bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of hematocrit, temperature and shear rate on the viscosity of blood from a high-energy-demand teleost, the yellowfin tuna Thunnus albacares
Authors: Brill Richard W. , Jones David R. 
Published: April 2021

ABSTRACT
The high cardiac output, arterial blood pressure and cardiac energy demand of tuna make it likely that blood viscosity has an important influence on cardiovascular function. Furthermore, tuna regularly subject themselves to ambient temperature changes of 10 °C or more during their daily vertical migrations. They can also maintain muscle temperatures several degrees Celsius above ambient and reach maximum muscle temperatures of approximately 15 °C above ambient. The blood of tuna is, therefore, subjected to more frequent and rapid temperature changes than those that occur in other teleosts. Nothing is known, however, about the effects of temperature, shear rate or hematocrit on the viscosity of tuna blood.
Viscosity of yellowfin tuna blood (hematocrits of 0–55 %) was measured at 15, 25 and 35 °C and at shear rates of 45, 90, 225 and 450 s−1 using a cone-plate viscometer. As found for the blood of other vertebrates, viscosity increased with increasing hematocrit. Viscosity also increased nonlinearly with decreasing shear rate, until a shear rate of 90 s−1 was reached. There was no significant increase in viscosity when shear rate was decreased further, to 45 s−1. Because of the relatively flat hematocrit–viscosity curves, predicted optimal hematocrit curves were nearly flat above a hematocrit of approximately 30 %.
A stimulus paradigm for analysis of near-field hydrodynamic sensitivity in crustaceans
Authors: Wilkens Lon A. , Douglass John K. 
Published: April 2021

ABSTRACT
We present several relatively simple procedures for studying the physiology of near-field mechanoreceptors in crustaceans which extend previous measures of sensitivity. The advantages include the quantitative analysis of range fractionation and directionality of receptors and interneurons in the sensory hierarchy of the central nervous system (CNS), based on a stimulus paradigm that is reproducible and easy to use. The technical considerations for quantitative fluid-coupled stimulation addressed by this paper are the complexity of dipole flow fields, reflected interference from traveling waves, and the underlying stimulus wave form. The techniques described here offer corresponding advantages for physiological experiments using other aquatic organisms.
The physiology of sensory cells in the ventral scoloparium of the stick insect femoral chordotonal organ
Authors: Büschges Ansgar 
Published: April 2021

ABSTRACT
The leg joints of invertebrates are governed by neural control loops that control their position and velocity during movements (for reviews, see Bässler, 1983, 1993). These neural control loops rely on sensory feedback about the position and velocity of the controlled leg joint. In invertebrates, this sensory feedback is provided by external (e.g. hair fields, hair rows) and/or internal sense organs (e.g. chordotonal organs). The femoral chordotonal organ (fCO) serves as the main proprioceptor in the control loop governing the femur–tibia (FT) joint of the insect leg. The fCO measures the position and movement of this joint (e.g. Bässler, 1965, 1993; Burns, 1974; Usherwood et al. 1968; Zill, 1985).
Modulation of ionic currents by dopamine in an interneurone of the respiratory central pattern generator of Lymnaea stagnalis
Authors: Barnes Steven , Syed Naweed I. , Bulloch Andrew G. M. , Lukowiak Ken 
Published: April 2021

ABSTRACT
Dopamine elicits alternating bursts of activity in the respiratory interneurones of the snail Lymnaea stagnalis. One of the neurones (VD4) was isolated in culture, and the effects of dopamine on both membrane voltage and current were studied utilising the whole-cell tight-seal recording technique. Dopamine had little effect on resting potentials near −60 mV, nor did it affect spike threshold or input resistance measured near −60 mV. However, it did alter the excitability of the cell, changing the response to current injection from one of repetitive spiking to one of rapid accommodation. Under voltage-clamp, VD4 responded to dopamine (EC50=92 nmol l−1) with increased net outward current at all potentials more positive than −60 mV. This was due primarily to an increase in voltage-gated potassium current and a decrease in calcium current. A reduction of Cd2+-sensitive outward current, possibly calcium-gated potassium current, was also evident at potentials more positive than +60 mV. The physiological actions of dopamine on these cells in vivo are consistent with the inhibitory mechanisms presented in this study.
Potential differences influence amino ACID/Na+ symport rates in larval Manduca sexta midgut brush-border membrane vesicles
Authors: Parthasarathy R. , Harvey William R. 
Published: April 2021

