bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Temperature on Ryanodine Sensitivity and the Force-Frequency Relationship in the Myocardium of Rainbow Trout
Authors: Hove-Madsen* Leif
Published: April 2021

The relationship between stimulation frequency and contraction was established for ventricular strips from rainbow trout heart at 5,15 and 25°C. Compared to mammalian species, changes in temperature had little impact on force development in trout ventricle at physiologically relevant stimulation frequencies. However, the force-frequency relationship was changed from a biphasic response with a minimum around 0.2 Hz at 5 and 15°C to a monophasic decline in force with increasing frequency at 25°C. Ryanodine reversed the negative force-frequency relationship at 25°C. Potentiation of twitch force after a 5 min rest period was increased from 121 ±4% at 15°C to 209±12% at 25°C. A similar augmentation was seen for the maximal rate of force development. Rest potentiation of both force and maximal rate of force development (dF/dT) was abolished by ryanodine at both 15 and 25°C. The ryanodine concentration causing a half-maximal reduction in rest potentiation of force was 51 nmol l−1 at 25°C and 483 nmol l−1 at 15°C. Rest potentiation was maximally reduced by 10μmoll−1 ryanodine to 50 and 79% of the value in the absence of ryanodine at 25 and 15°C, respectively. At 5°C, rest potentiation was similar to that at 15°C. At 5°C, there was no rest potentiation of dF/dT and ryanodine did not reduce rest potentiation of force. Instead, rest potentiation was correlated with a potentiation of time to peak tension (TPT) at 5°C. Thus, in trout ventricle, force correlates with TPT at 5°C and seems to be regulated by a ryanodine-insensitive mechanism, while at 25°C force is correlated with the maximal rate of force development and the sarcoplasmic reticulum appears to contribute significantly to excitation-contraction coupling.
Degenerative Changes in the Function of Neuromuscular Junctions of Manduca Sexta During Metamorphosis
Authors: Sonea Ioana M. , Rheuben Mary B.
Published: April 2021

In Manduca sexta the decline in neuromuscular function during metamorphic degeneration was compared in two muscles which differed characteristically with regard to pre- and postsynaptic physiological properties. In both muscles, morphological evidence indicated that a significant number of the active zones within the population of neuromuscular junctions on a given fiber were nonfunctional. Nevertheless, the degenerating nerve terminals were able to produce an above-threshold excitatory junction potential (EJP) which was facilitated in a manner characteristic of the muscle being observed. Abnormal findings during the early stages of degeneration included a larger than normal EJP, a decline in EJP amplitude over a 20 min period even with low frequencies of stimulation, an increase in EJP duration, a decline in muscle fiber resting potential amplitude with age, a decrease or disappearance of post-tetanic potentiation and long-term facilitation, and an increased likelihood that the motor nerve would fail to conduct a stimulus. The two muscles were qualitatively similiar but quantitatively different with regard to these degenerative changes. It is suggested that this combination of relatively normal function with abnormal properties might be associated with the withdrawal of glial processes from the neuromuscular junctions, changes in the cable properties associated with shrivelling of the muscle fibers, and a decline in the metabolic functions supporting both muscle fiber resting potentials and those underlying transmitter synthesis, mobilization and release.
The Identification of Motor and Unpaired Median Neurones Innervating the Locust Oviduct
Authors: Kalogianni E. , Pflüger H.-J.
Published: April 2021

The different classes of neurones supplying the locust oviduct were individually identified by intracellular recording and staining. We could thus show that different regions of the oviduct are innervated by different sets of neurones. Three motor neurones (oviductal neurones 1–3, OVN1-3) supply the oviduct via nerve N2B of the seventh abdominal ganglion. Whereas all three motor neurones innervate the junctional area of the lateral and the common oviduct (OVNI, 2 and 3), the lateral oviduct is innervated by only one motor neurone (OVN2) and the common oviduct by two motor neurones (OVNI and 2). The cell bodies of all three motor neurones lie ventrally, near the origin of the sternal root, and their neuropilar branches are confined to the seventh abdominal ganglion. The neuropilar branches of OVNI and 2 extend mainly in the ipsilateral half of the ganglion; those of OVN3 reside exclusively in the contralateral half.

