bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies in Animal Locomotion
Authors: Gray J.
Published: April 2021

When a body is moving in water it encounters a resistance in the direction of its motion, and consequently the body must be supplied with energy if motion is to occur at a uniform speed. A study of the mechanism of propulsion of a fish falls therefore into two parts, (1) a study of the forces resisting motion through the water, and (2) a study of the mechanism whereby the fish utilises the energy liberated by its muscles for overcoming the forces of resistance. To some extent these two aspects of the problem are interdependent and involve considerable hydrodynamical difficulties, but in the present paper an attempt will be made to show that the movements of a fish’s body1 are such as to generate forces capable of opposing the forces of resistance whatever be the nature or magnitude of the latter. The problem was attacked two centuries ago by Borelli and by Pettigrew in 1873 since then comparatively little attention has been devoted to the subject except by Breder (1926), whose results will be considered later.
On the Cephalopod Phosphagen
Authors: Baldwin Ernest
Published: April 2021

Cephalopod tissues contain a hitherto undescribed phosphagen compound. The rate of acid hydrolysis is comparable with those of creatine and arginine phosphates, but is minimal in N/10 acid, while the retardation produced by the molybdate ion is only about 3 − 4 times. The finding of a new compound in the Cephalopoda, the Lamellibranchiata being already known to contain arginine phosphate, is possibly of evolutionary significance.
Is Cleavage Rate a Function of the Cytoplasm or of the Nucleus?
Authors: Moore A. R.
Published: April 2021

There are two views of the relative roles which the nucleus and the cytoplasm play in forming the embryo. One view is the working hypothesis of the geneticist according to which the cytoplasm of the fertilised egg is a passive and plastic substrate on which the chromosomes of the nucleus work to mould the form of the new being. In its extreme form this hypothesis ignores the facts of segregation and localisation of formative substances in the egg. The other view holds that the cyto-plasm is characteristic of the species and therefore determines the general form and pattern of the embryo, that in the early stages of development the cytoplasm is supreme in this respect, and only later do the chromosomes induce superficial modifications in the developing individual.
The Temperature and Humidity Relations of the Cockroach (Blatta Orientalis)
Authors: Gunn D. L.
Published: April 2021

In a series of studies, of which this is the first, I propose to bring experimental methods to bear upon the relation between a convenient insect—Blatta orientalis— and some of the physical factors in the environment—namely temperature and humidity. The cockroach is very susceptible to desiccation (Zabinski, 1929; Gunn, 1931), and this paper is concerned with the relation between the speed of desiccation and the dryness of the air1 at various temperatures.
Control of the Foetal Circulation
Authors: Mott J. C.
Published: April 2021

Foetal cardiac output is high, and the heart has not been shown to have the sustained reserves demonstrated in the adult heart. About 40% (∼ 200 ml. kg body weight−1. min−1) of the combined output of both ventricles (CVO) in unanaesthetized foetal lambs in late gestation is directed to the umbilical circulation. At least one-half of the systemic flow (∼ 300 ml. kg body weight−1. min−1) goes to skin and carcass. About 50 % of the remainder (10% CVO) is shared by brain, heart and kidney and the rest by other viscera; less than 6% CVO perfuses the lungs. Hypoxaemia, acidaemia and various vasomotor agents influence the partition of cardiac output between systemic and umbilical circulations, with or without relatively small changes of blood pressure, which is low by adult standards. In general, the conductance of systemic circuits is more susceptible to change than that of the umbilical. Both cerebral and myocardial blood flow increase several-fold during hypoxaemia. The additional volume flow of blood demanded by such vasodilatation in organs forming a relatively small proportion of body weight is more than accounted for by concurrent vasoconstriction in muscle (which contributes a substantial fraction of body weight) and other tissues. Both humoral and reflex neural mechanisms are involved in these adjustments.
The Control of Respiration and Circulation in Fish During Exercise and Hypoxia
Authors: Randall David
Published: April 2021

Gas exchange across fish gills is reviewed and the respiratory and cardio-vascular changes associated with exercise and hypoxia described.

Heart rate is controlled by inhibitory vagal cholinergic activity which increases during hypoxia and decreases during exercise. Stimulation of receptors on the first gill arch during hypoxia initiates bradycardia. The increase in stroke volume during hypoxia in dogfish appears to be related to cardiac slowing rather than β-adrenergic stimulation of the heart.

Stimulation of cardiac β-adrenergic receptors causes positive inotropic and chronotopic responses in many fish, whether these are operative during exercise and hypoxia is not clear.

Gill water flow is inversely related to arterial oxygen content in resting fish and there is probably an arterial oxygen content receptor coupled to gill ventilation. Little is known of the control of breathing during exercise, the switch from rhythmic to ram ventilation at high water velocities may be initiated by mechanoreceptors on the gill surface.
Respiratory Gas Exchange at Lungs, Gills and Tissues: Mechanisms and Adjustments
Authors: Piiper Johannes
Published: April 2021

