bluuebunny/crossref_metadata_2025 huggingface dataset:
Oscillating Contractions in Protoplasmic Strands Of Physarum: Mechanical and Thermal Methods of Phase Shifting for Studying the Nature of the Synchronizing Factor and its Transmission*
Authors: Achenbach U. , Wohlfarth-Bottermann K. E.
Published: April 2021

A new experimental investigation chamber was used to analyse the control of rhythmic contractile activity in Physarum. A strand was mounted in such a way that isometric tension measurements of contraction forces could be made on two regions independently, the two regions remaining connected. It was possible to disturb one region experimentally and to compare its behaviour with the other.

A short time after being set up in the apparatus, the isometric contraction cycles in the two regions became synchronous. Stretching one region by 50% of its original length induced a phase delay relative to the other. A brief unilateral cold shock (Δt = 5–15°C) had a similar phase-retarding effect. Synchrony was subsequently reattained, unless the connecting region was cut or, for example, treated with 30 mm benzamide.

In approximately 25% of the investigated strands, a rapid change to a higher temperature (Δt = 2–5 °C) caused the warmed side to be phase-advanced. However, 75 % of the strands did not show a phase shift, suggesting that a rapid phase regulation is supported by increased temperature.

The described experimental assay is suitable for analysing the pathway and the nature of signal transmission in plasmodial strands.
Carbon Dioxide Exchange and its Effects on pH and Bicarbonate Equilibria in the Blood of the Amphibian, Xenopus Laevis
Authors: Emilio M. G. , Shelton G.
Published: April 2021

The elimination of CO2 through the lungs and skin of Xenopus laevis and its distribution between plasma and erythrocytes were determined during breathing and submergence periods. CO2 output does not decrease during submergence, as lack of lung ventilation is compensated by an increase in cutaneous exchange. The total CO2 carried in the blood decreases after a 30 min dive, but the fraction carried in red blood cells increases substantially, due to an increase in the haematocrit values. This increase is related to a decrease in plasma volume during diving. During short dives the blood shows changes characteristic of respiratory acidosis but longer dives result in a combination of respiratory and metabolic acidosis.
A Locust Wind and Ocellar Brain Neurone
Authors: Simmons Peter
Published: April 2021

One of the large descending brain neurones in each half of the central nervous system of a locust is probably important in regulating the attitude of the locust’s flight in the pitch plane. This function is suggested by a consideration of the stimuli which excite the interneurones, and of the muscles whose motoneurones they excite. Each of these interneurones has its cell body in the protocerebrum and its axon descends the ipsilateral connective and has branches in all of the thoracic ganglia. The interneurones are excited by currents of air directed at the front of the head. An increase in the intensity of light falling on the median ocellus causes a reduction in the frequency of spikes produced by stimulation of the wind-sensitive hairs, and a reduction in the intensity of this light causes an increase in the frequency of these spikes. Each interneurone makes excitatory connexions with motoneurones of the subalar and dorsal longitudinal flight muscles ipsilateral to it.
Binaural Interaction in the Cod
Authors: Horner Kathleen , Sand Olav , Enger Per S.
Published: April 2021

Recordings were made from 93 single units in the acoustical lobes and the torus semicircularis of the cod during sound stimulation and anodal blocking of the posterior saccular nerves. Most medullary sound responses were phase locked to the stimulus to some degree. The phase locking was less pronounced in the torus semicircularis, and sound stimulation sometimes caused clear inhibition of activity in this area. A large fraction of the units in both recording loci was insensitive to our sound stimuli, which acted mainly via the swimbladder. Peripheral blocking caused decreased activity and inhibition of sound responses in the acoustic lobes, indicating excitatory ascending input to this region. Binaural interaction was found in 8 of 29 medullary units tested during both ipsi- and contralateral block. Single-sided blocking experiments revealed both inhibitory and excitatory input to the torus semicircularis region. Binaural interaction was found in 3 of the 5 units tested during both ipsi- and contralateral block in this area.
Protein Synthesis Requirement of the Aplysia Circadian Clock Tested by Active and Inactive Derivatives of the Inhibitor Anisomycin
Authors: Jacklet Jon W.
Published: April 2021

The circadian rhythm of compound action potential frequency recorded from the isolated eye of Aplysia in culture medium and darkness was subjected to 6 h pulse treatments with either anisomycin, a protein synthesis inhibitor, or inactive derivatives of anisomycin. Anisomycin caused phase-dependent phase shifts of the rhythm as expected from previous experiments, but none of the derivative molecules caused phase shifts or perturbed the rhythm. Anisomycin inhibited eye-protein synthesis by 75% at the concentrations (10-6 M) used in the phase shifting experiments but none of the derivatives inhibited synthesis. Only those molecules that actually inhibited protein synthesis caused phase shifts of the clock, although the inactive derivatives differed from anisomycin by only an acetyl group. The results strengthen the conclusion that the inhibition of protein synthesis caused by anisomycin is important in perturbing the timing of the circadian clock and not some other characteristic effect of the inhibitor molecule. Together with the results from other systems, these findings imply that the daily synthesis of protein is a general requirement for circadian clocks.
Postsynaptic Inhibition of Crayfish Tonic Flexor Motor Neurones By Escape Commands
Authors: Kuwada J. Y. , Hagiwara G. , Wine J. J.
Published: April 2021

The crayfish abdomen contains separate slow and fast neuromuscular systems that mediate posture and escape tailflips (Kennedy & Takeda, 1965 a,b). It was recently demonstrated that impulses in the medial and lateral giant axons, which trigger escape responses, also inhibit both spontaneous and evoked activity in the tonic, or slow, flexor motor neurones (Kuwada & Wine, 1979). The evidence for inhibition was based exclusively on extracellular recordings of the spontaneously active tonic flexor motor neurones. We have now used intracellular recordings from the somata and neuropilar processes of the tonic flexor motor neurones to clarify the nature of inhibition.

