bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of ecdysis in the mothManduca sexta
Authors: Fuse Megumi , Truman James W. 
Published: April 2021

SUMMARYThe sequential behaviours shown by insects at ecdysis are due to the sequential release of various hormones, but the transition from one phase to the next can be fine-tuned by inhibitory influences. The ecdysis sequence in the moth Manduca sexta was initiated by injecting sensitive animals with the neuropeptide ecdysis-triggering hormone (ETH). Exposure to ETH stimulates the release of eclosion hormone (EH) which, in turn, activates a set of neurons containing crustacean cardioactive peptide (CCAP) by elevating their levels of intracellular cyclic GMP. We characterized a set of non-CCAP containing neurons that also appear to be EH targets because of their response to cyclic GMP at ecdysis. The neurons did not display leucokinin-,diuretic-hormone- or FMRFamide-like immunoreactivity. They are probably the bursicon-containing cells described previously. After release of EH, there is a transient inhibition of the abdominal centers responsible for ecdysis. Transection experiments suggested that this suppression is viadescending inhibitory units from the suboesophageal and thoracic ganglia. The duration of this inhibition appears to depend on the levels of cyclic GMP and can be extended by pharmacologically suppressing cyclic GMP breakdown. We further found that brief exposure to CO2 caused premature ecdysis. Since the CO2 treatment was effective only after EH release, it probably acts by suppressing descending inhibition. Studies on adult eclosion suggest that CO2, given at the appropriate time, can uncouple the basic larval motor program from modulatory influences provided by the adult pterothoracic ganglion. CO2 therefore appears to be a novel and non-invasive tool for studies of ecdysis behavior in insects.
Distribution and effects of PACAP, VIP, nitric oxide and GABA in the gut of the African clawed frogXenopus laevis
Authors: Olsson Catharina 
Published: April 2021

SUMMARYThe distribution and possible effects on gastrointestinal motility of pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP), nitric oxide and γ-amino-butyric acid(GABA) were investigated in the African clawed frog (Xenopus laevis)using immunohistochemistry and in vitro strip preparations. PACAP-and VIP-immunoreactive nerve fibres were common in the myenteric plexus as well as in the longitudinal and circular muscle layers all along the gastrointestinal tract. Double labelling demonstrated a close correlation between PACAP and VIP immunoreactivities, indicating that the two neurotransmitters are colocalised within the enteric nervous system. Occasionally, PACAP- and VIP-positive nerve cell bodies were seen in the myenteric or submucous plexa. In addition, VIP immunoreactivity coexisted with helospectin immunoreactivity. Nitric oxide synthase (NOS)-immunoreactive nerve cells were found in the myenteric plexus at an average density for the whole gastrointestinal tract of 4584±540 cells cm-2. The NOS-immunoreactive nerve cells were usually multipolar with an average size of 11.3±3.7 × 23.2±6.6 μm. Some NOS-immunoreactive nerve fibres were VIP-immunoreactive but not all VIP-positive fibres showed NOS immunoreactivity. GABA immunoreactivity was found in nerve fibres and nerve cells in the myenteric plexus of all regions of the gut. Few GABA-immunoreactive nerve fibres were VIP-immunoreactive. PACAP 27, VIP,sodium nitroprusside (a nitric oxide donor; NaNP) and GABA caused similar responses on spontaneously contracting circular preparations of the cardiac stomach of X. laevis. The mean force developed was decreased, mainly by a reduction in resting tension, while the amplitude of contractions was not necessarily affected. The NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) increased the mean force developed, indicating a nitrergic tone in the preparations. In contrast, PACAP 27, VIP, NaNP, GABA and L-NAME had no significant effect on longitudinal strip preparations from the duodenum. These results indicate that PACAP, VIP, nitric oxide and GABA, which are known to be important inhibitory neurotransmitters in other vertebrates, are widely spread in the enteric nervous system of Xenopus laevis and may be involved in the inhibitory control of gastric motility. Although no effect of PACAP,VIP, nitric oxide or GABA on the longitudinal strips of the duodenum was seen in this study, this does not rule out the possibility that they might play an important role in controlling intestinal motility as well.
The effects of continuousversuspartial reinforcement schedules on associative learning, memory and extinction inLymnaea stagnalis
Authors: Sangha Susan , McComb Chloe , Scheibenstock Andi , Johannes Christine , Lukowiak Ken 
Published: April 2021

