bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Calcium-Activated Nonspecific Cation Channel From Olfactory Receptor Neurones of the Silkmoth Antheraea Polyphemus
Authors: Zufall F. , Hatt H. , Keil T. A. 
Published: April 2021

ABSTRACT
Single-channel patch-clamp techniques were used to identify and characterize a Ca2+-activated nonspecific cation channel (CAN channel) on insect olfactory receptor neurones (ORNs) from antennae of male Antheraea polyphemus. The CAN channel was found both in acutely isolated ORNs from developing pupae and in membrane vesicles from mature ORNs that presumably originated from inner dendritic segments. Amplitude histograms of the CAN single-channel currents presented well-defined peaks corresponding to at least four channel substates each having a conductance of about 16 pS. Simultaneous gating of the substates was achieved by intracellular Ca2+ with an EC50 value of about 80 nmol 1−1. Activity of the CAN channel could be blocked by application of amiloride (IC50-&lt;100nmoll−1). Moreover, in the presence of lμmoll−1 Ca2+, opening of the CAN channel was totally suppressed by 10μmoll−1 cyclic GMP, whereas ATP (1 mmol 1−1) was without effect. We suggest that the CAN channel plays a specific role in modulation of cell excitability and in shaping the voltage response of ORNs.
The Role of Blood Glucose in the Restoration of Muscle Glycogen During Recovery from Exhaustive Exercise in Rainbow Trout (Oncorhynchus Mykiss) and Winter Flounder (Pseudopleuronectes Americanus)
Authors: Pagnotta Antonella , Milligan C. Louise 
Published: April 2021

ABSTRACT
The role of blood-borne glucose in the restoration of white muscle glycogen following exhaustive exercise in the active, pelagic rainbow trout (Oncorhynchus my kiss) and the more sluggish, benthic winter flounder (Pseudopleuronectes americanus) were examined. During recovery from exhaustive exercise, the animals were injected with a bolus of universally labelled [14C]glucose via dorsal aortic (trout) or caudal artery (flounder) catheters. The bulk of the injected label (50–70%) remained as glucose in the extracellular fluid in both species. The major metabolic fates of the injected glucose were oxidation to CO2 (6–8%) and production of lactate (6–8%), the latter indicative of continued anaerobic metabolism post-exercise. Oxidation of labelled glucose could account for up to 40% and 15% of the post-exercise in trout and flounder, respectively.
Exhaustive exercise resulted M˙O2 in a reduction of muscle glycogen stores and accumulation of muscle lactate. Glycogen restoration in trout began 2–4 h after exercise, whereas in flounder, glycogen restoration began within 2h. Despite a significant labelling of the intramuscular glucose pool, less than 1% of the infused labelled glucose was incorporated into muscle glycogen. This suggests that blood-borne glucose does not contribute significantly to the restoration of muscle glycogen following exhaustive exercise in either trout or flounder and provides further evidence against a prominent role for the Cori cycle in these species.
The Midgut as a Model System for Insect K+-Transporting Epithelia: Immunocytochemical Localization of a Vacuolar-Type H+ Pump
Authors: Klein Ulla , Löffelmann Günter , Wieczorek Helmut 
Published: April 2021

ABSTRACT
In Manduca sexta midgut, a vacuolar-type H+-ATPase and a K+/nH+ antiport represent the functional elements of the electrogenic K+ pump. This vacuolar-type ATPase was localized by immunofluorescence and immunogold staining using monoclonal antibodies to defined subunits of the midgut ATPase. The antibodies labelled the membrane projections of the goblet cell apical plasma membrane, the site of active K+ transport. Furthermore, an immunologically related epitope was localized in the apical brush border of Manduca Malpighian tubules. In addition, cross-reactivity of protein bands corresponding to the major subunits of the midgut vacuolar-type ATPase was found in crude homogenates of Malpighian tubules and antennal sensory epithelium of Manduca by immunostaining with a polyclonal anti-holoenzyme serum to the midgut ATPase. This comparative immunological approach suggests that a vacuolar-type ATPase may be a common constituent of insect plasma membranes bearing the insect K+ pump. These results support the hypothesis that a vacuolar-type H+-ATPase provides an alternative to the Na+/K+-ATPase in energizing animal plasma membranes.
Behavioral and Neurophysiological Demonstration of a Lateralis Skin Photosensitivity in Larval Sea Lampreys
Authors: Ronan Mark , Bodznick David 
Published: April 2021

