bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular analysis of FMRFamide- and FMRFamide-related peptides (FaRPS) in the cuttlefish Sepia officinalis
Authors: Loi Poh Kheng , Tublitz Nathan 
Published: April 2021

ABSTRACT
The display of complex color patterns of the cuttlefish Sepia officinalis is under the regulation of the FMRFamide-related peptide (FaRP) family, but their exact identities are unknown. We report the isolation and characterization of a full-length FaRP cDNA from the brain of S. officinalis. This cDNA is 1850 base pairs long, including an open reading frame of 996 base pairs. The cDNA encodes a precursor protein containing four FaRPs: ALSGDAFLRF, FIRF, FLRF and FMRF. Each propeptide has a C-terminal glycine residue that is presumably converted post-translationally to an amide. Every FaRP propeptide is also flanked by basic amino acid residues at the amino and carboxy termini, indicative of putative cleavage sites during post-translational processing. Each of the four FaRPs encoded by this cDNA causes chromatophore expansion when assayed in an in vitro chromatophore bioassay. Thus, it is likely that one or more of the FaRPs identified in this study are involved in controlling chromatophore activity in cuttlefish.
Reporter Gene Constructs Suggest That the Caenorhabditis Elegans Avermectin Receptor β-Subunit is Expressed Solely in the Pharynx
Authors: Laughton David L. , Lunt George G. , Wolstenholme Adrian J. 
Published: April 2021

ABSTRACT
Gene promoter/LacZ reporter constructs were made in order to analyse the expression of the β-subunit of the Caenorhabditis elegans glutamate-gated Cl− channel (Glu-Cl) receptor. Southern blot analysis of the C. elegans cosmid C35E8 identified a 4 kbp EcoRI fragment which contained the 5′ portion of the Glu-Cl β coding sequence together with 5′ flanking sequences. This was subcloned and used as the template for polymerase chain reaction (PCR) amplification of a DNA fragment encoding the first 24 amino acid residues of Glu-Cl β together with 1.4 kbp of 5′ genomic sequence. The fragment was subcloned into the LacZ expression vector pPD22.11 to form a translational reporter fusion. After injection of the construct into worms, six stably transformed lines were established and assayed for β-galactosidase activity. Stained nuclei were observed in the pharyngeal metacorpus in adults and in all larval stages, and stained nuclei were seen in many embryos undergoing morphogenesis. Additional stained nuclei towards the terminal bulb of the pharynx were observed in larval stages. These results provide further evidence that the Glu-Cl receptor mediates the glutamatergic inhibition of pharyngeal muscle via the M3 motor neurone and point to inhibition of pharyngeal pumping as a major mode of action for avermectins.
Wavelengths of Bioconvection Patterns
Authors: Bees M. A. , Hill N. A. 
Published: April 2021

ABSTRACT
Bioconvection occurs as the result of the collective behaviour of many micro-organisms swimming in a fluid and is realised as patterns similar to those of thermal convection which occur when a layer of water is heated from below. A methodology is developed to record the bioconvection patterns that are formed by aqueous cultures of the single-celled alga Chlamydomonas nivalis. The analysis that is used to quantify the patterns as a function of cell concentration, suspension depth and time is described and experimental results are presented.
Hummingbird Hovering Energetics During Moult of Primary Flight Feathers
Authors: Chai Peng 
Published: April 2021

ABSTRACT
How does a hovering hummingbird compensate for the loss of flight feathers during moult when the mechanism of lift force generation by flapping wings is impaired? The flight performance of five individual ruby-throated hummingbirds with moulting primary flight feathers and reduced wing area was compared with that before their moult. Hummingbirds were flown in reduced air densities using normoxic heliox so that a range of flight energetics was displayed. The rate of moulting and the extent of wing area loss varied among individuals. One female could tolerate a 30 % loss of wing area in moulting and flew with only three outer primaries per wing. Further exploratory study using the artificial reduction of wing area, either by cutting the tips of the outer primaries of a male or by plucking the secondaries of two females, suggested that secondaries play a minor role in lift force generation during hovering whereas the tip area of primaries is crucial. For the five birds, ranges of whole-bird oxygen consumption rates, wingbeat kinematics (stroke amplitude) and lift coefficients did not vary during the moult. This constancy was mainly achieved through weight loss that alleviated aerodynamic force requirements for weight support during hovering. Since the metabolic power expenditure during moult was similar to that of normal birds but the mechanical power requirement was reduced, the flight efficiency also showed a sharp reduction during moult. This increased cost of flight may result from disruption of the integrity of the flight machinery. Overall, the control of body mass in hummingbirds can provide similar aerodynamic, muscle mechanical and physiological capacities under conditions of variable flight demand.
Serotonin-Induced Modulation of Excitability in an Identified Helisoma Trivolvis Neuron
Authors: Achee Nicole L. , Zoran Mark J. 
Published: April 2021

