bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of the respiratory central pattern generator by chloride-dependent inhibition during development in the bullfrog (Rana catesbeiana)
Authors: Broch Lise , Morales Rey D. , Sandoval Anthony V. , Hedrick Michael S.
Published: April 2021

Isolated brainstem preparations from larval (tadpole) and adult Rana catesbeiana were used to examine inhibitory mechanisms for developmental regulation of the respiratory central pattern generator (CPG). Preparations were superfused at 20-22 °C with Cl--free artificial cerebrospinal fluid (aCSF) or with aCSF containing agonists/antagonists ofγ-aminobutyric acid (GABA) or glycine receptors. Respiratory motor output from the CPG, measured as neural activity from cranial nerve roots, was associated with fictive gill ventilation and lung ventilation in tadpoles and with fictive lung ventilation in adults. In tadpoles, fictive lung burst frequency was 0.8±0.2 min-1 and did not change significantly with Cl--free aCSF superfusion; however, lung burst amplitude increased by nearly 400 % (P<0.01). Fictive gill ventilation averaged 41.6±3.3 min-1 and was reversibly abolished by Cl--free aCSF. Superfusion with Cl--free aCSF abolished lung bursts in two of seven adult preparations, and overall lung burst frequency decreased from 3.1±0.7 to 0.4±0.03 min-1(P<0.01), but burst amplitude was unchanged. Low concentrations of GABA (0.5 mmol l-1) produced a significant increase in lung burst frequency followed by almost complete inhibition at 5.0 mmol l-1,accompanied by the abolition of gill ventilation at 2.5-5.0 mmol l-1. By contrast, fictive lung ventilation in adults was inhibited in a dose-dependent manner by glycine and GABA, and inhibition occurred at approximately 10-fold lower concentrations compared with tadpoles. The glycine receptor antagonist strychnine (2.5-25.0 μmol l-1) and the GABAA receptor antagonist bicuculline (1-10 μmol l-1)inhibited fictive gill ventilation and increased fictive lung ventilation in tadpoles. However, bicuculline and strychnine inhibited fictive lung ventilation in adults. These results suggest that lung ventilation in the tadpole brainstem may be driven by a pacemaker-like mechanism since Cl--free aCSF failed to abolish lung ventilation. Lung ventilation in adults and gill ventilation in tadpoles, however, appear to be dependent upon conventional Cl--mediated synaptic inhibition. Thus, there may be a developmental change in the fundamental process driving lung ventilation in amphibians. We hypothesize that maturation of the bullfrog respiratory CPG reflects developmental changes in glycinergic and/or GABAergic synaptic inhibitory mechanisms.
The mechanical basis ofDrosophilaaudition
Authors: Göpfert Martin C. , Robert Daniel
Published: April 2021

In Drosophila melanogaster, antennal hearing organs mediate the detection of conspecific songs. Combining laser Doppler vibrometry, acoustic near-field measurements and anatomical analysis, we have investigated the first steps in Drosophila audition, i.e. the conversion of acoustic energy into mechanical vibrations and the subsequent transmission of vibrations to the auditory receptors in the base of the antenna. Examination of the mechanical responses of the antennal structures established that the distal antennal parts (the funiculus and the arista) together constitute a mechanical entity, the sound receiver. Unconventionally, this receiver is asymmetric, resulting in an unusual, rotatory pattern of vibration; in the presence of sound, the arista and the funiculus together rotate about the longitudinal axis of the latter. According to the mechanical response characteristics, the antennal receiver represents a moderately damped simple harmonic oscillator. The receiver's resonance frequency increases continuously with the stimulus intensity, demonstrating the presence of a non-linear stiffness that may be introduced by the auditory sense organ. This surprising,non-linear effect is relevant for close-range acoustic communication in Drosophila; by improving antennal sensitivity at low song intensities and reducing sensitivity when intensity is high, it brings about dynamic range compression in the fly's auditory system.
Urine makes the difference
Authors: Breithaupt Thomas , Eger Petra
Published: April 2021

Chemical communication is a widespread phenomenon in aquatic animals but is difficult to investigate because the signals are not visible. Here, we present the results of a study into chemical communication in blindfolded fighting crayfish (Astacus leptodactylus) in which we employed a new method:visualisation of urine using the dye Fluorescein. The probability of urine release is greater during fights than during non-social activities or inactivity. The eventual winners are more likely to release urine during fights than the eventual losers. In both winners and losers, urine release is coupled to offensive behaviours, and the probability of urine release increases with increasing levels of aggression. In A. leptodactylus,urine is carried to the opponent by the forward-projecting gill currents. During spontaneous release, urine is fanned laterally with the aid of the exopodites of the maxillipeds. Aggressive behaviour is effective in intimidating blindfolded opponents only in conjunction with urine release:receivers decrease offensive behaviour and increase defensive behaviour. Aggressive behaviour alone does not intimidate opponents. The loser of a recent fight is deterred equally well by a familiar and an unfamiliar opponent. Hence, in crayfish, individual recognition of the urine scent of a dominant individual does not appear to be significant for the maintenance of dominance hierarchies. Our results suggest that urine contains information about the fighting ability and/or aggressiveness of the signaller. The chemical signals thus far unidentified appear to be important in determining the outcome of a fight.
Energetics of median and paired fin swimming, body and caudal fin swimming, and gait transition in parrotfish (Scarus schlegeli) and triggerfish (Rhinecanthus aculeatus)
Authors: Korsmeyer Keith E. , Steffensen John Fleng , Herskin Jannik
Published: April 2021

