bluuebunny/crossref_metadata_2025_split huggingface dataset:
Migrating young pied flycatchers Ficedula hypoleuca do not compensate for geographical displacements
Authors: Mouritsen Henrik , Næsbye Larsen Ole 
Published: April 2021

ABSTRACT
The present study tested whether young Scandinavian pied flycatchers, Ficedula hypoleuca, would direct their orientation back towards their southwest-directed migratory route in autumn if displaced by the maximal biologically realistic distance due south or due west. The aim was to clarify the nature of their inherited spatiotemporal orientation programme. Forty-eight young pied flycatchers were caught and tested at Christiansø, Denmark. They were then divided into three groups of equal size and orientation, of which one group was displaced due south and another due west, while the third remained as a control at Christiansø. Three different experimenters then simultaneously tested their orientation. The birds oriented in the same direction at all localities, showing no signs of compensatory orientation. This result suggests that young pied flycatchers on their first autumn migration use a simple clock-and-compass strategy to reach their wintering area. If this suggestion holds, then all the prerequisites (a compass and an internal clock) for orientation during the autumn migration seem to be known at present, at least at the behavioural level. In addition, the present study provides further evidence supporting the assumption that observations in an orientation funnel reflect the orientation of actual migration.
Evolution of Osmotic Stress Signaling Via Map Kinase Cascades
Authors: Kültz Dietmar , Burg Maurice 
Published: April 2021

ABSTRACT
Cells respond to changes in osmotic pressure with compensatory molecular adaptations that allow them to re-establish homeostasis of osmotically disturbed aspects of cell structure and function. In addition, some cell types respond to osmotic stress by changing their phenotype or, if their tolerance threshold is exceeded, by initiating programmed cell death. To understand how cells achieve these different types of adaptive response to osmotic stress, it is necessary to identify the key elements of osmosensory signal transduction and to analyze the complex networks that process osmotic stimuli imposed upon cells by their environment. This review highlights mitogen-activated protein kinase (MAPK) cascades as important intracellular signal-transduction pathways activated in response to changes in osmolality. A unifying theme of osmotic stress signaling via MAPKs seems to be regulation of the cell cycle as part of the cellular stress response. This very important physiological capacity may have been conserved throughout evolution as a major function of MAPKs from many different subfamilies. The evidence for this conjecture is discussed, and our current knowledge about osmotic stress signaling pathways in yeast, animals and plants is briefly reviewed.
Ambient Temperature Does not Affect the Tactile Sensitivity of Mystacial Vibrissae in Harbour Seals
Authors: Dehnhardt G. , Mauck B. , Hyvärinen H. 
Published: April 2021

ABSTRACT
Vibrissae provide pinnipeds with tactile information primarily in the aquatic environment, which is characterized by its high thermal conductivity and large potential cooling power. Since studies of thermal effects on human tactile sensitivity have revealed that cooling below normal skin temperature impairs sensitivity, the present study investigates the tactile sensitivity of the vibrissal system of harbour seals at varying ambient temperatures. Using plates bearing gratings of alternating grooves and ridges, the texture difference thresholds of two adult seals were determined under water. We took advantage of the natural difference in ambient temperature between summer and winter. Mean water temperature was 1.2 °C during the winter and 22 °C during the summer. During the cold season, the thermal status of both seals was examined using an infrared-sensitive camera system. The texture difference threshold of both seals remained the same (0.18 mm groove width difference) under both test conditions. The thermographic examination revealed that the skin areas of the head where the mystacial and supraorbital vibrissae are located show a substantially higher degree of thermal emission than do adjacent skin areas. This suggests that, in the vibrissal follicles of harbour seals, no vasoconstriction occurs during cold acclimation, so that the appropriate operating temperature for the mechanoreceptors is maintained.
Analysis of Fluid Dynamics in Perfused Glomeruli of the Hagfish Eptatretus Stouti (Lockington)
Authors: Riegel J. A. 
Published: April 2021