Our main findings are that synaptic potentials (from unknown sources) appear to underlie the spontaneous activity of the tonic flexor motor neurones, and that impulses in the giant axons cause large-amplitude, hyperpolarizing IPSPs in the tonic flexor motor neurones and EPSPs or spikes in the peripheral inhibitor. Of the six tonic flexor neurones in each half ganglion, we have recorded from f 3, f5, f6 and possibly f4 (the motor neurones are numbered 1−6 according to increasing size, with f5 being the peripheral inhibitor). The motor neurones were identified by the size of their extracellularly recorded axon spikes and by the positions of their somata (Wine, Mittenthal & Kennedy, 1974). Results are from six preparations.

General methods were the same as those used earlier (Kuwada & Wine, 1979). For intracellular recordings we used 3 M-KCI electrodes of 15−80 MΩ, inserted into desheathed ganglia of isolated nerve cords. The giant axons were stimulated via focal suction electrodes placed directly over them in sheathed connectives. Examples of tonic flexor motor neurone activity and inhibition of it by giant axon spikes are shown in Fig. 1.

The following points can be made.
Use of an Operational Amplifier Signal Differentiator Reveals That Octopamine Increases the Rate of Development of Neurally Evoked Tension in Insect Muscle
Authors: Buchan P. B. , Evans P. D.
Published: April 2021

Octopamine is a biogenic amine that is widespread in the insect nervous system (Evans, 1978; Dymond & Evans, 1979). In the locust, it potentiates the amplitude and increases the rate of relaxation of tension, in the extensor tibiae muscle of a hindleg, induced by the stimulation of the slow excitatory motoneurone (SETi) (Evans & O’Shea, 1977; O’Shea & Evans, 1979). O’Shea & Evans (1979) determined relaxation rates by graphical analysis of the data; a process which proved to be very time consuming and subject to error in the measurement at high relaxation rates. The device we describe here allows the continuous measurement of contraction and relaxation rates, and any changes in these parameters, during the course of an experiment. It was developed for use in a comparative pharmacological study of the octopamine receptors producing the above effects (Evans, 1980; P. D. Evans, in preparation).
Mechanisms of Body-Temperature Regulation in Honeybees, Apis Mellifera II. Regulation of Thoracic Temperature at High Air Temperatures
Authors: Heinrich Bernd
Published: April 2021

Honeybees could remain in continuous free flight at extremely high air temperatures (up to at least 46 °C). The metabolic rate in free flight, 80-85 ml O2 g body weight-1 h-1, was independent of air temperature (TA) over a span of at least 22 °C. The bees’ ability to fly at high TA was due to their ability to maintain thoracic temperature (TTh) near TA despite prodigious rates of heat production. Mechanisms of preventing TTh from overheating at high TA were investigated. Bees in flight at high TA regurgitated fluid from their honeycrop and large droplets sometimes spread over the anterior portion of the thorax. Bees without the first two sets of legs, or without a ‘tongue’, maintained as low TH and TTh as intact bees. The abdomen serves only a minor function as a heat exchanger. In tethered bees, heating of the thorax to 45-50 °C resulted in significant, yet relatively little, temperature increase of the abdomen above that of dead or non heat-stressed animals. Similarly, in free flight abdominal temperatures (TAb) were close to TA at all TA. Thoracic heating to near lethal temperatures did not result in droplet extrusion from the mouth nor in significant physiologically facilitated heat transfer to the head. Furthermore, it resulted in no, or in relatively small, changes in pulsation of the aorta and the heart. However, the bees prevented the head from overheating, and the head served as a heat sink for excess heat from the thorax. Keeping TH< TA resulted in keeping TTh near TA. It is concluded that during flight at high TA regulation of TH by evaporative cooling is the primary mechanism of reducing TTh.
Mechanisms of Acid-Base Adjustment in Dogfish (Scyliorhinus Stell Aris) Subjected to Long-Term Temperature Acclimation
Authors: Heisler N. , Neumann P. , Holeton G. F.
Published: April 2021

Specimens of Larger Spotted Dogfish (Scyliorhinus stellaris) were acclimated to a range of temperatures for 22–28 days. The relationships of pH to acclimation temperature in the extracellular space and in three intracellular compartments were essentially the same as previously observed in 24 h acclimated dogfish (Heisler, Weitz & Weitz, 1976).

In dogfish subjected to elevated inspired during acclimation to low temperature, there was an inversion in the relationship of acclimation temperature to plasma , and in that to plasma bicarbonate, whereas the relationships to pH values were unchanged.

