bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of Mechanical and Energetic Estimates of Flight Cost for Hovering Sphinx Moths
Authors: Casey Timothy M.
Published: April 2021

Mechanical power output, based on measured power input, is compared with calculated values for aerodynamic and inertial power output in sphinx moths ranging from 350 to 3400 mg. Aerodynamic power output, calculated from momentum and blade-element aerodynamic theories, scales with the 1·08 power of body mass, amounting to about 40% of the mechanical power output of large moths to about 15% in the smallest individuals. Calculated value for the inertial power cost of hovering represents a larger fraction of the mechanical power output than the aerodynamic cost in all moths, with the value increasing as body mass decreases. Independent estimates of inertial power output based on metabolic data are similar to those obtained from calculations of the moment of inertia for the wings. These data suggest that inertial power output represents the largest power requirement for hovering sphinx moths, and that elastic torques do not significantly reduce the mechanical power output. Higher mass-specific power input of small sphinx moths appears to be the result of greater mass-specific inertial power requirements. Estimates of flight cost based on morphology and flight mechanics of sphinx moths yield values for mechanical power output which are similar to values estimated from their flight metabolism.
Effects of Speed and Extent of Stretching on The Elastic Properties of Active Frog Muscle*
Authors: Cavagna Giovanni A. , Citterio G. , Jacini P.
Published: April 2021

The work done during fast recoil of active striated muscle (as in a jump) was measured at 2 and 12 °C by making tetanized frog sartorii shorten from about 2 mm above slack length, l0, at high speed(6–9 l0. s-1)( 1) during a state of isometric contraction and (2) after stretching the muscle, while active, at different speeds and by different amounts. The work done increases with the force developed by the muscle according to a sigmoidal curve, having a point of inflexion that is displaced to greater values of force at 12 °C than at 2 °C. Previous stretching leads to an upward shift of this curve, i.e. to an iso-force gain of energy. This gain increases towards a maximum as the speed and extent of stretching are increased, attaining 60–80% of the total work done from a state of isometric contraction ; this fraction decreases when stretching begins from lengths smaller than l0. The apparent elastic behaviour of muscle is thus described by a set of curves rather than by a single curve. Active muscle behaves as a more rigid structure when it transmits the generated force to an external load (as in an isometric contraction) and as a more compliant structure when, stretched by an external force, it has the opportunity to store external mechanical energy.
An Electromyographic Analysis of the Elevator/Depressor Muscle Motor Programme in the Freely-Walking Scorpion, Paruroctonus Mesaensis
Authors: Bowerman Robert F.
Published: April 2021

Electromyograms from the elevator and depressor muscles, together with tarsal claw receptor activity, were recorded from the fourth legs of freely walking scorpions. The slope of the depressor burst duration versus step cycle time was less for short cycle times, below about 600 ms, than it was for longer cycles. The opposite was true for the elevator burst duration versus step cycle relationship, and the slope for longer cycle times was not significantly different from zero. The switching of motor activity between antagonists at the stance to swing phase transition was different from that of the swing to stance phase. The depressor burst invariably terminated before the elevator burst, while the elevator burst frequently did not terminate until after the depressor burst had begun. A similar asymmetry of the elevator/depressor motor programme has been described for insect and crustacean preparations. The termination of the depressor muscle burst represents the initial peripheral indicator that the decision to step has been made centrally. The latency between the central decision and the time when the leg is lifted, as determined by tarsal claw receptor burst termination, can be as much as 125 ms. This observation is of importance when considering both intrasegmental and intersegmental neural control mechanisms of scorpion locomotion.
Respiratory, Ventilatory, Acid-Base And Ionoregulatory Physiology Of The White Sucker Catostomus Commersoni: The Influence Of Hyperoxia
Authors: Wilkes P. R. H. , Walker R. L. , Mcdonald D. G. , Wood C. M.
Published: April 2021

Blood gases, acid-base status, plasma ions, respiration, ventilation and cardiovascular function were measured in white suckers, using standard cannulation methods. Basic respiratory parameters under normoxia were compared to those in the active, pelagic rainbow trout and in other benthic teleosts. Sustained environmental hyperoxia (350-550 torr) increased arterial O2 (102-392 torr) and venous O2 (17-80 torr) tensions so that blood O2 transport occurred entirely via physical solution. Dorsal aortic blood pressure and heart rate fell, the latter due to an increase in vagal tone. Ventilation volume declined markedly (by 50%) due to a decrease in ventilatory stroke volume, but absolute O2 extraction rose so that O2 consumption was unaffected. While the preceding effects were stable with time, arterial and venous CO2 tensions approximately doubled within 4 h, and continued to increase gradually thereafter. This CO2 retention caused an acidosis (7·993-7·814) which was gradually compensated by an accumulation of plasma [HCO3–]. However, even after 72 h, arterial pH remained significantly depressed by 0·10 units. The gradual rise in plasma [HCO3–] was accompanied by a progressive fall in both [Na+] and [Cl–] ; [K+] and [Ca2+] remained unchanged. The responses of the sucker to hyperoxia are compared to those of the rainbow trout.
Renal Electrolyte and Fluid Excretion in the Atlantic Hagfish Myxine Glutinosa
Authors: Alt Jeannette M. , Stolte Hilmar , Eisenbach Georg M. , Walvig Finn
Published: April 2021

