bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Acclimation Effects on Carp Nerve: a Comparison of Nerve Conduction, Membrane Fluidity and Lipid Composition
Authors: Harper A. A. , Watt P. W. , Hancock N. A. , Macdonald A. G. 
Published: April 2021

ABSTRACT
This paper describes the effects in vitro of temperature (5–35°C) on the conduction properties of vagus nerves from freshwater carp Cyprinus carpio L., either cold-(8°C) or warm-(28°C) acclimated. The results are related to changes in the physical state and lipid composition of brain membrane fractions. The temperature dependence of the conduction velocity of the C (unmyelinated) component of the compound action potential (AP) were determined using Arrhenius plots. The relationship between log time-to-peak AP and the reciprocal of absolute temperature (1/K) is best described by two linear components. The grouped data for the warm-acclimated group had a break point at 23.6°C. At temperatures above 24°C the activation energy Ea was 18.3±8.33kJmol−1 and below 24°C Ea was 49.7±3.78kJmol−1. The break-point for cold-acclimated nerves was 17.4°C with Ea values of 41.2±2.65 and 13.2±3.63 kJ mol−1 below and above this temperature, respectively. The Arrhenius plots of the fast-conducting A (myelinated) component of the AP for the warm-and for the cold-acclimated group were better fitted by two linear relationships with Ea values of 42.0±2.16 and 86.9±4.55 Kj mol−1 above and below the break at 13.1°C for the warm-and cold-activated nerves, respectively, and Ea values of 18.0±5.45 and 58.8±4.08 kJ mol−1 above and below the break point, 19.3°C, for warm-and cold-acclimated nerves, respectively. Steady-state fluorescent polarization of 1,6-diphenyl-1,3,5-hexatriene-(DPH) labelled synaptosomal and myelin fractions of carp brain indicated partial homeoviscous adaptation in the membranes. Since there were no appreciable differences in their fatty acids, changes in membrane composition other than in the phospholipid fatty acids presumably occurred.
Is ‘Reflectance’ Basking Real?
Authors: Heinrich Bernd 
Published: April 2021

ABSTRACT
Various kinds of butterflies raise both (or sometimes one) of their pairs of wings while basking with their body at approximately right angles to the incident solar radiation and with their wings held at an acute angle to the incident sunlight. I here test the effects of wing posture on thoracic temperature in so-called ‘reflectance’ basking.
Butterflies with pale yellow or white dorsal wing surfaces held with their wings at 45, 90 or 180° with respect to each other (or 22–23, 45 and 90°with respect to the solar radiation) heated to mean thoracic temperatures (Tth) of 38.2, 39.5 and 39.9°C, respectively, in direct sunlight. These closely similar values of Tth are significantly different (P&lt;0.02) from each other, but the difference is in the opposite direction to that predicted by the solar reflectance hypothesis. The Tth of butterflies tested under a sun lamp in the laboratory showed the same trend of Tth with wing angle. Reflectance from the wings thus makes little or no practical contribution to the animal’s heating response. Butterflies with wings at 45°that were heated from above with a sun lamp showed an immediate increase in Tth when turned at right angles to a gentle air stream. Thoracic temperature immediately declined when they were again turned to face the air stream. Those butterflies that were at right angles to the air stream showed an immediate increase in Tth when the wings were raised from 180 to 45°, and their Tth again declined to previous values when the wings were again lowered. However, little or no effect of wing angle on Tth was observed when the wing angle of butterflies parallel to the air stream was altered.
These results indicate that wing elevation in basking butterflies does not increase Tth by way of solar reflection from the wings. Instead, the raised wings increase Tth by reducing convective cooling. ‘Reflectance’ basking is a form of dorsal basking used by species of butterflies that perch above vegetation rather than above a heated substratum.
Pyruvate Kinase From the Land Snail Otala Lactea: Regulation by Reversible Phosphorylation During Estivation and Anoxia
Authors: Whitwam Ross E. , Storey Kenneth B. 
Published: April 2021

