bluuebunny/crossref_metadata_2025_split huggingface dataset:
Haemolymph Acid–Base Status, Tracheal gas Levels and the Control of Post-Exercise Ventilation Rate in Grasshoppers
Authors: Krolikowski Katherine , Harrison Jon F. 
Published: April 2021

ABSTRACT
In grasshoppers, ventilation rate increases after jumping, in association with decreases in haemolymph pH and tracheal and increases in haemolymph and tracheal . Are these changes in haemolymph acid–base status or tracheal gas composition causally responsible for the increases in post-locomotion ventilation rate? To answer this question, we manipulated haemolymph acid–base status with injections into the haemocoel and independently manipulated tracheal and with tracheal perfusions. Using a new technique, we continuously monitored ventilation rate and ventilatory pressures on virtually unrestrained insects. Changes in haemolymph acid–base status or tracheal did not affect post-exercise ventilation rate, clearly demonstrating that the ventilatory stimulus associated with locomotion is not dependent on negative feedback from these variables. Post-exercise ventilation rate varied with tracheal , with the lowest ventilation rates observed at the lowest tracheal values, a result opposite to that expected if negative feedback from internal levels were to drive the increase in ventilation rate. Particularly after activity, there was considerable heterogeneity in unperfused animals between tracheal and haemolymph , and between tracheal in the thorax and leg, consistent with unidirectional airflow and a considerable role for diffusion gradients in the gas exchange of grasshoppers.
The Erythrocyte Na+ /H+ Exchangers of Eel (Anguilla Anguilla) and Rainbow Trout (Oncorhynchus Mykiss): a Comparative Study
Authors: Gallardo Romero María , Guizouarn Hélène , Pellissier Bernard , Garcia-Romeu Federico , Motais René 
Published: April 2021

ABSTRACT
Trout and eel red blood cell Na+ /H+ exchangers show widely different regulatory properties. Catecholamines, cyclic AMP and phorbol esters, which activate the trout red cell antiporter, do not affect the eel exchanger. Unlike the trout red cell exchanger, the eel red cell exchanger is strongly activated by cell shrinkage, allowing a remarkable cell volume recovery. These different regulatory properties probably indicate the existence of different isoforms of the exchangers in nucleated erythrocytes, since sensitivity to catecholamines is known to be dependent upon the presence of protein kinase A consensus sites on the cytoplasmic domain of the antiporter.
After shrinkage of eel erythrocytes, the Na+ /H+ exchange rate gradually increases to reach a maximum value after about 10 min. The magnitude of activation is a graded function of cell shrinkage. Deactivation, like activation, is induced by a volume change and occurs after some delay (lag time).
The response of the trout antiporter (βNHE) to cell shrinkage is much reduced compared with that of the eel antiporter. In addition, the antiporter is deactivated prior to restoration of the normal control volume, leaving cell volume regulation notably defective. The trout red cell antiporter, which is desensitized and enters a refractory state following hormonal activation, is only deactivated (it can be reversibly reactivated) after shrinkage-induced activation. This dual control may occur by both phosphorylation-dependent and phosphorylation-independent mechanisms.
In view of the similarities in the regulatory properties of eel and salamander (Amphiuma sp.) Na+ H+ exchangers, the expression of a putative K+ /H+ exchange mediated by the Na+ H+ exchanger was sought in eel erythrocytes. However, neither osmotic swelling nor calyculin-A-dependent phosphorylation revealed such a K+ /H+ exchange.
Respiratory and Cutaneous Evaporative Water Loss at High Environmental Temperatures in a Small Bird
Authors: Wolf Blair O. , Walsberg Glenn E. 
Published: April 2021