ABSTRACT
Exogenous serotonin (5-hydroxytryptamine; 5-HT) induced inhibitory effects in Helisoma trivolvis buccal neuron 5 (B5), which included a hyperpolarization of the membrane potential, a reduction in input resistance and a decrease in the stimulus-evoked spiking rate. The reversal potential for the 5-HT-induced hyperpolarization was −88.7 mV, suggesting the involvement of an enhanced K+ conductance. Input/output curves measuring the number of action potentials evoked by current injection demonstrated a 5-HT-induced reduction in B5 neuronal excitability that was dose-dependent with a 50 % inhibitory concentration (IC50) of 1.1 μmol l−1. These inhibitory effects on neuron B5 were in striking contrast to the excitatory effects of this neurotransmitter on the buccal radular tensor motoneuron B19. In this neuron, 5-HT elicited a sustained depolarization and enhanced spiking activity. Previous cell culture studies have demonstrated that 5-HT also inhibits B19 growth cone motility and neurite outgrowth, but has no effect on the extension of neuritic processes from neuron B5. These effects, and the divergent effects of 5-HT on the outgrowth of neurons B5 and B19, probably result from differential effects of 5-HT on neuronal membrane potential and excitability. Modulation of the levels of spiking activity, translated into changes in neuronal Ca2+ levels, would cause alterations in growth cone motility. Previous studies have shown that the effects of 5-HT on B19 membrane potential and neurite extension are cyclic-AMP-dependent. We have used specific activators and inhibitors of signal transduction mechanisms to demonstrate that the 5-HT-induced reductions in B5 neuronal excitability are cyclic-AMP-independent and may involve the lipoxygenase pathway of arachidonic acid metabolism. Our results support the hypothesis that modulatory signals and signal transduction pathways regulating the plasticity of mature neural circuits may also modulate the differentiation of the neurons comprising those networks during development.
Characterization of Voltage- and Ca2+-Activated K+ Channels in Squid Olfactory Receptor Neurons
Authors: Lucero Mary T. , Chen Nansheng 
Published: April 2021

ABSTRACT
We performed whole-cell voltage-clamp experiments on isolated olfactory receptor neurons from the squid Lolliguncula brevis. Total outward currents were composed of three identifiable K+ currents: a delayed rectifier K+ current that showed slow inactivation and was sensitive to 5 mmol l−1 tetraethylammonium; a rapidly inactivating, 4-aminopyridine (4-AP)-sensitive, A-type K+ current and a Ca2+-sensitive K+ current that was blocked by 200 nmol l−1 charybdotoxin and 10 mmol l−1 Cd2+ but was insensitive to apamin. The proportion of each current type varied from cell to cell, suggesting that responses to a given odorant would depend on the complement of channels present. The kinetics of the K+ currents were affected by temperature, with Q10 values ranging from 2 to 6. The identification and characterization of these K+ currents will greatly aid our understanding of action potential generation in these cells and will facilitate modelling of how odor responses are transduced and coded in squid olfactory receptor neurons.
The Role of Ca2+ in Deflection-Induced Excitation of Motile, Mechanoresponsive Balancer Cilia in the Ctenophore Statocyst
Authors: Lowe Brian 
Published: April 2021

