bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ventilatory CO2 Drive in the Tortoise Testudo Horsfieldi
Authors: Benchetrit G. , Dejours P. 
Published: April 2021

ABSTRACT
Ventilation was recorded by pneumotachography, before and after bilateral vagotomy, in conscious tortoises (Testudo horsfieldi) (breathing o, 2, 3 or 4% CO2 in air or oxygen). Each breath consists of expiratory and inspiratory phases and an apneic plateau (absence of air flow). Inhalation of hypercapnic mixtures led to increased ventilatory flow, augmentation of tidal volume, and an increase in respiratory frequency through the shortening of the apneic plateau. Intact tortoises breathing hypercapnic-hyperoxic mixtures hyperventilated less than with hypercapnic-normoxic mixtures. In bivagotomized animals, the respiratory frequency decreased, the expiratory and inspiratory durations lengthened, and the apneic plateau was prolonged. The tidal volume was increased, but ventilation, nevertheless, decreased slightly. Bivagotomized animals breathing hypercapnic-normoxic or hypercapnic-hyperoxic mixtures hyperventilated, but less than intact animals under the same conditions. It is concluded that in tortoises there are : ( 1 ) peripheral chemoreceptors which are innervated by branches of the vagus nerves, and are sensitive to CO2; and (2) an extrathoracic, probably central, ventilatory CO2 drive.
Automatic Continuous Variation of Solute Concentration in a Perfusate
Authors: Buchan P. B. 
Published: April 2021

ABSTRACT
Many physiological experiments involve switching between two or more solutions. For example, when drugs are applied to tissues the concentration of the drug is usually changed as a step function, by switching from a control saline to a saline containing the drug. There are many instances where it would be advantageous to change the concentration according to some other function such as a ramp. This paper describes how this has been achieved by a mixing valve under electronic control.
Spectral Sensitivity and Retinal Pigment Movement in the Crab Leptograpsus Variegatus (Fabricius)
Authors: Stowe Sally 
Published: April 2021

ABSTRACT
The retina of Leptograpsus contains five types of movable screening pigment. The positions of these were found under various conditions of illumination in the day and at night. Intracellular recordings were made of the spectral responses of retinula cells R1–7 under the same conditions, with the eye in situ. The spectral absorptions of the individual screening pigments were measured by ultramicrospectrophotometry. Calculations based on a simple model of screening pigment action suggest that the observed variation in spectral sensitivity with light and dark adaptation may be largely explicable in terms of the effects of these screening pigments on a rhodopsin of peak absorbance at 485 nm. Light-adapted angular sensitivities are comparable to those of insects with high acuity apposition eyes.
The Hydraulic Mechanism of the Predatory Strike in Dragonfly Larvae
Authors: Tanaka Yoshitaka , Hisada Mituhiko 
Published: April 2021

ABSTRACT
Aeschna larvae catch prey with a fast-moving elongated labium. The mechanism of this movement was analysed by high-speed cinematographs and by hydrostatic and electrophysiological measurements. The strike movement consists of an initial, mid and late phase. The angular acceleration of the joints of the labium is 2·6 × 105 and 7·8 × 105 deg. s−2 during the initial and mid phase respectively. The torque necessary for the acceleration was calculated to be 1·3 × 10−5 and 4·0 × 10−5 N.m for the initial and mid-phases respectively. The relation between the pressure applied to the labium and the extension torque at the joints has been established. No torque develops about the postmentum-prementum joint as long as the click of the flexed labium is engaged. The power production of the extensor muscles is less than the power output of the mid phase. The power for the mid phase is derived from the internal body pressure developed by the contraction of the abdominal dorso-ventral muscles. The required pressure for the mid phase is about 60 cm H2O if the resistance is neglected and 80 cm H2O when the resistance is considered. Abdominal dorso-ventral muscles contract 110–500 ms before the onset of the strike and the body pressure of the animal increases to a peak of 40–120 cm H2O at the onset of the strike. The geometry of the labial joints gives the primary flexor muscles of the labium a large mechanical advantage over the extensor muscles in the fully flexed labium, and allows the extensor muscles to contract almost isometrically. The extensor muscles and the primary flexor muscles co-contract for 75–100 ms before the strike. The strike movement begins when the flexor muscles relax. The stored energy in the extensor system is released suddenly and disengages the click producing the initial phase. Once the click is disengaged the internal pressure produces the large torque to move the labium with great acceleration during the mid phase.
Flight Energetics and Heat Exchange of Gypsy Moths in Relation to Air Temperature
Authors: Casey Timothy M. 
Published: April 2021

