bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reflex and Rhythmical Movements in the Dogfish
Authors: Le Mare D. W. 
Published: April 2021

ABSTRACTThe active part played by the two dorsal and anal median fins, and the passive part played by the caudal fin in the normal swimming of Scylliorhinus are emphasised. It is pointed out that when the nerve cord of Scylliorhinus is transected at any level, that part of the trunk below the level of transection produces rhythmical swimming movements. This is interesting when compared with certain teleosts, in which rhythmical swimming movements are only produced when the transection of the cord is at the anterior end of the medulla. In these teleosts the neurons controlling swimming are probably confined to the medulla, while in the dogfish they are dispersed throughout the length of the cord, representing a more primitive condition. The movements are accentuated during and after mechanical stimulation, the tip of the caudal fin and the ventral region near the cloaca being the most sensitive regions. Mechanical stimulation of certain regions produces well-defined reflexes of the body which are superimposed upon the rhythmical swimming movements. These distortions of the normal swimming movements thus produced are interpreted as foreshadowing the more marked, typical reflexes seen in the teleosts. The swimming movements may be inhibited by holding either of the dorsal fins. On release of the inhibitory stimulus, a post-inhibitory rebound in the swimming movements of the fish occurs. A regular secondary periodic rhythm superimposed upon the normal swimming rhythm of the fish is described. On supplying the dogfish with the nerve cord transected at the anterior end of the medulla with extra carbon dioxide, or stopping the oxygen supply, the Cheyne-Stokes rhythm, which is typical of respiration in mammals under abnormal conditions of oxygen and carbon dioxide supply, was found to take the place of the normal swimming rhythm. In spinal fish no such change was recorded. Consequently it is concluded that the neurons in the medulla which control the respiratory movements in some way also influence those responsible for the trunk musculature, so that this typical respiratory rhythm was translated into the swimming rhythm.
Observations on Pigmentary Co-Ordination in Elasmobranchs
Authors: Wykes Ursula 
Published: April 2021

ABSTRACT
Section of the spinal nerves to the pectoral fins in Raia brachyura, R. maculata and Scyllium canicula had no effect on the state of the chromatophores in the black adapted fish, nor did it prevent the development of uniform pallor on a white ground. Electrical stimulation of (a) spinal nerves to the pectoral fins, (b) the haemal canal, (c) the skin, in Raia brachyura, Rhina squatina and Scyllium catulus did not result in any chromatophore changes. Excised skin of Raia brachyura, R. mandata, Rhina squatina and Scyllium canicula placed in adrenaline chloride solution showed little or no change in melanophore index during one hour and could not be differentiated from control pieces placed in elasmobranch Ringer. The injection of adrenaline chloride caused a slight paling in Raia brachyura and Rhina squatina. This may be a secondary effect due to the vaso-constrictor action of this hormone. White adapted specimens of Raia brachyura, which were placed on a black ground after ligature of the dorsal aorta, became dark anterior to the point of ligature within 3 hours. The posterior region was still completely pale at this time and did not become fully dark for 24 hours.
Electrophysiological Properties of Crayfish Retinal Photoreceptors
Authors: Picones Arturo , Aréchiga Hugo 
Published: April 2021

ABSTRACTElectrical properties of crayfish retinular photoreceptors were studied in the dark-adapted state and during responses to light. In fully dark-adapted photoreceptors, the resting potential was −49.8±3.3 mV and input resistance was 31.3±5.4MΩ (mean±S.E.). The current-voltage relationship showed rectification near the resting potential, with decreased resistance within the depolarizing range. A value of 29.8±5.0kΩcm2 was calculated for specific resistance, and 3.0±0.4 μFcm−2 for specific capacitance. Electrotonic analysis showed that the photoreceptor was isopotential.During the light response, membrane conductance increased depending on the stimulus intensity. This relationship was steeper for the conductance change during the initial transient of the receptor potential than during the plateau. A depolarizing afterpotential usually ensued at the end of the light response, concurrent with a residual increased conductance. The time course of the conductance increase during the receptor potential showed two kinetic components, suggesting that at least two distinct membrane processes were involved in its generation.
Predicting Wingbeat Frequency and Wavelength of Birds
Authors: Pennycuick C. J. 
Published: April 2021

