bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Spherical Form of the Mammalian Erythrocyte
Authors: Ponder Eric 
Published: April 2021

ABSTRACT
Some time ago I published an account of the change in shape, from disc to sphere, which occurs when mammalian red cells, suspended in saline, are placed between a slide and a closely applied cover-glass (Ponder, 1929). Later I briefly described a similar transformation which occurs in plasma or serum to which small quantities of lecithin have been added, the normally discoidal cells again becoming perfect spheres without change in volume (Ponder, 1933), and recently I have observed a disc-sphere transformation in systems containing red cells and dyes of the fluorescein series. To avoid difficulties associated with the peculiar shape of the mammalian red cell, several observers have worked with the spherical form in lecithin-treated plasma (Ponder, 1933, for finding volumes, 1935, in conductivity studies; Race, 1934, in sedimentation experiments; Fricke and Curtis, 1935, in conductivity and capacity experiments) ; no detailed description of the phenomenon itself, however, has yet appeared, and the disc-sphere transformation which occurs with the dyes of the fluorescein series is altogether new.
The Digestive Enzymes of the Onychophora (Peripatopsis Spp.)
Authors: Heatley Norman G. 
Published: April 2021

ABSTRACT
An investigation has been made of the digestive enzymes of Peripatopsis spp. The pH of the gut varies between 6·0 and 8·2; it is usually about 7·0. The salivary glands elaborate amylase, glycogenase, protease and carboxy-polypeptidase. The gut digestive enzymes consist of invertase, maltase, lipase, esterase, amino- and carboxypolypeptidase and dipeptidase. Gelatin is also liquefied by the gut, but at pH 3·0 only. The properties of some of the individual enzymes have been examined.
Regeneration in Clavelina Lepadiformis
Authors: Berrill N. J. , Cohen Arthur 
Published: April 2021

ABSTRACT
The polarity of a developing isolated piece of stolon of Clavelina lepadiformis is the same as that of the zooid from which it came in the case of straight or simply branched pieces. In pieces with congested ampullary branches the original polarity is lost and a secondary polarity acquired. The number of rows of stigmata formed during the development of a stolon fragment varies directly with the size of the fragment. In very small pieces development may become arrested at almost any stage, the stage of arrest depending on the quantity of mesenchyme contained in the proximal region of the stolon piece. If sufficient is present to enable development to proceed to the formation of a functional heart, a circulation is established that includes food reserves in the distal part of the stolon and development proceeds to completion. In shorter pieces, less than 0-4 mm. long, development or regeneration does not begin. The total failure to develop is correlated with the absence of a region of relatively columnar epidermis, and it is suggested that the area of columnar epidermis in pieces that do develop is a visible indication of the presence and extent of a morphogenetic field.
Experimental Studies in Insect Parasitism
Authors: Salt George 
Published: April 2021

ABSTRACT
Trichogramma evanescens is able to distinguish healthy from parasitised hosts, and when few hosts are available can restrain itself for 8 hours to the deposition of 5 per cent, of its available eggs.
As far as is yet known, the discriminative ability is perfect ; but the restraint is limited and, in a longer period of time or when several parasites are together, it breaks down and superparasitism occurs.
When the superparasitism is slight and only two or three eggs are laid in a host, the competition between the parasite progeny leads to the victory and emergence of one; but when it is severe either a dwarfed or imperfectly developed individual or none at all emerges.
As the density of parasites in a fixed population of hosts is increased, more and more superparasitism occurs, and the following effects on the populations are observed : The number of hosts that escape steadily decreases; but even at high densities of parasites some hosts occasionally escape.The number of hosts that die without yielding either hosts or parasites steadily increases.The number of parasite progeny reaches a maximum and then decreases.The number of progeny of the individual parasites steadily decreases.An increasing proportion of the emergents are imperfectly developed.An increasing proportion of the emergents are males.
The Role of Divalent Cations and Ionic Strength in the Osmotic Sensitivity of Glutamate Oxidation in Oyster Gill Mitochondria
Authors: Ballantyne James S. , Moyes Christopher D. 
Published: April 2021

