bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Ventilation, Extraction and Uptake of Oxygen in Undisturbed Flounders, Platichthys Flesus: Responses to Hypoxia Acclimation
Authors: Kerstens A. , Lomholt J. P. , Johansen K. 
Published: April 2021

ABSTRACT
Gill ventilation , extraction of O2 from the ventilatory current and O2-uptake were measured in three groups of undisturbed flounders naturally buried in sand. Two groups were acclimated to normoxic water . One was studied in normoxic water, the other during acute exposure to hypoxic water (P1, O2 = 30 mmHg). A third group was acclimated to and studied in hypoxic water. Gill ventilation was measured directly using an electromagnetic flowmeter. The flowprobe, fitted to a plastic funnel, was placed over the fish’s mouth without making physical contact with the fish. Exhaled water for calculation of O2-extraction was siphoned from another plastic funnel placed over the upper operculum of the flounder. Acute hypoxia exposure of normoxic fish caused nearly a doubling in ventilation volume. In flounders acclimated to chronic hypoxia and studied in hypoxic water the ventilation volume reached a value approximately 3-5 times that of normoxic fish. O2-extraction averaged 76% in normoxic flounders. During acute hypoxia the value declined to 52%, the same O2-extraction was obtained in the chronically hypoxic fish. for the normoxia acclimated fish in normoxic water was 0 · 45 ml O2 · kg −1 .min − 1 declining to 0-12ml O2.kg − 1.min − 1 during acute exposure to hypoxia. of hypoxia acclimated fish in hypoxic water was 0 · 24 ml O2. kg − 1. min − 1. When compared in hypoxic water, the hypoxia acclimated fish show an unchanged O2-extraction of 52% in spite of a nearly two-fold increase in ventilation relative to that of the normoxia acclimated fish. Possible causes for this may be a left shift of the O2-Hb dissociation curves and an increase in the transfer factor for O2 over the gills in the hypoxia acclimated fish.
Salt and Water Balance in Rainbow Trout (Salmo Gairdneri) Rapidly Transferred from Fresh Water to Sea Water
Authors: Bath R. N. , Eddy F. B. 
Published: April 2021

ABSTRACT
Physiological responses of rainbow trout (mean weight 13·3 g) to sudden changes in salinity were investigated. An initial period lasting about 8 h was characterized by increased drinking and an increase in plasma and body ions. Fish failed to survive more than 2 days in full strength sea water but in two-thirds sea water there were few mortalities and adaptation was complete in 7–10 days. During this period there were gradual physiological changes resulting in normal plasma ion concentrations but significantly increased body ionic content. The intracellular concentrations of muscle chloride showed the greatest increase.
The Variable Effects of Ambient and Artificial Light:Dark Cycles On Embryonic Diapause in A Laboratory Population of the Annual Fish Nothobranchius Guentheri
Authors: Markofsky Jules , Matias J. R. , Inglima K. , Vogelman J. H. , Orentreich N. 
Published: April 2021

ABSTRACT
The effects of light:dark cycles (L;D) on embryonic development in a laboratory population of the East African annual fish Nothobranchius guentheri were studied. Under ambient light conditions (40° N) there was a low frequency of embryos entering diapause between June and October. Beginning in November there was an increasing frequency of diapausing embryos with a peak in December, and a lower frequency by February. Under artificial light conditions there was an increasing frequency of diapausing embryos as the L:D changed from 16:8 to 9:15. When individual fish or groups of fish were followed it was found that, even under the same light conditions, variable frequencies of diapausing and non-diapausing embryos were produced and that the frequencies often changed with time. The L: D cycle under which the embryos were incubated had no effect on diapause. As in some species of insects the ‘diapause factor’ was of maternal origin. The ability of the fish to produce both diapausing and non-diapausing embryos under the same and variable L : D is most likely an adaptive trait related to the survival of the fish in the harsh environments of alternating rainy and dry seasons.
Timing of the Action of Photoperiod and Temperature On Events Leading to Diapause and Development in Pupae of Heliothis Punctigera (Lepidoptera: Noctuidae)
Authors: Browning T. O. 
Published: April 2021

