bluuebunny/crossref_metadata_2025_split huggingface dataset:
5-Hydroxytryptamine in the Salivary glands Of Adult Female Aedes Aegypti and its Role in Regulation of Salivation
Authors: Novak Mark G. , Ribeiro José M. C. , Hildebrand John G. 
Published: April 2021

ABSTRACT
A dense plexus of axons, immunoreactive to antisera against 5-hydroxytryptamine (5-HT, serotonin) and surrounding the proximal medial lobe of the salivary gland of adult female Aedes aegypti mosquitoes, was demonstrated by means of whole-mount fluorescence immunocytochemistry. This innervation originates in the stomatogastric nervous system. 5-HT-immunoreactive innervation is absent in male salivary glands, suggesting that 5-HT is involved in blood-feeding. Furthermore, female mosquitoes treated with the 5-HT-depleting agent α-methyltryptophan (AMTP) and then allowed to feed on a rat exhibited a significantly longer mean probing period and a lower blood-feeding success rate than did control mosquitoes. When female mosquitoes were experimentally induced to salivate into mineral oil, AMTP-treated individuals secreted significantly less saliva than did control mosquitoes. These samples of saliva also contained significantly lower concentrations of apyrase, an enzyme important in blood-feeding. Injection of 5-HT into both AMTP-treated and control mosquitoes elicited significant increases in the volume of secreted saliva and/or its apyrase content. We conclude that 5-HT plays an important role in the control of salivation in adult female A. aegypti.
Thermoregulation of the Intra-Abdominal Testes of the Bottlenose Dolphin (Tursiops Truncatus) During Exercise
Authors: Pabst D. A. , Rommel S. A. , McLellan W. A. , Williams T. M. , Rowles T. K. 
Published: April 2021

ABSTRACT
Dolphins possess a vascular countercurrent heat exchanger (CCHE) that functions to cool their intra-abdominal testes. Spermatic arteries in the posterior abdomen are juxtaposed to veins returning cooled blood from the surfaces of the dorsal fin and tail flukes. In this study, we investigated the effect of exercise on CCHE function in the bottlenose dolphin. The CCHE flanks a region of the bowel in the posterior abdomen and influences colonic temperatures. A rectal probe housing a linear array of seven copper–constantan thermocouples was designed to measure colonic temperatures simultaneously at positions anterior to, within and posterior to the region of the colon flanked by the CCHE. Immediately after vigorous swimming, temperatures at the CCHE decreased relative to resting and pre-swim values: post-swim temperatures at the CCHE were maximally 0.5 °C cooler than pre-swim temperatures. These data suggest that the CCHE has an increased ability to cool the arterial blood supply to the testes when the dolphin is swimming. This ability could offset the increased thermal load on the testes in an exercising dolphin. To the best of our knowledge, this is the first report of deep body cooling in an exercising mammal that is not undertaking a dive.
Oxygen Availability and Embryonic Development in Sand Snail (Polinices Sordidus) Egg Masses
Authors: Booth David T. 
Published: April 2021

ABSTRACT
The oxygen transport physiology of sand snail Polinices sordidus egg masses was investigated using oxygen microelectrodes and open-flow respirometry. P. sordidus eggs are laid in a jelly matrix that rapidly absorbs water and swells into a horseshoe-shaped sausage. The average diameter of these sausages is 37 mm. Eggs are enclosed in capsules that are distributed throughout the jelly matrix, but 65 % of the eggs are located within 3 mm of the outer surface. There is no circulatory or canal system within the matrix so all gas exchange between developing embryos and the environment must occur by diffusion through the jelly matrix.
Oxygen tension in the outer layer remains moderately high throughout incubation but decreases rapidly in more centrally located regions, so that by day 4 embryos in this region are exposed to extremely hypoxic conditions . This hypoxia limits oxygen consumption of embryos to low levels and appears to slow embryonic development or even to arrest it. From day 4 onwards, the central region gradually become less hypoxic because the hatching of peripherally located embryos causes the outer layers of the jelly matrix to disintegrate and thus reduces the diffusion distance for oxygen between the centrally located embryos and the surrounding sea water. As the oxygen tension rises, development accelerates and the embryos eventually hatch as viable veligers, apparently unharmed by their prolonged exposure to hypoxia.
Immunocytochemical Localization Of Multiple Cholecystokinin-Like Peptides In The Stomatogastric Nervous System Of The Crab Cancer Borealis
Authors: Christie Andrew E. , Baldwin David , Turrigiano Gina , Graubard Katherine , Marder Eve 
Published: April 2021

