bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measuring Aerodynamic Interference Drag Between a Bird Body and the Mounting Strut of a Drag Balance
Authors: Tucker Vance A. 
Published: April 2021

ABSTRACT
The drag of a bird body mounted on the strut of a drag balance in a wind tunnel is more than the sum of the drags of the isolated strut and the isolated body. The strut changes the air flow around the body and generates additional drag, known as interference drag. This paper describes practical methods for measuring the drag of bird bodies: a strain-gauge drag balance, dimensions for struts made with machine or hand tools, and a procedure for correcting drag measurements for interference drag. Interference drag can be measured by extrapolating a relationship between the drag of isolated struts with different cross-sectional sizes and shapes and the drag of a body mounted on those struts. The interference length -the length of an isolated strut that produces drag equal to the interference drag -is a useful quantity for predicting interference drag. The relationship mentioned above is a straight line for a model peregrine falcon (Falco peregrinus L.) body mounted on smooth struts -struts with convex cross-sectional shapes ranging from streamlined to circular. This finding simplifies the determination of interference drag in three ways: (i) the line can be found from measurements with just two struts -a standard strut with low drag and a calibration strut with high drag; (ii) the two struts need not have the same shape -for example, the standard strut can be changed to a calibration strut by attaching a spoiler without disturbing the body mounted on the strut -and (iii) a single value of interference length (33.1mm) describes smooth struts with a range of shapes and sizes. These struts had drag coefficients between 0.33 and 0.91 at Reynolds numbers between 2100 and 10800. The interference length of a strut supporting the actual falcon body with a feathered surface is not significantly different from that of the strut supporting the model body with a rigid surface. As a hypothesis, interference length (h1, in metres) of a smooth strut varies with the size of the body mounted on it: where m is the body mass (in kg) of the intact bird. 95 % of the interference drag appears to arise from a 15 mm length of the strut nearest the body.
Temperature Regulation by Respiratory Evaporation in Grasshoppers
Authors: Prange Henry D. 
Published: April 2021

ABSTRACT
Grasshoppers of the species Schistocerca nitens (Thünberg), Locusta migratoria (L.) and Tmethis pulchripennis (Bolivar) are able to withstand air temperatures higher than lethal internal temperature (48 °C) for more than an hour, during which time they maintain an internal temperature as much as 8°C below air temperature.
Rates of evaporation at high air temperatures are much greater than those observed for cuticular transpiration alone. The rate of evaporation and the ventilation frequency remain relatively constant at temperatures of up to about 45°C, above which they both increase markedly.
The depression of internal temperature thus appears to be caused by increased tracheal ventilation for evaporative cooling. This finding contradicts the common assumption that evaporative cooling is of little adaptive advantage for thermoregulation in insects.
In L. migratoria, the increase in ventilation appears to be achieved almost entirely by an increase in frequency of ventilation, although other species may alter tidal volume as well.
Control of Red Blood Cell Metabolism in Rainbow Trout After Exhaustive Exercise
Authors: Wood Chris M. , Walsh Patrick J. , Thomas Serge , Perry Steve F. 
Published: April 2021

ABSTRACT
Metabolic responses (rates of CO2 production from 14C-labelled glucose or lactate, and total O2 consumption) of red blood cells were monitored in rainbow trout (Oncorhynchus mykiss) at rest and during 12 h of recovery from exhaustive exercise. Extracellular acid-base status, red blood cell intracellular pH (pHi), and plasma.metabolite and catecholamine levels were recorded simultaneously. Despite a post-exercise rise in plasma glucose level, glucose oxidation was depressed, at least partly because of a rise in plasma lactate level. However, lactate oxidation was stimulated markedly, especially at 0–2 h post-exercise. Subsequent multifactorial experiments in vitro demonstrated that augmentation of lactate oxidation was due partly to increased plasma lactate, and partly to separate stimulatory effects of elevated and catecholamine levels. Changes in pH and HCO3− level were not directly involved, but the stimulatory effects of catecholamines occurred only under acidotic conditions. Total red cell O2 consumption remained generally stable after exercise. Similar multifactorial experiments in vitro demonstrated that respiratory, metabolic and mixed acidoses all inhibited , an effect largely attributable to the lowered pH. This inhibition was reversed by typical post-exercise levels of epinephrine and norepinephrine; again, catecholamines had no effect under control conditions. Red cell pHi regulation was achieved without an increase in above resting levels. Our results indicate a complex sensitivity of red cell metabolism to acid-base status and a shift in substrate preference for oxidation after strenuous exercise. The mobilization of catecholamines plays an important coordinating role and helps sustain normal rates of oxidative metabolism by red cells in the face of post-exercise blood acidosis.
Eye Movements in the Rock Crab Pachygrapsus Marmoratus Walking Along Straight and Curved Paths
Authors: Paul H. , Nalbach H.-O. , Varjú D. 
Published: April 2021

