bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE Ins(1,4,5)P3-Sensitive Ca2+ Store of Non-Muscle Cells: Endoplasmic Reticulum or Calciosomes?
Authors: Pozzan Tullio , Volpe Pompeo , Zorzato Francesco , Bravin Mariangela , Krause Karl H. , Lew Daniel P. , Hashimoto Sadimatsu , Bruno Bernardino , Meldolesi Jacopo 
Published: April 2021

ABSTRACT
The binding of a number of extracellular ligands (hormones, growth factors, neurotransmitters etc.) to their plasma membrane receptors causes hydrolysis of phosphatidylinositol bisphosphate to initiate the formation of two second messengers, inositol 1,4,5-trisphosphate [Ins(l,4,5)P3] and diacylglycerol, DAG. DAG has been shown to activate protein kinase C, whereas Ins(l,4,5)P3 induces the release of Ca2+ from an intracellular pool. This rapidly mobilizable, Ins(l,4,5)P3-sensitive Ca2+ store has until now been identified as the endoplasmic reticulum, ER. We demonstrate that this is untenable and provide evidence for the existence of an unrecognized organelle, the ‘calciosome’. This conclusion is based on the following experimental evidence. (1) There is no correlation between the abundance of ER and the amount Ins(l,4,5)P3-sensitive Ca2+ release. (2) There is no correlation between ER markers and those for the Ca2+ store [Ins(l,4,5)P3 binding and sensitivity, Ca2+ uptake]. (3) A protein similar to striated muscle calsequestrin, CS, has been identified in microsomal fractions from a number of tissues; it copurifies with markers of the Ca2+ store, but not with those of ER. (4) Subcellular localization of the CS-like protein by electron microscopy reveals that in all cells so far analysed this protein is localized in small, membrane-enclosed structures, calciosomes, which are also stained by an anti-Ca2+-ATPase antibody. Calciosomes appear to be morphologically distinct from any other known cell organelle. (5) Although they stain different portions of the calciosomes (membrane and lumen, respectively), anti-Ca2+-ATPase and anti-CS antibodies do not recognize any antigen in ER cysternae; antibodies directed against known components of ER do not bind to calciosomes.
The Photic Control of Pigmentary Responses in Teleost Fishes
Authors: Wykes Ursula 
Published: April 2021

ABSTRACT
Many shallow-water teleosts, e.g. Gobius paganellus and G. ruthensparri, Ctenolabrus rupestris, Lepadogaster gouani and Phoxinus phoxinus, when blinded, show a pigmentary response to photostimulation. This response was analysed quantitatively in Lepadogaster gouani. The melanophores of the blinded animal contract in darkness and expand when illuminated by a 100-watt lamp. In the normal animal on a light background the latter response is checked by a secondary contraction. The dermal response of these fishes is closely comparable to that of the chameleon and it is possible that it may be similarly controlled. No dermal response was observed in adult Pleuronectes platessa.
The Oxygen Uptake of Suspensions and Cultures of A Free-Living Bacterium
Authors: Meiklejohn Jane 
Published: April 2021

ABSTRACTThe oxygen uptake of pure cultures and suspensions of a free-living bacterial species has been measured at 26° C. At this temperature, liquid cultures reach the maximum stationary phase of growth about 96 hours after inoculation. The greatest total oxygen uptake was observed in samples taken from cultures 72 hours after inoculation, and the greatest uptake per cell at 48 hours after inoculation. The oxygen uptake in cultures which have reached the stationary state falls off rapidly, at each successive sampling, to a very low value. In suspensions deprived of nitrogen, and showing no growth, and in cultures in the stationary phase, oxygen uptake proceeds at a constant rate. In both suspensions and cultures, where active growth is taking place, the rate of oxygen uptake rises continuously; after a preliminary period of adjustment this rise is logarithmic. The rise in oxygen uptake in a growing suspension is proportionately greater than the rise in bacterial numbers. It is suggested that the oxygen uptake of a growing culture can be divided into two parts; “maintenance” respiration and “growth” respiration, and a technique is outlined for estimating the amount of oxygen uptake due to each factor.
Storage of Oxygen in the Bladders of the Seaweed Ascophyllum Nodosum and Their Adaptation to Hydrostatic Pressure
Authors: Damant G. C. C. 
Published: April 2021

