bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coordination of Locomotor and Cardiorespiratory Networks of Lymnaea Stagnalis by A Pair of Identified Interneurones
Authors: Syed N. I. , Winlow W. 
Published: April 2021

ABSTRACT
The morphology and electrophysiology of a newly identified bilateral pair of interneurones in the central nervous system of the pulmonate pond snail Lymnaea stagnalis is described. These interneurones, identified as left and right pedal dorsal 11 (L/RPeDll), are electrically coupled to each other as well as to a large number of foot and body wall motoneurones, forming a fast-acting neural network which coordinates the activities of foot and body wall muscles. The left and right sides of the body wall of Lymnaea are innervated by left and right cerebral A cluster neurones. Although these motoneurones have only ipsilateral projections, they are indirectly electrically coupled to their contralateral homologues via their connections with L/RPeDll. Similarly, the activities of left and right pedal G cluster neurones, which are known to be involved in locomotion, are also coordinated by L/RPeDll. Selective ablation of both neurones PeDll results in the loss of coordination between the bilateral cerebral A clusters. Interneurones L/RPeDll are multifunctional. In addition to coordinating motoneuronal activity, they make chemical excitatory connections with heart motoneurones. They also synapse upon respiratory motoneurones, hyperpolarizing those involved in pneumostome opening (expiration) and depolarizing those involved in pneumostome closure (inspiration). An identified respiratory interneurone involved in pneumostome closure (visceral dorsal 4) inhibits L/RPeDll together with all their electrically coupled follower cells. Both L/RPeDll have strong excitatory effects on another pair of electrically coupled neurones, visceral dorsal 1 and right parietal dorsal 2, which have previously been shown to be sensitive to changes in the partial pressure of environmental oxygen . Although L/RPeDll participate in whole-body withdrawal responses, electrical stimulation applied directly to these neurones was not sufficient to induce this behaviour.
Auditory Interneurones in the Metathoracic Ganglion of the Grasshopper Chorthippus Biguttulus: II.Processing of Temporal Patterns of the Song of the Male
Authors: Stumpner Andreas , Ronacher Bernhard , von Helversen Otto 
Published: April 2021

ABSTRACT
Auditory interneurones originating in the metathoracic ganglion of females of the grasshopper Chorthippus biguttulus were investigated with respect to their processing of models of the male’s song. In these models two temporal configurations were varied: (i) the song pattern, consisting of ‘syllables’ and ‘pauses’, and (ii) the duration of short gaps within syllables. A precise encoding of the song pattern is found only among receptors and ‘thoracic’ neurones (SN1, TNI), but not among ascending neurones. The only ascending neurone that reacts tonically at all intensities (AN6) encodes the song pattern much less precisely than do receptors. Other ascending neurones (AN3, AN11) encode the gross pattern of model songs, but only at low intensities. One spontaneously active ‘local’ neurone (SN6) is tonically inhibited and encodes the pauses of a model song. A similar response, however, is not found in three ascending neurones (AN13, AN14, AN15), which are merely inhibited. Among ascending neurones, AN12 is the most reliably influenced by the syllable-pause structure of the songs. Its phasic burst marks the onset of every syllable in a behaviourally attractive song. Its activity could account for the rising part of the corresponding behavioural response curve. However, no ascending neurone shows activity corresponding to the falling part of the behavioural response. Among local neurones, the phasic BSN1 neurones are most clearly influenced by varying syllable-pause combinations. Gaps within the song syllables cause a complete inhibition of the activity of AN4. The response of AN4 to syllables with and without gaps is strikingly similar to the behavioural response and is maintained over the whole intensity range tested. Several local neurones, especially SN6, are strongly influenced by gaps within model songs - though only in certain intensity ranges. In accordance with behavioural results, the pathways for information on song pattern and sound direction appear to be separated among ascending neurones. Among local interneurones, however, this separation does not appear to take place, since the most directional local neurone, BSN1, might also be suited for pattern-filtering tasks.
Effect of Endurance Swimming on the Lactate Kinetics of Rainbow Trout
Authors: Weber Jean-Michel 
Published: April 2021