To determine the energetic costs of rigid-body, median or paired-fin (MPF)swimming versus undulatory, body-caudal fin (BCF) swimming, we measured oxygen consumption as a function of swimming speed in two MPF swimming specialists, Schlegel's parrotfish and Picasso triggerfish. The parrotfish swam exclusively with the pectoral fins at prolonged swimming speeds up to 3.2 total lengths per second (L s-1; 30 min critical swimming speed, Ucrit). At higher speeds, gait transferred to a burst-and-coast BCF swimming mode that resulted in rapid fatigue. The triggerfish swam using undulations of the soft dorsal and anal fins up to 1.5 L s-1, beyond which BCF undulations were recruited intermittently. BCF swimming was used continuously above 3.5 L s-1, and was accompanied by synchronous undulations of the dorsal and anal fins. The triggerfish were capable of high, prolonged swimming speeds of up to 4.1 L s-1 (30 min Ucrit). In both species, the rates of increase in oxygen consumption with swimming speed were higher during BCF swimming than during rigid-body MPF swimming. Our results indicate that, for these species,undulatory swimming is energetically more costly than rigid-body swimming, and therefore support the hypothesis that MPF swimming is more efficient. In addition, use of the BCF gait at higher swimming speed increased the cost of transport in both species beyond that predicted for MPF swimming at the same speeds. This suggests that, unlike for terrestrial locomotion, gait transition in fishes does not occur to reduce energetic costs, but to increase recruitable muscle mass and propulsive surfaces. The appropriate use of the power and exponential functions to model swimming energetics is also discussed.
Redistribution of immunofluorescence of CFTR anion channel and NKCC cotransporter in chloride cells during adaptation of the killifishFundulus heteroclitusto sea water
Authors: Marshall W. S. , Lynch E. M. , Cozzi R. R. F.
Published: April 2021

Cellular distribution of cystic fibrosis transmembrane conductance regulator (CFTR) immunofluorescence was detected by monoclonal antibody directed to the C terminus of killifish CFTR (kfCFTR) in chloride cells of fresh water (FW) adapted fish and animals transferred to sea water (SW) for 24h, 48h and 14+ days. Confocal microscopy allowed localization within mitochondria-rich (MR) cells to be determined as superficial (i.e. in the apical membrane) or deeper within the cytoplasm of the cells. In FW, 90 % of MR cells had diffuse kfCFTR immunofluorescence in the central part of the cytosol, with only 8.1 % having apical kfCFTR, which was 6.6±0.54 μm below the microridges of surrounding pavement cells. Curiously, FW but not SW pavement cells also had positive immunofluorescence to kfCFTR. After 24h in SW, a time when kfCFTR expression is elevated, a condensed punctate immunofluorescence appeared among 18.8 % of MR cells, 13.4±0.66 μm(mean ± S.E.M.) below the surface of the cells. By 48h, a majority(76.3 %) of MR cells had punctate kfCFTR distribution and the distance from the surface was less (7.8±0.2 μm), a distribution approaching the SW-acclimated condition (i.e. all MR cells showing kfCFTR immunofluorescence,6.1±0.04 μm below the surface). In contrast, NKCC immunofluorescence was condensed and localized in lateral parts of MR cell complexes in FW animals and then redistributed to the whole basal cytoplasm after acclimation to SW. CFTR, the anion channel responsible for Cl- secretion in marine teleosts, redistributes in MR cells during SW acclimation by condensation of a diffuse distribution below the apical crypt, followed by translocation and insertion in the apical membrane. NKCC, the cotransporter that translocates Cl- across the basolateral membrane, moves from an eccentric cytosolic location in FW to a diffuse basolateral localization in SW chloride cells.
Force enhancement following stretching of skeletal muscle
Authors: Herzog W. , Leonard T. R.
Published: April 2021

We investigated force enhancement following stretching in the in situ cat soleus muscle on the ascending and descending limb of the force-length relationship by varying the amount and speed of stretching and the frequency of activation (5 Hz, 30 Hz). There was a small but consistent(P<0.05) amount of force enhancement following muscle stretching on the ascending limb of the force—length relationship for both stimulation frequencies. The steady-state active isometric forces following stretches of 9 mm on the descending limb of the force—length relationship were always equal to or greater than the corresponding forces from the purely isometric contractions at the length at which the stretch was started. Therefore, force production for these trials showed positive stiffness and was associated with stable behavior. Following active stretching of cat soleus on the descending limb of the force—length relationship,the passive forces at the end of the test were significantly greater than the corresponding passive forces for purely isometric contractions, or the passive forces following stretching of the passive muscle. This passive force enhancement following active stretching increased with increasing magnitude of stretch, was not associated with structural damage, and only disappeared once the muscle was shortened. For stretches of 6 mm and 9 mm, the passive force enhancement accounted for more than 50 % of the total force enhancement,reaching a peak contribution of 83.7 % for the stretches of 9 mm at a speed of 3 mm s-1. The results of this study suggest that a passive structural element provides a great part of the force enhancement on the descending limb of the force—length relationship of the cat soleus. Furthermore, the results indicate that mechanisms other than sarcomere length non-uniformity alone are operative.
Peripheral Nerve and Regeneration in Crustacea
Authors: Needham A. E.
Published: April 2021

