bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relationship between body mass and rate of rewarming from hibernation and daily torpor in mammals
Authors: Geiser F. , Baudinette R. V. 
Published: April 2021

ABSTRACTRewarming rate from torpor and body mass were inversely related in. 86 mammals ranging in body mass between 2 and 8500 g. Most of the mammalian taxa investigated showed a similar change of rewarming rate with body mass. Only the insectivores showed a more pronounced increase in rewarming with a decrease in body mass than did the other taxa. The rates of rewarming of marsupials were similar to those of placentals. At low air temperature (Ta), the rate of rewarming of marsupials was not related to body mass, although a strong relationship between the two variables was observed in the same species at high Ta. The slopes relating rewarming rates and body mass of the mammalian groups and taxa analysed here were similar to those obtained earlier for mass-specific basal metabolic rate (BMR) and body mass in mammals, suggesting that the rate of rewarming and BMR are physiologically linked.
Patch-clamp Study of the Properties of the Sodium Current in Cockroach Single Isolated Adult Aminergic Neurones
Authors: Lapied Bruno , Malécot Claire O. , Pelhate Marcel 
Published: April 2021

ABSTRACTThe properties of the fast Na+ inward current of the aminergic neurosecretory dorsal unpaired median (DUM) cells isolated from the sixth abdominal ganglion of the cockroach Periplaneta americana were studied with the whole-cell clamp technique in the presence of Ca2+ and K+ channel blockers. In about 80% of the cells, the current activated at –35 mV, was maximal at –10 mV and reversed at +48mV (Vrev), very close to VNa, the equilibrium potential for Na+ (+47.9mV). Vrev followed VNa when the external Na+ concentration was varied and the current was entirely suppressed by 1.0×10−7mol l−1 saxitoxin (STX), indicating that it was carried by Na+. In the remaining cells, an STX-sensitive maintained current was observed, the peak current–voltage relationship having almost the same characteristics except that an additional small shoulder was present between –90 and –35 mV, suggesting the existence of two types of Na+ channels. Na+ channels were half-inactivated at –41.1 mV and half-activated at –25.8mV. The overlap of inactivation (h∞) and activation (m∞) parameters was important (–70 to + 10mV). h∞ was not well fitted by a single Boltzmann distribution for potentials more negative than –70mV, indicating more than one process of inactivation. The half-times of activation and of inactivation of the Na+ current were voltagedependent, strongly decreasing with increasing pulse amplitude. The time courses of both inactivation and recovery from inactivation were best described by the sum of two exponentials. The two components of inactivation did not contribute equally to the decay of the current; the fast component accounting for more than 90% of the inactivation at positive potentials. Taken together, the results suggest that the Na+ channels of DUM neurones have more than one open state and/or more than one inactivated state.
Do Cicadas Radiate Sound through their Ear-Drums?
Authors: Young David 
Published: April 2021

ABSTRACTSound output was investigated in males of two cicada species, Cyclochila australasiae Donovan and Macrotristria angularis Ståhl. These are large insects, about 4·5 cm in length, with a typical arrangement of sound-producing organs. Songs produced by both species consist of continuous trains of sound pulses, with a fundamental frequency close to 4 kHz. Higher harmonics fall below the 4 kHz peak by 20–30 dB. These songs are the loudest yet recorded among insects: 110 dBSPL at 20cm for the protest songs of both species, and values as high as 115 dB for the vigorous calling songs of C. australasiae (mean 113 dB). The male tympanum (ear-drum) is between 3·3 (M. angularis) and 5·5 (C. australasiae) times greater in area than that of the female, which does not sing. The tympana and folded membranes, as well as the sound-generating tymbals, vibrate vigorously during singing; other parts of the insect do not vibrate. Sound output is greatest at the gap between the tympana and their protective coverings, the opercula. High values are also found close to the tymbals but not over the rest of the body. When the gap between tympana and opercula is held closed, rather than open, sound output falls by 11 dB. In the field, calling males adopt a characteristic posture, which keeps this opercular gap wide open. Ablating the tympana makes no difference to the sound output. But ablating the posterior half of the abdominal air sac produces a mean fall of 8.6 dB, together with a great broadening of the song’s frequency content. The above results support the conclusion that the majority of sound is radiated through the tympanal opening in typical cicadas, with the tympana being driven passively by the resonant vibrations of air in the air sac. This system can be modelled as a Helmholtz resonator, with the tympanal opening representing the neck of the resonator.
Scaling Effects on Muscle Function: Power Output of Isolated Fish Muscle Fibres Performing Oscillatory Work
Authors: Altringham John D. , Johnston Ian A. 
Published: April 2021

ABSTRACTBundles of 3–10 live fast fibres were isolated from the abdominal myotomes of cod (Gadus morhua L.) 13–67 cm in length. The preparations performed work under conditions simulating their activity during swimming: sinusoidal length changes were imposed about in situ fibre length, and the fibres were stimulated at a selected phase in each cycle. Strain amplitude, and the number and timing of stimuli were chosen to give maximum power output over a wide range of cycle/tailbeat frequencies. For each preparation power output was maximal at a particular frequency, although the peaks were rather broad. As the size of the fish increased the cycle frequency for maximum power output (fopt) decreased, from 12.5 Hz (13 cm fish) to 5 Hz (67 cm fish) (fopt=1.67 L−0.52, where L is body length).
Electrolyte and Gas Exchange During the Moulting Cycle of a Freshwater Crayfish
Authors: Wheatly Michele G. , Ignaszewski Lori A. 
Published: April 2021

ABSTRACTWhole-animal net electrolyte fluxes (Ca2+, apparent H+, titratable acidic equivalents, ammonia, Na+, Cl−, K+, Mg2+, phosphate and sulphate) and respiratory gas exchange were monitored throughout the moulting cycle in juvenile freshwater crayfish Procambarus clarkii (Girard) at 21 °C. Intermoult crayfish were essentially in ion balance. As crayfish approached ecdysis (–3 days, where t=0 is the day when the cuticle is shed), there was a net efflux of Ca2+ (–1000μmol kg−1 h−1) correlated with a corresponding uptake of acidic equivalents (or base output) of +2000 μmol kg−1 h−1. Following ecdysis, both fluxes switched vector; uptake of Ca2+ (+2000/mol kg−1 h−1) and basic equivalents (+4000μmol kg−1 h−1) were completed within 6 days. The moulting cycle also affected fluxes of electrolytes other than those involved in CaCO3 resorption and deposition. Crayfish remained in Na+ and Cl− balance from intermoult up to ecdysis. Following ecdysis, both were taken up actively at rates of around +500μmol kg−1 h−1 for 3 days, presumably restoring the haemodilution that would have resulted from water loading. A premoult efflux of K+ was partially offset by postmoult uptake. Meanwhile, crayfish experienced increased efflux of phosphate following ecdysis, probably because of increased integumentary permeability. Rates of O2 uptake and CO2 excretion increased to peak values (double intermoult rates) immediately prior to ecdysis. While recovered during postmoult, dropped precipitously, significantly reducing the gas exchange ratio. Since the deficit agreed well with the postmoult basic equivalent uptake, the latter is probably attributable to HCO3− uptake for calcification.
Leg-Induced Steering in Flying Crickets
Authors: May Michael L. , Hoy Ronald R. 
Published: April 2021

ABSTRACTOver 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

ABSTRACTGABA-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

ABSTRACTData 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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTIntracellular 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

ABSTRACT
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.