A general model for external gas exchange organs of vertebrates is presented, in which the main parameters are the ventilatory, diffusive and perfusive conductances for O2 and CO2. The relevant properties of the exemal medium (air or water) and of the internal medium (blood) are analysed in terms of capacitance coefficients (effective solubilities) for O2 and CO2. The models for the main types of gas exchange organs (fish gills, amphibian skin, and avian and mammalian lungs) are compared in terms of their intrinsic gas exchange efficacy. The adjustments to increased metabolic rate or to hypoxia are achieved by increasing the conductances. The gas exchange at tissue level is analysed using the Krogh cylinder and a simplified model containing a diffusive and a perfusive conductance. The adjustments to increased load (exercise, hypoxia) consist in both increased local blood flow and in improvement of diffusion conditions (enlargement and recruitment of capillaries). Some particular features of respiration in transitional (unsteady) states, such as occurring at the beginning of exercise and of hypoxia, are examined. The additional physical variables are the O2 (and CO2) stores acting according to their capacitances and partial pressure changes. Delayed increase in O2 uptake at the beginning of exercise is due to the limited speed of physiological adjustments. The ensuing O2 debt is energetically covered by anoxidative energy releasing processes (hydrolysis of high-energy phosphates and anaerobic glycolysis). Finally, the reduction of metabolic rate as adjustment to hypoxia is discussed.
Generation and Maintenance of the Respiratory Rhythm
Authors: Richter D. W.
Published: April 2021

Activities of the phrenic and internal intercostal nerves show that the central nervous rhythm of respiration consists of 3 phases: inspiratory, postinspiratory and expiratory. The discharge patterns of medullary respiratory neurones of the anaesthetized, paralysed cat can be correlated with these phases of the central respiratory cycle, and the postsynaptic activity of individual cells can be analysed to obtain information about the populations of neurones converging upon them. Inferences are drawn about respiratory neurone connectivity and a theory is developed that the respiratory network primarily employs inspiratory-related neurones and that medullary expiratory neurones are less important for the rhythmogenesis of respiration. It is suggested that the inspiratory network consists of a ramp generating excitatory loop network of interneurones whose discharge is brought to an end (‘off-switched’) by inhibitory late-inspiratory interneurones. The discharge pattern of the latter type of neurone is explained by inhibition arriving from early-inspiratory interneurones. Subsequent to ‘off-switching’ the ramp generator is assumed to be immediately gated by a very powerful postinspiratory inhibition whereas expiratory activity seems to be disfacilitated at this time. This is the period when ‘passive’ (stage 1) expiration occurs. Following this interposed postinspiratory phase ‘active’ (stage 2) expiration may begin, depending on the amount of excitatory inflow to the inspiratory ramp generator. When expiratory neurones are activated the inspiratory system is again synaptically inhibited and the frequency of ventilation is markedly slowed.
Reflex Reversal Resulting from Active Movements in the Antenna of the Rock Lobster
Authors: Vedel Jean-Pierre
Published: April 2021

In the rock lobster, Palinurus vulgaris, study was made of the effect of active flexion of the J3 joint of the flagellum upon the reflex produced by passive movement of this joint. Active flexion was accompanied by activity of motoneurones to musdes assisting the movement. Passive flexion not immediately preceded by active flexion was accompanied by activation of muscles to resist the movement (resistance reflex). When the passive movement followed slow active flexion (7·5°/s), there was some activity to assist the movement. If preceded by an active flexion of high velocity (25 °/s), the assistance reflex predominated. Passive extension produced a resistance reflex that was usually facilitated by preceding active flexion. The functional significance of the reversal is discussed.
Aedes Aegypti: Energetics of Osmoregulation
Authors: Edwards H. A.
Published: April 2021

Oxygen consumption of A. aegypti larvae, about 210 μlg−1 tissue wet weight h-1, does not change when the salinity of the environment is changed. The number of mitochondria in the anal papillae, a salt-absorbing epithelium, increases as the external medium is diluted. There is no difference in oxygen consumption between isolated anal papillae in 0, 2 and 20% sea water. The papillae represent about 5 % of body volume and their oxygen consumption is about 2% of the animal’s total. The theoretical minimum energy cost of osmoregulation is four orders of magnitude smaller than the measured figure for the anal papillae alone. Osmoregulatory phenomena which would explain the recorded observations are discussed.
Gas Transfer in A Spontaneously Ventilating, Blood-Perfused Trout Preparation
Authors: Davie Peter S. , Daxboeck Charles , Perry Steve F. , Randall David J.
Published: April 2021

A spontaneously ventilating, blood-perfused trout preparation is described and its suitability for the study of gas exchange in fish assessed. Cardiovascular dynamics closely approximated those found in vivo; perfusion flow rate .100 g−1, ventral aortic pressure (VAP) = 58·8 cm H2O, dorsal aortic pressure (DAP) = 34·8 cm H2O. Gas exchange characteristics in the branchial and systemic circulations also were similar to those described for resting, intact rainbow trout. All preparations showed consistent oxygen uptake . Min−1.100 g−1) and carbon dioxide excretion rates . Min−1.100 g−1) acro the gills. Across the systemic circulation, oxygen was extracted .min−1.100 g−1) and carbon dioxide produced by the metabolizing tissue (.min−1, 100 g−1). The respiratory quotient (REJ for gas transfer across the gills was 1·85. This high value was a reflection of the fact that much more oxygen than carbon dioxide was added to venous blood in the tonometer. The respiratory quotient for the tissues (RQs) was 0·83, a more reasonable value. Breathing rate (fg) was maintained at 69·4 ventilations. Min−1. The mean vascular resistance of blood-perfused gills (Rg) was 14·2 cm H2O.ml−1.min. 100 g−1, a value higher than that usually measured in vivo. Mean systemic vascular resistance (Rs) was 19·2 cm H2O. ml−1. min. 100 g−1 which is similar to that measured in intact fish. Cardiovascular responses to hypoxia and adrenergic responses in the branchial and systemic circulations of these preparations also closely approximated those found in vivo. This preparation is deemed suitable for studies of the cardiovascular system as well as gas transfer. The results from these experiments are representative of the in vivo condition in fish.
Active HCO3- Secretion in the Rectal Salt Gland of A Mosquito Larva Inhabiting NaHCO3–CO3 Lakes
Authors: Strange K. , Phillips J. E. , Quamme G. A.
Published: April 2021

