mol l−1 picrotoxin but was not affected by 10−5moll−1 bicuculline. In the whole-cell voltage-clamp conditions, 50 μmol l−1 GABA evoked an inward current that was accompanied by an increase in current noise. Fluctuation analysis of the noise gave a mean channel opening time of 11·8 ms for GABA and 6 5 ms for muscimol. The single-channel conductance was 18·6 pS for GABA and 15·2 pS for muscimol. When 50 μmoll−1 GABA was applied in the presence of the benzodiazepine, flunitrazepam, there was an increase in both the evoked current and the accompanying current noise. Analysis of this noise gave values of 14·3 ms for the mean channel opening time and 18·3 pS for the singlechannel conductance. The variance of the noise was increased by approximately 60% in the presence of flunitrazepam, suggesting that this drug potentiates the GABA responses of cockroach neurones by increasing the frequency of channel events.
Statocyst Control of Uropod Righting Reactions in Different Planes of Body Tilt in the Norway Lobster, Nephrops Norvegicus
Authors: Newland Philip L. , Neil Douglas M.
Published: April 2021

The righting reactions of the uropod exopodites of the Norway lobster, Nephrops norvegiens, induced by stimulation of the statocysts, were studied during both imposed body tilts in different vertical planes and freely expressed manoeuvres. The opening and closing movements of the uropod exopodite were brought about by the reciprocal activity of the dorsal abductor muscles and the reductor muscles, respectively. The uropods were held symmetrically open when the animal was upright, but adopted an asymmetrical pattern, with the downward uropod open and the upward uropod closed, during imposed body roll. In an imposed pitch of the body, the uropods closed symmetrically on headdown movement and opened symmetrically on head-up movement. The response pattern which occured in roll persisted through intermediate vertical planes to within 10° of true pitch. Removal of the statolith from a single statocyst caused the zone of symmetrical uropod responses to shift towards the operated side, but did not alter its angular dimensions. Bilateral statolith removal abolished the uropod reaction to tilt. Animals released in mid-water exactly in the pitch plane recovered their upright posture by a pitching movement, using symmetrical motor reactions of the abdomen and its appendages. Animals released at all other possible orientations used an initial rolling movement, involving an asymmetrical disposition of the appendages. The chelipeds did not contribute significantly to righting in roll, but both the lateral beating of the swimmerets and the asymmetrical disposition of the uropods produced righting torques as the animal descended through the water. These results are discussed in terms of the hydromechanical effect of asymmetrical uropod postures, and the functional significance of the distinct switching between symmetrical and asymmetrical patterns. Implications for the mechanisms of statocyst control of uropod righting reactions, in terms of both the magnitude and the direction of body tilt, are also considered.
Structure and innervation of the third axillary muscle of Manduca relative to its role in turning flight
Authors: Rheuben M. B. , Kammer A. E.
Published: April 2021

The morphology, ultrastructure, innervation and physiology of the third axillary muscle in Manduca sexta were examined to investigate the role of this muscle in flight. The muscle consists of three parts: the upper bundle, which originates on the episternum, and the middle and lower bundles, which originate on the epimeron; all three parts insert on the tip of a projection from the third axillary sclerite. The middle bundle is composed of tonic fibres, and is innervated by a single slow axon, while the other two bundles consist of intermediate fibres and are each innervated by a single fast axon. The shape and position of the third axillary sclerite within the wing hinge are such that its primary function appears to be remotion of the wing. The length of the third axillary muscle determines the amount of remotion, independently of the degree of elevation or depression of the wing and independently of the amount of remotion of the contralateral wing. Electrophysiological recordings from the three parts of the muscle during tethered flight indicate that they may each function independently of each other and in different ways. The tonic (middle) bundle is capable of maintaining tension to hold the wings in the folded position at rest and is active when the wings are folded at the end of flight. The intermediate (upper and lower) bundles are activated phasically with impulses that may occur with various relationships to the timing of activation of a direct depressor, the subalar, or of several of the elevators. The findings are consistent with the hypothesis that the third axillary muscles on both sides are important in determining the asymmetric degrees of remotion observed in turning flight.
The actions of FMRFamide-like peptides on visceral and somatic muscles of the snail Helix aspersa
Authors: Lehman H. K. , Greenberg M. J.
Published: April 2021

Phe-Met-Arg-Phe-NH2(FMRFamide) and pyroGlu-Asp-Pro-Phe-Leu-Arg-Phe-NH2(pQDPFLRFamide) occur in the ganglia and tissues of the snail, Helix aspersa. This report describes the effects of these two neuropeptides on five visceral organs or somatic muscles isolated from the snail (Table 1).

