bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Drosophila Melanogaster Homologue of an Insect Calcitonin-Like Diuretic Peptide Stimulates V-ATPase Activity in Fruit Fly Malpighian Tubules
Authors: Coast Geoffrey M. , Webster Simon G. , Schegg Kathleen M. , Tobe Stephen S. , Schooley David A. 
Published: April 2021

ABSTRACT
The Drosophila melanogaster homologue of an insect calcitonin-like diuretic hormone was identified in a BLAST search of the Drosophila genome database. The predicted 31-residue amidated peptide (D. melanogaster DH31; Drome-DH31) was synthesised and tested for activity on fruit fly Malpighian tubules. It increases tubule secretion by approximately 35 % of the response obtained with a myokinin from the housefly Musca domestica (muscakinin; Musdo-K) and has an EC50 of 4.3 nmol l−1.
The diuretic activities of Drome-DH31 and Musdo-K were additive when tested at threshold and supra-maximal concentrations, which suggests that they target different transport processes. In support of this, Drome-DH31 increased the rate of secretion by tubules held in bathing fluid with a reduced Cl− concentration, whereas Musdo-K did so only in the presence of Drome-DH31. Stimulation with Drome-DH31 increased the lumen-positive transepithelial potential in the main secretory segment of the tubule. This was attributed to activation of an apical electrogenic proton-translocating V-ATPase in principal cells, since it was associated with hyperpolarisation of the apical membrane potential and acidification of secreted urine by 0.25 pH units.
Exogenous 8-bromo-cyclic AMP and cyclic GMP increased tubule secretion to the same extent as Drome-DH31 and, when tested together with the diuretic peptide, their activities were not additive. Stimulation with Drome-DH31 resulted in a dose-dependent increase in cyclic AMP production by tubules incubated in saline containing 0.5 mmol l−1 3-isobutyl-1-methylxanthine, whereas cyclic GMP production was unchanged. Taken together, the data are consistent with Drome-DH31 activating an apical membrane V-ATPase via cyclic AMP. Since the K+ concentration of the secreted urine was unchanged, it is likely that Drome-DH31 has an equal effect on K+ and Na+ entry across the basolateral membrane.
The Dynamics and Scaling of Force Production During the Tail-Flip Escape Response of the California Spiny Lobster Panulirus Interruptus
Authors: Nauen Jennifer C. , Shadwick Robert E. 
Published: April 2021

ABSTRACT
The tail-flip escape behavior is a stereotypical motor pattern of decapod crustaceans in which swift adduction of the tail to the thorax causes the animal to rotate, move vertically into the water column and accelerate rapidly backwards. Previous predictions that a strong jet force is produced during the flip as the tail adducts to the body are not supported by our simultaneous measurements of force production (using a transducer) and the kinematics (using high-speed video) of tail-flipping by the California spiny lobster Panulirus interruptus. Maximum force production occurred when the tail was positioned approximately normal to the body. Resultant force values dropped to approximately 15 % of maximum during the last third of the flip and continued to decline as the tail closed against the body. In addition, maximum acceleration of the body of free-swimming animals occurs when the tail is positioned approximately normal to the body, and acceleration declines steadily to negative values as the tail continues to close. Thus, the tail appears to act largely as a paddle. Full flexion of the tail to the body probably increases the gliding distance by reducing drag and possibly by enhancing fluid circulation around the body.
Morphological measurements indicate that Panulirus interruptus grows isometrically. However, measurements of tail-flip force production for individuals with a body mass (Mb) ranging from 69 to 412 g indicate that translational force scales as Mb0.83. This result suggests that force production scales at a rate greater than that predicted by the isometric scaling of muscle cross-sectional area (Mb2/3), which supports previously published data showing that the maximum accelerations of the tail and body of free-swimming animals are size-independent. Torque (τ) scaled as Mb1.29, which is similar to the hypothesized scaling relationship of Mb4/3. Given that τ∝Mb1.29, one would predict rotational acceleration of the body (α) to decrease with increasing size as Mb−0.37, which agrees with previously published kinematic data showing a decrease in α with increased Mb.
Limits to sustained energy intake
Authors: Johnson M. S. , Thomson S. C. , Speakman J. R. 
Published: April 2021

