bluuebunny/crossref_metadata_2025 huggingface dataset:
Osmotic and volaemic effects on drinking rate in elasmobranch fish
Authors: Anderson W. Gary , Takei Y. , Hazon N.
Published: April 2021

An increase in drinking rate of two species of marine elasmobranch fish, Scyliorhinus canicula and Triakis scyllia, acclimated to 80% sea water was observed following the introduction of 100 % sea water to experimental tanks. The drinking response in both species was found to be maximal within 6 h, and a significant increase was sustained for up to 24 h in T. scyllia. Plasma osmolality was significantly increased within 6 h following introduction of 100 % sea water, and this increase was principally due to elevated plasma Na+ and Cl- concentrations. Administration of 2 mol l-1 mannitol, 75 % sucrose and vehicle(elasmobranch Ringer) did not induce a significant increase or decrease in the drinking rate of S. canicula. However, injection of 20 % NaCl was found to decrease drinking rate significantly in S. canicula 60 min after administration. Controlled haemorrhage of approximately 5.7 % of total blood volume in S. canicula induced a rapid 36-fold increase in drinking over basal levels. The present study demonstrates a physiological dipsogenesis in response to hypovolaemia in marine elasmobranch fish as part of their overall iso/hyperosmoregulatory strategy.
Characterization of yeast V-ATPase mutants lacking Vph1p or Stv1p and the effect on endocytosis
Authors: Perzov Natalie , Padler-Karavani Vered , Nelson Hannah , Nelson Nathan
Published: April 2021

Subunit a of V-ATPase in the yeast Saccharomyces cerevisiae, in contrast to its other subunits, is encoded by two genes VPH1 and STV1. While disruption of any other gene encoding the V-ATPase subunits results in growth arrest at pH 7.5, null mutants of Vph1p or Stv1p can grow at this pH. We used a polyclonal antibody to yeast Stv1p and a commercially available monoclonal antibody to Vph1p for analysis of yeast membranes by sucrose gradient fractionation, and two different vital dyes to characterize the phenotype of vph1 ▵ and stv1 ▵mutants as compared to the double mutant and the wild-type cells. Immunological assays of sucrose gradient fractions revealed that the amount of Stv1p was elevated in the vph1 ▵ strain, and that vacuoles purified by this method with no detectable endosomal contamination contain an assembled V-ATPase complex, but with much lower activity than the wild type. These results suggest that Stv1p compensates for the loss of Vph1p in the vph1 ▵ strain. LysoSensor Green DND-189 was used as a pH sensor to demonstrate unexpected changes in vacuolar acidification in stv1▵ as the Vph1p-containing V-ATPase complex is commonly considered to acidify the vacuoles. In the vph1 ▵ strain, the dye revealed slight but definite acidification of the vacuole as well. The lipophilic dye FM4-64 was used as an endocytic marker. We show that the null V-ATPase mutants, as well as the vph1 ▵ one, markedly slow down endocytosis of the dye.
Temperature adaptation inGillichthys(Teleost: Gobiidae)A4-lactate dehydrogenases
Authors: Fields Peter A. , Kim Yong-Sung , Carpenter John F. , Somero George N.
Published: April 2021

Alternative conformations of proteins underlie a variety of biological phenomena, from prion proteins that cause spongiform encephalopathies to membrane channel proteins whose conformational changes admit or exclude specific ions. In this paper, we argue that conformational differences within globular `housekeeping' enzymes may allow rapid adaptation to novel environments. Muscle-type lactate dehydrogenases (A4-LDHs) from the gobies Gillichthys seta and G. mirabilis have identical amino acid sequences but show potentially adaptive differences in substrate affinity (apparent Michaelis constants for pyruvate, KmPYR) as well as differences in thermal stability. We examined the A4-LDH of each species using fluorescence spectroscopy, near- and far-ultraviolet circular dichroism (CD)spectroscopy and hydrogen/deuterium exchange (H/D) Fourier-transform infrared spectroscopy to determine whether structural differences were apparent, the extent to which structural differences could be related to differences in conformational flexibility and whether specific changes in secondary or tertiary structure could be defined. The fluorescence spectra and far-ultraviolet CD spectra of the A4-LDH from the two species were indistinguishable, suggesting that the two conformations are very similar in secondary and tertiary structure. Apparent melting temperatures(Tm) followed by fluorescence and CD spectroscopy confirmed that the G. mirabilis A4-LDH is more thermally stable than the G. seta form. H/D exchange kinetics of Gillichthys A4-LDH was described using double-exponential regression; at 20 °C, G. seta A4-LDH has a higher exchange constant, indicating a more flexible and open structure. At 40°C, the difference in H/D exchange constants disappears. Second-derivative analysis of H/D exchange infrared spectra indicates that α-helical, but not β-sheet structure, differs in conformational flexibility between the two forms. Second-derivative ultraviolet spectra indicate that at least one of the five tyrosyl residues in the Gillichthys LDH-A monomer is located in a more hydrophobic environment in the G. mirabilis form. Homology models of A4-LDH indicate that Tyr246 is the most likely candidate to experience a modified environment because it is involved in subunit contacts within the homotetramer and sits in a hinge between a staticα-helix and one involved in catalytic conformational changes. Subtle differences in conformation around this residue probably play a role both in altered flexibility and in the potentially adaptive differences in kinetics between the two A4-LDH forms.
Torque patterns of the limbs of small therian mammals during locomotion on flat ground
Authors: Witte Hartmut , Biltzinger Jutta , Hackert Rémi , Schilling Nadja , Schmidt Manuela , Reich Christian , Fischer Martin S.
Published: April 2021