ABSTRACT
Ascophyllum nodosum secretes oxygen into its bladders so freely that the total gas pressure within them is usually above atmospheric pressure. The plant draws on this store of oxygen during the night and when shaded; the advantage of storing the gas under pressure is that withdrawals do not diminish the volume or buoyancy of the bladder whose efficiency as a float is of importance to the plant when competing for sunlight. As the bladder walls are somewhat permeable, the contained gas tends to diffuse out into the sea. Disastrous loss of gas may take place if, during an abnormally high tide, hydrostatic pressure overcoming the resistance of the bladder causes it to collapse with formation of a “dimple”. In this event the gas inside takes up the pressure of the water outside and diffuses away more rapidly than before the collapse took place. The bladders lose buoyancy and can no longer support the plant properly ; as a result it is starved of sunlight, fails to replace the lost gas and becomes permanently crippled. Plants growing in situations where they are exposed to severe hydrostatic pressure show an adaptive thickening of the bladder walls which enables them to resist deformation and the sequence of events detailed in (2). This adaptation is so closely fitted to the environment that in a zone of A. nodosum fifteen feet wide the plants of the upper level are unable to withstand the hydrostatic pressure obtaining at the lower and, if transplanted there, lose all their gas and perish.
The Movements of the Proboscis inGlycera DibranchiataEhlers
Authors: Wells G. P. 
Published: April 2021

ABSTRACTIn an earlier paper (Wells, 1937), the writer studied experimentally the movements of the proboscis in Arenicola marina, a worm which lives in a burrow and feeds by taking in the surrounding mud, and in which the brain and sense organs are very much reduced. It was shown that the intact worm, observed in a glass tube, generally exhibits periodic outbursts, either of rhythmic extrusion and withdrawal of the proboscis or, in less vigorous worms, of movements of similar type which do not result in actual extrusion, the activity outbursts alternating in either case with periods of rest. This probably means that the worms, under natural conditions, have a “feeding rhythm”, ingesting mud for a few minutes, then resting, and so on. Moreover, by considering a series of dissected preparations, it was shown that the pacemaker determining this rhythm was situated in the oesophageal wall. Periodic outbursts of excitation originate in the oesophagus and are transmitted forwards along the wall of the proboscis to the central nervous system, calling forth correlated movements of the musculatures of the proboscis itself and of the body wall.
Quantitative Studies on the CiliateGlaucoma
Authors: Harding J. P. 
Published: April 2021

ABSTRACTAlthough it is a matter of common observation that ciliates and other Protozoa when starved become smaller in size, and often more slender in shape, very little quantitative work has been done on these changes. It is the purpose of this paper to deal in a quantitative way with the effects of the starvation of Glaucoma; in particular with the changes that result in size and shape. It is hoped that this study may throw some light on the mechanism by which the shape of ciliates is controlled.
The Triple Innervation of Crayfish Muscle and Its Function in Contraction and Inhibition
Authors: Van Harreveld A. , Wiersma C. A. G. 
Published: April 2021

ABSTRACTThe innervation of the muscles of the cheliped of Cambarus clarkü has been investigated both anatomically and physiologically. It is found that at least three of the six principal muscles of the cheliped show a triple innervation. Each of these muscles in the unregenerated claw is innervated by three axons only. Such “completely” innervated muscles are the extensor and flexor of the carpopodite and the flexor of the propodite. The extensor of the propodite and the abductor of the dactylopodite have only a double innervation. Both these muscles together are innervated by three axons; one fibre gives branches to each of the muscles, a second to the abductor only, and a third to the extensor. An extension of the last fibre can, in a number of cases, be seen to join two fibres for the adductor of the dactylopodite, making the innervation of this muscle complete. In other preparations the third fibre for the adductor is very thin.It is shown for the flexor of the carpopodite that each of the three fibres of this “completely” innervated muscle has a different function. Stimulation of the thickest fibre gives a fast contraction, stimulation of the second in size a slow contraction and stimulation of the third fibre, the smallest, causes inhibition. Both the fast and the slow contraction can be inhibited, but the slow contraction is more sensitive in this respect (see Fig. 4). It is shown that the axon which the abductor and the extensor of the propodite have in common is of the excitatory type. This makes these muscles two parts of one motor unit, each part having its own inhibitory fibre.
Quantitative Studies on the CiliateGlaucoma. Excretion of Ammonia
Authors: Doyle W. L. , Harding J. P. 
Published: April 2021

