bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foetal-Maternal Blood Respiratory Properties of an Ovoviviparous Snake the Cottonmouth, Agkistrodon piscivorus
Authors: Birchard Geoffrey F. , Black Craig P. , Schuett Gordon W. , Black Virginia 
Published: April 2021

ABSTRACT
The respiratory properties of maternal, foetal and juvenile whole blood were studied in the ovoviviparous snake, Agkistrodon piscivorus. Haematocrit, haemoglobin concentration, O2 capacity, Bohr effect and Hill coefficients were not significantly different in foetal and maternal blood and were similar to values previously reported from snakes. A significant difference in foetal-maternal blood P50 (foetal 19·5, maternal 48·8) was found. Nucleoside triphosphate (NTP) levels were lower in foetal than in maternal and juvenile snakes. The foetal-maternal difference in P50 and NTP levels disappeared soon after birth (juvenile P50 45·5). Starch gel electrophoresis revealed no difference in foetal and maternal haemoglobins. We suggest that the foetal-maternal shift in blood oxygen affinity is modulated directly and/or indirectly by NTP levels.
The Transition to Air Breathing in Fishes: III. Effects of Body Size and Aquatic Hypoxia on the Aerial Gas Exchange of the Swamp Eel Synbranchus Marmoratus
Authors: Graham Jeffrey B. , Baird Troy A. 
Published: April 2021

ABSTRACT
Synbranchus marmoratus (Bloch) breathes air during terrestrial excursions and while dwelling in hypoxic water and utilizes its gills and adjacent buccopharyngeal epithelium as an air-breathing organ (ABO). This fish uses gills and skin for aquatic respiration in normoxic (air-saturated) water but when exposed to progressive aquatic hypoxia it becomes a metabolic O2 conformer until facultative air breathing is initiated. The threshold (aquatic O2 tension or partial pressure in mmHg) that elicits air breathing in S. marmoratus is higher in larger fish. However, neither air-breathing threshold nor the blood haemoglobin (Hb) concentration of this species were changed following hypoxia acclimation. In hypoxic water S. marmoratus supplies all of its metabolic O2 requirement through air breathing. ABO volume scales with body weight raised to the power of 0 ·737 and the amount of O2 that is removed from each air breath depends upon the length of time it is held in the ABO. Ambient directly affects the air-breath duration of this fish, but the effect is smaller than in other species. Also, average air-breath duration (15·7 min at mmHg) and the average inter-air-breath interval (15 1 min) of 5. marmoratus are both longer than those of other air-breathing fishes. Although the gills of 5. marmoratus are involved in aerial O2 uptake, expelled air-breath CO2 levels are not high and always closely correspond to ambient , indicating that virtually no respiratory CO2 is released to air by this fish. CO2 extrusion therefore must occur aquatically either continuously across another exchange surface or intermittently across the gills during intervals between air breaths. This study with S. marmoratus from Panama reveals physiological differences between this population and populations in South America. The greater Hb content of South American S. marmoratus may be the result of different environmental selection pressures.
The Effects of Reducing Gill Area on the Capacity to Regulate Oxygen Uptake and on Metabolic Scope in a Cephalopod
Authors: Wells M. J. , Wells J. 
Published: April 2021

ABSTRACT
Octopus vulgaris is able to maintain its oxygen uptake at a steady level down to a of below 80 mmHg. This capacity is scarcely affected by surgical reduction of the gill area to between 30 and 50%, a finding which confirms previous work suggesting that regulation is achieved by increasing the affinity of the haemocyanin rather than by circulatory adjustments. The same reductions in gill area seriously reduce the already very limited metabolic scope of Octopus. Experiments in an exercise wheel show that this is in the region of 115 ml kg-1 h-1 (against an SMR of 42 for a 1-kg animal at 21 C) in the intact Octopus; reduction of the gill area to 30–50% approximately halves this figure. Animals with their gills reduced will run in the wheel until they have accumulated an oxygen debt in the region of 22ml kg-1, and then stop; recovery is slower than in intact animals.
Acclimation of the Euryhaline Toad Bufo Viridis to Hyperosmotic Solution (NaCl, Urea and Mannitol)
Authors: Katz U. , Degani G. , Gabbay S. 
Published: April 2021