In three species of small therian mammals (Scandentia: Tupaia glis, Rodentia: Galea musteloides and Lagomorpha: Ochotona rufescens) the net joint forces and torques acting during stance phase in the four kinematically relevant joints of the forelimbs (scapular pivot,shoulder joint, elbow joint, wrist joint) and the hindlimbs (hip joint, knee joint, ankle joint, intratarsal joint) were determined by inverse dynamic analysis.

Kinematics were measured by cineradiography (150 frames s-1). Synchronously ground reaction forces were acquired by forceplates. Morphometry of the extremities was performed by a scanning method using structured illumination.

The vector sum of ground reaction forces and weight accounts for most of the joint force vector. Inertial effects can be neglected since errors of net joint forces amount at most to 10 %. The general time course of joint torques is comparable for all species in all joints of the forelimb and in the ankle joint. Torques in the intratarsal joints differ between tailed and tail-less species. The torque patterns in the knee and hip joint are unique to each species.

For the first time torque patterns are described completely for the forelimb including the scapula as the dominant propulsive segment. The results are compared with the few torque data available for various joints of cats(Felis catus), dogs (Canis lupus f. familiaris),goats (Capra sp.) and horses (Equus przewalskii f. caballus).
The Influence of Various Physical and Biological Factors of the Environment on Honeybee Activity. An Examination of the Relationship Between Activity and Nectar Concentration and Abundance
Authors: Butler C. G.
Published: April 2021

As the quantity of nectar of a given species of plant becomes smaller, irrespective of its sugar concentration, so the number of bees working that species of plant becomes reduced. This is not due to old bees that have been working this crop for some time deserting it in favour of a more profitable crop, but to the natural death of these old bees and the fact that their places are not taken by new bees. Young foragers are not attracted to the crop concerned because its presence is not communicated to them by the old bees still working upon it. The range of nectar concentration (% total carbohydrate) in the flowers of many species of plants growing in a given district varies from day to day and even from hour to hour. Such changes are almost certainly directly due to changes in the atmospheric humidity. The changes are greatest in flowers, such as hawthorn, with relatively unprotected nectaries. Honeybees respond to the concentration of nectar secreted by the flowers of plants, working in the greatest numbers on those plants with the highest nectar concentration. When two or more species of ‘bee-plants’ are in flower simultaneously the species which will attract most honeybees will be that in the flowers of which the nectar is most highly concentrated. This accounts for the occasional failure of honeybees to work the flowers of fruit trees when other flowers are available to them. Both nectar abundance and nectar concentration appear to have considerable effect upon honeybee activity. From the data at present available it appears correct to conclude tentatively that nectar concentration decides in the first instance which species of plant will be visited in preference to others in flower at the same time, and that nectar abundance then determines the proportion of the foraging population of a colony which will work the flowers in question.
Transpiration Through the Cuticle of Insects
Authors: Wigglesworth V. B.
Published: April 2021

The cuticle of most insects is an effective barrier to the evaporation of water. Since the work of Kühnelt (1928,1939) it has been known that this impermeability is a property of the outermost layer. It is usually ascribed to the epicuticle—defined as the layer, of the order of 1 μ in thickness, that is not penetrated by the pore canals, contains no chitin, and resists solution in cold concentrated hydrochloric or sulphuric acids. From chemical tests Kühnelt concluded that the epicuticle contained fatty acids and cholesterol-like bodies. He therefore refers to it as a ‘lipoid cuticula’.
An Improved Radiation Integrator for Biological Use
Authors: Gunn D. L. , Kirk R. L. , Waterhouse J. A. H.
Published: April 2021

A new radiation integrator is described similar to one previously described by Buxton. Methods of construction are given in detail to facilitate the standardization of future instruments. Instruments of different sensitivities have been constructed by the use of either alcohol or water as the volatile liquid. The alcohol instruments can be used for determining changes in intensity over short periods of time; the water instruments are of most value for determining the mean daily intensity of sunshine. The instruments have been calibrated against absolute measurements with a pyrheliometer. Compared with previous instruments of the same type a very much improved efficiency has been obtained. The value of this type of instrument for work in the field is discussed; its limitations are briefly indicated.
Facilitation in Sea Anemones
Authors: Ross D. M.
Published: April 2021