SUMMARYA continuous schedule of reinforcement (CR) in an operant conditioning procedure results in the acquisition of associative learning and the formation of long-term memory. A 50 % partial reinforcement (PR) schedule does not result in learning. The sequence of PR—CR training has different and significant effects on memory retention and resistance to extinction. A CR/PR schedule results in a longer-lasting memory than a PR/CR schedule. Moreover,the memory produced by the CR/PR schedule is resistant to extinction training. In contrast, extinction occurs following the PR/CR schedule.
The Distribution of Vitamin C in Nyctotherus Cordiformis Ehrenberg, Opisthioglyphe Ranae Frölich, and Toxocara Canis Werner
Authors: Smyth J. D. , Bingley W. J. , Hill G. R. 
Published: April 2021

ABSTRACT
The localization of vitamin C in Nyctotherus cordiformis, Toxocara canis and Opisthioglyphe ranae was investigated by means of the silver nitrateacetic acid technique. In Nyctotherus, the vitamin C is distributed uniformly throughout the cytoplasm in the form of globules of varying sizes. No vitamin is present in the ectoplasmic layer or in the region of the nuclei. In the same preparations specimens of Opalina show no trace of any vitamin C present. In Toxocara, the vitamin is localized in relatively large quantities in all the cells of the intestine. In these cells it is aggregated mainly in the region between the nucleus and the free cell border. A series of fine granules of the vitamin also line the lower cell walls. Only a few scattered granules are present in the remaining tissues. In Opisthioglyphe, the vitamin is concentrated on the walls of the excretory system which in this trematode has the form of two longitudinal canals joining in the posterior region to form a single median canal. A line, of disk-like elements of the vitamin is also present immediately below the epidermis. In the remaining tissues only very small scattered grains are found. It is believed that in the case of Toxocara, the presence of the vitamin in the gut cells may indicate that the parasite is capable of absorption of vitamin C from the food of the host. It is suggested that in heavy parasitic infections the parasites may play some part in the disturbance of the vitamin C balance of the host.
On the Behaviour of Wireworms of the Genus Agriotes Esch. (Coleoptera, Elateridae) in Relation to Temperature
Authors: Falconer D. S. 
Published: April 2021

ABSTRACT

I
1. The highest temperature which wireworms could withstand for an indefinite period without becoming paralysed was found to-be between-35 and 36 ° C. The resistance to high temperature was not influenced by the previous temperature. 2. The resistance of wireworms to low temperature was found to be greatly influenced by the rate at which the temperature was reduced. When the temperature fell rapidly, all were killed by 6 days’ exposure to – 3°C., and by 4 hr. exposure to –7°C. The resistance to low temperature was not increased by a previous exposure of 24 hr. at o°C., when the subsequent fall of temperature was rapid. When the temperature was lowered in small stages, however, the resistance was considerably increased, and a few wireworms survived for at least a day at − 10°C. 3. The published data of soil temperatures suggest that temperatures above 30 ° C. or below about − 1 ° C. are not of regular occurrence in England, and it is concluded that wireworms in England are not normally liable to encounter lethal temperatures..

II
4. The relationship between the wireworms’ speed of crawling and the temperature was found to be nearly linear between 8 and 25°C. 5. Burrowing activity was uniformly greater at higher than at lower temperatures between 6 and 33°C. Temperature influenced the speed but not the continuity of the activity. After adaptation had taken place the burrowing activity was almost nil at 6°C. When subjected to a sudden fall of temperature from 16 to 6 °C., the wire worms’ burrowing activity in the first 2 hr. was significantly greater than it was at the same temperature 16 hr. later. 6. The weight of wheat eaten by wire worms was found to be greatest at 32 ° C., but feeding activity was most continuous at about 18°C. At 7°C. and at 34° C. little feeding took place.

