bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osmotic Regulation in the Green Toad (Bufo Viridis)
Authors: Gordon Malcolm S. 
Published: April 2021

ABSTRACT
The osmotic and ionic regulatory abilities of adults of a freshwater population of the green toad (Bufo viridis) have been studied. These toads tolerated environmental salinities as high as 19%,, at temperatures near 25°C. Two individuals of another population of this species tolerated salinities as high as 23 ‰. Changes in body weight of toads transferred to different environmental salinities indicate that the skin of this form is permeable to water. Rapid return to control levels of body weight indicate that drinking of external medium may be an important part of the initial adjustment to high salinities. Above salinities of about 8%0 plasma Δ rises with increasing environmental Δ. Marked hypertonicity of the plasma is maintained in low salinities, but isotonicity with the medium is approached in higher salinities. Increases in plasma concentration above freshwater levels are due primarily to increased NaCl concentration (about 84%), partly to increased concentrations of urea (5–10%) and other osmotically active substances. Urinary Δ is much lower than plasma Δ in dilute media, but becomes identical with plasma Δ above salinities of about 15 ‰. Increases in urine concentration above freshwater levels are also due primarily to NaCl increase (74%). Considerable quantities of salt are lost via the urine. The kidneys seem to lose much of their ability to regulate urinary salt concentrations in high-salinity media. Measurements of electrical potential and short-circuit current indicate that active uptake of inorganic ions by the skin continues in concentrated media, but at reduced rates. Changes in muscle water, Na and K contents indicate the occurrence of some redistribution of water and salts between various body-fluid compartments as part of the salinity adaptation process. In preference experiments, B. viridis chooses the land over any aquatic environment. Among aquatic environments it prefers those with salinities below 8‰. When combined with some earlier data by other workers who studied other populations of B. viridis, the present data indicate great uniformity of ionic and osmotic regulatory abilities among populations of this species. The marked differences between salinity tolerances of different populations are indicated to be due to differences in tissue tolerance of high body-fluid salinities.
Force Exerted by a Single Cilium of Mytilus Edulis
Authors: Yoneda Mitsuki 
Published: April 2021

ABSTRACT
A cilium can be stopped by applying the tip of a glass microneedle during the effective stroke. The force required to stop the cilium has been measured by the author by the displacement of a flexible needle on the basis of its compliance. This force was expressed in terms of a torque, at the base of the cilium, which was 4× 10−7 dyne. cm. The second step would be to know the magnitude of the torque when the cilium is beating freely without constraint. Such a study would require a hydrodynamical treatment, as was given in the case of swimming spermatozoa (Taylor, 1951, 1952; Hancock, 1953; Gray & Hancock, 1955; Machin, 1958; Carlson, 1959).
Proprioceptive Control of Posture in the Crayfish Abdomen*
Authors: Fields Howard L. 
Published: April 2021

ABSTRACT
Sense organs responsive to the changes produced by an animal’s own musculature are common in complex, flexible motor systems, and it is probably safe to assume that proprioceptive feedback is required for these systems to operate with precision. The crustacean muscle receptor organ (MRO) first described by Alexandrowicz (1951) has, because of its accessibility, ease of isolation and hardiness, proven particularly amenable to electrophysiological study. However, the study of this receptor has until recently been confined to mechanisms of transduction and to the excitatory and inhibitory control of its output.
The Motion of Euglena Viridis: The Role of Flagella
Authors: Holwill M. E. J. 
Published: April 2021

ABSTRACT
Analysis of high-speed cine-films of Euglena viridis reveal that the organism traverses a complex three-dimensional path while helical waves are propagated from base to tip along the flagellum. Theoretical analysis shows that the rapid forward velocity of the organism cannot be produced by the body movement alone. The propulsive force generated by the flagellum is sufficient to maintain the observed velocities. Although the euglenoid flagellum bears mastigonemes the thrust produced by it is in the direction to be expected if the flagellum were smooth. Possible explanations of this observation are given.
Gradients in the Insect Segment: The Orientation of Hairs in the Milkweed Bug Oncopeltus Fasciatus
Authors: Lawrence Peter A. 
Published: April 2021

