bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Functional Morphology of Singing in the Cricket
Authors: Pfau H. K. , Koch U. T. 
Published: April 2021

ABSTRACT
We describe the functional morphology of the singing apparatus of the cricket. There are three main functional sections of song mechanics, which partly overlap: (1) preparation for singing (lifting of the wings) and the reverse process (lowering of the wings at the end of the song); (2) singing movements (closing and opening of the wings); and (3) movements that adjust the pressure of the plectrum on the file (engagement force).
In the case of song preparation, the mesotergum + first axillaries + second axillaries + wings form a functional unit. This unit is moved around a transverse hinge axis, which runs through both fulcrum joints. The muscles suitable for wing lifting are the prothoracic furca muscle and the mesothoracic tegula muscle. Those suitable for wing lowering are the prothoracic dorsolongitudinal muscles and the mesothoracic axillary 4, subalar and furca muscles. Lifting and lowering of the wings are superimposed by bistable mechanisms, which are adjustable (mesothoracic medial dorsolongitudinal muscles).
In the case of closing movements (dorsoventral muscles) and opening movements (basalar and subalar muscles), the mesotergum and the wings are moved relative to each other, as for flight movements, but with the wings remaining folded back. The mesotergum is rotated down (closing) and up (opening) around a transverse hinge axis that runs through the caudal joints between the mesotergum and postnota. The path of movement of the wing and its sound-generating structure (i.e. plectrum or file respectively) is determined by an obliquely oriented hinge axis between the mesotergum and first axillary. During opening and closing, the lifted singing position of the wings is stabilized by the medial dorsolongitudinal muscles. We also discuss the role of other muscles that affect singing movements.
The third axillary (and its muscle) and the postnotum [and its muscles, the furca muscle and the lateral (short) dorsolongitudinal muscle] are the main elements in the system that adjusts the engagement force of the wings. When left axillary 3 muscle contracts, the medial part of the left third axillary is rotated caudally (in its vertical hinge joint with the first median plate) against the anal part of the wing. The anal part is bent and rotated upwards, increasing the pressure of the left plectrum against the right file. Conversely, the right axillary 3 muscle, which moves the file away from the plectrum, is able to reduce the pressure. The left furca muscle (the antagonist of left axillary 3 muscle) and the left lateral (short) dorsolongitudinal muscle (the ‘synergist’ of left axillary 3 muscle), and the corresponding muscles on the right side (which have opposite functions), allow a large range of different engagement forces. The results are compared with the work of other authors on the functional morphology of this system and with the results of electrophysiological investigations. New aspects of the evolution of the singing mechanisms are discussed.
Integrated Responses to Exhaustive Exercise and Recovery in Rainbow Trout White Muscle: Acid–Base, Phosphogen, Carbohydrate, Lipid, Ammonia, Fluid Volume and Electrolyte Metabolism
Authors: Wang Yuxiang , Heigenhauser George J. F. , Wood Chris M. 
Published: April 2021

ABSTRACT
White muscle and arterial blood plasma were sampled at rest and during 4 h of recovery from exhaustive exercise in rainbow trout. A compound respiratory and metabolic acidosis in the blood was accompanied by increases in plasma lactate (in excess of the metabolic acid load), pyruvate, glucose, ammonia and inorganic phosphate levels, large elevations in haemoglobin concentration and haematocrit, red cell swelling, increases in the levels of most plasma electrolytes, but no shift of fluid out of the extracellular fluid (ECF) into the intracellular fluid (ICF) of white muscle. The decrease in white muscle pHi was comparable to that in pHe; both recovered by 4 h. Creatine phosphate and ATP levels were both reduced by 40% after exercise, the former recovering within 0.25 h, whereas the latter remained depressed until 4 h. Changes in creatine concentration mirrored those in creatine phosphate, whereas changes in IMP and ammonia concentration mirrored those in ATP. White muscle glycogen concentration was reduced 90% primarily by conversion to lactate; recovery was slow, to only 40% of resting glycogen levels by 4 h. During this period, most of the lactate and metabolic acid were retained in white muscle and there was excellent conservation of carbohydrate, suggesting that in situ glycogenesis rather than oxidation was the major fate of lactate. The redox state ([NAD+]/[NADH]) of the muscle cytoplasm, estimated from ICF lactate and pyruvate levels and pHi, remained unchanged from resting levels, challenging the traditional view of the ‘anaerobic’ production of lactate. Furthermore, the membrane potential, estimated from levels of ICF and ECF electrolytes using the Goldman equation, remained unchanged throughout, challenging the view that white muscle becomes depolarized after exhaustive exercise. Indeed, ICF K+ concentration was elevated. Lactate was distributed well out of electrochemical equilibrium with either the membrane potential (Em) or the pHe–pHi difference, supporting the view that lactate is actively retained in white muscle. In contrast, H+ was actively extruded. Ammonia was distributed passively according to Em rather than pHe–pHi throughout recovery, providing a mechanism for retaining high ICF ammonia levels for adenylate resynthesis in situ. Although lipid is not traditionally considered to be a fuel for burst exercise, substantial decreases in free carnitine and elevations in acyl-carnitines and acetyl-CoA concentrations indicated an important contribution of fatty acid oxidation by white muscle during both exercise and recovery.
The Acquisition of Forward Motility in the Spermatozoa of the PolychaeteArenicola Marina
Authors: Pacey A. A. , Cosson J. C. , Bentley M. G. 
Published: April 2021

