bluuebunny/crossref_metadata_2025_split huggingface dataset:
Na+, K+ and Ca2+ Currents in Identified Leech Neurones in Culture
Authors: Stewart R. R. , Nicholls J. G. , Adams W. B. 
Published: April 2021

ABSTRACT
Na+, K+ and Ca2+ currents have been measured by voltage-clamp in Retzius (R), anterior pagoda (AP) and sensory (pressure, touch and nociceptive) cells dissected from the central nervous system (CNS) of the leech. These cells maintain their distinctive membrane properties and action potential configurations in culture. Currents carried by the individual ions were analysed by the use of channel blockers and by their kinetics. Since the cells are isopotential they can be voltage-clamped effectively. Depolarization, as expected, gave rise to an early inward Na+ current followed by a delayed outward K+ current. In Na+-free medium containing tetraethylammonium (TEA+), and in the presence of 4-aminopyridine (4-AP), inward Ca2+ currents were revealed that inactivated slowly and were blocked by Cd2+ and Mn2+. Na+ and Ca2+ currents were similar in their characteristics in R, AP and sensory neurones. In contrast, K+ currents showed marked differences. Three principal K+ currents were identified. These differed in their time courses of activation and inactivation and in their responses to Ca2+ channel blockers. K+ currents of the A-type (IA) activated and inactivated rapidly, were not affected by Ca2+ channel blockers and were eliminated by steady-state inactivation at holding potentials of −30 mV. A-type K+ currents were found in AP cells and as a minor component of the outward current in R cells. A Ca2+-activated K+ current (IC), that inactivated more slowly and was reduced by Ca2+ channel blockers, constituted the major outward current in R cells. The third K+ current resembled the delayed rectifier currents (IK1 and IK2) of squid axons with slow activation and inactivation kinetics. Such currents were found in R cells and in the sensory neurones (T, P and N). The principal differences in membrane properties of identified leech neurones can be explained in terms of the numbers of Na+ channels and the distinctive kinetics of K+ channels in each type of cell.
Distribution of Intersegmental Interneurones That can Reset the Respiratory Rhythm of the Locust
Authors: Ramirez J. M. , Pearson K. G. 
Published: April 2021

ABSTRACT
Interneurones in the respiratory rhythm generator of the locust were identified by means of intracellular recording and staining techniques. A description is made of the properties and structures of nine intersegmental neurones which reset the respiratory rhythm when injected with current pulses. All but one of these neurones discharged in phase with expiration. The injection of constant depolarizing current into these interneurones altered the respiratory rate (increase for six, decrease for three). The respiratory rhythm generator extends more posteriorly within the ventral nerve cord than the metathoracic ganglion. In the first fused abdominal ganglion, four individual interneurones were identified descending into the unfused abdominal ganglia. In the first unfused abdominal ganglion an intemeurone which reset the respiratory rhythm was found ascending into the metathoracic ganglion. The respiratory rhythm generator also extends more anteriorly within the ventral nerve cord than the metathoracic ganglion. Two interneurones influencing the respiratory rhythm send their axons from the first fused abdominal ganglion into the meta- and mesothoracic ganglia. One of these directly excited a mesothoracic intemeurone which also influenced the respiratory rhythm when injected with current. In the suboesophageal ganglion another intemeurone was found which, although capable of resetting the respiratory rhythm, was not alway active during respiration. We conclude that the respiratory rhythm generator is distributed over abdominal, thoracic and suboesophageal ganglia. At least one part of the respiratory rhythm generator (in the suboesophageal ganglion) is not always active and can be recruited during vigorous respiration. Thus the number of active components in the respiratory rhythm generator is variable and additional elements can be recruited depending on the behavioural situation.
Strontium is Required for Statolith Development and Thus Normal Swimming Behaviour of Hatchling Cephalopods
Authors: Hanlon Roger T. , Bidwell Joseph P. , Tait Richard 
Published: April 2021