ABSTRACT
Bufo viridis were acclimated to hyperosmotic solutions of NaCl, urea or mannitol. The toads could not be acclimated to mannitol solutions of osmotic strength higher than 300 mosmol kg-1 H2O, but could be acclimated easily to NaCl and urea higher than 500 mosmol kg-1 H2O. Water uptake diminished under mannitol acclimation while the apparent osmotic permeability under NaCl and urea acclimation increased. Urea and sodium influx across the isolated skin changed inversely upon hyperosmotic acclimation, but they did not seem to depend on one another. The adaptational advantages of the observed changes are discussed.
A Particle Velocity Microphone for the Song of Small Insects and Other Acoustic Measurements
Authors: Bennet-Clark H. C. 
Published: April 2021

ABSTRACT
Conventional particle velocity microphones (see Olson, 1957) are not readily available, are expensive, fragile and large, so they are not commonly used in biological research, though their use in one situation where the source is highly reactive, the recording of Drosophila song, is now standard practice. Here, the particle velocity produced by the fly is far louder than the sound pressure, so high quality recordings can be made with minimal sound insulation (see Bennet-Clark, 1971; Bennet-Clark, Leroy & Tsacas, 1980). The microphones can also be used to localize sources of echoes and to measure other reactive conditions. The present design was developed as an alternative to the fragile aluminum-ribbon microphones used previously (Bennet-Clark, 1973) and has the advantages of low cost, small size, robustness and a broad frequency response.
Rhythmic and Bilaterally Coordinated Motor Activity in the Isolated Brain of Pleurobranchaea
Authors: London J. A. , Gillette R. 
Published: April 2021

ABSTRACT
Rhythmic ingestive behaviour in the predatory marine snail Pleurobranchaea is characterized by cycles of protraction and retraction of the buccal mass, during which food material is taken into the buccal cavity and swallowed (Davis & Mpitsos, 1971). Fictive feeding is demonstrable in the isolated nervous system; the rhythmic motor programme appropriate to feeding behaviour can occur spontaneously or can be elicited by stimulation of different populations of ‘command’ neurones (Davis et al. 1975; Gillette & Davis, 1977; Croll & Davis, 1981; Gillette & Gillette, 1983). Oscillatory motor output is most striking in the isolated buccal ganglion; however, cyclic activity has been recorded in the brain (the cerebropleural ganglion) when it was isolated from the buccal ganglion by cutting the cerebrobuccal connectives (CBCs) (Davis, Siegler & Mpitsos, 1973). Such cyclic activity was recorded in the nerves of the brain while the CBC was stimulated by repetitive electrical shocks. These and other results were interpreted as indicating that oscillators existed both in the brain and the buccal ganglion. Interneurones were identified in both the brain and buccal ganglion which appeared to coordinate the oscillators via axons in the CBCs (Davis et al. 1973; Gillette & Davis, 1977; Gillette, Kovac & Davis, 1978, 1982).
Excitatory Effects of Dopamine on the Cardiac Ganglia of the Crabs Portunus Sanguinolentus and Podophthalmus Vigil
Authors: Miller Mark W. , Benson Jack A. , Berlind Allan 
Published: April 2021

ABSTRACT
Dopamine, a cardioexcitor in decapod crustaceans, increased the frequency and/or duration of bursts of action potentials in the semi-isolated cardiac ganglia of two species of crabs. The number of motoneurone action potentials in each burst was increased, which in the intact heart would increase the force and amplitude of heart contraction. The effects were concentration-dependent, with a threshold concentration of 10−8M or lower when dopamine was applied by continuous perfusion. At 5 × 10−6M, dopamine increased burst frequency by 200%. The main site of dopamine action was the group of four posterior small interneurones which normally function as the pacemaker for the cardiac ganglion system. Effects on the five large motoneurones occurred at higher concentrations. This regional difference in sensitivity was demonstrated by selective applications of dopamine to different parts of the cardiac ganglion and by the use of preparations in which the two ends of the ganglion had been functionally separated by a ligature around the ganglionic trunk. In the small neurones, dopamine was found to stimulate the slow tetrodotoxin-resistant regenerative depolarizations known as driver potentials. The effects on driver potential frequency and train duration were concentration dependent. In one of the two species of crabs, in which electrotonic connections between small and large neurones are strong, large neurone driver potentials were indirectly induced by dopamine. In the tetrodotoxin-treated large motoneurones, dopamine, at a concentration about ten-fold higher than needed to activate the small neurones, decreased the threshold for current-induced driver potentials, and slightly reduced membrane resistance. We suggest that the excitatory action of dopamine on the untreated cardiac ganglion can in large part be accounted for by its action on driver potential production in the small neurones.
Effects of Perfusion Pressure on the Isolated Heart of the Lobster, Panulirus Japonicus
Authors: Kuramoto Taketeru , Ebara Arinobu 
Published: April 2021