The action of a number of drugs which affect the neuromuscular systems of vertebrates has been examined on the sea anemone, Calliactis parasitica. In contrast to their action in vertebrates, no drugs directly cause contraction in the muscles of the anemone. Some drugs of the group which act at cholinergic junctions in the vertebrates, including acetylcholine itself, were ineffective on Calliactis. Atropine and nicotine, of the same group, had depressant effects. Some drugs of the group which act at adrenergic junctions in vertebrates, including adrenaline itself, were ineffective on Calliactis. On the other hand, tyramine, tryptamine and 933 F enhanced and sensitized the response to nervous excitation. Thus responses to single stimuli occurred, whereas normally responses only follow the second and subsequent stimuli. Cocaine enhanced and ergotoxine depressed the responses of Calliactis in a manner analogous to their effects in vertebrates. No significant effects were observed with other substances, including strychnine, veratrine, histamine, betaine and tetramethylammonium hydroxide. The limitation of the drug effects to enhancement and sensitization supports the view that neuromuscular transmission in Calliactis cannot be a simple chemical process as in the vertebrates. In general the results support the hypothesis that there is a separate process of sensitization which must precede the excitation of the muscle in these animals. On the other hand, the drugs which have sensitizing effects on Calliactis do not possess all the properties that would be expected of a natural ‘sensitizer’ or ‘facilitator’ carrying out this process of sensitization at the nerve ending.
Facilitation in Sea Anemones
Authors: Ross D. M.
Published: April 2021

Extracts of the sea anemones, Calliactis parasitica and Metridium senile, have been prepared and their effects on the neuromuscular response of these anemones tested. The presence of extract sensitizes the organism so that a response is given to a single stimulus, whereas normally this occurs only on the second and subsequent stimuli. No other significant effects were observed. The sensitizing effect of the extract differs from the effect of a sensitizing drug like tyramine; it appears more quickly, more regularly, and it is rarely accompanied by an increase in the size of the muscular contraction. The fact that a substance with sensitizing properties has been detected in anemones supports the view that a ‘sensitizer’or’ facilitator’ exists and takes part in neuromuscular transmission in these animals. Nevertheless, the extract, like the sensitizing drugs, lacks some of the properties that would be expected of a true ‘sensitizer’ or ‘facilitator’.
Blood Pressure and Pulse Rate in the Foetal Sheep
Authors: Barcroft Joseph , Barron D. H.
Published: April 2021

A method (the needle method) is described for the measurement of the pressure in the stream going through a vessel. In the foetal sheep the needle method applied to the umbilical artery gives substantially the same results as the mercurial manometer applied to the carotid, until about half-way through the gestation period. As gestation proceeds the needle method applied at the first moment at which it can be applied to the umbilical artery (or a branch) gives readings substantially lower, and increasingly lower as gestation proceeds, than does the mercurial manometer read at the first moment at which it can be read. The discrepancy is due to the sum of a number of causes which are discussed, but of these the most important is an actual rise of pressure between the time of delivery and the completion of the dissections contingent on the use of the mercurial manometer. The cause of this is not at present demonstrated, but either or both of two factors may be concerned : (a) a dulling of the central nervous system which weakens the depressor reflfex; (b) the establishment of a greater degree of vasomotor tone consequent on the bombardment of the central nervous system with sensory stimuli. The pulse rates in utero and just after delivery of the foetus into a saline bath at 39 –40°C. (the umbilical circulation being unimpaired) are not significantly different. The pulse rate quickens up to the 70th-8oth day, after which it becomes slower as gestation proceeds. If both vagi be severed, the pulse rate tends to quicken throughout gestation. The pulse, therefore, comes increasingly under vagus inhibition from the Soth-qoth day onwards. Even after the vagi have been cut after the 120th day (it has not been tried before) adrenalin in sufficient quantity will cause a further quickening of the pulse. The earliest date at which stimulation of the peripheral end of the right vagus was observed to slow the heart was the 77th day. On the 85th day peripheral stimulation of the left vagus also failed, but succeeded on the 101st day. Central stimulation of the left vagus, with the right vagus intact, produced slowing on the 77th day. Slowing of the heart synchronous with rise of arterial pressure has been observed on the 11th day. Slowing of the heart which bears evidence of being reflex has been obtained by raising the blood pressure (clamping the cord) on the 121st day and by injection of adrenalin on the 118th day. Approaching term both the carotid sinus and cardiac depressor mechanisms are functional. Lowering of the blood pressure as the result of stimulation of the central end of the vagus and with both vagi severed can be demonstrated late in gestation.
Studies on Tapeworm Physiology
Authors: Smyth J. D.
Published: April 2021

