bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reproduction and Growth of Mice of Three Strains, After Transfer to −3°C
Authors: Barnett S. A. , Manly Brenda M. 
Published: April 2021

ABSTRACT
‘Wild’ house mice (Mus musculus L.) breed in cold stores kept at about–10° C (Laurie, 1946), and laboratory mice of the same species can be bred at an environmental temperature of–3° C., given nesting material (Barnett & Manly, 1954; Barnett, 1956). The response of mice to low temperatures varies with different inbred strains. The differences are reflected in mortality (especially of young), growth, numbers of young born and weaned, and in internal, especially endocrine, changes. All these, and other aspects of the maintenance of the lives of mice at low temperatures, are to be discussed in future communications.
Activation of Eggs by Hypothermia in Rats and Hamsters
Authors: Austin C. R. 
Published: April 2021

ABSTRACT
Hamster eggs appear unique among known mammalian eggs in that nearly 80% were found to undergo spontaneous activation, extruding the second polar body, within 24 hr. of ovulation. Often the eggs showed spontaneous early parthenogenesis the development of one or occasionally two nuclei and the formation of a haploid first cleavage spindle took place in a manner that closely resembled the corresponding stages in fertilization. Time relations, too, were much the same. Rarely, however, does the cleavage spindle pass into mitosis, but instead it breaks up and the chromosomes become scattered. Only one normal-looking 2-cell egg was found.
Rat and hamster eggs were very resistant to activation by hypothermia while still in the ovary. After ovulation, however, 100% of rat eggs were activated by body temperatures between 0 and 1° C. and about 60-70% of hamster eggs by temperatures between 0 and 16° C. In view of the high incidence of spontaneous activation in hamster eggs, the effect of chilling in this animal can be regarded as merely that of hastening the change.
Hypoxia alone activated 36% of rat eggs. Relative tissue anoxia is therefore probably the immediate effective agent in activation by anaesthetics and is partly responsible for activation by low temperatures. Cold-shock itself, however, is evidently a more potent activator. Hamster eggs were not activated by hypoxia, probably because a less severe tissue anoxia was induced.
Rat eggs activated by hypothermia showed less tendency to early parthenogenesis than those activated by local chilling of the Fallopian tube.
Nucleus and spindle formation was rather better in artificially than in spontaneously activated hamster eggs, but the prospects of extensive parthenogenetic development did not seem in any way improved. Only two 2-cell eggs resembling fertilized eggs were seen.
Nuclei in activated hamster eggs achieved a volume similar to that of male or female pronuclei at full development. Total nucleolar volume was equal to the sum of the nucleolar volumes of male and female pronuclei.
Early Reactions of the Rodent Egg to Spermatozoon Penetration
Authors: Austin C. R. , Braden A. W. H. 
Published: April 2021

ABSTRACT
In the rat, mouse and hamster the spermatozoon passes rapidly through the thick, homogeneous zona pellucida surrounding the egg and the head almost immediately becomes attached to the surface of the inner cytoplasmic mass or vitellus. As a result of this attachment a block to polyspermy is developed in rat and mouse eggs. In the hamster a block is apparently not formed. It seems likely, therefore, that the disappearance of cortical granules in the hamster egg, also an outcome of contact with the spermatozoon head, could signal the release of an agent that is responsible, after crossing the perivitelline space, for bringing about the zona reaction, reducing the penetrability of the zona pellucida to spermatozoa. Data suggest that this mechanism exists also in rats and mice, although a cortical granule response has not been distinguished in these animals. Thus, attachment of the spermatozoon head to the vitellus probably elicits both the zona reaction and the block to polyspermy.
These changes appear to be specific to spermatozoon penetration and to be initiated before the spermatozoon head passes through the surface of the vitellus and before the resumption of the second meiosis.
Acrasin, the Chemotactic Agent in Cellular Slime Moulds
Authors: Shaffer B. M. 
Published: April 2021