There is now good evidence that in the Vertebrata peripheral nerves exert an important trophic effect on the regeneration of the structures which they innervate (Millot, 1931; Needham, J. 1942; Hamburger, 1944). In invertebrates the nervous system is not always necessary; Millot (1931, p. 117) concluded that in types where regenerative powers are comparatively limited (e.g. Mollusca, some Nemer-tinea), the nervous system is necessary, while in types with extensive regenerative powers (Tunicata, many Platyhelmia) it may be unnecessary. Some of the Crustacea are outstanding among the higher invertebrates for their extensive regenerative powers, and from the evidence available in 1927 (Korschelt, 1927, pp. 600–1) it seemed probable that in this group regeneration does not depend on the nerve supply. Subsequent publications have not materially affected this conclusion. In the present experiments evidence on the question is. sought from the regeneration of a pair of thoracic limbs in Asellus aquaticus (L.).
The Oxygen Affinities of Certain Invertebrate Haemoglobins
Authors: Fox H. Munro
Published: April 2021

For a variety of physiological and ecological reasons it is of importance to know the oxygen pressures at which the haemoglobins of different animals take up or part with oxygen. In the relatively few cases in which this has been studied in small animals, particularly invertebrates, the blood, since it is only available for investigation in very small amounts, has generally been considerably diluted with water. But the position of the oxygen dissociation curve of dilute haemoglobin is not necessarily the same as that in whole blood: the oxygen affinity may increase with dilution (Florkin et al., 1941). To survey the oxygen affinities of various invertebrate haemoglobins I therefore devised a method of working with one or two drops of whole, or very slightly diluted, blood. The method is as follows.
The Nutrition of the Larva of Aedes Aegypti L. I
Authors: Meillon B. De , Golberg L. , Lavoipierre M.
Published: April 2021

Insects, because of their great diversity of form and habit, offer a very wide field for physiological research. Apart from the purely academic aspect it is obvious that there is much more hope of controlling harmful insects or encouraging beneficial ones if their life processes are more thoroughly understood. There is also the possibility that some of these life processes are similar or related to those of the vertebrates including man himself, in which case insects may yield interesting and valuable information of more direct importance. In fact, when more is known about them there appears to be no reason why some should not come into use as laboratory animals. A start in this direction has already been made since the larva of the wax moth Galleria mellonella has been used for the estimation of nicotinic acid (Rubinstein & Shekun, 1939).
The Nutrition of the Larva of Aedes Aegypti L. II. Essential Water-Soluble Factorb From Yeast
Authors: Golberg L. , Meillon B. De , Lavoipierre M.
Published: April 2021

The study of the nutritional requirements of mosquito larvae has made comparatively little progress since Trager (1935) reported that they could be brought to maturity in a sterile medium consisting only of autoclaved yeast and liver extract. Subsequently a number of random observations were reported, dealing with the factors necessary for growth and metamorphosis of mosquito larvae. No concerted effort, however, has been made to replace the yeast-liver extract medium of Trager by a mixture of known components. This is the immediate object of our investigations, and the results presented below serve to bring it yet another stage nearer realization.
The Mechanism of Absorption from the Rumen as Exemplified by the Behaviour of Acetic, Propionic and Butyric Acids
Authors: Danielli J. F. , Hitchcock M. W. S. , Marshall R. A. , Phillipson A. T.
Published: April 2021

The following conclusions were reached by placing a solution of sodium acetate, propionate and butyrate in the rumen of sheep and studying the rate at which these substances are absorbed :

When the rumen contents are at pH 7·5, fatty acid anion only is absorbed, i.e. no free fatty acid is absorbed, and the anion is accompanied by a roughly equivalent amount of sodium. The anion is absorbed by passage through water-filled pores, the diameter of which is large compared with butyric acid. These pores probably lie in the intercellular cement of the rumen epithelium. When the rumen contents are at pH 5·8, free acid is lost from the rumen in large amounts in addition to the loss of fatty acid anion. Part of this free acid is absorbed by passage through water-filled pores, but the greater part of it passes through the lipoid membranes of the epithelial cells. In consequence of the difference in the two mechanisms, at alkaline pH the substances are lost in the order acetate > propionate > butyrate, whereas at acid pH the order is butyrate > propionate > acetate. All the substances studied (fatty acid anions, sodium and water) move from regions of higher to regions of lower concentration. The total fatty acid absorbed from the rumen of a sheep on pasture grass may readily be twice that absorbed from the rumen by the same sheep on hay. The permeability of the rumen epithelium is such that the pH of the ingesta tends to move towards neutrality, independently of the neutralizing action of the saliva.
The Growth of Brown Trout (Salmo Trutta Linn.)
Authors: Brown Margaret E.
Published: April 2021

