bluuebunny/crossref_metadata_2025 huggingface dataset:
Duration of Testis Activity of Sturnus Vulgaris in Relation to Type of Illumination1
Authors: Bissonnette Thomas Hume , Robert Wadlund Arthur Pehr
Published: April 2021

Between January 24th and April 22nd, 32 male starlings, with females, were subjected to (a) no added light (controls), (b) 1-7 foot candles of filtered red light together with the total light from a General Electric Company’ s “sunlamp” at about 3 ft. distance, approximating to midsummer mid-day sunlight, and (c) 1-7 foot candles of filtered red light, after dark for 6 hours, in addition to a 912 hours constant daily daylight period (about 18 min. reduction from the daylight period in nature at the beginning of the experiment). Samples from (a), (b) and (c) groups were killed for study after 18, 25, 32 and 60 days, and from (c) group also at 88 days. Testes of controls (a) underwent a slight regression, remained smaller than at the first killing, and did not increase in germ-cell or other gonadal activity. Testes of birds in (c) group were slower to reach their maximum size and spermatogenesis (60 days) than were those from (b) group (32 days), with their more intense light and approximately double the amount of red rays. Both sets of birds failed to maintain their maximum size and spermatogenesis, though the more slowly reacting (c) group maintained it longer than did the (b) group. The reaction differences are such as to indicate that differences in light intensity and amount of red rays caused the observed differences in relative length of the phases of the sexual cycle and, particularly, in the length of periods of maximum testis size and activity rather than any specific action of ultra-violet rays or excess of green light. Even on the highly stimulating exposures to light used, the duration of maximum spermatogenic activity was limited and varied with different birds, with different exposures to light, and with different types of light, and the consequent rates of germ-cell activity. The duration of any phase of the sexual cycle bore an inverse relation to the effectiveness of the stimulating exposure to light, which, in turn, depended on the daily period, intensity, wave-length and rate of change of illumination. Alternative modes of causation of these phenomena and the probable mediation of the anterior lobe of the hypophysis in the reactions are discussed.
Studies on the Nutrition of Blow-Fly Larvae
Authors: Hobson R. P.
Published: April 2021

Investigation of the feeding of Lucilia larvae on meat suggested that the chief factors involved are mechanical maceration and the alkaline reaction which results in the first place from bacterial action. Larvae suck the fluid serum from acid muscle ; they ingest semi-liquid food only when the reaction is alkaline or the free liquid has been removed. Predigestion of the muscle substance is apparently not essential, as the crop contents often consist of insoluble protein. The proteolytic enzymes in the larval excreta, which include a collagenase, probably serve to digest the structural parts of muscle tissue.
Studies on the Nutrition of Blow-Fly Larvae
Authors: Hobson R. P.
Published: April 2021

Lucilia larvae fail to grow at the usual rate when reared aseptically on sterile unheated muscle (guinea-pig). Infection with B. coli, a non-liquefying organism which does not form ammonia, restores normal growth. Adding yeast extract to muscle produces the same effect on larval growth as infection with bacteria. It is therefore concluded that muscle is deficient in a growth-promoting factor which is normally supplied by the natural flora ; also, that bacterial action is not essential for the liquefaction of the muscle. From preliminary experiments the growth factor does not appear to be identical with vitamin Bj or B2. Yeast extract which has been autoclaved at an alkaline reaction retains most of its activity and is not less potent than ox-liver extract. When larvae are reared aseptically on muscle, they feed at first on the serum owing to the persistence of the acid reaction. However, this does not explain their slow development since sterile larvae grow well on beef juice.
Iodine Compounds and Fertilisation
Authors: Carter G. S.
Published: April 2021

In the earlier papers of this series (Carter, 1930-32) it has been shown that a compound which is related to thyroxine in chemical structure plays an essential part in the fertilisation of the gametes of Echinus esculentus and E. miliaris. Evidence has been brought forward that this substance is present in the ripe egg, being formed during the later stages of its ripening, and that it is concerned in the increase of chemical activity which occurs in the egg after fertilisation. It is probably identical with or closely related to Lillie’s fertilizin. It is also present in the egg secretions and in the ripe sperm. Further, the similarity between the effects produced by the secretions and by thyroxine on sperm which was not perfectly ripe (in the sense previously defined, 1931 a, p. 180), and the fact that the behaviour of such sperm in the presence of thyroxine became identical with that of ripe sperm led to the conclusion that this substance is formed within the sperm during the later stages of its ripening, as it is formed in the ripening of the egg.
Swimming Energetics of Striped Bass (Morone Saxatilis) and Bluefish (Pomatomus Saltatrix): Hydrodynamic Correlates of Locomotion and Gill Ventilation
Authors: Freadman M. A.
Published: April 2021

