bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Maximum Sustainable Swimming Performance in Rainbow Trout (Oncorhynchus Mykiss)
Authors: Wilson Rod W. , Egginton Stuart 
Published: April 2021

ABSTRACT
Levels of swimming activity in fishes have been divided into three categories on the basis of the time a given speed can be maintained before the onset of fatigue (Beamish, 1978): sustained (more than 200 min), prolonged (20 s to 200 min) and burst swimming (less than 20 s). The locomotory capacity of a given species reflects both its lifestyle and its body form, although definitions of performance may vary. It is generally accepted that only the aerobic (‘red’) muscle fibres should be active at truly sustainable swimming speeds, i.e. at speeds that can be maintained indefinitely without fatigue. However, the standard laboratory method of evaluating the maximum sustainable swimming speed (Ucrit; Brett, 1964) almost certainly entails the recruitment of at least some of the rapidly fatigable fast glycolytic (‘white’) fibres at sub-critical speeds and undoubtedly complicates the evaluation of maximal cardiovascular performance. It would therefore be useful to have an objective and reproducible measure of truly sustainable performance that, by definition, relies solely on aerobic muscle activity. Electromyography (EMG) has been used to examine the pattern of white muscle recruitment following thermal acclimation in striped bass, Morine saxatilis (Sisson and Sidell, 1987). We wished to incorporate this method into a study of the acclimatory responses to chronic changes in environmental temperature of the cardiovascular and locomotory systems in rainbow trout (Wilson and Egginton, 1992). The present communication presents results on the cardiovascular performance and blood chemistry, at rest and during maximal aerobic exercise, of rainbow trout acclimated to 11°C, as a validation of the methodology currently in use with fish acclimated to seasonal temperature extremes (Taylor et al. 1992). Different acclimation temperatures are known to produce compensatory changes in the relative proportions of red and white muscle mass (Sidell and Moerland, 1989). The aim of these continuing investigations is to compare the anatomical, cardiovascular and locomotory limitations to aerobic exercise over the full temperature range of a eurythermal fish species.
Localization Of Angiotensin Ii Responses In The Trout Cardiovascular System
Authors: Olson Kenneth R. , Chavez Angelica , Conklin Daniel J. , Cousins Katherine L. , Farrell Anthony P. , Ferlic Randy , Keen John E. , Kne Tanya , Kowalski Kimberly A. , Veldman Timothy 
Published: April 2021

ABSTRACTThe renin/angiotensin system (RAS) is a tonic anti-drop regulator of arterial blood pressure in many teleosts. In trout, angiotensin II (ANG II) has no direct constrictor effect on large arteries or veins and the identity of specific cardiovascular pressor effectors is unknown. Potential targets of angiotensin activation were examined in the present experiments using perfused organs and isolated tissues from the rainbow trout Oncorhynchus mykiss.Perfused gill (arches 2 and 3), perfused skeletal muscle-kidney (via the dorsal aorta; PDA) and perfused splanchnic (via the celiacomesenteric; PCM) circulations vasoconstrict in response to salmonid ANG II in a dose-dependent manner. ANG II was significantly (P⩽0.05) more potent in the PCM than in the PDA, and both preparations were more responsive than the gills: pD2=8.0±0.20 (10) for PCM; pD2=7.5±0.07 (13) for PDA; pD2=6.9 ±0.21 (8) for gill arch 3; pD2=6.7±0.23 (8) for gill arch 2; mean ± S.E.M. (N), respectively. Salmonid angiotensin I (ANG I) also produced a dose-dependent constriction of the PDA and PCM. Angiotensin converting enzyme (ACE) activated nearly 100% of ANG I to ANG II in a single pass through the PDA, whereas PCM conversion was estimated to be less than 10%. Inhibitors of adrenergic constriction partially prevented ANG II responses in the PDA but did not affect PCM responses.ANG II did not affect paced rings of ventricular muscle in the presence of high or low [Ca2+] or epinephrine concentrations, nor did it have any inotropic or chronotropic effects in the in situ perfused heart. Red blood cell swelling was unaffected by ANG II. Similarly, the effects of ANG II on gut, urinary bladder and gall bladder smooth muscle were negligible or non-existent; thus, an increase in splanchnic resistance due to extravascular compression can be discounted.These results indicate that, in trout, the systemic microcirculation is the major cardiovascular effector of angiotensin-mediated pressor responses. In addition, the RAS has little direct effect on non-vascular smooth muscle or the heart. From an evolutionary perspective, the initial site of direct systemic RAS action appears to be the vascular microcirculation.
Glucose Metabolism by Sea Raven (Hemitripterus Americanus) and Rainbow Trout (Oncorhynchus Mykiss) Erythrocytes
Authors: Sephton Dawn H. , Driedzic William R. 
Published: April 2021