ABSTRACT
Freely walking rock crabs (Pachygrapsus marmoratus Fabricius) were videotaped from above in a quasi-natural environment. The angular position of the long axis of the body and of both eyes in the horizontal plane were studied. Compensatory eye. movements are elicited along both straight and curved paths only during body rotation around the yaw axis. Hence, eye movements reduce the rotational component of the visual image flow during locomotion. Fast saccades, which reset the eyes after a slow compensatory excursion relative to the body, are simultaneously initiated on both sides. They occur either after or before a body turn starts. Therefore, they are partially of central origin. Crabs with one or both eyes blinded are still capable of performing compensatory eye-stalk movements. Thus, nonvisual cues, such as leg proprioceptive afferences or statocyst signals, are also effective in freely walking crabs. However, reducing the number of legs does not substantially impair the movements of the eyes in either seeing or blinded animals. Fixing the seeing eyes to the carapace characteristically alters the pattern of locomotion. Body rotations are jerky in a stationary environment. The tendency to follow a rotating panorama by means of body turns is much higher than in intact animals.
Sensory Basis and Functional Role of Eye Movements Elicited During Locomotion in the Land Crab Cardisoma Guanhumi
Authors: Barnes W. Jon P. , Barnes P. 
Published: April 2021

ABSTRACT
Eye movements in the horizontal plane and the rotatory component of body movement have been continuously recorded in land crabs, Cardisoma guanhumi Latreille, walking freely in an arena.
The results show that the eyes compensate for locomotor turns by moving in the opposite direction to the body, thus reducing the image motion of surrounding objects on the retina. Gains often approach unity, so that stabilization of the rotatory component of self-generated image motion is good. Of the three compensatory eye reflexes that could contribute to these responses, optokinetic responses play a major role, since the gain of the responses of freely walking blinded crabs was about half that of crabs that could see. Since blinded crabs held above a ball moved their eyes whenever they rotated the ball about a vertical axis (i.e. turned), a significant role for leg proprioceptor-driven eye movements is also presumed. It is unclear whether vestibular nystagmus, driven by the statocysts, also has a role to play.
In contrast to the high-gain compensatory responses that accompany turns, the translatory component of locomotion elicits compensatory eye movements only under the most favourable circumstances, when the crab walks along a runway facing a set of stripes. Even then, the responses are of very low gain (0.02-0.09). Amongst several possible factors, this is partly because lateral ommatidia, which drive the optokinetic responses, will face the poles of the flow field during sideways walking, and partly because stationary contrasts (as occur at the poles of the flow field) reduce the gain of optokinetic responses.
It is argued that, by compensating for turns but not translatory locomotor movements, crabs effectively separate the rotatory from the translatory components of the visual flow field around them. Since only the former can be used in course control, while only the latter provides information on ground speed and the three-dimensional layout of the environment, such a separation makes good functional sense.
Effect of Imposed Head Vibration on the Stability and Waveform of Flagellar Beating in Sea Urchin Spermatozoa
Authors: Shingyoji Chikako , Gibbons Ian R. , Murakami Akira , Takahashi Keiichi 
Published: April 2021