ABSTRACT
The lactate turnover rate of rainbow trout (Oncorhynchus mykiss) was measured by bolus injection of [U-14C]lactate at rest and during prolonged swimming at 85% Ucrit to determine the importance of this metabolic fuel for endurance locomotion in fish, to assess whether lactate exchange between white and red muscle could be a possible mechanism for supplying oxidizable fuel to their lateral red muscle, and to compare the contribution of lactate to total energy provision between teleost and mammalian species. Turnover rate only increased from 4.41±0.33 to 9.71±1.69 μmolkg−1min−1 between rest and prolonged swimming, and the contribution of lactate oxidation to total metabolism declined during exercise. Lactate exchange between white and red muscle is, therefore, not a significant mechanism to fuel the active lateral red musculature during prolonged swimming. The lactate turnover rate of teleosts is one or two orders of magnitude lower than in mammals of equivalent size, but lactate has the same importance as a fuel in both vertebrate groups. However, lactate turnover rate and oxidation rate do not scale with body mass in the same fashion as does metabolic rate. The slope of the mammalian relationship for whole-body lactate turnover and oxidation is much lower (0.58) than the slope of the classic relationship for metabolic rate (0.75), indicating that lactate is a much more important oxidative substrate for small than for large animals.
L-Proline Transport Systems of Starfish Pyloric Caeca
Authors: Ahearn Gregory A. , Behnke Rachel D. 
Published: April 2021

ABSTRACT
Purified brush-border membrane vesicles (BBMV) of starfish [Pycnopodia helianthoides (Brandt)] pyloric caecal epithelium were prepared by magnesium precipitation in order to characterize the possible role of this organ in amino acid transport. L-[3H]proline uptake by these vesicles was Na+-dependent and greater at pH7.5 than at pH5.5. L-Pipecolate was a competitive inhibitor of L-proline influx into these BBMV, exhibiting a Ki value of 0.02 mmol l−1. The amino acid inhibitors, L-pipecolate, L-alanine and L-leucine were used as test substrates to block L-proline influx by the IMINO, NBB and L transport systems, respectively, in order to estimate the contribution of each process to total L-proline entry into pyloric caecal cells. The carrier-mediated transport constants for L-proline transfer by these three systems were: Kt=0.18mmoll−1 (IMINO), 0.13mmoll−1 (NBB) and 0.21 mmol T1 (L); Jmax= 1310 pmol mg−1 protein 30 s −1 (IMINO), 360 pmol mg−1 protein 30 s−1 (NBB) and 470pmolmg−1protein30s−1 (L). L-Proline influxes through both the IMINO and NBB systems were sigmoidal functions of the external [Na+], while transfer by the L system was Na+-independent. Multiple sodium ions (e.g. 2 or 3 Na+/L-proline) appear to be associated with L-proline transport by both Na+-dependent transport systems, but the nature of this association (i.e. activation or energization) is unclear. Results suggest that starfish pyloric caecal epithelium possesses a similar array of L-proline transport proteins to those found in similar cell types of mammalian intestine or kidney, providing tentative support for an absorptive function for this organ.
Electrogenic 2Na+/H+ Antiport in Echinoderm Gastrointestinal Epithelium
Authors: Ahearn Gregory A. , Franco Pierette 
Published: April 2021