It is concluded that the temperature adaptation of the acid-base parameters is complete after 24 h of temperature acclimation. At least the following mechanisms are involved in the adjustment of pH with changes of temperature: changes of changes of buffer pK values, and transmembrane transfer of bicarbonate. Apparently only one of them, the transmembrane transfer of bicarbonate, can be modulated in a sufficient range and is responsible for the final pH adjustment.
The Antennal Motor System of the Rock Lobster: Competitive Occurrence of Resistance and Assistance Reflex Patterns Originating From the Same Proprioceptor
Authors: Vedel Jean-Pierre
Published: April 2021

Skeletal, muscular and neural organization of the two distal joints (J 2 and J3) of the antenna of the rock lobster Palinuros Palinurus has been described. Motor innervation (nine motoneurones) of the two distal joints of the antenna has been determined by anatomical and physiological methods. Extensor and flexor muscles of J2 and J3 are each innervated by one specific excitatory tonic motoneurone. One excitatory phasic motoneurone is common to both the J2 and J3 extensor muscles, another to the J2 and J3 flexor muscles. The J3 extensor muscle also receives a specific phasic motoneurone. An accessory extensor muscle which spans J2 and J3 is innervated by one excitatory motoneurone. A common inhibitory motoneurone innervates the two flexor and the two extensor muscles of J2 and J3. Movements of J2 and J3 are sensed by a proprioceptor (chordotonal organ). Reflex patterns involving this proprioceptor have been extensively studied. Sinusoidal extension-flexion movements imposed on the J3 joint induced intra-segmental reflexes (on the J3 muscle innervations) and intersegmental reflexes (on the J2 muscle innervations) which exclusively involved the tonic excitatory motoneurones and the common inhibitory motoneurone. Resistance reflexes (activation of the muscle stretched by the imposed movements) occurred whatever the excitability level of the animal and involved both flexor and extensor motoneurones. The motoneurones spiked at a higher frequency when the velocity of the imposed movement was increased. The common inhibitor motoneurone was activated during extension movements. In preparations which became ‘more excitable’, assistance reflexes could be induced by joint stimulations which formerly induced resistance reflexes. Sometimes assistance reflexes could be induced by increasing the velocity of the movements imposed on J3. Assistance reflexes mainly involved extensor motoneurones. The role of the tonic, phasic and inhibitory innervations and the functional significance of resistance and assistance reflexes are discussed in relation to the behavioural role of the rock lobster antenna.
Coding of Directional Information by Single Neurones in the S-Segment of the Fm Bat, Myotis Lucifugus
Authors: Jen Philip H.-S.
Published: April 2021

Response parameters of S-segment neurones of the FM bat Myotis lucifugus were measured as a sound was delivered from different azimuthal angles around the animal’s head. The response parameters investigated were the amplitude and threshold of the evoked potential (N3) of the S-segment, together with the threshold, latency and number of impulses (per stimulus pulse) of single units. All the neurones studied had their lowest thresholds either at 20–40° contralateral, or 20–40° ipsilateral or at the front (o°). The amplitude of the sound affected the relationship between stimulus direction and the amplitude of a non-monotonic N3, and the relationship between stimulus direction and the number of impulses of a non-monotonic single unit. It had no such effects with a monotonic N3 and a monotonic single unit. From a study of N3 amplitudes and numbers of impulses of single neurones, it appeared that an azimuthal difference as small as 3° could be easily coded at a 95% correct level with stimuli presented at around 20° ipsilateral, 20° contralateral, and at the front. The inter-aural pressure difference (IPD), which is considered an essential cue for echolocation in Myotis (Shimozawa et al. 1974), changed linearly with angle from 0 to 40° lateral at a rate of 0·4 dB/degree for sounds between 33·5 and 49·0 kHz. Assuming the just-detectable IPD to be 0·5 dB (as in man), the minimum detectable azimuthal difference of Myotis around the median plane would be 1·25°.
Cardiovascular Dynamics and Adrenergic Responses of the Rainbow Trout In Vivo
Authors: Wood Chris M. , Shelton Graham
Published: April 2021

Cardiac output and dorsal aorta, ventral aorta, caudal artery, caudal vein, and subintestinal vein pressures have been directly measured in intact unanaesthetized trout. Cardiac output (Q̇) averaged 36·7 ml/kg.min. The pressure drop across the systemic vascular resistance (Rs) was approximately twice that across the gill resistance (Rg), and a significant positive pressure persisted in the venous system. α-Adrenergic blockade revealed a considerable endogenous vasomotor tone resulting from latent adrenergic constriction of RS. Intravenous adrenaline caused a pressor response throughout the circulatory system which has been analysed in detail with the aid of previous studies on isolated parts of the trout circulation. The complex and variable form of the pressor response reflected differential contributions from changes in Q̇, Rg, and Rs. Increases in R3 (α-receptor activation) were the principal cause of all pressor responses. Rg usually declined slightly due to passive dilation and/or β-receptor stimulation, but occasionally increased due to a-receptor activation. The cardiac response reflected a varying balance between a direct β-stimulatory effect of adrenaline on Q̇ and an indirect passive inhibition of Q̇ by the increase in peripheral resistance. Both effects were mediated through changes in stroke volume. Occasional tachycardia or more frequent reflex bradycardia were minor components of the cardiac response. The in vivo actions of other adrenergic agents have been similarly analysed.
The Reflex Control of Heart Rate and Cardiac Output in the Rainbow Trout: Interactive Influences of Hypoxia, Haemorrhage, and Systemic Vasomotor Tone
Authors: Wood Chris M. , Shelton Graham
Published: April 2021

