bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural Evidence for Gabaergic Input onto Cercal Afferents in the Locust (Locusta Migratoria)
Authors: Watson A. H.
Published: April 2021

Ultrastructural studies have revealed input synapses on the central terminals of many sensory afferent neurones in both vertebrates (Maxwell et al. 1982; Ralston et al. 1984) and invertebrates (Altman et al. 1980; Watson and Pflüger, 1984). Indeed presynaptic modulation of sensory information flowing into the central nervous system appears to be a very widespread phenomenon. It may take the form of either inhibition (Eccles, 1964) or facilitation (Klein and Kandel, 1980), but it is the former that is most widely known from physiological experiments. Several mechanisms can bring about presynaptic inhibition. (1) Depolarization of an afferent terminal may reduce the amplitude of the action potential, leading to a reduction of the calcium influx and, consequently, of transmitter release (Miledi and Slater, 1966; Blagbum and Sattelle, 1987). (2) A conductance increase in the terminal may reduce the height of an action potential regardless of the direction of the potential change (Baxter and Bittner, 1981; Hue and Callec, 1983) and block spike conduction through small-diameter axonal branches (Atwood, 1976). The most widely suggested mechanism for this in both vertebrates (Nicholl and Alger, 1979) and invertebrates (Kennedy et al. 1980) is an increase in chloride conductance mediated by GABA. (3) The presynaptic calcium current may be reduced by the direct action of a neurotransmitter (Shapiro et al. 1980).
Dactyl Sensory Influences on Rock Lobster Locomotion: I. Intrasegmental and Intersegmental leg Reflexes During Standing and Walking
Authors: Müller U. W. E. , Clarac François
Published: April 2021

Recordings of activity of the rock lobster dactyl sensory nerve during walking on a driven belt showed that the receptors of this nerve were mainly active during the power stroke when the leg was loaded. This nerve contains in particular the afferent fibres of the funnel canal organ (FCO) which are bimodal sensillae located in the cuticle of the dactylopodite of crustacean walking legs. In the standing animal, brief electrical stimulation of the dactyl nerve had an influence on the proximal leg muscles of the stimulated leg. The promotor and levator muscles were excited and the remotor and depressor muscles were inhibited. The opposite reaction was observed in adjacent ipsilateral legs in response to stimulation of a middle leg: the promotor and levator were inhibited and the remotor and depressor excited. The resulting movement by the stimulated leg was stereotyped and always consisted of a lift-off from the substratum and a slight shift in the forward direction. The response in the adjacent legs was not powerful enough to elicit a movement. In the walking animal the response of a single leg was dependent on the phase at which a stimulus arrived during the step cycle: during a power stroke (PS) this cycle was interrupted and a return stroke (RS) was initiated and continued. A stimulation at the normal switch from PS to RS had little effect, whereas a stimulation at late RS very often delayed the start of the following PS. Opposite reactions were given by the adjacent unstimulated legs: an RS was interrupted and a PS initiated or prolonged by the stimulus. A comparison between ipsilateral walking legs showed the existence of some obvious differences: legs 4 and 5 were able to reset the walking pattern of all the legs, whereas the more anterior leg 3 returned to its old trajectory after stimulation and thus had no influence on the other legs.
A directionally selective motion-detecting neurone in the brain of the locust: physiological and morphological characterization
Authors: Rind F. Claire
Published: April 2021

The anatomy and physiology of a directionally selective motion-detecting (DSMD) neurone in the locust are described. The neurone was descending, with the cell body in the protocerebrum. The axon lay in the dorsolateral quadrant of the nerve cord and has been traced as far as the metathoracic ganglion. It arborized, ipsilateral to the cell body, from the dorsal intermediate tract (DIT) in the suboesophageal and thoracic ganglia. The neurone was binocular and sensitive to motion in the horizontal plane. It had a preferred direction backwards over the ipsilateral eye and forwards over the contralateral eye. Motion in the opposite direction suppressed the discharge, which had a frequency of 5–20 spikes s−1 at resting membrane potential. The neurone showed a clear directional response to stimuli with temporal frequencies between 0.7 and 44Hz, with a peak response at 11–22 Hz. It responded with spikes to light ON and light OFF. The neurone responded directionally to spatial frequencies of 0.28 cycles degree−1 (3.7° stripe period) to above 0.025 cycles degree−1 (40° stripe period). The maximum response was at around 0.035 cycles degree-1 (29° stripe period). No evidence of adaptation was seen in the responses of the neurone to real or apparent continuous horizontal motion in either the preferred or the null direction.
Production of thiosulphate during sulphide oxidation by mitochondria of the symbiont-containing bivalve Solemya reidi
Authors: O’Brien John , Vetter Russell D.
Published: April 2021