ABSTRACTIt was at one time generally thought that excretion in the Protozoa was a function of the contractile vacuole. This idea has now been largely discarded (except in relation to the excretion of water) and the authors considered it of interest to correlate the rate and amount of nitrogenous excretion with the activities of other cytoplasmic constituents.
Kinetics of Calcium Fluxes Across The Intestinal Mucosa of the Marine Teleost, Gadus Morhua, Measured Using an in vitro Perfusion Method
Authors: Sundell Kristina , Björnsson Björn thrandur 
Published: April 2021

ABSTRACT
An in vitro technique for perfusion of the intestinal vasculature and lumen was developed and used to measure calcium (Ca2+) fluxes across the intestinal mucosa of the marine teleost, the Atlantic cod (Gadus morhua). Saturable and nonsaturable components of the calcium influx and efflux were determined.
The calcium influx had one passive component and one saturable component, following Michaelis-Menten kinetics with Km = 8·41 mmol l−1 and Vmax = 0·604μmol Ca2+ kg−1 h−1. At physiological Ca2+ concentrations in the vascular ([Ca2+] = 1·9mmoll−1) and luminal ([Ca2+] = 14·9mmoll−1) perfusion fluids, the saturable component amounted to 60% of the Ca2+ influx. The high-affinity Ca2+-ATPase inhibitor chlorpromazine (CP, 10−4moll−1) antagonized 45% of the Ca2+ influx.
The Ca2+ efflux across the intestinal mucosa of the cod was a saturable process, following Michaelis-Menten kinetics with Km = 6·15 mmol l−1 and Vmax = 3·79μnolCa2+ kg−1 h−1, but insensitive to CP (10−5 moll−1). The Ca2+ efflux was l·22μmolCa2+kg−1 h−1, representing about 20% of the total calcium excretion and about 50% of the extrarenal excretion of the Atlantic cod in vivo.
Kangaroo Rat Locomotion: Design for Elastic Energy Storage or Acceleration ?
Authors: Biewener Andrew A. , Blickhan Reinhard 
Published: April 2021

ABSTRACT
Mechanical stresses (force/cross-sectional area) acting in muscles, tendons and bones of the hindlimbs of kangaroo rats (Dipodomys spectabilis) were calculated during steady-speed hops and vertical jumps. Stresses were determined from both high-speed ciné films (light and X-ray) and force plate recordings, as well as from in vivo tendon force recordings. Stresses in each hindlimb support element during hopping (1·6-3·1 m s−1) were generally only 33% of those acting during jumping (3=40cm height): ankle extensor muscles, 80 ±12 (S.D.) versus 297 ±42kPa; ankle extensor tendons, 7·9 ±1·5 versus 32·7 ±4·8 MPa; tibia, −29 ±5 versus – 110 ±25MPa (all values are for hopping versus jumping). The magnitude of stress in each structure during these locomotor activities was similarly matched to the strength of each element, so that a consistent safety factor to failure is achieved for the hindlimb as a whole (1·5–2·0). The large stresses during jumping were correlated with a three-fold increase in ground reaction forces exerted on the ground compared with the fastest steady hopping speeds. We conclude that, for its size, the kangaroo rat has disproportionately large hindlimb muscles, tendons and bones to withstand the large forces associated with rapid acceleration to avoid predation, which limits their ability to store and recover elastic strain energy. Middle ear morphology and behavioural observations of kangaroo rats jumping vertically to avoid predation by owls and rattlesnakes support this view.
Classical Conditioning Alters the Efficacy of Identified Gill Motor Neurones in Producing Gill Withdrawal Movements in Aplysia
Authors: Lukowiak Ken , Colebrook Elaine 
Published: April 2021

ABSTRACT
In a semi-intact preparation of Aplysia californica Cooper, classical conditioning training leads to changes in the synaptic strength at the sensory-motor neurone synapse. However, these changes are neither necessary nor sufficient to bring about the observed behavioural changes of the gill withdrawal reflex. We therefore tested whether the ability of a gill motor neurone to elicit a gill withdrawal response was altered following classical conditioning training of the reflex. We found that following classical conditioning training, the ability of a gill motor neurone to elicit a gill withdrawal response was significantly potentiated. In addition, in control preparations which did not receive classical conditioning training, the ability of a gill motor neurone to elicit a gill response was decreased. Thus, associative learning of this reflex appears to involve alteration in neuronal activity at loci distal to the sensory-motor neurone synapse.
Ultrastructure, Morphology and Organization of Biogenic Magnetite from Sockeye Salmon, Oncorhynchus Nerka: Implications for Magnetoreception
Authors: Mann Stephen , Sparks Nicholas H. C. , Walker Michael M. , Kirschvink Joseph L. 
Published: April 2021

