bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of ATP- and Na+-gradient driven Ca2+ transport in basolateral membranes from gills of freshwater- and seawater-adapted tilapia
Authors: Verbost P. M. , Schoenmakers T. J. , Flik G. , Wendelaar Bonga S. E. 
Published: April 2021

ABSTRACT
Plasma membranes of the gills of freshwater- and seawater-adapted tilapia were analyzed for Ca2+-ATPase and Na+/Ca2+ exchange activity. The relative importance of ATP-driven and Na+-gradient-driven Ca2+ transport in Ca2+ extrusion was evaluated on the basis of kinetic analyses in vitro. The Na+/Ca2+ exchangers in branchial membranes from freshwater or seawater fish displayed similar kinetics. The ATP-driven Ca2+ pump, however, showed a somewhat lower affinity for Ca2+ in membranes isolated from seawater gills than in membranes from freshwater gills; no difference in Vmax was found. The activity of the exchanger was estimated to be 50 % of that of the ATP-driven pump at prevailing cytosolic Ca2+ concentrations (10−7 mol l-1).
Opercular ionocyte densities and branchial Na+/K+-ATPase content were not significantly different in fish residing in fresh water or sea water. We conclude that the gills of tilapia living for prolonged periods in fresh water or sea water do not differ in the make-up of their basolateral membrane with regard to Ca2+-ATPase, Na+/Ca2+ exchange and Na+/K+-ATPase activity. Apparently, the densities of these carriers suffice for calcium and sodium homeostasis under these vastly different ambient conditions.
Neuromuscular control and kinematics of intermittent flight in budgerigars (Melopsittacus undulatus)
Authors: Tobalske Bret W. , Dial Kenneth P. 
Published: April 2021

ABSTRACT
Kinematic and electromyographic data were collected from budgerigars (parakeets), Melopsittacus undulatus, flying at different speeds in a variable-speed wind tunnel. Birds exhibited flap-gliding at low speeds and flap-bounding at high speeds. The percentage of time spent flapping generally decreased at intermediate speeds. These behavior patterns are consistent with minimizing energy expenditure according to aerodynamic theory. During intermittent glides, the pectoralis exhibited an isometric contraction while the supracoracoideus was inactive. During bounds, both muscles were inactive.
Contrary to earlier work, our studies indicate that budgerigars do not exhibit simultaneous twitch contractions of the pectoralis during each wingbeat, but rather generate typical multiple-spike electromyographic bursts that represent motor unit action potential trains or asynchronous twitch contractions from different motor units. The relative intensity of electromyographic bursts from the primary flight muscles increased with flight speed. This may indicate an increase in force production.
Our observations of isometric contractions during glides, along with patterns of variation in muscle activity and wingbeat frequency, do not support the hypothesis that small birds such as the budgerigar use flap-bounding as their only means of reducing power output during flight.
Directional sensitivity of hair cell afferents in the Octopus statocyst
Authors: Budelmann Bernd U. , Williamson Roddy 
Published: April 2021

ABSTRACT
Changes in threshold sensitivity of hair cell afferents of the macula and crista of the Octopus statocyst were analyzed when the hair cells were stimulated with sinusoidal water movements from different directions. The experiments indicate that cephalopod statocyst hair cells are directionally sensitive in a way that is similar to the responses of the hair cells of the vertebrate vestibular and lateral line systems, with the amplitude of the response changing according to the cosine of the angle by which the direction of the stimulus (the deflection of the ciliary bundle) deviates from the direction of the hair cell’s morphological polarization.
Contractile properties of a high-frequency muscle from a crustacean: I. Activation patterns in vivo
Authors: Josephson Robert K. , Stokes Darrell R. 
Published: April 2021

ABSTRACT
The flagella of crustaceans are small appendages, borne on the maxillipeds, which beat repetitively when active. Flagellar movement is brought about by contraction of a single muscle, the flagellum abductor (FA). The stroke frequency of the flagella of the green crab, Carcinus maenas, was about 11 Hz at 15 °C and was relatively independent of animal size [frequency is proportional to (animal mass)−0.07], even though scaling considerations suggest that, for constant muscle stress, frequency should be proportional to mass−0.33. The coefficient of variation for intervals between successive strokes of a flagellum was about 4 %. The FA is innervated by two excitatory motoneurones. Each of the neurones fired 0–5 times during a stroke. The interspike interval when a neurone fired more than once during a stroke was 3–4 ms.
Integration of positive and negative feedback loops in a crayfish muscle
Authors: Skorupski Peter , Vescovi Paul J. , Bush Brian M. H. 
Published: April 2021

