bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inositol-1,4,5-Trisphosphate-Binding Proteins Controlling the Phototransduction Cascade of Invertebrate Visual Cells
Authors: Kishigami Akio , Ogasawara Tomio , Watanabe Yutaka , Hirata Masato , Maeda Tomoko , Hayashi Fumio , Tsukahara Yasuo 
Published: April 2021

ABSTRACT
The main phototransduction cascade in invertebrate visual cells involves the turnover of phosphatidylinositol, an important biochemical mechanism common to many signal-transduction systems. Light-activated rhodopsin stimulates guanine nucleotide exchange on the Gq class of G-protein, which activates phospholipase C to hydrolyze phosphatidylinositol 4,5-bisphosphate to inositol-1,4,5-trisphosphate and diacylglycerol. Subsequently, inositol-1,4,5-trisphosphate-binding proteins continue the signal cascade. Here, we report on the first inositol-1,4,5-trisphosphate-binding proteins demonstrated in an invertebrate visual system with our investigation of the photosensitive rhabdoms of squid. We screened the ability of proteins to interact with inositol-1,4,5-trisphosphate by affinity column chromatography with an inositol-1,4,5-trisphosphate analogue. We detected an inositol-1,4,5-trisphosphate-binding affinity in phospholipase C, receptor kinase and five other proteins in the cytosolic fraction and, surprisingly, rhodopsin in the membrane fraction. A binding assay with 3H-labelled inositol-1,4,5-trisphosphate demonstrated the inositol-1,4,5-trisphosphate affinity of each of the purified proteins. Since rhodopsin, receptor kinase and phospholipase C are involved upstream of phosphatidylinositol turnover in the signal cascade, our result suggests that phosphatidylinositol turnover is important in feedback pathways in the signalling system.
Effects of weather on daily body mass regulation in wintering dunlin
Authors: Kelly John P. , Warnock Nils , Page Gary W. , Weathers Wesley W. 
Published: April 2021

SUMMARYWe investigated the influence of changes in weather associated with winter storms on mass balance, activity and food consumption in captive dunlin (Calidris alpina) held in outdoor aviaries, and compared the aviary results with weather-related body mass differences in free-living dunlin collected at Bolinas Lagoon, California. Captive birds fed ad libitum increased their body mass at higher wind speeds and lower temperatures, suggesting regulation of energy stores, whereas free-living birds exhibited patterns suggesting thermoregulatory limits on body mass regulation. Daily energy expenditure in aviary dunlin was 2.85 kJ g d–1, or 2.8× basal metabolic rate (BMR), with thermostatic costs averaging 59 % of daily expenditure. Slight but significant increases in body mass and energy expenditure in captive birds on rainy days, adjusted for possible external water mass, suggested rainfall as a proximate cue in regulating daily body mass. Body mass changes under artificial rainfall indicated similar results, and field masses suggested that free-living birds have greater body mass on days with measurable rainfall. Increased activity costs under artificial rainfall were associated with an increase in maintenance activities, relative to controls. Whether activity costs increased on days with natural rates of rainfall was unclear. Our results are consistent with current hypotheses regarding the role of body mass regulation in providing insurance against increased starvation risk during deteriorating thermal or foraging conditions, or in reducing the costs of extra mass as conditions improve.
A comparison of nutritional regulation in solitarious- and gregarious-phase nymphs of the desert locust Schistocerca gregaria
Authors: Simpson S. J. , Raubenheimer D. , Behmer S. T. , Whitworth A. , Wright G. A. 
Published: April 2021