ABSTRACTWingbeat frequencies were observed in the field for 32 morphologically diverse bird species, representing 18 families, and ranging in mass from 20 g to nearly 5 kg. A combination of multiple regression and dimensional analysis was used to show that wingbeat frequency (f) may be estimated by: where m is the bird’s body mass, g is the acceleration due to gravity, b is the wing span, S is the wing area and ρ is the air density. The predicted wingbeat frequency can be used to estimate the power available from a bird’s flight muscles, and an estimate of the power required to fly can be obtained for comparison from the computer programs of Pennycuick (1989a). Field observations of airspeed are given for 30 of the 32 species. These are combined with the observations of wingbeat frequency to estimate wingbeat wavelength, and the ratio of wavelength to wing span, which is closely related to the ‘advance ratio’ as used by Ellington (1984).
Reversible Alkalinization by Manduca Sexta Midgut
Authors: Dow Julian A. T. , O’Donnell Michael J. 
Published: April 2021

ABSTRACT
Midguts of the larva of the tobacco hornworm larva, Manduca sexta, were isolated, pinned out and double perfused on the stage of an inverted microscope. The pH gradients across the anterior, middle and posterior regions of the gut were measured with a double-barrelled pH microelectrode, simultaneously with electrical potentials and the transepithelial potential difference (TEP). The microenvironment surrounding the apical surface is more alkaline, and that surrounding the basal surface more acid, than either the perfusion medium or the intracellular pH. Under double perfusion, a stable gradient of 1.4 pH units is observed across the middle midgut. A similar gradient is found across the anterior midgut, but no significant pH difference occurs across the posterior midgut. The pH gradient across the middle midgut is reversibly and symmetrically collapsed by anoxia, implying that it is sustained by a process requiring oxidative phosphorylation. The time course of decay and reconstitution of the pH gradient matches closely the activity of electrogenic K+ pumping, as measured by the TEP. These results are consistent with a model for high pH generation which links electrogenic K+ transport into the goblet cavities with net alkalinization of the lumen of the anterior and middle midgut regions.
Long-term anoxia in crucian carp: changes in the levels of amino acid and monoamine neurotransmitters in the brain, catecholamines in chromaffin tissue, and liver glycogen
Authors: Nilsson G. E. 
Published: April 2021

ABSTRACTCrucian carp (Carassius carassius L.), which are extremely anoxia-tolerant, were exposed to 17 days of anoxia at 8 °C. One group of fish was transferred to normoxic water for 1–8 h immediately after the anoxic period.All the eight amino acids measured in brain (including four putative neurotransmitters) were more or less strongly affected by anoxia. Gamma-aminobutyric acid (GABA) displayed a nearly fivefold increase during anoxia. It is hypothesized that the increased level of this inhibitory transmitter, maybe in combination with the decrease seen in excitatory amino acids (glutamate and aspartate), causes a lowered brain activity and, hence, is a key factor behind the decrease in physical activity and systemic energy metabolism seen in anoxic Carassius.The brain levels of serotonin, dopamine and norepinephrine were remarkably well preserved after anoxia (although their synthesis is oxygen-dependent), suggesting adaptive mechanisms. However, anoxia reduced the norepinephrine level in kidney (chromaffin tissue) by 92 % and, in contrast to previous results on shorter anoxic periods (3–7 days), the peripheral catecholamine store showed little sign of recovery during the subsequent normoxia.Anoxia was found to deplete the liver glycogen store severely, and the few fish that died after 15–17 days of anoxia contained no detectable liver glycogen.
Effects of Bicarbonate on Salt and Water Transport Across the Intestine of the Seawater EEL
Authors: Ando Masaaki 
Published: April 2021

