bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Messenger RNA Pools in Active and Dormant Artemia Franciscana Embryos: Evidence for Translational Control
Authors: Hofmann Gretchen E. , Hand Steven C.
Published: April 2021

In response to environmental anoxia, embryos of the brine shrimp Arteimia franciscana enter a dormant state during which energy metabolism and development are arrested. The intracellular acidification that correlates with this transition into anaerobic dormancy has been linked to the inhibition of protein synthesis in quiescent embryos. In this study, we have addressed the level of control at which a mechanism mediated by intracellular pH might operate to arrest protein synthesis.

Two independent lines of evidence suggest that there is an element of translational control when protein synthesis is arrested in dormant embryos. First, as determined by in vitro translation techniques, there were no significant quantitative differences in mRNA pools in dormant as compared to actively developing embryos. In addition, fluorography of the translation products showed that there are no large qualitative changes in mRNA species when embryos become dormant. These data suggest that there was no net degradation of mRNA pools in dormant embryos and that protein synthesis may therefore be controlled more strongly at translation than at transcription. Second, polysome profile studies showed that dormant embryos possess reduced levels of polysomes relative to those found in cells of active embryos. The disaggregation of polysomes is an indication that the initiation step in protein synthesis is disrupted and is further evidence that the mechanism involved in protein synthesis arrest in dormant Artemia involves translational control.
Identified Neurones Involved in the Control of Rhythmic Buccal Motor Activity in the Snail Achatina Fulica
Authors: Yoshida Masayuki , Kobayashi Makoto
Published: April 2021

In the land snail Achatina fulica, it has been suggested that two pairs of cerebral neurones, ventral cerebral distinct neurones (v-CDNs) and Cl neurones, and a pair of buccal motoneurones (B1s) are involved in the control of rhythmic motor activity (RMA) in the buccal ganglia. These neurones, when tonically fired by depolarizing current injection, could individually initiate and maintain RMA in previously quiescent isolated ganglia. The rhythm elicited by v-CDN persisted for several cycles after the firing of v-CDN stopped, while that elicited by Cl or B1 ceased immediately after the firing of these neurones stopped. RMA also occurred spontaneously and could be induced by labial nerve stimulation in a reduced preparation. Nevertheless, such rhythms were not always accompanied by the firing of v-CDN, Cl or BL. Thus, the firing of these neurones appears to be sufficient, but not essential, for rhythm generation in the experimental conditions.

Taste stimulation of the lip in semi-intact preparations often induced RMA in the buccal ganglia. However, v-CDN and B1 were not tonically excited by the stimulation. It seems unlikely that v-CDN and B1 are critical elements in the generation of the feeding rhythm. Cl responded to taste stimuli with excitation after RMA had begun, suggesting that Cl is involved in the taste-induced buccal rhythm.
Intra-Nasal Zinc Sulphate Irrigation in Pigeons: Effects on Olfactory Capabilities And Homing
Authors: Schlund Wolfgang
Published: April 2021

Depriving homing pigeons of olfactory information by applying a local anaesthetic, gingicain, to their olfactory epithelium results in systemic effects. Furthermore, anosmia persists reliably for only an hour. In contrast, intra-nasal irrigation with 18 % zinc sulphate solution results in anosmia that persists for at least 5 days. No systemic effects of zinc sulphate on anosmie pigeons could be detected while monitoring their olfactory capabilities using the orienting response. To compare the orientation and homing of definitely anosmie, zinc-sulphate-treated pigeons with those of controls, I made releases from two different distances (9−24km, 63−70km). At shorter distances, pigeons treated with zinc sulphate showed no directional preference in their vanishing bearings, whereas both groups of control birds (sham-treated controls and untreated super controls) were well oriented. At the longer distances, the situation was more complex: pigeons treated with zinc sulphate were oriented but the chosen direction did not correspond with the home direction. The control groups did not show any directional preference. In all cases, fewer anosmie pigeons homed and they did so more slowly than did the controls.
Climbing Performance of Migrating Birds as A Basis for Estimating Limits for Fuel-Carrying Capacity and Muscle Work
Authors: Hedenström Anders , Alerstam Thomas
Published: April 2021