In cannulated trout there was no cholinergic vagal tone as revealed by atropine blockade during normal heart rates. Reductions in heart rate occasionally occurred under normoxia without apparent external stimuli (‘spontaneous’ bradycardia) and always occurred under environmental hypoxia (hypoxic bradycardia) due to the imposition of significant vagal tone. Direct measurements of cardiac output during these bradycardias showed that increases in cardiac stroke volume compensated for the falls in heart rate so that total remained unchanged or increased slightly. Sudden experimental reductions in arterial blood pressure via blockade of systemic vasomotor tone with yohimbine or via haemorrhage had no effect on heart rate during normal rates, but caused cardioacceleration during both types of bradycardia. These increases in heart rate never exceeded the point of zero vagal tone (normal heart rate) and were largely or wholly due to reductions in endogenous vagal tone. These cardioaccelerations were temporary; spontaneous bradycardia could re-occur at any time, while hypoxic bradycardia always re-occurred if the hypoxic stimulus were maintained. The results are interpreted in terms of a central interaction between the baroreceptor and chemoreceptor reflexes.
A Simple Method to Determine Drag Coefficients in Aquatic Animals
Authors: Bilo D. , Nachtigall W.
Published: April 2021

The drag coefficient CD= 2.D/(Aρν2) (D drag, A characteristic area of the object, ρ density of medium, ν relative speed between object and medium) is important in determining energetic requirements of a biological or technical ‘construction’ that is moving in a fluid. A small value indicates low energetic requirements. Before World War II drag coefficients of cares were usually determined by deceleration measurements. We have modified the measuring system and developed a simple method of analysis to determine CD values without influencing the swimming animal in any way. Gentoo penguins (Pygoscelis papua) were filmed during decelerating underwater gliding (‘Ausgleiten’) without any movements of extremities, parallel to a large underwater window of a penguinarium. From these films distance-time functions were plotted (Fig. 1 a). Using distance-differences Ax and time differences Δt between two points, momentary velocity ν = Δx/Δt can be determined. The reciprocal velocity ν-1 as a function of time t gives a straight line in the case of undisturbed deceleration as explained by the following.
The Influence of Calcium on the Physiological Responses of the Rainbow Trout, Salmo Gairdneri, to Low Environmental pH
Authors: McDONALD D. G. , Hobe H. , Wood C. M.
Published: April 2021

The physiological responses of 1- to 2-year-old rainbow trout to low pH are dependent on the environmental calcium concentration. Trout, maintained for 5 days in moderately hard water ([Ca2+] = 1·6 −2·7 m-equiv/1) at a mean pH of 4·3, developed a major blood acidosis but exhibited only a minor depression in plasma ion levels. In acidified soft water ([Ca2+] = 0·3 m-equiv/1), only a minor acidosis occurred, but plasma ion levels fell and there were substantially greater mortalities. Lethal bioassays performed on fingerling trout over a range of pH levels (3·0−4·8) revealed an important influence of external [Ca2+] on resistance to acid exposure. Terminal physiological measurements on adult fish succumbing to low pH in soft water indicate the singular importance of iono-regulatory failure as the toxic mechanism of action under these circumstances.
The Transepithelial Potential and Osmotic Regulation in the Green Hydra
Authors: Chain Benjamin M.
Published: April 2021

The properties of the ion-transporting systems in the green Hydra were investigated by measuring the trans-epithelial potential and the potential profile across the body wall. The major potential step occurs across the inner ectodermal membrane, and is produced by an inwardly directed electrogenic sodium pump, which is sensitive to ethacrynic acid but not to ouabain. Calcium ions inhibit sodium transport across the epithelium. Calculations using data for the short-circuit current across the epithelium show that sodium transport requires a relatively high rate of energy expenditure, as would be expected ‘a priori’ for a small organism.
Ventilatory and Circulatory Responses to Hyperthermia in the Mute Swan (Cygnus Olor)
Authors: Bech C. , Johansen K.
Published: April 2021

Ventilatory parameters of mute swans were measured at thermoneutral conditions and during heat stress. Deep body temperature increased from 39·5 to 41·1 °C. Breathing frequency increased 29 times, compared to the thermoneutral condition. Tidal volume decreased to 18 % of the pre-panting value, and the total ventilatory volume increased by 5·4 times. End-tidal and , values decreased and increased, respectively.

The swans developed a slight respiratory alkalosis; arterial decreased from an average of 27·1 to 25·7 mmHg and arterial pH increased from 7·501 to 7·559

Cardiac output, heart rate and stroke volume were 106%, 154%, and 70%, respectively, of the values at thermoneutrality. Mean arterial blood pressure and total peripheral resistance were slightly reduced.