The epiphallus, as well as the rest of the male reproductive tract, was contracted by both FMRFamide and pQDPFLRFamide, and the threshold was usually below 5 × 10−9mol 1−1(Fig. 1). Both peptides also reduced the resting tone of the crop and decreased the force and frequency of its rhythmic activity; FMRFamide is about 10 times more potent (Fig. 4). In contrast, pQDPFLRFamide was about 100 times more potent than FMRFamide as a cardioexcitatory agent (Fig. 5). The actions of the peptides on the pharyngeal and tentacle retractor muscles were markedly different: FMRFamide primarily contracted these muscles; and pQDPFLRFamide usually had no effect alone, but relaxed or diminished contractions induced by FMRFamide and acetylcholine (ACh) (Figs 6, 8, 9). Other analogues of FMRFamide were tested, but none was as effective a relaxing agent as pQDPFLRFamide. The effects of FMRFamide and pQDPFLRFamide on all of the preparations could be distinguished from those produced by ACh and 5-hydroxytryptamine (5-HT); thus the actions of the neuropeptides were not mediated by cholinergic or serotonergic neurones.

The stimulation of the musculature in the male reproductive tract and the inhibition of motility of the digestive system by FMRFamide and pQDPFLRFamide implicate these peptides in the control of reproductive behaviour. The effectiveness of pQDPFLRFamide in relaxing the retractor muscles and as a cardioexcitatory agent led to the hypothesis that this heptapeptide and FMRFamide, acting at distinct receptors, cooperate to regulate the excitability and contractility of the snail’s musculature between the extremes of aestivation and active locomotion.
Regulation of the Synthesis of Nerve Growth Factor
Authors: Heumann Rolf
Published: April 2021

Through nearly 40 years of research nerve growth factor (NGF) has become a paradigm for neurotrophic factors. NGF is synthesized and released from innervated target tissues in limiting amounts, thereby regulating the cell number and the differentiated properties of responsive neurones. Three distinct cell types are responsive to NGF: peripheral sensory and sympathetic neurones and certain types of central cholinergic ones. The effects of NGF are mediated through interaction with a specific receptor which activates a transmembrane second-messenger system. NGF synthesis is regulated during development and in the adult animal. In the developing whisker pad, NGF synthesis commences with its sensory innervation, but sensory neurones lack NGF receptors at the stage when their fibres are growing to their target. These findings indicate that NGF does not attract sensory nerve fibres chemotactically to their target fields during development, but is involved in target-controlled neuronal cell death and in regulation of the density of innervation of target tissues. In non-neuronal cells of the sciatic nerve, NGF synthesis is up-regulated during development and after nerve lesion. Thus the changes in NGF levels after lesion in the adult animal are consistent with the hypothesis that the nonneuronal cells relapse into an earlier developmental stage. Regenerating fibres penetrating into the distal nerve stump restore the low adult levels of NGF. Recent evidence indicates that macrophages invading the nerve after transection produce signals which increase NGF synthesis.
Strengthening of Synaptic Inputs After Elimination of A Single Neurone Innervating the Same Target
Authors: Parnas I.
Published: April 2021

The problem of ‘competition’ between neurones innervating the same target can be studied in simple neural systems such as the central nervous system of the leech and the lobster neuromuscular junction. Intracellular injection of pronase to kill selectively a single neurone shows that, in the leech, removal of one neurone is a sufficient signal to produce compensatory changes. After removal of a given neurone, only neurones of the same function respond to innervate the ‘vacant territory’. This was shown both for a motor neurone (annulus erector) and sensory neurones (T or N). Thus the response is very specific.