ABSTRACT
We measured rates of respiratory and cutaneous evaporative water loss as a function of air temperature in a small desert bird, the verdin Auriparus flaviceps. Birds were placed in a two-compartment metabolic chamber that separately collected water evaporated from the bird’s head and body. Cutaneous and respiratory evaporative water loss, as well as CO2 production, were measured in resting birds at 2 °C intervals between 30 and 50 °C. Metabolic rate was lowest at 38 °C (19 mW g−1 ) and increased to 28 mW g−1 at 50 °C. At the lowest air temperature, 30 °C, resting metabolic rate was 34 mW g−1. As air temperature increased from 30 to 50 °C, cutaneous water loss increased from 3.3 to 10.3 mg g−1 h−1 and respiratory water loss increased from 2.1–64.1 mg g−1 h−1. At moderate air temperatures (30–36 °C), water loss was divided almostevenly between respiratory and cutaneous components. As air temperature increased, however, verdins became heavily dependent on respiratory evaporation for heat dissipation. Evaporative water loss data for other species at high air temperatures suggest that partitioning of water loss may follow two different patterns. Evaporative heat dissipation may depend primarily on either cutaneous or respiratory modes of evaporative heat transfer. The physiological mechanisms and functional significance of these contrasting patterns of evaporative heat loss remain unknown.
Muscle Length Changes During Swimming in Scup: Sonomicrometry Verifies the Anatomical High-Speed Cine Technique
Authors: Coughlin David J. , Valdes Lexia , Rome Lawrence C. 
Published: April 2021

ABSTRACT
Recent attempts to determine how fish muscles are used to power swimming have employed the work loop technique (driving isolated muscles using their in vivo strain and stimulation pattern). These muscle strains have in turn been determined from the anatomical high-speed cine technique. In this study, we used an independent technique, sonomicrometry, to attempt to verify these strain measurements and the conclusions based on them.
We found that the strain records measured from sonomicrometry and the anatomical-cine techniques were very similar. The ratio of the strain measured from sonomicrometry to that from the anatomical-cine technique was remarkably close to unity (1.046±0.013, mean ± S.E.M., N=15, for transducers placed on the muscle surface and corrected for muscle depth, and 0.921±0.028, N=8, in cases where the transducers were inserted to the average depth of the red muscle). These measurements also showed that red muscle shortening occurs simultaneously with local backbone curvature, unlike previous results which suggested that white muscle shortening during the escape response occurs prior to the change in local backbone curvature.
The Effects Of Repeated Physical Stress On The β-Adrenergic Response Of The Rainbow Trout Red Blood Cell
Authors: Perry Steve F. , Reid Stephen G. , Salama Annika 
Published: April 2021

ABSTRACT
The effects of a 7-day period of daily physical stress (chasing until exhaustion) on the β-adrenergic response of the rainbow trout (Oncorhynchus mykiss) red blood cell (rbc) were examined in vitro. Physical stress was associated with pronounced increases in the circulating levels of the catecholamine hormones (adrenaline and noradrenaline) measured on days 1, 3 and 7 of the stress regime. After 7 days, the numbers of high-affinity cell surface β-adrenoceptors were reduced in the physically stressed fish when measured in vitro under conditions of normoxia (20 % reduction) or hypoxia (30 % reduction). Under hypoxic conditions, the binding affinity of the rbc β-adrenoceptor was significantly higher in the stressed fish.
Although the stressed fish had fewer β-adrenoceptors, rbc adrenergic responsiveness was enhanced after 7 days of physical stress as determined from dose–response curves relating noradrenaline concentration to water and Na+ accumulation (indices of rbc adrenergic Na+/H+ exchange activity). The EC50 values (concentrations yielding half-maximal responses) for noradrenaline were lowered significantly by 1.7-to 3.9-fold in the blood from physically stressed fish. The enhanced adrenergic responsiveness of the rbcs appeared to be unrelated to changes in the initial steps of the -adrenergic signal transduction pathway leading to cyclic AMP production because physical stress was without effect on the magnitude or the dose-dependency of rbc cyclic AMP accumulation.
To determine whether post-cyclic-AMP events were affected by physical stress, water and Na+ accumulation were measured in rbcs that had been incubated with the permeable cyclic AMP analogue 8-bromo cyclic AMP. The EC50 values for 8-bromo cyclic AMP were lowered by 1.6-to 1.7-fold in the blood from stressed fish.
These experiments demonstrate that repeated physical stress significantly enhances the adrenergic responsiveness of the rainbow trout rbc, presumably by modifying the sensitivity of the Na+/H+ exchanger (or the steps immediately preceding exchanger activation) to cyclic AMP. The results are discussed with respect to the interrelationships between chronic and acute stress responses in fish.
Operant Conditioning of Aerial Respiratory Behaviour in Lymnaea Stagnalis
Authors: Lukowiak Ken , Ringseis Erika , Spencer Gaynor , Wildering Wic , Syed Naweed 
Published: April 2021

