bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Active K Transport in the Isolated Midgut of Hyalophora Cecropia by T1+
Authors: Zerahn Karl
Published: April 2021

The midgut of the American silkworm transports potassium actively from blood side to lumen. The active K transport was measured by short-circuiting the gut.

The K transport is inhibited by T1 in the lumen solution. A Lineweaver-Burk plot showed that the inhibition with T1 is competitive with the active K transport. The Km was found to be 5·7 ± 0·7 and Ki = 0·1. It was concluded that T1 acts on the K pump which is located close to the lumen of the gut. When T1 was applied to the blood-side, only about half inhibition is found, yet, paradoxically, T1 concentration in the gut tissue was ten times as high as when T1 was applied to the lumen side.
Respiration in Exercising Fowl. III. Ventilation
Authors: Brackenbury J. H. , Gleeson M. , Avery P.
Published: April 2021

Minute volume , respiratory frequency (f) and tidal volume (VT) were continuously measured in domestic fowl running on a treadmill at speeds of 1·24–4·3 km h−1 in air temperatures of 18 ± 2 °C and 35 ± 2 °C. Oxygen extraction (E) was estimated using previously measured values of oxygen consumption. At 18±2 °C and VT rose abruptly at the start of exercise and and f continued to rise except at the slower running speeds. and f continued to rise throughout exercise at all speeds in the heat-stressed birds. In both groups VT reached a maximum at the start of exercise then fell to a new steady-state level. Steady-state ,f and VT increased with exercise speed at 18 ±2 °C. At 35-37 °C steady-state and VT increased with speed but f changed relatively little. E remained close to resting (0·21) at low speeds in room temperatures but decreased to 0·17 at 4·3 km h−1. In contrast E rose from 0·05 at rest in heat-stressed birds to 0·14 at 3·6 km h−1. The changes in oxygen extraction and respiratory pattern in the two groups during exercise are discussed in connexion with the control of ventilation by thermal and non-thermal factors. It is suggested that the latter play a predominant role during heavy exercise and that this accounts for the convergence of respiratory patterns in both heat-stressed and non heat-stressed birds at maximum work rates.
The Function of Photomechanical Movements in the Retina of the Rainbow Trout (Salmo Gairdneri)
Authors: Douglas R. H.
Published: April 2021

The function of photomechanical movements in the retina of rainbow trout (Salmo gairdneri) was investigated by determining both the effect of light on the level of extractable visual pigment, and the electroretinographic b-wave sensitivity, during various stages of photomechanical light and dark adaptation. Dark-adapted fish, light-adapted fish, and dark-adapted fish exposed to ten minutes direct sunlight had on average visual pigment concentrations of 100, 82 and 36% respectively. The intensity of illumination required to bleach a specified amount of visual pigment in the light-adapted retina was found to be 1·29 log units higher than that needed to bleach the same amount of visual pigment in a dark-adapted eye. The level of extractable visual pigment was observed to be relatively constant over natural twilight periods. A close temporal correlation was observed between the time course of electroretinographic adaptation, measured by the b-wave sensitivity, and photomechanical changes. All these observations tend to support the hypothesis that photo-mechanical movements serve, at least in part, to protect the rod visual pigment from overstimulation in the light-adapted retina.
pHi, Contractility and Ca-Balance Under Hypercapnic Acidosis in the Myocardium of Different Vertebrate Species
Authors: Gesser H. , Jørgensen E.
Published: April 2021

The influence of hypercapnic acidosis upon the heart was examined in four vertebrate species. The CO2 in the tissue bath was increased from 2·7 to 15 % at 12 °C for flounder (Platichthys flesus) and cod (Gadus morhua) and from 3 to 13% at 22 °C for turtle (Pseudemys scripta) and rainbow trout (Salmo gairdneri).

During hypercapnia, as previously described, there was a decline and recovery of contractility in heart strips of flounder and turtle, and a sustained decrease in cod and rainbow trout.

At high CO2 the increase in contractile force following increases in the extracellular Ca-concentration were smaller for the cod myocardium than for the other myocardia.

The intracellular pH (pHi), measured with the DMO method, in heart strips of turtle and trout was significantly lower at high than at low CO2. This acidifying effect expressed as the increase in the intracellular concentration of hydrogen ions was larger in the turtle than in the trout myocardium.

Intracellular Ca-activity, measured by efflux of 45Ca from preloaded heart strips, was unaffected by high CO2 in trout, but was raised in the other three species.

Thus the ability to counteract the negative inotropic effect of hypercapnia is apparently not due to cellular buffering or extrusion of hydrogen ions. More probably it involves (a) a release of intracellular Ca; (b) a positive inotropic effect of an increase in intracellular Ca-activity.
The Effects of Osmoregulatory Solutes On Tension Generation by Dogfish Skinned Muscle Fibres
Authors: Altringham J. D. , Yancey P. H. , Johnston I. A.
Published: April 2021

Many marine organisms accumulate high concentrations of solutes in their tissues to maintain osmotic balance. Osmoregulatory solutes are usually end-products of metabolism rather than inorganic ions (Prosser, 1973). For example, skeletal muscle from marine elasmobranchs, holocephalans and the coelacanth contains high concentrations of both urea (300–600 mm) and methylamine compounds, such as trimethylamine oxide (175–250 mm) (Pang, Griffith & Atz, 1977). Urea is a potent protein destabilizer, and most elasmobranch enzymes examined are inhibited by urea (Yancey, 1978). However, it has recently been found that TMAO acts as a general protein stabilizer and can offset the effects of urea on enzyme Km and maximal velocity in vitro (Yancey & Somero, 1979, 1980).
Inhibition by Recurrent Excitation: A Mechanism for Spike Synchronization in A Network of Coupled Neuronal Oscillators
Authors: Egelhaaf M. , Benjamin P. R.
Published: April 2021