Unidentified plerocercoids of the family Diphyllobothriidae were removed aseptically from the coelomic cavity of Gasterosteos aculeatus and cultivated at 40°C. in various liquid nutrient and saline media under sterile conditions. The most successful results were obtained with peptone-broth+10% horse serum in which larvae remained active and behaved normally for 10 days. Broth without peptone gave poor results (max. 2 days) but the addition of peptone (max. 7 days) greatly improved the activity. The addition of glucose or yeast to peptonebroth was not significantly beneficial. Survival times in all nutrient media were considerably longer than the periods of normal behaviour. In strength Locke’s saline, the maximum period of normal behaviour was 4 days. The addition of glucose (0·25-1 %) to this saline was detrimental to the behaviour of the larvae. Histochemical investigation showed that fresh larvae were rich in glycogen but almost fat-free. The occurrence of glycogen in larvae after cultivation in various nutrient and non-nutrient media was such that no conclusions regarding the carbohydrate metabolism could be drawn. All larvae after cultivation, however, contained great quantities of intracellular fat, from which it was concluded that fat is a by-product of metabolism. During cultivation in the more favourable media, larvae became firmly attached to the walls of the culture tube by means of their bothria; the strobila also became greatly elongated, and segmented in some cases. Histological examination failed to detect mitosis in the nuclei of the strobila and it was concluded that growth of the strobila had not taken place. The elongation of the strobila was presumed to be a result of the relaxation of the longitudinal musculature. Of eight larvae kept in broth+1% peptone+ 0·5% glucose at room temperatures, seven still showed active undulation on exposure to light after 80 days’ cultivation.
The Physiology of Sea-Urchin Spermatozoa
Authors: Rothschild Lord
Published: April 2021

An investigation has been made into the causes of the interrelated phenomena of Senescence and the Dilution Effect in the spermatozoa of Echinus esculentus. The Dilution Effect is the increase in O2 uptake and in movement observed when a concentrated sperm suspension, obtained by partial dilution of semen, is diluted with sea water. The supernatant sea water obtained by centrifuging partially metabolized sperm suspensions contains no substances which depress the respiration or motility of the spermatozoa of the same species. This supernatant sea water has a small but definite protective action on spermatozoa in maintaining but not increasing their O2 consumption. The effect is enhanced by agitating the suspensions before centrifugation, E. esculentus spermatozoa do not glycolyse aerobically, anaerobically, or in the presence of 5% O2 in CO. The absence of aerobic acid production proves that the reduced O2 uptake per sperm of dense suspensions is not due to a lowering of the pH of the medium. As the Dilution Effect is observed in manometric experiments in which CO2 is continuously and adequately removed, neither accumulation of CO2 nor a reduction in pH resulting from the accumulation of CO2 are responsible for the reduced O2 uptake of dense suspensions. The O2 uptake of dense sperm suspensions ( > 109 sperm/ml.) is altered by changes in O2 tension. O2 consumption in 100% oxygen is nearly double that in 10% O2 in Ns. An increase in O2 tension has no stimulating action on dilute suspensions. An atmosphere of 100% O2 has a gradual toxic effect on dense and dilute sperm suspensions. Carbon monoxide has a greater inhibitory action on dilute than on concentrated sperm suspensions. The difference between the effects of varying O2 tensions or CO on dense and dilute suspensions is partly, or perhaps wholly, due to gaseous diffusion being a limiting factor. This may partly explain the Dilution Effect. Apart from photo-reversibly inhibiting respiration, CO exerts an irreversible toxic influence on sea-urchin spermatozoa. Illumination of spermatozoa with a wave-length of light outside the region of photo-chemical absorption by CO cytochrome oxidase enables visual examination to be made in the presence of CO. The O2 uptake of a suitable concentration of spermatozoa is 70% inhibited by 5% O2 in CO. The same inhibition occurs when the suspension is illuminated by light of wave-length 548 mμ, but there is no equivalent decrease in motility. After motility and respiration have ceased sea-urchin spermatozoa still contain oxidizable substrates and the appropriate dehydrogenases as evidenced by their ability to reduce methylene blue in an evacuated Thunberg tube.
Studies on Animal Carotenoids
Authors: Steven D. M.
Published: April 2021

The principal carotenoids of the trout are b-carotene, lutein and astacene. Carotenoids occur in the skin, muscles, ovary, liver and eyes, but the different types are distributed in a characteristic way in the various tissues. Carotene is found in significant amounts only in the liver and ovaries; lutein and astacene together in the skin, muscles and ovaries; lutein alone in the eyes. Xanthophylls, mainly lutein, occur also in the liver. Other carotenoids occur in trace amounts only. The lutein and astacene of skin are in the form of esters. They are located in the xanthophores and erythrophores, of which they are the characteristic pigments. Yellow areas of skin yield mainly lutein, red areas mainly astacene, and their concentration in all parts of the skin is normally several times greater than in any other tissue. In muscle and ovaries both lutein and astacene are present as free hydroxy-carotenoids. Liver contains both free and esterified xanthophylls, the eye tissues only esters. The concentration of the different carotenoid fractions in various tissues was measured with a photoelectric colorimeter in terms of standard preparations of pure carotenoids. Direct measurements of the absorption spectra of xanthophores and erythrophores show that the former contain only lutein, the latter only astacene. Living xanthophores show absorption maxima at 487, about 450 and at 425 mμ; erythrophores a single maximum close to 490 mμ. The maxima in the blue-green are displaced some 10 –12 mμ towards the red from their positions in hexane. The concentration of pigment in fully contracted chromatophores was estimated by a visual matching method. Xanthophores were found to contain about 0 ·00001 –0 ·00003 γ of lutein per cell, erythrophores about 0 ·00020 –0 ·00035 γ per cell. Trout kept on a diet low in carotenoids lose most of their red and yellow pigments. Astacene disappears from the skin, and the lutein falls to about one-sixth of the normal level. Feeding with natural foods rich in carotenoids may restore the skin coloration, and fish reared on a natural diet develop normal wild-type pigmentation. Supplements of pure carotenoids added to the basal diet failed to raise the pigment levels of depigmented fish. Trout do not appear to be able to convert one type of carotenoid to another.
A Simplified Ultra-Micro Kjeldahl Method for the Estimation of Protein and Total Nitrogen in Fluid Samples. of Less Than 1·0μ1
Authors: Shaw J. , Beadle L. C.
Published: April 2021