ABSTRACT
Diapause in H. punctigera occurs in the pupa at some stage between pupation and the pupal-adult apolysis. Its occurrence is induced by 12 L: 12 D photoperiod, which is specifically effective during the last half of larval life, and by low temperature (19 °C). Irrespective of the conditions during larval life, the insects do not diapause if subjected to high temperature (28 °C) after feeding ceases and before the pupal ecdysis. The insects are most sensitive to high temperature during the short perioid between the larval-pupal apolysis and pupal ecdysis. At both 28° and 19 °C the brain and thoracic glands secrete almost simultaneously to trigger the larval-pupal apolysis, which occurs almost immediately after the release of the hormones. High temperature during the prepupal period results in an increased rate of development from pupal ecdysis to emergence of the adult.
Pharmacological Properties of Axonal Sodium Channels in the Cockroach Periplaneta Americana L.
Authors: Pelhate M. , Hue B. , Sattelle D. B. 
Published: April 2021

ABSTRACT
Condylactis toxin induces a prolonged falling phase in action potentials recorded from giant axons of the cockroach Periplaneta americana L. A distinct plateau potential can be recorded in the presence of Condylactis toxin at concentrations of 0·5 mg/ml and above. In cockroach axons, voltageclamp experiments show that Condylactis toxin acts primarily by slowing the sodium current turn-off without affecting either the time-course of the sodium conductance increase or the peak amplitude of the transient sodium current.
The Role of Vortices and Unsteady Effects During the Hovering Flight of Dragonflies
Authors: Savage Stuart B. , Newman Barry G. , Wong Denis T.-M. 
Published: April 2021

ABSTRACT
Weis-Fogh and Norberg concluded that steady-state aerodynamics is incapable of explaining how the dragonfly supports its weight during hovering. Norberg also concluded that the wing kinematics of Aeschna juncea L., as determined photographically, are incompatible with those proposed by Weis-Fogh for his Flip mechanism. The present paper has proposed an alternative lift-generating mechanism, various aspects of which are novel from the standpoint of animal flight. Flow visualization tests performed in water established the flow field during a complete cycle of the idealized wing motion. Using this information and unsteady inviscid flow theory the forces were analysed. A plausible balance of horizontal forces and more than sufficient lift were obtained. A physical explanation of the theory is provided for those who do not wish to study the mathematical details.
Electrical Properties of Insect Neurones with Spiking and Non-Spiking Somata: Normal, Axotomized, and Colchicine-Treated Neurones
Authors: Goodman Corey S. , Heitler W. J. 
Published: April 2021

ABSTRACT
The paired motorneurones in the metathoracic ganglion of the locust have non-spiking somata whereas the dorsal unpaired media (DUM) neurones have spiking somata. We have studied the electrical properties of two identified neurones in the metathoracic ganglion that have spiking axons innervating the same muscle: the fast extensor tibiae (FETi) motomeurone has a non-spiking soma and the dorsal unpaired median extensor tibiae (DUMETi) neurone has a spiking soma. The inward current of the peripheral axon spikes of both DUMETi and FETi is carried predominantly by Na+, since the spikes are blocked only by removal of Na+ or addition of tetrodotoxin (TTX). The inward current of the soma spike of DUMETi is carried by Na+ and Ca2+, since it is blocked by either removal of Na+, addition of TTX, or addition of Co2+. The non-spiking soma of FETi shows delayed rectification. When some of the outward K+ current is blocked by TEA or 3-AP, the soma is capable of generating overshooting action potentials. The inward current of the TEA-induced soma spike of FETi is carried by Na+ and Ca2+, since it is blocked by either removal of Na+, addition of TTX or addition of Co2+. Axotomy or treatment with colchicine converts the non-spiking soma of FETi into a spiking soma within 4 days. The inward current of the soma spike is carried predominantly by Na+, since it is blocked only by removal of Na+. Five days after axotomy of one of the peripheral axons of DUMETi, Na+ is sufficient for the generation of the soma spike. Increased excitability is also observed in the neuropil of DUMETi after axotomy. When some of the outward K+ current is blocked by Ba2+, the normal and axotomized somata of FETi and DUMETi are all capable of generating long duration Ba2+ action potentials that are blocked by addition of Co2+. The overshooting Ba2+ action potentials in all cases are similar in amplitude and duration. It is concluded that the soma membrane of DUMETi and FETi normally contains both Na+ and Ca2+ inward current channels. The normal difference in excitability between these two somata may result in part or entirely from differences in the outward K+ current. It is suggested that axotomy or colchicine treatment cause an increase in the number of active Na+ channels in the soma membrane, which overcomes any differences in the outward K+ current and results in both cells being able to produce soma spikes.
Comparison of Slow Larval and Fast Adult Muscle Innervated by the Same Motor Neurone
Authors: Rheuben M. B. , Kammer A. E. 
Published: April 2021