Two bilateral clusters of 2–7 peripheral-neurones (‘Peripheral Bursters’) are located on the left and right branches of the post-buccal nerve of the snail Lymnaea stagnalis quite separate from the ganglia of the CNS (Carriker, 1946; Egelhaaf, 1981 a, A; M. Egelhaaf & P. R. Benjamin, in preparation). Isolation of single cells from these peripheral clusters shows that they are endogenously capable of bursting (Egelhaaf, 1981a; M. Egelhaaf & P. R. Benjamin, in preparation). In addition, the cells within one cluster as well as in heterolateral clusters are electrotonically coupled to one another, the coupling being stronger in the former case. Detailed evidence for this is given elsewhere (Egelhaaf, 1981a; M. Egelhaaf & P. R. Benjamin, in preparation). This has allowed the investigation of the interactions between the endogenous oscillatory properties of single cells and network properties due to electrotonic coupling in a system which can easily be separated from the influence of other neurones (Egelhaaf, 1981a, A; M. Egelhaaf & P. R. Benjamin, in preparation). In this paper interactions among homolateral Peripheral Bursters will be discussed and it will be shown phenomenologically how spike synchrony can be established within bursts of cells which tend to fire asynchronously due to slightly different levels of excitability.
Fast-Start Resistance of Trout
Authors: Webb P. W.
Published: April 2021

Rainbow trout (Salmo gairdneri Richardson) with a body mass of 268 ± 36 g were used to determine the acceleration resistance of a fish during fast-starts. The mass of the fish was increased by mass loads of 75, 150, 225 and 335 g. The loads were made from nesting horseshoe-shaped brass saddles which fitted snugly over the fish so that the extra mass was equally distributed in all planes about the stretched-straight body centre of mass. The weight of the saddles was taken up by a 291 cm line attached to the dorsal surface of the fish above its centre of mass. The other end of the line was attached to the ceiling. The performance of the fish with and without saddles was measured during fast-starts, initiated by a 1 v.cm−1 d.c. electric shock. Performance was determined in terms of the distance travelled with time, measured from high speed movie films (240 frames s−1). The relationships between distance travelled and time were described by power functions for fish with and without mass loads. Exponents were not significantly different for the fish with various mass loads showing that frictional and form drag made negligible contributions to acceleration resistance in a fast-start. The resistance of the fish in a fast-start, due to fish mass and a resistance component of added water mass (apparent mass), was calculated using hydromechanical theory for representative fast-start sequences. The apparent mass was estimated at 320 g, which is 1·2 × fish body mass.
Physiological and Ultrastructural Studies on the Longitudinal Retractor Muscle of a Sea Cucumber Stichopus Japonicus: I. Factors Influencing the Mechanical Response
Authors: Sugi H. , Suzuki S. , Tsuchiya T. , Gomi S. , Fujieda N.
Published: April 2021

The physiological properties of contraction and the ultrastructure of the longitudinal retractor muscle (LRM) of a sea cucumber Stichopus japonicus were studied to give information about the sources of activator Ca in echinoderm somatic smooth muscles. The magnitude of ACh- and K-induced contractures was dependent on [Ca]0, and both contractures were eliminated in Ca-free solution, while they were not markedly influenced by Mn ions (10 mM) and low pH (4·0). Procaine (5 mM) decreased ACh-contracture tension with a long lasting after-effect, which was removed by the application of high [K]o. ACh-contractures were markedly potentiated shortly after the termination of mechanical response to the removal of external Na. The LRM could also be made to contract by caffeine (10 mM), the removal of external divalent cations and hypertonic solutions, indicating the presence of intracellularly stored Ca available for the activation of the contractile mechanism. The LRM fibres contain poorly developed intracellular membranous structures. The inner surface of the plasma membrane and small vesicles located underneath the plasma membrane seem to be two of the sources of activator Ca.
Physiological and ultrastructural studies on the longitudinal retractor muscle of a sea cucumber Stichopus japonicus. II. Intracellular localization and translocation of activator calcium during mechanical activity
Authors: Suzuki S. , Sugi H.
Published: April 2021

The intracellular localization and translocation of activator Ca in the longitudinal retractor muscle (LRM) of a sea cucumber Stichopus japonicus were studied by fixing the LRM in a 1 % OsO4 solution containing 2 % K pyroantimonate. In the resting LRM fibres, electron-opaque pyroantimonate precipitate was mostly localized along the inner surface of the plasma membrane and at the subsarcolemmal vesicles in close apposition to the plasma membrane. In the LRM fibres fixed during the mechanical response to ACh and high [K]o, the precipitate was diffusely distributed in the myoplasm in the form of numerous particles with corresponding decrease in the amount of the precipitate at the peripheral structures. Electron probe X-ray microanalysis showed the presence of Ca in the precipitate, indicating that the precipitate provides a valid measure of Ca localization. These results accord with the view that, in the LRM, the contractile mechanism is activated by the release of Ca from the intracellular structures as well as by the inward movement of extracellular Ca.
Properties of synapses made by IVN command-interneurones in the stomatogastric ganglion of the spiny lobsterPanulirus interruptus
Authors: Sigvardt Karen A. , Mulloney Brian
Published: April 2021

