bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemistry and Molecular Biology of the Vesicular Monoamine Transporter from Chromaffin Granules
Authors: Henry J.-P. , Botton D. , Sagne C. , Isambert M.-F. , Desnos C. , Blanchard V. , Raisman-Vozari R. , Krejci E. , Massoulie J. , Gasnier B.
Published: April 2021

Prior to secretion, monoamines (catecholamines, serotonin, histamine) are concentrated from the cytoplasm into vesicles by vesicular monoamine transporters (VMAT). These transporters also carry non-physiological compounds, e.g. the neurotoxin methyl-4-phenylpyridinium. VMAT acts as an electrogenic antiporter (exchanger) of protons and monoamines, using a proton electrochemical gradient. Vesicular transport is inhibited by specific ligands, including tetrabenazine, ketanserin and reserpine. The mechanism of transport and the biochemistry of VMAT have been analyzed with the help of these tools, using mainly the chromaffin granules from bovine adrenal glands as a source of transporter.

Although biochemical studies did not suggest a multiplicity of VMATs, two homologous but distinct VMAT genes have recently been cloned from rat, bovine and human adrenal glands. The VMAT proteins are predicted to possess 12 transmembrane segments, with both extremities lying on the cytoplasmic side. They possess N-glycosylation sites in a putative luminal loop and phosphorylation sites in cytoplasmic domains.

In rat, VMAT1 is expressed in the adrenal gland whereas VMAT2 is expressed in the brain. In contrast, we found that the bovine adrenal gland expressed both VMAT1 and VMAT2. VMAT2 corresponds to the major transporter of chromaffin granules, as shown by partial peptidic sequences of the purified protein and by a pharmacological analysis of the transport obtained in transfected COS cells (COS cells are monkey kidney cells possessing the ability to replicate SV-40-origin-containing plasmids). We discuss the possibility that VMAT1 may be specifically addressed to large secretory granules vesicles, whereas VMAT2 may also be addressed to small synaptic vesicles; species differences would then reflect the distinct physiological roles of the small synaptic vesicles in the adrenal gland.
K+/H+ Antiport in the Tobacco Hornworm Midgut: the K+-Transporting Component of the K+ Pump
Authors: Lepier Alexandra , Azuma Masaaki , Harvey William R. , Wieczorek Helmut
Published: April 2021

The midgut of the tobacco hornworm secretes K+ across the apical plasma membrane of its goblet cells. This secondary K+ transport results from K+/H+ antiport energized by the proton-motive force generated by a primary, H+-transporting plasma membrane V-ATPase. Thus, the lepidopteran midgut constitutes a well-established example of the emerging concept that the proton-motive force is an alternative to the classical sodium-motive force for the energization of animal plasma membranes.

K+/H+ antiport in the tobacco hornworm midgut is electrophoretic, exchanging 2H+ for 1K+. Under physiological conditions, it is energized by the voltage component of the proton-motive force. The strong coupling of electrophoretic K+/2H+ antiport with the electrogenic V-ATPase provides, in principle, the minimal device for the alkalization of the midgut lumen to pH values higher than 11.

K+/H+ antiport is insensitive to bafilomycin A1, but is inhibited by amiloride or Concanavalin A. Lectin staining of blots after SDS–PAGE revealed several glycosylated polypeptides in the goblet cell apical membrane which are not part of the V-ATPase and thus are candidates for the antiporter protein. Current efforts are focused on the isolation of the K+/H+ antiporter.
Respiratory Muscle Activity in Relation to Vocalization in Flying Bats
Authors: Lancaster Winston C. , Henson O. W. , Keating A. W.
Published: April 2021

The structure of the thoracic and abdominal walls of Pteronotus parnellii (Microchiroptera: Mormoopidae) was described with respect to their function in respiration and vocalization. We monitored electromyographic activity of respiratory and flight muscles in relation to echolocative vocalization. In flight, signals were telemetered with a small FM transmitter modified to summate the low-frequency myopotentials with biosonar signals from a ceramic-crystal microphone. Recordings were also made from the same bats confined to a small cage. Vocalizations were used as the parameter by which all muscle activities were correlated. A discrete burst of activity in the lateral abdominal wall muscles accompanied each vocalization. Diaphragmatic myopotentials occurred between groups of calls and did not coincide with activity of the abdominal wall or with vocalizations. Flight muscles were not active in resting bats. During flight, vocalizations and the abdominal muscle activity that accompanied them coincided with myopotentials of the pectoralis and serratus ventralis muscles.

We propose that contractions of the lateral abdominal wall provide the primary power for the production of intense biosonar vocalization in flying and in stationary bats. In flight, synchronization of vocalization with activity of the pectoralis and serratus ventralis jointly contribute to the pressurization of the thoraco-abdominal cavity. This utilization of pressure that is normally generated in flight facilitates respiration and allows for the production of intense vocalizations with little additional energetic expenditure.
Peripheral Regeneration and Central Sprouting of Sensory Neurone Axons in Aplysia Californica Following Nerve Injury
Authors: Steffensen Isabella , Dulin Michael F. , Walters Edgar T. , Morris Catherine E.
Published: April 2021

