bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Lanthanum Ions on Neuromuscular Transmission in Insects
Authors: Washio Hiroshi , Miyamoto Takenori 
Published: April 2021

ABSTRACTThe effect of extracellular lanthanum on neuromuscular transmission was studied in cockroach leg muscle and larval mealworm ventral muscle by means of microelectrodes. Miniature excitatory postsynaptic potential (MEPSP) frequency was markedly increased after lanthanum was added, in the presence and absence of calcium. The potentiation by La3+ was suppressed in a high Ca2+ saline and enhanced in the absence of Ca2+. Lanthanum ions blocked neuromuscular transmission at a concentration as low as 0-1 mm. The quantal content estimated by the failure method was reduced by 80% in the presence of 0·1 mm-La3+. The reduction in the EPSP amplitude by La3+ may be due to a decrease in the amount of transmitter released by a nerve impulse. The response to L-glutamate applied iontophoretically was also reduced in the presence of La3+. It seems unlikely that La3+ and L-glutamate were competing for a common binding site on the postsynaptic membrane since the apparent maximum of the dose-response curve for glutamate-induced depolarization was reduced in the presence of La3+. External recording of MEPSPs showed that adding lanthanum to the bathing medium increased the time constant of decay of the potential. These results suggest that lanthanum does indeed have a postsynaptic action in addition to its prejunctional action in insect muscle fibres.
Cardiac Performance in thein SituPerfused Fish Heart During Extracellular Acidosis: Interactive Effects of Adrenaline
Authors: Farrell A. P. , Macleod K. R. , Driedzic W. R. , Wood S. 
Published: April 2021

ABSTRACTThe physiological integrity of the in situ perfused heart of the ocean pout was established by its ability to maintain cardiac output (Q̇) over a range of work loads, and by the dependence of Q̇ upon the filling pressure of the heart. Similar observations have been reported previously for the in situ perfused heart of the sea raven. Physiological levels of extracellular acidosis (pH 7·6/1% CO2 and pH 7·4/2% CO2) significantly depressed cardiac performance in sea raven and ocean pout hearts in situ. Negative chronotropic and inotropic responses were observed. Adrenaline (AD; 10−7M) under control conditions (pH7·9/0·5% CO2) produced a sustained tachycardia. The tachycardia reduced filling time of the ventricle and stroke volume was compromised because of the constant preload to the heart. Consequently, AD produced only an initial, transient increase in stroke volume and Q̇. Thereafter, stroke volume was reduced in proportion with the increase in heart rate, and Q̇ remained unchanged. The combined challenge of extracellular acidosis and AD demonstrated interactive effects between AD and acidosis in situ. Q̇ and power output were maintained in both species at both levels of extracellular acidosis during the combined challenge. Thus AD alone can maintain (but not improve upon) basal 0 during extracellular acidosis. The effects of extracellular acidosis, circulating catecholamines and venous return pressure to the heart are discussed in relation to the regulation of Q̇ following exhaustive exercise.
Graded Potentials and Spiking in Single Units of the Oval Organ, A Mechanoreceptor in the Lobster Ventilatory System
Authors: Bush B. M. H. , Pasztor V. M. 
Published: April 2021

ABSTRACT
The peripheral dendritic arborizations of sensory units X, Y and Z of the oval organ have similar branching patterns. All three permeate the whole array of connective tissue strands without apparent regionalization or specialization. The analogue components of sensory responses elicited in fibres X, Y and Z when the connective tissue array is stretched show considerable diversity: fibre Z has a higher threshold than X and Y; the dynamic peak values of X and Y saturate at pulls mid-range for Z; X, Y and Z form a spectrum of increasing adaptation. Application of TTX abolishes impulse generation in fibre X earlier than in fibre Y, indicating diversity in spike initiating mechanisms from one fibre type to another. Fibre X only spikes between certain limits of membrane depolarization. Usually the response includes one to five spikes which occur during the dynamic phase of a trapezoidal stretch stimulus. Fibre Y fires throughout the stimulus duration for pulls of moderate amplitude and velocity. Spiking inactivation and a low maximum firing frequency (approximately 80s−1) limit the range of length sensitivity in fibre Y. Fibre Z attains higher firing frequencies than either X or Y (approximately 110 s−1). The initial burst frequency (velocity dependent) may equal the firing rate of the dynamic peak.
Graded Potentials and Spiking in Single Units of the Oval Organ, a Mechanoreceptor in the Lobsterventilatory System Iii. Sensory Habituation to Repetitive Stimulation
Authors: Pasztor V. M. , Bush B. M. H. 
Published: April 2021