Aedes dorsalis larvae are one of the few organisms capable of inhabiting hypersaline NaHCO3-CO3 lakes. Under laboratory conditions larvae can survive and develop normally in saline media with pH values of 10·5, HCO3− concentrations of 250 mm, or CO32− concentrations of 100 mm. Despite ingestion of alkaline media at a rate equal to 130% of larval body wt/day, these insects regulated haemolymph pH (7·55–7·70) and HCO3− concentration (8·0–18·5 mm) within narrow limits. Analysis of fluid obtained by micropuncture or microcannulation indicated that rectal secretion is an important mechanism of pH and HCO3− regulation. The lumen-to-haemocoel HCO3− and CO32− gradients generated by isolated, microcannulated recta were 21 :1 and 241 :1, respectively. Transepithelial potential in cannulated recta was – 14·2 to –23·3 mV (lumen negative), demonstrating that net HCO3− secretion occurs against a large electrochemical gradient.
Azaserine Affinity Labelling of γ-Glutamyl Transferase of Hydra Attenuata Without Inactivation of the Glutathione Receptor
Authors: Heagy Wyrta , Danner Jean , Lenhoff Howard , Cobb Melanie H. , Marshall Garland
Published: April 2021

Intrigued by similar specificities of the hydra feeding receptor and γ-glutamyl transferase activity toward GSH, we examined the possibility that these two GSH-binding activities might reside in the same protein. We find that the two activities differ in specificity toward the γ-glutamyl moiety of GSH. The hydra transferase recognizes L-azaserine, L-GlU, D-GlU and L-Gln. The feeding receptor recognizes only L-GlU and L-Gln; L-azaserine and D-GlU have no effect. L-azaserine, known to bind covalently to the γ-glutamyl donor site of mammalian transferase, irreversibly inactivates hydra transferase activity. The transferase affinity label, however, has no effect on the GSH-stimulated feeding response, permitting us to demonstrate that these two activities have different GSH recognition sites and appear to reside in different proteins.
Osmoregulation by the Prenatal Spiny Dogfish, Squalus Acanthias
Authors: Evans David H. , Oikari Aimo , Kormanik Gregg A. , Mansberger Leigh
Published: April 2021

Late in gestation of the ovoviviparous dogfish, Squalus acantinas, the uterine fluids are essentially sea water, while the plasma of the ‘pup’ is similar to that of the female, i.e. isotonic to sea water/uterine fluids, with significantly less Na and Cl, and substantial concentrations of urea. Early ‘candle’ embryos are bathed in ‘candle’ fluid and uterine fluid which contains Na and Cl concentrations intermediate between maternal plasma and sea water levels, K concentrations above sea water levels, and urea concentrations slightly below those found in the maternal plasma. Both fluids are isotonic to sea water and maternal plasma. Incubation of ‘candles’ with associated embryos in sea water for 4–6 days resulted in significant increases in ‘candle’ fluid Na and Cl concentrations, and a decline in ‘candle’ fluid K and urea levels. However, under these conditions, the ‘candle’ embryo is still able to regulate plasma Na, Cl, K and urea concentrations. The efflux of Cl is approximately 5 times the efflux of Na from the prenatal ‘pup’ ; however, both effluxes are equivalent to those described for adult elasmobranchs. The transepithelial electrical potential (TEP) across the ‘pup’ is –4·4 mV in sea water, which indicates that both Na and Cl are maintained out of electrochemical equilibrium. Cloacal fluid flows vary diurnally with Na and Cl concentrations significantly above those of the plasma. Rectal gland efflux can account for 50–100 % of the Na efflux, but less than 25 % of the Cl efflux. Removal of the rectal gland resulted in an increase in plasma Na and Cl concentrations 48 or 72 h after the operation, but in both cases it appears that some extra rectal gland excretory system balances at least some of the net influx of both salts. Our results demonstrate that even very young ‘candle’ embryos of S. acanthias are capable of osmoregulation, and that older embryos (‘pups’) osmoregulate against sea water intra-utero and display the major hallmarks of elasmobranch osmoregulation, including a reduced ionic permeability and a functional rectal gland for net extrusion of NaCl. In addition, it appears that other pathways exist for salt extrusion in addition to the rectal gland.
Ferromagnetism in Two Mouse Tumours
Authors: Kirschvink Joseph L. , Tabrah Frank L. , Batkin Stanley
Published: April 2021

