bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Pharmacology of Cholinoceptors on the Somatic Muscle Cells of the Parasitic Nematode Ascaris Suum
Authors: Colquhoun L. , Holden-Dye L. , Walker R. J. 
Published: April 2021

ABSTRACT
Acetylcholine (ACh) elicited depolarization and an increase in input conductance of the somatic muscle cells of the parasitic nematode Ascaris suum. The relative potency of nicotinic and muscarinic agents was studied in this preparation. The order of potency of these compounds was metahydroxy phenylpropyltrimethylammonium (HPPT) &gt; 1,1 dimethyl–4-phenylpiperazinium (DMPP) &gt; ACh&gt; carbachol&gt; nicotine&gt; tetramethylammonium (TMA+)&gt; muscarone&gt; furtrethonium&gt; arecoline. Decamethonium was also a weak agonist. McN-A-343 elicited a very weak depolarization at concentrations above 1 mmol 1−1. Bethanechol and methacholine were without effect up to 1 mmol 1−1. Pilocarpine and muscarine elicited a slight hyperpolarization of up to 3 mV with a threshold for the response of around 500 μmol 1−1. Oxotremorine (1 mmol 1−1) was without effect. The nitromethylene insecticide 2(nitromethylene)tetrahydro 1,3-thiazine (NMTHT), an agonist at insect nicotinic receptors, was without effect on Ascaris muscle cells up to 1 mmol 1−1. Mecamylamine and benzoquinonium were the most potent antagonists of the acetylcholine response. The order of potency of the other antagonists was tetraphenylphosphonium (TPP) &gt; quinacrine &gt; pancuronium, curare &gt; trimethaphan &gt; atropine &gt; chlorisondamine, Decamethonium &gt; hexaméthonium &gt; dihydro-β-ery throidine. The agonist profile of the Ascaris muscle cell ACh receptor clearly indicates that it is nicotinic. The potency of ganglionic and neuromuscular nicotinic receptor antagonists in Ascaris does not enable a further subclassification of this nicotinic receptor. The Ascaris nicotinic receptor seems to possess some of the pharmacological properties of each type of vertebrate nicotinic receptor. The pharmacology of the Ascaris nicotinic receptor is discussed in relation to that of nicotinic receptors in other invertebrate preparations and in vertebrate preparations.
The Physiology of the Alligator Heart: the Cardiac Cycle
Authors: Shelton G. , Jones D. R. 
Published: April 2021

ABSTRACT
Pressure recordings from the heart and major arteries of the alligator show that a conventional relationship exists between the left ventricle and the right aorta. Pressure gradients from ventricle to aorta during systole are very small. Right aortic blood flow rises rapidly to a single peak and then falls more gradually until aortic valve closure.
The right ventricle is connected both to the pulmonary arteries and to the left aorta. Right ventricular pressures show that systole is a two-stage process. Initially, blood leaves to the low-resistance lung circuit, though appreciable pressure gradients exist across the pulmonary outflow tract. Active contraction of the pulmonary outflow tract stops pulmonary ejection and a second-stage pressure rise is seen in the right ventricle.
When systemic blood pressures are high, this second-stage pressure does not reach the levels recorded in the left aorta, and the left aortic valves remain closed so that lung and body circuits are functionally separate. An alternation of flow is found in the left aorta under these conditions, with reversed flow during systole and forward flow during diastole. Flow rates are extremely low, compared with those in the right aorta or pulmonary arteries, and the foramen of Panizza has very little significance in the cardiac cycle.
If the systemic blood pressures are low, the second stage of systole in the right ventricle gives rise to pressures that are higher than those in the left aorta, the left aortic valves open and blood is ejected to the systemic circulation, giving a right-to-left shunt. This can occur with no changes in pulmonary pressures or flows. Left aortic flow is not dependent on increased constriction of the pulmonary outflow tract, which continues to function as an on-off active valve. Constriction within the lung vasculature may, on some occasions, be significant in establishing left aortic flow, but it is clear from the present work that low systemic blood pressure is a factor of crucial importance.
Kinematics of Tongue Projection in Chamaeleo Oustaleti
Authors: WAINWRIGHT PETER C. , KRAKLAU DAVID M. , BENNETT ALBERT F. 
Published: April 2021

