bluuebunny/crossref_metadata_2025_split huggingface dataset:
A test of altitude-related variation in aerobic metabolism of Andean birds
Authors: Gutierrez-Pinto Natalia , Londoño Gustavo A. , Chappell Mark A. , Storz Jay F. 
Published: April 2021

ABSTRACT
Endotherms at high altitude face the combined challenges of cold and hypoxia. Cold increases thermoregulatory costs, and hypoxia may limit both thermogenesis and aerobic exercise capacity. Consequently, in comparisons between closely related highland and lowland taxa, we might expect to observe consistent differences in basal metabolic rate (BMR), maximal metabolic rate (MMR) and aerobic scope. Broad-scale comparative studies of birds reveal no association between BMR and native elevation, and altitude effects on MMR have not been investigated. We tested for altitude-related variation in aerobic metabolism in 10 Andean passerines representing five pairs of closely related species with contrasting elevational ranges. Mass-corrected BMR and MMR were significantly higher in most highland species relative to their lowland counterparts, but there was no uniform elevational trend across all pairs of species. Our results suggest that there is no simple explanation regarding the ecological and physiological causes of elevational variation in aerobic metabolism.
Investigations on the Regional Determination of the Central Nervous System
Authors: Nieuwkoop P. D. 
Published: April 2021

ABSTRACT
With the aseptic operation method of Woerdeman (1930) it is possible to rear duplicitas larvae, formed after grafting of the dorsal blastoporal lip in the place of the ventral one at the early gastrula stage (Spemann, 1918), till an age of about 4 weeks, a time at which they have completely consumed their yolk material. Various forces acting in the normal development and in the development of the duplicitas larvae are discussed in connexion with the external form and the internal organization of the latter. The sources of errors in the method of graphic reconstruction of the brain used in this investigation are checked and their elimination is discussed. The structure of the duplicitas shows that there exists a mediolateral and probably also a cranio-caudal regulation in grafts of the dorsal blastoporal lip of the early gastrula. In the brain one may distinguish between ‘primary’ structures which are always present, and ‘secondary’ structures which are more variable. Therefore, one may probably divide the causal analysis of the development of the central nervous system into the determination of the ‘ground plan’ of the primary structures and the more dependent development of the ‘secondary ‘ones (specific formations). The brains of the secondary embryonic rudiments of these duplicitas are formed in all cases up to a certain level; caudally to this level the brain-parts are normally proportioned, but the most anterior part may be reduced in size. This material can be arranged into a complete regression series, beginning with the reduction of the telencephalon and ending with a completely acephalic embryo. From this development one may conclude that the determination of the central nervous system occurs in a large number of successive zones, which are qualitatively ‘equivalent’, and which are determined by (qualitatively or quantitatively) different values of the organizing ‘agent’. There are indications that the infundibulum and hypophysis are determined by a triple contact between presumptive neural plate, prechordal plate and cephalic ectoderm after the appearance of the neural plate. After special staining these incomplete nervous systems may form a very important source of data for the causal analysis of the development of tracts and nuclei in the central nervous system. With the conclusions drawn from these experiments and the data given in the extensive literature on this subject, a new working hypothesis on the determination of the central nervous system is put forward. This theory involves the assumption (among others) of an equilibrium reaction between a strong mesodermal and a weak ectodermal gradient. The character of the determination process probably changes from being at first purely quantitative to become qualitative with increasing age. Finally, the regional determination of the secondary rudiment in duplicitas is probably determined by a triple interaction between the induction field of the graft, the primary regional structure of the ectoderm and the regional influences of the primary rudiment.
Experimental Modification of the Sexual Cycle of the Greenfinch
Authors: Damsté P. H. 
Published: April 2021