ABSTRACT
When the oval organ is stimulated repetitively at frequencies imitating normal scaphognathite beating the responses of the three sensory afferents decline. The number of spikes per response diminishes, the firing rate declines and the latency of the first spike may increase. The term ‘sensory habituation’ is proposed to describe the decline in response of a primary sensory unit to a repetitive train of identical stimuli. The decline in spiking performance is shown to be due to some or all of these underlying changes: (a) a decline in the rate of rise of the graded potential, (b) a decline in amplitude of the graded potential, (c) a decline in the rate of growth of the active process leading to spike initiation and (d) a rise in spiking threshold. The graded potential undergoes less of a reduction than impulse generation. Tetrodotoxin-treated fibres show little habituation to stretch. Normal fibres habituate to repetitive pulses of depolarizing current. It is suggested that during regular quiet ventilation the analogue signal alone provides feedback. Any extraneous perturbation or change in scaphog nathite rhythm restores spiking.
α-Bungarotoxin Blocks Excitatory Synaptic Transmission Between Cercal Sensory Neurones and Giant Interneurone 2 of the Cockroach,Periplaneta Americana
Authors: Sattelle D. B. , Harrow I. D. , Hue B. , Pelhate M. , Gepner J. I. , Hall L. M. 
Published: April 2021

ABSTRACTAutoradiographic localization of an 125I-α-bungarotoxin binding component revealed that specific binding was distributed mainly in the neuropile and to some extent in the periphery of the terminal abdominal ganglion of the cockroach, Periplaneta americana (L.). Action potentials recorded from the axon of GI2 under current-clamp conditions were not affected by exposure to 1·0 X 10−5M α-bungarotoxin. Excitatory postsynaptic potentials recorded from GI2, evoked by stimulation of cereal sensory neurones, were sensitive to block by relatively low concentrations (1·0 X 10−9-l·0x 10−7 M) of α-bungarotoxin. The timecourse for blockade was found to depend on toxin concentration and frequency of afferent stimulation. Excitatory postsynaptic potentials recorded from GI 2 were not affected by exposure to 1·0 X 10−6M quinuclidinyl benzilate. We conclude that at least a portion of the 12SI-α-bungarotoxin binding component represents cholinergic receptors which have a postsynaptic function at synapses between cereal sensory neurones and GI 2.
Patterns and Control of Neurosecretion for the Cytochromogenic Hormone in Blaberus Discoidalis Cockroaches
Authors: Hayes Timothy K. , Keeley Larry L. 
Published: April 2021

ABSTRACT
Corpora cardiaca (CC) from immature and adult Blaberus discoidalis Serville of both sexes contained approximately equal amounts of activity for the cytochromogenic hormone (CGH), a neurohormone which stimulates cytohaem synthesis in fat body mitochondria on day 4 of adult life. CGH activity remained at a constant level in the CC of males during days 0 and 1 of adult life, decreased during days 2 and 3, and then returned to the original level by day 4. Female CC followed a similar pattern except that the period of low CGH activity occurred 1 day later. Variations in early adult feeding patterns or in daily photoperiod did not change the secretory pattern of CGH. However, injections of juvenile hormone III stimulated a precocious release of CGH on days 0–1. Thus, CGH and juvenile hormone may function in this insect as a coordinated endocrine sequence directing metabolic maturation of the fat body during early adult life.
The Disappearance of Moulting Fluid in the Tobacco Hornworm, Manduca Sexta
Authors: Cornell John C. , Pan M. L. 
Published: April 2021

ABSTRACT
In Manduca sexta, and other insects, moulting fluid (MF) accumulates after apolysis in the exuvial space which underlies the old cuticle, and then most of it disappears shortly before ecdysis (see reviews by Zacharuk, 1976; Jungreis, 1979). Moulting fluid digests and weakens the old endocuticle so that the animal may free itself at ecdysis, and the digested components of the old endocuticle are reabsorbed. In M. sexta, Jungreis (1979) found that MF is produced between 30 and 12 h before the larval-pupal ecdysis (LPE) and it begins to disappear about 9 h before the LPE (LPE –9h). By LPE –3 h, most, but not all, of the MF has disappeared. We have found that MF represents a significant fraction of the total body water, 14·7% body weight (bw) [0·579 ± ·042 (5) ml, mean ± S.E. (N)] at LPE –6h.
Influence Of Some Common Methylxanthines on Contractile Responses and Calcium Mobilization of Ileal, Vas Deferens and Bladder Smooth Muscle
Authors: Huddart H. , Bayton E. , Shanklin J. 
Published: April 2021