The kinematics of prey capture by the chamaeleonid lizard Chamaeleo oustaleti were studied using high-speed cinematography. Three feeding sequences from each of two individuals were analyzed for strike distances of 20 and 35 cm, at 30°C. Ten distances and angles were measured from sequential frames beginning approximately 0.5 s prior to tongue projection and continuing for about 1.0 s. Sixteen additional variables, documenting maximum excursions and the timing of events, were calculated from the kinematic profiles. Quantified descriptions of head, hyoid and tongue movements are presented. Previously unrecognized rapid protraction of the hyobranchial skeleton simultaneously with the onset of tongue projection was documented and it is proposed that this assists the accelerator muscle in powering tongue projection. Acceleration of the tongue occurred in about 20ms, reaching a maximum acceleration of 486 m s−2 and maximum velocity of 5.8m s−1 in 35 cm strikes. Deceleration of the tongue usually began within 5 ms before prey contract and the direction of tongue movement was reversed within 10 ms of prey contact. Retraction of the tongue, caused by shortening of the retractor muscles, reached a maximum velocity of 2.99 ms−1 and was complete 330 ms after prey contact. Projection distance influences many aspects of prey capture kinematics, particularly projection time, tongue retraction time and the extent of gape and head movements during tongue retraction, all of which are smaller in shorter feedings. Though several features of the chameleon strike have apparently been retained from lizards not capable of ballistic tongue projection, key differences are documented. Unlike members of a related family, the Agamidae, C. oustaleti uses no body lunge during prey capture, exhibits gape reduction during tongue projection and strongly depresses the head and jaws during tongue retraction.
Note:
Present address: Department of Biological Sciences, Florida State University, Tallahassee, FL 32306, USA.
New Experiments on Colour Vision in Bees
Authors: Hertz Mathilde 
Published: April 2021

ABSTRACTUnder the condition of full, normal daylight illumination a surface which reflects a fair proportion of ultra-violet, as well as the visible spectrum, is neutral or white in the vision of the bee. If the percentage of reflexion of 3600 A. is less than one-third, or about one-quarter, of the percentage of reflexion in the visible light, a degree of coloration is obtained which is sufficient to be noticed by the bees in training experiments.When both are placed under ultra-violet absorbing filters, white paper in the vision of the bee most closely resembles a blue-green paper that possesses the highest amount of reflexion at 4900 A. Bees which have been trained to visit a blue-green surface covered by a filter glass do not do so any longer, if, by removing the filter, ultra-violet fight is added to the reflexion. The paper that possesses now two peaks of maximum reflexion, one at 4900 and the other at 3600 A., appears a light grey to the bee. On the other hand, when bees have been trained to visit an ultra-violet surface—white paper under a filter that absorbs the visible light completely—do not do so any longer if by lifting the filter the whole range of visible light is added to the reflexion of ultra-violet. The white paper at once becomes unattractive to the bee.There remains no doubt, that among the four qualities of colour discriminated by the bee (see Fig. 1) the first and the third on one side and the second and fourth on the other are complementary colours for this insect and presumably for many others.In the European flowers visited by bees three principal colours are now finally known: (1) that colour which is perceived if the main bulk of light reflected by the petals lies between 6500 and 4900 A. (orange-yellow for bee and man), (2) that which is perceived if the reflexion’extends from 4900 to 4000 or 3500 A. (blueviolet for bee and man), and (3) that which is perceived if the reflexion extends from 6500 A., or nearer to the red end of the visible spectrum, to 4000 A. (blue-green for the bee, but white, pink, light purple, bluish or yellowish for man).Ultra-violet seems never to occur in European flowers in such a way as to make petals which are brilliantly white for man to appear equally white for the bee.
The Physiology of Contractile Vacuoles
Authors: Kitching J. A. 
Published: April 2021

ABSTRACT
In peritrich ciliates many food vacuoles without visible solid contents may be formed. The water in these vacuoles passes into the general cytoplasm. In fresh-water Peritricha the rate of uptake of fluid in food vacuoles generally amounts to between 8 and 20% of the rate of output of fluid by the contractile vacuole. The greater part of the water evacuated is presumed to enter the animal by osmosis through the general body surface. In marine Peritricha the rate of uptake of fluid by food vacuoles approximately balances the rate of output by the contractile vacuole. The elimination of the water taken in by food vacuoles is believed to be the main function of the contractile vacuole in marine ciliates.
Chemical Mediation in Crustaceans
Authors: Welsh John H. 
Published: April 2021