ABSTRACT
A study has been made of acrasin, the agent inducing chemotaxis in the amoebae of cellular slime moulds. A method has been developed for subjecting sensitive amoebae to a fluctuating gradient set up by an artificial source that can be renewed at intervals of as little as a few seconds with fresh test solution. Amoebae orient to a gradient maintained with the cell-free liquid freshly obtained from the immediate surroundings of a natural source. Acrasin solution as secreted loses its activity very rapidly at room temperature. A highly active stable solid is obtained by drying methanolic culture extracts ; it resists boiling and exposure to acids and alkalis. Its solubility decreases rapidly in passing up the alcohol series. The original instability has been shown to be due to the presence of another extracellular slime-mould product, possibly an enzyme; it, unlike acrasin, cannot pass rapidly across a dialysis membrane, is heat labile, and can be precipitated by ammonium sulphate. The advantages of the organism’s itself inactivating acrasin are considered. Some of the advantages of a source’s releasing acrasin in pulses are discussed ; but it is not essential for orientation for it to do so. Sensitive amoebae not only are oriented by an acrasin solution but are caused to secrete acrasin: this is the basis of a chemotactic relay system.
Tetanic Force and Shortening in Locust Flight Muscle
Authors: Weis-Fogh Torkel 
Published: April 2021

ABSTRACT
The maximum tetanic force and shortening was studied in the isolated, dorsal-longitudinal muscle of the hindwings of the desert locust (Schistocerca gregaria). The muscle tended to die when isolated in artificial salines but after penicillin had been added it survived well for more than 8 hr. at 32° C. The cause is discussed. The flight muscle is very sensitive to lack of oxygen and, at room temperature and above, it is necessary to perfuse the main tracheae with air. No difference was observed between indirect and direct stimulation. The natural activity consists of repetitive twitches. Tetanic contractions always caused rapid fatigue and tended to injure the muscle, partly because of excessive shortening (‘delta state’) and partly because the muscle ‘gave’ at the comparatively small total tension of 2-2·5 kg.cm.-2. The length-force diagram at 11° C. resembles that of ordinary skeletal muscle, but the maximum shortening (o-45L6) and the maximum isometric tension (1·6 kg.cm.-2) are smaller than in frog muscle at that temperature. As in mammahan muscle, the isometric tension increases much with temperature and was estimated indirectly as 3 kg.cm.-2 at 25° C. and 4 kg.cm.-2 at 35° C. The largest observed shortening was 0·55Lb. At ordinary body temperature, tension and work are of the’ same magnitude as in skeletal muscle of vertebrates. The flight muscle is less extensible than frog muscle and the maximum isometric force is produced at a lower I-band/sarcomere ratio (0-2). As in frog muscle, passive stretch only affects the I-bands, while the A-bands remain at constant length, at least in the fixed material used here. It is probable that the mechanical specialization of the flight muscle mainly concerns the sarcolemma and the other passive-elastic elements; the contractile elements do not seem to differ from ordinary muscle.
An Inexpensive Type of Sound-Proof Room Suitable for Zoological Research
Authors: Thorpe W. H. , Hinde R. A. 
Published: April 2021

ABSTRACT
The design of an inexpensive sound-proof room, virtually sound-proof to audiofrequencies of 2 kc. and above, is described. Since for the purposes of many zoological experiments low frequencies can safely be disregarded, it is felt that on account of cheapness and relative ease of construction, this type of sound-proof room has much to recommend it.
Hearing in Certain Orthoptera
Authors: Haskell P. T. 
Published: April 2021

