bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osmotic Effects on Amino Acid Oxidation in Skate Liver Mitochondria
Authors: Moyes Christopher D. , Moon Thomas W. , Ballantyne James S. 
Published: April 2021

ABSTRACT
The mechanism responsible for the osmotic sensitivity of sarcosine oxidation by liver mitochondria from the little skate, Raja erinacea Mitchill, is examined. Assay medium tonicity, rather than a solute effect (urea or trimethylamine oxide), is probably responsible for the inverse relationship between osmolarity and the rate of oxidation of sarcosine by these mitochondria. Sarcosine oxidation proceeds through the flavin-linked sarcosine oxidase with the resultant glycine catabolized in the NAD-linked glycine cleavage system. The tonicity-sensitive component of the sarcosine oxidative pathway is not the glycine cleavage system. Sarcosine oxidation in the presence of rotenone is sensitive to medium tonicity. Oxidation of serine, which is also catabolized through the glycine cleavage system, is not as sensitive to tonicity as is sarcosine oxidation. Mitochondrial volume changes also appear to affect the transport of glycine. Although sarcosine does not appear to share the glycine transporter, it is possible that sarcosine transport is similarly sensitive to medium tonicity. The effects of osmolarity on the oxidation of dimethylglycine appear to support this hypothesis. Tonicity effects on sarcosine oxidase cannot yet be eliminated.
Cholinergic Action on the Heart of the Leech, Hirudo Medicinalis
Authors: Calabrese Ronald L. , Maranto Anthony R. 
Published: April 2021

ABSTRACT
Experiments were performed to determine the role of acetylcholine (ACh) in neuromuscular transmission in the heart of the leech Hirudo medicinalis.
Superfused or iontophoretically applied ACh rapidly depolarized both isolated heart muscle cells and muscle cells in isolated hearts in a dose-dependent manner. The depolarization was associated with a conductance increase of the muscle membrane that had a reversal potential of −9 mV. Eserine potentiated the response to superfused ACh, reducing the threshold from 10−6 to 10−8moll−1. Acetylcholinesterase was localized histochemically to be in the immediate area of neuromuscular terminals. Superfused nicotinic agonists mimicked the effects of ACh, while superfused nicotinic antagonists reversibly blocked the iontophoretic response of heart muscle fibres to ACh. 5×10−7moll−1 curare, 5x10−5moll−1 nicotine and l×10−4moll−1 atropine reduced the iontophoretic response to half its original amplitude. Alpha-bungarotoxin did not block the response of heart muscle cells to iontophoretically applied ACh. Curare was used to determine whether the neurones that innervate the heart - HE motor neurones and HA modulatory neurones - use ACh as a neuromuscular transmitter. The fast depolarizing component of the HE cell’s neuromuscular transmission was reversibly blocked by 10−4moll−1 curare, while the HA cell’s modulatory effects on the heart were apparently unaffected by 10−4moll−1 curare.
Our results indicate that heart muscle cells have nicotinic acetylcholine receptors that open in the presence of ACh, thereby increasing membrane conductance. The HE motor neurone is probably cholinergic and engages these receptors in its neuromuscular transmission, while the HA modulatory neurone is probably not cholinergic.
The Segmental Giant Neurone of the Hermit Crab Eupagurus Bernhardus
Authors: Heitler W. J. , Fraser K. 
Published: April 2021

ABSTRACT
The anatomy and physiology of the segmental giant (SG) neurone of the fourth abdominal ganglion of the hermit crab is described. The SG has an apparently blindending axon in the first root and a small cell body in the anterior ipsilateral ventral quadrant of the ganglion. There is a large ipsilateral neuropile arborization with prominent dendrites lined up along the course of the ipsilateral giant fibre (GF). The SG receives 1:1 input from the ipsilateral GF via an electrical synapse which is usually rectifying. SG activation produces a large EPSP in all ipsilateral and some contralateral fast flexor excitor (FF) motor neurones. The major input to FFs resulting from GF activation appears to be mediated via the SG. It also produces a small EPSP in ipsilateral and contralateral motor giant neurones. The properties of the hermit crab SG are compared to those of the crayfish SG, and the implications of the SG for the possible evolutionary paths of the giant fibre system are discussed.
The Wake of A Jackdaw (Corvus Monedula) in Slow Flight
Authors: Spedding G. R. 
Published: April 2021