Isolated mitochondria of the bivalve Solemya reidi Bernard oxidize sulphide and couple this oxidation to ADP phosphorylation. The products of mitochondrial sulphide oxidation were analyzed by HPLC using monobromobimane derivatization. Concurrent measurements of respiration were made using sulphideinsensitive oxygen electrodes. 5. reidi mitochondria oxidized sulphide exclusively to thiosulphate. The reaction occurred in two steps. One sulphide molecule was first oxidized to sulphite. A second molecule of sulphide was then added oxidatively to form the free product thiosulphate. This oxidation was obligately linked to mitochondrial electron transport and could be inhibited by the cytochrome c oxidase inhibitor hydrogen cyanide, or by low oxygen concentration. The site II inhibitor antimycin A did not inhibit thiosulphate production, indicating that sulphide oxidation is linked through only one ATP coupling site (site III). A calculation of the respiratory potential for ATP synthesis by fully intact mitochondria indicated that 2.0–3.25 ATP per sulphide may be synthesized using the proton potential generated by sulphide oxidation. This estimate far exceeds the published phosphorylation ratios for S. reidi (0.5–1.2 ATP per sulphide). This difference may be accounted for by partial uncoupling of phosphorylation from sulphide-based respiration. This hypothesis is supported by the observation that the respiratory control ratio of mitochondria respiring on sulphide is 41 % lower than that of mitochondria respiring on succinate. The respiratory control ratio is an index of the tightness of coupling of respiration to ADP phosphorylation. When the adenylate pool of a eukaryotic cell is mostly phosphorylated, respiration is very slow, owing to the maintenance of a high mitochondrial membrane potential. Uncoupling of oxidative phosphorylation from respiration would be an adaptive advantage to the animal in that it allows for continuous, rapid removal of the toxic molecule hydrogen sulphide.
Leucine uptake in brush-border membrane vesicles from the midgut of a lepidopteran larva, Philosamia cynthia
Authors: Sacchi V. Franca , Giordana Barbara , Campanini Flavia , Bonfanti Patrizia , Hanozet Giorgio M.
Published: April 2021

A potassium- or sodium-activated cotransport of leucine occurs in brush-border membrane vesicles prepared from the midgut of larvae of Philosamia cynthia (Drury). The potassium chemical gradient can drive a twofold accumulation of leucine, which is greatly increased under experimental conditions that presumably provide an electrical potential difference (Δ ψ).

Kinetic parameters show that leucine transport is improved by these conditions and by a pH gradient similar to that occurring in vivo. However, these gradients cannot drive an intravesicular accumulation of leucine in the absence of potassium. The potassium-dependence of leucine uptake shows that 20% of the transport is potassium-independent and that K50 and Vmax are 30.3±3.2mmol l−l and 2584±148 pmol 7 s−1 mg−1 protein, respectively. The potassium-independent component of leucine transport is also carrier-mediated and some evidence is reported suggesting that the same carrier can cross the membrane as binary (carrier and leucine) or ternary (carrier, leucine and potassium) complexes, each having a different mobility.
Identification of directionally selective motion-detecting neurones in the locust lobula and their synaptic connections with an identified descending neurone
Authors: Rind F. Claire
Published: April 2021

The anatomy and physiology of two directionally selective motion-detecting neurones in the locust are described. Both neurones had dendrites in the lobula, and projected to the ipsilateral protocerebrum. Their cell bodies were located on the posterio-dorsal junction of the optic lobe with the protocerebrum. The neurones were sensitive to horizontal motion of a visual stimulus. One neurone, LDSMD(F), had a preferred direction forwards over the ipsilateral eye, and a null direction backwards. The other neurone, LDSMD(B), had a preferred direction backwards over the ipsilateral eye.

Motion in the preferred direction caused EPSPs and spikes in the LDSMD neurones. Motion in the null direction resulted in IPSPs. Both excitatory and inhibitory inputs were derived from the ipsilateral eye. The DSMD neurones responded to velocities of movement up to and beyond 270°s−1. The response of both LDSMD neurones showed no evidence of adaptation during maintained apparent or real movement. There was a delay of 60–80 ms between a single step of apparent movement, in either the preferred or the null direction, and the start of the response. There was a monosynaptic, excitatory connection between the LDSMD(B) neurone and the protocerebral, descending DSMD neurone (PDDSMD) identified in the preceding paper (Rind, 1990). At resting membrane potential, a single presynaptic spike did not give rise to a spike in the postsynaptic neurone.
Analysis of calcium channel properties in cultured leech retzius cells by internal perfusion, voltage-clamp and single-channel recording
Authors: Bookman RJ , Liu Y
Published: April 2021

The properties of voltage-dependent calcium channels have been measured in Retzius cells isolated from the central nervous system of the leech and maintained in tissue culture. Macroscopic divalent cation currents were isolated after blocking Na+ and K+ currents by bathing the cells with Na+-free solutions containing TEA+ and 4-AP, and internally perfusing them with Cs+ and TEA+. Depolarizing voltageclamp pulses activated inward currents that were larger for Sr2+ than for Ba2+ or Ca2+. The peak currents were observed at +15 mV for Ca2+ and Ba2+ and at +7 mV for Sr2+. Divalent cation currents were blocked by Cd2+ and Mn2+ but not by dihydropyridine blockers. The activation kinetics of Ba2+ currents was sigmoid. The inactivation was approximately 10% at the end of a 50ms depolarizing pulse. Decay of Sr2+ and Ca2+ currents was larger and showed two kinetic phases. Activation and inactivation of the calcium channels were not significantly influenced by the holding potential. Deactivation kinetics observed during tail currents consisted of two exponential components. At a closing voltage of −60 mV, the time constant was ≈200 ps for the fast component and 1.9 ms for the slow component. Both time constants of deactivation were voltage-dependent over the range from −80 to −20 mV, and increased at more depolarized closing voltages. Single-channel activity was recorded with cell-attached patches in solution containing 75 mmol l−1 Ba2+. Taken together, the results define the characteristics of a distinctive type of calcium channel in isolated Retzius cells.
Enhanced maximum frequency and force development of fish hearts following temperature acclimation
Authors: Bailey John R. , Driedzic William R.
Published: April 2021

Inotropic and chronotropic responsiveness of yellow perch (Perca flavescens Mitchill) and smallmouth bass (Micropterus dolomieui Lacépède) hearts, following low temperature acclimation, was assessed with ventricle strips mounted for isometric force recording. Animals were acclimated to 20° and 5°C, and the performance of ventricle strips from both acclimation temperatures was monitored at 20° and 5 °C.