Morphological methods were used to examine injury-induced growth of peripheral and central axons of nociceptive mechanosensory neurones in the ventrocaudal (VC) clusters of the pleural ganglia of Aplysia californica. Pedal nerve crush transected all axons in the nerve while leaving the overlying sheath largely intact. Immunohistochemical staining was performed with an antibody to a sensory-neurone-specific peptide, sensorin-A. Following bilateral crush of pedal nerve p9, which innervates the tail, sensorin-A immunofluorescence was lost distal to the crush site within 2 days. Fine immunopositive fibres began to invade the crush region within 5 days. These fibres arborized in the crush region and gradually extended down the crushed nerve. Immunopositive fibres were found near the tail within 3 weeks. Similar results were obtained after injecting individual sensory neurone somata in the tail/p9 region of the VC cluster with biocytin. Biocytin injections and horseradish peroxidase injections 3 weeks after ipsilateral pedal nerve crush revealed new fibres projecting rostrally from the tail/p9 region of the VC cluster and entering the pleural–cerebral and pleural–abdominal connectives. Such projections were never observed in control, uncrushed preparations. These results demonstrate that nerve injury triggers extensive growth of both peripheral and central processes of the VC sensory neurones.
Plasma Ammonia Concentration in Brown Trout in Soft Acidic Water and its Relationship to Decreased Swimming Performance
Authors: Beaumont M. W. , Butler P. J. , Taylor E. W.
Published: April 2021

Adult brown trout (300–600 g) were acclimated for 2 weeks to an artificial soft water (Ca2+, 50 μmol l−1) and maintained at either 5 °C (October to March) or 15 °C (May to August). Following insertion of a cannula into the dorsal aorta under MS-222 anaesthesia and a recovery period of 2 days, the fish were exposed to a 4 day episode of sub-lethal copper levels at pH 5 or kept at control conditions of pH 7 without copper. The copper concentrations had been predetermined by toxicity testing and were approximately 0.47 μmol l−1 at 5 °C and 0.08 μmol l−1 at 15 °C. At 5 °C, a group of fish was also exposed to approximately 0.08 μmol l−1 copper at pH 5.

Plasma total ammonia (Tamm) concentration was significantly elevated by exposure to copper and pH 5. In resting trout exposed to the appropriate sub-lethal copper concentration at pH 5, Tamm was six and 7.5 times greater at 5 and 15 °C, respectively, than those of control trout at the respective temperatures. Although unconfirmed, an elevation of ammonia production alone seems unlikely to account for such substantial increases. From previous studies, there is little evidence of impairment of respiratory gas exchange in trout exposed to these copper concentrations and yet, in the acidic test waters, the gradient of NH3 partial pressure between fish and water was 5.5–6 times greater than that under control conditions.

Swimming performance determined by the critical swimming speed (Ucrit) was reduced by copper and acid exposure, and a significant relationship existed between Ucrit and the plasma ammonia concentration of exercised trout. Ammonium ions influence several key enzymes involved in energy metabolism, and elevated ammonia levels might, therefore, reduce the capacity of muscle to exercise. Alternatively, ammonia may have affected the nervous coordination of exercise either centrally or by disrupting peripheral motor innervation.
Interactions of Cortisol and Nitrogen Metabolism in the Ureogenic Gulf Toadfish Opsanus Beta
Authors: Hopkins Todd E. , Wood Chris M. , Walsh Patrick J.
Published: April 2021

We examined the relationship between plasma cortisol levels, hepatic glutamine synthetase (GNS) activity and the form of nitrogen excreted (e.g. urea, ammonia) in undisturbed versus confined/crowded (acutely stressed) gulf toadfish. Specifically, we tested the hypothesis that acute increases in plasma cortisol levels are required to trigger the increase in GNS activity induced by the confinement/crowding stress. Toadfish responded to the stress of confinement/crowding with an initial cortisol surge (approximately 37 ng ml-1 at 2 h), which was rapidly cleared and was indistinguishable from resting levels (approximately 10 ng ml-1 by 24 h). Treatment of fish with metyrapone (which inhibits cortisol synthesis) successfully blocked the acute 2 h confinement/crowding-induced surge in plasma cortisol levels. Additionally, GNS activity in confined fish 24 h after metyrapone injection also did not differ from that of control fish, indicating that acute GNS activation probably requires the earlier (2 h) cortisol peak.

In post-absorptive fish, a strong relationship between total nitrogen excretion rate and plasma cortisol levels was evident. The percentage of nitrogen excreted as ammonia was inversely related to liver GNS activity. However, GNS activity explained only part (at most 57 %) of the variability in the percentage of nitrogen excreted as ammonia/urea, suggesting that this is not the sole factor setting the degree of ureogenesis. When toadfish are fed, the relationships between total nitrogen excretion rate and cortisol levels, and between percentage nitrogen excreted as ammonia and GNS activity, are virtually absent. Taken together, our results indicate that a stress response may be only one of several mechanisms by which ureogenesis is activated in gulf toadfish.
The Role of the Muscle Receptor Organ in the Control of Abdominal Extension in the Crayfish Cherax Destructor
Authors: Mccarthy Bernard J. , Macmillan David L.
Published: April 2021