ABSTRACT
The biochemical mechanism responsible for the osmotic sensitivity of glutamate oxidation in oyster (Crassostrea virginica Gmelin) gill mitochondria was examined. The relative roles of osmotically induced changes in matrix divalent cation concentration and ionic strength were determined. The calcium-magnesium ionophore A23187 inhibited glutamate oxidation in both low-(40% of control rate) and high-(25 % of control rate) osmolarity media. Addition of MgCl2 reversed A23187 inhibition, but at each MgCl2 concentration (1–5 mmoll−1) the rate of glutamate oxidation in the high-osmolarity medium was about 45 % that in the low-osmolarity medium. EDTA (4 mmol l−1) stimulated glutamate oxidation at both osmolarities (more pronounced at high osmolarity), removing the dependency on assay medium osmolarity. The stimulation in response to EDTA was correlated with mitochondrial swelling, which required the presence of monovalent cations for maximal effect. These data suggest that osmotically induced changes in matrix [Mg2+] or [Ca2+] are not responsible for the osmotic sensitivity of glutamate oxidation by oyster gill mitochondria in vitro. Changes in extramitochondrial [Mg2+] may be involved in regulating the rate of glutamate oxidation in vivo, through effects on mitochondrial volume. The maximal rate of glutamate dehydrogenase was not very sensitive to the ionic strength of the assay medium. The rate of electron transport was highly dependent on ionic strength, with the maximal rate occurring in 50 mmol l−1 salt. The osmotic sensitivity of glutamate oxidation in oyster gill mitochondria is apparently due to the effects of changes in matrix ionic strength on the rate of electron transport.
Maximum Lift Production During Takeoff in Flying Animals
Authors: Marden James H. 
Published: April 2021

ABSTRACT
Maximum lift production during takeoff in still air was determined for a wide variety of insects and a small sample of birds and bats, and was compared with variation in morphology, taxonomy and wingbeat type. Maximum lift per unit flight muscle mass was remarkably similar between taxonomic groups (54–63 N kg−1), except for animals using clap-and-fling wingbeats, where muscle mass-specific lift increased by about 25 % (72–86 N kg−1). Muscle mass-specific lift was independent of body mass, wing loading, disk loading and aspect ratio. Birds and bats yielded results indistinguishable from insects using conventional wingbeats. Interspecific differences in short-duration powered flight and takeoff ability are shown to be caused primarily by differences in flight muscle ratio, which ranges from 0·115 to 0·560 among species studied to date. These results contradict theoretical predictions that maximum mass-specific power output and lift production should decrease with increasing body mass and wing disk loading.
Swimming Patterns and the Activity of Identified Equilibrium Interneurones in the Shore Crab, Carcinus Maenas
Authors: Fraser P. J. , Bévengut M. , Clarac F. 
Published: April 2021

ABSTRACT
Swimming behaviour in crabs is electromyographically described in relation to the involvement of the discharge of the equilibrium interneurones. In intact crabs or crabs with only the fifth legs remaining, swimming consists of cyclic out-of-phase sculling movements of the last pair of pereïopods (P5). In these legs, all muscles are involved within a single swimming cycle; antagonistic muscles burst alternately, as do bilateral pairs of muscles. Bursting in the four proximal muscles ensures the appendage rotation while distal muscles set the scull in the best propulsive position.
Swimming evoked by tilt in the sagittal plane starts with symmetrical remotor activity before alternate bursting begins. Tilt in the plane of a statocyst vertical canal leads to asymmetrical onset of remotor bursting, starting with the muscle contralateral to the stimulated statocyst.
Tilt in defined vertical planes elicits the discharge of identified equilibrium interneurones. Of these, interneurones C and D are active before and during swimming. Sensory inputs from the statocysts and/or the leg proprioceptors to these interneurones are both adequate to drive swimming. Moreover, our experiments suggest that cell C activity is strongly involved in the onset and the maintenance of swimming behaviour.
Swimming can be altered by autotomy of legs on one side performed a few days in advance, and leads to the same turning tendency as does contralateral cutting of a connective. This may be due to modification in the strength of the remaining central connections to compensate for those lost.
Telemetered Electromyography of the Fast and Slow Extensors of the Leg of the Brown Lemur (Lemur Fulvus)
Authors: Anapol F. C. , Jungers W. L. 
Published: April 2021