The oviductal motor neurones, produce a phasic motor pattern, the oviductal rhythm, which causes neurogenic contractions of the junctional area and the common oviduct. These contractions serve to retain eggs in the lateral oviduct.

The oviduct is also supplied by a large number (16–20) of median neurones with bilateral axons. All of these appear to innervate the lateral oviduct, but only two project to the junctional area and the common oviduct. The cell bodies of the median neurones are situated in the seventh abdominal ganglion and are arranged in two groups: a posterior group made up of 10–12 cells and an anterior group with 6–8 cells. Their primary neurites run towards the centre of the ganglion in the dorsal plane, where they bifurcate, sending a secondary neurite through each oviductal nerve. Their neuropilar branches are confined to the seventh abdominal ganglion, but some also possess thin axon collaterals projecting to the terminal abdominal ganglion. The anterior and posterior median neurones show considerable differences in their branching pattern within the ganglion. The posterior cells are all likely to be neurones of the well-known DUM cell group, but the anterior median cells probably represent a different class of neurone. Posterior median neurones support overshooting soma action potentials of 60–80 mV amplitude, with a characteristic undershoot of 6–15 mV. Orthodromic stimulation of these neurones results in a reduction of the amplitude and frequency of the oviductal contractions, suggesting that they have a modulatory role.
Cardiac Output and Blood flow Distributiont During Swimming and Voluntary Diving of the Tufted Duck (Aythya Fuligula)
Authors: Bevan R. M. , Butler P. J.
Published: April 2021

Cardiac output and blood flow distribution were continuously measured in the tufted duck when diving voluntarily. Blood flows through pulmonary, ischiadic, carotid and brachiocephalic arteries were recorded using miniature pulsed Doppler flow probes. By measuring these flows, cardiac output and blood flow to the leg muscles and to the flight muscles could be calculated.

Heart rate and were well correlated, making the former a very good indicator of any changes in the latter. Blood flow to the leg muscles increased substantially during both swimming and diving to five times the resting rate. Cardiac output, though, was lower during the later portions of a dive than it was during swimming. A consequence of this lower was that the proportion of supplying the leg muscles was much greater during diving than it was whilst the duck was swimming. This indicates that more extensive peripheral vasoconstriction was occurring during diving. The blood flow to the wing muscles during diving was found to be significantly lower than that at rest but there was no net change in blood flow through the brachiocephalic arteries as the blood flow to the head increased.

Peripheral vasoconstriction must, therefore, have been occurring in other parts of the body during diving, possibly within the vascular beds supplying the gastrointestinal tract, the skin and the respiratory muscles. This study supports the prediction that voluntary diving in tufted ducks is a compromise between the physiological response to involuntary submergence and that to exercise in air, but with the bias towards the latter.
Scaling of Muscle Fibres and Locomotion
Authors: Rome Lawrence C.
Published: April 2021

To reconcile the scaling of the mechanics and energetics of locomotion to recent data on the scaling of the mechanics of muscle fibres, I have extended the theory of Taylor and colleagues that the energetic cost of locomotion is determined by the cost of generating force by the fibres. By assuming (1) that the cost of generating force in a fibre is proportional to Vmax (maximum velocity of shortening) and (2) that, at physiologically equivalent speeds, animals of different body sizes recruit the same fibre types, this extension quantitatively predicts the scaling of the energetics of locomotion, as well as other observations, from the scaling of Vmax of the muscle fibres. First, the energetic cost of locomotion at physiologically equivalent speeds scales with Mb−0 16, where Mb is body mass, as does Vmax of a given fibre type. However, the energetic cost at absolute speeds (cost of transport) scales with Mb−0.30, because small animals must compress their recruitment order into a narrower speed range and, hence, recruit faster muscle fibre types at a given running speed. Thus, it costs more for small animals to move 1kg of their body mass 1 km not only because a given muscle fibre type from a small animal costs more to generate force than from a large one, but also because small animals recruit faster fibre types at a given absolute running speed.