A platform was lowered from beneath suspended crayfish, Cherax destructor, to evoke slow abdominal extension. The movements were filmed and the length between segments plotted as a function of time. Unlike abdominal flexion, which starts posteriorly and progresses anteriorly, extension occurs at all joints simultaneously. Although the duration of extension varied from trial to trial for an individual, the movement was organised in a stereotyped manner: the abdomen achieved a consistent position for any given proportion of the time for complete extension. We examined the role of the abdominal muscle receptor organs (MROs) in extension by cutting the nerves of selected MROs to abolish their input. The extension movement was measured before and after nerve section for animals with either unloaded or loaded abdomens. Removal of MRO input had no significant effect on extension of the unloaded abdomen. In animals with a loaded abdomen, the extension at joints spanned by sectioned MROs was slowed, whereas that at joints with intact MROs was not. The findings are consistent with the hypothesis that the MRO is an error detector in a servo-loop controlling abdominal position. The results provide the first demonstration that this load-compensating reflex loop operates during naturally evoked extension of the abdomen under constant load.
The Avian Lung: Is There an Aerodynamic Expiratory Valve?
Authors: Brown Richard E. , Kovacs Christopher E. , Butler James P. , Wang Ning , Lehr John , Banzett Robert B.
Published: April 2021

The unidirectional gas-flow pattern through the avian lung is thought to result from ‘aerodynamic valves’; support for this hypothesis lies mainly in the failure to find any evidence for anatomical valves. During expiration, air flows from the caudal air sacs through the major exchange area of the lung, the paleopulmonic parabronchi, instead of bypassing the lungs via the intrapulmonary bronchus. We tested whether the effectiveness of this expiratory flow control mechanism depends on aerodynamic factors, especially convective inertial forces that depend on gas density and flow velocity. In pump-ventilated, anaesthetized geese, a bolus of tracer gas was introduced into both the right and left caudal thoracic air sacs during an end-inspiratory pause. During the first expiration, the rise of tracer levels within the caudal trachea was measured. Valve efficacy was positively correlated with the AO rate of expiratory gas flow, (range 8–200 ml s-1). At flows assumed to occur during exercise in geese , the expiratory valve efficacy was approximately 95 %; it was less effective at lower flows. Surprisingly, the density (ρ) of the background gas (ρ of He/O2=0.43 g l-1, Ar/O2=1.72 g l-1 or SF6/O2=5.50 g l-1) had no effect on expiratory valving. We suggest two possible mechanisms that might explain this unusual combination of flow dependence without density dependence. (1) If airway geometry changes occurred between experiments with different gases, flow in the vicinity of the expiratory valve may have varied independently from flow measured at the airway opening. (2) Alternatively, valving may depend on dynamic compression of the intrapulmonary bronchus, which could depend mainly on viscous resistance and thus on flow velocity but not gas density.
Effect of Dietary Salt Load on Transepithelial Na+ Exchange in Freshwater Rainbow Trout (Oncorhynchus Mykiss)
Authors: SMITH N. F. , EDDY F. B. , TALBOT C.
Published: April 2021

Dietary Na+ loads (0.5–70 mmol kg-1 fish) were almost completely absorbed within 7 h, and branchial Na+ excretion commenced within 1 h. Na+ loads of less than 1 mmol kg-1 were lost through the gills through a significant decrease in Na+ influx with unaltered Na+ efflux rate (compared with Na+ fluxes in unfed fish). At higher salt loads (>18 mmol kg-1 ), Na+ loss increased as a result of significantly higher Na+ efflux rates, with no further decrease in Na+ influx rate. Tissue Na+ concentrations were unchanged, apart from a significant increase in blood plasma Na+ concentration in fish loaded above 18 mmol kg-1 . The results show that branchial Na+ fluxes may be rapidly adjusted in response to prevailing conditions, and possible control mechanisms are discussed.
Variations on a segmental theme: muscle receptor organs and extensor neuromusculature in the squat lobster Munida quadrispina (Anomura, Galatheidae)
Authors: Wallis E. J. , Paul D. H. , Antonsen B. L. , Hollenberg R.
Published: April 2021

Extensor neuromusculature and the muscle receptor organs (MROs) associated with them have been conserved during the evolution of malacostracan crustaceans, despite species-specific differences between homologous segments in divergent taxa. Investigations of these differences could provide insight into how sensory and neuromuscular elements are modified to accommodate changing behavioural patterns. The most obvious differences between squat lobsters (galatheid anomurans) and macruran decapods, such as crayfish, are the greater dorso-ventral flattening of the galatheid abdomen and its flexed resting posture. To investigate whether the evolution of this altered posture affected extensor neuromusculature and MRO morphology and physiology, we used Methylene Blue staining, cobalt backfilling and extracellular recording techniques to describe these elements in the caudal thoracic and six abdominal segments of the squat lobster Munida quadrispina and compared our results with published descriptions of homologous elements in macrurans. In M. quadrispina, there is segmental variation both in the orientation of the MROs along the abdomen and in their physiological responses to stretch: apparent sensitivity is higher in caudal than rostral MROs. Homologues of three of the four accessory neurones found in crayfish occur, but AN#1 has a major dendrite not present in crayfish. Intersegmental differences in size and morphology of extensor motoneurones occur in M. quadrispina, as have been reported in crayfish, but are dissimilar in the two: abdominal ganglion 5 extensor motoneurones are the largest in M. quadrispina and the smallest in crayfish; this difference correlates with the difference in relative size of axial muscles along the abdomen reported previously for these species. M. quadrispina also differs from macrurans in having a single tonic, and no phasic, MRO on each side of the last abdominal segment. Together, these observations suggest that galatheids have evolved modified or additional neurobehavioural control(s) for the abdomen and tailfan.
Epaxial muscle function during locomotion in a lizard (Varanus salvator) and the proposal of a key innovation in the vertebrate axial musculoskeletal system
Authors: Ritter Dale
Published: April 2021