The IVN command interneurones synapse directly onto 11 identified neurones in the stomatogastric ganglion : the two pyloric dilators (PDs), the anterior burster (AB), ventricular dilator (VD), the four gastric mill neurones (GMs), the two lateral posterior gastric neurones (LPGNs), and Interneurone 1 (Int 1). The IVN p.s.p.s in PD and AB are biphasic, and consist of a fast depolarizing component followed by a slower hyperpolarizing component. The hyperpolarizing component of this biphasic postsynaptic potential is inhibitory, and appears to be the result of a conductance increase to K+ and Cl-. The IVN p.s.p. in VD is excitatory and can drive VD one-for-one. The IVN p.s.p.s in GM and LPGN are inhibitory. The amplitude of a single p.s.p. is small but, at high frequency, summation of p.s.p.s holds the postsynaptic membrane potential below threshold. The facilitation characteristics of the p.s.p.s in each neurone are described. The functional significance of these synaptic characteristics is discussed in terms of the modification of motor output caused by a burst of the IVN interneurones.
Importance of Calcium And Magnesium Ions for Postexcitatory Hypersensitivity in the Jumping Spider (Menemerus) Eye
Authors: Tateda Shigeki Yamashita and Hideki
Published: April 2021

Hypersensitivity of the anterior median eye of the jumping spider Menemerus confusus, following illumination, was unaffected by the concentration of Na+ or K+, was depressed by increase of Ca2+ concentration, and was dependent upon the presence of Mg2+. Sensitivity of the dark-adapted eye was also inversely related to Ca2+ concentration, but to a lesser extent.
Acid Tolerance and Effects of Sublethal Acid Exposure on Iono-Regulation and Acid-Base Status in Two CrayfishProcambarus ClarkiandOrconectes Rusticus
Authors: Morgan D. O. , Mcmahon B. R.
Published: April 2021

Acid-toxicity tests were performed using two crayfish species, Procambarus clarki Girard and Orconectes rusticus Girard to determine the median lethal pH (LC5O) after 4 days exposure to acid. Four-day LC50 values of pH 2*5-2-8 were observed, indicating that these animals are more acid-tolerant than most fish species. Haemolymph acid-base variables and major ion concentrations were measured during 4 days exposure of P. clarki to sublethal acid H2SO4, pH 3-8) levels. A major haemolymph acidosis was observed. While minimal changes were seen in haemolymph [Cl−], [K+], and [Mg2+], haemolymph [Na+] decreased. Haemolymph [Ca2+] increased significantly during acid exposure, suggesting that dissolution of exoskeletal carbonate buffers was being employed as a compensatory mechanism for the acidosis; this process would be expected to contribute to exoskeletal rigidity problems in the long term.
The effect of temperature on the tension responses of the anterior byssal retractor muscle (abrm) ofMytilus edulis
Authors: Linehan Catherine M.
Published: April 2021

The effect of ambient temperature on the response of the ABRM of Mytilus edulis to acetylcholine and 5-hydroxytryptamine has been examined. As the ambient temperature was increased, the latent period and the maximum tension developed decreased while the rate of tension development and the rate of relaxation increased. The relationship between temperature and the rate of tension development showed three distinct linear phases from 2–25, 25–35 and 35–45 °C. The reduction in peak tension with temperature could also be resolved into three portions from 2–25, 25–40 and above 40 °C. As the temperature was increased above approximately 27 °C the rate of relaxation in the absence of 5-HT approached the rate of relaxation in the presence of 5-HT. The significance of these results and possible explanations for them are considered.
Effects of Body Size and Slope on Sprint Speed of a Lizard (Stellio (Agama) Stellio)
Authors: Huey Raymond B. , Hertz Paul E.
Published: April 2021

The agamid lizard Stellio stellio L. accelerates quickly and reaches maximum speed over short distances. Maximum speed on the level is proportional to body mass to the power. This relation differs from predictions based on an interspecific scaling model of “geometric” similarity (M0) and is intermediate between predictions based on interspecific scaling models of “elastic” similarity and of “static stress” similarity . Maximum speed was also measured on slopes ranging from –15° to + 60°. The effect of slope on speed varies with body mass. The maximum speed of large lizards decreases on steep slopes, but that of small lizards is remarkably independent of slope.
Actions of insect toxin and other toxins derived from the venom of the scorpion Androctonus australis on isolated giant axons of the cockroach (Periplaneta americana)
Authors: Pelhate M. , Zlotkin E.
Published: April 2021

Insect toxin, mammal toxins I and II and crustacean toxin were obtained from the venom of the scorpion Androctonus australis. Their effects on the isolated giant axon of the cockroach Periplaneta americana were investigated by current-clamp and voltage-clamp techniques. ‘ In current-clamp conditions, mammal toxins and crustacean toxin (1·3–13 μM) induced a large prolongation of the falling phase of the evoked action potentials. Insect toxin (0·13–3·3 μM) induced a progressive slow depolarization of the membrane potential and repetitive firing of action potentials. No changes in the time-course of the action potential were induced by insect toxin. In voltage-clamp conditions, mammal and crustacean toxins induced a slowing of the turn-off of the transient inward sodium current, with either no change or a small increase in the peak sodium current. Insect toxin by contrast induced an increase in the peak sodium current and a slowing of the sodium current turn-off, this effect being greatest at lower values of the clamped membrane voltage. It is concluded that the repetitive activity induced by insect toxin results from a voltage-dependent modulation of sodium inactivation coupled with an increase in both the resting and active sodium permeabilities of the cockroach axonal membrane.
Eye Movements of the Crab Leptograpsus Variegatus Elicited By Imposed Leg Movements
Authors: Varju D. , Sandeman D. C.
Published: April 2021

