bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ventilatory Action of the Hypaxial Muscles of the Lizard Iguana Iguana: A FuncTion Of Slow Muscle
Authors: Carrier David R. 
Published: April 2021

ABSTRACT
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 (&lt;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

ABSTRACT
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

ABSTRACT
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 (&gt;1s, &gt;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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.