The pattern of electromyographic activity in the epaxial muscles of walking and running lizards (water monitors, Varanus salvator) was quantified with high-speed video and synchronized electromyography. Muscle denervation experiments were performed and ground reaction forces were recorded to evaluate hypotheses of muscle function. Water monitors exhibit unilateral, uniphasic activation of the epaxial muscles ipsilateral to rear limb support. The iliocostalis and longissimus dorsi muscles are active throughout the support phase of the rear limb, while the transversospinalis is active only during the second half of the support phase. The timing of muscle activity does not support the presumed locomotor function of the epaxial muscles of lizards (lateral bending of the trunk). Bilateral denervation of the two most lateral epaxial muscles (iliocostalis and longissimus dorsi) caused no significant change in the amplitude of lateral trunk bending. These two epaxial muscles do not appear to be necessary for lateral bending of the trunk, nor do they appear to be involved in resisting lateral bending of the trunk. On the basis of the data reported in this study, as well as a re-evaluation of previously existing data, it is proposed that the locomotor function of the epaxial muscles of lizards is to stabilize the trunk against the vertical component of the ground reaction forces; i.e. the epaxial muscles function in a postural role during locomotion in lizards, as they do in other amniotes. This proposed postural role of the epaxial muscles may represent a key innovation of amniotes, made possible by the loss of an aquatic larval stage in their common ancestor.
The role of the pericardium and the effects of adrenaline and changes in oxygen tension on the performance of an in situ perfused crocodile heart
Authors: Axelsson Michael , Franklin Craig E.
Published: April 2021

An in situ perfused crocodile (Crocodylus porosus) heart preparation was used to examine the mechanical responses of the heart to increases in adrenaline concentration, to a decrease in oxygen tension and to opening of the pericardium. Starling and power curves were constructed before and after these experimental manipulations. Increasing adrenaline concentration in the perfusate from 5 nmol l−1 to 0.5 μmol l−1 produced a significant increase in heart rate and a decrease in stroke volume, leaving cardiac output unchanged. With maximal adrenergic stimulation, the left ventricle was able to generate greater power outputs at high right aortic output pressures; however, the right ventricle showed a decrease in performance with increasing output pressure.

Decreasing the of the perfusate to 10 kPa resulted in a significant bradycardia. Both the flow and pressure-generating capabilities of the perfused heart preparation were reduced, although the heart was able to maintain low work levels at this .

Opening the pericardium permitted greater movement/expansion of the cardiac chambers and resulted in an increase in heart rate. Higher flows were generated at low filling pressures during the input pressure challenge as a result of an increase in the sensitivity of the Starling response.
Glycerol synthesis in the rainbow smelt Osmerus mordax
Authors: Raymond James A.
Published: April 2021

Rainbow smelt, Osmerus mordax, maintain high glycerol levels in winter to avoid freezing. After intramuscular injection of 14C-labeled glucose, [14C]glycerol was found in the blood, liver and muscle, indicating that glycogen is a source of glycerol. Levels of both the active and inactive forms of glycogen phosphorylase were higher in muscle in winter than in autumn, although the fraction in the active form did not change significantly. More of the phosphorylase was in the active form in the liver than in the muscle. Short-term starvation resulted in a significant decrease in the level of glycogen soon after the stomachs were emptied, presumably to replace glycerol lost to the water. However, tissue glycerol levels remained relatively high, despite a near depletion of glycogen reserves. Triglyceride levels increased slightly during starvation, indicating that triglycerides were not involved in glycerol synthesis. After intramuscular injection of 14C-labeled pyruvate, [14C]glycerol was found in the blood, liver and muscle, indicating a second route, presumably from muscle protein, to glycerol synthesis. Liver phosphoenolpyruvate carboxykinase activity was slightly higher in winter, possibly to assist in the conversion of pyruvate to glycerol.
Potassium Transport in the Freshwater Bivalve Dreissena Polymorpha
Authors: Wilcox Shawn J. , Dietz Thomas H.
Published: April 2021

