bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Aminergic and Peptidergic Innervation of Insect Salivary Glands
Authors: Ali Declan W. 
Published: April 2021

ABSTRACT
Insect salivary glands are glands associated with nutrient intake whose secretions are generally involved in the digestion and lubrication of food. They are under the control of neuroactive substances and may be innervated from several sources including the suboesophageal ganglion, the stomatogastric nervous system and the unpaired median nerves. Both amines and peptides have been suggested to play roles in the control of insect salivation, as indicated by their association with terminals on salivary glands, their effects in salivary gland bioassays and their ability to alter second messenger levels and ion channel conformations. Serotonin and dopamine appear to be the most prominent amines associated with insect salivary glands. Either one or both of these amines are found associated with the salivary glands of the locust, stick insect, cockroach, cricket, dragonfly, mosquito, adult moth and kissing bug. Their roles, although not fully elucidated, appear to be in the control of salivary secretion. Several peptides, including members of the FMRFamide-related family of peptides, are also found associated with insect salivary glands. Sources of peptidergic innervation are as varied as those for aminergic innervation, but information regarding the physiological role of these peptides is lacking. The relevance of the different levels of complexity of salivary gland innervation, which range from the absence of innervation in some species (blowfly) to the presence of several distinct sources in others (locust, cockroach), is not well understood. This review serves to consolidate what is known of the phenotype of salivary neurones in relation to the control of salivation.
Modulation of Prey-Capture Behavior in the Plethodontid Salamander Ensatina Eschscholtzii
Authors: Deban Stephen M. 
Published: April 2021

ABSTRACT
The hypothesis that salamander prey-capture behavior is highly stereotyped was tested in the plethodontid salamander Ensatina eschscholtzii using high-speed videography and kinematic analysis of feedings on two types of prey (waxworms and termites). The results show that E. eschscholtzii is capable of modulating the timing and magnitude of tongue and jaw movements in response to prey type. Feedings on waxworms, the larger prey, were characterized by shorter durations and higher velocities of tongue and jaw movements compared with feedings on termites, particularly in the latter portion of the feeding sequence (i.e. after prey contact). To test the hypothesis that sensory feedback through the tongue pad plays a role in modulating feeding movements in response to prey type, the ramus lingualis of the glossopharyngeal nerve (cranial nerve IX), which is known to carry sensory information from the tongue pad in salamanders, was transected bilaterally. This experimental deafferentation of the tongue pad had no effect on the degree or direction of differences in feeding kinematics across prey type. These results refute the glossopharyngeal feedback hypothesis, but are consistent with the hypothesis that E. eschscholtzii responds more vigorously to larger prey by assessing prey size visually.
Heart Rate and Stroke Volume Contributions to Cardiac Output in Swimming Yellowfin Tuna: Response to Exercise and Temperature
Authors: Korsmeyer Keith E. , Lai N. Chin , Shadwick Robert E. , Graham Jeffrey B. 
Published: April 2021

ABSTRACT
Cardiac performance in the yellowfin tuna (Thunnus albacares, 673–2470 g, 33–53 cm fork length, FL) was examined in unanesthetized fish swimming in a large water tunnel. Yellowfin tuna were fitted with either electrocardiogram electrodes or a transcutaneous Doppler blood-flow probe over the ventral aorta and exposed to changes in swimming velocity (range 0.8–2.9 FL s−1) or to an acute change in temperature (18–28 °C). Heart rates (fH) at 24±1 °C (30–130 beats min−1) were lower on average than previous measurements with non-swimming (restrained) tunas and comparable with those for other active teleosts at similar relative swimming velocities. Although highly variable among individuals, fH increased with velocity (U, in FL s−1) in all fish (fH=17.93U+49.93, r2=0.14, P&lt;0.0001). Heart rate was rapidly and strongly affected by temperature (Q10=2.37).
Blood flow measurements revealed a mean increase in relative cardiac output of 13.6±3.0 % with exercise (mean velocities 1.23–2.10 FL s−1) caused by an 18.8±5.4 % increase in fH and a 3.9±2.3 % decrease in stroke volume. These results indicate that, unlike most other fishes, cardiac output in yellowfin tuna is regulated primarily through increases in fH. Acute reductions in ambient temperature at slow swimming velocities resulted in decreases in cardiac output (Q10=1.52) and fH (Q10=2.16), but increases in stroke volume (Q10=0.78). This observation suggests that the lack of an increase in stroke volume during exercise is not due to the tuna heart operating at maximal anatomical limits.
Oxygen Transport and Cardiovascular Responses to Exercise In The Yellowfin Tuna Thunnus Albacares
Authors: Korsmeyer Keith E. , Lai N. Chin , Shadwick Robert E. , Graham Jeffrey B. 
Published: April 2021