ABSTRACT
A heart-accelerating principle for crustaceans which had been found in extracts of their eye-stalks is shown not to be identical with the chromatophorotropic hormone, and is present in nerve tissues other than those of the eye. Extracts of muscle have an inhibitory action on the various hearts. Excess potassium stimulates the action of nerve extracts but it is not present in them in sufficient amounts to be responsible for their effects. Adrenalin excites the crustacean heart but it is probably not the nerve substance in question. Acetylcholine excites this heart and in various concentrations produces a series of effects very similar to those produced by nerve extracts. By appropriate extraction methods and methods of bioassay relatively large amounts of acetylcholine were found in crustacean nerve tissues ; more being present in ganglia than in nerve fibres. Hence the active principle in question is, with little doubt, acetylcholine.
Studies on the Growth of Tissues in Vitro
Authors: Pomerat C. M. , Willmer E. N. 
Published: April 2021

ABSTRACT
In a previous paper of this series (Trowell & Willmer, 1939) an account was given of the effects on the growth of chick periosteal fibroblasts of the addition of saline extracts of various organs from the growing and fully grown bird. Attention was called to the fact that those organs and tissues which yielded growth-promoting extracts were just those which have been shown by Warburg and his school (Warburg, 1930) to possess considerable powers of glycolysis. The parallelism is illustrated in Fig. 1. In the upper series are plotted the mean mitotic indices for the fibroblast cultures during the period from the tenth to the twentieth hour after the addition of the tissue extracts, at which time the effects produced by such extracts have been shown to be most comparable. In the lower series, the anaerobic glycolytic activities, as measured by lactic acid production, of the corresponding tissues are plotted. Comparison of these two sets of figures at once suggests that the organ extracts may exert their effects by influencing the carbohydrate metabolism of the tissues to which they are applied. The only apparent exception is the thyroid, and the effects of extracts of that organ on the growth of cultures were very variable and probably other factors were involved.
The Function of the Gills of Mayfly Nymphs from Different Habitats
Authors: Wingfield C. A. 
Published: April 2021

ABSTRACT
The oxygen consumption of normal and gill-less nymphs of the mayflies Baetis sp., Cloeon dipterum and Ephemera vulgata has been measured at various oxygen concentrations. It has been found that over the complete range of oxygen concentrations studied, the tracheal gills do not aid oxygen consumption in Baetis sp. In Cloeon dipterum, at all oxygen concentrations tested, no gaseous exchange takes place through the gills ; at low oxygen concentrations, however, the gills function as an accessory respiratory mechanism in ventilating the respiratory surface of the body and so aid oxygen consumption. In Ephemera vulgata the gills aid oxygen consumption even at high oxygen concentrations. In this species the gills may function both as true respiratory organs and as a ventilating mechanism. It is shown that the differences in gill function can be related to the oxygen content of the habitat of each species.
The Thermal Resistance of Mayfly Nymphs from Ponds and Streams
Authors: Whitney R. J. 
Published: April 2021

ABSTRACT
Temperature is a factor of great importance in determining the distribution of animals. There are many references in ecological literature to a correlation between distribution of animals and the temperature conditions prevailing in the habitats occupied by the animals. Particular instances of this correlation are the distribution of stream turbellarians (Steinmann, 1906; Thienemann, 1913) and the effects of abnormal temperature conditions on local faunas (Allee, 1923; Stephens, 1938). The great significance of temperature to the animals themselves is shown by the many physiological studies of its action on living matter (Bélehrádek, 1935), and is also evident in the ecologists’ use of the terms stenotherm and eurytherm. This correlation between temperature and distribution has rarely, however, been investi-gated from the experimental standpoint. One line of approach has been the experimental investigation of the thermal resistances of animals from different habitats.
An Identifiable Molluscan Neuron Responds to Changes in Earth-Strength Magnetic Fields
Authors: Lohmann Kenneth J. , Willows A. O. Dennis , Pinter Robert B. 
Published: April 2021