Swimming patterns of striped bass and bluefish were monitored using a miniature accelerometer to record instantaneous acceleration and instantaneous deceleration during tail-thrusts over a wide range of swimming speeds. In addition, ventilatory excurrent flow patterns were visualized in swimming striped bass by injecting milk via a buccal catheter. Both species accomplish steady swimming with both symmetric and asymmetric thrusts; other transient swimming patterns were observed as well. Over the transition range from active branchial to ram gill ventilation, no measurable change in forward acceleration amplitude occurred with adoption of ram gill flow in both species; this can only occur if drag does not change over the ventilatory transition. From metabolic measurements and from implications about swimming drag deduced from acceleration amplitude, the cost of active ventilation just prior to adoption of ram gill ventilation was estimated to be 8-i % and 8-4% of total metabolism for striped bass and bluefish respectively. Ventilatory effluent flow patterns during cyclic ventilation in swimming striped bass induce substantial turbulence and probably boundary layer separation. Flow patterns during ram ventilation result in streamlined flow over most of the length of the fish. The results show that transfer from active to branchial to ram gill ventilation provides important hydrodynamic advantages to these fishes at cruising velocities.
Further Observations on the Serotonergic Cerebral Neurones of Helisoma (Mollusca, Gastropoda): The Case for Homology with the Metacerebral Giant Cells
Authors: Granzow Bonnie , Rowell C. H. Fraser
Published: April 2021

A bilaterally symmetrical pair of serotonergic neurones in the cerebral ganglia of the snail Helisoma trivolvis has major features in common with the serotonergic cerebral cells of other gastropods, including those of Helix and Aplysia. The cells were found to receive a high level of inhibitory synaptic activity which is important in determining their firing level. In the cells of isolated cerebral ganglia, tonic inhibitory synaptic potentials, uniform in frequency and amplitude, occur continually at a rate of about 2/s. In the cells of cerebral ganglia left intact with the periphery and buccal ganglia, phasic inhibitory activity occurs in addition to the tonic activity. Phasic inhibitory input could be observed at regular intervals, correlated with feeding motor activity in the buccal ganglia. Other properties of these cells include: a linear relationship between membrane potential and current injected into the cell; communication between bilateral cells in about 50% of the preparations studied; and sodium-based somatic action potentials. Some of these properties of Helisoma SCCs are different from those of Helix and Aplysia. We propose that the Helisoma SCCs are homologous to those in other gastropods and that the differences observed are the result of evolutionary adaptation of the cells to different functional roles.
Studies on Water in Barnacle Muscle Fibres II. Role of ions and Organic Solutes in Swelling of Chemically-skinned Fibres
Authors: Clark M. E. , Hinke J. A. M. , Todd M. E.
Published: April 2021

Single muscle fibres from the giant barnacle, Balanus nubilis, were chemically skinned (2 % Tween 20), then equilibrated for 40 h in salt solutions ranging in ionic strength from 0·025 to 0·6 m at pH 7·0. The water content of the fibres and the net charge on the myofilaments increased with increasing salt concentration. Cation accumulation in the fibres was about equal to anion exclusion at all salt concentrations. When an organic solute (trimethylamine oxide, glycine, alanine, serine, proline, or glycerol) in the concentration range from 0·1 to 0·6 m was added to the salt solution, cation accumulation increased and water content decreased. Myofilament architecture was disrupted when the fibres were equilibrated in high salt (> 0·4 m) solutions and preserved when 0·5 M-triethylamine oxide was also added. The results are consistent with the view that organic solutes enhance the association between the fixed charge sites and their counterions. This hypothesis is examined quantitatively using the Oosawa relationship between the volume and the counterion association for cylindrical polyelectrolytes. The results illustrate that organic solutes can influence fibre volume in a way other than through osmo-regulation.
Vascular Resistance Responses of an Eel Tail Preparation: Alpha Constriction and Beta Dilation
Authors: Davie Peter S.
Published: April 2021

An isolated, saline-perfused, eel tail preparation is described. This preparation was easily prepared and did not suffer from progressive deterioration, as indicated by stable baseline resistance with time and maintained responsiveness to drugs. Elevation of caudal venous pressure caused a reduction in resistance of about 10% per 0·5 kPa. Addition of 3% or 5% human serum to the perfusate increased baseline resistance and imparted a degree of autoregulation to the preparation. Full dose-response curves for the preparation’s resistance responses to adrenaline (AD), noradrenaline (NA), and isoprenaline are presented. AD and NA increased resistance, indicating the presence of alpha adrenergic receptors. AD was more potent than NA; the mean potency ratio was 2·78:1 ·00 (AD: NA). Isoprenaline decreased resistance, indicating beta adrenergic receptors. From the relative potencies of isoprenaline ≪ AD < NA in stimulating these receptors, they are classified as beta two adrenergic receptors. The possible physiological functions of alpha and beta responses of the eel tail are discussed.
Thoracic Leg Control of Abdominal Extension in the Crayfish, Procambarus Clarkii
Authors: Page Charles H.
Published: April 2021

Postural extensions of the abdomen of the crayfish, Procambarus clarkii, could be evoked by mechanical stimulation of a single thoracic leg. Movement of a single leg joint was sufficient to initiate an extension response. Vigorous abdominal extensions were initiated either by depression of the whole leg (WLD) or by flexion of the mero-carpal joint (MCF). Weaker extension responses were obtained by depression of the thoracic-coxal and coxo-basal joints. Similar stimulation of the chelipeds did not elicit an abdominal extension response.

Single-frame analysis of motion pictures of crayfish responding to WLD or MCF stimulation of a 2nd thoracic leg showed that the responses evoked by the two different stimulus situations were nearly identical. They differed principally in the responses of the leg located contralateral to the stimulated leg.

