bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophysiology of the Mantle of Anodonta Cygnea
Authors: Coimbra J. , Machado J. , Fernandes P. L. , Ferreira H. G. , Ferreira K. G. 
Published: April 2021

ABSTRACT
When gassed with a CO2-containing mixture, under short-circuit conditions, the isolated outer mantle epithelium (OME) of Anodonta cygnea generated a current which exhibited cyclic variations throughout the year. The intracellular potential, under short-circuit conditions, had an average value of –31 ±0·5 mV (N =65). The potential was sensitive to changes in concentration of potassium and chloride on the haemolymph side of the preparation, but not on the shell side, and was insensitive to changes in sodium concentration on either side. When the preparation was gassed with pure oxygen the current fell by 85 ± 1% (N = 8). A similar fall in current (88 ± 2%, N = 8) was observed when the solution bathing the apical side of the epithelium was prepared without bicarbonate and gassed with 95% O2 + 5% CO2. If this same bathing solution was gassed with 100% oxygen, the current fell by 67 ± 2% (N= 8) at pH7·2 and by 92±4% (N =8) at pH4·5. The short-circuit current was inhibited by DIDS (0·5 mmol 1−1) and SITS (0·5 mmol 1−1) when these drugs were applied on the haemolymph side. The current was also inhibited by DNP (1 mmol 1−1), iodoacetamide (1 mmol 1−1) and diamox (1 mmol 1−1). Amiloride (1 mmol 1−1) blocked the current but only when applied on the haemolymph side. Ouabain (0-1 mmol 1−1) did not affect the current. The net fluxes of rubidium (used as a tracer for potassium), chloride and calcium, measured with 86Rb, 36C1 and 45Ca, respectively, were very small when compared with the short-circuit current. There was a small net flux of sodium (measured with 22Na) towards the haemolymph side. The net flux of bicarbonate (measured with [14C]bicarbonate) was equal to the short-circuit current and was inhibited by DIDS. The permeability of the preparation to calcium was an order of magnitude higher than the permeability to sodium, potassium or chloride. The intracellular concentrations of potassium and chloride measured with ion-sensitive microelectrodes were 26·5 ±1·1 (N =16) and 7·9 ±0·3 (N =30) mmol 1−1, respectively. When these concentrations were measured with chemical methods the values found were 29·4 ±0·4 (N =20) and 12·9 ±0·6 (N =20) mmol 1−1, respectively. The chemically measured intracellular concentration of sodium was 14·0 ± 0·4 (N = 20) mmoll−1. When bicarbonate was removed from the haemolymph side the intracellular concentration of chloride increased. The movements of calcium across the OME are by simple diffusion and the calcification of the shell probably results from the balance between a diffusion of calcium towards the extrapallial compartment when a favourable electrochemical gradient for this ion is created and the equally passive movement of calcium which results from the uphill transport of bicarbonate ions carried out by the epithelium. The balance between these two processes might undergo annual cyclic variations.
Nonspiking Stretch Receptors of the Crayfish Swimmeret Receive an Efference Copy of the Central Motor Pattern for the Swimmeret
Authors: Paul Dorothy H. 
Published: April 2021

ABSTRACT
In crayfish, the movement of each swimmeret is monitored by a pair of nonspiking stretch receptors (NSR) with central somata and dendrites that are embedded in an elastic strand at the base of the appendage. I provide evidence that the neuropile segments of these primary sensory neurones receive synaptic input from the hemiganglionic central pattern generator for the swimmeret.
In nonbursting isolated abdominal nerve cords of Pacifastacus leniusculus Dana, the membrane potentials of the NSRs (recorded in the neuropile) are stable; whenever the central pattern generator is active, they oscillate in phase with the motor output. Every perturbation of the central pattern generator’s activity is precisely reflected in analogous changes (in phase and/or amplitude) of the NSRs’ oscillations. This activity must arise via central, synaptic input to the NSRs, because it occurs when all ganglia except the sixth are deafferented.
Lucifer Yellow dye-fills show that the neurites of the NSRs are confined to the ipsilateral lateral neuropile, which is the region of the hemiganglion where swimmeret functions are integrated.
These results imply that during rhythmic beating of the swimmerets, the NSRs receive an efference copy of the motor output to the limb whose movements they monitor. In vivo, therefore, the incoming sensory signal must be subject to modulation (gating) by the limb’s central pattern generator.
Feedback from Motor Neurones to Pacemaker Neurones in Lobster Cardiac Ganglion Contributes to Regulation of Burst Frequency
Authors: Berlind A. 
Published: April 2021