Ventricle strips from yellow perch acclimated to 20 °C showed an increase in resting tension when tested at 5 °C in the presence of high levels of extracellular calcium. An increase in resting tension did not occur in preparations from 5°C-acclimated fish tested at 5 °C. This suggests failure of intracellular calcium regulation which may be ameliorated following an acclimation period.

Ventricle strips were subjected to a force-frequency challenge over the range of 12–48 contractions min−1 at 1 mmol l−1 and 3 mmol l−1 extracellular calcium. Time to 50 % relaxation of ventricle strips tested at 5 °C was significantly lower for hearts from perch acclimated at 5 °C than from those acclimated at 20 °C. This was associated with an ability to maintain function at higher pacing rates. Similar trends were exhibited by hearts from smallmouth bass. As calcium extrusion is a prime determinant of relaxation time, these findings further suggest an enhancement in calcium handling capabilities following acclimation to low temperature.

Ventricle strips from both species acclimated to 20 °C and tested at 20 °C were able to maintain force development to the highest contraction frequencies. Hearts from specimens acclimated to 5 °C and tested at 20 °C showed a negative force–frequency relationship at low extracellular calcium levels. In yellow perch, this effect was minimized by an increase in calcium availability. This is considered to be a potential mechanism by which animals acclimated to low temperature could make transient excursions into warm water.
What causes edge fixation in walking flies?
Authors: Osorio D. , Srinivasan M. V. , Pinter R. B.
Published: April 2021

The orientation of freely walking flies (female Lucilia cuprina) to lines and stripes in a circular arena is described. The following observations were made.

The flies walked straight towards a dark line using the frontal eye region, but a pale line on a dark background was only weakly attractive. In bright conditions flies walked in a curved line towards a black-white edge, the path being convex towards the dark side of the border. The curves indicated that the flies were heading for a point about 5–10° to the dark side of the edge. In dim conditions the edge of a dark region was not especially attractive and flies headed towards any point in the dark area.

These observations can be accounted for by assuming that the fly walks towards the darkest region in its visual field (scototaxis). In bright conditions the edges of a dark region become more attractive than its centre. This change could be explained if lateral inhibition creates a ‘Mach-band’ effect, making the edges appear darker than the centre. Thus, fixation behaviour in walking Lucilia females seems to be a simple taxis.
Energetics of ascent: insects on inclines
Authors: Full R. J. , Tullis A.
Published: April 2021

Small animals use more metabolic energy per unit mass than large animals to run on a level surface. If the cost to lift one gram of mass one vertical meter is constant, small animals should require proportionally smaller increases in metabolic cost to run uphill. To test this hypothesis on very small animals possessing an exceptional capacity for ascending steep gradients, we measured the metabolic cost of locomotion in the cockroach, Periplaneta americana, running at angles of 0, 45 and 90° to the horizontal. Resting oxygen consumption was not affected by incline angle. Steady-state oxygen consumption increased linearly with speed at all angles of ascent. The minimum cost of locomotion (the slope of the versus speed function) increased with increasing angle of ascent. The minimum cost of locomotion on 45 and 90° inclines was two and three times greater, respectively, than the cost during horizontal running. The cockroach’s metabolic cost of ascent greatly exceeds that predicted from the hypothesis of a constant efficiency for vertical work. Variations in stride frequency and contact time cannot account for the high metabolic cost, because they were independent of incline angle. An increase in the metabolic cost or amount of force production may best explain the increase in metabolic cost. Small animals, such as P. americana, can easily scale vertical surfaces, but the energetic cost is considerable.
FMRFamide-like peptides in the locust: distribution, partial characterization and bioactivity
Authors: Robb S. , Evans P. D.
Published: April 2021

The quantitative distribution of FMRFamide-like peptides in the nervous system and in their putative target sites in the locust Schistocerca gregaria is described using radioimmunoassay techniques. The nature of the immunoreactive material has been characterized by high-pressure liquid chromatography. At least six peaks of FMRFamide-like immunoreactivity can be separated in extracts of locust nervous tissue. The relative proportions of these peaks vary from tissue to tissue, suggesting a differential expression of FMRFamide-like peptides in different parts of the locust nervous system. The bioactivity of the endogenous FMRFamide-like peptides has been assessed on the extensor tibiae neuromuscular preparation and on the locust heart. The results suggest that FMRFamide-like peptides in the locust function both as circulating neurohormones and as locally released neuromodulators or neurotransmitters.
Arrhythmic breathing, apnea and non-steady-state oxygen uptake in hibernating little brown bats (Myotis Lucifugus)
Authors: Thomas Donald W. , Cloutier Danielle , Gagné Daniel
Published: April 2021

