bluuebunny/crossref_metadata_2025_split huggingface dataset:
What a Drag it is Getting Cold: Partitioning the Physical and Physiological Effects of Temperature on Fish Swimming
Authors: Fuiman Lee A. , Batty Robert S. 
Published: April 2021

ABSTRACT
The influence of temperature-induced changes in water viscosity on the swimming performance and kinematics of larval Atlantic herring (Clupea harengus) was examined using high-speed video recording. The physical effects of viscosity were measured separately from the physiological (Q10) effects of temperature by increasing the viscosity using methyl cellulose. Voluntary swimming speeds of large larvae (18.2 mm total length) were characterized by Reynolds numbers based on length (ReL) between 100 and 500 and varied with temperature and viscosity. Speeds of small larvae (9.6 mm) at ReL between 25 and 125 were strongly affected by viscosity, but virtually unaffected by temperature at equal viscosities. Speeds of large larvae were modulated by transverse tail speed. Small (viscosity-dominated) larvae altered both transverse tail speed and tail amplitude to vary their swimming speed. Stride lengths for both sizes of larvae followed predictions for viscous-regime swimming until ReL&gt;450. The combined data suggest that the viscous hydrodynamic regime for larval herring extends to at least ReL=300 and that viscosity could be important up to ReL of approximately 450. Because the physical effects of viscosity supplement the physiological effects of temperature on locomotor performance (when ReL is below approximately 300), indices such as Q10 can greatly overestimate the dependence of physiological processes on temperature, as demonstrated by an example.
Physiological Mechanisms of Evolved Desiccation Resistance in Drosophila Melanogaster
Authors: Gibbs Allen G. , Chippindale Adam K. , Rose Michael R. 
Published: April 2021

ABSTRACT
We investigated physiological characters associated with water balance in laboratory populations of Drosophila melanogaster selected for resistance to desiccating conditions for over 100 generations. Five replicate, outbred, desiccation-selected (D) populations were compared with their control (C) populations. Water loss rates of female D flies were approximately 40 % lower than those of C females. Although excretory water loss was reduced in desiccation-selected flies, it comprised less than 10 % of total water loss, indicating that the D populations have evolved reduced cuticular and/or respiratory water loss rates. Total surface lipid amounts did not differ between the C and D flies. Cuticular hydrocarbons from D flies were longer than those from C flies and melted at slightly higher temperatures, possibly contributing to reduced water loss rates. Desiccation-selected flies contained approximately 30 % more bulk water than controls, as well as more glycogen. However, total metabolic water stores did not differ between the stocks owing to higher lipid levels in the C populations. The ability to tolerate water loss, as measured by water content at the time of death, did not differ between D and C flies. Thus, evolution of increased desiccation resistance has occurred by multiple physiological mechanisms, but some potential adaptive differences have not evolved.
Changes in Na+/K+-Atpase Expression During Adaptive Cell Differentiation In Avian Nasal Salt Gland
Authors: Hildebrandt Jan-Peter 
Published: April 2021

ABSTRACT
Chronic salt stress in ducklings (Anas platyrhynchos) resulted in a sustained accumulation of cyclic AMP in the secretory cells of the nasal salt glands. Adaptive increases in the activity of the Na+/K+-ATPase, measured as ATP hydrolysis rates in freshly isolated tissue, were observed after 12 h of salt stress. This change in enzyme activity was associated with increases in protein abundance in the α-as well as in the β-subunit of Na+/K+-ATPase and an increase in β-subunit glycosylation. We investigated whether the increase in the cytosolic cyclic AMP concentration and the adaptive changes in Na+/K+-ATPase activity were causally related.
Using an organotypic tissue culture system for salt gland slices from unstressed (naive) ducklings, we produced similar changes in Na+/K+-ATPase activity and subunit abundance by treating cultured tissue with drugs that elevate cytosolic cyclic AMP levels (forskolin, 8-CPT-cAMP) during a 15 h culture period. Protein synthesis assays using cultured tissue revealed that elevations in cytosolic cyclic AMP level mediate increases in Na+/K+-ATPase subunit abundance by slowing down the degradation of ATPase subunits. This increase in the amount of enzyme protein was associated with a significant increase in Na+/K+-ATPase activity in tissue homogenates. The time course of these changes in cyclic-AMP-treated cultured tissue resembled that observed in salt-stressed intact animals, indicating that the elevation in cyclic AMP level in salt gland tissue may constitute a portion of the signalling events ultimately leading to the adaptive increase in Na+/K+-ATPase activity in vivo.
Modulation of Buccal Pressure During Prey Capture in Hexagrammos Decagrammus (Teleostei: Hexagrammidae)
Authors: Nemeth Donna Henriques 
Published: April 2021

