bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Aldehyde Fixatives to Determine the Rate of Synaptic Transmitter Release
Authors: Smith J. E. , Reese T. S.
Published: April 2021

Aldehyde fixation continues to be useful to prepare synapses for freeze fracture, but it may increase the rate of transmitter release. The effects of different aldehyde fixatives on spontaneous quantal release (m.e.p.p.s), and on the corresponding synaptic vesicle exocytosis at frog nerve-muscle synapses were investigated with the hope of finding a way to minimize side effects of fixation. Increases in m.e.p.p.s of up to 50 s−1 occurred during fixation, despite the species of aldehyde used in the fixative, and this fixative effect decreased only slightly as aldehyde concentration was increased. Increases in m.e.p.p. frequency were not blocked by tetrodotoxin, by lowering external calcium and raising external magnesium concentration, or by lowering the total osmotic strength of the fixative. The smallest increase in m.e.p.p. frequency was in 3% glutaraldehyde and corresponded to the lowest levèl of synaptic vesicle exocytosis seen by freeze-fracture, 0·15 per μm of active zone. The effects of aldehyde fixation on m.e.p.p. frequency and synaptic vesicle exocytosis could not be avoided, but this study suggests how its effect on morphological changes in synapses might be minimized.
Substance P and Neurotensin: Discovery, Isolation, Chemical Characterization and Physiological Studies
Authors: Leeman Susan E.
Published: April 2021

During the course of work directed towards the purification of a corticotropin-releasing factor, two other biological active substances were discovered in bovine hypothalamic extracts : one a sialogogic peptide, the other a vaso-active substance easily separated from the sialogogic agent by ion-exchange chromotography. The sialogogic peptide was subsequently characterized as substance P (SP); the other substance, also a peptide, was named neurotensin (NT). These peptides were isolated, their amino acid sequences determined (substance P; arg-pro-lys-pro-gln-gln-phe-phe-gly-leu-met-NH2; neurotensin: < glu-leu-tyr-glu-asn-lys-pro-arg-arg-pro-tyr-ile-leu-OH), synthetic material prepared, and radioimmunoassays developed. Subsequent studies from many laboratories have yielded much information relevant to the physiological roles of these peptides. In addition to its uneven distribution throughout the CNS, SP is also present in the peripheral nervous system. Data is presented on its distribution in sympathetic ganglia and its depletion by pretreatment with capsaicin. Release of immunoreactive substance P (I-SP) has been demonstrated in vivo from mammalian spinal cord after activation of nociceptive afferents. Neurotensin is also unevenly distributed throughout the CNS and is present in the GI tract. Neurotensin containing cells have been demonstrated scattered throughout the small intestinal epithelium of every mammalian and avian species. The concentration of immunoreactive NT has been measured to increase in hepatic portal vein plasma after infusing a micellar solution of lipid through the small intestine of rats. Neurotensin has been demonstrated to be present in a cell line derived from a rat medullary thyroid carcinoma permitting studies on the regulation of neurotensin release from these cells in culture.
A Note on the Blood of the Hag-Fish Polistotrema Stouti (Lockington)
Authors: Bond Richard M. , Cary M. Katharine , Hutchinson G. E.
Published: April 2021

The blood of Polistotrema stouti (Lockington) has been shown by Greene (1904) to be approximately isotonic with the sea-water in which the animal lives, thus resembling the elasmobranchs and marine invertebrates and differing from the teleosts and in all probability the marine lampreys (Fontaine, 1930). It does not appear to be known whether this isotonic condition is primarily due to inorganic constituents as in invertebrates or to some organic substance comparable to the urea of elasmobranch blood. Since one of us (R. M. B.) has recently had access to a supply of Polistotrema, it seemed desirable to investigate the matter.
The Influence of Temperature on the Rate of Growth of Saprophytic Actinomyces
Authors: Haines R. B.
Published: April 2021

Actinomyces occur commonly in commercial cold stores. They can be isolated from the walls but are obtained in greatest number from straw on the floor of the store. Measurements of the rate of growth of actinomyces from cold stores show that the majority of the strains studied have their optimum temperature at 37° C. They are capable of growth from 40° to 5° C., growth becoming infinitely slow at just above 0° C. One strain, however, had its optimum temperature for growth less sharply defined at 20°-30° C. and grew well, though slowly, at o°C. The curve obtained by plotting the “velocity constant of growth” against temperature suggests that growth becomes infinitely slow at about—5° C. Application of the Arrhenius equation to the results obtained is discussed. Comparison with certain strains isolated from soil, having their optimum temperature at 37° C., gave results analogous to those obtained with strains from cold stores, also having their optimum at 37° C. The significance of actinomyces in imparting “musty” flavours to stored foodstuffs is indicated.
The Effect of Fertilisation on the Permeability to Water and on Certain Other Properties of the Surface of the Egg of Psammechinus Miliaris
Authors: Hobson A. D.
Published: April 2021

Among the numerous changes in the sea-urchin egg which have been shown by various workers to occur at the time of and subsequent to fertilisation none have attracted more attention than that of increased permeability. R. S. Lillie (1916) showed that fertilisation or artificial activation by means of butyric acid causes the eggs of Arbacia to swell more rapidly when placed in hypotonic sea water. He concluded from his experiments that the surface of the sea-urchin egg becomes more permeable to water as the result of activation.
The Adrenal Secretion of Xenopus Laevis (The South African Clawed Toad)
Authors: Epstein D. , Gunn J. W. C. , Epstein E. , Rimer G.
Published: April 2021

