bluuebunny/crossref_metadata_2025_split huggingface dataset:
in Vitro Metabolic Depression of Tissues From the Aestivating Frog Neobatrachus Pelobatoides
Authors: Flanigan James E. , Withers Philip C. , Guppy Michael 
Published: April 2021

ABSTRACT
The desert frog Neobatrachus pelobatoides reduced its resting metabolism in vivo by 60–70% during 5–7 weeks of aestivation (summer dormancy). The rate of oxygen consumption (V˙O2) of isolated and intact skeletal muscle, measured in vitro, was 70% lower for aestivating frogs compared with non-aestivating frogs. The cause of the reduced V˙O2 of aestivating frog muscle must lie in the tissue itself rather than being induced by external factors such as oxygen supply or bloodborne metabolites (because these were identical in the in vitro assay conditions), by any short-term effects produced by hormones (as these would have been washed out of the tissues during incubation) or by tissue dehydration (as the tissues from aestivating frogs had rehydrated to non-aestivating levels). The reduced in vitro muscle V˙O2 accounted for 60–77% of the frogs in vivo metabolic depression that accompanied aestivation. Other tissues of the aestivating frog, namely intestine, liver, skin and fat, did not have a reduced in vitroV˙O2. We suggest that metabolic depression is initiated by reduced energy demand in cells and this consequently leads to reduced energy production.
Simultaneous Measurements of Spiracular and Cuticular Water Losses in Periplaneta Americana: Implications for Whole-Animal Mass Loss Studies
Authors: Machin J. , Kestler P. , Lampert G. J. 
Published: April 2021

ABSTRACT
Spiracular and cutaneous water loss through the cuticle and spiracles of Periplaneta americana was measured in animals of differing initial water contents under controlled temperature, humidity and airflow conditions, by continuous weighing (resolution ±10μg). Stable water loss rates (2.09×10−8 to 3.47 ×10−8 g h−1 cm−2 Pa−1) were as much as an order of magnitude less than those reported in earlier studies employing intermittent weighing techniques. We suggest that increased water loss caused by substantial increases in ventilatory water loss during the episodic disturbances required by intermittent weighing is the principal contributor to this discrepancy.
Water losses, as well as the interval between spiracular ventilations, decreased with water content. However, greater variation was primarily due to interruptions of the regular cyclic pattern of ventilation by highly variable, activity-related bouts of increased ventilatory loss. Variations in water loss appear to be too large and too rapid to be convincingly explained in terms of cuticular conductance. Our results suggest that previous experiments using 5% CO2 anaesthesia, linking changes in total water loss to the conducting properties of the cuticle, were not valid. There seems to be no adaptive value for the proposed voluntary increases in cuticular permeability in an animal where ventilatory water losses can be so high.
Kinematic and Electromyographic Analysis of the Functional Role of the Body Axis During Terrestrial and Aquatic Locomotion in the Salamander Ambystoma Tigrinum
Authors: Frolich Larry M. , Biewener Andrew A. 
Published: April 2021

ABSTRACT
Aquatic neotenic and terrestrial metamorphosed salamanders (Ambystoma tigrinurn) were videotaped simultaneously with electromyographic (EMG) recording from five epaxial myotomes along the animal’s trunk during swimming in a flow tank and trotting on a treadmill to investigate axial function during aquatic and terrestrial locomotion. Neotenic and metamorphosed individuals swim using very similar axial wave patterns, despite significant differences in axial morphology. During swimming, both forms exhibit traveling waves of axial flexion and muscle activity, with an increasing EMG-mechanical delay as these waves travel down the trunk. In contrast to swimming, during trotting metamorphosed individuals exhibit a standing wave of axial flexion produced by synchronous activation of ipsilateral epaxial myotomes along the trunk. Thus, metamorphosed individuals employ two distinct axial motor programs -one used during swimming and one used during trotting. The transition from a traveling axial wave during swimming to a standing axial wave during trotting in A. tigrinurn may be an appropriate analogy for similar transitions in axial locomotor function during the original evolution of terrestriality in early tetrapods.
Abdominal Postural Motor Responses Initiated by The Muscle Receptor Organ in Lobster Depend Upon Centrally Generated Motor Activity
Authors: Sukhdeo Suzanne C. , Page Charles H. 
Published: April 2021