Movements of most of the cephalic, thoracic and abdominal appendages accompanied the abdominal extension response. Only the eyes remained stationary throughout the response. The mean values of the latencies for the initiation of appendage movement ranged from 125 to 204 ms; abdominal movement had a mean latency of about 220 ms.

The abdominal extension reflex resulted from the activity of the tonic superficial extensor muscles. The deep phasic extensor muscles were silent during the response. The mean latencies for the initiation of superficial extensor muscle activity by WLD and MCF stimulation were 53·7 and 50·0 ms respectively.
Activity of Excitor and Inhibitor Claw Motor Neurones During Habituation and Dishabituation of the Crayfish Defence Response
Authors: Hawkins R. D. , Bruner J.
Published: April 2021

The activity of the opener excitor and inhibitor motor neurones was recorded during habituation and dishabituation of the defensive claw opening response in partially restrained crayfish (Astacus sp.). Claw opening evoked by brief tactile stimulation of the thorax undergoes habituation if the stimulation is repeated at 30 s or 1 min intervals. This habituation is accompanied by a progressive decrease in evoked excitor activity, while the activity of the inhibitor remains unchanged. The habituated claw opening response can be dishabituated by tactile stimulation of the claw or head, or by visual stimulation. Dishabituation is accompanied by both an increase in evoked excitor activity and a decrease in evoked inhibitor activity. Dishabituation is also accompanied by potentiation of claw opening: that is, the same number of excitor and inhibitor spikes produce greater claw opening following dishabituating stimulation. The potentiation of claw opening following dishabituation is due in part to post-tetanic potentiation (PTP) at the excitor neuromuscular junction. PTP was demonstrated with physiological parameters of stimulation in isolated claw preparations, and is of sufficient magnitude and duration to account for the observed potentiation. These results contradict the conclusion from an earlier study (see Schone, 1961) that habituation of the claw opening response is due to an increase in inhibitor activity. They also provide new evidence for a role in dishabituation of both disinhibition and PTP.
Innervation Patterns of Fast and Slow Motor Neurones During Development of A Lobster Neuromuscular System
Authors: J Costello Walter , Hill Russell , Lang Fred
Published: April 2021

Relationships between motor innervation and muscle fibre type were examined in the closer muscle of the claws of the lobster Homarus americanus. The dimorphic claws of the adult-the cutter and crusher-were compared with the claws of the juvenile (stages 4–6) when differentiation takes place. The muscle is known to receive a fast and a slow motor axon. Previous findings have shown that the crusher contains mostly slow fibres ; the cutter and juvenile claws have both fast and slow fibres. In the adult, the majority of fibres in the crusher received fast and slow axons; in the cutter most fibres received the fast axon. Fast fibres in the cutter claw were innervated by the fast axon, alone or with the slow axon. Slow fibres in both claws could receive the slow axon only, or both axons. Some slow fibres in the crusher claw were innervated primarily or solely by the fast axon. In the juvenile, most fibres in each claw were innervated by both axons. The juvenile synapses were immature; postsynaptic potentials fluctuated greatly with frequent failures. The homologous fast axons in these claws formed fatigue-resistant synapses. In both adult and juvenile, regardless of fibre type, fast axon synapses had poor facilitation ; slow axon synapses had moderate-to-high facilitation.
A Note On the Cell Water Density in Amphibian Eggs
Authors: Mild Kjell Hansson , Løvtrup Søren
Published: April 2021

In a recent publication of ours on cell water density in amphibian eggs (Hansson Mild, Løvtrup & Forslind, 1979), the relation between the egg density, ρ, and the water content was established experimentally. It was then assumed that ρ could be theoretically related to the cell water density, ρω, and the density of the solids in the cell, ρs, on a weight average basis (equation (10) in Hansson Mild et al. 1979). However, this assumption is not correct, a fact which has been brought to our attention by Drs W. Drost-Hansen and J. Clegg (personal communication, 1980). Instead the egg density should be related to ρω and ρs on the basis of volume fractions as derived below.
Underwater Hearing in the Frog, Rana Catesbeiana
Authors: Lombard R. Eric , Fay Richard R. , Werner Yehudah L.
Published: April 2021

Comparable auditory sound pressure level (SPL) and sound intensity level (SIL) threshold curves were determined in air and under water in Rana catesbeiana. Threshold curves were determined using chronic metal electrode implants which detected multi-unit responses of the torus semicircularis to incident sound. In terms of SPL, hearing thresholds in water and air are similar below 0·2 kHz. Above 0·2 kHz, the sensitivity under water falls off at about 16 dB/octave to reach an average loss of about 30 dB above 0·4 kHz. In terms of SIL, the organism is about 30 dB more sensitive under water than in air below 0·2 kHz and equally sensitive in air and water above 0·4 kHz. The relative merits of the two measures are discussed and an attempt is made to relate the results to morphology of the middle and inner ears. This report is the first to compare aerial and underwater hearing abilities in any organism using electrode implants.
Hindlimb Muscular Activity, Kinetics and Kinematics of Cats Jumping to Their Maximum Achievable Heights
Authors: Zajac Felix E. , Zomlefer Michael R. , Levine William S.
Published: April 2021