ABSTRACT
Muscles innervated by an identified set of motor neurones were compared between larval and adult stages. The structure of the larval muscle is typically tonic: long sarcomeres, irregular Z-bands, and 10–12 thin filaments around each thick filament. The structure of the adult muscle is phasic : 3–4 μm sarcomeres, regular Z-bands, 6–8 thin filaments around each thick filament, and large mitochondrial volume. The tensions produced by these muscles were correspondingly different. The larval twitch was about 7 times slower and the tetanus/twitch ratio 10 times greater than those of the adult. No structural or physiological differences were observed in the neuromuscular junctions of the two stages. The relatively unchanging functional relationship of a single motor neurone with two different muscle fibre types during two developmental stages is compared with the converse situation in which it has been reported that implantation of a different type of motor nerve into a muscle modifies contractile properties.
Ionic and Osmotic Influences on Prostaglandin Release from the Gill Tissue of A Marine Bivalve, Modiolus Demissus
Authors: Freas William , Grollman Sigmund 
Published: April 2021

ABSTRACT
Prostaglandin E2 (PGE2) was identified in Modiolus demissus gill tissue on the basis of solvent extraction, thin layer and column chromatography, bioassay, and radioimmunoassay. The presence of PGE2 was detected in both tissue and sea water incubate surrounding the tissue. Both hyposmotic stress and magnesium-free sea water significantly increased release of prostaglandins into sea water. Hyposmotic stress also significantly increased prostaglandin synthesis. Examination of tissues revealed that homogenates of the mantle and lower visceral mass contained significantly fewer nanograms immunoreactive prostaglandins per gram wet weight than homogenates of the gill, posterior adductor muscle, upper visceral mass, or siphon tissue. Prostaglandin release could be increased by addition of arachidonic acid, and inhibited by addition of acetylsalicylic acid or indomethacin.
The Response of the Kidney of the Freshwater Rainbow Trout to True Metabolic Acidosis
Authors: Kobayashi Kenneth A. , Wood Chris M. 
Published: April 2021

ABSTRACT
Infusion of lactic acid into the bloodstream of trout produced a short-lived depression of blood pH and a long-lasting elevation of blood lactate. The lactate injected was distributed in a volume of 198 ml/kg. Renal excretion of lactate anion and total acid increased by approximately equal amounts during the period of high blood lactate levels, but total renal loss over 72 h accounted for only 2% of the lactate load and 6% of the proton load. Comparable differences in the time courses of blood lactate and pH changes occurred when lactacidosis was induced endogenously by normocapnic hypoxia. The immediate response of the kidney was similar to that with lactic acid infusion, but there was a long-lasting (12–72+ h) elevation of urinary acid efflux that was not associated with lactate excretion. Following hypoxia, renal excretion over 72 h accounted for 1 % of the estimated lactate load and 12-25% °f proton load. A renal lactate threshold of 4–10 μequiv/ml prevents significant urinary lactate excretion. The response of the trout kidney to true metabolic acidosis is similar to that of the mammalian kidney.
Patterns of Activity And Axonal Projections of the Cerebral Giant Cells of the Snail, Lymnaea Stagnalis
Authors: McCrohan C. R. , Benjamin P. R. 
Published: April 2021

ABSTRACT
The paired cerebral giant cells (CGCs) of Lymnaea were studied using electrophysiological and anatomical techniques. A strong electrotonic junction coupling the CGCs is located in the buccal ganglia, several millimetres distal to the cell bodies. This leads to i : i spike activity in the two cells. The CGCs receive phasic and tonic inputs which appear to be common to the two cells. Two types of phasic input are synchronous with synaptic input to feeding motoneurones in the buccal ganglia. Morphological studies, using three separate dye injection techniques, confirm the axonal projections shown by electrophysiological methods. The CGCs project ipsilaterally into one lip nerve, the cerebrobuccal connective, and all buccal nerves. Symmetry of anatomy and of firing activity cause the CGCs to function as a single neural unit.
Control of Sound Production in the Syrinx of the Fowl Gallus Gallus
Authors: Brackenbury John 
Published: April 2021