ABSTRACT
Diverse animals can orient using geomagnetic cues, but little is known about the neurophysiological mechanisms that underlie magnetic field detection. The marine mollusc Tritonia diomedea (Bergh) has a magnetic sense and its nervous system is amenable to cellular-level electrophysiological analysis. In a semi-intact whole-animal preparation, intracellular recordings from the large, visually identifiable neurons left pedal 5 (LPe5) and right pedal 5 (RPe5) in the brain of Tritonia revealed enhanced electrical activity in response to changes in ambient earth-strength magnetic fields. No such changes in activity were observed in approximately 50 other neurons subjected to identical magnetic stimuli. The responses of LPe5 were characterized by increases in spiking frequency occurring about 6–16 min after the ambient magnetic field had been rotated to a new position. The response was abolished when the brain had been isolated from the periphery of the animal by severing nerves, a procedure that also transected prominent neurites of LPe5. We hypothesize that LPe5 is one component of a neural circuit mediating detection of the earth’ s magnetic field or orientation to it.
Evidence for the Presence of an Electrogenic Proton Pump on the Trout Gill Epithelium
Authors: Lin Hong , Randall David 
Published: April 2021

ABSTRACT
Ion transport inhibitors, amiloride, SITS, vanadate and acetazolamide, were added to the water to determine the effect of ion transfer mechanisms on the acidification of water passing over the gills. In neutral water, proton excretion causes a marked reduction in gill water pH. If water pH is 2.5 units lower than blood pH, however, then this proton excretion is inhibited and all water pH changes can be accounted for by CO2 hydration and ammonia protonation. Proton excretion across the gills is insensitive to 0.1 mmol l−1 amiloride and SITS but sensitive to vanadate, acetazolamide and water pH; thus, we conclude that proton excretion is mediated by an active proton pump on the apical membrane of the gill epithelium similar to that reported for the frog skin. Higher concentrations of amiloride (0.5 and 1 mmol l−1) reduced both ammonia and acid excretion, presumably because of inhibition of Na+/K+-ATPase on the basolateral border of the gill epithelium.
The Initial Orientation of Homing Pigeons at the Magnetic Equator: Compass Mechanisms and The Effect of Applied Magnets
Authors: Ranvaud Ronald , Schmidt-Koenig Klaus , Ganzhorn Jörg U. , Kiepenheuer Jakob , Gasparotto Odival C. , Britto Luiz R. G. 
Published: April 2021

ABSTRACT
Homing pigeons are thought to use the earth’s magnetic field for direction finding. Though the sensory system and the characteristics of the magnetic field used are unknown, it can be hypothesized that pigeons have an inclination compass, as do some migratory birds. When released at the magnetic equator, this inclination compass ought to be suspended. In addition, releasing pigeons when the sun is at or very close to the zenith renders the sun compass inoperational. However, released under these conditions, homing pigeons are not disorientated. Though they vanish on average in a different direction from pigeons released when the sun compass is available, they still show a directional preference close to magnetic north. This directional preference could be disrupted in some years by the application of magnets to the pigeons’ back. In other years this treatment as well as another magnetic treatment did not produce any difference between experimental pigeons and controls. These results confirm once more that, if magnetic effects exist, they are of a rather discrete nature.
The Effects of Branchial Denervation and Pseudobranch Ablation on Cardioventilatory Control in an Air-Breathing Fish
Authors: McKenzie David J. , Burleson Mark L. , Randall David J. 
Published: April 2021

ABSTRACT
The role of sensory afferent information from the gills of Amia calva in cardiovascular and ventilatory control was investigated by bilateral branchial denervation and pseudobranch ablation.
Aquatic hypoxia or 1 mg of sodium cyanide (NaCN) in the water flowing over the gills stimulated bradycardia, and gill and air ventilation in sham-operated fish. Sodium cyanide, noradrenaline (NA) and adrenaline (A) infusion into the dorsal aorta increased gill ventilation, and NA and A infusion also stimulated tachycardia and an increase in blood pressure.
Following denervation and pseudobranch ablation, O2 consumption (V˙O2) air-breathing frequency (fAB) and arterial O2 tension (PaO2) declined, and circulating NA levels increased, as compared with sham-operated fish. Cardiovascular and air-breathing responses to hypoxia were abolished and gill ventilatory responses attenuated. All ventilatory and cardiovascular responses to NaCN were abolished and gill ventilatory responses to NA and A were attenuated in animals following denervation and pseudobranch ablation.
These results demonstrate that O2-sensitive chemoreceptors in the gills and pseudobranch control reflex bradycardia and air-breathing responses in Amia, but that gill ventilatory responses to hypoxia, NA and A are partially mediated by extrabranchial mechanisms. Plasma NA levels increased during hypoxia in sham-operated and denervated animals, indicating that circulating NA may have mediated gill ventilatory responses in denervated animals.
Activities of Key Metabolic Enzymes in the Heater Organs of Scombroid Fishes
Authors: Tullis Alexa , Block Barbara A. , Sidell Bruce D. 
Published: April 2021

