bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of burst swimming and adrenaline infusion on O2 consumption and CO2 excretion in rainbow trout, Salmo gairdneri
Authors: Steffensen J. F. , Tufts B. L. , Randall D. J. 
Published: April 2021

ABSTRACT
Immediately following burst swimming, the oxygen consumption of rainbow trout increased by 71%, carbon dioxide excretion by 104% and the respiratory exchange ratio by 17%. 80 min after burst swimming all of these parameters had returned to levels which were not significantly different from control values. Infusion of adrenaline into resting fish had no significant effect on oxygen consumption or carbon dioxide excretion and therefore there was no significant change in the respiratory exchange ratio. This infusion of adrenaline caused a significant elevation in the red blood cell pH which was still present 80 min later. The present results contrast with those of van den Thillart, Randall & Lin (1983), who demonstrated carbon dioxide retention after burst swimming. While it is possible that catecholamines may inhibit bicarbonate flux through the red blood cell, our experiments indicate that this inhibition would not result in detectable changes in carbon dioxide excretion or, therefore, in the respiratory exchange ratio.
Anaerobic Metabolism and Changes in Acid-Base Status: Quantitative Interrelationships and pH Regulation in the Marine Worm Sipunculus Nudus
Authors: Pörtner Hans-Otto 
Published: April 2021

ABSTRACT
The quantitative influence of anaerobic metabolism on acid-base status and on acid-base regulation is investigated in Sipunculus nudus L. Proton generation by metabolism is calculated from theoretical predictions. The quantitative comparison of metabolic protons with non-respiratory protons found in the acid-base status is performed assuming a simplified model of the total animal. Taking the protonequivalent ion exchange between animals and ambient water into account, changes in the anaerobic acid-base status can be explained exclusively by proton generation in metabolism. It is concluded that the classical concept of acid-base physiology is adequate and that the consideration of strong ions is not required for a quantitative treatment of the acid-base status.
The hypothesis that a quantitative correlation exists between metabolic and acid-base events is tested by comparing changes in acid-base status and in metabolism in animals exhibiting different metabolic rates. For this purpose, a method is developed for the calculation of intracellular pH from metabolite concentrations and extracellular acid–base parameters. Proton exchange between intra-and extracellular compartments, which is found to depend upon the total amount of accumulated non-respiratory protons, demonstrates that pHi is regulated even during anaerobiosis. The defended pH1 value, however, is lower during anaerobiosis than during subsequent recovery.
Identification of Agrin in Electric Organ Extracts and Localization of Agrin-Like Molecules in Muscle and Central Nervous System
Authors: Smith Martin A. , Yao Yung-Mae M. , Reist Noreen E. , Magill Catherine , Wallace Bruce G. , Mcmahan U. J. 
Published: April 2021

ABSTRACT
The portion of the muscle fibre’s basal lamina that occupies the synaptic cleft at the neuromuscular junction contains molecules that cause the aggregation of acetylcholine receptors and acetylcholinesterase on regenerating muscle fibres. Agrin, which is extracted from basal lamina-containing fractions of the Torpedo electric organ and causes the formation of acetylcholine receptor and acetylcholine esterase aggregates on cultured myotubes, may be similar, if not identical, to the acetylcholine receptor- and acetylcholinesterase-aggregating molecules at the neuromuscular junction. Here we summarize experiments which led to the identification of agrjn and established that the basal lamina at the neuromuscular junction contains molecules antigenically similar to agrin. We also discuss results which raise the possibility that agrin-like molecules at the neuromuscular junction are produced by motor neurones.
Selective Innervation of Types of Fibres in Developing Rat Muscle
Authors: Thompson W. J. , Soileau L. C. , Balice-Gordon R. J. , Sutton L. A. 
Published: April 2021