ABSTRACT
The fate of extracellular glucose in blood isolated from sea raven (Hemitripterus americanus) and rainbow trout (Onchorhynchus mykiss) was determined. In blood from both species incubated in vitro at low physiological pH, the decrease in plasma glucose concentration was more than adequate to support oxygen consumption. Glucose disappearance could not be accounted for by increases in lactate, red blood cell (RBC) glucose or RBC glycogen concentrations. Rates of 14CO2 production from [6-14C]glucose over a 2 h incubation period were less than 1% of metabolic rate. Only small amounts of label appeared in RBC protein, lipid or glycogen fractions relative to metabolic rates, but label accumulated in the intracellular acid-soluble fraction (presumably free glucose, glycolytic intermediates, amino acids, citric acid cycle intermediates, etc.) at rates consistent with oxygen consumption and glucose disappearance. The simplest explanation for the mismatch between 14CO2 production and the other estimates of metabolic rate is that incubation times were too short for equilibration to occur. A consequence is that studies of this nature cannot use 14CO2 production to elucidate rates of aerobic fuel utilization. By default, the data imply that glucose serves as a primary aerobic metabolic fuel for the RBCs, at least under some conditions.
Melatonin is Crucial for the Migratory Orientation of Pied Flycatchers (Ficedula Hypoleuca Pallas)
Authors: Schneider Thomas , Thalau Hans-Peter , Semm Peter , Wiltschko Wolfgang 
Published: April 2021

ABSTRACT
After pinealectomy, young pied flycatchers tested in the geomagnetic field have been found to be disoriented. In order to examine the possible role of the pineal hormone melatonin, handraised flycatchers were pinealectomized (PX) at the age of 8 weeks. From the day of operation onward, the PXMEL group received 100 μg of melatonin every evening 1 h before darkness, the PXSOL group was injected with the solvent only, and the PX group was untreated. Unoperated birds served as controls. During the following autumn migration, the birds were tested for directional preference in the local geomagnetic field, in the absence of visual cues. The controls were oriented in the species-specific southwesterly direction; pinealectomized birds without additional melatonin (PXSOL, PX) did not show directional preferences. The PXMEL birds that had received daily injections of melatonin also showed significant southwesterly tendencies; their orientation did not differ from that of the controls. This indicates that melatonin is involved in migratory orientation, either in the processes of expressing the genetically encoded information on the migratory course as a direction with respect to the geomagnetic field or in the time programme controlling the specific migratory direction at a given time.
Effects of Environmental Temperature on the Metabolic and Acid–base Responses of Rainbow Trout to Exhaustive Exercise
Authors: Kieffer James D. , Currie Suzanne , Tufts Bruce L. 
Published: April 2021

ABSTRACT
In vivo experiments were conducted to determine how the physiological response to exhaustive exercise in rainbow trout (Oncorhynchus mykiss) is affected by environmental temperature. The white muscle acid–base status (e.g. pH, HCO3−and ) and metabolite (e.g. lactate, phosphocreatine, ATP and glycogen) content, and the acid–base status and lactate concentrations in the blood, were measured at rest and during recovery from burst exercise in rainbow trout acclimated to either 5 or 18°C.
Trout acclimated to the warmer temperature had higher resting levels of white muscle phosphocreatine (PCr) and also utilized a greater proportion of their muscle ATP and glycogen stores during burst activity compared with trout acclimated to the colder temperature. Recovery of muscle PCr and glycogen levels was independent of acclimation temperature, but muscle ATP levels recovered faster at 18°C. Exhaustive exercise resulted in a similar lactacidosis in the muscle of trout acclimated to either temperature. In contrast, temperature had a marked influence on the lactacidosis in the blood. Blood lactate and metabolic proton concentrations following exercise were about twofold greater in fish acclimated to 18°C than in fish acclimated to 5°C. Despite the more severe acidosis and the greater lactate accumulation in the plasma of fish acclimated to warmer temperatures, the time required for recovery of these variables was similar to that at 5°C. Taken together, these results suggest that acclimation temperature does not significantly affect anaerobic capacity in rainbow trout, but may account for much of the documented variability in the dynamics of the lactacidosis in blood following exhaustive exercise in fish.
The Cooling Power of the Pigeon Head
Authors: St-Laurent Robert , Larochelle Jacques 
Published: April 2021

