bluuebunny/crossref_metadata_2025_split huggingface dataset:
Generation and Maintenance of the Respiratory Rhythm
Authors: Richter D. W. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTAll 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

ABSTRACT
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

ABSTRACT
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 (&lt; 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

ABSTRACT
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

ABSTRACT
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.