The presence of adrenal bodies in Xenopus laevis has long been a controversial point. Although these bodies are present as well-defined, yellowish masses in the kidneys of most Amphibia, morphologists have usually stated that none can be demonstrated in the kidneys of Xenopus (5). To account for this absence, other workers have sought for accessory adrenal glands, but their search has proved fruitless up to the present.
The Effect of Temperature on the Growth and Respiration of Fish Embryos (Salmo Fario)
Authors: Wood A. H.
Published: April 2021

In a series of recent papers Gray (1926–8) has shown that the growth-rate of the embryo of Salmo fario is proportional to its size and to the quantity of yolk present in the yolk sac. The yolk is used for two simultaneous processes—it is being converted into embryonic tissue and it is providing the material which is used up by the embryo in respiration ; there is, according to Gray, no measurable amount of yolk used for any other purpose. Under these circumstances the dry weight of the embryo at the conclusion of development must be equal to the dry weight of yolk in the newly fertilised egg, less the amount which is required for maintaining the respiration of the embryo. By incubating eggs at 16°, 10° and 5° C., Gray concluded that the higher the temperature of incubation the smaller was the final size of the embryo and the greater was the percentage of the original yolk consumed by the respiration of the embryo during development. This conclusion is in harmony with the observations of Graham-Smith (1920) who showed that the lower the temperature of incubation the greater is the maximum population of bacteria which can be obtained from a given volume of culture medium. The work of Bathélemy and Bonnet (1926) with the eggs of the frog are, however, at variance with these conclusions—at least to some extent. In one experiment performed by these authors the results conform to those obtained by Gray with the eggs of the trout, but in another experiment the temperature of incubation appeared to have no effect on the final size of the embryo.
The Osmotic Properties of the Eggs of the Trout (Salmo Fario)
Authors: Gray J.
Published: April 2021

The normal healthy eggs of the trout are impermeable both to water and to intracellular electrolytes. The barrier to diffusion of both water and salts lies in the vitelline membrane, whose static properties maintain the normal hypertonicity of the yolk without expenditure of energy. When eggs are exposed to conditions which destroy the normal impermeability of the vitelline membrane, exosmosis occurs suddenly at the end of a latent period, and once it has begun exosmosis is usually rapidly completed. Exosmosis is a sign of an unhealthy cell. The osmotic stability of the vitelline membrane varies with four factors: (a) the age of the eggs, (b) the degree of mechanical disturbance caused by the environment, (c) the presence or absence of calciuip in the environment, (d) the nature and concentration of the exosmotic reagent used. Loss of the impermeable properties of the vitelline membrane is accompanied by a drastic change in the distribution of the material of the membrane and in the organisation of the egg cell.
The Reactions of Normal and Mutant Types of Gammarus Chevreuxi to Light
Authors: Wolsky A. , Huxley J. S.
Published: April 2021

A method is described for obtaining statistical results on the phototaxis of G. chevreuxi. A long tube is illuminated from one end and the numbers of animals in two arbitrarily delimited end-sections counted at regular intervals. Wild-type specimens in normal conditions show a moderate degree of negative phototaxis. Animals with one eye varnished show circus movements; hence the phototaxis is true tropotaxis (Frankel, 1931). The sense of reaction can be reversed and the animals made to show a moderate positive phototaxis by the addition of acetic acid. Caffein has no effect. Red-eyed mutants, which lack most of the melanin eye pigment, behave similarly to the wild type, though there are indications that they are often rather more sensitive to light, as shown by stronger negative phototaxis in normal conditions, weaker positive phototaxis after addition of acid. The variability of the results, however, is too great to permit of definitive conclusions being drawn. Albino and colourless mutants, which possess neither retinulae nor optic nerves, show no phototaxis.
Na and Cl Transport across the Isolated Anterior Intestine of the Plaice Pleuronectes Platessa
Authors: Ramos M. M. P. , Ellory J. C.
Published: April 2021

The tissue was found to have a serosa negative potential, and shortcircuit currents equivalent to the net Cl transport. A significant part of the Cl uptake was Na dependent and a similar fraction of the Na uptake was Cl dependent. Short-circuit current and uptake of both ions were inhibited by loop diuretics and analogues. 4. Isc and p.d. were abolished by ouabain. The observations are consistent with the idea of a coupled NaCl entry into the cell, using the energy inherent in the Na gradient; Na being pumped out of the cells by the Na pump and followed electrically by Cl−. Net chloride transport and the serosa negative potential would be a consequence of the permselective properties of the junctions allowing Na but not Cl to recycle back to the mucosal solution.
An Aerodynamic Analysis of Bird Wings as Fixed Aerofoils
Authors: Withers Philip C.
Published: April 2021

The aerodynamic properties of bird wings were examined at Reynolds numbers of 1·5 × 104 and were correlated with morphological parameters such as apsect ratio, camber, nose radius and position of maximum thickness. The many qualitative differences between the aerodynamic properties of bird, insect and aeroplane wings are attributable mainly to their differing Reynolds numbers. Bird wings, which operate at lower Reynolds numbers than aerofoils, have high minimum drag coefficients (0·03–0·13), low maximum lift coefficients (0·8–1·2) and low maximum lift/drag ratios (3–17). Bird and insect wings have low aerofoil efficiency factors (0·2–0·8) compared to conventional aerofoils (0·9–0·95) because of their low Reynolds numbers and high profile drag, rather than because of a reduced mechanical efficiency of animal wings.