ABSTRACT
The heads of live spermatozoa of the sea urchin Hemicentrotus pulcherrimus were held by suction in the tip of a micropipette mounted on a piezoelectric device and vibrated either laterally or axially with respect to the head axis. Within certain ranges of frequency and amplitude, lateral vibration of the pipette brought about a stable rhythmic beating of the flagella in the plane of vibration, with the beat frequency synchronized to the frequency of vibration [Gibbons et al. (1987), Nature 325, 351–352], The sperm flagella, with an average natural beat frequency of 48 Hz, showed stable beating synchronized to the pipette vibration over a range of 35–90 Hz when the amplitude of vibration was about 20 μm or greater. Vibration frequencies below this range caused instability of the beat plane, often associated with irregularities in beat frequency. Frequencies above about 90 Hz caused irregular asymmetrical flagellar beating with a marked decrease in amplitude of the propagated bends and a skewing of the flagellar axis towards one side; the flagella often stopped in a cane shape. In flagella that were beating stably under imposed vibration, the wavelength was reduced at higher frequencies and increased at lower frequencies. When the beat frequency was equal to or lower than the natural beat frequency, the apparent time-averaged sliding velocity of axonemal microtubules, obtained as twice the product of frequency and bend angle, decreased with beat frequency in both the proximal and distal regions of the flagella. However, at vibration frequencies above the natural beat frequency, the sliding velocity increased with frequency only in the proximal region of the flagellum and remained essentially unchanged in more distal regions. This apparent limit to the velocity of sliding in the distal region may represent an inherent limit in the intrinsic velocity of active sliding, while the faster sliding observed in the proximal region may be a result of passive sliding or elastic distortion of the microtubules induced by the additional energy supplied by the vibrating pipette.
Axial vibration with frequencies either close to or twice the natural beat frequency induced cyclic changes in the waveform, compressing and expanding the bends in the proximal region, but did not affect bends in the distal region or alter the beat frequency.
Metabolic and Behavioural Consequences of the Procedures of the Doubly Labelled Water Technique on White (MF1) Mice
Authors: Speakman J. R. , Racey P. A. , Burnett A. M. 
Published: April 2021

ABSTRACT
The effects of the doubly labelled water technique (intraperitoneal injection, temporary food deprivation and blood sampling) on the energy expenditure, food intake and behaviour of 18 white (MF1) mice was investigated.
There were no significant differences in mean energy expenditure or food intake between experimental and control animals, on which the techniques were not performed, over the first 24 h after manipulation. These data indicate that there are no direct metabolic consequences associated with the procedures.
During the 100 min immediately after blood sampling, the behaviour of experimental animals involved significantly more grooming, mostly at the site of the blood sample wound, more feeding and more general activity, at the expense of resting, when compared with controls. Twenty hours later the behavioural differences were less marked, but still statistically significantly different, and reversed: experimental animals spent more time resting and less in general activity or feeding.
The effects of the technique on the behaviour of white mice had trivial consequences for their daily energy expenditure. This may reflect the restricted behavioural repertoire of these captive animals within respirometry chambers. The effect on wild animals may be more profound and requires investigation.
Lidocaine and Barium Distinguish Separate Routes of Transbasal K+ Uptake in the Posterior Midgut of the Tobacco Hornworm (Manduca Sexta)
Authors: Moffett David F. , Koch Alan 
Published: April 2021

ABSTRACT
The isolated posterior midgut of the tobacco hornworm maintains a vigorous transepithelial K+ transport from the hemolymphal side to the lumen side at a rate accurately measured by its short-circuit current. Previous studies using the K+ channel blocker Ba2+ suggested that partial inhibition of the short-circuit current by hemolymphal Ba2+ was due to blockage of one of at least two parallel transbasal entry routes for K+ into the intracellular transport pool. The present studies show that the local anesthetic lidocaine, at a concentration of 5 mmol I-1 on the hemolymphal side, partly inhibits net transepithelial K+ transport. The inhibition is accompanied by hyperpolarization of the basal membrane and an increase in transbasal resistance, suggestive of a block of transbasal K+ conductance. The effects of lidocaine and Ba2+ are additive, suggesting that the inhibitors distinguish separate, parallel K+ uptake processes.
Power Output and the Frequency of Oscillatory Work in Mammalian Diaphragm Muscle: the Effects of Animal Size
Authors: Altringham John D. , Young Iain S. 
Published: April 2021

