bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Biological Basis of Sexual Behaviour in Amphibia
Authors: Shapiro H. A. 
Published: April 2021

ABSTRACT
The complete disappearance of all sexual activity in Xenopus laevis, male or female, is observed under laboratory conditions. A technique is described whereby the mating reflex (coupling) can be established in the laboratory during the pond breeding season as well as midway between breeding seasons, by means of injections of human pregnancy urine extracts, or by acid extracts of the anterior lobe of the pituitary gland of sheep and goats. The mating reflex has been induced in 101 different pairs of toads with pregnancy urine extracts and in 39 different pairs of toads with anterior pituitary extracts. The reflex induced by anterior pituitary extracts in no way differs from that produced by pregnancy urine extracts. The possibility that the extract acts through the intermediation of the gonads is considered. The mating reflex is described, and attention is drawn to the passive role of the female, while the male is stimulated to activity. It is suggested that a stimulus from the female reflexly activates the male to clasping activity. Fertilised ova from coupling pairs have been reared successfully to an advanced tadpole stage (4-5 months). Tadpoles can be reared also midway between breeding seasons. The injected extract, acting possibly through the intermediation of the gonads, may be suggested to inhibit the clasping reflex inhibitory centre in the brain described by Steinach and others. The mating reflex appears to be independent of the pituitary mechanism associated with chromatic response in Xenopus laevis. The larger doses (500 mg. fresh tissue) of anterior pituitary extract required to produce in summer a response of the same magnitude as that produced by smaller doses (192 mg. fresh tissue) in winter cannot be attributed to a diminished sensitivity of the ovaries. Control extracts of male urine and of sheep and goat brains repeatedly gave negative results.
A Failure of Induction in Normal Development
Authors: Waddington C. H. 
Published: April 2021

ABSTRACT
The just formed side-plate mesoderm from the gastrula in the medium-sized yolk-plug stage can induce the formation of an extra neural plate when implanted into the blastocoel of a young gastrula. The dorsal lip of a young gastrula, substituted for the side-plate mesoderm mentioned in (1), evocates a neural plate. The failure of evocation by the side-plate mesoderm in normal development can only be explained by supposing both that the evocating capacity of the sideplate mesoderm is lower than that of the dorsal lip and that the lateral ectoderm does not react to an evocating stimulus as easily as does the young gastrula ectoderm. The weakness of the evocating capacity of the side-plate mesoderm might be due either to its intrinsic nature or to an active suppression by the rest of the mesoderm. The evidence suggests that both factors may be involved, but it can be shown that the latter factor by itself is not sufficient to explain the facts. Isolated gastrula ectoderm retains its competence to be evocated to neural tissue at least until the age of an open neural plate embryo. Thus the normal loss of competence by the lateral ectoderm is not due to an inherent process. Nor is it caused solely by a continued connection with the neural plate. It cannot be due merely to the presence of side-plate mesoderm; but it may be due to an influence proceeding from side-plate mesoderm which is part of a mesoderm field, or it may be dependent on a preparation of the ectoderm by reason of its connection with the neural plate, or, more probably, by an inherent process, so that by the stage at which the side-plate mesoderm forms, the ectoderm has become such that it reacts with side-plate mesoderm with rapid loss of competence.
Studies in Animal Locomotion
Authors: Gray J. 
Published: April 2021