ABSTRACT
The wake of a jackdaw in slow forward flight is described. The three-dimensional velocity field was investigated qualitatively and quantitatively by analysis of multiple-flash stereophotographs of the motion of neutrally buoyant helium bubbles. The best description of the wake structure appears to be a chain of planar, nearcircular, discrete, small-cored, vortex loops, each produced by vorticity shed during a single downstroke.
However, the momentum measured in such a wake is approximately 35 % of that required for weight support under these flight conditions. Some evidence is presented that this apparent wake momentum deficit may arise because the description of the real wake vorticity distribution is too simplistic.
The implications of these results for theoretical models of bird flight are briefly discussed.
Adduction Levers And Adductor Muscle Function in the Mandibular System of the Shore Crab Carcinus Maenas
Authors: Abby-Kalio N. J. , Warner G. F. 
Published: April 2021

ABSTRACT
The lever systems, and structure and function of the adductor muscles, of the mandibles of large male Carcinus maenas (L.) were investigated. The functional mechanical advantage (FMA) of the external adductor muscles, measured at the middle of the biting edge of the mandible, was 1·53 ± 0·01; the ideal mechanical advantage (IMA), calculated from measured lever lengths, was 1·78 ± 0·03 (mean ± S.E.). The FMA of the internal adductor muscles was 0·53 ± 0·01 and the IMA was 0·62 ±0·02
When slowly loaded, the external adductor system broke at 3·09 ± 0·16 N; when rapidly loaded, the system broke at 7·16 ± 0·79 N. Short duration loading at 2·0 N or more was found to result in histologically detectable damage at the pivot. When slowly loaded, the internal adductor system broke at 0·68 ± 0·05 N. When a load of 0·39 N was applied to the internal adductor system, the failure point on slow loading of the external adductor system was not significantly increased.
The mean maximum force of contraction of the external adductor muscles on electrical stimulation was 0·98 ± 0·03 N, with a stress of 627 kN m-2 in the fibres. The internal adductors contracted with a mean maximum force of 0·33 ± 0·01 N. The total maximum bite force is therefore about 3·3 N, only 10% being contributed by the internal adductors. The safety factor of both internal and external systems is about 2.
The mean sarcomere length of half-contracted fibres of the external adductor muscles was 11· 62 ± 0·11 μm.
Perfusion-Secretion Relationships in the Isolated Elasmobranch Rectal Gland
Authors: Shuttleworth T. J. , Thompson J. L. 
Published: April 2021

ABSTRACT
Perfusion and sodium secretion parameters were measured in the isolated rectal gland of Scyliorhinus canicula L. perfused at in vivo pressures, and the effect of stimulation of secretory activity by cyclic AMP and theophylline on these parameters was determined. Stimulation resulted in large increases in secretion flow rate, percentage extraction of sodium from the perfusing fluid, and arteriovenous sodium concentration difference, but did not affect perfusion flow rate or the sodium concentration of the secreted fluid. Reduction of perfusion flow rate to values below 65% of the control level, achieved by reducing perfusion pressure, produced a marked decline in sodium secretion -a process accompanied by increases in the percentage extraction of sodium and arteriovenous concentration difference of sodium, but again without any change in the sodium concentration of the secreted fluid. The in vivo consequences of these findings are discussed with reference to related findings for the avian nasal salt gland.
The normal rate of secretion, its sodium concentration, and the nature of the dependence of secretion rate on perfusion flow below certain levels, were essentially unaffected by a reduction in the availability of oxygen to the gland by approximately 80%. It is concluded that the observed relationship between perfusion flow and sodium secretion rate in the stimulated gland is not related to oxygen availability, and hence that the primary underlying function of the synchronized secretion-related vasodilation seen in the gland is not to increase the supply of oxygen to the stimulated secretory tissue. We discuss possible reasons why this erroneous conclusion has been reached by other workers.
Multimodality of Ocellar Interneurones of the American Cockroach
Authors: Ohyama Takahiro , Toh Yoshihiro 
Published: April 2021