ABSTRACTSperm activation in the polychaete annelid Arenicola marina was investigated using video microscopy following the in vitro and in vivo manipulation of gametes. Careful observation of spermatozoa obtained from spawning animals indicated that they were immotile immediately after their release from the gonopores, but that they subsequently became motile following dilution in sea water. It was determined that under the pH conditions of the coelomic cavity (pH 7.3) sperm motility was suppressed, whereas upon dilution in sea water buffered at pH 8.2, motility was triggered. It is hypothesised that sperm activation, under normal conditions, occurs in two stages. The first results in the liberation of free spermatozoa from sperm morulae, allowing them to be spawned; this process is stimulated by an endocrine factor and occurs in vivo during normal spawning. The second involves the switching on of the sperm flagellar apparatus, which occurs when spermatozoa are subjected to change in extracellular pH associated with their dilution in sea water. Pharmacological agents such as ammonium chloride and quinacrine are shown to stimulate the breakdown of sperm morulae and the acquisition of sperm motility. Motile spermatozoa of A. marina, in artificial sea water buffered at pH 8.2, can remain motile for over 5 h, have a beat frequency of approximately 50 Hz and have average path velocities of between 100 and 120 μm s−1. Motile spermatozoa under these conditions can also display the phenomenon of intermittent swimming.
Sodium-Coupled Neurotransmitter Transport: Structure, Function And Regulation
Authors: Kanner Baruch I. 
Published: April 2021

ABSTRACT
The removal of neurotransmitters by their transporters – located in the plasma membranes of nerve terminals and glial cells – plays an important role in the termination of synaptic transmission. In the last 3 years, many neurotransmitter transporters have been cloned. Structurally and functionally they can be divided into two groups: glutamate transporters, of which to date three have been cloned, couple the flow of glutamate to that of sodium and potassium. The second group of transporters includes those for GABA, glycine, taurine, norepinephrine, dopamine and serotonin. They are sodium-and chloride-dependent, but do not require potassium for function. One of these, the GABAA transporter, encoded by GAT-1, is perhaps the best characterized. It has been purified and reconstituted and has a molecular mass of around 80 kDa, of which 10–15 kDa is sugar. Amino and carboxyl termini (around 50 amino acids each) are not required for function. The transporter is protected against proteolysis at multiple sites by GABA, provided that the two cosubstrates – sodium and chloride – are present. Several amino acid residues that are critical for function have been identified in the GABA transporter. These include arginine-69 and tryptophan-222 located in the first and fourth putative transmembrane helices, respectively. The first is possibly involved in the binding of chloride. The tryptophan appears to serve as a binding site for the amino group of GABA.
Structure, Function and Brain Localization of Neurotransmitter Transporters
Authors: Jursky Frantisek , Tamura Shigehiko , Tamura Akiko , Mandiyan Sreekala , Nelson Hannah , Nelson Nathan 
Published: April 2021

