bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation Of A Peptidergic Synapse Locally Modulates Postsynaptic Calcium Influx
Authors: Richmond J. E. , Funte L. R. , Smith W. L. , Price D. A. , Haydon P. G. 
Published: April 2021

ABSTRACT
We examined the synaptic connection between Phe-Met-Arg-Phe-NH2 (FMRFamide)-immunoreactive neurone VD4 and its target neurone Pl, both found in the central nervous system of the pond snail Helisoma trivolvis. The major FMRFamide-like peak in neurone VD4 appears to be FMRFamide itself, based on its high performance liquid chromatography (HPLC) elution time and immunoreactivity before and after oxidation, but small peaks are also present at the elution times of Phe-Leu-Arg-Phe-NH2 (FLRFamide) and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide).
The modulatory actions of the neuropeptides found in neurone VD4 were tested on the postsynaptic target cell Pl. Bath application of both the tetrapeptides FMRFamide and FLRFamide at a concentration of 10−5 mol l−1 reduced the macroscopic voltage-sensitive calcium current of neurone Pl in culture; FMRFamide by 45% and FLRFamide by 51%. Bath application of the heptapeptide GDPFLRFamide (10−5 mol l−1) reduced the calcium current by only 8%.
We reconstructed the synaptic connection between VD4 and Pl in culture. Action-potential-evoked calcium transients in neurites growing from Pl cells in culture were monitored using Fura-2. Addition of FMRFamide, FLRFamide or GDPFLRFamide reduced the magnitude of the calcium transient in Pl. Stimulation of VD4 mimicked the effects of peptide application and caused localized reductions in the action-potential-evoked calcium transients in Pl at the points of contact between the neurites of neurones VD4 and Pl. These results suggest that neurone VD4 modulates the calcium influx of neurone Pl through the release of endogenous FMRFamide-related peptides and that this modulatory action is restricted to sites of synaptic interaction.
Adaptations to a Terrestrial Existence by the Robber Crab Birgus Latro: VII. The Branchial Chamber and its Role in Urine Reprocessing
Authors: Morris S. , Taylor H. H. , Greenaway P. 
Published: April 2021

ABSTRACT
The branchial chambers of the terrestrial anomuran Birgus latro L. were examined as potential sites for urine reprocessing. The antennal glands opened at the bases of the second antennae within the anterior extension of the branchial chambers. The adjacent mouth parts and scaphognathites and the cuticle lining the ventral folds of the branchiostegite bear hydrophilic hairs. The hairs retained urine in the branchial chamber and conducted it to either the gills or the mouth. Irrigation of the branchial chambers with artificial urine demonstrated the strong net uptakes of Na+ and Cl− to be similar at approximately 4.5 μmolh−1g−1 from full-strength urine, diluting the fluid to a threshold below 20 mmol l−1.
Na+/K+-ATPase and Ca2+-ATPase activities of gill homogenates indicated Vmax values (65–127 and 11 nmol min−1 mg−1 protein, respectively) similar to those of marine species but low Km values (sodium Km=0.2–2.4mmoll−1, potassium Km=0.03–0.2mmoll−1, calcium Km=4–9 μmol l−1), which are more characteristic of freshwater species. The gills are considered to be a site of ion reclamation from the urine and this is achieved by specific morphological, biochemical and behavioural adaptations.
The Olfactory Memory of the Honeybee Apis Mellifera: I. Odorant Modulation of Short- and Intermediate-Term Memory After Single-Trial Conditioning
Authors: Smith Brian H. 
Published: April 2021

ABSTRACT
In the first 15 min after a single learning trial the olfactory memory of the honeybee, Apis mellifera, proceeds through different processing phases during which time the memory is differentially sensitive to a cooling treatment that causes amnesia. During learning about floral odours in a natural situation, several decisions would normally be made about floral choice within that period. In order to study these phenomena in more detail, single-trial proboscis extension conditioning to different odorants was used. Several stimulus-specific effects on memory consolidation in the honeybee are shown. From previous experiments it was predicted that certain odorants would be more salient conditioning stimuli. This result is confirmed. Second, generalization from the conditioned odorant to a different odorant depends on the conditioned odorant and the time postconditioning. In some combinations, responses to a novel odorant are significantly stronger than responses to the conditioning odorant after memory consolidation. These data indicate that memory recall in the honeybee, as it is evidenced by proboscis extension, is sensitive to several aspects of stimulus identity and presentation. The acquisition and recall processes are therefore much more dynamic processes than realized previously.
Electrosensory Frequency and Intensity Discrimination in the Wave-Type Electric Fish Eigenmannia
Authors: Kramer Bernd , Kaunzinger Ivo 
Published: April 2021

