bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short Communications: The Egg Case of the Oviparous Elasmobranch, Raja Erinacea, Does Osmoregulate
Authors: Evans David H. 
Published: April 2021

ABSTRACT
Like many other elasmobranchs (Wourms, 1977), the little skate, Raja erinacea, lays individual eggs covered with a specialized structure termed the egg case or ‘Mermaid’s Purse’. Collagen is the major component of the egg case, which is secreted by the shell gland in the anterior region of the oviduct (Wourms, 1977). Smith (1936) and Price & Daiber (1967) suggested that the egg case provided an osmotically isolated environment until the embryo was capable of urea retention and osmoregulation. However, Reed (1968a) showed that the encapsulated embryos of the skate, Raja binoculata, possess the enzymes of the Krebs omithine-urea cycle and are able to retain near-adult levels of both urea and trimethylamine oxide, even at very early stages (Reed, 1968b). The retention of urea seems to be secondary to a urea-impermeable embryonic membrane since Needham & Needham (1930) found that the egg cases of Syllium (= Scyliorhinus) canicula are permeable to urea, and this has been substantiated by recent work on the egg cases of the same species (Hornsey, 1978; Foulley & Melinger, 1980). Despite the ability to maintain high urea levels, it appears that the full complement of elasmobranch osmoregulatory mechanisms is not present in at least the early stages of encapsulated elasmobranch development since Libby (1959) found that R. eglanteria cannot survive in sea water if it is removed from the egg case before day 20 of the 64-day developmental period. In this species, at day 20 a mucous plug in the egg case is dissolved and sea water enters. This opening of the egg case to sea water during the later stages of development is also found in other oviparous elasmobranch species (Wourms, 1977).
Short Communications: The Association of Uropod Steering with Postural Movement of the Abdomen in Crayfish
Authors: Takahata Masakazu , Yoshino Masami , Hisada Mituhiko 
Published: April 2021

ABSTRACT
Decapod crustaceans have elaborate statocysts to detect changes in the body position. They utilize these organs to initiate and control various equilibrium reactions so that they can always maintain an upright posture. In macrurans, these reactions consist of asymmetrical movements of walking legs, swimmerets and uropods, as well as compensatory movements of the eyestalks and antennae. They have been previously described in terms of a simple input (i.e. the tilt angle)-and-output (i.e. the magnitude of the resultant reaction) relationship (e.g. Schöne, 1954). But do these equilibrium reactions occur whenever the animal tilts? We report here that one of them, the uropod steering movement, does not occur by itself and always occurs together with the abdominal movement which is unrelated to the equilibrium reaction. It is shown that this association of two independent movements is not mediated by any peripheral sense organ. Quantitative aspects of the uropod steering movement were described elsewhere (Yoshino, Takahata & Hisada, 1980).
Is the Position of the Femur-Tibia Joint Under Feedback Control in the Walking Stick Insect?: I. Force Measurements
Authors: Cruse H. 
Published: April 2021

ABSTRACT
It is known that a feedback system is involved in the position control of the femur-tibia joint of a fixed stick insect. Force measurements indicate that the control system also mediates negative feedback in the walking animal, the gain of the reflex loop and the half-time value of the reflex response being decreased. The biological significance of this effect is discussed. The results agree with similar experiments on man by other authors.
Symmetrically Organized Dorsal Unpaired Median (Dum) Neurones and Flash Control in the Male Firefly, Photuris Versicolor
Authors: Christensen Thomas A. , Carlson Albert D. 
Published: April 2021