SUMMARY
Nutritional regulatory responses were compared for the cryptic ‘solitarious’ and the conspicuously coloured, aggregating ‘gregarious’ phases of the desert locust Schistocerca gregaria. The desert locust has the genetic potential to exist in either phase, changing between them within a lifetime and epigenetically across generations. Our aim was to compare final-instar nymphs of the two phases with respect to key nutritional variables, including (i) points of regulated intake (the ‘intake target’) for protein and carbohydrate, (ii) the nature of trade-offs between over-eating nutrients in excess and under-eating those in deficit when fed nutritionally unbalanced foods, (iii) diet-related patterns of nutrient utilisation, and (iv) the performance consequences of eating nutritionally unbalanced diets. When provided with pairs of nutritionally unbalanced but complementary foods, both phases regulated their intake of protein and carbohydrate to a similar point. However, when confined to foods that were of unbalanced protein to carbohydrate ratio, gregarious nymphs ate more than solitarious insects. Both phases regulated protein growth, but gregarious insects did so to a lower adult body protein content and converted ingested protein to growth less efficiently. When fed a food high in carbohydrate and low in protein, gregarious nymphs deposited more body lipid and survived less well than did solitarious insects. Solitarious nymphs developed more quickly than gregarious nymphs except on the two most extremely unbalanced diets, on which development time was similar. The results are discussed with respect to the different nutritional ecologies of the two phases and used to develop the hypothesis that animals have evolved to trade-off the cost of eating excess of a nutritionally unbalanced diet against the probability of encountering foods of complementary composition in the future.
Direct observation of syringeal muscle function in songbirds and a parrot
Authors: Larsen Ole Næsbye , Goller Franz 
Published: April 2021

SUMMARYThe role of syringeal muscles in controlling the aperture of the avian vocal organ, the syrinx, was evaluated directly for the first time by observing and filming through an endoscope while electrically stimulating different muscle groups of anaesthetised birds.In songbirds (brown thrashers, Toxostoma rufum, and cardinals, Cardinalis cardinalis), direct observations of the biomechanical effects of contraction largely confirm the functions of the intrinsic syringeal muscles proposed from indirect studies. Contraction of the dorsal muscles, m. syringealis dorsalis (dS) and m. tracheobronchialis dorsalis, constricts the syringeal lumen and thus reduces airflow by adducting connective tissue masses, the medial (ML) and lateral (LL) labia. Activity of the medial portion of the dS appears to affect the position of the ML and, consequently, plays a previously undescribed role in aperture control. Under the experimental conditions used in this study, full constriction of the syringeal lumen could not be achieved by stimulating adductor muscles. Full closure may require simultaneous activation of extrinsic syringeal muscles or the supine positioning of the bird may have exerted excessive tension on the syrinx. Contraction of m. tracheobronchialis ventralis enlarges the syringeal lumen and thus increases airflow by abducting the LL but does not affect the ML. The largest syringeal muscle, m. syringealis ventralis, plays a minor role, if any, in direct aperture control and thus in gating airflow.In parrots (cockatiels, Nymphicus hollandicus), direct observations show that even during quiet respiration the lateral tympaniform membranes (LTMs) are partially adducted into the tracheal lumen to form a narrow slot. Contraction of the superficial intrinsic muscle, m. syringealis superficialis, adducts the LTMs further into the tracheal lumen but does not close the syringeal aperture fully. The intrinsic deep muscle, m. syringealis profundus, abducts the LTMs through cranio-laterad movement of a paired, protruding half-ring. The weakly developed extrinsic m. sternotrachealis seems to increase tension in the ipsilateral LTM but does not move it in or out of the syringeal lumen.
Structural flexibility of the small intestine and liver of garter snakes in response to feeding and fasting
Authors: Starck J. Matthias , Beese Kathleen 
Published: April 2021

SUMMARYGarter snakes Thamnophis sirtalis parietalis feed frequently but also tolerate extended periods of fasting when food is unavailable. We studied the dynamics, reversibility and repeatability of size changes of the small intestine and liver using ultrasonography. We employed light and transmission electron microscopy and flow cytometry to study the tissue mechanism that drives this flexibility. We compared garter snakes that fed every other day,snakes that fed once a week and fasting snakes. In all feeding trials, the size of the small intestine and the liver increased rapidly after feeding. Constantly feeding snakes maintained an elevated level of organ size, while snakes that were fed only once a week showed a marked up- and downregulation of organ size. Histology revealed the mucosal epithelium to be a transitional epithelium that can change cell configuration considerably to accommodate organ size changes. Upregulation of small intestine and liver size was always associated with the incorporation of lipid droplets into enterocytes and hepatocytes. Cell proliferation was not involved in upregulation of organ size. In contrast, cell proliferation increased during downregulation of organ size, indicating that cells worn out during digestion were replaced. The dynamics of flexibility and the functional features of the tissue were the same as described for the Burmese python Python molurus bivittatus. We suggest that garter snakes employ the same energetically cheap mechanism of organ size regulation as pythons, which allows for rapid, repeated and reversible size changes with no cell proliferation involved. Comparative evidence suggests that the transitional mucosal epithelium is an ancestral character of snakes and that feeding ecology is not directly related to the cytological features of the mucosal epithelium.
The freeze-avoidance response of smeltOsmerus mordax
Authors: Treberg Jason R. , Wilson Connie E. , Richards Robert C. , Ewart K. Vanya , Driedzic William R. 
Published: April 2021