ABSTRACT
We studied four different cDNAs encoding GABA transporters and three different cDNAs encoding glycine transporters in mouse and rat brains. A genomic clone of two of the glycine transporters (GLYT1a and GLYT1b) revealed that they derive from differential splicing of a single gene. The third glycine transporter (GLYT2) is encoded by a separate gene. Antibodies were raised against seven of these neurotransmitter transporters and their cytochemical localization in the mouse brain was studied. In general, we observed a deviation from the classical separation of neuronal and glial transporters. It seems that each of the neurotransmitter transporters is present in specific places in the brain and is expressed in a different way in very specific areas. For example, the GABA transporter GAT4, which also transports β-alanine, was localized to neurons. However, GAT1, which is specific for GABA, was localized not only to neurons but also to glial cells. The recently discovered glycine transporter GLYT2 was of particular interest because of its deviation from the general structure by a very extended N terminus containing multiple potential phosphorylation sites. Western analysis and immunocytochemistry in frozen sections of mouse brain demonstrated a clear caudal–rostral gradient of GLYT2 distribution, with massive accumulation in the spinal cord and brainstem and less in the cerebellum. Its distribution is typically neuronal and it is present in processes with varicosities. A correlation was observed between the pattern we obtained and that observed previously from strychnine binding studies. The results indicate that GLYT2 is involved in the termination of glycine neurotransmission at the classical inhibitory system in the hindbrain. The availability of four different GABA transporters made it possible to look for specific binding sites upon the neurotransmitter transporters. An extensive program of site-directed mutagenesis led us to identify a potential neurotransmitter binding site on the GABA transporters.
Role of the Invertebrate Electrogenic 2Na+/1H+ Antiporter in Monovalent and Divalent Cation Transport
Authors: Ahearn G. A. , Zhuang Z. , Duerr J. , Pennington V. 
Published: April 2021

ABSTRACT
In recent years, an electrogenic 2Na+/1H+ antiporter has been identified in a variety of invertebrate epithelial brush-border membranes of gut, kidney and gill tissues. The antiporter differs significantly in its physiological properties from the electroneutral 1Na+/1H+ antiporter proposed for vertebrate cells. In all invertebrate cells examined, the antiporter displayed a 2:1 transport stoichiometry, responded to an induced transmembrane potential and exhibited a high binding affinity for the divalent cation Ca2+, which acted as a competitive inhibitor of Na+ transport. A monoclonal antibody specific for the crustacean electrogenic antiporter inhibited 2Na+/1H+ exchange, but was without effect on Na+-dependent D-glucose transport. Immunoreactivity was localized at hepatopancreatic brush-border and vacuolar membranes, antennal gland coelomosac podocytes and posterior gill epithelial cells – all locations where published reports described unique cation exchange kinetics. Significant fractions of Ca2+ transport into invertebrate cells across brush-border membranes occurred by an electrogenic, amiloride-sensitive exchange process, probably by the 2Na+/1H+ antiporter, and this transport was markedly inhibited by exogenous zinc and cadmium. A recently identified electroneutral, amiloride-sensitive, hepatopancreatic epithelial basolateral Na+/H+ antiporter was uninfluenced by the brush-border monoclonal antibody, exhibited an apparent 1:1 transport stoichiometry and possessed a minimal divalent cation specificity. Calcium transport at this epithelial pole occurred by the combination of a Ca2+/Na+ antiporter, an ATP-dependent Ca2+-ATPase and a verapamil-sensitive calcium channel. These crustacean brush-border and basolateral transporters may play significant roles in calcification and heavy metal detoxification.
The Molecular Basis of Chloride Transport in Shark Rectal Gland
Authors: Riordan John R. , Forbush Bliss , Hanrahan John W. 
Published: April 2021