The horizontal component of eyestalk movements elicited by moving the legs of blinded crabs is described. The animals’ bodies were fixed to a stand and the legs were supported on either a sphere or platform and subjected to movement around the three major axes (yaw, pitch, and roll). Both sinusoidal and stepped movements of the legs were studied. The effect of moving the legs on one side only, homolateral or contralateral to the eyestalk was also studied. The eyestalk excursion elicited by sinusoidal leg excursion around the vertical axis (yaw) is a nearly linear function of the leg excursions over the range of 1–40° peak to peak at 0·1 Hz. The amplification of the system is about 0·4 when the animal’s legs are supported on a ball, and 0·8–1·0 when the legs are supported on a platform. The frequency response of the system to yaw is nearly flat for eye excursions of 16° peak to peak, over the range of 0·005–0·1 Hz. The visual system has a powerful braking effect on the eye rotation, when this is generated by the imposed leg movements. Eyestalk responses to yaw can be interpreted to be compensatory in that they stabilize the eyes in space in freely moving animals. Eyestalk movements to pitch and roll are complex. In roll, their horizontal component indicates the presence of considerable rectification in the leg proprioceptor-eye system. The functional significance of the eyestalk movements in the horizontal plane is discussed.
Movements and Motor Patterns of the Buccal Mass ofPleurobranchaeaDuring Feeding, Regurgitation And Rejection
Authors: McClellan Andrew D.
Published: April 2021

Feeding, regurgitation, and rejection in the marine gastropod Pleuro-branchaea all involve similar but not identical rhythmic movements of buccal mass structures such as the radula, jaws and lips. The part of the motor pattern which produces rhythmic radula movement, as recorded in the major external muscles of the buccal mass of behaving semi-intact preparations, was similar during the three different types of behaviour, suggesting that they share a common motor-pattern generator. Other parts of the motor pattern were only obviously different during the vomiting phase of regurgitation. Differences in the function and motor patterns of feeding and rejection are presumably accounted for by differences in the activity of muscles which could not be recorded from in this study (e.g. jaw muscles). A general conclusion is that buccal rhythms in gastropods cannot automatically be assumed to underlie feeding, and this is particularly true for dissected preparations which do not execute a clear behavioural response. It would be necessary either to record motor activity that is unique for a given behaviour, or to employ preparations which execute unambiguous behavioural responses.
Anatomy of Motoneurones Innervating Mesothoracic Indirect Flight Muscles in the Silkmoth,Bombyx Mori
Authors: Kondoh Y. , Obara Y.
Published: April 2021

The anatomy and innervation of mesothoracic indirect flight muscles, dorsal longitudinal (DLM) and dorsoventral muscles (DVM) are described. The major DLMs depress the forewing, the major DYMs elevate it. The morphology of the motoneurones and unpaired median neurones (UM-neurone) innervating these muscles was investigated by back-filling with cobalt. The DLMs are innervated by eight paired motoneurones and one UM-neurone: one of these motoneurones has its cell body in the contralateral side of the mesothoracic ganglion, and the others have theirs in the ipsilateral side of the prothoracic ganglion. The DVMs are innervated by nine paired motoneurones and one UM-neurone, with their cell bodies in the ipsilateral and the median portion of the mesothoracic ganglion, respectively. All of the paired DLM and DVM motoneurones have many dendritic processes, mainly in the dorso-ipsilateral neuropile of the ganglia, but the DLM motoneurones also have processes in the contralateral neuropile. Each UM-neurone has its cell body in the postero-medial cortex of the mesothoracic ganglion, extending a single median neurite anteriorly to the dorsal neuropile where it bifurcates to form a right and left axon. The arrangement of the mesothoracic indirect flight motoneurones in different insect orders is discussed in terms of the neural organization of the flight system.
Mechanical Design of Spicule-Reinforced Connective Tissue: Stiffness
Authors: Koehl M. A. R.
Published: April 2021

Many animals from different phyla have, embedded in their pliable connective tissues, small bits of stiff material known as spicules. The tensile behaviour of spicule-reinforced connective tissues from various cnidarians and sponges, as well as of model spiculated ‘tissues’, is here investigated in order to elucidate the effects on mechanical properties of spicule size and shape, and of their packing density and orientation within a tissue. The main conclusions are :

Spicules increase the stiffness of pliable connective tissues probably by mechanisms analogous to those by which filler particles stiffen deformable polymers -local strain amplification, and interference with molecular rearrangement in response to a load. The greater the volume fraction of spicules, the stiffer the tissue. The greater the surface area of spicules per volume of tissue, the stiffer the tissue. Thus, a given volume of spicules of high surface-area-to-volume-ratio (S/V) have a greater stiffening effect than does an equal volume of spicules of low S/V. Furthermore, a high volume fraction of large spicules in a tissue can have the same stiffening effect as a lower volume fraction of smaller spicules. Spicules that are anisometric in shape have a greater stiffening effect parallel to their long axes. Spicules with very high aspect ratios appear to act like reinforcing fibres -stress is transferred by shearing from the pliable matrix to the stiff fibres, which thus bear in tension part of the load on the composite. Spicule-reinforced tissues exhibit stress-softening behaviour, which is more pronounced in heavily spiculated tissues.
The Function of Chemo- and Mechanoreceptors in Lobster (Homarus Americanus) Feeding Behaviour
Authors: Derby Charles D. , Atema Jelle
Published: April 2021