Hagfishes (Myxine glutinosa, Cyclostomata) are the only vertebrates whose body fluids are isoosmotic to seawater due to high sodium and chloride concentrations in the plasma. The unique mode of fluid and electrolyte handling of Myxine has been studied by micropuncture methods at the single nephron level. In the archinephric duct, which assumes the function of the tubular apparatus of higher vertebrates, no fluid or sodium is reabsorbed from the glomerular filtrate. Calcium, glucose and magnesium are reabsorbed whereas potassium and phosphate are excreted. The intravascular volume of M. glutinosa is mainly regulated by the filtration rate which greatly increases with increasing arterial as well as venous pressure.
Na+ and C1– Effluxes and Ionic Regulation in Tilapia Grahami, a Fish Living in Conditions of Extreme Alkalinity
Authors: Eddy F. B. , Bamford O. S. , Maloiy G. M. O.
Published: April 2021

The osmoregularity ability of the cichlid Tilapia grahami enables this fish to live in conditions of extreme alkalinity (Reite, Maloiy & Aashaug, 1974; Maloiy et al. 1978). In this paper we describe the ionic balance of T. grahami from Lake Magadi (East African Rift Valley) which has a pH value of around 10, temperature in the range 30–40 °C and an osmotic pressure of about 500 mOsm, the principal inorganic ions being sodium carbonate and bicarbonate (Table 1). We also describe ionic balance of fish in water with a high NaCl concentration and in fresh water.
Ocellar Excitation of the Dcmd: An Identified Locust Interneurone
Authors: Simmons Peter J.
Published: April 2021

Locusts, like most other insects, possess three ocelli, or simple eyes, in addition to two large compound eyes. Focussed images are not formed on the retinae of the ocelli (Parry, 1947; Wilson, 1978a) and ocellar neurones are influenced by changes in light intensity occurring over wide areas of the visual field. Some of the second-order neurones which extend from the retina of each ocellus to the brain have large axons -amongst the largest found in the locust central nervous system. They are expected to convey information about changes in light intensity to the brain with some urgency. At least two different ways in which these large second-order ocellar neurones (L-neurones) could influence the behaviour of a locust have been suggested. First, by monitoring changes in the orientation of the visual horizon they could contribute to the stability of flight (Wilson, 1978a; Stange & Howard, 1979; Simmons, 1980a). Second, they could facilitate the responses of some central neurones, such as those driven by the compound eyes, when light intensity is reduced (Parry, 1947) – for instance, when a shadow falls over the locust. The observations reported here show that the L-neurones boost the responsiveness of a pair of well-characterized central neurones when the overall light intensity is rapidly decreased.
Correlation of Flight-Muscle Size and Body Mass in Cooper’s Hawks: A Natural Analogue of Power Training
Authors: Marsh Richard L. , Storer Robert W.
Published: April 2021

Muscle hypertrophy in response to increased load (e.g. power training) is well documented in laboratory animals and in man (see, for example, Thorstensson, 1976; Gonyea, Ericson & Bonde-Peterson, 1977), but this phenomenon has not been quantitatively linked to changes in the use of muscles by wild animals. In free-living animals, and sometimes even in those used in laboratory studies, predicting the stress placed on an individual muscle is difficult. Thus, evaluating a compensatory response in relation to a change in muscle use is also difficult. The flight muscles of birds, however, represent a system in which changes in muscle size can be quantitatively compared to the power output required for flight. We describe here a correlation of flight-muscle mass with body mass in Cooper’s hawks (Accipiter cooperii). We believe this correlation represents a natural analogue of power training. The variation in muscle mass between individuals can be directly related to differences in the power requirements for flight caused by differences in body mass.
The Effect of Progressive Hypoxia on Heart Rate, Ventilation, Respiratory Gas Exchange and Acid-Base Status in the Crayfish Austropotamobius Pallipes
Authors: Wheatly Michèle G. , Taylor E. W.
Published: April 2021

Male and female crayfish, Austropotamobius pallipes (Lereboullet) maintained a constant rate of O2 uptake during a progressive reduction in ambient O2 tension down to a critical tension (Pc) of 40 mmHg at 15 °c. Heart rate (fH) slowed progressively during hypoxia but blood flow was maintained by an increase in cardiac stroke volume. At a , of 50 mmHg the rate of ventilation had increased to 2·8 times the normoxic value. This was effected by a doubling in respiratory frequency (fR) accompanied by increases in both the mean amplitude of the pressure pulse and the mean hydrostatic pressure recorded in the branchial chambers. The effectiveness of removal of O2 from the water ventilating the gills was maintained (Ew), and there is evidence that the ability of the respiratory surface to transfer O2 improved during hypoxia. The hyperventilation enhanced CO2 elimination so that CO2 tensions were halved and respiratory alkalosis occurred in the haemolymph. This alkalosis had the effect of increasing the affinity of the blood pigment for O2, reducing the half saturation pressure (P50) from 8 to 4·5 mmHg. Thus despite reductions in pre- and postbranchial O2 tensions by 50% the arteriovenous O2 content difference was maintained and the effectiveness of removal of O2 into the blood (Eb) remained high in moderately hypoxic water ( 63 ± 1 mmHg). At , levels below 40 mmHg, when crayfish were denied access to air, they were unable to sustain the hyperventilation. Haemolymph O2 content and the a – v O2 content difference decreased, and as the haemolymph was no longer saturated with O2 on its passage through the gills, Eb was reduced. As a consequence of these changes fell. Under these conditions a partial switch to anaerobic metabolism occurred, with lactic acid accumulating in the haemolymph. The resultant metabolic acidosis partially offset the respiratory alkalosis.
Aerodynamic Capabilities of Flies, as Revealed by a New Technique
Authors: Blondeau Jean
Published: April 2021