ABSTRACT
The capillary tuft of glomeruli of the hagfish mesonephros contains both ‘low’-pressure and ‘high’-pressure glomerular vessels (LPGVs and HPGVs). The existence of the HPGV raised the possibility that pressure filtration could occur in the hagfish kidney when the blood pressure was sufficiently high. Therefore, measurements of glomerular capillary pressure were made in HPGVs and LPGVs whilst single glomeruli were perfused with hagfish Ringer’s solution that contained the colloid Ficoll 70. Calculations of the effective colloid osmotic pressure in perfused capillaries were made; these showed that hydrostatic pressures within the HPGV were inadequate to effect pressure filtration except at high rates of perfusion. However, high rates of perfusion provoked perfusion pressures that exceeded the highest values measured in the renal blood supply of lightly anaesthetised hagfish. It was concluded that some process other than pressure filtration must account for formation of the primary urine by hagfish glomeruli.
The proportion of the perfusate that became urine, the single glomerulus filtration fraction (SGFF), bore a strong positive relationship to the vascular resistance of perfused glomeruli. Both the SGFF and the vascular resistance were inversely related to the rate of perfusion except when that rate was very high. From these two observations it was concluded that at least two flow pathways exist in hagfish glomeruli: one that has a high vascular resistance and that contributes to the elaboration of the urine, and one that has a low vascular resistance and does not contribute to urine formation. The possible anatomical location of the various flow pathways through hagfish glomeruli and how they may function are discussed.
Feeding mechanism of the atlantic guitarfish rhinobatos lentiginosus: modulation of kinematic and motor activity
Authors: Wilga Cheryl D. , Motta Philip J. 
Published: April 2021

ABSTRACT
The kinematics and muscle activity pattern of the head and jaws during feeding in the Atlantic guitarfish Rhinobatos lentiginosus are described and quantified using high-speed video and electromyography to test hypotheses regarding the conservation and modulation of the feeding mechanism. Prey is captured by the guitarfish using suction. Suction capture, bite manipulation and suction transport behaviors in the guitarfish are similar to one another in the relative sequence of kinematic and motor activity, but can be distinguished from one another by variation in absolute muscle activation time, in the presence or absence of muscle activity and in the duration of muscle activity. A novel compression transport behavior was observed that is strikingly different from the other feeding behaviors and has not been described previously in elasmobranchs. The mechanism of upper jaw protrusion in the guitarfish differs from that described in other elasmobranchs. Muscle function and motor pattern during feeding are similar in the plesiomorphic cranial muscles in the guitarfish and the spiny dogfish probably because of their shared ancestral morphology. Modulation in recruitment of jaw and hyoid depressor muscles among feeding behaviors in the guitarfish may be a consequence of duplication of muscles and decoupling of the jaws and hyoid apparatus in batoids.
Neuromuscular control of anguilliform locomotion: patterns of red and white muscle activity during swimming in the american eel anguilla rostrata
Authors: Gillis Gary B. 
Published: April 2021

ABSTRACT
Two areas that have received substantial attention in investigations of muscle activity during fish swimming are (1) patterns of fiber type recruitment with swimming speed and (2) the timing of muscle activation in relation to muscle strain. Currently, very little is known about either of these areas in eels, which represent an extreme body form among fishes and utilize a mode of locomotion found at one end of the undulatory spectrum (anguilliform locomotion). To assess how this swimming mode and body form influence the neuromuscular control of swimming, I recorded electromyographic data from red and white muscle at four positions, 0.3L, 0.45L, 0.6L and 0.75L, where L is body length, in eels (Anguilla rostrata) simultaneously video- taped (250 fields s−1 ) swimming at three speeds, 0.5, 0.75 and 1.0 L s−1. As in other fish, exclusively red muscle is used at slow swimming speeds and white muscle is additionally recruited at higher swimming speeds. However, this study also revealed a novel posterior-to-anterior pattern of muscle recruitment with increasing swimming speed. At slow speeds, anteriorly located muscles are never active, muscle strain is negligible and forward thrust must be generated by posterior muscles. As speed increases, more anterior muscles are additionally recruited. Electromyogram (EMG) burst durations typically occupy between 0.2 and 0.3 undulatory cycles, irrespective of speed or position. EMG burst intensity increases significantly with swimming speed. The onset of EMG activity typically occurred near the end of muscle lengthening, whereas the offset of EMG activity occurred during shortening (typically before the muscle’s return to resting length). There was a significant shift in red muscle onset times such that anterior muscles were typically active later in their strain cycle than posterior muscles. When red muscle activity patterns across various fish taxa are compared, differences in propulsive wavelength among species are related to differences in muscle activity, providing insight into the underlying neuromuscular bases of differences among undulatory swimming modes.
Transport and metabolism of glucose in isolated enterocytes of the black bullhead ictalurus melas: effects of diet and hormones
Authors: Soengas José L. , Moon Thomas W. 
Published: April 2021

