bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of the Neuropeptide FMRFamide on Aplysia Californica Siphon Motoneurons Involves Multiple Ionic Currents That Vary Seasonally
Authors: Belkin Kira J. , Abrams Thomas W. 
Published: April 2021

ABSTRACT
The molluscan neuropeptide FMRFamide has a number of inhibitory actions on the sensory neurons and motoneurons mediating the defensive gill and siphon withdrawal reflex pathway of Aplysia californica. Exogenous application of FMRFamide has a biphasic, dual-polarity effect on the majority of LFS siphon motoneurons, causing a transient depolarization followed by a prolonged hyperpolarization. FMRFamide induces this response in LFS neurons by causing an increase in multiple ionic currents, including a transient Na+ current, a slow prolonged Na+ current, a 4-aminopyridine (4-AP)-sensitive K+ current and a 4-AP-insensitive K+ current. We have found that a subset of LFS neurons exhibits an exclusively excitatory, biphasic response to FMRFamide, consisting of a transient depolarization followed by a prolonged depolarization of reduced magnitude. Over a period of 29 months, we consistently observed an increase in the incidence of the exclusively excitatory response during the summer months (June to September). From October to May, we observed an exclusively excitatory response to FMRFamide in 19 % of LFS neurons; yet, in the summer months, 51 % of LFS neurons exhibited this response pattern. We compared the ionic basis of the exclusively excitatory response to FMRFamide with the ionic mechanisms mediating the more frequently observed excitatory/inhibitory response. The exclusively excitatory response involves three of the same ionic components as the more typical excitatory/inhibitory response, including the activation of a transient Na+ current, a slow prolonged Na+ current and a 4-AP-insensitive K+ current. The principal difference between the two response types is that FMRFamide fails to activate a 4-AP-sensitive K+ current in those LFS neurons that exhibit an exclusively excitatory response to the peptide. In addition, LFS neurons with an exclusively excitatory response tend to show a coordinated increase in the magnitude of the inward current component of the FMRFamide response. Together, these changes during the summer months may enable this modulatory peptide to bring LFS neurons to suprathreshold levels of activity for eliciting a siphon withdrawal and should substantially alter the neuromodulatory effects of the peptide.
Changes in the Reproductive System of the Snail Helix Aspersa Caused by Mucus From the Love Dart
Authors: Koene Joris M. , Chase Ronald 
Published: April 2021

ABSTRACT
The function of the love dart in certain species of terrestrial snails is unknown. In Helix aspersa, the dart is a sharp calcareous structure that is used to pierce the partner’s skin during courtship. When expelled, the dart is covered with a thick mucus. The hypothesis tested here is that the mucus contains a biologically active substance. Extracts of the digitiform glands that produce this mucus were applied to parts of the reproductive system in vitro. The extracts triggered an initial reconfiguration of the copulatory canal that caused the bursa tract diverticulum to become more accessible to the spermatophore. The reconfiguration of the copulatory canal also closed off the tract leading to the bursa copulatrix, a sperm-digesting organ. A few minutes after the initial contraction, the peristaltic contractions in the diverticulum became significantly more frequent. This latter effect continued for at least 1 h, provided that the mucus extract remained in the saline bath. The minimum effective dosage was less than the 2.2 mg of mucus transferred with the dart.
Sperm competition is expected in Helix aspersa since multiple matings occur before eggs are laid. By influencing the female organs involved in the processing of foreign sperm, the dart shooter may increase the chance that his sperm will fertilise eggs.
Utilisation of Substrates During Tethered Flight with and without Lift Generation in the African Fruit Beetle Pachnoda Sinuata (Cetoniinae)
Authors: Auerswald Lutz , Schneider Peter , Gäde Gerd 
Published: April 2021

