bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Physiological Action of Abnormally High Temperatures on Poikilotherm Animals1
Authors: Fraenkel G. S. , Herford G. V. B. 
Published: April 2021

ABSTRACT
The oxygen consumption of blowfly larvae at sublethal and lethal high temperatures at the beginning of the determination is entirely dependent on the okygen pressure, but after about 1 hr. at 42°C. it is higher at 20 and 10 % partial pressure of oxygen than at either 100 or 5 %. Death at high temperatures is not due to lack of oxygen, but may be due to the accumulation of acid waste products of the metabolism.
The basal oxygen consumption remains unchanged for some time after the organism has been irreversibly injured by the high temperature.
Blowfly larvae resist the damaging effect of high temperatures slightly better in air (20 % oxygen) than in either very high (100 %) or very low (less than 10 %) concentrations of oxygen.
Experimental Production of Functioning Reduplications—A Triple and a Functioning Quintuple Hindlimb in the Frog1
Authors: Brandt Walter 
Published: April 2021

ABSTRACT
Experimentally produced functioning reduplications, triple and quintuple hind limbs of the frog have not yet been described.
Supernumerary limbs can be produced either by transplantation methods or by the methods described in this paper.
In order to prevent confusion between a reduplication of the primordium itself and a doubling after orthotopic transplantation of a limb bud, the author distinguished (1925) (i) reduplication of the limb primordium and (ii) pseudo reduplication consisting of an orthotopic transplanted limb of a donor and a regenerated limb of the host. This grouping was accepted by Smook (1934).
In the following description the above-mentioned terms will be applied in the sense given.
A Further Study of the Relation Between Toxicity and Solution Pressure, with Polycelis Nigra as Test Animal
Authors: Jones J. R. Erichsen 
Published: April 2021

ABSTRACT
The degree of toxicity of the hydrogen ion and the ions of eighteen metals to Polycelis nigra (Müller) has been assessed by determining in each case the concentration the animal survives for approximately 48 hr. at 15-18° C. On a mg./I. basis their order of increasing toxicity is: Sr Na Ca Mg Mn″ Pb″ K Al Co″ Cr‴ Ni″ As‴ Zn Cd″ H Au‴ Cu″ Hg″ Ag On a molar concentration basis the order is as follows : Na Sr Ca Mg Mn″ K Al Pb″ Cr‴ Co″ Ni″ H As‴ Zn Cd″ Cu″ Au‴ Ag Hg″ The position of iron is uncertain; the toxicity of ferric chloride solutions appears to be due to their acidity. Irregular results were obtained with solutions of barium salts, which appear to effect excessive stimulation of the musculature of the animal and induce convulsive movements which eventually result in the rupture of the body and extrusion of the tissues. On a mg./l. or molar concentration basis there is a decided relationship between the solution pressures of the metals and the degree of toxicity of their salts, the general result being very similar to that obtained in an earlier investigation with Gasterosteus aculeatus as test animal. This relationship suggests that the degree of toxicity of ions is largely determined by their affinity for their electrical charges, this affinity determining the readiness with which they tend to abandon the ionic state to enter into chemical combination with protoplasmic compounds.
The Permeability of Gregarine Protozoa from the Gut of the Meal-Worm1
Authors: Adcock Elsa M. 
Published: April 2021

ABSTRACT
Gregarina contains a large amount of osmotically inactive material, chiefly glycogen. In this respect it resembles other parasites such as Ascaris. It possesses no mechanism for regulating its internal osmotic pressure; therefore it quickly reaches a state of equilibrium with the medium in which it is placed. It is more permeable to substances of high lipoid solubility than to those of low lipoid solubility even though the former may have a larger molecule than the latter. In this respect it resembles other cells which have been studied, but it is more permeable than these cells to substances of low lipoid solubility and large molecular size such as glucose and fructose.
Strenuous Exercise-Induced Remodelling of Mature Bone: Relationships Between In Vivo Strains and Bone Mechanics
Authors: Loitz Barbara J. , Zernicke Ronald F. 
Published: April 2021

