bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osmoregulation in elephant fishCallorhinchus milii(Holocephali), with special reference to the rectal gland
Authors: Hyodo Susumu , Bell Justin D. , Healy Jillian M. , Kaneko Toyoji , Hasegawa Sanae , Takei Yoshio , Donald John A. , Toop Tes 
Published: March 2007

SUMMARYOsmoregulatory mechanisms in holocephalan fishes are poorly understood except that these fish are known to conduct urea-based osmoregulation as in elasmobranchs. We, therefore, examined changes in plasma parameters of elephant fish Callorhinchus milii, after gradual transfer to concentrated (120%) or diluted (80%) seawater (SW). In control fish, plasma Na and urea concentrations were about 300 mmol l–1 and 450 mmol l–1, respectively. These values were equivalent to those of sharks and rays, but the plasma urea concentration of elephant fish was considerably higher than that reported for chimaeras, another holocephalan. After transfer to 120% SW, plasma osmolality, urea and ion concentrations were increased, whereas transfer to 80% SW resulted in a fall in these parameters. The rises in ion concentrations were notable after transfer to 120% SW,whereas urea concentration decreased predominantly following transfer to 80%SW. In elephant fish, we could not find a discrete rectal gland. Instead,approximately 10 tubular structures were located in the wall of post-valvular intestine. Each tubular structure was composed of a putative salt-secreting component consisting of a single-layered columnar epithelium, which was stained with an anti-Na+,K+-ATPase serum. Furthermore,Na+,K+-ATPase activity in the tubular structures was significantly increased after acute transfer of fish to concentrated SW(115%). These results suggest that the tubular structures are a rectal gland equivalent, functioning as a salt-secreting organ. Since the rectal gland of elephant fish is well developed compared to that of Southern chimaera, the salt-secreting ability may be higher in elephant fish than chimaeras, which may account for the lower plasma NaCl concentration in elephant fish compared to other chimaeras. Since elephant fish have also attracted attention from a viewpoint of genome science, the availability of fish for physiological studies will make this species an excellent model in holocephalan fish group.
Annual changes in body mass and resting metabolism in captive barnacle geese (Branta leucopsis): the importance of wing moult
Authors: Portugal Steven J. , Green Jonathan A. , Butler Patrick J. 
Published: March 2007

SUMMARY
Many different physiological changes have been observed in wild waterfowl during the flightless stage of wing moult, including a loss of body mass. We aimed to determine whether captive barnacle geese (Branta leucopsis)would show the characteristic decrease in body mass during their wing moult,even though they had unlimited and unrestricted access to food. Fourteen captive geese were weighed at 1–2-week intervals for two complete years. During the flightless period of the moult, body mass decreased by approximately 25% from the pre-moult value. To understand the basis of this change, the rate of oxygen consumption was measured during daytime and nighttime at six points in the second year, and at three points (before,during and after wing moult) behavioural observations were made. Measurements of the rate of oxygen consumption showed an 80% increase above that of the nonmoulting periods of the year. We propose that metabolism was increased during moult because of the cost of feather synthesis. Although food was available, the captive birds chose not to forage and instead increased the proportion of time spent resting. It is likely that this behaviour in response to wing moult is a strategy to avoid predation in the wild. Thus, the innate nature of this behaviour has potential survival value for wild birds of this species. We conclude that the increase in metabolism led to the use of endogenous energy reserves because the birds reduced rather than increased their food intake rates, and as a result, the barnacle geese lost body mass during wing moult.
What comes first, the zebra finch or the egg: temperature-dependent reproductive, physiological and behavioural plasticity in egg-laying zebra finches
Authors: Salvante Katrina G. , Walzem Rosemary L. , Williams Tony D. 
Published: March 2007