For bird wings there is clearly a trade-off between lift and drag performance. Bird wings with low drag generally had low maximum lift coefficients whereas wings with high maximum lift coefficients had high drag coefficients. The pattern of air flow over bird wings, as indicated by pressure-distribution data, is consistent with aerodynamic theory for aeroplane wings at low Reynolds numbers, and with the observed lift and drag coefficients.
Instantaneous Measurements of Oxygen Consumption During Pre-Flight Warm-Up and Post-Flight Cooling in Sphingid and Saturniid Moths
Authors: Bartholomew George A. , Vleck David , Vleck Carol M.
Published: April 2021

A method for instantaneous measurement of oxygen consumption in an open flow respirometry system is described. During pre-flight warm-up in both sphingids and saturniids, oxygen consumption reaches levels 20 to 70 times resting values. , required to maintain the thorax at flight temperature by intermittent wing-quivering and fluttering is about one-third the maximum , during warm-up. The Q10 of resting , averages 2 ·4 in both sphingids and saturniids. At any given thoracic temperature, during post flight-cooling exceeds , at rest.

Factorial scope (maximum resting ) during warm-up is independent of mass and thoracic temperature. In sphingids it averages 39, in satuniids, 43. Absolute metabolic scope in both groups increases with thoracic temperature and is roughly proportional to . In saturniids about 49 % of the heat produced during warm-up is stored in the thorax; in sphingids the figure is about The data on metabolic scope, power requirements for flight, Q10 and body mass are used to develop equations that predict thoracic temperature during flight for both sphingids and saturniids.
Changes in Membrane Properties of the Drosophila Dorsal Longitudinal Flight Muscle Induced by Sodium Pump Inhibitors
Authors: Henon Barbara K. , Ikeda Kazuo
Published: April 2021

Drosophila dorsal longitudinal flight muscle fibres made anoxic by passing nitrogen through the tracheal system or treated with 10−5m ouabain or strophanthidin show a reversible fall in resting membrane potential of 16·5 mV (s.e. 0·96), 13·7 mV (s.e. 0·87), and 17·0 mV (s.e. 2·8), respectively. The reversible depolarization obtained with these sodium pump blockers occurred within 10–15 min. The depolarization of the muscle fibres was accompanied by a decrease in input resistance of 21·2% (s.e. 3·8) in anoxia, 21·4% in ouabain, and 25·6% (s.e. 6·7) in strophanthidin. The resistance decrease in strophanthidin and ouabain was transient and returned to above the resting level while the muscle fibres were still exposed to these agents. Recovery of membrane potential in cells exposed to anoxia is biphasic. An initial ‘fast’ phase of recovery occurs within 15 s upon return to air followed by a late ‘slow’ phase lasting several minutes. Recovery of input resistance in cells exposed to N2 coincided with the ‘fast’ phase of the recovery of resting membrane potential. Recovery of membrane potential following exposure to strophanthidin is a long, slow process which occurs at conductance values at the resting level or below. The tendency towards spontaneous action potentials was increased by anoxia and the action potentials occurring in anoxia were elongated into plateau potentials of about 18 s duration. These results are consistent with the hypothesis that anoxia and cardioactive steroids inhibit a metabolic process, possibly an electrogenic ion pump, that is essential for maintenance of the resting membrane potential in Drosophila flight muscle. Exposure to these agents also results in changes in input resistance. Both of these effects could contribute to the depolarization and affect the excitable properties of the muscle fibre membrane.
Studies on Water in Barnacle Muscle Fibres I. The Dry Weight Components of Fresh Fibres
Authors: Clark M. E. , Hinke J. A. M.
Published: April 2021

The dry weight components comprise 25 % of the total weight of fresh muscle fibres of the giant barnacle Balanus nubilis. Half of the solids are water insoluble; 6 % of this material is fat, and the rest is mostly myofilament protein. Less than 3 % of the dry weight consists of inorganic ions, and these account for only a quarter of the osmotic activity in the fibre water. Seventy per cent of the osmotic activity is due to nitrogenous solutes which comprise 18% of the dry weight. Glycine predominates, followed by TMAO + betaine, proline, glutamine + asparagine, arginine, and taurine. About 13% of the dry weight is soluble protein and not more than 10 % is an unidentified soluble substance of high molecular weight. Thus, Balanus conforms with other marine invertebrates in the high content of osmotically active nitrogenous solutes in its myoplasm.
The Exoskeleton and Insect Proprioception. I. Responses of Tibial Campaniform Sensilla to External and Muscle-Generated Forces in the American Cockroach, Periplaneta Americana
Authors: Zill Sasha N. , Moran David T.
Published: April 2021