ABSTRACT
Gypsy moths elevate thoracic temperature (Tth) during flight by endogenous heat production but do not regulate it. Thoracic temperature of moths in free, near-hovering flights exceeded air temperature by approximately 6–7 °C at all Ta’s between 17 and 32 °C. Mean rates of mass specific oxygen consumption varied between 40 and 47 ml O2 (g·h) −1 and were not correlated with air temperature. Wing-beat frequency increased from 27 to 33 (s) −1 between air temperatures of 18 and 35 °C. Thoracic heating and cooling constants are similar in live and dead moths, and removal of thoracic scales increases heating constants by about 12%. Preflight warm-up occurs at low Ta’s but the moths are capable of immediate, controlled flight at Ta’s above 22 °C. Relatively low levels of heat production by the flight muscles are a consequence of low power requirements associated with the flight morphology of gypsy moths. Calculated rates of thoracic and respiratory heat loss of free-flying moths are slightly lower than values of heat production.
Electrogenesis in the Euryhaline Osmoconformer Cordylophora Lacustris (Hydrozoa)
Authors: Chain Benjamin M. 
Published: April 2021

ABSTRACT
The electrical signals propagated through the ectodermal epithelium of Cordylophora lacustris (the Josephson pulses) were recorded as trans-epithelial action potential-like events. Experiments on the ionic basis of electrogenesis of these action potentials suggested that they result from an outward flow of chloride ions from the ectodermal cells into the enteron. Further evidence for this hypothesis came from measurements of the ionic concentrations in the tissues of Cordylophora, which showed that these cells have unusually high levels of chloride. Chloride dependent electrogenesis allows this excitable system to function in media of low and variable ionic strength, which are a typical feature of this organism ‘s natural environment.
Physiology of Pupal Ecdysis in the Tobacco Hornworm, Manduca Sexta
Authors: Truman James W. , Taghert Paul H. , Reynolds Stuart E. 
Published: April 2021

ABSTRACT
The time of pupal ecdysis in Manduca sexta can be accurately predicted by the appearance of external markers late in pupal development. Eclosion hormone injections resulted in premature ecdysis of staged pharate pupae. The latency between injection and initiation of ecdysis movements was inversely correlated with dosage and served as the basis for a sensitive, rapid, and quantitative bioassay for the hormone.
Behavioural responsiveness to the hormone arose about 8 h before normal ecdysis at 23 °C. When insects were injected at these early times the larval cuticle was not sufficiently digested to allow its rupture and these animals remained permanently trapped inside the larval cuticle.
Measurement of eclosion hormone in the blood of pharate pupae showed the appearance of biological activity in the blood about 30 min before the onset of ecdysis.
It is concluded that pupal ecdysis is under endocrine control and that the hormone involved is likely to be the eclosion hormone.
Physiology of Pupal Ecdysis in the Tobacco Hornworm, Manduca Sexta
Authors: Taghert Paul H. , Truman James W. , Reynolds Stuart E. 
Published: April 2021

ABSTRACT
Eclosion hormone activity was found in the brain and ventral ganglia of pharate pupae of Manduca sexta. No activity was detected in the corpora cardiaca-corpora allata complex. At the time of ecdysis the store of activity dropped by 50−75 % in the ventral cord whereas the hormone level in the brain remained unchanged. Also, larvae whose brains were removed at the wandering stage subsequently showed pupal ecdysis behaviour and also had essentially normal levels of hormonal activity in their blood at the start of the behaviour. It was concluded that at pupal ecdysis the hormone responsible for the initiation of the behaviour is released from the ventral nerve cord rather than from the brain.
The chemical characteristics of the pharate pupal eclosion hormone were determined. The factors from the brain and ventral nerve cord were both active in a number of adult and pupal eclosion hormone bioassays. Both showed an apparent molecular weight of 8500 daltons and an isoelectric point of about 5−0, values essentially the same as that seen for the adult form of the hormone. We concluded that pupal ecdysis and adult eclosion are triggered by the same hormone but for the former it is released from the ventral nerve cord and, for the latter, from the brain. The choice of release site may depend on whether or not the release is under circadian control.
The Detection of Waterborne Vibration by Sensory Hairs on the Chelae of the Crayfish
Authors: Tautz J. , Sandeman D. C. 
Published: April 2021