ABSTRACT
Mature bone can adapt to strenuous exercise, but no study has correlated the changes in bone in vivo strains, remodelling and mechanical properties that occur as a consequence of strenuous training. Therefore, we examined exercise-related remodelling and in vivo strains in the tarsometatarsus (TMT) of three groups of adult (post-physial closure) White Leghorn roosters: basal control (30 weeks of age), age-matched control (39 weeks) and exercise (39 weeks). Exercise birds ran for 1 h a day, 5 days a week for 9 weeks at 70-75% of predicted maximum aerobic capacity. During treadmill locomotion, in vivo strains were recorded from miniature rosette strain gauges implanted on anterior, medial and lateral TMT cortices. TMT mechanical properties were measured with three-point bending tests to failure. Cortical morphometry was digitized from photographic slides of a 1-mm thick mid-diaphysial cross section of each bone. Exercise and age-matched control TMTs had significantly greater cortical area and maximum load than had basal controls. Exercise axial strains significantly exceeded basal and age-matched control strains along the anterior and lateral surfaces. Age-matched control anterior axial strain was twice that of the basal control. The mature bone remodelling suggested that the structural properties optimized by exercise-induced remodelling may differ from those optimized by age-related remodelling. The findings support the osteoregulatory role of strain but contradict earlier data suggesting that strain magnitudes do not change significantly with age or exercise.
Pigeons at Magnetic Anomalies: the Effects of Loft Location
Authors: Walcott Charles 
Published: April 2021

ABSTRACT
Homing pigeons from our old lofts at Fox Ridge Farm in Lincoln, MA, were disoriented when released at places where the earth’s magnetic field was irregular - so-called ‘magnetic anomalies’. The orientation of pigeons raised in our lofts at Cornell in Ithaca, NY, was unaffected by anomalies. Further experiments in Lincoln showed that sibling pigeons raised and trained to lofts only 2.5 km apart behaved differently when released at a strong magnetic anomaly. Pigeons from the loft situated in a magnetic gradient of 450 nT km−1 were disoriented at anomalies, whereas birds raised in a loft in a magnetic gradient of 88nTkm−1 were well oriented. This suggests that the location of the home loft may play an important role in determining which cues pigeons use for their navigation, and that these cues are learned sometime after weaning from their parents at 4-6 weeks after hatching.
Scaling of Power Output in Fast Muscle Fibres of the Atlantic Cod During Cyclical Contractions
Authors: Anderson M. Elizabeth , Johnston Ian A. 
Published: April 2021

ABSTRACT
Fast muscle fibres were isolated from abdominal myotomes of Atlantic cod (Gadus morhua L.) ranging in size from 10 to 63 cm standard length (Ls). Muscle fibres were subjected to sinusoidal length changes about their resting length (Lf) and stimulated at a selected phase of the strain cycle. The work performed in each oscillatory cycle was calculated from plots of force against muscle length, the area of the resulting loop being net work. Strain and the number and timing of stimuli were adjusted to maximise positive work per cycle over a range of cycle frequencies at 8°C.
Force, and hence power output, declined with increasing cycles of oscillation until reaching a steady state around the ninth cycle. The strain required for maximum power output (Ẇmax) was ±7–11% of Lf in fish shorter than 18 cm standard length, but decreased to ±5% of Lf in larger fish. The cycle frequency required for Ẇmax also declined with increasing fish length, scaling to Ls−0.51 under steady-state conditions (cycles 9–12). At the optimum cycle frequency and strain the maximum contraction velocity scaled to Ls-0 79. The maximum stress (Pmax) produced within a cycle was highest in the second cycle, ranging from 51.3 kPa in 10cm fish to 81.8kPa in 60cm fish (Pmax=28.2Ls0.25). Under steady-state conditions the maximum power output per kilogram wet muscle mass was found to range from 27.5 W in a 10cm Ls cod to 16.4 W in a 60cm Ls cod, scaling with Ls−0.29 and body mass (Mb)−010.
Kinematics of Feeding Behaviour in Oplurus Cuvieri (Reptilia: Iguanidae)
Authors: Delheusy Veronique , Bels Vincent L. 
Published: April 2021