The behaviour of lobsters preying on live mussels (Mytilus edulis) was observed before and after chemosensory or chemosensory-mechanosensory deafferentation of different sensory appendages. Deafferentation of the antennules, leg tips, or maxillipeds (but not the carapace or proximal leg segments) interfered with feeding performance by causing an increase in the time necessary to crush a mussel after search initiation. In addition, deafferentation of the leg tips or the maxillipeds caused a decline in number of mussels crushed but for different reasons: leg-treated lobsters walked over the mussels without picking them up, whereas maxilliped-treated lobsters grasped the mussels as usual but either did not crush or did not eat them as readily as did normal lobsters. Deafferentation of leg chemoreceptors resulted in the same behavioural deficiencies as deafferentation of leg chemo- and mechanoreceptors, demonstrating that it is the leg chemoreceptors that are essential in releasing this grasping response. Chemoreceptors on different appendages of lobsters therefore fulfill different functional roles in their feeding behaviour.
Mechanism and Characteristics of Coxal Fluid Excretion in the Argasid TickOrnithodorus Moubata
Authors: Kaufman Susan E. , Kaufman William R. , Phillips John E.
Published: April 2021

Adult ticks (Omithodorus moubata Murray, Acari, Argasidae) were fed on human blood at 37 °C in a beaker covered with chicken skin. 14C-labelled inulin and 3–0[14CH3]glucose were rapidly cleared from haemolymph to coxal fluid ; the coxal tubule appeared not to reabsorb either substance. Glucose was reabsorbed from tubular fluid via a phlorrhizin-sensitive mechanism. Reabsorption of amino acids varied between o and 90 % but was greatest for those amino acids which were scarce in the meal. During normal feeding conditions, there was positive correlation between haemocoelic hydrostatic pressure and rate of coxal fluid excretion. Unilateral cannulation of a coxal organ so as to eliminate back pressure of a valve at the coxal orifice led to a twofold increase in rate of coxal fluid production compared to the contralateral side. The above data confirm that coxal fluid excretion occurs by a filtration resorption mechanism.
Protein and Glycoprotein Antifreezes in the Intestinal Fluid of Polar Fishes
Authors: O’grady S. M. , Ellory J. C. , DeVries A. L.
Published: April 2021

Measurements of ion concentrations, freezing points and melting points of intestinal fluid were made for several Antarctic fishes and two North Atlantic species. These measurements indicated that plasma and intestinal fluid are nearly isosmotic. Freezing points of intestinal fluid were approximately 0·9 °C below the melting points, suggesting the presence of glycoprotein antifreeze within the intestinal fluid of the Antarctic fishes. Polyacrylamide gel electrophoresis and specific immunoprecipitation with glycoprotein antifreeze antibody confirmed the presence of appreciable quantities of antifreeze and showed that the major antifreeze fractions present in the intestinal fluid are low molecular weight glycopeptides.
Acid-Base Imbalance in Lizards During Activity and Recovery
Authors: Gleeson Todd T. , Bennett Albert F.
Published: April 2021

The effects of treadmill exercise on oxygen consumption carbon dioxide production arterial blood lactate concentration ([L−]a), arterial blood pH and arterial gas tensions ( and ) were measured in 3 species of lizards (Varanus salvator, V. exanthematicus, Iguana iguana) Varanus salvator was exercised 45 min at an intensity which required 85% of its V. salvator utilized supplementary anaerobic metabolism during the first 10 min of this sustainable exercise, as evidenced by a 16 mmol/1 increase in [L−]a. Respiratory exchange ratios (R, where R =) exceeded 1·2 when [L−]a and [H+]a were maximal. One half of the accumulated lactate was removed from the blood during the remainder of the 45 min exercise period, while blood pH returned to resting levels. In a second set of experiments, high intensity exercise led to exhaustion after 5 to 10 min in all three species, resulting in large lactate ( +Δ [L−]a = 14–20 mmol/l) and hydrogen ion ( + Δ [H+]a = 23–57 nmol/l) accumulations. R values ranged from 1·2–1·8 at exhaustion. Recovery from both sustainable and non-sustainable exercise was characterized as a period of rapid lactate removal. Respiratory exchange ratios were low (0·3–0·5) as metabolic CO2 was retained, replacing depleted bicarbonate stores. We conclude that all three lizard species make ventilatory adjustments during and after exercise that minimize disturbances to resting hydrogen ion concentrations and acid-base balance. Varanus salvator demonstrate the ability to re-establish resting acid-base status during sustained exercise requiring 85% of their Changes in R appear to be a useful non-invasive indicator of net blood lactate accumulation.
A Gold-Plated Suction Electrode for Extracellular Recording and Dye Infusion
Authors: Theophilidis G. , Burns M. D.
Published: April 2021