ABSTRACT
Larval lampreys respond to skin illumination with a delayed burst of swimming in an attempt to escape the light. The photoresponse, which is independent of the lateral eyes and pineal organs, is most readily elicited by light shone on the tail. Behavioral studies in larval lampreys demonstrate that photosensory afferents innervating the tail are carried by a trunk lateral line nerve supplying regions caudal to the head. The present results confirm that bilateral transection of this nerve in larval sea lampreys markedly diminishes the photoresponse. The trunk lateral line nerve consists of the recurrent ramus of the anterior lateral line nerve and a ramus of the posterior lateral line nerve. Bilateral transection of the recurrent ramus does not affect the photoresponse, indicating that lateralis photosensory afferents enter the brain via the posterior lateral line nerve and terminate in the medial octavolateralis nucleus. Photosensory units were subsequently recorded in the trunk lateral line nerve, posterior lateral line nerve and the lateral line area of the medulla. Medullary photosensory units were localized to the medial nucleus, previously regarded as the primary mechanosensory nucleus. Photosensory units in lateral line nerves and the brain exhibited low, irregular spontaneous activity and, after latencies of 1–4 s, responded to tail illumination with repeated impulse bursts. Response thresholds were 0.1–0.9 mW cm−2. Responses to sustained illumination were slowly adapting. A skin photosense is thus an additional lateralis modality in lampreys.
The K+-Driven Amino Acid Cotransporter of the Larval Midgut of Lepidoptera: Is Na+ an Alternative Substrate?
Authors: Hanozet G. M. , Sacchi V. F. , Nedergaard S. , Bonfanti P. , Magagnin S. , Giordana B. 
Published: April 2021

ABSTRACT
Amino acid accumulation within brush-border membrane vesicles (BBMV) from the larval midgut of Lepidoptera is driven by a K+ gradient. However, it can also be driven by a Na+ gradient, although with reduced efficiency. To examine the possibility that sodium and potassium ions are handled by the same amino acid transporter, glycine uptake into BBMV from Philosamia cynthia Drury was measured in the presence of a pH gradient and of a transmembrane electrical potential difference, i.e. in simulated ‘physiological’ conditions. The kinetics of glycine uptake at extravesicular saturating Na+ or K+ concentrations discloses a higher affinity of the cotransporter for the amino acid in the presence of Na+ but a maximum transport rate with K+. Glycine uptake at a fixed concentration as a function of external Na+ or K+ concentration yields curves that show saturation but do not fit a rectangular hyperbola, with Hill coefficients less than 1 with Na+ and greater than 1 with K+. These coefficients vary according to glycine concentration. Increasing the concentration of extravesicular Na+ at a saturating external K+ concentration reduced glycine uptake to 70% of the control value. This inhibition curve is compatible with competition between the two cations for the same cotransporter and with the presence of different kinetic constants with Na+ or K+. The data are consistent with a steady-state random two-substrate mechanism for glycine transport, with Na+ and K+ as alternative substrates.
Effect of Manduca Sexta Diuretic Hormone and Related Peptides on Isolated Malpighian Tubules of the House Cricket Acheta Domesticus (L.)
Authors: Coast Geoffrey M. , Hayes Timothy K. , Kay Iain , Chung Jum-Sook 
Published: April 2021

ABSTRACT
Previously, a corticotropin releasing factor (CRF)-like diuretic peptide (Man-duca-DH) has been isolated from Manduca sexta and shown to stimulate fluid excretion in vivo in post-eclosion Pieris rapae adults and in pre-wandering postfeeding Manduca sexta larvae. However, Manduca-DH was reported to have no effect on Malpighian tubules in vitro.
Manduca-DH and [Nle2,11]-Manduca-DH were synthesized in Texas and assayed in London on isolated Malpighian tubules of Acheta domesticus. Man-duca-DH stimulated fluid secretion by about 60% of the maximum response achievable with extracts of corpora cardiaca and increased the production of cyclic AMP. In combination with 10−4moll−1 3-isobutyl-l-methyl xanthine (IBMX), Manduca-DH stimulated maximal secretion. A number of CRF-related peptides also stimulated fluid secretion and cyclic AMP production in cricket tubules, and the CRF antagonist α-helical-CRF[9–41] blocked the stimulation of fluid secretion by Manduca-DH. [Nle2,11]-Manduca-DH was more active than Manduca-DH in both assays, suggesting that methionine residues in the natural peptide may become oxidized.
Taken in conjunction with previous in vivo studies, the present findings suggest that a Manduca-DH-like diuretic peptide is the hormone controlling post-eclosion diuresis in butterflies, and Manduca-DH was shown to stimulate both fluid secretion and cyclic AMP production in Malpighian tubules from 1–12 h posteclosion Pieris rapae adults. The function of the peptide in Manduca sexta is discussed.
Influence of Substrate on Retraction of Neurites Following Electrical Activity of Leech Retzius Cells in Culture
Authors: Grumbacher-Reinert Simone , Nicholls John 
Published: April 2021