ABSTRACT
It is now well established that in arthropods movement-related feedback may produce positive, as well as negative, feedback reflexes (Bässler, 1976; DiCaprio and Clarac, 1981; Skorupski and Sillar, 1986; Skorupski et al. 1992; Vedel, 1980; Zill, 1985). Usually the same motor neurones are involved in both negative feedback (resistance) reflex responses and positive feedback reflexes. Reflex reversal involves a shift in the pattern of central inputs to a motor neurone, for example from excitation to inhibition.
Function of the tensor muscle in the cicada Tibicen linnei
Authors: Hennig R. M. , Weber T. , Moore T. E. , Huber F. , Kleindienst H.-U. , Popov A. V. 
Published: April 2021

ABSTRACT
The calling song and the disturbance squawk of the cicada Tibicen linnei (Insecta: Homoptera) are described in terms of their physical parameters. The calling song is composed of quiet parts, which are very similar to the disturbance squawk, and loud parts, which are amplitude-and rate-modulated. The role of the tensor muscle acting on the tymbal frame in modulating the sound pulse amplitude was investigated. We demonstrate by tensor nerve recordings, by mechanical mimicking of the tensor muscle action and by electrical stimulation of the tensor nerve, that the contraction of the tensor muscle is responsible for (a) initiating sound production and (b) modulating the sound pulse amplitude. These results allow us to construct a model which suggests that the tensor shifts the tymbal into a mechanical working range that enables sound production and modulation of the sound pulse amplitude.
Oxygen transport in marine green turtle (Chelonia Mydas) hatchlings: blood viscosity and control of hemoglobin oxygen-affinity
Authors: Wells R. M. G. , Baldwin J. 
Published: April 2021

ABSTRACT
Erythrocytes from green turtle hatchlings contain a single embryonic component, unlike those from other cleidoic eggs, in which adult hemoglobin (Hb) constitutes a significant fraction of total Hb at hatching. The functional properties of the isolated and purified green turtle hatchling Hb that distinguish it from adult Hb are a high affinity for oxygen and marked sensitivity to organic phosphate modulators. Hatchling erythrocytes also contain higher concentrations of ATP and 2,3-diphosphoglyceric acid, but their oxygen affinity is indistinguishable from that of adult erythrocytes. Hatchling erythrocyte mean cell volume is approximately half of the adult value, but hematocrit, blood hemoglobin concentration and blood viscosity of hatchlings and adults are similar. Oxygen-carrying capacity in green turtles, unlike that of other diving vertebrates, corresponds with a theoretically derived optimum. The possibility of allosteric control of Hb oxygen-binding in hatchlings may relate not to the challenge of exercise during the dispersal phase but to conditions in the late embryo in the nest.
Cyclic amp stimulation of electrogenic uptake of Na+ and Cl− Across the gill epithelium of the chinese crab Eriocheir Sinensis
Authors: Riestenpatt S. , Zeiske W. , Onken H. 
Published: April 2021

ABSTRACT
Split gill lamellae (epithelium plus cuticle) of hyperregulating Chinese crabs acclimated to fresh water were mounted in a modified Ussing chamber. Active and electrogenic absorption of sodium and chloride were measured as positive amiloride-sensitive and negative Cl−-dependent short-circuit currents (INa, ICl), respectively. Both currents were characterized before and after treatment of the tissue with theophylline or dibutyryl cyclic AMP. Both drugs increased INa and ICl. A simple circuit analysis showed that INa stimulation reflected a marked increase in the transcellular Na+ conductance, whereas the respective electromotive force was unchanged. The Michaelis constant (KNa) for Na+ current saturation was decreased after INa stimulation, indicating an increased affinity of the transport mechanism for its substrate. Consequently, the affinity for the Na+ channel blocker amiloride decreased as expected for a competitive interaction between substrate and inhibitor. Analysis of the amiloride-induced current-noise revealed a marked increase in the number of apical Na+ channels after INa stimulation with theophylline, whereas there was little change in the single-channel current. Stimulation of Cl− absorption was accompanied by a substantial increase in both transcellular conductance and electromotive force, indicating an activation of the apical H+ pump that provides the driving force for active Cl− uptake via apical Cl−/HCO3− exchange and basolateral Cl− channels.
Gas transport in the haemolymph of arachnids I. Oxygen transport and the physiological role of haemocyanin
Authors: Paul R. J. , Bergner B. , Pfeffer-Seidl A. , Decker H. , Efinger R. , Storz H. 
Published: April 2021