The lobster neuromuscular junction, with its multiple excitatory and inhibitory innervation, has advantages for the study of changes in synaptic efficacy of the remaining neurones after removal of a defined neurone releasing the same or a different transmitter. Killing the inhibitory neurone produced prolongation of the excitatory’ synaptic current because of a prolonged channel open time. When an excitatory axon is killed the remaining excitatory axon releases more transmitter. Over a period of 10 days, there is first a strengthening of existing synapses, then the appearance of new release sites and sprouting. Only those terminals of a neurone that innervate a territory with reduced innervation become stronger, while other terminals of the same axon remain normal. Cutting of axons produces different responses from those seen after killing single neurones.
The Use of Peripheral Nerve Grafts To Enhance Neuronal Survival, Promote Growth and Permit Terminal Reconnections in the Central Nervous System of Adult Rats
Authors: Bray Garth M. , Villegas-Pérez Maria Paz , Vidal-Sanz Manuel , Aguayo Albert J.
Published: April 2021

During both development and regeneration, the survival of neurones and the growth of axons are controlled by inherent neuronal properties, conditions in the axonal environment, and the establishment of appropriately timed and specific functional contacts. To study the effects of extrinsic influences on the survival, growth and connectivity of axotomized neurones in the mature mammalian CNS, we replaced the optic nerve in adult rats with segments of autologous peripheral nerve (PN) and used morphometric techniques, neuroanatomical tracer substances and immunological cell markers to examine retinal ganglion cells (RGCs), their axons in the PN grafts and their terminals in the superior colliculi (SC) of these animals. We observed that: (1) the survival of axotomized RGCs was enhanced by the PN grafts; (2) in the PN-grafted eyes, approximately 20% of the surviving RGCs regrew their axons into the grafts and (3) some of the RGC axons that regenerated along the PN grafts bridging the eye and the tectum re-entered the SC, arborized and made synaptic contacts with tectal neurones. It is not known if the terminal connections established between RGCs and cells in the SC are appropriate, functional or capable of influencing the long-term survival of their cells of origin.
Net Uptake of CO2 Driven by Sulphide and Thiosulphate Oxidation in the Bacterial Symbiont-Containing Clam Solemya Reidi
Authors: Anderson A. E. , Childress J. J. , Favuzzi J. A.
Published: April 2021

Solemya reidi Bernard is a gutless clam that lives in burrows in reducing sediments, and harbours intracellular sulphur-oxidizing bacteria in its gills. Clams were incubated in various concentrations of sulphide and thiosulphate for up to 65 h in a flow-through respirometer. Fluxes were determined by continuous sampling of the respiratory medium with analysis of CO2, O2 and sulphide by gas chromatography and analysis of thiosulphate, sulphite (and sulphide) by HPLC using mono-bromobimane-derivatized discrete samples. Net CO2 uptake was shown to occur with exposure to 50–100 μmol l−1 sulphide and greater than 225 μmoll−1 thiosulphate; sulphide oxidation and thiosulphate uptake were also demonstrated. 45CaCO3 deposition in the shells of S. reidi was found to be insignificant compared to the net CO2 flux measured in the presence of low levels of sulphide.

In experiments conducted under various O2 conditions, O2 limitation, produced by a combination of low [O2] and low water flow, was shown to inhibit sulphide oxidation and to prevent CO2 uptake. However, if O2 supply was not limited by low flow rates, in the presence of low [O2] (25–40 μmol l−1) S. reidi showed rates of O2 and sulphide consumption and CO2 uptake near the maximum levels determined under high [O2] conditions, indicating the potential for net CO2 uptake in the low [O2] conditions presumed to exist in the animal’s burrows.

Thiosulphate levels in the blood of S. reidi were analysed and shown to increase rapidly during incubation in sulphide. These levels reached an apparent steady state (approx. 300 μmoll−1) in recently captured clams after 1 h of incubation. However, both O2 limitation and time in captivity (>43 days after capture) caused a marked increase in the blood thiosulphate levels, which exceeded 2·5 mmol l−1 after 16 h of exposure to sulphide. These results indicate that blood thiosulphate is transported to the bacteria and further oxidized, and that sulphide and thiosulphate oxidation are oxygen-dependent. In analyses of gill tissues for elemental sulphur, we found a wide range in the levels of sulphur stores. Calculations indicated these to be a small fraction of the total flux of sulphur maintained during continuous sulphide oxidation.