ABSTRACT
The aim of these experiments was to determine how electrical stimulation of identified neurones in culture influences their growth on defined substrates. Single Retzius cells isolated from the central nervous system (CNS) of the leech were plated in culture dishes coated with the plant lectin Concanavalin A or with extracellular matrix extract containing leech laminin to promote neurite outgrowth. Stimuli were applied by a fine tungsten microelectrode placed close to the cell surface. The efficacy of electrical stimulation was checked occasionally by recording intracellularly with a microelectrode. After the period of stimulation had ended, there was a short delay before neurones plated on leech laminin retracted their neurites. Of 112 neurones, only 11 failed to respond to stimulation. Neurite retraction in each cell was nonuniform, some processes retracting while others did not. After having retracted, most neurites subsequently showed clear regrowth. The degree of retraction depended on the duration of the stimulus train: whereas a few minutes was sufficient to produce observable effects, prolonged periods of stimulation caused more extensive retraction. Trains of impulses at 4 s−1 were equally effective when they were delivered in intermittent bursts or continuously. The time in relation to growth at which stimuli were applied was of critical importance. Neurones stimulated during the phase of rapid outgrowth on leech laminin did not retract their neurites, which continued to elongate during and after stimulation. Neurones that had not retracted during the early phase were stimulated again later, when extension and outgrowth of neurites had ceased or slowed. At this stage stimulation was followed by retraction and subsequent regrowth. Retzius cells plated on a substrate of Concanavalin A instead of leech laminin failed to show any retraction after stimulation. To investigate the possible role of Ca2+, cells were grown with raised concentrations of Mg2+ in the bathing fluid. Raised [Mg2+] did not influence the rate or the extent of neurite outgrowth. It reduced, but did not block, the effects of electrical stimulation. Earlier experiments have shown that growth on Concanavalin A occurs without obvious Ca2+ entry following stimulation. Together with the present experiments, the results suggest that Ca2+ entry following impulses in cells grown on laminin is responsible for the massive retraction.
Gas Exchange, Metabolite Status and Excess Post-Exercise Oxygen Consumption After Repetitive Bouts of Exhaustive Exercise in Juvenile Rainbow Trout
Authors: Scarabello M. , Heigenhauser G. J. F. , Wood C. M. 
Published: April 2021

ABSTRACT
Juvenile rainbow trout (approximately 6 g) were exercised to exhaustion in two 5 min bouts given 6h apart. Resting levels of whole-body lactate and glycogen were restored prior to the second bout. The rate of O2 consumption increased about threefold 5 min after each bout of exercise, while recovery time decreased from 4h after the first bout to 2–3h after the second. The excess post-exercise oxygen consumption, i.e. ‘oxygen debt’, was significantly reduced by 40% after the second exercise bout, despite almost identical rates of lactate clearance and glycogen resynthesis. The rates of CO2 and ammonia excretion increased sixfold and threefold, and recovery times decreased from 4–6 h to 3h and from 3h to 1.5 h, respectively. After the first bout, whole-body lactate levels peaked at 5 min post-exercise at about 8.5 times pre-exercise levels. After the second bout, lactate levels peaked at 0 min post-exercise and fell more rapidly during recovery. Whole-body glycogen levels decreased by 70% and 80% and ATP levels decreased by 75% and 65% after the first and second bouts, respectively, while glucose levels increased about 1.5-fold immediately after both bouts. Creatine phosphate levels decreased by 70% and 80% after the first and second bouts, respectively. After 6h of recovery, creatine phosphate levels were higher after the second bout than after the first. These findings suggest that exhaustive exercise may cause a ‘nonspecific’ increase in metabolic rate not directly related to the processing of metabolites, which is reduced upon a subsequent exercise bout. This is in contrast with the classical ‘oxygen debt hypothesis’, which states that the oxygen debt and lactate clearance are linked. Furthermore, it appears that two sequential exercise bouts are sufficient to induce a ‘training effect’, i.e. improved rates of metabolic recovery.
Effect of Season and Temperature Acclimation on the Function of Crucian Carp (Carassius Carassius) Heart
Authors: Matikainen Nina , Vornanen Matti 
Published: April 2021