ABSTRACT
In this study, we operantly conditioned the aerial respiratory behaviour of the freshwater snail Lymnaea stagnalis. Aerial respiration in Lymnaea stagnalis is accomplished by the spontaneous opening and closing of its respiratory orifice, the pneumostome, at the water surface. Weak tactile stimulation of the pneumostome area, when the pneumostome is open, evoked only the pneumostome closure response, which is one aspect of the escape–withdrawal reflex. Pneumostome stimulation resulted in its closure and the termination of aerial respiratory activity. A contingent tactile stimulation paradigm was used to operantly condition the animals. Stimulation of the pneumostome whenever the animal attempted to breathe resulted in significantly fewer attempts to open the pneumostome as training progressed. The latency of the first breath (subsequent to stimulation), the number of breaths and the total breathing time were measured before and after each training period. Significant, quantifiable changes in these behavioural parameters were observed only in the operant conditioning group animals. Control animals receiving tactile stimulation to their pneumostome not contingent upon pneumostome opening movements (yoked controls) or those that were physically prevented from surfacing to breathe (hypoxic controls), did not exhibit significant changes in these behavioural parameters. Our data provide the first direct evidence for operant conditioning of respiration in any animal.
Locomotory behavior in the hawkmoth Manduca sexta: kinematic and electromyographic analyses of the thoracic legs in larvae and adults
Authors: Johnston Rebecca M. , Levine Richard B. 
Published: April 2021

ABSTRACT
During metamorphosis in Manduca sexta, muscles and most sensory structures of the thoracic legs undergo extensive changes while the motor neurons that are present in the larva persist into the adult. The main goal of this work was to identify similarities and dissimilarities in thoracic leg movements during crawling in larvae and walking in adults. This information provides a foundation for understanding the extent to which centrally located neural elements are reorganized during metamorphosis to accommodate changes in locomotion. Analysis of electromyographic activity from leg muscles synchronized with video-taped recordings of the leg movements during larval crawling and adult walking revealed differences in cycle periods as well as intersegmental and intrasegmental patterns of coordination. Larval crawling was characterized by synchronous movements of segmental pairs of legs as activity proceeded slowly from the more posterior to the more anterior segments. During crawling, antagonistic muscles maintained a strict reciprocity. In contrast, walking in adults was characterized by fast, alternating movements of the left and right prothoracic legs and more variable coordination patterns in the mesothoracic and metathoracic legs (ranging from synchrony to alternation). In adults, sensory information, possibly associated with the weight-bearing or postural demands of walking on an incline, contributed to a strong dependence between the duration of muscle activity and cycle period and to the extent that the muscle activity overlapped during walking.
Effects of Pineal Indoles and Parachlorophenylalanine on Seasonal Reproduction in the Pigeon
Authors: Ramachandran A. V. , Patel M. M. , Patel C. S. 
Published: April 2021

ABSTRACT
The effect of melatonin, methoxytryptophol (ML), methoxytryptamine (MT) and parachlorophenylalanine (p-CPA) on the mass and histology of the testes and the adrenal and thyroid glands and on serum thyroid hormone levels have been studied in the recrudescent phase of the feral pigeon Columba livia. All the pineal indoles showed a common anti-gonadal effect, resulting in the arrest of spermatogenesis and the degeneration of germ cells. Treatment with melatonin resulted in adreno-cortical enlargement and medullary hypertrophy, whereas ML, MT and p-CPA induced medullary enlargement and hypertrophy without having much influence on the cortex. Treatment with melatonin and ML brought about colloid retention in the thyroid follicles, while MT and p-CPA induced colloid depletion and hypertrophy of the follicular epithelium. From the present study, it can be concluded that both pineal indoles and p-CPA induce testicular regression in the breeding phase but do so by different mechanisms.
The Peripheral Auditory Characteristics of Noctuid Moths: Responses to the Search-Phase Echolocation Calls of Bats
Authors: Waters Dean A. , Jones Gareth 
Published: April 2021

