bluuebunny/crossref_metadata_2025 huggingface dataset:
Leg-Induced Steering in Flying Crickets
Authors: May Michael L. , Hoy Ronald R.
Published: April 2021

Over the past 50 years, researchers have speculated that flying insects use their legs as part of the steering mechanism. This hypothesis developed from observing that insects making a right turn, for example, swing their right metathoracic and sometimes mesothoracic leg in the direction of the turn. Several insects exhibit this behaviour, including crickets (Moiseff et al. 1978), locusts (Gettrup and Wilson, 1964; Dugard, 1967; Baker, 1979; Cotter, 1979; Taylor, 1981), flies (Hollick, 1940; Götz et al. 1979; Nachtigall and Roth, 1983) and bugs (Govind and Burton, 1970; Govind, 1972). In locusts, Camhi (1970) noted that the inside metathoracic leg (i.e. on the same side as the turn) moves out from the body and into the path of the hindwing during yaw steering; however, the aerodynamic effect was untested. Here we demonstrate that in the Australian field cricket (Teleogryllus oceanicus) the metathoracic leg produces a significant aerodynamic effect on yaw steering by impeding the downstroke of the hindwing on the inside of the turn.
Single-Channel Recordings from Insect Neuronal Gaba-Activated Chloride Channels
Authors: Malécot Claire O. , Sattelle David B.
Published: April 2021

GABA-receptor-operated chloride ion channels are widely distributed on membranes of insect nervous tissue (for a review, see Sattelle, 1990). For example, in the cockroach Periplaneta americana radioligand binding (Lummis and Sattelle, 1986), autoradiography (Lummis and Sattelle, 1985) and GABA-activated 36Cl flux (Wafford et al. 1987) studies have demonstrated the presence of GABA-operated chloride channels throughout the nervous system. Electrophysiological studies initiated by R. M. Pitman, J-. J. Callec, R. J. Walker and colleagues have demonstrated the presence of many GABA-sensitive neurones in the cockroach central nervous system (Pitman and Kerkut, 1970; Walker et al. 1971; Callec, 1974). Recent studies on identified neurones (Wafford and Sattelle, 1986; Sattelle et al. 1988) and cultured neurones (Beadle and Lees, 1986; Neumann et al. 1987; Shimahara et al. 1987) have enhanced our understanding of the pharmacology of cockroach GABA receptors. However, few studies have yielded data on the unitary conductance properties of insect neuronal GABA-operated chloride channels. Shimahara et al. (1987) have used noise analysis to estimate that the conductance of chloride channels activated by GABA (5.0×10−5mol l−1) on cultured embryonic cockroach (Periplaneta americana) brain neurones is 18.6pS, with a mean open time of 11.8 ms. Attempts to obtain recordings of insect GABA-activated chloride channels using the patch-clamp technique have proved difficult, and this has been attributed to non-uniformity of the distribution of GABA receptors on embryonic cells (Pichon and Beadle, 1988). No such data are available for adult neurones, and the present study provides an initial description of GABA-operated chloride channels of dissociated neurones from thoracic ganglia of the adult cockroach (Periplaneta americana).
Slow Discontinuous Ventilation in the Namib Dune-sea AntCamponotus Detritus(Hymenoptera, Formicidae)
Authors: Lighton John R.
Published: April 2021

Data on discontinuous ventilation phenomena in Camponotus detritus (Emery), an ant from the hyper-arid Namib Desert, are described and compared to equivalent data from two mesic insects, including Camponotus vicinus (Mayr). Although rate of CO2 production and body size were equivalent in C. detritus and C. vicinus, the ventilation rate of C. detritus was fourfold lower, significantly reducing predicted respiratory water loss rates. Ventilation rate was presumably modulated by , and low ventilation frequency was maintained in part by significant gas exchange during the fluttering-spiracle phase of the ventilation cycle, which is generally characterized by low rates of respiratory water loss.
The formation of cooperative cell assemblies in the visual cortex
Authors: Singer W.
Published: April 2021

During a critical period of postnatal development of the mammalian visual cortex, synaptic connections are susceptible to use-dependent modifications. Synaptic connections strengthen if pre- and postsynaptic elements are active simultaneously and postsynaptic depolarization is sufficient to allow for the activation of N-methyl-D-aspartate (NMDA)-receptor-gated conductances. By contrast, synaptic gain decreases if postsynaptic activation exceeds a critical threshold and presynaptic afferents are not capable of activating NMDA- receptor-dependent conductances. These processes lead to selective stabilization of connections between neuronal elements which often exhibit correlated activity and thus modify connectivity according to functional criteria, it is suggested that such experience-dependent selection of circuits serves different purposes at different levels of visual processing. At the input stage to the striate cortex it contributes to optimize the match between the representations of the two eyes. At a later stage of processing it participates in the development of selective connections between cortical columns and thereby serves to establish neuronal representations for frequently occurring constellations of features.