ABSTRACT
Bundles of muscle fibres were isolated from the diaphragm of mouse, rat and rabbit. Mean oscillatory power output was determined during phasic stimulation and imposed sinusoidal length changes. Maximum power output was measured over a range of cycle frequencies. The cycle frequency for maximum power output (fopt) decreased with increasing body mass and was described by the equation, fopt=4.42M−016, where M is body mass. A very similar relationship has been reported between body mass and the frequency of the trot-gallop transition in terrestrial, quadrupedal mammals [Heglund et al. (1974), Science186, 1112-1113), and the significance of this similarity is discussed.
Rat Atriopeptin Dilates Vascular Smooth Muscle of the Ventral Aorta from the Shark (Squalus Acanthias) and the Hagfish (Myxine Glutinosa)
Authors: Evans David H. 
Published: April 2021

ABSTRACT
Recent evidence suggests that atriopeptin (AP) may play a role in osmoregulation in fishes (Evans, 1990) via hemodynamic and ionic transport effects analogous to those described for mammalian volume regulation (e.g. Genest and Cantin, 1988). Specifically, heterologous mammalian AP has now been shown to produce natriuresis (Duff and Olson, 1986), even in an aglomerular teleost (Lee and Malvin, 1987), inhibit intestinal salt uptake (O’Grady et al. 1985) and stimulate gill sodium extrusion (Scheide and Zadunaisky, 1988) in teleosts, all responses that favor osmoregulation in dehydrating sea water, rather than volume-loading fresh water. The proposition that AP may be primarily involved in salt extrusion rather than volume regulation is supported by recent studies showing that plasma immunoreactive atriopeptin (APir) levels are higher when euryhaline teleost fishes are acclimated to high salinities (Westenfelder et al. 1988; Evans et al. 1989). The recent finding that mammalian AP produces vasodilation in the ventral aorta and branchial vasculature of the marine toadfish (Evans et al. 1989) suggests that AP may also play a role in controlling gill hemodynamics. However, an increase in gill perfusion would presumably exacerbate the osmoregulatory problems in either the marine or freshwater environment, since the gill is the site of passive ionic and water movements in teleost fishes (Evans, 1979).
Determination of Movements of African Penguins Spheniscus Demersus Using a Compass System: Dead Reckoning May be an Alternative to Telemetry
Authors: Wilson Rory P. , Wilson Marie-Pierre T. , Link Rudi , Mempel Helgi , Adams Nigel J. 
Published: April 2021

ABSTRACT
Determination of animal movements is essentially achieved by a temporal sequence of positional fixes. Currently, evaluation of animal positions depends on energy transmission between the animal and the perceiver. The distance between animal and perceiver and the type of medium separating them determine the proportion of energy transmitted in relation to that received. Visual localization of animals is most used, but transmission of optical images is highly variable and rarely effective over decametres. Superior sonic transmission in water and radio-transmission in air have led researchers to fit animals with power sources so that positional information can be obtained by triangulation with specialized receivers (Priede, 1983; Kenward, 1987). This increases perceptive range, but the ‘distance’ and ‘medium’ problems still apply (Kenward, 1987). Moreover, the accuracy of positional fixes decreases with increasing transmitter/receiver distance (Heezen and Tester, 1967; Springer, 1979) so that, for far-ranging animals, only gross movements can be determined. Satellite tracking systems (Jouventin and Wei-merskirch, 1990) set a specific limit on this form of error but, even so, extended transmitter/receiver distances require large power sources to allow reception of a viable signal despite attenuation by the intervening medium. Ultimately, the viability of most telemetric systems is a balance between having a small enough power source so that animal behaviour is minimally altered (Holliday et al. 1988; Wanless et al. 1989) but large enough to enable signal transmission.
Changes in Red Cell Atp Concentration and Oxygen-Affinity Following Birth in the Neonatal Garter Snake Thamnophis Elegans
Authors: Ingermann Rolf L. , Berner Nancy J. , Ragsdale Frances R. 
Published: April 2021

ABSTRACT
The neonate of viviparous reptiles is clearly precocial relative to the mammalian neonate and shows a rapid transition to independent life following parturition. This suggests major physiological changes occur quickly at, and just after, parturition. In this study, we examined the temporal changes that occur in the respiratory properties of red blood cells in the garter snake Thamnophis elegans at birth.
Hyperosmotic Oral Fluid Secretion During Active Water Vapour Absorption and During Desiccation-Induced Storage-Excretion by the Unfed Female Tick Amblyomma Americanum
Authors: Sigal Marvin D. , Machin John , Needham Glen R. 
Published: April 2021