Groups of trout fry of the same parentage were grown in environments where the following factors were controlled : temperature, amount and intensity of illumination, rate of water flow, aeration and chemical composition of the water, amount of living space and quality of food supply. They were allowed to eat as much as they would, and individual weights were recorded during the first 8 months after the beginning of feeding. There was soon an increase in the range of individual weight in each group of fry, and thereafter the larger fry grew faster than smaller ones. When the larger fry were removed, the smaller ones grew at an increased specific rate, and when larger fry were added, the smaller ones grew more slowly. It is suggested that a ‘size hierarchy’ was established within each group, and an individual’s specific growth rate depended on its position in the order of decreasing weight. There was an optimum degree of crowding for maximum productivity. Compared with the fry in this group, the specific growth rates of individuals in larger, more crowded groups depended on the number of fish of larger size, while in smaller, less crowded groups, individuals grew at rates depending on the proportion of fish which were larger and smaller. Alevin weight had little effect on the specific growth rates of fry. There were differences between the growth histories of fry derived from alevins of the same weight and descended from the same father but different mothers (all of the same stock, age and size). The specific growth rates decreased as the fry grew older, but there was no correlation between body weight and specific growth rate, except for the size hierarchy effect within each group. This effect had a greater influence on the size of individual fry than had either alevin weight or heredity.
The Growth of Brown Trout (Salmo Trutta Linn.)
Authors: Brown Margaret E.
Published: April 2021

Since fish form an important source of human food, a considerable amount of data is available concerning their distribution and size under natural conditions. This is especially true for the Salmonidae because of their popularity with sporting fishermen. With the development of commercial hatcheries, there has been a certain amount of experimental work concerning the effect of various factors on the growth and life history, particularly of ‘trout’—Salmo trutta, S. irideus and Salvelinus fontinalis. However, it is impossible to define the effect of any particular factor on trout growth, since several environmental factors varied at the same time, without being measured accurately. In some experiments (Surber, 1935; Pentelow, 1939) individual trout were isolated and their growth recorded, while in others (McCay & Tunison, 1935, 1937; Wingfield, 1940) the fish were kept in groups and their average sizes recorded at intervals. There is thus no record of the effect of intraspecific relationships on the growth of individuals.
The Development of the Rat Eye in Graft
Authors: Tansley Katharine
Published: April 2021

Successful grafts were obtained when 15-day embryo rat eyes were transplanted into the brains of 2-day old rats. In the grafts differentiation of the various ocular tissues proceeded at the normal rate. The lens and retina first degenerate and then regenerate, the lens from its epithelium, the retina from its ciliary area. It was not possible to establish whether or not Wolffian regeneration of the lens can occur in the rat.
Run and hide: visual performance in a brittle star
Authors: Sumner-Rooney Lauren , Kirwan John D. , Lüter Carsten , Ullrich-Lüter Esther
Published: April 2021

Spatial vision was recently reported in a brittle star, Ophiomastix wendtii, which lacks discrete eyes, but little is known about its visual ecology. Our aim was to better characterize the vision and visual ecology of this unusual visual system. We tested animal orientation relative to vertical bar stimuli at a range of angular widths and contrasts, to identify limits of angular and contrast detection. We also presented dynamic shadow stimuli, either looming towards or passing the animal overhead, to test for potential defensive responses. Finally, we presented animals lacking a single arm with a vertical bar stimulus known to elicit a response in intact animals. We found that O. wendtii orients to large (≥50 deg), high-contrast vertical bar stimuli, consistent with a shelter-seeking role and with photoreceptor acceptance angles estimated from morphology. We calculate poor optical sensitivity for individual photoreceptors, and predict dramatic oversampling for photoreceptor arrays. We also report responses to dark stimuli moving against a bright background – this is the first report of responses to moving stimuli in brittle stars and suggests additional defensive uses for vision in echinoderms. Finally, we found that animals missing a single arm orient less well to static stimuli, which requires further investigation.
Algorithms underlying flexible phototaxis in larval zebrafish
Authors: Chen Alex B. , Deb Diptodip , Bahl Armin , Engert Florian
Published: April 2021

To thrive, organisms must maintain physiological and environmental variables in suitable ranges. Given that these variables undergo constant fluctuations over varying time scales, how do biological control systems maintain control over these values? We explored this question in the context of phototactic behavior in larval zebrafish. We demonstrate that larval zebrafish use phototaxis to maintain environmental luminance at a set point, that the value of this set point fluctuates on a time scale of seconds when environmental luminance changes, and that it is determined by calculating the mean input across both sides of the visual field. These results expand on previous studies of flexible phototaxis in larval zebrafish; they suggest that larval zebrafish exert homeostatic control over the luminance of their surroundings, and that feedback from the surroundings drives allostatic changes to the luminance set point. As such, we describe a novel behavioral algorithm with which larval zebrafish exert control over a sensory variable.
Observations On the Effect of Microclimate on Biting by Aedes Aegypti (L.) (Dipt., Culicid.)
Authors: Lumsden W. H. R.
Published: April 2021