Use-dependent changes of synaptic gain can also be induced in the mature visual cortex. These modifications follow the same rules as those occurring during early development and appear to depend on similar molecular mechanisms. However, in the adult the changes of synaptic gain do not seem to be followed by major rearrangements of connectivity. This suggests developmental alterations in mechanisms responsible for growth, removal and stabilization of synaptic connections. Actually, many of the cellular mechanisms thought to be involved in use-dependent synaptic plasticity change during development but it is still unclear which of them are responsible for the definitive stabilization of functionally confirmed pathways.
Synaptic connections made by axons regenerating in the central nervous system of adult mammals
Authors: Aguayo A. J. , Bray G. M. , Rasminsky M. , Zwimpfer T. , Carter D. , Vidal-Sanz M.
Published: April 2021

The restoration of connections in the injured central nervous system (CNS) of adult mammals is hindered by the failure of axons to grow back to their natural fields of innervation. Following transection of the optic nerve of adult rodents, the guided regeneration of retinal ganglion cell (RGC) axons along a transplanted segment of peripheral nerve (PN) has shown that these neurones retain their capacities to form well-differentiated synapses in both normal and abnormal targets. The main aim of this review is to describe the anatomical and functional characteristics of some of these connections and to suggest that their terminal distribution and morphology may be the result of a persistence in these targets of molecular determinants that influence normal connectivity in the intact animal.
The Influence of Temperature on Muscle Velocity and Sustained Performance in Swimming Carp
Authors: Rome Lawrence C. , Funke Roel P. , Alexander R. Mcneill
Published: April 2021

The aim of this study was to evaluate how fish locomote at different muscle temperatures. Sarcomere length excursion and muscle shortening velocity, V, were determined from high-speed motion pictures of carp, Cyprinus carpio (11–14cm), swimming steadily at various sustained speeds at 10, 15 and 20°C. In the middle and posterior regions of the carp, sarcomeres of the lateral red muscle underwent cyclical excursions of 0·31 μm, centred around the resting length of 2·06 urn (i.e. from 1·91 to 2·22 μm). The amplitudes of the sarcomere length excursions were essentially independent of swimming speed and temperature. As tail-beat frequency increased linearly with swimming speed regardless of temperature, the sarcomeres underwent the same length changes in a shorter time. Thus, V increased in a linear and temperature-independent manner with swimming speed. Neither temperature nor swimming speed had an influence on tail-beat amplitude or tail height.

Our findings indicate that muscle fibres are used only over a narrow, temperature-independent range of V/Vmax (0·17–0·36) where power and efficiency are maximal. Carp start to recruit their white muscles at swimming speeds where the red muscle V/Vmax becomes too high (and thus power output declines). When the V/Vmax of the active muscle falls too low during steady swimming, carp switch to ‘burst-and-coast’ swimming, apparently to keep V/Vmax high. Because Fmax (maximum velocity of shortening) of carp red muscle has a Q10 of 1–63, the transition speeds between swimming styles are lower at lower temperatures. Thus, carp recruit their white anaerobic muscle at a lower swimming speed at lower temperatures (verified by electromyography), resulting in a lower maximum sustainable swimming speed. The present findings also indicate that, to generate the same total force and power to swim at a given speed, carp at 10°C must recruit about 50% greater fibre cross-sectional area than they do at 20 °C.
A Patch-Clamp Study of Acetylcholine-Activated Ion Channels in Ascaris Suum Muscle
Authors: Pennington A. J. , Martin R. J.
Published: April 2021