We measured the breathing pattern and oxygen consumption of hibernating little brown bats (Myotis lucifugus) in open-and closed-circuit metabolic chambers. At 5 °C, hibernating M. lucifugus showed bouts of ventilation lasting on average 1.24 min and separated by periods of apnea lasting on average 47.59 min. The bats consumed 0.014 ml O2g−1 during ventilation bouts and 0.002 ml g−1 during apnea. The total O2 uptake was 0.016 ml g−1 for a complete ventilationapnea cycle, giving a of 0.020 ml g−1 h−1. This value is considerably lower than most values previously published for Myotis spp. and we suggest that studies using open-circuit systems that did not account for the intermittent nature of gas exchange during hibernation may be in error. Based on the dimensions of the respiratory tract, we estimate that 0.026 ml O2 g−1 h−1 and 0.009ml CO2g−1 h−1 could diffuse down the tract if the glottis was open. The low O2 uptake during apnea indicates that the glottis was closed. If CO2 retention acts to depress metabolism in hibernators, a closed glottis and arrhythmic breathing may be adaptive strategies in hibernation.
The influence of salinity acclimation on the temperature sensitivity of oxygen binding to the haemocyanin of the prosobranch Neptunea Antiqua
Authors: Brix O. L. E. , Condó Saverio G. , Colosimo Alfredo , Giardina Bruno
Published: April 2021

The thermal sensitivity of oxygen binding has been studied at 10, 15, 20 and 25 °C in whole blood from specimens of Neptunea antiqua acclimated to ambient salinities of 24 and 35 ‰. The O2 affinity is strongly pH-dependent, demonstrating a large reversed Bohr shift below pH 8.0. The magnitude of the Bohr shift is not significantly influenced by temperature or ionic concentration. At 35 ‰, the blood O2-affinity is strongly influenced by temperature (ΔHapp≈ −58.6 kJ mol−1), while at 24 ‰ there is almost no temperature sensitivity (ΔHapp<−18.8 kJ mol−1).
Aerodynamics of gliding flight in a harris’ hawk, Parabuteo Unicinctus
Authors: Tucker Vance A. , Heine Carlton
Published: April 2021

A Harris’ hawk with a mass of 0.702 kg and a maximum wing span of 1.02 m glided freely in a wind tunnel at air speeds between 6.1 and 16.2 ms−1. The glide angle varied from 8.5° at the slowest speed to a minimum of 5° at speeds between 8.0 and 14.7 ms−1. The maximum ratio of lift to drag was 10.9 and the minimum sinking speed was 0.81 ms−1. Wing span decreased when either air speed or glide angle increased. Wing area was a parabolic function of wing span. Lift and profile drag coefficients of the wings fell in a polar area similar to that for a laggar falcon (Falco jugger) and a black vulture (Coragyps atratus). A single polar curve relating lift coefficients to minimum profile drag coefficients can predict the maximum gliding performance of all three birds when used with a mathematical model for gliding flight. The parasite drag values that have been used with the model are probably too high. Thus, the profile drag coefficients determined from the polar curve mentioned above are too low, and the predicted wing spans for gliding at maximum performance are too large. The predicted curve for maximum gliding performance is relatively unaffected. The maximum lift coefficient for the Harris’ hawk in the wind tunnel was 1.6. This value is probably less than the maximum attainable, since the hawk’s wings never appeared to stall. The best estimate of the minimum profile drag coefficient is 0.026 at a lift coefficient of 0.60.
Maximum Load-Lifting and Induced Power Output of Harris’ Hawks are General Functions of Flight Muscle Mass
Authors: Marden James H.
Published: April 2021

Pennycuick et al. (1989) recently reported results of an experiment in which climbing rate and load-lifting ability were measured for two trained Harris’ hawks (Parabuteo unicinctus Audubon) flying with various amounts of experimentally applied loads. These data were used to estimate climbing power, maximum aerodynamic power output, and performance consequences of loads in the form of radiotracking equipment.
Effects of Intranasal Application of the Local Anaesthetic Xylocaine on Vestibulo-, Opto-Collic and Postural Reflexes of the Head, and on Tonic Immobility in Homing Pigeons: Implications for Experiments on Pigeon Homing
Authors: Dornfeldt K. , Bilo D.
Published: April 2021

Spraying lidocaine (Xylocaine), a local anaesthetic, into the nasal cavity of homing pigeons is a technique widely used to study the role of olfaction in pigeon homing. Studies in the laboratory revealed that Xylocaine suppressed vestibular and optokinetic nystagmus, roughly for as long as it suppressed olfaction, interfered with control of the head posture when the body was tilted in the sagittal plane, and prolonged tonic immobility. Amplitude and duration of both optokinetic and vestibular nystagmus were affected to the same extent. The effects are most probably caused by the drug’s rapid absorption via the mucous membranes in the nasal cavity and its transport in the blood to brain structures involved in integrating vestibular and visual inputs. The results provide room for nonolfactory explanations of the manifold effects on pigeon homing following administration of local anaesthetics to the nasal chambers.
Proprioception In Insects
Authors: Pringle J. W. S.
Published: April 2021