ABSTRACT
Systolic contractions of the isolated heart were usually composed of a first and second systolic contraction (FSC and SSC) which corresponded to the first and second large potentials (FLP and SLP), respectively, recorded in the cardiac muscle cells and represented excitatory junction potentials produced by impulse bursts of the large cells of the cardiac ganglion. Under constant pressure, the magnitudes of the FSC and the SSC appeared to change according to the amplitudes and durations of the FLP and the SLP. Further, the total amplitude of systole was often affected by the time of occurrence of the SSC (or the SLP). Internal perfusion pressure and heart tonus were linearly related over a considerable range. With an increase in heart tonus (0-30mg), the magnitude of the FSC was enhanced markedly in the absence of equivalent increases in the amplitude and duration of the FLP. The elevation of heart tonus was also related to an increase in beat frequency. The SSC decreased in magnitude and disappeared when the beat frequency exceeded approx. 1 Hz under high perfusion pressure. Further, the abolition of the SSC resulted in a steeper slope in the curve relating beat frequency to tonus. The SSC was absent during the decline of beating caused by rapid reduction of the pressure. The SSC was abolished by transverse cuts of the ganglionic trunk between the 4th and 5th large cells or between the 5th large and the 6th small cells, but the SSC often remained after the trunk was severed at the region between the 6th and 7th small cells. After severing the trunk, the heart still had the ability to respond to pressure as detected by a change of the beat frequency. Spontaneous slow contractions of the cardioarterial valves were often observed.
Reduced aerobic capacity and locomotory endurance in thyroid-deficient lizards
Authors: John-Alder H. B. 
Published: April 2021

ABSTRACT
This study was undertaken to examine the effects of thyroid hormonal deficiency on (1) standard (SMR) and maximal (max) rates of O2 consumption, (2) tissue glycolytic and oxidative capacities and (3) submaximal locomotory endurance in a lizard (Dipsosaurus dorsalis). Surgical thyroidectomy induced hypothyroidism in all animals as determined by levels of plasma thyroxine. Hypothyroid lizards had lower levels of SMR (−48 %), max (−16 %) and citrate synthase activity in liver, heart and skeletal muscle compared to controls. There was a correlated decrease in locomotory endurance in thyroid-deficient animals. Pyruvate kinase activity (an index of glycolytic capacity) in all tissues, and myofibrillar ATPase activity (an index of contractile velocity) in white iliofibularis muscle, showed no significant changes in thyroid-deficient animals. Thyroid hormones appear to be important in ultimately establishing an animal’s capacity for locomotory endurance. These findings suggest a new selective context for understanding the evolution of thyroid function.
On the Visual System of Nautilus Pompilius
Authors: Muntz W. R. A. , Raj U. 
Published: April 2021

ABSTRACT
The anatomy of the eye of Nautilus pompilius Linnaeus was studied, using light and electron microscopy. The outer and inner surfaces of the iris were found to be lined with columnar epithelium bearing microvilli, except for the groove running ventrally from the pupil over the outer surface of the iris, where the epithelial cells bear cilia. Many mucus cells are also present.
The epithelium of the inner surface of the iris merges smoothly with the retina. There is no significant variation in receptor packing or rhabdome length between different parts of the retina. Screening pigment is present, but shows no photomechanical movements in response to light. Immediately beneath the retina the nerves are collected into well-organized bundles, which run in a direction suggesting that they may form an optic chiasma analogous to that found in other cephalopods.
Visual acuity was also determined, using the optomotor response. The minimum separable angle was found to lie between 11·25 and 5·5°. This agrees well with the value expected on the basis of the gross dimensions of the eye and pupil, and also with expectation based on photographing a visual test chart with a scale model of the eye. It is, however, considerably worse than would be expected from the dimensions of the receptor mosaic.
Potentials Associated With the Blood-Brain Barrier of an Insect: Recordings from Identified Neuroglia
Authors: Schofield P. K. , Swales L. S. , Treherne J. E. 
Published: April 2021