ABSTRACT
Changes in intraoral pressure during prey capture were recorded for a trophic generalist, Hexagrammos decagrammus, feeding on different prey species. Prey were grouped into elusive (shrimps), grasping (isopods and crabs) and non-elusive (pieces of shrimp) categories. Elusive and grasping prey elicited strikes with a larger and faster reduction in buccal pressure than did non-elusive prey. The suction force generated by the predator differed for strikes among the shrimp genera in the elusive prey category. The most sedentary shrimps (Crangon alaskensis and C. nigricauda) elicited the fastest and greatest reduction in pressure relative to the most evasive shrimps (Pandalus danae and Heptacarpus stylus). A preparatory phase, during which the buccal cavity is compressed prior to the strike, occurred significantly more frequently in strikes at grasping prey than in strikes at elusive and non-elusive prey, and more frequently for elusive than for non-elusive prey. Prey size did not influence the suction force generated by the predator. No differences in buccal pressure patterns were detected between strikes that resulted in a capture or a miss, suggesting that misses were due to the escape behavior of the prey and were not the result of an inappropriate suction force. These data support the current view that fish can modify their feeding mode in response to prey behavior, and they emphasize that the behavioral responses of the individual prey must be considered when defining the appropriate strategy for prey capture. The use of a flexible, modifiable feeding behavior is associated with a broad diet in H. decagrammus and may increase capture success on diverse prey relative to that of other species showing stereotypical feeding responses.
Developmental Changes in Chemoreceptive Control of Gill Ventilation in Larval Bullfrogs (Rana Catesbeiana) II. Sites Of O2-Sensitive Chemoreceptors
Authors: Jia Xi Xi , Burggren Warren W. 
Published: April 2021

ABSTRACT
The time course of reflex changes in gill ventilation variables caused by a step-wise change in of inspired water and by the introduction of NaCN into inspired water was measured in two populations of unanesthetized larval bullfrogs (Rana catesbeiana) – one with intact gill arches and a second with bilateral ablation of the first gill arch. Developmental stages TK V–VII, IX–XI and XVII–XIX were examined. Inspiring hypoxic water or a pulse of NaCN significantly increased gill ventilation within 7 s in control larvae. Ablation of the first gill arches in larval R. catesbeiana eliminated the initial, quick response of gill ventilation to changes in the of inspired water and to the presence of NaCN in all three developmental groups. These data suggest that O2-sensitive chemoreceptors are located on the first gill arch and are responsible for the initial rapid ventilatory response. However, a slow response (&gt;15 s) to changes in of inspired water persisted even after removal of the first gill arch. This response is far slower than the minimum blood circulation time (approximately 5–8 s as measured in all three groups), indicating that a second population of receptors is not directly monitoring arterial or venous blood. Instead, this second population of receptors is likely to be located ‘behind’ a significant diffusion barrier, possibly monitoring cerebrospinal fluid.
Actin-Based Vesicular Transport in the First 20 Min after Dusk is Crucial for Daily Rhabdom Synthesis in the Compound Eye of the Grapsid Crab Hemigrapsus Sanguineus
Authors: Matsushita Atsuko , Arikawa Kentaro 
Published: April 2021