ABSTRACT
The temperature dependence of heart rate and isometric contractile properties of cardiac tissue was determined in thermally acclimated crucian carp (Carassius carassius L.). Fish were adapted for more than 3 weeks to 5 and 15°C during both summer and winter. At all but the lowest experimental temperatures, heart rate (FH), maximal isometric force (Fmax) and pumping capacity were higher in summer fish acclimated to 15°C than in winter fish acclimated to 5°C. Except for fH, similar acclimation effects were observed when comparing cold- and warm-acclimated crucian carp in both seasons. In contrast, the kinetics of isometric contraction was not modified either by seasonal acclimatization or by thermal acclimation within a given season: the temperature dependence of time to peak force (TPT) and time to half-relaxation (T1/2R) was independent of the previous thermal history of the fish. The hearts of winter fish were about 10% smaller than those of summer fish. These results show that acclimation to cold does not induce positive compensatory changes in function or size of crucian carp heart, as happens in many other teleost fishes. Instead, an inverse or noncompensatory acclimation was found. Owing to the inverse thermal acclimation, in winter (at 4°C) the contractile performance of the crucian carp heart is less than one-third of that in summer (at 20°C). The low cardiac activity in cold-acclimated crucian carp seems to be associated with its inactive life style, which is necessary during the winter months to minimize energy consumption in a severely hypoxic environment.
Calcium Transients In Identified Leech Glial Cells In Situ Evoked By High PotaSsium Concentrations And 5-Hydroxytryptamine
Authors: Munsch Thomas , Deitmer Joachim W. 
Published: April 2021

ABSTRACT
We have recorded the fluorescence of Fura-2-loaded, identified glial cells in the neuropile of the central nervous system of the leech Hirudo medicinalis using the ratio of emission at 350 nm excitation to that at 380 nm excitation as an indicator of intracellular Ca2+ concentration ([Ca2+]i). The neuropile glial cells were exposed by mechanically removing the overlying ganglionic capsule and the neuronal cell bodies and were then impaled using a microelectrode under visual control to inject Fura-2 ionophoretically. The resting Ca2+ level was measured using digitonin or Triton to permeabilize the cell membrane at different external concentrations of Ca2+; it was found to vary between 5 and 79 nmol l−1 and averaged 32±23nmol l−1 (±S.D., N=7). Raising the external K+ concentration from 4 to 20mmol l−1 or adding 50 μmol l−1 5-hydroxytryptamine (5-HT) produced a rapid, reversible rise in [Ca2+]i During prolonged exposure to high [K+] or 5-HT, [Ca2+]i remained high. Upon restoring normal external [K+] or removing 5-HT, [Ca2+], returned to its initial resting value within 1–2 min. The responses of [Ca2+]i to high [K+] and 5-HT were greatly reduced in nominally Ca2+-free saline, suggesting that the [Ca2+], transients required an influx of Ca2+ into the cells. In the presence of 5-HT, the rise in [Ca2+]i was accompanied by a decrease in the resistance and an increase in the responsiveness to K+ of the glial cell membrane, indicating the existence of a Ca2+-dependent K+ conductance elicited by 5-HT.
Can we Determine When Marine Endotherms Feed? A Case Study With Seabirds
Authors: Wilson Rory P. , Cooper John , Plötz Joachim 
Published: April 2021

ABSTRACT
The foraging ecology of marine endotherms was, until recently, obscure because most species spend the greater part of their life at sea where they are difficult to observe. However, advances in solid state technology have made it possible to develop units that can be attached to animals to give information on movements (e.g. Jouventin and Weimerskirch, 1990; Wilson et al. 1991) or activity (e.g. Ponganis et al. 1991; Thompson et al. 1991) while animals are at sea. Information on the prey consumed may be obtained by stomach lavage techniques (e.g. Wilson, 1984). Assessment of stomach contents allows researchers to determine prey types but not when prey were ingested. To build up a more comprehensive picture of foraging activity of marine endotherms a unit is needed to record information on prey ingestion.
Endogenous Rhythms in the Amounts of 11-cis Retinal in the Compound eye of Ligia Exotica (Crustacea, Isopoda)
Authors: Hariyama Takahiko , Tsukahara Yasuo 
Published: April 2021