III
7. No vertical movements in response to gravity were exhibited by the wireworms under any conditions of temperature. 8. When given a choice of temperatures in an alternative-chamber apparatus, the wireworms showed a clear preference for 17°C. as against 11·5 and 21°C. or higher temperatures. The temperature preference was not found to be influenced to any great extent by the previous perature. 9. The mechanism by which the wireworms reacted at a temperature boundary was of the nature of a ‘shock reaction’, their direction of movement being reversed.
No evidence of a klinokinetic response to change of temperature was obtained from wireworms burrowing in sand.
On the Movement of Wireworms of the Genus Agriotes Esch. (Coleoptera, Elateridae) on the Surface of the Soil and Their Sensitivity to Light*
Authors: Falconer D. S. 
Published: April 2021

ABSTRACT
During the course of experimental work on the behaviour of wireworms in relation to temperature (Falconer, 1945), stocks of wireworms were kept in sand in glass jars, and it was often noticed after a jar had been left undisturbed for some time that the surface of the sand was pierced by many small holes of the size of a wireworm burrow. This fact suggested that, contrary to general belief, wireworms might sometimes come out on to the surface of the soil and wander about before re-entering, perhaps at a different point. If this were the case, the fact might have considerable importance in connexion with migration and possibly with food finding. Reference to the matter is scanty in the literature. Subklew (1934) stated that though the larvae are well adapted to life in the soil, they are also able to crawl about extensively on the surface : in a later paper, however (Subklew, 1935), he concluded that a wireworm which had come out on to the surface would at once be led below ground again by its thigmotactic response. Guéniat (1937) speaks of collecting abundant wireworm material in early spring without digging, the larvae being found under stones and lumps of earth: these larvae, he says, eat young grass shoots and dandelion leaves. Though it is not explicitly stated, his remarks strongly suggest that wireworms in Switzerland habitually move about on the surface of the soil in early spring. There does not, however, appear to be any evidence of similar behaviour on the part of wireworms in England.
The Mechanism of Locomotion in Gastropod Molluscs: I. Kinematics
Authors: Lissmann H. W. 
Published: April 2021

ABSTRACT
Whereas the broad outline of the mechanical events of locomotion can in most animals be readily visualized, the mechanism of propulsion in gastropods is less easily observed. Since the seventeenth century (Lister, 1694) a great deal of attention has been paid to this problem and a wealth of suggestions has been forthcoming; there is, however, a significant absence of convincing experimental data. To some extent the problem is confusing on account of the diversity of locomotory mechanisms existing within the group (Vlès, 1907; Parker, 1911; Olmsted, 1917; Weber, 1925). Nevertheless, there can be no room for doubt that one characteristic type of movement depends upon the propagation of waves of muscular activity over the surface of the animal’s foot. So far as is known, no adequate account has yet been, given of the method whereby this type of activity propels the animal over the surface of the ground. The present paper deals with these problems in respect to three representative genera, Helix, Haliotis and Pomatias.
Internal Oxygen Environment of the Brains of Post-Mature Rabbit Embryos
Authors: Barcroft Joseph , Young I. Maureen 
Published: April 2021

ABSTRACT
In 1935 Barcroft, Flexner, Herkel, McCarthy & McClurkin, working on rabbits, showed that the oxygen saturation of the blood leaving the uterus dropped from an average value of about 70 % at the 18th day of gestation to about 30 % saturation on the 30th day. During the period in question the foetuses are in active growth, whilst growth of the placenta is only trifling. On the 18th day the combined weight of the foetuses is approximately the same as that of the foetal portions of the placentas to which they are attached; on the 30th day the foetuses weigh about fifteen times as much as the placentas.
The Biology and Behaviour of Ptinus Tectus Boie. (Coleoptera, Ptinidae), A Pest of Stored Products
Authors: Gunn D. L. , Knight R. H. 
Published: April 2021

