bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acid-base regulation and ion transfers in the carp (Cyprinus carpio): pH compensation during graded long- and short-term environmental hypercapnia, and the effect of bicarbonate infusion
Authors: Claiborne J. B. , Heisler N. 
Published: April 2021

ABSTRACT
To study both temporal and quantitative effects of hypercapnia on the extent of pH compensation in the arterial blood, specimens of carp (Cyprinus carpio) were exposed to a of about 7·5mmHg (1 mmHg = 133·3Pa) (1% CO2) in the environmental water for several weeks, and a second group of animals was subjected to an environmental of about 37 mmHg (5 % CO2) for up to 96 h. A third series of experiments was designed to test the possibility that infusion of bicarbonate would increase the extent of plasma pH compensation. Dorsal aortic plasma pH, and [HCO3−], as well as net transfer of HCO3−-equivalent ions, NH4+, Cl− and Na+, between fish and ambient water, were monitored throughout the experiments.
Exposure to environmental of 7·5 mmHg resulted in the expected respiratory acidosis with the associated drop in plasma pH, and subsequent compensatory plasma [HCO3−] increase. The compensatory increase of plasma bicarbonate during long-term hypercapnia continued during 19 days of exposure with plasma bicarbonate finally elevated from 13·0 mmol l−1 during control conditions to 25·9 mmol l−1 in hypercapnia, an increase equivalent to 80% plasma pH compensation.
Exposure to 5 % hypercapnia elicited much larger acid-base effects, which were compensated to a much lesser extent. Plasma pH recovered to only about 45 % of the pH depression expected at constant bicarbonate concentration. At the end of the 96-h exposure period, plasma [HCO3−] was elevated by a factor of 2·5 to about 28·2mmol l−1.
The observed increase in plasma bicarbonate concentration during 5 % hypercapnic exposure was attributable to net gain of bicarbonate equivalent ions from ( or release of H+-equivalent ions to) the environmental water. Quantitatively, the gain of 15·6 mmol kg−1 was considerably larger than the amount required for compensation of the extracellular space, suggesting that acid—base relevant ions were transferred for compensation of the intracellular body compartments. The uptake of bicarbonate-equivalent ions from the water was accompanied by a net release of Cl− and, to a smaller extent, by a net uptake of Na+, suggesting a 75 % contribution of the Cl−/HCO3− exchange mechanism.
Infusion of bicarbonate after 48 h of exposure to 7·5 mmHg had only a transient effect on further pH compensation. The infused bicarbonate was lost to the ambient water, and pre-infusion levels of bicarbonate were reattained within 24 h. Repetition of the infusion did not result in a notable improvement of the acid-base status. These observations are consistent with the idea of a ‘threshold’ of the bicarbonate retaining and resorbing structures of the fish.
Blood gases and respiratory pattern in exercising fowl: comparison in normoxic and hypoxic conditions
Authors: Brackenbury J. H. 
Published: April 2021

ABSTRACT
Clavicular air sac pressure, arterial blood gases and pH, and rectal temperature were measured in treadmill-exercised cockerels breathing air, 10% O2 in N2 or a mixture of 10 % O2/3 % CO2 in N2. Air sac pressures were used to estimate changes in the rate and the relative depth of breathing. In air-breathing conditions exercise took place at two intensities corresponding to treadmill speeds of 3·2 and 5·0 km h−1, respectively. Rectal temperature increased by 0·5°C but there was no sign of thermal hyperventilation and arterial remained constant. Increased ventilation was mainly brought about by changes in respiratory rate, with relatively small increases in depth. During exercise at 3·2kmh−1 inhalation of 10% O2 in N2 produced a 35 % increase in ventilation and breathing became faster and shallower. Arterial fell by 3–4 Torr, apparently as a result of lung hyperventilation. Addition of 3 % CO2 to the hypoxic gas restored normal arterial and reversed the trend to polypneic breathing. However, it failed to produce an exact matching of respiratory characteristics with those observed during isocapnic exercise hyperpnea. It is concluded that rapid, shallow breathing during hypocapnic hypoxia in running birds serves as a mechanism to minimize lung hyperventilation and CO2 washout. This reflex, which may stem from the intrapulmonary CO2 receptors, occurs in the face of a severe hypoxic challenge. Failure to match respiratory characteristics during isocapnic hypoxia and isocapnic exercise may be due to an inibitory effect of the inhaled CO2 on these receptors.
Withdrawal Reflex and Conduction Block in the Giant Axons of a Sabellid Worm (Pseudopotamilla Occelata)
Authors: Higuchi Takashiro , Nakamura Hiroyuki , Sawauchi Katsuhiko , Okumura Hiroshi 
Published: April 2021