SUMMARYSmelt (Osmerus mordax) were maintained at either ambient water temperature or approximately 5°C and various aspects of their freeze-avoidance response were examined from early winter until early spring. Plasma levels of glycerol, trimethylamine oxide (TMAO) and urea were elevated by December 15 and continued to increase in fish held in ambient conditions. In contrast, fish held under warm conditions exhibited decreased glycerol and urea content in plasma, muscle and liver. Plasma and liver TMAO levels also decreased in these fish while muscle TMAO did not vary from the initial values. The activity of liver enzymes involved with the production of glycerol did not differ significantly between groups and had decreased by the end of the study. Antifreeze protein (AFP) expression increased over the duration of the experiment. In January samples, AFP activity (thermal hysteresis) did not vary significantly between groups but mRNA levels were significantly lower in the smelt held at warm temperatures.
The use of viewing posture to control visual processing by lateralised mechanisms
Authors: Tommasi Luca , Andrew Richard J. 
Published: April 2021

SUMMARY
Chicks were trained and tested to run to a dish and feed from it under one of four conditions. In three of these, the dish was covered by a light lid that the chicks readily learned to remove. The square lid (SL) had slightly protruding corners, so that it could be removed by a blow of the bill at a range of positions. A round lid (UL), which fitted snugly, could best be removed by inserting the bill into a medial U-shaped indentation. A round lid(STR), which fitted all the way round to the edge of the dish, could be removed by grasping and tugging a centrally placed piece of string. The final dish had no lid (NOL). The dish and the layout of the arena were otherwise identical under all conditions. Chicks trained and tested with lids predominantly fixated the dish during approach with the right eye and showed leftward deviation from the direct line of approach (which facilitated right eye use). NOL chicks fixated with the left eye and deviated rightwards. The right eye is thus used when a motor plan has to be set up and sustained. The use of the left eye is expected when topographical information has to be used. Here, the approach was so simple and practised that the assumption of left eye viewing is likely to be a default condition. It would facilitate detection of any change in layout.
A standard set of head positions were used, particularly by SL and NOL chicks, showing that the head was aligned with some reference point, perhaps the centre of the dish. These fell into two series (used by both eyes), and in both the peaks of frequent use were 10° apart. One (20°, 10°) was probably generated by head saccades ending with the bill pointing directly at the dish (0°). The other (35°, 25°, 15°) is best explained by slight divergence of the optic axes. The 25° right eye position was consistently used by STR chicks at the beginning of approach. The STR condition requires the most difficult manipulation, and the manipulandum is most obvious from a distance. This is consistent with right eye use during establishment of a motor plan. Head postures consistent with divergence were also used when close to the dish under conditions where choice between targets was necessary. This was clear in the NOL condition, where the chick could see the food grains as it approached. Here, it is likely that both eyes are used in independent search. If so, it may be that divergence is used as a strategy during establishment of a motor plan (as in STR chicks) to increase the independence of the right eye system.
Isometric and isovelocity contractile performance of red musle fibres from the dogfishScyliorhinus canicula
Authors: Lou F. , Curtin N. A. , Woledge R. C. 
Published: April 2021