It is concluded that the increased ventilation during panting mainly constitutes dead space ventilation resulting from the great reduction in tidal volume. Parabronchial ventilation remains nearly unchanged, resulting in only a slight hypocapnic alkalosis.
Mechanisms of Resorption and Deposition of Calcium in the Carapace of the Crab Carcinus Maenas
Authors: Roer Robert D.
Published: April 2021

Premoult resorption of Ca from the carapace of Carcinus involves the active inward transport of Ca by the hypodermis with maximal rates occurring in stage D2 of the moult cycle. Postmoult calcification of the carapace involves the active outward transport of Ca by the hypodermis with maximal rates occurring in stages A1 and A2 of the moult cycle. Bidirectional active transport of Ca by Carcinus hypodermis may be accomplished by means of a quercitin-sensitive Ca-ATPase and a Na/Ca exchange mechanism in conjunction with observed changes in epithelial cell shape and size.
A Micropuncture Study of Kidney Function in the River Lamprey Lampetra Fluviatilis Adapted to Sea Water
Authors: Logan A. G. , Morris R. , Rankin J. C.
Published: April 2021

Micropuncture techniques have been used to investigate kidney function in lampreys adapted to hyperosmotic media. Plasma electrolyte concentrations were maintained well below corresponding concentrations in the external environment. Urine composition was variable, but generally showed high concentrations of magnesium, sulphate and chloride ions. Lampreys in 50% sea water produced urine which was hypo or iso-osmotic to plasma, whereas those in 100% sea water produced hyperosmotic urine. Urine flow rate in 50% sea water was one tenth of that in fresh water, due to a reduction in filtration rate and an increase in water reabsorption by the kidney. As in fresh water, little if any filtered water was reabsorbed by the proximal segment. Almost 90% of filtered water was reabsorbed by the kidney of 100% sea water lampreys and most of this must have occurred in the distal and collecting segments.
An Arthropod Muscle Innervated by Nine Excitatory Motor Neurones
Authors: Phillips Christine E.
Published: April 2021

The anatomical and physiological organization of the locust metathoracic flexor tibiae was examined by a combination of intracellular recording and electron microscopy. Nine excitatory motor neurones, three fast, three intermediate and three slow innervate the muscle ; each is uniquely identifiable using a combination of physiological response and soma location. A simple spatial distribution of inputs to the muscle from the individual motor neurones was not found. Individual muscle fibres responded to as many as seven of the motor neurones in various combinations.

The muscle fibres are heterogeneous, ranging from slow (tonic) to fast (phasic) in a continuum from predominantly phasic proximally to tonic distally. This is demonstrated by contraction and relaxation rates to direct and indirect stimulation, as well as contraction elicited by action potentials in a single flexor motor neurone. The fast and slow contractile properties of the muscle fibres are matched by appropriate ultrastructures.

Such a high degree of complexity of neuromuscular innervation as that found in the metathoracic flexor tibiae has not previously been described for an arthropod muscle.
Cholinergic Motor Control of Sea Urchin Tube Feet: Evidence for Chemical Transmission Without Synapses*
Authors: Florey E. , Cahill M. A.
Published: April 2021

Isolated tube feet of Strongylocentrotus franciscanus contract briefly when the outer epithelium is touched. Similar twitch-like contractions can be induced by electrical stimulation of the outer surface of the tube foot. These responses appear to be chemically mediated. The following evidence indicates that the transmitter substance may be acetylcholine (ACh): ACh causes muscle contraction. This effect and that of electrical stimuli is potentiated by anticholinesterase agents and is antagonized by cholinergic blocking agents. Anaesthesia with chloralhydrate or chloretone abolishes responsiveness to mechanical or electrical stimulation but not to ACh. Desensitization with carbachol prevents responses to ACh and to mechanical or electrical stimulation.

There are no neuromuscular synapses and no axons can be detected which cross the connective tissue layer which separates the muscle fibres from the subepithelial nerve plexus. The latter is known to contain conspicuous amounts of ACh ; nerve terminals containing clear vesicles invest the outer surface of the connective tissue layer. All evidence indicates that chemical transmission involves diffusion of ACh (released from activated nerve terminals) across this connective tissue layer which is around 5 μm thick in fully extended tube feet but may have a thickness of 20 or even 25 μm in less extended ones. Calculations based on equations describing transmitter diffusion prove the feasibility of such a mechanism.
A Ca-Induced Na-Current In Paramecium
Authors: Saimi Yoshiro , Kung Ching
Published: April 2021