Acetylcholine-activated single-channel currents were recorded from cell-attached and inside-out patches of isolated muscle vesicles from Ascaris suum. Acetylcholine (1–10 μmol I−1) activated cation-selective channels of two amplitudes: 40–50 pS and 25–35 pS. Both channels had linear l/V relationships and mean open durations independent of voltage. The larger conductance was analysed in detail to determine its open-, closed-and burst-time kinetics; the open and burst durations were composed of two components (short and long), while closed durations had at least three components (short, intermediate and long). The data were then corrected to allow for missing short events in order to estimate various parameters including corrected mean open time (1·26+0·11 ms, mean±s.E.). Values were also derived for the efficacy (β/ α=4·9) and affinity [1/KD =147×103 (moll−1)−1] of acetylcholine at this receptor. Larger concentrations of acetylcholine (25–100 μmol I−1) were shown to produce desensitization and caused single-channel currents to occur in clusters with long closed times (mean 171 s) between clusters. It was concluded that the extrasynaptic muscle of Ascaris suum contains two types of acetylcholine-activated ion channel and these are possible sites of action of various anthelmintic drugs. This paper is the first to describe acetylcholine-activated single-channel currents in invertebrate muscle.
Oxygen Uptake of Rainbow Trout Oncorhynchus Mykiss Phagocytes Following Stimulation of the Respiratory Burst
Authors: Nagelkerke L. A. J. , Pannevis M. C. , Houlihan D. F. , Secombes C. J.
Published: April 2021

The in vitro oxygen uptake of rainbow trout phagocyte-enriched head kidney leucocyte and head kidney macrophage suspensions was monitored. Stimulation of these cells with zymosan or phorbol myristate acetate induced a two- to 10-fold increase in oxygen uptake, the so-called respiratory burst. This respiratory burst activity was markedly enhanced in the presence of the calcium ionophore A23187 and inhibited in the presence of the NADPH oxidase inhibitor diphenyl iodonium or when glucose was absent from the buffer. The presence of sodium azide also inhibited the response of phagocyte-enriched suspensions by approximately 36 %, but only by 16 % for macrophage suspensions. The possible pathways responsible for the respiratory burst in fish phagocytes and its biological significance are discussed.
Characterisation of Amino Acid transport in Red Blood Cells of a Primitive Vertebrate, the Pacific Hagfish (Eptatretus Stouti)
Authors: Fincham Daron A. , Wolowyk Michael W. , Young James D.
Published: April 2021

Intracellular amino acid levels and the characteristics of amino acid transport were investigated in red blood cells of a primitive vertebrate, the Pacific hagfish (Eptatretus stouti Lockington). In contrast to red cells from euryhaline teleosts and elasmobranchs, which contain high concentrations of β-amino acids, those from hagfish exhibited an intracellular amino acid pool (approx. 100 mmol l−1 cell water) composed almost entirely of conventional α-amino acids. Red celkplasma distribution ratios for individual amino acids ranged from 219, 203 and 173 for alanine, α-amino-n-butyrate and proline, respectively, to 11 and 13 for lysine and arginine. Corresponding distribution ratios for Na+, K+ and Cl− were 0.043, 21 and 0.32, respectively. The cellular uptake of amino acids, with the exception of L-proline and glycine, was Na+-independent. Compared with mammalian and avian red cells, those from hagfish exhibited 104-fold higher rates of L-alanine transport. Uptake of this amino acid from the extracellular medium was concentrative, but occurred as a 1:1 exchange with intracellular amino acids. The L-alanine transport mechanism was identified as an asc type system on the basis of its Na+-independence and selectivity for neutral amino acids of intermediate size. A volume-sensitive amino acid channel, which is found in both euryhaline teleosts and in elasmobranchs, is absent from hagfish red cells.
SEVEN FMRFamide-RELATED AND TWO SCP-RELATED CARDIOACTIVE PEPTIDES FROM HELIX
Authors: Price D. A. , Lesser W. , Lee T. D. , Doble K. E. , Greenberg M. J.
Published: April 2021

Pulmonate snails have a more complex array of cardioexcitatory peptides than other molluscs, and Helix has a more complex array than most other pulmonates. Since a full characterisation of the cardioexcitatory peptides is necessary for an understanding of physiology, we sought to identify the members of two families of such peptides - the small cardioactive peptides (SCPs) and the FMRFamide-related peptides (FaRPs) - from Helix aspersa. We characterised the peaks of immunoreactivity from HPLC both by their elution times and by their molecular weights as determined by fast atom bombardment mass spectrometry (FABms). These two criteria, used in parallel, facilitated our identification of several known peptides: MNYLAFPRMamide, identical to SCPB of Aplysia; two tetrapeptide FaRPs, FMRFamide and FLRFamide; and three heptapeptide FaRPs, NDPFLRFamide, SDPFLRFamide and pQDPFLRFamide. Of these peptides, only FMRFamide and pQDPFLRFamide have previously been reported from Helix. We also discovered an additional SCP and two novel FaRPs and sequenced them. The SCP is Ser-Gly-Tyr-Leu-Ala-Phe-Pro-Arg-Met-amide (SGYLAF-PRMamide), and the heptapeptide FaRPs are Asn-Asp-Pro-Tyr-Leu-Arg-Phe-amide (NDPYLRFamide) and Ser-Glu-Pro-Tyr-Leu-Arg-Phe-amide (SEPYLRF-amide). When these nine peptides were tested on isolated Helix ventricles, the SCPs were the most potent cardioexcitors, the heptapeptide FaRPs were next, and the tetrapeptides had the least activity.
Measuring Aerodynamic Interference Drag Between a Bird Body and the Mounting Strut of a Drag Balance
Authors: Tucker Vance A.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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, >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.
Circulatory Mechanics in the Toad Bufo Marinus: II. Haemodynamics of the Arterial Windkessel
Authors: Gibbons Carol A. , Wick Robert E. Shad
Published: April 2021