ABSTRACT
During metamorphosis in Oncopeltus the hair-forming cells orient to some unseen influence in the epidermis. The hairs can thus be used as indicators of the polarity of this influence. Excision of the intersegmental membrane can cause a total inversion of the direction of hair outgrowth in the nearby region. Individual insects, each with a large gap in the intersegmental membrane and an associated pattern of hairs which are unusually oriented, occur occasionally in the culture. A study of these defects, and of Locke’s observations on the segmental gradient of Rhodnius, leads to the development of a sand model which can be applied not only to the experiments of Locke on the ripple pattern of Rhodnius, but also to those of Piepho on the orientation of scales in Galleria. The sand model helps in a description of the hypothetical chemical basis of the gradient in the insect segment. The relationship between the gradient and pattern is briefly discussed.
Sodium Regulation in the Amphipod Gammarus Duebeni from Brackish-Water and Fresh-Water Localities in Britain
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
A quantitative study of sodium influx and loss rates was made on Gammarus duebeni obtained from brackish-water localities. Both influx and loss rates were immediately doubled by a rise in temperature from 10 to 20 ° C. It is estimated that when animals are fully acclimatized to a series of media decreasing from 50 to 2 % sea water the rate of sodium uptake at the body surface is doubled to balance the rate of sodium loss, which is also doubled. The increased loss rate is due equally to an increase in the rate of diffusion across the body surface and to loss in hypotonic urine containing about 160 − 190 mM/1. sodium. Diffusion losses normally account for at least 35 % of the total losses, even when the urine is isotonic with the blood. The sodium-transporting system at the body surface is fully saturated at an external concentration of about 10 mM/1. NaCl (2% sea water). The system has a low affinity for sodium ions and is only half-saturated at 1·5 − 2·5 mM/1. sodium. The overall rate of uptake is increased to its maximum rate to balance sodium losses when in fresh water. When acclimatized to fresh water (0·25 mM/1. NaCl) the sodium loss rate is greatly reduced. This was partly due to a lower rate of diffusion across the body surface following a fall in the blood sodium concentration, and mainly due to elaboration of a very dilute urine. It is suggested that increases in sodium uptake in the antennary glands, resulting in a hypotonic urine, are linked with increases in uptake at the body surface. Both uptake systems are possibly activated by a single internal regulator responding to changes in the blood concentration. Sodium regulation at concentrations below 10 mM/1. NaCl was examined in G. duebeni obtained from fresh-water streams on the Lizard peninsula, the Kintyre peninsula, and the Isle of Man. The regulation of sodium uptake and loss is very similar to regulation in brackish-water animals, and the sodium-transporting system has the same low affinity for sodium ions at concentrations below about 10 mM/1. It is suggested that fresh-water localities in north-west Europe, excluding Ireland, have been colonized from brackish water without any modifications in the sodium-regulatory mechanism. But the fresh-water animals tolerate very low sodium concentrations better than brackish-water animals. This is apparently due to natural selection of individuals in which the sodium uptake rate is higher than the average uptake rate in brackish-water animals.
Case Construction, Movement, Spatial Distribution and Substrate Selection in the Larva of Chironomus Riparius Meigen
Authors: Edgar W. D. , Meadows P. S. 
Published: April 2021

ABSTRACT
Larvae of Chironomus riparius construct their cases from algae in a stereotyped manner. Mud and a mixture of mud and algae can be used instead of algae, although not so successfully. Larvae cannot build cases from sand, and when presented with this substrate they alternate periods of active swimming with resting on the substrate. This is reminiscent of the behaviour of marine larvae as they test substrates before settling. Larvae space out on an algal substrate. Nearest-neighbour analysis has been used to quantify spacing out, and has shown that under experimental conditions initially clumped animals become regularly distributed over a period of time. As larvae age, they move more slowly and are also less likely to move. In substrate-choice experiments larvae prefer an algal to a sand/gravel substrate. Substrate selection is less marked in old larvae. This could be due either to a loss of ability to discriminate between substrates with age, or to a reduction in the rate of movement with age.
Burst Activity and Cellular Interaction in the Pacemaker Ganglion of the Lobster Heart
Authors: Connor John A. 
Published: April 2021

