bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibitory Effect of L-Glutamate on the Neuropile Arborizations of Flight Motoneurones In locusts
Authors: Dubas F. 
Published: April 2021

ABSTRACT
In vertebrates, L-glutamate (glutamate) is a major excitatory neurotransmitter in the brain, acting on at least three separate receptors (Fagg, 1985). In insects, there is strong evidence that glutamate is the excitatory neurotransmitter at the neuromuscular synapse (Usherwood, 1981). Since some motoneurones make central synapses (Watson and Burrows, 1982; Burrows et al. 1989), it is probable that glutamate is also released centrally. Indeed, Bicker et al. (1988) found glutamate-like immunoreactivity in the central projections of known glutamatergic motoneurones and in interneurones in the locust, and Watson (1988) has shown it to be localized at central synapses. Furthermore, isolated insect neuronal somata respond to glutamate by activation of a chloride conductance (Usherwood et al. 1980), and ionophoretic applications of glutamate in certain areas of the neuropile cause motoneurones to depolarize and to spike (Sombati and Hoyle, 1984). In cultured embryonic cockroach brain neurones, Horseman et al. (1988) found both excitatory and inhibitory responses to glutamate. Wafford and Sattelle (1989) found only hyperpolarizing responses to glutamate on the fast coxal depressor motoneurone soma in situ, but they recorded depolarizing responses to kainate and quisqualate. These experiments indicate that receptors for glutamate are present on insect neuronal somata. However, since insect neuronal somata play no role in synaptic transmission and are generally not electrically excitable (Gwilliam and Burrows, 1980), the function of somal neurotransmitter receptors is unclear. To study the role of putative neurotransmitters in mediating or modulating normal synaptic inputs it is necessary to apply the substances to the neuropile where the synapses are and to record the effects there. It is also necessary to use an animal preparation where normal synaptic inputs can be recorded. In this study, the effects of topical pressure applications of glutamate were monitored by means of intracellular recordings, in the neuropile, from flight motoneurones (FMNs) during fictive flight behaviour. While this procedure does not ensure that only synaptic receptors are activated, it does enable one to activate synaptic receptors or study the effect that extrasynaptic receptors have on synaptic activity.
Ultrastructural Evidence for Gabaergic Input onto Cercal Afferents in the Locust (Locusta Migratoria)
Authors: Watson A. H. 
Published: April 2021

ABSTRACT
Ultrastructural studies have revealed input synapses on the central terminals of many sensory afferent neurones in both vertebrates (Maxwell et al. 1982; Ralston et al. 1984) and invertebrates (Altman et al. 1980; Watson and Pflüger, 1984). Indeed presynaptic modulation of sensory information flowing into the central nervous system appears to be a very widespread phenomenon. It may take the form of either inhibition (Eccles, 1964) or facilitation (Klein and Kandel, 1980), but it is the former that is most widely known from physiological experiments. Several mechanisms can bring about presynaptic inhibition. (1) Depolarization of an afferent terminal may reduce the amplitude of the action potential, leading to a reduction of the calcium influx and, consequently, of transmitter release (Miledi and Slater, 1966; Blagbum and Sattelle, 1987). (2) A conductance increase in the terminal may reduce the height of an action potential regardless of the direction of the potential change (Baxter and Bittner, 1981; Hue and Callec, 1983) and block spike conduction through small-diameter axonal branches (Atwood, 1976). The most widely suggested mechanism for this in both vertebrates (Nicholl and Alger, 1979) and invertebrates (Kennedy et al. 1980) is an increase in chloride conductance mediated by GABA. (3) The presynaptic calcium current may be reduced by the direct action of a neurotransmitter (Shapiro et al. 1980).
Dactyl Sensory Influences on Rock Lobster Locomotion: I. Intrasegmental and Intersegmental leg Reflexes During Standing and Walking
Authors: Müller U. W. E. , Clarac François 
Published: April 2021