ABSTRACT
Changes in the configuration of the fowl syrinx during experimental stimulation of the extrinsic syringeal muscles were assessed by monitoring simultaneous changes in the airway resistance at a constant airflow rate. Stimulation of the caudal part of the tracheolateralis muscle produced a change away from the sound-producing configuration. The tympanum was drawn craniad, the external tympaniform membranes were stretched and airway resistance fell as the syringeal lumen enlarged. Stimulation of the sternotrachealis muscles produced a change towards the sound-producing configuration. The tympanum was drawn caudad, the membranes relaxed and airway resistance rose due to the constriction of the syringeal lumen. Tetanic stimulation of the cranial parts of both tracheolateralis and tracheohyoideus produced a marked retraction of the larynx and rostral part of the trachea. The threshold levels of air-sac pressure and airflow rate necessary to produce sound by passive ventilation of the respiratory system were monitored. Passive sound could be abolished either by stimulating the tracheolateralis muscle or by marginally increasing the tracheal resistance, simulating glottal constriction. Results are discussed in relation to current opinions on the importance of active and passive factors during vocalization in birds. It is concluded that the involvement of the extrinsic muscles may be necessary when producing low volume sounds by relatively weak physical effort. Passive factors appear to be more important during vigorous calling, such as crowing. In the latter case the main function of the extrinsic muscles may be to ensure the retraction of the larynx and changes in shape of the anterior respiratory tract.
The Forces Exerted on the Substrate By Walking and Stationary Crickets
Authors: Harris Jack , Ghiradella Helen 
Published: April 2021

ABSTRACT
The gait and the protraction/retraction ratios (P/R ratios) for the cricket are described. They are essentially the same as for the cockroach and the grasshopper. The vertical forces exerted on the substrate by all six legs of walking and stationary crickets are measured. On the basis of the ‘forceprints’ obtained and differences in P/R ratios among the legs of different thoracic segments, it is pointed out that all segments are not functionally identical. Specifically, the greater irregularity of the forceprints of the prothoracic legs, and the lower magnitude of peak force exerted on the substrate by the prothoracic legs suggest that the prothoracic legs are more involved in balancing or searching than in propulsion. The metathoracic legs exert an increased vertical force on the substrate just before the initiation of protraction. This increase correlates with an extension of the leg apparently through extension of the femoral-tibial joint. A slight decrease in the force exerted on the substrate by the meso-thoracic legs occurs when the leg is at right angles to the body. Placing or lifting one mesothoracic leg does not affect the force exerted by the contralateral mesothoracic leg in a regular way. This argues against mechanical interactions between the legs and in favour of theories invoking central generation of pattern. At a stepping frequency of below 2 steps s−1 the shapes of the forceprints of all legs are no longer repetitive. Also, below 2 steps s−1 there is an increase in the variability of the peak force exerted on the substrate. It is possible that the animal switches to a more sensory sensitive mode below a step frequency of 2 s−1. During stationary periods the forces exerted on the substrate continue to show oscillations which may be metachronal. This suggests a mechanism whereby a central oscillatory mechanism can account for the behaviour of an animal starting to walk following such a stationary period.
The Role of Physico-Chemical Buffering and of Bicarbonate Transfer Processes in Intracellular pH Regulation in Response to Changes of Temperature in the Larger Spotted Dogfish (Scyliorhinus Stellaris)
Authors: Heisler N. , Neumann P. 
Published: April 2021

ABSTRACT
In order to evaluate the contributions of physico-chemical buffering to the adjustment of intracellular pH in response to changes of temperature in tissues of dogfish (Scyliorhinus stellaris), the CO2 equilibration method for the determination of intracellular buffer values was modified to yield data for the mathematical simulation of the intracellular compartments as closed buffer systems, and for the calculation of transmembrane bicarbonate transfer in vivo.
The respective buffer values of imidazole-like and phosphate-like buffer substances were estimated to be about 39 and 11 in white muscle, 21 and 18 in red muscle and 27 and 10 mequiv/(pH.l cell water) in heart muscle. In white muscle, the observed changes of intracellular pH can be explained by physico-chemical buffering and changes of . In red muscle and heart muscle considerable amounts of bicarbonate have additionally to be transferred across the cell membrane to achieve the temperature-dependent variations of pH observed in vivo.
Localization of Baroreceptors and Gain of the Baroreceptor-Heart Rate Reflex in the Lizard Trachydosaurus Rugosus
Authors: Berger P. J. , Evans B. K. , Smith D. G. 
Published: April 2021