ABSTRACT
Male fireflies of the species Photuris versicolor produce a species-typical triple-pulsed flash which is used as a courtship signal. The neural anatomy was examined to determine if this complex behaviour could be attributed to the organization within the central nervous system. The lantern is innervated primarily by the two most posterior abdominal ganglia. Bilateral roots from these ganglia form a symmetrical pattern of innervation to both sides of the lantern tissue. With minor exceptions, this pattern is similar to that described for other firefly species. The neural organization within the lantern ganglia was determined by back-filling the roots with cobalt or Lucifer Yellow CH, and then examining the ganglia in whole mount. Clusters of three or four large dorsal unpaired median (DUM) neurone somata, each sending bilateral processes out of the lantern roots, were found in both lantern ganglia. The DUM neurone axons bifurcate several times and ramify throughout the dorsal surface of the lantern tissue. More than one DUM neurone may innervate a particular region of photogenic tissue. When dye was back-filled into peripheral branches of the lantern roots that do not innervate photogenic tissue, no DUM somata were stained. Instead, the fibres that filled carried the dye anteriorly up the nerve cord through the ipsilateral connective. No fibres were observed to cross the gang-lion midline or exit from the contralateral root, nor were any fibres stained in the contralateral connectives. DUM neurones within the lantern ganglia have resting potentials between 30 and 45 mv and they exhibit multiple, as well as single-peaked spontaneous action potentials. The presence of multiple spikes might reflect the special bilateral morphology of these neurones. The lantern nervous system is organized in an arrangement capable of synchronizing the excitation of all the lantern photocytes. This neural organization could aid in the control of the complex flash pattern displayed by male Photuris versicolor fireflies.
Post-Metamorphic Development of the Frequency Selectivities and Sensitivities of the Peripheral Auditory System of the Bullfrog, Rana Catesbeiana
Authors: Shofner William P. , Feng Albert S. 
Published: April 2021

ABSTRACT
Acoustic response characteristics of single fibres were studied in the VIIIth cranial nerve of adult and early post-metamorphic bullfrogs (Rana catesbeiana). Based on the distribution of units’ best excitatory frequencies, three populations of auditory fibres were found in each group of frogs. The sharpness of the tuning curves and temporal firing patterns of primary fibres were similar in both adults and froglets. However, the distributions of the populations were different between the two groups, and it was found that froglets responded to higher frequencies than did adults. There were also differences in the distributions of thresholds of excitation between the froglets and adults. The excitation thresholds of low-frequency selective and high-frequency selective fibres tended to be higher in froglets. Low-frequency selective fibres in both groups of frogs exhibited two-tone inhibition, and the best inhibitory frequencies were higher in froglets than in adults. These results demonstrate that changes in the response properties of primary auditory fibres occur during the development of the bullfrog. These functional changes presumably reflect morphological changes which may occur in the peripheral auditory system.
Contribution of Compound Eyes and Ocelli to Steering of Locusts in Flight
Authors: Taylor Charles P. 
Published: April 2021

ABSTRACT
Locusts (Orthoptera, Acrididae) were induced to fly while tethered within a simulated horizon display. Rotation of the horizon about the animal’s long axis caused changes in the relative timing of the spikes of homologous flight muscles of either side. Changes in relative timing paralleled the pattern of head motions (Taylor, 1981) elicited by horizon rotation. Systematic changes in relative spike timing were also seen after the compound eyes were surgically disconnected and in response to forced head rotation. These results are discussed in relation to the functions of the compound eyes, the ocelli, and the cervical proprioceptive hairs for visual flight stabilization.
Respiration in the Land Crab, Gecarcinus Lateralis
Authors: Taylor A. C. , Davies P. Spencer 
Published: April 2021

ABSTRACT
The oxygen consumption, ventilation and blood gas transport were investigated in the tropical land crab Gecarcinus lateralis to determine the adaptations of the respiratory system for aerial respiration. The gills of Gecarcinus are reduced in size and specialized, in part, for salt and water uptake. The epibranchial space of the branchial chamber is very much enlarged and lined with what is probably a respiratory epithelium. There is a high ventilatory air-flow, produced by the beating of the scaphognathites, but the percentage extraction of oxygen is extremely low. This may be the result of ventilatory ‘shunts’, whereby a proportion of the air does not come into contact with the respiratory surfaces. The energetic cost of a high ventilation rate need not be high, because of the low inertial mass of air in comparison with water. A high oxygen tension gradient of 103 torr is maintained across the respiratory surfaces. This is interpreted as an adaptation to achieve a high oxygen diffusion rate through the reduced surface area of the gills. The blood has a relatively high oxygen capacity which is again thought to be an adaptation to compensate for the reduced gill surface area. Carbon dioxide tensions and content were high as in other terrestrial animals. Overall, the respiratory adaptations are thought to be related primarily to the reduction in the respiratory surface area which has evolved to deal with the problems of water conservation in these terrestrial animals.
Respiration in Exercising Fowl
Authors: Brackenbury J. H. , Avery P. , Gleeson M. 
Published: April 2021