ABSTRACT
Three anti-cholecystokinin antibodies were used to label the stomatogastric nervous system of the crab Cancer borealis. Labeled tissues were examined as whole mounts using laser scanning confocal microscopy. Although each of the anti-cholecystokinin antibodies labeled a variety of structures within the stomatogastric nervous system (including somata, fibers and neuropil), the pattern of labeling produced by each antibody was distinct. These results indicate that there is a family of cholecystokinin-like molecules that are differentially distributed among a subpopulation of the neurons in the stomatogastric nervous system of Cancer borealis.
Evolutionary Adaptation of Contractile Performance in Muscle of Ectothermic Winter-Flying Moths
Authors: Marden James H. 
Published: April 2021

ABSTRACT
temperature-sensitivity of muscle performance in a winter-flying ecotothermic moth (Operophtera bruceata) was examined and compared with that of a summer-flying endothermic hawkmoth (Manduca sexta). O. bruceata muscle contracted over a temperature range of 1–28 °C, whereas M. sexta muscle contracted at temperatures of 13–42.5 °C. Maximum (unloaded) contraction velocity (Vmax) was greater in O. bruceata over most of the range of temperatures where muscle from both species was excitable (3–4 lengths s−1versus 0.6–3.6 lengths s−1 at 13–28 °C), but M. sexta muscle achieved a much higher Vmax at the temperature that this species maintains during flight (10 lengths s−1 at 40–42.5 °C). The capacity of O. bruceata muscle to generate tension was approximately twice that of M. sexta muscle (peak tetanic tension of 13.9 versus 7.0N cm−2). This greater force-generating capacity in O. bruceata largely offset its lower shortening velocity, such that maximum instantaneous power output was equivalent in both species at temperatures below 35 °C (approximately 100–120 W kg−1). M. sexta muscle achieved instantaneous power outputs of up to 202 W kg−1 at temperatures of 40–42.5 °C. Muscle activation and deactivation (measured by times to peak tension and to half-relaxation during isometric twitches) were most rapid for O. bruceata at temperatures of 15–30 °C and for M. sexta at temperatures of 30–40 °C.
Data for power output of flight muscle from these moths are combined with estimates of induced power required for flight in order to show how adaptations for thermal sensitivity of muscle power output interact with morphology (low wing-loading, high flight muscle ratio) to allow O. bruceata moths to fly at extremely low body temperatures, and to construct a model showing how the fecundity of flightless O. bruceata females would decline if they were to regain the ability to fly. Marginal flight over a narrow range of temperatures for O. bruceata females would require a 17 % reduction in fecundity; to fly over as large a range of temperatures as do males would require an 82 % reduction in fecundity.
The Thermal Acclimation of Burst Escape Performance in Fish: An Integrated Study of Molecular and Cellular Physiology and Organismal Performance
Authors: Johnson Timothy P. , Bennett Albert F. 
Published: April 2021

ABSTRACT
Goldfish (Family Cyprinidae, Carassius auratus) and killifish (Family Cyprinodontidae, Fundulus heteroclitus) were acclimated to 10, 20 and 35 °C for 4 weeks. The thermal acclimation of C-start (escape swimming) performance and the physiological properties of fast twitch muscle fibres that underlie it were investigated in these species at the molecular (myosin isoform expression), biochemical (myofibrillar ATPase activity), cellular (contractile kinetics) and organismal levels of organisation. Peptide maps were obtained for fast muscle myosin heavy chains, isolated from 10 °C- and 35 °C-acclimated fish. Different myosin heavy chain isoforms were expressed in response to a change in acclimation temperature in goldfish, but myosin heavy chain isoform expression was unaffected by acclimation temperature in killifish. Compared with fish acclimated to 35 °C, acclimation to 10 °C increased the activity of fast muscle myofibrillar ATPase assayed at 10 °C fivefold in goldfish and only 50 % in killifish. Muscle twitch contraction time at 10 °C decreased significantly in response to acclimation to 10 °C in both species; however, the magnitude of this response was much greater in goldfish (100 %) than in killifish (30 % or less). In goldfish, these changes in the physiological properties of fast twitch fibres during 10 °C acclimation resulted in a six-to eightfold increase in the speed and turning velocity of fish performing C-starts at 10 °C. By comparison, the somewhat smaller acclimatory response of killifish fast muscle properties was accompanied by only a minor (50 % or less) adjustment in locomotor performance. Thermal acclimatory responses of fast muscle at the molecular, biochemical and cellular levels of organisation are clearly reflected in alterations in organismal escape performance.
Central Circuitry in the Jellyfish Aglantha Digitale: II. The Ring Giant and Carrier Systems
Authors: Mackie G. O. , Meech R. W. 
Published: April 2021

