bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Cellular Basis for the Differences in Regulation of Synthesis and Secretion of Acth/Endorphin Peptides in Anterior and Intermediate Lobes of the Pituitary
Authors: Rosa Patricia A. , Policastro Paul , Herbert Edward 
Published: April 2021

ABSTRACT
The focus of research in our laboratory over the past few years has been the regulation of synthesis, processing and release of the ACTH/LPH family of peptides. These peptides are derived from a common precursor protein that is found in both the anterior and intermediate lobes of the pituitary (Roberts et al. 1978) and in the hypothalamus (Liotta et al. 1979). In the anterior lobe this protein gives rise to α (1–39)ACTH, β-lipotropin and an N-terminal fragment of undefined function. In addition, a variety of intermediate lobe pituitary peptides can be derived from the precursor by further processing of ACTH and β-LPH. In this paper we compare the structure of the precursor in the anterior and intermediate lobes of mouse and rat pituitary. Processing of the precursor to its constituent hormones is then contrasted in primary cultures of anterior and intermediate lobe cells using pulse label and pulse chase techniques with radioactive amino acids and sugars. Finally, we discuss the difference in behaviour of anterior and intermediate lobe cells in culture with regard to their rates of secretion and intracellular turnover of hormones and regulation of these processes by hypothalamic factors, glucocorticoids and catecholamines.
Factors That Influence Regeneration of the Neuromuscular Junction
Authors: McMAHAN U. J. , Edgington D. R. , Kuffler D. P. 
Published: April 2021

ABSTRACT
Regeneration of neuromuscular junctions after trauma occurs in an orderly way and relies on communication between nerve and muscle. This paper summarizes evidence that factors which direct the growth and differentiation of both pre- and postsynaptic components of regenerating neuromuscular junctions are associated with the extracellular matrix of muscles.
On Some Cellular Reactions to X-Radiation
Authors: Butler Elmer G. 
Published: April 2021

ABSTRACT
The wall of the developing neural tube of young chick embryos contains two types of cells; one type, the germinal cells, with nuclei conspicuously active in mitosis, is restricted to the innermost layer of the neural wall; the other type of cell with nuclei in the resting state and none in division, forms the main mass of the neural wall, the mantle layer. A study of the neural tube after radiation with a single non-lethal dose of X-rays reveals a series of cellular changes: an initial period of mitotic depression during which mitotic figures in the germinal cells disappear entirely; a period of pseudo-recovery during which mitotic activity reappears; a period of degeneration characterised by severe nuclear changes among the cells in the resting state; and a period of remarkable regeneration and recovery resulting in a return of the tissue to its normal condition.
On the Vitelline Membrane of the Egg of Psammechinus Miliaris and of Teredo Norvegica
Authors: Hobson A. D. 
Published: April 2021

ABSTRACT
It has been assumed very generally that the unfertilised eggs of many animals are surrounded by a clear surface layer, discontinuous with the general protoplasm, which is known as the vitelline membrane. In marine forms this layer is commonly supposed to be separated from the true surface of the egg at the time of, or soon after, fertilisation and then becomes the fertilisation membrane.
Studies on the Pituitary
Authors: Hogben Lancelot , Charles Enid 
Published: April 2021

ABSTRACT
The injection of fresh saline suspensions of ox pituitary produces a prolonged fall in the calcium content of the serum of normal female rabbits and rabbits deprived of their ovaries. After sexual excitement there is a fall of blood calcium in the female rabbit beginning within 4 hours from association with the buck, followed by a secondary rise at the time when ovulation occurs with a further fall subsiding by the time the corpus luteum is fully formed. The removal of the ovaries from sexually mature rabbits does not produce any significant change in the calcium or magnesium level of the serum.
Iodine Compounds and Fertilisation
Authors: Carter G. S. 
Published: April 2021