ABSTRACTCaffeine and theophylline (0·1–5· MM) relaxed rat ileal muscle and reduced spontaneous rhythmicity. They inhibited the K-induced tonic contractures of rat vas deferens and bladder muscle strips but were without significant effect on the phasic responses to K. Theobromine (1·0–2·5 mm) induced contractures in ileal muscle and enhanced both the phasic and tonic components of K-induced contractures in vas deferens and bladder muscle strips. Theophylline and caffeine inhibited by varying degrees the 45Ca efflux from ileal, vas deferens and bladder muscle strips during the slow intracellular phase, but theobromine significantly stimulated 45Ca slow compartment efflux in all three types of muscle. Caffeine and theophylline both depressed, to varying degrees, the 45Ca influx into all three muscles while theobromine stimulated 45Ca influx in all cases. Caffeine and theophylline were either without much effect or slightly stimulated calcium binding by microsomes and mitochondria isolated from ileum, vas deferens and bladder, while theobromine significantly inhibited calcium binding by both sub-cellular fractions in all three muscles. The inhibitory action of caffeine and theophylline on these muscles appears to be due to inhibition of calcium influx coupled with some stimulation of intracellular binding. Theobromine’s excitatory action appears to be related to stimulation of calcium influx and inhibition of cellular calcium binding.
Actions of Cholinergic Pharmacological Agents on the Cell Body Membrane of the Fast Coxal Depressor Motoneurone of the Cockroach (Periplaneta Americana)
Authors: David J. A. , Sattelle D. B. 
Published: April 2021

ABSTRACT
The pharmacological properties of cholinergic receptors on the cell body membrane of the fast coxal depressor motoneurone (Df) of the cockroach (Periplaneta americana) have been investigated. Parallel dose-response curves were obtained for the depolarizing actions of four bath-applied agonists, with the following order of effectiveness: nicotine &gt; acetylcholine (ACh), in the presence of 1·0×10−7M neostigmine &gt; carbamylcholine &gt; tetramethylammonium. By contrast, dimethyl–4-phenyl piperazinium, suberyldicholine, D,L-muscarine, oxotremorine, acetyl-β-methylcholine and sebacinylcholine were practically ineffective. Of the three putative receptor-specific ligands used to date in binding studies on insect CNS tissues, α-bungarotoxin (α-BGTX) was much more effective (I50 = 6·4x 10−8M) in blocking the depolarization resulting from ionophoretic application of ACh, than either quinuclidinyl benzilate (QNB) (I50 =1·6×10−4 M) or decamethonium (I50 = 2·8×10−3 M). The order of effectiveness of ligands that were particularly effective in blocking ACh depolarization was β-BGTX &gt; α-cobratoxin (α-COTX) &gt; mecamylamine &gt; dihydro-β-erythroidine &gt; benzoquinonium. Less potent and almost equally effective were atropine, rf-tubocurarine, pancuronium and quinuclidinyl benzilate. Even less effective were hexamethonium, gallamine, decamethonium and succinylcholine, all requiring concentrations of ∼ 1·0× 10−3M and higher to produce a significant block of the ACh response. Not all reversibly acting antagonists were equally effective in preventing irreversible block of the ACh-induced depolarization by α-BGTX. Whereas α-COTX protected the receptors, mecamylamine did not. With the cell body of Df voltage clamped, the degree of antagonism of the ACh-induced current was assessed at potentials in the range −120 mV to −60 mV. a-BGTX, dihydro-β-eryth-roidine, benzoquinonium, QNB and décaméthonium appeared to be voltage-independent over this potential range, whereas J-tubocurarine and atropine were strongly voltage-dependent in their blocking actions. Sites of action of cholinergic antagonists at the insect ACh receptor/ion channel complex are discussed.
Properties of Ventral Cerebral Neurones Involved in the Feeding System of the Snail, Lymnaea Stagnalis
Authors: Mccrohan C. R. 
Published: April 2021