Work on the factors controlling the avidity of Aëdes aegypti females for a blood meal previously reported by Seaton & Lumsden (1941) was continued. Mosquitoes were kept after hatching for 96–120 hr. in darkness at about 25° C. and 80% relative humidity, and were then offered a blood meal on the human arm in darkness. Wide variations in the light intensity during the few minutes’ manipulation immediately previous to offering the host did not significantly affect the numbers feeding. The relative humidity of the environment at the time of biting appeared to be of little or no importance. The optimum environmental temperature for biting was near 35° C. At 35° C., out of batches of ten mosquitoes offered 5 min. opportunity to feed, means of 8·8 ± 0·44 and 9·2 ± 0·33 fed at high and low humidities respectively. Large proportions of A. aegypti females, confined within 8·5 cm. of a host and in darkness, were able to locate the host and to feed when environmental temperatures approximated closely to the skin temperature or even were above it. Some factor other than the presence of a temperature gradient rising to the skin must therefore be responsible for their orientation to, and probing of, the host. In the majority of fed mosquitoes blood was found in the stomach alone, but partly fed mosquitoes showed a higher proportion with blood in the diverticula than did those fully gorged. Such an effect is probably due to regurgitation of blood from the stomach when feeding is interrupted before its normal completion.
Molecular and physiological characterization of a crustacean cardioactive signaling system in a lophotrochozoan – the Pacific oyster (Crassostrea gigas): a role in reproduction and salinity acclimation
Authors: Réalis-Doyelle Emilie , Schwartz Julie , Dubos Marie-Pierre , Favrel Pascal
Published: April 2021

The crustacean cardioactive peptide (CCAP) is an important neuropeptide involved in the regulation of a variety of physiological processes in arthropods. Although this family of peptides has an ancestral origin, its function remains poorly understood among protostome species – apart from arthropods. We functionally characterized three G protein-coupled receptors (GPCRs) in the oyster Crassostrea gigas, phylogenetically related to ecdysozoan CCAP receptors (CCAPRs) and to chordate neuropeptide S receptors (NPSRs). Cragi-CCAPR1 and Cragi-CCAPR2 were specifically activated by the Cragi-CCAP1 and Cragi-CCAP2 peptides, respectively, both derived from the same CCAP precursor. In contrast, Cragi-CCAPR3 was only partially activated by CCAP1 and CCAP2 at high concentrations. The Cragi-CCAPR1 and Cragi-CCAPR2 genes were expressed in various adult tissues. They are both most expressed in the gills, while Cragi-CCAPR3 is mainly expressed in the visceral ganglia (VG). Cragi-CCAP precursor transcripts are higher in the VG, the labial palps and the gills. Receptor and ligand-encoding transcripts are more abundantly expressed in the gonads in the first stages of gametogenesis, while the Cragi-CCAP precursor is upregulated in the VG in the last stages of gametogenesis. This suggests a role of the CCAP signaling system in the regulation of reproductive processes. A role in water and ionic regulation is also supported considering the differential expression of the CCAP signaling components in oysters exposed to brackish water.
The Physiology of Sea-Urchin Spermatozoa
Authors: Rothschild Lord
Published: April 2021

Echinus esculentus spermatozoa are normally motionless in undiluted semen. They become active when the semen is diluted with sea water or seminal plasma obtained by gentle centrifugation (1500 r.p.m., 12 cm. radius, for 15 min.). A sperm-immobilizing substance can, however, be obtained in seminal plasma by more prolonged centrifugation of semen. Spermatozoa can be made motile in undiluted semen by increasing the O2 tension in the atmosphere surrounding the semen. This O2 activation is completely inhibited by N2; the N2 effect is reversible. Measurements of seminal O2 tension were made with an O2 electrode. The O2 tension of semen is low, being at most 15 mm. Hg. It was not possible to decide whether this residual tension was due to O2 or some other substance reacting at the electrode. The K content of seminal plasma is about 1·55 mg./ml., which is four times higher than that of perivisceral fluid or sea water. The pH of semen is lower than that of sea water, being approx. 7·5. Neither K concentration nor pH is responsible for the inactivity of sperm in semen. A hormone, Androgamone I, is often considered to be responsible for the inactivity of spermatozoa in non-mammalian semen. No support has been found for this view and it is concluded that in E. esculentus semen the spermatozoa are motionless through lack of O2.
The Water-Balance Principle of Crustacean Eye-Stalk Extracts
Authors: Heller H. , Smith B.
Published: April 2021

Eye-stalks of the brackish water-crab, Carcinus moenas, and of the fresh-water crayfish, Potamobius fluviatilis, were extracted according to the pharmacopoeia! method for the extraction of posterior pituitary glands. Injection of such eye-stalk extracts resulted in a temporary increase in the body water of frogs. The increase produced by the extract of one eye-stalk of Carcinus was approximately equal to that produced by the injection of 20 milliunits pitocin ( = oxytocic fraction of mammalian posterior pituitary extract). The crustacean eye-stalk extracts had no significant oxytocic, chloruretic, or antidiuretic effect.
The Effect of Sex-Hormones on the Performance of a Learned Response
Authors: Douglas J. W. B. , Hanson D. A. , Zuckerman S.
Published: April 2021