Estimates of CO2:O2:sulphide ratios suggest CO2 fixation efficiencies similar to those of chemolithoautotrophic bacteria. Assuming translocation and oxidation of symbiont-fixed organic compounds, the net uptake of CO2 by S. reidi in the presence of reduced sulphur compounds suggests that this intact symbiosis may be able to meet its organic carbon needs through autotrophy.
Carbohydrate Use in the Flight Muscles of Manduca Sexta During Pre-Flight Warm-Up
Authors: Joos Barbara
Published: April 2021

Although fat is the principal fuel for flight in moths and butterflies, some use of carbohydrate fuels during activity would be predicted on energetic and biochemical grounds, particularly in nectivores. The present study evaluates the use of carbohydrate fuels during pre-flight warm-up in the endothermic sphinx moth Manduca sexta (L.). Carbohydrate content of moths was measured at intermediate points during the pre-flight warm-up cycle and at take-off. Muscle glycogen content declined during the initial phases of warm-up, whereas glucose and trehalose concentrations were unchanged. Abdominal carbohydrates were not mobilized during warm-up. Energy budget analysis suggests that glycogen oxidation supplies about 39% of the energy needed for the initial phase of warm-up and about 6% of the total cost of warm-up. Glycogen use during warm-up may be correlated with the capacity for endothermic warm-up at low ambient temperatures. Carbohydrates appear to be more important as fuels for activity in some lepidopterans than has been previously reported for other members of this diverse Order.
Acid-Base and Ionic Regulation in the American Eel (Anguilla Rostrata) During and After Prolonged Aerial Exposure: Branchial and Renal Adjustments
Authors: Hyde D. A. , Perry S. F.
Published: April 2021

The involvement of the gill and kidney in acid-base regulation was examined in the American eel, Anguilla rostrata, during 36h of continuous air-exposure and subsequent return to water. While in air, eels developed a severe mixed respiratory/-metabolic acidosis. Renal acid excretion increased only slightly during the latter stages of air-exposure. A pronounced reduction in urine flow rate was important to minimize dehydration but essentially eliminated the kidney as a route for excess acid excretion. Upon return to the water, eels had accrued an extracellular metabolic acid load of 9·53 mmol 1−1. The metabolic acid was cleared from the extracellular compartment at an exceptionally low rate (approximately 70μmol kg−1 h−1) and about 50 % of the acid load remained after 18 h of recovery in water. The clearance of metabolic acid was accounted for by enhanced branchial acid excretion which was related primarily to adjustments of unidirectional Na+ fluxes. Unidirectional Cl− fluxes were undetectable using radiotracer methods. We speculate that the inefficiency of acid-base regulation in the eel compared to other teleosts is, in part, related to the absence of significant branchial C1−/HCO3− exchange.
A Functional Analysis Of The Primary Upstroke And Downstroke Muscles In The Domestic Pigeon (Columba Lima) During Flight
Authors: Dial K. P. , Kaplan S. R. , Goslow G. E. , Jenkins F. A.
Published: April 2021

In domestic pigeons (Columba livia), the electrical activity of the major depressor muscle of the wing, the pectoralis (pars thoracicus), begins in late upstroke well before the wing begins its downstroke excursion. The two architecturally distinct heads of the pectoralis, the sternobrachialis and the thoracobrachialis, are differentially recruited during take-off, level flight and landing. In addition to wing depression, the sternobrachialis protracts the humerus and the thoracobrachialis retracts the humerus. At the point of transition from wing upstroke to downstroke, the pectoralis EMG signal typically exhibits a reduction in amplitude. The supracoracoideus, in addition to an expected EMG associated with wing elevation, is co-activated with the pectoralis about 50% of the time.
Acid-Base Regulation Following Acute Acidosis in Seawater-Adapted Rainbow Trout, Salmo Gairdneri: A Possible Role for Catecholamines
Authors: Tang Yong , Nolan Steven , Boutilier Robert G.
Published: April 2021