SUMMARY
To determine whether mice were limited in their capacity to absorb energy during late lactation, we attempted to increase the energy burden experienced by a group of female mice during late lactation by mating them at the postpartum oestrus, hence combining the energy demands of pregnancy and lactation. These experimental mice were therefore concurrently pregnant and lactating in their first lactation, and were followed through a normal second lactation. In a control group, females also underwent two lactations but sequentially, with the second mating after the first litter had been weaned. Maternal mass and food intake were measured throughout the first lactation, second pregnancy and second lactation. Maternal resting metabolic rate (RMR) was measured prior to the first mating and then at the peak of both the first and second lactations. Litter size and litter mass were also measured throughout both lactations. In the first lactation, experimental mice had a lower mass-independent RMR (F1,88=5.15, P=0.026) and raised significantly heavier pups (t=2.77, d.f.=32, P=0.0093) than the control mice. Experimental mice delayed implantation at the start of the second pregnancy. The extent of the delay was positively related to litter size during the first lactation (F1,19=4.58, P=0.046) and negatively related to mean pup mass (F1,19=5.78, P=0.027) in the first lactation. In the second lactation, the experimental mice gave birth to more (t=2.75, d.f.=38, P=0.0092) and lighter (t=−5.01, d.f.=38, P&lt;0.0001) pups than did the controls in their second lactation. Maternal asymptotic daily food intake of control mice in the second lactation was significantly higher (t=−4.39, d.f.=37, P=0.0001) than that of the experimental mice and higher than that of controls during their first lactation. Despite the added burden on the experimental females during their first lactation, there was no increase in their food intake, which suggested that they might be limited by their capacity to absorb energy. However, control females appeared to be capable of increasing their asymptotic food intake beyond the supposed limits estimated previously, suggesting that the previously established limit was not a fixed central limitation on food intake. As RMR increased in parallel with the increase in food intake during the second lactation of control mice, the sustained energy intake remained at around 7.0×RMR.
Limits to sustained energy intake
Authors: Johnson M. S. , Speakman J. R. 
Published: April 2021

SUMMARY
We have previously observed that female MF1 mice appeared to reach a limit in their food intake and milk production during late lactation, reaching a plateau between days 13 and 16 of lactation and between litter sizes of 9 and 15. These mice did not increase their food intake when forced to raise more offspring or when manipulated to be concurrently pregnant during late lactation, yet they did eat significantly more food at the peak of their second sequential lactation or when challenged with food of reduced energy content. These data suggest that apparent limits on sustained energy intake in this strain may not reflect central limitations but rather peripheral constraints at the mammary glands. In this study, we aimed to determine whether these were indeed limits by increasing the demands on the females during late lactation by cold-exposure (8°C). Females responded to this manipulation by significantly increasing their food intake (F1,73=77.53, P&lt;0.001) above that of lactating females kept in warmer conditions (21°C). In addition, there was a significant reduction in the number of pups raised in the cold (t=2.36, d.f.=18, P=0.03), with the majority of the mortality occurring within the first 2 days of cold-exposure. The mean mass of the pups raised in the cold was significantly lower (F1,74=13.8, P&lt;0.001) than that of those raised in the warm. Despite the cold-exposure and the increased food intake, there was no difference in the resting metabolic rates of the two groups of mothers or in the lengths of their small intestine. The greater food intake of lactating mice during cold-exposure supported our previous observations that they were capable of eating more food than the previously suggested limit of 23.1gday−1. However, the milk energy output of females in the cold was also significantly higher than in the warm (F1,15=11.99, P=0.003), indicating that the asymptotic food intake of females in the warm was not mediated by limitations in their milk production. Sustained energy intake in these mice does not appear to be centrally or peripherally limited. Rather, the mice may restrain their use of energy during their first lactation because of life-history consequences for future reproductive attempts.
Shape, flapping and flexion: wing and fin design for forward flight
Authors: Combes S. A. , Daniel T. L. 
Published: April 2021