ABSTRACT
Motile, mechanoresponsive cilia (balancers) in ctenophore statocysts, like vertebrate hair cells, are excited or inhibited depending upon the direction in which they are deflected. Balancers, however, may become either excited (beat rapidly) or inhibited (beat slowly) by deflection in the same direction, depending on the sign of ctenophore geotaxis (positive or negative). The beat frequency of many cilia is controlled by concentrations of Ca2+, membrane potential and neural input. How these factors affect deflection-induced ciliary beating in balancers was investigated. Deflection-induced excitation of balancers in whole Mnemiopsis leidyi larvae and dissected adult (Mnemiopsis leidyi, Pleurobrachia pileus) statocysts was reversibly inhibited by the Ca2+ channel inhibitors Co2+, Mg2+, Ni2+ and Mn2+. Deflection-induced excitation in balancers of isolated adult M. leidyi balancer groups was also inhibited by Co2+ or by Ca2+-free medium. Isolated balancer group cilia, like balancer cilia of intact ctenophores, exhibited responses to either sign of geotaxis and graded responses to deflection. Isolated balancers that were chemically depolarized in high-[K+], Ca2+-free medium were excited by local application of Ca2+ onto the ciliary bases, but not onto the cell bases or the ciliary tips. It is proposed that deflection-induced excitation of balancers is due to influx of Ca2+ through stretch- and voltage-activated channel activity. The sign of geotaxis of whole larvae and dissected adult statocysts was switched by electrical stimulation. Thus, neural input may participate in reversing the directional sensitivity of balancer cells.
Analysis of Epithelial Transport by Measurement of K+, Cl− and pH Gradients in Extracellular Unstirred Layers: Ion Secretion and Reabsorption by Malpighian Tubules of Rhodnius Prolixus
Authors: Collier K. A. , O’donnell M. J. 
Published: April 2021

ABSTRACT
The pH and concentrations of K+ and Cl− in the unstirred layer (USL) associated with the basolateral surfaces of the upper and lower Malpighian tubules of Rhodnius prolixus were measured using extracellular ion-selective microelectrodes. When stimulated with 5-hydroxytryptamine (5-HT) in vitro, the upper Malpighian tubule secretes Na+, K+, Cl− and water at high rates; the lower Malpighian tubule reabsorbs K+ and Cl− but not water. Concentrations of K+ and Cl− in the unstirred layer of the lower Malpighian tubule ([K+]USL, [Cl−]USL) were greater than those in the bathing saline, consistent with the accumulation of K+ and Cl− in the USL during 5-HT-stimulated KCl reabsorption. [K+]USL exceeded [K+]Bath by as much as 5.3-fold. Calculations of K+ flux based on measurements of [K+]USL at various distances from the tubule surface agreed well with flux calculated from the rate of fluid secretion and the change in K+ concentration of the secreted fluid during passage through the lower tubule. Concentrations of K+ in the unstirred layer of the upper Malpighian tubule were reduced relative to those in the bathing saline, consistent with depletion of K+ from the USL during 5-HT-stimulated secretion of K+ from bath to lumen. Changes in [K+]USL during 5-HT-stimulated K+ secretion from single upper Malpighian tubule cells could be resolved. Although differences between [K+]USL and [K+]Bath were apparent for upper and lower tubules in an in situ preparation, they were reduced relative to the differences measured using isolated tubules. We suggest that convective mixing of the fluids around the tubules by contractions of the midgut and hindgut reduces, but does not eliminate, differences between [K+]USL and [K+]Bathin situ. The USL was slightly acidic relative to the bath in 5-HT-stimulated upper and lower tubules; contributions to USL acidification are discussed. The results also show that the techniques described in this paper can resolve rapid and localized changes in ion transport across different regions of Malpighian tubules in response to stimulants or inhibitors of specific membrane transporters.
Kinematic and Electromyographic Analysis of Steady Pectoral Fin Swimming in the Surfperches
Authors: Drucker Eliot G. , Jensen Jeffrey S. 
Published: April 2021