ABSTRACT
The blood-brain barrier of the insect nervous system is thought to be formed by the neuroglia. It is associated with a positive interstitial potential relative to the bathing medium (‘sheath’ potential), and with positive changes in potential that can be induced by raising the potassium level in the bathing medium. In central nervous connectives of the cockroach, Periplaneta americana, these potential differences (p.d.s) were measured just below the perineurium at the same magnitude as comparable p.d.s recorded deeper, indicating that they are produced by the perineurium. The interstitial p.d. apparently results from the presence of a paracellular resistance, and from the generation of less electromotive force (e.m.f.) by the basolateral membrane than by the apical (adglial). Recordings from cells identified by injection of peroxidase showed that the initial change in interstitial p.d. induced by high K was accompanied by: a depolarization of greater magnitude across the basolateral membrane, a small depolarization of the apical membrane, and no depolarization of sub-perineurial glial cells or axons. It therefore appears that the depolarization of the basolateral membrane by high K gives rise, by electrical coupling, to the shift in interstitial p.d. and the depolarization of the apical membrane. There was then a gradual depolarization of all membranes, consistent with a leak of K into the sub-perineurial interstitial system, and where the depolarization of the basolateral membrane would be produced by coupling to the apical. If the perineurium contains an intercellular resistance, then it must restrict diffusion of water-soluble substances.
Localization of the Blood-Brain Barrier of an Insect: Electrical Model and Analysis
Authors: Schofield P. K. , Treherne J. E. 
Published: April 2021

ABSTRACT
The perineurium was found to form the principal barrier to diffusion across the blood-brain barrier system of the cockroach, Periplaneta americana, since the resistance across this layer was much greater than that across the underlying neuroglia. An equivalent electrical circuit of the perineurium was then used to analyse recordings made in apparent perineurial cells and the interstitial system. Trans-perineurial resistance was at least 900 Ω cm2, while the ratio between basolateral and apical membrane resistances was 11:1, indicating that the apical membrane had an area much greater than that of the basolateral membrane. Raising the potassium concentration in the saline produced changes in potential difference (p.d.) and resistance that were interpreted as due to the effect of potassium upon the basolateral membrane. Analysis indicated that the resting electromotive force (e.m.f.) generated by the basolateral membrane was less than that generated by the apical, although the K level in the saline was near that considered to be in the interstitial system. The analysis also yielded a value of 9 for the ratio of shunt resistance to apical resistance. Most changes in recorded values following the K elevation could be simulated by use of the estimated parameters, and an estimation of a change in interstitial K level. From these results, the shunt can be calculated to be an important contributor to the resistance across the perineurium, having a resistance about 0·9 times that of the transcellular resistance.
Quantitative Analysis Of Cellular and Paracellular Effects Involved in Disruption of the Blood-Brain Barrier of an Insect by Hypertonic Urea
Authors: Schofield P. K. , Swales L. S. , Treherne J. E. 
Published: April 2021

ABSTRACT
Brief exposure of central nervous connectives of the cockroach, Periplaneta americana, to 3 M-urea, a treatment known to increase the leak of cations across the blood-brain barrier system, caused a reduction in the resistance and potential difference (p.d.) across the perineurium, which forms the principal component of the barrier. There was also a reduction in the p.d. across the apical membrane of perineurial cells which might indicate a higher interstitial potassium level. There was no effect upon the p.d. recorded across the basolateral membrane of the cells, but there was some reduction in the ratio between the resistances of the basolateral and apical membranes. When the potassium level in the saline was raised, the depolarization of the basolateral membrane was less reduced by urea than the change in p.d. across the perineurium. During high K, the gradual depolarization of the perineurial membranes was speeded by urea treatment, as was the change in axon resting potential, as to be expected with more rapid entry of K into the interstitial system. Analysis of the initial effects of high K upon the electrical characteristics of the perineurium indicated that urea had reduced the resistance of the paracellular pathway by 73 % and the resistance of the basolateral membrane by 44%. Most of the electrical events in urea-treated preparations could be simulated from the estimated parameters and an estimation of the rise in interstitial K level during the high K exposure. The study indicates that the increased leak across the perineurium caused by urea treatment results chiefly from a decrease in intercellular restriction.
Oxygen consumption and luminescence of Porichthys photophores stimulated by potassium cyanide
Authors: Mallefet J. , Baguet F. 
Published: April 2021