ABSTRACT
The time-dependent fluorescence intensity of an intravesicular potential-sensitive dye was used to probe the real-time kinetics of potential difference (PD)-dependent amino acid/Na+ symport at pH 9 into brush-border membrane vesicles obtained from larval Manduca sexta midgut. Neutral amino acids (alanine, proline) are symported at higher rates as the vesicles are hyperpolarized. The symport rates of acidic (glutamate) and basic (arginine) amino acids are almost PD-independent. The half-saturation constant of alanine is PD-independent between −108 and −78 mV, although the maximal symport velocity increases by half as the voltage is increased. Amino acid throughput is evidently enhanced as the relatively high transmembrane PDs (&gt;150 mV, lumen positive) measured in vivo are approached. The half-saturation concentrations of Na+ were in the range 15–40 mmol l−1 for most of the amino acids examined and increased with voltage for alanine. The Vmax observed as a function of cation or amino acid concentration increased as the vesicle was hyperpolarized in the case of leucine and alanine. The data support the hypothesis that carrier and substrates are at equilibrium inasmuch as substrate translocation seems to be the rate-determining step of symport.
The Localization of Phosphatase in Cells in Tissue Cultures
Authors: Willmer E. N. 
Published: April 2021

ABSTRACT
In a recent paper, Gomori (1941) has described a histochemical method for the localization of phosphatase in animal tissues. The method depends on the fact that the enzyme is not destroyed by moderate treatment with 80 % alcohol, in which the tissues are fixed. After fixation the tissues are sectioned; the sections are incubated with sodium glycerophosphate and calcium chloride in buffered-solution and calcium phosphate is deposited at the site of phosphatase activity. This can be rendered visible by treatment with cobalt nitrate solution followed by ammonium sulphide, when the site of the phosphatase is marked by a black precipitate. By the use of such methods he has described, among other things, the occurrence of phosphatase in capillary endothelial cells in different animals, not with absolute regularity, but in a large number of cases. In those instances in which a positive reaction was not obtained it was shown to be an idiosyncrasy of the particular tissue rather than a failure of the method. It seemed possible therefore that an attempt to separate endothelial cells from other mesenchymal cells growing in vitro might be assisted by the use of this method.
The Rate of Regeneration of Nerve
Authors: Gutmann E. , Guttmann L. , Medawar P. B. , Young J. Z. 
Published: April 2021