ABSTRACT
Body contraction in the sabellid worm, Pseudopotamilla occelata, during the rapid withdrawal reflex occurred only in the anterior half of the body. End-to-end shortening was never observed. The longitudinal muscles are well-developed in the anterior half, and poorly developed in the posterior half. Conduction of action potentials along the giant axons was blocked at the midbody, and was responsible for the anteriorly restricted body contraction. Electrophysiological and histological studies excluded the possibility that conduction block resulted from a safety factor attributable to the special geometry of the axons. Current injection across the giant axon membrane in the region of the conduction block indicated that changes in the properties of the membrane were responsible for the conduction block.
Kinematics and aerodynamics of the greater horseshoe bat,Rhinolophus ferrumequinum, in horizontal flight at various flight speeds
Authors: Aldridge H. D. 
Published: April 2021

ABSTRACTThe kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at a range of velocities are described. As flight speed increases there is a gradual change in the bat’s wingbeat kinematics, wingbeat frequency decreasing and wingbeat strokeplane angles increasing. Associated with these changes are changes in the wings’ incidence angles, particularly during the upstroke. At low speeds these are large and negative, suggesting thrust generation, while at high speeds these are positive and large, indicating that weight support and negative thrust are being generated. The change from one kinematic pattern to the other occurred gradually. The possible energetic and aerodynamic reasons for these changes are discussed.
Downstream pH Changes in Water Flowing Over the Gills of Rainbow Trout
Authors: Wright Patricia , Heming Tom , Randall David 
Published: April 2021

ABSTRACT
We investigated the pH of interlamellar water of trout (Salmo gairdneri) by following changes in the downstream pH of expired water using a stopped-flow method. As water flowed over the gills of control fish, there was a significant decrease in water pH. Acetazolamide added to the water increased the CO2 disequilibrium, while carbonic anhydrase (CA) eliminated the CO2 disequilibrium relative to control water. Mucus excreted by the fish was found to contain CA activity by the pH-stat technique. We conclude water acidification is due to the conversion of excreted CO2 to HCO3- and H+ at the gill surface.
Short Communications: Non-Invasive Measurement of Respiratory Tidal Volume in Aquatic, Air-Breathing Animals
Authors: Funk G. D. , Webb C. L. , Milsom W. K. 
Published: April 2021

ABSTRACT
In recent years, a method which allows breathing patterns to be fully quantified in aquatic, air-breathing species while free-ranging and undisturbed, has come into common use (Brett & Shelton, 1979; Glass, Boutilier & Heisler, 1983, 1985; Butler, Milsom & Woakes, 1984; Silver & Jackson, 1985; Milsom & Chan, 1986). Use of this method in our laboratory, however, has revealed several potential sources of error in the normal procedures used for calibrating this system for the measurement of tidal volume (VT). In the present study we have systematically studied these potential sources of error under a variety of conditions and describe a technique for eliminating these errors in routine measurements.
Thermal dependence of sprint performance of the lizard Sceloporus occidentalis
Authors: Marsh R. L. , Bennett A. F. 
Published: April 2021

ABSTRACT
Sprint velocity of the lizard Sceloporus occidentalis was maximal at preferred body temperature (Tb, 35°C). Mean running velocity (VR) and stride frequency (f) at this temperature were 3·23 ± 0·7 (mean ± S.E.M.) ms−1 and 15·6 ± 0·3 s−1, respectively. VR and f did not change significantly when Tb was raised to 40°C. At Tb values between 25 and 35°C the thermal dependencies of VR (Q10= 1·23) and f (Q10= 1·12) were quite low. At Tb values below 25°C the thermal dependence of these factors increased markedly. Stride length (Ls) was independent of Tb from 15 to 40°C. Lizards with a Tb of 10°C were largely incapacitated, and VR, f and Ls were all greatly reduced. Comparisons with measurements of the contractile properties of skeletal muscle of this species suggest that stride frequency is limited by the twitch contraction time at temperatures below 23°C. At higher temperatures, sprint performance is nearly independent of the thermal effects on the muscles.
Interspecific Comparisons of Endothermy in Honey-Bees (APIS): Deviations from the Expected Size-Related Patterns
Authors: Dyer Fred C. , Seeley Thomas D. 
Published: April 2021