SUMMARY
Both kinematics and morphology are critical determinants of performance in flapping flight. However, the functional consequences of changes in these traits are not yet well understood. Traditional aerodynamic studies of planform wing shape have suggested that high-aspect-ratio wings generate more force per area and perform more efficiently than low-aspect-ratio wings, but these analyses may neglect critical components of flapping flight such as unsteady fluid dynamics and wing or fin flexion. In this paper, we use an unsteady potential flow analysis that incorporates wing flexion to test predictions of optimal wing shape under varying degrees of unsteady motion and wing flexion. We focus on forward flapping flight and examine the effects of wing/fin morphology and movements on thrust generation and efficiency. We test the model by comparing our predictions with kinematic data derived from the aquatic flight of the ratfish Hydrolagus colliei. Our analyses show that aspect ratio and the proportion of area in the outer one-fifth of the wing can characterize wing shape in terms of aero- or hydrodynamic performance. By comparing the performance of wings that vary in these two parameters, we find that traditional predictions of optimal wing shape are valid only under limited circumstances (when flapping frequency is low, wings are stiff or wings are tapered at the tips). This indicates a complex relationship between locomotor traits and performance and helps explain the diversity of wing kinematics and morphologies observed in nature.
Expression and function of brain-derived neurotrophin factor and its receptor, TrkB, in ovarian follicles from the domestic hen (Gallus gallus domesticus)
Authors: Jensen T. , Johnson A. L. 
Published: April 2021

SUMMARY
This report summarizes patterns of mRNA expression for the brain-derived neurotrophic factor (BDNF) together with its high-affinity neurotrophin receptor trkB within the hen ovary during follicle development, describes hormonal mechanisms for the regulation of trkB gene expression and provides preliminary evidence for a novel function for BDNF-mediated TrkB signaling within the granulosa layer. Levels of BDNF mRNA in the thecal layer and of trkB mRNA within the granulosa cell layer increase coincident with entrance of the follicle into the preovulatory hierarchy. Localization of the BDNF mRNA transcript correlates with expression of BDNF protein within the theca interna of preovulatory follicles, while localization of trkB mRNA and protein occurs extensively within the granulosa cell layer of preovulatory follicles. This pattern of expression suggests a paracrine relationship between theca and granulosa cells for BDNF signaling via TrkB. Vasoactive intestinal peptide and gonadotropin treatments stimulate increases in levels of trkB mRNA within cultured granulosa cells derived from both prehierarchal and preovulatory follicles, and this response is increased by co-treatment with 3-isobutyl-1-methylxanthine. Finally, BDNF treatment of cultured granulosa cells from preovulatory follicles results in a modest, but significant, reduction in basal progesterone production, whereas this effect was reversed by k252a, an inhibitor of Trk kinase activity. These results support the proposals that BDNF functions as a paracrine signal in hen granulosa cells and that its physiological functions may include the modulation of steroidogenesis.
Reflective properties of iridophores and fluorescent ‘eyespots’ in the loliginid squidAlloteuthis subulataandLoligo vulgaris
Authors: Mäthger L. M. , Denton E. J. 
Published: April 2021