ABSTRACT
’Mewing’ of song-birds is a traditional practice of Dutch bird-catchers who make use of it to produce singing decoys in the autumn. The birds are encaged early in May, the daylight is progressively reduced by means of curtains during May and the birds are kept in darkness throughout June, July and the first half of August. From the middle of August onwards the curtains are gradually opened and by the end of the month the birds are in daylight and in full song once more. This procedure was carried out with the greenfinch (Chloris chloris) under laboratory conditions in order to study the behaviour, song and moulting of the birds and the histology of their gonads before, during and after mewing. In the early stages of mewing the testes decrease in size till in total darkness they have the same diameter as the inactive testis. When the birds are exposed to normal daylight again the testes enlarge rapidly until after some weeks of increasing spermatogenesis they are fully mature. By this time the birds are in full song and it is likely that song coincides with sexual maturity and is induced by the male sex hormone. The diameter of the testis tubules varies in the same way as the diameter of the gonads. In the middle of October, after some weeks of sperm production, regression of the testis sets in. During the ensuing stage of sexual inactivity some birds were exposed to increasing quantities of (electric) light from the beginning of December until the beginning of February. These birds showed increasing spermatogenesis and developed their full song. Thus by means of mewing and ‘extra lighting’ it was possible to bring birds into breeding condition three times within one year.
Visual Responses of Mosquitoes Artificially Rendered Flightless
Authors: Rao T. Ramachandra 
Published: April 2021

ABSTRACT
Most females of Anopheles maculipennis and Culex molestus which had been rendered flightless by removal of wings or by sticking the wings together, tended to move towards a black vertical band when it was presented to them in an arena uniformly illuminated from below. The narrowest width of the band to which they could consistently respond was 0 · 5 cm. at a distance of 3 · 5 cm. corresponding to an angle of about 8 °.
When the edge of a wide black band was exactly in front of the mosquito or at about 45 ° to one side the movement towards it was consistent, but when the band was placed more and more posteriorly consistency of the responses progressively decreased.
When offered simultaneously two black bands of equal or different widths the movement was to one of them. If a new band came into the view when the mosquito was already moving towards another, a turning response towards the new one took place very frequently.
Unilaterally blinded specimens performed circus movements in uniform light. When a narrow black band came into the visual field of the functional eye there was an immediate turning response towards it.
The negative phototaxis continued even at and after dusk at a time when flying mosquitoes were showing natural movement towards the evening light. Reduction of intensity of illumination and also the natural fading of the light at dusk both failed to bring about a reversal of response. For some undetermined reason mosquitoes rendered flightless always tend to move away from light.
The mechanism of orientation seems to be in conformity with current ideas of negative phototropotaxis. No evidence of a photohorotaxis was secured.
The neuropeptide RhoprCCHamide2 inhibits serotonin-stimulated transcellular Na+ transport across the anterior midgut of the vector of Chagas disease, Rhodnius prolixus
Authors: Capriotti Natalia , Gioino Paula , Ons Sheila , Ianowski Juan P. 
Published: April 2021

ABSTRACT
Rhodnius prolixus is a blood-feeding insect vector of Trypanosoma cruzi, a protozoan parasite that causes Chagas disease. During each blood meal, the animals ingest large volumes of blood, that may be up to 12 times the unfed body mass. These blood meals impose a significant osmotic stress for the animals due to the hyposmotic condition of the ingested blood compared with the insect's hemolymph. Thus the insect undergoes a massive postprandial diuresis that allows for the excretion of the plasma fraction of the blood in less than two hours. Diuresis is performed by the excretory system, consisting of the Malpighian tubules and gut, under the control of diuretic and anti-diuretic factors. We investigated the ion transport machinery triggered by stimulation with the diuretic factor serotonin in the anterior midgut (i.e. crop) and the effect of the diuretic modulator RhoprCCHamide2. Ussing chamber assays revealed that serotonin-stimulated increase in transepithelial short-circuit current (Isc) was more sensitive to the blockage with amiloride than 5-N-ethyl-N-isopropyl amiloride (EIPA), suggesting the involvement of Na+ channels. Incubation in Na+-free, but not Cl−-free saline, blocked the effect of serotonin on Isc. Moreover, treatment with Na+–K+–2Cl− cotransporter (NKCC) and Na+–Cl− cotransporter (NCC) blockers had no effect on fluid secretion but was blocked by amiloride. Blockage of Na+/K+-ATPase with ouabain inhibited Isc but the H+-ATPase inhibitor bafilomycin had no effect. The neuropeptide RhoprCCHamide2 diminished serotonin-stimulated Isc across the crop. The results suggest that Na+ undergoes active transport via an apical amiloride-sensitive Na+ channel and a basolateral ouabain-sensitive Na+/K+-ATPase, while Cl− is transported through a passive paracellular pathway.
A Further Study of the Reactions of Fish to Toxic Solutions
Authors: Erichsen Jones J. R. 
Published: April 2021