ABSTRACT
Purified brush-border membrane vesicles (BBMV) of starfish (Pycnopodia helianthoides) pyloric caecal epithelium were prepared by a magnesium precipitation technique in order to compare the properties of Na+/H+ exchange in this invertebrate tissue with those of an apparently unique recently described crustacean electrogenic antiporter. In starfish BBMV 22Na uptake was markedly enhanced by an outwardly directed pH gradient and membrane potential (inside negative) compared to control short-circuited vesicles. External amiloride abolished the stimulatory capacity of the proton gradient and membrane potential as driving forces for sodium transport. Sodium influx, in the presence of an outwardly directed proton gradient, was a sigmoidal function of [Na+]o and yielded a Hill coefficient of 2.6, suggesting that more than one sodium ion was exchanged with each internal proton during the exchange event. Two additional findings were used to establish the number of external Na+ binding sites and the transport stoichiometry of the starfish antiporter. First, amiloride acted as a competitive inhibitor of Na+ binding to two external sites with markedly dissimilar apparent amiloride affinities (Kil=28μmoll−1; Ki2= I650μmol F1). Second, a static head flux ratio analysis resulted in a 2Na+/H+ exchange stoichiometry where a balance of driving forces (e.g. no net Na+ flux) was attained with a combination of a 10:1 Na+ gradient and a 100:1 H+ gradient. Results suggest that the electrogenic 2Na+/H+ exchanger previously characterized for crustacean epithelia also occurs in echinoderm cells and may be a widely distributed invertebrate antiporter.
Distribution of Carbonic Anhydrase in the Uterus of Late-Term Pregnant Spiny Dogfish (Squalus Acanthias)
Authors: Flügel Cassandra , Lütjen-Drecoll Elke 
Published: April 2021

ABSTRACT
Carbonic anhydrase (CA) activity was localized in the late-term pregnant spiny dogfish uterus using the modified histochemical staining method of Hansson. Staining was found in the cytoplasm of red blood cells and in the membranes of the endometrial epithelial cells. Under the electron microscope, reaction products were seen in the basolateral membranes of the superficial cells, whereas the apical membranes were unstained. The cells of the underlying layer contacting the stromal capillaries showed staining in all their membranes. This staining pattern is similar to that found in other epithelia noted for active ion transport.
Noninvasive Detection of Electrical Events During the Startle Response in Larval Medaka
Authors: Featherstone Dave , Drewes Charles D. , Coats Joel R. 
Published: April 2021

ABSTRACT
In teleosts, a startle response occurs when one of a pair of Mauthner cells (M-cells) originating in the fish hindbrain is excited by sensory afferents and fires a single action potential. This action potential propagates caudally along the M-axon, which crosses the midline and continues tailward within the spinal cord. In passage, the M-spike excites (via collaterals) primary motor neurons within the spinal cord which, in turn, activate nearby axial musculature. The most obvious behavioral result of this highly conserved (at least in teleosts) and stereotypic sequence is a fast body bend toward the side of the active M-axon such that the fish forms the shape of the letter C. This is stage 1 of the teleost ‘C-start’, also previously called the M-reflex (for reviews, see Nissanov and Eaton, 1989; Eaton and DiDomenico, 1986; Eaton and Nissanov, 1985; Eaton and Hackett, 1984; Eaton and Bombardieri, 1978; Diamond, 1971).
Waveform Discrimination in the Electric Fish Eigenmannia: Sensitivity for the Phase Differences Between the Spectral Components of a Stimulus Wave
Authors: KRAMER BERND , OTTO BRUNHILDE 
Published: April 2021

Eigenmannia lineata is a tropical South American gymnotiform fish that is both electrogenic and electroreceptive. Its electric organ generates a constant-frequency wave discharge (EOD) that is sexually dimorphic in waveform and harmonic content. Eigenmannia discriminates digitally synthesized, natural male and female EOD waveforms of identical frequency and amplitude. Experiments were devised to investigate behaviourally the sensory mechanism of this discrimination.
Both the content in higher harmonics (as seen in an amplitude spectrum) and the waveform (phase spectrum) could provide the cues Eigenmannia uses for discrimination. Five Eigenmannia were trained to discriminate artificially generated stimuli composed of the fundamental frequency, f1, and its harmonic, f2, of a frequency twice that of f1 and of weaker intensity (−13 to −3dB re f1; a similar variation is found among the EODs of different Eigenmannia individuals). The rewarded stimulus, S+ (with a strong f2 intensity of −3dB re f1), remained constant throughout the experiments. The family of negative (S-) stimuli all had a phase difference of 0°, that is, no phase difference, between their harmonics, while the S+ stimulus had a phase difference of 90°. Therefore, all S- stimuli differed from the S+ stimulus in waveform, while one S- stimulus had an amplitude spectrum identical to that of the S+ stimulus.
All fish discriminated any S- signal tested from the S+ stimulus, including the S- stimulus with an identical amplitude spectrum, both when the test signals had identical energy contents (that is, slightly different peak-to-peak amplitudes) and when they had identical peak-to-peak amplitudes (hence, slightly different energy contents).
These results arc evidence for a true waveform (time domain) sensitivity of Eigenmannia. A sensory mechanism is proposed that enables Eigenmannia to assess the P/N ratio of a wave signal, that is, the duration ratio of positive (P) and negative (N) half-waves between zero-crossings of a stimulus cycle (the S+ and all S- stimuli, as well as female and male EODs, differ in this regard).
Mechanical Properties of Demembranated Flight Muscle Fibres from a Dragonfly
Authors: PECKHAM M. , WHITE D.C. S. 
Published: April 2021