ABSTRACT
Oxygen consumption, respiratory frequency, and the of expiratory and interclavicular air sac gases were continuously monitored in six female domestic fowl trained to exercise on a treadmill for 10 min periods at normal or elevated air temperatures. At normal temperatures (20 ± 2 °C) the cost of locomotion rose from 0·46 ml O2 kg-1 m-1 at 0−3 km h-1 to 0·77 ml O2 kg-1 m-1 at the maximum speed of 4·3 km h-1. At 32 ± 2°C, increased by as much as 20% compared to normal temperatures. Hyperventilation occurred at all speeds and at both normal and elevated temperatures. End-tidal and interclavicular increased in a parallel manner with speed, the latter remaining consistently 6−7 Torr less than the former both at rest and during exercise.
The Parameters and Properties of A Group of Electrically Coupled Neurones in the Central Nervous System of A Hydrozoan Jellyfish
Authors: Spencer A. N. 
Published: April 2021

ABSTRACT
Swimming of the jellyfish Polyorchis penicillatus is controlled by a network of large, electrically coupled, motor neurones in the inner nervering (Fig. 3). Recordings from pairs of neurones, even at widely separated positions, display essentially the same electrical activity (Fig. 1). Electrical coupling between neurones is via gap-junctions and is very strong, giving the network a space constant of approximately 7·1 mm (Figs. 2, 4, 5). The network acts as a low-pass filter progressively attenuating signals with frequencies greater than 1 Hz (Figs. 4, b). I/V experiments demonstrate that the neurones show rectifying properties since membrane resistance decreases noticeably with depolarizations greater than about 25 mV (Figs. 7, 8). A number of electrical constants of the network were measured or calculated: rm = 3·55 MΩ cm-1, Rm = 98 kΩ cm2, ri = 7 MΩ) cm-1, input = 2·5 MΩ, Cm = I·52µF cm-2. Stimulated action potentials are conducted in the network at approximately 112 cm s-1 while spontaneous action potentials have velocities up to 200 cm s-1. As an action potential propagates from its initiation site its duration decreases from about 30 ms to 8 ms when it reaches the opposite side of the margin. Epithelial impulses, which mediate crumpling, cause large i.p.s.p.s in the motor network that can inhibit swimming for several seconds.
Acid-Base and Electrolyte Status in Carp (Cyprinus Carpio) Exposed to Low Environmental pH
Authors: Ultsch G. R. , Ott M. E. , Heisler N. 
Published: April 2021

ABSTRACT
Carp (Cyprinus carpio) were exposed to environmental water pH (pHw) step changes from 7·4 to 5·1, 5·1 to 4·0 and 4·0 to 3·5. pH, , and lactate in dorsal aortic blood, [Na+], [K+] and [Cl−] in dorsal aortic plasma, base loss, and ammonia excretion were determined as a function of time after each pHw step change.
At pHw 5·1 the measured blood acid-base and electrolyte parameters remained essentially unchanged; the base loss, however, was increased by a factor of 2. When pHw was lowered to 4·0 an additional severe increase in the ‘net base loss’, expressed as the difference between base loss and ammonia excretion, resulted in progressive reduction of arterial pH and [HCO3−]. The electrolyte status was also severely disturbed by progressively falling plasma [Na+] and [Cl−], which is attributed to failure of the active H+/Na+ and HCO3− /C1− exchange mechanisms in the gills.
At pHw 4·0 the acid-exposure syndrome is characterized by acid-base and electrolyte disturbances apparently not related to hypoxia. However, at pHw 3·5, tissue hypoxia, due to disturbances of gill gas exchange and to Bohr and Root effects, appears to be an additional important factor aggravating the disturbances of acid-base and electrolyte status.
Physiology and Energetics of Pre-Flight Warm-Up in the Eastern Tent Caterpillar Moth Malacosoma Americanum
Authors: Casey Timothy M. , Hegel Jeri R. , Buser Charlene S. 
Published: April 2021