Sustained climb rates and airspeeds in flapping flight were measured by radar tracking fifteen species of migrating birds ranging in body mass between 10 g and 10 kg. There was an inverse correlation between body size and climb rate: the lowest mean climb rate, 0.32 m s−1, was observed in the mute swan and the highest mean value, 1.63 m s−1, in the dunlin. Some dunlin flocks achieved sustained climb rates exceeding 2ms−1, up to 2.14ms−1. Assuming that the migrants expend maximum sustained power during their climbs, the climbing power can be used as a conservative estimate of the power margin. Estimates of climbing power for the species tracked by radar were used, in conjunction with aerodynamic theory, to calculate the amount of extra load the migrants should be able to carry if their power margin was used for load transportation rather than for climbing. Calculated ratios of total body mass with maximum load to lean body mass ranged between 1.28 and 2.75, showing an overall negative correlation with body size. There was a broad agreement with maximum fuel loads observed among free-living birds, indicating that the upper limits of fuel-carrying capacities and flight ranges in migrating birds are determined by power margin constraints in sustained flapping flight. Markedly reduced climb rates have been recorded for shorebirds departing with very large fuel reserves from W. Africa and Iceland, supporting the calculated trade-off between climb rate and fuel load. Total power consumption was estimated as the sum of calculated aerodynamic power for forward flight and climbing power. The ratio of total power to the expected minimum aerodynamic power was 1.1–1.3 in the three largest species, increasing to 2–4 in the smallest species. Medium-and small-sized species seem to allocate power in excess of the minimum aerodynamic power not only for climbing but also for maintaining a forward speed faster than the minimum power speed. Given provisional estimates of flight muscle masses and wingbeat frequencies, the mass-specific sustained muscle work for the different climbing bird species was calculated to be in the range 16–41 joules per kilogram muscle mass, showing a significant positive correlation with body mass.
Evidence for a Role of Gaba in Metabolic Depression During Anoxia in Crucian Carp (Carassius Carassius)
Authors: Nilsson Göran E.
Published: April 2021

Anoxia-tolerant vertebrates decrease their metabolic rate by 70% or more during anoxia, while the major inhibitory neurotransmitter in the vertebrate brain, GABA, increases in concentration. To test the possibility that GABA could be a mediator of anoxic metabolic depression, crucian carp (Carassius carassius L.) were given an inhibitor of GABA synthesis, isoniazid, and the rate of anoxic ethanol production (ethanol being the main end product of energy metabolism in anoxic crucian carp) as well as the rates of normoxic and hypoxic oxygen consumption were measured. Isoniazid (500 mg kg−1), which significantly inhibited the anoxia-induced rise in brain GABA concentration, caused a nearly threefold increase in anaerobic ethanol production without affecting normoxic oxygen consumption. The GABA synthesis inhibitor 3-mercaptopropionic acid (3-MP, 200 mg kg−1) and the GABA receptor antagonist securinine (20 mg kg−1) caused similar rises in anoxic ethanol production. Nevertheless, crucian carp given 250-500mgkg−1 isoniazid, 200mgkg−1 3-MP or 20mgkg−1 securinine all recovered after anoxia, suggesting that a complete depression of the rate of metabolism may not be essential for survival during short-term anoxia. These results indicate that GABA is a mediator of anoxic metabolic depression in crucian carp.
Steering Reactions as Adaptive Components of the Tail-Flip in the Spiny Lobster Jasus Lalandii
Authors: Newland Philip L. , Cattaert Daniel , Neil Douglas M. , Clarac Francois
Published: April 2021

Steering movements of the abdomen and the terminal appendages, the uropods, of the rock lobster Jasus lalandii have been examined during slow postural responses and during tail-flips using a combination of movement and force measurements and by monitoring muscle activity. Gentle mechanical stimulation on one side of the animal elicits a postural steering response of the uropods. The activities of the individual uropod muscles that underlie these movements have been determined.

Progressively intense mechanical stimuli initiate tail-flips, which may incorporate steering responses dependent upon the position of the stimulus. Symmetrical stimuli cause both uropods to open and close symmetrically and only a longitudinally directed force to be produced. However, stimuli delivered to only one side elicit asymmetrical movements of the uropods and rotation of the abdomen to the stimulated side during the preflexion phase of the tail-flip. The pattern of activity in the uropod muscles during this preflexion phase is the same as that in the postural steering response. During flexion itself, the uropods open to their full extent while the abdomen rotates further to the stimulated side. As a result of these movements, appropriate steering forces are produced to take the animal away from the point of stimulation. During re-extension, the uropods close and the abdomen re-extends.