Under a voltage clamp, step depolarization and repolarization can induce a sustained inward current and a tail inward current in Paramecium tetraurelia bathed in a solution containing 8 mm-Na+. These currents are best seen in the ‘paranoiac’ mutant. The I-V plot of the sustained inward current can have a region of negative resistance around – 20 mV. This current is absent when Na+ is excluded from the bath solution, and it increases as the Na+ concentration increases from 2 to 8 mm. Injection of Na+ into the cell suppresses this inward current. This current develops very slowly, reaching its maximum seconds after the step depolarization and decays with a time constant of hundreds of milliseconds after the repolarization. This slow current is dependent on Ca2+. It can be suppressed by reduction or deletion of external Ca2+ or by iontophoretic injection of EGTA. ‘Pawn’ mutants with defective Ca-conductance also lack this current. We conclude that Paramecium has a Ca-induced conductance through which the Na-current flows. Although more prominent in the ‘paranoiac’ mutant, this Ca-induced Na-current is also seen in the wild type. This conductance may function in generating plateau depolarizations lasting seconds or even minutes and the corresponding prolonged backward swimming away from sources of irritation and stress.
Oxygen Consumption by the Sea Anemone Calliactis Parasitica (Couch)
Authors: Brafield A. E.
Published: April 2021

Oxygen consumption by Calliactis parasitica, measured in a continuous-flow polarographic respirometer, yielded a slope of 0-92 when plotted against body weight on log scales. This high value is discussed in terms of the sea anemone’s basically laminate nature. Strip-chart records of the oxygen concentration of water which had just passed a specimen of Calliactis commonly showed rhythmic fluctuations, either of low amplitude and high frequency or high amplitude and low frequency (mean cycle lengths 11 and 34 min respectively). The fluctuations are explained in terms of rhythmic muscular contractions which irrigate the enteron for respiratory purposes. Analysis of the slow fluctuations indicates that the endoderm is responsible for about 18 % of the total oxygen consumption.

The oxygen concentration of water in the enteron, measured and recorded continuously, was 4–27% of the air-saturation level. These strip chart records also frequently showed rhythmic fluctuations (mean cycle length 12 min), apparently resulting from the muscular contractions.
The Physical Properties of the Pedal Mucus of the Terrestrial Slug, Ariolimax Columbianus
Authors: Denny Mark W. , Gosline John M.
Published: April 2021

The pedal mucus of gastropods functions in locomotion by coupling the movements of the foot to the substratum. The pedal mucus of the terrestrial slug, Ariolimax columbianus, is suited to this role by the following unusual physical properties.

At small deformations the mucus is a viscoelastic solid with a shear modulus of 100–300 Pa. The mucus shows a sharp yield point at a strain of 5–6, the yield stress increasing with increasing strain rate. At strains greater than 6 the mucus is a viscous liquid (η = 30–50 poise). The mucus recovers its solidity if allowed to ‘heal’ for a period of time, the amount of solidity recovered increasing with increasing time.
An Improved Capacitative Position Transducer for Biological Systems
Authors: Forman R. , Brumbley D.
Published: April 2021

A capacitative position transducer for biological systems has been described by Sandeman (1968). This device permits the measurement of excursions of a small appendage without requiring excessive loading of the moving part.
Opioid Peptides: Aspects of Their Origin, Release and Metabolism
Authors: Hughes J. , Beaumont A. , Fuentes J. A. , Malfroy B. , Unsworth C.
Published: April 2021

At the present time there is evidence for two families of related peptides which act as ligands for opiate receptor sites. The endorphin group of peptides are derived from the ACTH/LPH precursor pro-opiocortin. The enkephalins appear to be formed from a separate precursor or precursors that have yet to be fully characterized. There appear to be a number of different types of opiate receptors and this may be related to the multiplicity of peptide ligands that have so far been identified. The enkephalins and related peptides appear to have a much wider distribution than the endorphins but the latter may act as circulating hormones unlike the enkephalins. It is likely that both endorphins and enkephalins are involved in sensory modulation processes and release of these peptides has been demonstrated during brain stimulation for pain relief. The enkephalins are very rapidly inactivated by tissue proteases, the aminopeptidases appear largely responsible for the inactivation of exogenously administered enkephalins but the dipeptidyl carboxypeptidase, termed enkephalinase, may have a special inactivating function at enkephalinergic synapses.

Evidence will be presented for the biosynthesis, the release and inactivation of the enkephalins relating to the above points.
Development of an Amphibian Neuromuscular Junction in Vivo And in Culture
Authors: Cohen M. W.
Published: April 2021

During normal development presumptive synaptic sites in the myotomes of Xenopus laevis begin to acquire a high density of ACh receptors within as little as 2 h after the arrival of the nerve fibres. Synaptic function also begins very shortly after the arrival of the nerve fibres. Initially synaptic currents are some eight times longer lasting than at maturity and are not prolonged by anticholinesterase. During the first day after nerve-muscle contact is made there is a considerable decrease in synaptic current duration, sensitivity to anticholinesterase develops, and synaptic ultrastructure becomes apparent. Schwann cells do not arrive until later. Synaptic development proceeds with a similar rapid time course in cultures of dissociated myotomes and spinal cord derived from Xenopus embryos. The cultured muscle cells also develop synaptic specializations in the absence of nerve including sites of high ACh receptor density, cholinesterase activity, and postsynaptic ultrastructure. Studies on mixed nerve and muscle cultures have further revealed that muscle impulse and contractile activity is unnecessary for the development of synaptic ultrastructure or for the localization of ACh receptors, that the localization of ACh receptors at nerve-muscle contacts is nerve-induced and involves a redistribution of surface receptors, and that the development of synaptic specializations does not occur at nerve-muscle contacts when the source of nerve is dorsal root ganglia or sympathetic ganglia rather than spinal cord.
Preliminary Studies On the Use of Monoclonal Antibodies as Probes for Sympathetic Development
Authors: Chun Linda L. Y. , Patterson Paul H. , Cantor Harvey
Published: April 2021

The precise structural organization and proper functioning of the adult nervous system depend on the ability of neurones to make highly ordered synaptic connexions. To define molecules involved in the development of these connexions and to study their functional roles, we use primary cultures of dissociated rat sympathetic neurones grown in the virtual absence of nonneuronal cells. These neurones can develop adrenergic or cholinergic properties, depending on the environment in which they are grown.