In addition, this analysis provides evidence that Vmax scales similarly to 1/tc (where tc is foot contact time) and muscle shortening velocity (V), in agreement with recent models. Finally, this extension predicts that, at physiologically equivalent speeds, the weight-specific energetic cost per step is independent of body size, as has been found empirically.
Intracellular Recordings From Intact Locusts Flying Under Closed-Loop Visual Conditions
Authors: Hensler Klaus
Published: April 2021

The flight path of locusts is under permanent visual and mechanoreceptive control (the latter evaluates changes in wind direction). Involuntary course deviations are compensated immediately by a neuronal feedback system or ‘autopilot’, which induces corrective steering movements of the wings, abdomen and legs and which are generally accompanied by compensatory head movements (Taylor, 1981; Hensler and Robert, 1990). During apparently straight flight the flight path is not perfectly straight, but instead the insect oscillates slightly along a mean course (Robert, 1988; Hensler and Robert, 1990).
Pollutant-Induced Depression of the Transmembrane Sodium Gradient in Muscles of Mussels
Authors: Børseth Jan Fredrik , Aunaas Tore , Einarson Sigrun , Nordtug Trond , Olsen Anders Johny , Zachariassen Karl Erik
Published: April 2021

This study deals with the effects of chemical pollutants on the transmembrane potential difference for sodium in smooth muscle cells of Mytilus edulis. A method for indirect determination of extracellular space, intracellular ion concentrations and has been developed and is applied in the investigations. The determination is based on concentration data from haemolymph and muscle tissue samples. The precision of the method used was tested by direct measurements of the apparent intracellular concentration of sodium and the membrane potential. On the basis of these tests, the method was evaluated as reasonably good.

The method was used to study the sensitivity of the transmembrane in Mytilus edulis to 96 h exposures to various sublethal concentrations of formaldehyde, methanol and mercury. Both formaldehyde and mercury induced a depression of . The observed depressions could be ascribed to a change in both the electrogenic and the chemical components of . A depression of was associated with subsequent clinical injury and death. Methanol did not cause death or any changes in . Because of the observed correlation between depression of and clinical injury, is suggested to have a potential as an indicator of toxicity.
Flow Visualization Experiments on Tethered Flying Green Lacewings Chrysopa Dasyptera
Authors: Grodnitsky Dmitry L. , Morozov Pahvel P.
Published: April 2021

Experiments on dust visualization of the flow around tethered flying green lacewings showed that, contrary to expectations based on the Weis-Fogh clap-and-fling mechanism, a leading edge separation bubble does not exist near either fore-or hindwings. At the beginning of the stroke cycle each wing operates as an independent generator of vorticity. The vortex bubbles of all the four wings then unite, producing a single U-shaped bubble. A hypothetical spatial structure for the vortex wake is derived from a series of registrated sections of the wake illuminated with a flat light beam. Some problems of wing functional morphology and insect flight aerodynamics are also discussed.
Energy Allocation and Yield and Cost of Growth in Young Esox Lucius and CoregonuS Lavaretus (Teleostei): Influence of Species, Prey Type and Body Size
Authors: Wieser Wolfgang , Laich Andreas , Medgyesy Nikolaus
Published: April 2021

Energy partitioning was studied in the larvae and early juveniles of two species of freshwater fish with different life styles, Coregonus lavaretus and Esox lucius, by measuring simultaneously the rates of feeding, oxygen consumption and growth in long-term experiments. Comparison between the two species is based on measurements at 15°C, but a group of C. lavaretus was also monitored at 10°C.

The intensity of routine oxygen consumption was mass-independent in the smallest larvae, but above about 10 mg wet body mass (m) it scaled with an allometry of m−0.103 in C. lavaretus and m−0.154 in E. lucius. Routine, minimum and maximum rates of metabolism were higher in C. lavaretus than in E. lucius, whereas the mass-specific rate induced by feeding showed a quite different and more complex relationship to species.

The mass-specific rate of growth scaled with m−0.133 (r=0.54) in C. lavaretus but with m−0 24 (r=0.90) in E. lucius.

