bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature-Related Changes in the Erythrocytic Carbonic Anhydrase (Acetazolamide-Sensitive Esterase) Activity of Goldfish, Carassius Auratus*
Authors: Houston Arthur H. , Mearow Karen M. 
Published: April 2021

ABSTRACT
Carbonic anhydrase activity in ‘membrane ‘and’ cytosol ‘fractions of goldfish erythrocytes was assayed by the p-nitrophenyl acetate procedure following thermal acclimation. The thermal sensitivity of ‘membrane’-associated activity was apparently unaltered by acclimation. ‘Cytosol’ activity in warm-accfimated specimens was somewhat more thermosensitive than that of animals maintained at low temperature. Significant increases in specific activity, and activity per unit volume of packed cells and blood were observed at higher temperatures when assays were conducted at the temperatures at which the system actually functions in the fish. By contrast, when determinations were carried out at a standard temperature (41°C) corresponding to the upper incipient lethal for this species, activity was either unaffected, or declined as acclimation temperatures increased. Changes in carbonic anhydrase activity following acclimation are consistent with the hypothesis that this system is implicated in the maintenance of stable plasma chloride levels, and the suggestion that alterations in red cell chloride levels with temperature are, in part at least, attributable to concomitant variations in enzyme activity.
The Effects of Acclimation Temperature on A Neuromuscular System of the Crayfish, Astacus Leptodactylus
Authors: Harri Mikko , Florey Ernst 
Published: April 2021

ABSTRACT
Crayfish, Astacus leptodactylus, were acclimated to 12°C and to 25°C. Nerve muscle preparations (closer muscle of walking legs) were subjected to temperatures ranging from 6 to 32°C. The resting membrane potential of muscle fibres was found to increase with temperature in a linear manner, but with a change in slope at around 17° in cold-acclimated preparations, and around 24°C in warm-acclimated ones. Temperature acclimation shifted the temperature range of maximal amplitudes of fast and slow e.j.p.s toward the acclimation temperature. Optimal facilitation of slow e.j.p.s also occurred near the respective acclimation temperature. E.j.p. decay time is nearly independent of temperature in the upper temperature range but increases steeply when the temperature falls below a critical range around 17°C in preparations from cold-acclimated animals, and around 22°C after acclimation to 25°C. Peak depolarizations reached by summating facilitated e.j.p.s are conspicuously independent of temperature over a wide range (slow and fast e.j.p.s of cold-acclimated preparations, fast e.j.p.s of warm-acclimated ones) which extends to higher temperatures after warm acclimation in the case of fast e.j.p.s. In warm-acclimated preparations the peak depolarization of slow e.j.p.s first falls then rises and falls again as the temperature increases from 8 to 32°C. Tension development elicited by stimulation of the slow axon at a given frequency reaches maximal values at the lower end of the temperature range in cold-acclimated preparations. The maximum is shifted towards 20°C after warm acclimation. Fast contractions decline with temperature; possible acclimation effects are masked by the great lability of fast contractions in warm-acclimated preparations. It is suggested that changes in the composition of membrane lipids may be responsible for the effects of acclimation on the electrical parameters and their characteristic temperature dependence.
Block Intensification of Neurones Stained with Cobalt Sulphide: A Method for Destaining and Enhanced Contrast
Authors: Pitman Robert M. 
Published: April 2021