Potassium transport and blood ion composition were examined in the freshwater bivalve Dreissena polymorpha. Animals acclimated to artificial pondwater (APW, [K+]=0.05 mmol l−1) for 4 weeks gradually lost Na+ and Cl−, but the blood K+ concentration remained constant near 0.5 mmol l−1. Blood [K+] in D. polymorpha declined by 41% after 1 week of exposure to K+-free APW. Conversely, blood [K+] rose to 1.52±0.05 mmol l−1 (mean ± S.E.M.) 24 h after exposure to 0.5 mmol l−1 K+ APW. Total tissue K+ content remained stable in animals maintained in APW, but fell significantly in animals exposed to K+-free APW for 2 weeks. The net K+ flux (Jnet) for animals incubated in APW, with an average K+ concentration of 0.07 mmol l−1, was -0.27±0.06 µequiv g−1 dry tissue h−1, significantly different from the value of 0.50±0.08 µequiv g−1 dry tissue h−1 for animals transferred to 0.30 mmol l−1 K+ APW. A transepithelial membrane potential of -3.6±0.7 mV (blood negative compared with the bathing medium) was measured in APW-acclimated mussels. Potassium influx was measured with 42K and displayed Michaelis–Menten saturation kinetics at dilute K+ concentrations. The Km was 0.084±0.054 mmol l−1 and the Jmax was 1.74±0.39 µequiv g−1 dry tissue h−1. Both the Km and Jmax for animals exposed to K+-free APW for 7 days were unchanged. Using 86Rb, qualitatively similar transport characteristics were observed for animals incubated in K+-free, Rb+ APW, but the 22 day K+ depletion time significantly increased Jmax. D. polymorpha compensated for changes in the ionic composition of the acclimation medium by tolerating alterations in blood solute composition and adjusting ion transport rates.
Neural Control of Hindleg Steering in Flight in The Locust
Authors: Lorez M.
Published: April 2021

Corrective flight steering with the hindlegs was investigated in intact tethered flying locusts inside a wind tunnel as well as in animals dissected for intracellular recording and showing fictive flight activity.

In intact tethered flying animals, activity in the second coxal abductor muscle (M126) was highly correlated with hindleg steering and was coupled to the elevator phase of the flight cycle.

Fictive flight and steering could also be elicited in animals dissected for intracellular recording of motoneurones innervating M126. During fictive flight activity, motoneurones 126 were rhythmically excited in the elevator phase, presumably from central elements of the neuronal oscillator generating the flight motor pattern, as is the case for motoneurones innervating wing muscles. During fictive straight flight, this input was subthreshold, and it could be demonstrated that simulated deviation from the flight course resulted in recruitment of motoneurones 126.

Statistical analysis of the latencies of fast muscle spikes in M126 and in one wing elevator muscle showed that both received common input during flight steering. One source of this common input was identified as the sensory information from the lateral ocelli, which play an important role in the detection of course deviation.

The experiments demonstrated that processing in the sensory-motor system for hindleg steering is probably organized in a very similar way to that responsible for steering with the wings.
Serotonergic Modulation of Swimming Speed in the Pteropod Mollusc Clione Limacina:I. Serotonin Immunoreactivity in the Central Nervous System and Wings
Authors: Satterlie Richard A. , Norekian Tigran P. , Jordan Sheryl , Kazilek Charles J.
Published: April 2021

Serotonin-immunoreactive somata in the pteropod mollusc Clione limacina were restricted to the cerebral and pedal ganglia. 10–14 pairs of cells were consistently found in the cerebral ganglia, including one large pair that had soma positions and axon branching patterns reminiscent of those of the metacerebral cells of other molluscs. Two clusters of somata were found on the midline near the cerebral commissure, one on the anterio-lateral margin and one posterio-laterally. A distinct paired cluster of up to nine somata was found on the dorso-lateral margin of the pedal ganglia, near the emergence of the pedal commissure. Up to five of these cells innervated the ipsilateral wing via the wing nerve. Dye-fills of these cells showed that they branch repeatedly in the ipsilateral wing and innervate the swim musculature. Double-labelling experiments indicated that the filled neurons were also serotonin-immunoreactive. Neurobiotin fills that were processed for electron microscopy revealed two types of terminals associated with the swim musculature: direct contacts and reactive terminals adjacent to non-labelled presynaptic terminals. Additional immunoreactive neurons in the pedal ganglia included the asymmetrical heart excitor neuron of the left pedal ganglion and up to nine ventral somata.
Serotonergic Modulation of Swimming Speed in the Pteropod Mollusc Clione Limacina:II. Peripheral Modulatory Neurons
Authors: Satterlie Richard A.
Published: April 2021

A symmetrical cluster of serotonin-immunoreactive neurons in the pedal ganglia of Clione limacina has been described morphologically and physiologically. At least five of the cluster neurons send axons to the ipsilateral wing that branch throughout the entire wing area. Activation of these cells did not produce a motor effect in non-swimming preparations, but did enhance contractility in swimming preparations. Activity in the pedal neurons did not produce detectable central effects as neither swim interneuron nor swim motor neuron activities were altered. Most notable was a lack of a change in swim frequency, a characteristic of swim acceleration. Activity in the pedal neurons did enhance the size of muscle junctional potentials and spike-like responses, but only in slow-twitch muscles. The peripheral modulatory effect was blocked by the serotonin antagonist mianserin.
Regulatory Responses of the Coxal Organs and the Anal Excretory System to Dehydration and Feeding in the Spider Porrhothele Antipodiana (Mygalomorpha: Dipluridae)
Authors: Butt A. G. , Taylor H. H.
Published: April 2021

The roles of coxal and anal excretion in the regulation of haemolymph osmolality, [Na+] and [K+] were studied in the mygalomorph spider Porrhothele antipodiana (mass 0.7–1.0 g) under differing conditions of feeding and hydration state. Dehydration of starved spiders by removal of drinking water caused progressive mass loss at a rate of about 2.5 % of initial body mass per day and was associated with increases in the whole-body [Na+] and [K+] and in the osmolality, [Na+] and [K+] of the haemolymph. On provision of prey, feeding partially restored this mass loss but further elevated body and haemolymph ion concentrations. Dehydration reduced fluid excretion by the anal excretory system and the four coxal organs in both starved and feeding spiders. Starved hydrated spiders initially produced anal urine at 5 μl day-1 and this was progressively reduced to zero after 4 days of water deprivation. Spiders dehydrated to less than 12 % mass loss would nevertheless feed and this initiated a small post-prandial anal diuresis (<5 μl day-1 compared with >30 μl day-1 in fed hydrated spiders). Coxal fluid was produced by dehydrated spiders only during feeding and was delivered into the prey, the rate of production by single organs decreasing from about 19 μl h-1 g-1 body mass in hydrated spiders to about 4 μl h-1 g-1 body mass in spiders dehydrated to 11 % mass loss.