ABSTRACT
It is well known that certain aquatic vertebrates (notably dolphins and some of the larger teleostean fishes) are able to travel at surprisingly high speeds. The movements performed by such animals during rectilinear locomotion are all of the same type, for the hind end of the body vibrates rhythmically in a plane at right-angles to the axis of locomotion; the plane of vibration of the dolphin is dorso-ventral, whereas that of a fish is transverse to the long axis of the body. In all cases the orientation of the hind end of the body and of the caudal fin, in particular, is such that during both phases of each vibration the leading surface (relative to the direction of the vibration) is inclined at an angle to its own direction of motion through the water and is directed obliquely backwards relative to the head of the animal (Gray, 1933). The anatomical arrangements of the propulsive muscles of a dolphin appear to be simpler than those of a fish, since the locomotory movements are produced by four bands of musculature connected to the base of the caudal fin by strong tendons ; on the ventral side of the vertebral column the two muscle bands extend forward to the region of the diaphragm, whereas the two dorsal bands extend over the whole back of the animal. The weight of the dorsal musculature is approximately twice that of the ventral muscles. The tail is deflected upwards by the contraction of the dorsal muscles and downwards by contraction of the ventral muscles. Reciprocity thus exists between the dorsal and ventral muscle groups, whereas, in a fish, reciprocity of this type is restricted to the right and left musculature of individual segments. Apart from these anatomical differences the propulsive mechanisms of a fish and of a dolphin appear to be of essentially the same type.
The Further Effects of Irradiation on the Oestrous Cycle of the Ferret
Authors: Marshall F. H. A. , Bowden F. P. 
Published: April 2021

ABSTRACT
In our previous paper (1934) it was shown that the recurrence of oestrus in the female ferret is greatly accelerated by irradiation with light, and is retarded by darkness, thus confirming and extending the observations of Bissonette (1932). It was also shown that heat rays and the near infra-red (λ7500Å.) were inactive. The active radiation extended throughout the spectrum from the red (λ 6500 Å.) to the ultra-violet (λ3650Å.). Further, the animals irradiated with ultra-violet light remained on heat far longer than any of the others, although the irradiation had been for a long time discontinued. Of the two ferrets which are recorded as having been still on heat on August 1, 1933, one (No. 2) remained in a state of full oestrus until August 28, but the vulval swelling did not finally disappear until October 2, while the second ferret (No. 14) began to go off heat on September 11, but was not completely anoestrus until November 14.
A Note on the Mechanism of Salt and Water Balance in the Heterotrichous Ciliate, Spirostomum Ambiguum
Authors: Picken L. E. R. 
Published: April 2021

ABSTRACT
Although considerable attention has been paid to the kinetics of water balance in the Protozoa, e.g., Adolph (1926), and more recently Kitching (1934) and Kamada (1935), comparatively little is known of the instantaneous distribution of salt, water and colloidal substances in the body of a protozoon, and nothing is known of the magnitude of the hydrostatic pressure within the animal and its possible importance in the process of excretion. The experiments described here were made in order to obtain direct information on the total osmotic concentration of the body fluid, the maximum value for the colloid osmotic pressure of the cell contents, and the hydrostatic pressure within the organism.
Some Reactions of the Ammocoete
Authors: Francis Eric T. B. , Horton Frances M. 
Published: April 2021

ABSTRACT
Experiments are described which show that the threshold value for the light energy, which will initiate swimming movements in the ammocoete, is in the region of 3 foot-candles. The part of the spectrum which is most active is in the green-blue region (0.55μ-0.4μ). Ammocoetes are very strongly thigmotactic, the most sensitive region being the sides of the trunk. Ammocoetes between 40 and 70 mm. long are not rheotactic. The relation of these responses to one another and their relative importance to the ammocoete in its natural environment are discussed.
Modulation of crayfish retinal sensitivity by 5-hydroxytryptamine
Authors: Aréchiga Hugo , Bañuelos Enrique , Frixione Eugenio , Picones Arturo , Rodríguez-Sosa Leonardo 
Published: April 2021

ABSTRACT
The responsiveness of crayfish retinal photoreceptors to light was enhanced by exposure to 5-hydroxytryptamine (5-HT), either following injection into whole animals or following topical application to isolated eyestalks or retinas. The effect was measured as an increment in the amplitude of the receptor potential, and was dose-dependent in the range 10−6–10−3mol l−1 (injected as a 0.1 μl dose in intact animals). It was more pronounced at low levels of illumination and was reversibly blocked by methysergide.
The enhancement was a consequence of a dual effect: (a) retraction of the proximal pigment granules within the photoreceptors, with a corresponding increase in the light-admittance function of the retina; and (b) a direct effect, facilitating a membrane conductance increase which mediated the generation of the receptor potential. A set of axons in the lamina ganglionaris with a 5-HT-like immunoreactivity was found in the vicinity of the photoreceptor axons. 5-HT antagonists were capable of blocking the physiological retraction of pigment granules in photoreceptors at night, suggesting that 5-HT acts as a modulator during the nocturnal phase of the circadian cycle in the crayfish retina.
Non-voltage-gated calcium channels in snail heart ventricle cells
Authors: Brezden B. L. , Gardner D. R. 
Published: April 2021