ABSTRACT
Eigenmannia’s frequency and intensity discrimination thresholds were determined for a range of seven frequencies (50–1700Hz), centered on a fish’s individual discharge frequency, using a conditioned go/no-go paradigm. The threshold criterion was ‘50% correct choices’ (of the rewarded stimulus, S+, over the unrewarded stimulus, S−); this was validated by testing for statistically significantly shorter response latencies for the S+ compared with the S− stimulus.
The stimuli consisted of sine wave bursts presented for up to 20 s, repeated at 2 s−1 (rise and fall times of an individual burst, 50 ms; holding time, 250 ms; silence, 150ms). When testing for frequency discrimination, the sine wave bursts alternated in frequency (Δf); for intensity discrimination, every other sine wave burst was of increased intensity (ΔI). The reference stimulus intensity was 30 dB with reference to a fish’s individual absolute threshold for a continuous sine wave at that frequency, previously determined using a conditioned go response.
Sensory discrimination was best close to a fish’s individual discharge frequency. At 30 dB sensation level, fish discriminated frequency differences as small as 0.52 Hz (0.60 and 0.79 Hz in two other individuals) and intensity differences as small as 0.56dB (1 dB in two other fish).
At stimulus frequencies different from a fish’s discharge frequency, Eigenmannia’s frequency discrimination declined at lower frequencies at a rate of up to 1 Hz octave−1, and at higher frequencies at a rate of up to 3 Hz octave−1. For Eigenmannia’s intensity discrimination a similar loss was observed: at frequencies lower than a fish’s discharge frequency, intensity discrimination thresholds rose at a rate of less than 1 dB octave−1, while the rate was below 2 dB octave−1 for higher frequencies.
Compared with other acoustico-lateral senses in lower vertebrates, Eigenmannia’s electrosensory frequency and intensity discrimination is unusually high, in the range of that known for audition in the most sensitive higher vertebrates with a cochlea (for example, human). This emphasizes Eigenmannia’s specialized ‘active’ electrosensory system, which detects the presence of a stimulus field as the modulation of a fish’s own ‘carrier’ signal in amplitude and phase (beat analysis), as opposed to ‘passive’ sensory systems, which must deal with unpredictable signals from the environment as they occur.
How Stimulus Direction Determines the Trajectory of the Mauthner-Inthated Escape Response in a Teleost Fish
Authors: Eaton Robert C. , Emberley Deanna S. 
Published: April 2021

ABSTRACT
Fishes use the Mauthner-initiated C-start for short-latency evasion of predators. C-starts consist of a sudden turn (stage 1) and a rapid acceleration (stage 2). We analyzed high-speed ciné films of goldfish C-starts elicited by dropping a ball into the water. It was previously thought that stage 1 angle does not vary concomitantly with the angle of the threatening stimulus relative to the position of the fish. We found, however, a significant inverse relationship between the direction of the impact of the ball and the angle turned by the end of stage 1. When starting near a wall, or when its usual trajectory was blocked by a wall, the fish used an escape route that was not predictable from the stimulus angle. The fish did not appear to correct its trajectory if it began to turn towards the ball. This behavioral evidence supports the previous notion that the underlying neural command is ballistic and does not use sensory information from the stimulus once the movement begins. If this is so, the fish probably utilizes information on obstacle location in the interval leading up to the trigger stimulus.
Vortex Formation in the Tethered Flight of the Peacock Butterfly Inachis IO L. (Lepidoptera, Nymphalidae) and Some Aspects of Insect Flight Evolution
Authors: Brodsky A. K. 
Published: April 2021