Comparison of five experimental groups, differing from each other with respect to species, type of prey (Artemia nauplii or Rutilus rutilus larvae), experimental temperature and body size, suggested a general pattern of energy partitioning, with 62±3.7% of metabolizable food energy being allocated to growth, and 38±3.7% to metabolic expenditures.

The relationship between metabolic rate and growth rate, expressed as the ‘yield ratio’, mg dry body mass μmol−1O2, the inverse of the net cost of growth, proved to be nearly invariant in all experimental groups, namely 0.043 mg μmol−1. However, two experiments with the smallest pike larvae led to higher growth rates per metabolic expenditure, suggesting that in E. lucius oxygen consumption may reach an aerobic maximum for growth at a routine rate of about 200–220 μmol O2g−1 dry bodymassh−1.

Gross costs of growth include mass-dependent maintenance expenditures. Expressed in mass-independent units, E. lucius was more efficient in converting food energy into growth than was C. lavaretus’, its superiority in this respect ranged from 7 to 17% depending on body mass and diet.

The results are discussed with regard to the question of whether in small poikilothermie metazoans the allocation of metabolic energy follows the rules of addition or compensation. Furthermore, growth performance of the fish larvae is compared with that of microorganisms on the basis of the ‘yield ATP’ concept.
Multisegmental Analyses of Acoustic Startle in the Flying Cricket (Teleogryllus Oceanicus): Kinematics and Electromyography
Authors: Miles Carol I. , May Michael L. , Holbrook Eric H. , Hoy Ronald R.
Published: April 2021

Tethered, flying Australian field crickets (Teleogryllus oceanicus) stimulated with ultrasound respond with a rapid, short-latency turn from the sound source. We analyzed the kinematics of two behavioral components of this acoustic startle response and recorded electromyograms from the muscles involved in producing them. The two behavior patterns studied were the swing of the metathoracic leg, which has been shown to elicit a short-latency turn, and a lateral swing of the antennae, for which a direct role in steering has not been demonstrated.

The kinematic data showed that when a pulse of ultrasound was presented to one side of the animal (1) the contralateral metathoracic leg abducted and elevated, while the ipsilateral leg remained in place, (2) both antennae swung laterally, but the contralateral antenna moved farther than the ipsilateral antenna, (3) increases in stimulus intensity elicited larger movements of the leg and contralateral antenna, while the ipsilateral antenna showed little sensitivity to stimulus intensity, and (4) for the leg, the latency to the onset of the swing decreased and the duration of the movement increased with increasing stimulus intensity.

Electromyograms were recorded from the leg abductor M126 and two antennal muscles: the medial scapo-pedicellar muscle M6 and the lateral scapo-pedicellar muscle M7. M7 moves the antenna laterally, M6 moves it medially. Upon stimulation with ultrasound (1) both M126 and M7 showed increasing spike activity with increasing intensity of the ultrasound stimulus, (2) M126 showed a decrease in latency to the first spike and an increase in the duration of spike activity with increasing stimulus intensity, (3) latencies for M6 and M7 were not correlated with stimulus intensity, but M7 had significantly shorter latencies than M6 and the contralateral M7 had significantly shorter latencies than the ipsilateral M7, and (4) the ipsilateral M126 spiked in response to ultrasound in 6 of the 10 animals tested. In these cases, however, latency to the first spike was substantially longer, and the spike frequency was lower than for the muscle’s response to contralateral stimuli. We attempt to correlate these electromyogram data with the kinematic data and relate them to the relevance of the two behavior patterns to the execution of an escape response.
Directional Sensitivity and Mechanical Coupling Dynamics of Campaniform Sensilla During Chord-Wise Deformations of the Fly Wing
Authors: Dickinson Michael H.
Published: April 2021

The complex morphology of an insect campaniform sensillum is responsible for transforming strains of the integument into a displacement of the campaniform dome and subsequently a deformation of the dendritic membrane. In this paper, the first step in this coupling process was investigated in identified campaniform sensilla on the wing of the blowfly by stimulating the sensilla with chord-wise deflections of the wing blade. Campaniform sensilla neurones were sensitive to both dorsal and ventral deflections of the wing, and thus exhibited no strong directional sensitivity to the chord-wise components of wing deformation. These results are consistent with a simplified mechanical model in which the wing veins act as cylinders that undergo bending and torsion during chord-wise wing deformation.