This study examines the importance of vascular elasticity to arterial haemodynamics in a poikilothermic vertebrate. Pulsatile blood pressure, flow and vessel diameter were recorded at several locations within the arterial tree of the toad, Bufo marinus. We then determined the dynamic elastic modulus, the pulse wave velocity and the hydraulic impedance characteristics of the aorta. The relatively low heart rate and short arterial tree, and a pulse velocity of about 2.5ms−1, combine to give a transit time for the pressure pulse through aorta that is only 3% of the cardiac cycle. Consequently, wave propagation effects seen in mammals, such as peripheral amplification, distortion and secondary pressure peaks due to reflections, are not apparent. Instead, the aorta acts as a simple Windkessel and inflation by the heart occurs almost simultaneously throughout. Pressure waveforms are nearly identical at proximal and distal locations, and flow pulsatility is reduced progressively through the elastic aorta.
Dragonfly Flight: Power Requirements at High Speed and Acceleration
Authors: May Michael L.
Published: April 2021

Most studies of insect flight deal primarily with hovering or with forward flight at constant, moderate speed. This paper reports investigations of flight characteristics that are especially relevant to the performance of dragonflies at high and/or changing velocity. Dragonflies were filmed in free flight in the field to determine velocity and acceleration. The power required for repeated acceleration is shown to be large, in some circumstances, relative to the estimated maximum available power and probable top power requirements for steady flight. Distributions of velocity and acceleration, and concomitant power requirements, differ markedly among species, however. In addition, parasite drag was measured in winds of 2–7ms−1 and drag coefficients determined to be about 0.40 at Reynolds number greater than 104. This result implies substantially lower power requirements at high speeds, compared to previous estimates. Other aspects of power output, including the probable magnitude of inertial power, are considered in relation to published data.
Early Life Stages of Carp (Cyprinus Carpio L.) Depend on Ambient Magnesium for Their Development
Authors: Van Der Velden J. A. , Spanings F. A. T. , Flik G. , Bonga S. E. Wendelaar
Published: April 2021

Carp eggs, fertilized in vitro, were allowed to develop in fresh water with magnesium concentrations varying from 0·001 to 0·100 mmol l−1. Magnesium concentrations below 0·010 mmol l−1 seriously impeded carp embryonic development: the incidence of deformed larvae and mortality increased steeply to 100% at water magnesium concentrations of 0·001 mmol l−1. Thus, early life stages of carp require ambient magnesium for survival and successful development. The magnesium and calcium concentrations of the developing eggs were dependent on the ambient magnesium concentration. The uptake of magnesium by eggs decreased and the uptake of calcium increased with decreasing ambient magnesium concentrations. However, the uptake of the sum of these divalent ions seemed to be independent of ambient magnesium concentration. This indicates a competition between magnesium and calcium for (passive) uptake into developing eggs.
Behavioral Analysis of the Escape Response in the Juvenile Lobster Homarus Americanus Over the Molt Cycle
Authors: Cromarty S. I. , Cobb J. S. , Kass-Simon G.
Published: April 2021

Components of the escape response of the American lobster were compared over the molt cycle. Number of tailflips, frequency, duration and distance were measured. Velocity, acceleration, force and work were computed from the above measurements, using time-lapse video-recordings of escaping lobsters. Soft-shelled postmolt lobsters (stage B) traveled further, spent more time tailflipping and performed a larger number of tailflips than hard-shelled premolt lobsters (stage D). Hard-shelled lobsters had a more forceful initial power swim, achieved a higher overall velocity and acceleration and, therefore, produced more forceful swims with greater energy expenditure (measured by work output) than soft-shelled animals. Among hard-shelled lobsters, velocity, acceleration, force and work fell off markedly in the latter part of their subsequent swims as a consequence of the prolonged duration and reduced frequency of these swims. Soft-shelled lobsters sustained their swimming velocity, acceleration, force and work for their entire subsequent swimming response. There are likely to be large molt-related differences in energy metabolism, endocrinology and nerve and muscle physiology which lead to the observed differences in the escape response.
The Whole-Body Withdrawal Response Of Lymnaea Stagnalis I. IdentificatIon Of Central Motoneurones And Muscles
Authors: Ferguson Graham P. , Benjamin Paul R.
Published: April 2021