ABSTRACT
Stretch stimulation of the abdominal muscle receptor organ of the lobster Homarus americanus initiated spike discharge of its tonic sensory neuron (SRI). This sensory response evoked a series of tonic postural reflex responses in the motor neurons that innervate the superficial extensor and flexor muscles of the abdominal postural system. The type of motor response depended on whether a flexion or extension pattern of spontaneous activity was being generated by the postural efferents. Spontaneous shifts between these centrally generated motor activities completely changed the SRl-evoked reflex responses. During spontaneous centrally initiated flexion activity, tonic SRI neuron discharge elicited an assistance response that included excitation of a medium-sized flexor excitor (f3) and the peripheral extensor inhibitor (e5), and inhibition of at least one extensor excitor. Neither the other flexor excitors nor the peripheral flexor inhibitor (f5) were affected by SRI excitation. During spontaneous centrally initiated extension activity, SRI activity elicited a response that included excitation of the extensor excitors and the flexor peripheral inhibitor (f5) only, f3 and e5 spontaneous activities were unchanged. This response was a resistance reflex, since SRI discharge normally resulted from an imposed abdominal flexion. The SRl-initiated control of postural motor activity in lobster differs from previously published results in the crayfish Procambarus clarkii.
Thermosensitivity of Different Parts of the Spinal Cord of the Pigeon (Columba Livia)
Authors: Østnes Jan E. , Bech Claus 
Published: April 2021

ABSTRACTIn the present study we compared the metabolic responses to selective cooling of the cervical (C9–Th1) and the thoracic (Th1–Th5) parts of the spinal cord of pigeons. To obtain selective cooling of the two parts, two thermodes (4.5 cm) were inserted into the vertebral canal through an aperture in the first thoracic vertebra. During the experiments, one of the two thermodes was perfused with water at a constant temperature for periods of 15 min. The thermosensitivity was defined as the relationship between the amount of extra heat produced and the amount of heat extracted from the stimulated area. Cooling of the thoracic part resulted in a substantially higher increase in metabolic heat production and body temperature (Tb) than did cooling of the cervical part. It is concluded that the thoracic part of the spinal cord has a greater thermosensitivity than the cervical part. In addition, it was found that the difference in elevation of Tb during cooling of the two parts was not simply a result of differences in the amount of heat produced. When the changes in Tb were related to the difference between the extra heat produced and the amount of heat extracted, the increase in Tb during thoracic cooling was greater than that recorded during cervical cooling. This indicates that cooling of the two different parts of the spinal cord also had different effects on the thermoregulatory effector mechanisms that influence thermal conductance.The study seems to provide evidence in favour of afferent transmission of cold signals in the spinal cord.
Influence of Ambient Calcium Levels on Stanniocalcin Secretion in the European EEL (Anguilla Anguilla)
Authors: Hanssen R. G. J. M. , Mayer-Gostan N. , Flik G. , Bonga S. E. Wendelaar 
Published: April 2021

ABSTRACT
The cells of the corpuscles of Stannius appeared to be more active in eels acclimated to sea water than in eels acclimated to fresh water. In acclimated eels, however, total and ionic plasma calcium concentrations and stanniocalcin titers did not differ. This suggests that levels of stanniocalcin in freshwater-acclimated eels are sufficient to maintain normocalcemia in sea water. When freshwater-acclimated eels were transferred directly to sea water, total and ionic calcium concentrations in the plasma increased significantly within 24 h but there was no apparent effect on the corpuscles of Stannius within the same time. This suggests that changes in secretory activity of the corpuscles of Stannius do not occur rapidly when they are presented with a hypercalcemic challenge. Conversely, when seawater-acclimated eels were transferred to fresh or distilled water there appeared to be a very rapid reduction in secretory activity in the corpuscles of Stannius, as indicated by the rapid accumulation of secretory granules. These data suggest that stanniocalcin turnover is more rapid in seawater-acclimated eels and that the secretory activity of the corpuscles of Stannius is rapidly reduced when a hypercalcic challenge is removed.
Electrical Responses to Chemical Stimulation of Squid Olfactory Receptor Cells
Authors: Lucero Mary T. , Horrigan Frank T. , Gilly Wm F. 
Published: April 2021