ABSTRACT
The analysis of the secretions which diffuse from the eggs of Echinoderms and other marine invertebrates is a subject which has attracted the attention of many biologists, who have approached it from many different points of view. As a result, there is available a large amount of varied work on the subject and the conclusions which have been drawn from this work have also been varied. There can be no doubt that the secretions are always complex, in the sense that they always contain more than a single chemical substance, and very little doubt that the secretions of different species are to some extent different in nature. In spite of this variability in the nature of the secretions and of the lack of agreement between the workers who have experimented with them, some broad conception of the constitution of the secretions has been obtained and may be summarised as follows.
Phosphagen and Protozoa
Authors: Needham Dorothy Moyle , Robertson Muriel , Needham Joseph , Baldwin Ernest 
Published: April 2021

ABSTRACT
The comparative investigations of Eggleton and Eggleton(6), Meyerhof and Lohmann (11), Meyerhof(10), and Needham, Needham, Baldwin and Yudkin(12) have established a considerable body of information concerning the distribution of the phosphagens in the animal kingdom, and the character and implications of this knowledge have recently been analysed by Needham and Needham (13). But from all discussions hitherto, any mention of the Protozoa has been absent. This gap in our knowledge is unfortunate for two reasons, firstly because from a phylogenetic point of view it would be very desirable to ascertain the lower limit of distribution of such important compounds, and secondly because the Protozoa, or at least certain examples of them, would afford an interesting test of any possible association between phosphagen metabolism and ciliary, as well as muscular movement. With regard to the first of these reasons, the Coelenterates yielded interesting results in the work of Needham, Needham, Baldwin and Yudkin(12), for whereas a Cteno-phore, Pleurobrachia pileus, contained considerable amounts of arginine phosphate (43 per cent, of the free and labile water-soluble phosphorus), none was discoverable in the Actinozoa, Anthea rustica and cereus. Further work on the phosphagen of the Coelenterates would be very useful, but it is perhaps significant in this connection that Kutscher and Ackermann (9), though able to isolate free arginine from many marine invertebrates, could only obtain guanidine and agmatine from Geodia gigas. The question whether phosphagen was to be found elsewhere than in the Metazoa clearly merited examination. And with regard to the second of the reasons given above, some indications were found by Needham, Needham, Baldwin and Yudkin (12) that phosphagen might occur in situations primarily characterised by ciliary activity, e.g. the swimming gastrulae and plutei of echinoids.
The Heart Rate of the Developing Chick
Authors: Bogue J. Yule 
Published: April 2021

ABSTRACT
Several authors have measured the heart rate of the chick embryo, but in all cases their methods involved opening the egg. The effect of this procedure on the heart rate is unknown, and therefore the writer investigated the possibility of recording the electrical variation of the embryo heart and thus obtaining a record of the heart rate with the minimum of interference with the embryo.
Experimental Studies on the Struggle for Existence
Authors: Gause G. F. 
Published: April 2021

ABSTRACT
Although the phenomena of variation and heredity have in recent years become amenable to quantitative treatment, our knowledge of the struggle for existence has been increased to an almost negligible extent during the past fifty years. In the present paper an account is given of a series of experiments which constitute an attempt to apply experimental methods to the study of the struggle for existence. The work has been carried out with two species of yeast, and observations have been made on the effect of the presence of one species on the rate of reproduction of another. This situation has recently been considered from a mathematical point of view by Lotka (1925) and by Volterra (1931).
Fertilisation in the Rabbit
Authors: Pincus G. , Enzmann E. V. 
Published: April 2021

ABSTRACT
In a previous paper (Pincus, 1930) it was concluded that for the fertilisation of the ovum of the rabbit it takes the spermatozoa from 2 to 3 hours after ovulation, to reach and effectively fertilise the egg. This conclusion was based on experiments in which ova, taken from the tubes at various intervals after fertile matings, were cultured in vitro. It was found that “the proportion of ova from fertile matings that divide in culture is very low for ova recovered between 11 and 12 hours after copulation, increases for ova obtained from 12 to 13 hours after copulation, and practically all ova recovered from 14 hours after copulation onward divide in culture.” Since ovulation in the rabbit normally occurs at about 10 hours after copulation there is a period from ovulation to about 3 hours later when the significant events associated with sperm penetration occur. It was decided therefore to examine with some care the state of rabbit ova as recovered from the tubes during this critical period.
Observations on Digestion in the Ruminant
Authors: Magee H. E. 
Published: April 2021