There was an increase in urine [K+] and in the rate of anal K+ excretion associated with ad libitum feeding in dehydrated spiders. However, urine [Na+] and the rate of anal excretion of Na+ were not increased by feeding. This was associated with an increase in [K+] of the stercoral fluid above that observed in either fed or starved hydrated spiders, but no significant change in [Na+]. Conversely, [Na+] of the coxal fluid produced during feeding was increased by dehydration whereas [K+] was not. These observations are consistent with the previously postulated roles of the coxal organs (Na+) and anal system (K+) in the excretion of ions ingested with the prey.

Full elimination of the prey ions was accomplished only after drinking water was resupplied, which initiated further anal and coxal diureses. Smaller anal and coxal diureses also occurred on rehydration of unfed spiders. The production of coxal fluid in the absence of prey is further evidence that the coxal organs have a true excretory function besides, presumably, assisting ingestion. During dehydration and feeding, P. antipodiana, unlike many insects, is unable simultaneously to conserve water and to eliminate ions by production of a highly concentrated excretory fluid. Both coxal fluid and anal urine were approximately iso-osmotic to the haemolymph and the urine was markedly hypo-ionic.
Extensive Erythrocyte Deformation in Fish Gills Observed by In Vivo Microscopy: Apparent Adaptations for Enhancing Oxygen Uptake
Authors: Nilsson Göran E. , Löfman Carl O. , Block Mats
Published: April 2021

The secondary lamellae of the gills are the primary sites of oxygen uptake in fish. We have used epi-illumination microscopy in vivo to observe the microcirculation directly in secondary lamellae of rainbow trout (Oncorhynchus mykiss) and roach (Rutilus rutilus).

Our observations point at previously unrecognised factors in fish respiratory physiology. Erythrocytes passing through secondary lamellae became greatly deformed. We propose that this deformation plays a role in oxygen uptake by diminishing the diffusion boundary layer (adhesion layer) of fluid around the erythrocyte and possibly also by mixing intracellular haemoglobin molecules. Moreover, the erythrocytes were apparently slowed down and forced to travel over an extended path to pass through the lamella, making it tempting to speculate that plasma passes more readily than erythrocytes through the lamella, resulting in a local elevation of the haematocrit.
Scaling the Feeding Mechanism of the Largemouth Bass (Micropterus Salmoides): Motor Pattern
Authors: Wainwright Peter C. , Richard Barton A.
Published: April 2021

We present the first analysis of scaling effects on the motor pattern of a feeding vertebrate. Data are presented for the effects of body size on the pattern of activity in four head muscles during prey capture in the largemouth bass, Micropterus salmoides. Electromyographic (EMG) recordings were made from three expansive-phase muscles (the epaxialis, the sternohyoideus and the levator arcus palatini) and one compressive-phase muscle (the adductor mandibulae), during the capture of small fish prey. Recordings were made of 181 prey-capture events from 19 bass that ranged in size from 83 to 289 mm standard length. We measured seven variables from the myogram of each capture to quantify the temporal pattern of muscle activation, including the duration of activity in each muscle and the onset time of each muscle, relative to the onset of the sternohyoideus muscle. Regressions of the mean value of each variable for the 19 individuals on standard length revealed that only the onset time of the adductor mandibulae changed with fish body size. The increase in onset time of the adductor muscle appears to reflect the longer time taken to open the mouth fully in larger fish. Other research shows that the kinematics of the strike in this species slows significantly with increasing body size. The combined results indicate that the duration of the EMG signal is not directly correlated with the duration of force production in muscles when compared between fish of different sizes. The lack of scaling of burst duration variables suggests that the reduced speeds of prey-capture motion are explained not by changes in the envelope of muscle activity, but rather by the effects of scale on muscle contractile kinetics. These scaling effects may include changes in the relative resistance of the jaw and head structures to movement through water and changes in the intrinsic contractile properties of the muscles of the feeding apparatus.
Kinematics of Prey Capture in A Flatfish, Pleuronichthys Verticalis
Authors: Gibb Alice C.
Published: April 2021