A variety of living organisms has been found recently that are biochemically able to precipitate the ferromagnetic mineral magnetite (Fe3O4). Originally discovered in the radular teeth of a primitive marine mollusc (Lowenstam, 1962), magnetite has since been reported in bacteria (Frankel, Blakemore & Wolfe, 1979), arthropods (Gould, Kirschvink & Deffeyes, 1978), and vertebrates (Walcott, Gould & Kirschvink, 1979; Zoeger, Dunn & Fuller, 1981; Walker & Dizon, 1981). Although the presence and biological origin of this material are clear, very little is yet known about the distribution or metabolic function of ferromagnetic minerals in vertebrate tissue. Magnetic remanence, which uniquely indicates the presence of ferromagnetic particles, has been previously detected in localized areas associated with the dura membranes of homing pigeons (Walcott et al. 1979) and dolphins (Zoeger et al. 1981), in pigeon neck muscles (Presti & Pettigrew, 1980), in the mid-brain of monkeys, and in human adrenal glands (Kirschvink, 1981). We report here the first discovery of anomalously high concentrations of ferromagnetic material in two strains of neoplasms, YC-8 lymphoma and Lewis lung tumour, as well as the apparent absence of such material in three human carcinomas (gastric, colon and renal).
Oxygen Uptake in A Spontaneously Ventilating, Blood-Perfused Trout Preparation
Authors: Daxboeck Charles , Davie Peter S. , Perry Steve F. , Randall David J.
Published: April 2021

A spontaneously ventilating, blood-perfused trout preparation was used to examine gas exchange across the gills. The blood flow rate and input oxygen content to the branchial circulation were manipulated to assess the contributions of perfusion and diffusion limitations to oxygen transfer. Increases in the flow rate or the haematocrit (Hct) were positively correlated with increases in the oxygen uptake across the gills Manipulation of pulse pressure or frequency of the pump, with no changes to had no effect on Addition of adrenaline (1 × 10−6 M) to the blood also did not effect Calculations of cardiac output from the Fick principle always yielded values which were overestimates of the actual cardiac output set by the mechanical pump. The difference between the measured oxygen uptake by the fish from the water and the amount of oxygen transferred to the blood across the gills was a reflection of gill tissue metabolism. It is concluded that trout gills, like mammalian lungs, are primarily perfusion limited for oxygen uptake under resting normoxic conditions, but decreases in diffusion limitations come into play under stress conditions, such as environmental hypoxia or exercise.
On the Instability of K+ Influx in Erythrocytes of the Rainbow Trout, Salmo Gairdneri, and the Role of Catecholamine Hormones in Maintaining In Vivo Influx Activity
Authors: Bourne P. K. , Cossins A. R.
Published: April 2021

The rate of K+ influx in washed trout erythrocytes was not stable and declined by 60 % over a 6 h period, but decreased only slowly thereafter. During this initial period the cells shrank, although [K+]1 was maintained constant. Both ouabain-sensitive and furosemide-sensitive K+ influx were reduced by approximately equal amounts.

Extensive modification of the saline composition produced no diminution of the loss of K+ influx activity, making it unlikely that the response was due to deficiencies in saline composition.

The rate of K+ influx in unwashed cells was affected only slightly by noradrenaline and adrenaline. By contrast, K+ influx in cells which had been washed and incubated overnight before assay was stimulated 100–250% by these hormones. Half-maximal stimulation was at 2× 10−6 and 8 × 10−6 M respectively. Replacement of plasma by a saline containing 5 × 10−6 M adrenaline and noradrenaline resulted in high and stable K+ influx rates over a 6 h period.

These results support the hypothesis that K+ influx in erythrocytes of freshly drawn blood is high as a result of stimulation by catecholamine hormones. Removal of the normal hormonal milieu, by washing of the cells, results in the rapid loss of K+ influx activity.
Active Potassium Transport by the Isolated Lepidopteran Larval Midgut: Stimulation of Net Potassium Flux and Elimination of the Slower Phase Decline of the Short-Circuit Current
Authors: Wolfersberger Michael G. , Giangiacomo Kathleen M.
Published: April 2021

Adenosine 3’:5’-cyclic monophosphate (cyclic AMP), Antibiotic A23187, caffeine, cholera toxin, dibutyryladenosine 3’ :5’-cyclic monophosphate (dbcAMP), 5-hydroxytryptamine (5-HT), larval blood, and theophylline were tested for their effects on active potassium transport, as measured by the short-circuit current (SCC), in isolated Manduca sexta larval midgut. None of the tested materials affected the short-circuit current during the rapid phase of its usual exponential decline, and only dbcAMP and larval blood affected the short-circuit current during the slower phase of its exponential decline. Dibutyryl-cyclic AMP stimulated an increase in short-circuit current and net potassium flux (measured using 42K). Both unidirectional potassium fluxes increased but there was no effect on the flux ratio or on the rate at which net potassium transport declined with time. A dialysable extract of fifth instar larval blood effected potassium transport in a manner similar to that of dbcAMP, indicating that larval blood contains natural transport-stimulating factors. A dialysable extract of fourth instar larval blood not only stimulated potassium transport but also prevented the slow phase of decline in the short-circuit current. Therefore, in addition to transport-stimulating factors present in fifth instar blood, fourth instar blood appears to contain substances which prevent degeneration of at least the transport related functions of midgut in vitro. It is argued that the action of the transport-stimulating factor in larval blood on the electrogenic cation pump in larval midgut cells is mediated by cyclic AMP without involving a change in intracellular calcium ion concentration.
Thermal Soaring Compared in Three Dissimilar Tropical Bird Species,Fregata Magnificens, Pelecanus OccidentalsandCoragyps Atratus
Authors: Pennycuick C. J.
Published: April 2021