ABSTRACT
Pyruvate kinase (PK) from tissues of the desert snail Otala lactea (Müller) undergoes a stable modification of its kinetic properties during estivation or in response to anoxia stress. In foot muscle and mantle, the kinetic changes induced by either state were virtually identical and were consistent with a less active enzyme form in estivation or anoxia: S0.5 PEP increased, and I50 values for Mg-ATP and L-alanine decreased, compared to the enzyme in control (aroused) snails. Estivation and anoxia also changed the properties of PK from hepatopancreas; some changes were consistent with a more active enzyme form (S0.5 PEP decreased, I50 values for Mg-ATP and L-alanine increased) but the enzyme lost all sensitivity to the potent activator fructose-l,6-bisphosphate. A time course of changes in I50 Mg-ATP for foot PK and S0.5 PEP for hepatopancreas PK revealed that estivation-induced changes in enzyme properties occurred between 12 and 48 h after snails were deprived of access to food and water, whereas the reversal of these changes occurred within as little as 10 min in foot muscle after arousal was initiated. The molecular basis of the stable modification of PK kinetics appears to be reversible protein phoshorylation. The action of added cyclic-AMP-dependent protein kinase on foot or hepatopancreas PK from control (aroused) snails changed PK kinetic parameters to those characteristic of the enzyme form in estivating animals; the addition of stimulators of endogenous cyclic-GMP-dependent protein kinase or protein kinase C had the same effect. Conversely, treatment with added phosphatases reconverted the properties of foot muscle PK from estivating snails to those characteristic of the control enzyme. The data suggest that reversible phosphorylation control over the activity state of regulatory enzymes of glycolysis is one mechanism contributing to the overall metabolic rate depression of the estivating state.
Regional Variation in the Current Flow Across an Insect Blood–Brain Barrier
Authors: Smith P. J. S. , Shipley A. 
Published: April 2021

ABSTRACT
One notable characteristic of the insect and vertebrate central nervous system is the presence of a clearly defined blood-brain barrier. In the insect this barrier is made up of the perineurial glial cells, and shows a heterogeneity in structure and possibly function between the connectives and ganglia. In this paper we have used a two-dimensional vibrating probe to investigate the net flow of electrical current across the barrier at various locations in the abdominal nervous system. The results show clear differences between different areas. There is a strong and consistent outward current flow (3.16 μAcm−2) perpendicular to the ganglion surface over the equatorial plane. Current returns through the peripheral nerves and the connectives. A detailed study of the latter shows that the net inward flow is principally over the initial section, immediately adjacent to the ganglia (2.1μAcm−2). The different current polarities can be correlated with structural differences in the underlying glial cells.
Characteristics of Five Types of K+ Channel in Cultured Locust Muscle
Authors: Miller B. A. , Usherwood P. N. R. 
Published: April 2021

ABSTRACT
K+ channel activity in cultured locust myofibres was investigated using gigaohm patch-clamp techniques. After 2 months in vitro the myofibres had a mean resting potential of -39±7mV (±S.D., N=42). Five types of K+ channel were identified at this time. The majority of single-channel events recorded from cell-attached patches were due to a small-conductance (type 1) and a large-conductance (type 2), inward rectifier, K+ channel. In cell-attached patches, with 180 mmol 1−1 KC1 in the patch pipette, the type 1 channel had a chord conductance of 43 pS for inward currents and 8pS for outward currents; the type 2 channel had a chord conductance of 115 pS for inward currents and 29 pS for outward currents. The type 2 channel exhibited bursting kinetics, was ATP-sensitive and could be blocked by Ba2+. Two other channels (types 3 and 4) had linear conductances of 130pS and 207pS, respectively. The type 3 channel was Ca2+-sensitive. A further channel (type 5) appeared to be an inward rectifier with a conductance of 5pS. Openings of types 3, 4 and 5 channels occurred less frequently than openings of the other two channels. Types 1, 2, 3 and 4 channels possessed multiple closed and open states with non-linear gating mechanisms.
A Temperature-Induced Switch From Diffusive to Convective Ventilation in the Honeybee
Authors: Lighton John R. B. , Lovegrove Barry G. 
Published: April 2021