The campaniform sensilla on the legs of Periplaneta are similar in action to those on the palps, and respond to strains in the cuticle. They are arranged in groups at the joints, with parallel orientation of the sensilla of a group. Tests with various chemical substances show a complete absence of sensitivity to olfactory stimuli. A theory is given of the mode of action of the sensilla in terms of a mechanical model based on their observed structure. Each group of parallel sensilla should act as a unit, responding to those forces which have a compression component of shear in the direction of their long diameters. This theory makes it possible to predict the behaviour of the sensilla from their anatomical arrangement. Most if not all the groups on the legs are so arranged as to be sensitive to the forces present when the insect is standing on the ground. The sensilla probably provide the basis for the sense of contact pressure postulated by Holst (1935), Hoffmann (1933), Crozier & Stier (1928-9), Fraenkel (1932) and others. Comparison of this proprioceptive mechanism with that of the vertebrate limb reveals an absence of qualitative sensitivity that may have an important bearing on the question of the evolution of behaviour.
The Physiology Of Contractile Vacuoles
Authors: Kitching J. A.
Published: April 2021

The rate of output of fluid from the contractile vacuoles of fresh-water peritrich ciliates was reduced in solutions of sulphide of concentration not less than M/1000. This effect was reversible. Cyanide depressed the rate of vacuolar output in a concentration of M/100,000, but was more effective in higher concentrations (M/1000). In cyanide solutions there was (a) either a severe initial check or a temporary stoppage of the vacuole, and then later (b) a partial recovery of the rate of output to a value which was still much below the normal. During the initial check the body swelled. Return of the organism from cyanide solution to tap water was followed by a sharp increase in the rate of vacuolar output to an abnormally high value. The body then shrank gradually to its normal size, and the rate of output also fell slowly to normal. The swelling of the body which followed treatment of the organism with cyanide could be exactly counteracted by the addition of sucrose to the outside medium in a 0·05 M concentration. It is concluded that the normal difference of osmotic pressure across the body surface is equivalent to that of a 0·05 M sucrose solution, and that this difference is maintained by the contractile vacuole. The permeability of the body surface to water is estimated as 0·125–0·25 ubic miera per square micron per atmosphere per minute.
Experimental Studies On The Sexual Cycle Of The South African Clawed Toad (Xenopus Laevis). III
Authors: Bellerby C. W. , Hogben Lancelot
Published: April 2021

Removal of the whole pituitary gland of Xenopus laevis or of the anterior lobe alone is accompanied by (a) reduced food intake, (b) diminished growth of the body as a whole, (c) retrogression of the gonads in both sexes. Since there is no significant reduction in the main fat reserves of the body (corpora adiposa) the retrogression of the gonads is not the direct result of reduced food intake at an all-round lower metabolic level. Since the reduction of food intake is proportionately much greater in females than in males, the metabolic demands of the gonad seems to be the controlling agency of food intake. The relatively greater reduction of growth rate in females is due to the large bulk of the ovaries coupled with the fact that ovarian retrogression accompanies the lowering of growth in the rest of the body. Since the food demand of the active ovary is far in excess of the minimum requisite for body growth, the results of this enquiry provide additional confirmation for the view that seasonal variations of food supply are mainly responsible for seasonal variations in the condition of the ovaries of Xenopus in its natural habitat.
The Biophysics of the Egg Surface of Echinus Esculentus During Fertilization and Cytolysis
Authors: Rothschild Lord
Published: April 2021

When an egg is fertilized, well-defined morphological changes occur. In spite of this, physico-chemical differences between fertilized and unfertilized eggs have been difficult to find. Nor have the increases in permeability and metabolic rate found in certain eggs been shown to be of general incidence. Investigations of the electrical properties of eggs are few, and the results have been inconclusive and contradictory.
The Morphogenetic Function of A Vestigial Organ in the Chick
Authors: Waddington C. H.
Published: April 2021

The pronephros opposite any given somite in the chick is probably determined just before the early neural plate stage at that level, and thereafter develops independently of the somite or lateral plate mesoderm. The Wolffian duct, which is first formed by the union of the pronephric tubules, grows backwards by the multiplication of its own cells. If this elongation is checked by a transverse cut made posterior to the end of the duct, the duct does not appear behind the cut. In the absence of the Wolffian duct, the mesonephros is not properly developed, appearing only as very small patches of tissue with no lumen. The Wolffian duct may therefore be said to induce the mesonephros, which, however, has a feeble power of self-differentiation as a double assurance. This provides a confirmation of previous suggestions that an organ which is vestigial in the sense that it has lost its physiological function may be retained in ontogeny because it still fulfils the morphogenetic function of providing a stimulus essential for the development of other, physiologically more important, structures.
Sex Hormones and Their Effect Upon Conditioned Responses in the Rudd (Leuciscus Leuciscus)
Authors: Vanderplank F. L.
Published: April 2021

Since the effects of the sex hormones on the fish do not show any sex differences, the results of the experiments on both males and females can be summarized together.