ABSTRACT
Recordings of activity of the rock lobster dactyl sensory nerve during walking on a driven belt showed that the receptors of this nerve were mainly active during the power stroke when the leg was loaded. This nerve contains in particular the afferent fibres of the funnel canal organ (FCO) which are bimodal sensillae located in the cuticle of the dactylopodite of crustacean walking legs. In the standing animal, brief electrical stimulation of the dactyl nerve had an influence on the proximal leg muscles of the stimulated leg. The promotor and levator muscles were excited and the remotor and depressor muscles were inhibited. The opposite reaction was observed in adjacent ipsilateral legs in response to stimulation of a middle leg: the promotor and levator were inhibited and the remotor and depressor excited. The resulting movement by the stimulated leg was stereotyped and always consisted of a lift-off from the substratum and a slight shift in the forward direction. The response in the adjacent legs was not powerful enough to elicit a movement. In the walking animal the response of a single leg was dependent on the phase at which a stimulus arrived during the step cycle: during a power stroke (PS) this cycle was interrupted and a return stroke (RS) was initiated and continued. A stimulation at the normal switch from PS to RS had little effect, whereas a stimulation at late RS very often delayed the start of the following PS. Opposite reactions were given by the adjacent unstimulated legs: an RS was interrupted and a PS initiated or prolonged by the stimulus. A comparison between ipsilateral walking legs showed the existence of some obvious differences: legs 4 and 5 were able to reset the walking pattern of all the legs, whereas the more anterior leg 3 returned to its old trajectory after stimulation and thus had no influence on the other legs.
A directionally selective motion-detecting neurone in the brain of the locust: physiological and morphological characterization
Authors: Rind F. Claire 
Published: April 2021

ABSTRACT
The anatomy and physiology of a directionally selective motion-detecting (DSMD) neurone in the locust are described. The neurone was descending, with the cell body in the protocerebrum. The axon lay in the dorsolateral quadrant of the nerve cord and has been traced as far as the metathoracic ganglion. It arborized, ipsilateral to the cell body, from the dorsal intermediate tract (DIT) in the suboesophageal and thoracic ganglia. The neurone was binocular and sensitive to motion in the horizontal plane. It had a preferred direction backwards over the ipsilateral eye and forwards over the contralateral eye. Motion in the opposite direction suppressed the discharge, which had a frequency of 5–20 spikes s−1 at resting membrane potential. The neurone showed a clear directional response to stimuli with temporal frequencies between 0.7 and 44Hz, with a peak response at 11–22 Hz. It responded with spikes to light ON and light OFF. The neurone responded directionally to spatial frequencies of 0.28 cycles degree−1 (3.7° stripe period) to above 0.025 cycles degree−1 (40° stripe period). The maximum response was at around 0.035 cycles degree-1 (29° stripe period). No evidence of adaptation was seen in the responses of the neurone to real or apparent continuous horizontal motion in either the preferred or the null direction.
Production of thiosulphate during sulphide oxidation by mitochondria of the symbiont-containing bivalve Solemya reidi
Authors: O’Brien John , Vetter Russell D. 
Published: April 2021

ABSTRACT
Isolated mitochondria of the bivalve Solemya reidi Bernard oxidize sulphide and couple this oxidation to ADP phosphorylation. The products of mitochondrial sulphide oxidation were analyzed by HPLC using monobromobimane derivatization. Concurrent measurements of respiration were made using sulphideinsensitive oxygen electrodes. 5. reidi mitochondria oxidized sulphide exclusively to thiosulphate. The reaction occurred in two steps. One sulphide molecule was first oxidized to sulphite. A second molecule of sulphide was then added oxidatively to form the free product thiosulphate. This oxidation was obligately linked to mitochondrial electron transport and could be inhibited by the cytochrome c oxidase inhibitor hydrogen cyanide, or by low oxygen concentration. The site II inhibitor antimycin A did not inhibit thiosulphate production, indicating that sulphide oxidation is linked through only one ATP coupling site (site III). A calculation of the respiratory potential for ATP synthesis by fully intact mitochondria indicated that 2.0–3.25 ATP per sulphide may be synthesized using the proton potential generated by sulphide oxidation. This estimate far exceeds the published phosphorylation ratios for S. reidi (0.5–1.2 ATP per sulphide). This difference may be accounted for by partial uncoupling of phosphorylation from sulphide-based respiration. This hypothesis is supported by the observation that the respiratory control ratio of mitochondria respiring on sulphide is 41 % lower than that of mitochondria respiring on succinate. The respiratory control ratio is an index of the tightness of coupling of respiration to ADP phosphorylation. When the adenylate pool of a eukaryotic cell is mostly phosphorylated, respiration is very slow, owing to the maintenance of a high mitochondrial membrane potential. Uncoupling of oxidative phosphorylation from respiration would be an adaptive advantage to the animal in that it allows for continuous, rapid removal of the toxic molecule hydrogen sulphide.
Leucine uptake in brush-border membrane vesicles from the midgut of a lepidopteran larva, Philosamia cynthia
Authors: Sacchi V. Franca , Giordana Barbara , Campanini Flavia , Bonfanti Patrizia , Hanozet Giorgio M. 
Published: April 2021