ABSTRACT
Many insects possess two or three dorsal ocelli in addition to the paired compound eyes. The dorsal ocellus is characterized by a high convergent ratio of many retinular axons upon several thick second-order neurones in the posterior region of the ocellus. The thick second-order neurones extend towards the brain as an ocellar nerve together with other thin processes, and their central projections have been well demonstrated by cobalt backfills in many insects (reviewed by Goodman, 1981). However, our knowledge about how information is processed in the ocellar system is limited (but see Chappell & Dowling, 1972; Wilson, 1978a,b; Goodman, 1981; Simmons, 1981). In the present study we present some evidence that in the cockroach, Periplaneta americana, the ocellar second-order neurones function as CNS integrative multimodal neurones.
Natural and Induced Magnetization in the Bobolink, Dolichonyx Oryzivorus (Aves: Icteridae)
Authors: Beason Robert C. , Brennan William J. 
Published: April 2021

ABSTRACT
The magnetic characteristics of the heads from 28 bobolinks [Icteridae: Dolichonyx oryzivorus (L.)] were analysed using remanence magnetometers. The natural remanent magnetization of 12 freshly preserved heads averaged 3·20×10−7 electromagnetic units (e.m.u.) (le.m.u. = 103Am−1) and was oriented horizontally from side to side. An electromagnet was used to induce magnetization with external field strengths of up to 0·7 Tesla (T). The average saturation isothermal remanent magnetization (sIRM) for 23 bobolink heads was 2·49X10−5 e.m.u. Because the IRM was attained partially below 0·1 T and totally below 0·3 T, we believe that the magnetic material in the bobolink is at least partially single domain magnetite. The relationship between the IRM acquisition and alternating field (a.f.) demagnetization curves indicates that the single or pseudo-single domain grains of magnetite interact. Similar results were obtained on one savannah sparrow (Emberizidae: Passerculus sandwichensis) head and one indigo bunting (Emberizidae: Passerine cyanea) head.
When some bobolink heads were subdivided, most or all of the magnetization was concentrated in the area from the nasal cavity to the orbit. Light microscopy and histochemical tests confirm the localization of inorganic iron in this region.
Action Potentials in Rhodnius Oocytes: Repolarization is Sensitive to Potassium Channel Blockers
Authors: O’Donnell M. J. 
Published: April 2021

ABSTRACT
Depolarization of Rhodnius oocytes evokes action potentials (APs) whose rising phase is calcium-dependent. The ionic basis for the repolarizing (i.e. falling) phase of the AP was examined.
Addition of potassium channel blockers (tetraethylammonium, tetrabutylammonium, 4-aminopyridine, atropine) to the bathing saline increased the duration and overshoot of APs. Intracellular injection of tetraethylammonium had similar effects. These results suggest that a voltage-dependent potassium conductance normally contributes to repolarization. Repolarization does not require a chloride influx, because substitution of impermeant anions for chloride did not increase AP duration. AP duration and overshoot actually decreased progressively when chloride levels were reduced.
Current/voltage curves show inward and outward rectification, properties often associated with potassium conductances. Outward rectification was largely blocked by external tetraethylammonium. Possible functions of the rectifying properties of the oocyte membrane are discussed.
Gas exchange, storage and transport in voluntarily diving Xenopus laevis
Authors: Boutilier R. G. , Shelton G. 
Published: April 2021

ABSTRACT
A closed, extracorporeal loop, containing oxygen and carbon dioxide electrodes, was developed in order to make continuous measurements of lung gas and in undisturbed Xenopus laevis. Pulmonary R values are about 0 ·8 during periods of lung ventilation in resting animals, but they fall very rapidly as a voluntary dive proceeds. In fact, the instantaneous R values for lung eventually fall to zero during a voluntary dive, since continues to decline whilst (after an initial increase) comes into a steady state as transcutaneous CO2 losses balance metabolic production. These relationships change during spontaneous underwater activity, aquatic hypercapnia or enforced diving, with significantly higher levels being found at any value than in resting animals. Emergence from such dives is marked by a considerable hyperventilation, leading to lung R values which are 2–3 times higher than those seen during lung ventilation of animals at rest. The lungs of Xenopus are therefore important in eliminating the CO2 stored during a period of breath-holding but not of major importance in forming part of that store themselves.
The lungs of Xenopus are, however, important sources of stored oxygen during voluntary dives, the rate of use being clearly related to activity levels and dive durations. There could be sudden changes in the rate of depletion during a dive, suggesting that factors additional to the metabolic rate of the cells may be important in determining the way in which the lung store is used.
In a parallel series of experiments, O2 and CO2 partial pressures were determined in lung gas samples and in simultaneously drawn samples of blood from the femoral artery (systemic arterial) and left auricle (pulmonary venous) of animals making voluntary dives. These blood/gas data, together with results of previous experiments on Xenopus, have been used to develop an idealized model of O2 exchange, storage and transport during a 30-min voluntary dive. The volume of the O2 stores held in the lungs and various subdivisions of the circulation are shown in the model by plotting the of the store against its respective O2 capacitance. The model illustrates the overall importance of the lung as a source of oxygen during breathholding and that early use of a large systemic venous O2 store may be an important basic function for cardiovascular adjustments seen in a dive.
Electrophysiological Studies on the Temporal Organ of the Japanese House Centipede, Thereuonema Hilgendorfi
Authors: Yamana Kenjiro , Toh Yoshihiro , Tateda Hideki 
Published: April 2021