ABSTRACT
We have investigated the pattern of metabolic changes during tethered flight with and without lift generation in the African fruit beetle Pachnoda sinuata.
Two distinct metabolic phases occur during lift-generating flight. The first phase is characterised by a high rate of oxygen consumption and a rapid change in proline and alanine levels in the haemolymph and flight muscles and in glycogen level in the flight muscles. Carbohydrates are released from the fat body into the haemolymph. These carbohydrates are oxidised during the second phase. Changes in proline and alanine levels in the haemolymph and flight muscles and in glycogen level in the flight muscles are minor during the second phase and the rate of oxygen consumption is reduced.
During lift-generating flight, metabolic changes are rapid. Proline concentrations in the haemolymph and flight muscles fall dramatically during the first 30 s of flight, while alanine concentrations rise concomitantly. While haemolymph concentrations of proline and alanine remain virtually unchanged thereafter, further changes in the levels of these amino acids occur in the flight muscles during 5 min of flight. The initial levels of the two amino acids in the flight muscles are re-established over 1 h of rest following a 5 min flight, while this process takes longer in the haemolymph. The concentration of haemolymph carbohydrates increases during the first 30 s of flight and declines thereafter during 5 min of flight. The pre-flight levels are restored after 1 h of subsequent rest. The stores of glycogen in the flight muscles are rapidly diminished during the first 10 s of flight and decrease at a lower rate during further flight lasting up to 5 min. A subsequent 1 h of rest is sufficient almost to restore pre-flight levels. Haemolymph lipid levels are slightly but significantly increased during 11 min of flight and after 1 h of subsequent rest.
During flight without lift production, the metabolic changes are considerably slower and beetles fly approximately seven times longer than during lift-generating flight.
Resting basalar (BM), dorso-ventral (DVM) and dorso-longitudinal (DLM) flight muscles show no differences in levels of proline, alanine and glycogen. After different periods of flight, during which lift and wing loading were minimised, the DVM was found to have the highest level of proline after 5 min of flight. Levels of alanine in the DVM were lower than in the DLM. There was no evidence to suggest that different flight muscles are specialised for either proline or carbohydrate utilisation.
Proline and carbohydrates participate equally in supplying energy to the flight muscles during lift-generating flight. The contribution to the energy supply by the flight muscles is 54 %, while that of the haemolymph is 46 %.
Nitrogen Recycling or Nitrogen Conservation in an Alga–Invertebrate Symbiosis?
Authors: Wang J.-T. , Douglas A. E. 
Published: April 2021

ABSTRACT
When corals and allied animals are deprived of their symbiotic algae, the ammonium content in their tissues rises. This is commonly interpreted as evidence for nitrogen recycling (i.e. algal assimilation of animal waste ammonium into amino acids that are released back to the animal), but it can also be explained as nitrogen conservation by the animal (i.e. reduced net ammonium production in response to the receipt of algal photosynthetic carbon). This study discriminated between these interpretations in two ways. First, the increased ammonium concentration in the sea anemone Aiptasia pulchella, caused by darkness or depletion of the alga Symbiodinium, was partially or completely reversed by supplementing the medium with organic carbon compounds (e.g. α-ketoglutarate). Second, the activity of the ammonium-assimilating enzyme glutamine synthetase and the concentration of protein amino acids in the free amino acid pool of the animal, which were depressed by darkness and algal depletion, were restored by exogenous carbon compounds. It is concluded that organic carbon, whether derived from algal photosynthate or exogenously, promotes the animal’s capacity for ammonium assimilation and reduces ammonium production from amino acid degradation. These processes contribute to nitrogen conservation in the animal, but they confound the interpretation of various studies on nitrogen recycling by symbiotic algae.
Localizing transepithelial conductive pathways using a vibrating voltage probe
Authors: Somieski Petra , Nagel Wolfram 
Published: April 2021

ABSTRACT
A model simulation of the electrical field distribution for the voltage-activated Cl− current across amphibian skin has been carried out for two potential pathways, i.e. transcellularly, through the mitochondria-rich cells (MRCs), or paracellularly, across the tight junctions (TJs) between the outermost living cell layer. The calculations are based on the mean density of MRCs and the typical dimensions of stratum granulosum cells of amphibian skin. It is demonstrated that current flow across MRCs would be detectable by scanning with the vibrating voltage probe in the extracellular space above the epithelium, whereas accurate representation of current flow through the TJs cannot be obtained using a probe of the present design. The experimental data indicate that field patterns corresponding to an MRC origin for the Cl− current are never observed. It is concluded that the voltage-activated Cl− conductance is localized to ion-selective structures in the paracellular pathway which may be regulated by the TJs.
The effects of walking on heart rate, ventilation rate and acid–base status in the lobster Homarus americanus
Authors: Rose R. A. , Wilkens J. L. , Walker R. L. 
Published: April 2021