Two muscle systems mediated the whole-body withdrawal response of Lymnaea stagnalis: the columellar muscle (CM) and the dorsal longitudinal muscle (DLM). The CM was innervated by the columellar nerves and contracted longitudinally to shorten the ventral head-foot complex and to pull the shell forward and down over the body. The DLM was innervated by the superior and inferior cervical nerves and the left and right parietal nerves. During whole-body withdrawal, the DLM contracted synchronously with the CM and shortened the dorsal head-foot longitudinally. The CM and the DLM were innervated by a network of motoneurones. The somata of these cells were located in seven ganglia of the central nervous system (CNS), but were especially concentrated in the bilaterally symmetrical A clusters of the cerebral ganglia. The CM was innervated by cells in the cerebral and pedal ganglia and the DLM by cells in the cerebral, pedal, pleural and left parietal ganglia. Individual motoneurones innervated large, but discrete, areas of muscle, which often overlapped with those innervated by other motoneurones. Motoneuronal action potentials evoked one-for-one non-facilitating excitatory junction potentials within muscle fibres. No all-or-nothing action potentials were recorded in the CM or DLM, and they did not appear to be innervated by inhibitory motoneurones. The whole network of motoneurones was electrotonically coupled, with most cells on one side of the CNS strongly coupled to each other but weakly coupled to cells on the contralateral side of the CNS. This electrotonic coupling between motoneurones is probably important in producing synchronous contraction of the CM and DLM when the animal retracts its headfoot complex during whole-body withdrawal.
Visual and Acoustic Course Control in the Cricket Gryllus Bimaculatus
Authors: BÖHM HARTMUT , SCHILDBERGER KLAUS , HUBER FRANZ
Published: April 2021

T he influence of visual and acoustic stimuli on course control was studied in crickets walking on an air-supported sphere under open-loop conditions. The speed of walking elicited by a calling song was greater in the presence of visual targets than it was in the dark. The precision of phonotactic orientation was improved in the presence of visual cues. Visual and acoustic stimuli induced turning and when both stimuli were present at the same time their effects were additive. A further enhancement was observed when visual and acoustic stimuli were presented from the same direction. Optomotor stimuli also shifted the response to the calling song in an additive way.
Evaporative Cooling in the Desert Cicada: Thermal Efficiency and Water*sol;Metabolic Costs
Authors: HADLEY NEIL F. , QUINLAN MICHAEL C. , KENNEDY MICHAEL L.
Published: April 2021

Using plant xylem water for evaporative cooling, the desert cicada Diceroprocta apache can maintain a body temperature as much as 5°C below ambient (Ta=42°C). Simultaneous measurements of water loss and gas exchange for cicadas feeding on perfused twigs show substantial increases in transpiration at temperatures at which evaporative cooling begins (between 37 and 38°C), but only modest increases in Vo2 and Vco2. The extent and duration of evaporative cooling depend on the cicada's hydration state and the rate of water flux from cuticular pores located on the surface of the thorax and abdomen.
Electrophysiology of Swim Musculature in the Pteropod Mollusc Clione Limacina
Authors: SATTERLIE RICHARD A.
Published: April 2021

Intracellular recordings from the swim musculature of the pteropod mollusc Clione limacina revealed two types of activity during spontaneous swimming movements. One group of muscle cells produced either excitatory junctional potentials (EJPs) or spike-like responses during both slow and fast swimming. The second group of muscle cells were either silent or produced extremely small EJPs during slow swimming, and EJPs or spike-like responses during fast swimming. Injections of horseradish peroxidase (HEP) into the two types of muscle cells indicated that the former are slow-twitch fibers while the latter are fast-twitch fibers. A comparison of the two muscle cell types indicated that the slow-twitch fibers are larger and have less negative resting potentials than the fast-twitch cells. Electrical coupling was detected between pairs of slow-twitch cells, but could not be demonstrated between pairs of fast-twitch cells or between mixed pairs of cells. Spike-like responses in both cell types exhibited non-synaptic facilitation in response to direct depolarizing stimulation. Both the maximum size and the initial rate of facilitation were frequency-dependent. Spike-like responses were followed by a depolarizing afterpotential that apparently summed to produce a baseline depolarization that may be involved in non-synaptic facilitation.