ABSTRACT
The ring giant axon in the outer nerve ring of the jellyfish Aglantha digitale is a multinucleate syncytium 85 % of which is occupied by an electron-dense fluid-filled vacuole apparently in a Gibbs–Donnan equilibrium with the surrounding band of cytoplasmic cortex. Micropipette recordings show small (-15 to -25 mV) and large (−62 to -66 mV) resting potentials. Low values, obtained with a high proportion of the micropipette penetrations, are assumed to be from the central vacuole; high values from the cytoplasmic cortex. Background electrical activity includes rhythmic oscillations and synaptic potentials representing hair cell input caused by vibration. After the ring giant axon has been cut, propagating action potentials evoked by stimulation are conducted past the cut and re-enter the axon on the far side. The system responsible (the carrier system) through-conducts at a velocity approximately 25 % of that of the ring giant axon and is probably composed of small neurones running in parallel with it. Numerous small neurones are seen by electron microscopy, some making one-way and some two-way synapses with the ring giant. Despite their different conduction velocities, the two systems normally appear to fire in synchrony and at the velocity of the ring giant axon. We suggest that, once initiated, ring giant spikes propagate rapidly around the margin, firing the carrier neurones through serial synapses and giving them, in effect, the same high conduction velocity. Initiation of ring giant spikes can, however, require input from the carrier system. The spikes are frequently seen to be mounted on slow positive potentials representing summed carrier postsynaptic potentials. The carrier system fires one-for-one with the giant axons of the tentacles and may mediate impulse traffic between the latter and the ring giant axon. We suggest that the carrier system may also provide the pathways from the ring giant to the motor giant axons used in escape swimming. The findings show that the ring giant axon functions in close collaboration with the carrier system, increasing the latter’s effective conduction velocity, and that interactions with other neuronal sub-systems are probably mediated exclusively by the carrier system.
Electrosensory Stimulus-Intensity Thresholds in the Weakly Electric Knifefish Eigenmannia: Reduced Sensitivity at Harmonics of its own Organ Discharge
Authors: Kaunzinger Ivo , Kramer Bernd 
Published: April 2021

ABSTRACT
The South American knifefish Eigenmannia sp. can detect the electric organ discharges (EODs; 250–600 Hz) of conspecifics when they are superimposed over its own EOD. This study investigates the minimum frequency difference necessary for such signal perception, using the application of sine-wave stimuli. Electrosensory stimulus-intensity thresholds were determined for trained fish using stimuli associated with food rewards. These sine-wave stimuli were ‘clamped’ to the EOD frequency of the fish. Electrosensory thresholds were also determined for the spontaneous jamming avoidance response (JAR; a change in EOD frequency evoked by a stimulus of sufficiently similar frequency), in this case using unclamped stimuli.
Over the wide frequency range investigated (0.3–3.01 times EOD frequency), the lowest stimulus-intensity thresholds of 0.6 µV cm−1 (peak-to-peak) (0 dB) at a water conductivity of 100 µS cm−1 were found close to (but not exactly at) the EOD fundamental frequency. At exact frequency identity between the EOD and the stimulus, the stimulus-intensity response threshold rose abruptly by more than 10 dB compared with slightly higher or lower stimulus frequencies. A similar ‘needle-like’ threshold increase was found at exactly two and three times the EOD frequency, but neither at harmonic ratios between stimulus and EOD frequency that represent fractions (e.g. at 5:4=1.25, 4:3=1.33, 3:2=1.5 or 5:3=1.67 times EOD frequency) nor at subharmonics such as half or two-thirds of the EOD frequency. The steepest increase of stimulus-intensity response threshold was in the range 0.998–1.002 times EOD frequency, corresponding to a threshold change, or electrosensory filter slope, of 5000 dB per octave.
For the spontaneous JAR, a similar stimulus-intensity threshold increase was observed when EOD frequency equalled stimulus frequency. Because of the longer rise time for the stimulus amplitude (400 ms rather than 35 ms) the stimulus intensity threshold was higher (up to 32 dB; mean, 20 dB) than in the other experiments (up to 15 dB; mean, 13 dB).
A difference in frequency between the EOD and the applied stimulus as small as 1 Hz (that is, 0.2 % of the EOD frequency) was sufficient for good signal perception in Eigenmannia sp. The JAR appears to be useful in avoiding insensitivity at exact integer harmonics of the EOD frequency.
Matrix of neuromodulators in neurosecretory structures of the crab Cancer borealis
Authors: Christie Andrew E. , Skiebe Petra , Marder Eve 
Published: April 2021