ABSTRACT
It is known that many insects emit CO2 in widely spaced ‘bursts’ or discontinuous ventilation events, usually characterized by active abdominal ventilation. We describe the discontinuous CO2 emission characteristics of the honeybee (Apis mellifera ligustica Spinola), and utilize its ‘chill coma’ temperature threshold (12°C) to effect transitions from continuous, diffusive to discontinuous, convective ventilation regimes. Increasing temperature abruptly switched the dynamics of ventilation from diffusive and continuous (⩽11 °C) to convective and discontinuous (&gt;12°C). The ventilation cycle frequency was 7.84 mHz and CO2 output per ventilation event (burst phase) was 1.56μl neither variable was temperaturedependent in the range 12–15 °C. The rate of CO2 emission did not change significantly in the range 7–15 °C, possibly owing to increased membrane leakiness at lower temperatures. At 15°C, honeybee metabolic rate (2.69 W kg−1, mean mass 0.094 g) is similar to that of other similarly sized insects capable of significant endothermy.
An Interneurone Mediating Motor Programme Switching In The Ventilatory System of the Crab
Authors: Dicaprio Ralph A. 
Published: April 2021

ABSTRACT
The central pattern generator controlling ventilation in the crab can generate two distinct motor programmes, which determine the direction of water flow during irrigation of the gills. An interneurone has been identified that depolarizes when the ventilatory motor output switches from forward to reverse ventilation and remains depolarized for the duration of the reverse motor progamme. Depolarization of this neurone by intracellular current injection causes a switch in the motor programme from forward to reverse ventilation, which persists for the duration of the current step. Hyperpolarization of this cell during reverse ventilation terminates the reverse motor programme. The possible role of this reversal switch interneurone is considered in the context of the observed changes in the activity of other ventilatory interneurones and motor neurones during reverse ventilation.
Haemolymph Buffering in the Locust Schistocerca Gregaria
Authors: Harrison Jon F. , Wong Calvin J. H. , Phillips John E. 
Published: April 2021

ABSTRACT
The biochemical basis of buffering in the haemolymph of insects has received little attention, and the chemical complexity of insect haemolymph (reviewed by Mullins, 1985) suggests that the relative importance of various compounds to buffering may be quite different from that in other arthropods or vertebrates. Moreover, the role of bicarbonate as a buffer in insect haemolymph is difficult to evaluate because precautions to prevent carbon dioxide loss during sampling from insect haemolymph have generally been ignored, and titration techniques previously used to measure haemolymph buffer value allowed inadequate time for equilibration of the bicarbonate buffer system. In this study, we describe the biochemical basis of haemolymph buffering in the migratory locust Schistocerca gregaria.
Effect Of Boundary Layers On Cutaneous Gas Exchange
Authors: Pinder Alan W. , Feder Martin E. 
Published: April 2021

ABSTRACT
Boundary layers may offer significant resistance to cutaneous oxygen uptake by amphibians in water. This hypothesis was tested by measuring resistance to oxygen uptake as a function of water velocity in bullfrogs submerged at 5 °C and by direct measurements of the boundary layer with oxygen microelectrodes.
The oxygen diffusion boundary layer was easily measurable with oxygen microelectrodes. The proportion of the total resistance to oxygen uptake represented by the boundary layer increased from 35 % at a water velocity of 5cms−1 to over 90% at 0.1 cm s−1. At water velocities below 1cms−1 oxygen uptake was limited by the resistance of the boundary layer. At 0.1 cm s−1, the partial pressure of oxygen immediately adjacent to the skin was only 2 kPa (15 mmHg); placing an immobilized frog ln still water was tantamount to placing lt in anoxic water. Body movements disrupted boundary layers efficiently; even occasional small movements by the animal (1min−1) were sufficient to maintain oxygen uptake in still water.
GTP-γ-S Increases the Duration of Backward Swimming Behavior and the Calcium Action Potential in Marine Paramecium
Authors: Bernal Juan , Kelsey Anita Mcilveen , Ehrlich Barbara E. 
Published: April 2021