ABSTRACT
Present-day knowledge of the physiology of digestion in ruminants is very limited and to a great extent it is based on anatomical deductions. Some of these are doubtless correct ; but many of them must be regarded merely as speculations until such time as adequate experimental proof is brought forward. It was with the object of providing this proof that the present work was undertaken. The experiments were concerned chiefly with the progress of the food through the alimentary canal, and, consequently, with the movements of the different sections of the canal itself. The ruminant owes its unique position amongst mammals to the anatomical complexity of the stomachs, and, for this reason, attention was directed particularly to the movements of these viscera. It will be an advantage, before taking up the experimental part of this paper, to consider certain important1 anatomical features and postmortem appearances and to discuss the physiological significance which it is believed can be attributed to them.
The Functional Design of the Insect Excretory System
Authors: Maddrell S. H. P. 
Published: April 2021

ABSTRACT
Insects have a slowly operating excretory system in which the passive rate of movement of haemolymph solutes into a slowly secreted primary excretory fluid is restricted by a reduction in the area available for passive transfer. They may have come to possess such an energy-saving system as a result of their evolution as small animals in osmotically and ionically stressful environments. Although the possession of a waxy cuticle is a major element in their ability to live in such environments, insects have a very high surface-area/ volume ratio and this is likely to have conferred a selective advantage on individuals able to withstand unusually variable extracellular conditions. Among their major adaptations evolved to allow them to tolerate such conditions are the lack of a blood-borne respiratory pigment to be affected and the development of a system whereby their most sensitive tissues are protected by the regulatory activities of special covering epithelia. Because of these features it follows that there has been less evolutionary pressure for rapid excretory control of the haemolymph composition. With an excretory system that only slowly filters the haemolymph, less energy expenditure is involved in the production of the primary excretory fluid and in reabsorption of useful substances from it. In addition, insects are able to maintain in circulation high concentrations of substances such as amino acids, trehalose, and lipids. They can also eliminate excess fluid at very high rates with the loss of only trace amounts of haemolymph solutes. It is argued that terrestrial insects owe much of their success to their ability to recover virtually all the water from the slow flow of primary excretory fluid. The hindgut cells that are responsible for this recovery are aided by their cuticular lining which protects them from contact with the very high concentrations of potentially interfering compounds in the excretory material.
A Sodium-dependent ‘Twitch’ Muscle in a Coelenterate: The Ectodermal Myoepithelium of the Gastrozooids in Agalma SP. (Siphonophora)
Authors: Chain Benjamin M. 
Published: April 2021

ABSTRACT
Intracellular recordings were obtained from the ectodermal cells of the gastrozooids of the siphonophore, Agalma sp. Stimulated gastrozooids undergo rapid longitudinal contractions that are immediately preceded by a series of action potentials which propagate throughout the epithelium. These rapid potentials arise from a much slower graded depolarization. Both potentials are abolished in low sodium solutions. Fast action potentials persist in the presence of manganese ions but both the slow potentials and contraction are abolished.
Measurements of Unsteady Periodic Forces generated by the Blowfly Flying in a Wind Tunnel
Authors: Buckholz Richard H. 
Published: April 2021

ABSTRACT
A technique was developed for the measurement of the instantaneous lift and drag forces generated by the blowfly, Sarcophaga bullata, flying fixed in a wind tunnel. Apparatus for the measurement of insect-generated forces was checked in part for mean force accuracy by measurement of the drag on a circular cylinder. Our experimental device detects the sum of the aerodynamic forces and wing inertial forces as experienced by the thorax. The streamwise and vertical force waveforms show a surprising lack of higher harmonic content. Wind speeds in the neighbourhood of the known preferred flying speed were used, without an explicit attempt to nullify the mean vertical and horizontal forces to simulate free flight. Several measurements of the phase angle between the force waveform and the wing beating kinematics indicated that vertical forces in the liftward direction achieved a maximum during the downstroke and thrustward forces achieved a maximum during the upstroke.
Song Energetics of the Bladder Cicada, Cystosoma Saundersii
Authors: Nally Ralph Mac , Young David 
Published: April 2021