To record extracellular nerve activity, wires or polyethylene suction electrodes are commonly used, which are modified according to particular experimental requirements. For electrophysiological studies in a dissected animal, a length of the nerve under investigation may be lifted on to silver wires (Pearon, Stein & Malhotra, 1972), or a fine wire hook (Wilkens & Wolf, 1974), often under mineral oil. These methods produce good records but the mineral oil and the wires around the nerve and its associate muscle reduce the visibility of the preparation. This may cause difficulties when simultaneous records are required from other parts of a small preparation.
Biophysics of Underwater Hearing in Anuran Amphibians
Authors: Hetherington Thomas E. , Lombard R. Eric
Published: April 2021

A standing wave tube apparatus was used to determine the biophysical basis of underwater hearing sensitivity in 3 species of Rana and in Xenopus laevis. A speaker inside the base of a vertical, water-filled 3 m steel pipe produced standing waves. Pressure and particle motion were measured with a hydrophone and geophone respectively and were spatially 90° out of phase along the length of the tube. Microphonic responses were recorded from the inner ear of frogs lowered through pressure and particle motion maxima and minima. The air-filled lungs of whole frogs produced distortions of the sound field. Preparations of heads with only an air-filled middle ear produced little distortion and showed clear pressure tracking at sound intensities 10–20 dB above hearing thresholds from 200–3000 Hz. Filling the middle ear with water decreased or abolished microphonic responses. Severing the stapes reduced responses except at certain frequencies below about 1000 Hz which varied with body size and likely represent resonant frequencies of the middle ear cavity. We conclude that the frog species examined respond to underwater sound pressure from about 200–3000 Hz with the middle ear cavity responsible for pressure transduction.
Light Organ and Eyestalk Compensation to Body Tilt in the Luminescent Midwater Shrimp, Sergestes Similis
Authors: Latz Michael I. , Case James F.
Published: April 2021

The posterior light organ and eyestalk of the midwater shrimp, Sergestes similis Hansen, are capable of 140° of angular movement within the body during pitch body tilt, maintaining the organs at near horizontal orientations. Counter-rotations compensate for 74–80% of body inclination.

These responses are statocyst mediated. Unilateral statolith ablation reduces compensation by 50%. There is no evidence for either homolateral or contralateral control by the single functioning statocyst. Bilateral lith ablation abolishes counter-rotation. Light organ and eyestalk orientations are unaffected by the direction of imposed body tilt.

Bioluminescence is emitted downward from horizontal animals with an angular distribution similar to the distribution of oceanic light. The amount of downward directed luminescence in tilted animals decreases at large angles of body inclination due to less than total compensation by the light organs.

Eye turning towards a light source is induced by upward-directed illumination. The resulting change in eyestalk orientations never amounts to more than 25°. The turning is abolished by bilateral statolith ablation. Downward directed illumination, comparable in intensity to oceanic light, generally does not generate significant eye turning.

Light organ orientations remain unaffected by directional illumination, both before and after bilateral statolith ablation.

The compensatory counter-rotations by the posterior light organ and eyestalk suggest that counter-illumination by S. similis remains effective in inclined animals.
Ion-dependent Viscosity of Holothurian Body Wall and its Implications for the Functional Morphology of Echinoderms
Authors: Eylers John P.
Published: April 2021

Dermis from the holothurian Thyone inermis was subjected to constant load and its rate of plastic deformation (creep) was used to calculate tissue viscosity. During these tests the material was bathed in distilled water, sea water, or solutions of sodium, potassium, calcium, and magnesium salts in various combinations. Distilled water caused a threefold increase in viscosity which was reversed by sea water. Sodium and potassium decreased viscosity, while calcium and magnesium in combination with sodium increased it. Ionic cross-links shielded by monovalent ions but facilitated by divalent cations are proposed to explain this behaviour, and the relationship between this and other anomalies of echinoderm connective tissue physiology is discussed.
The acid-base responses of gills and kidneys to infused acid and base loads in the channel catfish,Ictalurus punctatus
Authors: Cameron J. N. , Kormanik G. A.
Published: April 2021

Acid and base loads infused into the dorsal aorta of the freshwater channel catfish (Ictalurus punctatus Rafinesque) were excreted by both gills and kidneys. The gills excreted 2–3 times as much as the kidneys.

After a 2 mmol.kg−1 load of NaHCO3, the gills excreted 50% of the net OH- load in the first 5 h, while the kidneys excreted 18% in the first 6 h. After a 2 mmol.kg−1 load of NH4C1, the gills excreted 32% of the load in 6 h, and 16% was excreted renally in 20 h. There was no evidence of tissue damage after either NaHCO3 or NH4C1 infusions, whereas infusion of 2 mmol. kg−1 HC1 or 1 mmol. kg−1 of L( + )-lactic acid caused significant kidney damage and extensive tissue necrosis within 24 h.

After both NaHCO3 and NH4C1 infusions, the majority of the load had been transferred to the intracellular compartment within 2 h. From there it was excreted slowly, presumably by transfer back through the extracellular compartment. Due to the relative compartment volumes and buffer values, the change in intracellular pH was less than 0·05 units, while the blood pH was changed by as much as 0·3 units.
The central nervous origin of the swimming motor pattern in embryos ofXenopus laevis
Authors: Kahn J. A. , Roberts A.
Published: April 2021

Rhythmic motor nerve activity was recorded in stage 37/38 Xenopus embryos paralysed with curare. The activity was similar to the swimming motor pattern in the following ways: cycle period (40–125 ms), alternation of activity on either side of a segment, rostro-caudal phase lag. Episodes of rhythmic motor activity could be evoked by stimuli that evoke swimming and inhibited by stimuli that normally inhibit swimming. On this basis we conclude that the swimming motor pattern is generated by a central nervous mechanism and is not dependent on sensory feedback.