ABSTRACT
The noctuid moths Agrotis segetum and Noctua pronuba show peak auditory sensitivity between 15 and 25 kHz, and a maximum sensitivity of 35 dB SPL. A. segetum shows a temporal integration time of 69 ms. It is predicted that bats using high-frequency and short-duration calls will be acoustically less apparent to these moths. Short-duration frequency-modulated (FM) calls of Plecotus auritus are not significantly less acoustically apparent than those of other FM bats with slightly longer call durations, based on their combined frequency and temporal structure alone. Long-duration, high-frequency, constant-frequency (CF) calls of Rhinolophus hipposideros at 113 kHz are significantly less apparent than those of the FM bats tested. The predicted low call apparency of the 83 kHz CF calls of R. ferrumequinum appears to be counteracted by their long duration. It is proposed that two separate mechanisms are exploited by bats to reduce their call apparency, low intensity in FM bats and high frequency in CF bats. Within the FM bats tested, shorter-duration calls do not significantly reduce the apparency of the call at the peripheral level, though they may limit the amount of information available to the central nervous system.
Retinal Development and Visual Sensitivity of Young Pacific Sockeye Salmon (Oncorhynchus Nerka)
Authors: Flamarique Iñigo Novales , Hawryshyn Craig W. 
Published: April 2021

ABSTRACT
The development of photoreceptor cell types and the visual sensitivity of young sockeye salmon were examined. In contrast to previous findings from rainbow trout, rod outer segments were observed in the embryo 1.5 weeks before hatching. At this stage, a full square mosaic with accessory corner cones was visible in the central retina. Post-hatching retinal development is similar to that of other fish species. During the first 11 months of development, the fibrous and interplexiform layers, the outer nuclear layer, the visual cell layer and the retinal pigment epithelium thicken. The ganglion cell layer and the inner nuclear layer regress. In addition, the mean diameter of the cones increases, with that of double cones increasing faster than that of either of the single cone types. As is the case for other salmonids, the density of accessory corner cones diminishes after smoltification (a developmental stage in salmonids). The retina of smolts exhibits a full square mosaic pattern in some peripheral areas and near the central embryonic fissure. However, unlike findings from rainbow trout, compound action potential recordings from the optic nerve of smolt sockeye reveal the presence of four cone mechanisms with sensitivity maxima at 380 (ultraviolet), 425 (short), 520 (middle) and 635 nm (long wavelength). There is also a rod mechanism with maximum sensitivity around 530 nm. Smolts also exhibit polarization sensitivity to 380 nm light under a white crepuscular background.
Differential Protein Profiles Reflect the Different Lifestyles of Symbiotic and Aposymbiotic Anthopleura Elegantissima, a Sea Anemone from Temperate Waters
Authors: Weis Virginia M. , Levine R. Paul 
Published: April 2021

ABSTRACT
Mutualistic associations are prevalent in virtually all environments yet relatively little is known about their complex biochemical and molecular integration and regulation. The endosymbiosis between cnidarians such as the sea anemone Anthopleura elegantissima and the photosynthetic dinoflagellate Symbiodinium californium, in which the algal symbionts are housed in vacuoles within animal endodermal cells, is an ideal model for the study of highly integrated associations at the biochemical and molecular levels. This study describes differential protein synthesis between symbiotic A. elegantissima, collected from environments with high levels of light in the intertidal zone and A. elegantissima that naturally lack symbionts (aposymbiotic), collected from nearby deep-shade habitats. Two-dimensional gel electrophoresis profiles of both steady-state and newly synthesized proteins were compared between the two types of animals using scanning densitometry and image analysis. Symbiotic and aposymbiotic animals share a majority of proteins; however, striking differences in several abundant proteins in steady-state profiles occur. Two proteins are unique to symbiotic animals, one at 32 kDa with an isoelectric point (pI) of 7.9 and another at 31 kDa, pI 6.3. Levels of six proteins with an apparent molecular mass of 25 kDa and pI values ranging from 4.8 to 5.5 are greatly enhanced in aposymbiotic animals. Furthermore, profiles of newly synthesized proteins from symbiotic animals contain a unique cluster of proteins ranging from 25 to 30 kDa and pI 6.6 to 6.9. These marked differences in protein profiles must be a reflection either of underlying differences in the regulation of gene expression or in post-translational modification of common proteins. Identifying the symbiosis-specific products present in A. elegantissima and identifying the inter-partner signaling and cues that result in differential expression will provide an insight into the understanding of these highly integrated associations.
Continuous Tracer Infusion to Measure in Vivo Metabolite Turnover Rates in Trout
Authors: Haman François , Weber Jean-Michel 
Published: April 2021