ABSTRACT
The response of the temporal organ (organ of Tömösváry) has been studied electrophysiologically in the Japanese house centipede (Thereuonema hilgendorfi : Chilopoda).
Receptor cells of the temporal organ show spontaneous discharges (15–40 impulses s-1) which are depressed in a phasic-tonic manner by carbon dioxide stimuli. Perfusion of the presumed receptor site with a carbon dioxide-containing solution also changes the impulse frequency. The impulse frequency of a receptor cell decreases linearly with a logarithmic increase in carbon dioxide concentration ranging from 0·001 % to 0·1 % in the phasic state and from 0·05% to 5·0% in the tonic state. These results suggest that the temporal organ of the house centipede functions as a carbon dioxide receptor, though it responds to other stimuli as described below. Changing the pH of a carbon dioxide-containing solution changes the impulse frequency, probably by changing the molar fraction of CO2 molecules in the lymph surrounding the receptor site. pH also directly influences the impulse frequency of the receptor cell, but the effect is smaller than that of CO2 molecules. Receptor cells respond to humidity changes, but the response is smaller than that to carbon dioxide. When receptor cells are stimulated by moist air (100% relative humidity, RH) after adaptation to dry air (0% RH), the impulse frequency increases by a factor of 1·29 ±0·37 (mean ± S.D. measured for the first second, N = 29), and 1·16 ± 0·28 (measured after adaptation to moist air, N = 29). Air-borne chemicals also affect the impulse frequency of a receptor cell; it is increased by amines and decreased by fatty acids and aldehydes. Effects of these chemicals are discussed in relation to changing the pH of lymph bathing the receptor site.
The relative distribution of pulmocutaneous blood flow in Rana catesbeiana: effects of pulmonary or cutaneous hypoxia
Authors: Boutilier R. G. , Glass M. L. , Heisler N. 
Published: April 2021

ABSTRACT
The distribution of pulmocutaneous heart output to lungs and skin was determined in non-anaesthetized, fully recovered bullfrogs (Rana catesbeiana) by application of the microsphere method in order to study the modulation of blood flow to different gas exchange sites in amphibians during environmental air and water hypoxia. The relative perfusion of various skin areas was found to be rather heterogeneously distributed with an over-proportionately high blood flow to the ventral body surface. This distribution of flow among different skin areas remained unaffected by any type of environmental hypoxia. The relative perfusion of lungs and skin, however, was significantly affected by the pattern of environmental oxygen partial pressure. The relative lung perfusion (≈80 % of pulmocutaneous flow in normoxic control conditions) was increased during water hypoxia, and reduced with lowered inspired . This mechanism could be interpreted as a readjustment of blood flow towards the gas exchange site with higher oxygen partial pressure, but may also represent a mechanism to prevent oxygen loss from the body stores at gas exchange sites of low oxygen tension.
The absence of an arterial pressure effect on filtration by perfused glomeruli of the hagfish, Eptatretus stouti (Lockington)
Authors: Riegel J. A. 
Published: April 2021

ABSTRACT
Single renal corpuscles of hagfish were perfused with a Ringer solution containing Ficoll 70 to simulate the colloid osmotic pressure of hagfish plasma. Simultaneous measurements were made of single glomerulus filtration rate (SGFR), perfusion pressure and the pressure in a vessel of the renal vasculature. The results confirm that SGFR is independent of pressure in the glomerular capillaries (PGC). The results also suggest that flow through glomeruli and SGFR are closely linked. Studies of the pressures in glomerular capillaries during periods when the perfusion rate was varied indicate that PGC reflects the area of the active capillaries and the rate of perfusion. Therefore, in the hagfish, PGC appears to be an effect of factors that cause glomerular filtration, not the main cause of that process.
Iron-containing cells in the honey-bee (Apis mellifera): I. Adult morphology and physiology
Authors: Kuterbach D. A. , Walcott B. 
Published: April 2021