ABSTRACT
In the crab Hemigrapsus sanguineus, maintained under a 12 h:12 h light:dark cycle, the amount of vesicular smooth endoplasmic reticulum (vesicular sER) in the photoreceptor cell body increases after the light is turned off. This paper demonstrates that actin filaments in the photoreceptor cell body are involved in the transport of vesicular sER towards the rhabdom. To specify the time of actin contribution to rhabdom synthesis, we disrupted the organization of actin filaments in the cell body with cytochalasin D at various time around dusk. We then measured the rhabdom size and also examined the ultrastructure of the photoreceptor cell body 3 h after extinguishing the light. When cytochalasin D was applied from either 1 h before or immediately after extinguishing the light, the rhabdom size did not increase, whereas vesicular sER accumulated in the cell body. In contrast, cytochalasin D applied to the eyes from 20 min after turning the light off did not inhibit rhabdom synthesis. These results indicate that the first 20 min after the light is turned off is particularly important for the transport of vesicular sER towards the rhabdom by the cell body actin filaments.
The Effects of Artificial Lung Inflation on Pulmonary Blood Flow And Heart Rate In The Turtle Trachemys Scripta
Authors: Herman Jay , Wang Tobias , Smits Allan W. , Hicks James W. 
Published: April 2021

ABSTRACT
As for most ectothermic vertebrates, the breathing pattern of turtles is episodic, and pulmonary blood flow (Q̇;pul) and heart rate (fH) normally increase several-fold during spontaneous ventilation. While some previous studies suggest that these cardiovascular changes are caused by stimulation of pulmonary stretch receptors (PSRs) during ventilation, it has been noted in other studies that blood flows often change prior to the initiation of breathing. Given the uncertainty regarding the role of PSRs in the regulation of central vascular blood flows, we examined the effect of manipulating lung volume (and therefore PSR stimulation) on blood flows and heart rate in the freshwater turtle Trachemys scripta.
Turtles were instrumented with blood flow probes on the left aortic arch and the left pulmonary artery for measurements of blood flow, and catheters were inserted into both lungs for manipulation of lung volume. In both anaesthetized and fully recovered animals, reductions or increases in lung volume by withdrawal of lung gas or injection of air, N2, O2 or 10 % CO2 (in room air) had no effect on blood flows. Furthermore, simulations of normal breathing bouts by withdrawal and injection of lung gas did not alter Q̇pul or fH. We conclude that stimulation of PSRs is not sufficient to elicit cardiovascular changes and that the large increase in Q̇pul and fHnormally observed during spontaneous ventilation are probably caused by a simultaneous feedforward control of central origin.
Hypoxia and Ischaemia in Buffer-Perfused Toad Hearts
Authors: Mckean Tom , Scherzer Anna , Park Han 
Published: April 2021

ABSTRACT
Previous studies on the effects of ischaemia or hypoxia in ectothermic vertebrate hearts have generally used preparations that were not performing at physiological levels of pressure and flow. The conclusions that ischaemia or hypoxia are not stressful to these organisms were examined in another species, Bufo marinus, in which a buffer-perfused heart was performing physiological levels of work. The in situ preparation demonstrated the Frank–Starling relationship and mechanical characteristics similar to the hearts of intact animals. The hearts recovered from 60 min of ischaemia and reperfusion with no reduction in pressure, flow or heart rate parameters. Hearts exposed to 30 min of hypoxia at physiological filling and diastolic afterload pressures ceased generating a continuous cardiac output during the hypoxia. In most cases, there was a gradual reduction of cardiac output to zero, but in 27 % of the hearts studied, intermittent beating was observed. During reoxygenation, the hearts recovered 50–90 % of their prehypoxic function and were damaged. Hearts exposed to hypoxia with reduced filling and diastolic afterload continued to develop a cardiac output throughout the hypoxia and demonstrated an overshoot phenomena with the onset of reoxygenation. If demand is in the normal range at the onset of hypoxia, the hearts intrinsically reduce demand either by reducing pressure development or by conversion to intermittent beating. Toad hearts appear not to be damaged by ischaemia, a condition in which demand is low.
Role of V-ATPase-rich cells in acidification of the male reproductive tract
Authors: Brown Dennis , Smith Peter J. S. , Breton Sylvie 
Published: April 2021

ABSTRACT
Specialized proton-secreting cells play important physiological roles in a variety of tissues. On the basis of the immunocytochemical detection of carbonic anhydrase and V-ATPase in distinct epithelial cells of the epididymis and vas deferens, we predicted that the vacuolar V-ATPase that is located on the apical membrane of these cells should be a major contributor to luminal acidification in parts of the male reproductive tract. Physiological studies using the proton-selective vibrating probe in the vas deferens confirmed this hypothesis. As discussed recently, maintenance of the pH of the reproductive tract is probably under tight physiological control, by analogy with the situation in the kidney. Manipulation of luminal pH might, therefore, provide a point of intervention for the regulation of male fertility. In addition, it is possible that some cases of unexplained male infertility might result from defective acidification, resulting either from pathological states or potentially from environmental factors that may inhibit proton secretory pathways.
Role of the Ca2+-Sensing Receptor in Divalent Mineral Ion Homeostasis
Authors: Hebert Steven C. , Brown Edward M. , Harris H. William 
Published: April 2021