ABSTRACT
American lobsters Homarus americanus were exercised on an underwater treadmill at speeds from 1.7 to 8 m min−1 to determine the effects of exercise on heart rate, ventilation rate and acid–base status. Heart and ventilation rates showed almost instantaneous increases at the start of exercise, but the magnitude of the increase was not related to speed. Maximum heart rate was approximately 80–90 beats min−1 and maximum ventilation rate was 175–180 beats min−1 at all speeds tested.
Exercise at all speeds caused a decrease in haemolymph pH, with the acidosis after exercise at 8 m min−1 being significantly greater than at the other three speeds. Concomitant with this acidosis was a large increase in partial pressure of carbon dioxide, with the largest increase occurring after exercise at 8 m min−1. The concentration of lactate in the haemolymph increased to similar levels at all speeds of walking. Davenport analysis indicates that the acidosis was predominantly respiratory in nature.
Although it was anticipated that heart and ventilation rates would show increases proportional to the speed of exercise, this was not the case. Rather, the responses were fixed regardless of walking speed. The reason for this phenomenon remains unexplained.
Energetics of Bipedal Running: I. Metabolic Cost of Generating Force
Authors: Roberts Thomas J. , Kram Rodger , Weyand Peter G. , Taylor C. Richard 
Published: April 2021

ABSTRACT
Similarly sized bipeds and quadrupeds use nearly the same amount of metabolic energy to run, despite dramatic differences in morphology and running mechanics. It has been shown that the rate of metabolic energy use in quadrupedal runners and bipedal hoppers can be predicted from just body weight and the time available to generate force as indicated by the duration of foot–ground contact. We tested whether this link between running mechanics and energetics also applies to running bipeds. We measured rates of energy consumption and times of foot contact for humans (mean body mass 78.88 kg) and five species of birds (mean body mass range 0.13–40.1 kg). We find that most (70–90 %) of the increase in metabolic rate with speed in running bipeds can be explained by changes in the time available to generate force. The rate of force generation also explains differences in metabolic rate over the size range of birds measured. However, for a given rate of force generation, birds use on average 1.7 times more metabolic energy than quadrupeds. The rate of energy consumption for a given rate of force generation for humans is intermediate between that of birds and quadrupeds. These results support the idea that the cost of muscular force production determines the energy cost of running and suggest that bipedal runners use more energy for a given rate of force production because they require a greater volume of muscle to support their body weight.
Differential Effects of Temperature on Specific and Nonspecific Immune Defences in Fish
Authors: Morvan Caroline Le , Troutaud Danielle , Deschaux Pierre 
Published: April 2021

ABSTRACT
The susceptibility of fish to disease is partly dependent on their environment, in particular on water temperature. It is generally accepted that lower temperatures adversely affect specific immune responses mediated by T helper cells. The probable mechanisms involved in such suppression in teleost fish are reviewed. Furthermore, the effects of temperature on nonspecific defences, such as phagocytosis and cytotoxicity, are described and total immune competence in teleosts at low environmental temperatures is discussed.
Energized Ca2+ Transport by Hepatopancreatic Basolateral Plasma Membranes of Homarus Americanus
Authors: Zhuang Zhenpeng , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
Ca2+ transport by hepatopancreatic basolateral mem-brane vesicles of Atlantic lobster (Homarus americanus) occurred by at least two independent processes: (1) an ATP-dependent carrier transport system, and (2) a Na+-gradient-dependent carrier mechanism. The sensitivity of ATP-dependent Ca2+ transport to vanadate indicated that it was probably due to a P-type ATPase. This system exhibited an extremely high apparent affinity for Ca2+ (Kt=65.28±14.39 nmol l−1; Jmax=1.07±0.06 pmol µg−1 pro-tein 8 s−1). The Na+-gradient-dependent carrier transport system exhibited the properties of a Ca2+/Na+ antiporter capable of exchanging external Ca2+ with intravesicular Na+ or Li+. Kinetic analysis of the Na+-dependence of the antiport indicated that at least three Na+ were exchanged with each Ca2+ (n=2.91±0.22). When Li+ replaced Na+ in exchange for 45Ca2+, the apparent affinity for Ca2+ influx was not significantly affected (with Na+, Kt=14.57±5.02 µmol l−1; with Li+, Kt=20.17±6.99 µmol l−1), but the maximal Ca2+ transport velocity was reduced by a factor of three (with Na+, Jmax=2.72±0.23 pmol µg−1 pro-tein 8 s−1; with Li+, Jmax=1.03±0.10 pmol µg−1 protein 8 s−1). It is concluded that Ca2+ leaves hepatopancreatic epithelial cells across the basolateral membrane by way of a high-affinity, vanadate-sensitive Ca2+-ATPase and by way of a low-affinity Ca2+/Na+ antiporter with an apparent 3:1 exchange stoichiometry. The roles of these transporters in Ca2+ balance during the molt cycle are discussed.
Gas Exchange During Hovering Flight in a Nectar-Feeding Bat Glossophaga Soricina
Authors: Winter York , Voigt Christian , Helversen Otto Von 
Published: April 2021