ABSTRACT
Oxygen equilibrium curves and the relationships between the partial pressure of CO2 and pH were determined for the haemolymph of the arachnids Eurypelma californicum, Pandinus imperator and Cupiennius salei. A new type of experimental apparatus was constructed, tested and used to make these measurements on small undiluted cell-free haemolymph samples. Most of its components were made in our workshop and were inexpensive. The apparatus proved to be very reliable as demonstrated by control (oxygen concentration) experiments. In previous reports on O2 equilibrium curves of E. californicum haemocyanin, Tris–HCl buffer was used to set the pH, whereas in our experiments, pH was adjusted by altering the partial pressure of CO2. The O2 concentration measurements demonstrate an increase in oxygen affinity of E. californicum haemocyanin when using Tris–HCl buffer. The position and shape of the O2 equilibrium curves of E. californicum and P. imperator haemocyanin show a distinct dependency on pH. Oxygen affinity is lower in E. californicum and cooperativity changes with pH in E. californicum, but not in P. imperator. Oxygen transport in the haemolymph of E. californicum during rest, activity and recovery was calculated on the basis of the O2 equilibrium curves of undiluted haemolymph. Apart from oxygen transport, there are indications that haemocyanin is also involved in other physiological processes. For example, it may function as a storage protein.
Neurosecretion of crustacean hyperglycemic hormone evoked by axonal stimulation or elevation of saline K+ concentration quantified by a sensitive immunoassay method
Authors: Keller R. , Haylett B. , Cooke I. 
Published: April 2021

ABSTRACT
A sandwich-type enzyme-linked immunosorbent assay (ELISA) was utilized to quantify crustacean hyperglycemic hormone (as Carcinus maenas equivalents) released by single X-organ–sinus gland systems of the crab Cardisoma carnifex during continuous perifusion. Basal rates of secretion (20–60 pg min−1) were stable for at least 4 h. Electrical stimulation (600 stimuli in 5 min) of the axon tract increased secretion two-to threefold, but only if it resulted in neural activity that was propagated to the terminals of the sinus gland. No difference was observable when stimuli were given repetitively or as a series of trains. Perifusion with saline having ten times the normal K+ concentration augmented secretion by as much as fivefold. Augmented secretion of crustacean hyperglycemic hormone evoked by either electrical or K+ stimulation appeared abruptly but declined slowly (over tens of minutes) after stimulation was stopped. K+-evoked secretion of crustacean hyperglycemic hormone was maintained without decrement for at least 1 h. Basal secretion increased in saline from which Ca2+ had been omitted, but decreased in saline containing Mn2+. Neither electrical stimulation nor high [K+] augmented secretion in Ca2+-deficient saline or if Mn2+ was present. Introduction of Mn2+ during K+-evoked secretion immediately reduced release to unstimulated levels; secretion resumed promptly upon removal of Mn2+. Tetrodotoxin reversibly blocked both electrical and secretory responses to axonal stimulation, but it did not block basal or K+-evoked secretion.
Release of crustacean hyperglycemic hormone by isolated axon terminals was augmented two-to threefold by perifusion with saline having ten times the normal K+ concentration. The responses were similar to those of the intact systems, having a rapid onset, well-maintained secretion and a long ‘tail’ of secretion after removal of the K+ stimulus.
Blind mexican cave fish (Astyanax Hubbsi) respond to moving visual stimuli
Authors: Teyke Thomas , Schaerer Stephanie 
Published: April 2021