ABSTRACT
Two recently identified channel types in Lymnaea stagnalis heart muscle cells were shown to conduct Na+ in the absence of extracellular Ca2+. They did not appear to be ‘voltage-gated’ as they were not activated by voltage. Also, they remained active over a wide range of membrane potentials. However, they were weakly ‘voltage-sensitive’ as their activity usually tended to increase with depolarization. The weak voltage-sensitivity and similarity to other non-voltage-gated Ca2+ channels suggested that one or both of these channels may be receptor-operated Ca2+ channels. One of the two channels had a slope conductance of 15 pS. The other appeared to have at least two subconductance states with slope conductances of 50 and 72 pS. Both these conductance states had very similar open dwell-time constants and identical reversal potentials. The open dwell-time constants of both conductance states were not affected by voltage, suggesting that the channels’ weak voltage-sensitivity was mediated by one of the closed states. With divalent cations in the patch pipette, non-voltage-gated Ba2+ and Ca2+ currents were also detected. The Ba2+ conductance (12 pS) was similar to the Ca2+ conductance (11 pS).
Ultrastructure of Aerobic Muscle in Antarctic Fishes may Contribute to Maintenance Of Diffusive Fluxes
Authors: Londraville Richard L. , Sidell Bruce D. 
Published: April 2021

ABSTRACT
Quantitative ultrastructural analyses were performed on red (oxidative) and white (glycolytic) skeletal muscles from two species of antarctic fish to identify features of subcellular structure that may be related to muscle metabolism at cold body temperature. Trematomus newnesi (Boulenger) is an active pelagic species and Notothenia gibberifrons (Lönnberg) is a sluggish bottom-dweller. White fibres of both species are poorly vascularized [capillary density, NA(c,f), for T. newnesi is 73.9±11.3 mm−2; for N. gibberifrons is 76.0±14.1 −2], and have low percentages of cell volume occupied by mitochondria [volume density, Vv(mit,f), for T. newnesi is 0.014±0.005; for N. gibberifrons is 0.006±0.003]. Ultrastructure of oxidative fibres in both species resembles that of cold-acclimated temperate-zone fishes. Mitochondrial volume densities of red fibres reflect differences in ecotype between species [Vv(mit,f) for T. newnesi is 0.348±0.012; for N. gibberifrons is 0.249± 0.007], The less clustered array of mitochondria in oxidative fibres of T. newnesi compared with N. gibberifrons may support an equivalent flux of aqueous metabolites between mitochondrial and cytoplasmic compartments, despite a greater mean intracellular diffusion distance (τh) between these compartments in T. newnesi than in N. gibberifrons (τh=1.05±0.07μm and 0.77±0.06μm, respectively). Although Vv(mit,f) is higher in red fibres of the active species, capillary supply is less extensive [capillary length density, Jv(c,f), for T. newnesi is 481.3±49.0mmmm−3; N. gibberifrons is 696.3±33.7 mm mm’− 3] and the maximal diffusion-distance for oxygen is greater in T. newnesi than in N. gibberifrons (Krogh’s radius, N=26.3±1.64μm and 21.5±0.51 μm, respectively). A mismatch appears to exist between oxygen supply [Jv(c,f)] and oxygen demand [Vv(mit,f)] in T. newnesi red fibres in view of published data for other fishes. The twofold higher volume density of lipid [Vv(lip,f)] in T. newnesi compared with N. gibberifrons may resolve this paradox [Vv(lip,f) is 0.026±0.002 and 0.012±0.004, respectively]. Because oxygen is at least four times more soluble in lipid than in aqueous cytoplasm, lipid may enhance oxygen flux through oxidative muscle and play a role similar to myoglobin in these myoglobin-poor fishes.
Comparative Study of Chill-Coma Temperatures and Muscle Potentials in Insect Flight Muscles
Authors: Goller Franz , Esch Harald 
Published: April 2021