The mechanical properties of demembranated muscle fibres of synchronous flight muscle from a dragonfly Libellula quadrimaculata, asynchronous flight muscle from the giant waterbug Lethocerus indicus and synchronous psoas muscle from rabbit were compared in relaxed, active and rigor conditions. The properties were compared to the known structure and protein compositions of these muscles. We found that active tension of L. indicus flight muscles was stretch-activated (tension was low and was significantly increased following a rapid stretch of 1 % of muscle length), whereas both dragonfly flight muscle and rabbit psoas muscle were not (active tension was high and did not significantly increase following a rapid stretch of 1%). Three different properties have been suggested to give rise to stretch activation in asynchronous muscles: (1) a matching of the helix periodicities of actin target sites to myosin crossbridge heads, (2) a special form of troponin subunit called troponin-H, and (3) the high resting stiffness of these muscles inducing strain in the thick filaments. Rabbit psoas muscle has none of these properties. Dragonfly flight muscles do not have the helix matching, but they do have a form of troponin-H and a high resting stiffness. It seems most likely that dragonfly flight muscles are not stretch-activated because they do not have the helix matching.
Note:
Present address: Department of Biophysics, King's College London, 26–29 Drury Lane, London, WC2B 5RL, UK.
Neural Control of Fibrillar Muscles in Bees During Shivering and Flight
Authors: ESCH HARALD , GOLLER FRANZ 
Published: April 2021

The big indirect flight muscles in the thorax of honeybees and bumblebees show two modes of action: they contract with ‘conventional’ twitches in response to slowly repeated muscle potentials and go into tetanus at higher muscle potential frequencies. They can also contract much faster when quickly stretched (stretch activation).
We observed contractions of DV (dorsoventral) and DL (dorsal longitudinal) muscles optically with the help of a tiny mirror glued to the scutellum. We noticed that DL muscles contracted much more than DV muscles during pre-flight warmup. During warm-up, muscle potential frequencies in DL muscles were higher than in DV muscles (DL frequency/DV frequency =1.3), whereas during flight the ratio reversed (DL/DV=0.8). The scutal fissure was completely closed during shivering warm-up, apparently because the DL muscles shortened as much as they could. As a consequence, fast antagonistic stretching was not possible. However, the scutal fissure oscillated between wide open and closed during flight, and antagonists could stretch each other quickly. Flight was started by highly synchronized ‘conventional’ contractions of many muscle elements in DV muscles. Antagonistic stretch-activation during flight led to faster shortening than during shivering warm-up and synchronized all activated muscle elements to produce maximal contractions.
The indirect flight muscles of bumblebees were in tetanic contractions during shivering warm-up over the whole range of temperatures between 8 and 36°C. These tetanic contractions probably prevented other researchers from observing mechanical muscle activity. Our results, which for the first time allow us to detect tetanic contractions directly, make it very improbable that non-shivering thermogenesis occurs in bumblebees, as has been proposed previously.
Acid-Base Variables in Malpighian Tubule Secretion and Response to Acidosis
Authors: STAGG ANDREW P. , HARRISON JON F. , PHILLIPS JOHN E. 
Published: April 2021