ABSTRACT
Transepithelial Cl− secretion in vertebrates is accomplished by a secondary active transport process brought about by the coordinated activity of apical and basolateral transport proteins. The principal basolateral components are the Na+/K+-ATPase pump, the Na+/K+/2Cl− cotransporter (symporter) and a K+ channel. The rate-limiting apical component is a cyclic-AMP-stimulated Cl− channel. As postulated nearly two decades ago, the net Cl− movement from the blood to the lumen involves entry into the epithelial cells with Na+ and K+, followed by active Na+ extrusion via the pump and passive K+ exit via a channel. Intracellular [Cl−] is raised above electrochemical equilibrium and exits into the lumen when the apical Cl− channel opens. Cl− secretion is accompanied by a passive paracellular flow of Na+. The tubules of the rectal glands of elasmobranchs are highly specialized for secreting concentrated NaCl by this mechanism and hence have served as an excellent experimental model in which to characterize the individual steps by electrophysiological and ion flux measurements. The recent molecular cloning and heterologous expression of the apical Cl− channel and basolateral cotransporter have enabled more detailed analyses of the mechanisms and their regulation. Not surprisingly, since hormones acting through kinases control secretion, both the Cl− channel, which is the shark counterpart of the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator), and the cotransporter are regulated by phosphorylation and dephosphorylation. The primary stimulation of secretion by hormones employing cyclic AMP as second messenger activates CFTR via the direct action of protein kinase A (PKA), which phosphorylates multiple sites on the R domain. In contrast, phosphorylation of the cotransporter by as yet unidentified kinases is apparently secondary to the decrease in intracellular chloride concentration caused by anion exit through CFTR.
Physiological Effects of two Fmrfamide-Related Peptides from the Crayfish Procambarus Clarkii
Authors: Skerrett Martha , Peaire Amy , Quigley Patricia , Mercierf A. Joffre 
Published: April 2021

ABSTRACT
The present study examined the effects of two recently identified neuropeptides on crayfish hearts and on neuromuscular junctions of the crayfish deep abdominal extensor muscles. The two peptides, referred to as NF1 (Asn-Arg-Asn-Phe-Leu-Arg-Phe-NH2) and DF2 (Asp-Arg-Asn-Phe-Leu-Arg-Phe-NH2), increased the rate and amplitude of spontaneous cardiac contractions and increased the amplitude of excitatory junctional potentials (EJPs) in the deep extensors. Both effects were dose-dependent, but threshold and EC50 values for the cardiac effects were at least 10 times lower than for the deep extensor effects. The heart responded equally well to three sequential applications of peptide in any given preparation, but the responses of the deep extensors appeared to decline with successive peptide applications. The results support the hypothesis that these two neuropeptides act as neurohormones to modulate the cardiac and neuromuscular systems in crayfish.
Quantal synaptic current recordings from the deep extensor muscles indicate that both peptides increase the number of quanta of transmitter released from synaptic terminals. Neither peptide elicited a measurable change in the size of quantal synaptic currents. NF1 caused a small increase in muscle cell input resistance, while DF2 did not alter input resistance. These data suggest that DF2 increases EJP amplitudes primarily by increasing transmitter release, while the increase elicited by NF1 appears to involve presynaptic and postsynaptic mechanisms.
Localisation And Characteristics of Natriuretic Peptide Receptors in the Gills of the Atlantic Hagfish Myxine Glutinosa (Agnatha)
Authors: Toop Tes , Donald John A. , Evans David H. 
Published: April 2021

ABSTRACT
Specific binding of iodinated natriuretic peptides 125I-ANP and 125I-CNP was examined in the gill of the Atlantic hagfish Myxine glutinosa by tissue section autoradiography, saturation and competition analysis of binding to membrane preparations, affinity cross-linking, followed by SDS-PAGE and guanylate cyclase assays. Autoradiographs showed specific, saturable binding on the respiratory lamellar epithelium. In vitro analysis of the binding sites demonstrated that 125I-ANP bound to two receptor sites with the same affinity (Kd=15.4±1.6 pmoll−1; Bmax=45.9±3.0fmol mg−1 protein). 125I-CNP bound to high- and low-affinity receptor sites; variables for the high-affinity site (Kd=12.9±4.7pmoll’; Bmax=23.4±6.5fmol mg−1 protein) did not differ from those for the 125I-ANP sites. The low-affinity site had an apparent Kd and Bmax of 380±80 pmoll−1 and 120±21fmol mg−1 protein, respectively. All receptors had an apparent molecular mass of approximately 150 kDa, with no indication of a mammalian type NPR-C at a lower apparent molecular mass. 1 nmol l−1 unlabelled rANP and 20 and 30 nmol l−1 unlabelled pCNP and C-ANF, respectively, competed for 50% of 125I-ANP sites. 0.1nmoll−1 rANP and pCNP and 8 nmol l−1 C-ANF competitively inhibited 50 % of 125I-CNP binding. Both rANP and pCNP stimulated cyclic GMP production, although rANP was a more potent stimulator than was pCNP. C-ANF did not stimulate cyclic GMP production. These data suggest the existence of an ANP guanylate-cyclase-linked receptor similar to the mammalian NPR-A and an ANP/CNP receptor that may be similar to, although not structurally homologous with, the mammalian NPR-C clearance receptor.
Behavioural Evidence for the Use of Magnetic Material in Magnetoreception by a Migratory Bird
Authors: Beason Robert C. , Dussourd Natalie , Deutschlander Mark E. 
Published: April 2021