ABSTRACTTo elucidate whether the Na+/K+/Cl− cotransport system depends on HCO3− in the seawater eel intestine, the effects of HCO3− on the transepithelial potential difference (PD) and on net water and ion fluxes were examined. When HCO3− buffer was replaced with phosphate buffer, the serosa-negative PD and net Na+, Cl− and water fluxes from mucosa to serosa were inhibited, indicating that the Na+/K+/Cl− cotransport system is inhibited in phosphate-buffered solutions. Similar inhibitory effects were also observed in solutions buffered with Hepes, Tris or Tes, indicating that the inhibitory effects are not specific for the phosphate buffer but are caused by omission of the HCO3− buffer system. Although the HCO3− buffer system consists of HCO3− and CO2, higher CO2 pressure with constant HCO3− concentration did not enhance, but inhibited, the PD and the net water flux: this indicates that the inhibition observed after removal of the HCO3− buffer system is due to omission of HCO3− rather than CO2. The inhibition of PD and the net water flux was greater after removal of HCO3− from the serosal side than from the mucosal side. Similarly, the inhibitory effects of 4, ′ -diisothio-cyanostilbene-2,2′-disulphonic acid (DIDS), an inhibitor of HCO3− transport, were more pronounced on the serosal side than on the mucosal side. Mucosal Ba2+ also inhibited PD and the short-circuit current (Isc) and enhanced the tissue resistance (Rt), presumably through partially blocking the apical K+ channels. However, these effects of Ba2+ were completely abolished after pretreatment with serosal DIDS, suggesting that Ba2+ and DIDS evoked the same effect. These results are combined and a possible role for HCO3− in the Na+/K+/Cl− co transport system is discussed.
Potassium and Rubidium Uptake in Freshwater Bivalves
Authors: Dietz T. H. , Byrne R. A. 
Published: April 2021

ABSTRACTPotassium transport characteristics were investigated in three species of freshwater bivalves: a corbiculid, Corbiculafluminea, and two unionids, Carunculina texasensis and Ligumia subrostrata. Using 42K, all three were found to take up potassium from dilute artificial pondwater ([K+] about 0.05 mmol l−1). The influx (Ji) was 0.72 μequivg−1 dry tissue h−1 in the corbiculid, significantly higher than the value of about 0.40/zequivg−1 dry tissueh−1 in the unionids. The K+ uptake displayed saturation kinetics in the range 0.05–0.36 mmol l−1: in Co. fluminea, there was a Jmax of 3.56 μequivg−1 dry tissueh−1 and the affinity coefficient (Km) was 0.27 mmol l−1; in Ca. texasensis, Jmax had a value of 1.8 μequivg−1 dry tissueh−1 and Km was 0.16 mmol l−1. Using K+-free artificial pondwater containing 0.03–0.04 mmol l−1 Rb+, the Rb+ influx was 0.41μequivg−1 dry tissueh−1 in the corbiculid and 0.28μequivg−1 dry tissueh−1 in Ca. texasensis. All animals lost K+ during the rubidium flux studies, and since they contained no Rb+, the Rb+ efflux was zero and the net flux was equal to the influx. The Jmax values for Rb+ were lower than the corresponding values for potassium: in Co. fluminea, Jmax was 1.4 μequivg−1 dry tissueh−1, significantly higher than in Ca. texasensis, which had a Jmax of 0.84 μequivg−1 dry tissueh−1. The rubidium Km (approx. 0.05 mmol l−1) values were significantly lower than corresponding values for potassium. Salt depletion increased the rubidium transport rate fourfold for both Co. fluminea and Ca. texasensis. High rates of net K+ uptake may account for the bivalves’ inability to tolerate elevated environmental potassium.
The Spleen in Hypoxic and Exercised Rainbow Trout
Authors: Wells R. M. G. , Weber R. E. 
Published: April 2021

ABSTRACTThe teleost spleen is a discrete organ containing, in addition to erythrocytes sequestered from the circulation, erythropoietic tissue involved in the synthesis of new erythrocytes. In this division into supply and synthesis, there appear to be some species differences. The eel spleen is an erythrocyte reservoir but is not thought to be a major erythropoietic organ (Johansson-Sjobeck, 1979). The splenic mass in goldfish does not change with induced anaemia (Houston et al. 1988). The trout spleen, in contrast, plays an erythropoietic role during anaemia (Lane, 1979), in addition to serving as a store of erythrocytes (Randall and Daxboeck, 1982). Exercise in trout is accompanied by haemoconcentration (Black et al. 1966; Stevens, 1968) and the spleen appears to contribute to elevated circulating haemoglobin levels (Stevens, 1968). Capture stress induced a 25% reduction in spleen haemoglobin concentration, [Hb], in the marine teleost Girella tricuspidata, and splenic histology revealed melano-macrophagic centres and erythropoietic tissue indicative of a major role in erythrocyte destruction and synthesis (Ling, 1984). Neither role can be played by the spleen of the icefish, which lacks haemoglobin (Wells et al. 1990).
The Intracellular pH of a Molluscan Smooth Muscle During a Contraction–Catch-Relaxation Cycle Estimated by the Distribution of [14C]DMO and by 31P-NMR Spectroscopy
Authors: Zange J. , Pörtner H. O. , Jans A. W. H. , Grieshaber M. K. 
Published: April 2021