ABSTRACT
Sensory hairs on the chelae of the Australian freshwater crayfish Cherax destructor are grouped together into pits. Electrophysiological recordings from the sensory axons of isolated chelipeds show that the hairs are maximally sensitive to water vibration frequencies between 150−300 Hz. The amplitude threshold is about 0·2 µm water molecule oscillation.
The Suction Feeding Mechanism in Sunfishes (Lepomis): An Experimental Analysis
Authors: Lauder George V. 
Published: April 2021

ABSTRACT
The process of prey capture by inertial suction was studied in three species of sunfishes (Lepomis auritus, L. macrochirus, and L. gibbosus) by the simultaneous recording of buccal and opercular cavity pressures in order to test current hydrodynamic models of feeding in fishes. Synchronous high-speed films permitted the correlation of kinematic patterns of jaw bone movement with specific pressure waveforms. Opercular cavity pressures averaged one-fifth buccal pressures and pressure magnitude was correlated with prey type. Peak buccal and opercular pressures were — 650 cm H2O and — 150 cm H2O respectively; peak rate of pressure change was — 100 cm H2O/ms. Buccal pressure magnitude varied inversely with degree of predator satiation.
Opercular pressure waveforms have an initial positive phase followed by a prolonged negative phase and then a final positive phase. The initial positive pressure may be absent during slow strikes at worms. Buccal pressure waveforms show considerable variability. The modal waveform consists of a sharp negative pressure pulse followed by a positive phase and finally by another pressure reduction. Delayed opercular abduction relative to mouth cavity compression correlates with the presence of a positive buccal phase. The second buccal negative pressure is the result of rapid mouth closing causing a pressure reduction (water hammer effect) as water flow continues posteriorly. These data indicate that (1) the buccal and opercular cavities are functionally separated by a gill curtain of high resistance, (2) that inertial effects of water are important in the description of the suction feeding process, (3) that a reverse flow of water (opercular to buccal cavity) may occur during the early phase of mouth opening prior to establishment of a buccal to opercular flow regime, and (4) current models of respiratory pressure and flow pattern cannot be applied to feeding. Current hydrodynamic models of suction feeding in fishes are re-evaluated in the light of this analysis.
Protein Phosphorylation and The Regulation of Cation Cotransport
Authors: Palfrey H. Clive , Alper Seth L. , Greengard Paul 
Published: April 2021

ABSTRACT
The turkey erythrocyte is a useful system in which to investigate the relationship between protein phosphorylation and membrane transport. This cell possesses a catecholamine-and cyclic AMP-stimulated Na+-K+ ‘cotransport’ system in its plasma membrane, and the physiological properties of this system have been partially elucidated. It is distinct from the Na+-K+ ‘pump’ and is insensitive to ouabain, but can be blocked by certain diuretic agents such as furosemide and bumetanide.
A plasma membrane protein of MW 230000, called goblin, has been identified as the major protein whose state of phosphorylation increases upon incubation of turkey erythrocytes with catecholamines or cyclic AMP. The kinetics of phosphorylation of goblin at its cyclic AMP-sensitive sites correlate well with the kinetics of Na+-K+ cotransport activation under various conditions. This protein may play a role in the regulation of the Na+-K+ cotransport system by catecholamines and cyclic AMP
Use of Aldehyde Fixatives to Determine the Rate of Synaptic Transmitter Release
Authors: Smith J. E. , Reese T. S. 
Published: April 2021

ABSTRACT
Aldehyde fixation continues to be useful to prepare synapses for freeze fracture, but it may increase the rate of transmitter release. The effects of different aldehyde fixatives on spontaneous quantal release (m.e.p.p.s), and on the corresponding synaptic vesicle exocytosis at frog nerve-muscle synapses were investigated with the hope of finding a way to minimize side effects of fixation. Increases in m.e.p.p.s of up to 50 s−1 occurred during fixation, despite the species of aldehyde used in the fixative, and this fixative effect decreased only slightly as aldehyde concentration was increased. Increases in m.e.p.p. frequency were not blocked by tetrodotoxin, by lowering external calcium and raising external magnesium concentration, or by lowering the total osmotic strength of the fixative. The smallest increase in m.e.p.p. frequency was in 3% glutaraldehyde and corresponded to the lowest levèl of synaptic vesicle exocytosis seen by freeze-fracture, 0·15 per μm of active zone. The effects of aldehyde fixation on m.e.p.p. frequency and synaptic vesicle exocytosis could not be avoided, but this study suggests how its effect on morphological changes in synapses might be minimized.
Substance P and Neurotensin: Discovery, Isolation, Chemical Characterization and Physiological Studies
Authors: Leeman Susan E. 
Published: April 2021