ABSTRACT
We report the first measurements of thoracic flight temperature (Tth) in foragers of the three Asian honey-bee species (genus Apis), which, together with the European species A. mellifera, span a five-fold range in body mass from the smallest species to the largest. Over a 15°C range in ambient temperature (Ta), we found that Tth in each species is strongly dependent upon T” as previously shown for A. mellifera. However, the temperature gradients (Tth-Ta) at a given T, do not appear to increase with body size in the four species, as expected from many previous studies of endothermy in insects. The smallest species, A. florea, shows the smallest Tth-Ta, but the intermediate-sized A. cerana and A. mellifera both show a consistently higher Tth-Ta than the largest species, A. dorsata. We found that the rate of passive convective heat loss from the thorax scales linearly and inversely with body size in the four species, as in most insects, and that there is no striking anatomical evidence for differences in efficiency with which heat flow from the thorax to the abdomen is restricted. However, two important correlates of heat production -wing-loading and flight speed -are disproportionately high in A. cerana and A. mellifera relative to A. dorsata and A. florea, suggesting that an elevated mass-specific metabolic rate in flight may account for their unexpectedly high Tth-Ta. Furthermore, compared on a mass-specific basis, A. dorsata and A. florea are more similar to each other than either is to the other two species. This physiological dichotomy among the four species parallels a dichotomy in nesting behaviour and colony demography. Hence our results, in addition to raising many questions about physiological mechanisms in the energetics of honey-bees, suggest that there may be functional links between the energetic constraints on individuals and on colonies.
Gas Exchange and Ventilatory Responses to Hypoxia and Hypercapnia inAmphisbaena Alba(Reptilia: Amphisbaenia)
Authors: Abe Augusto S. , Johansen Kjell 
Published: April 2021

ABSTRACTTotal and cutaneous gas exchange and ventilatory responses to breathing hypoxic and hypercapnic gases were studied in Amphisbaena alba (Linnaeus), a burrowing squamate reptile. This species shows a very low oxygen uptake rate compared with other squamates of the same size (= 15·4, 36·2 and 49·0mlkg−1 h−1, at 20, 25 and 30°C, respectively). Cutaneous gas exchange represents a large fraction of the total uptake. Oxygen uptake was strongly affected by temperature [Q10 = 5·5 (20–25°C); 1·8 (25–30°C); 3·2 (20–30°C)]. A. alba shows a biphasic ventilatory pattern under hypoxic and hypercapnic conditions. A single breathing cycle, consisting of expiration-inspiration, includes a ventilatory period (VP) followed by a non-ventilatory (breath hold) period (NVP) of variable duration. When breathing air at 25°C the NVP typically occupied about 2 min. The ventilatory period occupied only 0·075 parts of a complete breath-to-breath cycle. Breathing hypoxic gases caused a pronounced rise in ventilation volume (VE) from an increase in tidal volume (VT) and frequency (f) at inspired O2 concentrations below 7%. Breathing hypercapnic gas mixtures induced a minor change in VT at CO2 concentrations below 3%, and VE increased mostly because of increases in f. End tidal O2 and CO2 tensions changed with increasing VE while breathing hypoxic and hypercapnic gas. The results are discussed in relation to the fossorial habits of A. alba, and are compared with data from other squamates.
Innervation of the Anterior and Posterior Levator Muscles of the Fifth Leg of the Crab Carcinus Maenas
Authors: Moffett Stacia , Yox Daniel P. , Kahan Linda B. , Ridgway Richard L. 
Published: April 2021