ABSTRACT
Isolated photophores of Porichthys notatus, maintained in saline at 20 °C, do not luminesce and show an oxygen consumption rate of 0·07 ± 0·01 nmol min−1 photophore−1. In the presence of 10−6 M-KCN, the photophores do not luminesce but the resting respiration decreases by about 50%. In the presence of 10−5 M-KCN, some photophores do not luminesce and their respiration rate decreases by about 75 %. Others show a response and resting oxygen consumption slowly increases. At high concentration (10−4 and 10−3 M), KCN induces a large light emission and increase in oxygen consumption. The stimulatory effect of KCN on the photophore oxygen consumption is tentatively explained by an activation of the luciferin-luciferase system by calcium ions.
A possible role of the kidney and urinary bladder in urea conservation of Bufo viridis under high salt acclimation
Authors: Katz U. , Ben-Sasson Y. 
Published: April 2021

ABSTRACT
The toad Bufo viridis can be acclimated to high salt solutions up to 800 mosmol kg−1 of NaCl (Tercafs & Schoffeniels, 1962; Katz, 1973). Despite extensive studies on various aspects of adaptation to high salt in this species (Gordon, 1962; Katz, 1979; Katz, Garcia-Romeu, Masoni & Isaia, 1981) only little attention has been paid to the osmoregulatory roles of the kidneys and urinary bladder during high salt acclimation. In/tana cancrivora, a species which can be acclimated to salinities even higher than B. viridis (and which shares the property of urea accumulation) Schmidt-Nielsen & Lee (1962), found a lower urine flow under high salt and consequently reduced urea secretion, while Gordon & Tucker (1968) observed urea retention at first, but increasing loss at salinities higher than 400 mosmol kg−1. Ferreira & Jesus (1973), presented evidence in salt adapted B. bufo suggesting increased osmolarity (mainly sodium) in the urinary bladder. We therefore attempted to assess the turnover of water and urea in B. viridis with special emphasis on the contribution of the renal and the urinary bladder.
The Control of Respiratory Movements in Crustacea by Oxygen and Carbon Dioxide
Authors: Fox H. Munro , Johnson M. L. 
Published: April 2021

ABSTRACT
The respiratory movements of the barnacle Balanus and of the phyllopod Cheirocephalus are not accelerated either by decreased oxygen or by increased carbon dioxide tension in the water. The rate of movement of the scaphognathite of the crayfish Astacus is accelerated by a fall in oxygen but not by a rise in carbon dioxide tension of the environment. The rate of movement of the pleopods of the fresh-water isopod Asellus is accelerated by a fall in oxygen but not by a rise of carbon dioxide tension. In the sea-shore isopod Ligia, submerged in sea water, the rate of pleopod movement is not accelerated by a decrease in oxygen tension below that in equilibrium with air, but a rise in oxygen tension above the latter value slows respiratory movements. Carbon dioxide has no accelerating effect. Both a decrease in oxygen and an increase in carbon dioxide tension accelerate the respiratory pleopod movements of the amphipods Gammaruspulex and G. locusta. Whereas in the fresh-water G. pulex the quickened respiratory rhythm is permanent at each decreased oxygen and increased carbon dioxide tension, in the marine G. locusta these changes in rate of beat are transitory. This is correlated with the greater oxygen consumption of the marine species.
Some Observations on Potential Differences Across the Ectoplasm Membrane of Paramecium
Authors: Kamada Takeo 
Published: April 2021

ABSTRACT
As might be expected, a measurable potential difference is found between a pair of micro-electrodes, one of which is inside a Paramecium and the other in the external medium. The magnitude of this potential depends on the nature of the external solution. A brief account of the influence of the environment on the nature of the potential observed is given in the following pages.