The tibial campaniform sensilla are a group of mechanoreceptors in the cockroach leg that respond to cuticular strain. Each sensillum consists of a single bipolar neurone whose dendrite inserts into an ovoid cuticular cap embedded in the exoskeleton. The tibial campaniform sensilla are consistently separable into two subgroups with mutually perpendicular cap orientation: the long axis of the caps of proximal subgroups are oriented perpendicular to the tibial long axis; caps of the distal subgroup are parallel to the tibia. The responses of individual, identified sensilla from both subgroups were tested to the following forces: bending forces (perpendicular to the leg long axis), axial forces (parallel to the leg axis), torques (twisting about the leg long axis) and forces generated by the tibial muscles. The tibial campaniform sensilla respond vigorously to bending forces imposed in the plane of movement of the adjacent femorotibial joint. Individual sensilla exhibit orientation-dependent directional sensitivity in their response: the proximal sensilla respond only to dorsal bending; the distal sensilla respond only to ventral bending. Sensilla respond less vigorously to bending forces in other planes. Responses are weak but directionally sensitive to axial forces: the proximal sensilla fire upon axial compression; the distal sensilla fire upon axial tension. Both subgroups respond simultaneously but weakly to imposed torques. Contractions of the tibial muscles produce strong orientationdependent responses: the proximal sensilla respond only to flexor muscle contractions; the distal sensilla respond only to extensor muscle contractions. These responses are accurately predicted from a simple model in which the tibia behaves as a cylinder under stress. The tibial campaniform sensilla respond as directionally sensitive strain gauges. Each individual sensillum responds only to compressions perpendicular to the long axis of its cuticular cap. Tibial campaniform sensilla respond best to those forces that the animal can most effectively control.
Effects of Afference Sign Reversal on Motor Activity in Walking Stick Insects (Carausius Morosus)
Authors: Graham D. , Bässler U.
Published: April 2021

The apodeme of the femoral chordotonal organ of a middle leg can be moved from its normal position close to the extensor tendon and inserted into a clot cut in the flexor tendon. This inverts the output of the sense organ and produces a ‘wrong’ afference.

During walking on a pair of light wheels the operated leg either makes walking steps or is raised and extended in a ‘salute’ posture. The coordination is similar to that for an intact animal if the operated leg walks but changes to the middle leg amputee timing when the operated leg ‘salutes’.

The transitions between saluting and the normal walking behaviour of the operated leg can be explained if it is assumed that the animal depends heavily upon the C.O. for determining the tibia position during both walking and the saluting behaviour.

Motor output to the levators and depressors of the femur and the protractors and retractors of the coxa shows bursting activity during the salute at the frequency of 3–4 Hz. The depressor bursts are also modulated at a frequency of ∼ 1 Hz and produce strong regular depressions of the femur which are co-ordinated with the movements of the other legs.

The maintenance of regular depressor contractions during the salute shows that an important part of the motor output to the saluting leg (depressor activity) arises from an internal oscillation or rhythmic command which maintains its co-ordinated activity when the normal peripheral sensory input to the leg it is attempting to operate is absent. Retractor activity wanes during the salute suggesting that propulsion is much more dependent upon peripheral input than is the support musculature (depressors),

The creation of a ‘wrong’ afference can be used to map the importance of the operated organ in different sub-units of behaviour.
Synchronous and Asynchronous Muscles in Cicadas*
Authors: Josephson Robert K. , Young David
Published: April 2021

The tymbal muscles of the cicada Cyclochila australasiae Donovan are synchronous, those of Platypleura capitata (Oliv.) asynchronous. The tymbal structure and the individual sound pulses are similar in the two species. The sound pulse frequency during calling song is higher in P. capitata (389 Hz) than in C. australasiae (234 Hz). Muscle action potentials during protest songs are simultaneous in the two tymbal muscles of P. capitata, alternating in C. australasiae. Each action potential, or direct electrical stimulus to the muscle, is followed by a single, sometimes bimodal, sound pulse in C. australasiae, and by a burst of sound pulses in P. capitata. The isometric twitch duration (30 °C) is much longer in P. capitata (107 ms) than in C. australasiae (18 ms) and the tetanic fusion frequency correspondingly lower. Myofibrils are slightly wider and sarcoplasmic reticulum much sparser in tymbal muscles of P. capitata than in those of C. australasiae;, otherwise the muscles are structurally similar. Flight muscles in both species are synchronous with an action potential for each contraction. Tymbal muscles of the two species are used to illustrate the diagnostic features of synchronous and asynchronous muscles.
Cardiovascular Changes in the Lingcod (Ophiodon Elongatus) Following Adrenergic and Cholinergic Drug Infusions
Authors: Farrell A. P.
Published: April 2021

Adrenergic and cholinergic agonists were infused into the ventral aorta to evoke gill vasoactivity in the lingcod, Ophiodon elongatus. Arterial blood pressures were changed, and cardiac output and stroke volume were increased. As a consequence both the pressure and flow profiles across the gill were altered, and these changes should alter the pattern of lamellar perfusion. The changes in cardiac function were apparently reflexly mediated.
A 24-Hour Cycle in Single Locust and Mantis Photoreceptors
Authors: Horridge G. A. , Duniec J. , Marčelja L.
Published: April 2021