ABSTRACT
This paper records some further observations on the reactions of fish to toxic solutions. The method of experimentation resembles that described in a previous paper by the writer (Jones, 19476). In every case the solution is presented as an alternative to the Aberystwyth tap water, which is well aerated, very soft, of pH 6·8,
In experiments with sodium sulphide a supply system is arranged in which dilute sodium sulphide solution, brought to pH 6·8 by the addition of sulphuric acid, is automatically made up as it runs into the observation vessel. Gasterosteus aculeatus L. reacts negatively to a 0·001N solution almost immediately; at greater dilution the ‘reaction time’ lengthens, at 0·00008N is about 47 min. Over the concentration range tested the reaction time is always shorter than the survival time.
Gasterosteus is positive to 0·04N lead nitrate. As a positive reaction is also displayed to equivalent concentrations of calcium nitrate, sodium nitrate and sodium chloride it is possible that the osmotic pressure of the solution is its attractive feature.
At 0·01 N the positive response to lead nitrate disappears and at 0·004N is replaced by a very definite negative reaction which is maintained down to 0·00002 N. The minnow (Phoxinus phoxinus L.) is also negative to dilute lead nitrate and will detect and avoid a 0·000004 N solution.
Gasterosteus will avoid water more acid than pH 5·6 or more alkaline than pH 11·4. Over the range 5·8-11·2 the fish are indifferent or very vaguely positive.
Gasterosteus is negative to 0·04 and 0·01 N ammonia solution, positive to 0·001 and 0·0001 N. The general result with ammonia is thus the converse of that observed with lead nitrate.
The Oxygen Requirements and Thermal Resistance of Chironomid Larvae from Flowing and from Still Waters
Authors: Walshe Barbara M. 
Published: April 2021

ABSTRACT
Extensive surveys of the distribution of chironomid larvae have established the fact that the majority of species are strikingly restricted in their habitat: the causes of this specialization, however, remain largely undetermined. For a few species comprehensive ecological work has made it possible to deduce the factors important in determining distribution (Thienemann, 1923, 1928; Lenz, 1925), but an experimental attack on the physiology and behaviour of larval and adult chironomids in relation to their choice of habitat remains almost a virgin field.
Third Report On A Test of Mcdougall’s Lamarckian Experiment on the Training of Rats
Authors: Agar W. E. , Drummond F. H. , Tiegs O. W. 
Published: April 2021

ABSTRACT
Our First Report on this experiment was published in 1935, and dealt with the first five generations. The Second Report, 1942, included the first twenty generations. This Third Report adds another sixteen generations, and reviews the whole experiment up to date.
The Sensory Physiology of the Sheep Tick, Ixodes Ricinus L
Authors: Lees A. D. 
Published: April 2021

ABSTRACT
The sensory perceptions of several species of ticks, notably Argas persicus (Hindle & Merriman, 1912), Boophilus annulatus and Rhipicephalus sanguineus (Krijgsman, 1937), Ixodes ricinus (Totze, 1933) and I. persulcatus (Mironov, 1939), have been studied systematically in the laboratory. There are, in addition, many scattered references in the literature to the behaviour of ticks and some incomplete descriptions of their sense organs. The chief aim of the present work has been to investigate the orienting reactions of the sheep tick, and the role of the special senses, in relation particularly to those stimuli the tick will encounter in its natural environment. With such an object in view, a knowledge of the ecology and behaviour is clearly a desirable, if not an essential, starting-point. There was little understanding of these subjects at the time Totze was writing and, in consequence, there was a tendency for the laboratory observations to lack meaning or to acquire a distorted significance. A fresh examination of the sensory physiology is justified by the increased knowledge of the ecology of the sheep tick in Britain, a subject which has been studied intensively from 1932 onwards. As a preliminary to the present work some weeks were spent observing the behaviour of a population of active ticks under natural conditions. These observations proved of value both by suggesting lines of investigation and, finally, in attempting an interpretation of the significance of the reactions observed in the laboratory.
Vapour Pressure Changes in the Frog’s Egg at Fertilization
Authors: Picken L. E. R. , Rothschild Lord 
Published: April 2021