ABSTRACT
Five different methods have been used to estimate the rate of advance of regeneration along nerves in the rabbit. Not all give the same result. When the advance of the axon tips is studied a higher rate is recorded than when the times necessary for functional recovery are considered. In the latter case the experiment gives a measure of the rate of advance not of the tips of the axons but of completed nerve fibres, able to function. The ‘scar delay’, or period before arrival of new axon tips in the peripheral stump, is nearly constant in all well-made sutures (7·3 days). After interruption of a nerve by complete crushing at one spot this delay is only slightly shorter (5·2 days). There is a further delay before maturation to the level of functional completion begins to advance down the nerve, so that the total latent period before advance of recovery begins is about 36 days after suture and 20 days after crushing a nerve. The rate of advance of the fastest axon tips was determined by finding the furthest point from the lesion at which reflexes could be elicited by pinching the nerve. After suture of the n. peroneus in the rabbit this rate was 3·5 and after crushing 4·4 mm./day. This rate of the axon tips is not significantly different after crushing the nerve at different distances from the nerve cell body, namely high in the thigh or below the knee. This rate is similar in the tibial, peroneal and sural divisions of the sciatic in the rabbit. The rate of advance of functional completion of nerve fibres was measured by making lesions at various levels and studying (a) the time necessary for return of response to nociceptive stimuli to a given point on the skin and (b) the time for recovery of a given motor function, namely, spreading of the toes. Both methods give rates of 2·0 mm./day after suture, and 3·0 mm./day after crushing. Analgesic areas on the foot shrink at the rate of 2·1 mm./day during recovery after crushing the nerve, 1·6 mm./day after suture. Comparison of the times of recovery of muscles at varying distances from a lesion gives an estimate of rate of advance of functional completion of 2·2 mm./day after crushing a nerve, but this method is only approximate in the rabbit. In rabbits of 1 month old the rate of advance of the axon tips is not greatly different from that in adults, but the delay in the scar is less, and maturation of the nerve fibres proceeds more rapidly.
Neural Induction in Epidermal Explants in Liquid Medium
Authors: Shen S. C. 
Published: April 2021

ABSTRACT
In previous communications (Waddington, 1938; Shen, 1939), it has been shown that a water-soluble derivative of a carcinogenic hydrocarbon is a potent neuralizing agent when implanted with the coagulum of egg albumen into a young gastrula. The present paper describes a similar study with the following modifications: (1) pieces of completely isolated presumptive epidermis were used instead of the whole gastrulae; and (2) the evocatory substance, Na-1:2:5:6-dibenzan-thracene-α-β-endo-succinate, was not tested in the form of a solid implant in admixture with the coagulum of ovoalbumen, but as a solute dissolved in a neutral salt solution in which the epidermal explants were cultivated.
The Storage of Protein, Fat, Glycogen and Uric Acid in the Fat Body and Other Tissues of Mosquito Larvae
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
It is generally agreed that the main function of the fat body of insects is the storage of those reserve substances which require rapid mobilization during moulting and metamorphosis. But little attention has been given to the part taken by other organs and tissues in building up reserves and almost none to the influence of the composition of the food upon the type of reserve substance laid down.
Observations on the Distribution of Ascorbic Acid (Vitamin C) in Explanted Cells
Authors: Barnett S. A. 
Published: April 2021

ABSTRACT
A Survey was recently made of the distribution of ascorbic acid in the embryonic tissues of the chick (Barnett & Bourne, 1941, 1942). Its results raised a number of. problems which can only be solved experimentally. A study was therefore under-taken of ascorbic acid in cultured tissues from chick embryos. Owing to the war this work could not be completed, but it is considered desirable to record the few observations which have been made.
Some Developmental Effects of X-Rays in Drosophila
Authors: Waddington C. H. 
Published: April 2021

ABSTRACT
If Drosophila larvae homozygous for the third chromosome recessive straw-3 are treated with X-rays, back-mutations of the straw-3, gene to its normal allelomorphs take place in somatic cells, and the cells of the wings give rise to hairs which can be recognized as wild type (Waddington, 1940b). In one attempt to follow out this matter in more detail high doses (7000 r. units) were applied. The resulting mortality was, it might be said, 100 %. That is, no flies emerged; but on dissecting the pupa cases, it was found that a considerable proportion had developed up to the hatching stage, but had not been able to free themselves from the pupal integuments. These flies were found to exhibit some rather remarkable deformities, and the experiment has therefore been repeated a number of times. It is the purpose of the present paper to describe in some detail the developmental abnormalities produced by such heavy doses of X-rays. Friesen (1936) originally described some abnormalities (which he termed ‘Roentgenmorphoses’) produced by slightly smaller doses, and some further notes on such cases have been published by Enzmann & Haskins (1938a, b) and Haskins & Enzmann (1937). All the abnormalities found by these authors can probably be considered as due to inhibitory actions of X-rays on various developmental processes; but, as will be clear later, the striking feature of the animals to be discussed in the present communication is that in some of them the growth of certain rudiments has been actually stimulated by the radiation. A preliminary communication of the experiments recorded in this paper has been published (Waddington, 1942).
Studies On the Physiology of Arenicola Marina L.
Authors: Wells G. P. , Ledingham I. C. 
Published: April 2021