All three species were observed in straight flight, and circling in thermals, from Flamenco Island, Panama. Measurements were made by or-nithodolite, an instrument which records a series of timed, threedimensional position estimates, from which speeds, circle diameters and rates of climb can be calculated. Mean lift coefficients in straight glides ranged from 0·72 to 0·84, except in slope soaring, where a mean of 1·6 was recorded for both the frigatebird and black vulture. Mean circling radii were proportional to wing loading, and varied from 12·0 m for the frigatebird to 18·0 m for the pelican. Mean rates of climb ranged from 0·40ms−1 for the black vulture to 0·57ms−1 for the pelican. All species showed mean circling lift coefficients between 1·33 and 1·45, and angles of bank between 22·9° and 24·7°. It is argued that the frigatebird is adapted to stay airborne continuously, day and night, for extended periods, by exploiting thermals over the sea under trade wind cumulus clouds. The low wing loading is seen as an adaptation to circling in narrow thermals, and the low disc loading as an adaptation giving low minimum power, when flapping cannot be avoided. Take-off appears to be possible only by dropping from an elevated perch, not from the ground or water surface. The low aspect-ratio, tip-slotted wings of the black vulture are certainly less efficient for soaring, but appear to be better for upward take-off from the ground. The pelican also has tip-slotted wings. Although its aspect ratio is higher, it is still capable of taking off from a level water surface.
Gas Exchange and Energy Cost of Flight in the White-Necked Raven, Corvus Cryptoleucus
Authors: Hudson Dennis M. , Bernstein Marvin H.
Published: April 2021

Energy expenditure during steady-state, wind tunnel flights was estimated from O2 and CO2 exchange in five white-necked ravens (Corvus cryptoleucus, mean mass, 0 ·48 kg) at air speeds of 8–11 m/s. Power input was closely similar to allometric predictions based on data from other species of smaller birds. It increased significantly with air speed and flight angle above horizontal, and decreased with increasing angles below horizontal. Maximum power input reached seven times the preflight value measured under resting but not basal conditions, 14 times the previously measured basal values and three times the calculated maximum for a similar sized running mammal. Energy cost to travel 1 km decreased with increasing air speed. These trends are similar to those previously observed in smaller birds.
Locomotion in the North American Mink, A Semi-Aquatic Mammal
Authors: Williams Terrie M.
Published: April 2021

Oxygen consumption during surface swimming and total body drag were investigated in the North American mink, Mustela vison Schreber. Over the range of 0·13–0·70 ms−1, increased curvilinearly with speed for minks swimming against a current in a water flume. Similarly, body drag of a mink carcass increased non-linearly with speed and was described by the equation, Drag = 1·24 velocity1·82. A streamlined body shape, characteristic of many mustelids, aided in reducing drag at high speeds. Net swimming efficiencies were comparatively low (< 1·8%) and were attributed to high levels of drag when on the water surface and the absence of appendage specialization for aquatic locomotion. This lack of specialization probably contributes to high energetic costs but enables the mink to forage in both the aquatic and terrestrial environments.
Aquatic Gas Exchange in the Freshwater/ Land Crab, Holthuisana Transversa
Authors: Greenaway Y Peter , Ventura J. Bona , Taylor H. H.
Published: April 2021

Holthuisana transversa (von Martens), a freshwater/land crab from arid areas of Australia, is an efficient bimodal breather. In water, resting M˙o2 (1·65μmolg-− h−1 ) and (15·6mlg−1 h−1) at 25°C were lower than in other aquatic crabs whilst percentage extraction of oxygen was quite high (47 %). M˙o2 was not regulated at low ambient PO2 but could be increased at least three times during exercise. Normoxic PaO2 was low (18 Torr) compared with other water-breathing crabs. The haemolymph contained haemocyanin which had a moderate affinity for oxygen (P50 = 80 Torr) and carried over 90% of the oxygen transported. Oxygen content of post-branchial haemolymph was low (346μmol l−1). There was a small positive Bohr shift (log P50/pH-0·33). The strategy of gas exchange in water is discussed and compared with that of aquatic crabs.
Effects of Ethanol and Temperature On A Crab Motor Axon Action Potential: A Possible Mechanism for Peripheral Spike Generation
Authors: Stephens Philip J. , Frascella Paul A. , Mindrebo Norman
Published: April 2021

In autotomized walking limbs of Pachygrapsus crassipes, microelectrode recordings of evoked action potentials were made in the meropodite from the E2 excitor axon to the bender muscle. The action potential spike was followed by a depolarizing after potential. Increases in temperature resulted in a decline in the amplitude and time course of the spike, and an increase in the amplitude of the after potential. Low levels of ethanol or increased levels of calcium increased the size of the after-potential and decreased the temperature threshold for peripheral spike generation. At high temperatures a single orthodromic E2 axon spike provoked the generation of additional impulses at the periphery, with an inter-spike interval of 2–3·5 ms. The after-potential lasted longer than the refractory period following the spike. The axon membrane, therefore, was depolarized after the refractory period and this resulted in a period of low threshold for spike generation. Increases in temperature shortened the refractory period. We suggest that additional spikes are generated at the periphery where the E2 axon diameter is decreased. The increased membrane resistance at these sites increases the size of the depolarizing after-potential. Therefore, if the depolarization following the refractory period is at or above threshold for firing, additional action potentials will be generated at the periphery.
Contribution of Net Ion Transfer Mechanisms to Acid-Base Regulation After Exhausting Activity in the Larger Spotted Dogfish (Scyuorhinus Stellaris)
Authors: Holeton George F. , Heisler Norbert
Published: April 2021

Specimens of the larger spotted dogfish (Scyliorhinus stellaris) were electrically stimulated to exhaustion in a closed seawater recirculation system. The production of large quantities of lactic acid by anaerobic metabolism and the resultant efflux of the dissociation products, H+ and lactate, from the white musculature resulted in severe acid-base disturbances and in increases in plasma lactate concentration, the two effects having extremely different time courses. Plasma pH and bicarbonate were maximally depressed 15–30 min after exercise, whereas peak lactate concentrations of up to 30 mm were not attained before 4–8 h after exercise. The acid-base status was restored to normal 10–14 h after exercise, long before the aerobic processing of surplus lactic acid was complete 22–30 h after exercise.