ABSTRACT
Males of Cystosoma saundersii produced their calling songs while tethered to holders. Oxygen consumption during singing was 0·136 ml min−1, equivalent to 45· 0 mW, an increase of 42· 55 mW over the resting metabolic rate. Maximum sound output was 90·6 dB at 20 cm. The whole sound-field was measured and represents a power output of 0·35 mW. The efficiency of sound production is 0·82%. Heat production, estimated from the weight of singing muscle, was 28·7 mW. This leaves 13·5 mW of output unaccounted for. Comparison with other species of insects suggests that none are more than an order of magnitude more efficient than C. saundersii.
Participation of an Unpaired Motor Neurone in the Bilaterally Organized Oesophageal Rhythm in the Lobsters Jasus Lalandii and Palinurus Vulgaris
Authors: Moulins M. , Nagy F. 
Published: April 2021

ABSTRACT
The main oesophageal motor neurone (OD1) of the rock lobster is an unpaired bifurcating nerve cell. The cell body is located in the oesophageal ganglion and the left and right axonal branches pass through the left and right commissural ganglia to innervate all the oesophageal dilator muscles. Three types of potentials are recorded in the cell body in vitro; each type is associated with an extracellular spike recorded from the nerves connecting the ganglia. Comparison between the three types of potentials (and the extracellular spikes) and collision experiments shows that all three are spikes. Spontaneous collisions can sometimes occur and it is concluded that one spike is generated in the oesophageal ganglion (somatofugal a-spike) while the other two are generated in the left commissural ganglion (somatopetal b-spike) or the right commissural ganglion (somatopetal c-spike). Each spike initiating zone is synaptically driven. The commissural zones fire short phasic bursts; each burst is composed of only one type of spike (b-or c-). The oesophageal (a-) zone gives a tonic discharge interrupted when the other zones are firing. Finally, combined firing of the spike initiating zones can generate three different patterns of discharge. OD1 participates in the oesophageal motor rhythm produced by two oscillators (one in each commissural ganglion) which fire alternated series of bursts. It is concluded that the three axonal spike initiating zones enable the motor neurone (1) to follow the oesophageal motor rhythm at any time regardless of which oscillator is in operation and (2) to co-ordinate phasic and tonic activation of the oesophageal dilator muscles.
Temperature Regulation and Heat Balance in Flying White-necked Ravens, Corvus Cryptoleucus
Authors: Hudson Dennis M. , Bernstein Marvin H. 
Published: April 2021

ABSTRACT
During level flight at 10 m.s−1 in a wind tunnel, white-necked ravens (Corvus cryptoleucus, mass 0·48 kg) exhibited an increase in body temperature to steady-state levels as high as 45 °C, exceeding resting levels by nearly 3 °C. This reflects the storage of up to half of the metabolic heat produced (Hp) during 5 min of flight. During steady-state flight, body heat was dissipated in part by respiratory evaporation and convection (13–40% of Hp) evoked by increases in ventilation proportional to body temperature. Remaining heat was lost by cutaneous evaporation (10 % of Hp) as well as by radiation and convection from the external body surface. The results suggest strategies that might be used by ravens during flight under desert conditions.
A Comparison of Mechanical and Energetic Estimates of Flight Cost for Hovering Sphinx Moths
Authors: Casey Timothy M. 
Published: April 2021

ABSTRACT
Mechanical power output, based on measured power input, is compared with calculated values for aerodynamic and inertial power output in sphinx moths ranging from 350 to 3400 mg. Aerodynamic power output, calculated from momentum and blade-element aerodynamic theories, scales with the 1·08 power of body mass, amounting to about 40% of the mechanical power output of large moths to about 15% in the smallest individuals. Calculated value for the inertial power cost of hovering represents a larger fraction of the mechanical power output than the aerodynamic cost in all moths, with the value increasing as body mass decreases. Independent estimates of inertial power output based on metabolic data are similar to those obtained from calculations of the moment of inertia for the wings. These data suggest that inertial power output represents the largest power requirement for hovering sphinx moths, and that elastic torques do not significantly reduce the mechanical power output. Higher mass-specific power input of small sphinx moths appears to be the result of greater mass-specific inertial power requirements. Estimates of flight cost based on morphology and flight mechanics of sphinx moths yield values for mechanical power output which are similar to values estimated from their flight metabolism.
Effects of Speed and Extent of Stretching on The Elastic Properties of Active Frog Muscle*
Authors: Cavagna Giovanni A. , Citterio G. , Jacini P. 
Published: April 2021