ABSTRACT
High-speed filming has been used to investigate the performance of the peacock butterfly Inachis io while flying in a wind-tunnel. The wake of the butterfly in ‘feeding’ flight is a system of discrete pairs of vortex rings: in each pair the vortex rings are coupled at right angles. The flow distribution around the butterfly and the dynamics of the vortex rings suggest that useful force is produced continuously throughout the wingbeat. The butterfly’s flapping flight can be divided into three successive stages: during the downstroke, force generation can be explained by quasi-steady aerofoil action; during the upstroke and supination, by unsteady aerofoil action; and during pronation, by a jet mechanism.
The study of airflow around the peacock butterfly throws light on the evolutionary changes in the pattern of interaction between insect wings and the air. At the first stage of the evolution of insect flight, documented in a subimago of the mayfly Heptagenia sulphurea and some other primitive insects, flapping wings generate a system of coupled vortex rings; the aerodynamic force, being perpendicular to the stroke plane, coincides with the direction of the longitudinal body axis. At the second stage, this force is directed forwards and upwards relative to the body axis; the vortex wake is the same as that at the first stage. From this point, two paths of evolution are possible. The first leads to the vortex pattern recorded in the peacock butterfly. The second is typically found in higher orders, where the narrow and relatively short wings flap with lower amplitude and higher frequency, leaving in their wake two chains of uncoupled small vortex rings.
Behavioral Responses to Chemical Stimulation of the Olfactory Organ in the Squid Loligo Opalescens
Authors: Gilly Wm F. , Lucero Mary T. 
Published: April 2021

ABSTRACT
Behavioral experiments were carried out on restrained, but otherwise fully active, squid to test the chemoreceptive capabilities of the olfactory organ. Specific chemical substances stimulated high-pressure jet escape responses when ejected from a small pipette into the area immediately around the olfactory organ. These included squid ink and L-Dopa (3,4 dihydroxyphenylalanine) as well as agents that block voltage-dependent potassium channels, such as quaternary ammonium ions and 4-aminopyridine. Experiments designed to map chemosensitivity spatially identified the olfactory organ as the receptive site. Unilateral application of a topical local anesthetic to an olfactory organ selectively and reversibly abolished responsiveness on the treated side only. The olfactory organ can thus mediate detection of water-borne chemicals. This detection, in turn, is linked to motor control pathways involved in initiating escape-jetting behavior.
The Ionic Basis of the Receptor Potential of Frog Taste Cells Induced by Sugar Stimuli
Authors: Okada Yukio , Miyamoto Takenori , Sato Toshihide 
Published: April 2021

ABSTRACT
The ionic mechanism underlying the receptor potential in frog taste cells induced by sugar stimuli was studied with conventional microelectrodes by replacing the superficial and interstitial fluids of the tongue with modified solutions. The taste cell generated a depolarizing receptor potential accompanying a remarkable reduction of input resistance in response to stimulation with galactose and sucrose. The magnitude of the receptor potential in response to galactose solution increased linearly with decreasing pH in the pH range 6-8, but remained constant above pH 8. The reversal potential was increased by only 29 mV by a 10-fold increase in the H+ concentration of the stimulus, suggesting that there are pH-dependent and pH-independent components in the mechanism generating the receptor potential. The use of Na+-free, Ca2+-free and K+-free interstitial fluids did not affect the receptor potential, but the elimination of Cl- from the interstitial fluid largely abolished it. Interstitial 0.1 mmol 1-1N,N’-dicyclohexyl-carbodiimide (DCCD) completely inhibited the receptor potential and interstitial 0.1 mmol 1-1 N-ethylmaleimide (NEM) decreased the potential to 40% of the control value. Lowering the pH of interstitial fluid from 7.2 to 6.3 decreased the receptor potential to 30 % of the control value. It is concluded that part of the receptor potential in frog taste cells induced by sugar stimuli may be produced by an inflow of H+ through the taste-receptive membrane. The intracellular pH of the taste cell may be regulated by a Cl--dependent H+ pump in the basolateral membrane.
Dietary Selection Behaviour in Spodoptera Littoralis: The Effects of Conditioning Diet and Conditioning Period on Neural Responsiveness and Selection Behaviour
Authors: Simmonds M. S. J. , Simpson S. J. , Blaney W. M. 
Published: April 2021