ABSTRACT
The vapour pressure of unfertilized and fertilized frogs’ eggs has been measured by the differential thermal method. The following results were obtained ; they are expressed as decimal fractions of the vapour pressure of a 1 % aqueous solution of sodium chloride : These results are in serious disagreement with those of Backmann & Runn-ström (1912) and Backmann & Sundberg (1912), but in general agreement with those of Krogh et al. (1938). It is concluded that while there is probably a slight difference between the vapour pressure of fertilized eggs in tap water half an hour after fertilization, and of unfertilized eggs half an hour after transfer to tap water, the difference is negligible after 3 hr. The initial difference may be due to a more rapid interchange between egg and environment in fertilized eggs. In the case of unfertilized eggs, the effect of transfer to a hypotonic medium may be interpreted as an abortive response to a parthenogenetic stimulus.
The Theory of the Fovea
Authors: Pumphrey R. J. 
Published: April 2021

ABSTRACT
The structure and distribution of the two principal types of fovea are briefly described. Using the convexiclivate central fovea of the eagle as a type the effect of refraction at the boundary of retina and vitreous humour on the foveal image is computed. It is shown that, when aberration and diffraction are taken into account, no improvement in acuity can result from refraction at the fovea. On the contrary, the results strongly suggest that the convexiclivate fovea is a device for achieving improved fixation and improved sensitivity to movement of objects in the visual field at some sacrifice of acuity.
The application of these results to other variants of fovea is discussed, and a scheme indicating possible relations between function and geometrical form is proposed.
Some Observations on Water-Soluble Factors Which Accelerate the Growth in Aseptic Culture of Larvae of Drosophila Melanogaster
Authors: Begg M. 
Published: April 2021

ABSTRACT
An effective technique is described for the aseptic culture of larvae of Drosophila melanogaster. Factors which accelerate the growth of Drosophila in aseptic culture on a basal medium containing casein as a source of amino acids can be extracted from both yeast and pancreas in water-soluble form. Part of the activity of such fractions can be removed by adsorption on anion exchange resins, or on charcoal; and eluted with ammonia. The whole activity is dialysable and recoverable from the dialysate by evaporation under reduced pressure. The active components are heat stable. The active fraction is insoluble in N-butanol, ethanol, acetone, pyridine and ether. Some evidence is presented for the presence of at least two components. The possibility that one of the factors may be a peptide is considered. It is thought unlikely that it is an amino acid.
The Physiology of Sea-Urchin Spermatozoa
Authors: Rothschild Lord 
Published: April 2021

ABSTRACTSea-urchin spermatozoa {Echinus esculentus) are extremely sensitive to changes in the pH of the suspending medium, their respiration being proportional to pH between 7· 6 and 8· 4. In a manometric experiment in which semen was diluted 1·25 with sea water (CO2 absorbed), the pH of the suspension was 7· 5 at the beginning of the experiment and 8· 2 at the end, after 180 min. incubation at 150 C. Sea water, buffered with glycyl glycine, 0-025 M and brought to pH 8 3, was added to a sperm suspension whose pH was 7· 5 at the beginning of the experiment, after a period of incubation. There was a pronounced respiratory Dilution Effect. When the sea water was buffered with glycyl glycine and brought to pH 7·8, and this diluent was added to the same sperm suspension, there was a negligible respiratory Dilution Effect. The O2 uptake of suspensions prepared in buffered sea water at pH 8·3 was markedly higher than that in the same buffered sea water at pH 8-o. These observations cast doubt on the reality of the respiratory Dilution Effect when observed in experiments in which sea water is the suspending medium and respiration is measured by a method involving the absorption of CO2. An exception to this generalization was observed in buffered sea water at a low pH, 7 · 6. In this case, the O2 uptake of dilute suspensions was greater, per unit number of spermatozoa, than that of dense suspensions. 2,4-dinitrophenol, 6 × 10−5 M, stimulated the O2 uptake and depressed the motility of spermatozoa more in dense than in dilute suspensions. Versene, 10−3 M, reversed the action of 2,4-dinitrophenol. The results of other workers on adding suspensions of usnic acid to sea-urchin spermatozoa were not confirmed. This substance is more toxic to spermatozoa in dilute than in dense suspensions.
Glycogenolysis in the Liver of the Common Frog, Rana Temporaria
Authors: Tindal J. S. 
Published: April 2021