This ability to manipulate neuronal phenotype is being used in an attempt to identify cell surface macromolecules that are important in the development or function of adrenergic and cholinergic properties. We have produced monoclonal antibodies against the surface membranes of these neurones and are in the process of characterizing them. Results are presented on the binding specificity of one of these antibodies and on the effect of two other antibodies on neurotransmitter synthesis, uptake, and release.
Cell Interactions in Nerve and Muscle Cell Cultures
Authors: Christian C. N. , Bergey G. K. , Daniels M. P. , Nelson P. G.
Published: April 2021

The neurotransmitter synthesized by a given class of neurones is subject to modification and, indeed, a qualitative switchover in transmitter biochemistry recently has been demonstrated (Furshpan, Potter & Landis, 1980; Walicke, Campenot & Patterson, 1977). In conjunction with the specification of transmitter biosynthesis that becomes established in a given neurone, a complementary specification of appropriate receptor production is required in any cell functionally post-synaptic to that neurone. An additional requirement of peculiar force in the nervous system has to do with the spatial organization of the receptors in the surface membrane of the post-synaptic cell once the receptors are synthesized. Inappropriately distributed receptors are useless receptors. The perfect registration of a variety of types of presynaptic release sites with high post-synaptic concentrations of appropriate receptors constitutes one of the outstanding features of nervous-system organization that must be accounted for. We report some experiments directed toward understanding the cell biology of regulation of receptor distribution over the surface membrane of muscle cells.
The Physiological Significance of Urea
Authors: Simpson W. W. , Ogden Eric
Published: April 2021

Inasmuch as they are the end products of katabolism, the carbon dioxide and urea in the blood have been regarded merely as waste products on their way to the excretory organs until the former was shown to play a very important role as the regulating stimulus to the respiratory apparatus. Urea, on the other hand, has not up to the present time been shown to subserve any useful function in the animal body. Nevertheless it is well known that the kidney maintains the concentration of urea in the blood at a remarkably constant level and that only very slight variations of this level are found in health.
Growth of the Chick Embryo in Relation to Its Food Supply
Authors: Byerly T. C.
Published: April 2021

The rate of growth of the chick embryo depends upon an inherent growth rate, probably identical for all breeds. This rate is modified during incubation in direct proportion to a function of egg size. The increments in wet weight of the embryo are proportional to a function of the weight of the yolk sac, from the time of establishment of the circulation to the time of the changes preparatory to hatching. Both function and proportionality are probably identical for all breeds of chicken, regardless of egg size.

The growth in weight of the allantois and the yolk sac have been measured quantitatively for the first time. The weight of the allantois in eggs of different sizes is roughly proportional to the two-thirds power of egg weight after the first three or four days of its growth. During the initial period of its development the relative size is apparently independent of breed, egg size, or embryo weight. The yolk-sac weight in eggs of different sizes is roughly proportional to the circumference of the yolk after a similar initial period of independent growth.

Inclusion of the living material in the embryonic membranes in calculations of the rate of physiological processes of the embryo indicates that they are probably of the same order of magnitude throughout the incubation period rather than of sharply decreasing magnitude as supposed by some previous workers.
Factors Involved in the Production of Annual Zones on the Scales of the Rainbow Trout (Salmo Irideus). II
Authors: Bhatia D.
Published: April 2021

Rainbow trout fed uniformly does not exhibit any periodic zones on its scales whether the temperature is normal or high or low. At both high and low temperatures (17° C. and 4° C.) fish fed abundantly show on their scales a peripheral band of comparatively broad rings, and fish starved show a peripheral band of narrow rings. Bands of broad and narrow rings, resembling the so-called “annual zones,” could be produced on the scales by altering the food supplies of the fish irrespective of the temperature of the medium. Variations in temperature have no direct effect on the production of the periodic rings on the fish scales.
The Growth of the Pituitary Body in the Female Rabbit
Authors: Allanson Marjorie
Published: April 2021

In order to determine the relation of pituitary weight to body weight in the female rabbit, data were collected from 48 female rabbits. These data appear to fall on a straight line when the logarithm of the pituitary weight is plotted against the logarithm of cleaned body weight, and a straight line was fitted using the formula y = axk. The value of the constant k was found to be 0 · 61. From the data from 31 male rabbits a straight line was obtained by the same formula. The value of the constant k was found to be 0 · 57 as compared with the value 0 · 55 obtained by Robb for male rabbits. The growth rate of the pituitary does not show any marked difference after puberty in male and female rabbits as has been recorded for the rat (Hatai). Ten female rabbits were killed at varying periods after copulation and the relation of pituitary weight to body weight examined. No change in the relative size of the pituitary was detectable by the methods used, and it is concluded that any change in weight of the pituitary following copulation, if it occurs, must be slight.
Studies on the Nutrition of Blow-Fly Larvae
Authors: Hobson R. P.
Published: April 2021