ABSTRACT
Although ferromagnetic material has been detected in the tissues of a variety of animals that are known or suspected to respond to magnetic fields, in only a few cases has the material been identified and its suitability for use in magnetoreception been determined. Using high-resolution transmission electron microscopy (HRTEM), we have studied magnetic particles isolated from ethmoid tissue of the sockeye salmon, Oncorhynchus nerka. Low-magnification electron micrographs showed chains containing up to 58 (median = 21-25) electron-dense particles that were held together by intimately attached organic material. The particle size range was 25-60 nm with a mean of 48 nm and a standard deviation of 8-5 nm. Elemental analysis, by energy-dispersive X-ray analysis (EDXA), electron diffraction patterns and HRTEM lattice images, showed that many of the particles were structurally well-ordered and crystallographically single-domain magnetite. These results imply that the production of the biomineral is under precise biological control. The crystal morphology was cubo-octahedral with the {111} faces of adjacent crystals lying perpendicular to the chain axis. The magnetic moments of the particles will therefore be aligned along the chain axis and will sum to produce a total moment dependent on the number of particles present in each chain. In the presence of the geomagnetic field, the mean moment for the particles will give a magnetic to thermal energy ratio of about 0·2. The corresponding calculations for individual chains gave two clusters of ratios ranging between 2·7 and 5·3 and between 6·6 and 9·5. The implications of these results in the possible use of the particles in magnetoreception are discussed.
Central Synaptic Coupling of Walking Leg Motor Neurones in the Crayfish: Implications for Sensorimotor Integration
Authors: Skorupski Peter , Sillar Keith T. 
Published: April 2021

ABSTRACT
We present electrophysiological evidence for the presence of central output synapses on crayfish walking leg motor neurones. The effect of these central outputs is that a motor neurone can exert tonic graded control over other motor neurones without the requirement for spiking. Excitatory interactions among synergists and inhibitory interactions among antagonists are described. This central coupling among leg motor neurones profoundly affects their responses to afferent input from an identified stretch receptor, the thoracocoxal muscle receptor organ (TCMRO). Injecting current into a motor neurone can change the gain of TCMRO reflexes in other motor neurones. Some motor neurones are also capable of reversing the sign of TCMRO reflexes by inhibiting reflex firing of antagonists and facilitating reflex activity in synergists. The implications of these central interactions of motor neurones in motor control are discussed.
Temperature Effects on Haemolymph Acid-Base Status in vivo and in vitro in the Two-Striped Grasshopper Melanoplus Bivittatus
Authors: Harrison Jon M. 
Published: April 2021

ABSTRACT
In this study, I examine the effect of temperature on haemolymph acid-base status in vivo and in vitro in the two-striped grasshopper Melanoplus bivittatus. Melanoplus bivittatus experience wide (up to 40 °C) diurnal body temperature fluctuations in the field, but maintain body temperature relatively constant during sunny days by behavioural thermoregulation. Haemolymph pH was statistically constant (7·12) between 10 and 25°C, but decreased by –0·017 units °C− 1 from 25 to 40 °C. Relative alkalinity and fractional protein dissociation were conserved only at body temperatures at which feeding and locomotory activity occur, above 20°C. Haemolymph total CO2 (Ctot) increased from 10 to 20°C and decreased from 20 to 40°C. Haemolymph increased from 10 to 20°C and was statistically constant between 20 and 40°C. Carbonic acid pKapp in haemolymph was 6·122 at 35 °C, and decreased with temperature by –0·0081 units °C− 1. Haemolymph buffer value averaged – 35mequivl− 1pHunit− 1. Haemolymph pH changes with temperature were small (less than –0·004 units °C− 1) in vitro at constant . Therefore, passive physicochemical effects cannot account for the pattern of acid-base regulation in vivo. The temperature shift from 10 to 20°C was accompanied by a net addition of 4·2–0·2 mmol I− 1 of bicarbonate equivalents to the haemolymph. The temperature shift from 20 to 40°C was accompanied by a net removal of 10–14 mmol I− 1 of bicarbonate equivalents from the haemolymph. Haemolymph acid-base regulation in vivo during temperature changes is dominated by active variation of bicarbonate equivalents rather than by changes in as observed for most other air-breathers.
The Actions of L-Glutamate at the Postsynaptic Membrane of the Squid Giant Synapse
Authors: Adams D. J. , Gillespie J. I. 
Published: April 2021

