bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress-Induced Failure of Osmoregulation in the Parasitic Nematode Pseudoterranova Decipiens: Indirect Evidence for Hormonal Regulation
Authors: Davey K. G. , Sommerville R. I. , Fusé M. 
Published: April 2021

ABSTRACT
When third-stage larvae of Pseudoterranova decipiens maintained at 5°C are placed in either 40% artificial sea water (ASW, iso-osmotic) or 15% ASW (hypo-osmotic) and weighed once at 0h and again at 24h, they neither lose nor gain weight, and the osmotic pressure (OP) of their pseudocoelomic fluid (PCF) remains unchanged. In contrast, when worms are weighed six additional times during the 24h interval, those maintained in iso-osmotic conditions lose weight, while those maintained in hypo-osmotic conditions gain weight. Worms which had been exposed to hypo-osmotic conditions and weighed at various times between 0 and 24h exhibited an increase in weight which was correlated with the number of weighings. Worms exposed to hypo-osmotic conditions and weighed three additional times between 0 and 24h also gained weight, and the OP of the PCF decreased such that worms experiencing the greatest increase in weight suffered the greatest dilution of the PCF. In worms ligatured at the head or tail or at the head and tail, and then exposed to either 15% or 40% ASW, the effect of multiple weighings is exaggerated in a complex way. The presence of a ligature on the tail in worms immersed in an iso-osmotic medium leads to an increase in weight and to a very marked additional increase in weight in worms immersed in a hypo-osmotic medium. The presence of a head ligature in worms in an iso-osmotic medium leads to a decrease in weight and to a smaller weight gain in a hypo-osmotic medium. The addition of a head ligature to worms ligatured at the tail increases the weight gain in both iso-osmotic and hypo-osmotic media. These results demonstrate that stress induced by handling disrupts the normal capacity to osmoregulate in P. decipiens; they are consistent with the stress-induced release of postulated diuretic and antidiuretic factors.
Rapid Respiratory Changes in Trout Red Blood Cells During Na+/H+ Exchange Activation
Authors: Perry S. F. , Thomas S. 
Published: April 2021

ABSTRACT
Respiratory variables of rainbow trout (Oncorhynchus mykiss) blood were monitored continuously in vivo using an extracorporeal circulation or in vitro using blood flowing in a semi-closed loop. The experiments were designed to assess the rapid effects of endogenous catecholamines on red blood cell (RBC) O2 and CO2 transport. The addition of catecholamines (nominal final blood concentrations were 250nmol l−1 adrenaline and 20nmol l−1 noradrenaline) caused activation of RBC Na+/H+ exchange both in vivo and in vitro as indicated by the reductions in whole-blood pH.
In both experimental systems, the activation of Na+/H+ exchange was associated with a rapid reduction of blood , indicating a sudden net movement of plasma CO2 into the RBC. In vitro the initial reduction of blood was followed by a pronounced elevation as a result of the titration of plasma HCO3− by H+ extruded from the RBC. Blood fell markedly in a transitory manner after the addition of catecholamines. The decreases in were probably caused by rapid increases in the affinity/capacity of haemoglobin for O2 which, in turn, caused O2 molecules to enter the RBC from the plasma. The results are discussed with reference to the role of circulating catecholamines in rapidly modifying blood O2 and CO2 transport in rainbow trout.
Ammonia, Na+, K+ and Cl− Levels in Rainbow Trout Yolk-Sac Fry in Response to External Ammonia
Authors: Paley R. K. , Twitchen I. D. , Eddy F. B. 
Published: April 2021

ABSTRACT
Body ammonia content of rainbow trout alevins was about 0.6μmol g−1 but increased to 4 μmol g−1 after 24h of exposure to an external ammonia concentration of 36.2 μmol l−1 NH3 (15.8mmol l−1 ammonia) at pH7 and 10°C. During ammonia loading, the mass of alevins remained unchanged, but body ion concentrations decreased by about 28% for Na+ and Cl− and by 35% for K+. These effects were reduced at lower ammonia concentrations. Exposure for 24h to 36.2 μmol l−1 NH3 (15.8mmol l−1 ammonia) at pH7 and 10°C resulted in a build up of body ammonia that was almost complete within 10h, whereas Na+ loss from the body was delayed and commenced after about 5h of exposure. After exposure, ammonia unloading from the body was complete in about 10h but there was a delay of about 5h before Na+ uptake commenced. During ammonia exposure, alevins lost substantial amounts of K+ (14 μmol g−1) that were not replaced for several days after exposure to ammonia. Ammonia exposure has major effects on ionic regulation in juvenile fish and possible regulatory processes are discussed.
An Evaluation of Factors Limiting Carbon Dioxide Excretion by Trout Red Blood Cells in Vitro
Authors: Perry Steve F. , Gilmour Kathleen 
Published: April 2021