ABSTRACT
It is well established that some acarines, insects and isopods maintain water balance in subsaturated air by actively absorbing water from the atmosphere (O’Donnell and Machin, 1988). Investigations of water balance physiology by Lees (1946) in the Ixodoidea demonstrated that partially desiccated ticks gain weight in water vapour activities (av=relative humidity/100) significantly lower than that of the haemolymph activities (av≥0.98). Subsequent research confirmed that active water vapour uptake is a common phenomenon in ticks (for reviews, see Rudolph and Knülle, 1978; Needham and Teel, 1986). The gnathosomal region was identified as the site of water vapour uptake when Rudolph and Knülle (1974) blocked various body surfaces of predesiccated adult Amblyomma variegatum with paraffin wax and monitored weight changes during exposure to a subsaturated av. A net weight gain occurred except when the gnathosoma was occluded. The external gnathosoma of the ixodid tick projects anteriorly from the basis capitulum as an assemblage of five processes (Fig. 1A). The most lateral appendages are a pair of palps that can be abducted from the inner dorsal chelicerae during attachment and blood feeding. The paired burrowing chelicerae and a singular ventral hypostome secure the oral sucking apparatus into the host feeding lesion during haematophagy. Wax-occlusion techniques have identified the proximal hypostome-cheliceral junction as a more specific site for vapour uptake in A. americanum (L.); and a correlation was found between palp abduction splaying behaviour and the critical equilibrium activity at which ticks were held (CEA) (M. D. Sigal, in preparation).
The Effects and Physiological Consequences of Raised Levels of Cortisol on Rainbow Trout (Oncorhynchus Mykiss) Erythrocyte β-Adrenoreceptors
Authors: Reid Scott D. , Perry Steve F. 
Published: April 2021

ABSTRACT
We have investigated the influence of cortisol on the β-adrenoreceptor population of rainbow trout [Oncorhynchus mykiss (Walbaum)] erythrocytes and determined what impact it has on the adrenergic responsiveness of erythrocytes in vitro to exogenous catecholamines. To do so, the erythrocyte β-adrenoreceptors were characterized in fish with chronically elevated plasma cortisol levels (118±5.9ngml−1, &gt;10 days) and compared with shams, using radioreceptor assay techniques. The number of ‘internalized’, low-affinity receptors was increased when cortisol levels were raised, but the number of high-affinity, ‘surface’ receptors was not altered. The physiological significance of this response was ascertained by assessing the in vitro sensitivity (or responsiveness) of erythrocytes to adrenaline and noradrenaline (10–1000 nmol I−1) under normoxic or hypoxic conditions. Erythrocyte sensitivity to catecholamines, as determined by changes in both whole-blood pH (ΔpHe) and intracellular cyclic AMP content, was greater in hypoxic than in normoxic blood. Although cortisol further enhanced the responsiveness of erythrocytes to catecholamines, this amplification in sensitivity was observed only during hypoxia.
When the radioreceptor assay was conducted using erythrocytes from the catecholamine sensitivity experiments, results were consistent with initial receptor density data. An increase in surface receptor density was associated with hypoxia in vitro. This hypoxia-specific increase in surface β-adrenoreceptors was significantly enhanced in the cortisol-treated erythrocytes, showing that cortisol had a significant impact on erythrocyte β-adrenoreceptor dynamics in addition to the direct influence of hypoxia.
This study has shown (1) that, by itself, in vitro hypoxia simultaneously initiates the movement of internal receptors to the cell surface, where they become physiologically active, and the replenishment of the internal receptor pool,(2) that cortisol increases receptor availability by increasing the internal pool of low-affinity receptors in the absence of any stimulus for receptor mobilization, and (3) that the sensitivity of erythrocytes to catecholamines is directly proportional to the number of high-affinity receptors present at the erythrocyte surface. Thus, we suggest that, under conditions of chronic stress, cortisol may pre-adapt the erythrocytes to receive additional physiological inputs that can ultimately enhance respiratory performance beyond that which would be possible in the absence of chronically elevated levels of cortisol.