This behaviour can be explained on the basis of an interaction of transfer rates, buffer values and equilibria between intracellular and extracellular compartments with the transient net transfer of surplus H+ ions to the environmental water. About half of the original quantity of H+ was transferred net to the environment via the branchial epithelium during the first 8–10 h, and it was later taken up again at the rate of aerobic lactic acid processing in the metabolism of the fish, whereas a transfer of lactate was not observed at any time during the experiment. As a result, the distribution patterns of H+ and lactate differed from each other and varied with time elapsed after anaerobic exercise, leading to the apparent ‘H+ ion deficit’ which has been observed in the blood of several fish species during lactacidosis.

Net transfer of H+ ions to the environment facilitates rapid normalization of the acid-base status long before the original stress, lactic acid, is removed from the organism and thus represents an effective regulatory mechanism for the defence of the internal milieu in fish.
Lactate and Proton Dynamics in the Rainbow Trout (Salmo Gairdneri)
Authors: Turner Jeffrey D. , Wood Chris M. , Clark Donna
Published: April 2021

Chronically cannulated rainbow trout were subjected to 6 min of severe burst exercise and monitored over a 12 h recovery period. There were short-lived increases in haematocrit, haemoglobin, plasma protein, Na+ and Cl− levels. Plasma [Cl−] later declined below normal as organic anions accumulated. A much larger and more prolonged elevation in plasma [K+] probably resulted from intracellular acidosis. An intense extracellular acidosis was initially of equal respiratory (i.e. ) and metabolic (i.e. ) origin. However was rapidly corrected while the metabolic component persisted. Plasma ammonia increases had negligible influence on acid-base status. Elevations in blood lactate (ΔLa−) were equal to immediately post-exercise but later rose to twice the latter. Simultaneous white muscle biopsies and blood samples demonstrated that muscle to blood gradients of lactate and pyruvate were maximal immediately post-exercise. As blood levels rose and muscle levels declined, an approximate equilibrium was reached after 4 h of recovery. Intra-arterial infusions of lactic acid in resting trout produced a severe but rapidly corrected metabolic acidosis. The rates of disappearance of and ΔLa− from the blood were equal. Infusions of similar amounts of sodium lactate produced a small, prolonged metabolic alkalosis with a much slower ΔLa− disappearance rate. It is suggested that the excess of ΔLa− over in the blood after exercise is associated with differential release rates of the two species from white muscle rather than differential removal rates from the bloodstream, and that the majority of the lactic acid load in muscle is removed by metabolism in situ.
Studies on The Plasma Colloid Osmotic Pressure of The River Lamprey, Lampetra Fluviatilis, L
Authors: Mcvicar A. J. , Rankin J. C.
Published: April 2021

Values for the total plasma protein concentration of different teleost species range from 3·5–7·0 g% (Field, Elvelhjem & Juday, 1943; Fine, Boffa & Drilhon, 1963; Larsson & Lewander, 1972; Hargens, Millard & Johansen, 1974) and this considerable interspecific variation is reflected in values for the plasma colloid osmotic pressure which ranged from 0·87–2·75 kPa (Keys & Hill, 1934; Hargens et al. 1974).
The Mechanism of Intracardiac Shunting in the Lizard Varanus Exanthematicus
Authors: Heisler N. , Neumann P. , Maloiy G. M. O.
Published: April 2021

Intracardiac shunting was studied in unanaesthetized and unrestrained specimens of Varanus exanthematicus by simultaneous injection of radio- actively labelled microspheres (15 μm) into the right and left atria. Lung ventilation was monitored by intratracheal pneumotachography. It was found that intracardiac shunting was not significantly affected by the spontaneously occurring periods of ventilation and apnoea: the right-to-left shunt averaged 29 and 31%, respectively, and the left-to-right shunt was 11% in both conditions. The observed shunting, although rather constant with time and independent of the ventilatory state, varied in different individuals. Anatomical studies and intracardiac pressure measurements revealed that, in spite of crocodilian-like systolic pressure separation between pulmonary and systemic circulation (based on the muscular ridge, ‘Muskelleiste’, between cavum venosum and cavum pulmonale), the cavum venosum is shared by both the pulmonary and the systemic circulation. Intracardiac shunting appears to be mainly due to wash-out of the cavum venosum: blood remaining in this chamber at the end of systole (oxygenated) or at the end of diastole (deoxygenated) is washed into the respective ‘inadequate’ vascular bed during the next half-cycle of heart action. Thus the extent of intracardiac shunting is expected to depend primarily on the volume and the changes in volume of the cavum venosum during the cardiac cycle.
Giant Fibre Activation of Direct Flight Muscles in Drosophila
Authors: Tanouye Mark A. , King David G.
Published: April 2021