ABSTRACT
The highest temperature at which Ptinus tectus should be reared is near 24 ·7 ° C. Humidities higher than 70 % cannot conveniently be used because of the growth of moulds. Lower humidities prolong development. The best food tried was 95 % whole ground wheat with 5 % dried brewers ‘yeast. The smallest quantity of this food which permits completion of development is about 3 mg. per animal. This produces miniature adults, one-third of the normal weight, in almost normal time. About 30 mg. is required to produce full-sized adults. These statements apply to individuals reared in isolation. When a group of several larvae are reared in one container, development is prolonged by up to 40 % (which does not occur at all with isolated animals even if food is so short as to cause severe stunting), while some diminution of size (20 %) is found. This is called the ‘group effect’. With groups of 8 larvae, as much as 5 g. of food per larva is required before the group effect disappears, too times as much as is needed for full and speedy development by an isolated larva. With quantities of food per larva which are optimal or supra-optimal for isolated larvae, the group effect reaches its highest expression with 8 larvae in the group. It diminishes at smaller group sizes. Mass cultures show the effect to about the same extent as groups of 8. Animals reared in groups show a wider range of variation in size than those reared in isolation, but their duration of development is not more variable. No adequate explanation has yet been found for the group effect and no method has yet been found of producing from mass cultures animals as uniform in size as those reared singly. Adults come into full and fertile lay about a week after emergence from the cocoon. The rate of laying is markedly diminished if the animals are not given fresh food and water to drink daily. A female can live for a year and lay nearly a thousand eggs. In starting mass cultures, it is best to allow a large number of animals in good condition to lay for a day or so. No better result will be obtained by leaving the animals longer.
On the Penetration of Insecticides Through the Insect Cuticle
Authors: Webb J. E. , Green R. A. 
Published: April 2021

ABSTRACT
Using Melophagus ovinus, the sheep ked, as test insect, it was found that certain organic solvents of diphenylamine, such as the cresols, benzyl alcohol and 4-methyl-cyclohexanol, greatly increase the rate of action of this insecticide. Others, strcn as carbitol and methyl benzoate, gave little or no improvement in the time of kill. The degree to which a solvent induces rapid penetration of an insecticide is referred to as its ‘carrier efficiency’. The influence of the physical properties of the solvents on carrier efficiency was investigated. It was found that a high carrier efficiency could be correlated with a high rate of penetration through beeswax, a high partition coefficient of the solvent between beeswax and water and a high solubility of insecticide in a solution of the solvent in water. The volatility of the solvent and the solubility of insecticide in solvent were also contributory factors. Mixtures of two solvents, each showing no carrier efficiency but together possessing all the essential physical properties, were tested and showed a carrier efficiency considerably higher than that of either constituent. This is taken as supporting evidence that carrier efficiency depends on certain physical properties of a solvent. Using a range of solvents shown to exhibit various degrees of carrier efficiency with diphenylamine, comparable results were obtained with dixanthogen, ω-nitrostyrene dibromide and rotenone and showed that the synergy could be extended to other insecticides. It is suggested that certain solvents increase the rate of penetration of contact insecticides through the insect cuticle : By transporting the insecticide through the lipoid elements of the epicuticle to the interface between this layer and the water permeating the exocuticle. By concentrating the insecticide at the interface between the epicuticle and the exocuticle, as the. solvent passes into the exocuticle, and thus increasing the diffusion gradient of the insecticide across that interface. By increasing the solubility of the insecticide in the water permeating exo-and endo-cuticles and thus, by raising its partition coefficient between solvent in the epicuticle and water in the exocuticle, further increasing its rate of diffusion, not only across this interface, but also through exo- and endo-cuticles to the hypodermis.
Differentiation of Ectoderm Implanted into the Primordium of the Limb Bud in the Amphibian Embryo and its Influence Upon the Limb*
Authors: Brandt Walter 
Published: April 2021

ABSTRACT
It was shown by Brandt (1944) that phocomelias and atrophied limbs can be produced experimentally after deep implantation of embryonic ectoderm into the primordium of the limb bud in the tail-bud stage (Harrison’s stage no. 35) of the amblystoma embryo. The following microscopical analysis of the operated specimens shows some new results which concern the histological changes of the implanted embryonic ectoderm within the tissues of the host embryo and their effect on the limb primordium.
Peripheral Nerve and Regeneration in Crustacea. II
Authors: Needham A. E. 
Published: April 2021