ABSTRACT
The ‘isolated extrovert’ of the lugworm consists of the proboscis with a short length of oesophagus attached. It remains active for over 24 hr. in sea water and gives a remarkable rhythmic pattern consisting of outbursts of vigorous activity alternating with periods of relative rest (Wells, 1937). We have already published its reactions to changes in osmotic pressure and magnesium concentration (Wells & Ledingham, 1940a, b). We now continue our study of its relations with its bathing medium by describing the effects of varying the potassium concentration. As many authors have found that potassium: magnesium antagonism is important in invertebrate preparations, and as the extrovert behaves normally in a fluid whose magnesium content is high, we have paid particular attention to the possibility of antagonism between the two ions in the present case.
Quantitative Aspects of the Disk-Sphere Transformation Produced by Lecithin
Authors: Ponder Eric 
Published: April 2021

ABSTRACT
This paper is concerned with quantitative aspects of the disk-sphere transformation of the mammalian red cell produced by lecithin (Ponder, 1935 a). This shape transformation, brought about when lecithin is added to mammalian red cells in saline or in plasma, and reversed by washing off the lecithin or by adding an excess of plasma, is very suitable for quantitative study, since, unlike the shape transformations produced by rose bengal and other lysins, it is not soon followed by haemolysis. Exact work on the factors involved, however, has been very difficult, for two reasons. (1) An unrelated disk-sphere transformation occurs when red cells in saline, whether lecithin-treated or not, are placed between a slide and a closely applied cover-glass (Ponder, 1929), and so it has not been possible to examine the lecithin shape transformation of the cells in saline except in uncovered preparations or in hanging drops. Even under these circumstances, the two factors responsible for the slide-slip transformation, removal of anti-sphering substance by the glass and diffusion of alkali from the glass (Furchgott, 1940; Furchgott & Ponder, 1940) interfere with the observations. This difficulty can now be avoided by using plastic slides and cover-slips, between which these interfering phenomena do not occur. (2) The original method of adding lecithin to plasma or saline by mechanical emulsification is not satisfactory, as the amount of lipoid emulsified is usually unknown and its physical state is variable. Recently I have used sols of lecithin in saline, in which the dispersion approaches uniformity and a known quantity of lipoid is present.
The Mechanism of the Nervous Regulation of the Crayfish Heart
Authors: Wiersma C. A. G. , Novitski E. 
Published: April 2021

ABSTRACT
A preparation is described in which the peripheral inhibitor and accelerator nerves of the crayfish (Cambarus clarkii) heart can be separately or simultaneously stimulated. The effect of different frequencies of stimulation were investigated; complete stoppage of the heart was obtained only with rather high frequencies (45 per sec.); maximal acceleration, with lower frequencies (30 per sec.). No difference in effects between left and right nerves was found. Perfusion with acetylcholine and stimulation of the accelerator nerve produce identical effects. Perfusion with eserin does not influence the normal heart beat but enhances the effect of acceleration.
The nerve of Lemoine has no regulatory influence on the heart.
Special inhibitory and acceleratory tracts have been prepared in the suboesophageal commissures. Each of these tracts makes heterolateral as well as homolateral connexions. The influence of the frequency of stimulation on the central tracts has been studied.
An hypothesis with regard to the mechanism of the crayfish heart beat and its control is presented.
Observations On the Forces of Morphogenesis in the Amphibian Embryo
Authors: Waddington C. H. 
Published: April 2021