The Hull ‘Goal-Gradient Alley’ is described, and its advantages in the analysis of the effect of hormonal stimulation upon conditioning are discussed. The rate at which spayed rats run the goal-gradient alley was tested before and after the administration of oestrogen alone and oestrogen combined with androgen. It was found that a decrement in the speed of running for food occurs at varying times from 6 to 102 hr. after the administration of oestradiol benzoate. The decrement is still apparent when testosterone propionate and oestradiol benzoate are administered in the proportion 20:1, but is not present when the proportion is 50 :1. The possible physiological mechanisms of this response decrement are considered.
The Physiology of Contractile Vacuoles
Authors: Kitching J. A.
Published: April 2021

The rate of output of the contractile vacuole in a fresh-water peritrich ciliate (Carchesium aselli) varies with temperature with a Q10 of about 2·5–3·2, or a μ of about 17,000, over the range 0–30° C. There is a slow decline in output during exposure for several hours to high temperatures (25–30° C.). At still higher temperatures (34° C.) a high rate of output is maintained for a few minutes, but swelling and death rapidly ensue. The frequency of uptake of food vacuoles also varies with temperature, increasing from o to about 24° C., but decreasing at higher temperatures. At about o° C. and at temperatures above about 30° C. no food vacuoles are taken up and the adoral cilia remain extended and motionless. No change in body volume could be detected during exposure to high temperatures (25–30° C.) for two or more hours, even though the rate of vacuolar output was increased to three or four times its normal level at 15° C. It is concluded that the rate of uptake of water from the outside medium must have been increased correspondingly. It is suggested that temperature affects the permeability of the organism to water, and that the rate of vacuolar output is adjusted accordingly, although on the evidence so far presented other explanations are possible.
The Metabolism of Fertilized and Unfertilized Sea-Urchin Eggs
Authors: Rothschild Lord
Published: April 2021

An investigation has been made into the effect of light and carbon monoxide on the respiration of sea-urchin eggs (Psammechinus miliaris), with special reference to unfertilized eggs. The O2 uptake of unfertilized eggs in air is 38% higher in the dark than in light. This inhibitory action of light persists when gas mixtures containing CO and O2 are substituted for air. Fertilized and unfertilized eggs differ in that the former’s respiration is only about 10% inhibited by light. In 80% CO in O2 in the dark, the O2 uptake of unfertilized eggs is 55% higher than in 80% N2 in O2 in the dark. In 95% CO in O2 in the dark, the O2 uptake of unfertilized eggs is only 7% higher than in 95 % N2 in O2 in the dark, showing that at this partial pressure, CO exerts an inhibitory action on respiration. There is no difference between O2 uptake in 80% CO in O2 in light and dark. O2 uptake in 95 % CO in O2 in light is 45 % higher than in this gas mixture in the dark, showing that at this partial pressure of CO, photo-reversal of respiratory inhibition occurs. Results similar to those in 80% CO in O2 were obtained with gas mixtures containing lower partial pressures of CO. Cytochromes a and were identified spectroscopically in unfertilized eggs. It is concluded that respiration is mediated through the cytochrome system before and after fertilization. In theories which postulate that cytochrome is ‘thrown into circulation’ at fertilization, the simultaneous light-inhibition of respiration, stimulation of O2 uptake by CO, and photo-reversible inhibition of O2 uptake by CO have not been taken into consideration.
The Osmotic Relations of the Earthworm
Authors: Ramsay J. A.
Published: April 2021

Osmotic pressure and chloride concentration have been determined for the coelomic fluid, blood and urine of earthworms kept in various saline media. About 50% of the osmotic pressure of the coelomic fluid and of the blood can be accounted for as chloride. The blood is very slightly hypotonic to the coelomic fluid. As the concentration of the medium is increased the osmotic pressure of the body fluids also increases and is always greater than that of the medium; the chloride increases proportionately, but is less than that of the medium when the latter exceeds 0·35% NaCl. The urine is always strongly hypotonic to the body fluids except possibly in the most concentrated media (over 1·0% NaCl). The osmotic relations of the earthworm are such as are characteristic of fresh-water animals generally.
A New Method of Freezing-Point Determination for Small Quantities
Authors: Ramsay J. A.
Published: April 2021

A method is described for determining the freezing-point of small quantities (0·1 - 1·0 × 10-3cu.mm.) of fluid. Tested on solutions of NaCl of concentration up to 2% the probable error of the method is less than 0·01% NaCl. The potentialities of the method are discussed.
The Relation Between the Epidermal Mitotic Activity and the Blood-Sugar Level in the Adult Male Mouse, Mus Musculus L
Authors: Bullough W. S.
Published: April 2021