These results are discussed in terms of the relationship between postural reactions and the preflexion phase of the tail-flip, the relative contribution of the different abdominal motor systems to tail-flip steering and the occurrence of steering in different forms of the tail-flip.
Insect Cardioactive Peptides in Manduca Sexta: A Comparison of the Biochemical And Molecular Characteristics of Cardioactive Peptides in Larvae and Adults
Authors: Tublitz N. J. , Cheung C. C. , Edwards K. K. , Sylwester A. W. , Reynolds S.E.
Published: April 2021

The role of neurally derived peptides affecting insect visceral muscle has been explored by many investigators over the past thirty years (e.g. Raabe, 1982; Miller, 1985; Huddart, 1985). One set of myoactive neuropeptides that have been well characterized physiologically is the cardioacceleratory peptides (CAPs) found in the tobacco hawkmoth Manduca sexta. The CAPs act as cardioregulatory neurohormones in the adult moth, increasing heart rate during wing inflation (Tublitz and Truman, 1985a,b; Tublitz and Evans, 1986) and flight (Tublitz, 1989). In addition to their involvement in adult behaviour, one of the CAPs, CAP2, has been implicated in the modulation of the embryonic hindgut in Manduca sexta. Broadie et al. (1990) demonstrated that CAP2 is released in the latter half of embryonic development to aid in the digestion of extra-embryonic yolk by stimulating frequency of gut contractures. This interpretation was supported by quantitative immunocytochemical studies using an anti-CAP monoclonal antibody to identify a group of central nervous system (CNS) neurones that were CAP-immunoreactive (Broadie et al. 1990).
Characterization of a Vasodilator from the Salivary Glands of the Yellow Fever Mosquito Aedes Aegypti
Authors: Ribeiro José M. C.
Published: April 2021

Salivary gland homogenates and oil-induced saliva of the mosquito Aedes aegypti dilate the rabbit aortic ring and contract the guinea pig ileum. The vasodilatory activity is endothelium-dependent, heat-stable, sensitive to both trypsin and chymotrypsin treatments, and both smooth muscle activities cross-desensitize to the tachykinin peptide substance P. Both bioactivities co-elute when salivary gland homogenates are fractionated by reversed-phase HPLC. Molecular sieving chromatography indicates a relative molecular mass of 1400. A monoclonal antibody specific to the carboxy terminal region of tachykinins reacts with material in the posterior part of the central lobe of paraformaldehyde-fixed salivary glands. The presence of a vasodilatory peptide of the tachykinin family in the salivary glands of A. aegypti is proposed and its role in blood feeding is discussed.
Orientation-Disturbing Magnetic Treatment Affects The Pigeon Opioid System
Authors: Papi Floriano , Luschi Paolo , Limonta Patrizia
Published: April 2021

Keeping homing pigeons in an oscillating magnetic field of low intensity is known to increase the scattering of initial bearings and/or their deflection towards a specific direction. To determine whether these effects on orientation are the outcome of direct interference with the birds’ navigational mechanism or are the side-effect of problems in another biological system, experiments were performed to test whether the same effects could be induced by non-magnetic treatments. The initial orientation of pigeons treated with the prototypic opiate antagonist naloxone (1 mg kg-1) displayed similar disturbances to those observed in magnetically treated birds. In both cases, the orientation was significantly different from that of control birds.

The concentration and affinity of the brain’s μ-opiate receptors were then assessed in magnetically treated birds by using [3H]dihydromorphine as a ligand. The concentration of μ-opiate receptors fell significantly in these birds, whereas the affinity of the receptors was unaffected.

We conclude that it appears improbable that the navigational mechanism of pigeons is directly influenced by magnetic treatments. What these do seem to produce is a lack of compensation for the stress experienced by pigeons subjected to a test release.
Conditional Inhibition of Screening-Pigment Aggregation by Lidocaine in Crayfish Photoreceptors and Frog Retinal Pigment Epithelium
Authors: Mondragón Ricardo , Frixione Eugenio
Published: April 2021

Lidocaine, at concentrations equal to or lower than those that inhibit fast axoplasmic transport, was found to interfere with the dark-adapting migration of the screening pigments along crayfish photoreceptors and within the cells of the frog retinal pigment epithelium (RPE). The effects of the anesthetic on pigment movements were studied in isolated eyes incubated under light or dark conditions in media of different ionic compositions. Treatment of crayfish eyes with 25 mmol l−1 lidocaine in normal Van Harreveld’s saline arrested pigment migration to the dark-adapted position or caused migration towards the light-adapted position in the dark. Similar results were obtained with frog eyecups exposed to 5 mmol l−1 lidocaine in Ringer’s solution. In each case, the inhibition of dark adaptation was reversible and dependent on the levels of Na+ and Ca2+ in the incubation medium. A dark-adapted position of both pigments was compatible with lidocaine treatment provided that low-Na+, or high-Ca2+ or CO2+ containing solutions were used. These results indicate that light-adapted and dark-adapted pigment positions in both types of retinal cells can occur in the absence of local nervous input. Further, the data suggest a direct effect of lidocaine upon the photoreceptors or RPE cells. The inhibition of pigment aggregation is interpreted to be a consequence of an anesthetic-induced increase in the permeability of the plasma membrane, which in turn affects the intracellular ionic balance that controls pigment position.
Hypoxic Boundary Layers Surrounding Skin-Breathing Aquatic Amphibians: Occurrence, Consequences and Organismal Responses
Authors: Feder Martin E. , Booth David T.
Published: April 2021