ABSTRACT
Quantitative telemetered electromyography from the four heads of the quadriceps femoris (vastus medialis, rectus femoris, vastus intermedius and vastus lateralis) during normal postures and locomotion (quadrupedal resting, walk/run, gallop and leaping) is presented for the brown lemur, Lemur fulvus. The vastus intermedius is the sole contributor to muscle recruitment during quadrupedal resting postures. It exhibits consistently high levels of electrical activity during all locomotory behaviour. The vastus medialis is recruited least among these muscles during walk/run and tends to be ‘saved’ for galloping and leaping. The rectus femoris and vastus lateralis are recruited at similarly high levels during all phasic activities. The rectus femoris appears to be used eccentrically, storing ‘elastic strain energy’ during all phasic activities. The vastus lateralis combines exceptionally high potential effective force with relatively high potential velocity and resistance to fatigue and probably develops the majority of force in all phasic activities. These results support previously documented structural and histochemical data that imply a functional division of labour among these muscle synergists.
Interactions Between Acid-Base Balance and Cutaneous Ion Transport in Larval Ambystoma Tigrinum (Amphibia: Caudata) in Response to Hypercapnia
Authors: Stiffler Daniel F. , Ryan Sandra L. , Mushkot Robert A. 
Published: April 2021

ABSTRACT
Larval Ambystoma tigrinum (Green) were cannulated non-occlusively in the truncus arteriosus and allowed to recover for 20–24 h. They were then subjected to 24 h of hypercapnia in three groups : those adapted to tap water, 100 mmol l−1 NaCl or running distilled water. The animals in tap water displayed a 32% compensation for the respiratory acidosis in that [HCO3−] and strong ion difference (SID) were elevated to return pH back towards the control level. The animals in 100 mmol l−1 NaCl behaved similarly. However, the animals in running distilled water were unable to compensate by increasing either [HCO3−] or strong ion difference until NaCl was added to the medium. The clear requirement for NaCl in the medium of salamanders that are compensating for a respiratory acidosis led to measurements of Na+ and Cl− fluxes. The influx of Na+ increased by 123 % in animals immersed in NaCl and by 39% in animals in Na2SO4. The influx of Cl− decreased by over 50% in animals immersed in NaCl and by over 30% in those in choline chloride. The transcutaneous potential difference increased rapidly and reversibly during hypercapnia and the increase was blocked by propranolol. These data suggest that the cutaneous active transport of Na+ into the extracellular space is stimulated and that the active transport of Cl− is simultaneously inhibited during hypercapnia. Measurement of circulating interrenal steroids (RIA) revealed a clear increase in aldosterone concentration during hypercapnia and a possible accompanying increase in corticosterone. The results suggest that the compensatory response to hypercapnia in larval A. tigrinum involves alterations in cutaneous ion transport which increase the extracellular SID. These cutaneous responses may be under the shortterm control of catecholamines and under the long-term control of interrenal steroids.
The Sexually Dimorphic Jamming Avoidance Response in the Electric Fish Eigenmannia (Teleostei, Gymnotiformes)
Authors: Kramer Bernd 
Published: April 2021