ABSTRACT
Maximal in vitro activities of key metabolic enzymes were measured in brain and eye heaters of five species of scombroid fishes. Istiophorid billfishes (blue marlin, striped marlin and Mediterranean spearfish), xiphiid billfishes (Pacific and Mediterranean stocks) and a scombrid fish (butterfly mackerel) were included in the analysis. Our main objectives were (1) to assess the maximum possible substrate flux in heater tissue, and (2) to determine what metabolic substrates could fuel heat production. Heater tissue of all scombroids examined showed extremely high oxidative capacity. Activities of citrate synthase, a commonly measured index of oxidative metabolism, included the highest value ever reported for vertebrate tissue. In most billfishes, citrate synthase activities were similar to or higher than those found for mammalian cardiac and avian flight muscle. Marker enzymes for aerobic carbohydrate metabolism (hexokinase) and fatty acid metabolism (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) also displayed extraordinarily high activities. Activities of carnitine palmitoyl-transferase measured in heater organs were among the highest reported for vertebrates. These results indicate that heat production could be fueled aerobically by either lipid or carbohydrate metabolism. Inter- and intraspecifically, heater organs of fishes from the colder Mediterranean waters had a higher aerobic capacity and, hence, a greater heat-generating potential, than fishes from the warmer waters of the Pacific. This difference may be attributed to different thermal environments or it may result from allometry, since fishes caught in the Mediterranean were considerably smaller than those caught in the Pacific.
Hydroid Stolonal Contractions Mediated by Contractile Vacuoles
Authors: Schierwater B. , Piekos B. , Buss L. W. 
Published: April 2021

ABSTRACT
The growth and development of colonial hydroids is dependent upon a flow of gastrovascular fluid through a common vasculature. Gastrovascular flow is believed to be driven by polyp contractions, stolonal contractions and endodermal ciliation. In the athecate hydroid Hydractinia symbiolongicarpus we found that polyp contractions, stolonal contractions and gastrovascular flow were only weakly correlated on a local scale. Stolons isolated from vascular continuity to polyps were found to display contraction frequencies indistinguishable from those observed in intact colonies. Transmission electron micrographs reveal a unique organelle, with characteristics of a contractile vacuole, in the apical stolonal endoderm. The activity of this organelle, inferred from static observations, correlates with the observed pattern of stolonal contractions. This is the first record of a contractile vacuole in an eumetazoan animal. Its description calls for a revision of existing interpretations of the mechanism of stolonal contractions in hydroids.
Stiffness and Damping Forces in the Intervertebral Joints of Blue Marlin (Makaira Nigricans)
Authors: Long John H. 
Published: April 2021

ABSTRACT
The stiffness and damping moments that are transmitted by intervertebral joints during sinusoidal bending were determined in the blue marlin, Makaira nigricans Lacépède. Using a dynamic bending machine, the angular stiffness (N m rad−1) and damping coefficient (kgm2 rad−2 s−1) of the intervertebral joints were measured over a range of bending frequencies, amplitudes and positions along the backbone. Angular stiffness increases with increasing bending amplitude, but, for some joints, the rate at which it changes with increasing bending frequency is negative. The precaudal intervertebral joints are less stiff than the caudal joints. The damping coefficient, which also shows regional variation, does not change with amplitude but does decrease with increasing bending frequency in joint positions three and five. Stiffness moments along the vertebral column, given the same amount of bending at each joint, are always greater than the damping moments. However, damping moments increase by an order of magnitude with an increase in bending frequency from 0.5 to 5.0Hz. The stiffness and damping moments determine the work that an external moment, such as muscle, must do over a complete cycle of bending. The external moments and work needed to bend an intervertebral joint are determined largely by the stiffness moments of the intervertebral joints.