ABSTRACT
The uptake and metabolism of glucose were assessed in enterocytes isolated from black bullhead Ictalurus melas. The objective of this study was to examine the effects of diet and hormone treatment on glucose transport and metabolism, so the enterocyte was the most appropriate preparation. Glucose transport was estimated using specific inhibitors: glucose uptake measured in the presence of phlorizin presumably represents transport at the basolateral membrane, whereas glucose uptake in the presence of cytochalasin B presumably represents transport at the brush border. Feeding bullheads a standard diet resulted in maximum enterocyte rates of glucose uptake of 438.2±35.5 nmol mg−1 cells h−1 for transport in the presence of cytochalasin B and 427.0±49.7 nmol mg−1 cells h−1 (means ± S.E.M., N=12) for transport in the presence of phlorizin. These values represent 50 % of the total 3-O-methylglucose transported. The rate of transport in the presence of cytochalasin B was increased in bullheads fed a high-carbohydrate diet. Incubating bullhead enterocytes with glucagon or glucagon-like peptide-1 (GLP) at 10−8 mol l−1 and with dexamethasone or isoproterenol at 10−6 mol l−1 significantly increased the rate of brush-border transport, but not the apparent affinity constant (Kt). Activation was dependent on hormone concentration. In contrast, insulin was without effect on transport rates, nor did it counteract activation by glucagon-family peptides. CO2 production rates from D- [14 C]glucose indicated that glucose metabolism was not limited by transport rates in the enterocytes. Glucagon and GLP decreased maximal oxidation rates, whereas dexamethasone, isoproterenol and insulin did not alter these rates. The activities of enterocyte hexokinase exceeded the rate of glucose oxidation but not the rate of transport of glucose, at least at maximum activities, implicating this enzyme as one component of the strategy to ensure that glucose is maximally available to the blood of this species.
CHANGES IN H+-TRANSLOCATING VACUOLAR-TYPE ATPase IN THE ANTERIOR SILK GLAND CELL OF BOMBYX MORI DURING METAMORPHOSIS
Authors: Azuma Masaaki , Ohta Yasuhiko 
Published: April 2021

ABSTRACT
A proton-translocating vacuolar-type ATPase (V-ATPase) was identified and characterized in the anterior silk gland of Bombyx mori. By incubating the intact tissue with the fluorescent dye Acridine Orange, the acidified compartment was detected at the apical pole of the epithelial cells. This was observed throughout the feeding period of the fifth-instar larva until the onset of spinning. Acidification was prevented completely and reversibly by 0.8 μmol l−1 bafilomycin A1, a specific inhibitor of V-ATPase. The presence of V-ATPase in a microsomal fraction was verified by immunoblots using an antiserum to the V-ATPase holoenzyme from Manduca sexta midgut. The antiserum localized the V-ATPase to the apical plasma membrane of the anterior silk gland cells, suggesting that the enzyme is functionally active in pumping protons out of the cell towards the glandular lumen of feeding silkworm larvae. In spinning larvae, the acidification produced by the V-ATPase appears to cease, because acidic compartments were seen rarely and only in the periphery of basal cytoplasm, and because immunocytochemical staining for the V-ATPase was greatly reduced at the apical surface. The metamorphic changes in relation to the occurrence of V-ATPase corresponded well with the ultrastructural changes in the anterior silk gland cell of Bombyx mori larvae.
Gating of Sensory Responses of Descending Brain Neurones During Walking in Crickets
Authors: Staudacher Erich , Schildberger Klaus 
Published: April 2021