SUMMARYAvian reproduction is generally timed to synchronize chick-rearing with periods of increased food abundance. Consequently, the energetically demanding period of egg production may coincide with periods of lower food availability,fluctuating temperature and more unstable weather. Little is known about the physiological mechanisms underlying temperature-induced variation in egg production. We therefore examined the influence of low ambient temperature(7°C vs 21°C) on reproductive output (e.g. egg mass, clutch size, laying interval, laying rate), daily food consumption and lipid variables in zebra finches Taeniopygia guttata. When faced with egg production at 7°C, laying zebra finches increased energy intake by 12.67 kJ day–1, and were thus able to maintain body condition (e.g. body mass, fat and muscle score) and circulating triacylglyceride at levels comparable to those at 21°C. However, when producing eggs at 7°C,females took longer to initiate egg laying (6.5 vs 6.1 days at 21°C), and ultimately laid fewer eggs (5.5 vs 6.0 eggs) at a slower rate (0.90 eggs day–1vs 0.95 eggs day–1). These temperature-related declines in reproductive output were accompanied by decreases in modal (from 36.6 at 21°C to 24.3 nm at 7°C) and median very low density lipoprotein (VLDL) particle diameter (from 29.6 to 26.4 nm) and in the proportion of VLDL particles that were capable of passing through the pores in the ovary to access the developing ovarian follicles (i.e. particles with diameters between 25 and 44 nm; from 45.90% to 32.55%). However, variation in reproductive output was not related to any static concentration or structural measure of VLDL. Therefore,other temperature-dependent mechanisms must be involved in the physiological processes that regulate reproductive output of passerine birds at low ambient temperatures.
The aerodynamic benefit of wing–wing interaction depends on stroke trajectory in flapping insect wings
Authors: Lehmann Fritz-Olaf , Pick Simon 
Published: March 2007

SUMMARYFlying insects may enhance their flight force production by contralateral wing interaction during dorsal stroke reversal (`clap-and-fling'). In this study, we explored the forces and moments due to clap-and-fling at various wing tip trajectories, employing a dynamically scaled electromechanical flapping device. The 17 tested bio-inspired kinematic patterns were identical in stroke amplitude, stroke frequency and angle of attack with respect to the horizontal stroke plane but varied in heaving motion. Clap-and-fling induced vertical force augmentation significantly decreased with increasing vertical force production averaged over the entire stroke cycle, whereas total force augmentation was independent from changes in force produced by a single wing. Vertical force augmentation was also largely independent of forces produced due to wing rotation at the stroke reversals, the sum of rotational circulation and wake capture force. We obtained maximum (17.4%) and minimum(1.4%) vertical force augmentation in two types of figure-eight stroke kinematics whereby rate and direction of heaving motion during fling may explain 58% of the variance in vertical force augmentation. This finding suggests that vertical wing motion distinctly alters the flow regime at the beginning of the downstroke. Using an analytical model, we determined pitching moments acting on an imaginary body of the flapping device from the measured time course of forces, the changes in length of the force vector's moment arm,the position of the centre of mass and body angle. The data show that pitching moments are largely independent from mean vertical force; however,clap-and-fling reinforces mean pitching moments by approximately 21%, compared to the moments produced by a single flapping wing. Pitching moments due to clap-and-fling significantly increase with increasing vertical force augmentation and produce nose-down moments in most of the tested patterns. The analytical model, however, shows that algebraic sign and magnitude of these moments may vary distinctly depending on both body angle and the distance between the wing hinge and the animal's centre of mass. Altogether, the data suggest that the benefit of clap-and-fling wing beat for vertical force enhancement and pitch balance may change with changing heaving motion and thus wing tip trajectory during manoeuvring flight. We hypothesize that these dependencies may have shaped the evolution of wing kinematics in insects that are limited by aerodynamic lift rather than by mechanical power of their flight musculature.
Take-off and landing forces and the evolution of controlled gliding in northern flying squirrelsGlaucomys sabrinus
Authors: Paskins Keith E. , Bowyer Adrian , Megill William M. , Scheibe John S. 
Published: March 2007