ABSTRACT
The physiology of sound reception by tympanal organs, long hair sensillae on the anal cerci, and hair sensillae on the thorax and abdomen has been studied by electrophysiological methods in four species of Acrididae, namely Stenobothrus lineatus, Omocestus viridulis, Chorthippus parallelus and C. brunneus. The discharge in the tympanal nerve of all four species on stimulation by pure tones was asynchronous and showed no equilibration or fatigue. Comparative data are given for threshold sensitivity to pure tones for the four species over the range 0-20 kc./s., and shows the sensitivity to be very similar throughout the group. The tympanal organs of all four species responded to pulsed sound with synchronous volleys of spikes up to pulse repetition frequencies between 90 and 100 pulses per second ; at higher rates synchronism broke down. Long-hair sensillae on the anal cerci responded to gross air movements with bursts of spikes and to pure tones up to 300 c./s. with a synchronous discharge. The cereal nerves synapse with fibres in the ventral nerve cord, and the postganglionic discharges on continuous maximal stimulation of the cereal sensillae show accommodation. It is concluded that these cereal sensillae are similar in response and innervation to those on the cerci of the cricket, cockroach and migratory locust, but that owing to their small number and restricted frequency range they are probably not concerned with reception of natural stridulation. Discharges were evoked in segmental nerves of the third thoracic ganglion in the four species in response to vibration of the substratum and stimulation by airborne sounds. The sensillae mediating the vibration response are hair sensillae situated on the abdominal stenites. The receptors mediating response to air-borne stimuli may be hair sensillae on the abdominal pleura and stenites, or segmental chordotonal sensillae. The present work indicates that the former are probably the receptors concerned, but further work to elucidate the roles played by the two types of organ is required. Data are given on the response and threshold of the hair organs. The responses of all the sound receptors investigated were independent of age and sex and also, in females, of the state of the ovaries.
Hearing in Certain Orthoptera
Authors: Haskell P. T. 
Published: April 2021

ABSTRACT
The pattern of nervous discharge from tympanal organs and abdominal hair sensillae resulting from stimulation by natural and imitation stridulation has been studied in four species of Acrididae, namely Stenobothrus lineatus, Omocestus viridulus, Chorthippus parallelus and C. brunneus. Experiments with tympanal organs stimulated repeatedly with identical sound pulses show that the resultant volleys of spikes, although synchronous with the pulse frequency of the stimulus, were variable in themselves, and that this variability was random, bearing no simple relationship to any quality of the stimulus. This variability in the structure of the impulse bursts was manifested with both natural and imitation stridulation. The response of abdominal hair sensillae showed them to be capable of signalling the duration of supra-liminal stimuli, and responses signalling pulse repetition frequencies were limited to cases where the pulse rates did not exceed 5 per second. In the present species, this meant that only the normal songs of C. brunneus and C. parallelus would produce impulse bursts in tergal nerves synchronous with the pulse frequency of the stimulus. On the basis of this evidence it is adduced that the characteristic of stridulation which enables inter-specific recognition to be effected is the pulse repetition rate of the songs. Comparative data from the four species show that the auditory receptors throughout are very similar, and thus the pattern of nervous discharge will be, in its essential element of the rate of impulse burst, the same for all species when exposed to the same stimulus. The discrimination process must thus be a central one, and it is suggested that this problem might be examined in relation to the ‘Reafferenzprincip’ of von Holst & Mittelstaedt (1950).
A Study of Ovarial Development and Its Relation to Adult Nutrition in the Blowfly Protophormia Terrae-Novae (R.D.)
Authors: Harlow Phyllis M. 
Published: April 2021

ABSTRACT
A method has been developed for obtaining 200-300 flies daily from a culture of Protophormia terrae-novae reared on whale-meat. Normal growth changes in adults have been described, and five stages in ovarial development have been defined. Experimental conditions affecting ovarial growth in adults have been investigated and a satisfactory routine method for examining the effect of adult nutrition on ovarial growth has been devised. Precautions were taken against bacterial contamination of food although non-sterile conditions were used. Ovarial development was not related to relative humidity, if above 55 % R.H., nor to the weight of the adults at emergence. Evidence has been given for the conversion of food material from pupal to adult fat body and for the transfer of material from fat body to ovaries at yolk formation. Healthy adult females can be maintained on a diet of sucrose and water. Addition to the diet of protein or amino-acids produces only slight enlargement of the ovaries. Yolk formation only occurs if the diet is further supplemented by accessory factors, or substances required only in small amount. Ovarial maturation requires considerable amounts of protein, though not more than 0-4 mg. per fly is needed and food solutions must be concentrated. The accessory factors have not been identified but are known to be resistant to slow boiling and are dialysable. Certain mineral salts and B vitamins are thought to be involved. Tryptophane is an essential part of the amino-acid mixture. Protein hydrolysates or equivalent amino-acid mixtures can be substituted for the whole protein but are less effective. The proportions of amino-acids present are very critical, particularly when the amino-acids are in a free state. The aminoacid mixtures have no toxic effect and the presence of some D-isomers do not inhibit growth, although some D-isomers cannot be used by the flies for growth. A chemically defined diet similar to that used for Drosophila did not promote ovarial growth in Protophormia. A mixture containing ten B vitamins, ribose nucleic acid and mineral salts and cholesterol contained some effective accessory substances but lacked some unidentified factor required for yolk formation. The missing factor was not vitamin B12. Penicillin had no significant effect on ovarial growth whether used in minute or in antibiotic concentration.
The thermal sensitivity of the lateralis organs of Xenopus
Authors: Murray R. W. 
Published: April 2021