ABSTRACTThe intracellular pH (pHi) of the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. was estimated during rest and during a contraction-catch-relaxation cycle by the distribution of [14C]DMO and by 31P-NMR spectroscopy. The pHi of resting muscles was found to be nearly the same whether it was determined with DMO (7.41±0.06, N=51) or by 31P-NMR spectroscopy (7.44±0.02, N=5). During catch the pHi was not significantly different from its value at rest. Serotonin (10−5moll−1) induced a rapid relaxation and a significant increase in pHi (DMO: 7.56±0.05, N=11; 31P-NMR: 7.57±0.02, N=5). In resting ABRM serotonin (⩾10−6moll−1) also induced an alkalosis. It was shown that cyclic AMP, the second messenger of serotonin, elicited an increase of pHi. Dopamine (10−5moll−1) did not cause an increase in either cyclic AMP levels or pHi. The rates by which tonically contracted ABRM loaded at 0.1 N were stretched were significantly increased by an alkalosis elicited by the addition of 10 or 20 mmol l−1 methylamine. Acidosis elicited by 10 mmol l−1 DMO caused a significant decrease in the rate of relaxation.
The Regulation of Intracellular pH Estimated By 31P-Nmr Spectroscopy in the Anterior Byssus Retractor Muscle ofMytilus EdulisL
Authors: Zange J. , Grieshaber M. K. , Jans A. W. H. 
Published: April 2021

ABSTRACTThe regulation of the intracellular pH (pHi) in the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. during an acidic and alkaline load was studied by 31P-NMR spectroscopy. Under aerobic conditions, a total intracellular buffer capacity of 26.5±0.7mmol l−1 pH unit−1 (N=3) was estimated. In the absence of serotonin, active acid extrusion was by a Na+-independent, primary active transport mechanism coupled to anion transport. Base equivalents appear to be extruded by a C1−/HCO3− exchanger. Serotonin (10−5 moll−1) induced an increase in pHi through additional activation of a Na+/H+ exchanger.
Ultrasound-triggered, flight-gated evasive maneuvers in the praying mantisParasphendale agrioninaI. Free flight
Authors: Yager David D. , May Michael L. , Fenton M. Brock 
Published: April 2021

ABSTRACTFree-flying male praying mantises Parasphendale agrionina (Gerst.) perform evasive maneuvers when stimulated by ultrasound and when attacked by hunting, echolocating bats. They do not, however, respond in any way when standing on a substratum. The maneuvers are graded in intensity with distance from the sound source: far from the source they are simple turns, whereas close to the source they are steep diving turns or spirals. The maneuvers are made under power, and the male’s velocity doubles to almost 4 ms−1 by the end of a steep dive. The mantis does not show any directional preference. The behavioral threshold of 64 dB SPL and minimum latency to course change of 125 ms indicate that these mantises should have adequate time to evade bats using calls of greater than 85-90 dB SPL (at 10 cm). In field experiments.with wild, hunting bats, P. agrionina successfully evaded capture in all five attacks to which they responded with evasive maneuvers. Out of three attacks on P. agrionina and three on a normally non-responding mantis, Miomantis paykullii Stål, in which there were no evasive maneuvers, the mantis was captured in five cases.
The Mechanism by Which Aphids Adhere to Smooth Surfaces
Authors: Dixon A. F. G. , Croghan P. C. , Gowing R. P. 
Published: April 2021

ABSTRACTThe adhesive force acting between the adhesive organs and substratum for a number of aphid species has been studied. In the case of Aphis fabae, the force per foot is about 10 μN. This is much the same on both glass (amphiphilic) and silanized glass (hydrophobic) surfaces. The adhesive force is about 20 times greater than the gravitational force tending to detach each foot of an inverted aphid. The mechanism of adhesion was considered. Direct van der Waals forces and viscous force were shown to be trivial and electrostatic force and muscular force were shown to be improbable. An adhesive force resulting from surface tension at an air-fluid interface was shown to be adequate and likely. Evidence was collected that the working fluid of the adhesive organ has the properties of a dilute aqueous solution of a surfactant. There is a considerable reserve of fluid, presumably in the cuticle of the adhesive organ.
Effect of activity on performance and morphology in ischaemic rat slow muscles
Authors: Corsi A. , Granata A. L. , Hudlicka O. 
Published: April 2021