ABSTRACT
The location of arterial baroreceptors was studied in unanaesthetized Trachydosaurus rugosus by inflation of strategically placed perivascular cuffs. There was no evidence for baroreceptors at the site homologous with the carotid sinus of mammals or at the site homologous with the aortic arch baroreceptors of mammals and birds. The baroreceptors of T. rugosus probably lie in the truncus arteriosus. When the sensitivity or gain of the cardiac response to changes in systemic arterial pressure was expressed as change in heart period per unit change in mean aortic blood pressure, the value for 6 animals was 1370 ms/ kPa (100 ms/mmHg). This is very much greater than reported values for rabbits. If, instead, gain was calculated as the percentage increase in heart rate per unit fall in mean aortic pressure, a mean gain of 98%/kPa (7·2%/ mmHg) was obtained. It is suggested that the latter method provides the better comparative value. Adrenergic neurone blockade with bretylium and muscarinic blockade with atropine or hyoscine indicated that sympathetic fibres probably play the dominant role in generating the gain of the cardiac baroreflex.
Microtubules and the Propagation of Bending Waves by the Archigregarine, Selenidium Fallax
Authors: Mellor J. S. , Stebbings H. 
Published: April 2021

ABSTRACT
The trophozoites of Selenidium fallax propagate bending waves at rates of up to 35 μm s−1, of a similar character to those manifested by eukaryotic cilia and flagella. A beat frequency of 0·12–0·15 Hz appears average, though rates outside this range have been recorded. Translatory locomotion at up to 6 μm s−1 has been observed. The protozoan demonstrates the presence of an active bending mechanism, probably along its entire length, and a means of coordinating adjacent bends. The Reynolds number for the motion is 10−5-10−4, suggesting that the hydrodynamic aspects of the trophozoite movement are amenable to analysis by similar means to those already employed for cilia and flagella. It is possible that the protozoans exhibit a sliding microtubule mechanism, which could be very usefully compared with that occurring in the ciliary axoneme.
The Function of Hair Sensilla on the Locust’s Leg: the Role Of tibial hairs
Authors: Pflüger Hans-Joachim 
Published: April 2021

ABSTRACT
In Schistocerca americana gregaria hairs of the simple trichoid sensillum type on the hind tibia near the tibia-tarsus joint can mediate an avoidance response during which the hind leg is lifted by flexion of several joints. The responsiveness of this reflex can be improved by partially isolating the metathoracic ganglion. In these operated animals, the response can even be elicited after stimulation of one hair.
Myograms from various muscles in the tibia, femur, coxa and thorax revealed which muscles were active during the avoidance response. The delay times between the stimulus (bending several hairs with an eyelash) and the first muscle activity are variable (median values 150–200 msec). It is concluded that the pathway is polysynaptic and situated within the metathoracic ganglion.
Repriming of Delayed Potassium Conductance in Frog Skeletal Musclex
Authors: Ballou E. W. 
Published: April 2021

ABSTRACT
A dissection of the semitendinosus muscle from Rana pipiens was developed for three-microelectrode voltage-clamp studies of the delayed potassium-selective conductance system. The delayed conductance inactivates in muscles bathed in high concentrations of potassium or rubidium, but can be reprimed by hyperpolarizing voltage pulses to membrane potentials beyond –80 mV. The repriming time-course was studied by measuring the delayed conductance that could be activated following hyperpolarizing pulses of varying duration. Responses following 20–100 s pulses to potentials between –90 and – 140 mV could not be reconciled with an exponential approach to the conductance present in normally polarized fibres. The sigmoid appearance of the early ( &lt; 25 s) time course was exaggerated by cooling from 20 to 10 °C. This effect was described by a sequential model invoking two inactivated states with different temperature dependences. An explanation is suggested for differences in the kinetics and voltage dependence of repriming between briefly and chronically depolarized muscle cells.