ABSTRACT
The form of the temperature-glycogenolysis curve of frog’s fiver slices, when incubated with Ringer solution, was determined over the range 7-21° C. for samples of frogs over a period of 18 months. Three types of curve were observed: (a) Low linear, interpreted as being the least complex form, in which the action of temperature is not complicated by other factors.(b) Type B, which showed a disproportionate increase in glucose production above a certain temperature, attributed to the potentiation of sympathomimetic material.(c) High linear. Both the addition of adrenaline and noradrenaline to the incubation medium caused an increase in glucose production at all temperatures. Also, the dispropor-tionate increase in glucose production of the type B curve occurred at a lower temperature in the presence of either of these agents. Thyroxine had no effect on the form of the temperature-glycogenolysis curve, and there was no correlation between the state of activity of the thyroid gland and the type of temperature-glycogenolysis curve. Glucose production of Ever slices was lowered at all temperatures by the in vivo administration of insulin 19 hr. prior to an experiment. Insulin in vitro had no action. Dibenzyline lowered glucose production of Ever sEces at aU temperatures, and raised the temperature at which the extra glucose production, associated with a type B curve, occurred. The extrapolation of the lower portion of the mean curve after dibenzyline to 210 C. gave a line almost identical with the mean low linear curve. The environmental temperature at which frogs were maintained prior to an experiment did not affect the form of the temperature-glycogenolysis curve. The seasonal variation in Ever-glycogen content was found to agree closely with the values obtained by Smith (1950).
The Behaviour of Minnows (Phoxinus Phoxinus L.) in A Light Gradient
Authors: Woodhead P. M. J. 
Published: April 2021

ABSTRACT
Minnows in a light gradient tank were almost constantly active, but were restricted in their movements by light above a certain intensity. The value of the limiting intensity differed for individual fish but lay between o·2 and 0·002 m.c. These values are of the same order as the threshold for light stimulation of the pineal complex in blind minnows, described by Scharrer. It is suggested that the pineal might be the receptor for the light limit, and evidence supporting this suggestion is discussed. Hungry minnows were not limited by light, and spent a considerable percentage of the observation time in the lightest parts of the tank. After feeding they assumed normal limited behaviour. In mid-April, prior to spawning, minnows examined in the gradient were extremely active and showed little sign of a light limit. The mean swimming speed of fish in mid-April was 159 % faster than that of fish observed in December.
The Behaviour of Minnows in Relation to Light Intensity
Authors: Harden Jones F. R. 
Published: April 2021

ABSTRACT
Minnows kept in a tank are active during the day and quiet at night. Their behaviour is reversed if they are given hollow bricks in which they take cover and so avoid bright light. When cover is available they are very active at sunrise and sunset. Minnows have no inherent daily rhythm of locomotory activity. Blind minnows respond to daily variations in light intensity, and are more active at night than during the day. Minnows will not cross a light-dark boundary when the intensity on the light side is greater than 0.17-0.08 m.c A minnow shoal disperses between intensities of 0.024 and 0.0034 m.c. Minnows catch Dapknia better in bright light than in the dark. The change from visual to ‘dark’ feeding takes place between 0.0007 and 0.00007 m.c. Minnows appear to avoid bright light by a comparison of intensities if the light-dark boundary is sharp, but they may also respond to light photokinetically. It should be noted that these results, obtained in the laboratory, may not be true for minnows under natural conditions.