ABSTRACT
In characterizing neurones it is important to have both physiological and morphological information. This was first realized in a practical sense by Stretton & Kravitz (1968), who explored the use of the Procion series of dyes and used them to study the morphology of identified lobster neurones. Initially, Procion dyes were injected into single neurones using microelectrodes. However, it was later found that Procion Yellow could be introduced into the cut end of axons (Iles & Mulloney, 1971). This made it possible both to stain small neurones which would be hard to impale with microelectrodes, and also to determine rapidly the position of the cell bodies of neurones with axons in a given nerve trunk. Subsequently, it was found that neurones could be stained by introduction of cobalt ions followed by the formation of a black precipitate of cobalt sulphide (Pitman, Tweedle & Cohen, 1972). This method had the advantage that intact neurones could be observed in whole-mount preparations. A great improvement on the resolution of the cobalt sulphide method was obtained using a modification of the Timm ‘s sulphide-silver intensification procedure (Tyrer & Bell, 1974). This made it possible to visualize fine branches of neurones which were too lightly stained to be seen using the original cobalt sulphide method. It is also relatively permanent, whereas unintensified preparations often fade. However, a disadvantage of this modification was that it required sectioning of the tissue before intensification. More recently, block intensification methods have been described (Strausfeld & Obermayer, 1976; Bacon & Altman, 1977). These permit whole-mount viewing of entire neurones with intensely stained fine processes.
Size-Dependent Variation in the Evasive Behaviour of the Bivalve Mollusc Spisula Solidissima
Authors: Prior David J. , Schneiderman Anne M. , Greene Sharon I. 
Published: April 2021

ABSTRACT
The evasive jump response of Spisula can be elicited by contact of the siphons with the tube feet of a starfish (Asterias forbesi). The level of responsiveness varies with the size of the individual clam; small clams (2·0–5·0 cm) being very responsive, large clams (12·0–18·0 cm) being totally unresponsive. The cell bodies of touch-sensitive neurones subserving the siphons are located in the visceral ganglion. The mean area of the receptive fields of these neurones in small clams is 33·8 mm2 and in large clams is 9·7 mm2. In small clams the large proportion of the total siphon surface innervated by single touch-sensitive neurones results in considerable overlap of receptive fields. As a result of this overlap, numerous touch-sensitive neurones are activated by a point stimulus. The variation in jump responsiveness of large and small clams is correlated with the size of the receptive fields of touch-sensitive neurones.
Crayfish Escape Behaviour: Commands for Fast Movement Inhibit Postural Tone and Reflexes, and Prevent Habituation of Slow Reflexes
Authors: Kuwada John Y. , Wine Jeffrey J. 
Published: April 2021

ABSTRACT
Organized behaviour requires central neural mechanisms to prevent the simultaneous occurrence of incompatible movements. We investigated neural pathways in crayfish that suppress slow flexion of the abdomen during rapid flexions (‘tailflips’) produced by a separate set of muscles. The slow flexors are innervated in each half segment of the abdomen by five motor neurones and one peripheral inhibitor. In isolated preparations of the abdominal nervous system, stimulation of identified command neurones, which trigger tailflips in intact animals, inhibited spontaneous activity in the motor neurones to the slow flexors and excited the peripheral inhibitor. These effects are mediated by a population of interganglionic interneurones interposed between the command cells and the slow flexor efferents.
Slow flexor reflexes also were inhibited by escape commands. This inhibition includes pathways that act upon early stages of sensory input. As a result, habituation of reflexes, which normally is produced by repeated stimulation, is abolished if each sensory stimulus is preceded by a burst of impulses in the command neurone.
Photobiology of the Chloroplast Hosting Mollusc Elysia Timida (Opisthobranchia)
Authors: Rahat M. , Monselise Edna Ben-Izhak 
Published: April 2021

ABSTRACT
Photoreactive behaviour of Elysia timida was examined with regard to the posture of its parapodia, covering or exposing its symbiotic chloroplasts. In the dark, the parapodia are held dorsally close together, but they open and spread out in light, at 3 × 103 to 3 × 105 ergs. cm−2. s−1. At higher light intensities (up to 6×105 ergs. cm−2. s−1) the parapodia close up again. This behaviour is identical in normal and eyeless individuals. At a wavelength of 540 nm, the slugs open their parapodia as above, but the eyeless E. timida will not close their parapodia at the higher light intensities at this wavelength. At 445 and 650 nm, no photoreaction is observed.
It is postulated that E. timida has three photoreceptor systems. (1) An extraocular photoreceptor that differentiates between light and dark, which causes, respectively, opening or closing of parapodia. (2) The eyes, which can differentiate between optimal and above optimal light intensities (the latter causing closure of the parapodia). These photoreceptors perceive light at 540 nm, and could thus contain carotenoid photoreactive pigments. (3) An extraocular photoreceptor, which, like the eyes, can differentiate above optimal light intensities and cause parapodial closure, but only in ‘white’ light. An interaction of the first two photoreceptors could be an alternative for the function of the latter.
The form or location of the extraocular photoreceptors is unknown. It is proposed that although the symbiosis of algal chloroplasts and E. timida might be of recent evolution, this symbiosis has already affected the behaviour of the slug.
The Integration of the Patterned Output of Buccal Motoneurones During Feeding in Tritonia Hombergi
Authors: Bulloch A. G. M. , Dorsett D. A. 
Published: April 2021