ABSTRACT
Thoracic temperature (Tth) during pre-flight warm-up increased linearly with time at all air temperatures (Ta). The rate of pre-flight warm-up increased from 3·3 to 12·7 °C/min between Ta’s of 14 and 28 °C. Head temperature remained within a few °C of Tth during warm-up, while ventral abdominal temperature remained within a few °C of Ta. Pulsation rate of the dorsal vessel in the thorax increased directly with thoracic temperature. Wing-stroke frequency (n) varied from 15 s−1 at Tth = 16 °C to 58 s−1 at Tth= 40 °C and was similar at any given Tth between Ta’s of 14 and 28 °C. While stroke amplitude varied significantly between warmup and tethered flight, stroke frequency was similar for the two activities in the same Tth range. Calculated rates of heat production were tightly coupled to Tth and did not vary with Ta. The change in heat production during warm-up was dependent entirely on changes in frequency of muscle contraction. Stroke work was constant at 0·68 mW between Tth of 15 and 40 °C.
Morphology of the Giant Dopamine-Containing Neurone, R.Pe.D.1, in Lymnaea Stagnalis Revealed by Lucifer Yellow CH
Authors: Haydon P. G. , Winlow W. 
Published: April 2021

ABSTRACT
The morphology of the giant dopamine-containing neurone of Lymnaea stagnalis, R.Pe.D.1, was studied by injection of Lucifer Yellow CH and by electrophysiological, techniques.
R.Pe.D.1 was found to project to the periphery via the nerve trunks of the right parietal and visceral ganglia. Neurites bearing varicosities were found in each ganglion through which the axon passed. The neurites consistently arose from the same regions of the axon and the neuritic fields were similar in each preparation.
Temperature Effects On Neuromuscular Transmission (Opener Muscle of Crayfish, Astacus Leptodactylus)
Authors: Fischer Ludwig , Florey Ernst 
Published: April 2021

ABSTRACT
In experiments on the opener muscle of the third walking legs of crayfish (Astacus leptodactylus) it was found that the mechanical tension developed in response to repetitive stimulation of the single motor axon increases over the entire temperature range from 30 down to 0 °C. In contrast to this, the tension elicited by depolarizing single muscle fibres decreases with decreasing temperature ; the threshold for excitation-contraction coupling is not significantly altered.
With decreasing temperature the resting potential decreases (up to 2 mV/°C) but the amplitude and decay time of the e.p.s.p.’s increase. The time constant, τ, of e.p.s.p. decay has a Q10 of less than – 2 in the range above 15 °C but reaches a value of –7 between 10 and 0 °C. This pattern of temperature dependence is fully accounted for by a parallel change of membrane resistance and its reciprocal, the membrane conductance. The corresponding activation energies computed from τ-values approximate 3 kcal/mol at high temperature and 46 kcal/mol in the low temperature range.
The combined effects of a lowered resting potential, an increased amplitude, and especially an increased decay time of e.p.s.p.s result in a drastic enhancement of the depolarization reached during summation of e.p.s.p.s as the temperature is decreased. These effects overcompensate the declining effectiveness of excitation-contraction coupling so that the entire process of neuromuscular transmission becomes more and more effective as the temperature declines. In order to reach the same tension lower frequencies of nerve stimulation are needed at lower temperatures.
Absorption of Fluid by the Midgut of Rhodnius
Authors: Farmer J. , Maddrell S. H. P. , Spring J. H. 
Published: April 2021

ABSTRACT
Isolated midguts of 5th-instar Rhodnius prolixus will transport fluid from the lumen that is close to iso-osmotic with the luminal contents. The transported fluid contains sodium and chloride ions as its major constituents. Fluid transport can be attributed to active transport of sodium ions from the lumen. The haemolymph side of the epithelium, towards which transport is directed, is at a potential positive with respect to the lumen; this potential difference is greatly increased if the lumen contains only impermeant anions, and the rate of fluid transport is strongly dependent on the concentration of sodium ions in the luminal fluid. The rate of fluid transport is increased approximately six times by treatment with 5-hydroxytryptamine (2 × 10−7 M) or cyclic AMP (2 × 10−3 M). The transepithelial potential is increased by such treatment but the major effects are on the short-circuit current, which increases by about five times, and on the electrical resistance of the epithelium, which falls to about a quarter of its earlier value.
Light and High Potassium Cause Similar Phase Shifts of the Aplysia Eye Circadian Rhythm
Authors: Jacklet Jon W. , Lotshaw David P. 
Published: April 2021