ABSTRACT
The divalent mineral cations Ca2+ and Mg2+ play many and diverse roles both in the function of cells and in extracellular processes. The metabolism of these cations is a complex process involving the coordinated function of several organ systems and endocrine glands. A recently cloned G-protein-coupled receptor responds to extracellular calcium concentration (Ca2+o-sensing receptor, CaSR) and mediates several of the known effects of Ca2+o on parathyroid and renal function. The CaSR, which is also expressed in a number of other tissues including thyroidal C-cells, brain and gastrointestinal tract, may function as a Ca2+o sensor in these tissues as well. Thus, Ca2+o is a first messenger (or hormone) which, via CaSR-mediated activation of second messenger systems (e.g. phospholipases C and A2, cyclic AMP) leads to altered function of these cells. Several mutations in the human CaSR gene have been identified and shown to cause three inherited diseases of calcium homeostasis, clearly implicating the CaSR as an important component of the homeostatic mechanism for divalent mineral ions.
Ca2+ and Mg2+ losses from the body are regulated by altering the urinary excretion of these divalent cations. The localization of the CaSR transcripts and protein in the kidney not only provides a basis for a direct Ca2+o (or Mg2+o) -mediated regulation of Ca2+ (and Mg2+) excretion but also suggests a functional link between divalent mineral and water metabolism. In the kidney, the thick ascending limb of Henle (TAL) plays crucial roles in regulating both divalent mineral reabsorption and urine concentration. Recent studies have suggested models whereby extracellular Ca2+, via the CaSR expressed in the TAL as well as in the collecting duct system, modulates both Ca2+o and Mg2+o as well as water reabsorbtion. When taken together, these studies suggest that the CaSR not only provides the primary mechanism for Ca2+o-mediated regulation of parathyroid hormone secretion from parathyroid glands but also for direct modulation of renal divalent mineral excretion and urinary concentrating ability. These latter functions may furnish a mechanism for integrating and balancing water and divalent cation losses that minimizes the risk of urinary tract stone formation. This mechanism can explain hypercalcemia-mediated polyuria (diabetes insipidus).
Intracellular Ca2+ Signalling in Secretory Cells
Authors: Shuttleworth Trevor J. 
Published: April 2021

ABSTRACT
The secretion of ions and fluid plays a critical role in a variety of physiological activities that are vital to homeostatic mechanisms in animals. Control of such secretory activity is achieved by a range of neurotransmitters and hormones many of which act intracellularly by generating the second messenger inositol 1,4,5-trisphosphate (InsP3) and increasing cytosolic free calcium ion concentrations ([Ca2+]i). These increases are achieved by a combination of the InsP3-induced release of Ca2+ from specific intracellular stores and the activation of Ca2+ entry from the extracellular environment. The [Ca2+]i signal represents a balance between the adequate activation of components of the secretory mechanism and the avoidance of [Ca2+]i levels that are toxic to the cell. Resting [Ca2+]i is maintained low by the action of Ca2+ pumps on the intracellular stores and plasma membrane, with the result that gradients for Ca2+ movement into the cytosol from either of these two sources are very large and there is considerable potential for achieving rapid increases in [Ca2+]i. Consequently, for successful Ca2+ signalling, it is imperative that these two mechanisms of raising [Ca2+]i (i.e. Ca2+ release and Ca2+ entry) are closely integrated. Current models emphasize the activation of Ca2+ entry as a downstream result of the emptying of the intracellular stores (‘capacitative’ model). Whilst this may be true for situations of maximal stimulation, recent experiments on the oscillatory [Ca2+]i responses typical of more physiological levels of stimulation indicate a previously unsuspected, independent activation of Ca2+ entry involving arachidonic acid.
This arachidonic-acid-activated entry plays a key role, along with InsP3, in inducing the repetitive release of Ca2+ from the stores to produce the [Ca2+]i oscillations. In this way, the two components responsible for the elevation of [Ca2+]i are intimately related and their dual effects closely coordinated, resulting in the finely tuned control of agonist-induced changes in [Ca2+]i.
Association of the Band 3 Protein with a Volume-Activated, Anion and Amino Acid Channel: A Molecular Approach
Authors: Motais René , Fiévet Bruno , Borgese Franck , Garcia-Romeu Federico 
Published: April 2021