ABSTRACT
During the course of work directed towards the purification of a corticotropin-releasing factor, two other biological active substances were discovered in bovine hypothalamic extracts : one a sialogogic peptide, the other a vaso-active substance easily separated from the sialogogic agent by ion-exchange chromotography. The sialogogic peptide was subsequently characterized as substance P (SP); the other substance, also a peptide, was named neurotensin (NT). These peptides were isolated, their amino acid sequences determined (substance P; arg-pro-lys-pro-gln-gln-phe-phe-gly-leu-met-NH2; neurotensin: &lt; glu-leu-tyr-glu-asn-lys-pro-arg-arg-pro-tyr-ile-leu-OH), synthetic material prepared, and radioimmunoassays developed. Subsequent studies from many laboratories have yielded much information relevant to the physiological roles of these peptides. In addition to its uneven distribution throughout the CNS, SP is also present in the peripheral nervous system. Data is presented on its distribution in sympathetic ganglia and its depletion by pretreatment with capsaicin. Release of immunoreactive substance P (I-SP) has been demonstrated in vivo from mammalian spinal cord after activation of nociceptive afferents. Neurotensin is also unevenly distributed throughout the CNS and is present in the GI tract. Neurotensin containing cells have been demonstrated scattered throughout the small intestinal epithelium of every mammalian and avian species. The concentration of immunoreactive NT has been measured to increase in hepatic portal vein plasma after infusing a micellar solution of lipid through the small intestine of rats. Neurotensin has been demonstrated to be present in a cell line derived from a rat medullary thyroid carcinoma permitting studies on the regulation of neurotensin release from these cells in culture.
A Note on the Blood of the Hag-Fish Polistotrema Stouti (Lockington)
Authors: Bond Richard M. , Cary M. Katharine , Hutchinson G. E. 
Published: April 2021

ABSTRACT
The blood of Polistotrema stouti (Lockington) has been shown by Greene (1904) to be approximately isotonic with the sea-water in which the animal lives, thus resembling the elasmobranchs and marine invertebrates and differing from the teleosts and in all probability the marine lampreys (Fontaine, 1930). It does not appear to be known whether this isotonic condition is primarily due to inorganic constituents as in invertebrates or to some organic substance comparable to the urea of elasmobranch blood. Since one of us (R. M. B.) has recently had access to a supply of Polistotrema, it seemed desirable to investigate the matter.
The Influence of Temperature on the Rate of Growth of Saprophytic Actinomyces
Authors: Haines R. B. 
Published: April 2021

ABSTRACT
Actinomyces occur commonly in commercial cold stores. They can be isolated from the walls but are obtained in greatest number from straw on the floor of the store. Measurements of the rate of growth of actinomyces from cold stores show that the majority of the strains studied have their optimum temperature at 37° C. They are capable of growth from 40° to 5° C., growth becoming infinitely slow at just above 0° C. One strain, however, had its optimum temperature for growth less sharply defined at 20°-30° C. and grew well, though slowly, at o°C. The curve obtained by plotting the “velocity constant of growth” against temperature suggests that growth becomes infinitely slow at about—5° C. Application of the Arrhenius equation to the results obtained is discussed. Comparison with certain strains isolated from soil, having their optimum temperature at 37° C., gave results analogous to those obtained with strains from cold stores, also having their optimum at 37° C. The significance of actinomyces in imparting “musty” flavours to stored foodstuffs is indicated.
The Effect of Fertilisation on the Permeability to Water and on Certain Other Properties of the Surface of the Egg of Psammechinus Miliaris
Authors: Hobson A. D. 
Published: April 2021