Hornyhead turbot, Pleuronichthys verticalis (Pleuronectiformes: Pleuronectidae), are morphologically asymmetrical teleosts with substantial bilateral asymmetry in the neurocranium, suspensorium and anterior jaws. In order to quantify the kinematics of prey capture and to test for functional bilateral asymmetries, four individuals of this species were video-taped feeding using a high-speed video system at 200 fields s−1. Frame-by-frame analysis revealed several features not commonly found in prey capture behavior of previously studied ray-finned fishes. These features include (1) extreme lateral compression of the suspensorium and opercular series prior to mouth opening, indicating the consistent presence of a preparatory phase during feeding, (2) apparent dissociation of hyoid retraction and lower jaw depression, (3) prolonged hyoid retraction throughout much of the feeding cycle, and (4) concomitant dorsal rotation of the neurocranium and closing of the jaws. P. verticalis also demonstrate a significant degree of functional bilateral asymmetry during prey capture. When approaching prey, fish flex their heads towards the ocular (anatomically the right) side of the body. During prey capture, their jaws bend out of the midline towards the blind (left) side. Comparisons of the displacement and timing for movements of homologous anatomical features on the ocular and blind sides of the head reveal that maximum gape is always larger on the blind side of the head than on the ocular side. In contrast, other kinematic variables measured are similar on both sides of the head. These results suggest that P. verticalis possess unique functional features of prey capture behavior and that morphological bilateral asymmetry of the head and jaws is associated with, and perhaps causally related to, the functional bilateral asymmetry present during feeding.
The Effects of Thiocyanate on the Intracellular Ion Concentrations of Branchial Epithelial Cells of Brown Trout
Authors: Morgan I. J. , Potts W. T. W.
Published: April 2021

Exposure of brown trout (Salmo trutta) in fresh water to 0.15 mmol l−1 external thiocyanate for 1 h resulted in a significant decrease in chlorine concentration in the branchial mitochondria-rich (MR) cells from 37 mmol l−1 to 22 mmol l−1 . The intracellular sodium concentration in these cells decreased by a similar amount, whilst the intracellular phosphorus concentration increased significantly. In contrast to the MR cells, 0.15 mmol l−1 external thiocyanate had no effect on the intracellular ion concentrations in the pavement epithelial cells. Thiocyanate is known to inhibit chloride uptake in a number of freshwater animals and therefore these data suggest that it is only the MR cells that are involved in the uptake of Cl− in brown trout.
Is Chemosensory Input Essential for the Rapid Rejection of Toxic Foods?
Authors: Glendinning John I.
Published: April 2021

Herbivorous insects often rapidly reject foods containing toxic plant compounds. While the functional significance of this rejection response is clear, the mechanistic basis is not. The role of peripheral chemoreceptors in the rapid rejection of toxic foods was examined using a model system consisting of nicotine and the tobacco hornworm (Manduca sexta), which is a pest of tobacco plants. When offered diets containing naturally occurring concentrations of nicotine, larvae initially fed readily, but abruptly stopped feeding within 30 s. A high percentage of larvae also exhibited toxic responses mediated by the central nervous system (twitching and writhing) to the ingested nicotine within 30 s, indicating that nicotine could have been absorbed within the same time as the rejection response. Two lines of evidence are provided against a role of peripheral chemoreceptors in this rapid rejection response. First, all mouthpart chemoreceptors were ablated from the larvae, and they were then subjected to feeding tests with diets containing either nicotine or a compound (caffeine) that is known to stimulate deterrent taste receptors in M. sexta. Whereas the ablations virtually eliminated the rejection response to caffeine, they had no measurable impact on the rejection response to nicotine. Second, sensory recordings from two important gustatory sensilla (the medial and lateral styloconica) failed to demonstrate a plausible role of sensory input from either sensillum in the rapid rejection of nicotine. The most parsimonious interpretation of these results is that the nicotine rejection response was mediated by a rapidly acting post-ingestive mechanism.
Spatial Patterns of Olfactory Neurons Expressing Specific Odor Receptor Genes in 48-Hour-Old Embryos of Zebrafish Danio Rerio
Authors: Vogt Richard G. , Lindsay Sara M. , Byrd Christine A. , Sun Ming
Published: April 2021

Olfactory neurons have a complex phenotype characterized by their expression of a specific odor receptor (OR) gene and their targeting of an equally specific locus in the olfactory bulb. In the adult fish, olfactory neurons expressing specific ORs are broadly distributed in the epithelium, intermingling with neurons expressing other OR phenotypes. This distributed adult pattern has led to the suggestion that olfactory neuron phenotype is determined by a stochastic process, independent of external positional cues. However, when the fish olfactory system is established during embryogenesis it is simple in its organization, with few olfactory neurons and an olfactory epithelium that has not yet folded into the adult morphology. It is possible that positional cues might act in the embryo to establish an initial population and pattern of olfactory neuron phenotypes and that subsequent morphogenesis and neuronal addition lead to the randomized distribution of neurons. To test this possibility, we examined the spatial patterns of olfactory neurons expressing specific OR genes in 48 h embryos, a time of relative simplicity in the developing olfactory epithelium. Three-dimensional plots of neuron distributions were made, and comparisons of OR expression patterns were made between right and left epithelia, between individual animals and between different OR genes. The patterns of OR gene expression were not conserved in these comparisons. Mathematical analysis of 21 epithelia for the degree of order in the distribution of olfactory neurons argued strongly that the neurons expressing given ORs are randomly distributed in the 48 h embryos. These results are consistent with those observed from adult tissue and support models suggesting that extrinsic positional cues do not have a major role in specifying olfactory neuron phenotypes.
The Energetic Cost of Activation of White Muscle Fibres from the Dogfish Scyliorhinus Canicula
Authors: Lou F. , Curtin N. A. , Woledge R. C.
Published: April 2021