When fixed during the night the rhabdom of the locust and mantis is much broader than when fixed during the day. Dark-adapted ommatidia of the locust and mantis by day and night have a zone of vacuoles around the rhabdom tip, but when light-adapted this zone is replaced by cytoplasm rich in mitochondria. Illumination of the rhabdom in the night state causes the microvilli to swell and the rhabdom to break down over the course of about 1 h. A diurnal rhythm is apparent in the spontaneous breakdown of the rhabdom in the morning even though the eye has seen no light for 12 h. Intensity/response curves (peak of the response in mV plotted against log intensity of stimulus) show an increase in sensitivity during the night even though the stimulus is a point source on axis. On the other hand, counts of bumps (quantal responses to individual photons) show no change in photon capture efficiency at night when the stimulus is a point source. Strong illumination of the eye in the night state causes a desensitization which continues for 1 h. Measurements of the acceptance angle in the dark-adapted day and night states show that field size is an indicator of the diameter of the rhabdom tip, but actual fields are larger than those calculated from the anatomical dimensions.
Na+Fluxes Across Isolated Perfused Gills of the Chinese Crab Eriocheir Sinensis
Authors: Pequeux A. , Gilles R.
Published: April 2021

Sodium transport processes in the branchial epithelium of euryhaline crustaceans have been investigated using a perfused preparation of gills isolated from Chinese crabs Eriocheir sinensis acclimated to dilute (FW) and to concentrated (SW) media.

The results clearly establish the existence of a functional difference between the different pairs of branchiae with respect to their participation in the regulation of the blood Na+ content.

In FW-acclimated animals, the Na+ active uptake which counterbalances the salt loss along the concentration gradient is mostly achieved across the three posterior pairs of gills. Conversely, the Na+ fluxes measured in the three anterior pairs are essentially passive and carrier-mediated.

Further characterization of the Na+ uptake system present in the posterior gills by means of inhibitors like ouabain and ethacrynic acid indicates the existence of at least two spatially separated components of the Na+ carrying system.

It is shown that NH4+ may be used as co-ion for Na+ but that such a coupling can only account for a very small part of the Na+ actively transported inward. The existence of an electrogenic mechanism or of another coupled system has thus to be postulated but remains at present a matter of speculation.

To study FW-to-SW and SW-to-FW acclimation, Na+ fluxes were measured in isolated gills of SW-acclimated crabs and of FW crabs perfused and incubated in SW conditions.

During acclimation to SW the Na+ active uptake in the posterior gills is abolished primarily as a result of inhibition of the Na+carrier activity.
Coordinated Walking of Stick Insects on a Mercury Surface
Authors: Graham D. , Cruse H.
Published: April 2021

Adult stick insects walk on a mercury surface at step frequencies in the range 1–4 Hz with a coordination similar to that found in free-walking adults at their maximum step frequency of 3 Hz. The amplitude of leg movement covers the same range as that found in free-walking animals. The use of a mercury substrate effectively removes mechanical interactions between the legs, showing that such influences cannot be the cause of the coordinated behaviour observed in this experimental situation. The dependence of the maximum step frequency upon the resistance to retraction provided by the substrate suggests that feedback from the periphery determines the step period. The variation in the anterior extreme position of a leg is less than that of the posterior extreme position, indicating that the latter may be more strongly influenced by coordinating interactions between the legs.
The Effect of Load on Locomotion in Crayfish
Authors: Grote J. R.
Published: April 2021

Leg movements and leg muscle activity were monitored in unrestrained crayfish walking freely under several different load conditions. A variety of changes in the character of locomotion was found to vary with load including: (1) the timing and frequency of the step cycle and in particular the power stroke duration; (2) significant leg-positional changes which result in increased mechanical advantage under load; and (3) the (load-induced) recruitment of the depressor muscle. In restrained, immobile animals, isometric loading of depression resulted in inhibition of motor activity in the depressor-remotor nerve, an effect similar to the vertebrate tendon reflex.
Ferromagnetic crystals (magnetite?) in human tissue
Authors: Kirschvink JL
Published: April 2021

In recent years, a variety of animals have been found which are able to synthesize the ferromagnetic mineral magnetite (Fe3O4). Lowenstam (1962) originally recognized biogenic magnetite in the radular teeth of a primitive marine mollusc, the chiton (Polyplacophora), and since then it has been identified as a precipitate in several magnetically sensitive organisms, including honey bees (Gould, Kirschvink & Deffeyes, 1978), homing pigeons (Walcott, Gould & Kirschvink, 1979) and in magnetotactic bacteria (Frankel, Blakemore & Wolfe, 1979). Zoeger, Dunn & Fuller (1980) also report a localized concentration of magnetite in dolphin heads, although magneto-sensory behavioural experiments have not as yet been done on them.
Is the Position of the Femur-Tibia Joint Under Feedback Control in the Walking Stick Insect ?
Authors: Cruse H. , Pflüger H.-J.
Published: April 2021

From earlier force measurements it was assumed that the system controlling the position of the femur-tibia joint in the middle leg of the stick insect is active in walking animals. This hypothesis is confirmed by electro physiological recordings and is discussed in relation to several earlier findings concerning the function of the control system of the femur-tibia joint.
Branchial and Renal Acid and Ion Fluxes in the Rainbow Trout, Salmo Gairdneri, at Low Environmental pH
Authors: McDONALD D. G. , Wood C. M.
Published: April 2021