Forces and torques exerted by fixed flying Calliphora erythrocephala were monitored with strain gauges. Calliphora was shown to have independent control of all possible parameters of motion (lift, thrust, side-slip, roll, yaw, pitch). During voluntary manoeuvres, the fly modulated several or all of these parameters simultaneously. Modulations of certain parameters were strongly correlated. Possible applications of the strain gauge apparatus and limitations in the use of open-loop experiments for the study of flight behaviour are discussed.
Neural Control of the Male Photuris Versicolor Firefly Flash
Authors: Carlson Albert D.
Published: April 2021

Continuous electrical stimulation of the ventral nerve cord or the lantern of the decapitated male Photuris versicolor firefly over a wide range of stimulus frequencies can produce a flash that is multi-peaked, like the courtship flash of this species. The central nervous system does not shape these stimulated compound flashes because they can be induced in deganglionated posterior lantern segments. The stimulated compound flashes show a fixed oscillatory character with peak frequencies independent of stimulation frequency. They can be generated by individual lantern areas. Compared with the peaks of courtship flashes the peaks of stimulated flashes show higher frequency, significantly lower temperature coefficients (Q)10, and incomplete extinction. P. lucicrescens males produce a courtship flash that has a single peak and their lanterns respond to continuous stimulation with an unstructured glow.
Ultrafiltration in the Branchial Heart Appendage of Dibranchiate Cephalopods: A Comparative Ultrastructural and Physiological Study
Authors: Schipp R. , Hevert F.
Published: April 2021

It is shown that ultrafiltration could be the first step in urine formation in Sepia officinalis and Octopus vulgaris. The organization of the podocytes indicates that ultrafiltration can occur through these cells. They have a thick basal lamina in contact with the peripheral blood lacunae, and the cell apices lie in infoldings of the lumen of the appendage. Comparison between the colloid-osmotic and the hydrostatic pressures of the fluids in the branchial heart and the pericardial coelom shows that an ultrafiltration can take place during the branchial heart systole as well as during a long phase of the diastole. Comparison of the osmolalities of blood, coelomic fluid, renal-sac fluid, and sea water shows that these species are hypoosmotic regulators.
The Effect of Filming Speed on the Interpretation of Arthropod Locomotion
Authors: Ward T. M. , Humphreys F.
Published: April 2021

Films of spider locomotion taken at about 270 frames per second (f.p.s.) were reanalysed to give effective filming speeds of 100, 50 and 25 f.p.s. Reanalysis of the data shows that mean values and variance for phase lag, period, stepping frequency and protraction/retraction ratios depart from the control values (270 f.p.s.) at slower sampling rates. Guidelines are presented for filming arthropod locomotion with high stepping frequencies and high or low p/r ratios. Most film analysis of arthropod locomotion has had insufficient time resolution to examine resolution-sensitive parameters such as the p/r ratio. Filming speeds giving sampling rates greater than 40 frames per step do not increase accuracy.
Coordination of Respiratory and Hydrostatic Functions of the Swimbladder in the Central Mudminnow, Umbra Limi
Authors: GEE JOHN H.
Published: April 2021

1. Observations of behaviour and changes in buoyancy of Umbra limi, a facultative air-breathing fish, were studied to understand coordination of respiratory and hydrostatic functions of the swimbladder. 2. Fish were exposed to either normoxic or hypoxic water in either undisturbed or disturbed (simulating predator presence) conditions. Declines in swimbladder volume occurred between air-breaths as O2 was removed. These varied between treatments averaging 1.3% in disturbed normoxic conditions, 4.1% and 6.4% in undisturbed treatments (normoxic and hypoxic conditions respectively), and 8.3% in disturbed hypoxic conditions. 3. To minimize the extent and rate of such changes and thereby reduce energy costs of a non-optimal buoyancy, fish either maintained a continuous positive buoyancy at the water surface, compressed the swimbladder gases after inspiration and gradually reduced the pressure to compensate for O2 uptake, or increased their reliance on aquatic O2. The use of any of the above mechanisms was determined by the amount of dissolved O2 and presence or absence of disturbance. 4. In normoxic water fish without access to the surface maintained neutral buoyancy despite a very limited ability to secrete swimbladder gases. 5. The frequency of air-breathing in normoxic water was independent of swimbladder O2 levels, indicating that fish breathe air in normoxic water in response to a decline in swimbladder volume. 6. The potentially conflicting roles of the swimbladder are well co-ordinated.
Analysis of the Flagellar Beat Pattern of Male Ectocarpus Siliculosus Gametes (Phaeophyta) in Relation to Chemotactic Stimulation by Female Cells
Authors: Geller Annette , Müller Dieter G.
Published: April 2021