ABSTRACT
A convenient isolated preparation of the lateralis organs and nerve of Xenopus laevis is described. An average of two active units can be obtained by cutting between the groups of organs in the skin. There is a basic discharge, which is irregular and which varies directly with steady temperatures. An opposite response is obtained to temperature changes. On cooling there is an increase in frequency adapting to the new steady level with a time-constant of 20 sec., and on warming there is a corresponding decrease in frequency. The threshold for temperature change is 1-2° C., representing a rate of change of temperature of ο⋅3-ο⋅6° C./sec. at the surface of the skin. In the more sensitive preparations the basic frequency is doubled or com­pletely inhibited by a change of 5° C. The threshold change of temperature for similar preparations of skin and segmental cutaneous nerve is 5-10° C. The discharge frequency can be increased by mechanical stimulation, but only at intensities high enough to act at the nerve endings directly and not by way of the sensory cells. The sensitivity is comparable to that of the segmental cutaneous nerves.
Absorption of Water by the Egg of the Garden Chafer, Phyllopertha Horticola L
Authors: Laughlin Roger 
Published: April 2021

ABSTRACT
Many insect eggs absorb water during the incubation period. Buxton (1932), Roonwal (1936) and Matthée (1951) review the numerous reports published since 1740 when Réaumur noticed that eggs of sawflies and ants increased in size during development.
Effects of High Hydrostatic Pressures on Actinophrys Sol (Heliozoa)
Authors: Kitching J. A. 
Published: April 2021

ABSTRACT
The axopods of Actinophrys sol are caused to collapse by the application of high hydrostatic pressures. Axopods grow out again on release of pressure or on reduction of pressure below a certain critical value. Temperature and pressure act in opposition as regards the outgrowth and maintenance of axopods. At 15° C., the average critical value for the restoration of axopods is about 3500 p.s.i. (207 atm.). An increase of temperature by ro° C. counteracts an increase in pressure of 1200 p.s.i. (82 atm.).
Transplantation of Melanomas from Platyfish-Swordtail Hybrids Into Embryos of Swordtails, Platyfish and Their Hybrids
Authors: Humm Douglas G. , Clark Eloise E. , Humm Jane H. 
Published: April 2021

ABSTRACT
The melanomas in the platyfish–swordtail hybrid are produced genetically, as shown by Gordon (1951), by the interaction between the macromelanophore growth-modifying factors from the swordtail and a dominant platyfish sex-linked allele controlling the appearance and distribution of macromelanophores. The genic interaction manifests itself phenotypically in that the macromelanophores appear in the hybrid much earlier than in the normal platyfish and the growth of the pigmented cells seems relatively unchecked, resulting in hyperpigmentation of the animal and ultimately in the production of a tumour. (See Reed & Gordon (1931) and Gordon & Smith (1938) for a detailed description of the phases of tumour development.)
An Apparatus for the Study of the Locomotion of Fish
Authors: Bainbridge Richard , Brown R. H. J. 
Published: April 2021