SUMMARYObservations were made of the reflective properties of the iridophore stripes of the squid Alloteuthis subulata and Loligo vulgaris, and the likely functions of these stripes are considered in terms of concealment and signalling.In both species, the mantle muscle is almost transparent. Stripes of iridophores run along the length of each side of the mantle, some of which, when viewed at normal incidence in white light, reflect red, others green or blue. When viewed obliquely, the wavebands best reflected move towards the blue/ultraviolet end of the spectrum and their reflections are almost 100% polarised. These are properties of quarter-wavelength stacks of chitin and cytoplasm, predicted in theoretical analyses made by Sir A. F. Huxley and Professor M. F. Land. The reflecting surfaces of the individual iridophores are almost flat and, in a given stripe, these surfaces are within a few degrees of being parallel. Both species of squid have conspicuous, brightly coloured reflectors above their eyes. These ‘eyespots’ have iridescent layers similar to those found on the mantle but are overlaid by a green fluorescent layer that does not change colour or become polarised as it is viewed more obliquely. In the sea, all reflections from the iridophore stripes will be largely confined to the blue-green parts of the spectrum and all reflections in other wavebands, such as those in the red and near ultraviolet, will be weak. The functions of the iridophores reflecting red at normal incidence must be sought in their reflections of blue-green at oblique angles of incidence. These squid rely for their camouflage mainly on their transparency, and the ventral iridophores and the red, green and blue reflective stripes must be used mainly for signalling. The reflectivities of some of these stripes are relatively low, allowing a large fraction of the incident light to be transmitted into the mantle cavity. Despite their low reflectivities, the stripes are very conspicuous when viewed from some limited directions because they reflect light from directions for which the radiances are much higher than those of the backgrounds against which they are viewed. The reflective patterns seen, for example, by neighbouring squid when schooling depend on the orientation of the squid in the external light field and the position of the squid relative to these neighbours.
Heart rate as an indicator of oxygen consumption: influence of body condition in the king penguin
Authors: Froget G. , Butler P. J. , Handrich Y. , Woakes A. J. 
Published: April 2021

SUMMARYThe use of heart rate to estimate field metabolic rate has become a more widely used technique. However, this method also has some limitations, among which is the possible impact that several variables such as sex, body condition (i.e. body fat stores) and/or inactivity might have on the relationship between heart rate and rate of oxygen consumption. In the present study, we investigate the extent to which body condition can affect the use of heart rate as an indicator of the rate of oxygen consumption.Twenty-two breeding king penguins (Aptenodytes patagonicus) were exercised on a variable-speed treadmill. These birds were allocated to four groups according to their sex and whether or not they had been fasting. Linear regression equations were used to describe the relationship between heart rate and the rate of oxygen consumption for each group. There were significant differences between the regression equations for the four groups.Good relationships were obtained between resting and active oxygen pulses and an index of the body condition of the birds. Validation experiments on six courting king penguins showed that the use of a combination of resting oxygen pulse and active oxygen pulse gave the best estimate of the rate of oxygen consumption V̇O2. The mean percentage error between predicted and measured V̇O2 was only +0.81% for the six birds.We conclude that heart rate can be used to estimate rate of oxygen consumption in free-ranging king penguins even over a small time scale (30min). However, (i) the type of activity of the bird must be known and (ii) the body condition of the bird must be accurately determined. More investigations on the impact of fasting and/or inactivity on this relationship are required to refine these estimates further.
Ammonia detoxification and localization of urea cycle enzyme activity in embryos of the rainbow trout (Oncorhynchus mykiss) in relation to early tolerance to high environmental ammonia levels
Authors: Steele Shelby Louise , Chadwick Terry David , Wright Patricia Anne 
Published: April 2021