In addition to the swimming pattern, another pattern of motor activity (‘synchrony’) was sometimes recorded in curarized embryos. In this, the rhythmic bursts on either side of a segment occurred in synchrony, and the rhythm period (20–50 ms) was half that in swimming. This was probably not an artifact of curarization as there were indications of a similar pattern in uncurarized embryos. Its function remains unclear.
Characterization of Lymnaea Neurones by determination of Action Potential Trajectories
Authors: Winlow W. , Holden A. V. , Haydon P. G.
Published: April 2021

Phase plane techniques have been used to demonstrate that identifiable neurones of Lymnaea stagnalis may be characterized by their action potential trajectories. These trajectories are consistent from preparation to preparation, but may be altered by strong synaptic inputs or by injection of current into neurones. There is a pronounced hysteresis in the maximum rates of depolarization and the maximum rates of repolarization of many cells following a period of hyperpolarization. Curves relating and to injected current have been constructed for each neurone type investigated and may be used to identify the neurones. We conclude that phase plane portraits of action potentials together with measures of and are useful in identification of neurones when structural criteria are not available.
Regulation of Blood Oxygen Affinity in the Australian BlackfishGadopsis Marmoratus
Authors: Dobson G. P. , Baldwin J.
Published: April 2021

The regulation of whole blood oxygen affinity in the freshwater black-fish Gadopsis marmoratus Richardson has been examined, and correlations made between oxygen-binding properties and the habitat and swimming behaviour of the fish. Blackfish whole blood has a low oxygen affinity relative to other fish bloods reported in the literature. This is not due to a low oxygen affinity of the stripped haemoglobins, but arises from interactions between haemoglobin and intraerythrocytic modulators. The presence of high concentrations of ATP, and to a lesser extent GTP, in the erythrocyte, together with the effect of these nucleoside triphosphates on the oxygen affinity of haemoglobin solutions at physiological NTP: Hb4 molar ratios, demonstrates that this class of compounds is a major regulator of oxygen affinity in blackfish blood. The oxygen affinities of whole blood and haemoglobin solutions are sensitive to pH, with haemoglobin solutions displaying a relatively large alkaline Bohr coefficient of-– 1·05 over the physiologically relevant pH range of 6·5–7·0. Although increasing lowers the oxygen affinity of whole blood, it does so only through the effect on pH, as pH-buffered haemoglobin solutions show no oxygen-linked CO2 binding. This lack of oxygen-linked CO 2 binding has not been reported for any other naturally occurring vertebrate haemoglobins. Muscle morphology and biochemistry, and behavioural observations, indicate that the blackfish uses anaerobic energy metabolism during rapid swimming and in recovery. It is concluded that the oxygen-binding properties of blackfish blood reflect adaptations for maintaining adequate tissue oxygenation for animals at rest and during slow sustained swimming in waters of high oxygen tensions.
Metabolic Support of Chloride-dependent Short-Circuit Current Across Locust Rectum*
Authors: Chamberlin M. , Phillips J. E.
Published: April 2021

Recta of desert locusts were short-circuited and depleted of endogenous substrates by exposing them to saline containing cyclic AMP but no metabolites. Individual substrates were then added to substrate-depleted recta and the change in short-circuit current (Isc) monitored. Proline or glucose (50 mm) caused by far the largest increase in Isc of all substrates tested. Stimulation of the /sc by proline was not dependent upon external sodium, but did require external chloride. Physiological levels of proline also caused a large increase in Isc, while physiological levels of glucose produced a much smaller stimulation. Over 90% of the proline-dependent Isc stimulation can be produced by adding 15 mm proline solely to the lumen side of the tissue. These results are discussed with regard to rectal oxidative metabolism and availability of metabolic substrates in vivo. High levels of proline in Malpighian tubule fluid are probably the major substrate source for rectal Cl- transport.
Do the Extraocular Muscles in the Carp Compensate for Eye Displacements Induced by Respiratory Movements?
Authors: Jüch P. J. W.
Published: April 2021

The eyes in normally respiring carp are induced by elements of the respiratory pumping system to make small displacements in phase with the respiratory cycle. The ocular movements were studied by film analysis during the normal respiratory cycle and the cough. In the course of the movement, the optic axis remains nearly parallel to its starting position. This results in a smaller retinal image shift than would be produced by angular movements.

Electromyography of the extraocular muscles showed that the external rectus and superior oblique muscles contribute to image stabilization during strong respiration, and the external rectus and the superior oblique muscles contribute during the cough.
Responses to Hypersaline Exposure in the Euryhaline CrayfishPacifastacus Leniusculus
Authors: Wheatly Michèle G. , McMahon B. R.
Published: April 2021