ABSTRACT
Three phases of activity may be recognized in the buccal mass of Tritonia hombergi during the feeding cycle. These have been termed Protraction, Retraction and Flattening. Each phase is driven by a group of motoneurones along the posterior border of the buccal ganglia. The patterned bursting observed in the motoneurone groups during feeding activity is phased by synaptic inputs which are common to two or more groups. Evidence is presented which indicates these inputs are derived from three unidentified multi-action interneurone sources within each buccal ganglion, and whose action primarily determines the patterned output of the motoneurones. Electrical coupling between between synergistic motoneurones and, in one case, post-inhibitory rebound, contribute to the synchronization of group activity. Proprioceptive input to the motoneurones was not identified, but may project to the interneurones.
Some small neurones having synaptic inputs on the motoneurones appropriate to two of the interneurones were found, but require confirmation in this role. The cerebral giant cells synapse on representatives of three motoneurone groups, and also activate the buccal interneurones driving the feeding cycle. The patterned activity of the motoneurones can occur in the absence of cerebral cell activity.
Direct Measurements of the Stiffness of Echinoderm Sperm Flagella
Authors: Okuno Makoto , Hiramoto Yukio 
Published: April 2021

ABSTRACT
The stiffness (flexural rigidity) of some echinoderm sperm flagella was measured, using a flexible glass microneedle. Values of 0·3–1·5 × 10− 21 N m2 were obtained for the stiffness of live flagella which were immobilized with CO2-saturated sea water. The immobilized live flagellum was uniform in stiffness along its entire length, except in a particular plane of imposed bending in which flexible regions were observed. Demembranated flagella (Hemicentrotus pulcherrimus) in an ATP-free solution were about ten times stiffer (1·1 × 10− 20 N m2) than immobilized live ones (0·5–0·9 × 10− 21 N m2). The stiffness was decreased by addition of ATP to the solution and became equivalent to that of live ones when the solution contained 10 mm ATP. In the demembranated flagella, the effects of ADP and ATP on the stiffness were similar. Other nucleotide phosphates and inorganic phosphate did not reduce the stiffness. Young’s modulus of microtubules is estimated to be 2–5 × 10− Nm2 on the basis that the microtubules have no tight connexion with one another in immobilized live flagella.
Do Frogs Drink?
Authors: Bentley P. J. , Yorio T. 
Published: April 2021

ABSTRACT
Drinking in response to dehydration and exposure to saline solutions was measured in adult Rana pipiens, Bufo marinus and Xenopus laevis, and tadpoles of Rana catesbeiana. These animals normally occupy quite different types of environments where the possible advantages of drinking may differ. Small amounts of the external media were swallowed by all the animals and the quantity usually increased when they were placed in hyperosmotic NaCl solution. However, no relationship between the oral intake of water and the particular conditions, such as the degree of dehydration, was observed. Usually 80–90% of the total water uptake occurred by absorption across the skin. Thus although ‘secondary’ type drinking takes place, ‘primary’ drinking did not appear to occur. These results directly confirm the general popular impression that amphibians, in contrast to other tetrapods and marine teleosts, do not drink in order to rehydrate.
An Analysis of Acid-Base Disturbances in the Haemolymph Following Strenuous Activity in the Dungeness Crab, Cancer Magister
Authors: McDonald D. G. , McMahon B. R. , Wood C. M. 
Published: April 2021