ABSTRACT
The crustacean cardiac ganglion has traditionally been viewed as a two-layered system in which pacemaking is a function of the four small cells which trigger the five follower motor neurones via chemical and electrotonic synaptic excitation. The work reported here shows that there is strong feedback from motor neurones to small cells, by which endogenous burst-organizing potentials (driver potentials or DPs) and their hyperpolarizing afterpotentials contribute to regulation of bursting frequency. Isolated cardiac ganglia were placed in a two-chamber perfusion system which allowed independent treatment of small cells and motor neurones. When the motor neurones were silenced with tetrodotoxin (TTX), the small cells continued organizing bursts of activity which recurred at an average frequency 41 % higher than bursting by normal ganglia in saline. The average burst duration was not altered. Driver potentials were evoked in TTX-treated motor neurones by electrical stimulation, by ionic alteration of the medium, or by treatment with the cardioexcitor peptide proctolin. DPs which occurred synchronously with small-cell bursts prolonged and intensified the bursts (more spikes per burst). When DPs were evoked in motor neurones during the interburst interval, they triggered small-cell bursts even at very short intervals after a spontaneous burst had occurred. All small-cell bursts which were associated with motor neurone DPs were followed by interburst intervals of longer than normal duration. The decrease in instantaneous burst frequency (increase in total burst cycle duration) caused by motor neurone DPs whs similar in magnitude to the drop in burst frequency observed when the ganglion recovered normal activity after T1X washout.
Physiological Bases of Feeding Behaviour in Salamanders: Do Motor Patterns Vary With Prey Type?
Authors: Reilly S. M. , Lauder G. V. 
Published: April 2021

ABSTRACT
Muscle activity patterns (motor patterns) of the jaw musculature of all vertebrates studied to date (primarily fishes and amniotes) vary considerably when they feed on different types of prey. Previous data on buccal pressure patterns suggested that feeding in the aquatic salamander, Ambystoma mexicanum (Shaw), is highly stereotyped. This hypothesis was tested by quantifying the motor pattern used during feeding on two prey types: earthworms and guppies. Twenty-nine variables were measured from the activity pattern of six cranial muscles in the feeding mechanism of Ambystoma mexicanum. These variables included the area under the electromyogram of each muscle, relative muscle onset times, and the amplitudes and durations of muscle bursts. Univariate and multivariate statistical analyses demonstrate that the feeding motor pattern of Ambystoma mexicanum is stereotyped and does not change with prey type, in contrast to motor patterns of other vertebrates studied to date. Individual salamanders use significantly different motor patterns from one another during feeding, but do not alter their motor pattern during feeding on different prey.
Prey Processing in Haemulid Fishes: Patterns of Variation in Pharyngeal Jaw Muscle Activity
Authors: Wainwright Peter C. 
Published: April 2021

ABSTRACT
This study examines patterns of variation in 15 electromyographic (EMG) variables measured from recordings of pharyngeal jaw muscle activity during prey processing in four species of the perciform fish family Haemulidae. Two questions were of primary interest. (1) Are motor patterns conserved across the four species? (2) Do the fishes alter (modulate) muscle activity patterns when feeding on different prey types? The experimental design used allowed the partitioning of variance in EMG variables among species, among individuals within species, among days within individuals, among feedings within days, and among prey types. Only one variable exhibited a significant species effect, indicating that the four species used virtually the same motor pattern during prey processing. In response to three prey types differing in hardness, all four species demonstrated an ability to modulate several EMG variables that characterized the intensity of electrical activity. However, variables characterizing the relative timing of muscle activities were not influenced by prey type. A significant variance component was found among recording days and, together with the possibility of variation among experimental preparations, this raises questions about the extent of previously reported inter-individual variation in EMGs. These results support a growing data base on aquatic feeding in lower vertebrates which finds that: (1) motor patterns tend to be highly conserved among closely related taxa; (2) the ability to modulate motor patterns in response to different prey types appears to be a general property of teleost fish feeding mechanisms; and (3) variation in experimental EMG data is ubiquitous and, when unaccounted for, confounds comparisons among treatment groups.
Effects of Anoxia on Serotonin Metabolism in Crucian Carp Brain
Authors: Göran E. Nilsson 
Published: April 2021