Electrical stimuli delivered to the brain were used to activate the giant fibre of Drosophila. The giant fibre drove a prominent wing opening movement. Intracellular microelectrode recordings from direct wing opener muscle fibres showed that giant fibre activation of an anterior pleural muscle, pa3, was responsible for the wing opening movement. The giant fibre drove a slight wing elevation movement. Intracellular recordings from direct wing elevator muscle fibres showed that these muscles were not activated by the giant fibre. It is suggested that giant fibre-driven wing elevation movements were mediated by the tergotrochanter muscle (TTM).
Locomotion in the North American Mink, A Semi-Aquatic Mammal II. the Effect of an Elongate Body on Running Energetics and Gait Patterns
Authors: M. Williams Terrie
Published: April 2021

Oxygen consumption of minks increased non-linearly with running speed over the range of 0·70–6·40 km h−1. A break in the vs speed relationship occurred at approximately 3·94km h−1 and corresponded to the transition from a walking to a half-bounding gait pattern. Incremental transport costs associated with bounding were 36% lower than for walking at similar speeds. The lower energetic cost of bounding was attributed in part to low stride frequencies and in part to spinal flexion. The latter was particularly important in circumventing stride length restrictions associated with the short limbs of these animals. As a result, stride frequency and stride length of these elongate mustelids at the gait transition speed were similar to values predicted for conventionally-shaped mammals.
Eye Movement Dynamics in the Dogfish
Authors: Montgomery J. C.
Published: April 2021

A method is described of obtaining the relationship between electrical stimulation of the abducens nerve and horizontal eye movement in the dogfish. The stump of the Vlth nerve was stimulated intracranially in a fish in which the brain had been removed, but in which the circulation remained intact, and the gills were perfused with sea water. Horizontal rotation of the eye was monitored with an opto-electronic movement detector. Eye rotation was linearly related to stimulus frequency in the 0–20 Hz range, and was maximal at frequencies above 40 Hz. Stimulation of the Vlth nerve, with a pulse train whose frequency was modulated sinusoidally between 0 and 20 Hz, produced sinusoidal eye movements. The frequency response of the system approximates a first order low pass filter with a characteristic frequency of 0·23 Hz, and an additional phase lag equivalent to a time delay of approximately 50 ms.
Control of a Central Pattern Generator By an Identified Modulatory Interneurone in Crustacea I. Modulation of the Pyloric Motor Output
Authors: Nagy F. , Dickinson P. S.
Published: April 2021

In the lobsters Jasus lalandii and Palinurus vulgaris, the rhythmical activity of the pyloric pattern generator of the stomatogastric nervous system is strongly modified by the firing of a single identified interneurone, whose activity we have recorded from the cell body, in vitro.

The cell body of this interneurone, the anterior pyloric modulator (APM), is located in the oesophageal ganglion and sends two axons to the stomatogastric ganglion via the inferior oesophageal nerves, the commissural ganglia, the superior oesophageal nerves and the stomatogastric nerve.

Firing of neurone APM modifies the activity of all the neurones of the pyloric network, including pacemaker and follower neurones. Its effects are both quantitative (increase in the frequency of the rhythm and in the frequency of spikes within cell bursts) and qualitative (modifications in relative efficacies of the synaptic relationships within the pyloric network, which in turn lead to changes in the phase relationships between the discharges of the neurones).

The effects on pyloric activity induced by firing of neurone APM are established slowly (one or two seconds) and are of long duration (ten times the duration of APM’s discharge). These modifications most probably involve muscarinic cholinergic receptors.

APM’s influences on the activity of pyloric neurones appear to be characteristic of a neuromodulatory process and are such that they may be of behavioural significance in the intact animal.
Factors Affecting Lactate and Proton Efflux From Pre-Exercised, Isolated-Perfused Rainbow Trout Trunks
Authors: Turner Jeffrey D. , Wood Chris M.
Published: April 2021

Glycolysis in muscle during the anaerobic component of severe exercise rapidly produces lactate (La−) and metabolic protons in equal amounts, some of which may enter the blood (Krebs, Wood & Alberti, 1975). In vivo experimentation using strenuously exercised fish has yielded two patterns: La− accumulating in blood either in greater or lesser amounts than . It was rare to find both species at the same concentration, as is the usual case in man (Keul, Keppler & Doll, 1967). In the dogfish (Piiper, Meyer & Drees, 1972) and rainbow trout (Turner, Wood & Clark, 1983a) after exercise, ΔLa− in blood greatly exceeded . The opposite discrepancy occurred in the starry flounder (Wood, McMahon & McDonald, 1977), muskellunge (Beggs, Holeton & Crossman, 1980), and flathead sole (Turner, Wood and Hōbe, 1983b), where ΔLa− was consistently lower than These discrepan cies could be caused either by differential removal rates of the two ionic species from the blood space or by differential release rates from the myotome. We have recently argued that the latter is the dominant process (Turner et al. 1983a,b). However, this is extremely difficult to prove with in vivo methodology, as measurements in a single body compartment with periodic sampling give little information about the dynamic equilibrium between production, metabolism and fluxes between compartments. In vitro muscle preparations can be used to overcome many of these difficulties (e.g., Mainwood & Worsley-Brown, 1975; Benadé & Heisler, 1978). Isolated-perfused rainbow trout trunks have been employed to examine the physiology of systemic vascular resistance control (Wood & Shelton, 1975; Wood, 1977) and substrate utilization by muscle (Moen & Klungsoyr, 1981). In the present study, by strenuously exercising intact trout, then rapidly preparing them as isolated-perfused trunks, it was possible to determine net and La− movement from muscle to perfusate during recovery while simultaneously monitoring muscle [La−] by repetitive biopsy.
Occurrence of Resilin in Elastic Structures in the Food-Pump of Reduviid Bugs
Authors: Edwards H. A.
Published: April 2021