ABSTRACT
Enforced activity causes a marked depression of haemolymph pH in Cancer magister. Both lactate concentration and PCO2 of the haemolymph are elevated immediately following exercise but resting PCO2 is restored within 30 min whereas resting lactate levels are not restored for at least 8 h. The haemolymph acid-base disturbance is caused largely by elevated haemolymph lactate levels but a Davenport analysis based on measurements of pH and total CO2 reveals a marked discrepancy between the amount of metabolic acid buffered by the haemolymph and the lactate anion concentration. This appears due to a more rapid release of lactate from the tissues than H+ ions produced with lactate.
Reactions of the spiny lobster Palinurus Vulgaris to substrate tilt
Authors: Neil Douglas M. , Schöne Hermann 
Published: April 2021

ABSTRACT
The input-output properties of the eyestalk responses of Palmurus vul­garis to substrate tilt are described in both the time and frequency domains. Trapezoidal substrate movements elicit phaso-tonic eyestalk move­ments which decay from the phasic peak to the tonic plateau with time constants of 9-2 s (tilt) and 6⋅ι s (return) (Fig. 1). Average eye excursions for tilt and return are equivalent (Fig. 2). The relationship to tilt amplitude is non-linear (Fig. 3), and with step­wise tilts in opposite directions a marked hysteresis is evident (Fig. 4). Sinusoidal stimuli produce consistent eyestalk responses (Fig. 5), and a frequency analysis reveals a high gain, phase-leading region below 0-25 Hz (Fig. 6). Around this frequency the eyestalk response is effectively a compensation with respect to both amplitude and phase position. The results are considered in relation both to the experimental arrange­ment with fixed body and vision excluded, and to the normal biological situation.
Iodine Compounds and Fertilisation
Authors: Carter G. S. 
Published: April 2021

ABSTRACT
In a previous paper (Carter, 1930) it was shown that the presence of thyroxine produces effects upon the oxygen consumption of suspensions of the spermatozoa of Echinus miliaris which are in some respects similar to those produced by the secretions of the eggs of the same species. It was suggested that the secretions contain a body which has similar physiological action to thyroxine, and may be related to it in chemical structure.
The observations to be recorded in the present paper form a part of an investigation undertaken with the object of comparing the action of these substances on the phenomena of fertilisation more widely. In this paper the results of further experiments on the oxygen consumption of suspensions of spermatozoa are given. Other aspects of fertilisation will be considered in later papers. Although it is clear that such an investigation should not be confined to the gametes of one species or of one group of animals, it is also clear that the study of each species should be as complete as possible. For this reason the present paper is confined to two species of Echinus, E. esculentus and E. miliaris, the spermatozoa of which behave very differently. The experiments discussed in the previous paper were concerned with the second of these two species, and the results on that species here given are intended to extend those given in that paper.
Latitude and Relative Growth in the Razor Clam, Siliqua Patula1
Authors: Weymouth F. W. , McMILLIN H. C. , Rich Willis H. 
Published: April 2021

ABSTRACT
The present paper is a study of the growth of a clam (Siliqua patula) under natural conditions and over a wide range of latitude. Various constants derived from the growth data are compared for the different localities. For this species, over the range considered, growth in the southern localities as compared with the northern is initially more rapid but less sustained, leads to a smaller total length and is associated with a shorter life span. Reasons are presented for considering the relative growth-rate as a particularly significant constant leading to more sound biological conclusions than the use of the absolute growth-rate. On the basis of the relative growth-rate, current mathematical expressions for the course of growth are discussed and a formula used which emphasises Minot’s conception of a growth-rate constantly declining with age.
This expression in which L = length at time t, e = base of natural logarithms, and B, c and k are constants, is found to graduate the extensive data in clam growth with significant accuracy.
The Thermal Death-Point of Rhodnius (Rhynchota, Heteroptera) Under Controlled Conditions of Humidity
Authors: Buxton P. A. 
Published: April 2021