The energetic cost of activation was measured during an isometric tetanus of white muscle fibres from the dogfish Scyliorhinus canicula. The total heat production by the fibres was taken as a measure of the total energetic cost. This energy consists of two parts. One is due to crossbridge interaction which produces isometric force, and this part varies linearly with the degree of filament overlap in the fibres. The other part of the energy is that associated with activation of the crossbridges by Ca2+, mainly with uptake of Ca2+ into the sarcoplasmic reticulum by the ATP-driven Ca2+ pump. Total heat production was measured at various degrees of filament overlap beyond the optimum for force development. Extrapolation of heat versus force production data to evaluate the heat remaining at zero force gave a value of 34±5 % (mean ± S.E.M., N=24) for activation heat as a percentage of total heat production in a 2.0 s isometric tetanus. Values for 0.4 and 1.0 s of stimulation were similar. Comparison with values in the literature shows that the energetic cost of activation in dogfish muscle is very similar to that of frog skeletal muscle and it cannot explain the lower maximum efficiency of dogfish muscle compared with frog muscle. The proportion of energy for activation (Ca2+ turnover) is similar to that expected from a simple model in which Ca2+ turnover was varied to minimize the total energy cost for a contraction plus relaxation cycle.
The Metabolic Cost Of Swimming In Marine Homeotherms
Authors: Hind A. T. , Gurney W. S. C.
Published: April 2021

This paper describes a model of the metabolic cost of swimming in pinnipeds and its application to other marine homeotherms. The model takes account of both hydrodynamic and thermal processes. The thermal component incorporates both free and forced convection and takes account of the effect of hair on free convection. Using data from the literature to evaluate all but two of the parameters, we apply the model to metabolic rate data on phocid seals, otariids (sea lions), penguins and minke whales. We show that the model is able to reproduce two unusual features of the data; namely, a very rapid increase in metabolic rate at low velocities and an overall rise in metabolic rate with velocity which is slower than the rise in hydrodynamic drag force. The work shows the metabolic costs of propulsion and thermoregulation in a swimming homeotherm to be interlinked and suggests differing costs of propulsion for different modes of swimming. This is potentially of ecological significance since the swimming speed that minimises the cost of transport for an animal will change with changes in water temperature.
Dragonfly Flight: I. Gliding Flight and Steady-State Aerodynamic Forces
Authors: Wakeling J. M. , Ellington C. P.
Published: April 2021

The free gliding flight of the dragonfly Sympetrum sanguineum was filmed in a large flight enclosure. Reconstruction of the glide paths showed the flights to involve accelerations. Where the acceleration could be considered constant, the lift and drag forces acting on the dragonfly were calculated. The maximum lift coefficient (CL) recorded from these glides was 0.93; however, this is not necessarily the maximum possible from the wings. Lift and drag forces were additionally measured from isolated wings and bodies of S. sanguineum and the damselfly Calopteryx splendens in a steady air flow at Reynolds numbers of 700–2400 for the wings and 2500–15 000 for the bodies. The maximum lift coefficients (CL,max) were 1.07 for S. sanguineum and 1.15 for C. splendens, which are greater than those recorded for all other insects except the locust. The drag coefficient at zero angle of attack ranged between 0.07 and 0.14, being little more than the Blassius value predicted for flat plates. Dragonfly wings thus show exceptional steady-state aerodynamic properties in comparison with the wings of other insects. A resolved-flow model was tested on the body drag data. The parasite drag is significantly affected by viscous forces normal to the longitudinal body axis. The linear dependence of drag on velocity must thus be included in models to predict the parasite drag on dragonflies at non-zero body angles.
A Tympanal Hearing Organ in Scarab Beetles
Authors: Forrest T. G. , Read M. P. , Farris H. E. , Hoy R. R.
Published: April 2021

We describe the paired hearing organ of the scarab beetle Euetheola humilis. The auditory structures of the beetle are typical of other insect ears in that they have a thinned tympanic membrane backed by a tracheal airsac with associated chordotonal sensory structures. The tympanic membranes of the beetle are part of its cervical membrane and are located behind the head, where the cervix attaches dorsally and laterally to the pronotum. Each membrane is approximately 3 μm thick. The chordotonal sensory organ, which lies within the tracheal airsac, contains 3–8 scolopidia that attach by accessory cells directly to the tympanic membrane. Neurophysiological recordings from the neck connective of the beetle revealed that the auditory system is sensitive to frequencies between 20 and 80 kHz and has a minimum threshold of approximately 58 dB at 45 kHz. The neurophysiological audiogram is identical to the behavioral audiogram for a head roll, one behavioral component of the beetle’s startle response elicited by ultrasound. Blocking experiments show that the membranous structures on the cervix are indeed the hearing organs. Neurophysiologically determined thresholds increased by more than 35 dB when drops of water covered the tympanic membranes and were essentially restored to the control level when the water was later removed. At least three other genera of Dynastinae scarabs have similar tympanum-like structures located in their cervical membranes. Behavioral and neurophysiological data show that the frequency tuning of species in two of these genera, Cyclocephala and Dyscinetus, is nearly identical to that of E. humilis. Our discovery represents only the second group of beetles known to respond to airborne sounds. However, the hearing organs of these scarab beetles differ in structure and placement from those of the tiger beetles, and thus they represent an independent evolution of auditory organs in the Coleoptera.