The intestinal flora of Lucilia larvae consists mainly of non-lactose-fermenting, gram-negative bacilli which do not liquefy gelatine. Proteolytic organisms are not present in the gut in significant numbers, but they occur in blown meat. A method of rearing larvae aseptically is described. The eggs are sterilised by treatment with c 1 per cent, mercuric chloride solution and the larvae reared on heated brain mush, sterility being tested by inoculating aerobic and anaerobic media. The absence of symbionts transmitted inside the egg has been concluded from an examination of stained smears and sections of “sterile” larvae. When larvae are reared aseptically on sterilised brain, the reaction of the gut contents is normal, tryptase is present in the intestine and excreta, and the growth rate is almost the same as in the presence of bacteria. It is, therefore, concluded that micro-organisms play no part in intestinal digestion. Sterile larvae excrete ammonia, but the amount is insufficient to make the food alkaline until the third or fourth day of larval growth. With infected cultures the reaction is distinctly alkaline on the second day. The ammonifying bacilli isolated from normal larvae are probably responsible for the rapid appearance of ammonia in blown meat.
The Utilisation of Proteoses by Chicken Heart Fibroblasts Growing in vitro
Authors: Willmer E. N. , Kendal L. P.
Published: April 2021

The growth of chicken heart fibroblasts in physiological saline media, e.g. Tyrode, is not materially increased by the addition of pure proteoses. In the presence of plasma, the addition of proteoses causes increased growth of the tissues, probably owing to the slow digestion of the proteoses to utilisable amino acids by the enzymes of the plasma. If small quantities of embryo extract are also present in the plasma, then the beneficial effect of the proteoses on the rate of growth is very greatly increased. A thermostable substance has been separated from Witte’s peptone, and from fibrin digests, which is capable of stimulating cells to increased activity and division. The activity of this substance is not dependent on the presence of plasma. The effective agent is associated with, or is actually, a heteroproteose, and its action is probably not to supply nitrogen, but rather to stimulate the cells in some other way. It is present in certain preparations of proteoses and partly accounts for their activity. Suggestions are put forward to account for the manner in which the various media described affect the rate of growth of the cells.
Iodine Compounds and Fertilisation
Authors: Carter G. S.
Published: April 2021

The results given in the previous papers of this series (1930, 1931 a, b, 1932 a, b) have shown that thyroxine, and, to a much smaller extent, certain related iodine compounds, resemble the egg secretions of E. esculentus and E. miliaris in their action upon the eggs and sperm of these species and that this resemblance extends to several distinct phenomena. The conclusion has been reached that the secretions contain a substance which is not only similar to thyroxine in its physiological action but is also chemically related to it. Further, the evidence has led to the conclusion that this substance is the component of the secretions which is essential to the activation of the egg, and is therefore the fertilizin of Lillie (1914).
Experiments with the Stipes of Fucus and Laminaria
Authors: Delf(Mrs Percy Smith) E. Marion
Published: April 2021

Marine algae may be briefly characterised as either intertidal or totally submerged forms.

The intertidal algae have a dual existence : they are land plants at low tide and aquatics when covered by the sea. The proportion of time spent in the aerial or aquatic medium must vary with the position on the shore and the factors influencing tidal periodicity. The more exposed plants must have a tolerance for various light intensities and for a wide range of conditions affecting water loss ; and they must also, if fixed to the substrate, be able to withstand more or less violent movements of the water. These movements may be partly due to currents and partly to waves, frequently reinforced by wind.

Currents are said to have little influence on littoral plants, but wave action is certainly an important factor, influencing the mechanical stresses and strains to which the plants are subjected. These stresses differ from those to which land plants are exposed in being predominantly a series of intermittent pulls or jerks, applied to plants with little initial rigidity and great flexibility.
Some Aspects of Chemical Changes During Insect Metamorphosis
Authors: Evans Alterbury Coulston
Published: April 2021

The changes in carbohydrate content, fatty acid content, and nitrogen distribution are described in detail during the metamorphosis from larva to adult in the sheep blow-fly, Lucilia sericata Meigan.

Carbohydrate decreases rapidly until the thirteenth day, after which it remains constant. Glycogen is present.

The fatty acid content decreases rapidly until the ninth day. A synthesis of fatty acid now occurs, reaching a maximum on the fourteenth day, after which a decrease sets in until emergence of the adult. The amount of saturated fatty acid present remains constant, the unsaturated fatty acids only being utilised.

The course of histolysis and histogenesis is reflected in the nitrogen distribution curves. The initial decrease in insoluble protein correlated with a rise in peptone is associated with the formation of the hard chitinous puparium. Continued decrease of the insoluble protein accompanied by a fall in peptone and an increase of soluble protein continues until histogenesis of the imaginal thoracic muscles commences. The insoluble protein now abruptly rises and the soluble protein shows a corresponding decrease. Formation of excretory-N occurs mainly during histolysis.