SUMMARYFlying squirrels are well known for their ability to glide between trees at the top of a forest canopy. We present experimental performance and behavioural evidence that flight in flying squirrels may have evolved out of a need to control landing forces. Northern flying squirrels were filmed jumping from a horizontal branch to a much larger vertical pole. These were both slightly compliant (less than 1.9 mm N–1), and instrumented using strain gauges so that forces could be measured. Take-off and landing forces were both positively correlated with horizontal range between 0.5 and 2.5 m (r=0.355 and r=0.811, respectively, P&lt;0.05), but not significantly different to each other at each range tested. Take-off forces ranged from 1 to 10 bodyweights, and landing forces were between 3 and 10 bodyweights. Glide angles increased rapidly with horizontal range, approaching 45° at 3 m, above which they gradually decreased, suggesting that northern flying squirrels are optimised for long distance travel. We show that northern flying squirrels initiate full gliding posture at ranges of less than 1 m, without landing any higher than an equivalent ballistic projectile. However, this gliding posture enables them to pitch upwards, potentially stalling the wing, and spreads the landing reaction force over all four extended limbs. At steeper approach angles of close to 45°, flying squirrels were unable to pitch up sufficiently and landed forelimbs first, consequently sustaining higher impact forces. We investigate four hypotheses to explain the origin of flight in these animals and conclude that the need to reduce landing impact forces was most likely to have stimulated the development of aerial control in flying squirrels.
The effect of decoupling olfactory and visual stimuli on the foraging behavior ofManduca sexta
Authors: Goyret Joaquín , Markwell Poppy M. , Raguso Robert A. 
Published: March 2007

SUMMARYWithin an appetitive context, Manduca sexta, a nectivorous nocturnal hawkmoth, can be attracted by a range of stimuli including floral volatiles and visual display, carbon dioxide and water vapor. Several studies on this and other flower-visiting insects have shown how olfactory and visual stimulation play (or do not play) a role in attraction and feeding. Nevertheless, these studies have consistently manipulated stimuli in a`presence–absence' manner. Here, we experimentally decoupled the presentation of both stimuli spatially and temporally in a wind tunnel, rather than entirely eliminating either one, and found that the decision-making process based on these stimuli is more flexible and complex than previously asserted. Manduca sexta was most responsive when both cues were present and emanated from the same source. When stimuli were spatially separated, responsiveness levels were comparable to those elicited by a single stimulus. However, transient olfactory stimulation either before or after visually guided approach (temporal decoupling) enhanced responsiveness to an odorless visual target. Additionally, searching times were increased by either a transient olfactory stimulation before take-off or by having the flower model spatially separated from the odor source tracked by the moths. Finally,in a dual-choice experiment, moths showed a strong bias for the visual display over the odor plume, suggesting the former to be the ultimate indicator of a nectar source. Our manipulation of floral cues shows that the feeding behavior of M. sexta, and probably of other nectivorous insects, is based not only on the sensory stimulation per se but also on the temporal and spatial pattern in which these stimuli are perceived.
Pregnancy block by MHC class I peptides is mediatedviathe production of inositol 1,4,5-trisphosphate in the mouse vomeronasal organ
Authors: Thompson Roger N. , McMillon Ronald , Napier Audrey , Wekesa Kennedy S. 
Published: March 2007

SUMMARYThe vomeronasal organ (VNO) has evolved to link an animal's behavior to its environment in a highly species-specific fashion. In mice, it is thought to be the primary sensory system responsible for the detection of pheromones. Pheromones regulate a variety of responses including mate recognition in the context of selective pregnancy failure. MHC (major histocompatibility complex)class I peptides have been identified as compounds that elicit the pregnancy block effect via the VNO. However, the transduction cascade of these molecules is unknown and it is not known if the production of these compounds are androgen dependent. By using male urine and MHC peptides, we show that female mice treated with MHC peptides (in urine or PBS) and urine from castrated males or juvenile mice of different haplotypes respond to the Bruce Effect paradigm in a manner equivalent to female mice exposed to whole urine. In addition to providing new evidence that urine from castrated or juvenile males and MHC peptides can induce pregnancy block, we show correlation of the effect with an increase in inositol 1,4,5-trisphosphate.
Parameters influencing the dissolved oxygen in the boundary layer of rainbow trout (Oncorhynchus mykiss) embryos and larvae
Authors: Ciuhandu Cosima S. , Wright Patricia A. , Goldberg Jeffrey I. , Stevens E. Don 
Published: March 2007