Rainbow trout were exposed for 4 days to an environmental pH averaging 4·2, an exposure which resulted in a continuous net branchial influx of acid. The influx provoked a progressive depression in blood pH and [HCO3−], virtually complete by 48 h, and a marked increase in renal acid excretion, also complete by 48 h. The increase in the latter was sufficient to remove, at maximum, about half of the protons entering at the gills; those remaining were buffered in body fluids. The low pH exposure also impaired gill ion regulation as indicated by continuous net branchial losses of Na+, Cl− and K+ and by a progressive decline in plasma Na+ and Cl− levels. Evidence is presented which indicates that there was a significant contribution by the intracellular compartment both to the total body ion losses and to the buffering of the body acid load.
Ion and Water Transport in Locust Alimentary Canal: Evidence from In Vivo Electrochemical Gradients
Authors: Dow Julian A. T.
Published: April 2021

Sodium occurs at a much lower electrochemical potential in all gut regions than in the blood. The observed gradients do not decrease with time; the maintenance of the high blood sodium levels therefore requires active uptake against an electrochemical gradient. Potassium occurs at a much higher electrochemical potential in all gut regions than in the blood. The observed gradients do not decrease with time; the maintenance of the low blood potassium therefore requires active excretion against an electrochemical gradient. The highest luminal concentration is observed in the posterior midgut. Chloride appears to be passively distributed across the gut. As with potassium, the highest luminal activity is observed in the posterior midgut. Calcium and magnesium are similarly distributed. They both occur at a fairly high level in the blood, crop, caeca and anterior midgut, and at a much lower level in the rest of the gut. The crop and caecal fluids become markedly hyperosmotic to the blood in freshly-fed locusts, but the midgut fluid is isosmotic at all times. The fluid in the ileum is significantly hyposmotic; the shortfall in osmolality, compared with the fluid in the posterior midgut, corresponds to the observed drop in KC1 level. The anterior caeca are the only parts of the alimentary canal to possess a lumen-negative transepithelial potential difference. They differ significantly from the other regions studied, notably the posterior caeca, in this respect.
Dynamic Tensile Properties of the Plantaris Tendon of Sheep (Ovis Aries)
Authors: Ker Robert F.
Published: April 2021

The stresses applied during fast locomotion are sufficient to stretch the tendon far into the linear region of the load-extension plot. The tangent modulus in the linear region is about 1·65 GN.m−2 and is independent of frequency for oscillations in the range 0·22 to 11 Hz. Internal damping dissipates about 7 % of the mechanical energy applied during oscillations. The load range (o to about 1 kN) and frequencies (0·22 to 11 Hz) were comparable to those arising during locomotion. The rate of rise of temperature, during the initial period of an oscillation, was consistent with the mechanical measurement of power loss. The dynamic mechanical properties are appropriate for the hypothesis of energy saving by storage in tendons during fast locomotion.
The Handling of Macromolecules by the Kidney of the River Lamprey, Lampetra Fluviatilis
Authors: Logan A. G. , Morris R.
Published: April 2021

Micropuncture and renal clearance techniques have been used to investigate the effect of molecular size on glomerular permeability in the river lamprey, Lampetra fluviatilis, and to investigate tubular absorption of native and foreign macromolecules.

Polyvinyl pyrrolidone (PVP) molecules of 16 Å in molecular radius were freely filterable but there was significant retention of 37 Å molecules. The estimated sieving coefficients for PVP of 160000 and 360000 in molecular weight (molecular radii > 100 Å) were 07·06 and 07·01 respectively, indicating that the glomerular barrier is relatively leaky.

Up to 50% of microinjected protein was absorbed by the nephron and the results with bovine serum albumin demonstrated that protein uptake occurs chiefly in the proximal brush border segment. The relative rates of uptake for different proteins and different concentrations of injected solutions indicated that the uptake mechanism is easily saturated and unable to distinguish between native and foreign proteins of high molecular weight.

Most lamprey plasma proteins are > 100000 in molecular weight. This, together with other factors such as molecular charge and tubular reabsorption, could account for the low urinary protein concentration of 0-05 mg/ml.
A Hormone Effecting Immobilization in Pupariating Fly Larvae
Authors: Zdarek Jan , Rohlf Rebecca , Blechl Jim , Fraenkel Gottfried
Published: April 2021

The haemolymph of 1–2 h old (orange) puparia of Sarcophaga bullata contains a factor (PIF) which immobilizes mature fly larvae, most strongly 6–24 h before pupariation. It has all the properties of a protein: a mol. wt. of between 100000 and 300000 daltons, it is heat labile, non-dialysable, destroyed by trypsin, and precipitated by NH4SO4. It is possibly identical with the anterior retraction factor (ARF) because the activity of both always went hand in hand. Its action seems to be unspecific in cyclorrhaphous flies. Much about PIF has been learned from studying changes in internal haemolymph pressure of larvae injected with PIF before and during pupariation. Its function is probably to shut off muscular activity after the puparium is completed. It may also function in very small dosages at the beginning of pupariation when the activity of the larvae decreases.
The Effect of Salt Adaptation and Amiloride on the In Vivo Acid-Base Status of the Euryhaline Toad Bufo Viridis
Authors: Katz U.
Published: April 2021