ABSTRACT
Yellowfin tuna Thunnus albacares (1400–2175 g) instrumented with electrocardiogram electrodes and pre- and post-branchial catheters were subjected to incremental swimming velocity tests. Increasing velocity, from a minimal speed of 1.0 FL s−1, where FL is fork length, resulted in a 1.4-fold increase in heart rate (from 61.4 to 84.6 beats min−1), an elevated ventral-aortic blood pressure (from 10.8 to 12.2 kPa) and a decreased systemic vascular resistance. Relative branchial vascular resistance at minimal speed ranged from 24.4 to 40.0 % of total vascular resistance and tended to increase with velocity. Yellowfin blood has a high oxygen-carrying capacity (16–18 ml O2 dl−1), and a low in vivo oxygen affinity (P50=5.3 kPa). Exercise caused a rise in arterial saturation (from 74 to 88 %) and a decline in venous saturation (from 48 to 44 %), resulting in a 1.3-fold increase in tissue oxygen extraction from the blood (arterial–venous oxygen content difference). Whereas arterial oxygen partial pressure () tended to increase with exercise, venous remained unchanged (approximately 5.3 kPa). The observed decrease in venous oxygen content was brought about by a lowered blood pH (from 7.80 to 7.76) and a large Bohr shift. Cardiac output and the increased blood oxygen extraction are estimated to have contributed nearly equally to the increased oxygen consumption during exercise. The large venous oxygen reserve still available to yellowfin tuna at maximal prolonged velocities suggests that the maximal oxygen delivery potential of the cardiovascular system in this species is not fully utilized during aerobic swimming. This reserve may serve other aerobic metabolic processes in addition to continuous swimming.
Excitation of Identified Serotonergic Neurons by Escape Command Neurons In Lobsters
Authors: Hörner Michael , Weiger Wendy A. , Edwards Donald H. , Kravitz Edward A. 
Published: April 2021

ABSTRACT
Serotonin-containing neurosecretory neurons in the first abdominal ganglion (A1 5-HT cells) of the lobster (Homarus americanus) ventral nerve cord have been shown previously to function as ‘gain setters’ in postural, slow muscle, command neuron circuitries. Here we show that these same amine neurons receive excitatory input from lateral (LG) and medial (MG) giant axons, which are major interneurons in phasic, fast muscle systems. Activation of either LG or MG axons elicits short-latency, non-fatiguing, long-lasting excitatory postsynaptic potentials (EPSPs) in A1 5-HT cells which follow stimulus frequencies of up to 100 Hz in a 1:1 fashion. Single spikes triggered in either giant axon can produce EPSPs in the A1 5-HT cells of sufficient magnitude to cause the cells to spike and to fire additional action potentials after variable latencies; action potentials elicited in this way reset the endogenous spontaneous spiking rhythm of the A1 5-HT neurons. The giant-axon-evoked EPSP amplitudes show substantial variation from animal to animal. In individual preparations, the variation of EPSP size from stimulus to stimulus was small over the first 25 ms of the response, but increased considerably in the later, plateau phase of each response. When tested in the same preparation, EPSPs in A1 5-HT cells evoked by firing the LG axons were larger, longer-lasting and more variable than those triggered by firing the MGs. Firing A1 5-HT cells through an intracellular electrode, prior to activation of the giant fiber pathway, significantly reduced the size of LG-evoked EPSPs in A1 5-HT cells. Finally, morphological and physiological results suggest that similarities exist between giant fiber pathways in lobsters and crayfish. The possible functional significance of an involvement of these large amine-containing neurosecretory neurons in both tonic and phasic muscle circuitries will be discussed.
Slow Inhibition of Na+ Current in Crayfish Axons by 2-(1Non-8Enyl)-5-(1Non-8Enyl)Pyrrolidine (Pyr9), a Synthetic Derivative of an ant Venom Alkaloid
Authors: Lebrun Bruno , Cattaert Daniel 
Published: April 2021