ABSTRACT
Eigenmannia’s, jamming avoidance response (JAR) is a frequency change of its electric organ discharge (EOD) in response to an electric stimulus of similar frequency (small ΔF; ΔF = FFish – FStim). It is assumed that the response to an unclamped stimulus, ΔR = FResponse – FRest, is stereotyped and non-habituating, and improves the fish’s electrolocation performance in the presence of a jamming stimulus, such as the EOD of a nearby conspecific.
Adult females gravid with eggs (N = 3) gave good responses (frequency decrease of at least 3 Hz) to – ΔF (stimulus frequency higher than fish frequency), but no response or only weak responses (&lt;0·5 Hz) to + ΔF (stimulus frequency lower than fish frequency). After 2·75 years, a sexually mature female still showed the same behaviour, whereas an immature female (see below) had changed its behaviour considerably on becoming sexually mature.
Large males (N = 4) did not give JARs to +ΔF, and no JARs or only weak ones to – ΔF (| ΔR| &lt; 0·7 Hz). Increasing the stimulus intensity by +10 or +20 dB did not change this result. After 2·5 years, two large males were still found to be almost unresponsive. However, large males gave rapid frequency modulations (‘short rises’ and ‘interruptions’), which have been described from threatening fish likely to attack, even at the weakest stimulus intensity.
One group of juveniles (N=4; probably females) gave only a weak increase in frequency (AR &lt;0 ·9 Hz) in response to +ΔF but a strong frequency decrease (|ΔR|&gt;2Hz) in response to –ΔF. Another group of juveniles (N=4; probably males) gave strongest responses (ΔR &gt;3 Hz) to ΔF = 0Hz. In these juveniles, the ‘equilibrium point’ of no response was at ΔF ≈ – 0·6 Hz to – 1Hz instead of at ΔF = 0 Hz. They thus increased, rather than decreased, their EOD frequency even at small – ΔFs, which would have been more economical. A decrease in frequency was weaker than an increase. A significant frequency change could even be elicited by stimuli of ΔF = 0 Hz that are phase-locked to the EOD.
The accuracy of assessment of ΔF, as determined in juvenile fish giving good + ΔRs and – ΔRs, was not better than ±0·3 Hz (at ΔF = – 0·6 Hz). The JAR showed strong habituation.
Dedicated to Professor Kurt Fiedler on his 60th birthday.
None of the 14 fish showed a frequency difference vs response curve close to optimal for the purpose of jamming avoidance. An alternative function of the JAR in social communication is considered.
Effects of Trimetaphan on Locust Muscle Glutamate Receptors
Authors: Ashford M. L. J. , Boden P. , Ramsey R. L. , Shinozaki H. , Usherwood P. N. R. 
Published: April 2021

ABSTRACT
Effects of trimetaphan have been tested on locust retractor unguis and extensor tibiae nerve–muscle preparations. Trimetaphan reversibly reduced the neurally evoked twitch amplitude of the retractor unguis muscle, dependent upon dose and partly upon stimulus frequency. Contractions evoked by both glutamate (10−4moll-1) and L-quisqualic acid (10− 4moll− 1) were abolished by Immoll− 1 trimetaphan. Dose-response curves for ionophoresis of L-glutamate were shifted to the right by trimetaphan, with a reduction in peak glutamate potential amplitude. The depression of the ionophoretic glutamate potential was partly dependent upon previous stimulation history, and this action was eliminated by concanavalin A. Trimetaphan had no effect on transmitter release. Within certain limits, trimetaphan reduced the extracellular postsynaptic current (EPSC) amplitude and rise time in a concentration-dependent and voltage-dependent manner. At high concentrations (&gt;5x 10− 4mol l− 1) its effectiveness was reduced with large hyperpolarizations. The EPSC decay was prolonged and usually biphasic in the presence of trimetaphan, although at some junctional sites a mixture of biphasic and apparently monophasic EPSC decays was seen. It is concluded that trimetaphan exerts more than one effect on locust muscle glutamate receptors. It is likely that it enhances desensitization and also blocks the receptor channel when in the open state.
Swimming in the California sea lion: morphometrics, drag and energetics
Authors: Feldkamp Steven D. 
Published: April 2021