ABSTRACT
The technique of glycogen depletion has been used to identify the types of muscle fibres innervated by individual motor neurones in the neonatal rat. This analysis shows that neonatal motor units are highly biased in their fibre type composition, even at times when the fibres receive extensive polyneuronal innervation. This finding suggests that the innervation of muscle fibres is somehow sorted according to type during early development. This sorting does not appear to occur during the removal of the polyneuronal innervation because little, if any, increase in the bias of unit compositions occurs as the number of synapses present in the muscle is reduced 2-to 3-fold. To determine whether the sorted innervation might be explained by a selective synaptogenesis, a study was made of the type compositions of units formed by reinnervation of neonatal soleus muscle. Glycogen depletion of single units 2 weeks following crush of the soleus nerve at postnatal day 2 showed that most of them (10/12) had biased type compositions which could not be explained by a random reinnervation. The location of fibres in the reinnervated motor units suggests that the regenerating axons innervated a novel set of fibres. The differentiation of fibres into types was apparently not changed during their reinnervation. These results imply that regenerating motor neurones in the neonatal rat selectively reinnervate muscle fibre types. These and other studies further imply that the organization of fibres into motor units during normal development does not occur, as is widely believed, by a random innervation of naive fibres and their subsequent differentiation under the influence of innervation.
Mechanisms of Function of Neural Grafts In The Adult Mammalian Brain
Authors: Dunnett Stephen B. , Björklund Anders 
Published: April 2021

ABSTRACT
Evidence for the survival, growth and function of grafted neural tissues in the adult mammalian brain is reviewed. In addition to considering the viability of grafts in the different model systems that have been investigated, consideration is given to alternative mechanisms by which the grafts might exert a functional influence over the host brain and the host animal′s behaviour: (a) acute influence over spontaneous recovery of function, (b) chronic but diffuse secretion of neurochemicals into the host neuropile, (c) tonic reinnervation of the host brain, (d) bridging grafts, and (e) reciprocal reinnervation and full incorporation of graft tissue into host circuitry. It is concluded that no one mechanism is primary, but that different levels of reorganization can take place in different graft paradigms and neural systems.
Immune Reactivity in the Nervous System: Modulation of T-lymphocyte Activation By Glial Cells
Authors: Wekerle H. , Sun D. , Oropeza-Wekerle R. L. , Meyermann R. 
Published: April 2021

ABSTRACT
The vertebrate central nervous system (CNS) has been traditionally thought to be inaccessible for the passenger lymphocytes of the immune system. This does not seem to be the case: activated T-lymphocytes can readily cross the endothelial blood-brain barrier (BBB) and some glial cells, notably the astrocytes, seem to be programmed to act as most efficient and complex partners for antigen-specific T-lymphocytes.
We used myelin basic protein (MBP) specific permanent rat T-lymphocyte lines as probes to assess the immune status of the CNS. These cells, upon activation in vitro, are able to transfer lethal, experimentally induced autoimmune-encephalomyelitis (EAE) to normal syngeneic recipients. Activated T-lymphocytes, but not resting ones, can break through the BBB irrespective of their antigen specificity. Immune surveillance of the CNS thus seems to be executed by activated T-lymphocytes.
Having crossed the BBB, the activated T-cells interact with local glial cells by releasing factors, including interferon-y, which induce astrocytes to synthesize and express, on their membranes, class II major histocompatibility antigens (la determinants), which are critically required for immunogenic presentation of antigens to T-cells. Indeed, la-induced astrocytes of the CNS (and the Schwann cells of peripheral nerves) are efficient antigen presenter cells, which are able strongly to up-regulate antigen-reactive T-lymphocytes.
In addition, it has recently been shown that at least some astrocytes are able to down-regulate immune cells. Some, but not all, astrocytes are capable of suppressing activation of T-cells. This suppression can be modulated by interferon-y, and is sensitive to irradiation. The question of whether suppression is mediated by direct cell-to-cell contact or via soluble mediators (e.g. apolipoprotein E) is under investigation. Astrocytes have been found to be most subtle regulators of immunocompetent T-cells. Most probably they are centrally involved in physiological immune reactivity of the CNS, and it will be tempting to learn how far glial cells are involved in transmitting regulatory signals between the immune and nervous systems.
Functional Significance and Neural Basis of Larval Lamprey Startle Behaviour
Authors: Currie S. N. , Carlsen R. C. 
Published: April 2021