An investigation has been made of the relation between the concentration of the blood sugar and the mitotic activity of the ear epidermis of the adult male mouse. It has been shown that, within limits, an increase in the blood-sugar level, induced by subcutaneous injections of starch, results in an increased mitosis rate. Conversely, a decrease in the blood-sugar level, induced by insulin, causes a decreased mitosis rate. A deep mitosis depression is also caused by injections of phloridzin. Since it is known that phloridzin interferes with the phosphorylation of sugar, and since it is also shown that injections of phosphate augment the effect produced by starch alone, the tentative suggestion is put forward that sugar may act by satisfying the energy requirements of mitosis. However, in the normal animal the diurnal changes in the blood-sugar level are the inverse of the diurnal changes in mitotic activity, the concentration of the blood sugar being relatively low during sleep when the mitosis rate is relatively high. It is therefore evident that, within normal limits, the level of the blood sugar as such is not an important factor in the control of the diurnal mitosis cycles. It is considered probable that the critical factor in the control of these cycles is the concentration of sugar, or glycogen, within the tissues themselves. Thus during sleep, sugar is probably deposited in the tissues, as it is known to be in the liver, so accounting simultaneously for the fall in the level of the blood sugar and the rise in the mitosis rate.
Influence of the Corpus Allatum on the Oxygen Consumption of Adult Calliphora Erythrocephala Meig
Authors: Thomsen Ellen
Published: April 2021

The possible influence of the corpus allatum on the metabolism of adult Calliphora erythrocephala was studied by measuring the oxygen consumption of allatectomized females and males by means of the Warburg apparatus. As a basis for the experiments on operated flies, the oxygen consumption of normal unoperated females and males was measured. The oxygen consumption of the two sexes was found to be of the same order. In the females allatectomy resulted in a decrease in the oxygen consumption of 24%. Implantation of three corpora allata from females into females which retained their own corpus allatum increased the oxygen consumption by 19%. In the males allatectomy likewise caused a reduction in the oxygen consumption, but the exact amount of the decrease was somewhat difficult to evaluate owing to a great number of abnormally high values in the operated controls. Implantation of three corpora allata from males into males which retained their own corpus allatum did not raise the oxygen consumption. A possible cause of this negative result is discussed. It was thus found that the corpus allatum is necessary for the normal metabolism of Calliphora.
The Fertilization Reaction in the Sea-Urchin Egg
Authors: Rothschild Lord
Published: April 2021

The first sign that a sea-urchin egg has been fertilized is a change in cortical structure which spreads over the egg surface from the point of attachment of the fertilizing spermatozoon (Rothschild & Swann, 1949). The velocity of propagation is not uniform, there being a reduction in rate when the change approaches the equator of the egg relative to the point of attachment of the spermatozoon, and a marked increase when the cortical change has nearly covered the egg surface. The conduction mechanism of the cortical change might be similar to that occurring in stimulated nerve or muscle. Alternatively, it might be due to the diffusion of a substance, directly or indirectly derived from the head of the spermatozoon, found the cortex or through the cytoplasm, a change in cortical structure being effected by the arrival at the cortex of a particular concentration of the diffusing substance. If this hypothetical substance diffuses round the cortex and not through the cytoplasm, we must postulate a sympathetic reaction by ‘affected’ parts of the cortex, or an entirely separate cytoplasmic reaction, also initiated by the spermatozoon, to account for the intracellular changes that precede mitosis. By ‘affected’ parts of the cortex, reference is made to that fraction of the cortex which, owing to the arrival of a particular concentration of the diffusing substance, has changed its structure. On the other hand, if diffusion takes place through the cytoplasm, the one process might account for the two phenomena, cortical and intracellular changes, if cortex and cytoplasm are affected at different rates by the diffusing molecules.
Age and Mitotic Activity in the Male Mouse, Mus Musculus L
Authors: Bullough W. S.
Published: April 2021

A study has been made of the mitosis rate and of the diurnal cycles of male mice during each of the first 20 months of life. The mice used belonged to the Kreyberg’s white label and the Strong’s CBA strains. Most of the observations were made on the ear epidermis, but some attention was also given to other tissues. It was discovered that, when judged from the point of view of mitotic activity, the life of a male mouse consists of four ages. During the immature age the animals are still growing and their mitosis rate is generally high, although the ear epidermis provides an exception to this rule. During the mature age which lasts from about the 3rd to the 12th month the mitosis rate is lowered. During the middle age which follows the mitosis rate increases, but in senility it is again reduced. Coincident with these changes in the mitosis rate are changes in the spontaneous bodily activity. The mice are most active during immaturity and maturity. In middle age their activity is reduced by about half, and in senility they spend almost the whole time resting. Particularly in the Strong’s CBA mice there are also changes in the timing of the diurnal cycle of spontaneous bodily activity, and these are immediately mirrored by changes in the timing of the diurnal cycle of mitotic activity so that throughout life a general inverse relationship between bodily activity and mitotic activity is maintained. In middle-aged Strong’s CBA males the daily rest period extends almost without interruption from 06.00 to 18.00 hr. However, the most active cell division develops only at the beginning of this period, and it is evident that in prolonged sleep a lack of some vital factor develops. It is shown that subcutaneous injections of starch overcome this lack in sleeping mice and result almost immediately in the redevelopment of a high mitosis rate. Thus it would appear that sugar is the vital factor involved, and that the sugar content of the tissues is quickly used up during high mitotic activity. These results are discussed particularly in relation to the problem of carcinogenesis.
Studies On Animal Carotenoids
Authors: Steven D. M.
Published: April 2021

In the first paper of this series (Steven, 1948) it was shown that the tissues of the trout (Salmo trutta Linn.) normally contain β-carotene, lutein and astacene. Lutein and astacene occur as esters in the red and yellow chromatophores of the skin, and may also be present in the muscles as free hydroxy-carotenoids. Carotene is present in the liver, which also contains xanthophylls but no astacene. The ripening oocytes, however, contain all three types of carotenoid. Red and yellow chromatophores first appear during the larval period of development before the young fish has commenced to feed independently, and appear to obtain their pigment from the carotenoids laid down in the yolk. This paper records the chemical changes and distribution of these substances from the maturation of the oocytes to the stage of metamorphosis of the larva.