ABSTRACT
The actions of L-glutamate on the postsynaptic membrane of the squid giant synapse were investigated using two methods of application: ionophoresis and bath perfusion. Bath perfusion of 10 mmol l−1 sodium glutamate did not produce an appreciable depolarization of the postsynaptic membrane but reversibly blocked the neurally evoked postsynaptic potential (PSP). The postsynaptic membrane depolarized when L-glutamate was applied ionophoretically. The sensitivity to glutamate application was not uniform, but sharply localized to sites which may correspond to synaptic contacts made by branching colaterals from the postsynaptic axon. The relationship between membrane potential and amplitude of the glutamate-activated postsynaptic potential (PSP) examined under currentclamp conditions was linear over the voltage range studied (–110 to –60 mV) with an extrapolated reversal potential of –36mV. The amplitude of the glutamate-activated PSP was reduced either by replacing Na+ in the external solution with Tris+ (Na+-free) or by raising the extracellular K+ concentration to 20 mmol l−1 and was abolished by removing both Na+ and Ca2+ from the bath solution. The PSP amplitude was insensitive to changes in the extracellular Mg2+ concentration. The extrapolated reversal potential of the glutamate PSP was shifted to more positive potentials in both Na+-free and raised-K+ bathing solutions and was unchanged by anion substitution.
The depolarization induced by L-glutamate increased with increasing ionophoretic current and reached a maximum with large pulses. Double logarithmic plots of the coulomb dose-response relationship gave a limiting slope in the range 1·7–2·2, suggesting that two glutamate molecules are required for receptor activation. The time course of desensitization of the glutamate response was studied using a double-pulse method. The initial decrease in the ratio, PSP2/PSP1, is followed by a slower time-dependent recovery of the postsynaptic response with a time constant of 8·5 s. Prolonged perfusion of the squid giant synapse with concanavalin A failed to abolish desensitization of the glutamate-evoked PSP.
The Concentration Dependence of the Stimulatory Effects of Catecholamines on the Rate and Force of Contraction of the Heart of Dogfish (Scyliorhinus Canicula)
Authors: Van Vliet B. N. , Metcalfe J. D. , Butler P. J. , West N. H. 
Published: April 2021

ABSTRACT
An adrenergic control of the elasmobranch heart has been inferred from pharmacological studies. Catecholamines have been repeatedly demonstrated to stimulate the frequency and/or force of the dogfish heart (MacDonald, 1925; Lyon, 1926; Hiatt, 1942; Ostlund, 1954; Fange & Ostlund, 1954; Capra & Satchell, 1977), and such effects have been shown to be reduced by propranolol, a beta-adrenergic antagonist (Capra & Satchell, 1977). However, the mechanism and functional significance of an adrenergic control of the elasmobranch heart remain to be demonstrated.
Synaptic Transmission Between Second- and Third-Order Neurones of Cockroach Ocelli
Authors: Mizunami Makoto , Tateda Hideki 
Published: April 2021

ABSTRACT
The insect ocellus contains a large number of photoreceptors which converge on a small number of large second-order neurones, called L neurones. The L neurones exit from the ocellus and project into the ocellar tract of the brain, where they make synapses with third-order neurones (reviewed by Goodman, 1981). Response characteristics of L neurones have been well documented (Goodman, 1981; Mizunami et al. 1986), but less is known about ocellar third-order neurones. In locusts, three types of ocellar third-order neurones, which descend to the thoracic ganglia, have been found (Simmons, 1980,1981; Reichert et al. 1985), and the transmission characteristics between L neurones and some of these descending neurones have been documented (Simmons, 1981). In the present paper, we examine whether the transmission characteristics reported by Simmons (1981) are specific to descending ocellar third-order neurones or are generally applicable to a variety of ocellar third-order neurones, including those terminating within the brain. Experiments were made on cockroaches, Periplaneta americana.