ABSTRACT
In the brain, oxygen is required for both the synthesis and the degradation of monoamine transmitters, so monoaminergic systems can be expected to be strongly affected by anoxia. However, crucian carp (Carassius carassius L.) may survive anoxia for many days or even weeks. In the present study, crucian carp were exposed to anoxia for 22, 76, and 160 h at 8°C. All survived and were found to excrete ethanol at a constant rate. The brain concentrations of serotonin and its two main metabolites, 5-hydroxyindole-3-acetic acid (5-HIAA) and 5-hydroxytryptophol, were analysed after each experiment. In a preliminary experiment, it was found that the brain of the crucian carp contained about the same amount of serotonin and 5-HIAA as two species less tolerant to anoxia - the common carp and the rainbow trout. The levels of the serotonin metabolites decreased drastically (by 80–90%) during anoxia, whereas serotonin levels were only slightly reduced (by 15 % or less). These results suggest a complete or nearly complete stop in serotonin metabolism during anoxia.
Attached Magnets Impair Magnetic Field Discrimination by Honeybees
Authors: Walker Michael M. , Bitterman M. E. 
Published: April 2021

ABSTRACT
Evidence that honeybees respond to magnetic fields comes from both orientation (Lindauer & Martin, 1968, 1972; Towne & Gould, 1985) and conditioning experiments (Walker & Bitterman, 1985; Walker et al. 1988a). Perhaps because suitable behavioural methods have not yet been developed, the effects obtained are not very large. They are, however, reliable enough to permit evaluation of the ferromagnetic transduction hypothesis (Ising, 1945; Lowenstam, 1962; Gould et al. 1978; Kirschvink & Walker, 1985), to which the discovery of large numbers of single-domain particles of magnetite in the anterodorsal abdominal region of honeybees lends credence (Gould et al. 1978), and which alone among the various transduction hypotheses that have been proposed (Kirschvink & Gould, 1981; Kirschvink & Walker, 1985; Yorke, 1981; Kalmijn, 1974; Jungerman & Rosenblum, 1980; Leask, 1977; Korall & Martin, 1987) predicts that discrimination can be abolished by magnets attached in the vicinity of those particles (Jungerman & Rosenblum, 1980; Kirschvink & Walker, 1985). Free-flying honeybees were trained in two experiments to discriminate a local anomaly in the ambient magnetic field. Animals carrying small pieces of magnetized steel wire glued to the anterodorsal abdomen failed in the task, but untreated animals and control animals carrying small pieces of nonmagnetic wire succeeded. The results imply that the magnetite crystals in the anterodorsal abdomen play a critical role in magnetoreception by honeybees.
κ-Bungarotoxin Blocks Nicotinic Transmission at an Identified Invertebrate Central Synapse
Authors: Chiappinelli V. A. , Hue B. , Mony L. , Sattelle D. B. 
Published: April 2021

ABSTRACT
A comparison was made between the effects of κ-bungarotoxin and κ-bungarotoxin upon nicotinic cholinergic transmission at an identified synapse (the cereal afferent, giant interneurone 2 synapse) in the central nervous system of the cockroach (Periplaneta americana), κ-Bungarotoxin, a snake venom x-neurotoxin, completely blocked nicotinic unitary excitatory postsynaptic potentials (EPSPs) and evoked composite EPSPs when applied at a concentration of l·0×10−7mol l−1. No recovery was observed after a 2h wash in normal saline. κ-Bungarotoxin produced a decrease in acetylcholine-induced nicotinic responses which paralleled decreases in nicotinic synaptic potentials and currents, indicating that κ-bungarotoxin blocked postsynaptic nicotinic receptors. This blockade appeared to be specific as resting membrane potential, input resistance and the ability to elicit an action potential in response to direct stimulation of giant interneurone 2 were unchanged following prolonged toxin exposures. Samples of α-bungarotoxin which were free from κ-neurotoxin contamination were also found to be potent antagonists of cockroach neuronal nicotinic receptors. It is concluded that the cockroach receptor is the first reported example of a neuronal nicotinic receptor which is sensitive to blockade by both α-neurotoxins and α-neurotoxins.
No Relationship Between Progressive Muscle Hyperaemia and Temperature in Exercising Rats
Authors: Delp M. D. , Laughlin M. H. , Armstrong R. B. 
Published: April 2021