ABSTRACT
Glossophagine nectar-feeding bats exploit flowers while hovering in front of them. Aerodynamic theory predicts that power output for hovering flight in Glossophaga soricina is 2.6 times higher than during horizontal flight. We tested this prediction by measuring rates of gas exchange during hover-feeding. Five individuals of Glossophaga soricina (mean mass 11.7 g) were trained to feed from a nectar dispenser designed as a flow-through respirometry mask. Single hover-feeding events lasted for up to 4.5 s. Measured rates of gas exchange varied as a function of hovering duration. and during short hovering events (up to 1 s) were 20.5±6.7 ml g−1 h−1 (N=55) and 21.6±5.6 ml g−1 h−1 (N=39) (means ± S.D.), respectively. These values are in the range of a previous estimate of the metabolic power input for level forward flight (23.8 ml O2 g−1 h−1). However, during hovering events lasting longer than 3 s, oxygen uptake was only 16.7±3.5 ml g−1 h−1 (N=73), which is only 70 % of the value expected for forward flight. Thus, bats reduced their rate of oxygen uptake during longer periods of hovering compared with level forward flight. This result is in contrast to the predicted hovering cost derived from aerodynamic theory. The exact metabolic power input during hovering remains uncertain. During longer hovering events, bats were probably not in respiratory steady state, as indicated by the deviation of the respiratory exchange ratio from the expected value of 1 (oxidization of nectar sugar) to the measured value of 0.8.
Persistent Desensitisation of the β2 Adrenoceptors Expressed by Cultured Equine Sweat Gland Epithelial Cells
Authors: Rakhit Soma , Murdoch Ruth , Wilson Stuart M. 
Published: April 2021

ABSTRACT
Adrenaline, forskolin and ATP all evoked accumulation of cyclic AMP in equine sweat gland epithelial cells, although the response to adrenaline was more transient than that to forskolin and ATP. Cells preincubated in adrenaline (10 µmol l−1, 32 min) showed essentially complete, homologous desensitisation, and this phenomenon reversed slowly (half-time 6.3±0.9 h). After 10 min of recovery from preincubation in adrenaline, isobutylmethylxanthine (IBMX, 5 mmol l−1) had no effect upon the desensitisation and the cells showed no loss of sensitivity to ATP and forskolin. After 10 h, however, the persistent desensitisation was partially reversed by IBMX and the cells showed reduced responses to ATP and forskolin. Increased phosphodiesterase activity may thus contribute to the persistent desensitisation. Experiments using forskolin-preincubated (100 µmol l−1, 32 min) cells suggested that increased cytosolic cyclic AMP levels did not underlie the initial loss of sensitivity to adrenaline but that this second messenger may initiate the series of events leading to the generalised loss of sensitivity seen after 10 h.
Cardiovascular Responses In Vivo to Angiotensin II and the Peptide Antagonist Saralasin in Rainbow Trout Oncorhynchus Mykiss
Authors: Fuentes Juan , Eddy F. Brian 
Published: April 2021

ABSTRACT
The effects of [Asn1,Val5 ]-angiotensin II (AngII) and [Sar1,Val5,Ala8 ]-angiotensin II (saralasin) on dorsal aortic blood pressure, pulse pressure and heart rate were examined in rainbow trout in vivo. AngII when administered as a single dose of 25 µg kg−1 induced a biphasic response in blood pressure, with a significant hypertensive response during the initial 10 min, followed by a significant hypotension of 70–75% compared with the initial blood pressure after 50 min and continuing until approximately 80 min post-injection. The co-administration of AngII (25 µg kg−1 ) and saralasin (50 µg kg−1 ) resulted in the same hypertensive response during the initial phase, but abolished the hypotensive effect of AngII. Heart rate was significantly increased in response to AngII, but the administration of AngII and saralasin together attenuated the increase by approximately 44%. Stimulation of the endogenous renin–angiotensin system using a vasodilator, sodium nitroprusside, significantly increased drinking rate in rainbow trout fry, a response inhibited by saralasin, indicating a role for AngII-induced hypotension in drinking. For the first time, a decrease in blood pressure in response to AngII in vivo has been demonstrated in fish, and this is discussed in relation to homeostasis of blood pressure and a possible role in the control of drinking.
Effects Of Incline On Speed, Acceleration, Body Posture And Hindlimb Kinematics In Two Species Of Lizard Callisaurus Draconoides And Uma Scoparia
Authors: Irschick Duncan J. , Jayne Bruce C. 
Published: April 2021