We have used oxygen microelectrodes to characterize the relationship between the partial pressure of oxygen and the distance from the skin in a variety of amphibians immersed in unstirred normoxic water. A substantial hypoxic boundary layer surrounded the skin in nearly every case, with the at the skin-medium interface typically varying between 2 and 4 kPa at both 10 and 20°C. The degree of hypoxia varied little among the anatomical sites examined.

We hypothesized that the formation of hypoxic boundary layers should abbreviate voluntary diving in amphibians that use cutaneous oxygen uptake from water to supplement oxygen stores in the body during dives. To test this, we compared voluntary submergence times of amphibians diving in stirred and unstirred normoxic water. The dives of frogs (Xenopus laevis) and salamanders (Siren lacertina) in stirred water averaged 2·3–2·5 times longer than dives in unstirred water. Diving Xenopus also underwent more voluntary movements (other than swimming to the surface to breathe air) in unstirred water than in moving water. A closed extracorporeal loop containing an oxygen electrode was used to record the of lung gas during forced dives in Xenopus to determine the time required to deplete pulmonary oxygen stores to a level normally associated with the end of voluntary dives . In normoxic water flowing at 0·54 cm s−1 or faster, the decline in pulmonary to this level required on average 18.7 min; in unstirred normoxic water, the average time was 13·8 min. This difference is tantamount to a 36 % extension of submergence time in flowing water.

These findings and those of companion studies suggest that hypoxic boundary layers have a major and pervasive influence on the respiratory status of skinbreathing amphibians in water.
Coupling Between The Heart and Sucking Stomach During Ingestion in a Tarantula
Authors: Dunlop Jason A. , Altringham John D. , Mill Peter J.
Published: April 2021

Electrocardiograms (ECGs) and electromyograms (EMGs) from the dorsal musculature of the sucking stomach of tarantulas (Grammastola cala) were recorded simultaneously from unrestrained animals during ingestion. Resting heart rates averaged 33.6±1.9 beats min−1, which increased significantly to an average of 51.6±3.8 beats min−1 during ingestion. This is not significantly different from the average sucking stomach rate of 53.6±3.9 cycles min−1. Activity of the sucking stomach constrictor muscles started with a phase shift of 0.64±0.007 cycles relative to dilator activity. In some cases the stomach dilators were active almost in synchrony with heart systole (phase shift of 0.10±0.009 relative to ECG), and the constrictors were active later in the cycle, during diastole, with a phase shift of 0.71±0.007 relative to the ECG. These data suggest that, during ingestion, fluid flows in the anterior aorta and midgut are negatively coupled as the fluids traverse the pedicel. Although such coupling was observed in about half the traces, other results were obtained that showed no evidence of coupling. Possible mechanisms for coupling and the sequence of events in the pedicel during ingestion are discussed.
Constrained and Flexible Features of Rhythmical Hindlimb Movements in Chicks: Kinematic Profiles of Walking, Swimming and Airstepping
Authors: Johnston Rebecca M. , Bekoff Anne
Published: April 2021

Although studies of walking have generated many of the principles for motor control, walking is but one of the many behaviors that an animal produces. This study investigates the relationships among the kinematic profiles of three behaviors in chicks: walking, swimming and airstepping. In addition to describing features of the hindlimb movements, such as retraction and protraction, we also examined the intra-and interjoint coordination patterns at the hip, knee and ankle. By using multiple levels of analysis, we identified some features that are common to all three behaviors, and therefore appear to be constrained, as well as some dissimilar or flexible features. Specifically, we show that resistance differentially affects the hip, knee and ankle joints. Our results also show that each joint plays a distinctive role in these behaviors. For example, we suggest that the hip stabilizes the hindlimb and regulates the rhythmicity of its movements. We also show that movement at the knee consistently precedes movement at the other joints in each behavior. Finally, differences in ankle movements are the key features that discriminate one behavior from another. Continuity among prenatal, perinatal and postnatal behaviors in chicks is discussed.
Undulatory Swimming: How Traveling Waves are Produced and Modulated in Sunfish (Lepomis Gibbosus)
Authors: Long John H. , McHenry Matthew J. , Boetticher Nicholas C.
Published: April 2021