ABSTRACT
The crustacean stomatogastric ganglion, which is situated in the ophthalmic artery, can be modulated by both intrinsically released molecules and hormones. In the crab Cancer borealis, over a dozen neuroactive compounds have been identified in the input axons that project into the stomatogastric neuropil. However, little is known about the modulator content of the two major neurohemal organs, the sinus glands and the pericardial organs, in this crab. We now report the results of a series of immunocytochemical experiments designed to identify putative neurohormones in these tissues. We find that the majority of modulators present in the input axons of the stomatogastric ganglion are also present in at least one of the neurohemal organs. Specifically, allatostatin-like, buccalin-like, cholecystokinin-like, FLRFamide-like, GABA-like, locustatachykinin-like, myomodulin-like, proctolin-like, red pigment concentrating hormone-like and serotonin-like immunoreactivities are all present in both the stomatogastric neuropil and at least one of the neurohemal organs. Thus, these substances are likely to serve a dual role as both local and hormonal modulators of the stomatogastric network. Two other substances, β-pigment dispersing hormone and crustacean cardioactive peptide, are not present in the stomatogastric neuropil, but β-pigment dispersing hormone immunoreactivity is present in the sinus glands and crustacean cardioactive peptide immunoreactivity is present in the pericardial organs. It is likely that crustacean cardioactive peptide exerts its influence on the stomatogastric neural circuit via hormonal pathways. Double-labeling experiments show that the patterns of modulator co-localization present in the stomatogastric neuropil are different from those in the neurosecretory organs, suggesting that few rules of co-localization hold across these tissues.
Differential scanning calorimetry studies on the cysts of the potato-cyst nematode Globodera rostochiensis during freezing and melting
Authors: Wharton D. A. , Ramløv H. 
Published: April 2021

ABSTRACT
Differential scanning calorimetry (DSC) was used to determine the thermal events associated with freezing and melting of the cysts of the potato-cyst nematode Globodera rostochiensis. There were no thermal events during the cooling of dry cysts from 5 to –60 °C and warming back to 5 °C, indicating the absence of water freezing in the dry cysts. During heating of dry cysts from 5 to 80 °C, two overlapping endothermic events were observed at 55 °C, indicating the irreversible destruction of the permeability barrier of the eggshell by the melting of the lipids which constitute the lipid layer.
The first exothermic event (T=–9 °C) during the cooling of hydrated cysts indicates the presence of an ice-nucleating agent. A broad exotherm at –38 °C is due to the freezing of eggs. DSC thus confirms that the eggshell prevents exogenous ice nucleation and allows the eggs to supercool in the presence of external ice. The enthalpy of the egg exotherm increased during hydration of the cysts. The temperature of the egg exotherm was elevated after heating of the sample to 70 °C. This is thought to be due to the loss of trehalose from the eggs following the destruction of the permeability barrier of the eggshell.
During melting, three endothermic events were observed. These became merged after the destruction of the permeability barrier of the eggshell by heating, and only two peaks were observed in isolated eggs. The sample is thus considered to consist of three freezable compartments: (1) the water surrounding the cyst, (2) the solution between the cyst wall and the eggs and (3) the egg contents.
The Young’s Modulus of Feather Keratin
Authors: Bonser Richard H. C. , Purslow Peter P. 
Published: April 2021

ABSTRACT
The flexural stiffness of the rachis varies along the length of a primary feather, between primaries and between species; the possible contribution of variations in the longitudinal Young’s modulus of feather keratin to this was assessed. Tensile tests on compact keratin from eight species of birds belonging to different orders showed similar moduli (mean E=2.50 GPa) in all species apart from the grey heron (E=1.78 GPa). No significant differences were seen in the modulus of keratin from primaries 7–10 in any species. There was a systematic increase in the modulus distally along the length of the rachis from swan primary feathers. Dynamic bending tests on swan primary feather rachises also showed that the longitudinal elastic modulus increases with increasing frequency of bending over the range 0.1–10 Hz and decreases monotonically with increasing temperature over the range -50 to +50°C. The position-, frequency-and temperature-dependent variations in the modulus are, however, relatively small. It is concluded that, in the species studied, the flexural stiffness of the whole rachis is principally controlled by its cross-sectional morphology rather than by the material properties of the keratin.
A GabaB Receptor on an Identified Insect Motor Neurone
Authors: Bai Donglin , Sattelle David B. 
Published: April 2021