Heterocontic male Ectocarpus siliculosus gametes respond to the sexattractant ectocarpen by changing their locomotive behaviour. However, the mode of action of the flagella is not changed by the presence of ectocarpen. High-speed cinemicrography shows that gametes moving close to a coverglass perform planar bending waves with their front flagellum. Straight or slightly curved swimming paths are generated by enhanced upward bends of the front flagellum to compensate for the asymmetrical insertion of both flagella. Narrower curves are connected with increasing downward bends of the front flagellum. There is a negative linear correlation between the average deflexion of the front flagellum (μm) from the cell axis and the radius of track (correlation coefficient 0·94). Additionally, freely swimming gametes exhibit elliptical and rotary wave motions, suggesting a relationship between thigmotaxis and mode of action of the front flagellum. The rigid hind flagellum performs one rapid sideward beat when the gametes swim in narrow curves. This appears to provide a steering function.
The Control of Transepithelial Potential Oscillations in the Salivary Gland of Calliphora Erythrocephala
Authors: Rapp P. E. , Berridge M. J.
Published: April 2021

The effects of the hormone 5-hydroxytryptamine, its analogues and its antagonists on the electrical activity and secretion rate of isolated salivary glands of the blowfly Calliphora erythrocephala were investigated. The secretion rate increases linearly with the logarithm of hormone concentration between 10−9 and 10−8M. At >10−8M the transepithelial potential depolarizes and rapidly attains a new stable value. However, at intermediate hormone concentrations, the potential does not maintain a stable intermediate value but displays sustained oscillations. These oscillations are not an artifact resulting from periodic variations in hormone concentration. The frequency of the oscillations increases with hormone concentration and with the concentration of external calcium and hormone analogues. The frequency decreases following the addition of lanthanum to the perfusion medium.

The experimental results suggest that the potential oscillation may be driven by an oscillation in the intracellular concentrations of cyclic AMP and calcium. It is argued that oscillatory control provides a reliable, noiseresistant strategy for controlling secretion rate.
Intracellular Recording of Electrical Activity in Muscle Cells of Intact and Isolated Dorsal Blood Vessel of the Earthworm Lumbricus Terrestris
Authors: Drewes C. D. , Denney M. R. , O’Gara B. , Vining E. P.
Published: April 2021

Intracellular electrical records from muscle cells in intact dorsal blood vessels of the earthworm, Lumbricus terrestris, showed a polarization rhythm which consisted of : (a) a prolonged ramp of depolarization, (b) one or a series of several non-overshooting spike potentials, (c) a sustained, hump-like depolarization, and (d) a complete repolarization. The polarization rhythm of the intact vessel was reset by intracellular current injection. Simultaneous recordings of intracellular electrical and mechanical activities during rhythmic pulsation waves of the intact vessel indicated that the ramp-like depolarization corresponded temporally to a gradual filling of the vessel with blood. Spike potentials occurred during the later portion of filling, and constriction began near the peak of the slow, sustained depolarization. Simultaneous intracellular and extracellular electrical records during rhythmic pulsations of the intact vessel indicated a close temporal correspondence between spike potentials in both electrical records. The repolarization phase in intracellular records corresponded to a small, slow wave in extracellular records. A polarization rhythm was usually absent in isolated preparations of the dorsal blood vessel, but in a few preparations rhythmic activity persisted for up to 1 h. In quiescent isolated preparations membrane potentials were stable (mean resting potential = −66·7 mV), but active membrane responses (non-overshooting spikes and sustained depolarizations), were evoked by intracellular current injection or by stretching of the vessel. Evidence from dual intracellular recordings in isolated dorsal vessels suggest that muscle cells are electrically coupled. The intracellular activity patterns in intact and isolated vessels, and the responsiveness of cells to current injection and stretching, suggest that both initiation and conduction of pulsation waves in the dorsal blood vessel are myogenic.
The Role of Venous Pressure in Regulation of Output from the Heart of the Octopus, Eledone Cirrhosa (Lam.)
Authors: Smith P. J. S.
Published: April 2021

The influence of perfusion pressure on stroke volume and heart rate was examined in the isolated ventricle. Input pressure, within the physiological range (10–20 cm of water), had a direct effect upon stroke volume and heart rate. Output back pressure had an inverse effect upon stroke volume and no effect upon heart rate. Sites that could vary input pressure were investigated by selective denervation in the whole animal. The results indicated that the efferent branchial vessel and auricle may be involved, as well as the branchial hearts and lateral venae cavae. It is proposed that the pressure of venous blood has a limited effect upon ventricular output in vivo.
Calcium Action Potentials in the Skeletal Muscle Fibres of the Stick Insect Carausius Morosus
Authors: Ashcroft Frances M.
Published: April 2021

The ionic requirements for the generation of action potentials in the ventral longitudinal muscle fibres of the stick insect, Carausius morosus, were investigated. Ca-free Ringer rapidly and reversibly abolished the action potential. In the presence of tetraethylammonium (TEA) ions (to suppress outward currents) the overshoot of the action potential changed 26 mV for a 10-fold change in [Ca]o. The maximum rate of rise of the action potential (measured in TEA Ringer) showed saturation at high [Ca]o. Cobaltous ions (20 mm) and the organic Ca antagonist D 600 (5 × 10−4 g/ml) reversibly inhibited the action potential ; the inhibitory effect of 1 mm-La3+ was irreversible. Barium and strontium, but not magnesium, were able to substitute for calcium as charge carriers. These results suggest that an inward movement of Ca2+ underlies the action potential of Carausius fibres.
Multiple Postsynaptic Actions of the Giant Dopamine-Containing Neurone R.Pe.D.1 of Lymnaea Stagnalis
Authors: Winlow W. , Haydon P. G. , Benjamin P. R.
Published: April 2021