Adult trout were obtained alive from a reservoir near Edinburgh. Some ova were obtained from ripe fish in the laboratory, and fertilized with sperm from males of the same batch. Larger numbers were supplied by the Howietoun and Northern Fisheries, Stirling, as ‘eyed’ ova, and were used for most of the experiments on the larval period of development. Ova and larvae were reared in batches of about 100 each in glass aquarium jars, which were immersed nearly to the rim in a larger tank through which passed a rapid flow of water taken direct from the mains supply. This arrangement gave satisfactory temperature stabilization for the period of the experiments, from January to the end of March. Temperature variation was less than 1° C. for periods of more than a week, and remained within the range 4–6° C. for the whole period.
Phases of Activity in the Sea-Anemone,Metridium Senile(L.), and Their Relation to External Stimuli
Authors: Batham E. J. , Pantin C. F. A.
Published: April 2021

We have shown in a previous paper (Batham & Pantin, 1950b) that the sea-anemone Metridium senile exhibits continual very slow muscular activity. It is most evident in the changes of shape of the column caused by the reciprocal contractions of the circular muscle sheet, and of the longitudinal parietal musculature which runs at the junction of each mesentery with the body wall. This inherent activity varies, so that in the same individual it presents a different pattern on different occasions. The pattern may remain constant for hours on end, and may then change over a comparatively short period. Thus a moderately filled anemone giving fairly regular and substantial contractions may pass into a condition with a larger volume and much less apparent activity, or it may pass into a condition of prolonged and almost complete contraction. These patterns of activity often endure for long periods—hours or even days. It is convenient to refer to such patterns as ‘phases’, and these phases form the subject of this paper.
The Influence of Water and Light Upon the Pigmentary System in the Common Frog Rana Temporaria
Authors: Rowlands Anne
Published: April 2021

A significant influence of water in relation to colour change in Rana temporaria has been established. Its action on the melanophores in relation to background shows it exerts an independent influence. Thus (a) with a black illuminated environment, water accentuates the background response, (b) with a white illuminated environment there is antagonism, (c) in darkness the presence of water induces extreme expansion, and drying induces contraction, but only after prolonged periods. Immersion on a white illuminated background causes immediate expansion, and prolonged drying even upon a black background induces contraction. During the breeding cycle, the males fail to darken when immersed upon a white illuminated background. This particular seasonal effect is not shown by the females. It was further shown that the water response is independent of the primary response. The greater the degree of immersion, the greater the degree of expansion maintained upon a white illuminated background, so that the area of contact is significant, and it is highly probable that skin receptors are concerned. The lower oxygen tension of water as compared with that of the atmosphere was not a significant factor in the expansion of the melanophores due to immersion.
The Integration of Activity Cycles in the Behaviour of Arenicola Marina L
Authors: Wells G. P. , Albrecht Elinor B.
Published: April 2021

The common lugworm exhibits two distinct types of spontaneous activity cycle. Each of them has been described in some detail, but the method of approach was rather different in the two cases, and their integration has not yet been discussed. The experiments to be described were made to throw light on their mutual relations. The work was done at the laboratory of the Marine Biological Association of the United Kingdom, at Plymouth, in March and April 1950.

The relevant features of the two cycles, as hitherto described, will first be summarized. For a more detailed review see Wells (1950).
The Role of Oesophageal Rhythms in the Behaviour of Arenicola Ecaudata Johnston
Authors: Wells G. P. , Albrecht Elinor B.
Published: April 2021

The British fauna includes three species of Arenicola. The most abundant is the common lugworm, A. marina L., which Uves in great numbers on tidal sand flats and mud flats. The other two, A. ecaudata Johnston and A. branchialis Aud. & Edw. (=A. grubii Claparède), are found, usually together, in. coarse, rather foul, sandy material, between stones and rocks.
The Temperature-Pulse Rate Curve of the Isolated Frog’s Heart (Rana Temporaria)
Authors: Smith C. L.
Published: April 2021

A seasonal difference in the temperature-pulse rate curve of the isolated frog’s heart was described by Barcroft & Izquierdo (1931). In the summer they found an almost linear relation between temperature and frequency of pulsation from 5 to 20° C., while in the winter the relation was exponential over the same temperature range. Carter (1933) investigated the effects of various endocrine and related substances on the form of the temperature-pulse rate curve. He found that the addition of thyroxine to the medium perfusing the heart transformed the curve given by the winter heart into the summer form, but had no effect on that of the summer heart. He concluded that the seasonal change in the temperature effect on heart rate was controlled by the endocrine system, and that the thyroid by increase in its activity in the summer was the effective agent.