ABSTRACT
During prolonged submaximal exercise muscle blood flow has been shown to increase progressively in rats and miniature swine. This study was designed to test the hypothesis that the increases in muscle blood flow are associated with progressive elevations in body temperature in rats. Colonic temperature and muscle blood flow (determined using radioactive microspheres) were measured after 15, 30 and 45 min of exercise in rats exercising on a treadmill at 15 m min−1 on a 0·) incline. Total hindlimb muscle blood flow increased from 79 ± 8 ml min−1100 g−1 at 15 min to 95 ± 10 ml min−1100 g−1 at 30 min (P&lt; 0·05). The greatest increases in blood flow occurred in the deep extensor muscles of the hindlimb. For example, in the red portion of the gastrocnemius muscle, blood flow increased from 197 ± 15 ml min−1100 g−1 at 15 min to 285 ± 17 ml min−1100 g−1 at 30min (P&lt;0·05). Colonic temperature, however, remained stable at 38·5°C over this period. These data indicate that the progressive hyperaemia in muscle was unrelated to body temperature.
Span-Ratio Analysis Used to Estimate Effective Lift: Drag Ratio in the Double-Crested Cormorant Phalacrocorax Auritus From Field Observations
Authors: Pennycuick C. J. 
Published: April 2021

ABSTRACT
A method is described for measuring the effective lift: drag ratio of a bird in flapping flight from the bird’s span ratio; that is, the ratio of the wing span in the upstroke to that in the downstroke. The method depends on the assumptions that the circulation on the wing is constant, and that the lift varies in proportion to the span. With some simplifications, it can be applied in the field to birds that cruise in steady, continuous flapping flight. Double-crested cormorants, observed on foraging flights, flew at a mean airspeed of 14·7ms−1, with a span ratio of 0·70. The effective lift: drag ratio, taking account of mechanical components of power only, was estimated to be 14·8. A much lower estimate (8·96) was obtained from a power curve program (Pennycuick, 1989). The discrepancy could be due (at least partly) to bias in the observations, but it is also suggested that one or more of the default values, used in the program for calculating induced, profile and parasite power, may be in need of downward revision.
Blood Acid-Base Balance in the Lugworm Arenicola Marina Ventilating in Hypo-or Hyperoxic Sea Water
Authors: Toulmond André , Tchernigovtzeff Catherine 
Published: April 2021

ABSTRACT
The time course of variation in blood acid-base balance was examined in lugworms, Arenicola marina (L.), experimentally acclimated for up to 72 h in hypoxic (1 mmHg = 133-3 Pa), normoxic ) or hyperoxic sea water. In hyperoxic animals, a blood acidosis is entirely compensated 12 h after the beginning of the acclimation. In hypoxic animals, a blood alkalosis develops very quickly, persists and increases, reaching a maximum 72h after the beginning of the acclimation. In both cases, variation in blood acid-base balance is mainly of respiratory origin. These data are consistent with previous results showing that the lugworm hypoventilates in hyperoxic sea water and hyperventilates in hypoxic sea water.
Climbing Performance of Harris’ Hawks (Parabuteo Unicinctus) With Added Load: Implications for Muscle Mechanics and for Radiotracking
Authors: Pennycuick C. J. , Fuller M. R. , McALLISTER Lynne 
Published: April 2021

ABSTRACT
Two Harris’ hawks were trained to fly along horizontal and climbing flight paths, while carrying loads of various masses, to provide data for estimating available muscle power during short flights. The body mass of both hawks was about 920g, and they were able to carry loads up to 630 g in horizontal flight. The rate of climb decreased with increasing all-up mass, as also did the climbing power (product of weight and rate of climb). Various assumptions about the aerodynamic power in low-speed climbs led to estimates of the maximum power output of the flight muscles ranging from 41 to 46 W. This, in turn, would imply a stress during shortening of around 210 kPa. The effects of a radio package on a bird that is raising young should be considered in relation to the food load that the forager can normally carry, rather than in relation to its body mass.
Voltage-Independent Block of a Neuronal Nicotinic Acetylcholine Receptor by N-Methyl Lycaconitine
Authors: Sattelle David B. , Pinnock Robert D. , Lummis Sarah C. R. 
Published: April 2021