Oestrone inhibited an artificially produced conditioned response. Prolan and progesterone had no effect upon the functioning of the conditioned response, although several or prolonged injections of prolan are likely to cause inhibition due to natural causes, e.g. maturation of ova in oviducts. Progesterone, although foreign to the Pisces, terminates the inhibition brought about by previous injections of oestrone. Death caused by injection of progesterone can be prevented by injection of oestrone.
A Portable Apparatus for the Determination of Oxygen Dissolved in A Small Volume of Water
Authors: Fox H. Munro , Wingfield C. A.
Published: April 2021

In 1888 Winkler published his well-known method for the determination of oxygen dissolved in water. The principle of the method is as follows. A solution of manganous chloride is added to the water to be analysed, followed by a solution of sodium hydroxide containing potassium iodide. A precipitate of manganous hydroxide is first formed thus:
Anterior Pituitary and Growth in the Axolotl (Amblystoma Tigrinum(Green) Neotenic Form)
Authors: Howes N. H.
Published: April 2021

A method is described by which the food intake of axolotls during a given period can be compared with their growth during the same period. The method has been applied to animals injected with growth-promoting hormone. The ratio has been calculated for batches of ten axolotls injected with muscle extract, Schockaert’s extract of anterior pituitary, phyone, prolactin (Bates & Riddle, 1935), prolactin plus phyone. This ratio was 2·66 ± 0·20 for animals injected with muscle extract, 1·47 ± 0·12 for Schockaert’s extract, 1·60 ± 0·11 for phyone, 2·21 ± 0·16 for prolactin and 1·68 ± 0·12 for prolactin and phyone together. The effect is attributed to increased nitrogen anabolism.
Studies in Animal Locomotion
Authors: Gray J. , Lissmann H. W.
Published: April 2021

The kinetics of locomotion in the earthworm and the nature of the factors which control the various phases of the ambulatory cycle have been subjects of extensive investigation. Numerous theories have been advanced, but a general survey of the literature suggests that the time has not yet been reached at which the more outstanding observations can be fitted into a relatively precise picture. The observations recorded in this paper are, however, relevant for this purpose.
Anterior Pituitary and Growth in the Axolotl (Amblystoma Tigrinum (Green) Neotenic Form)
Authors: Clements D. I. , Howes N. H.
Published: April 2021

The effects of injection of (a) Schockaert’s extract of anterior pituitary, (b) Van Dyke & Wallen-Lawrence’s phyone and (c) prolactin, upon the growth of larval neotenic Amblystoma tigrinum, have been investigated. The normal growthrate was established before injections were begun and controls were injected with muscle extract. The dosage adopted in all cases was equivalent to 1 mg. of fresh tissue per gram of axolotl per day. This was probably supramaximal. Schockaert’s extract and phyone caused a marked increase in the rate of growth, prolactin a slight increase. Of the ten animals injected with Schockaert’s extract, all except one showed some of the signs usually associated with metamorphosis in A. tigrinum. The other experimental animals did not. In no case were there any abnormal changes in the bodily proportions or in the shape of the skeleton. The growth of half the animals after injections had been stopped was also investigated. In the case of most of the animals injected with Schockaert’s extract or with phyone, there was a loss of weight, followed by recovery and growth in the case of the latter only. The prolactin-injected animals showed no such reaction.
Linear and Nonlinear Encoding Properties of an Identified Mechanoreceptor on the Fly Wing Measured with Mechanical Noise Stimuli
Authors: Dickinson Michael H.
Published: April 2021

The wing blades of most flies contain a small set of distal campaniform sensilla, mechanoreceptors that respond to deformations of the cuticle. This paper describes a method of analysis based upon mechanical noise stimuli which is used to quantify the encoding properties of one of these sensilla (the d-HCV cell) on the wing of the blowfly Calliphora vomitoria (L.). The neurone is modelled as two components, a linear filter that accounts for the frequency response and phase characteristics of the cell, followed by a static nonlinearity that limits the spike discharge to a narrow portion of the stimulus cycle. The model is successful in predicting the response of campaniform neurones to arbitrary stimuli, and provides a convenient method for quantifying the encoding properties of the sensilla.

The d-HCV neurone is only broadly frequency tuned, but its maximal response near 150 Hz corresponds to the wingbeat frequency of Calliphora. In the range of frequencies likely to be encountered during flight, the d-HCV neurone fires a single phase-locked action potential for each stimulus cycle. The phase lag of the cell decreases linearly with increasing frequency such that the absolute delay between stimulus and response remains nearly constant. Thus, during flight the neurone is capable of firing one precisely timed action potential during each wingbeat, and might be used to modulate motor activity that requires afferent input on a cycle-by-cycle basis.
Comparison of Encoding Properties of Campaniform Sensilla on the Fly Wing
Authors: Dickinson Michael H.
Published: April 2021

The wing blade of the blowfly Calliphora vomitoria (L.) carries an array of campaniform sensilla which have previously been divided into slowly and rapidly adapting classes based on their responses to step indentations. In the present study, the physiological characteristics of six sensilla of these two classes are examined within a 20–400 Hz frequency range, using a noise analysis that quantifies linear and nonlinear encoding properties. Both classes exhibit a broad response maximum near 150 Hz, corresponding to the typical wingbeat frequency of the blowfly, and display rectification, limiting the spike response to a narrow portion of a stimulus cycle. The similarity in the encoding properties between the two groups is largely a consequence of the high wingbeat frequency of flies, which precludes any individual neurone from acting as a magnitude detector. Instead, during flight the campaniform neurones might act as ‘one-shot’ detectors, firing a single action potential at a precise phase of each wing stroke cycle. An array of such detectors would be capable of monitoring the passage of a deformational wave as it travels along the wing during each wingbeat.
The ventilatory movements of the avian pelvis and tail: function of the muscles of the tail region of the pigeon (Columba livia)
Authors: Baumel J. J. , Wilson J. A. , Bergren D. R.
Published: April 2021