ABSTRACT
Resting pigeons preheated to a stable core temperature of 43.2°C, which is within the range of body temperatures recorded during flight, were able to cool their body at high rates if their head and upper neck were exposed to an air stream at 23.5°C. The heat dissipation capacity of the head and neck, estimated from measurements made at a wind speed (100 km h−1) corresponding to fast flight, was 9.8 W, or 4.5 times the resting heat production. Since the greater part of this capacity, about 8 W, was attributable to the inner surfaces of the mouth, ram ventilation of the buccal cavity appears to be an important mechanism for increasing evaporative heat loss during flight. Accordingly, wind-assisted mouth cooling should be utilized by resting pigeons, since exposure to a slight breeze (approximately 10 km h−1) could augment their dissipating power by an amount equivalent to their resting metabolic rate. It is concluded that beak opening, together with a source of convection other than panting and gular flutter, is required to exploit fully the heat dissipation capacity of the buccopharyngeal mucosa of birds.
Short-Term Cell Volume Regulation in Mytilus Californianus Gill
Authors: Silva Arnold L. , Wright Stephen H. 
Published: April 2021

ABSTRACT
Long-term acclimation of Mytilus californianus to 60% artificial sea water (585 mosmol l−1; ASW) led to a 30–40% decrease in the taurine (53.5–36.9 μmol g−1 wet mass) and betaine (44.8–26.2 μmol g−1 wet mass) content of gill tissue, compared with that of control animals held in 100% ASW (980 mosmol l−1). The K+ content of gills did not change following long-term acclimation to reduced salinity. In contrast, losses of all three solutes during a brief (60 min) exposure to 60% ASW were less than or equal to 15%. Nevertheless, the swelling of gill cells that occurred after acute exposure to 60% ASW was followed by a return towards the control volume. Direct optical measurement of single gill filaments confirmed that, during an acute exposure to reduced salinity, ciliated lateral cells increased in cell height (volume) and then underwent a regulatory volume decrease (RVD) with a half-time of approximately 10 min. This short-term RVD was completely inhibited by exposure to 1 mmol l−1 quinidine, a K+ channel blocker, but only when the drug was applied to the basolateral aspect of the gill epithelium. Application of 1 μmol l−1 valinomycin relieved the inhibition by quinidine of the gill RVD. However, addition of valinomycin did not accelerate the rate of RVD observed in the absence of quinidine. These results indicate that long-term acclimation of Mytilus californianus gill in dilute sea water involves primarily losses of taurine and betaine, whereas short-term regulation of cell volume may involve an electrically conductive loss of intracellular K+ and a counter ion.
Immunolocalization of H+-ATPase in the gill epithelia of rainbow trout
Authors: Lin Hong , Pfeiffer David C. , Vogl A. Wayne , Pan Jie , Randall David J. 
Published: April 2021

ABSTRACT
The localization of proton pumps (H+-ATPase) in gill epithelia of rainbow trout [Oncorhynchus mykiss (Walbaum)] was elucidated by immunofluorescence microscopy, using rabbit polyclonal antibodies against the 70 kDa subunit of H+-ATPase purified from clathrin-coated vesicles of bovine brain. In the gill epithelia of freshwater trout, the immunostaining was uniformly distributed along the lamellae and generally concentrated in apical regions. It is concluded, therefore, that H+-ATPase is located in the apex of both chloride cells and epithelial cells of freshwater fish. Hypercapnic treatment resulted in a non-polarized and restrictive distribution of H+-ATPase in the chloride cell. No fluorescent staining was observed in the gill epithelium of seawater-adapted rainbow trout, except in some unidentified anucleate surface material. The presence of the 70 kDa subunit in fish gill epithelia was confirmed by Western blot. These results support the proposed role of a proton pump in sodium uptake in freshwater fish and demonstrate that the H+-ATPase in fish gills is of the vacuolar type, antigenically similar to the H+-ATPase in mammalian brain and kidney.
Mechanical Determinants of the Minimum Energy Cost of Gradient Running in Humans
Authors: Minetti A. E. , Ardigò L. P. , Saibene F. 
Published: April 2021