ABSTRACT
In the fifth pair of legs, the anterior levator muscle of the basi-ischiopodite (AL) consists of a dorsal thoracic head (ALd), two closely aligned ventral thoracic heads (ALv) and a small coxal head (ALc). Major thoracic subdivisions are separately innervated, whereas the nerve innervating the coxal head projects from ALd. The posterior levator (PL) is located in the coxa and is separately innervated.
Nerve recordings, dye backfilling, muscle fibre recordings and nerve crosssections yielded somewhat different estimates for the levator motor innervation.
Nerve backfills reveal at least 10 motoneurones supplying AL: six shared by ALd and ALv, one unique to ALv and three unique to ALd.
Nerve recordings reveal six motoneurones supplying ALd and five supplying ALv. Four (including the common inhibitor) are shared by ALd and ALv and six project from ALd to ALc.
Most AL muscle fibres are innervated by two or three motoneurones, but fibres innervated by five were encountered. Postsynaptic potentials ranging from small (&lt;l–5 mV) to large (15–25 mV) were found distributed throughout AL.
PL is innervated by two excitors not shared with AL and by the common inhibitor.
Electron micrographs reveal more axons than any of the methods for counting motoneurones. Neurones with axon diameters below 3 μm are likely to be sensory.
In Vitro and In Vivo Protein Synthesis Rates in a Crustacean Muscle During the Moult Cycle
Authors: El Haj A. J. , Houlihan D. F. 
Published: April 2021

ABSTRACT
In vivo protein synthesis rates were measured in the carpopodite extensor muscle of the shore crab, Carcinus maenas, following a single, high-dose injection of [3H]phenylalanine, which stabilized specific radioactivities in the free pools. In intermoult animals the percentage of protein mass synthesized per day (the fractional rate of protein synthesis) was 1·15% day−1 for the whole extensor muscle. The small, slow-type tonic fibres in the extensor had fractional rates of protein synthesis some 2·1 times higher than those of the large, fast-type phasic fibres.
Measurement of protein synthesis rates of extensor muscles from intermoult animals using an in vitro incubation over 2h gave fractional synthesis rates three times lower than those found in in vivo experiments. Compared with the intermoult animals, six- and three-fold increases in fractional synthesis rates were found in the extensor muscles from stages immediately preceding and following ecdysis, respectively. Microdissection of the muscle fibres revealed that the increased synthesis in postecdysial animals was occurring mainly at the external cuticular end of the muscle fibres. Autoradiographic analysis confirmed the cuticular end of the muscles as the major site of muscle protein synthesis. We conclude that the postecdysial increase in muscle fibre length and the associated increase in the sarcomere number is accompanied by an increase in protein synthesis in the muscles.
Temperature Regulation, Energy Metabolism and Mate-Searching in Rain Beetles (PleocomaSpp.), Winter-Active, Endothermic Scarabs (Coleoptera)
Authors: Morgan Kenneth R. 
Published: April 2021

ABSTRACTMale rain beetles (Pleocoma; Scarabaeidae) of western North America engage in intense mate-searching activity at night during the winter. They may achieve a temperature excess greater than 35 °C in flight, even though their thoracic pile is ineffective as insulation. Males also maintain thoracic temperature at high levels while walking on the ground in search of females. Female Pleocoma are flightless and are non-endothermic. In the laboratory, males maintained elevated body temperatures for as long as 4·2 h while walking in a respirometer chamber at an ambient temperature of 9°C. Energy metabolism and body temperature during these periods of sustained endothermy oscillated. Walking speed increased exponentially with body temperature. Male rain beetles compete (scramble competition) for opportunities to mate. It is likely that their mating success and ability to avoid predators depend on flight and rapid walking, which in turn depend on their having a high internal temperature.
Developmental endocrinology of larval moulting in the tobacco hornworm, Manduca sexta
Authors: Bollenbacher W. E. , Granger N. A. , Katahira E. J. , O’Brien M. A. 
Published: April 2021