ABSTRACT
2,5-Dialkylpyrrolidines present in the venom of ants from the genus Monomorium are natural insecticides causing a flaccid paralysis. The mechanism of action of 2-(1non-8enyl)-5-(1non-8enyl)pyrrolidine (Pyr9), a synthetic derivative of 2,5-dialkylpyrrolidines, has been investigated in vitro on preparations of the ventral nerve cord of the crayfish Procambarus clarkii. Our results clearly indicate that Pyr9 blocks spike conduction without affecting the resting potential. Voltage-clamp experiments carried out on axons demonstrate that this blockade is due to a dual expression of Na+ current inhibition: a tonic inhibition developing slowly (90 % of inhibition within 20 min for a Pyr9 concentration of 50 μmol l−1) and independently of stimulation, and a phasic inhibition developing during repetitive stimulation (5 Hz), the accumulation kinetics of which is 0.072 pulse−1 at 5 Hz, according to the Courtney model. These findings suggest that tonic and phasic inhibition are due to different mechanisms. In addition, Pyr9 induces a shift of the Na+ inactivation curve towards more hyperpolarized potentials, which is in agreement with a higher affinity of Pyr9 for inactivated than for resting Na+ channels.
Evidence for Cholinergic Inhibitory and Serotonergic Excitatory Neuromuscular Transmission in the Heart of the Bivalve Mercenaria Mercenaria
Authors: Kuwasawa Kiyoaki , Hill Robert B. 
Published: April 2021

ABSTRACT
The heart of Mercenaria mercenaria is innervated bilaterally at the atria. A pair of cardiac nerves arise as a branch of the cerebro-visceral connective and run to the posterior end of the junction between each atrium and its efferent branchial vessel. Innervation evidently spreads over the heart, since both inhibitory and excitatory junctional potentials (IJPs and EJPs) can be recorded from the atria, the atrio-ventricular (AV) valve or the ventricle. The cardiac nerves contain inhibitory and excitatory axons. Neural stimulation can cause increases in the frequency or amplitude of beating, depending on the strength and frequency of stimulation. Electrical stimulation of the nerves to the incurrent and excurrent siphons causes bradycardia or tachycardia even after cutting the cerebro-visceral connective at a site anterior to the origin of the cardiac nerves. This may indicate a reflex pathway involving neurons whose cell bodies are located in the visceral ganglion.
Neural depression of myocardial action potentials is mediated by discrete IJPs, which follow nerve stimuli one-to-one. IJPs can be recorded from the atria, the AV valve or the ventricle. A long-lasting hyperpolarization follows cessation of excitatory stimulation of the cardiac nerve.
IJPs may be produced by cholinergic nerves and are mediated primarily by Cl−. They are blocked by Mytolon and by d-tubocurarine (dTC), but not by methylxylocholine. In low-[Cl−] solution, IJPs are inverted into depolarizing junctional potentials, which are blocked by Mytolon and dTC.
Neurally induced tachycardia is mediated by discrete EJPs, which also follow stimuli applied to the cardiac nerve in a one-to-one manner. EJPs can be recorded from the atria, the AV valve and the ventricle.
The myocardium and the AV valve were excited by application of serotonin. EJPs recorded from these sites were reduced in amplitude by methysergide (1-methyl-d-lysergic acid butanolamide), suggesting that the EJPs may be serotonergic.
Just after entering the heart, at the posterior end of the junction with the efferent branchial vessel, the cardiac nerves contain thick processes which show serotonin-like immunoreactivity. These processes spread along the ramifications of the nerves, which extend to the atrium, the AV valve, the ventricle and even into the wall of the aorta.
This study provides direct electrophysiological evidence for serotonergic EJPs and cholinergic IJPs, plus immunocytochemical evidence for neural processes containing serotonin, in the myocardium.
Modulation of Attack Behavior and its Effect on Feeding Performance in a Trophic Generalist Fish, Hexagrammos Decagrammus
Authors: Nemeth Donna Henriques 
Published: April 2021