ABSTRACT
This paper forms part of our study of the behavioural and neural mechanisms involved in dietary selection behaviour of larvae of the polyphagous noctuid Spodoptera littoralis (Boisduval). Larvae were conditioned on one of four chemically defined artificial diets for 4, 8 or 12 h. Diets differed in their proportions of protein and digestible carbohydrate: the PC diet contained 20% protein and 10% carbohydrate; the P diet contained 20 % protein but the 10 % carbohydrate was replaced by indigestible cellulose; the C diet contained 10% digestible carbohydrate and the protein was replaced by cellulose, and the 0 diet lacked both protein and carbohydrate. After conditioning, the larvae were exposed to either behavioural or electro-physiological experiments. In the behavioural choice experiment, larvae were provided with both P and C diets for 9 h. The conditioning diets P and 0 influenced which of the two choice diets was first contacted; significantly higher proportions of the larvae conditioned on the P diet initially contacted the C choice diet and significantly higher proportions of larvae conditioned on the 0 diet initially contacted the P choice diet. Larvae fed on the diet they first contacted and the probability of stopping the first meal was greater when that diet was P, regardless of the conditioning diet. The duration of the first meal on the C choice diet was significantly longer for larvae conditioned on diets lacking digestible carbohydrate (P and 0) than for those conditioned on either PC or C diets. Larvae were observed to compensate for a deficiency in protein by increasing the frequency of feeding contacts with the P choice diet but not the duration of these contacts. To compensate for a deficiency in digestible carbohydrate, the larvae increased the duration of their feeding contacts with the C choice diet. In the electrophysiological experiment, the maxillary styloconic sensilla were stimulated with an amino acid mixture and sucrose. Neural responses were recorded from two groups of larvae, one after they had been conditioned on one of the four diets for 4, 8 or 12 h and the other after they had subsequently been exposed to the choice diets for 9h. Larvae in the first group that had been conditioned on diets lacking sucrose (P and 0) were more responsive to sucrose than larvae conditioned on diets containing sucrose (PC and C). The reverse occurred with the response to the amino acid mixture, with larvae conditioned on diets containing protein (PC and P) being less responsive to the amino acid mixture than those conditioned on diets lacking protein (C and 0). After the 9h choice period, the responsiveness of sensilla was no longer related to the conditioning diet.
Characterization of Oscillatory Olfactory Interneurones in the Protocerebrum of the Crayfish
Authors: Mellon Deforest , Sandeman David C. , Sandeman Renate E. 
Published: April 2021

ABSTRACT
We obtained intracellular electrophysiological recordings from local interneurones within the hemi-ellipsoid neuropile of the brain in the freshwater crayfish Cherax destructor and Procambarus clarkii. The recordings were made from perfused, isolated head preparations that provided several indications of a healthy physiological condition. The hemi-ellipsoid interneurones are spontaneously active, generating bursts of action potentials at regular intervals. The inter-burst period differs among neurones, varying from about 1.0 s at the shortest periods to around 30 s for the longest periods. Evidence from both electrophysiological recordings and from injection of Lucifer Yellow and Neurobiotin dyes into hemi-ellipsoid interneurones suggests that some of the cells in the populations are electrically coupled to one another. Hemi-ellipsoid interneurones are driven postsynaptically by axons within the lateral protocerebral tract. Experiments with focal electrical stimulation strongly suggest that the pathways responsible include axons of the olfactory–globular tract. These findings support our previous electron microscopical data showing that olfactory–globular tract axons are presynaptic to the hemi-ellipsoid interneurones. These findings support the conclusion that hemi-ellipsoid interneurones are an integral link in the central olfactory pathway of the crayfish.
Allosteric Modulation of Haemocyanin Oxygen-Affinity by L-Lactate and Urate in the Lobster Homarus Vulgaris:II. Characterization of Specific Effector Binding Sites
Authors: Nies A. , Zeis B. , Bridges C. R. , Grieshaber M. K. 
Published: April 2021

ABSTRACT
The haemocyanin of Homarus vulgaris possesses specific binding sites for L-lactate and urate, two allosteric modulators of haemocyanin oxygen-affinity. The affinities for both ligands have been determined. The dissociation constants, KD, are 0.87±0.26mmoll−1 for L-lactate and 0.03±0.01mmoll−1 for urate at 15°C and pH 8.0. The affinity of the haemocyanin is about 40 times larger for urate than for L-lactate. The stoichiometry of the binding is two ligands per dodecamer in both cases.
L-Lactate does not compete with urate for its binding site and vice versa, indicating that the ligand binding sites are independent of each other.
The specificity of urate binding to haemocyanin was investigated in competition experiments with allantoin, caffeine and hypoxanthine. The purine derivatives caffeine and hypoxanthine reduce the binding of urate to haemocyanin, whereas allantoin has no effect. Thus, the purine ring system seems to be essential for the binding of urate to haemocyanin.
Oxygen Radical Production in the Sea Anemone Anthopleura Elegantissima and Its Endosymbiotic Algae
Authors: Dykens James A. , Shick J. Malcolm , Benoit Craig , Buettner Garry R. , Winston Gary W. 
Published: April 2021