ABSTRACT
The patterned burst activity of cardiac pacemaker ganglion cells in Homarus americanus has been studied by means of intracellular recording electrodes. Burst activity, highly similar to that seen in cells of intact ganglia, has been demonstrated in ganglion sections containing as few as two large-cell bodies. Studies of the sectioned preparations have shown that potential deflexions during the burst period are mainly endogenous activity of the respective cells and not post-synaptic potentials. The behaviour of the cells in the period between bursts suggests the action of an inhibitory conductance change in each of the cells during this period.
Water Uptake and Embryonic Development in Eggs of Chorthippus Brunneus Thunberg (Saltatoria: Acrididae)
Authors: Moriarty F. 
Published: April 2021

ABSTRACT
The pattern of water absorption by eggs of Chorthippus brunneus varies greatly between individuals. The time at which water is absorbed does not have a close relationship with the stage of embryonic development. Water absorption is not essential for prediapause development. Eggs can only undergo blastokinesis and further development, after diapause is broken, if some water has been absorbed. The rate of water loss or gain varies with the osmotic pressure of sodium chloride solutions. Eggs which have started to absorb water appear to become desiccated more rapidly than eggs which have not.
Locust Wind Receptors
Authors: Camhi Jeffrey M. 
Published: April 2021

ABSTRACT
The cervical connective of the desert locust contains interneurones giving responses of four different types to wind stimulation of the facial wind receptor setae. The four categories are : (a) ‘Wind-indicator cells’, giving a slowly adapting response to wind from any of a wide range of directions. (b) ‘Wind-direction cells’, displaying fairly slowly adapting responses, and sensitive to wind only within a very narrow range of directions. Pivoting wind into a cell’s optimal direction evokes a full response. (c) ‘Recentre cells’, showing rapidly adapting responses to wind onset from a fairly wide directional range. Rapidly shifting the wind direction from only one preferred side into the centre evokes a vigorous burst. (d) ‘Acceleration cells’, giving a rapidly adapting response which is especially pronounced for rapid wind accelerations. Interneurones connect with several sensory setae, whose spatial distribution and angles of curvature are unique to each interneurone type. A suggested integrative mechanism relates the angles of curvature of the input setae to the direction response of each interneurone type. The responses suggest roles for certain interneurone categories in flight maintenance and yaw-correcting reflexes.
Membrane Properties of the Somatic Muscle (Obliquely Striated Muscle) of the Earthworm
Authors: Hidaka T. , Ito Y. , Kuriyama H. 
Published: April 2021

ABSTRACT
The membrane properties of the longitudinal muscle fibre of the earthworm Pheretima communissima were investigated by intra- and extracellular stimulating methods. The membrane potential was − 35·4 mV., and spontaneous discharges with overshoot (mean +18 mV.) and after-hyperpolarization (− 60 mV.) were recorded. Tetrodotoxin (10−7 g./ml.) blocked nervous activity but did not influence the spontaneous discharges or the spikes elicited in the muscle fibre by intracellular stimulation. The critical membrane potential required to elicit a spike was not constant, and the falling phase of the spikes was markedly dependent on the level of the membrane potential. The chronaxie, measured from the intensity-duration relation to elicit a spike by intracellular stimulation, was 55 msec. When nervous activity was excluded the propagation of excitation in longitudinal muscles was decremental.
Neuromuscular Transmission in the Longitudinal Layer of Somatic Muscle in the Earthworm
Authors: Hidaka T. , Ito Y. , Kuriyama H. , Tashiro N. 
Published: April 2021