ABSTRACT
Electrical properties of isolated olfactory receptor cells were studied using voltage- and current-clamp techniques based on whole-cell patch-clamp methods. Squid olfactory receptor cells contain voltage-gated Na+ and K+ channels and are capable of generating action potentials. Chemicals that elicit escape-jetting responses in behavioral experiments affect the excitability of isolated receptor cells. One set of such chemicals, including quaternary ammonium ions and aminopyridines, blocks K+ channels and increases excitability. Squid ink and L-Dopa also elicit escape jetting, but these substances increase membrane conductance, hyperpolarize the receptor cell and decrease excitability. These experiments indicate that sensory neurons of the olfactory organ are capable of detecting chemical signals and that at least two different transduction mechanisms can lead to similar behavioral responses.
Integumental Taurine Transport in Mytilus Gill: Short-Term Adaptation to Reduced Salinity
Authors: Silva Arnold L. , Wright Stephen H. 
Published: April 2021

ABSTRACT
Taurine, a principal osmolyte in molluscan integument, is actively transported from sea water by Mytilus gill by means of a Na+-dependent process. In this study we examined the response of this transport to reductions in external salinity, i.e. the response to reductions in osmotic concentration as well as Na+ concentration. Acute exposure of isolated gill tissue to 60 % artificial sea water (ASW) resulted in a greater than 85 % inhibition of taurine uptake, substantially more than the 45 % inhibition predicted on the basis of the acute reduction in external [Na+], Within 60min, however, taurine transport recovered to the level predicted by the Na+ concentration in dilute sea water. Isolated gills acutely exposed to 60% ASW made isosmotic to normal (100 %) ASW with mannitol had rates of taurine uptake comparable to gills acclimated for 60min. Taurine uptake by gill tissue exposed to 60% ASW for 60 min and then returned to 100% ASW for 90 min was not significantly different from that of control gills held in 100% ASW. Glucose uptake by the gill during acute exposure to reduced salinity responded in a pattern similar to that of taurine. Gill tissue increased by 20 % in wet mass within 2 min of exposure to 60% ASW, but returned to control mass within 30-60 min, presumably reflecting cell volume regulation. Long-term (12 days) exposure to reduced salinities was not accompanied by increases in taurine transport over that of gills observed following the 60min ‘short-term’ acclimation. These results suggest that Mytilus gill undergoes a rapid (albeit incomplete) recovery from the extreme inhibition of transport associated with abrupt changes in salinity, and the extent of recovery is defined by the availability of Na+ in the external medium. The extreme sensitivity of taurine uptake observed after acute exposure of gills to reduced salinity is related to the osmotic concentration of the medium, and is possibly linked to a change in cell volume.
Evidence for a Brain Factor That Stimulates Deposition of Puparial Hydrocarbons in Diapausing Flesh Flies
Authors: Yoder Jay A. , Denlinger David L. 
Published: April 2021

ABSTRACT
Puparia from diapausing pupae of the flesh fly Sarcophaga crassipalpis are lined with twice as much hydrocarbon as puparia from nondiapausing pupae (J. A. Yoder, D. L. Denlinger, M, W. Dennis and P. E. Kolattukudy, unpublished observations). The additional hydrocarbon favors water conservation during diapause by reducing water loss, enhancing water vapor absorptivity and elevating the critical transition temperature (Yoder and Denlinger, 1991). In this study we seek to identify the source of a hormonal modulator that would account for this difference in hydrocarbons. Our results suggest that a factor unique to the brains of diapause-programmed larvae is responsible for increasing the quantity of hydrocarbon deposited on the puparium. Cyclic AMP elicits the same effect, suggesting that the factor is probably a neuropeptide or another modulator that uses cyclic AMP as a second messenger.
Adenosine Release in the Anoxic Turtle Brain: A Possible Mechanism for Anoxic Survival
Authors: Nilsson Göran E. , Lutz Peter L. 
Published: April 2021