ABSTRACT
Single descending brain neurones were recorded and stained intracellularly in the neck connectives of crickets while they walked upon a styrofoam ball under open-loop conditions. The animal’s translational and rotational velocities were measured simultaneously, and various stimuli were used to investigate the neuronal response characteristics. Stimulation with a moving grating or an artificial calling song of 5 kHz induced optomotor behaviour and positive phonotaxis. An acoustic stimulus of 20 kHz elicited negative phonotaxis.
We report the first clear evidence for behaviourally dependent gating of sensory responses of identified descending brain neurones. Most descending cells only responded to visual stimuli or to an artificial calling song of 5 kHz while the animal was walking, indicating that the responses to these stimuli were gated by the walking activity of the animal. In contrast to this, responses to stimuli that elicit negative phonotaxis, such as acoustic stimuli of 20 kHz, were not gated. This indicates that the gating of sensory responses in these cells depends on the behavioural context of the stimulus.
From these findings, we conclude that significant information about the properties of sensory processing in higher-order neurones can only be gained from tests in behaviourally relevant paradigms. Important characteristics might otherwise be missed, thus leading to misinterpretations regarding their function.
Effects Of Speed on the Hindlimb Kinematics of the Lizard Dipsosaurus Dorsalis
Authors: Fieler Carrie L. , Jayne Bruce C. 
Published: April 2021

ABSTRACT
Lizards are the most diverse extant lineage of vertebrates believed to have retained the sprawling limb posture of ancestral tetrapods and, although the sprinting speeds of lizards are well documented, quantitative analyses of limb movements are lacking. We therefore examined a wide range of steady running speeds to quantify variation in the kinematics of a morphologically generalized hindlimb in the lizard Dipsosaurus dorsalis. From speeds of 50 to 350cm s−1, stride length, step length and stride frequency all had significant curvilinear increases from 13.3 to 39.4cm, from 8.9 to 12.8cm and from 3.9 to 8.6Hz, respectively, whereas duty factor (percentage of cycle when foot is on ground) decreased from 63 to 34% with increased speed. For five standardized speeds ranging from 50 to 250cm s−1, analyses of variance detected highly significant (P&lt;0.001) effects of speed on 27 out of a total of 46 kinematic variables. The height of the hip at the time of footfall increased significantly with increased speed, whereas the amount of pelvic rotation in the horizontal plane (mean 36°) per stride was unaffected by speed. The orientation of the long axis of the foot changed by nearly 50° with increased speed such that the foot was nearly straight forward at 250cm s−1, and at high speeds the heel often did not touch the ground. The effective length of the limb at footfall nearly doubled with increased speed as a combined result of increased plantar flexion and knee extension and a more erect femur. The pervasive effects of speed on hindlimb kinematics observed for this species do not conform simply with previous generalizations of lizards as having plantigrade foot posture and sprawling limbs.
Blood Volume, Plasma Volume and Circulation Time in a High-Energy-Demand Teleost, the Yellowfin Tuna (Thunnus Albacares)
Authors: Brill Richard W. , Cousins Katherine L. , Jones David R. , Bushnell Peter G. , Steffensen John F. 
Published: April 2021

ABSTRACT
We measured red cell space with 51Cr-labeled red blood cells, and dextran space with 500 kDa fluorescein-isothiocyanate-labeled dextran (FITC-dextran), in two groups of yellowfin tuna (Thunnus albacares). Red cell space was 13.8±0.7 ml kg−1 (mean ± S.E.M.) Assuming a whole-body hematocrit equal to the hematocrit measured at the ventral aortic sampling site and no significant sequestering of 51Cr-labeled red blood cells by the spleen, blood volume was 46.7±2.2 ml kg−1. This is within the range reported for most other teleosts (30–70 ml kg−1), but well below that previously reported for albacore (Thunnus alalunga, 82–197 ml kg−1). Plasma volume within the primary circulatory system (calculated from the 51Cr-labeled red blood cell data) was 32.9±2.3 ml kg−1. Dextran space was 37.0±3.7 ml kg−1. Because 500 kDa FITC-dextran appeared to remain within the vascular space, these data imply that the volume of the secondary circulatory system of yellowfin tuna is small, and its exact volume is not measurable by our methods. Although blood volume is not exceptional, circulation time (blood volume/cardiac output) is clearly shorter in yellowfin tuna than in other active teleosts. In a 1 kg yellowfin tuna, circulation time is approximately 0.4 min (47 ml kg−1/115 ml min−1 kg−1) compared with 1.3 min (46 ml kg−1/35 ml min−1 kg−1) in yellowtail (Seriola quinqueradiata) and 1.9 min (35 ml kg−1/18 ml min−1 kg−1) in rainbow trout (Oncorhynchus mykiss). In air-breathing vertebrates, high metabolic rates are necessarily correlated with short circulation times. Our data are the first to imply that a similar relationship occurs in fishes.
Mechanics of Lung Ventilation in a Large Aquatic Salamander, Siren Lacertina
Authors: Brainerd Elizabeth L. , Monroy Jenna A. 
Published: April 2021