We have developed an experimental procedure in which the in situ locomotor muscles of dead fishes can be electrically stimulated to generate swimming motions. This procedure gives the experimenter control of muscle activation and the mechanical properties of the body. Using pumpkinseed sunfish, Lepomis gibbosus, we investigated the mechanics of undulatory swimming by comparing the swimming kinematics of live sunfish with the kinematics of dead sunfish made to swim using electrical stimulation. In electrically stimulated sunfish, undulatory waves can be produced by alternating left–right contractions of either all the axial muscle or just the precaudal axial muscle. As judged by changes in swimming speed, most of the locomotor power is generated precaudally and transmitted to the caudal fin by way of the skin and axial skeleton. The form of the traveling undulatory wave – as measured by tail-beat amplitude, propulsive wavelength and maximal caudal curvature – can be modulated by experimental control of the body’s passive stiffness, which is a property of the skin, connective tissue and axial skeleton.
Note on the Calculation of Propeller Efficiency Using Elongated Body Theory
Authors: Cheng Jian-Yu , Blickhan Reinhard
Published: April 2021

The elongated body theory has been widely used for calculations of the hydrodynamic propulsive performance of swimming fish. In the biological literature, terms containing the slope of the amplitude function at the tail end have been neglected in the calculations of thrust and efficiency, and a slope of zero has been assumed. However, some fishes, such as saithe and trout, have non-zero values of the slope near the tail end and, when this term is taken into account, the efficiency may be reduced by as much as 20% and approaches the result given by the three-dimensional waving plate theory. The inclusion of the slope in the efficiency considerations results in an optimum ratio of the swimming speed to the wave speed that is clearly less than 1. It is suggested that the slope terms should be included in the estimation of propulsive performance for fish swimming with variable amplitude.
Modulation of Negative Work Output from a Steering Muscle of the Blowfly Calliphora Vicina
Authors: Tu Michael S. , Dickinson Michael H.
Published: April 2021

Of the 17 muscles responsible for flight control in flies, only the first basalar muscle (b1) is known to fire an action potential each and every wing beat at a precise phase of the wing-beat period. The phase of action potentials in the b1 is shifted during turns, implicating the b1 in the control of aerodynamic yaw torque. We used the work loop technique to quantify the effects of phase modulation on the mechanical output of the b1 of the blowfly Calliphora vicina. During cyclic length oscillations at 10 and 50 Hz, the magnitude of positive work output by the b1 was similar to that measured previously from other insect muscles. However, when tested at wing-beat frequency (150 Hz), the net work performed in each cycle was negative. The twitch kinetics of the b1 suggest that negative work output reflects intrinsic specializations of the b1 muscle. Our results suggest that, in addition to a possible role as a passive elastic element, the phase-sensitivity of its mechanical properties may endow the b1 with the capacity to modulate wing-beat kinematics during turning maneuvers.
Assessment of Maximum Sustainable Swimming Performance in Rainbow Trout (Oncorhynchus Mykiss)
Authors: Wilson Rod W. , Egginton Stuart
Published: April 2021

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

The 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

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

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

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

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

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

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

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

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

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

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

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.
5-Hydroxytryptamine in the Salivary glands Of Adult Female Aedes Aegypti and its Role in Regulation of Salivation
Authors: Novak Mark G. , Ribeiro José M. C. , Hildebrand John G.
Published: April 2021

A dense plexus of axons, immunoreactive to antisera against 5-hydroxytryptamine (5-HT, serotonin) and surrounding the proximal medial lobe of the salivary gland of adult female Aedes aegypti mosquitoes, was demonstrated by means of whole-mount fluorescence immunocytochemistry. This innervation originates in the stomatogastric nervous system. 5-HT-immunoreactive innervation is absent in male salivary glands, suggesting that 5-HT is involved in blood-feeding. Furthermore, female mosquitoes treated with the 5-HT-depleting agent α-methyltryptophan (AMTP) and then allowed to feed on a rat exhibited a significantly longer mean probing period and a lower blood-feeding success rate than did control mosquitoes. When female mosquitoes were experimentally induced to salivate into mineral oil, AMTP-treated individuals secreted significantly less saliva than did control mosquitoes. These samples of saliva also contained significantly lower concentrations of apyrase, an enzyme important in blood-feeding. Injection of 5-HT into both AMTP-treated and control mosquitoes elicited significant increases in the volume of secreted saliva and/or its apyrase content. We conclude that 5-HT plays an important role in the control of salivation in adult female A. aegypti.