Evidence is presented that the giant neurone R.Pe.D.1 is mono-synaptically connected to follower cells in the right parietal and visceral ganglia and has excitatory, inhibitory and biphasic postsynaptic actions. The spike to e.p.s.p. latency is increased to a new fixed value by high calcium saline, but not by saline in which both the Ca2+ and Mg2+ concentrations have been increased in proportion to one another. Three distinct classes of p.s.p. latency exist. Short e.p.s.p. and b.p.s.p. latencies of ca. 16·0 to 20 ms have been observed, as have longer e.p.s.p. and b.p.s.p. latencies, ca. 38−44 ms. An i.p.s.p. with a latency to onset of ca. 182 ms occurs on the J cells.
Electrical Activity and Relative Length Changes of Dog Limb Muscles as A Function of Speed and Gait
Authors: Goslow G. E. , Seeherman H. J. , Taylor C. R. , McCUTCHlN M. N. , Heglund N. C.
Published: April 2021

Electrical activity and length changes of 11 muscles of the fore- and hindlimbs of dogs walking, running, and galloping on a treadmill, were measured as a function of forward speed and gait. Our purpose was to find out whether the activity patterns of the major limb muscles were consistent with the two mechanisms proposed for storage and recovery of energy within a stride : a ‘pendulum-like’ mechanism during a walk, and a ‘spring-like’ mechanism during a run.

In the stance phase of the walking dog, we found that the supraspinatus, long head of the triceps brachii, biceps brachii, vastus lateralis, and gastrocnemius underwent only minor length changes during a relatively long portion of their activity. Thus, a major part of their activity during the walk seems consistent with a role in stabilization of the joints as the dog ‘pole-vaulted’ over its limbs (and thereby conserved energy).

In the stance phase of trotting and/or galloping dogs, we found that the supraspinatus, lateral head of the triceps, vastus lateralis, and gastrocnemius were active while being stretched prior to shortening (as would be required for elastic storage of energy), and that this type of activity increased with increasing speed.

We also found muscular activity in select limb flexors that was consistent with storage of kinetic energy at the end of the swing phase and recovery during the propulsive stroke. This activity pattern was apparent in the latissimus dorsi during a walk and trot, and in the biceps femoris during a trot and gallop.

We conclude that, during locomotion, a significant fraction of the electrical activity of a number of the dog’s limb muscles occurs while they undergo little or no length change or are being stretched prior to shortening and that these types of activities occur in a manner that would enable the operation of pendulum-like and spring-like mechanisms for conserving energy within a stride. Therefore these forms of muscular activity, in addition to the more familiar activity associated with muscle shortening, should be considered to be important during locomotion.
Homologies Between Body Movements and Muscular Contractions in the Locomotion of Two Decapods of Different Families
Authors: Paul Dorothy Hayman
Published: April 2021

The movements performed by the abdomen and tailfan during tailflipping in the sand crab Blepharipoda occidentalis (family Albuneidae) are described from an analysis of high-speed cinematic film (Figs. 1, 2, 3 A), and compared with component movements in the swimming-by-uropod-beating behaviour of the sand crab Emerita analoga (Family Hippidae) (Fig. 3 B; Paul, 1971). The most striking qualitative difference is the absence of uropod retraction and protraction in Blepharipoda. Comparisons of clectromyo-grams recorded from some of the principal muscles involved in these overtly very different behaviour patterns reveal that homologous muscles in the two sand crabs tend to be activated at comparable phase positions (Table 1). Tailflipping and uropod beating in the two crabs appear to be homologous, and to have been derived from ancestral macruran tailflipping.
The Involvement of Nerves in the Epithelial Control of Crumpling Behaviour in A Hydrozoan Jellyfish
Authors: King Michael G. , Spencer Andrew N.
Published: April 2021

The excitation pathways mediating the protective crumpling behaviour of Polyorchis penicillatus were studied with electrophysiological and ultrastructural techniques. Stimulating the subumbrellar endoderm consistently resulted in a complex crumpling potential when recorded with suction electrodes from radial muscle (the prime effector). The potential represents the summation of a quick radial muscle potential (RMP) and a slow endodermal canal pulse (ECP). The latencies of ECPs recorded from radial muscle during crumpling were directly proportional to the distance between the recording electrode and the subumbrellar stimulating electrode. Conversely, the latencies of RMPs, which were not tightly time-coupled to ECPs, were more directly related to the distance of the recording and stimulating electrodes from the marginal or apical termini of the radial muscle. Stimulating the exumbrellar ectoderm resulted in a variable crumpling response, typically occurring after facilitation of numerous exumbrellar pulses (EPs). Since exumbrellar stimulation did not usually excite endoderm, the response recorded from radial muscle normally involved a simple RMP, unassociated with an ECP. Typical synaptic junctions were observed between radial muscle processes and marginal neurites and between radial muscle and neurites of the radial nerve bundles along the length of the muscle. The independence of the ECP and RMP conducting pathways demonstrates that endoderm does not provide the direct source of radial muscle excitation and the initiation of RMPs at points of known (marginal) and suspected (apical) nerve-muscle contact suggests the involvement of nerves in the control of crumpling behaviour. These results are discussed in the light of other examples of active neuronal-epithelial interaction.
The Role of the Salivary Glands in Feeding in Rhodnius Prolixus
Authors: Ribeiro J. M. C. , Garcia E. S.
Published: April 2021