Haemolymph iono- and osmoregulation and acid-base balance were recorded after 48 h exposure at 15 °C to a range of increasing ambient salinities (0,25, 50 and 75% seawater) in the euryhaline crayfish Pacifastacus leniusculus (Dana). Except for K+, concentrations of all measured inorganic ions and osmolality were significantly elevated in 50 and 75 % SW. When compared with ambient changes there was evidence of a transition from hyper- to hypoionic regulation above 44 % SW. Ca2+ was regulated for a constant blood-medium difference. A progressive reduction in total CO2 was recorded ; pH was maintained except in 75% SW where a haemolymph acidosis developed. To permit calculation of CO2 tension carbon dioxide solubility coefficient and the apparent first dissociation constant of carbonic acid were experimentally determined in vitro. decreased progressively with acclimation salinity but was unaffected by circulating protein. decreased as a function both of physiological pH and increasing haemolymph ionic strength. calculated using these empirical constants, progressively decreased with high-salinity acclimation. The resulting ‘hypocapnic alkalosis’ was partially offset by a metabolic acidosis, whose correlation with extracellular anisosmotic and intracellular isosmotic regulation is discussed.
Automatic classification of esophageal disease in gastroscopic images using an efficient channel attention deep dense convolutional neural network
Authors: Du Wenju , Rao Nini , Dong Changlong , Wang Yingchun , Hu Dingcan , Zhu Linlin , Zeng Bing , Gan Tao
Published: April 2021

The accurate diagnosis of various esophageal diseases at different stages is crucial for providing precision therapy planning and improving 5-year survival rate of esophageal cancer patients. Automatic classification of various esophageal diseases in gastroscopic images can assist doctors to improve the diagnosis efficiency and accuracy. The existing deep learning-based classification method can only classify very few categories of esophageal diseases at the same time. Hence, we proposed a novel efficient channel attention deep dense convolutional neural network (ECA-DDCNN), which can classify the esophageal gastroscopic images into four main categories including normal esophagus (NE), precancerous esophageal diseases (PEDs), early esophageal cancer (EEC) and advanced esophageal cancer (AEC), covering six common sub-categories of esophageal diseases and one normal esophagus (seven sub-categories). In total, 20,965 gastroscopic images were collected from 4,077 patients and used to train and test our proposed method. Extensive experiments results have demonstrated convincingly that our proposed ECA-DDCNN outperforms the other state-of-art methods. The classification accuracy (Acc) of our method is 90.63% and the averaged area under curve (AUC) is 0.9877. Compared with other state-of-art methods, our method shows better performance in the classification of various esophageal disease. Particularly for these esophageal diseases with similar mucosal features, our method also achieves higher true positive (TP) rates. In conclusion, our proposed classification method has confirmed its potential ability in a wide variety of esophageal disease diagnosis.
Datengetriebene Geschäftsmodelle: Konzeptuelles Rahmenwerk, Praxisbeispiele und Forschungsausblick
Authors: Strahringer Susanne , Wiener Martin
Published: April 2021

Datengetriebene Geschäftsmodelle (DGGM) vereinen zwei zentrale Trends des digitalen Zeitalters: die steigende Bedeutung von („Big“-)Daten und den zunehmenden Fokus auf das Geschäftsmodell als zentrale Gestaltungsebene. Nichtsdestotrotz sind die konzeptuellen Grundlagen und spezifischen Eigenschaften entsprechender Geschäftsmodelle bislang nur unzureichend erforscht und systematisiert. Basierend auf relevanten Vorarbeiten stellen wir in diesem Grundlagenbeitrag drei wesentliche Typen von DGGM vor (Datennutzer, Datenlieferanten und Datenbefähiger) und geben einen Überblick über zentrale „datengetriebene“ Konzepte, die wir in ein konzeptuelles Rahmenwerk zur weiterführenden Charakterisierung von DGGM integrieren. Die Anwendbarkeit und Nützlichkeit der drei DGGM-Typen und des entwickelten Rahmenwerks illustrieren wir anhand von drei Praxisbeispielen (KAESER, Shell Telematics und Celonis). Der Beitrag schließt mit einer Diskussion von vielversprechenden, thematischen Ansatzpunkten für zukünftige Forschungsarbeiten zu DGGM.
Mapping the fake news infodemic amidst the COVID-19 pandemic: A study of Indian fact-checking websites
Authors: Laskar Kaifia Ancer , Reyaz Mohammad
Published: April 2021

Fake news, a term that was never heard a decade back, has established a subculture of misinformation and disinformation, whether intentionally or unintentionally, on social media by its users. The personal bias as well as unverified content sharing through the click of a button has not only led to the epidemic of fake content across the world, but in countries like India, it has also led to lynching and violence in various places. This article tries to find the rate of debunked or fact-checked content during the COVID-19 pandemic in India related to the enforcement of the nationwide lockdown, false claims of cure or immunity boost, political blame gaming, the impact of the pandemic on economy, religious polarization, as well as fake news on related issues concerning other countries apart from India. We try to discern in this article whether fact-checked items of disinformation were more on communal issues than the cure/claims of alternative medicines. We also try to unearth if there were a larger number of international items covered by the fact-checking sites given the status of the COVID-19 crisis in other countries than the lockdown (issues related to nationwide lockdown declared in India). Using content analysis of two fake news debunking websites Boom Live and Alt News, for six months (March–August 2020) during the COVID-19 pandemic, we argue that there were a lesser number of disinformation or fake news on treatment-related fake news compared to those on polarizing issues. We also posit that there were more fake news on the nationwide lockdown imposed in India than on its impact on the economy. In a bid to map the fake news and disinformation debunked by these two select websites, we find that the genealogy of fake news works with our personal biases and fears, thereby making media literacy all the more indispensable given the reach of internet-based news. The urgent need for stringent regulations by an autonomous body of the government to curb the fake news ecosystem is recommended by us along with emphasizing digital media literacy.