ABSTRACT
This paper describes a double dorsal aorta catheterization technique allowing the measurement of substrate turnover rates by continuous infusion of metabolic tracers in rainbow trout. The placement of both catheters can be performed in about 30 min with minimal surgical training. As a practical example of a routine substrate flux measurement, glucose turnover rate of resting trout was measured by primed continuous infusion of 6-[3H]glucose through one of the catheters and blood sampling from the other. The animals maintained resting metabolic rate, normal blood glucose and low blood lactate concentrations throughout the experiments. Glucose isotopic steady state was achieved in less than 40 min, and mean turnover rate was 9.0±0.7 μmol kg-1 min−1 (N=8). Comparison with published glucose turnover rates measured in trout and other teleost species suggest that values previously obtained using the ‘bolus injection technique’ are underestimates of true flux rates. We conclude that the simple surgical technique presented here opens the door to the dynamic study of substrate kinetics under a variety of experimental conditions and that it can be adapted to the investigation of most metabolic substrates, including fatty acids, glycerol, amino acids and lactate, in addition to glucose. Future application of the continuous infusion technique under steady-state as well as non-steady-state conditions will add a new dimension to the general understanding of fish metabolism.
The Discharge Mechanism of Acontial Nematocytes Involves the Release of Nitric Oxide
Authors: Salleo Alberto , Musci Giovanni , Barra Paolo F. A. , Calabrese Lilia 
Published: April 2021

ABSTRACT
The events which trigger the activation of nematocytes are still poorly understood, and no evidence has been presented so far on either the nature of the activatory signal for the nematocyte or the transduction mechanism. In this paper, we present evidence for a role of NO in the discharge of acontial nematocytes. A citrulline-forming enzymatic activity, significantly decreased by the NO synthase inhibitor Nw-nitro-L-arginine (L-NNA) and by the Ca2+-chelating agent EGTA, was found in the acontial tissue of Aiptasia diaphana. Staining for NADPH diaphorase suggested that NO synthase is localized in supporting cells surrounding the nematocytes. The ability of K+ to induce the discharge of nematocytes in situ could be abolished by preincubation of acontia with L-NNA and restored by addition of excess L-arginine. Direct measurements on K+-induced discharging nematocytes in situ confirmed that NO was released by stimulated acontia. Both in situ and isolated acontial nematocytes promptly discharged when perfused with an aqueous solution of NO. The responsiveness to NO of isolated nematocytes was not abolished in Ca2+-free medium or by treatment with La3+, a well-known Ca2+ channel inhibitor. Since the discharge of in situ nematocytes is known to be Ca2+-dependent, it is proposed that activation of in situ acontial nematocytes is triggered by a Ca2+-dependent release of NO from supporting and/or sensory cells.
Sulfide May Directly Modify Cytoplasmic Hemoglobin Deoxygenation in Solemya Reidi Gills
Authors: Kraus David W. , Doeller Jeannette E. , Powell C. Stephen 
Published: April 2021

ABSTRACT
The clam Solemya reidi, which survives in sulfide-rich sediments, houses intracellular sulfide-oxidizing bacteria as symbionts in its gills. The gill bacteriocytes also contain a high concentration of cytoplasmic hemoglobin. Although the in situ hemoglobin optical spectrum was not altered in the presence of hydrogen sulfide, hemoglobin deoxygenation was significantly slowed and incomplete when sulfide was present. A sulfide-mediated decrease in oxygen consumption rate, a shift in intracellular pH or the conversion of hemoglobin to an unusual derivative could all slow in situ hemoglobin deoxygenation. However, under low sulfide levels at which deoxygenation is incomplete, oxygen consumption rate was not inhibited, intracellular pH decreased by less than 0.1 units and the only hemoglobin derivatives present were deoxyhemoglobin and oxyhemoglobin. These results and preliminary measurements of the isolated gill hemoglobin dissociation rate constants suggest that sulfide or a rapidly formed oxidation product may directly influence the rate of Solemya reidi gill hemoglobin deoxygenation.