ABSTRACT
An evaluation of several potential factors limiting carbon dioxide excretion by rainbow trout (Oncorhynchus mykiss) red blood cells was performed in vitro using a recently developed radioisotopic assay. Red blood cell (RBC) CO2 excretion was reduced by pre-treatment (30min) of blood with the carbonic anhydrase inhibitor acetazolamide (final nominal concentration 10−4 mol l−1) or the Cl−/HCO3− exchange inhibitor SITS (4-acetamido-4′-isothiocyanatostilbene-2,2′-disulphonic acid; 10−4 mol l−1). The addition of bovine carbonic anhydrase to plasma stimulated CO2 excretion in a dose-dependent manner, with maximal levels of CO2 excretion achieved at a concentration of 3mgml−1. These results confirmed that carbonic anhydrase activity and/or Cl−/HCO3− exchange velocity are potential limiting factors in CO2 excretion.
Increasing the haematocrit elevated the rate of RBC CO2 excretion, although the effect was apparent only between 0 and 15% haematocrit; the rate of CO2 excretion was unaffected by further increases in haematocrit between 15 and 35%. Acute elevation of plasma HCO3− levels increased the rate of CO2 excretion in blood but not in plasma (with or without added carbonic anhydrase). These data suggest that HCO3− availability may limit CO2 excretion at higher haematocrits when the Cl−/HCO3− exchange sites are most plentiful.
Lysis of RBCs and the accompanying release of intracellular carbonic anhydrase into the plasma significantly increased CO2 excretion at all haematocrit and HCO3− levels, indicating that the velocity of Cl−/HCO3− exchange does indeed limit trout RBC CO2 excretion. The addition of carbonic anhydrase (3mgml−1) to lysed blood caused a further increase in the rate of CO2 excretion but only at the low haematocrit of 5%. This result suggests that the activity of RBC carbonic anhydrase does not normally limit CO2 excretion except at unusually low haematocrits, such as might occur during severe anaemia.
The rapid oxygenation of partially deoxygenated blood during the 3min assay caused a marked stimulation of CO2 excretion that was concurrent with a significant decrease of RBC intracellular pH (pHi). These data indicate that the supply of Bohr protons during the oxygenation of the blood is a key factor limiting CO2 excretion. Oxygenation of the blood prior to performing the assay also lowered RBC pHi, although CO 2 excretion was actually reduced, indicating a possible specific effect of pHi on Cl−/HCO3− exchange activity or HCO3− dehydration. The results are discussed with reference to the control of carbon dioxide excretion in fish.
The Sensing of Electrical Capacitances by Weakly Electric Mormyrid Fish: Effects of Water Conductivity
Authors: Emde Gerhard Von Der 
Published: April 2021

ABSTRACT
Weakly electric fish can perceive electric properties of objects by monitoring the responses of their epidermal electroreceptors (mormyromasts) to their own electric organ discharges (EOD), a process known as active electrolocation. Mormyrid fish can distinguish capacitative from resistive properties of objects. It is mainly animate objects that possess capacitative properties. Water conductivity is a critical environmental factor that varies widely from season to season and has strong effects on the emitted EOD.
The two goals of this study were: (1) to investigate the ability of Gnathonemus petersii to detect the properties of capacitative objects in waters of different ion content and (2) to test a recently formulated hypothesis which states that the detection of the features of a capacitative object depends on a comparison of the inputs from the two types of mormyromast primary afferents. Individuals of G. petersii were tested in a conditioned electrolocation procedure.
With increasing water conductivities from 50 to 1100 μS cm−1, EOD amplitude decreased and the detection threshold for small capacitances increased. At 50 μS cm−1, the smallest detectable capacitative value was below 0.5nF; this increased to about 20nF at 800 μS cm−1. When conductivity approached about 1000 μS cm−1, fish were no longer able to electrolocate, probably because of the reduction in EOD amplitude at high conductivities.
The fish’s ability to discriminate a capacitative object unequivocally from every resistive object was also tested at different conductivities. Below about 800 μS cm−1, all fish could do so. Above that conductivity, however, fish could no longer discriminate between capacitative and resistive objects of similar impedance, although they could still discriminate between objects of different impedances. The two types of receptor afferents (from the ‘A’ and ‘B’ cells) of mormyromast electroreceptor organs have different thresholds, with the B afferents being more sensitive. I suggest that only the B receptor cells remain active at about 800 μS cm-1, when the EOD amplitude is much reduced. With input from B afferents only, an unambiguous capacitance detection was no longer possible. This supports the hypothesis that capacitance detection is achieved by comparing inputs of A and B electroreceptor cells.
Glucose Concentration Regulates Freeze Tolerance In the Wood Frog Rana Sylvatica
Authors: Costanzo Jon P. , Lee Richard E. , Lortz Peter H. 
Published: April 2021