The acid-base status of the blood of the toad Bufo viridis was studied during adaptation to high salinity and in tap water containing amiloride. Both salt adaptation and immersion for 2 – 3 days in 5 × 1−4 M amiloride in tap water resulted in a decrease in blood pH (from 7·720 ± 0·026 in tap water to 7·4561 0·051 in 500 mOsm NaCl-adapted toads ; mean ± S.E.), and a simultaneous decrease in the concentration of HCO3− (from 17·8 ±1·4 in tap water to 9·5 + 1·2 in salt-adapted toads). In vitro determination of Na+/H+ exchange across the skin showed a 1:1 relation in skins from tap-water-adapted toads; this exchange was inhibited by amiloride. H+ secretion was abolished in skins from salt-adapted toads and the uptake of sodium was reduced.
Landing Reaction of Musca Domestica
Authors: Chillemi S. , Taddei-Ferretti Cloe
Published: April 2021

Electrophysiological recordings from the sub-oesophageal ganglion and cervical connective of Musca domestica have revealed the existence of units which integrate visual stimuli that elicit landing behaviour (light-off stimulus or expansion of a spatial pattern) and those which cause inhibition of a landing behaviour already in progress (light-on stimulus or contracting pattern).
Energetics of Cockroach Locomotion
Authors: Herreid Clyde F. , Full Robert J. , Prawel David A.
Published: April 2021

Cockroaches, Gromphadorhina portentosa, were run at different speeds for 20 min on a miniature treadmill enclosed in a lucite respirometer while oxygen consumption was continuously monitored. The data collected on these 5 g insects are remarkably similar to those obtained on vertebrates.

rises rapidly with the onset of exercise ; the on-response was about 1 min with steady-state reached within 4 min at the fastest speed, 0-12 km/h. Recovery was rapid ; the off-response was 4-6 min, with total recovery achieved in less than 1 h. The tracheal system appears to be a highly efficient mode of O2 conductance in contrast to the crustacean method of delivery involving gills and circulation.

(ml O2/g.h) at steady-state running varies directly with velocity (V). The regression equation at 24 °C is . The F-intercept, at zero velocity, is 2·4 times the actual resting rate of 0-19 ml O2/g.h. Temperature does not change the slope of the regression line but shifts it up or down in accordance with a simple Q10 effect. Incline running produces no changes compared to level running.

The minimum cost of transport, the lowest necessary to transport a given mass a specific distance, is high in cockroaches (4-92 ml O2/g.km) and comparable to that expected for a small quadrupedal or bipedal pedestrian vertebrate.
Physiological Identification and Asymmetry of Lobster Claw Closer Motoneurones
Authors: Govind C. K. , Lang F.
Published: April 2021

The somata of the fast closer exciter (FCE) and slow closer exciter (SCE) motoneurones to the dimorphic claw muscles of the lobster Homarus americanas were physiologically identified in an isolated claw-ganglion preparation, by recording from a cell body simultaneously with recording from an identified axon. The FCE, SCE, and opener exciter (OE) somata are the largest cells in the anterior ventral region of the ganglion and appear consistently as a triad. A marked asymmetry occurred in the responsiveness of the identified FCE and SCE somata to sensory stimulation via the 2nd root. The SCE soma produced a longer burst with higher spike frequencies than the FCE soma in either cutter or crusher claw. When homologous somata were compared, the crusher FCE and SCE produced higher frequencies and longer bursts of spikes than their cutter counterparts. Since this occurred in response to both sensory stimulation via the 2nd root and depolarization of the soma it suggests that differences in motor output between homologous motoneurones have an extrinsic and intrinsic origin. Furthermore, asymmetry sometimes occurred within an individual motoneurone with a larger number of spikes in the soma than in the axon. Thus the homologous FCE and SCE motoneurones are differentiated into physiologically different types.
Possible Roles of Vertebrate Neuroglia in Potassium Dynamics, Spreading Depression and Migraine
Authors: Gardner-Medwin A. R.
Published: April 2021

The membranes of glial cells are highly selectively permeable to potassium. The implications of this and the possible reasons for it are discussed. Glial cells may contribute to buffering the extracellular K+ concentration of brain tissue through several mechanisms. However, the only one that benefits from the K+ selective permeability is the so-called ‘spatial’ buffer mechanism, which acts more effectively than extracellular diffusion in many situations to speed the dispersal of local accumulations of potassium.

The role of glial cells in buffering the extracellular K+ concentration may help to prevent the occurrence of a phenomenon called Leão’s spreading depression (SD). A K+-induced K+ efflux from neurones, occurring when the EC K+ concentration rises above critical levels, is probably crucial in causing SD. The models that have been proposed to describe this process are discussed and related.