ABSTRACT
Four identified neurone types (CV3, 7, 5 and 6), located in the ventral cerebral ganglia of Lymnaea stagnalis, are described. These cells have axonal projections in one or more of the nerves innervating the lips. In addition, they show rhythmic synaptic inputs leading to strong burst activity in phase with cyclic output from the buccal ganglia, suggesting a role in the control of the oral aperture during feeding. The innervation of lip muscle by one of the cell types (CV7) is confirmed electrophysiologically. The relationship of rhythmic activity in CV cells with that in the buccal feeding system is discussed.
The Ionic Basis of the Resting Potential in a Cross-Striated Muscle of the Aquatic Snail Lymnaea Stagnalis
Authors: Brezden B. L. , Gardner D. R. 
Published: April 2021

ABSTRACT
The mean resting potential in the heart ventricle muscle cells of the freshwater snail Lymnaea stagnalis was found to be – 61·2±3·5(..)mV (ranging from –56mV to –68mV). The average intracellular potassium concentration was estimated to be 51·5 ± 14·6 (..) m (ranging from 27·8 m to 77·3 m). The membrane of the heart ventricle muscle cells appears to be permeable to both potassium and chloride, as changes in the extracellular concentration of either of these ions resulted in a change in the membrane potential. A ten-fold change in the extracellular potassium concentration was associated with a 50·4 ± 3·8 (..) mV slope when the potassium concentration was above about 6 m. Deviations from the straight-line relation predicted for a potassium electrode could be accounted for by introducing a term for sodium permeability. The ionic basis of the membrane potential in these cells can be described by a modified form of the Goldman-Hodgkin-Katz equation.
The Selective Permeability of Fleshfly Midgut to an Orally Toxic Cobra Venom Cardiotoxin
Authors: Fishman Lena , Primor Naftali , Zlotkin Eliahu 
Published: April 2021

ABSTRACT
The permeability of the midgut of the fleshfly, Sarcophaga falculata, to the orally toxic polypeptide (Mr∼7000), a cobra venom-cardiotoxin, was investigated by LM and EM autoradiography, using the radio-iodinated toxin. The histology of the normal and toxin affected midgut was also investigated.
The midgut could be classified into segments that were permeable, partially-permeable and non-permeable to the toxin. Histological comparison between the epithelial cells of the permeable and non-permeable segments revealed strong differences in the form of the cells, and in the distribution, form and organization of their microvilli, organelles and basal foldings. The movement of the toxin in the permeable region of the gut is progressive and includes the crossing of the peritrophic membrane, penetration into the apical region of the cell through the microvilli (5 min), movement in the cell’s cytoplasm and finally the passage of the midgut as shown by its appearance in extraintestinal tissues (30 min). The data strongly suggest that the crossing of the midgut by cardiotoxin did not follow the common pattern of pinocytotic uptake and vesicular transport. When applied orally in superlethal doses (10 LD50 units per fly), cardiotoxin strongly affected the integrity of the epithelial cells in the toxin permeable segment, as expressed in their collapse, rupture and final disintegration. The toxin had no histopathological effect on any other region of the midgut.
These data are interpreted in terms of a postulated specific composition and arrangement of phospholipids in the outer plasma membranes of the epithelial cells in the cardiotoxin-permeable segment of the midgut.
Contraction Dynamics of Flight and Stridulatory Muscles of Tettigoniid Insects
Authors: Josephson Robert K. 
Published: April 2021