The effect of salivarectomy on feeding in Rhodnius prolixus was studied. Salivarectomized insects drew less blood and at a lower rate than controls when fed on a rabbit. Operated insects also pierced host skin much more often (10 times in 5 min) than controls (1 or 2 times in 5 min). None of these differences was observed when feeding was performed artificially through latex membranes. Intradermal injection of salivary secretion in rat tails increased the duration of bleeding induced by small cuts made on the injection site. It is suggested that the antihaemostatic action of saliva is important for positioning of the maxillae inside blood vessels.
The Presence of Gap Junctions in the Septate Desmosomes of the Salivary Apparatus of the Cockroach, Nauphoeta Cinerea
Authors: Maxwell David J.
Published: April 2021

The acini of the cockroach salivary apparatus consists of two morphologically distinct types of cell. These have been described by Bland & House (1971) and have been called peripheral and central cells. Ducts which convey the saliva to the hypopharynx are also associated with the acini. Electrophysiological experiments (Ginsborg, House & Silinsky, 1974) have demonstrated the presence of low-resistance junctions between the cells of the acini (coupling resistance of less than 0·2 MΩ). Septate desmosomes are a common feature of the acini and ducts and have been observed to link all of the cell types (Bland & House, 1971). Although in the past several authors suggested that septate desmosomes could act as low-resistance couplings between cells (e.g. Loewenstein, 1966; Gilula, Branton & Satir, 1970), it now seems probable that gap junctions are the sites of low-resistance pathways between cells (for reviews see : Sotelo & Korn, 1978; Peracchia, 1980). Gap junctions are often incorporated in septate desmosomes (Berridge & Oschmann, 1972; Satir & Gilula, 1973; Noirot-Timothée et al. 1978).
Neuroglia And Spinal Fluids
Authors: Somjen George G.
Published: April 2021

It is quite usual to see clear fluid collecting continuously on the surface of the spinal cord of ‘functionally decapitate’ cat preparations which have no functioning choroid plexus. The activity of potassium and calcium ions in interstitial fluid of these decapitate spinal cords is equal to that in spinal cords of cats with intact choroid plexus function, similar to normal cerebrospinal fluid, and different from blood plasma. It follows that fluid is being formed within the spinal cord by a process different from ultrafiltration. Endothelial cells seem likely to form this interstitial fluid by actively transporting Na+, with water following by osmotic force. Potassium and other ion concentrations may be adjusted by independent transport processes. A role could be attributed to glial cells in these transports if exchange of material could be demonstrated between glia and endothelium.
Comparative Studies on Glial Markers
Authors: Roots Betty I.
Published: April 2021

Macromolecular markers for glial cells have been sought for a variety of reasons. One of the earliest was the need for a means of assessing the purity of cell and subcellular fractions prepared from nervous tissue. While there is still a requirement for this kind of tool, emphasis has shifted towards seeking information on biochemical differentiation among cells and their functional interactions. A brief general review will be made of glial markers and two of these, 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP) and glutamine synthetase (GS), will be considered in detail. Until recently studies of markers have been concentrated on the higher vertebrates and those on lower vertebrates and invertebrates have hardly begun. However, such comparative studies may lead to fresh insight into old problems. For example, CNP has long been regarded as a marker for myelin and oligodendrocytes but it has not been possible to attribute a functional role to it and its relation to myelination has remained obscure. The finding that it is present in the glia of a moth Manduca sexta which lacks myelin provides a stimulus for a fresh approach to the problem. Another example is provided by studies on GS. This enzyme is found in astrocyte feet and preliminary results indicate that it is localized also in the perineurial glia of Aplysia ganglia. These results lead to a reconsideration of the perennial question of the possible role of astrocyte feet in barrier mechanisms. Extension of comparative studies may not only raise, new questions but also provide some answers.
Effect of Non-Neuronal Cells on Peptide Content of Cultured Sensory Neurones
Authors: Mudge Anne W.
Published: April 2021

The peptide substances P (SP) and somatostatin (SOM) are present in small-diameter neurones of dorsal root ganglia (DRG) and in small-diameter fibres that project to the spinal cord dorsal horn. It is not known whether SP or SOM coexist with other transmitter molecules but, since both peptides can be released from sensory neurones and both can alter neuronal firing rates in the dorsal horn, it seems likely that they are involved in some way in synaptic transmission in the spinal cord. SP has generally excitatory effects in the spinal cord whereas SOM exerts inhibitory effects, and it is not at all clear which subclass of nociceptive afferents contain SP or SOM.

Mudge, Leeman & Fischbach (1979) have studied sensory neurones derived from chick DRG grown in dissociated cell culture. When the neurones are grown in the absence of non-neuronal cells, they contain SP but relatively little SOM. The amount of SOM produced by these neurones is greatly increased (c. 50-fold) when the neurones are grown together with ganglionic non-neuronal cells or with medium ‘conditioned’ by incubation with such cells. The increase in SOM content is not accompanied by an increase in SP content or a detectable change in neuronal survival.