Spreading depression is not known definitely to occur in man. It seems probable, however, that it occurs during attacks of ‘classical’ migraine, associated with neurological symptoms. These neurological symptoms have often been attributed to vasoconstriction rather than to SD since certain vasodilators can relieve the symptoms. Experiments with SD in anaesthetized rats show that at least one of these vasodilator interventions (administration of a CO2/O2 mixture) stops also the propagation of a wave of SD. This strengthens the evidence for a possible relationship between migraine and SD. The involvement of SD in migraine probably deserves more critical attention than has hitherto been devoted to it.
Glial Versus Neuronal Uptake of Glutamate
Authors: Currie D. Neil , Kelly John S.
Published: April 2021

Inactivation of amino acid neurotransmitters is generally held to be via high-affinity uptake into pre-synaptic neurones and glia, a model well established for monoaminergic systems. GABA for instance, is taken up at high affinity by glia and GABAergic neurones, and the two uptake systems have been distinguished by the use of competitive analogues in vivo and in vitro. Consequently, autoradiographic location of neuronal GABA uptake has become a useful method for recognition of GABAergic neurones. However, in the case of glutamate, the site(s) of high-affinity uptake are not well established and there are contradictions in the literature between results obtained by different methods. Biochemical studies on compartmentation in the metabolism of glutamate and the related amino acids GABA, aspartate and glutamine indicate strongly that glutamate uptake is exclusively located in glia. This is in accordance with the hypothesis of a neuronal-glial cycle in which glutamate passes from neurones to glia, and is returned to the neurones as glutamine. In vitro studies of uptake into isolated cell types show a high glial capacity for glutamate uptake. Studies of neuronal glutamate uptake in vitro are few and the results, although equivocal, indicate a lack of high-affinity uptake. Autoradiography of uptake of glutamate, or the non-metabolisable analogue, D-aspartate, has been performed in vivo by several groups of workers at the light and EM level. Some have reported only glial uptake, while others have reported a predominantly neuronal uptake of glutamate and have used this as a criterion for the presence of glutamatergic neurones. Considerable support for this interpretation comes from the finding that transection of the relevant pathways leads to a substantial reduction in the target tissue capacity for high-affinity glutamate uptake. Selective killing of supposed glutamatergic populations of neurones such as cerebellar granule neurones also leads to loss of glutamate uptake.
The Role of Support Cells in the Growth and Differentiation of Neurones in the Abdominal Ganglion of Aplysia
Authors: Schacher Samuel M.
Published: April 2021

During the late premetamorphic stages of development, the abdominal ganglion of Aplysia is surrounded by a group of support cells which later develop morphological properties characteristic of glial cells. These support cells contain large secretory granules whose contents are released primarily after the onset of the metamorphic phase. The release of the granule contents may signal the burst of neuronal growth and maturation that occurs following metamorphosis. The evidence supporting this idea is the following: (1) The release of the granule material after the onset of metamorphosis coincides with an increase in cell body growth and a more marked increase in the density of synapses within the neuropil. Both release and neuronal maturation can be blocked when metamorphosis is postponed by withholding the appropriate macroalgal substrate. (2) Premature release of the granule contents 2–3 weeks before metamorphosis with artificial sea water containing a high concentration of potassium results in an increase in cell body growth, density of synapses, and the number of spines formed and contacts received by specific identified cells. (3) Artificially inducing the release of the granule material in animals whose metamorphosis has been prevented (by withholding the appropriate substrate) still produces an increase in cell body growth and density of synapses. These results suggest that the release of material from support cell granules provides a general stimulus for neuronal differentiation including cell body growth, spine development, and synapse formation.
Invertebrate Neuroglia-Junctional Structure and Development
Authors: Lane Nancy J.
Published: April 2021

The morphological characteristics of the neuroglial cells of invertebrates are reviewed, including the ultrastructural and enzyme cytochemical features of their cell bodies and attenuated cytoplasmic processes, the various ways they ensheath the nerve cells, including the loosely myelinated condition, their modifications due to intraganglionic localization and their interactions with other glial cells in the form of homocellular junctions. The spectrum of heterocellular axo-glial associations that occur in invertebrates is considered with particular reference to the different kinds of intramembranous organization they exhibit as revealed by freeze fracture. Recent studies on glial cell development in a range of arthropods, during embryonic and pupal stages, reveal the importance of glial cell tight junctions in forming the tracer-excluding blood-brain barrier. These occluding junctions are now shown to be, in some cases, vertebrate-like in their complexity. The stages in their assembly, which may be concurrent with those of gap junction formation, reveal a number of differences from vertebrate glia. During metamorphosis, glial cells dissociate and the dynamics of the concomitant interglial junctional disruption and their intramembranous particle dispersal without apparent internalization, as well as their subsequent reassembly, are examined. The stimuli triggering these glial events and the physiological significance of the various glial modifications are considered.
Behavioural and Mechanosensory Neurone Responses to Skin Stimulation in Leeches
Authors: Kristan William B. , McGIRR STEPHEN J. , Simpson Gregory V.
Published: April 2021

Behavioural responses to electrical stimulation of mechanosensory neurones were characterized in two species of leeches, Hirudo medicinalis and Macrobdella decora. Depending upon the site and intensity of stimulation, the stimuli elicited one or a combination of five different responses: local bending, curling, shortening, whole-body bending or swimming. The electrical threshold for activating identified mechanosensory neurones, T (touch) cells and P (pressure) cells, was the same in all regions of the body. The voltage range over which the electrical stimuli produced progressively more mechanosensory impulses was the same as the range that produced different behavioural responses. These results suggest that the T and P mechanosensory neurones provide the entire sensory input for all the behavioural responses. The production of different behavioural responses to stimuli of different intensities at the same location are attributable to different firing rates of the same sensory cells, and different responses to the same stimulus at different locations suggest different interneuronal targets for the T and P cells in different body regions.