Cats were trained to jump from a force platform to their maximum achievable heights. Vertical ground reaction forces developed by individual hindlimbs showed that the propulsion phase consists of two epochs. During the initial ‘preparatory phase’ the cat can traverse many different paths. Irrespective of the path traversed, however, the cat always attains the same position, velocity and momentum at the end of this phase. Starting from this dynamic state the cat during the subsequent ‘launching phase’ (about 150 ms long) generates significant propulsion as its hindlimbs develop force with identical, stereotypic profiles. Cinematographic data, electromyographic data, and computed torques about the hip, knee and ankle joints indicate that during the jump proximal extensor musculature is activated before distal musculature. During terminal experiments when the hindlimb was set at positions corresponding to those in the jump, isometric torques produced by tetanic stimulation of groups of extensor and flexor muscles were compared with computed torques developed by the same cat during previous jumps. These comparisons suggest that extensor muscles of the hindlimb are fully activated during the maximal vertical jump.
The Effect of Long-Term Aerial Exposure on Heart Rate, Ventilation, Respiratory Gas Exchange and Acid-Base Status in the Crayfish Austropotamobius Pallipes
Authors: Taylor E. W. , Wheatly Michèle G.
Published: April 2021

When first removed into air, crayfish showed transient increases in heart rate (fH) and scaphognathite rate (fR) which rapidly recovered to submerged levels and were unchanged for 24 h. The rate of O2 consumption increased from an initially low level and was then maintained for 24 h in air at the same level as in settled submerged animals. There was an initial acidosis in the haemolymph which was both respiratory and metabolic due to the accumulation of CO2 and lactate. Progressive compensation by elevation of the levels of bicarbonate buffer in the haemolymph and reduction of circulating lactate levels returned pH towards submerged levels after 24 h in air. Exposure to air resulted in a marked internal hypoxia with haemolymph O2 tensions, both postbranchial and prebranchial remaining low throughout the period of exposure. The oxygen content of the haemolymph was initially reduced, with content difference close to zero. Within 24 h both and had returned towards their levels in submerged animals. These changes are explained by the Bohr shift on the haemocyanin consequent upon the measured pH changes. After 48 h in air, and fH were significantly reduced and ventilation became intermittent. There was a slight secondary acidosis, increase in lactic acid levels and reduction in content difference in the haemolymph. When crayfish were returned to water after 24 h in air, ,fH and fR were initially elevated by disturbance and there was a period of hyperventilation. In the haemolymph there was an initial slight alkalosis, and an increase in and lactic acid. All variables returned to their settled submerged levels within 8 h.
Branchial Ionic Uptake and Acid-Base Regulation in the Rainbow Trout, Salmo Gairdneri
Authors: Perry S. F. , Haswell M. S. , Randall D. J. , Farrell A. P.
Published: April 2021

Amiloride (10−4 M) inhibited sodium uptake in rainbow trout by 78% and was associated with a pronounced acidosis and decreases in both plasma total CO2* and [HCO3−]. 4-acetamiao-4′-iso-thiocyanatostilbene-2,2′disulphonicacid (SITS) (10−4 *m) in the bathing medium inhibited chloride uptake by 66% and following 6 h a significant decrease in plasma [H +] and significant increases in and [HCO3−] were observed. Inhibition of chloride uptake (50%) with external sodium bicarbonate (12 mm) resulted in a more rapid and pronounced alkalosis than did SITS inhibition. Hypercapnic acidosis had no significant effect on the rates of branchial sodium and chloride uptake. Increasing the concentration of sodium in the bathing water resulted in a less pronounced acidosis and a more rapid pH recovery during hypercapnia. These results are discussed with reference to the gill as an acid-base regulating structure. These findings are consistent with a gill model previously presented by Haswell, Randall & Perry (1980).
Locomotion in Burrowing and Vagrant Wolf Spiders (Lycosidae)
Authors: Ward T. M. , Humphreys W. F.
Published: April 2021

Locomotion in the vagrant wolf spider Trochosa ruricola is compared to that in the burrow dwelling wolf spider Lycosa tarentula (Araneae: Lycosidae). L. tarentula takes relatively shorter steps than T. ruricola. At high speeds T. ruricola approximates an alternating tetrapod gait but this does not occur in L. tarentula. Phase lag differs between species and varies marginally with speed except for ipsilateral phase lags in L. tarentula which are erratic if they include leg 1. In both species the protraction/retraction ratio is directly related to both running speed and stepping frequency, but the relationship is more marked in L. tarentula. The protraction/retraction ratio is more variable in leg 1 and varies between legs along the body but by a greater amount in L. tarentula. In these spiders, in contrast to the situation in many insects, both the duration of protraction and retraction show marked inverse relationships to stepping frequency. The power stroke (retraction) occupies a variable proportion of the stepping cycle, which is not the case in other spiders, and this proportion is lower than for other spiders.