ABSTRACT
The volume of the rhabdom of Ligia exotica changes diurnally, with the rhythm persisting autogenically in continuous darkness. The morphological changes are accompanied by variations in the amounts of the different chromophores making up the visual pigment. The amount of 11-cis retinal was found to be high at night (26.2±3.5 pmol per eye) and low during the day (10.9±2.6pmol per eye) and to display an endogenous rhythm. At dawn and dusk, the amount was 19.1 ±1.2 pmol. This rhythmicity persisted in continuous darkness, although the average amount of 11-cis retinal present gradually increased. In the case of all-trans retinal, changes in the amount were rhythmic in light-dark conditions. The amount of all-trans retinal present in the eye increased shortly after the onset of light and decreased soon after the end of illumination. There was about twice as much 11-cis retinyl ester as 11-cis retinal in the compound eye of Ligia exotica. Rhythmicity in the amount of 11-cis retinyl ester present during the light-dark cycle was observed, but it was opposite in phase to that of 11-cis retinal. Under conditions of continuous darkness a clear rhythm was not apparent: the amount of 11-cis retinyl ester increased not only during the subjective day but also during the following subjective night. Thus, a clear correlation exists between changes in structural organization of the rhabdom and the amounts of 11-cis retinal present. Both show features of a circadian rhythm.
The Influence of Temperature on Ryanodine Sensitivity and the Force-Frequency Relationship in the Myocardium of Rainbow Trout
Authors: Hove-Madsen* Leif 
Published: April 2021

ABSTRACT
The relationship between stimulation frequency and contraction was established for ventricular strips from rainbow trout heart at 5,15 and 25°C. Compared to mammalian species, changes in temperature had little impact on force development in trout ventricle at physiologically relevant stimulation frequencies. However, the force-frequency relationship was changed from a biphasic response with a minimum around 0.2 Hz at 5 and 15°C to a monophasic decline in force with increasing frequency at 25°C. Ryanodine reversed the negative force-frequency relationship at 25°C. Potentiation of twitch force after a 5 min rest period was increased from 121 ±4% at 15°C to 209±12% at 25°C. A similar augmentation was seen for the maximal rate of force development. Rest potentiation of both force and maximal rate of force development (dF/dT) was abolished by ryanodine at both 15 and 25°C. The ryanodine concentration causing a half-maximal reduction in rest potentiation of force was 51 nmol l−1 at 25°C and 483 nmol l−1 at 15°C. Rest potentiation was maximally reduced by 10μmoll−1 ryanodine to 50 and 79% of the value in the absence of ryanodine at 25 and 15°C, respectively. At 5°C, rest potentiation was similar to that at 15°C. At 5°C, there was no rest potentiation of dF/dT and ryanodine did not reduce rest potentiation of force. Instead, rest potentiation was correlated with a potentiation of time to peak tension (TPT) at 5°C. Thus, in trout ventricle, force correlates with TPT at 5°C and seems to be regulated by a ryanodine-insensitive mechanism, while at 25°C force is correlated with the maximal rate of force development and the sarcoplasmic reticulum appears to contribute significantly to excitation-contraction coupling.
Degenerative Changes in the Function of Neuromuscular Junctions of Manduca Sexta During Metamorphosis
Authors: Sonea Ioana M. , Rheuben Mary B. 
Published: April 2021

ABSTRACT
In Manduca sexta the decline in neuromuscular function during metamorphic degeneration was compared in two muscles which differed characteristically with regard to pre- and postsynaptic physiological properties. In both muscles, morphological evidence indicated that a significant number of the active zones within the population of neuromuscular junctions on a given fiber were nonfunctional. Nevertheless, the degenerating nerve terminals were able to produce an above-threshold excitatory junction potential (EJP) which was facilitated in a manner characteristic of the muscle being observed. Abnormal findings during the early stages of degeneration included a larger than normal EJP, a decline in EJP amplitude over a 20 min period even with low frequencies of stimulation, an increase in EJP duration, a decline in muscle fiber resting potential amplitude with age, a decrease or disappearance of post-tetanic potentiation and long-term facilitation, and an increased likelihood that the motor nerve would fail to conduct a stimulus. The two muscles were qualitatively similiar but quantitatively different with regard to these degenerative changes. It is suggested that this combination of relatively normal function with abnormal properties might be associated with the withdrawal of glial processes from the neuromuscular junctions, changes in the cable properties associated with shrivelling of the muscle fibers, and a decline in the metabolic functions supporting both muscle fiber resting potentials and those underlying transmitter synthesis, mobilization and release.