ABSTRACT
When cephalopod eggs were incubated in artificial sea water it was found that they sometimes resulted in hatchlings with defects of the statocyst suprastructure, leading to the severe behavioural defect of uncontrolled swimming. Experiments in defined media (seven basic salts mixed in deionized water) with seven species of cephalopods demonstrated clearly that there is 100 % normal development of the aragonite statoliths when strontium levels were 8 mg l−1. Conversely, statoliths did not develop when strontium was absent. In cuttlefish, the growth of the cuttlebone was also affected adversely when strontium was absent. In mariculture production tanks, supplementing commercial artificial sea water with strontium to normal levels of 8 mg l−1 almost eliminated the occurrence of abnormal hatchlings. Circumstantial evidence indicates that there is a critical window in development during which strontium is required for normal development. The role of strontium in biomineralization during embryogenesis is unknown, but it appears to be important in the Mollusca.
Regional Differences in Cuticular Permeability in the Desert Cicada Diceroprocta Apache: Implications for Evaporative Cooling
Authors: Hadley Neil F. , Toolson Eric C. , Quinlan Michael C. 
Published: April 2021

ABSTRACT
The cuticular permeability of the desert cicada Diceroprocta apache was measured in vivo from three regions of the dorsal surface: (1) the midline of the thorax (= dorsal thorax), a region that contains large pores (7–8 μm in diameter) located in a central tract; (2) the lateral thorax, a region in which large pores are absent, and (3) the midline of the abdomen, a region in which large pores are uniformly distributed over the surface. Transcuticular water flux rates were similar for all three areas at 27·0°C; however, at 41·5°C rates increased sharply for the dorsal thorax and abdomen, with tracings showing numerous irregular peaks that represent cycles of water extrusion. Transcuticular water flux for the lateral thorax, in contrast, was relatively unaffected by the temperature increase and the tracings remained relatively flat. Death of the animal at the higher temperature resulted in a significant decrease in water loss rates and a loss of the cycling pattern in both the dorsal thorax and abdomen, whereas water loss through the lateral thorax did not change. The active extrusion of water begins at 39·2–39·3°C in both male and female cicadas. Our findings confirm that the large pores are the routes by which water reaches the surface and that the temperature at which this active extrusion of water begins corresponds to the point where cicadas must seek milder microclimates to prevent body temperature from reaching lethal levels.
The Relationship Between Diving Activity and Oxygen Storage Capacity in the Tufted Duck (Aythya Fuligula)
Authors: Stephenson R. , Turner D. L. , Butler P. J. 
Published: April 2021

ABSTRACT
For a period of 6 months, a group of eight tufted ducks (‘control’ ducks) were kept on a shallow outdoor pond and performed short dives to obtain food (maximum depth, 0·;65 m; observed mean duration, 10·9 ± 0·54 s). At the same time, a group of seven tufted ducks (‘dive-trained’ ducks) were kept on an adjacent deeper and partly covered pond, and performed ‘extended’ dives under the surface mesh in order to feed (maximum distance to food, 10m; observed mean dive distance, 6·0 ± 0·25 m; observed mean duration, 24·8 ± 0·58 s). At the end of this time, the calculated total usable oxygen store was approximately the same in control and dive-trained ducks (44 and 42 mlO2STPD kg−1, respectively), although the relative quantities of usable oxygen in each of the three main storage sites (respiratory system, blood and skeletal muscle) differed between groups.
The end-expiratory lung/air sac volume was found to be significantly smaller (P&lt;0·01) in the dive-trained ducks (165 ml BTPs kg−1) than in the control ducks (232 ml BTPs kg−1). The dive-trained ducks, however, had a significantly greater (P&lt;0·01) blood volume (141 ml kg−1) than the control ducks (107ml kg−1), although the blood oxygen capacity and several haematological indices (measured haemoglobin content, red blood cell count and haematocrit, and calculated mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration) were statistically the same in both groups. Mean corpuscular volume was significantly greater (P&lt;0·05) in the dive-trained ducks. The myoglobin content of the myocardium was the same in both groups. The pectoralis muscle and the locomotory leg muscles, however, contained significantly higher concentrations of myoglobin in the dive-trained ducks than in the control ducks (pectoralis, P&lt;0·05; lateral gastrocnemius and semitendinosus, P&lt;0·01).
It is suggested that the anatomical adaptations which occur in response to chronic increases in diving activity may increase the aerobic diving capacity of the tufted duck by effecting a decrease in buoyancy (reduced end-expiratory lung/air sac volume) and an increase in blood oxygen storage capacity (hypervolaemia). Locomotory muscle function may be maintained in the face of decreasing oxygen delivery during extended dives by means of increased myoglobin content after dive-training.
Efficiency of Rat Medial Gastrocnemius Muscle in Contractions with and Without an Active Prestretch
Authors: Haan A. De , Van Ingen Schenau G. J. , Ettema G. J. , Huijing P. A. , Lodder M. A. 
Published: April 2021