ABSTRACT
We examined the effects of incline on locomotor performance and kinematics in two closely related species of iguanian lizards that co-occur in sandy desert habitats. Callisaurus draconoides differs from Uma scoparia of equal snout–vent length by being less massive and having greater limb and tail lengths. We analyzed high-speed video tapes of lizards sprinting from a standstill on a sand-covered racetrack which was level or inclined 30° uphill. C. draconoides sprinted significantly faster than U. scoparia on both level and uphill sand surfaces, although U. scoparia is considered to be more specialized for sandy habitats. Initial accelerations (over the first 50 ms) did not differ significantly either between species or between inclines within species. Overall, the effects of incline were more pronounced for C. draconoides than for U. scoparia. For example, the incline caused a significant decrease in the maximum stride length of C. draconoides but not in that of U. scoparia. For C. draconoides, uphill stride durations were significantly shorter than on the level surface, and this partially compensated for the effects of shorter uphill stride lengths on velocity. C. draconoides ran bipedally more often than did U. scoparia on both the level and uphill surfaces.
Evolutionary Link Between Prokaryotic and Eukaryotic K+ Channels
Authors: Derst Christian , Karschin Andreas 
Published: April 2021

ABSTRACT
Considering the importance of K+ channels in controlling the crucial K+ gradient across the plasma membranes of all living cells, it comes as no surprise that, besides being present in every eukaryotic cell, these integral membrane proteins have recently also been identified in prokaryotes. Today, approximately a dozen successfully completed and many more ongoing sequencing projects permit a search for genes related to K+ channels in the genomes of both eubacteria and archaea. The coding regions of homologues show a remarkable variety in primary structure. They predict membrane proteins with one, two, three and six hydrophobic segments surrounding a putative K+-selective pore (H5) and the presence or absence of a cytosolic putative NAD+-binding domain (PNBD) that probably senses the reducing power of the cell. The analysis of kinships on the basis of phylogenetic algorithms identifies sequences closely related to eukaryotic voltage-dependent Kv channels, but also defines members of a primordial class of prokaryotic K+ channel (containing the 2TMS/PNBD motif). Considering the unique mechanisms that may account for the assembly of modern proteins from different ancestral genes, and with more primary sequence data soon to appear, a scheme for the evolutionary origin of K+ channels comes within reach.
Molecular Cloning and Developmental Expression Patterns of the Myod and Mef2 Families of Muscle Transcription Factors in the Carp
Authors: Kobiyama Atsushi , Nihei Yoshiaki , Hirayama Yasushi , Kikuchi Kiyoshi , Suetake Hiroaki , Johnston Ian A. , Watabe Shugo 
Published: April 2021

ABSTRACT
cDNA clones encoding the myogenic regulatory factors (MRFs) myogenin, MyoD and myf-5 were isolated by reverse-transcription polymerase chain reaction from larvae and embryos of the common carp (Cyprinus carpio L.). Myocyte-specific enhancer factor 2 (MEF2) cDNAs were identified from a cDNA library from adult carp. Northern blot analysis showed that MyoD, myf-5 and MEF2C transcripts were present in three-somite embryos, whereas myogenin and MEF2A transcripts were not detected until the 15-somite stage. Intense signals of myogenin and MyoD transcripts were observed even in 1-month-old juveniles. Levels of MyoD, myogenin and MEF2A transcripts declined between 1 and 7 months after hatching, and myf-5 gave only a weak signal in the oldest fish. In contrast, levels of MEF2C transcripts were considerably higher in 7-month-old juveniles than in 1-month-old larvae. mRNAs encoding carp myosin heavy chain and α-actin were first detected at approximately the time of the first heartbeat, and levels were maximal in juveniles 1 month post-hatching. The relatively high levels of MRF mRNA in juvenile fish probably reflect the recruitment of new muscle fibres from the satellite cell population. It was concluded that the relative importance of the different members of the MyoD and MEF2 families of transcription factors for muscle differentiation changes during ontogeny in the carp.