SUMMARY
We investigated the influence of oxygen demand (developmental stage) and supply (hypoxia, water flow rate, the chorion and body movements) on the oxygen concentration within the boundary layer next to the chorion of embryos or skin of larvae of rainbow trout (Oncorhynchus mykiss). Oxygen microelectrodes were used to measure dissolved oxygen (DO) within the boundary layer of trout embryos and larvae. As the embryos and larvae developed, the DO gradient and the thickness of the boundary layer increased. The DO concentration within the boundary layer next to the chorion or skin surface decreased as the DO concentration in the free-stream water decreased. A decrease in water flow rate increased the magnitude of the gradient and thickness of the boundary layer. In normoxia, the DO in the perivitelline fluid inside the chorion was 16±3.0% saturation at 31 days post fertilization, indicating that the chorion was a significant barrier to oxygen diffusion. The number of body movements did not change when embryos were exposed to hypoxia before hatching, but after hatching, hypoxia resulted in a decrease in body movements of the larvae. Taken together, our data indicate that the oxygen boundary layer around trout embryos and larvae depends on both the oxygen demand and supply. The factors that significantly impacted boundary layer oxygen were developmental stage, free-stream oxygen levels, water flow rate, and the presence of the chorion.
Regulation of feeding behaviour and locomotor activity bytakeoutinDrosophila
Authors: Meunier Nicolas , Belgacem Yesser Hadj , Martin Jean-René 
Published: March 2007

SUMMARYThe hormonal regulation of feeding behaviour is well known in vertebrates,whereas it remains poorly understood in insects. Here, we report that the takeout gene is an essential component of nutritional homeostasis in Drosophila. takeout encodes a putative juvenile hormone (JH)binding protein and has been described as a link between circadian rhythm and feeding behaviour. However, the physiological role of takeout and its putative link to JH remain unknown. In this study, we show that takeout (to1) flies failed to adapt their food intake according to food availability and that most defects could be genetically rescued. When food is abundant, to1 are hyperphagic, yielding to hypertrophy of the fat body. When food reappears after a starvation period, to1 flies do not increase their food intake as much as wild-type flies. This defect in food intake regulation is partly based on the action of Takeout on taste neurons, because the sensitivity of to1 gustatory neurons to sugars does not increase after starvation, as in wild-type neurons. This lack of regulation is also evident at the locomotor activity, which normally increases during starvation, a behaviour related to food foraging. In addition, to1 flies lack sexual dimorphism of locomotor activity,which has previously been linked to the JH circulating level. Moreover,application of the JH analog methoprene rescues the phenotype. These results suggest that takeout plays a central role as a feeding regulator and may act by modulating the circulating JH level.
Social domination increases neuronal survival in the brain of juvenile crayfishProcambarus clarkii
Authors: Song Cha-Kyong , Johnstone Laurel M. , Schmidt Manfred , Derby Charles D. , Edwards Donald H. 
Published: March 2007

SUMMARYOlfactory cues are among the sensory inputs that crayfish use in establishing dominance hierarchies. Throughout their lives, new neurons are continuously added into brain cell clusters 9 and 10, which contain somata of olfactory local and projection interneurons, respectively. Using markers for DNA synthesis (bromodeoxyuridine) and mitosis (phospho-histone-3), we tested juvenile crayfish (Procambarus clarkii) to examine effects of pairwise social experience on proliferation and survival of cells in these brain regions. Proliferating and mitotic cells appeared within restricted neurogenic areas in both clusters and in `tails' extending from them. These tails, embedded in tubulin-positive strands, are linked by a patch of cells. Neither cell proliferation nor mitotic activity was affected by social dominance. Cell survival of neuronal precursors was affected by dominance:compared to dominants, subordinates had fewer newborn cells surviving in cluster 9 after 14 days of social experience. Social experience also affected body growth rate, but the effect of social experience on neurogenesis remained when differences in body growth rate were statistically controlled. We conclude that social domination enhances survival of new olfactory interneuronal precursors compared to social subordination but not compared to social isolation.
The role of calcium and magnesium in the concrete tubes of the sandcastle worm
Authors: Sun ChengJun , Fantner Georg E. , Adams Jonathan , Hansma Paul K. , Waite J. Herbert 
Published: March 2007