It is suggested that the first pair of legs is used more for sensory than for locomotory purpose and that this is more marked in the burrow dwelling species, L. tarentula.
Short Communications: Steady State Potential in the Developing Oocytes of Locusta Migratoria: Passive and Active Components
Authors: Wollberg Z. , Cocos R.
Published: April 2021

Ovarioles of the African migratory locust (Locusta migratoria) are of the panoistic type, where each oocyte is surrounded by a layer of follicle cells, and a single ovariole forms a longitudinal chain of ‘follicles’ held together by an ovariole sheath. In an earlier publication (Wollberg, Cohen & Kalina, 1976) we demonstrated that in this species, a potential difference exists across the ‘follicle’ wall (defined hereafter as ‘oocyte potential’), ranging between 30 and 55 mV (inside oocyte negative in respect to external grounded medium), with the more mature oocytes possessing larger potential differences than the less-mature oocytes. We have also shown that all the follicles along a single ovariole were electrotonically and histologically coupled by oocyte follicle cell gap junctions. The ionic basis of oocyte and egg potentials have been investigated in several animal species, invertebrates and vertebrates (e.g. Powers & Tupper, 1975; Miyazaki & Hagiwara, 1976; Shen & Steinhardt, 1976; Ziegler & Morrill, 1977). In most of these cases, oocyte membrane potentials were determined, primarily, by the passive distribution of potassium ions and to a lesser extent by sodium ions. For some species the involvement of an undefined metabolic electrogenic pump, in maintaining the steady-state oocyte potential, was proposed (Powers & Tupper, 1975; Miyazaki & Hagiwara, 1976; Ziegler & Morrill, 1977). In the present report we show that the steady-state oocyte potential of Locusta migratoria is mainly determined by the passive distribution of potassium ions and by an ouabain-sensitive electrogenic Na/K pump.
The Hydrodynamic Drag of Swimming Bluefish (Pomatomus Saltatrix) in Different Intensities of Turbulence: Variation With Changes of Buoyancy
Authors: Ogilvy Christopher S. , Dubois Arthur B.
Published: April 2021

Thrust and drag were calculated for ten bluefish using Newton’s law, F = ma, the measured acceleration of the fish, and one essential assumption, without which only the sum of thrust and drag could be determined. Any time the thrust is zero, the drag equals the mass of the fish times its negative acceleration. For reasons given in the full text, the thrust is believed to drop to zero twice per swimming cycle, and never become negative. Zero thrust thus occurs at the negative acceleration peaks. For acceleration waveforms that are symmetric, zero acceleration lies at a level half way between the levels of the positive and negative peaks, so the peak negative acceleration is half the peak-to-peak height of the waveform. It is further assumed that the instantaneous drag thus measured at the negative acceleration peaks equals the mean drag averaged over the whole swimming cycle, which in turn equals the mean thrust. Turbulence, induced in the water tunnel by two flat metal plates placed in the stream in front of the fish, or by rotation of a mixing rod, did not change the drag, or the fish’s ability to produce thrust, as indicated by the maximal swimming speed. The attachment of two pressure transducer enclosures to the tail did not alter the maximal swimming speed. Changes of buoyancy were produced by inflation or deflation of balloons sewn into the swim bladders of three fish. The thrust calculated from fluctuations in the forward acceleration of the fish measured at zero speed during neutral buoyancy was 0·0 to 0· 14 N. If the non-zero values are genuine, they must be balanced by rearward forces from the pectoral fins. The thrust increased linearly with speed at the rates of 0· 40, 0· 64, and 0· 71 N per m.s•1, respectively, at speeds between 0 and 0· 8 m.s−1. The mean tail thrust of a negatively buoyant fish at zero water speed equalled or exceeded the body’s weight in water. Its forward component must be balanced by a rearward component of the lift force from the flapping pectoral fins. Upward components of the two forces support the weight of the fish. With 45 ml air removed from the swim bladder of a bluefish, the tail thrust diminished from 0·64 N at zero water speed to a value of 0·46 N as the water speed was increased to between 0· 2 and 0· 4 m.s−1, and then increased to 0· 71 N at a water speed of 1 m.s−1.
Contribution of Compound Eyes and Ocelli to Steering of Locusts in Flight
Authors: Taylor Charles P.
Published: April 2021

Locusts (Orthoptera, Acrididae) were tethered inside a simulated horizon visual display. Rotation of the horizon elicited following motions of the animal’s head and rudderlike movements during flight. Head and steering motions were still elicited after either the compound eyes or the ocelli were surgically ablated. Head motions after ocellar cautery suggested that the ocelli may function synergistically with the compound eyes to (a) minimize the delay of visual responses and (b) augment visual responses when no sharp horizontal border is present. Flight steering motions were found not to depend on proprioception of head position. Three other species (Diptera and Odonata) also followed horizon rotations with head motion after their compound eyes had been ablated.
Differentiation of the Chloride Extrusion Mechanism During Seawater Adaptation of A Teleost Fish, the Cichlid Sarotherodon Mossambicus
Authors: Foskett J. Kevin , Logsdon Craig D. , Turner Timothy , Machen Terry E. , Bern Howard A.
Published: April 2021