An ultra-micro modification of the Kjeldahl method is described whereby nitrogen can be estimated in a blood sample of less than 1 μl. Volume. This is simpler than previously described methods as regards apparatus and procedure. The separate estimations of protein and total nitrogen are also introduced. For samples containing 1·0-10·0 μg. N the standard deviation is 0·02-0·04 μg. N. Preliminary tests indicate that for 0·1-1·0 μg. N the standard deviation would be of the order of 0·006-0·008 μg. N.
The Site of Formation of Hypotonic Urine in the Nephridium of Lumbricus
Authors: Ramsay J. A.
Published: April 2021

Methods for the collection of samples of urine from different parts of the nephridium of Lumbricus are described. The osmotic pressures of these samples have been measured by determination of freezing-point depression and have been compared with the osmotic pressure of the medium surrounding the nephridium. The results of this comparison indicate that the ability to form hypotonic urine is certainly present in the wide tube, is possibly present in the middle tube and is probably not present in the narrow tube. The analogy between the nephridium and the vertebrate nephron is discussed.
The Efferent Regulation of the Muscle Spindle in the Frog
Authors: Katz Bernhard
Published: April 2021

Matthews’s experiments (1931a, b) have established that the muscle spindle of the frog contains a sense organ which responds to stretch and ceases to respond when the surrounding muscle fibres shorten. In addition, the spindle is known to possess a motor supply of its own, a bundle of small striated ‘intrafusal’ muscle fibres. These fibres run through the spindle capsule (Barker, 1948 ; Katz, 1949, fig. 1) where they establish intimate contact with the sensory nerve, while being separated by a lymphatic space from the ‘extrafusal’ tissue. These muscle fibres are said to lose their striations at the region of contact with the sensory terminals. The anatomical arrangement suggests that the intrafusal muscle bundle pulls directly on the stretch receptor, in contrast with the ordinary muscle fibres which will release the tension on the sense organ if they shorten. A contraction of the intrafusal muscle fibres, therefore, must affect the response of the stretch receptor in a manner very different from that of the surrounding mass of ‘extrafusal’ fibres. The function of the intrafusal muscle fibres is believed to be a regulation of mechanical ‘bias’ on the sense organ, but little is known concerning their motor innervation and the physiological conditions under which they are thrown into activity.
The Structure of the Insect Egg-Shell in Relation to the Respiration of the Embryo
Authors: Tuft P. H.
Published: April 2021

Many insect eggs are able to avoid mechanical injury and desiccation because they are protected by an egg-shell or chorion which is tough, rigid and relatively waterproof. These properties tend to make it impermeable to gases, and since the egg contains a living embryo, there must be provision for the diffusion of an adequate volume of oxygen into the egg. The way in which this is achieved has never been satisfactorily explained. Specialized respiratory structures have been described in many species of insect egg, especially in those of parasites (Maple, 1937), and a respiratory function has sometimes been ascribed to the system of micropylar canals that penetrate the shell in hard-shell eggs, but until now there has been no direct evidence for the respiratory function of these structures. Indeed it seems unlikely, at first sight, that sufficient oxygen could diffuse through such small areas of the shell to satisfy the needs of the embryo, although in some species there can be little doubt that oxygen uptake is restricted to a small part of the shell; in certain species of capsid, for instance, the eggs are embedded in the tissues of a plant with only the caps exposed to the air.
Rectilinear Locomotion in a Snake (Boa Occidentalis)
Authors: Lissmann H. W.
Published: April 2021

The mechanics of three common modes of locomotion in snakes has been subjected to a detailed analysis (Gray, 1946; Gray & Lissmann, 1950). These three modes are (i) the serpentine or horizontal undulatory movement; (ii) the concertina movement; (iii) the crotaline or side-winding movement. A fourth, less common mode, described as ‘rectilinear movement’, has aroused considerable interest since Home (1812) published his ‘Observations intended to show that the progressive motion of snakes is partly performed by means of ribs’.
Seasonal Changes in Blood Sugar, Fat Body, Liver Glycogen, and Gonads in the Common Frog, Rana Temporaria
Authors: Smith C. L.
Published: April 2021