ABSTRACT
The kinematics of prey capture, reduction and transport to the oesophagus by the iguanian lizard Oplurus cuvieri were investigated using high-speed cinematography (100-200 frames s∼’) and cineradiography (60 frames s’1). Thirty feeding sequences from four individuals were analysed. Feeding sequences were divided into four phases: capture, reduction, transport to the oesophagus and cleaning. Quantified kinematic profiles of the head, jaws, hyoid-tongue complex and displacements of the prey to (capture) and within (other phases) the buccal cavity are presented from cinematographic frames. Twenty additional variables, depicting maximal displacements and the timing of events, were calculated from the profiles. Variables documenting gape cycles were used in a first principal component analysis for studying the kinematic relationships between the phases. Markers were placed in the tongue of two individuals for cineradiographic study to illustrate displacements of the tongue. During prey capture, the jaw cycle is divided into slow opening (SO I and SO II), fast opening (FO) and fast closing (FC) stages. During the reduction phase, jaw cycles do not always involve an SO stage and the first reduction cycle never exhibits an SO stage. During transport, the duration of the SO stages is highly variable. During reduction and transport of the prey, the cyclic tongue movements are very similar. Gape opening during cleaning is not divided into two successive stages. We conclude (1) that the capture, reduction and cleaning cycles may be derived from the transport cycle, (2) that the SO stage is determined by tongue displacements in all the phases, (3) that, in the extensive intraoral food processing, related cyclic tongue-jaw displacements are not different, (4) that gape cycles do not always follow the Bramble and Wake model, and (5) that the evolutionary features proposed for Amniota by Reilly and Lauder are present.
Mechanical Work Rate Minimization and Freely Chosen Stride Frequency of Human Walking: A Mathematical Model
Authors: Minetti Alberto E. , Saibene Franco 
Published: April 2021

ABSTRACT
The interplay between the work done to move the body centre of mass with respect to the environment (external work) and the work done to move the limbs with respect to the body (internal work) has been shown experimentally partially to determine the freely chosen stride frequency during walking. A mathematical model that estimates the two components of the mechanical work is proposed. The model, according to the criterion of work rate minimization (both positive and positive plus negative), is able to predict the natural stride frequency as a function of the average progression speed. The adequacy of the model and the validity of the assumptions have been checked against measurements of natural stride frequency in 11 subjects walking on a treadmill at several speeds (range 1–3ms−1). Comparison with theoretical predictions shows good agreement with the minimization of positive work rate at low speeds, while at high speeds the stride frequency is better explained by the model for minimum positive plus negative work rate.
The Kinematics of Prey Capture and the Mechanism of Tongue Protraction in the Green Tree Frog Hyla Cinerea
Authors: Deban Stephen M. , Nishikawa Kiisa C. 
Published: April 2021

ABSTRACT
Prey capture was studied in the green tree frog (Hyla cinerea) before and after denervation of either the m. genioglossus or m. submentalis using high-speed videography and kinematic analysis. The prey capture behavior and extent of tongue protraction of several members of the subfamilies Hylinae, Pelodryadinae and Phyllomedusinae were also studied. Results show that the m. genioglossus is necessary to produce complete tongue protraction and that the m. submentalis is necessary for mandibular bending, but not necessary for complete tongue protraction in Hyla cinerea. The tongue of Hyla cinerea resembles the weakly protrusible tongues of the archaeobatrachian frogs Ascaphus and Discoglossus more than the highly protrusible tongues of other neobatrachians, such as Rana or Bufo. A weakly protrusible tongue is present in the subfamilies Hylinae and Pelodryadinae, and a highly protrusible tongue is present in the subfamily Phyllomedusinae. These results suggest that hyline and pelodryadine hylids have retained the ancestral anuran tongue morphology and that highly protrusible tongues have evolved once within the family Hylidae, in the subfamily Phyllo-medusinae.
Analysis of Repolarization of Presynaptic Motor Terminals in Drosophila Larvae Using Potassium-Channel-Blocking Drugs and Mutations
Authors: Gho Michel , Ganetzky Barry 
Published: April 2021