ABSTRACT
Isometric contraction kinetics and force-velocity relations were examined in wing muscles of two tettigoniid insects, Neoconocephalus robustus and N. triops. The muscles were first tergocoxal muscles of the mesothoracic and metathoracic segments. The metathoracic muscle is a flight muscle. The mesothoracic muscle is used in flight and in stridulation. In the field, the wing stroke frequency during stridulation by N. triops is about 100 Hz ; the thoracic temperature during singing is about 30 C ; and the temperature gradient between the thorax and surround is about 15 C. Published data for N. robustus give the wing-stroke frequency during stridulation as about 200 Hz at a thoracic temperature of 35–40 C. The wing-stroke frequency during flight by both species is approximately 20 Hz at 25 C. The twitch time course is similar in equivalent muscles of the two species. At 35 C the twitch duration (onset to 50 % relaxation) is 5·5–6·5 ms for mesothoracic muscles and 11–13 ms for metathoracic ones. Twitch and tetanic tension per unit area are about twice as great in the metathoracic muscles as in the faster, mesothoracic ones. Despite the differences in isometric contraction kinetics, the maximum shortening velocity (Vmax) is similar in mesothoracic and metathoracic wing muscles. Vmax values (lengths per second, 35 C), determined by extrapolation of force-velocity curves, were 10·1 (mesothoracic) and 11·1 (metathoracic) for N. robustus; 12·2 (mesothoracic) and 16·1 (metathoracic) for N. triops. With N. triops, Vmax was also determined from the time taken to re-develop tension following quick release. The values obtained were somewhat higher than from extrapolation of force-velocity curves, but again similar for mesothoracic and metathoracic muscles. Twitch time course becomes more rapid and Vmax increases with increasing temperature. Neither twitch nor tetanic tension is greatly affected by temperature change in the range 25 – 35 C. As for many other fast muscles, force-velocity plots for these muscles have little curvature. It is suggested that the relative straightness of these plots is a consequence of internal viscosity.
Juvenile Hormone Involvement in Pupal Diapause of the Flesh Fly Sarcophaga Crassipalpis: Regulation of Infradian Cycles of O2 Consumption
Authors: Denlinger D. L. , Shukla M. , Faustini D. L. 
Published: April 2021

ABSTRACT
A cyclic pattern of juvenile hormone (JH) activity is retained during pupal diapause in the flesh fly, Sarcophaga crassipalpis. Cycles of JH activity correlate with infradian cycles of O2 consumption. JH activity progressively increases during a 4-day cycle and appears to trigger the onset of an peak. During the first 2 days of an cycle, pupae are insensitive to an application of JH analogue, but when JH analogue is applied during the last 2 days of the cycle, rises and the cyclic pattern is destroyed. When JH analogue is applied to third instar larvae, O2 consumption is sustained at a steady, high rate throughout pupal diapause. The cycles persist in abdomen-ligated pupae but disappear following head ligation.
Temperature-Induced Changes in Blood Gas Equilibria in the Albacore, Thunnus Alalunga, a Warm-Bodied Tuna
Authors: Cech Joseph J. , Laurs R. Michael , Graham Jeffrey B. 
Published: April 2021

ABSTRACT
Samples of unbuffered, whole blood from freshly-caught albacore (Thunnus alalunga Bonnaterre) were equilibrated at 5, 10, 15, 20, 25, 30 and 35 °C and at 0 and 1 % CO2 for construction of oxygen dissociation curves. A strong Bohr effect (− 1·17), a negligible Root effect, and a reverse temperature effect (ΔH = +1·72 for 0 % CO2 and +·26 for 1 % CO2) characterized these hyperbolic (Hill’s n = 1·1) curves. The unusual reverse temperature effect was especially pronounced when blood was quickly warmed or cooled, simulating passage through the heat exchanging, countercurrent vascular rete system of this warm-bodied fish. A diagrammatic model of blood gas dynamics in the rete incorporating these in vitro data illustrates protection of arterial oxygen from premature haemoglobin dissociation and consequent loss to the venous circulation as blood warms in the rete. More conventional temperature effects on the carbon dioxide equilibria of albacore blood lower the of venous blood being cooled in the rete. This reduces the venous-arterial gradient, thereby minimizing the diffusion of CO2 to arterial blood with resulting haemoglobin-oxygen dissociation via the strong Bohr effect. The temperature range (10–30 °C) over which the albacore haemoglobin-oxygen binding exhibits the reversed thermal effect closely matches the maximum thermal gradient (ambient water-core body temperature) typically present in this fish, suggesting that its highly specialized haemoglobin-oxygen dissociation characteristics evolved within – and now establishes thermal limits upon – the existing geographic distribution of this species.
Viscoelasticity of Holothurian Body Wall
Authors: Motokawa Tatsuo 
Published: April 2021

ABSTRACT
Stress-relaxation tests and creep tests were performed on the bodywall dermis of two sea cucumbers, Actinopyga echinites (Jäger) and Holothuria leucospilota Brandt. These viscoelastic connective tissues had mechanical properties which agreed well with those of a four-element mechanical model composed of two Maxwell elements connected in parallel. The elastic stiffness of the dermis of Actinopyga was 1·7 MPa and that of Holothuria was 0·42 MPa. The viscosity of the dermis showed great variation of more than two orders. Chemical stimulation with artificial sea water containing 100 mm potassium increased the viscosity but not elasticity. The viscosity change is suggested to be caused by the change in weak (non-covalent) bonds between macromolecules which constitute the dermis.