ABSTRACT
The metabolic cost and the mechanical work of running at different speeds and gradients were measured on five human subjects. The mechanical work was partitioned into the internal work (Wint) due to the speed changes of body segments with respect to the body centre of mass and the external work (Wext) due to the position and speed changes of the body centre of mass in the environment. Wext was further divided into a positive part and a negative part , associated with the energy increases and decreases, respectively, over the stride period. For all constant speeds, the most economical gradient was -10.6±0.5% (S.D., N=5) with a metabolic cost of 146.8±3.8 ml O2 kg−1 km−1. At each gradient, there was a unique ratio (which was 1 in level running), irrespective of speed, with a tendency for and to disappear above a gradient of +30% and below a gradient of -30%, respectively. Wint was constant within each speed from a gradient of -15% to level running. This was the result of a nearly constant stride frequency at all negative gradients. The constancy of Wint within this gradient range implies that Wint has no role in determining the optimum gradient. The metabolic cost C was predicted from the mechanical experimental data according to the following equation:
where eff− (0.80), eff+ (0.18) and effi (0.30) are the efficiencies of andWint, respectively, and el−and el+ represent the amounts of stored and released elastic energy, which are assumed to be 55 J step−1. The predicted C versus gradient curve coincides with the curve obtained from metabolic measurements. We conclude that partitioning and the eff+/eff−ratio, i.e. the different efficiency of the muscles during acceleration and braking, explain the metabolic optimum gradient for running of about -10%.
Neurotransmitter Transporters: Three Important Gene Families for Neuronal Function
Authors: Uhl George R. , Johnson Peter S. 
Published: April 2021

ABSTRACT
Three distinct gene families encode transporter proteins that aid in temporal and spatial buffering of neurotransmitter and neurotransmitter metabolite concentrations and allow neurons to cycle and recycle transmitter molecules. Analyses of these gene families and their products are likely to enhance understanding of the molecular neurobiology of neuronal function and may elucidate contributors to the genetic etiologies of neurological and psychiatric disease.
Molecular Structure and Regulation of Vertebrate Na+/H+ Exchangers
Authors: Bianchini Laurence , Pouysségur Jacques 
Published: April 2021

ABSTRACT
Na+/H+ exchangers (NHE), also called antiporters, are vital transmembrane transporters involved in multiple cellular functions including the regulation of intracellular pH, the control of cell volume and transepithelial ion transport. These transporters are highly regulated by a remarkably wide variety of stimuli which can modulate their expression level and activity. Five isoforms of Na+/H+ exchangers have been cloned and characterized to date; they define a new gene family of vertebrate transporters. These isoforms share the same overall structure but exhibit differences with respect to amiloride-sensitivity, cellular localization, kinetic variables, regulation by various stimuli and plasma membrane targeting in polarized epithelial cells. Biochemical techniques and molecular genetics tools provide the means of analyzing these transporters at the molecular level. The purpose of this manuscript is to give an overview of the main features of the Na+/H+ exchangers with emphasis on recent advances in comprehension of the structure–function relationship and regulation mechanisms of the ubiquitous isoform: NHE-1.
Induction of Ornithine-Urea Cycle Enzymes and Nitrogen Metabolism and Excretion in Rainbow Trout (Oncorhynchus Mykiss) During Early Life Stages
Authors: Wright Patricia A. , Felskie Andrew , Anderson Paul M. 
Published: April 2021