ABSTRACT
In Drosophila melanogaster muscles and neuronal cell bodies at least four different potassium currents have been identified whose activity shapes the electrical properties of these cells. Potassium currents also control repolarization of presynaptic terminals and, therefore, exert a major effect on transmitter release and synaptic plasticity. However, because of the small size of presynaptic terminals in Drosophila, it has not been possible to analyze the potassium currents they express. As a first approach to characterizing the ionic currents present at presynaptic motor terminals of Drosophila larvae, we recorded synaptic currents at the neuromuscular junction. From the alterations in evoked synaptic currents caused by various drugs and by mutations known to affect potassium currents in other tissues, we suggest that the repolarizing mechanism in presynaptic terminals consists of at least four distinct currents. One is affected by aminopyridines or Sh mutations, a second component is affected by the slo mutation, a third is sensitive to quinidine and one or more additional components are blocked by tetraethyl-ammonium. Depolarization depends on a presynaptic calcium current, which displays only slight voltage-dependent inactivation. Because the mechanism of repolarization exerts a major effect on synaptic activity, this analysis provides a framework for further genetic and molecular dissection of the basic processes involved in the regulation of transmitter release.
Suppression of Common Mode Signals within the Electrosensory System of the Little Skate Raja Erinacea
Authors: Bodznick David , Montgomery John C. , Bradley David J. 
Published: April 2021

ABSTRACT
The electroreceptors of elasmobranchs are strongly modulated by the fish’s own ventilation but this source of potential interference is suppressed within the medulla. The mechanism for the suppression is thought to be based on the common mode nature of the ventilatory noise, i.e. it is of the same amplitude and phase for all of the electroreceptors, compared with environmental electric fields which affect the receptors differentially. Evidence for the common mode suppression hypothesis is provided here in skates by the observation that the response to an artificial common mode stimulus that is independent of ventilation and delivered through an electrode inserted into the animal’s gut is also suppressed by the medullary neurons; the extent to which a particular neuron suppresses the responses to the gut stimulus and to ventilation is similar. In addition, a potential modulation of 5–150 μV is measured between the skate’s interior and the sea water during ventilation and this appears to be responsible for the self-stimulation. By passing d.c. or sinusoidal currents through the gut electrode it is demonstrated that this ventilatory potential is due to the variable shunting of a standing d.c. potential across the fish’s skin by the opening and closing of the mouth and gill slits during ventilation. Osmoregulatory ion-pumping appears to contribute to the production of the d.c. potential.
Mechanoreceptors and Minimal Reflex Activity Determining Claw Laterality in Developing Lobsters
Authors: Govind C. K. , Pearce Joanne 
Published: April 2021

ABSTRACT
Bilateral asymmetry of the paired claws of the lobster Homarus americanus is determined during the fourth and fifth juvenile stages by differential reflex activity; the side with the greater activity becomes the crusher while the contralateral side becomes the cutter. Juvenile lobsters reared during this critical period with a substratum that could not be grasped or with reduced input from predominantly internal mechanoreceptors (proprioceptors) (achieved by cutting the dactyl and its chordotonal organ or by tenotomizing the claw opener or closer muscles) failed to develop a crusher claw and hence remained bilaterally symmetrical: they developed paired cutter claws. Therefore, the proprioceptive component of the reflex activity is implicated in bringing about the initial lateralization of the claw ganglion into a crusher and a cutter side.
Moreover, lobsters with a single claw reared without a substratum developed a crusher on the intact side only if the intact claw was exercised. In the unexercised condition, differences in reflex activity between the side with a claw and the side without one were insufficient for the development of a crusher claw on the intact side. A minimal amount of reflex activity is necessary for the development of a crusher. Lobsters reared with this minimal amount of activity in both claws developed asymmetrical claws rather than paired crusher claws. This means that initial lateralization of the claw ganglion into a crusher side, on a random basis, inhibited the opposite side from also becoming a crusher. This would explain why we failed to produce lobsters with paired crusher claws and why they were seldom found in the wild.
Wind-Evoked Escape Running of the Cricket Gryllus Bimaculatus: II. Neurophysiological Analysis
Authors: Hörner Michael 
Published: April 2021