ABSTRACT
In studies on the swimming of fish using the small ‘fish wheel’ (Bainbridge, 1958) it became clear that to enable the research on swimming speeds to be extended to larger specimens and to give scope for the investigation of other problems, a larger apparatus was needed. With the generous support of Messrs Watts, Watts and Company Ltd., The British Steamship Company Ltd., and the British Thomson-Houston Company Ltd., the development of this large wheel became possible. The construction of the wheel itself was undertaken in the Zoological Department, Cambridge, while the electric drive was supplied by the British Thomson-Houston Company.
Embryonic Mortality in Relation to Ovulation Rate in the House Mouse
Authors: Bowman J. C. , Roberts R. C. 
Published: April 2021

ABSTRACT
Two series of observations were made to determine the time and amount of loss of eggs in relation to the number shed per ovary and per mouse. The correlations between sides within mice for eggs shed was −0·528, for corpora lutea counts −0·436, for implantations −0·300, and for live embryos −0·111. A positive linear trend of loss of fertilized eggs with increasing numbers of eggs per uterine horn has been shown to occur before implantation. Possible causative mechanisms for the loss are discussed in relation to observations on embryonic mortality previously reported by other workers. We wish to express our gratitude to Prof. C. H. Waddington for laboratory facilities, to Dr D. S. Falconer for much helpful criticism and advice and to Dr B. Woolf for statistical advice. J. C. Bowman gratefully acknowledges financial support from the Agricultural Research Council.
Chemotaxis of Bracken Spermatozoids
Authors: Brokaw C. J. 
Published: April 2021

ABSTRACT
Fern spermatozoids respond chemotactically to concentration gradients of malic or maleic acid salts (Pfeffer, 1884). They respond weakly to salts of a few other dicarboxylic acids, but do not respond to succinate or fumarate (Shibata, 1911; Rothschild, 1956). Previous workers concluded, without adequate justification, that the malate ion, and not the undissociated malic acid molecule, is chemotactically active; but no consideration has been given to the possibility that the bimalate ion may be the active species.
Effect of the Black Snake Toxin on the Gastrocnemius-Sciatic Preparation
Authors: Mohamed A. H. , Zaki O. 
Published: April 2021

ABSTRACT
When the toxin of the black snake (Walterinnesia aegyptea) was injected subcutaneously into albino rats, one of the common symptoms which appeared was the paralysis which takes place in the limb near the site of injection and extends to other limbs just before death.
The Efficiency of Adaptive Structures in the Nymph of Rhithrogena Semicolorata (Curtis) (Ephemeroptera)
Authors: Stuart A. M. 
Published: April 2021

ABSTRACT
The current-resisting powers of Rhithrogena semicolorata Curtis have been investigated and measured, and compared with those of Ecdyonurus sp. The part played by the gills as organs of adhesion is considered, and they are found to contribute little to the current-resisting powers of the nymph. The claws are regarded as being of more importance to the animal in clinging than the gills. The dorso-ventral flattening of the animal is considered to be a creviceseeking adaptation, and not a current-resisting one.
The Occurrence of 5-Hydroxytryptamine in Scorpion Venom
Authors: Adam K. R. , Weiss C. 
Published: April 2021

ABSTRACT
The constituents of scorpion venom have not yet been fully identified. During preliminary investigation of the venom of Leiurus quinquestriatus by paper chromatography, a spot corresponding in position to that due to 5-hydroxytryptamine (HT) was seen. This paper is concerned with the methods of identification and assay of this substance in venom, and also considers the histochemistry of the venom gland in relation to this finding.
A Conductimetric Method for the Estimation of Small Quantities of Ammonia
Authors: Shaw J. , Staddon B. W. 
Published: April 2021

ABSTRACTA method is described for the estimation of small quantities of ammonia down to 0·001 µg. N. The principle of the method is that ammonia is liberated from the sample and recovered in a solution of standard acid by Conway’s diffusion method; the electrical conductance of the acid falls as ammonia is absorbed, due to the difference in the mobility of hydrogen and ammonium ions. The results of estimations on standard ammonium sulphate solutions and biological fluids are tabulated. The method can deal with quantities down to 0·005 Mg-ammonia-N with an error &lt;±2% (standard deviation), 0·001 µg. ammonia-N with an error ±6−8%. An account is given of the construction of small diffusion chambers and small conductivity cells.