Resilin is a naturally occurring rubber. It is extremely efficient, returning almost all the energy stored during its deformation. Resilin was first described by Weis-Fogh (1960), who with Andersen (Andersen & Weis-Fogh, 1964) produced an extensive review covering the identification, physical and chemical properties of the substance. Andersen & Weis-Fogh set out five diagnostic characters for resilin and reported five sites of resilin occurrence: the wing hinge in all insects studied, includingSchistocerca gregaria and Periplaneta americana; tendons in Aeshna cyanea and Calliphora ery-throcephala; the hindleg spring of various fleas; the abdominal spring of Oryctes sp. and Melolontha sp.; and the clypeolabral spring of Schistocerca gregaria. This communication reports the occurrence of resilin in the food-pump of Reduviid bugs and discusses its functional significance.
Pardaxin Produces Sodium Influx in Theteleost Gill-Like Opercular Epithelia
Authors: Primor Naftali
Published: April 2021

Transport by the gill-like opercular epithelium of the teleost, Fundulus heteroclitus, was affected by pardaxin, a protein that is toxic to fish, isolated from the Red Sea flatfish Pardachirus marmoratus. Administration of pardaxin to the mucosal (seawater) side of the isolated short-circuited opercular epithelium, caused a transient stimulation of the active transport of ions (Isc), followed by an inhibition. The Isc stimulation was abolished by ouabain or/and in Na+-free Ringer but not in Cl−-or HCO3−-Ringer. When applied to the serosal (blood) side, pardaxin did not affect the Isc. Pardaxin produced a net transient Na+ current from the mucosal side to the serosal side of 2·2μequivcm−2h−1. It is concluded that this Na+ influx caused the Isc stimulation. The influx is suggested to be the mechanism of pardaxin’s toxicity in fish.
Cl−-Stimulated Adenosine Triphosphatase: Existence, Location and Function
Authors: Gerencser George A. , Lee Soon-Ho
Published: April 2021

The three universally accepted mechanisms of chloride transport across plasma membranes are: (i) sodium-coupled symport; (ii) anion-coupled antiport; and (iii) coupling to primary ion transport through electrical and/or chemical mechanisms. No direct evidence has been provided for primary chloride transport despite numerous reports of cellular, anion-stimulated ATPases and of chloride transport that cannot be accounted for by the three well-accepted chloride transport processes. Anion-stimulated ATPases are of mitochondrial origin and are a ubiquitous property of practically all animal cells. It also appears that there are other subcellular sites of anion-stimulated ATPase activity, especially the plasma membranes. Recent studies have provided indirect evidence (through parallel studies on the same tissue of anion-stimulated ATPase activity and chloride fluxes) which suggests a possible involvement of ATPase in net movement of chloride up its electrochemical gradient across plasma membranes. Further studies are required to substantiate a direct transport function to Cl−-stimulated ATPases located in the plasma membrane.
Paracellular and Transcellular Routes for Water and Solute Movements Across Insect Epithelia
Authors: O’Donnell M. J. , Maddrell S. H. P.
Published: April 2021

Because the frontal area of the intercellular clefts in Malpighian tubules is small, and the osmotic permeability of the cell membranes is large, the route for transepithelial water movement during fluid secretion is transcellular. Water movements appear to be a passive response to osmotic gradients of a few mosmol 1−1 produced in the cells and in the lumen by active ion transport.

The excretory functions of Malpighian tubules are discussed in relation to recent analyses of the routes of passive permeation for non-electrolytes. Uncharged molecules smaller than a disaccharide appear to move at significant rates through the cells whereas molecules as large as inulin traverse the epithelium by a paracellular path. In addition there are specific active transport mechanisms for a variety of organic molecules.

The routes and mechanisms proposed for water and solute movements are discussed in relation to comparable studies in other epithelia.
Introduction: Trends in Epithelialtransport and Control
Authors: Phillips John , Lewis Simon
Published: April 2021

Osmotic and ionic regulation ultimately depend on epithelial transport mechanisms and their control in most metazoans, although intracellular osmotic adjustments are probably more important in marine osmoconformers. There are a great variety of osmoregulatory organs throughout the animal kingdom and physiological information about many of these is still so incomplete that it seemed inappropriate to attempt a comprehensive review or synthesis of osmoregulation in a small discussion meeting of this type. However, given the general conservative nature of many cellular processes during the course of animal evolution, we might anticipate common protein carrier mechanisms which are organized and controlled in a limited number of ways within most epithelia. A number of such general concepts and models of epithelial transport have developed over the last ten years and these should prove useful in the future when less well studied osmoregulatory organs are investigated. With this in mind, we have included in this volume reports on some of the most intensively studied epithelia having a range of different regulatory functions. These papers will indicate (1) the types of primary and secondary transport mechanisms which are now well established and partially characterized, (2) their typical asymmetrical distribution in epithelia, and (3) cellular processes associated with their regulation. (4) Finally we consider the relative importance and characteristics of the paracellular route for ion and fluid transfer across epithelia.