ABSTRACT
Host animals in algal-invertebrate endosymbiotic associations are exposed to photosynthetically generated hyperoxia while in sunlight, conditions conducive to photodynamic excitations and production of cytotoxic oxygen-derived radicals such as the superoxide anion and the hydroxyl radical (.OH). All previous evidence of oxyradical production in symbiotic associations has been circumstantial. We here present direct evidence, from electron paramagnetic resonance studies on tissue homogenates of the photosymbiont-containing sea anemone Anthopleura elegantissima (Brandt), of substantial light-dependent .OH and production that is abolished by dichlorophenyldimethylurea (DCMU), an inhibitor of photosynthesis. Shade-adapted A. elegantissima lacking endosymbiotic algae likewise show .OH production upon illumination. The latter flux is not dependent on photosynthesis, and DCMU has no effect. Rather, .OH production in apozooxanthellate anemones is via direct photoexcitations. The selective reaction of dimethyl sulfoxide (DMSO) with .OH to form methane sulfinic acid allows quantification of .OH produced in vivo. Such in vivo measurements confirm the production of .OH in both host and algae in illuminated zooxanthel-late anemones, where the amount of .OH in the zooxanthellae is disproportionately large relative to their fractional contribution to the biomass of the symbiosis. In vivo studies using DMSO also suggest a photochemical production of .OH in apozooxanthellate anemones exposed to simulated sunlight enriched in ultraviolet (UV) wavelengths, and the enhancement by UV light of .OH production in zooxanthellate individuals. Such chronic radical exposure necessitates defenses against photooxidative stress, a cost that is seldom considered in these mutualistic symbioses.
Biochemical Comparison of Fast- and Slow-Contracting Squid Muscle
Authors: Kier William M. , Schachat Frederick H. 
Published: April 2021

ABSTRACT
The myofilament protein compositions of muscle fibres from the transverse muscle mass of the tentacles and the transverse muscle mass of the arms of the loliginid squid Sepioteuthis lessoniana were compared. These two muscle masses are distinct types, differing in their ultrastructural and behavioural properties. The transverse muscle of the tentacles consists of specialized muscle fibres that exhibit cross-striation and unusually short sarcomeres and thick filaments. The transverse muscle of the arms consists of obliquely striated muscle fibres that are typical of cephalopod skeletal muscle in general. The specialization of the tentacle muscle results in a high shortening speed and reflects its role in creating rapid elongation of the tentacles during prey capture. Comparison of samples of myofilament preparations of the two muscle fibre types using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and peptide mapping of myosin heavy chains from the two muscle fibre types, however, showed little evidence of differences in contractile protein isoforms. Thus, specialization for high shortening speed appears to have occurred primarily through changes in the dimensions and arrangement of the myofilament lattice, rather than through changes in biochemistry. The thick filament core protein paramyosin was tentatively identified in the squid muscle fibres. This protein was less abundant in the short thick filament cross-striated tentacle muscle cells than in the obliquely striated arm cells.
Allosteric Modulation of Haemocyanin Oxygen-Affinity By L-Lactate and Urate in the Lobster Homarus Vulgaris: I. Specific and Additive Effects on Haemocyanin Oxygen-Affinity
Authors: Zeis B. , Nies A. , Bridges C. R. , Grieshaber M. K. 
Published: April 2021

ABSTRACT
The specific effects of L-lactate and urate on oxygen binding by the haemo-cyanin of the lobster Homarus vulgaris were investigated. Increasing concentrations of L-lactate were found to increase haemocyanin oxygen-affinity. The relationship between the oxygen affinity (logP50) and [L-lactate] expressed as (AlogP5())(Δlog[L-lactate])−1 was −0.11 at L-lactate concentrations between 0.3 and 11 mmol l−1 and pH7.99±0.03. Urate, likewise, had a potentiating effect on haemocyanin oxygen-affinity: (ΔlogP50)( Δlog[urate])−1 was −0.18 at urate concentrations between 0 and 0.93 mmol l−1 and pH7.99±0.03. Cooperativity, expressed as n50, was reduced by the presence of both modulators.
The influence of the simultaneous presence of both factors on haemocyanin oxygen-affinity was also investigated. The effects of L-lactate and urate on haemocyanin oxygen-affinity were found to be additive. The possible physiological role of these modulators is discussed.