ABSTRACT
It has been felt for some time that the relations between insects and atmospheric humidity must often be responsible for determining the places and seasons at which particular species can exist, or be abundant. But it is not easy to devise experimental methods of testing this view, and investigating the water balance of an insect. One way of approaching the problem is explored in the present paper. I have set myself to delimit the precise conditions of temperature and humidity which are fatal to a particular insect: I hope to discover whether evaporation into dry air cools the insect and so allows it to survive higher air temperatures than it can in moist air; or whether evaporation kills the insect by causing undue loss of water; or whether the humidity of the air has little effect on the insect, even at temperatures which are nearly fatal. A serious objection to the method is that it is so laborious; allowing for preliminary work with imperfect apparatus, and for experiments with an exposure of 5 minutes which are not reported in full, I have performed over 200 experiments, using ten insects in each; as the rate of reproduction of Rhodnius (Buxton, 1930) is not very high, the work has occupied a part of my time for three years.
The Distribution of the Insoluble Nitrogen in Beta Leaves of Different Ages
Authors: Pearsall W. H. 
Published: April 2021

ABSTRACT
The distribution of nitrogen in the proteins of Beta leaves of widely varying ages has been examined. The basic N fraction is relatively abundant in the youngest stages of leaf growth, but shows no significant variations in leaves of full size. The amide N fraction rises very suddenly at the beginning of the photosynthetic stage. Its subsequent decrease has been confirmed. Possible explanations of these changes are examined.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Smith Michael 
Published: April 2021

ABSTRACT
The infertile egg shows no measurable consumption of oxygen.
Carbon dioxide is liberated from it at a rate which rapidly falls off from the time the egg is laid, and which varies with the temperature at which the egg is kept.
There is still an appreciable output of carbon dioxide (from 0.1 to 0.2 mg. per day per egg) from eggs kept for 100 days at 10°C.
The total amount of carbon dioxide obtained from a fresh egg (about 50 c.c.) appears too great to be accounted for on a basis of simple de-solution from the egg contents; in all probability some of it is actually generated during the storage of the egg, perhaps by the action of an acidic substance on the calcium carbonate of the shell.
There is no evidence from gas exchange for the existence of a respiratory activity, in the infertile egg, which might supply energy for maintaining an osmotic disequilibrium between yolk and white.
Influx Theory and Size of Potassium and Rubidium Pools in the Midgut of Hyalophora Cecropia
Authors: Wood John L. , Harvey William R. 
Published: April 2021

ABSTRACT
The midgut contains a ‘pool’ which must mix with tracer added to the blood-side, before the transported potassium reaches a steady specific activity. The size and mixing time of the pool can be deduced from the timecourse of rate of appearance of tracer on the lumen-side, the tracer influx. The theory has been extended to cover cases where the pool-size and the transport rate vary with time. By using 42K and 86Rb together, it is shown that the midgut treats potassium and rubidium differently, rubidium being transported nine-tenths as fast as potassium, when both are present in equal concentration. The influx pool for potassium is one-third larger than that for rubidium, but mixes four-fifths as fast with blood-side tracer. The size of the potassium pool decreases with time, but that for rubidium does not, and the ratios of mixing times and transport rates are constant. The implications of the results are discussed, both in terms of the accuracy of previous investigations and with respect to the probable intracellular location of part of the influx pool.
Compartmental Osmotic Pressures in the Rectal Complex of Tenebrio Larvae: Evidence For A Single Tubular Pumping Site
Authors: Machin J. 
Published: April 2021

ABSTRACT
The distribution of osmotic pressures derived from melting points of frozen sections of mealworm rectal complex is described. Animals rapidly frozen during atmospheric absorption show radially increasing values from lumen to Malpighian tubules suggesting that water uptake is driven by a single pump located in the area of highest solute concentration. Volume–concentration relationships of isolated rectal cuticle and perirectal fluid are consistent with their transmitting water passively to an area of lower solvent activity.
The rectum of animals frozen with some delay after atmospheric absorption show high osmotic pressures with no radial gradients, a condition which is thought to exist when the rectum is in its faecal dehydration mode. Rectal osmotic pressures in all absorbing animals increased towards the posterior end. Several, presumably extreme posterior tubular, osmotic pressures agree well with the 6·7 osmol.kg−1 value expected for an 88% R.H. threshold for atmospheric absorption.