The DRG non-neuronal cells consist of two major cell types-glial cells and fibroblasts. Indirect evidence suggests that glial cells rather than fibroblasts are responsible for the increased production of SOM by the neurones. Raff and his colleagues (Brockes, Fields & Raff, 1979) have used immunological techniques to obtain purified cultures of these two cell types. Work currently in progress is aimed at extending the above observations to the rat and firmly establishing whether glial cells can indeed influence SOM production in sensory neurones.
Influences of the Glial Environment on the Elongation of Axons After Injury: Transplantation Studies in Adult Rodents
Authors: Aguayo Albert J. , David Samuel , Bray Garth M.
Published: April 2021

Tissue transplantation methods, previously used to study neural development, myelination and inherited disorders of myelin can be applied also to the investigation of repair and regeneration in the mammalian CNS. The elongation of axons from injured peripheral nerve or CNS has been studied in adult mice and rats by observing the growth of axons into PNS or CNS tissue grafts.

Following spinal cord injury and also after transplantation of optic nerves into the PNS there is axonal sprouting but these neuronal processes fail to elongate more than a few mm into the surrounding glia. On the other hand if segments of a peripheral nerve are grafted into the transected spinal cord, axons arising from spinal neurons and dorsal root ganglia become associated with the transplanted Schwann cells and elongate along the graft, approximately 1 cm. Recently the elongation of axons from spinal and medullary neurones was studied using a new experimental model which employed PNS grafts as ‘bridges’ to connect the spinal cord and the brain stem. In a series of adult C57BL/6J mice and Sprague Dawley rats, autologous segments of sciatic nerve were used to create ‘bridges’ between the lower cervical or upper thoracic spinal cord and the medulla oblangata. The spinal cord between these two levels was left intact.

Grafted segments examined by light and electron microscope 1−7 months after surgery were well innervated by Schwann cell ensheathed axons that had grown the entire length of the graft (2 cm in mice and 3−5 cm in rats). The origin and termination of these axons were determined by transecting the regenerated grafts and applying horseradish peroxidase to the cut ends. Retrogradely labelled neurones were found to be distributed widely in the gray matter of the spinal cord and medulla near the sites of insertion of the graft. Anterogradely labelled fibres coursing within the graft penetrated the CNS for short distances, approximately 2 mm.

These new results indicate that following CNS injury a conducive glial environment does allow spinal and brain stem neurones to elongate axons for distances that can be greater than those they usually extend for in the intact animal. This evidence that the regenerative response of similar axons differs in CNS and PNS neuroglia supports the hypothesis that influences arising from the environment play an important role in the success or failure of regeneration. The regenerative potentiality of central neurones may be expressed only when the CNS neuroglial environment is changed to resemble that in the PNS.
Membrane Properties of Neuroglia in the Optic Nerve of Necturus
Authors: Orkand R. K. , Orkand P. M. , Tang C.-M.
Published: April 2021

The optic nerve of Necturus has proved a useful preparation for the study of glial cell membranes in vivo and in vitro with anatomical relations to axons intact and isolated following axon degeneration. The glial membrane potential behaves as a selective potassium diffusion potential; there is no evidence of a significant permeability to other naturally occurring ions. The specific membrane resistance of the glial cells is high compared to that of neurones; there are low-resistance intercellular connexions among the cells which permit the passage of both ions and the dye Lucifer Yellow. The cells are readily and reversibly uncoupled by procedures which decrease the intracellular pH. There is no evidence for voltage-sensitive sodium channels in the membrane. Following sodium gain and potassium loss the membrane displays a potassium-dependent strophanthidin-sensitive electrogenic sodium pump. The glial membrane is depolarized by potassium released from active axons as well as by glutamate. The glial depolarization contributes to potentials recorded with surface electrodes. Depolarization by K+ plays a role in the redistribution of K+ which locally accumulates around active neurones and also affects glial metabolism and glucose uptake.
Ionic and Possible Metabolic Interactions Between Sensory Neurones and Glial Cells in the Retina of the Honeybee Drone
Authors: Coles J. A. , Tsacopoulos M.
Published: April 2021

This is a review paper that includes original calculations and figures. The drone retina is composed of two essentially uniform populations of cells, the photoreceptors and the glial cells. The photoreceptors contain many mitochondria but no glycogen has been detected; the glial cells contain much glycogen and very few mitochondria. The oxygen consumption of the photoreceptors in the dark is 20 μl min−1 per g of retinal tissue and in response to a single flash of light there is an extra consumption that reaches a maximum of 40 μl min−1 per g. In addition, light stimulation of the photoreceptors leads to changes in the glycogen metabolism of the glial cells, and to movements of K+. Measurements with intracellular Insensitive micro-electrodes showed that during light stimulation with a series of flashes the K+ activity (aK) in the photoreceptors fell by an average of 27% while in the glial cells aK rose by an amount that is estimated to correspond to most of the quantity of K+ lost by the photoreceptors. The relative contributions to the clearance of extracellular K+ of extracellular diffusion, spatial buffering and possible net K+ uptake by glial cells are discussed.
Induced Magnetization in the Monarch Butterfly, Danaus Plexippus (Insecta, Lepidoptera)
Authors: Jones Douglas S. , Macfadden Bruce J.
Published: April 2021

Eighteen preserved monarch butterflies, Danaus plexippus L., were analysed for their magnetic characteristics using a superconducting cryogenic magnetometer. These dead butterflies were either non-magnetic or possessed a natural remanent magnetization (NRM) indistinguishable from the background noise of the magnetometer (2 × 10−8 e.m.u. or less). Using a 500-gauss magnet, each specimen was induced with a magnetization which had a mean value of 1·27 × 10−6 e.m.u., indicating the presence of magnetic material in the monarch body.