We have observed that birds of several different taxa move their tails in conjunction with sound production. These observations suggested to us that tail movements might also be associated with ventilation. Since we hypothesized that rhythmic movements of the tail and pelvis will ventilate the lungs, the activities of tail, epaxial and cloacal muscles of the pigeon were examined. Electromyograms (EMGs) were recorded from these muscles while ventilation was monitored. A muscle was considered to have ventilatory activity when the EMG activity had an obvious correlation to either inspiration or expiration. To obtain further information about the correlation between muscular activity and ventilation, we induced hyperpnea by administering 5 % CO2. We report that the tail muscles that function as expiratory muscles are the M. caudofemoralis, the M. pubocaudalis internus and the M. pubocaudalis externus. We refer to these as the suprapubic abdominal muscles to distinguish them from the infrapubic (ventral) abdominal muscles. These muscles depress the pelvis and the uropygium and compress the thoracoabdominal cavity. M. transversus cloacae functions as an expiratory muscle by protracting the cloaca or by reducing its compliance. Of the suprapubic muscles we studied, the only inspiratory muscle is the axial muscle, M. longissimus dorsi. M. longissimus dorsi acts at the notarial-synsacral junction to elevate the pelvis. The rocking movements of the notarial-synsacral joint appear to be important for ventilation during conditions in which the sternum is ‘fixed’, such as when the bird is resting on its breast. We suggest that a division of labor may exist between the infra- and suprapubic abdominal muscles during ventilation such as panting or vocalization.
Short Communication The moment of Inertia of Bird Wings
Authors: Kirkpatrick Sean J.
Published: April 2021

The moment of inertia of a wing about its proximal end must be known in order to calculate the inertial torque and power required during flapping flight (Ellington, 1984) and it is also one of the morphological features that affects flapping frequency (Pennycuick, 1975, 1990). At present, however, there are very few data on wing moments of inertia of flying animals and thus there is no way of predicting the wing moment of inertia of a flying animal from easily obtainable morphological measurements. Arguments predicting bird wingbeat frequencies (Pennycuick, 1975), following Hill’s (1950) argument that the maximum frequency of a vibrating limb is set by the mechanical properties of the muscles and tendons that accelerate and decelerate the limb at each end of the oscillation, have assumed geometric scaling of wing moment of inertia about the shoulder joint. The objective of this study was to determine if the wing moment of inertia of birds does indeed scale geometrically or, if not, how it actually does vary with body size.
Synthesis and Transport of Agrin-Like Molecules in Motor Neurons
Authors: Magill-Solc Catherine , McMahan U. J.
Published: April 2021

Several lines of evidence indicate that agrin, or a protein very similar to it, directs the formation and maintenance of the postsynaptic apparatus at the neuromuscular junction. We discuss the results of studies involving immunohistochemical, biochemical and in situ hybridization techniques that support the hypothesis that agrin or agrin-like molecules active at the junction are produced by motor neurons.
The influence of action potentials on the development of the central visual pathway in mammals
Authors: Kalil R. E.
Published: April 2021

The development of the mammalian visual system begins prenatally at distributed sites, where cells generated at different embryonic ages are destined to interconnect and form the visual pathways, and ends postnatally with the functional tuning of neuronal receptive-field properties. It is reasonable to assume that the earliest stages in this developmental sequence are completed prior to the onset of neural activity, and also that activity may play only a minor role or even none at all in primary axon outgrowth and pathway finding (Harris, 1981; Harris and Holt, 1990). However, recent evidence indicates that subsequent events in development, such as the sorting of axons at their targets, the cellular differentiation of target cells and the formation of synaptic contacts by developing axons, are all influenced by action potentials.

Action potentials in the developing retino-geniculo-cortical pathway can be eliminated by blocking the voltage-gated sodium channel with tetrodotoxin. Prenatal blockade prevents the laminar segregation of retinogeniculate axons. Postnatal blockade interrupts the formation of retinogeniculate synaptogenesis, slows the cytoarchitectonic differentiation of the lateral geniculate nucleus and produces abnormalities in the responses of lateral geniculate neurons. In the visual cortex, the development of cells and synapses is retarded and the eye-specific separation of geniculocortical axons is halted, thereby blocking the formation of ocular dominance columns. While the cellular mechanisms underlying these effects are not understood, a partial restoration of normal development can be produced by stimulating blocked axonal pathways electrically.
In vitro experiments on axonal guidance and growth-cone collapse
Authors: Müller B. , Stahl B. , Bonhoeffer F.
Published: April 2021

In the retinotectal projection, nasal retinal axons project to posterior tectum, while temporal axons project to the anterior part of the tectum. In in vitro experiments, a similar specificity can be observed: the nasal and temporal retinal axons can be guided by tectal membrane components so that, for example, temporal retinal axons, when growing on a striped substratum consisting of anterior and posterior tectal membranes, express a very strong preference for the anterior stripes. This preference is not due to attractivity of anterior membranes but rather to avoidance of posterior material, although the pure posterior membranes are a very good substratum for growth of temporal axons. The repellent guidance molecule has been identified. Interestingly, besides guidance this molecule causes another reaction: when growing temporal axons are exposed to medium containing either posterior membranes or artificial lipid vesicles containing the repellent guidance molecule, the axonal growth cones collapse. As in guidance, there is a clear regional specificity: e.g. the repellent guidance molecule derived from posterior tectum induces collapse of temporal but not of nasal axons.