ABSTRACT
A potassium- or sodium-activated cotransport of leucine occurs in brush-border membrane vesicles prepared from the midgut of larvae of Philosamia cynthia (Drury). The potassium chemical gradient can drive a twofold accumulation of leucine, which is greatly increased under experimental conditions that presumably provide an electrical potential difference (Δ ψ).
Kinetic parameters show that leucine transport is improved by these conditions and by a pH gradient similar to that occurring in vivo. However, these gradients cannot drive an intravesicular accumulation of leucine in the absence of potassium. The potassium-dependence of leucine uptake shows that 20% of the transport is potassium-independent and that K50 and Vmax are 30.3±3.2mmol l−l and 2584±148 pmol 7 s−1 mg−1 protein, respectively. The potassium-independent component of leucine transport is also carrier-mediated and some evidence is reported suggesting that the same carrier can cross the membrane as binary (carrier and leucine) or ternary (carrier, leucine and potassium) complexes, each having a different mobility.
Identification of directionally selective motion-detecting neurones in the locust lobula and their synaptic connections with an identified descending neurone
Authors: Rind F. Claire 
Published: April 2021

ABSTRACT
The anatomy and physiology of two directionally selective motion-detecting neurones in the locust are described. Both neurones had dendrites in the lobula, and projected to the ipsilateral protocerebrum. Their cell bodies were located on the posterio-dorsal junction of the optic lobe with the protocerebrum. The neurones were sensitive to horizontal motion of a visual stimulus. One neurone, LDSMD(F), had a preferred direction forwards over the ipsilateral eye, and a null direction backwards. The other neurone, LDSMD(B), had a preferred direction backwards over the ipsilateral eye.
Motion in the preferred direction caused EPSPs and spikes in the LDSMD neurones. Motion in the null direction resulted in IPSPs. Both excitatory and inhibitory inputs were derived from the ipsilateral eye. The DSMD neurones responded to velocities of movement up to and beyond 270°s−1. The response of both LDSMD neurones showed no evidence of adaptation during maintained apparent or real movement. There was a delay of 60–80 ms between a single step of apparent movement, in either the preferred or the null direction, and the start of the response. There was a monosynaptic, excitatory connection between the LDSMD(B) neurone and the protocerebral, descending DSMD neurone (PDDSMD) identified in the preceding paper (Rind, 1990). At resting membrane potential, a single presynaptic spike did not give rise to a spike in the postsynaptic neurone.
Analysis of calcium channel properties in cultured leech retzius cells by internal perfusion, voltage-clamp and single-channel recording
Authors: Bookman RJ , Liu Y 
Published: April 2021

ABSTRACT
The properties of voltage-dependent calcium channels have been measured in Retzius cells isolated from the central nervous system of the leech and maintained in tissue culture. Macroscopic divalent cation currents were isolated after blocking Na+ and K+ currents by bathing the cells with Na+-free solutions containing TEA+ and 4-AP, and internally perfusing them with Cs+ and TEA+. Depolarizing voltageclamp pulses activated inward currents that were larger for Sr2+ than for Ba2+ or Ca2+. The peak currents were observed at +15 mV for Ca2+ and Ba2+ and at +7 mV for Sr2+. Divalent cation currents were blocked by Cd2+ and Mn2+ but not by dihydropyridine blockers. The activation kinetics of Ba2+ currents was sigmoid. The inactivation was approximately 10% at the end of a 50ms depolarizing pulse. Decay of Sr2+ and Ca2+ currents was larger and showed two kinetic phases. Activation and inactivation of the calcium channels were not significantly influenced by the holding potential. Deactivation kinetics observed during tail currents consisted of two exponential components. At a closing voltage of −60 mV, the time constant was ≈200 ps for the fast component and 1.9 ms for the slow component. Both time constants of deactivation were voltage-dependent over the range from −80 to −20 mV, and increased at more depolarized closing voltages. Single-channel activity was recorded with cell-attached patches in solution containing 75 mmol l−1 Ba2+. Taken together, the results define the characteristics of a distinctive type of calcium channel in isolated Retzius cells.
Enhanced maximum frequency and force development of fish hearts following temperature acclimation
Authors: Bailey John R. , Driedzic William R. 
Published: April 2021