ABSTRACTMuscle performance and structure was studied in rat soleus muscle with limited blood supply in combination with chronic muscle stimulation. Blood supply to the lower leg was restricted by ligation of the common iliac artery, electrodes were implanted in the vicinity of the sciatic nerve and ankle flexors were denervated. Three days later, soleus and gastrocnemius muscles were stimulated at 4 Hz four times a day for a period of 20 min with 2h intervals between stimulations; this procedure was continued for 4 days. Muscle performance, histochemistry and ultrastructure were studied on the eighth day after operation in these muscles and in ischaemic unstimulated muscles with denervated ankle flexors. Both were compared with control animals. Muscles with limited blood supply developed less isometric twitch tension than control muscles (peak twitch tension in ischaemic muscle was 60.3±4.8 g g−1 muscle, mean±s.E.M., compared to 79.7±6.9gg−1 in control muscle; tensions after 5min contraction were 54.5±5.5gg−1in ischaemic muscle compared to 70.6±6gg−1 in controls). Stimulated muscles with limited blood supply had higher peak (85±16.6gg−1) and final (87±12gg−1) tensions, and also fatigued less than muscles with limited blood supply but no stimulation. Histochemical estimation of capillary density (by staining for alkaline phosphatase) and slow (SO) and fast (FOG) fibres (by myosin ATPase staining) revealed similar capillary to fibre ratios (2.5) and a similar proportion of FOG fibres (around 18%) in all muscles. The proportion of glycogen-depleted fibres (estimated from the periodic acid Schiff reaction, PAS) in muscles removed from animals 10 min after a 5 min period of isometric twitches was significantly lower in ischaemic muscles (45.1±1.9%) than in control (80.5±1.5%) or chronically stimulated ischaemic muscles (67.3±4.0 %). Electron microscopy showed disorganised myofibrils with Z-line streaming in 7.48±3.04% of fibres in muscles with limited blood supply. Swollen and degenerated mitochondria, dilated sarcoplasmic reticulum and areas of disrupted sarcolemma were also observed. Stimulated ligated muscles showed a significantly lower proportion of fibres with disorganised filaments (0.65±0.32 %) and other signs of damage were much less frequent. The reduced damage and improved performance of chronically stimulated slow muscle may be the result of improved microcirculation, preventing accumulation of lactate.
Involvement of cyclic AMP in multiple, excitatory actions of biogenic amines on the cardiac ganglion of the horseshoe crabLimulus polyphemus
Authors: Groome J. R. , Watson W. H. 
Published: April 2021

ABSTRACTCyclic AMP appears to be involved in several excitatory actions of amines on neurones of the Limulus cardiac ganglion. Amines selectively increase levels of cardiac ganglion cyclic AMP with a magnitude and time course similar to that observed for amine-induced excitation of cardiac ganglion burst rate. With respect to either the physiological or biochemical effect, the apparent order of potency is octopamine&gt;epinephrine≈dopamine&gt;norepinephrine. Elevation of cardiac ganglion cyclic AMP levels by octopamine or dopamine is dose-dependent and is potentiated by the phosphodiesterase inhibitor 3-isobutyl 1-methylxanthine (IBMX).Several pharmacological agents which influence cyclic nucleotide metabolism, including forskolin, IBMX and 8-substituted cyclic AMP analogues, have amine-like effects on the Limulus cardiac ganglion. These effects include increased burst rate of the isolated cardiac ganglion and decreased burst duration, interburst interval and number of spikes per burst in follower neurones. Forskolin and IBMX increase levels of cardiac ganglion cyclic AMP, and IBMX also increases cyclic GMP levels in this tissue.Amines, forskolin and IBMX have direct effects on follower neurones pharmacologically isolated from pacemaker cell input. Octopamine, forskolin and IBMX depolarize follower neurones, while dopamine hyperpolarizes these cells. Amines, forskolin and IBMX elicit burst-like potentials in follower neurones, and increase the size of evoked, unitary junction potentials recorded in cardiac muscle fibres. These pharmacological and biochemical data suggest that multiple, excitatory effects of biogenic amines on the Limulus cardiac ganglion are mediated by simultaneous increases in cyclic AMP at several loci within this neural network.