ABSTRACT
Behavioral and electrophysiological experiments were made to examine the hypothesis that G-proteins modulate the voltage-dependent calcium channel in the marine ciliate Paramecium calkinsi. It was found that guanosine-5’-O-(3-thiotriphosphate) (GTP-γ-S), an analogue of GTP that binds to and activates G-proteins, increased the duration of backward swimming behavior in reversibly permeabilized Paramecium in an irreversible and concentration-dependent manner. At 1 μmol 1−1 GTP-γ-S, the duration of backward swimming behavior was increased fivefold. Other nucleotides and related compounds did not have a significant effect on the backward swimming behavior. To evaluate whether the behavioral effects were due to ion channel modulation, the calcium action potential in intact Paramecium was monitored before and after guanine nucleotide injection. Within 5 min after the injection of GTP-γ-S or GTP into the cell, the duration of the calcium action potential was prolonged at least threefold. Like the behavioral response, the GTP-y-S effect on the calcium action potential duration was irreversible, whereas the effect of GTP began to decay after 6 min. GDP-β-S, which binds to and inactivates G-proteins, markedly reduced the calcium action potential within 5 min after injection. These results support the hypothesis that the voltage-dependent calcium channels present in Paramecium are modulated by GTP-binding proteins.
Cold-Tolerance Mechanisms of the Antarctic NematodePanagrolaimus Davidi
Authors: Wharton D. A. , Brown I. M. 
Published: April 2021

ABSTRACTWhen free of surface water in air or liquid paraffin, the antarctic nematode Panagrolaimus davidi is freezing intolerant but avoids freezing by supercooling. Survival of long-term exposure is enhanced by sub-zero temperatures compared with controls maintained at 99% relative humidity and 15 °C. In water the nematodes are seeded by exogenous ice nucleation and a proportion are freezing tolerant. Ice formation appears to be restricted to the pseudocoel. The degree of freezing tolerance is dependent upon the age of the culture and its thermal history. P. davidi is freezing tolerant when exposed to sub-zero temperatures in water and freezing intolerant when free of surface water and able to supercool. These two strategies are not mutually exclusive as they are often thought to be in arthropods.
Five Different States of Ciliary Activity in the Epaulette of Echinoplutei
Authors: Mogami Yoshihiro , Fujima Kikuyo , Baba Shoji A. 
Published: April 2021

ABSTRACT
Movement and spontaneous responses of the epaulette cilia of free-swimming eight-armed echinoplutei were analyzed by means of high-speed video microscopy. In addition to the two cyclic activities, normal beating for forward swimming and reversed beating for backward swimming, we identified another cyclic and two noncyclic states of ciliary activity. Intermediate beating was found during the transition from reversed beating to normal beating. One of the noncyclic states, the upright-inactive state, was found only after reversed beating and then changed to another noncyclic state, the inclined-inactive state, prior to a return to normal beating. Transitions within the cyclic and noncyclic states occurred in both directions, while transitions between the cyclic and the noncyclic states were in one direction.
Three Anthozoan Neuropeptides, Antho-RFamide and Antho-RWamides I and II, Modulate Spontaneous Tentacle Contractions in Sea Anemones
Authors: McFarlane Ian D. , Grimmelikhuijzen Cornelis J. P. 
Published: April 2021

ABSTRACT
Behavioural coordination in sea anemones involves both excitation and inhibition. Examples include reciprocal inhibition between longitudinal and circular muscles (Batham and Pantin, 1954), inhibitory actions during peristalsis (Ewer, 1960; McFarlane, 1974a), joint excitatory and inhibitory innervation of sphincter muscle (Lawn, 1976) and inhibition of neural pacemakers (McFarlane, 1974b).
Different Hemocyanin Oxygen-Affinities in Carcinus Maenas from Maine and Arcachon
Authors: Burnett Louis E. , Mangum Charlotte P. 
Published: April 2021

ABSTRACT
The green or shore crab Carcinus maenas (Linnaeus) is believed to have emigrated by ship from its native Europe to the Atlantic coast of North America. The chronological sequence of new records suggests the arrival in New York of pioneer individuals in the early 19th century, followed by gradual northward extension of the species range (Almaca, 1963; J. T. Carlton, personal communication). The number of immigrations and the present genetic relationships of various populations are unknown.
Patterns of Synaptic Drive to Ventrally Located Spinal Neurones inRana TemporariaEmbryos During Rhythmic And Non-Rhythmic Motor Responses
Authors: Soffe S. R. , Sillar K. T. 
Published: April 2021