A fall in blood pH was induced by intra-arterial infusion of HC1 in seawater-adapted rainbow trout (Salmo gairdneri). The acute acidosis resulting from HC1 infusion caused a short-lived decrease in plasma bicarbonate concentration ([HCO3−]) and an increase in arterial CO2 tension . Erythrocyte pH and bicarbonate concentrations were not significantly altered by the infusion of acid. Injection of acid did, however, stimulate a branchial net H+ efflux which could be primarily accounted for by a net uptake of bicarbonate equivalent ions from the environmental water.

Acid infusion of animals pre-treated with the β-adrenergic blocking agent, propranolol, induced a similar pattern of change in plasma acid-base status. However, the recovery of plasma pH and restoration of plasma [HCO3−] were slower than in animals infused with acid alone. Red cell pH fell significantly in the face of plasma acidosis in the β-blocked animals. Erythrocyte [HCO3−] showed a similar pattern of change to that of erythrocyte pH. Branchial net H+ efflux increased to a lesser extent following acid infusion in animals treated with propranolol.

We conclude that catecholamines released into the bloodstream during periods of acute acidosis may play an important role in facilitating branchial H+ efflux in seawater-adapted rainbow trout.
Discontinuous CO2 Emission in a Small Insect, the Formicine Ant Camponotus Vicixus
Authors: Lighton John R. B.
Published: April 2021

Standard rates of oxygen consumption and CO2 production were measured by constant-volume respirometry in the formicine ant, Camponotus vicinus Mayr, at temperatures ranging from 10 to 40°C. Over this range, the Q10 with regard to was 1·79, and with regard to , 1·84. Multiple regression equations relating and of inactive ants to mass (0·016–0·088 g) and temperature were calculated. Periodic CO2 emissions (‘bursts’) were monitored with flow-through respirometry. Burst frequency increased exponentially with temperature (Q10 = 3·05), from 8·14h−1 at 15°C to 81·4h−1 at 35°C, and was not significantly correlated with body mass over the mass range (0·041–0·086g) investigated. Burst volume, which could be accurately measured in one ant, decreased with temperature (Q10= 0·61), thus yielding the observed Q10 of 1·84.
Analysis of Haemolymph and Muscle Acid-Base Status During Aerial Exposure in the Crayfish Austropotamobius Pallipes
Authors: Tyler-Jones R. , Taylor E. W.
Published: April 2021

Exposure of the crayfish Auslropotamobius palhpes to air resulted in an acidosis in the postbranchial haemolymph (pHa) and the abdominal muscle. The haemolymph acidosis was subsequently compensated and, after 24 h in air, pHa had returned to the settled, submerged value. The intracellular acidosis remained uncompensated throughout the period of aerial exposure. When crayfish were first removed into air, lactate concentrations in the haemolymph and abdominal muscle increased substantially. After 24 h in air lactate concentrations in both compartments had returned towards submerged levels. Possibilities for the fate of lactate are discussed. Re-analysis of haemolymph acid-base data for crayfish exposed to air (Taylor & Wheatly, 1981) revealed discrepancies between observed and expected base excess. Initially these may arise from exchanges of H+ or HCO3− with other compartments. During long-term air exposure, the removal of lactate from the haemolymph and an independent accumulation of base, probably from the mobilization of an internal source of bicarbonate buffer, result in the observed pH compensation. Determination of base excess for the changes in abdominal muscle acid-base status after 3 h of exposure to air corroborated the results of the haemolymph analysis, suggesting a retention of H+ despite the efflux of lactate.
Functional Morphology of the Lungs of the Nile Crocodile, Crocodylus Niloticus: Non-Respiratory Parameters
Authors: Perry Steven F.
Published: April 2021