SUMMARYMaximum isometric tetanic force produced by bundles of red muscle fibres from dogfish, Scyliorhinus canicula (L.), was 142.4±10.3 kN m-2 (N=35 fibre bundles); this was significantly less than that produced by white fibres 289.2±8.4 kN m-2(N=25 fibre bundles) (means ± S.E.M.). Part, but not all, of the difference is due to mitochondrial content. The maximum unloaded shortening velocity, 1.693±0.108 L0 s-1(N=6 fibre bundles), was measured by the slack-test method. L0 is the length giving maximum isometric force. The force/velocity relationship was investigated using a step-and-ramp protocol in seven red fibre bundles. The following equation was fitted to the data:[(P/P0)+(a/P0)](V+b)=[(P0*/P0)+(a/P0)]b,where P is force during shortening at velocity V,P0 is the isometric force before shortening, and a, band P0* are fitted constants. The fitted values were P0*/P0=1.228±0.053, Vmax=1.814±0.071 L0s-1, a/P0=0.269±0.024 and b=0.404±0.041 L0 s-1(N=7 for all values). The maximum power was 0.107±0.005P0Vmax and was produced during shortening at 0.297±0.012Vmax. Compared with white fibres from dogfish, the red fibres have a lower P0 (49%) and Vmax (48%), but the shapes of the force/velocity curves are similar. Thus, the white and red fibres have equal capacities to produce power within the limits set by the isometric force and maximum velocity of shortening of each fibre type. A step shortening of 0.050±0.003L0 (N=7) reduced the maximum isometric force in the red fibres' series elasticity to zero. The series elasticity includes all elastic structures acting in series with the attached cross-bridges. Three red fibre bundles were stretched at a constant velocity, and force (measured when length reached L0) was 1.519±0.032P0. In the range of velocities used here, -0.28 to -0.63Vmax, force varied little with the velocity.
The digestive tract ofNautilus pompilius(Cephalopoda,Tetrabranchiata): an X-ray analytical and computational tomography study on the living animal
Authors: Westermann Bettina , Ruth Peter , Litzlbauer Horst Detlef , Beck Ingrid , Beuerlein Knut , Schmidtberg Henrike , Kaleta Erhard F. , Schipp Rudolf 
Published: April 2021

SUMMARYUsing X-ray analytical studies and computational tomography, the position of the digestive tract of the tetrabranchiate cephalopod Nautilus pompilius L. was demonstrated in a living animal. For the first time, a detailed analysis of the rate of digestion and the duration of the different phases of a digestive cycle has been made using these in vivomethods. At 20 min after food intake, the food has entered the stomach, where it is reduced to small pieces; most is stored in the crop, which is enlarged to approximately four times its original size. The chyme reaches the midgut gland 3 h and the rectal loop 5 h after food intake. The time between food intake and elimination is 12 h. Thus, in Nautilus pompilius,digestion takes approximately the same time as described for nectobenthic sepioids and benthic octopods but is approximately 6 h longer than in loliginids, which have a pelagic mode of life. Furthermore, the three-dimensional structure of the digestive tract of a living Nautilus pompilius L. was demonstrated using computational tomography.
Differential expression of mitochondria-encoded genes in a hibernating mammal
Authors: Hittel Dustin S. , Storey Kenneth B. 
Published: April 2021

SUMMARYA cDNA library constructed from kidney of the thirteen-lined squirrel, Spermophilus tridecemlineatus, was differentially screened for genes that were upregulated during hibernation. A clone encoding cytochrome c oxidase subunit 1 was found and confirmed to have been upregulated by northern blotting. Differential expression of Cox1 mRNA occurred in multiple organs during hibernation; in hibernating animals transcript levels were twofold higher in kidney and fourfold higher in heart and brown adipose tissue than in euthermic animals, but were unchanged in skeletal muscle. Transcript levels of mitochondrial-encoded ATP synthase 6/8 were similarly upregulated in these tissues whereas transcript levels of the nuclear encoded subunits Cox4 and ATP synthase α did not change during hibernation. Immunoblot analysis revealed a 2.4-fold increase in Cox 1 protein and a slight decrease in Cox 4 protein in kidney of hibernating squirrels, compared with euthermic controls. Hibernating mammals may increase the expression of the mitochondrial genome in general, and Cox1specifically, to prevent or minimize the damage to the electron transport chain caused by the cold and ischemia experienced during a hibernation bout.
Respiratory adaptations in a deep-sea orbiniid polychaete from Gulf of Mexico brine pool NR-1: metabolic rates and hemoglobin structure/function relationships
Authors: Hourdez Stéphane , Weber Roy E. , Green Brian N. , Kenney John M. , Fisher Charles R. 
Published: April 2021