ABSTRACT
The musculoskeletal mechanism of pectoral fin propulsion was investigated in representatives of the two subfamilies of the Embiotocidae (surfperches). Kinematic and electromyographic records of steady swimming by the open-water cruiser Amphistichus rhodoterus and the benthic maneuverer Embiotoca lateralis were compared at 80 % of the species’ respective pectoral–caudal gait transition speeds. Synchronized records of fin movement and the intensity of pectoral muscle activity allowed previous hypotheses of muscle function, based on anatomical lines of action, to be tested. Divisions of the pectoral musculature inserting on the central and trailing-edge fin rays serve simple functions of abduction and adduction. Muscles controlling the fin’s leading edge, by contrast, play more complex roles during the fin stroke, including deceleration of the fin at the downstroke–upstroke transition and rotation of the adducted fin during the non-propulsive period between fin beats.
In spite of their phylogenetic and ecological divergence, the surfperches exhibit a number of mechanistic similarities which probably characterize the family. The timings of kinematic events and the maximal excursions of the fin tip, as well as the temporal order of muscle activation and the time to peak activity, are largely conserved. The predominant dorsoventral component of fin movement during the stride is consistent with a lift-based mechanism of propulsion. E. lateralis exhibits a greater anteroposterior range of motion and a more continuous period of fine motor control of the fin than A. rhodoterus, differences which may correspond to the species’ respective capacities for maneuvering. Mechanistic variation in the family is associated with rather minor structural differences (in fin shape and fin base orientation). Owing to the similar functional demands placed on the pectoral fins of many fishes, it is probable that the mechanistic details of embiotociform swimming are widely distributed within the Perciformes.
Plateau Potentials in Motor Neurons in the Ventilatory System of the Crab
Authors: Dicaprio Ralph A. 
Published: April 2021

ABSTRACT
The motor neurons in the crab ventilatory system have previously been considered to be passive output elements in that the generation of bursts of action potentials in these neurons during ventilation was thought to be due to cyclic inhibition and excitation from the interneurons in the ventilatory central pattern generator. This study demonstrates that the large-amplitude depolarization that underlies bursts of action potentials in ventilatory motor neurons is produced by a plateau potential. These motor neurons satisfy a number of the experimental tests that have been proposed for plateau potentials, such as triggering of the burst by a brief depolarization, termination of the burst by a hyperpolarizing input, and an all-or-none suppression of the depolarizing potential by the injection of hyperpolarizing current.
Heat Increment of Feeding in Brünnich’s Guillemot Uria Lomvia
Authors: Hawkins P. A. J. , Butler P. J. , Woakes A. J. , Gabrielsen G. W. 
Published: April 2021

ABSTRACT
The rate of oxygen consumption , respiratory quotient (RQ) and deep body temperature (TB) were recorded during a single, voluntary ingestion of Arctic cod Boreogadus saida (mean mass 18.9±1.1 g, S.E.M., N=13) by five postabsorptive Brünnich’s guillemots (thick-billed murre, Uria lomvia). The birds were resting in air within their thermoneutral zone, and the fish were refrigerated to 0–2 °C. The rate of oxygen consumption increased by a factor of 1.4 during the first few minutes after ingestion, but there was no significant change in TB. Mean rate of oxygen consumption returned to preingestive levels 85 min after the birds ate the fish. The telemetered temperature of one fish reached TB within 20 min. This suggests that the persistent elevation in over the next hour corresponded to the obligatory component of the heat increment of feeding (HIF) and was not related to heating the fish. Abdominal temperature increases after diving bouts in free-ranging common guillemots (common murre, Uria aalge) are possibly achieved through the HIF, since meals are processed at sea. Of the increase in measured in the laboratory, it is calculated that 30 % is required to heat the fish, while 70 % is due to the HIF. In free-ranging birds, the excess heat provided by the HIF could contribute 6 % of the daily energy expenditure. This suggests that the HIF augments heat production in Uria spp. and thus reduces the energetic cost of thermoregulation.
The Role of the Nucleus Isthmi in Respiratory Pattern Formation in Bullfrogs
Authors: Kinkead Richard , Harris Michael B. , Milsom William K. 
Published: April 2021