ABSTRACT
The properties of the miniature inhibitory junction potentials (M.I.J.P.) and the inhibitory junction potentials (I.J.P.) elicited by nerve stimulation were investigated in longitudinal muscle fibres of the earthworm. Histograms of the amplitudes (mean, 0·71 mV.) and the intervals (mean, 101 msec.) of the M.I.J.P. showed skew curves. The polarity of the M.I.J.P. was reversed at about —60 mV. When the external chloride was substituted by glutamate the M.I.J.P. disappeared as an external chloride concentration of 15-20 mM, and further reduction reversed their polarity. Picrotoxin blocked generation of the M.I.J.P. and the I.J.P. The cross-over point of the current-voltage relation curves, with and without presence of GABA, occurred at a membrane potential of − 54 mV. in potassium-free solution, and at − 56 mV. in potassium-excess solution. Iontophoretic application of GABA produced slow hyperpolarization. The equilibrium potential of the GABA-potential was about − 60 mV. During the time course of the GABA-potentials an increase in the membrane conductance was observed. Miniature excitatory junction potentials (M.E.J.P.) and excitatory junction potentials (E.J.P.) could be recorded from the longitudinal muscle, but the M.E.J.P. were rare. D-tubocurarine, but not atropine, completely blocked the M.E.J.P. and E.J.P. Prostigmine enhanced their amplitude and duration. The reversal potential level for the E.J.P. was about o mV. Sodium-free solution lowered the reversal potential level for the M.EJ.P. to −20 mV.
The Mechanical Properties of the Longitudinal Muscle in the Earthworm
Authors: Hidaka T. , Kuriyama H. , Yamamoto T. 
Published: April 2021

ABSTRACT
A study of the mechanical properties of longitudinal muscle in relation to the membrane properties was carried out under isometric conditions. When the stimulus duration exceeded 50 msec., active tension development was followed by sustained contraction. The sustained contractions were not related to spike generation. The critical potassium concentration to produce the contracture depolarized the membrane from –36 to –20 mV. Reduced sodium concentration and increased calcium and increased potassium (up to 27 mM) concentrations enhanced the amplitude of the active tension. Reduced sodium concentration enhanced the amplitude and duration of the sustained tension, but increased potassium and calcium concentrations reduced them. Caffeine (12 mM) induced contractures of the muscle, and reduced the membrane resistance and capacitance. Spikes were not elicited by intracellular stimulation. 5-Hydroxytryptamine (10−6 g./ml.) blocked the generation of the sustained contraction but no effect was observed on the phasic tension.
Common Inhibitory Motoneurones in Insects
Authors: Pearson K. G. , Bergman S. J. 
Published: April 2021

ABSTRACT
The innervation patterns of the metathoracic posterior coxal levator muscles of the cockroach, Periplaneta americana, have been investigated, and the mechanical effects produced by activity in the axons to these muscles studied. These muscles are innervated by four excitatory and two inhibitory axons. The three smallest excitatory axons may be classified as slow and the largest as fast. Some single muscle fibres are quintuply innervated by all but the fast axon, and some may be innervated by all six. One of the inhibitory axons is a branch of a common inhibitory neurone. This neurone sends branches out all but one of the ipsilateral nerve trunks to innervate synergic and antagonistic muscles. A similar common inhibitory motoneurone has been found in both the locust species, Locusta migratoria and Schistocerca gregaria. In the locust two branches of this common inhibitory neurone correspond to the inhibitory axon innervating the extensor tibiae muscle and the inhibitory-conditioning axon innervating the anterior coxal adductor muscle. Possible functions of common inhibitory neurones in insects are discussed. In the cockroach this neurone may have a dual function: (a) to regulate leg position when the animal is standing, and (b) to facilitate relaxation of the depressor muscles; this allows a more rapid and stronger leg levation when the animal is walking.
Salt and Water Regulation in the Embryos of Freshwater Pulmonate Molluscs
Authors: Beadle L. C. 
Published: April 2021

ABSTRACT
The envelope and capsular membranes which separate the eggs from the external water are freely permeable to water and inorganic ions. The capsular membrane of B. sudanica is permeable to sucrose (M.W. 342) but not to raffinose (M.W. 504), that of L. stagnalis is permeable to raffinose but not to Carbowax (polyethylene glycol, M.W. 3000 – 3300). By means of 22Na it was shown that, as expected, the concentration of sodium in the capsular fluid of B. sudanica is approximately equal to that in the external water. The initial colloid osmotic pressure of the capsular fluid of B. sudanica is equivalent to that of approximately 1·5 mM/1. solution of non-electrolyte and of L. stagnate to that of 4 – 5 mM/1. Observations on embryos of B. sudanica extracted from the capsular fluid and kept in lake water support the contention that, at least from late cleavage stages onwards, they are capable of active salt and water regulation.
Salt and Water Regulation in the Embryos of Freshwater Pulmonate Molluscs
Authors: Beadle L. C. , Beadle S. F. 
Published: April 2021