ABSTRACT
In the brain of most vertebrates, anoxia or ischaemia rapidly causes a fall in ATP levels and in the activity of the Na+/K+ pump, resulting in general depolarization followed by a cascade of catastrophic events (Hansen, 1985; Hochachka, 1986). By contrast, the brain of freshwater turtles survives many hours of complete anoxia at 25°C. Hence, the turtle brain has become the archetype of an anoxia-tolerant brain, and considerable efforts have been devoted to finding the mechanisms underlying its exceptional ability to survive without oxygen. The turtle brain’s main strategy for anoxic survival seems to be to decrease energy utilization, so that ATP consumption can be met by glycolytic ATP production alone (Sick et al. 1982; Lutz et al. 1985; Chih et al. 1989). However, the mechanisms mediating the lowered energy consumption have remained obscure.
Non-Catch Contraction in Paramyosin-Containing Muscle in an Echinothuriid Sea Urchin Asthenosoma Ijimai
Authors: Tsuchiya Teizo , Obinata Takasi , Sato Makoto , Mori Takao , Suzuki Emiko , Amemiya Shonan 
Published: April 2021

ABSTRACT
It has long been known that certain molluscan smooth muscles become stretch resistant and can hold the shell closed for extended periods without fatigue and at low rates of oxygen consumption. This prolonged state of contraction is called catch, and the maintenance of catch force is at least 10 times more economical than the contraction that precedes catch. This mechanism has been extensively studied in the anterior byssus retractor muscle (ABRM) of Mytilus edulis (Rüegg, 1971, 1986).
Respiratory and Circulatory Adjustments During Aquatic Treadmill Exercise In The European Shore Crab Carcinus Maenas
Authors: Hamilton N. M. , Houlihan D. F. 
Published: April 2021

ABSTRACT
Carcinus maenas (L.) were exercised using a novel design of aquatic treadmill respirometer. Tethered exercise was performed in sea water at 5.8mmin−1 for 5 min. The rate of oxygen consumption and the heart and scaphognathite beat rates increased at the onset of exercise, reaching a steady state within 180 s. The estimated haemolymph flow rate rose 2.6-fold during exercise, achieved by a 1.8-fold increase in heart rate and a 1.5-fold increase in the estimated cardiac stroke volume. The haemolymph total oxygen content difference increased significantly during exercise. Haemolymph total carbon dioxide content did not change significantly during exerise, but haemolymph pH deceased as a result of an L-lactate-induced metabolic acidosis. The acidosis may also have led to a reduced Bohr shift. It is concluded that O2 and CO2 exchange were not impaired during exercise and that C. maenas relied primarily upon O2 to fuel underwater running at 5.8 m min−1.
A Method for Controlling the Feeding Behaviour of Aquatic Birds: Heart Rate and Oxygen Consumption During Dives of Different Duration
Authors: Bevan R. M. , Keijer E. , Butler P. J. 
Published: April 2021

ABSTRACT
Tufted ducks, Aythya fuligula, were trained to dive for different durations in shallow tanks using a computer-controlled system of lights. The birds were rewarded with food for a correct response, i.e. performing a dive of the required duration. When dive durations (td) elicited by the system were longer than the durations required, the extra time was spent feeding. As the required duration was increased, so the time spent feeding decreased, and the required and actual dive durations approached equality. This occurred at approximately 40 s, although some birds did perform dives of up to 45 s.
Heart rate (FH) and oxygen consumption () were measured from the birds during voluntary diving using an implanted radiotransmitter and respirometry, respectively. The oxygen consumption during submersion decreased with increasing mean td, and may reflect a reduction in aerobic metabolism as a dive progressed, possibly as a result of reduced buoyancy or through a gradual switch to anaerobic metabolism.
Over a total dive cycle (the time spent submerged plus that spent on the surface between dives), FH proved to be a very good predictor of , with an error of only +7.9%. This compares favourably with other methods used to determine the energy expenditures of animals, e.g. the doubly labelled water and the time energy budget methods, and shows that the electronic acquisition of fH could be a useful tool for estimating the energy usage of free-living, aquatic birds.
The Influence of Cerebellar Lesions on the Swimming Performance of the Trout
Authors: Roberts B. L. , Rossem A. Van , Jager S. De 
Published: April 2021

ABSTRACT
The influence of partial cerebellar ablation on the performance of rainbow trout, Oncorhynchus mykiss, swimming in a water tunnel was studied. Before surgery, all fish maintained a steady position in the water tunnel at all speeds tested. A linear relationship was found between the specific velocity (body lengths−1) and the tail-beat frequency. After partial cerebellectomy, the fish swam well in the tunnel at low speeds, retaining the relationship between tail-beat frequency and specific velocity, but they were unable to maintain a steady position at water speeds requiring tail-beat frequencies above 3.5 s−1 and were swept backwards. Two sham-operated fish swam at all water speeds tested. Post mortem histological investigation showed that the lesions were restricted to the cerebellar corpus. We conclude that the cerebellum plays no role in the generation of motor programmes but may be essential for their selection and implementation.
Responses to Freezing Exposure of Hatchling Turtles Trachemys Scripta Elegans: Factors Influencing the Development of Freeze Tolerance by Reptiles
Authors: Churchill Thomas A. , Storey Kenneth B. 
Published: April 2021