ABSTRACT
This study examines the ability of a temperate marine fish, Hexagrammos decagrammus, to modulate its prey capture behavior in response to differences in prey type. This species has an extremely broad diet, feeding on prey which demonstrate very different anti-capture behaviors. Video-taped attacks on three shrimp species, one crab and pieces of shrimp were analyzed to determine the relative contributions of suction-feeding and ram-feeding behaviors to prey capture. The prey capture behaviors used by the predator were related to differences in escape behavior among the three shrimp species. H. decagrammus used behaviors characteristic of other ram-feeding predators when feeding on the two most elusive shrimp species: high attack velocity, attack initiated at a greater distance from the prey, and greater movement of the predator relative to the prey. Strikes at crabs and pieces of shrimp elicited strikes more typical of other suction-feeding predators, with lower attack velocities, shorter initial predator–prey distances and greater relative movement of the prey towards the predator. Attacks on the least elusive shrimp species showed elements of both ram and suction feeding. Modulation of attack velocity increased capture success on elusive prey, supporting the hypothesis that diet diversity is associated with the presence of a repertoire of feeding behaviors. These data suggest that functional differences in prey anti-capture behavior, as well as the functional versatility of the predator, must be addressed in ecomorphological studies that try to correlate predator morphology with diet.
Chloride Secretion Drives Urine Formation in Leech Nephridia
Authors: Zerbst-Boroffka Irene , Bazin Brita , Wenning Angela 
Published: April 2021

ABSTRACT
The transport mechanisms underlying urine formation in leech nephridia were investigated in situ and in isolated preparations using pharmacological, electrophysiological and micropuncture techniques. Canalicular cells, which secrete the primary urine, function as a Cl--secreting epithelium. An apical Cl- conductance contributes to the lumen-negative potential which drives transcellular K+ transport and paracellular Na+ transport. On the basolateral side, a ouabain-sensitive Na+/K+-ATPase contributes substantially to the cellular and transcellular potential and provides the Na+ gradient necessary for a bumetanide-sensitive Na+/K+/2Cl- cotransport. Final urine is formed by subsequent reabsorption of ions along the central canal, where KCl and NaCl are reabsorbed in different portions.
The postprandial diuresis is not a consequence of the changes in blood osmolality or ion concentrations. Similar changes in the ionic environment do not promote diuresis in isolated nephridia. Apparently, the composition and volume of the primary urine cannot be separately controlled. Any increase in fluid secretion by leech canalicular cells involves upregulation of the paracellular pathway and stimulation of Cl- entry, which thereby changes the normally K+-enriched primary urine to the Na+-enriched primary urine characteristic of leeches in diuresis.
Developmental Changes in Chemoreceptive Control of Gill Ventilation in Larval Bullfrogs (Rana Catesbeiana) I. Reflex Ventilatory Responses to Ambient Hyperoxia, Hypoxia and Nacn
Authors: Jia XI XI , Burggren Warren W. 
Published: April 2021

ABSTRACT
The time course of reflex changes in gill ventilation frequency, buccal pressure, branchial stroke volume and minute ventilation caused by a step-wise change in of inspired water and by the introduction of NaCN into the inspired water was measured in unanesthetized larval bullfrogs (Rana catesbeiana) at developmental stages TK V–VII, IX–XI and XVII–XIX. The inspiration of hypoxic or hyperoxic water caused significant increases in gill ventilation within 7 s, while hyperoxic water had the opposite effect. Introduction of NaCN into the inspired water stream caused nearly instantaneous respiratory responses (&lt;3 s). Early and middle stage larvae showed a significantly faster and more pronounced reflex response than the older group in all experiments. The rapid changes in gill ventilation indicate the presence of a population of branchial receptors monitoring inspired water O2 levels or possibly blood O2 levels in the efferent branchial circulation. The progressive decrease in both the amplitude and rapidity of onset of the responses with development are consistent with the progressive degeneration of the gills and a reduction in the importance of branchial gas exchange in late larval stages.
Cellular Contraction Precedes Membrane Depolarization in Vorticella Convallaria
Authors: Shiono Hisashi , Naitoh Yutaka 
Published: April 2021

ABSTRACT
Application of a mechanical stimulus to the cell body of the peritrich ciliate Vorticella convallaria evoked an all-or-nothing membrane depolarization, the large pulse. This was always accompanied by an all-or-nothing cellular contraction, and simultaneous recordings of the two events revealed that the large pulse was always preceded by the cellular contraction. A smaller graded membrane depolarization (the medium pulse) was sometimes produced in response to a weaker mechanical stimulus. The medium pulse was accompanied by a small, graded, localized contraction of the cell body and was occasionally followed by a large pulse. When a large pulse occurred during a medium pulse, it reached the same peak level as that of a large pulse evoked without a preceding medium pulse. When a medium pulse occurred during a medium pulse, summation of the two pulses was observed. Sustained contraction causes V. convallaria to become rounded, and in this state a mechanical stimulus stronger than that used to evoke the large pulse evoked a graded depolarizing mechanoreceptor potential in the cell. We conclude that both the large and medium pulses are caused by an inward receptor current that is activated mechanically following contraction of the cell body. A localized contraction evokes a small mechanoreceptor current, causing a medium pulse. An all-or-nothing contraction evokes a saturated, all-or-nothing mechanoreceptor current, causing a large pulse.
Experimental simulation of the thrust phases of fast-start swimming of fish
Authors: Ahlborn B. , Chapman S. , Stafford R. , Blake R. W. , Harper D. G. 
Published: April 2021