ABSTRACTMuscle potentials in insect flight muscles decrease in amplitude and increase in duration with decreasing temperature. Amplitudes fall to zero at distinct temperatures, which are characteristic for different species. Chill-coma temperature is thus defined here as the critical temperature below which flight muscles cannot be activated. Chill-coma temperatures were 2°C in the species of butterflies measured and −2 to 0°C in the moths. In the species of Hymenoptera, Coleoptera and Diptera measured, chill-coma temperatures ranged from 3 to 14°C. The rate of decline of muscle potential amplitudes with decreasing temperature was different for different species. Rates were smaller over most of the temperature range for species that warm up from low environmental temperatures to reach thoracic temperatures necessary for flight. Amplitudes decreased faster at higher thoracic temperatures in species that start shivering only at higher ambient temperatures. Temperature has a similar effect on durations of muscle potentials in different species. Between 25 and 15°C, durations increased by 100% in all species. The results suggest that cold-adaptation is not strongly related to chill-coma temperature but is strongly related to the rate of decline of muscle potential amplitudes.
Rates of energy processing by blowflies: the uses for a joule vary with food quality and quantity
Authors: Hainsworth F. R. , Fisher G. , Precup E. 
Published: April 2021

ABSTRACT
Data on the variation of crop volumes with time for blowflies (Phormia regina Meigen) fed various volumes and concentrations of fructose or sucrose (from Gelperin, 1966, and Edgecomb et al. 1987) were used to characterize energy processing rates to test the assumption of food energy additivity of optimal foraging theories. Six regression models (linear, square root, cube root, hyperbolic, inverse cube root and exponential) were compared for data from Edgecomb et al. (1987) with measurements of crop volumes from 10 min to 5 h after blowflies were fed 9.7 or 14.5 μl of 0.25moll−1 sucrose. Only the hyperbolic regression could be discriminated as statistically different, and the linear model was selected as most parsimonious for examining rates of energy processing. About the same volume bypassed the crop for flies fed 9.7 or 14.5μ. Volume rates of crop emptying (from Gelperin, 1966) did not change at intermediate concentrations but decreased from lowest and to highest concentrations. Energy processing patterns indicate that long-term storage rates increase with meal size and at intermediate concentrations and decrease (3.0moll−1 fructose) or remain constant (2.0moll−1 sucrose) at high concentrations, so the uses for a unit of energy are not additive across concentrations and meal sizes. Animals that process energy in this way should attempt to maximize meal size and include high-energy foods in their diet out of proportion to the amount of energy gained for the time spent foraging.
Dual motor output interneurons in the abdominal ganglia of the crayfish Procambarus clarkii: synaptic activation of motor outputs in both the swimmeret and abdominal positioning systems by single interneurons
Authors: Murchison D. , Larimer J. L. 
Published: April 2021