ABSTRACT
In response to swelling, cells recover their initial volume by releasing intracellular solutes via volume-sensitive pathways. There is increasing evidence that structurally dissimilar organic osmolytes (amino acids, polyols, methyl amines), which are lost from cells in response to swelling, share a single pathway having the characteristics of an anion channel. However, the molecular identity of this pathway remains to be established. It has been suggested that the erythrocyte anion exchanger (AE1) or some AE1-related proteins could be involved. A direct evaluation of this possibility has been made by comparing the functional properties of two AE1s when expressed in Xenopus laevis oocytes: tAE1 is from a fish erythrocyte which releases taurine when swollen, and mAE1 is from a mammalian erythrocyte which does not regulate its volume when swollen. While mAE1 performs exclusively Cl−/Cl− exchange, tAE1 behaves as a bifunctional protein with both anion exchange and Cl−/taurine channel functions. Construction of diverse tAE1/mAE1 chimaeras allows the identification of protein domains associated with this channel activity. Thus, some AE1 isoforms could act as a swelling-activated osmolyte channel, a result having a potentially important implication in malaria. This review also discusses the possibility that several different proteins might function as swelling-activated osmolyte channels.
The mechanics of flight in the hawkmoth Manduca sexta I. Kinematics of hovering and forward flight
Authors: Willmott Alexander P. , Ellington Charles P. 
Published: April 2021

ABSTRACT
High-speed videography was used to record sequences of individual hawkmoths in free flight over a range of speeds from hovering to 5 m s−1. At each speed, three successive wingbeats were subjected to a detailed analysis of the body and wingtip kinematics and of the associated time course of wing rotation. Results are presented for one male and two female moths. The clearest kinematic trends accompanying increases in forward speed were an increase in stroke plane angle and a decrease in body angle. The latter may have resulted from a slight dorsal shift in the area swept by the wings as the supination position became less ventral with increasing speed. These trends were most pronounced between hovering and 3m s−1, and the changes were gradual; there was no distinct gait change of the kind observed in some vertebrate fliers.
The wing rotated as two functional sections: the hindwing and the portion of the forewing with which it is in contact, and the distal half of the forewing. The latter displayed greater fluctuation in the angle of rotation, especially at the lower speeds. As forward speed increased, the discrepancy between the rotation angles of the two halfstrokes, and of the two wing sections, became smaller. The downstroke wing torsion was set early in the halfstroke and then held constant during the translational phase.
Aerial performance of Drosophila melanogaster from populations selected for upwind flight ability
Authors: Marden James H. , Wolf Melisande R. , Weber Kenneth E. 
Published: April 2021

ABSTRACT
A computerized system for three-dimensional tracking of large numbers of individual free-flying insects was used to assess the performance of Drosophila melanogaster from populations that had undergone 160 generations of selection for upwind flight ability. Compared with control lines, the selected lines showed significant increases in mean flight velocity, decreases in angular trajectory and a significant change in the interaction between velocity and angular trajectory. Maximal flight velocity was apparent as a sharply defined upper boundary of the distribution of horizontal and vertical velocity as a function of angular trajectory; this upper bound (0.85 m s−1) differed little between the selected and control lines, although individuals from the selected lines attained maximal performance levels much more frequently. Maximum induced power output was calculated directly from the product of maximum vertical velocity and body weight. This measure (28W kg−1 muscle) was closely predicted by a scaling relationship derived from the load-lifting limits of larger insects and vertebrates, as well as tethered D. melanogaster stimulated via their optomotor reflex to produce maximal lift. These results indicate that selection for flight performance can readily alter the relative effort and/or the frequency of phenotypes capable of attaining population-wise maximal performance levels, but shows little ability to increase population-wise maximal performance.