ABSTRACTIntracellular recordings have been made from ventrally located neurones in the spinal cord of Rana temporaria embryos at around the time of hatching. Both short-latency ‘reflex’ and more prolonged rhythmic motor responses can be elicited by stimulation of the skin in immobilized embryos. Initial responses to single-sided skin stimuli usually involve excitation of neurones on the opposite side and strychnine-sensitive inhibition of neurones on the same side. Less reliable responses to dimming the lights also involve initial excitation on one side associated with inhibition on the opposite side. Intracellular recordings from single neurones during rhythmic activity show that on each cycle the same neurone can fire one or many spikes during the course of a single evoked or spontaneous episode. Bursts occur at longer cycle periods, generally at the start of episodes; single spikes occur at shorter cycle periods, generally later in episodes. During sustained rhythmic responses, neuronal membrane potential is generally depolarised and returns gradually to its resting level at the end of the episode. During the episode, relatively depolarising phases of synaptic excitation alternate with relatively hyperpolarising phases of chloride-dependent synaptic inhibition. Cell input resistance is reduced by around 50% throughout each episode. Within each cycle, input resistance is reduced further during the hyperpolarising phase than during the depolarising phase. Rhythmic excitation and inhibition of ventrally located neurones appears to be similar throughout the whole range of cycle periods, supporting the suggestion that a single rhythm-generating system with a wide ‘permissive’ range drives rhythmic movements in R. temporaria embryos.
Gigaohm Single-Channel Recording From Isolated Hermissenda Crassicornis Type B Photoreceptors
Authors: Etcheberrigaray R. , Huddie P. L. , Alkon D. L. 
Published: April 2021

ABSTRACT
Invertebrate photoreceptor electrophysiology has mainly been studied with intracellular microelectrodes. Single-channel recording has proved to be difficult, possibly because of unusual plasma membrane configurations; in Limulus polyphemus successful gigaohm seals were obtained only after pronase treatment and brief sonication (Bacigalupo and Lisman, 1983). Here we describe an isolated Hermissenda eye preparation that permits single-channel recording (Hamill et al. 1981) from identified type B photoreceptors; this photoreceptor sub-type has been assiduously studied with intracellular microelectrodes, under both current-clamp and voltage-clamp conditions. Associative conditioning of Hermissenda crassicornis (in the paired fight and rotation paradigm) is attributable in part to the reduction of potassium conductances in the type B photoreceptors (Alkon, 1984, 1987; Alkon et al. 1985). We have used the isolated eye preparation to characterize two types of potassium channels in photoreceptor plasma membranes.
The Role of the Pectoral Fins in Station-Holding of Atlantic Salmon Parr (Salmo Salar L.)
Authors: Arnold G. P. , Webb Paul W. , Holford B. H. 
Published: April 2021

ABSTRACT
Benthic fish resist downstream displacement in a current by balancing drag, the force orientated downstream, with the friction force. The friction force is μ (Wo—L), where μ is the friction coefficient, Wo the weight force of the fish in water (N), and L the lift force (N) acting on the body and fins (Arnold and Weihs, 1978). Above a critical speed, friction is insufficient to counteract drag and the fish must either swim or seek shelter from the flow. This note reports tests of the commonly proposed hypothesis (e.g. Kalleberg, 1958; Keenleyside and Yamamoto, 1962; Jones, 1975; Wankowski, 1981) that the pectoral fins are important to station-holding in Atlantic salmon, acting as hydrofoils generating negative lift.
Calcium Uptake by Mitochondria Isolated from Muskrat and Guinea Pig Hearts
Authors: McKEAN Thomas A. 
Published: April 2021

ABSTRACT
Subsarcolemmal and interfibrillar mitochondria were isolated from the hearts of the diving muskrat and non-diving guinea pig and direct and indirect measurements of calcium uptake were examined in vitro. The calcium-stimulated respiration rate and 45Ca uptake were measured and found to be greater in muskrat than in guinea pig mitochondria. Muskrat mitochondria were able to endure a greater external calcium concentration than guinea pig mitochondria before exhibiting indications of inner membrane damage. Calcium uptake by muskrat heart mitochondria was inhibited more by 1 mmol 1−1 MgCl2 than was uptake by guinea pig mitochondria. No differences were detected between the interfibrillar and subsarcolemmal populations of mitochondria within species. An increased ability to sequester calcium by mitochondria without causing them damage may aid an animal during recovery from hypoxia, ischemia or acidosis.