ABSTRACT
The vibration-evoked startle response mediates rapid withdrawal in burrowed larval lampreys (ammocoetes). Ammocoetes withdraw in response to vibration by contracting pre-existing lateral bends in the trunk and tail, thus pulling their heads deeper into the burrow. The motor effects of an ammocoete startle response are dependent on preexisting posture. Areas of lateral body curvature contract more and exhibit larger electromyogram (EMG) amplitudes on their inner sides than on their outer sides. Both of the anterior Mth and posterior Mth′ (Mauthner) cells and both of the B1 and B2 (bulbar) Müller cells fired action potentials in response to vibration of the otic capsules. Both B3 and B4 Müller cells were inhibited by vibration, while M (mesencephalic) and I1 (isthmic) Müller cells were inhibited by ipsilateral vibration and excited by contralateral vibration. Simultaneous action potentials in both of the anterior Mth cells were appropriate and sufficient for initiating the startle response EMG in a semi-intact preparation. This study demonstrates a Mauthner-initiated startle response which activates musculature on both sides of the body to produce a rapid withdrawal movement and is thus adapted to the eel-like form and burrowed lifestyle of larval lampreys.
Compensation of Progressive Hypercapnia in Channel Catfish and Blue Crabs
Authors: Cameron James N. , Iwama George K. 
Published: April 2021

ABSTRACT
Channel catfish (Ictalurus punctatus Rafinesque) were progressively acclimated to CO2 partial pressures of 7·5, 15, 30, 45 and 58mmHg (1, 2, 4, 6 and 8% CO2 in air) and blue crabs (Callinectes sapidus Rathbun) to 15, 30 and 45 mmHg, with 24 h at each partial pressure. Measurements of both conventional acid-base parameters (pH, total CO2) and ′strong′ ion concentrations (Na+, K+, Mg2+, Ca2+ and Cl−) were made at various times during each treatment. Intracellular [Na+], [K+] and [Cl−] were determined for red and white muscle in control and hypercapnic (8%) catfish. Extracellular [HCO3−] and strong ion difference (SID) both rose during hypercapnic compensation, with correlation coefficients (r) of 0·97 (P&lt;0·01) for catfish and 0·41 (NS) for blue crabs. Since [HCO3−] is calculated from two rapid measurements, and SID from four separate procedures, the former appears to be the measurement of choice. The results also dispel the notion of a 30mequivl−1 upper limit to bicarbonate compensation: [HCO3−] values over 50mequivl−1 were achieved in both animals, and %pH regulation remained around 70% at the highest . Due to superior intracellular buffering, the large change in extracellular SID did not lead to a measurable change in the concentrations of the major intracellular ions. The primary gill filaments of hypercapnic catfish showed a 30% increase in numbers and a 75 % increase in area of apical crypts of chloride cells. The chloride cell ′patches′ in crab gills increased in staining density after hypercapnia but did not enlarge.
Selective and Reversible Blocking of the Lateral Line in Freshwater Fish
Authors: Karlsen Hans Erik , Sand Olav 
Published: April 2021

ABSTRACT
Fish possess two separate systems for detection of low-level sound and water motions in the low-frequency range: the inner ear and the lateral line. The relative roles of these systems in normal fish behaviour is still not clear. There is, for instance, a lack of experimental evidence showing the involvement of the lateral line and the inner ear in detection of infrasound, in directional hearing in the near field, and in detection and attack of swimming prey below the surface. To provide a useful tool for such studies, we have developed a pharmacological method for selective and reversible blocking of the lateral line in the roach (Rutilas nitilus). By recording multi-unit activity from the lateral line nerve and microphonic potentials from the inner ear, we have shown that cobalt ions in the external water may completely block the mechanosensitivity of the lateral line without affecting the utricular microphonic activity. This inhibiting effect of Co2+ is antagonized by Ca2+, making the ratio between these ions the important blocking factor. For practical work, we recommend 12-24h exposure to 0·1mmoll−1 Co2+ at a Ca2+ concentration of less than 0-1 mmol l−1. The fish showed no sign of general behavioural disorders even after 1 week in this solution, and the microphonic sensitivity of the inner ear was not reduced. The blocking effect of Co2+ was clearly reversible, and the recovery was dependent upon both the duration of the Co2+ exposure and the Ca2+ concentration of the recovery solution.
The Effects of Salinity Acclimation on The Osmotic Properties of Mitochondria From The Gill of Crassostrea Virginica
Authors: Ballantyne James S. , Moyes Christopher D. 
Published: April 2021