ABSTRACT
Lung ventilation in Siren lacertina was studied using X-ray video, measurements of body cavity pressure and electromyography of hypaxial muscles. S. lacertina utilizes a two-stroke buccal pump in which mixing of expired and inspired gas is minimized by partial expansion of the buccal cavity during exhalation and then full expansion after exhalation is complete. Mixing is further reduced by the use of one or two accessory inspirations after the first, mixed-gas cycle. Exhalation occurs in two phases: a passive phase in which hydrostatic pressure and possibly lung elasticity force air out of the lungs, and an active phase in which contraction of the transverse abdominis (TA) muscle increases body cavity pressure and forces most of the remaining air out. In electromyograms of the lateral hypaxial musculature, the TA became active 200–400 ms before the rise in body cavity pressure, and activity ceased at peak pressure. The TA was not active during inspiration, and no consistent activity during breathing was noted in the external oblique, internal oblique and rectus abdominis muscles. The finding that the TA is the primary expiratory muscle in S. lacertina agrees with findings in a previous study of another salamander, Necturus maculosus. Together, these results indicate that the use of the TA for exhalation is a primitive character for salamanders and support the hypothesis that the breathing mechanism of salamanders represents an intermediate step in evolution between a buccal pump, in which only head muscles are used for ventilation, and an aspiration pump, in which axial muscles are used for both exhalation and inhalation.
Chloride Transport in Red Blood Cells of Lamprey Lampetra Fluviatilis: Evidence for a Novel Anion-Exchange System
Authors: Bogdanova Anna Yu. , Sherstobitov Alexander O. , Gusev Gennadii P. 
Published: April 2021

ABSTRACT
The existence of a furosemide-sensitive Cl− transport pathway activated by external Ca2+ and Mg2+ has been demonstrated previously in studies of Cl− influx across the lamprey erythrocyte membrane. The aim of the present study was to characterize further specific Cl− transport pathways, especially those involved in Cl− efflux, in the red blood cell membrane of Lampetra fluviatilis. Cl− efflux was inhibited by 0.05 mmol l−1 dihydroindenyloxyalkanoic acid (DIOA) (81 %), 1 mmol l−1 furosemide (76 %) and 0.1 mmol l−1 niflumic acid (54 %). Bumetanide (100 μmol l−1) and DIDS (100 μmol l−1) had no effect effect on Cl− efflux. Substitution of external Cl− by gluconate, but not by NO3−, led to a gradual decline of Cl− efflux. In addition, the removal of external Ca2+ resulted in a significant reduction in the rate of Cl− efflux. Membrane depolarization caused by increasing external K+ concentration or by inhibiting K+ channels with 1 mmol l−1 Ba2+ did not affect Cl− efflux. The furosemide-sensitive component of Cl− influx was a saturable function of external [Cl−] with an apparent Km of approximately 92 mmol l−1 and Vmax of approximately 17.8 mmol l−1 cells−1 h−1. Furosemide did not affect intracellular Cl− concentration (57.6±5.2 mmol l−1 cell water), measured using an ion-selective Cl− electrode, showing that a furosemide-sensitive pathway is not involved in net Cl− movement. A gradual fall (from 28.1±1.4 to 15.0±1.3 mmol l−1 cells−1 h−1) in unidirectional Cl− influx with time was observed within 3 h of cell preincubation in the standard physiological medium. These data provide evidence for the existence for an electroneutral furosemide-sensitive anion-exchange pathway in the lamprey erythrocyte membrane that accepts chloride and nitrate, but not bicarbonate or bromide.