ABSTRACT
N-Methyl lycaconitine is the most effective low molecular weight antagonist reported for an insect neuronal nicotinic receptor. In the present study, the citrate salt of this neurotoxin from the plant Delphinium brownii was found to inhibit [3H]-a-bungarotoxin binding to nerve cord extracts of the cockroach Periplaneta americana with a K, of 1·4 × 10−9moll−1. At a concentration of 1·0×10−7moll−1, V-methyl lycaconitine completely blocked the response to ionophoretically applied acetylcholine recorded from the cell body membrane of the fast coxal depressor motor neurone (Df) in the desheathed metathoracic ganglion of the cockroach. The block was voltage-independent over the range of membrane potential –100 to –30 mV. The effectiveness of N-methyl lycaconitine on the nicotinic receptor, which is present in very high concentrations in the insect nervous system, suggests that this alkaloid is a natural plant protection agent.
Time Course of Failure and Resumption of Excitatory and Inhibitory Transmission in the Denervated Muscle Fibres of the Cockroach
Authors: Washio Hiroshi 
Published: April 2021

ABSTRACT
Functional changes in neuromuscular transmission following denervation of the coxal depressor muscle of the cockroach Periplaneta americana have been studied by intracellular recording. Miniature postsynaptic potentials, both excitatory (MEPSPs) and inhibitory (MIPSPs), disappeared by about 24 h following nerve section or crush when animals were maintained at 26°C. Generally this was accompanied by the disappearance of excitatory and inhibitory junctional potentials. When animals were kept at 15°C, the onset of failure was delayed markedly, and excitatory transmission ceased a few days before inhibitory transmission, as found previously. Excitatory transmission resumed before inhibitory transmission: in animals maintained at 26°C after nerve crush, MEPSPs reappeared at 11 days and MIPSPs at 28 days. The resumption of transmission was accompanied by the reappearance of junctional potentials. It appears likely that the differences between excitatory and inhibitory transmission, in the timing of failure and of resumption of potentials, are related to the sizes of the axons innervating the coxal muscle of the insect leg.
Seasonal Adjustment of Solar Heat Gain in A Desert Mammal By Altering Coat Properties Independently of Surface Coloration
Authors: Walsberg Glenn E. , Schmidt Catherine A. 
Published: April 2021

ABSTRACT
Physical theory predicts that animals with fur or feather coats can adjust solar heat gain independently of surface coloration or environmental factors by altering coat structure or hair optical properties. This hypothesis is tested by examining seasonal changes in the solar heat load transferred to the skin by the pelage of a desert-dwelling mammal, the rock squirrel (Spermophilus variegatus). Although coat colour remains constant, solar heat gain at low wind speeds is about 20% greater in winter coats than in summer coats. This change is in an apparently adaptive direction and is predicted to have a major effect on the animal’s heat balance in nature. The determinants of these alterations in solar heat gain are explored using an empirically validated biophysical model and are found to result from changes in hair optics and coat structure. These results suggest the existence of a previously unknown mode of long-term thermoregulation that allows adjustment of solar heat gain without affecting the animal’s external appearance.
Rainbow Trout Hypocalcin Stimulates Bone Resorption in Embryonic Mouse Calvaria in Vitro in A Pth-Like Fashion
Authors: Lafeber Floris P. J. G. , Herrmann-Erlee M. P. M. , Flik G. , Bonga S. E. Wendelaar 
Published: April 2021

ABSTRACT
Hypocalcin, the major hormone with hypocalcaemic action in fish, was isolated from trout corpuscles of Stannius (SCs). The bioactivity of hypocalcin was assessed in a parathyroid hormone (PTH) bioassay involving bone resorption in embryonic mouse calvaria. Calcium and phosphate release and lactate production were stimulated in a dose-dependent manner by hypocalcin. On a molar basis about equal amounts of hypocalcin and PTH were required to obtain similar effects in this assay. Hypocalcin did not stimulate cyclic AMP production either in mouse calvaria or in cultured osteoblasts. In this respect hypocalcin resembles shortened or N-terminus-modified PTH molecules that induce bone resorption without increasing cyclic AMP levels. Since hypocalcin and PTH have comparable bioactivity in this mammalian bioassay (as well as in fish bioassays), we tentatively suggest that both hormones are structurally similar and that both hormones may act via the same receptors. The two hormones show no resemblance to one another in primary structure, so we suggest that they have similarities in tertiary structure.