ABSTRACT
The efficiency of positive work was measured for rat medial gastrocnemius muscle at 25°C during repeated contractions. Six muscles were stimulated to perform concentric contractions preceded by an active prestretch (PS contractions) and six muscles made to give concentric contractions from an isometric state (PI contractions). Both lengthening and shortening of the muscles (distance: 6 mm) occurred at a constant velocity of 20 mms−1 (1·5 fibre lengths s−1). Stimulation was started 150 ms prior to the onset of concentric contraction for both types of contraction. For the PS contractions this meant that the active state was developed during the last 2·4 mm of the lengthening.
Energy consumption (calculated from high-energy phosphate consumption) appeared to be equal for both types of contraction, although positive work output was 39·4% higher in the PS contractions than in the PI contractions. The efficiency of positive work was 36·8 ± 3·5 % in the PS contractions and 26 ± 2·0 % in the PI contractions. In contrast to results of previous studies, the positive work done by the muscle in the PS contractions was much larger than the negative work done on the muscle during stretch owing to the applied stimulation protocol which was intended to simulate in vivo conditions during running. The efficiency of positive work in the PS contractions is too low to explain the efficiencies of 40–70 % reported for human and animal running.
A Reappraisal of the Oil-Gap Technique for the Measurement of Transtubular Potentials in Insect Epithelia
Authors: Isaacson Leon , Nicolson Sue 
Published: April 2021

ABSTRACT
Transtubular potentials of insect Malpighian tubules and salivary glands are commonly measured in unperfused tubules in which the two ends are separated by means of an insulating oil gap. The validity of this method has been examined, using Malpighian tubules of a tenebrionid beetle, Onymacris plana. The measured interelectrode potential was found to depend not only on the transtubular potential but also on potentials within the oil gap and at the open end of the tubule, and upon the core resistance, the length constant and a small but finite electrical leak beneath the insulating oil. In perfused tubules of O. plana, the apparent transtubular potential recorded at the collecting end (analogous to the oil gap) was indistinguishable from that previously measured with the oil-gap technique. However, it was invariably lower than that recorded by an intraluminal pipette. The results demonstrate that the interelectrode potential observed with the oil-gap technique is a poor measure of the true transtubular potential.
Peripheral Neurosecretory Cells of Insects Contain a Neuropeptide with Bursicon-Like Activity
Authors: Garcia-Scheible Isabel , Honegger Hans-Willi 
Published: April 2021

ABSTRACT
In insects, neurosecretory cells have been found not only within ganglia of the central and stomatogastric nervous system, but also in the peripheral nerves (Fifield & Finlayson, 1978; Wasserman, 1985; Baudry-Partiaoglou, 1987). These peripheral neurones and their processes along peripheral nerves contain electron-dense granules and stain with various dyes for neurosecretory cells, suggesting that they produce, store and probably release neurosecretory material. The nature of this material, however, is unknown. Only the results of Raabe (1986), showing that some abdominal peripheral neurosecretory cells of three insects are glucagonimmunoreactive, have suggested that such cells are peptidergic. We demonstrate in this study that a group of peripheral neurosecretory cells in crickets contains such a peptide. Moreover, we are able to suggest a function for this peptide and thus for an identified set of peripheral neurosecretory neurones.
A Simple and Low-Cost Illumination System for in vivo Fluorescent Visualization of Neurones
Authors: Büschges A. , Koch U. T. , Breutel G. 
Published: April 2021

ABSTRACT
The use of fluorescent dyes for staining neurones has become very common since the introduction of Lucifer Yellow (Stewart, 1978) because it permits high-luminance stainings, for detailed structural analysis, with a minimum of filling time. Lucifer Yellow has been used in a variety of techniques in neurophysiology: in vitro visualization (Stewart, 1978); killing of neurones or parts of neurones (e.g. Miller & Selverston, 1979; Miller & Jacobs, 1984); and in vivo visualization (e.g. Reichert & Krenz, 1986; Kater & Hadley, 1982). We describe a new system for in vivo and in vitro visualization. It can be used with a standard dissecting microscope, features a very simple optical design and costs much less than other systems used previously.
Effects of Octopamine on Calcium Action Potentials in Insect Oocytes
Authors: O’donnell M. J. , Singh B. 
Published: April 2021