Opercular membranes isolated from the freshwater-adapted euryhaline teleost, Sarotherodon mossambicus, and mounted in Ussing-style chambers, have low conductance and current and do not actively transport chloride. In contrast, membranes isolated from seawater-adapted S. mossambicus have high conductance and generate large currents representing net chloride extrusion. Full development of this chloride secretion process requires 1–2 weeks, the time-course of which provides the first unambiguous measurement of changes in net extrarenal salt secretion associated with a teleost’s adaptation to seawater. Tissues from seawater-adapted fish contain typical chloride cells, when observed with the electron microscope, which appear as large cells with fluorescence microscopy after staining with dimethylamino-styrylaethylpyridiniumiodine. These cells are absent from the freshwater tissue, although rudimentary chloride cells are present, appearing as small cells with fluorescence microscopy. Following seawater transfer, the number of chloride cells increases only during the first 3 days. Subsequent chloride cell hypertrophy is highly correlated with the quantity of chloride extrusion. These data strongly implicate the chloride cell as the salt-secretory cell-type. When cortisol was injected into freshwater fish, chloride cell density increased but chloride secretion was not activated. It appears that development of salt extrusion involves increased numbers (controlled, at least in part, by cortisol) and differentiation of chloride cells, including activation of membrane active-transport sites. The opercular membrane from S. mossambicus provides a valuable model for studying these physiological and morphological events.
Fluid Balance in the Argasid Tick, Ornithodorus Moubata, Fed On Modified Blood Meals
Authors: Kaufman Susan E. , Kaufman William R. , Phillips John E.
Published: April 2021

The argasid tick Ornithodorus moubata Murray was fed on modified blood meals, the ionic strength and/or osmotic pressure of which was varied by additions of NaCl or glucose, and by dilution with distilled water or isosmotic glucose. The following parameters were monitored: total volume increase of tick, total volume of meal ingested, net increase in haemolymph volume, volume of coxal fluid excreted and ion concentrations and osmotic pressures of the gut contents, haemolymph and coxal fluid, as well as potential differences across the gut lumen. Absorption of fluid from the gut into the haemolymph appeared to be linked to the active transport of Na+ and Cl−, although the rate of absorption was an inverse function of the prevailing osmotic gradient across the gut epithelium. The tick can maintain a reasonably constant [Na+] and [Cl−] in the haemolymph when fed meals in which the concentration of these ions varies up to 6-fold, but only if the meal remains isosmotic with blood. The rate and volume of coxal fluid production are direct functions of the rate and volume of fluid absorption by the gut epithelium. Thus, during the feeding cycle, the coxal organ appears to function chiefly in an osmo- and volume-regulatory capacity in this species of argasid tick.
Localization and Characterization of Water Uptake from the Midgut of the Locust, Schistocerca Gregaria
Authors: Dow Julian A. T.
Published: April 2021

Water, potassium and sodium fluxes were measured across various regions of the locust gut under in vitro internal perfusion. The anterior caeca differed from the other gut regions, notably the posterior caeca, in being able to absorb water in the absence of an applied chemical or osmotic gradient. Absorption of sodium from the caecal lumen was active, and inhibited by 2,4-DNP or ouabain. Potassium was passively distributed across the caecal epithelium, and transmembrane fluxes were unaffected by toxins. A model for caecal water uptake was advanced, in which passive fluxes of potassium and chloride from the KCl-rich luminal fluid, combined with active sodium uptake, drives water into the blood, thus concentrating solutes within the caecal lumen.
Respiration in Exercising Fowl
Authors: Brackenbury J. H. , Gleeson M. , Avery P.
Published: April 2021

Respiratory water loss and rectal temperature were measured in domestic fowl running for 10 min on a treadmill at speeds of 1·24−4·3 hm h-1 in air temperatures of 20 ± 2 °C or 32 ± 2 °C. At given speeds the water loss at 32 ± 2 °C was approximately twice that at 20 ±2 °C and the end-exercise rectal temperature was 0·5−0·8 °C higher. At 20 ± 2 °C, respiratory evaporation accounted for 10−12 % of the total metabolic energy used at all speeds. At 32 + 2 °C, the fractional respiratory heat loss fell from 26−5 % at 1·24 km h-1 to 17 % at 3·6 km h-1. The fraction of the total metabolic energy stored as body heat rose progressively with air temperature.
Turnover of Monovalent Cations in Paramecium
Authors: Hansma Helen G.
Published: April 2021

Regulation of sodium and potassium by Paramecium was studied by measuring fluxes of 22Na and 86Rb respectively. Fluxes of these tracers had the following similarities. (1) Steady-state turnover showed approximately single-pool kinetics with 50% turnover in h. (2) Efflux of both cations showed a specific exchange diffusion when the medium contained the corresponding non-radioactive cation. (3) The net efflux of both cations was slow in the absence of exchange diffusion.

Fluxes showed the following differences. (1) The cells had 2 to 4 times as much K+Rb as Na. Therefore, (2) the K+Rb fluxes at steady state were 2–4 times larger than the Na fluxes, since the fractional turnover was the same for both cations. (3) Membrane excitation by Ba2+ stimulated the efflux of Rb but not Na. The efflux of 86Rb during membrane excitation appeared to represent the outward or delayed rectification that repolarizes the membranes after an action potential, since it was absent in a pawn mutant that is lacking in membrane excitation.
The Bidder Lecture, 1980: The Evolution of Fibrillar Muscle in Insects
Authors: Pringle J. W. S.
Published: April 2021

Fibrillar muscle is a peculiar type of striated muscle found only in the power producing flight muscles of certain higher Orders of insects and in the main timbal* muscle of the sound-production system of certain cicadas. It is recognizable both physiologically and histologically and is distinguishable from the tubular and ‘close-packed’ striated muscles found in nearly all other orders of insects in the flight system (Pringle, 1975). There are good reasons for thinking that tubular and close-packed muscles are the more primitive evolutionarily and that fibrillar muscle has arisen independently many times in the evolution of insects. Since it is inconceivable that, at any stage in these evolutionary developments, there was a loss of the capacity for flight or of sound-production, the problem arises of determining how the change could have come about. This is the subject of this lecture.
Homologies Between Neuromuscular Systems Serving Different Functions in Two Decapods of Different Families
Authors: Paul Dorothy Hayman
Published: April 2021