ABSTRACT
Among the numerous changes in the sea-urchin egg which have been shown by various workers to occur at the time of and subsequent to fertilisation none have attracted more attention than that of increased permeability. R. S. Lillie (1916) showed that fertilisation or artificial activation by means of butyric acid causes the eggs of Arbacia to swell more rapidly when placed in hypotonic sea water. He concluded from his experiments that the surface of the sea-urchin egg becomes more permeable to water as the result of activation.
The Adrenal Secretion of Xenopus Laevis (The South African Clawed Toad)
Authors: Epstein D. , Gunn J. W. C. , Epstein E. , Rimer G. 
Published: April 2021

ABSTRACT
The presence of adrenal bodies in Xenopus laevis has long been a controversial point. Although these bodies are present as well-defined, yellowish masses in the kidneys of most Amphibia, morphologists have usually stated that none can be demonstrated in the kidneys of Xenopus (5). To account for this absence, other workers have sought for accessory adrenal glands, but their search has proved fruitless up to the present.
The Effect of Temperature on the Growth and Respiration of Fish Embryos (Salmo Fario)
Authors: Wood A. H. 
Published: April 2021

ABSTRACT
In a series of recent papers Gray (1926–8) has shown that the growth-rate of the embryo of Salmo fario is proportional to its size and to the quantity of yolk present in the yolk sac. The yolk is used for two simultaneous processes—it is being converted into embryonic tissue and it is providing the material which is used up by the embryo in respiration ; there is, according to Gray, no measurable amount of yolk used for any other purpose. Under these circumstances the dry weight of the embryo at the conclusion of development must be equal to the dry weight of yolk in the newly fertilised egg, less the amount which is required for maintaining the respiration of the embryo. By incubating eggs at 16°, 10° and 5° C., Gray concluded that the higher the temperature of incubation the smaller was the final size of the embryo and the greater was the percentage of the original yolk consumed by the respiration of the embryo during development. This conclusion is in harmony with the observations of Graham-Smith (1920) who showed that the lower the temperature of incubation the greater is the maximum population of bacteria which can be obtained from a given volume of culture medium. The work of Bathélemy and Bonnet (1926) with the eggs of the frog are, however, at variance with these conclusions—at least to some extent. In one experiment performed by these authors the results conform to those obtained by Gray with the eggs of the trout, but in another experiment the temperature of incubation appeared to have no effect on the final size of the embryo.
The Osmotic Properties of the Eggs of the Trout (Salmo Fario)
Authors: Gray J. 
Published: April 2021

ABSTRACT
The normal healthy eggs of the trout are impermeable both to water and to intracellular electrolytes. The barrier to diffusion of both water and salts lies in the vitelline membrane, whose static properties maintain the normal hypertonicity of the yolk without expenditure of energy. When eggs are exposed to conditions which destroy the normal impermeability of the vitelline membrane, exosmosis occurs suddenly at the end of a latent period, and once it has begun exosmosis is usually rapidly completed. Exosmosis is a sign of an unhealthy cell. The osmotic stability of the vitelline membrane varies with four factors: (a) the age of the eggs, (b) the degree of mechanical disturbance caused by the environment, (c) the presence or absence of calciuip in the environment, (d) the nature and concentration of the exosmotic reagent used. Loss of the impermeable properties of the vitelline membrane is accompanied by a drastic change in the distribution of the material of the membrane and in the organisation of the egg cell.
The Reactions of Normal and Mutant Types of Gammarus Chevreuxi to Light
Authors: Wolsky A. , Huxley J. S. 
Published: April 2021

ABSTRACT
A method is described for obtaining statistical results on the phototaxis of G. chevreuxi. A long tube is illuminated from one end and the numbers of animals in two arbitrarily delimited end-sections counted at regular intervals. Wild-type specimens in normal conditions show a moderate degree of negative phototaxis. Animals with one eye varnished show circus movements; hence the phototaxis is true tropotaxis (Frankel, 1931). The sense of reaction can be reversed and the animals made to show a moderate positive phototaxis by the addition of acetic acid. Caffein has no effect. Red-eyed mutants, which lack most of the melanin eye pigment, behave similarly to the wild type, though there are indications that they are often rather more sensitive to light, as shown by stronger negative phototaxis in normal conditions, weaker positive phototaxis after addition of acid. The variability of the results, however, is too great to permit of definitive conclusions being drawn. Albino and colourless mutants, which possess neither retinulae nor optic nerves, show no phototaxis.