ABSTRACT
The ornithine-urea cycle (OUC) is present in elasmobranch fish and many terrestrial vertebrates. Recently, a functional OUC has been reported in a few teleost species, suggesting that all teleost fish have the genes for the OUC, but expression is relatively rare. We investigated the possibility that the OUC is expressed during early development in trout as a mechanism for detoxifying ammonia produced from the catabolism of yolk protein. We followed ammonia and urea excretion rates, tissue ammonia and urea levels and OUC enzyme activities in rainbow trout up to 93 days after fertilization. Both ammonia and urea tissue concentrations increased several-fold in the first 40 days after fertilization (embryo stage), peaking at 1.7mmolNl−1 and 2.5mmolNl−1, respectively. Ammonia excretion could be detected in 4-day-old embryos, but urea excretion was not initiated until after hatching (day 45). Urea excretion in larval fish (days 42–93) increased several-fold and by day 93 was 14% of total nitrogen excretion, as found in adult trout. Glutamine synthetase (GSase) and arginase activities were detected in ‘whole animal’ homogenates just after hatching and the levels of activity increased markedly to day 93. Carbamoyl phosphate synthetase (CPSase) and ornithine transcarbamylase (OTCase) were first detected in 40-day-old embryos; activities peaked between days 53 and 71 and then subsequently decreased. Adult liver enzyme activity for GSase was several-fold lower than in whole larval trout and OTCase and CPSase III (glutamine- and N-acetylglutamate-dependent CPSase catalysing the first step of the OUC) activities were essentially absent in adult liver. We conclude that embryonic and larval trout are primarily ammoniotelic. Urea is synthesized immediately after fertilization, but is not excreted until after the embryo is hatched. The results provide evidence for the presence of the OUC in larval rainbow trout, since four of the OUC enzymes are induced just after hatching and the levels of activity are relatively high compared with those in adult liver tissue. Furthermore, we suggest that all teleosts have retained the OUC genes, which are expressed only during certain stages of development (embryogenesis), and in a few rare species expression is maintained throughout the life cycle to cope with unusual environmental conditions (e.g. alkaline water, air exposure).
Metabolic Effects of Dehydration on an Aquatic Frog, Rana Pipiens
Authors: Churchill Thomas A. , Storey Kenneth B. 
Published: April 2021

ABSTRACT
Cellular responses to dehydration were analyzed in six organs of leopard frogs Ranapipiens. Frogs at 5 °C endured the loss of up to 50 % of their total body water content but water contents of individual organs were strongly defended. Skeletal muscle water content was strongly affected by dehydration, dropping from 80.7 % of wet mass in controls to 67.2 % in frogs that had lost 50 % of their total body water. However, water contents of internal organs dropped by only 3–8 % of their wet masses. Water contents of all organs except skeletal muscle were fully restored by 24 h of rehydration in water at 5 °C. Dehydration had no consistent effect on the protein content of five organs but in a sixth, the kidney, protein levels were elevated (by 60–72 %) at the higher levels of dehydration and during rehydration. Dehydration led to a rapid increase in glucose concentration in the liver; compared with control values of 13±2 nmol mg−1 protein, levels were doubled by 12.2 % dehydration and continued to increase to a maximum of 307±44 nmol mg−1 protein (20 μmolg−1 wet mass) in 50% dehydrated frogs. Glucose accumulation was supported by a decrease in liver glycogen content and a parallel rise in glucose 6-phosphate levels, but not in the levels of other glycolytic intermediates, confirming that glycogenolytic flux was being directed into glucose synthesis. Blood glucose levels also increased as a function of increasing dehydration, reaching values 13.8 times higher than controls, but only the kidney and brain showed a significant accumulation of glucose over the course of dehydration. All organs (except skeletal muscle) had increased lactate levels during dehydration, particularly at 36.6 and 50 % dehydration. Severe dehydration also compromised cellular energetics, with ATP levels dropping by 44 % in liver of 50 % dehydrated frogs. However, frogs readily recovered from dehydration stress and, after rehydration for 24 h, organ lactate levels were sharply reduced relative to 50 % dehydrated frogs and liver energy status was largely restored. The hyperglycaemic response elicited by dehydration in this semi-aquatic frog mirrors the extreme hyperglycaemia seen in freeze-tolerant frogs during comparable dehydration exposure at 5 °C or during freezing. This suggests that the cryoprotectant response of freeze-tolerant species may have grown out of a pre-existing hyperglycaemic response to dehydration, a common stress experienced by all anurans.