Since the guiding and the collapse-inducing activity are expressed by one and the same glycoprotein molecule (Mr33×103, linked to the membrane by phosphatidylinositol) and since another molecule has been identified by Keynes’ group which also expresses both guiding and collapse-inducing activity, one might speculate that axonal guidance and axonal collapse have something in common. Models of axonal guidance will be discussed.
Positional Discrimination and re-development of Synapses in the Leech Whitmania Pigra
Authors: Zhang Ren-Ji , Zhu Lixia , Wang Dan-Bing , Zhang Fan , Zou Dong-Jing
Published: April 2021

Identified neurones in the leech Whitmania pigra have a stable morphology with bilaterally symmetrical branching arborizations, and with axons on both sides arranged symmetrically in the connectives. Each anterior pagoda cell (AP) receives electrical and/or chemical synaptic input from mechanoreceptive cells on both sides of the body. The position in the body can be discriminated by the postsynaptic responses of the APs: as a rule, the responses to input from contralateral receptive neurones are stronger than those to input from ipsilateral ones, and the neurone with its receptive field on the dorsal side produces a stronger response than the neurone with a ventrally sited receptive field. APs integrate postsynaptic potentials and spikes. There are no connections between the two AP cells and so it is possible that positional discrimination depends upon a circuit comparing the inputs.

After the body wall has been cut round and rotated by 180°, the mechanoreceptive cells and annular erector motoneurones reinnervate the body wall strictly according to their original orientation, and repair is bilaterally synchronous. This eliminates a role for target cell guidance, particularly in the adult leech. When an extra Retzius cell is implanted into cultured ganglia, synapses develop between the host and the implanted neurone. Such synapses generally show lower coupling ratios or PSP fluctuations. However, the specific electrical connection between the Retzius cells shows a normal coupling ratio.
Water Vapour Absorption in Terrestrial Isopods
Authors: Wright Jonathan C. , Machin John
Published: April 2021

Continuous and intermittent gravimetric measurements have identified active water vapour absorption (WVA) in three species of terrestrial Isopoda. Water activity thresholds for uptake lie in the range 0.92–0.95. Above the threshold, WVA shows non-saturated kinetics; the rectum apparently serves as a supplementary avenue for fluid resorption during rapid uptake. Standardized uptake fluxes, corrected for vapour pressure deficit, can be varied, allowing animals to balance water losses accurately over long periods.

Blocking experiments have localised the ventral pleon as the uptake site. The pleopods display ventilatory cycling during WVA. Cycle frequency increases with humidity, compensating for changes in activity deficit between uptake fluid and air, and allowing uptake rate to be maximised. Freezing-point depression studies reveal hyperosmotic fluid in the ventral pleon. Osmolalities are compatible with prior uptake rates of the specimens studied.

WVA would allow terrestrial isopods to regulate their water balance in external activities below the haemolymph activity (approximately 0.99) and above the uptake threshold. Liquid water - an alternative source for hydration - is rapidly absorbed across the hydrophilic cuticle, posing severe danger of drowning.
Foreign Connections are Formed In Vitro by Aplysia Californica Interneurone L10 and Its In Vivo Followers and Non-Followers
Authors: Kleinfeld D. , Parsons T. D. , Raccuia-Behling F. , Salzberg B. M. , Obaid A. L.
Published: April 2021

Aplysia californica interneurone L10 forms a set of presynaptic connections with many postsynaptic ‘follower’ cells in the abdominal ganglion. These followers do not connect back to L10. The present study tests whether the direction and sign of these connections are obligatory and are reconstructed when neuronal processes regenerate in vitro. L10 was co-cultured with one of six different followers and two non-followers. In vitro connections that preserve the sign of those formed in vivo were made by L10 onto neurones L11, L12 and L13. The connections consisted of inhibitory postsynaptic potentials (IPSPs) with characteristic fast and slow components.In vitro connections that did not preserve the sign of connections found in vivo were made by L10 onto R15, R16 and L7. Neurones R15 and R16 receive excitatory inputs from L10 in vivo and L7 receives a dual-action input in vivo, with inhibition followed by excitation. A purely inhibitory connection from L10 was formed in vitro onto all these cells.Connections that have never been observed in vivo in terms of both direction and sign were formed in vitro. Followers L7, L11, L12, L13 and R16 and nonfollower L14A formed novel connections onto L10. All these connections were inhibitory and some were strong. For example, IPSPs with a magnitude of 20 mV were observed in L10 following a single action potential in L13.

Our results show that identified Aplysia neurones can form stereotyped specific connections in vitro. The specificity is different from that in the intact ganglion. The ubiquity of novel connections suggests that restrictions imposed on synapto-genesis in the animal are distinct from those regulating synapse formation in culture.