By comparing the responses of campaniform neurones to chord-wise deflections of the wing with those evoked by direct punctate stimulation of the dome, it is possible to estimate the dynamic properties of the coupling process that links wing deformation to dome deformation. In the identified campaniform neurone examined, wing-dome coupling attenuates high frequencies and transforms the chord-wise deflections of the wing into dome deformation similar in degree of excitation to that caused by direct punctate indentions that are two or more orders of magnitude smaller in size.
Studies on Adaptation to Salinity in Gammarus Spp
Authors: Beadle L. C. , Cragg J. B.
Published: April 2021

Four species of Gammarus were studied: the fresh-water G. pulex, the brackish water G. duebeni, and two normally marine species G. locusta and obtusatus, the former of which has also been recorded from brackish water. The relation between osmotic pressure and chloride of the blood and of the external medium, after sudden transfer to salinities which could be withstood for at least 24 hr., is shown in Fig. 1. The changes in blood osmotic pressure are due to salt and not to water movements. The marine species G. obtusatus and locusta maintain a very hypertonic blood in dilute sea water and can withstand 50% (270 mM.) and 25 % (135 mM.) sea water respectively. The brackish water G. duebeni has a tolerance range from pure sea water to water containing a trace of salt, but is not as well adapted to fresh water as G. pulex. For a wide salinity tolerance range two mechanisms are necessary, (a) for regulating the blood concentration within certain limits, and (6) for maintaining a low intracellular concentration of certain ions (e.g. Cl) in spite of changes in blood concentration. Defection of the latter mechanism can alone account for the inability of G. pulex to withstand direct transfer to more than about 40 % sea water (115 mM.). On the basis of this work and that of others on other animals the following hypothesis is suggested. Adaptation to fresh water has proceeded by two main stages : (a) Probably by active ion absorption, a high blood concentration is maintained (as in Eriocheir sinensis and Telphusa fluviatile) and is associated with a large blood/tissue Cl gradient. Such animals can still be transferred suddenly to a high concentration of sea water, (b) Evolution of the renal salt-reabsorption mechanism, and. lowering of both blood concentration and blood/tissue Cl gradient to levels more easily maintained (as in G. pulex and most fresh-water animals). The consequent loss of power to maintain a large blood/tissue Cl gradient entails inability to withstand transfer to more than low concentrations of sea water, unless, as in certain species, a special mechanism is evolved for preventing the blood concentration from rising.
The Effect of Testosterone Propionate on the Sex-Life of the Female Rat
Authors: Groome J. R.
Published: April 2021

The action of hormonic substances on the smaller experimental animals is usually assessed by killing the animal and examining its organs shortly after treatment. The present paper deals with a study of the effects of testosterone propionate injections on the subsequent life of the female rat.
The Effects of Castration by Parasites and X-Rays on the Secondary Sex Characters of Prawns (Leander Spp.)
Authors: Callan H. G.
Published: April 2021

Contrary to the assertion of Giard that Leander males when parasitized by Bopyrus undergo sex reversal, Leander xiphias and L. squilla show no modifications of the secondary sex characters, while the testes, although reduced in size, never produce oocytes. This is probably true also of L. serratus. The power of a parasite to induce sex reversal is probably limited by the degree of sex separation of the host species. The species which show sex reversal (“castration parasitaire”) are thus considered to possess a less complete sexseparating mechanism than those, such as Leander, which are not reversed by parasites. Breeding females of Leander develop an incubatory chamber under the abdomen, involving many structural changes. These “breeding characters” are not formed by parasitized females, nor by females castrated by X-rays. It is possible that there is a female sex hormone in Crustacea, but the evidence is not yet conclusive.
Local and General Factors in the Development of “Pattern” in Rhodnius Prolixus (Hemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