ABSTRACT
In spring, the lowest temperature during freezing that can be survived by wood frogs (Rana sylvatica) from southern Ohio is approximately −3°C. We investigated whether the thermal limit of freeze tolerance in these frogs is regulated by tissue levels of glucose, a putative cryoprotectant that is distributed to tissues during freezing. Frogs receiving exogenous glucose injections prior to freezing showed dose-dependent increases in glucose within the heart, liver, skeletal muscle and blood. Tissue glucose concentrations were further elevated during freezing by the production of endogenous glucose. Most glucose-loaded frogs survived freezing to −5°C, whereas all control (saline-injected) frogs succumbed. Further, we investigated some mechanisms by which glucose might function as a cryoprotectant in R. sylvatica. Organ dehydration, a normal, beneficial response that reduces freezing injury to tissues, occurred independently of tissue glucose concentrations. However, elevated glucose levels reduced both body ice content and in vivo erythrocyte injury. These results not only provided conclusive evidence for glucose’s cryoprotective role in R. sylvatica, but also revealed that tissue glucose level is a critical determinant of freeze tolerance capacity in this species.
Kinematics of Birdsong: Functional Correlation of Cranial Movements and Acoustic Features in Sparrows
Authors: Westneat Mark W. , Long John H. , Hoese William , Nowicki Stephen 
Published: April 2021

ABSTRACT
The movements of the head and beak of songbirds may play a functional role in vocal production by influencing the acoustic properties of songs. We investigated this possibility by synchronously measuring the acoustic frequency and amplitude and the kinematics (beak gape and head angle) of singing behavior in the white-throated sparrow (Zonotrichia albicollis) and the swamp sparrow (Melospiza georgiana). These birds are closely related emberizine sparrows, but their songs differ radically in frequency and amplitude structure. We found that the acoustic frequencies of notes in a song have a consistent, positive correlation with beak gape in both species. Beak gape increased significantly with increasing frequency during the first two notes in Z. albicollis song, with a mean frequency for note 1 of 3kHz corresponding to a gape of 0.4cm (a 15° gape angle) and a mean frequency for note 2 of 4kHz corresponding to a gape of 0.7cm (a 30° gape angle). The relationship between gape and frequency for the upswept third note in Z. albicollis also was significant. In M. georgiana, low frequencies of 3kHz corresponded to beak gapes of 0.2–0.3 cm (a 10–15° beak angle), whereas frequencies of 7–8kHz were associated with flaring of the beak to over 1cm (a beak angle greater than 50°). Beak gape and song amplitude are poorly correlated in both species. We conclude that cranial kinematics, particularly beak movements, influence the resonance properties of the vocal tract by varying its physical dimensions and thus play an active role in the production of birdsong.
Compartmentation of Liver Phosphoenolpyruvate Carboxykinase in the Aquatic Turtle Pseudemys Scripta Elegans: A Reassessment
Authors: Land Stephen C. , Hochachka Peter W. 
Published: April 2021

ABSTRACT
Phosphoenolpyruvate carboxykinase (PEPCK) catalyses the conversion of oxaloacetate to pyruvate in the first step of gluconeogenesis. Since oxaloacetate is impermeable to the inner mitochondrial membrane, the localisation of PEPCK within the cell plays a major role in defining substrate preferences for gluconeogenesis. As a result, the immunochemically distinct isoenzymes of PEPCK found within the mitochondrial and the cytosolic cell fractions vary in their proportion to one another between organs and species and with prandial state.
The Effect of Exercise on the Cardiac Output and Blood Flow Distribution of the Largescale Sucker Catostomus Macrocheilus
Authors: Kolok Alan S. , Spooner R. Michael , Farrell Anthony P. 
Published: April 2021