ABSTRACT
Measurements of the thrust and forward impulse of a simulated fish tail and mathematical modeling indicate that the propulsive forces of fast-start swimming can be optimized by three different effects: (i) exactly inverting the tail tip vortex that is generated with the initial stroke, (ii) using a moderately flexible tail, and (iii) introducing a specific delay between the initial stroke and the return stroke. Experiments were performed with a new computer-controlled fish-tail simulation apparatus, and the results confirm the theoretical predictions of a previous study.
The interactive effects of feeding and exercise on oxygen consumption, swimming performance and protein usage in juvenile rainbow trout (Oncorhynchus mykiss)
Authors: Alsop Derek H. , Wood Chris M. 
Published: April 2021

ABSTRACT
The impacts of feeding on the rate of O2 consumption aerobic swimming performance, nitrogenous waste excretion (ammonia-N and urea-N) and protein utilization as an aerobic fuel were investigated in juvenile rainbow trout. Feeding trout to satiation (in groups of 120) resulted in rapid growth and elevated routine by 68 % relative to fasted fish and by 30 % relative to trout fed a maintenance ration of 1 % of body mass daily. This in-tank of satiation-fed trout was approximately 70 % of the observed at the critical swimming speed (UCrit) when trials were performed on individual trout in swimming respirometers. Feeding increased at all swimming speeds; the absolute elevation (specific dynamic action or SDA effect) was dependent on ration but independent of swimming velocity. There was no difference in at UCrit amongst different ration treatments, but UCrit was significantly reduced by 15 % in satiation-fed fish relative to fasted fish. These results suggest that the irreducible SDA load reduces swimming performance and that is limited by the capacity to take up O2 at the gills and/or to deliver O2 through the circulatory system rather than by the capacity to consume O2 at the tissues. Ammonia-N and urea-N excretion increased with protein intake, resulting in a 6.5-fold elevation in absolute protein use and a fourfold elevation in percentage use of protein as an aerobic fuel for routine metabolism in satiation-fed trout (50–70 %) relative to fasted fish (15 %). Urea-N excretion increased greatly with swimming speed in all treatments, but remained a minor component of overall nitrogen excretion. However, even in satiation-fed fish, ammonia-N excretion remained constant as swimming speed increased, and protein did not become more important as a fuel source during exercise. These results suggest that the reliance on protein as a fuel is greatly dependent on feeding quantity (protein intake) and that protein is not a primary fuel for exercise as suggested by some previous studies.
Na+/H+ exchange and osmotic shrinkage in isolated trout hepatocytes
Authors: Fossat B. , Porthé-Nibelle J. , Pedersen S. , Lahlou B. 
Published: April 2021

ABSTRACT
The ability of rainbow trout liver cells to regulate their intracellular pH (pHi) was studied using two methods on hepatocytes isolated by collagenase digestion: (i) by monitoring pHi with the fluorescent dye BCECF-AM, and (ii) by measuring the amiloride-sensitive uptake of 22Na, which represents Na+/H+ exchange. In low-Na+ medium (⩽ 16 mmol l−1), Na+ uptake was reduced by approximately 70 % in the presence of amiloride derivatives (DMA or MPA, 10−4 mol l−1).
Changing separately either the extracellular pH (pHe) or the intracellular pH (pHi, clamped by treating the cells with nigericin in the presence of 140 mmol l−1 K+) between 6 and 8 induced an increase in the rate of Na+ uptake when pHe was raised or when pHi was reduced.
When transferred to hypertonic medium, hepatocytes shrank to nearly 72 % of their initial volume, and thereafter a slow and partial regulatory volume increase phase was observed, with an increase in the amiloride-sensitive rate of Na+ uptake and an increase in intracellular pH. As DIDS-sensitive Cl− uptake was concomitantly enhanced, it is suggested that hypertonic stress activates Na+/H+ and Cl−/HCO3− exchange.