Evidence is provided for homologies between specific parts of the tailfan neuromusculatures in two sand crabs, Emerita analoga (family Hippidae) and Blepharipoda occidentals (family Albuneidae). The gross anatomy of the tailfan, particularly of the telson, is very different in the two species, the biggest difference being the absence in Blepharipoda of a power-stroke muscle which in Emerita constitutes 50% by wet weight of the telson musculature. Homologies between motoneurones innervating telson muscles in the two crabs are established based on comparisons of their positions and central morphology. The derivation of the sand crab telson muscles and their innervation from neuromusculature in an ancestral macruran is proposed.
Ventilation and Oxygen Extraction in the Bat Pteropus Gouldii During Rest and Steady Flight
Authors: Thomas Steven P.
Published: April 2021

Tidal volume (VT) breathing frequency (f) and oxygen consumption were simultaneously measured in the bat Pteropus gouldii during quiet rest at 24 °C, and oxygen extraction (E) values were calculated from these data. VT and f were also measured at 24 °C from P. gouldii undertaking steady wind-tunnel flight at different speeds and angles, and this information together with appropriate data reported previously for this bat were used to calculate flight E values.

The oxygen extraction of resting P. gouldii was similar to that of a resting non-flying mammal of comparable size but lower than that of a resting bird. P. gouldii increases VT and/almost equally in going from quiet rest to level flight to achieve a 17-fold increase in minute ventilation. Compared to the resting bat, flying P. gouldii hyperventilates its respiratory system relative to its metabolic requirements. The level flight VT of P. gouldii compares favourably with that expected for a flying bird of the same body mass, and represents almost 90 % of the total lung capacity predicted for a non-flying mammal of comparable size. Because of the increased breathing frequency during flight, the minute ventilation requirement of P. gouldii during level flight exceeds that predicted for a similar-sized flying bird. E values calculated for flying P. gouldii are significantly lower than those reported for birds flying at comparable temperatures and flight conditions.
The Role Of CaCO3 Dissolution as A Source of HCO3− for the Buffering of Hypercapnic Acidosis in Aquatic and Terrestrial Decapod Crustaceans
Authors: Henry R. P. , Kormanik G. A. , Smatresk N. J. , Cameron J. N.
Published: April 2021

Blood calcium concentrations are elevated during a hypercapnic acidosis in the terrestrial crab Gecarcinus lateralis, but not in the aquatic Callincetes sapidus. The increase occurs concomitantly with a rise in blood HCO3− and partial restoration of resting blood pH values. It is believed that in G. lateralis that a source of CaCO3, possibly the shell, is being dissolved for buffering purposes.
Haemodynamic Responses to Haemorrhage in the Snake, Elaphe Obsoleta Obsoleta
Authors: Lillywhite Harvey B. , Smith Laurens H.
Published: April 2021

Haemodynamic responses to graded haemorrhage were studied in unanaesthetized black ratsnakes (Elaphe o. obsoleta) wherein fixed percentages of the blood volume were removed at regular intervals over periods which varied from one to several hours. Initially measured whole blood volumes averaged about 6 % of the body mass and were determined from plasma dilutions of Evans blue dye or the bleeding and washing out of red cells. In response to haemorrhage, heart rate increased, haematocrit decreased, plasma protein concentration decreased, and arterial pressure remained relatively constant until a critical blood loss at which pressure dropped precipitously. Critical volume deficits occurred at the withdrawal of 63-122% of the initially measured blood volume. It appears that cardiovascular reflexes assist the regulation of arterial pressure during haemorrhage; additionally, there occurs a progressive and significant restitution of plasma volume owing to the absorption of extravascular fluid. Fluid volumes absorbed by the circulation during haemorrhage replaced 20–71 % of the haemorrhaged blood loss and were correlated with the magnitude of the critical volume deficit. Body movements increased arterial pressure by improving venous cardiac return.
Cellular Discrimination Processes in Metal Accumulating Cells
Authors: Simkiss K.
Published: April 2021

A technique is described for investigating cellular fluxes and the accumulation of metal ions in the hepatopancreas of the snail Helix aspersa. The method involves the simultaneous administration of double isotopes into the haemocoel and the subsequent detection of these metals in tissues and granule materials. By comparing in vivo and in vitro data it is possible to detect two separate accumulation systems which appear to correspond with metallothionein and pyrophosphate granules. It is also possible to obtain some information of the nature of possible cellular transport systems.
The Exoskeleton and Insect Proprioception
Authors: Zill Sasha N. , Moran David T.
Published: April 2021