ABSTRACT
In the previous paper of this title (Needham, 1945) denervation of a thoracic limb of the isopod Asellus aquaticus at the time of amputation was shown to result in a marked retardation of regeneration, as compared with the partner limb amputated, without denervation, at the same time: In the present work it was hoped to throw more light on this neurotropic effect by experiments involving denervation at different times relative to amputation. Schotté & Butler (1944) find that the peripheral nerve is necessary for the early stages but not for the later stages of regeneration of amphibian limbs. In one series of the present experiments denervation was performed 5 days after amputation, and in a second series after normal regeneration for one instar, that is, at the first appearance of an externally visible regenerate, an average of 10 days after amputation. Such a regenerate is already partly functional, so that the possibility must be envisaged that denervation might lead to some disuse-atrophy in addition to its possible effect on regenerative growth; in a third series, therefore, the normally growing limb was denervated (without amputation), in order to obtain some measure of the extent of this disuseatrophy. The results of this third series may include an effect of denervation on normal (i.e. non-regenerative) growth also. In a fourth series the limb was denervated 5 days before amputation, the object being to ascertain whether tissue denervated some time previously to amputation and undergoing the consequent atrophic changes is capable of developing a regeneration blastema at the surface of amputation, and of regenerating at the normal rate as soon as the regenerating nerve reaches that surface (cf. Needham, 1945, p. 146).
The Growth of Brown Trout (Salmo Trutta Linn.)
Authors: Brown Margaret E. 
Published: April 2021

ABSTRACT
Temperature is a limiting factor in the distribution of many animals. The ova of brown trout (Salmo trutta) can develop without excessive mortality at water temperatures between 3 and 15o C. (Gray, 1928), while for adult trout, mortality is high above 20 and complete above 25o C. (Gardner & Leetham, 1914; Audigé, 1921 ; Gardner, 1926). It is generally assumed that temperature is the most important physico-chemical factor affecting the growth of fish, especially in temperate zones, where there is an annual variation. Allen (1940) deduced from examination of salmon scales from British rivers that parr do not grow when the water temperature is less than 7°C. Pentelow (1939) and Wingfield (1940) observed the growth of yearling trout in tanks where the temperature varied with that of the external environment and was recorded once a day. They found that there was no growth at temperatures less than 6°C., and it was most rapid between 10 and I5°C. Since other environmental factors varied at the same time, the correlation between growth rate and temperature was necessarily approximate.
Volatile Acid in the Digesta of Ruminants and Other Animals
Authors: Elsden S. R. , Hitchcock M. W. S. , Marshall R. A. , Phillipson A. T. 
Published: April 2021

ABSTRACT
A mixture of volatile organic acids, consisting for the most part of the fatty acids, acetic, propionic and butyric, is a characteristic product offermentation within the alimentary tract. It was shown previously that volatile acids are absorbed directly from the organ in which they are produced (Barcroft, McAnally & Phillipson, 1944), and this fact, together with a consideration of the quantities present in the digesta—a subject with which the present paper is concerned—suggest that they form a valuable part of the calorific material utilized by the animal.
The Reactions Of Isolated Parts Of Spirostomum
Authors: Clark A. M. 
Published: April 2021

ABSTRACT
The determination of the reactions and behaviour of isolated fragments of a protozoan is of value to the study of three problems, namely, the relationship between the nucleus and behaviour, the detection of any area in the organism specialized for the reception of external stimuli, and in the case of a cihate, the role played in normal swimming by the cilia of different regions of the body. Recently, an account has been given of the reactions of fragments of Amoeba proteus (Clark, 1944). The present paper is an extension of the work to include a ciliated form.
Local Factors and Regeneration in Crustacea
Authors: Needham A. E. 
Published: April 2021

ABSTRACT
The role of normal innervation in the regeneration of crustacean appendages has been illustrated in previous papers (Needham, 1945, 1946); it may, perhaps, be termed the ‘central’ factor in regeneration. In the present paper ‘local’ factors, such as properties of the tissues near the site of amputation, have been studied. The results of earlier work, chiefly on Amphibia, Planaria and Oligochaeta (Korschelt, 1927, pp. 639–40), have suggested that the rate of regeneration varies with (1) the extent of tissue damage at the site of amputation and (2) the amount of tissue removed. These two factors have been studied in the present experiments on the regeneration of the 7th thoracic limb of Asellus aquaticus (L.).