ABSTRACT
By means of 22Na it is shown that the embryo takes up sodium from the water via the capsular fluid so that its sodium content is increased more than seven times between the blastula and hatching. Experiments with water of low sodium content (Text-fig. 3): (a) suggest that sodium is taken up by the preblastula embryo, and (A) demonstrate that the embryo can develop with a sodium content less than one-seventh of the normal. Embryos at blastula or even cleavage stages, when deprived of access to external water and ions by mounting over paraffin, can still accomplish the greater part of their development, thus confirming the conclusion 2(b). These experiments also suggest other ions than sodium can be considerably reduced without harm to the embryo. There is evidence, however, that the ecologically inhibiting effect of very low salinity water is due to the low level of ions other than sodium. Reduction of dissolved oxygen to o· 1-0· 2 mg./l. for 12 hr. completely inhibits sodium uptake and visible development. These are both reversible but, though the normal rate of development is resumed at once, the rate of sodium uptake is not restored for several days after re-aeration. The ultimate effect of this treatment on some, but not all, embryos is an upset of water balance shown by swelling and the suppression of the final stages of development.
Salt and Water Regulation in the Embryos of Freshwater Pulmonate Molluscs
Authors: Beadle L. C. 
Published: April 2021

ABSTRACT
Subjection of 2-cell stages, later cleavage stages and blastulae of Biomphalaria sudanica to anoxia, 1 MM/1. cyanide and a temperature of about 7° C. causes a great swelling of the cleavage cavity and blastocoel. This effect is reversible if the treatment is not too prolonged. Such temporary treatment at early stages has no apparent permanent effect on many of the embryos, but in some the water-regulating mechanism breaks down again at a later stage (postgastrula). The subject may become enormously distended by swelling of the body cavity, and development is halted. Swelling in both (1) and (2) is apparently confined to the extracellular cavities, the cells remaining intact and not obviously swollen. The older embryos subject to delayed swelling (2) can remain in this condition for many days after control embryos from the same mass have hatched. Experiments with MNa on a delayed swollen embryo suggested that, though water control was seriously impaired, the mechanism for the uptake of sodium into the body cavity was still functioning. The possible significance of these observations in relation to the mechanism for fluid control in the normal embryo is discussed. Many problems remain unsolved and suggestions are made for further work.
Organization of the Giant Axons of the Cockroach Periplaneta Americana
Authors: Spira M. E. , Parnas I. , Bergmann F. 
Published: April 2021

ABSTRACT
Stimulation of the connectives between the suboesophageal and prothoracic ganglia of the American cockroach induced ipsilateral descending spikes in the abdominal giant axons with an average delay of 0·6 msec, per thoracic ganglion. Nicotine at 5 μ g./ml. had no effect on conduction in the abdomen but blocked ascending responses sequentially at the 6th abdominal ganglion then at the levels of T1; T2, and T3. Simultaneous descending and ascending impulses resulted in mutual extinction along the nerve cord with the point of collision depending on the interval between stimuli. It is suggested that a common pathway subserves ascending and descending giant impulses and models for bi-directional conduction are discussed.
Studies on the Permeability To Water Of Selected Marine, Freshwater And Euryhaline Teleosts
Authors: Evans David H. 
Published: April 2021

ABSTRACT
Measurements were made of the flux of tritiated water across various marine, freshwater and euryhaline teleosts. The effects of temperature, body size, species differences, salinity, stress and anaesthetization were studied. The Q10 of the flux of water across teleosts is approximately 1·90 and the flux is related to the o-88 power of the body weight. All of the freshwater species studied were more permeable to water than the marine species. Euryhaline teleosts appear to have about the same permeability as species to which they are most closely related. While the flounder and the yellow eel are more permeable to water in fresh water than in sea water, the silver eel and the brown trout do not change their permeability and the 3-spined stickleback is less permeable to water in fresh water than in sea water. While stress markedly increases the permeability to water of large brown trout, it has no effect on small brown trout and seems to decrease the water permeability of the plaice. Anaesthetization has no effect on the water permeability of the goldfish but markedly increases the permeability to water of the silver eel. The relationship between the flux of water and either the drinking rate in sea water or the urine flow in fresh water is discussed.