SUMMARY
The present study investigated the role of ammonia as a trigger for hatching, mechanisms of ammonia detoxification and the localization of urea cycle enzymes in the early life stages of freshwater rainbow trout (Oncorhynchus mykiss). The key urea cycle enzyme carbamoyl phosphate synthetase III was found exclusively in the embryonic body (non-hepatic tissues); related enzymes were distributed between the liver and embryonic body. ‘Eyed-up’ trout embryos were exposed either acutely (2h) to 10mmoll−1 NH4Cl or chronically (4 days) to 0.2mmoll−1 NH4Cl. Time to hatching was not affected by either acute or chronic NH4Cl exposure. Urea levels, but not ammonia levels in the embryonic tissues, were significantly higher than in controls after both acute and chronic NH4Cl exposure, whereas there were no significant changes in urea cycle enzyme activities. Total amino acid levels in the embryonic tissues were unaltered by chronic ammonia exposure, but levels of most individual amino acids and total amino acid levels in the yolk were significantly lower (by 34–58%) than in non-exposed controls. The data indicate that trout embryos have an efficient system to prevent ammonia accumulation in embryonic tissue, by conversion of ammonia to urea in embryonic tissues and through elevation of ammonia levels in the yolk.
Pathways for urea production during early life of an air-breathing teleost, the African catfishClarias gariepinusBurchell
Authors: Terjesen Bendik F. , Chadwick Terry D. , Verreth Johan A. J. , Rønnestad Ivar , Wright Patricia A. 
Published: April 2021

SUMMARYEmbryos and larvae of the African catfish Clarias gariepinus excrete significant quantities of urea. The present study focused on the potential urea-generating pathways during early development of this teleost; uricolysis, argininolysis and the ornithine–urea cycle (OUC). Uricase, allantoinase, allantoicase and ureidoglycollate lyase of the uricolytic pathway were expressed in all early life stages and in adult liver of C. gariepinus. Uricase activity increased in starved larvae compared with yolk-sac larvae. The key regulatory enzyme of the teleost OUC, carbamoyl phosphate synthetase III (CPSase III), was expressed predominantly in muscle of developing C. gariepinus larvae and showed negligible activity in the absence of its allosteric effector N-acetyl-l-glutamate. CPSase III and ornithine carbamoyl transferase activities increased in fed larvae compared with starved larvae. In contrast to the early developmental stages, adult C. gariepinus expressed only low and variable levels of CPSase III, suggesting that, under the experimental conditions employed, OUC expression is influenced by developmental stage in this species. The data indicate that early C. gariepinus life stages express the enzymes necessary for urea production by uricolysis, argininolysis and the OUC, and this may explain why urea tissue levels and urea excretion rates are substantial during the early development of this air-breathing teleost.
Comparative energetics during early development of two marine fish species, Solea senegalensis (Kaup) and Sparus aurata (L.)
Authors: Parra G. , Yúfera M. 
Published: April 2021

SUMMARY
Growth, energy content, ingestion and respiration rates and energetic efficiencies were measured in the larvae of two marine fish (Solea senegalensis and Sparus aurata) whose eggs have a similar diameter (approximately 1mm) and energy content (approximately 1J), but whose larvae reach a quite different mass after the first month of life. Experiments were carried out in populations reared under the same conditions in the laboratory during the first month after hatching. Solea senegalensis grow from hatching to the start of metamorphosis (approximately day 14) at twice the rate of Sparus aurata (specific growth rate for Solea senegalensis 0.25μgday−1; specific growth rate for Sparus aurata 0.12μgday−1). The tissues in Solea senegalensis larvae accumulated energetic reserves that were used during metamorphosis, which occurred during the third week after hatching. Ingestion and respiration rates differed in the two species during the experimental period. Although Solea senegalensis continued eating during metamorphosis, the specific ingestion rates decreased during the process. Nevertheless, no great differences in specific ingestion rates and rates of oxygen consumption were observed when comparing the same larval mass range. Larvae of both species showed an allometric relationship between respiration rate and biomass. The energetic efficiencies calculated in the present study denoted different metabolic patterns in each species. In Solea senegalensis, the energy used for growth increased progressively during the larval (pelagic) period and then, from the first signs of metamorphic transformation, remained almost constant. In this species, the energy allocated to growth was greater than that allocated to metabolic processes. Sparus aurata invested less energy in growth than in metabolic processes and displayed a constant energy allocation throughout the experimental period. During the first month after hatching, Solea senegalensis always allocated more energy for growth than did Sparus aurata.