ABSTRACT
In apparatus for measuring optomotor behaviour, blind Mexican cave fish, Astyanax hubbsi, increase their swimming velocity upon rotation of a striped cylinder, i.e. in response to a solely visual stimulus. The fish follow the movements of the stripes at (i) rotation velocities between 60 degrees s−1 and 80 degrees s−1, (ii) light intensities of less than 20 lx and, (iii) stimulus widths subtending an angle of less than 1 °.
Extirpation of the vestigial eye structures does not affect the response to the moving visual stimulus, which indicates that the response is mediated by extra-ocular photoreceptors.
An optomotor response can be reliably evoked in a round test aquarium. Fish do not respond when the test aquarium contains environmental cues, such as bars on the wall or when a section of the round aquarium is divided off. This indicates that the fish obtain information about their environment from different sensory sources and that the visual stimulus is effective only when no other means of orientation are available. We suggest a modified theory of the optomotor response, which emphasizes the crucial role of the environment in eliciting the response and which permits behaviours more complex than just following the stimulus.
Oxidative capacity distribution in skeletal muscle fibers of the rat
Authors: Philippi Maria , Sillau A. H. 
Published: April 2021

ABSTRACT
To study the distribution of oxidative capacity in muscle fibers, mitochondrial volume density and the oxidative capacity of isolated mitochondria were evaluated. Mitochondria were isolated from the subsarcolemmal and interfibrillar areas of the soleus (a muscle largely made up of slow oxidative fibers) and the gastrocnemius medial head (a muscle largely made up of fast glycolytic fibers) of the rat, and their oxidative capacities were evaluated using NADH- and FADH-generating substrates. In the soleus muscle, the subsarcolemmal mitochondria showed a lower oxidative capacity than interfibrillar mitochondria when NADH-generating substrates were used. This difference was not observed when FADH-generating substrates were used. In the gastrocnemius, there were no differences in the oxidative capacity of the subsarcolemmal and the interfibrillar mitochondria. Additionally, citrate synthase activity was found to be lower in mitochondria isolated from the subsarcolemmal area of the soleus than in the other mitochondrial preparations. These findings indicate that the difference in oxidative capacity of the isolated mitochondria is not related to differences in the inner mitochondrial membranes. Mitochondrial volume density was evaluated using electron micrographs of the subsarcolemmal and interfibrillar areas of slow oxidative fibers from the soleus and fast glycolytic fibers from the gastrocnemius. In the slow oxidative fibers, mitochondrial volume density in the subsarcolemmal area was four times higher than in the interfibrillar area. In the fast glycolytic fibers, mitochondrial volume densities in the subsarcolemmal and interfibrillar areas did not differ from that of the interfibrillar area of the slow oxidative fibers.
The oxidative capacity of the tissue, calculated by multiplying the mitochondrial oxidative capacities by the mitochondrial volume densities, was 2–4 times higher in the subsarcolemmal areas of the soleus fibers than in the other areas studied. This was true in spite of the fact that the oxidative capacity of the subsarcolemmal mitochondria of the slow oxidative fibers was lower than those of the other mitochondrial populations studied. These results indicate that the difference in oxidative capacity between slow oxidative fibers and fast glycolytic fibers is the result of the much greater mitochondrial volume density in the subsarcolemmal area of the slow oxidative fibers.
A Simple Colorimetric Micro-Method for Determining the Oxygen Content of Watery Solutions
Authors: Brinkman R. , Van Schreven A. 
Published: April 2021

ABSTRACT
Gilcreas (1935) describes a method for the approximate colorimetric determination of dissolved oxygen with 2-4-diaminophenol dihydrochloride, using a concentrated solution of this substance and a mixture of cobalt chloride and potassium dichro-mate solutions for colour comparison. The colour formed is described as a combination of red and yellow, which varies with the concentration of oxygen, but is not directly proportional to the oxygen content. It is intended for field work and not for accurate determinations.
The Alternation Problem in Animal Psychology
Authors: Honigmann H. 
Published: April 2021