ABSTRACT
Particulate iron was found within the trophocytes of the fat body of the adult honey-bee. These iron granules differed in their structure and composition from iron granules found in other biological systems. The granules had an average diameter of 0·32 ± 0·07 μm and were composed of iron, calcium and phosphorus in a noncrystalline arrangement. The granules were apparently randomly distributed within the cytoplasm of the cells, and were not associated with any particular cellular organelle.
Electron microscopy revealed the presence of cell junctions between the trophocytes. In tissues treated with colloidal lanthanum, 20-nm gaps were seen between the outer leaflets of the cells forming the cell junction. Physiological studies showed that these cells are electrically coupled, but the coupling ratio is low, as a result of extensive coupling to many cells.
Iron-containing cells in the honey-bee (Apis mellifera): II. accumulation during development
Authors: Kuterbach D. A. , Walcott B. 
Published: April 2021

ABSTRACT
The development of iron granules in honey-bee tissues was investigated using both anatomical and analytical methods. Iron granules are present only in the trophocytes of post-eclosion adults and have the same elemental composition as those in foraging adults. The granules increase in both size and number during ageing. Iron levels in developing worker honey-bees were measured by proton-induced X-ray emission spectroscopy. The rate of iron accumulation was directly related to iron levels in the diet, and the iron can be obtained from pollen and honey, both major food sources of the bee. In adults, the iron content of the fat body reached a maximum level (2·4 ± 0·15 μgmg−1 tissue), regardless of the amount of iron available for ingestion. Maximal iron levels are reached at the time when honey-bee workers commence foraging behaviour, suggesting that iron granules may play a role in orientation. Alternatively, accumulation of iron in granules may be a method of maintaining iron homeostasis.
The Modulatory Actions of FMRFamide and Related Peptides on Locust Skeletal Muscle
Authors: Evans Peter D. , Myers Camilla M. 
Published: April 2021

ABSTRACT
The modulatory actions of FMRFamide and related peptides on tension generated in the extensor-tibiae muscle of the locust hindleg by stimulation of the slow excitatory motor neurone (SETi) depend upon the frequency of stimulation of SETi. They have no effect on the tension induced by the fast motor neurone (FETi) or upon the myogenic rhythm present in this muscle. At low frequencies of SETi stimulation (1Hz and below) the predominant modulatory effects are increases in the amplitude, contraction rates and relaxation rates of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz) these effects are superimposed upon an increase of maintained tension. FMRF amide increases the amplitude and relaxation rate of slow twitch tension by different amounts in different regions of the extensor muscle. It is likely that the effects of FMRF amide are restricted to slow muscle fibres that are innervated by SETi but not FETi. The modulatory actions of FMRFamide on SETi-induced tension are additive to, but do not potentiate, the modulatory actions of octopamine and proctolin in this muscle. The actions of FMRFamide show some similarities with the modulatory actions of octopamine in this preparation but they are mediated by an independent receptor system that does not change cyclic nucleotide levels. Other actions of FMRFamide are similar to the actions of proctolin.
Slow Active Potentials in Walking-Leg Motor Neurones Triggered by Non-Spiking Proprioceptive Afferents in the Crayfish
Authors: Sillar Keith T. , Elson Robert C. 
Published: April 2021

ABSTRACT
Intracellular recordings have been made from walking-leg motor neurones of the crayfish, Pacifastacus leniusculus, in isolated preparations of the thoracic ganglia. Some motor neurones display slow depolarizations that can drive bursts of spikes and resemble ‘plateau’ potentials described in other invertebrate and vertebrate neurones. Evidence is presented which suggests that the potentials are regenerative and endogenous to the motor neurones, and are not the result of feedback from a neural network.
These potentials can be induced by synaptic inputs from the non-spiking afferent neurones of the thoracic-coxal muscle receptor organ, a basal limb proprioceptor. Reflex input from this receptor is augmented during the active depolarization of the motor neurone. The results are discussed in terms of the control of rhythmic motor output and the central modulation of reflexes in the crayfish’s thoracic nervous system.