In the cockroach tibia, the activities of campaniform sensilla that monitor cuticular strain have been recorded in free-walking animals. In walking, sensillum firing is correlated with myographic activity of the flexor and extensor tibiae muscles. The specific activity of a single campaniform sensillum depends upon the orientation of its cuticular cap. In slow walking, proximal sensilla, whose ovoid cuticular caps are oriented perpendicular to the leg long axis, fire in bursts that are initiated just prior to the onset of extensor tibiae activity in the stance phase of locomotion. The firing frequency within bursts of proximal sensilla is generally inversely related to the frequency of the slow extensor tibiae motoneurone and ceases when motoneurone activity exceeds 200 Hz. Distal campaniform sensilla, oriented parallel to the leg long axis, only fire when slow extensor tibiae activity exceeds 300 Hz. In slow walking, distal sensillum activity typically occurs as a short intense burst near the end of the stance phase of the step cycle, when slow extensor frequency is maximal. Distal sensillum firing is greatly increased when forward progression is impeded. The patterns of afferent activity seen in slow walking indicate that the campaniform sensilla function in load compensation and limitation of muscle tensions. The proximal sensilla respond to initial loading of the leg and can reflexly excite the slow extensor motoneurone in compensation. The distal sensilla respond to cuticular strains that result from large extensor contractions and can reflexly inhibit the slow motoneurone. In rapid walking, activities of both subgroups of campaniform sensilla shift in phase relative to slow extensor firing. Proximal sensilla activity occurs after the onset of slow extensor firing. Distal sensilla bursts follow the termination of slow extensor activity. These phase shifts limit the reflex functions of the tibial campaniform sensilla in rapid walking. Shifts in phase of afferent activity may contribute to the need for central programming of locomotion.
Sensory Fields and Properties of the Oesophageal Proprioceptors in the Mollusc, Philine
Authors: Dorsett D. A. , Sigger J. N.
Published: April 2021

The buccal ganglia of Philine each contain four mechanosensory neurones that are proprioceptors in the oesophageal wall. The sensory fields of the three small receptors are bilateral and separate from each other, but two are overlapped by the more extensive field of the largest cell. The sensory field of each receptor overlaps that of its contralateral homologue. The receptors respond to touch or stretch of the oesophageal wall or certain nerve trunks with a rapid burst of impulses, which adapt quickly to repetitive stimulation. The soma spike is characterized by a large undershoot that summates at high-impulse frequencies to hyperpolarize the cell. Repetitive stimulation leads to the axon spike failing to propagate to the soma. Blocking most probably occurs at a branch point on the main axon within the ganglion. Impulses generated in one part of the axon normally propagate to all parts of the cell. Conduction velocity increases in the axon as the soma is approached. Conduction velocity may vary in different branches of the axon.
Axon/Schwann-Cell Relationships in the Giant Nerve Fibre of the Squid
Authors: Villegas Jorge
Published: April 2021

This communication summarizes the experimental evidence obtained in the giant nerve fibre of the tropical squid Sepioteuthis sepioidea, on the nature of the mechanism responsible for the long-lasting effects of axonal excitation on the membrane potential of the Schwann cell. In these nerve fibres the propagation of a train of nerve impulses by the axon is followed by a prolonged hyperpolarization of the Schwann cell which can be reproduced, or modified,.by the external application of cholinergic compounds. The presence and exact localization of the different components of the acetylcholine system directly involved in such Schwann-cell responses was detected by means of pharmacological, histochemical and chemical procedures. Thus, the results of the experiments herein discussed revealed that, under physiological conditions: the Schwann cell is able to synthesize, store and release acetylcholine; and that it has acetylcholine receptors of the nicotinic type, and acetylcholinesterase enzyme activity in its plasma membrane. On the other hand, the axon has low acetyltransferase activity and acetylcholine concentration in its axoplasm, and a high acetylcholinesterase activity in its axolemma. It was also found that acetylcholine hyperpolarizes the Schwann cell by increasing its relative permeability to the potassium ion. The distribution pattern of the acetylcholine system indicates that it operates as a feedback mechanism for the regulation of the Schwann-cell membrane potential and ionic permeability following axonal excitation.
Studies on Cultured Schwann Cells: The Induction of Myelin Synthesis, and the Control of Their Proliferation by A New Growth Factor
Authors: Brockes J. P. , Fryxell K. J. , Lemke G. E.
Published: April 2021

We have recently described the use of immunological methods to identify and purify rat Schwann cells. In dissociated cultures of neonatal sciatic nerve, all of the cells can be identified by antigenic criteria as either Schwann cells or fibroblasts. The fibroblasts may be removed by treatment with antiserum to the Thy-1 antigen and complement. The purified Schwann cells have been used to study the regulation of the expression of myelin components, and the stimulation of Schwann cell division by a soluble growth factor.

Among the components of myelin, we have concentrated on the peripheral myelin glycoprotein P0, which constitutes 50–60% of the protein in peripheral myelin. We have studied the distribution of P0in vitro and in vivo by immunofluorescence, immuno-autoradiography on SDS gels, and solidphase radioimmunoassay. Our results support the hypothesis that P0 is induced specifically as a consequence of the interaction between the Schwann cell and the myelinated type of axon. The level of P0 in the myelin membrane is at least 1000-fold higher than in the Schwann cell membrane.

Purified Schwann cells divide very slowly in a conventional tissue culture medium. This has alowed us to purify a new growth factor from extracts of brain and pituitary, tentatively named Glial Growth Factor (GGF). The activity resides in a basic protein with a native molecular weight of 6×104 daltons and a subunit molecular weight of 3 ×104 daltons, which is active at levels comparable to those of epidermal growth factor. GGF is mitogenic for Schwann cells, astrocytes and muscle fibroblasts.