ABSTRACT
Inotropic and chronotropic responsiveness of yellow perch (Perca flavescens Mitchill) and smallmouth bass (Micropterus dolomieui Lacépède) hearts, following low temperature acclimation, was assessed with ventricle strips mounted for isometric force recording. Animals were acclimated to 20° and 5°C, and the performance of ventricle strips from both acclimation temperatures was monitored at 20° and 5 °C.
Ventricle strips from yellow perch acclimated to 20 °C showed an increase in resting tension when tested at 5 °C in the presence of high levels of extracellular calcium. An increase in resting tension did not occur in preparations from 5°C-acclimated fish tested at 5 °C. This suggests failure of intracellular calcium regulation which may be ameliorated following an acclimation period.
Ventricle strips were subjected to a force-frequency challenge over the range of 12–48 contractions min−1 at 1 mmol l−1 and 3 mmol l−1 extracellular calcium. Time to 50 % relaxation of ventricle strips tested at 5 °C was significantly lower for hearts from perch acclimated at 5 °C than from those acclimated at 20 °C. This was associated with an ability to maintain function at higher pacing rates. Similar trends were exhibited by hearts from smallmouth bass. As calcium extrusion is a prime determinant of relaxation time, these findings further suggest an enhancement in calcium handling capabilities following acclimation to low temperature.
Ventricle strips from both species acclimated to 20 °C and tested at 20 °C were able to maintain force development to the highest contraction frequencies. Hearts from specimens acclimated to 5 °C and tested at 20 °C showed a negative force–frequency relationship at low extracellular calcium levels. In yellow perch, this effect was minimized by an increase in calcium availability. This is considered to be a potential mechanism by which animals acclimated to low temperature could make transient excursions into warm water.
What causes edge fixation in walking flies?
Authors: Osorio D. , Srinivasan M. V. , Pinter R. B. 
Published: April 2021

ABSTRACT
The orientation of freely walking flies (female Lucilia cuprina) to lines and stripes in a circular arena is described. The following observations were made.
The flies walked straight towards a dark line using the frontal eye region, but a pale line on a dark background was only weakly attractive. In bright conditions flies walked in a curved line towards a black-white edge, the path being convex towards the dark side of the border. The curves indicated that the flies were heading for a point about 5–10° to the dark side of the edge. In dim conditions the edge of a dark region was not especially attractive and flies headed towards any point in the dark area.
These observations can be accounted for by assuming that the fly walks towards the darkest region in its visual field (scototaxis). In bright conditions the edges of a dark region become more attractive than its centre. This change could be explained if lateral inhibition creates a ‘Mach-band’ effect, making the edges appear darker than the centre. Thus, fixation behaviour in walking Lucilia females seems to be a simple taxis.
Energetics of ascent: insects on inclines
Authors: Full R. J. , Tullis A. 
Published: April 2021

ABSTRACT
Small animals use more metabolic energy per unit mass than large animals to run on a level surface. If the cost to lift one gram of mass one vertical meter is constant, small animals should require proportionally smaller increases in metabolic cost to run uphill. To test this hypothesis on very small animals possessing an exceptional capacity for ascending steep gradients, we measured the metabolic cost of locomotion in the cockroach, Periplaneta americana, running at angles of 0, 45 and 90° to the horizontal. Resting oxygen consumption was not affected by incline angle. Steady-state oxygen consumption increased linearly with speed at all angles of ascent. The minimum cost of locomotion (the slope of the versus speed function) increased with increasing angle of ascent. The minimum cost of locomotion on 45 and 90° inclines was two and three times greater, respectively, than the cost during horizontal running. The cockroach’s metabolic cost of ascent greatly exceeds that predicted from the hypothesis of a constant efficiency for vertical work. Variations in stride frequency and contact time cannot account for the high metabolic cost, because they were independent of incline angle. An increase in the metabolic cost or amount of force production may best explain the increase in metabolic cost. Small animals, such as P. americana, can easily scale vertical surfaces, but the energetic cost is considerable.
FMRFamide-like peptides in the locust: distribution, partial characterization and bioactivity
Authors: Robb S. , Evans P. D. 
Published: April 2021