ABSTRACT
Our experiments show that octopamine receptors are present on the developing follicles of an insect, Rhodniusprolixus. Application of D,L-octopamine decreased the duration and overshoot of calcium-dependent action potentials (APs), and increased the intrafollicular concentration of cyclic AMP. The threshold concentration of D,L-octopamine for the reduction in electrical excitability was between 1 and 5×10−7moll−1, and maximal effects of a 40–50% reduction in AP overshoot and duration were apparent at 10−4moll−1. At concentrations above 10−5moll−1, a small (&lt;10%) hyperpolarization of the resting potential was also apparent. Effects of D,L-octopamine on oocyte excitability were independent of these small shifts in resting potential.
Current injection experiments, in which calcium entry was blocked by cobalt, demonstrated that D,L-octopamine reduced membrane resistance at both hyperpolarizing and depolarizing potentials. Octopamine did not affect the maximum rate of rise of the AP, dV/dtmax, which is an indicator of inward calcium current. It is suggested that octopamine may mediate its effects on excitability through an increase in a voltage-dependent potassium conductance.
Application of other phenolamines indicated a rank order of potency of D,L-octopamine &gt; D,L-synephrine &gt; tyramine. The α-adrenergic agonists clonidine, naphazoline and tolazoline were without significant effect at 10−5–10−3moll−1. Reduction of excitability by D,L-octopamine was effectively blocked by phentol-amine and metoclopramide. Yohimbine and gramine were less effective as antagonists. Possible functions of octopamine receptors in insect follicles are discussed.
Renal Responses to Continuous and Short-Pulse Infusion of Arginine Vasotocin in the Toad Bufo Marinus
Authors: Toews Daniel P. , Mallet Maryse , Maclatchy Laura 
Published: April 2021

ABSTRACT
Chronically catheterized specimens of the toad Bufo marinus (L.) were given single bolus injections, periodic bolus injections, and continuous infusions (via peristaltic pump) of the neuropeptide arginine vasotocin (AVT). Urine flow and glomerular filtration rates (GFR) were monitored to quantify the antidiuretic response of the toad to AVT under these conditions. The response to single bolus injections was dissipated after 1 h, despite the continued presence of AVT, whereas continuous infusion of AVT at levels as high as 100 ng kg−1 was ineffective in lowering flow rates, suggesting that pulsatile increases in the hormone might be required to effect a more prolonged response. In toads which were ‘primed’ with AVT via continuous infusion with the pump, additional pulses of AVT were able to lower flow rates for 1 h, with sensitivity to the hormone decreasing with an increase in primed concentration of AVT. Pulses of AVT given to unprimed toads significantly lowered flow for over 2h. This study is the first to show that phasic bursts of AVT are more effective in regulating the renal response of the toad than are continuous, nonpulsatile infusions.
Selective Utilization of Serum Vitamin A for Visual Pigment Synthesis
Authors: Tsin Andrew T. C. , Gentles Suzanne N. , Castillo Elizabeth A. 
Published: April 2021

ABSTRACT
Two groups of goldfish (Carassius auratus) were subjected to light and temperature conditions known to promote a contrast in their scotopic visual pigment compositions. After 3 weeks, the porphyropsin/rhodopsin ratio in the neuroretina of these goldfish ranged from 99% porphyropsin in one group to 59% in the other. Samples of blood, liver and retinal pigment epithelium (RPE) were also removed from these animals and analysed by high-performance liquid chromatography (HPLC) for vitamin A composition. There was consistently more vitamin A2 than vitamin Aj (over 50% vitamin A2) in both vitamin A alcohol and vitamin A esters extracted from the liver and the RPE. In contrast, only 30% of all vitamin A extracted from the blood was vitamin A2. These observations suggest that it is mainly vitamin A1 that is transported in the blood, whereas vitamin A2 is selectively retained in the liver and in the RPE and used to form porphyropsin in the eye.
Aminergic and Peptidergic Modulation of Motor Function at an Identified Neuromuscular Junction in Helisoma
Authors: Zoran Mark J. , Haydon Philip G. , Matthews Paul J. 
Published: April 2021