ABSTRACT
The eye of Aplysia, with its circadian rhythm of spontaneous optic nerve impulses (Jacklet, 1969a), is a model system for studying the cellular mechanisms of circadian rhythms generated by nervous tissue (Jacklet, 1981). An approach to determine the mechanisms of rhythms is to apply pulses of experimental agents and then observe the shifts in phase of subsequent cycles of the rhythm. If the size and direction of the phaseshifts are dependent upon the phase of the cycle when the pulse was given (phasedependent phase shifts), it is evidence that the rhythm timing mechanism has been perturbed. The specific cellular process acted on is then believed to be important in the cellular clock mechanism. Some agents cause phase-dependent phase shifts and the shifts are plotted in phase response curves (PRCs). It is useful to compare the PRCs produced by different agents in order to identify similar or dissimilar actions on the cellular clock (Jacklet, 1978).
The Exoskeleton and Insect Proprioception
Authors: Zill Sasha N. , Moran David T. , Varela Francisco G. 
Published: April 2021

ABSTRACT
Mechanical stimulation of individual tibial campaniform sensilla produces specific reflex effects upon motoneurones to leg muscles. The reflex effects of a campaniform sensillum depend upon the orientation of its cuticular cap. The proximal sensilla, oriented perpendicular to the long axis of the tibia, excite slow motoneurones to the extensor tibiae and extensor trochanteris muscles and inhibit slow motoneurones to the flexor tibiae and flexor trochanteris muscles. The distal sensilla, oriented parallel to the tibia, exhibit reflexes of opposite sign, inhibiting the extensors and exciting the flexors. These reflexes constitute a negative feedback system. Individual sensilla specifically excite motoneurones which innervate muscles whose resultant tensions decrease the firing of those sensilla. It is postulated that individual campaniform sensilla can detect loading of the leg in various postures and can excite appropriate motoneurones in compensation. These receptors can also detect strains caused by large, resisted contractions of the antagonist muscles and inhibit the corresponding motoneurones.
Synaptic Actions of Oesophageal Proprioceptors in the Mollusc, Philine
Authors: Sigger J. N. , Dorsett D. A. 
Published: April 2021

ABSTRACT
The buccal ganglia of Philine each contain a group of mechanoreceptors, consisting of 1 large and 3 small cells, with receptive fields in the oesophagus. Synaptic contacts occur between the receptors; the large cell providing an EIPSP input to its contralateral partner and to the two groups of smaller receptors. The small receptors make weak excitatory contacts with both the large receptors.
The sensory cells synapse with other buccal motoneurones and interneurones, some of which show periodic activity associated with the feeding movements.
Protraction phase neurones are divisible into two groups, one of which receives EPSPs from the receptors, while the other group receives IPSPs. Retraction phase neurones receive a biphasic EIPSP.
The receptors provide excitatory synaptic input to a pair of interneurons which ‘gate’ the feeding cycle. A third class of neurones which are not rhythmically active during feeding receive a predominantly inhibitory EIPSP.
Membrane Structure in Mammalian Astrocytes: A Review of Freeze-Fracture Studies on Adult, Developing, Reactive and Cultured Astrocytes
Authors: Landis Dennis M. D. , Reese Thomas S. 
Published: April 2021

ABSTRACT
The application of freeze-fracture techniques to studies of brain structure has led to the recognition of two unsuspected specializations of membrane structure, each distributed in a specific pattern across the surface of astrocytes. ‘Assemblies’ (aggregates of uniform, small particles packed in orthogonal array into rectangular or square aggregates) are found to characterize astrocytic plasma membranes apposed to blood vessels or to the cerebrospinal fluid at the surface of the brain. These particle aggregates are much less densely packed in astrocytic processes in brain parenchyma. Assemblies are not fixation artifacts, have been shown to extend to the true outer surface of the membrane, are remarkably labile in the setting of anoxia, and are at least in part protein. The function of assemblies is unknown, but their positioning suggests that they may have a role in the transport of some material into or out of the blood and cerebrospinal fluid compartments. A second specialization of intramembrane particle distribution, the polygonal particle junction, links astrocytic processes at the surface of the brain, and also links proximal, large caliber astrocytic processes in brain parenchyma. The function of this membrane specialization also is unknown, but it may subserve a mechanical role.