SUMMARYMethanoaricia dendrobranchiata Blake (Polychaeta; Orbiniidae)occurs in large numbers in association with communities of the mussel Bathymodiolus childressi at hydrocarbon seeps on the Louisiana Slope of the Gulf of Mexico. Its microhabitat can be strongly hypoxic (oxygen is often undetectable) and sulfidic (sulfide concentrations can reach millimolar levels), which may seriously challenge aerobic metabolism. We describe a suite of adaptations to its low-oxygen environment. The worms are capable of regulating their rate of oxygen consumption down to partial pressures of approximately 870 Pa oxygen. This capability correlates with a large gill surface area, a small diffusion distance from sea water to blood, a very high hemoglobin oxygen-affinity (P50=27.8 Pa at 10°C and pH 7.6) and a Bohr effect that is pronounced at high oxygen saturations. When fully saturated, the hemoglobin binds sufficient oxygen for only 31 min of aerobic metabolism. However, these polychaetes can withstand extended periods of anoxia both in the absence and presence of 1 mmoll-1 sulfide(TL50=approx. 5.5 and 4 days, respectively).
Jumping in frogs: assessing the design of the skeletal system by anatomically realistic modeling and forward dynamic simulation
Authors: Kargo William J. , Nelson Frank , Rome Lawrence C. 
Published: April 2021

SUMMARYComparative musculoskeletal modeling represents a tool to understand better how motor system parameters are fine-tuned for specific behaviors. Frog jumping is a behavior in which the physical properties of the body and musculotendon actuators may have evolved specifically to extend the limits of performance. Little is known about how the joints of the frog contribute to and limit jumping performance. To address these issues, we developed a skeletal model of the frog Rana pipiens that contained realistic bones, joints and body-segment properties. We performed forward dynamic simulations of jumping to determine the minimal number of joint degrees of freedom required to produce maximal-distance jumps and to produce jumps of varied take-off angles. The forward dynamics of the models was driven with joint torque patterns determined from inverse dynamic analysis of jumping in experimental frogs. When the joints were constrained to rotate in the extension—flexion plane, the simulations produced short jumps with a fixed angle of take-off. We found that, to produce maximal-distance jumping,the skeletal system of the frog must minimally include a gimbal joint at the hip (three rotational degrees of freedom), a universal Hooke's joint at the knee (two rotational degrees of freedom) and pin joints at the ankle,tarsometatarsal, metatarsophalangeal and iliosacral joints (one rotational degree of freedom). One of the knee degrees of freedom represented a unique kinematic mechanism (internal rotation about the long axis of the tibiofibula)and played a crucial role in bringing the feet under the body so that maximal jump distances could be attained. Finally, the out-of-plane degrees of freedom were found to be essential to enable the frog to alter the angle of take-off and thereby permit flexible neuromotor control. The results of this study form a foundation upon which additional model subsystems (e.g. musculotendon and neural) can be added to test the integrative action of the neuromusculoskeletal system during frog jumping.
Cardiac effects of hypoxia in the neotenous tiger salamanderAmbystoma tigrinum
Authors: McKean Tom , Li Guolian , Wei Kong 
Published: April 2021

SUMMARYThe aquatic form of the tiger salamander Ambystoma tigrinum lives in high-altitude ponds and is exposed to a hypoxic environment that may be either chronic or intermittent. In many animal species, exposure to hypoxia stimulates cardiac output and is followed by an increase in cardiac mass. The working hypothesis of the present study was that the hearts of these aquatic salamanders exposed to 10-14 days of 5 % oxygen in a laboratory setting would become larger and would differentially express proteins that would help confer tolerance to hypoxia. During exposure to hypoxia, cardiac output increased, as did hematocrit. Cardiac mass also increased, but mitotic figures were not detected in the cardiac myocytes of colchicine-injected animals. The mass increase was probably due to hypertrophy, although a very slow rate of hyperplasia cannot be ruled out. Representational difference analysis indicated that at least 14 mRNAs were expressed in hearts from the hypoxic animals that were not expressed in hearts from normoxic animals. The differentially expressed genes were cloned and sequenced and confirmed as coming from the ventricles of the hypoxic salamanders. Genes differentially expressed include mitochondrial genes and genes for elongation factor 2, a protein synthesis gene. The mechanical performance of buffer-perfused hearts isolated from normoxic and hypoxic animals did not differ. Acute responses to hypoxia were also measured. The rate of oxygen consumption of unanesthetized salamanders in metabolism chambers decreased when chamber oxygen concentration was reduced below 12 % oxygen. At a chamber oxygen concentration of 4-6 %, the rate of oxygen consumption of the salamanders was reduced to approximately one-third of the normoxic rate.