ABSTRACT
Electrophysiological studies suggest that motoneurone B19 in the buccal ganglia of Helisoma makes monosynaptic, cholinergic connections with the supralateral radular tensor (SLT) muscle of the buccal mass. Serotonin (5-HT) and small cardioactive peptide B (SCPB) were found to have peripheral modulatory effects on this motor pathway that are consistent with their previously described central facilita tory effects. Both neurotransmitters, when applied exogenously (10−6moll−1) to isolated buccal ganglion-buccal muscle preparations, potentiated the magnitude of motoneurone B19-evoked muscle contractions (6·3 and 2·7 times, respectively) without affecting excitatory junctional potential (EJP) amplitudes. When applied to single dissociated SLT muscle fibres in cell culture, these modulators had similar effects on acetylcholine (ACh)-evoked muscle fibre shortening, demonstrating that these neuromodulators exert direct actions on the muscle cells.
The cardioactive peptide FMRFamide (10−6moll−1), although slightly potentiating muscle contractions in reduced neuromuscular preparations, significantly decreased both ACh-evoked muscle fibre shortening and depolarizing potentials in cultured SLTmuscle cells. The differential effects of FMRFamide may, in part, be due to the elimination of interactive effects between multiple neurotransmitters that might exist in semi-intact preparations and in vivo.
These results demonstrate that 5-HT, SCPB and FMRFamide in Helisoma can directly modulate the peripheral muscle targets of buccal motoneurones involved in the generation of cyclical feeding behaviour.
Desiccation Tolerance and Water-Retentive Mechanisms in Tardigrades
Authors: Wright Jonathan C. 
Published: April 2021

ABSTRACT
Tardigrades entering a state of anhydrobiosis (cryptobiosis) show considerable interspecific variation in desiccation tolerance, lower lethal humidities for initial desiccation ranging from 78 to 53%. Species most tolerant of rapid initial drying also show the most rapid acquisition of tolerance to low humidities (25–31% ) following drying in high humidity.
Surface area reduction during tun formation shows a significant positive regression against desiccation tolerance in the Eutardigrada. The most desiccation-tolerant species thus infold the largest areas of cuticle. By comparison, the heterotardigrade Echiniscus testudo shows a very poor capacity for surface area reduction. The thick dorsal plates may restrict cuticle intucking in this species.
When hydrated tardigrades are desiccated in 80% relative humidity they show a characteristic profile of mass loss, dehydrating rapidly in the first few minutes and then showing an abrupt reduction in transpiration (the ‘permeability slump’). This applies to living animals, which form tuns when desiccated, and to dead animals remaining extended. The permeability slump is not, therefore, a metabolic phenomenon and is not related to tun formation. Subsequent transpiration rates are very low and decline exponentially. The permeability slump allows animals to retain considerable amounts of internal water when desiccated, although less water is retained if the desiccation rate is increased. This may determine upper tolerable desiccation rates if a certain minimum quantity of water is required for the metabolic synthesis of membrane protectants. A significant positive regression between water retention and desiccation tolerance supports this hypothesis.
Acetylcholine-Activated Ion Channels In Embryonic Cockroach Neurones Growing In Culture
Authors: Beadle David J. , Horseman G. , Pichon Y. , Amar M. , Shimahara T. 
Published: April 2021

ABSTRACTApplication of acetylcholine and carbamylcholine to cultured cockroach neurones held under whole-cell voltage-clamp conditions evoked an inward current that was accompanied by an increase in current noise. Fluctuation analysis of the noise revealed the existence of two Lorentzian components in acetylcholine, of comer frequencies 10 ± 0·6 Hz and 116 ± 9 Hz, and one Lorentzian component in carbamylcholine, of corner frequency 35 ± 13 Hz. Single-channel analysis of the unitary currents evoked by acetylcholine or carbamylcholine in neurones held in the cell-attached mode of the patch-clamp technique revealed the presence of two categories of channel events. The large events had mean currents of 4·77 pA with acetylcholine and 5·09 pA with carbamylcholine, and the small events 1·92 pA (acetylcholine) and l·72pA (carbamylcholine) for a hyperpolarization of 60 mV. The reversal potentials for these currents relative to the resting potential were estimated to be −70 mV for acetylcholine and −68 mV for carbamylcholine, and the conductance values calculated from the l/V curves were 37 pS (large) and 19 pS (small) for acetylcholine and 52 pS (large) and 15 pS (small) for carbamylcholine. It is concluded that embryonic cockroach neurones growing in vitro possess two populations of acetylcholine-activated ion channels, and the possibility that one of these represents an embryonic receptor and the other an adult receptor is discussed.