ABSTRACT
The cells of early amphibian embryos contain ellipsoidal yolk granules. When a granule lies within the mitotic spindle, it is orientated with its long axis parallel to the direction ofthe spindle fibres. Yolk granules lying in the cytoplasm of cells are not specially orientated unless they lie in narrow spaces between cell surfaces; this is true in cells of the moving invagination streams, in the flask cells of the young blastopore, and in elongated cells of the neural groove and lens. The breaking strain of cell surfaces was tested by bringing the cells into surfaces of known strength and observing whether they withstood the applied tension. The evidence indicates: (a) That the breaking strain of cells from gastrula and tail-bud embryos is some tens of dynes per centimetre.(b) That the breaking strain is not the same in all cells, being highest in neural tissue and lowest in endoderm during the stages mentioned.(c) That the breaking strain gradually increases with age.(d) That in the neural groove stage the strength of the outer concave surface of the groove is greater than that of the inner convex surface. It is suggested that changes in surface tensions may be of importance in bringing about morphogenesis. The possibility is envisaged that the changes in tension may be connected with orientated fibrizations of the surface proteins.
Acquisition of magnetic directional preference in hatchling loggerhead sea turtles
Authors: Lohmann Kenneth J. , Fittinghoff Lohmann Catherine M. 
Published: April 2021

ABSTRACT
During their natal migration, hatchling loggerhead sea turtles (Caretta caretta L.) establish courses towards the open ocean and maintain them after swimming beyond sight of land. Laboratory experiments have demonstrated that swimming hatchlings can orient using the earth’s magnetic field. For the magnetic compass to function in guiding the offshore migration, however, hatchlings must inherit or acquire a magnetic directional preference that reliably leads them towards the open sea.
On land, hatchlings find the ocean using light cues associated with the seaward horizon. To determine whether turtles might acquire a preference for a specific magnetic direction on the basis of such cues, we studied the magnetic orientation of turtles initially exposed to light from either magnetic east or west. Hatchlings that had been exposed to light in the east subsequently oriented eastward when tested in darkness, whereas those that had been exposed to light in the west swam westward. Reversing the magnetic field resulted in a corresponding shift in orientation, indicating that the turtles were orienting to the ambient magnetic field.
These results demonstrate that light cues can set the preferred direction of magnetic orientation by loggerhead hatchlings. We therefore hypothesize that hatchlings initially establish a seaward course using visual cues available on or near land, then maintain the course using magnetic cues as they migrate into the open sea.
Extracellular ATP can activate autonomic signal transduction pathways in cultured equine sweat gland epithelial cells
Authors: Ko Wing Hung , O’Dowd John J. M. , Pediani John D. , Bovell Douglas L. , Elder Hugh Y. , Jenkinson David McEwan , Wilson Stuart M. 
Published: April 2021

ABSTRACT
Changes in intracellular free calcium concentration ([Ca2+]i) were monitored in a cell line that was derived from the equine sweat gland epithelium. ATP and closely related compounds could increase [Ca2+]i with a rank order of potency of UTP⩾ATP⪢ADPAMP=adenosine=α,β-methylene-ATP. The responses to ATP and to UTP were initiated by the release of calcium from an internal store and subsequently sustained by calcium influx. The rise in [Ca2+]i thus seems to be mediated by P2U receptors that are coupled to phosphoinositidase C. Some desensitisation of this response developed during repeated stimulation with ATP and this was blocked by staurosporine, an inhibitor of protein kinase C, and augmented by a phorbol ester which acts as an exogenous activator of this enzyme. A protein-kinase-C-dependent inhibitory pathway thus seems to become active during repeated stimulation with ATP. ATP and related compounds could also raise cellular cyclic AMP content. The order of potency was ATP&gt;ADP⪢AMP=adenosineUTP, suggesting that this response is mediated via a separate subclass of P2 receptor. The present results demonstrate that ATP can activate autonomic signal-transduction pathways in cultured equine sweat gland cells and suggest that there may be a purinergic component to the control of secretory activity in the equine sweat gland.