Cutting the specimens into pieces, re-applying a strong field, and remeasuring revealed that most (about two-thirds or more) of the magnetization is concentrated in the head-thorax rather than the abdomen in contrast to the opposite situation reported for honey bees. The direction of the induced NRM, particularly in the horizontal plane, closely tracked the direction of the applied field. The intensities of induced magnetization and tracking of the applied field are similar to those reported for honey bees. There is no significant difference in the intensity or alignment of induced magnetization between males and females.
The Effects of Cooling On an Identified Reflex Pathway in the Cockroach (Periplaneta Americana), in Relation to Chill-Coma
Authors: Bradfisch G. A. , Drewes C. D. , Mutchmor J. A.
Published: April 2021

The effects of cooling were studied in relation to (a) the impairment of locomotion (i.e. chill-coma) and (b) the functioning of various components of the monosynaptic trochanteral hair plate reflex in the cockroach, Peri-planeta americana. The mean temperature for onset of chill-coma was 10·5 °C. At this temperature animals were unable to right themselves and visible tremors of the legs and body occurred. Extracellular recordings from metathoracic nerve 5 indicated that cooling from 24 to 15 °C caused a decrease in the background spiking rate of motor neurone Ds. However, cooling from 12 to 9 °C caused a marked increase in the spiking frequency of both Ds and other unidentified neurones. This increase in spiking activity is the probable basis of leg and body tremors that occur during chill-coma. Monosynaptic coupling between hair plate afferent spikes and Ds spikes (following electrical stimulation of the hair plate) was markedly affected by cooling. At 25 °C, hair plate afferent and Ds spikes were always tightly coupled to one another, whereas at 10 °C coupling was very weak. Several lines of evidence suggest that this loss of coupling was the result of failure of central synaptic transmission. The reduced effectiveness of central synaptic transmission during cooling may be a critical factor in the impairment of locomotor ability associated with chill-coma.
Respiration and Acid-Base Physiology of the Spotted Gar, A Bimodal Breather
Authors: Smatresk Neal J. , Cameron J. N.
Published: April 2021

In normally aerated water, at 20 °C, gar accounted for 42 % of their MO2 from their lungs, while in hypoxic water (PO2≃ 12 torr) their entire MO2 was from the lung, and O2 was lost through the gills. CO2 excretion in both normoxia and hypoxia was primarily via the gills.

Lung ventilation increased 1150%, accompanied by an elevation of pulmonary perfusion from 5·9 to 12·1 ml · kg−1 · min−1 in hypoxia, which accounts for the enhanced pulmonary MO2. Cardiac output increased from 31 to 40·5 ml · kg−1 · min−1 and systemic perfusion was maintained in hypoxia.

The difference in acid-base status between pre-and post-branchial blood (PCO2, pH and total CO2), changed only slightly during hypoxia, but the oxygen difference reversed. Normal dorsal aortic (DA) PCO2 was 23·8 torr, ventral aortic (VA) 20·3; during aquatic hypoxia the mean values were 21·9 and 22·6, respectively. Blood pressure rose in both the VA and DA in hypoxia but the branchial vascular resistance did not change. The oxygen transfer factor did not change significantly between normoxia and hypoxia.

Anatomical studies of the gill microvasculature revealed a reduced and channelized lamellar circulation. No respiratory shunt pathways were found around the lamellae.

The physiological and anatomical data indicated that the gar did not change lamellar perfusion or use shunt pathways to avoid hypoxic O2 loss.
Respiration and Acid-Base Physiology of the Spotted Gar, A Bimodal Breather
Authors: Smatresk Neal J. , Cameron James N.
Published: April 2021

Transfer from fresh water to 50% sea water (SW) at 26 °C increased the blood osmolarity of spotted gar (Lepisosteus oculatus) from 275 to 310 mosmol during the first 24 h. It then returned slowly to freshwater levels by 5 days after the transfer. The arterial pH dropped sharply, from 7·69 in fresh water to 7·46 in 50% SW, as a result of a small elevation in the blood CO2 partial pressure, and a marked metabolic acidosis. The respiratory (CO2) portion of the acidosis appeared to be a result of the reduction in branchial ventilation, and possibly permeability as well. The metabolic portion of the acidosis was not due to the accumulation of lactic acid, but probably involved a disruption of the extracellular strong ion difference in the saltier medium. The metabolic acidosis did not diminish during 5 days.

The rate of air breathing rose from 7 to 20 bph during 50% SW exposure. The control of pulmonary ventilation was directly responsive to the availability of O2, in general increasing when O2 was limiting (e.g. 50% SW transfer, hypoxia) and decreasing in hyperoxia. CO2 had no affect on the rate of air breathing. Withdrawal from 5–20% of total lung volume elicited an immediate air breath during hypoxia, but the response was inconsistent in normally aerated water. Lung inflation with O2 prolonged the interval between air breaths, but inflation with N2 did not change the rate of air breathing. Thus, pulmonary ventilation was secondarily controlled by lung volume. Gill ventilation frequency fell in 50 % SW, despite a respiratory and metabolic acidosis, while gill ventilation increased in response to treatment with acetazolamide. Hyperoxia caused a marked depression of gill ventilation, despite a respiratory acidosis. The gill ventilation rate appears to be most closely linked to oxygen, but may be affected indirectly by CO2 through the Root or Bohr effects.