ABSTRACT
Cardiac output (Q̇) and blood flow distribution were measured in adult largescale suckers at rest and while swimming. Cardiac output was directly measured using an ultrasonic flowprobe in fish during the summer (16°C), fall (10°C) and winter (5°C).
Largescale suckers were adept at holding station against a current without swimming and, when engaged in this behavior, they did not signific.antly increase Q̇ relative to that found in fish in still water. When fish began to swim, Q̇ increased significantly. From 16 to 10°C, the critical swimming speed (Ucrit), maximum Q̇ and scope for Q̇ of the suckers did not change. However, from 10 to 5°C all three traits were significantly reduced. Thus, these fish respond to variation in water temperature in two different ways. From 16 to 10°C, the fish compensate perfectly for the change in temperature with respect to cardiac and swimming performance. From 10 to 5°C, however, largescale suckers experience a dramatic decline in cardiac and swimming performance that may be associated with a quiescent overwintering strategy.
Blood flow distribution in the fish at rest and while swimming was measured at 16°C using injection of colored microspheres. In the resting fish, over 10% of the microspheres were recovered from the kidney and over 43% were recovered from white muscle. When the fish were swimming, there was a 60-fold increase in blood flow to the red muscle while blood flow to all other tissues remained consistent with that at rest.
Muscle Temperature and Swim Velocity Profiles During Diving in a Weddell Seal, Leptonychotes Weddellii
Authors: Ponganis P. J. , Kooyman G. L. , Castellini M. A. , Ponganis E. P. , Ponganis K. V. 
Published: April 2021

ABSTRACT
Locomotory muscle temperature and swim velocity profiles of an adult Weddell seal were recorded over a 21h period. The highest temperatures occurred during a prolonged surface period (mean 37.3°C, S.D. 0.16°C). Muscle temperature averaged 36.8 and 36.6°C (S.D. 0.25°C, 0.19°C) during two dive bouts and showed no consistent fluctuations between dive and interdive surface intervals. Swim velocities were also constant, near 1.3 ms−1. These data indicate that past records of low aortic temperatures (35°C) during and after prolonged dives are not indicative of whole-body temperature changes, and that muscle temperature, even during dives as long as 45min, remains near 37°C.
Power Output of Glycerinated Bumblebee Flight Muscle
Authors: Gilmour K. M. , Ellington C. P. 
Published: April 2021

ABSTRACT
The properties of asynchronous insect flight muscle have been examined using a glycerol-extracted single-fibre preparation of dorsal longitudinal muscle from the bumblebees Bombus lucorum and B. terrestris. Chemical, mechanical and thermal conditions were controlled with the objective of maximizing power output. The problems arising from diffusion limitation were avoided through a combination of fibre paring and the use of an ATP backup system. Work and power output tended to increase with increasing oscillatory strain in the range 1–5%. Workloop shape, and hence work and power, varied with fibre extension; optimum extensions ranged from 4 to 12%. The mechanical performance of glycerinated bumblebee muscle fibres was strongly temperature-dependent, and rate processes (frequency, power) displayed higher thermal sensitivities than processes associated with tension development (work). The experimental conditions that maximized the power output were identified as: oscillatory strain ϵ=4–5%, extension ϵo=8–10%, oscillation frequency f=50Hz and temperature T=40°C. The maximum power output observed under these ‘optimal’ conditions was about 110 W kg−1 (muscle), demonstrating for the first time that glycerinated fibres are capable of producing the power predicted from free-flight studies to be required for flight: 100 W kg−1.
Screening-Pigment Migration in the Octopus Retina Includes Control by Dopaminergic Efferents
Authors: Gleadall Ian G. , Ohtsu Kohzoh , Gleadall Etsuko , Tsukahara Yasuo 
Published: April 2021