ABSTRACT
Glutamate oxidation in mitochondria from the gills of oysters (Crassostrea virginica Gmelin) acclimated to sea water (SW) is sensitive to assay medium osmolantv. Compared to a medium of the osmolarity of sea water, decreasing osmolarity stimulates glutamate oxidation and increasing osmolarity inhibits glutamate oxidation. Glutamate oxidation by mitochondria from oysters acclimated to dilute sea water (DSW) is 2·5-fold greater than in SW animals when each is assayed under isosmotic conditions. The maximal rates obtained in both acclimation groups are equal. Although the DSW animals were acclimated to an osmolarity approximately 660mosmol1−1 lower than SW animals, the osmotic optimum was only 100-200 mosmol 1−1 lower in the former group. Isolation medium osmolarity does not affect the osmolarity at which the maximum rate of glutamate oxidation is observed in either acclimation group. A low-osmolarity isolation medium reduces the oxidation rates and quality of the mitochondria, as assessed by the respiratory control ratio in both acclimation groups. These data suggest that an optimal matrix solute concentration or ionic strength is required for maximal rates of glutamate oxidation rather than an optimal mitochondrial volume. The optimal mitochondrial matrix milieu can be achieved both by acclimation to dilute sea water and by incubation in hypo-osmotic media.
Pigeon Homing: Familiarity With the Release Site Reduces the Release Site Bias
Authors: Kowalski Ute , Wiltschko Roswitha 
Published: April 2021

ABSTRACT
When homing pigeons are released, they usually do not depart directly towards home, but deviate from the home direction: the so-called ′release site bias′ (Keeton, 1973 as a translation of the German Ortseffekt by Wallraff, 1959a). These deviations, which were first described by Kramer (1957), vary in size. At most sites, they are not very large, but occasionally may be as much as 180°. Releases at the same site normally produce very similar results, which are independent of weather conditions, age and general experience of the birds (Wallraff, 1959b) so that the bias is characteristic for any given location (Keeton, 1973). In view of the modern concepts of a learned navigational ′map′ (see Wallraff, 1974; Wiltschko & Wiltschko, 1978, 1982, 1987) it is interesting to know how local experience at the site itself could affect the pigeons′ behaviour.
Temperature Regulation in Bee- and Wasp-Mimicking Syrphid Flies
Authors: Morgan Kenneth R. , Heinrich Bernd 
Published: April 2021

ABSTRACT
Thoracic temperatures were measured in 12 syrphid species. During field activity the flies maintained thoracic temperatures near 30°C by a combination of basking and endothermy. In the 10 species which were mimics of Hymenoptera, thoracic temperatures averaged a few degrees below those of their models. All of the syrphids tested demonstrated a marked capacity for endothermic warm-up in the laboratory. Warm-up rates ranged from 1·2–5·5°C min−1. The maximum rate of warm-up increased in a linear fashion with body mass, with a slope of 4-3. The flies sometimes sustained endothermy beyond the 2–5 min necessary for thoracic temperature to reach flight temperature. One individual maintained an average temperature excess of 13·4°C for more than 26 min. Cooling rates were highly dependent on body mass and did not differ significantly between pubescent Bombus mimics and glabrous species. Removal of pile from the thorax of Bombus mimics increased their cooling rates by about 30%. From the comparisons between wasp and bee mimics, we conclude that although the pubescence of Bombus-mimicking flies aids endothermy, it is not necessary to achieve it. Their pubescence has apparently evolved primarily to improve visual mimicry.
Indoor Flight Experiments With Trained Kestrels: I. Flight Strategies in Still Air With and Without Added Weight
Authors: Videler J. J. , Vossebelt G. , Gnodde M. , Groenewegen A. 
Published: April 2021

ABSTRACT
Two kestrels, a male and a female, were trained to fly over 50 and 125 m in a windless corridor. Both distances were flown with or without dead weights attached to the feet during 13 flight sessions for each bird. Added weight was either 0·3 N (31 g lead) or 0·6 N (61 g). Each session was devoted to one distance and one flight weight category. Flight duration was automatically recorded at the landing points and at four positions along the track. Gliding bouts were hand-clocked and flight altitudes were estimated with the aid of sidewall markings.
An analysis was made of 1226 flights by the female over a total of 100 km, and 1017 flights by the male over 84·6 km.
Different flight strategies were observed under the different experimental situations, and were compared with model predictions for optimal speeds.
In the unloaded situations the birds flew at velocities close to the maximum range speed. Under load, speeds were lower and close to the predicted speeds for minimum power when 0·6 N was added to the weight.
Circulation in the Leech, Hirudo Medicinalis L.
Authors: Hildebrandt Jan-Peter 
Published: April 2021