The complex, multicameral lungs of the Nile crocodile are characterized by rows of tubular chambers, which in cranial and ventral lung regions are broad and sac-like. The inner surface of the chambers is enhanced by cubicles (ediculae), the capillary-bearing walls of which are often perforated. Extrabronchial communication among chambers is infrequent. The ediculae end in a network of myoelastic trabeculae, which face the central lumen of the chambers. The trabecular epithelium is similar to that of mammalian bronchi and contains isolated endocrine-hke cells basally, whereas the edicular epithelium is similar to that of other reptiles and of mammals. The distribution of non-vascular smooth muscle, 64% in trabeculae and 36% in interedicular walls, is consistent with the hypothesis that these two antagonistically oriented muscle groups interact to effect lung patency. The volume-specific lung compliance is similar to that of much simpler, unicameral gekko lungs, implying that lung compliance is a function of parenchymal structure and not of primary structural type.
The Effects of Temperature on Flight Muscle Potentials in Honeybees and Cuculiinid Winter Moths
Authors: Esch Harald
Published: April 2021

Amplitudes of extracellular action potentials in indirect flight muscles of honey-bees and cuculiinid winter moths decline with decreasing muscle temperatures and fall suddenly to zero. Action potential durations increase with amplitude decline. Amplitudes at 11 °C are only 20% of values near 30°C in workers of Apis mellifera mellifera. They fall to zero at approx. 10°C. In the cuculiinid winter moth Eupsilia devia, amplitudes at 1°C are approx. 12% of values at 27°C. They fall to zero between 0 and 1°C. The duration of action potentials in bees and cuculiinid winter moths is about 7 ms at 27 °C and increases to 52 ms at 11 °C in bees and to 66 ms at 1°C in moths. The ratios of action potential rise time to fall time are about 1 at 27°C for bees and moths. They decrease to 0·45 at 11 °C in bees and to 0·56 at 1°C in moths. Results suggest that bees can heat flight muscles only if muscle temperatures are above 10°C, whereas cuculiinid winter moths can shiver with muscle temperatures near 0°C.
Ionic Currents in Neurones Cultured From Embryonic Cockroach (Periplaneta Americana) Brains
Authors: Christensen Burgess N. , Larmet Yves , Shimahara Takeshi , Beadle David , Pichon Yves
Published: April 2021

Neurones isolated from embryonic cockroach brains were maintained in culture for up to 8 weeks. A single patch electrode was used to record voltage changes in response to injected current, membrane ionic currents under whole-cell voltageclamp conditions or single-channel currents from isolated membrane patches. The voltage changes in response to injected current that depolarized the cell indicated increases in membrane permeability to calcium and potassium. These observations were confirmed using a voltage clamp. The potassium current observed in the youngest cultures turned on with a delay and was blocked by tetraethylammonium (TEA) and 4-aminopyridine (4-AP). Two kinds of decrease in the outward potassium current were observed. One may be associated with extracellular potassium accumulation, inactivation of the potassium channel or inactivation of a calcium channel. The other appears to be a voltage-dependent inactivation. The magnitude of the calcium permeability appeared to increase as the cultures developed, being most prominent in cultures more than 2 weeks old. Single-channel conductance measured from an analysis of records from six isolated membrane patches ranged from 15 to 110pS. Except for one channel, the probability of the channels being open did not change appreciably with membrane potential. Our results suggest that much of the increase in potassium permeability may be due an increase in intracellular calcium level.
Solubility of Nitrogen and Argon in Eel Whole Blood and its Relationship to pH
Authors: Pelster B. , Kobayashi H. , Scheid P.
Published: April 2021

The solubility coefficients (α) for the inert gases, nitrogen (N2) and argon (Ar), were measured by mass spectrometry in whole blood of the freshwater-adapted European eel, Anguilla anguilla, at varied pH and at two temperatures, 5 and 15°C. The pH was altered either by varying (0·75–75 mmHg; 1 mmHg = 133·3 Pa) or by adding fixed acid (HC1 or lactic acid).