ABSTRACT
Following the description of some typical variables of escape running in the cricket Gryllus bimaculatus in a companion paper, this study gives an account of the physiological characteristics of identified interganglionic cell types recorded during normal and wind-evoked walking.
Intracellular recording and staining of axons in the prothoracic ganglion revealed a group of intersegmental wind-sensitive neurones with large axons in the laterodorsal tract and somata in the pro-or mesothoracic ganglion. These interneurones rapidly conduct signals to their projections in the thoracic and cephalic ganglia. Wind pulses evoke strong, non-habituating spike reactions, which tend to summate during repeated stimulation. During walking, the sensory response to wind stimulation is suppressed in a velocity-dependent manner in all ascending interneurones tested (N=40). During slow walking, the sensory responsiveness is merely reduced, whereas it is completely blocked during fast escape running bouts. Conversely, during pauses occurring during wind-evoked escape behaviour, the sensory responsiveness in ascending cells is significantly enhanced. One type of interneurone that descends from the suboesophageal ganglion and projects to the thorax and abdominal connectives has been identified. In the resting animal, this neurone fires in the rhythm of abdominal ventilatory contractions. During walking, the rhythmic spike discharges disappear and, as in ascending interneurones, velocity-dependent spike suppression is observed. In contrast to all other types of interneurones, which uniformly showed reduced spike activity during walking, cells descending from the brain were tonically excited during walking. Brain cells (N=21) have been classified according to whether their spike activity during walking was correlated with forward speed or with the intended walking direction. Mechanisms underlying the observed gating of sensory responsiveness are discussed in terms of their possible functional significance. Modulated spike activity in ascending cells during walking suggests a role in tuning the thoracic motor centres for a central walking command. It is proposed that descending interneurones from the suboesophageal ganglion coordinate different behavioural rhythms. Possible functions of different types of brain neurones in the control of specific variables of walking behaviour are discussed.
The Influence of Temperature on Power Output of Scup Red Muscle During Cyclical Length Changes
Authors: Rome Lawrence C. , Swank Douglas 
Published: April 2021

ABSTRACT
To gain insight into how temperature affects locomotory performance, we measured power output of scup red muscle during oscillatory length changes at 10°C and 20°C. When we optimized work loop parameters, we found that maximum power was 27.9 W kg−1 at 20°C and 12.8 W kg−1 at 10°C, giving a Q10 of 2.29. Maximum power was generated at a higher oscillation frequency at 20°C (5 Hz) than at 10°C (2.5 Hz), and the Q10 for power output at a given oscillation frequency ranged from about 1 at 1Hz to about 5 at 7.5 Hz. An analysis of the results in terms of crossbridge kinetics suggests that the higher power output at 20°C is associated with both a higher Vmax (i.e. more power per cycling crossbridge) and faster activation and relaxation (i.e. a greater number of cycling crossbridges).
To obtain a more realistic understanding of the functional importance of temperature effects on muscle, we imposed on isolated muscle in vivo length changes and oscillation frequencies (measured during previous experiments on swimming scup) and the in vivo stimulus duty cycle (measured from electromyograms in this study). At 20°C, muscle bundles tested under these in vivo conditions produced nearly maximal power, suggesting that the muscle works optimally during locomotion and, thus, important contractile parameters have been adjusted to produce maximum mechanical power at the oscillation frequencies and length changes needed during swimming. At 10°C, muscle bundles tested under in vivo conditions produced much less power than was obtained during the ‘optimized’ work loop experiments discussed above. Furthermore, although ‘optimized’ work loop experiments showed that maximum power output occurs at 2.5 Hz, scup do not appear to swim with such a low tailbeat frequency. Although the reason for these apparent discrepancies at 10°C are not known, it shows that simple extrapolation from isolated muscle to the whole animal, without knowledge of how the muscle is actually used in vivo, can be misleading.
Swimming Performance and Haematological Variables in Splenectomized Rainbow Trout, Oncorhynchus Mykiss
Authors: Gallaugher P. , Axelsson M. , Farrell A. P. 
Published: April 2021

ABSTRACT
Haematological variables were measured during aerobic swimming (45–55% of Ucrit) and at critical swimming velocity (Ucrit) in acutely splenectomized and sham-operated rainbow trout. There was no correlation between haematocrit (Hct) and Ucrit in either group of fish. The control values for the haematological variables did not differ significantly between the two groups of fish. Some haematological variables changed during aerobic swimming and at Ucrit, but there were no significant differences between the two groups for any of the variables. Arterial blood oxygen tension was significantly reduced at Ucrit. Arterial blood oxygen content was maintained in sham-operated fish because the Hct increased significantly. However, in the splenectomized animals, decreased (compared to control values) during aerobic swimming and at Ucrit because the Hct did not change. Plasma concentrations of lactate and catecholamines were elevated only at Ucrit. We provide evidence of a graded spleen contraction during aerobic swimming.