ABSTRACT
The vertebrate GABAB receptor (GABABR) agonists 3-aminopropylphosphonous acid (3-APPA), SK&F97541 and 3-aminopropylphosphonic acid (3-APA) are able to induce a hyperpolarization on the cell body of motor neurone Df in the metathoracic ganglion of the cockroach (Periplaneta americana), although the classic vertebrate GABABR agonist L-baclofen fails to induce any responses on the same neurone. Consistent with the findings on vertebrate GABABRs, the 3-APPA-induced responses on Df were also insensitive to the GABAAR antagonists bicuculline and picrotoxin. However, the GABABR antagonists saclofen and CGP35348 also failed to block this GABAB-like response. These results indicate a novel pharmacology for the GABAB-like receptors on the Df neurone. The reversal potential indicates that these GABAB-like receptors may be coupled to K+ channels.
Effects of Oxygenation and the Stress Hormones Adrenaline and Cortisol on the Viscosity of Blood From the Trout Oncorhynchus Mykiss
Authors: Sørensen Bodil , Weber Roy E. 
Published: April 2021

ABSTRACT
Although the concentrations of the stress hormones adrenaline and cortisol in rainbow trout (Oncorhynchus mykiss) blood increase upon hypoxic exposure, the combined effects of these hormones and O2 lack upon fish blood rheology have not been investigated. Deoxygenated blood taken by caudal puncture exhibited lower viscosities than oxygenated samples at low shear rates, whereas the opposite was true at high shear rates. However, blood from cannulated trout had similar viscosities in its deoxygenated and oxygenated states. In the deoxygenated state, addition of adrenaline lowered viscosity at low shear rates and increased it at high shear rates, resembling the effects of deoxygenation observed in blood taken by venepuncture. In oxygenated blood on the contrary, no marked adrenaline effects were observed. In deoxygenated blood, addition of cortisol lowered viscosity at all measured shear rates compared with blood without cortisol. In oxygenated blood, however, no cortisol effects were observed. The viscosity effects observed in the presence of cortisol could not be attributed to concomitant changes in haematological variables, However, the effects in the presence of adrenaline manifested in deoxygenated ‘cannula’ blood and in uncannulated blood without added hormones appear to result from parallel increases in haematocrit and cell volume.
Protein Synthesis and Degradation in the Flight Muscles of Adult Crickets (Gryllus Bimaculatus)
Authors: Gomi Tadashi , Okuda Takashi , Tanaka Seiji 
Published: April 2021

ABSTRACT
The development and degeneration of the flight muscles in adult crickets, Gryllus bimaculatus, were studied (1) by determination of the total protein content, (2) by SDS one-dimensional polyacrylamide gel electrophoresis (SDS–PAGE) of muscle protein and (3) by in vitro culturing of the muscle. The total protein content of the dorso-longitudinal muscle (DLM) and metathoracic dorso-ventral muscle (DVM) increased during the early days of adult life in both sexes. This high protein content was maintained for at least a further 10 days in some individuals, while in others it declined to a low level. Mesothoracic DVMs in males also showed an increase in protein content after adult emergence but did not undergo histolysis, whereas those in females showed no significant temporal change in protein content. Removal of hind wings or artificial de-alation was found to be useful in inducing degeneration of DLMs and metathoracic DVMs. This treatment also stimulated ovarian development in females.
An analysis by SDS–PAGE provided no evidence for new protein synthesis prior to or during flight muscle degeneration. A high rate of [3H]-or [35S]methionine incorporation was observed in DLMs taken from newly emerged adults, but, in intact crickets, the rate declined rapidly during the first 3 days of adult life, a pattern consistent with that obtained from the measurement of total protein content. Compared with DLMs removed from intact crickets, DLMs taken from de-alated crickets showed reduced rates of protein synthesis during in vitro culturing. This, together with the onset of protein degradation, appears to cause the rapid decrease in total protein content of the muscle in de-alated crickets.