Seasonal changes in the weights of fat body, gonads and liver, liver-glycogen content, and blood sugar have been followed by observations on monthly samples of Rana temporaria which had been kept in captivity for 3 days without food. Three periods during which the blood sugar was high (from 54 to 62 mg./ 100 ml. of blood) were observed during the year: at the spawning season in March, in June and July, and in November. The hyperglycaemia of June and July was accompanied by the rapid development of the fat body. This phase was succeeded by that of gonad regeneration, during which there was no further storage of fat or liver glycogen, and the blood sugar was low (about 40 mg./ioo ml. of blood). When gonad regeneration was nearing completion glycogen storage in the liver became the dominant feature, and the blood sugar tended to rise again. A sex difference in blood sugar was observed at certain periods. From June to September the female blood sugar was higher than that of the male, but from September to January the relationship was reversed. This may be correlated with the differing rates of gonad regeneration in the two sexes. During the winter months, when the food intake was reduced, the frogs utilized some of their stored fat and glycogen and the blood sugar was low (about 40 mg./ioo ml.). The hyperglycaemia found at the spawning season was accompanied by the rapid depletion of the fat and glycogen stores. In April and May, after the breeding season, when the frogs were feeding actively, the blood sugar was low and apparently neither fat nor glycogen was being accumulated. It is suggested that this was a period of tissue repair and possibly of growth.
The Mechanics of the Blood Vascular System of Ascidiella Aspersa
Authors: Haywood C. A. , Moon H. P.
Published: April 2021

The reversal of the tunicate heart involves two problems: first, why it stops beating in a particular direction; and secondly, why having stopped it should then reverse. Two types of theory have been put forward, one based on the idea that a ‘back pressure’ is gradually built up which compels the heart to stop, and the other depending on opposing centres of contraction at each end of the heart taking control alternately. The present paper provides quantitative evidence, based on Ascidiella aspersa (O. F. Mueller), that a back pressure is built up. The faster the heart beats the more frequently reversals occur, a back pressure building up more rapidly when the heart beats quickly. Various criticisms of the back-pressure theory are considered and discussed. Examples are given of other closed contractile systems containing fluid which show reversal, the tunicate heart being by no means unique.
Muscular and Hydrostatic Action in the Sea-AnemoneMetridium Senile(L.)
Authors: Batham E. J. , Pantin C. F. A.
Published: April 2021

The majority of sea-anemones present to the eye an almost constant shape which only changes as the result of activities of a very simple kind. This is true, for instance, of Calliactis parasitica, the subject of an earlier study (Pantin, 1935). The unstimulated animal rarely departs from the form of a short cylinder surmounted by a disk bearing the tentacles round its edge and the mouth at its centre. In contrast with Calliactis, Metridium senile is notable for the variety of shapes which it assumes (Pl. 7). It may be fully expanded with a narrow or with a wide column (e, f). The same anemone may next day be found contracted down to a mere button-like object (d). It may indulge in a variety of contortions in which it is laterally bent, or possesses deep transverse constrictions locally or completely embracing the column (g, i). The whole anemone may on occasion temporarily assume a shrivelled and contracted condition (h), in which it might easily be discarded from the aquarium as dying ; but which, in fact, is a normal temporary state from which there is comparatively rapid recovery (i, f). At other times, particularly during locomotion, a part of the body may become greatly distended (c). Prolonged observation of Calliactis shows that even here there is some variation of shape, though less evident than with Metridium.
Some Properties of the Photoreceptors of the Brook Lamprey
Authors: Steven D. M.
Published: April 2021

This paper describes an investigation of the physiological characteristics of the light receptors situated in the skin of the ammocoete larva of the brook lamprey, Lampetra planeri (Bloch). The interest of these organs lies in the fact that they are the only type of simple photoreceptor among the Vertebrates of which we possess any precise information. They may well be considered a kind of functional link between the simpler types of photoreceptor systems, which are found in many Invertebrates, in Pholas, Mya and Ciona, for example, and the fully developed image-forming eye of Vertebrates. We are at present almost completely ignorant of the photosensitive processes of animals at levels of organization below that of the image-forming eye, and an analysis of the properties of these simpler types of receptors offers one of the most promising approaches to an understanding of the common pattern of photoreceptor processes in general.
The Fertilization Reaction in the Sea-Urchin Egg. The Effect of Nicotine
Authors: Rothschild Lord , Swann M. M.
Published: April 2021

Unfertilized eggs of Psammechinus miliaris which have been allowed to stand in sea water containing nicotine and are then inseminated in normal sea water are polyspermic. Polyspermy is not due to an increase in the speeds at which spermatozoa swim in these circumstances; nor to a decrease in the rate at which the change in cortical structure of the egg, the first sign of fertilization, is propagated over the egg surface. Experiments to test alternative explanations of the effect of nicotine have been carried out. The experiments do not enable a firm decision to be made between (a) a high-speed block to polyspermy (which has not been observed) with a high probability of a successful collision, and (b) a low-speed (20 sec.) block to polyspermy with a low probability of a successful collision.
The Determination of Sodium in Small Volumes of Fluid by Flame Photometry
Authors: Ramsay J. A.
Published: April 2021

A method of integrative flame photometry is described, by which the amount of sodium in biological fluids can be determined, using samples of the order of 10−3 cu.mm. With pure solutions of sodium chloride, of concentration from 0·05 to 2·0 %, the average error of the method is about 3 % of the concentration. When other substances are present systematic errors of up to 7·7 % have been recorded. The possibilities of reducing these systematic errors and of extending the method to deal with other elements are discussed.
Lipids of the Nervous System of the Squid Loligo Pealii
Authors: McColl J. D. , Rossiter R. J.
Published: April 2021