SUMMARY
Sandcastle worms Phragmatopoma californica build mound-like reefs by sticking together large numbers of sand grains with cement secreted from the building organ. The cement consists of protein plus substantial amounts of calcium and magnesium, which are not invested in any mineral form. This study examined the effect of calcium and magnesium depletion on the structural and mechanical properties of the cement. Divalent ion removal by chelating with EDTA led to a partial collapse of cement architecture and cement dislodgement from silica surfaces. Mechanical properties examined were sand grain pull-out force, tube resistance to compression and cement adhesive force. EDTA treatment reduced sand grain pull-out forces by 60% and tube compressive strength by 50% relative to controls. EDTA lowered both the maximal adhesive force and energy dissipation of cement by up to an order of magnitude. The adhesiveness of calcium- and magnesium-depleted cement could not be restored by re-exposure to the ions. The results suggest that divalent ions play a complex and multifunctional role in maintaining the structure and stickiness of Phragmatopoma cement.
Development of New Semiconducting Materials for Durable High-performance Air-stable Organic Field-effect Transistors
Authors: Takimiya Kazuo , Kunugi Yoshihito , Otsubo Tetsuo 
Published: April 2007

Abstract
New thiophene- and selenophene-fused aromatic compounds were successfully developed as high-performance semiconducting materials for organic field-effect transistors (OFETs). Among them, the most advanced compounds designed on consideration of structure–function relationship showed durable air-stable FET performance. This article highlights the research strategy and development of these superior compounds as well as the molecular factors for the improvement of mobility, sensitivity, and stability, which are very informative for the design of practical semiconductors.
Perinatal Risk Factors for Hospitalization for Pneumococcal Disease in Childhood: A Population-Based Cohort Study
Authors: Mahon Barbara E. , Ehrenstein Vera , Nørgaard Mette , Pedersen Lars , Rothman Kenneth J. , Sørensen Henrik T. 
Published: April 2007

OBJECTIVE. The objective of this study was to examine the relation of factors that are present at birth to subsequent hospitalization for childhood pneumococcal disease.METHODS. We conducted a cohort study of all singletons born in 3 counties in western Denmark from 1980 through 2001, using population-based registries to obtain data on pregnancy- and birth-related variables and hospitalizations through age 12. We calculated incidence rates of pneumococcal disease hospitalization overall and within strata of study variables and used Poisson regression to estimate rate ratios for pneumococcal disease hospitalization while accounting for other birth characteristics.RESULTS. Among 338504 eligible births, 1052 children were later hospitalized for pneumococcal disease. Pneumonia accounted for most hospitalizations (81.9%). The pneumococcal disease hospitalization rate was highest among 7- to 24-month-olds, followed by 0- to 6-month-olds and 25- to 60-month-olds. The highest rates, typically over 200 hospitalizations per 100 000 person-years, were in 0- to 6- and 7- to 24-month-old children who were born preterm or with low birth weight, a low 5-minute Apgar score, or birth defects. The hospitalization rate was lower for first-born children at 0 to 6 months but not at older ages. At older ages, hospitalization rates were not substantially different for children whose mothers smoked during pregnancy, but at 0 to 6 months, the rate was higher for children of multiparous nonsmokers than for others. Adjusted rate ratios were elevated across all age categories for several variables, including low birth weight, presence of birth defects, and low 5-minute Apgar. For several others, including preterm birth, maternal multiparity, age ≤20 years, and non-Danish/European Union citizenship, adjusted rate ratios were elevated only for 0- to 6-month-olds.CONCLUSIONS. This large cohort study of hospitalization for childhood pneumococcal disease clarifies the roles of some gestation and birth factors while raising new questions about how these factors work.