ABSTRACT
The work done during fast recoil of active striated muscle (as in a jump) was measured at 2 and 12 °C by making tetanized frog sartorii shorten from about 2 mm above slack length, l0, at high speed(6–9 l0. s-1)( 1) during a state of isometric contraction and (2) after stretching the muscle, while active, at different speeds and by different amounts. The work done increases with the force developed by the muscle according to a sigmoidal curve, having a point of inflexion that is displaced to greater values of force at 12 °C than at 2 °C. Previous stretching leads to an upward shift of this curve, i.e. to an iso-force gain of energy. This gain increases towards a maximum as the speed and extent of stretching are increased, attaining 60–80% of the total work done from a state of isometric contraction ; this fraction decreases when stretching begins from lengths smaller than l0. The apparent elastic behaviour of muscle is thus described by a set of curves rather than by a single curve. Active muscle behaves as a more rigid structure when it transmits the generated force to an external load (as in an isometric contraction) and as a more compliant structure when, stretched by an external force, it has the opportunity to store external mechanical energy.
An Electromyographic Analysis of the Elevator/Depressor Muscle Motor Programme in the Freely-Walking Scorpion, Paruroctonus Mesaensis
Authors: Bowerman Robert F. 
Published: April 2021

ABSTRACT
Electromyograms from the elevator and depressor muscles, together with tarsal claw receptor activity, were recorded from the fourth legs of freely walking scorpions. The slope of the depressor burst duration versus step cycle time was less for short cycle times, below about 600 ms, than it was for longer cycles. The opposite was true for the elevator burst duration versus step cycle relationship, and the slope for longer cycle times was not significantly different from zero. The switching of motor activity between antagonists at the stance to swing phase transition was different from that of the swing to stance phase. The depressor burst invariably terminated before the elevator burst, while the elevator burst frequently did not terminate until after the depressor burst had begun. A similar asymmetry of the elevator/depressor motor programme has been described for insect and crustacean preparations. The termination of the depressor muscle burst represents the initial peripheral indicator that the decision to step has been made centrally. The latency between the central decision and the time when the leg is lifted, as determined by tarsal claw receptor burst termination, can be as much as 125 ms. This observation is of importance when considering both intrasegmental and intersegmental neural control mechanisms of scorpion locomotion.
Respiratory, Ventilatory, Acid-Base And Ionoregulatory Physiology Of The White Sucker Catostomus Commersoni: The Influence Of Hyperoxia
Authors: Wilkes P. R. H. , Walker R. L. , Mcdonald D. G. , Wood C. M. 
Published: April 2021

ABSTRACT
Blood gases, acid-base status, plasma ions, respiration, ventilation and cardiovascular function were measured in white suckers, using standard cannulation methods. Basic respiratory parameters under normoxia were compared to those in the active, pelagic rainbow trout and in other benthic teleosts. Sustained environmental hyperoxia (350-550 torr) increased arterial O2 (102-392 torr) and venous O2 (17-80 torr) tensions so that blood O2 transport occurred entirely via physical solution. Dorsal aortic blood pressure and heart rate fell, the latter due to an increase in vagal tone. Ventilation volume declined markedly (by 50%) due to a decrease in ventilatory stroke volume, but absolute O2 extraction rose so that O2 consumption was unaffected. While the preceding effects were stable with time, arterial and venous CO2 tensions approximately doubled within 4 h, and continued to increase gradually thereafter. This CO2 retention caused an acidosis (7·993-7·814) which was gradually compensated by an accumulation of plasma [HCO3–]. However, even after 72 h, arterial pH remained significantly depressed by 0·10 units. The gradual rise in plasma [HCO3–] was accompanied by a progressive fall in both [Na+] and [Cl–] ; [K+] and [Ca2+] remained unchanged. The responses of the sucker to hyperoxia are compared to those of the rainbow trout.