Previous studies from this laboratory have indicated that the distribution of lipids in the mammalian central nervous system is very similar for a number of different species (Johnson, McNabb & Rossiter, 1948 a). The same is true for the lipids of peripheral nerve (Johnson et al. 1948 b). Johnson et al. (1949 a, b) concluded that free cholesterol, cerebroside and sphingomyelin are the principal lipids of the myelin sheath of a mammalian nerve fibre, although the recent work of Brante (1949) suggests that one of the components of brain kephalin, phosphatidyl serine, may also be present in considerable quantities in the myelin sheath. These lipids have been called the myelin lipids.
Giant Axons and Synergic Contractions in Branchiomma Vesiculosum
Authors: Nicol J. A. Colin
Published: April 2021

Conduction in the giant axons of annelids has been clarified by the work of Stough, Eccles and colleagues, Bullock, Rushton and others (reviewed by Nicol, 1948a). They are now known to be motor axons, or at least nerve fibres on the efferent side of reflex arcs, and they intermediate quick withdrawal movements effected by synergic contractions of widespread longitudinal muscles. Probably the most highly developed axons of this kind occur in the Serpulimorpha (Nicol, 1948 a, b, c, d). Our knowledge of the physiological activity of these nerve fibres, as components of a neuro-muscular unit, is still incomplete, however, and the sabellid worm Branchiomma vesiculosum (Montagu) has been investigated, as a suitable experimental animal. The present paper gives an analysis of giant axon functioning in the intact animal as revealed through muscular activity. A few observations on the functioning of the giant fibres in Myxicola infundibulum (a related species) have already been published (Nicol, 1948 c), and will be referred to in the present account. Budington (1902) described the results of stimulating pieces of the earthworm which contained nerve cord. His records show contractions of the longitudinal muscles, and it is probable that he was stimulating the giant axons of the animal.
Osmotic Regulation in Mosquito Larvae: The Role of the Malpighian Tubules
Authors: Ramsay J. A.
Published: April 2021

The part played by the Malpighian tubules in the salt and water balance of Aedes aegypti larvae has been studied ; the intestinal fluid and haemolymph have been compared in respect of freezing-point depression and sodium concentration. It appears highly probable that the fluid passing down the intestine is derived from the Malpighian tubules with little or no contribution from the midgut. When the larvae are kept in fresh water the intestinal fluid is very slightly hypotonic to the haemolymph (not isotonic as previously reported), but its sodium concentration is only about one-half that of the haemolymph. When the larvae are kept in solutions of NaCl the difference in sodium concentration between intestinal fluid and haemolymph decreases. In an external medium of i % NaCl the difference is abolished. There is thus evidence that when the external medium is poor in salts the Malpighian tubules can contribute to the work of salt retention by excreting a fluid containing less sodium than the haemolymph; but there is no evidence that under any conditions they can excrete a fluid containing more sodium than the haemolymph. Evidence of a decrease in the sodium concentration of the tubule fluid from distal region to proximal region is not statistically significant.
The Variation in Fat and Glycogen Content of the Bot Fly (Gastrophilus Intestinalis) Larva Tracheal Organ During Development
Authors: Levenbook L.
Published: April 2021

Numerous analyses on the chemical composition of various insects have shown that, as in mammals, fat and glycogen constitute the principal food reserves. Among holometabolic insects the accumulation of these two substances during the larval instars is, to a varying extent, utilized during the process of pupation. Most of the data on the chemical changes during metamorphosis are summarized by Needham (1942). However, as pointed out by Wigglesworth (1939), analyses of the body as a whole show only the gross alterations, and almost nothing is known concerning the composition of the separate organs. The only information available concerns the glycogen content of the isolated insect fat body; thus, Babers (1941) found that in the mature larva of Prodenia eridania (Lep.) the glycogen formed 23·3% of the fat body dry weight, while Yokoyama (1934) estimated the glycogen content of the silkworm fat body to vary from 2 to 17% of the dry weight according to age. No figures have been published for the fat content of the fat body, but histological evidence (Pardi, 1939; Wigglesworth, 1942) clearly demonstrates that fat is also present in high concentration.
Experiments on the Neural Crest of the Lamprey Embryo
Authors: Newth D. R.
Published: April 2021

The fate of the neural crest of the head in Lampetra planeri has been studied by experiments involving the removal or the homoplastic transplantation of short regions of this tissue. The results show that the neural crest of lamprey is normally destined to form part at least of the dorsal root ganglia, and that it probably gives rise to most, if not all, of the melanophores and to some of the ectomesenchyme. No evidence that the neural crest of the head was the source of the ‘trabeculae cranii ‘or the cartilages of the branchial basket was found. It is concluded that these structures are most probably not crest derivatives. The phylogenetic significance of the embryology of the lamprey ‘trabeculae cranii’ and visceral skeleton is discussed. The transplantation experiments provided some evidence that the form of the neural tube in lamprey is determined in the same manner as that established by Holtfreter (1933, 1934) for Amphibia.
On The Hormonal and Neural Control of the Release of Gametes in Ascidians
Authors: Carlisle D. B.
Published: April 2021