ABSTRACT
The extent of screening-pigment (SP) migration in the intact octopus retina and the amplitude of the early receptor potential (ERP) correspond with the degree of adaptation to light or darkness. The light-adapted retina has SP granules concentrated in an apical layer, at the tips of the photoreceptor rhabdoms and supporting cells, and the ERP is barely detectable. In the fully dark-adapted retina, the SP granules are mostly at the base of the rhabdoms, and the ERP is at its maximum. Retinae at intermediate stages, between the fully dark-and light-adapted states, show corresponding intermediate stages of SP migration and ERP amplitude.
A series of experiments demonstrates the effects on SP migration of the efferent nerves, which form a subset of fibres in the optic nerves. When the optic nerves to one half of the retina have been severed, there is a dramatic difference in the distribution of SP in areas of the retina (of the dark-adapted eye) connected with severed or intact nerves: apical versus basal, respectively. On incubation of a light-adapted retina with 5 μmol l−1 dopamine, but not with other catecholamines or other putative neurotransmitter substances, SP migrates basally and the ERP is significantly larger than for controls. In octopuses treated with reserpine, SP stays in an apical location and the ERP remains very small, regardless of the state of adaptation and of whether the optic nerves are intact. It is concluded that dopaminergic efferents from the optic lobes effect dark-adaptational SP migration in the cephalopod retina. The arrival in the retina of efferent signals that effect adaptational changes through the mediation of dopamine is a remarkable analogue of the vertebrate system.
Power Output and Propulsive Efficiency of Swimming Bottlenose Dolphins (Tursiops Truncatus)
Authors: Fish Frank E. 
Published: April 2021

ABSTRACT
The power output and propulsive efficiency of swimming bottlenose dolphins (Tursiops truncatus) were determined from a hydromechanical model. The propulsive movements were filmed as dolphins swam in large pools. Dolphins swam at velocities of 1.2–6.0 ms−1. Propulsion was provided by dorsoventral oscillations of the posterior body and flukes. The maximum angle of attack of the flukes showed a linear decrease with velocity, whereas the frequency of the propulsive cycle increased linearly with increasing velocity. Amplitude was 20% of body length and remained constant with velocity. Propulsive efficiency was 0.81. The thrust power computed was within physiological limits. After correction for effects due to swimming depth, the coefficient of drag was found to be 3.2 times higher than the theoretical minimum assuming turbulent boundary conditions. The motions of the body and flukes are primarily responsible for the increased drag. This analysis supports other studies that indicate that bottlenose dolphins, although well adapted for efficient high-performance swimming, show no unusual hydrodynamic performance.
Properties of Voltage-Activated Ionic Currents in cells from the Brains of the Triclad Flatworm Bdelloura Candida
Authors: Blair Kevin L. , Anderson Peter A. V. 
Published: April 2021

ABSTRACT
Cells were dispersed from the brains of the triclad flatworm Bdelloura candida and maintained in primary culture for up to 2 weeks. Cultured cells assumed a variety of morphologies consistent with those of neurones in vivo. Whole-cell voltage-clamp recordings from cultured cells revealed that these cells possess a variety of ionic currents, including a fast transient sodium current, a calcium current and several potassium currents. The sodium current does not inactivate completely but instead decays to a steady-state component which has the same physiology and pharmacology as the fast transient component, suggesting that the two components are carried by the same population of channels. The physiology and pharmacology of these various currents were not remarkable save for the fact that, contrary to earlier reports, all sodium currents examined were sensitive to tetrodotoxin (TTX). These animals are, therefore, the lowest animals known to possess TTX-sensitive sodium currents and, as such, represent a major stage in sodium channel evolution.
Excretion in the House Cricket: Stimulation of Rectal Reabsorption by Homogenates of the Corpus Cardiacum
Authors: Spring Jeffrey H. , Albarwani Sulayma A. 
Published: April 2021

ABSTRACT
We describe an in vitro perfused preparation of Acheta domesticus rectum which allows direct comparison of Malpighian tubule secretion and rectal absorption under identical conditions. Rectal absorption is stimulated four-to sixfold by corpora cardiaca (CC) homogenates and the stimulated rate is sufficiently rapid to account for all the fluid secreted by the tubules. The time course for increased fluid absorption is similar to that required to stimulate electrogenic chloride transport in locusts and grasshoppers. Chloride is rapidly absorbed by the rectum under all conditions, along with lesser amounts of Na+ and K+. Unlike the situation in locusts, K+ uptake is unaffected by CC homogenates and the stimulated absorbate is NaCl-rich, similar in composition to the NaCl-rich tubule fluid produced under stimulated conditions. The absorbate is always slightly hypo-osmotic to the perfusate, reaching a maximum differential of approximately 15 mosmoll-1 following CC stimulation. The antidiuretic factor that reduces tubule secretion does not promote fluid reabsorption by the rectum.