ABSTRACT
Many behavior patterns of the crayfish involve the positioning of the abdomen by the tonic motor system. Movements and positionings of the swimmerets are coordinated with these abdominal movements. Evidence from extracellular analyses suggested that single interneurons of the abdominal nerve cord could produce motor outputs in both the swimmeret and the abdominal positioning systems. Our intracellular investigation has revealed that many single cells can evoke outputs in both motor systems. Interneurons which produced fictive extension or flexion of the abdomen or inhibition of abdominal movement were also able to modulate a variety of swimmeret behavior including cyclic beating and excitation or inhibition of episodic outputs. Although interneurons were discovered that evoked each of the possible classes of dual-output combinations, those that evoked combinations frequently observed in the freely behaving animal were more common than those that evoked infrequently observed combinations.
Evidence also indicated that abdominal positioning inhibitors are present in greater numbers than previously suspected and that many are closely associated with the swimmeret circuitry. Interneurons with the ability to start and stop swimmeret cyclic outputs with current injections of opposite polarity are proposed to be higher-order cells, and some are shown to have the properties of trigger neurons. It is proposed that most dual-output cells are presynaptic to single-output cells and that groups of related dual-output cells may function together as command elements.
Fast-Start Performance of Rainbow TroutSalmo Gairdneriand Northern PikeEsox Lucius
Authors: Harper David G. , Blake Robert W. 
Published: April 2021

ABSTRACTThe escape performances of rainbow trout Salmo gairdneri (Richardson) and northern pike Esox lucius (Linnaeus) (mean lengths 0·32 m and 0·38 m, respectively) were measured with subcutaneously implanted accelerometers. Acceleration-time plots reveal two types of fast-starts for trout and three for pike. Simultaneous high-speed ciné films demonstrate a kinematic basis for these differences. Trout performing C-shaped fast-starts produce a unimodal acceleration-time plot (type I) while during S-shaped fast-starts a bimodal accelerationtime plot (type II) results. Pike also exhibit similar type I and II fast-starts, but also execute a second S-shaped fast-start that does not involve a net change of direction. This is characterized by a trimodal acceleration-time plot (type III).Intraspecific and interspecific comparisons of distance, time, mean and maximum velocity, and mean and maximum acceleration rate indicate that fast-start performance is significantly higher for pike than for trout, for all performance parameters. This indicates that performance is related to body form. Overall mean maximum acceleration rates for pike were 120.2±20.0ms−2 and 59.7±8.3ms−2 for trout.Performance values directly measured from the accelerometers exceed those previously reported. Maximum acceleration rates for single events reach 97.8ms−2 and 244.9ms−2 for trout and pike, respectively. Maximum final velocities of 7.06 ms−2 (18.95 Ls−1) were observed for pike and 4.19 ms−2 (13.09 Ls−1) for trout, where L is body length; overall mean maximum velocities were 2.77 m s−2 for trout and 3.97 m s−2 for pike.
Bicarbonate Transport Systems in the Intestine of the Seawater EEL
Authors: Ando Masaaki , Subramanyam M. V. 
Published: April 2021

ABSTRACTUtilizing a pH-stat method, the rates of mucosal and serosal alkalinization were measured separately in the seawater eel intestine. These two rates were dependent on contralateral HCO3− concentration and were inhibited by contralateral application of DIDS, an inhibitor of HCO3− transport, indicating that the mucosal and serosal alkalinization are due to HCO3− secretion and absorption, respectively. The mucosal alkalinization was enhanced after inhibiting Na+/K+/Cl− cotransport by treatment with bumetanide, furosemide or Ba2+, with a latent period of more than 10 min, suggesting that HCO3− absorption from mucosa to serosa depends on Na+/K+/Cl− cotransport. The serosal alkalinization caused by HCO3− absorption was completely abolished after mucosal application of bumetanide. After pretreatment with bumetanide, mucosal omission of Cl− halved the enhanced rate of mucosal alkalinization, and Na+ omission had no effect on it; this indicates that the exit of HCO3− into the lumen depends on luminal Cl−, i.e. on the existence of the usual C1−/HCO3− exchange on the brushborder membrane. When serosal Na+ was removed under the same conditions, mucosal alkalinization was reduced, indicating that HCO3− entry from the serosal fluid depends on Na+. Serosal omission of Cl− did not reduce mucosal alkalinization. In addition, serosal alkalinization was enhanced by serosal removal of Na+ but not of Cl−. These results suggest that there is a Na+/HCO3− cotransport on the basolateral membrane. A possible model for HCO3− transport systems in the seawater eel intestine is proposed, and a possible role for these transport systems is discussed in relation to Na+, Cl− and water transport.