ABSTRACT
A larval moult in the tobacco hornworm, Manduca sexta, involves an endocrine cascade that begins with the release of a cerebral peptide hormone, the pro-thoracicotropic hormone (PTTH). The release of PTTH is gated, occurs during the scotophase and appears to be developmentally cued. In fourth instar Manduca larvae, PTTH release into the haemolymph occurs as a single burst over a few hours during the head critical period, i.e. the time during which the head (brain) is needed for the initiation of the moult to the fifth (last) instar. Released PTTH activates the prothoracic glands (PGs), and within a few hours the cumulative effect of this event results in a dramatic increase in the haemolymph ecdysteroid titre, which then elicits the moult. An assessment of the capacity of the corpora allata (CA) to synthesize juvenile hormone (JH) in vitro indicates that the above sequence of endocrine events begins only when JH synthesis has reached a nadir for the instar. Since CA activity is an indirect measure of the haemolymph titre of the hormone, it is conceivable that the developmentally cued release of PTTH is permissively controlled by a decreasing haemolymph titre of JH. With the increase in the ecdysteroid titre which marks the end of this endocrine cascade, the CA again become active, presumably to cause the increase in the JH haemolymph titre which directs the larval moult. This in-vestigation has thus established the temporal and quantitative dynamics of the PTTH-PG axis that drive larval moulting and provides insight into the inter-endocrine regulatory relationships that may exist between the ecdysteroids and JHs. These possible relationships and the role of the brain in their regulation are discussed.
Integration of Wing Proprioceptive and Descending Exteroceptive Sensory Inputs by Thoracic Interneurones of the Locust
Authors: Elson Robert C. 
Published: April 2021

ABSTRACT
The campaniform sensilla on the wings of the locust are strain-sensitive mechanoreceptors that provide proprioceptive feedback about wing forces, particularly aerodynamic lift, experienced during flight. They can be excited by imposed deformations of the wing, including those caused by imposed wing twisting. The afferents of the single subcostal group of sensilla on the hindwing had the same directional selectivity for supinating twist and shared the properties of a dynamic sensitivity and adaptation. A group of strain-sensitive mechanoreceptors with similar properties, presumably campaniform sensilla, is also found in the forewings. Four types of thoracic interneurones influenced by these factors were recorded and stained intracellularly. The response of interneurone 5AA to imposed de-formations of the hindwing ipsilateral to its soma is determined by excitatory chemical synaptic input from the campaniform sensilla. Interneurone and sensilla have a common directional selectivity and optimal stimulus, and similar qualitative dynamics of response. Each spike of individual afferents is followed at short, constant latency by an excitatory postsynaptic potential (EPSP) in the interneurone, even at instantaneous frequencies of about 90 Hz. Physiological evidence is consistent with direct, chemically mediated synaptic inputs from campaniform sensilla afferents. Interneurone 5AA is also excited by a short-latency, chemical synaptic input from the ocelli when lights are turned off. EPSPs could be elicited by light-off stimuli to the median and contralateral, but not the ipsilateral, ocelli. In addition, the interneurone is excited when the head is moved relative to the thorax. The other three interneurones respond to strains in more than one wing. Inputs are derived from specific combinations of wings, with the sign of response depending on the neurone and the particular wing. Interneurones 3AA and 1AA are also phasically excited by light-off stimuli. In 1AA this response was shown to originate from the ocelli. Median and contralateral, but not ipsilateral, ocelli could evoke EPSPs. This neurone was also excited by imposed head movements. It is argued that the interneurones described here at suited to monitor lift production in particular wings and its pattern among several wings. Convergence of ocellar and head-motion inputs implies a function in the exteroceptive detection and correction of flight instability. It is inferred that these thoracic interneurones may act as the nexus for several different feedback pathways, proprioceptive and exteroceptive, which modulate flight motor output.
The thermal dependence of locomotor performance and muscle contractile function in the salamander Ambystoma tigrinum nebulosum
Authors: Else P. L. , Bennett A. F. 
Published: April 2021

ABSTRACT
The thermal dependence of locomotor performance and in vitro muscle mech-anical properties were studied after acclimation at 10° and 20°C in the salamander Ambystoma tigrinum nebulosum Hallowell. Performance measurements included burst and endurance capacities on land and in water. No significant differences in locomotor performance or muscle contractile properties were found between acclim-ation groups. Locomotor performance had only a slight thermal dependence, with Q10 values of 0·99—1·36 for running and swimming burst capacities (i.e. maximum speed and leg/tail cycling frequency). Running and swimming endurance capacities had thermal ratios of 1·58-1·66. Thermal dependence of muscle contractile rates was higher than that of locomotor performance: rates of force development for both isometric twitch and tetanus and maximal shortening velocity had Q10 values of 1·89—2·01. Maximal power output was also thermally dependent (Q10 = 2·33) and occurred at 38% of maximal (tetanic) force output. Force-generating capacities in isometric twitch and tetanus were relatively temperature-independent.