Most studies on morphogenesis have been made upon composite structures, such as eyes or appendages, whose form is controlled by the co-operation of a great number of cells. In insects, however, the tiny fragment of cuticle laid down by a single cell may possess morphological characters controlled by the activities of that cell alone. The cuticle of insects provides, therefore, an unusually simple medium for the study of morphogenesis and the nature of those processes which “determine” the activity of a given cell.
The Determination of Characters at Metamorphosis in Rhodnius Prolixus (Hemiptera)
Authors: Wigglesworth V. B.
Published: April 2021

Two factors have been recognized as regulating moulting and metamorphosis in Rhodnius prolixus: a “moulting hormone” and a so-called “inhibitory hormone” (Wigglesworth, 1934, 1936).
A Change in the Chromatophore Pattern of Crustacea at Sexual Maturity
Authors: Knowles F. G. W. , Callan H. G.
Published: April 2021

White chromatophores appear on the egg-bearing segments of female prawns and shrimps at sexual maturity. Such chromatophores do not appear in the females whose gonads have been destroyed by X-rays or by parasites. It is probable that this appearance of white chromatophores at sexual maturity is correlated with the metabolic changes occurring at yolk deposition in the ovaries.
The Protoplasmic Viscosity of Paramecium
Authors: Brown R. H. J.
Published: April 2021

Since Heilbrunn’s work in 1926 most workers have agreed that the viscosity of protoplasm is low; all the recent observations, with one exception, have given figures which are not markedly different from each other. The exception, the work of Fetter (1926) on Paramecium, gives a viscosity value which is much higher than that found in other material. The present paper constitutes a re-examination of the viscosity values given by Fetter.
The Toxicity of the Double Chlorides of Mercury and Sodium
Authors: Jones J. R. Erichsen
Published: April 2021

Mercuric chloride, one of the most toxic of inorganic substances, does not ionize in aqueous solution, but in the presence of sodium chloride forms the double chlorides NaHgCl3 and Na2HgCl4 which ionize readily. It has been variously claimed that the ionization of mercuric chloride, thus effected, is accompanied by an increase of toxicity, by a decrease of toxicity, or that the toxicity of the solution remains unaltered. In an investigation of the toxicity of mixed solutions of HgCl2 and NaCl to the minnow, Phoxinus phoxinus (L.), it is found that the addition, to HgCl2 solutions, of sufficient NaCl to convert the whole of the HgCl2 into the double chloride Na2HgCl4, and even ten times this quantity of NaCl effects no marked change in the toxicity of the solution. On the addition of a considerable excess of NaCl a marked prolongation of the survival time occurs, the maximum antagonistic effect being evident when the solution is approximately isotonic. Almost exactly the same result is obtained if the NaCl is replaced by quantities of glucose sufficient to effect equal changes in the osmotic pressure of the solutions, and thus the antagonistic action of the sodium chloride appears to be due to the physical, rather than the chemical, changes its addition brings about in the nature of the toxic solution.
Physiological Effects of a Hypotonic Environment
Authors: Wells G. P. , Ledingham Isabel C. , Gregory Mary
Published: April 2021

If polychaete rhythmic muscles are suspended in sea water, which is then suddenly replaced by dilute sea water, they typically respond to the change by showing, first excitation, then inhibition, then accommodation to the new fluid (Wells & Ledingham, 1940a). Shock effects, followed by accommodation, have also been shown to follow sudden salinity change in marine amoebae (Pantin, 1924) and in the hearts of Limulus, Carcinus and a tortoise (Carlson, 1905; Girault, 1935). The experiments here described were undertaken primarily in order to find out whether similar phenomena occur in cilia. The action of hypotonic fluids on the lamellibranch gill has been described by Fredericq (1922) and by Tomita (1934), but neither author paid any attention to the behaviour of the cilia immediately after salinity change.
The Physiological Action of Abnormally High Temperatures on Poikilotherm Animals1
Authors: Fraenkel G. S. , Herford G. V. B.
Published: April 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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.