It is argued that the neural gland ( + ciliated pit) of ascidians is homologous with the entire pituitary of vertebrates, adenohypophysis as well as neurohypophysis. Ciona and Phallusia are shown to respond to an injection of chorionic gonadotrophin by the release of gametes. They respond in the same way to feeding with eggs and sperm of their own species but not to those of other species. This response is prevented in both cases by section of the nerves from the ganglion to the region of the gonads. Destruction of the heart and removal of the blood does not prevent the response to feeding with gametes, nor to injection of gonadotrophin into the neural region; this operation does prevent the reaction if the site of injection is elsewhere. Destruction of the neural gland, leaving the ganglion intact, prevents the response to feeding with gametes, but does not prevent its following an injection of chorionic gonadotrophin. The hypothesis is advanced that the neural gland ( + ciliated pit) is the sense organ involved in this response to feeding, and that it produces gonadotrophin and passes it to the ganglion by a non-vascular route; the ganglion then stimulates by nervous pathways the gonads to release gametes. It is suggested that gonadotrophin is here fulfilling a sensory role in passing information from sense organ to the central nervous system. It may be contrasted with adrenalin which passes instructions from the central nervous system to effectors. Phallusia is shown to respond with gamete release to an injection of an extract of the neural complex of Ciona.
The Excretion of Sodium and Potassium by the Malpighian Tubules of Rhodnius
Authors: Ramsay J. A.
Published: April 2021

The very considerable changes in the concentrations of sodium and potassium in the urine of Rhodnius during the normal course of excretion are not reflected in the haemolymph which remains relatively constant in composition. The concentration of potassium in the haemolymph can be increased some tenfold by adding potassium chloride to the blood on which the insect feeds. Such increase in the concentration of potassium can be tolerated for several hours without loss of nervous co-ordination, but it is ultimately fatal. The upper portion of the Malpighian tubule can secrete a urine which contains more potassium and less sodium than the haemolymph. During the passage of this urine through the lower portion of the tubule the differences in concentration between urine and haemolymph became reduced. It is probable that water and sodium, but not potassium, are reabsorbed from the urine in the rectum during the later stages of excretion.
An Electron Diffraction Study of the Structure and Orientation of the Lipids in Yeast and Bacterial Cell Walls
Authors: Hurst H.
Published: April 2021

While it is generally agreed that many of the permeability relationships of different types of living cells depend on the chemical and physical properties of the lipids or lipo-proteins in the surface layers, no direct evidence of the nature of the molecular organization of these fatty components as they occur in situ has yet been produced. Such suggestions as have been made have been based mainly on permeability studies of cells and model membranes, while examinations of the properties and behaviour of the isolated components by the sensitive monolayer technique (Schulman & Rideal, 1937) has proved a useful guide to the possible molecular structure of the cell membrane. Supporting evidence has been derived from polarization and electron microscopy, and from impedance and electrophoresis measurements. The thinness of the cell membrane has so far prevented direct study by X-ray diffraction, although this method of analysis has successfully been applied to the study of isolated fatty components (Schmitt & Palmer, 1940).
A Comparative Study of the Lipids of the Vertebrate Central Nervous System
Authors: McColl J. D. , Rossiter R. J.
Published: April 2021

Previous studies from this laboratory have shown that the distribution of lipids in the brains of a number of different mammalian species is very similar (Johnson, McNabb & Rossiter, 1948). Evidence was presented for the view that free cholesterol and the two sphingosine-containing lipids,* cerebroside and sphingomyelin, are the principal lipids of the myelin sheath of a mammalian nerve fibre (Johnson, McNabb & Rossiter 1949a, b, 1950; Burt, McNabb & Rossiter, 1950). These lipids were called the myelin lipids. However, McColl & Rossiter (1950, 1951) showed that the lipids of the nervous system of certain invertebrates, notably Loligo, Limulus and Libinia, differed in a number of respects from those of the mammal.

In this paper, data are presented for the lipids of the brains of a series of vertebrates, including representatives of the cartilaginous and bony fishes, amphibians, reptiles, birds and mammals.
A Roundabout for Studying Sustained Flight of Locusts
Authors: Krogh August , Weis-Fogh Torkel
Published: April 2021

The purpose of the technique described here was to study the influence of external factors upon the flying speed and the ability of small ‘swarms’ of locusts to sustain prolonged flight. The wind forces acting on a flying animal depend only on the motion of its elements relative to the air mass, i.e. on the relative wind. Instead of investigating actual free flight, a locust can therefore be suspended in front of a wind tunnel and made to fly against a streamlined and uniform current of air, the wind speed being adjusted so as to correspond to the air speed of the freely flying insect. Under such conditions it has been possible to make a single individual fly for several hours. But a very large tunnel would be necessary for a number of animals to fly simultaneously as is required for quantitative work. Instead of moving the air mass, one can move the suspended animal through still air with a speed corresponding to the flying speed and so have several insects flying at once. Thus proper aerodynamic conditions for flight can be obtained by attaching the animals to a revolving ring, provided the ring is made so large that the angular velocity is kept small.