ABSTRACTDuring swimming, the California sea lion, Zalophus californianus (Lesson), generates thrust forces solely by means of its pectoral flippers. This study examines the drag, energetic cost and efficiency associated with this method of locomotion. Sea lions are highly streamlined, with a fineness ratio of 5·5 and maximum girth at 40 % of body length. This profile leads to reduced drag and swimming power requirements. Films of gliding animals showed the drag coefficient (based on wetted surface area) to be 0·0042 at a Reynolds number of 20×106. This value is comparable to that found for other aquatic vertebrates and suggests that the sea lion ‘s morphology helps to delay turbulent separation and maintain laminar flow over the forward portion of its body.Swimming metabolism was measured in a water flume at velocities up to 1·3 ms−1. Effective swimming speeds up to 2·7ms−1 were attained by increasing each animal ‘s drag. Oxygen consumption rose exponentially with velocity and for two animals was best described as where is in ml O2 min−1 kg−1 and U is in ms−1. Minimum cost of transport for these animals was 0·12 ml O2 kg−1 m−1 at a relative speed of 1·4 body lengths s−1. This is 2·5 times that predicted for a fish of similar size. Swimming efficiencies were determined from these results using power output values calculated from the measured drag coefficient and standard hydrodynamic equations. At the highest velocity, aerobic efficiency reached a maximum of 15 % while mechanical efficiency of the foreflippers was 80%. The results demonstrate that foreflipper propulsion is a highly efficient and comparatively inexpensive method of locomotion in aquatic mammals.
Physiological features of the opercularis muscle and their effects on vibration sensitivity in the bullfrog Rana catesbeiana
Authors: Hetherington T. E. 
Published: April 2021

ABSTRACT
The amphibian opercularis muscle connects a movable otic element (the operculum) to the pectoral girdle and can act in reception of ground vibrations. Various physiological parameters of the opercularis muscle of the bullfrog Rana catesbeiana were measured and compared with similar measurements on the iliofibularis muscle of the hindlimb. The opercularis muscle is a very slowly contracting muscle, with a Vmax of 1·81 muscle lengths s−1 compared to a Vmax of 6·24 muscle lengths s−1 for the iliofibularis muscle. The opercularis muscle develops tension slowly, taking about 10 s to attain maximum isometric tension when stimulated at 100 Hz. The muscle can retain high levels of tension for several minutes, and following stimulation has a time to half-relaxation of about 4–6s. The slow velocity of contraction, slow rate of tension development, fatigue-resistance and slow rate of relaxation of the opercularis muscle support morphological evidence that it consists mostly of tonic muscle fibres. Experiments were also made to examine the effects of muscle tension on reception of ground vibrations as measured by inner ear microphonics. Severing the nerve supplying the opercularis muscle produced slight decreases of no more than 2dB in responses to vibrations from 25 to 200 Hz. Artificial stimulation of the opercularis muscle after severing the nerve supplying the muscle increased responses to vibration across the entire frequency range. Higher tension levels produced greater increases in responses; at the highest tensions used (about 120 kN m−2) responses were increased by as much as 4· 5 dB. The opercularis muscle is therefore specialized for slow but prolonged contractions, and tension is important in its sensory function. A tensed opercularis muscle appears to transmit faithfully motion of the forelimb, produced by vibrations, to the operculum such that the latter moves relative to the inner ear fluids.
Intracellular Recording from Receptor Cells of the Temporal Organ of the Japanese House Centipede, Thereuonema Hilgendorfi: Receptor Potential and Conductance Changes
Authors: Yamana Kenjiro , Toh Yoshihiro 
Published: April 2021

ABSTRACT
The primary process of carbon dioxide reception in the temporal organ of the Japanese house centipede Thereuonema hilgendorfi has been studied by means of intracellular recording.
During adaptation to air containing no carbon dioxide, the membrane potential of receptor cells in the temporal organ ranged from –25 to –59 mV with an average of –39mV (N = 21). Input resistance ranged from 10 to 46MQ with an average of 22-6MQ (N= 16). Receptor cells responded to a carbon dioxide stimulus with a graded hyperpolarizing receptor potential, which reduced impulse frequency. The decrease in steady-state frequency was proportional to the amplitude of the receptor potential. During the receptor potential, the input resistance increased. Injection of hyperpolarizing current resulted in an increase in amplitude of receptor potential, while depolarizing current caused a decrease. These results suggest that the receptor potential is caused by a decrease in membrane permeability to ions whose equilibrium potential is more positive than the membrane potential adapted to 0 % carbon dioxide.