1. Malpighian tubule fluid from Schistocerca gregaria adults, starved for 1 day, was collected in situ by cannulation of the gut, both before and after injecting 10 μmol of HCl or NaCl into the haemocoel. 2. Haemolymph pH at the neck remained depressed by 0.3 units for at least 6 h in HCl- as compared to NaCl-injected locusts. A lower haemolymph pH persisted near the acid injection site for several hours. 3. The pH of tubule fluid remained about 0.5 units more acid than haemolymph under all conditions. Thus, net tubular acid secretion was proportional to haemolymph acid-base status. 4. The greater acidity of tubular fluid after acid injection was associated with lower estimated bicarbonate concentrations and higher Pcoco2 without any change in total CO2 when compared to controls. 5. The combined contribution of bicarbonate, phosphate and urate to total buffering capacity of tubular fluid was estimated to be 75°, with bicarbonate responsible for 55° of the total. 6. The maximum rate of acid removal by all Malpighian tubules of starved locusts, including H+ trapped in ammonium ions, was calculated to be very small in relation to the acid load injected into the haemocoel
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Acceleration of Haemolysis in Relation to Chemical Structure
Authors: Ponder Eric 
Published: April 2021

ABSTRACT
Since methods for measuring acceleration and inhibition of haemolysis were first described (Ponder, 1926), very little attention has been paid to the way in which accelerators and inhibitors act. The effects of only a few chemical substances have been studied, and detailed investigations on the accelerating and inhibiting effects of various ions, etc., have certainly not tended to simplify the situation (Yeager, 1929, 1931; Gordon, 1933 a,b); recently, however, the problem has become of interest from quite a different point of view.
The Effect of Phlorizin on the Metabolism of Cytolysing Sea-Urchin Eggs
Authors: Rothschild Lord 
Published: April 2021

ABSTRACT
Unfertilized sea-urchin eggs produce acid when they are cytolysed or fertilized (Ashbel,, 1929; Runnstr öm, 1933 a, 1935). Neither the post-fertilization nor the post-cytolysis acid has been identified. The number of different acids which might be released is large, and it has not so far been considered expedient to attempt direct analysis of the sea water surrounding the activated eggs. One way of establishing the nature of the acid is by observing the effect of specific metabolic inhibitors on its production. Runnström (1933 b, 1935) used this technique, but the inhibitors used were all negative in their effect, i.e. they did not inhibit acid production. Runnströom investigated the effect of inhibitors which affect one type of glycolysis.1 This paper is also concerned with the effect of a glycogen breakdown inhibitor. If the acid production after cytolysis is associated with the formation of hexose phosphate from glycogen, it should be partly or wholly inhibited in the presence of phlorizin (Lundsgaard, 1933).
Colorimetric Method for Estimation of Dissolved Oxygen in the Field
Authors: Johnson M. L. , Whitney R. J. 
Published: April 2021

ABSTRACT
The suitability of the Winkler method for the estimation of oxygen dissolved in water is well established (Standard Methods of Water Analysis, 1936; Fox & Wingfield, 1938). Its usefulness in the field, however, is limited by the fact that it is necessary either to titrate the iodine solutions in the field, or to carry back to the laboratory numerous samples of water. Moreover, the titration of iodine solutions necessitates the frequent standardization of the sodium thiosulphate solution. With the modification of the Winkler method described here, the oxygen content of water can be estimated quickly and easily in the field without bulky apparatus. As no standard solutions are required the method is particularly useful when estimations are made only occasionally.
Studies in Animal Locomotion
Authors: Gray J. 
Published: April 2021

ABSTRACT
The locomotory movements of a typical polychaete worm, such as Nereis diversicolor, are of interest in that they are effected by two distinct mechanisms, (i) a series of parapodia which act as levers comparable to the appendages of terrestrial animals, (ii) the longitudinal muscles of the body. When Nereis is moving slowly over a solid surface, only the parapodia are active; during more rapid motion, or when the animal is swimming through water, the movements of the parapodia are co-ordinated with those of the longitudinal muscles and the two mechanisms combine to give a highly co-ordinated locomotory mechanism.