ABSTRACT
Hatchling red-eared turtles Trachemys (=Pseudemys) scripta elegans (Wied) from a Louisiana population display a significant ability to withstand the freezing of extracellular body fluids. All animals survived at least 2 h of freezing at –2.5 or –4°C. At –2.5°C, survival declined to 50% after 6h of freezing and no animals recovered after 24 h or longer, when mean ice content reached 54.7± 1.4% of total body water. At –4°C, all turtles recovered from 4h of freezing exposure with a mean ice content of 49.6±2.4%, but survival dropped sharply thereafter with no animals recovering after 8h, when ice content had reached 64.5±0.7%. Survival times were substantially shorter and percentage ice values greater than comparable values for hatchling painted turtles (Chrysemys picta (Schneider)) from northern populations subjected to identical freezing exposures. The ability to synthesize cryoprotectants in response to freezing was poorly developed in T. s. elegans; maximal accumulation of glucose was only 3.2 μmolg−1 wet mass in liver. Lactate content increased two-to threefold in oxygen-sensitive organs (heart and brain) during freezing, but levels of lactate and other putative cryoprotectants were unchanged in other organs. Total free amino acid content rose significantly in liver, muscle and blood during freezing; increased taurine concentration was primarily responsible for the changes in liver and blood. The capacity for freezing survival by T. s. elegans hatchlings from southern populations would be of limited use for hibernation in a cold climate, but the metabolic responses to freezing displayed by these animals might be enhanced by northern populations to increase their freeze tolerance.
The Relationship Between β-Adrenoceptors and Adrenergic Responsiveness in Trout (Oncorhynchus Mykiss) and Eel (Anguilla Rostrata) Erythrocytes
Authors: Perry Steve F. , Reid Scott D. 
Published: April 2021

ABSTRACT
Experiments were performed invitro specifically to elucidate the underlying mechanism(s) of the attenuated adrenergic responses of eel (Anguillarostrata) erythrocytes. This was achieved by comparing β-adrenoceptor numbers and affinities in addition to (i) Na+/H+ exchange activity, (ii) cell swelling and (iii) cyclic AMP formation mediated by catecholamines in eel and trout (Oncorhynchusmykiss) erythrocytes under normoxic and hypoxic conditions.
Under normoxic conditions, eel erythrocytes displayed a total absence of Na+/H+ exchange activity (as determined from measurements of extracellular pH) after addition of noradrenaline (50–1000 nmol l− 1) in contrast to a pronounced dose-dependent response in trout. Incubation of the blood under hypoxic conditions, to achieve approximately 50% haemoglobin O2-saturation, further increased the extent of Na+/H+ exchange activation in trout and elicited a statistically significant, although physiologically small (10% of the response in trout), activation of H+ extrusion activity in eel. Catecholamine-mediated cell swelling, although obvious in trout, was absent in eel when estimated under hypoxic conditions.
Eel erythrocytes possessed approximately 50% fewer surface β-adrenoceptors than did trout erythrocytes, although the dissociation constants (KD) of these receptors did not differ between eel and trout. The numbers and affinities of the erythrocyte β-adrenoceptors were not significantly affected by the hypoxic incubation.
Both eel and trout erythrocytes displayed a dose-dependent elevation of cyclic AMP concentration in response to noradrenaline that was further increased by hypoxia. Surprisingly, eel erythrocytes produced larger quantities of cyclic AMP despite the lower numbers of surface ^adrenoceptors. Thus, the absence of adrenergic swelling and the attenuated H+ extrusion response in eel erythrocytes cannot be attributed to insufficient numbers of β-adrenoceptors or to functional uncoupling of these receptors from adenylate cyclase. Instead, the differences between trout and eel may reflect differing numbers of Na+/H+ exchangers or fundamental differences in the manner by which these exchangers are activated by cyclic AMP.