ABSTRACT
In the leech, the physiological significance of high-pressure phases (HIP) and low-pressure phases (LOP) of the lateral vessels was studied by intravascular pressure recordings and observation of blood flow in different parts of the circulatory system, and by measurements of the blood flow velocities in the dorsal vessel.
Different shapes of the pressure pulses were found in the anterior lateral vessel segments during HIP and LOP phases, according to the different modes of diastolic filling in both phases.
Pressure recordings in the lateral abdominal vessels showed the different action of the lateral abdominal sphincters in the HIP and LOP phases of the ipsilateral lateral vessel. The LOP contractions were responsible for the blood supply to the capillary networks of the organs and the body wall, with the possible exception of the intestine. The HIP contractions caused a forward bloodflow within the lateral vessel.
In the dorsal vessel, the blood pressure was about 0·9-l·9kPa in different animals. The blood flow was discontinuous with velocities of 0·5-10 mm s−1. Average blood flow in the dorsal vessel was 22·9μ1 min−1.
An improved model of the circulation in the leech is presented.
Vibration Sensitivity in the Statocyst of the Northern Octopus, Eledone Cirrosa
Authors: Williamson R. 
Published: April 2021

ABSTRACT
The question of whether cephalopods have a sense of hearing has recently received renewed attention in the literature (Moynihan, 1985; Hanlon & Budelmann, 1987). However, the scarcity of physiological data (Maturana & Sperling, 1963; see also Budelmann, 1977) has meant that both those taking the view that cephalopods are deaf (Moynihan, 1985) and those of the opposing view (Hanlon & Budelmann, 1987) have relied almost entirely on morphological and behavioural evidence. Unfortunately, the morphological evidence cannot be conclusive and some behavioural experiments indicate no reaction to sound by cephalopods (Hubbard, 1960), although this is contradicted by other observations (Maniwa, 1976).
A New Technique to Monitor the Flight Paths of Birds
Authors: Bramanti M. , Dall’antonia L. , Papi F. 
Published: April 2021

ABSTRACT
The study of the mechanisms which govern bird orientation and navigation is severely hindered by the difficulty of reconstructing the route taken by the bird. Several methods have been used to study bird flights: direct observation using binoculars; following the bird by aeroplane or helicopter (Griffin, 1943; Hitchcock, 1952; Fiaschi, Baldaccini, loalè & Papi, 1981); using a transmitter carried by the bird (Michener & Walcott, 1966; Schmidt-Koenig & Walcott, 1978); and location of the bird using radar techniques (Eastwood, 1967; Papi & Pardi, 1978). All these techniques require that the bird and the monitoring equipment always be within optical or electromagnetic ‘visibility’.
Eye/Photophore Coordination and Light-Following in Krill, Euphausia Superba
Authors: Grinnell A. D. , Narins P. M. , Awbrey F. T. , Hamner W. M. , Hamner P. P. 
Published: April 2021

ABSTRACT
Eight of the 10 photophores of the Antarctic krill, Ettphausia superba, are located at the ends of muscular stalks and exhibit coordinated orientation responses to incident white light; light emitted from the photophores is directed away from the incident light. Moreover, eye rotation occurs synchronously with photophore movement. Immobilization of one or both eyes eliminated the photophore light-following response in 40% of the trials, but in the remaining 60%, photophores continued to exhibit oriented, but less stable responses. In the presence of a stationary light source the eyes could be passively rotated without affecting photophore position. Furthermore, eye removal or covering the head with an opaque hood eliminated coordinated photophore movement. We conclude that vision is necessary for light-following responses by the photophores. In addition, the control signal for that movement is CNS-derived, may occur spontaneously or may be light-induced, and appears to be accompanied by a parallel signal governing eye rotation. Subtle differences in photophore response when krill were oriented other than horizontally imply that krill may have a gravity sense that could help them orient in darkness.