ABSTRACT
The biophysical mechanism of vertebrate magnetic sensory perception has not been completely resolved. We here provide evidence for the use of a magnetic material (probably magnetite) by a vertebrate to detect the earth’s magnetic field. The role of magnetite in bobolink (Dolichonyx oryzivorus) orientation was assessed by magnetizing the birds with a magnetic pulse in one of three orientations. Bobolinks magnetized with different polarities were significantly oriented in directions different from one another and from their controls. Treatment with a second pulse having the opposite polarity to the first resulted in random orientation for each group. These results indicate an effect specific to a particle-based magnetoreceptor. The use of magnetite particles for magnetoreception is not in conflict with other reports on the use of photopigments for this purpose. The two mechanisms could be used in a complementary manner for detecting the same or different aspects of the magnetic field.
Variation in the Respiratory Quotient of Birds and Implications for Indirect Calorimetry Using Measurements of Carbon Dioxide Production
Authors: Walsberg Glenn E. , Wolf Blair O. 
Published: April 2021

ABSTRACT
Determination of animal power consumption by indirect calorimetry relies upon accurate estimation of the thermal equivalent of oxygen consumed or carbon dioxide produced. This estimate is typically based upon measurement or assumption of the respiratory quotient (RQ), the ratio of CO2 produced to O2 consumed. This ratio is used to indicate the mixture of lipids, carbohydrates and proteins in the metabolic substrate. In this analysis, we report the RQ for two bird species, Passer domesticus and Auriparus flaviceps, under several dietary and fasting regimes. RQ commonly differed substantially from those typically assumed in studies of energy metabolism and often included values below those explainable by current knowledge. Errors that could result from these unexpected RQ values can be large and could present the primary limit to the accuracy of power consumption estimates based upon measurement of carbon dioxide production.
Physiology and Behaviour of Free-Swimming Atlantic COD (Gadus Morhua) Facing Fluctuating Temperature Conditions
Authors: Claireaux G. , Webber D. M. , Kerr S. R. , Boutilier R. G. 
Published: April 2021

ABSTRACT
Atlantic cod (Gadus morhua L.), acclimated to 5 °C, were equipped with ultrasonic transmitters which allowed the continuous monitoring of their vertical movements and heart rate. Fish were then placed in a 125 m3 tower tank in which the various thermal conditions they encounter in their natural environment were reproduced. Physiological and behavioural responses of cod were followed in parallel to the induced environmental changes. The experimental conditions studied in the tower tank were also reproduced in a swimming respirometer, where oxygen consumption and heart rate could be monitored within the activity range of a free-swimming animal.
In a homogeneous water column, a rise in temperature induced marked increases in fish swimming activity, heart rate and heart beat-to-beat variability. In a thermally stratified environment, voluntary activity also increased when the thermal structure of the water column was altered, though no temperature-dependent changes in heart rate were observed. In this case, fish avoided the new temperature conditions, exhibiting distinct thermoregulatory behaviour. Stratification of the water column also prompted daily cyclic changes in fish distribution, animals tending to be in deeper and colder water layers during the day and in shallower and warmer layers at night.
Respirometry experiments revealed that the thermoregulatory behaviour observed in free-ranging fish was probably driven by the energetic expedient of maintaining the physiological status quo – i.e. avoiding bioenergically costly reacclimation processes. Indeed, acute temperature increases or decreases of 2.5 °C led to marked differences in oxygen consumption, with metabolic rate changes of 15 and 30 %, respectively. The persistent linear relationship between heart rate and oxygen consumption allowed us to estimate, from the heart rate recorded in free-swimming fish, the entire range of metabolic responses that cod underwent voluntarily while experiencing a thermally stratified water column. The most profound metabolic effect, however, was observed with feeding, when oxygen consumption increased by as much as 80 %, resulting in an estimated 90 % reduction in their subsequent scope for activity.