No dependence of α on pH (range 5·5–8·4) or on lactate concentration (range 0·2–25 mmol l−1) was detectable. Average values (±S.D.) for α (μmol l−1 mmHg−1) were: at 5°C and at 15°C. These data yield values for Q10 of 0·87 for nitrogen and 0·82 for argon, and for activation energy, Ea (kJ mol−1 K−1), of –9· 2 for nitrogen and –13·4 for argon. The results do not support earlier reports on significant pH dependence of α in eel blood and suggest, in contrast, that no fundamental differences exist in respect of inert gas solubility between whole blood of the eel and of other vertebrates.
Empirical Estimates of Body Drag of Large Waterfowl and Raptors
Authors: Pennycuick C. J. , Obrecht Holliday H. , Fuller Mark R.
Published: April 2021

Measurements of the body frontal area of some large living waterfowl (Anatidae) and raptors (Falconiformes) were found to vary with the two-thirds power of the body mass, with no distinction between the two groups. Wind tunnel measurements on frozen bodies gave drag coefficients ranging from 0·25 to 0·39, in the Reynolds number range 145 000 to 462000. Combining these observations with those of Prior (1984), which extended to lower Reynolds numbers, a practical rule is proposed for choosing a value of the body drag coefficient for use in performance estimates.
Anhydrobiosis in Embryos of the Brine Shrimp Artemia: Characterization of Metabolic Arrest During Reductions in Cell-Associated Water
Authors: Glasheen J. S. , Hand Steven C.
Published: April 2021

Upon entry into the state of anhydrobiosis, trehalose-based energy metabolism is arrested in Artemia embryos (cysts). We have compared changes in the levels of trehalose, glycogen, some glycolytic intermediates and adenylate nucleotides in hydrated embryos observed under conditions of aerobic development with those occurring after transfer to 5·0mol 1−1 NaCl. This treatment is known to reduce cell-associated water into a range previously referred to as the ametabolic domain. The trehalose utilization and glycogen synthesis that occur during development of fully hydrated cysts are both blocked during desiccation. Upon return to 0·25 mol 1−1 NaCl both processes are resumed. Analysis of glycolytic intermediates suggests that the inhibition is localized at the trehalase, hexokinase and phosphofructokinase reactions. ATP level remains constant during the 6-h period of dehydration, as does the adenylate energy charge. An additional dehydration experiment was performed in 5·0moll−1 NaCl containing 50mmoll−1 ammonium chloride (pH9·0). The resulting level of gaseous ammonia in the medium has been shown to maintain an alkaline intracellular pH (pHi) in the embryos. The metabolic response to dehydration under these conditions was very similar to the previous dehydration series. Thus, these results are taken as strong evidence that the metabolic suppression observed during dehydration does not require cellular acidification, in contrast to the pronounced inhibitory role of low pHi during entry of hydrated embryos into the quiescent state of anaerobic dormancy. The arrest of carbohydrate metabolism seen during anhydrobiosis indeed appears to be a strict function of embryo water content.
Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae: II. the Transapical Electrochemical Gradients
Authors: Moffett David F. , Koch Alan R.
Published: April 2021

The apical surface of the midgut of Manduca sexta larvae is composed of the apical membranes of columnar cells, in the form of microvilli, and the apical goblet of goblet cells. Considerable evidence has suggested that the apical electrogenic pump that is responsible for transepithelial K+ transport is located on the apical membrane of goblet cells. In the present study the transapical potentials and K+ chemical activity [(K+)] gradients of columnar and goblet cells of posterior midgut were examined in the short-circuited gut. In some experiments the recording site was localized by ionophoresis of NiCl2 followed immediately by fixation in rubeanic acid.

The (K+) of goblet cavities was substantially higher than that of the free solution on the gut luminal side (mean value of 94mmol 1-1 in standard bathing solution). The goblet cavity was electrically positive to the gut lumen (mean value of 40 mV in standard bathing solution). When the rate of pumping of K+ into the goblet cavity was decreased by hypoxia or decreased bathing solution [K+], the electrical potential gradient between cytoplasm and goblet cavity decreased while intracellular (K+) and goblet cavity (K+) were relatively stable. These studies provide evidence that a negatively charged goblet matrix is present in goblet cavities. Furthermore, they suggest that it is the voltage-sensitivity of the apical pump to the electrical component of the transapical electrochemical gradient, and not a concentration-dependence of the pump, that exercises the major role in determining the relationship between extracellular (K+) and net K+ transport by the isolated gut.