ABSTRACT
The nucleus isthmi (NI) is a mesencephalic structure of the amphibian brain located between the roof of the midbrain and the cerebellum. From a neuroanatomical perspective, the NI can be compared with the pons which, in mammals, contributes to the control of breathing pattern. This study tested the hypothesis that the NI plays a critical role in breathing pattern formation in the bullfrog. More specifically, we postulated that this nucleus was the site responsible for clustering breaths into distinct episodes of breathing. This hypothesis was tested by comparing the respiratory motor output of decerebrate, paralyzed and artificially ventilated bullfrogs before and after bilateral lesions of the NI by pressure microinjections of lidocaine or kainic acid (KA) into this area. Bilateral microinjections of lidocaine or KA into the NI transformed the breathing pattern from episodic (many breaths per episode) to one of evenly spaced single breaths, without affecting the amplitude of the fictive breaths. These changes in breathing pattern were associated with an overall decrease in breathing frequency and a reduction in CO2-chemosensitivity. Breathing episodes of more than one breath reappeared during hypercarbia (3.5 % CO2 in air) after KA lesioning. Bilateral lesions to the NI did not affect the changes in the timing or the amplitude of the respiratory-related bursts elicited by pulmonary stretch receptor feedback, indicating that mechanoreflexes do not require NI input. We conclude that the NI is not responsible for the genesis of breathing episodes, but provides a tonic excitatory input to respiratory centers in the lower brainstem. The NI also plays an important role in either CO2 chemodetection or, more probably, integration of CO2 chemoreceptor information. This, in turn, contributes to the production of episodes of more than one breath.
Central Projections of the Maxillary and Antennal Nerves in the Mosquito Aedes Aegypti
Authors: Distler Paul G. , Boeckh Jürgen 
Published: April 2021

ABSTRACT
In the mosquito Aedes aegypti, CO2-sensitive receptor neurones are located together with two other types of chemoreceptor neurones in club-shaped sensilla basiconica on the most distal segment of the maxillary palps. In order to identify the central target neuropiles of these neurones and to determine whether antennal receptor neurones project into the same area, the palpal and antennal nerves were labelled by anterograde staining with horseradish peroxidase and by experimentally induced degeneration. The different methods revealed a consistent projection pattern. (1) Maxillary afferents project into the suboesophageal ganglion and ascend further into the ipsilateral antennal lobe. There, they terminate within an identified glomerulus of the ventroposterior lobe. (2) Afferents of the antennal flagellum project into all glomeruli of the ipsilateral antennal lobe, with the exception of the glomerulus innervated by the maxillary nerve. The present anatomical findings suggest that primary processing of information about CO2 levels takes place in a defined glomerulus which also receives input from other palpal chemoreceptor neurones.
Motor Patterns of Labriform Locomotion: Kinematic and Electromyographic Analysis of Pectoral Fin Swimming in The Labrid Fish Gomphosus Varius
Authors: Westneat Mark W. , Walker Jeffrey A. 
Published: April 2021

ABSTRACT
Labriform locomotion is a widespread swimming mechanism in fishes during which propulsive forces are generated by oscillating the pectoral fins. We examined the activity of the six major muscles that power the pectoral fin of the bird wrasse Gomphosus varius (Labridae: Perciformes). The muscles studied included the fin abductors (arrector ventralis, abductor superficialis and abductor profundus) and the fin adductors (arrector dorsalis, adductor superficialis and adductor profundus). Our goals were to determine the pattern of muscle activity that drives the fins in abduction and adduction cycles during pectoral fin locomotion, to examine changes in the timing and amplitude of electromyographic (EMG) patterns with increases in swimming speed and to correlate EMG patterns with the kinematics of pectoral fin propulsion. EMG data were recorded from three individuals over a range of swimming speeds from 15 to 70 cm s−1 (1–4.8 TL s−1, where TL is total body length). The basic motor pattern of pectoral propulsion is alternating activity of the antagonist abductor and adductor groups. The downstroke is characterized by activity of the arrector ventralis muscle before the other abductors, whereas the upstroke involves nearly synchronous activity of the three adductors. Most EMG variables (duration, onset time, amplitude and integrated area) showed significant correlations with swimming speeds. However, the timing and duration of muscle activity are relatively constant across speeds when expressed as a fraction of the stride period, which decreases with increased velocity. Synchronous recordings of kinematic data (maximal abduction and adduction) with EMG data revealed that activity in the abductors began after maximal adduction and that activity in the adductors began nearly synchronously with maximal abduction. Thus, the pectoral fin mechanism of G. varius is activated by positive work from both abductor and adductor muscle groups over most of the range of swimming speeds. The adductors produce some negative work only at the highest swimming velocities. We combine information from pectoral fin morphology, swimming kinematics and motor patterns to interpret the musculoskeletal mechanism of pectoral propulsion in labrid fishes.