ABSTRACT
The quantitative distribution of FMRFamide-like peptides in the nervous system and in their putative target sites in the locust Schistocerca gregaria is described using radioimmunoassay techniques. The nature of the immunoreactive material has been characterized by high-pressure liquid chromatography. At least six peaks of FMRFamide-like immunoreactivity can be separated in extracts of locust nervous tissue. The relative proportions of these peaks vary from tissue to tissue, suggesting a differential expression of FMRFamide-like peptides in different parts of the locust nervous system. The bioactivity of the endogenous FMRFamide-like peptides has been assessed on the extensor tibiae neuromuscular preparation and on the locust heart. The results suggest that FMRFamide-like peptides in the locust function both as circulating neurohormones and as locally released neuromodulators or neurotransmitters.
Arrhythmic breathing, apnea and non-steady-state oxygen uptake in hibernating little brown bats (Myotis Lucifugus)
Authors: Thomas Donald W. , Cloutier Danielle , Gagné Daniel 
Published: April 2021

ABSTRACT
We measured the breathing pattern and oxygen consumption of hibernating little brown bats (Myotis lucifugus) in open-and closed-circuit metabolic chambers. At 5 °C, hibernating M. lucifugus showed bouts of ventilation lasting on average 1.24 min and separated by periods of apnea lasting on average 47.59 min. The bats consumed 0.014 ml O2g−1 during ventilation bouts and 0.002 ml g−1 during apnea. The total O2 uptake was 0.016 ml g−1 for a complete ventilationapnea cycle, giving a of 0.020 ml g−1 h−1. This value is considerably lower than most values previously published for Myotis spp. and we suggest that studies using open-circuit systems that did not account for the intermittent nature of gas exchange during hibernation may be in error. Based on the dimensions of the respiratory tract, we estimate that 0.026 ml O2 g−1 h−1 and 0.009ml CO2g−1 h−1 could diffuse down the tract if the glottis was open. The low O2 uptake during apnea indicates that the glottis was closed. If CO2 retention acts to depress metabolism in hibernators, a closed glottis and arrhythmic breathing may be adaptive strategies in hibernation.
The influence of salinity acclimation on the temperature sensitivity of oxygen binding to the haemocyanin of the prosobranch Neptunea Antiqua
Authors: Brix O. L. E. , Condó Saverio G. , Colosimo Alfredo , Giardina Bruno 
Published: April 2021

ABSTRACT
The thermal sensitivity of oxygen binding has been studied at 10, 15, 20 and 25 °C in whole blood from specimens of Neptunea antiqua acclimated to ambient salinities of 24 and 35 ‰. The O2 affinity is strongly pH-dependent, demonstrating a large reversed Bohr shift below pH 8.0. The magnitude of the Bohr shift is not significantly influenced by temperature or ionic concentration. At 35 ‰, the blood O2-affinity is strongly influenced by temperature (ΔHapp≈ −58.6 kJ mol−1), while at 24 ‰ there is almost no temperature sensitivity (ΔHapp&lt;−18.8 kJ mol−1).
Aerodynamics of gliding flight in a harris’ hawk, Parabuteo Unicinctus
Authors: Tucker Vance A. , Heine Carlton 
Published: April 2021

ABSTRACT
A Harris’ hawk with a mass of 0.702 kg and a maximum wing span of 1.02 m glided freely in a wind tunnel at air speeds between 6.1 and 16.2 ms−1. The glide angle varied from 8.5° at the slowest speed to a minimum of 5° at speeds between 8.0 and 14.7 ms−1. The maximum ratio of lift to drag was 10.9 and the minimum sinking speed was 0.81 ms−1. Wing span decreased when either air speed or glide angle increased. Wing area was a parabolic function of wing span. Lift and profile drag coefficients of the wings fell in a polar area similar to that for a laggar falcon (Falco jugger) and a black vulture (Coragyps atratus). A single polar curve relating lift coefficients to minimum profile drag coefficients can predict the maximum gliding performance of all three birds when used with a mathematical model for gliding flight. The parasite drag values that have been used with the model are probably too high. Thus, the profile drag coefficients determined from the polar curve mentioned above are too low, and the predicted wing spans for gliding at maximum performance are too large. The predicted curve for maximum gliding performance is relatively unaffected. The maximum lift coefficient for the Harris’ hawk in the wind tunnel was 1.6. This value is probably less than the maximum attainable, since the hawk’s wings never appeared to stall. The best estimate of the minimum profile drag coefficient is 0.026 at a lift coefficient of 0.60.