ABSTRACT
The original aim of this paper was to give a contribution to the study of number conception in animals. It has been repeatedly maintained that birds can be trained to take every second and even every third from a row of identical grains. These experiments were carried out with rows of equidistant grains. Thus the bird’s achievement was possibly only a training to a certain distance. This eventuality has not previously been properly excluded, for we shall see that the apparently successful results after doubling or halving the usual distances between the grains are not convincing. Neither have attempts been made previously to train birds to select every second or third from a line of unequally spaced grains. Such an achievement, independent of any pecking rhythm and without the ‘figurai help’ of any pattern in the distribution of the grains, could be considered as a preliminary stage to counting. It was therefore intended to train birds first to select every second (or third) from a line of equidistant grains, and to extend this training later to rows with unequally spaced grains. Finally, the row of grains had to be covered by an opaque moving lid, so that it became visible to the bird not as a whole, but gradually. By modifying the speed of the lid any training to a temporal rhythm could be avoided, and by using a lid with a ‘window’ showing only one or two grains at a time a training to a figurai pattern could also be excluded.
The Fluctuation of pH and Organic Acids in the Rumen of the Sheep
Authors: Phillipson A. T. 
Published: April 2021

ABSTRACT
It has long been known that bacterial fermentation of cellulose in the rumen is associated with the production of a mixture of lower fatty acids, methane and carbon dioxide. It was first shown by Pringsheim (1912) and later confirmed by Woodman & Stewart (1928) that the addition of toluene to thermophilic cultures of cellulose-splitting bacteria resulted in the accumulation of glucose, and Woodman (1930) suggested that glucose was the product that was of nutritional value to the animal. Broadly speaking, theories regarding digestion of cellulose fall into two categories; those that emphasize the importance of the chemical products of fermentation, glucose and the lower fatty acids, and those that regard the food eaten by the animal as a substrate upon which the organisms of the rumen thrive, the bacteria and Protozoa forming the end-product which is subsequently digested by the sheep. Pochon (1935, 1938) put forward an ingenious explanation which belongs to the first school of thought; he isolated a cellulose-splitting organism which he named Plectridium cellulolyticum from the rumen of the ox and found that if the pH of the medium in which active cellulose fermentation was proceeding was reduced to 4, glucose accumulated. This change is similar to that which occurs when ingesta pass from the rumen to the abomasum, and he suggests that glucose is formed in the abomasum of the animal and the lower fatty acids that are formed in the rumen are waste products. Baker (1939) supports the second theory. He studied the decomposition of plant tissue microscopically with the use of polarized light and was able to observe the breakdown of cellulose by the loss of double refraction in the cell walls. Bacteria were intimately related to the areas where erosion was occurring and these organisms were iodophilic. He considers that the bacteria besides exerting cytoclastic activity take up the sugars formed by hydrolysis of cellulose and so protect them from further degradation. These sugars are condensed to an amylodextrin type of polysaccharide and so produce the blue staining reaction with iodine. The bacteria are subsequently digested by the ruminant either before or after ingestion by the ciliates of the rumen..
The Excitation of Nematocysts
Authors: Pantin C. F. A. 
Published: April 2021

ABSTRACT
Though an enormous amount of work has been done on nematocysts, the problem of how they are discharged remains unsolved. There are really two separate problems. First, what is the natural stimulus which excites the cnidoblast; second, what is the physical mechanism by which the nematocyst itself discharges? There is more work on the mechanics of discharge than on any other aspect of the problem, but it still awaits a satisfactory solution. As Graham (1938) points out, most of the work is remarkable for the chemical violence of the reagents used. Reactions to strong acids and alkalis, or to gross changes in osmotic or mechanical pressure can only throw an indirect light on the physical nature of the nematocysts’ diècharge. But it is not intended to discuss here the mechanics of discharge. Existing work has been reviewed by Weill (1934). This essay concerns the primary question of what is the effective stimulus to the cnidoblast, a problem to which much less work had been devoted.
Calcium magnesium phosphate granules: atomistic simulations explaining cell death
Authors: Simkiss K. , Taylor M. G. 
Published: April 2021

ABSTRACT
A large number of invertebrates have cells that produce intracellular granules of amorphous calcium magnesium phosphates that are thought to act as ion stores or sites of metal detoxification. The interatomic potentials and force constants have been calculated for these ions, and computer simulations of the crystal lattices have been used to determine the effects of ion substitutions on these lattice energies. The results provide insights into the mechanisms of granule formation and the effects of ion substitutions on cell physiology.